CA2110499C - Surface modified porous expanded polytetrafluoroethylene and process for making - Google Patents
Surface modified porous expanded polytetrafluoroethylene and process for makingInfo
- Publication number
- CA2110499C CA2110499C CA002110499A CA2110499A CA2110499C CA 2110499 C CA2110499 C CA 2110499C CA 002110499 A CA002110499 A CA 002110499A CA 2110499 A CA2110499 A CA 2110499A CA 2110499 C CA2110499 C CA 2110499C
- Authority
- CA
- Canada
- Prior art keywords
- porous expanded
- expanded polytetrafluoroethylene
- polytetrafluoroethylene according
- tubular shape
- degrees
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Lifetime
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Classifications
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J5/00—Manufacture of articles or shaped materials containing macromolecular substances
- C08J5/18—Manufacture of films or sheets
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- A—HUMAN NECESSITIES
- A01—AGRICULTURE; FORESTRY; ANIMAL HUSBANDRY; HUNTING; TRAPPING; FISHING
- A01K—ANIMAL HUSBANDRY; CARE OF BIRDS, FISHES, INSECTS; FISHING; REARING OR BREEDING ANIMALS, NOT OTHERWISE PROVIDED FOR; NEW BREEDS OF ANIMALS
- A01K91/00—Lines
- A01K91/12—Fly lines
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- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61L—METHODS OR APPARATUS FOR STERILISING MATERIALS OR OBJECTS IN GENERAL; DISINFECTION, STERILISATION OR DEODORISATION OF AIR; CHEMICAL ASPECTS OF BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES; MATERIALS FOR BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES
- A61L27/00—Materials for grafts or prostheses or for coating grafts or prostheses
- A61L27/14—Macromolecular materials
- A61L27/16—Macromolecular materials obtained by reactions only involving carbon-to-carbon unsaturated bonds
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D39/00—Filtering material for liquid or gaseous fluids
- B01D39/14—Other self-supporting filtering material ; Other filtering material
- B01D39/16—Other self-supporting filtering material ; Other filtering material of organic material, e.g. synthetic fibres
- B01D39/1692—Other shaped material, e.g. perforated or porous sheets
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C59/00—Surface shaping of articles, e.g. embossing; Apparatus therefor
- B29C59/14—Surface shaping of articles, e.g. embossing; Apparatus therefor by plasma treatment
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- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61L—METHODS OR APPARATUS FOR STERILISING MATERIALS OR OBJECTS IN GENERAL; DISINFECTION, STERILISATION OR DEODORISATION OF AIR; CHEMICAL ASPECTS OF BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES; MATERIALS FOR BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES
- A61L2400/00—Materials characterised by their function or physical properties
- A61L2400/18—Modification of implant surfaces in order to improve biocompatibility, cell growth, fixation of biomolecules, e.g. plasma treatment
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29K—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES B29B, B29C OR B29D, RELATING TO MOULDING MATERIALS OR TO MATERIALS FOR MOULDS, REINFORCEMENTS, FILLERS OR PREFORMED PARTS, e.g. INSERTS
- B29K2027/00—Use of polyvinylhalogenides or derivatives thereof as moulding material
- B29K2027/12—Use of polyvinylhalogenides or derivatives thereof as moulding material containing fluorine
- B29K2027/18—PTFE, i.e. polytetrafluorethene, e.g. ePTFE, i.e. expanded polytetrafluorethene
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29K—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES B29B, B29C OR B29D, RELATING TO MOULDING MATERIALS OR TO MATERIALS FOR MOULDS, REINFORCEMENTS, FILLERS OR PREFORMED PARTS, e.g. INSERTS
- B29K2105/00—Condition, form or state of moulded material or of the material to be shaped
- B29K2105/04—Condition, form or state of moulded material or of the material to be shaped cellular or porous
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J2327/00—Characterised by the use of homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by a halogen; Derivatives of such polymers
- C08J2327/02—Characterised by the use of homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by a halogen; Derivatives of such polymers not modified by chemical after-treatment
- C08J2327/12—Characterised by the use of homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by a halogen; Derivatives of such polymers not modified by chemical after-treatment containing fluorine atoms
- C08J2327/18—Homopolymers or copolymers of tetrafluoroethylene
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
- F23G—CREMATION FURNACES; CONSUMING WASTE PRODUCTS BY COMBUSTION
- F23G2202/00—Combustion
- F23G2202/20—Combustion to temperatures melting waste
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
- F23L—SUPPLYING AIR OR NON-COMBUSTIBLE LIQUIDS OR GASES TO COMBUSTION APPARATUS IN GENERAL ; VALVES OR DAMPERS SPECIALLY ADAPTED FOR CONTROLLING AIR SUPPLY OR DRAUGHT IN COMBUSTION APPARATUS; INDUCING DRAUGHT IN COMBUSTION APPARATUS; TOPS FOR CHIMNEYS OR VENTILATING SHAFTS; TERMINALS FOR FLUES
- F23L2900/00—Special arrangements for supplying or treating air or oxidant for combustion; Injecting inert gas, water or steam into the combustion chamber
- F23L2900/07005—Injecting pure oxygen or oxygen enriched air
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E20/00—Combustion technologies with mitigation potential
- Y02E20/34—Indirect CO2mitigation, i.e. by acting on non CO2directly related matters of the process, e.g. pre-heating or heat recovery
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10S128/00—Surgery
- Y10S128/14—Polytetrafluoroethylene, i.e. PTFE
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10S55/00—Gas separation
- Y10S55/05—Methods of making filter
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10S623/00—Prosthesis, i.e. artificial body members, parts thereof, or aids and accessories therefor
- Y10S623/901—Method of manufacturing prosthetic device
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
- Y10T428/00—Stock material or miscellaneous articles
- Y10T428/13—Hollow or container type article [e.g., tube, vase, etc.]
- Y10T428/1352—Polymer or resin containing [i.e., natural or synthetic]
- Y10T428/1362—Textile, fabric, cloth, or pile containing [e.g., web, net, woven, knitted, mesh, nonwoven, matted, etc.]
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
- Y10T428/00—Stock material or miscellaneous articles
- Y10T428/13—Hollow or container type article [e.g., tube, vase, etc.]
- Y10T428/1352—Polymer or resin containing [i.e., natural or synthetic]
- Y10T428/1372—Randomly noninterengaged or randomly contacting fibers, filaments, particles, or flakes
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
- Y10T428/00—Stock material or miscellaneous articles
- Y10T428/13—Hollow or container type article [e.g., tube, vase, etc.]
- Y10T428/1352—Polymer or resin containing [i.e., natural or synthetic]
- Y10T428/139—Open-ended, self-supporting conduit, cylinder, or tube-type article
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
- Y10T428/00—Stock material or miscellaneous articles
- Y10T428/13—Hollow or container type article [e.g., tube, vase, etc.]
- Y10T428/1352—Polymer or resin containing [i.e., natural or synthetic]
- Y10T428/1397—Single layer [continuous layer]
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
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- Y10T428/249921—Web or sheet containing structurally defined element or component
- Y10T428/249953—Composite having voids in a component [e.g., porous, cellular, etc.]
- Y10T428/249955—Void-containing component partially impregnated with adjacent component
- Y10T428/249958—Void-containing component is synthetic resin or natural rubbers
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
- Y10T428/00—Stock material or miscellaneous articles
- Y10T428/249921—Web or sheet containing structurally defined element or component
- Y10T428/249953—Composite having voids in a component [e.g., porous, cellular, etc.]
- Y10T428/249962—Void-containing component has a continuous matrix of fibers only [e.g., porous paper, etc.]
- Y10T428/249964—Fibers of defined composition
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
- Y10T428/00—Stock material or miscellaneous articles
- Y10T428/29—Coated or structually defined flake, particle, cell, strand, strand portion, rod, filament, macroscopic fiber or mass thereof
- Y10T428/2913—Rod, strand, filament or fiber
- Y10T428/2933—Coated or with bond, impregnation or core
- Y10T428/2935—Discontinuous or tubular or cellular core
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
- Y10T428/00—Stock material or miscellaneous articles
- Y10T428/29—Coated or structually defined flake, particle, cell, strand, strand portion, rod, filament, macroscopic fiber or mass thereof
- Y10T428/2913—Rod, strand, filament or fiber
- Y10T428/2973—Particular cross section
- Y10T428/2975—Tubular or cellular
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
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- Y10T428/31—Surface property or characteristic of web, sheet or block
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
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- Y10T428/00—Stock material or miscellaneous articles
- Y10T428/31504—Composite [nonstructural laminate]
- Y10T428/3154—Of fluorinated addition polymer from unsaturated monomers
- Y10T428/31544—Addition polymer is perhalogenated
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
- Y10T442/00—Fabric [woven, knitted, or nonwoven textile or cloth, etc.]
- Y10T442/60—Nonwoven fabric [i.e., nonwoven strand or fiber material]
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- Chemical & Material Sciences (AREA)
- Health & Medical Sciences (AREA)
- Life Sciences & Earth Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Engineering & Computer Science (AREA)
- Manufacturing & Machinery (AREA)
- Medicinal Chemistry (AREA)
- Environmental Sciences (AREA)
- Transplantation (AREA)
- Biodiversity & Conservation Biology (AREA)
- General Health & Medical Sciences (AREA)
- Public Health (AREA)
- Veterinary Medicine (AREA)
- Physics & Mathematics (AREA)
- Epidemiology (AREA)
- Plasma & Fusion (AREA)
- Animal Husbandry (AREA)
- Animal Behavior & Ethology (AREA)
- Oral & Maxillofacial Surgery (AREA)
- Dermatology (AREA)
- Materials Engineering (AREA)
- Polymers & Plastics (AREA)
- Organic Chemistry (AREA)
- Treatments Of Macromolecular Shaped Articles (AREA)
- Materials For Medical Uses (AREA)
- Manufacture Of Porous Articles, And Recovery And Treatment Of Waste Products (AREA)
- Chemical Or Physical Treatment Of Fibers (AREA)
Abstract
Porous expanded polytetrafluoroethylene material having a microstructure of nodes interconnected by fibrils wherein a surface of the material has been modified to have increased hydrophobicity as indicated by having a water droplet roll-off angle of less than about 10 degrees in comparison to a typical roll-off angle of greater than about 12 degrees for the unmodified material.
Under magnification, the surface morphology may be indistinguishable from that of the unmodified precursor material. The modification is preferably done by exposing the surface to radio frequency gas plasma discharge with a reactive etching gas for a lengthy amount of time such as about ten minutes. If surface etching is continued beyond a time adequate to produce the highly hydrophobic behavior, then the surface morphology includes the appearance of broken fibrils. Still further treatment results in complete removal of fibrils from the surface so that under magnification the surface has the appearance of freestanding node portions not interconnected by fibrils but rather having open valleys disposed between the freestanding node portions.
Under magnification, the surface morphology may be indistinguishable from that of the unmodified precursor material. The modification is preferably done by exposing the surface to radio frequency gas plasma discharge with a reactive etching gas for a lengthy amount of time such as about ten minutes. If surface etching is continued beyond a time adequate to produce the highly hydrophobic behavior, then the surface morphology includes the appearance of broken fibrils. Still further treatment results in complete removal of fibrils from the surface so that under magnification the surface has the appearance of freestanding node portions not interconnected by fibrils but rather having open valleys disposed between the freestanding node portions.
Description
WO 92/22604 P(~/US92/0481~
TITLE OF ~HE INVENTION
Surface Modified Porous Expanded Polytetrafluoroethylene and Process for Makin~
FIELD OF THE INVENTION
This invention relates to surface mod;fied porous expanded polytetrafluoroethylene and a method for making it.
BACKGROUND OF THE INYENTION
It has long been known to use various surface modification techniques including glow discharge plasma to change the surface characteristics of polymeric materials. For example, it may be advantageous to improve the bondability of an implantable polyme~ic medical device or to change the wettability of a polymeric fabric.
Fluorocarbons have frequently been used as both the surface modified substrate materials and as materials used to modify surfaces of other ; polymeric substrates.
These surface modifications can take several forms. Plasma polymerization by radio frequency gas plasma using polymerizing gases can polymeri2e a new material onto the surface of another substrate.
Unsaturated fluorocarbon gas plasmas can be used, for example, to polymerize a fluorocarbon layer onto a polystyrene substrate.
Alternatively, plasma activation is used with non-polymer forming gases such as oxygen or saturated fluorocarbons to chemically modify a substrate surface. The plasma activation of a fluoropolymer substrate ! I 25 surface with oxygen gas, for example, can result in the replacement of fluorine atoms from the substrate surface with oxygen in order to enhance the wettability of that surface. Still another technique is plasma cleaning or plasma etching where a reactive gas plasma is used to etch or roughen a surface by removing quantities of the substrate ~ 30 material comprising the surface. This can be done for surface ; cleaning or for increasing bondability, for example. Etching can also be accomplished with other energy sources such as ion beams~ Masking techniques can be used to selectively etch portions of a surface to 2 1 1 V '~ 9 9 PCI/US92/04812 produce a desired pattern. Alternatively, specific surface patterns can be produced in polymeric surfaces by molding techniques well known to those skilled in the art.
Plasma polymerization, plasma activation and plasma etching are all considered to be specific types of plasma treatment but are not considered as mutually exclusive categories. The plasma etching of some substrates to enhance bondability is, for example, sometimes called plasma activation.
An article in Medical Product Manufacturing News (Using Gas Plasma to Re-engineer Surfaces, Nancy B. Mateo, Sept/Oct 1990), provides a general description of known gas plasma surface modification methods. The author states that increasing surface wettability and adhesiveness are among the most routine uses for gas plasmas.
U.S. Patent 4,919,659 to Horbett, et al., teaches the modification of bio-material surfaces by radio frequency plasma~in order to enhance the growth of cell cultures on the bio-material surfaces. The modification involves the plasma polymerization of overcoat layers onto a surface of an implantable bio-material.
A paper by A.M. Garfinkle et al., ("Improved Patency in Small Diameter Dacron Vascular Grafts After a Tetrafluoroethylene Glow Discharge Treatment," presented at the Second World Congress on Biomaterials 10th Annual Meeting of the Society fnr Biomaterials, Wash~ngton, D.C., April 27-May 1, 1984) describes the use of plasma polymerization with the monomer TFE gas to modify the luminal surface of Dacron vascular grafts by depositing thereon a coating of tetrafluoroethylene.
An article by C. Tran and D. Walt (Plasma Modification and Çollagen Binding to PTFE Grafts. ~ournal of Colloid and Interface Science, Oct 15, 19B9, vol 132 no. 2, pp 373~381), describes the use of RF and electr1cal glow discharge plasma deposition systems to clean and coat the luminal surface of porous expanded polytetrafluoroethylene GORE-TEX~ Vascular Grafts. Cleaning was done with argon plasma for one hour followed consecutively by plasma polymerization with hexane and anhydrous ammonia for one hour each.
The grafts were then coated with collagen; Wet~ability of the plasma ~ modified polytetrafluoroethylene (hereinafter PTFE) surface was found :~
WO 92~22604 PCr/US92/0~812 to be increased. Y.S. Yeh et al. (Blood Compatibility of Surfaces Modified by Plasma Polymerization. Journal of Biomedical Materials Research 1988 22;795-818) used rf gas plasma in a hexafluoroethane/H2 atmosphere to polymerize the surface of GORE-TEX Vascular Grafts.
They described the surface morphology of the treated graft surfaces as being indistinguishable from untreated graft surfaces.
Y. Iriyama et al. (Plasma Surface Treatment on Nylon Fabrics by Fluorocarbon Compounds. Journal of Applied Polymer Science 1990 39;249-264) ptasma polymerized or alternatively plasma activated nylon fabrics with low temperature fluorocarbon plasmas so as to increase the hydrophobicity of these fabrics. They found,water droplet roll-off angle to be a better indicator of rough surface hydrophobicity , , than measurements of water droplet contact angles. A good description of the method of making water droplet roll-off angl,e measurements is provided.
In U.S.P. 4,946,903, J. Gardella et al., teach plasma activation of fluoropolymers with radio frequency glow discharge to increase the wettability of their surfaces. This is accomplished by substituting hydrogen and oxygen or oxygen-containing radicals for fluorine atoms ~ 20 in the surface of the fluoropolymer. Porous expanded PTFE was used as ; an example fluoropolymer.
M. Morra et al., (Contact Angle Hysteresis in Oxygen Plasma Treated Polytetrafluoroethylene, Langmuir 1989 5;872-876; Surface Characterization of Plasma-Treated PTFE, Surface and Interface Analysis 1990 16;412-417), exposed non-porous PTFF surfaces to both oxygen and argon gas plasmas. With oxygen plasmas they found that 15 minute treatments produced extensive plasma etching of the surface while argon treatment for the same time ~id not alter surface smoothness. ~he argon treated surfaces were found to be more hydrophilic than the untreated precursor material. Morra also described that the roughened surface resulting from oxygen plasma treatment showed increased hydrophobicity as a direct function of the increased surface roughness, with water advancing contact angles up to 1~6 degrees.
TITLE OF ~HE INVENTION
Surface Modified Porous Expanded Polytetrafluoroethylene and Process for Makin~
FIELD OF THE INVENTION
This invention relates to surface mod;fied porous expanded polytetrafluoroethylene and a method for making it.
BACKGROUND OF THE INYENTION
It has long been known to use various surface modification techniques including glow discharge plasma to change the surface characteristics of polymeric materials. For example, it may be advantageous to improve the bondability of an implantable polyme~ic medical device or to change the wettability of a polymeric fabric.
Fluorocarbons have frequently been used as both the surface modified substrate materials and as materials used to modify surfaces of other ; polymeric substrates.
These surface modifications can take several forms. Plasma polymerization by radio frequency gas plasma using polymerizing gases can polymeri2e a new material onto the surface of another substrate.
Unsaturated fluorocarbon gas plasmas can be used, for example, to polymerize a fluorocarbon layer onto a polystyrene substrate.
Alternatively, plasma activation is used with non-polymer forming gases such as oxygen or saturated fluorocarbons to chemically modify a substrate surface. The plasma activation of a fluoropolymer substrate ! I 25 surface with oxygen gas, for example, can result in the replacement of fluorine atoms from the substrate surface with oxygen in order to enhance the wettability of that surface. Still another technique is plasma cleaning or plasma etching where a reactive gas plasma is used to etch or roughen a surface by removing quantities of the substrate ~ 30 material comprising the surface. This can be done for surface ; cleaning or for increasing bondability, for example. Etching can also be accomplished with other energy sources such as ion beams~ Masking techniques can be used to selectively etch portions of a surface to 2 1 1 V '~ 9 9 PCI/US92/04812 produce a desired pattern. Alternatively, specific surface patterns can be produced in polymeric surfaces by molding techniques well known to those skilled in the art.
Plasma polymerization, plasma activation and plasma etching are all considered to be specific types of plasma treatment but are not considered as mutually exclusive categories. The plasma etching of some substrates to enhance bondability is, for example, sometimes called plasma activation.
An article in Medical Product Manufacturing News (Using Gas Plasma to Re-engineer Surfaces, Nancy B. Mateo, Sept/Oct 1990), provides a general description of known gas plasma surface modification methods. The author states that increasing surface wettability and adhesiveness are among the most routine uses for gas plasmas.
U.S. Patent 4,919,659 to Horbett, et al., teaches the modification of bio-material surfaces by radio frequency plasma~in order to enhance the growth of cell cultures on the bio-material surfaces. The modification involves the plasma polymerization of overcoat layers onto a surface of an implantable bio-material.
A paper by A.M. Garfinkle et al., ("Improved Patency in Small Diameter Dacron Vascular Grafts After a Tetrafluoroethylene Glow Discharge Treatment," presented at the Second World Congress on Biomaterials 10th Annual Meeting of the Society fnr Biomaterials, Wash~ngton, D.C., April 27-May 1, 1984) describes the use of plasma polymerization with the monomer TFE gas to modify the luminal surface of Dacron vascular grafts by depositing thereon a coating of tetrafluoroethylene.
An article by C. Tran and D. Walt (Plasma Modification and Çollagen Binding to PTFE Grafts. ~ournal of Colloid and Interface Science, Oct 15, 19B9, vol 132 no. 2, pp 373~381), describes the use of RF and electr1cal glow discharge plasma deposition systems to clean and coat the luminal surface of porous expanded polytetrafluoroethylene GORE-TEX~ Vascular Grafts. Cleaning was done with argon plasma for one hour followed consecutively by plasma polymerization with hexane and anhydrous ammonia for one hour each.
The grafts were then coated with collagen; Wet~ability of the plasma ~ modified polytetrafluoroethylene (hereinafter PTFE) surface was found :~
WO 92~22604 PCr/US92/0~812 to be increased. Y.S. Yeh et al. (Blood Compatibility of Surfaces Modified by Plasma Polymerization. Journal of Biomedical Materials Research 1988 22;795-818) used rf gas plasma in a hexafluoroethane/H2 atmosphere to polymerize the surface of GORE-TEX Vascular Grafts.
They described the surface morphology of the treated graft surfaces as being indistinguishable from untreated graft surfaces.
Y. Iriyama et al. (Plasma Surface Treatment on Nylon Fabrics by Fluorocarbon Compounds. Journal of Applied Polymer Science 1990 39;249-264) ptasma polymerized or alternatively plasma activated nylon fabrics with low temperature fluorocarbon plasmas so as to increase the hydrophobicity of these fabrics. They found,water droplet roll-off angle to be a better indicator of rough surface hydrophobicity , , than measurements of water droplet contact angles. A good description of the method of making water droplet roll-off angl,e measurements is provided.
In U.S.P. 4,946,903, J. Gardella et al., teach plasma activation of fluoropolymers with radio frequency glow discharge to increase the wettability of their surfaces. This is accomplished by substituting hydrogen and oxygen or oxygen-containing radicals for fluorine atoms ~ 20 in the surface of the fluoropolymer. Porous expanded PTFE was used as ; an example fluoropolymer.
M. Morra et al., (Contact Angle Hysteresis in Oxygen Plasma Treated Polytetrafluoroethylene, Langmuir 1989 5;872-876; Surface Characterization of Plasma-Treated PTFE, Surface and Interface Analysis 1990 16;412-417), exposed non-porous PTFF surfaces to both oxygen and argon gas plasmas. With oxygen plasmas they found that 15 minute treatments produced extensive plasma etching of the surface while argon treatment for the same time ~id not alter surface smoothness. ~he argon treated surfaces were found to be more hydrophilic than the untreated precursor material. Morra also described that the roughened surface resulting from oxygen plasma treatment showed increased hydrophobicity as a direct function of the increased surface roughness, with water advancing contact angles up to 1~6 degrees.
3~ U.S. Patent 4,933,060 to Prohaska, et al., teaches the plasma modification of a fluoropolymer surface by treatment with reacti~e gas plasma comprising primarily water, in order to increase the adhesive 4 PCr/US92/04812 2~10499 bondability of such surfaces. The surfaces are rendered hydrophilic, apparently by the defluorination and oxidation of the surface.
U.S. Patent 4,064,030 to J. Nakai et al.~ describes the modification of molded non-porous articles of fluorine resin by sputter etching with ion beams in order to provide better adhesion.
They state that their treated surfaces have superior adhering properties not attainable with conventional glow discharge treatment.
Nakai et al., noted that wettability of a surface can be modified by varying treatment time, discharge power or chamber pressure, however no modified surfaces were described as being more hydrophobic than untre~ted P~FE having contact angles up to about 120 degrees.
An article by S. R. Taylor, et al., ~Effect of Surface Texture On The Soft Tissue Response To Polymer Implants," Journal of Biomedical Materials Research 1983 17;205-227, John Wiley & Sons, lnc., describes ion beam etching by sputtering of non-porous PTFE surfaces. A
modified textured PTFE surface having conical projections was produced wherein the projections had a mean height of about 12 microns, a mean base width of about 4 microns and a mean tip radius of about 0.1 micron. Little or no apparent chemical changes in the modified surface were detected. When implanted in a living body, these modified PTFE surfaces produced fibrous capsules of only 30 percent of the thickness of fibrous capsules produced by unmodified PTFE
surfaces. The modified surfaces a~so demonstrated increased cell adhesion. Contact angle measurements were used to determine the surface energy of the modified PTFE surfaces, however, no results of surface energy analysis and no contact angle data were provided for the modified textured PTFE surfaces because of wicking of the diagnostic liquids on those surfaces.
G.L. Picha et al., (nIon-Beam Microtexturing of Biomaterials,"
Medical Device and Diagnostic Industry, vol. 6 no. 4, April 1984), describe the manufacture of textured surfaces in non-porous PTFE and polyurethane by etching surfaces with ion-beams, with and without the optional use of sputter masks, for the purpose of increasing bondability.
U.S. Patent 4,955,909 to Ersek et al., describes textured silicone surfaces for implantable materials wherein the surfaces comprise a series of formed pillars with valleys disposed between Wo 92/226n4 2 1 1 0 4 9 9 Pcr/US92/04812 them. ~he textured surface is produced by thrusting specifically selected molecules against a non-porous silicone rubber surface with sufficient impac~ to produce pillars or projections of 20 to 500 micron si~e.
U.S. Patents 4,767,418 and 4,869,714 to Deininger et al., describe a male mold useful for making tubular vascular grafts, the surface of the mold comprising a series of pillars. The basis for the mold is created by sputter-coating a layer of gold film onto the surface of a P~FE cylinder. The pillars are then formed by selectively photoetching the sputter-coated gold film with the aid of a masked photoresist.
SUMMARY OF THE INVENTION
The present invention relates to porous expanded ~; polytetrafluoroethylene (PTFE) material having a microstructure of nodes interconnected by fibrils and further having at least a substantial portion of one surface that is highly hydrophobic as indicated by having a water droplet roll-off angle of less than about 10 degrees. Water droplet roll-off angles for previoùsly available porous expanded P~FE surfaces have been greater than about 12 degrees and are typically ~reater than about 20 degrees. Porous expanded P~FE
surfaces having water droplet roll-off angles of less than about 10 degrees have heretofore been unknown. Some porous expanded PTFE
surfaces modified according to the present invention have achieved roll-off angles as low as about 2 degrees.
2~ The present invention may be practiced with porous expanded materials that are very thin, for example, membranes or films of thicknesses as little as about 5 microns.
By a substantial portion of one surface is meant that enough of the one surface has been modified to have an effect on the intended performance of the material, where the intended performance may, for example, involve improved bondability, inoreased hydrophobicity, improved resistance to the penetration of a fluid through the material or improved filtration ability.
W092/22604 2 i lU~99 PCI/US92/04812 The hydrophilicity or hydrophobicity of any surface is most commonly determined by measurements of the advancing and receding contact angles of distilled water droplets placed onto the horizontal surface in question. However, for purposes of the present invention, water droplet roll-off angle measurements have been found to be the preferred method for measuring high degrees of hydrophobicity. This will be further discussed below.
It has been found that lengthy exposure to radio frequency (rf) etching gas plasmas increases the hydrophobicity of porous expanded PTFE surfaces. This treatment of such a surface by rf gas plasma with most etching gases initially results in increased hydrophilicity.
This behavior is known and is in common with the treatment of non-porous PTFE surfaces. This increased hydrophilicity is generally explained in terms of chemical changes in the surface composition.
Continued gas plasma treatment results in the achievement of a peak value of hydrophilicity, still the same behavior as non-porous PTFE.
Under further treatment, non-porous PTFE remained more hydrophilic than prior to treatment Porous expanded PTFE, however, after achieving a peak value of hydrophilicity, became increasingly hydrophobic with further treatment and finally approached a maximum ~; level of hydrophobicity that substantially exceeded the degree of hydrophobicity possessed by the unmodified precursor porous expanded PTFE surface. This near-maximum level of hydrophobicity is indicated by a water droplet roll-off angle of less than about 10 degrees and will subsequently be described herein as ~highly hydrophobic." It may require more than an hour of treatment time to achieve. The treatmant time will depend primarily on the type of plasma etching gas used and on the amount of rf power applied. The gas pressure within the treatment chamber is also a factor.
While only rf gas plasma discharge has been used as the energy source to create the modified surface of the present invention, it is believed that other energy sources such as m~crowave gas plasma discharge may also be suitable. Other possible energy sources include x-rays, laser beams and ion beams. Lengthy treatment times or high energy levels may be required.
~hile many reactive gases have been found to be capable of ; increasing the hydrophobicity of a porous expanded PTFE surface, only ~:
WO 92/22604 2 1 1 ~ 4 9 ~ PCr/US92J04812 some of the reactive gases examined were capable of making the surface highly hydrophobic as indicated by a water droplet roll-off angle of less than about ten degrees.
The minimum treatment time necessary to produce this highly hydrophobic surface results in a surface appearance that is substantially indistinguishable from the surface of the untreated precursor porous expanded PTFE material when both are viewed microscopically. Continued treatment beyond the point of initial highly hydrophobic behavior results in a surface appeirance containing broken fibrils, that is, fibrils no longer having both ends connected to adjacent nodes. Still further treatment produces a surface from which the interconnecting fibrils have been removed entirely leaving the portions of the nodes closest to that surface in a freestanding condition, that is, no longer interconnected by fibrils but rather ha~ing open ~alleys disposed between these freestanding node portions.
Although the surface morphology undergoes these significant changes as indicated first by the appearance of broken fibrils and subsequently by the complete removal of fibrils, the high degree of hydrophobicity attained prior to the appearance of broken fibrils shows little if any further increase as indicated by water droplet roll-off angle measurements. The material below this modified surface, as evidenced by microscopic views of cross sections of the modified material, appears as conventional, unmodified porous expanded PTFE having a microstructure of nodes interconnected by fibri~s.
Surface modified porous expanded PTFE material, havin~ a microstructure of nodes interconnected by fibrils and further having a substantial portion of at least one sur~ace comprised of freestanding node portions with open valleys disposed between the freestanding node portions, is al50 within the scope of the present invention. This surface may or may not be highly hydrophobic depending primarily on the type of reactive gas plasma used for treatment.
The manufacture of porous expanded PTFE, the precursor material from which the present invention is made, is taught by U.S. Patents 3,953,566 and 4,18~,390.
Porous expanded PTFE having a surface according to the present invention may have many applications. For example, it may be possible to make waterproof breathable fabrics of increased performance fro,,~
WO 92/2t604 PCI /US92/0481 2 .als!~
the inventive material. Improved biocompatible porous expanded PTFE
medical implants may also be possible, such as dental implants, prosthetic ligaments, sutures, and patch and membrane materials. It may also be useful for blood-contact materials such as tubular Yascular grafts, where a material of increased hydrophobicity may prove to have increased antithrombogenic properties. A suture of cylindrical shape having a round cross section and made of porous expanded PTFE having an outer surface modified by the method of the present invention may offer enhanced knot retention. ~he surface modified porous expanded PTFE material may also prove to be a more effective filtration material in certain applications because of its increased hydrophobicity. The modified material surface may also possess enhanced bondability in comparison to unmodified precursor material. It is expected that a modified surface having increased hydrophobicity may improve the flotation characteristics of fly fishing lines having an outer surface of porous expanded PTFE. Wire insulations having an outer surface of porous expanded PTFE may also benefit from the modified surface of the present invention.
~:
BRIEF DESCRIPTION OF THE DRAWINGS
:
Figure 1 is a drawing of a device used for measuring water droplet roll-off angles for the material samples of this invention.
Figure 2 shows a pictorial representation of an enlarged cross sectional view of a precursor porous expanded PTFE material prior to plasma treatment.
Figure 2A shows a pictorial representation of an enlarged cross sectional view of the material of Figure 2 after rf gas plasma treatment with a reacti~e etching gas.
Figure 3 shows a graph of the change in water droplet roll-off angles of both non-porous P~FE and porous expanded PTFE surfaces as a ; 30 function of different treatment times by rf glow discharge gas plasma using nitrogen trifluoride (hereinafter NF3) gas.
Figure 4 shows a scanning electron photomicrograph (x500) of the surface of a porous expanded PTFE material (GORE-TEX~ Soft Tissue Patch) prior to rf gas plasma treatment.
; ::
WO 92/22604 2 i ~ O Ll ~.) 9 PCI/I S92/04812 Figure 4A shows a scanning electron photomicrograph (x500) of a perspective cross sectional view of the material of Figure 4 prior to rf gas plasma treatment.
Figure S shows a scanning electron photomicrograph (xlO00) of the surface of the same material as shown by Figure 4 after 2 minutes of rf gas plasma treatment with NF3 gas to make the surface hydrophilic.
Figure SA shows a scanning electron photomicrograph (x500) of a perspective cross sectional view of the material of Figure 4A
after 2 minutes of rf gas plasma treatment with NF3 gas to make the surface hydrophilic.
Figure 6 shows a scanning electron photomicrograph (xlO00) of the surface of the same material as shown by Figure 4 after 10 - minutes of rf gas plasma treatment with NF3 gas to make the sur~ace highly hydrophobic.
Figure 6A shows a scanning electron photomicrograph (x500) of a perspective cross sectional view of the same material as shown by Figure 4A after 10 minutes of rf gas plas~a treatment with NF3 gas to make the surface highly hydrophobic.
figure 7 shows a scanning electron photomicrograph (xlO00) of the surface of the same material as shown by Figure 4 after 15 minutes of rf gas plasma treatment with NF3 gas resulting in broken fibrils-at the material surface.
Figure 7A shows a scanning electron photomicrograph (x500) of a perspective cross sectional view of the same treated material as shown by Figure 4A after 15 minutes of rf gas plasma treatment with NF3 gas resulting in broken fibrils at the material surface.
Figure 8 shows a scanning electron photomicrograph ~xS00) of the ! . i ! surface of the same material as shown by Figure 4 after 60 minutes of rf gas plasma treatment with NF3 gas resulting in removal of the fibrils from the material surface leaYing the surface comprised of a series of freestanding node portions with open valleys disposed between the freestanding node portions~
Figure 8A shows a scanning electron photomicrograph (x200) of a perspective cross sectional view of the same material as shown by Figure 4A after 60 minutes of rf gas plasma treatment with NF3 gas resulting in removal of the fibrils from the material surface 4 ~ 9 - 1 o-leaving the surface comprised of a series of freestanding node portions with open valleys disposed between the freestanding nodP
portions.
Figure 9 shows a scanning electron photomicrograph (x500) of a surface view of the same material as shown by Figure 4 after 120 minutes of rf gas plasma treatment with air resu~ting in removal of the fibrils from the material surface leaving the surface comprised of a series of freestanding node portions with open valleys disposed between the freestanding node portions.
Figure 9A shows a scanning electron photomicrograph (x200) of a perspective cross.sectional view of the same material as shown by : Figure 4A after 120 minutes of rf gas plasma treatment with air : resulting in removal of the fibrils from the material surface leaving the surface comprised of a.series of freestanding node portions with open valleys disposed between the freestanding node ~: . portions.
.~ Figure 10 shows a graph of the change in water droplet roll-off angle of a porous expanded PTFE material (GOR~-~EX Soft Tissue Patch) as a function of different treatment times by glow discharge plasma for different gases.
Figure 11 shows a scanning electron photomicrograph (xlOOO) of the luminal surface of an alternative porous expanded PTFE material (20 mm diameter GORE-TEX Vascular Graft) prior to rf gas plasma treatment.
Figure 12 shows a scanning electron photomicrograph (xlOOO) of the luminal surface of the same material as shown by Figure 10 after 30 minutes of rf gas plasma treatment with oxygen resulting in the removal of fibrils from the surface leaving the surface , I comprised of freestanding node portions having open valleys disposed between the freestanding node portions.
Figure 13 shows a scanning electron photomicrograph (xlOOO) of the luminal vascular graft surface of the same material as shown by : Figure 10 after 120 minutes of rf gas plasma treatment with : oxygen resulting in the removal of fibrils from the surface leaving the surface comprised of freestanding node portions having open valleys disposed between the freestanding node .~ .
~ portions.
WO 92/22604 PCr/US92/04~12 i' li~'l99 DE~AIL~D DESCRIPTION OF THE INVENTION
All work described herein was done using a model B12 plasma unit from Advanced Plasma Systems, lnc., St. Petersburg, Florida. Typical surface treatment times ranged fro~ about ten minutes up to as long as about two hours per sample, however, reduced times may be possible with the use of higher rf power. The preferred plasma gas has been NF3 (Air Products, Allentown, Pa.), however, similar results have been achieved with air, argon, oxygen, ammonia and Polyetch~ (Matheson Gas Products, Inc., Utica, California). Suitable gases are those eapable of producing etching or ablation of the PTFE surface. Polymerizing gases, that is gases producing a surface coating of another material, are not suitable. All surface treatments were done at a frequency of 13.56 MHz, chamber pressure of G.300 torr and 300 watts power unless noted otherwise.
2.5 x 7.5 x 0.020 centimeter samples of porous expanded PTFE
GORE-TEX Soft Tissue Patch material (W. L. Gore and Associates, Inc.
Elkton, MD) were cut and placed into a special holder that gripped the edges of the sample while leaving the surfaces of the sample exposed.
~he holder with samples was placed inside the treatment chamber of the B-12 series plasma unit. The square aluminum chamber was of 3Q.5 centimeters per side having a grounded aluminum electrode in the form of a 23 centimeter per side, square, flat~ perforated plate placed vertically in the middle of the chamber and two powered aluminum electrodes of the same size and shape placed vertically on each side of the grounded electrode with their surfaces parallel to the surface of the grounded electrode. The spacing between eleotrodes was approximately 6.5 centimeters. The samples were suspended vertically between the electrodes with the surfaces to be treated facing a powered electrode.
The chamber was evacuated to 0.020 torr pressure and the desired plasma gas was allowed to flow freely through the chamber for 5 to 10 minutes. The pressure was adjusted to 0.300 torr using a flowmeter mounted on the inlet side of the chamber. After the pressure stabilized at 0.300 torr a plasma was ignited at a 300 watt power level and maintained at these conditions during the treatment.
WO g2J22604 PCI'/US92/0481 2 Treatment times used were 1, 2, 3, 4, 5, 10, 15, 20, 30, 60 and 120 minutes. A new set of samples was used for each treatment time.
Hydrophobicity measurements were made by measuring the water droplet roll-off angle for each treated sample. At least 12 measurements of water droplet roll-off angle were taken on each sample to establish a mean value for the sample. The 12 water droplets were placed on 12 different sites on the sample surface. Readings of the roll-off angle were recorded at the moment when the droplet began to roll. The average volume of a water droplet was 0.04 cm3.
It is believed that the increased hydrophobicity resulting from rf gas plasma treatment is due to fibrils, originally lying in or very close to the level of the upper node surfaces, first being depressed ; or lowered slightly below that level. Continued treatment nextresults in breakage of some of these fibrils and finally in their complete removal from the level of the upper node surfaces and downward to some depth below that level. Still further continued treatment increases the depth of fibril removal. Prolonged treatment results in microscopically visible node ablation that appears to ultimately limit the maximum achievable depth of fibril removal. This can be explained by the assumed slower rate of fibril removal at this depth. This maximum achievable depth appears to be a function of the microstructure of the precursor material as well as of the gas plasma application parameters.
The magnified appearance of the surface from which the fibrils have been entire~y removed is thus the appearance of the portions of the nodes closest to the surface in a freestanding condition, that is, no longer having fibrils interconnecting these freestanding node portions but rather having open valleys disposed between these freestanding node portions. The valley floors, that is, the bottom of the Yalleys, are generally comprised of fibrils~ Because the surface of the microstructure has been modified only to the extent of removal of the fibrils therefrom, no apparent difference to the surface is visible to the naked eye. Magnification of the surface is required in order to make the result of the modification visible. Surfaces ; 35 modified as taught by the macrostructural techniques of U.S. Patents 4,208,745, 4,332,035 and 4,647,416 are thus not within the scope of the present invention.
W 0 92/22604 2 1 1 0 4 9 9 PcT~uss2to48l2 The best mode of practicing the present invention is believed to be the use of rf gas plasma discharge with NF3 gas to modify a porous expanded PTFE surface for a long enough time to create a surface comprised of freestanding node portions having open valleys disposed between the freestanding node portions. NF~ is preferred because it is read~ly available, is relatively economical, requires less etching time than other gases examined heretofore and produces a highly hydrophobic surface.
The increased hydrophobicity of the plasma treated porous expanded PTFE surfaces, as indicated by either higher water droplet contact angles or by lower water droplet roll-off angles, is believed to be a result of the water droplet resting on i reduced surface area of the modified material. It is believed that plasma treatment initially causes depression of the fibrils from the level of the upper node surfaces, followed by breakage of those fibrils and finally followed by the entire removal of fibrils from the surface. Thus it appears that when hydrophobicity of the surface modified porous ; expanded PTFE is measured by the use of a water droplet that the droplet is only in contact with the upper node surfaces and that very few, if any, of the fibrils closest to the surface are in contact with the water droplet. This is in contrast to the unmodified material wherein both the upper node surfaces and the fibrils closest to the ' ~ material surface are believed to be in contact with the water droplet.
The hydrophllicity or hydrophobicity of any surface is most commonly determined by measurements of the advancing and receding contact angles of distilled watèr droplets placed onto the horizontal s~rface in question as taught by ASTM D 724-45. Material surfaces having water droplet contact angles less than 90 degrees are considered to be hydrophilic while contact angles greater than 90 degrees indicate hydrophobicity. A typical porous expanded PTFE
surface that has not been modified according to the present invention has a water droplet contact angle of about 120 to 160 degrees while such surfaces that have been modified as taught herein have contact angles generally greater than about 170 degrees. Apparently due to the increased roughness of the modified surfaces, it is difficult to achieve consistent water droplet contact angle measurements because of increased hysteresis between the advancing and receding contact ;~ ~
WO 92/22604 PCl/US92/~)4~12 2 ~ 9 angles. Furthermore, as the contact angle approaches 180 degrees, the angle becomes more difficult to project and measure accurately due to irregularities of the surface. ~ater droplet roll-off angle measurements have been found to be the preferred method of measuring the hydrophobicity of rough surfaces and in particular surfaces modified by the present invention. Water droplet roll-off angle measurements are more easily made and the results appear to be more cons~stent than contact angle measurements for such surfaces. This has been confirmed by Y. Iriyama et al., Plasma Surface Treatment on Nylon Fabrics by Fluorocarbon Compounds, Journal of Applied Polymer Science 1990 39;249-264.
Figure 1 shows the apparatus used to measure water droplet roll-off angles for hyd~phobicity measurements. A sample 12 of material to be measured is placed onto the plane surface 11 so that the sample 12 is uniformly in contact with the plane surface 11. An adjustment knob 14 connected to a right-angle gearhead 16 is used to rotate the plane surface 11 about axis 15. Axis 15 is hori~ontally oriented, that is, perpendicular to the direction of the force of gravity. A
protractor 17 is set up adjacent and perpendicular to the plane surface 11 with its center in line with axis 15, allowing easy measurement of the angle between the plane surface 11 and the horizontal. In use, the plane surface Ll is placed into a hori~ontal position and a material sample 12 is placed onto the plane surface 11 so that it uniformly contacts the plane surface 11. A droplet of distilled water 18 is placèd onto the surface of the material sample 12. The adjustment knob L4 is turned by hand to cause slow rotation of the plane surface 1,1 about axis L5 at an angular velocity of approximately one degree per second. When the water droplet 18 begins to roll off of the surface of the material sample 1~, the roll-off angle is ~easured from the protractor as the tilt angle of the plane surface 11. Multiple individual water droplets may be placed onto a single sample if the sample is of adequate area. In measurements descr~bed herein, the data represent the average roll-off angle of at least 12 water droplets.
Water droplet roll-off angles for unmodified porous expanded PTFE
surfaces are typically greater than about 20 degrees while water droplet roll-off angles of porous expanded PTFE surfaces treated by WO 92/22604 ~ 1 1 0 ~19 9 PCl/US92/04812 the method of the present invention are typically less than about 10 degrees. The lowest water droplet roll-off angle of known porous expanded PTFE surfaces has been that of the luminal surface of GORE-TEX Vascular Graft material (W. L. Gore and Associates, Inc., Elkton, MD), which typically measures about 12 degrees.
Figure 2 is a pictorial representation of a cross sectional view of a precursor porous expanded PTFE material prior to any modification. This figure shows the microstructure of nodes 21 interconnected by fibrils ~. The surface of the material is comprised of upper node surfaces 23 and fibrils 24 closest to the surface. Figure 2A is a pictorial representation of a cross sectional view of the same material after rf gas plasma treatment to modify the - surface to the extent of removing fibrils from the surface. This - figure shows freestanding node portions 25 with open valleys 26 disposed between the freestanding node portions ~. The modified surface of the material is comprised of the freestanding node portions 25 and fibrils 24 closest to the surface. The fibrils 24 closest to the surface now form the floors of the open Yalleys 26. The microscopically visible freestanding node portions 2~ are comprised of upper node surfaces 23 and exposed vertical node surfaces 27 no longer having interconnecting fibrils attached.
Figure 3 shows a graph of the change in water droplet roll-off angle of a porous expanded PTFE material surface in comparison to a non-porous PTFE surface when samples of both materials were treated with rf gas plasma for varying amounts of time. Water droplet roll-off angle is plotted on the vertical axis against treatment time on the horizontal axis. The plasma gas used was NF3. ~he porous expanded PTFE material was GORE-TEX Soft Tissue Patch.
As shown by the graph of Figure 3, the porous expanded PTFE
surface became increasingly wettable or hydrophilic as the surface was initially treated by gas plasma discharge. A maximum water droplet roll-off angle of about 80 degrees was achieved after about two minutes of treatment. Further treatment, howe~er, resulted in a decrease in hydrophilicity. As treatment continued, the porous expanded PTFE surface surpassed the degree of hydrophobicity it possessed prior to any treatment and became increasingly hydrophobic until a maximum degree of hydrophobicity was approached after about WO 92/22604 PCI'/US92/04812 2ii3'~9 ten minutes of treatment, as indicated by a water droplet rol)-off angle of about 5 degrees. Two hours of treatment resulted in no further significant increase in hydrophobioity.
The non-porous PTFE surface also described in Figure 3 showed similar behavior in that initial gas plasma treatment made the surface more hydrophilic. Continued treatment resulted in a decrease in hydrophiliciity until a water droplet roll-off angle of slightly less than about 40 degrees was ultimately achieved and beyond which no further change was seen. Thus, unlike the porous expanded PTFE
surface, the treated non-porous PTFE surface remained more hydrophilic than the untreated precursor material.
Figure 4 shows a scanning electron photomicrograph (x500) of the surface of the untreated precursor porous expanded PTFE material (GORE-TEX Soft Tissue Patch) which had a water droplet roll-off angle of 29 degrees as indicated by the graph of Figure 3. Figure 4~ shows ~i a photomicrograph (xSOO) of a perspective cross section of the,same untreated precursor material. The foreground material in the lower portion of the photom~crograph is the cross sectional view while the material shown in the upper part of the photomicrograph is the surface of the material shown in perspective. This presentation is typical of all perspective cross sections shown herein. Figures 5 (xlOOO) and SA
(x500) show surface and perspective cross sectional views respectively of the same material that has been gas plasma treated for 2 minutes as described by the graph of Figure 3. While the plasma treated surface shown by Figures 5 and 5A is much more hydrophilic than the unmodified surface shown by Figures 4 and 4A, the magnified treated and untreated surfaces do not appear to be visually distinguishable. Figures 6 (xlOOO) and 6A (xSOO~ show surface and perspective cross sectional views respectively of the same material that has been gas plasma treated for 10 minutes as described by the graph of Figure 3.
Although the plasma treated surface of Figures 6 and 6A was much more hydrophobic than the unmodified surface of Figures 4 and 4A, the magnified treated and untreated surfaces appear to be visually indistinguishable. While it is not visually apparent under microscopy, it is believed that the highly hydrophobic behavior of the ~ 10 minute NF3 plasma treated sample shown by Figures 6 and 6A is the :
WO 92~22604 PCr/US92/04812 result of the fibrils nearest the material surface being lowered or depressed downward away from the material surface.
Figures 7 (xl000) and 7A (xS00) are photomicrographs of the same porous expanded PTFE surface and perspective cross section that has been NF3 gas plasma treated, this time for 15 minutes, as described by the graph of Figure 3. The broken fibrils of the plasma treated surface of Figures 7 and ~A are apparent. Figures 7 and 7A show also the upper node surfaces to be somewhat elevated above the adjacent interconnecting fibrils as a probable result of the removal by etching of some surface fibrils. The photomicrograph of Figure 7 suggests subjectively that about 20 percent of the fibrils comprising the ; surface have been broken. Typical precursor materials do not appear to contain more than about l percent of broken fibrils out of the ; total number of fibrils visible at their surface. It is believed that a surface containing more than about 5 percent visible broken fibrils within the surface is unique to the highly hydrophobic material of the present ~nvention.
F1gures 8 (xS00) and 8A (x200) show a surface and perspective cross sectional view of the same material that has been NF3 gas plasma treated even longer, this time for 60 minutes as described by the graph of Figure 3. Figures 9 (xS00) and 9A (x200) show a surface and perspective cross sections of the same material that has been exposed to gas plasma treatment with air for a period of l20 minutes. These figures all show a surface from which the fibrils ha~e been entirely removed from between the node portions closest to the surface so that the sur~ace morphology is now comprised of freestanding node portions having open valleys disp~sed between the freestanding node portions.
The valley floors are oomprised of fibrils closest to the surface As w,ith the sample surface shown by Figures 7 and 7A, the surfaces of' Figures 8 and 8A are highly hydrophobic but only very slightly more than the sample surface shown by Figure 6. The comparative water droplet roll-off angle data is ~hown by the graph of Figure 3~ The surfaces shown by Figures 9 and 9A are not highly hydrophobic, having a water drbplet roll-off angle of about 18 degrees.
Figure l0 is a graph of water droplet roll-off angle versus treatment time for surface treatment of porous expanded PTFE (GORE-TEX
Soft Tissue Patch) for different types of gases. Air, NF3, argon, WO 92/22~i04 PCI'/US92/04812 ~liO~99 oxygen, ammonia and Polyetch are shown. All treatments shown ultimately produced increased hydrophobicity and a surface comprised of freestanding node portions having open valleys disposed between the freestanding node portions. However, some gases did not produce S highly hydrophobic surfaces as indicated by those surfaces ha~ing water droplet roll-off angles greater than about ten degrees. Very little difference was seen to result from the use of different gases as long as the chosen gas was a reactive etching gas. ~he primary difference seen between the different gases shown by Figure 10 was in the length of treatment time required to produce the surface comprised of freestanding node portions.
Figure 1I shows a scanning electron photomicrograph ~xlOOO) of an alternative porous expanded PTFE surface prior to any surface treatment. The material shown is a commercially available 20 mm GORE-TEX Vascular Graft. The surface shown is the tuminal surface of thevascular graft.
Figure 12 depicts a scanning electron photomicrograph (xlOOO) of the luminal surface of another sample of the same GORE-TEX Vascular Graft material after lengthy treatment by glow discharge plasma using oxygen as the plasma gas. The treatment time was 30 minutes. The removal of the fibrils that normally interconnect the nodes is apparent. No modification to the nodes appears to take place other than some ablation. Figure 13 (xlOOO) shows another sample of the same material surface after having been exposed to the same treatment for 120 minutes.
U.S. Patent 4,064,030 to J. Nakai et al.~ describes the modification of molded non-porous articles of fluorine resin by sputter etching with ion beams in order to provide better adhesion.
They state that their treated surfaces have superior adhering properties not attainable with conventional glow discharge treatment.
Nakai et al., noted that wettability of a surface can be modified by varying treatment time, discharge power or chamber pressure, however no modified surfaces were described as being more hydrophobic than untre~ted P~FE having contact angles up to about 120 degrees.
An article by S. R. Taylor, et al., ~Effect of Surface Texture On The Soft Tissue Response To Polymer Implants," Journal of Biomedical Materials Research 1983 17;205-227, John Wiley & Sons, lnc., describes ion beam etching by sputtering of non-porous PTFE surfaces. A
modified textured PTFE surface having conical projections was produced wherein the projections had a mean height of about 12 microns, a mean base width of about 4 microns and a mean tip radius of about 0.1 micron. Little or no apparent chemical changes in the modified surface were detected. When implanted in a living body, these modified PTFE surfaces produced fibrous capsules of only 30 percent of the thickness of fibrous capsules produced by unmodified PTFE
surfaces. The modified surfaces a~so demonstrated increased cell adhesion. Contact angle measurements were used to determine the surface energy of the modified PTFE surfaces, however, no results of surface energy analysis and no contact angle data were provided for the modified textured PTFE surfaces because of wicking of the diagnostic liquids on those surfaces.
G.L. Picha et al., (nIon-Beam Microtexturing of Biomaterials,"
Medical Device and Diagnostic Industry, vol. 6 no. 4, April 1984), describe the manufacture of textured surfaces in non-porous PTFE and polyurethane by etching surfaces with ion-beams, with and without the optional use of sputter masks, for the purpose of increasing bondability.
U.S. Patent 4,955,909 to Ersek et al., describes textured silicone surfaces for implantable materials wherein the surfaces comprise a series of formed pillars with valleys disposed between Wo 92/226n4 2 1 1 0 4 9 9 Pcr/US92/04812 them. ~he textured surface is produced by thrusting specifically selected molecules against a non-porous silicone rubber surface with sufficient impac~ to produce pillars or projections of 20 to 500 micron si~e.
U.S. Patents 4,767,418 and 4,869,714 to Deininger et al., describe a male mold useful for making tubular vascular grafts, the surface of the mold comprising a series of pillars. The basis for the mold is created by sputter-coating a layer of gold film onto the surface of a P~FE cylinder. The pillars are then formed by selectively photoetching the sputter-coated gold film with the aid of a masked photoresist.
SUMMARY OF THE INVENTION
The present invention relates to porous expanded ~; polytetrafluoroethylene (PTFE) material having a microstructure of nodes interconnected by fibrils and further having at least a substantial portion of one surface that is highly hydrophobic as indicated by having a water droplet roll-off angle of less than about 10 degrees. Water droplet roll-off angles for previoùsly available porous expanded P~FE surfaces have been greater than about 12 degrees and are typically ~reater than about 20 degrees. Porous expanded P~FE
surfaces having water droplet roll-off angles of less than about 10 degrees have heretofore been unknown. Some porous expanded PTFE
surfaces modified according to the present invention have achieved roll-off angles as low as about 2 degrees.
2~ The present invention may be practiced with porous expanded materials that are very thin, for example, membranes or films of thicknesses as little as about 5 microns.
By a substantial portion of one surface is meant that enough of the one surface has been modified to have an effect on the intended performance of the material, where the intended performance may, for example, involve improved bondability, inoreased hydrophobicity, improved resistance to the penetration of a fluid through the material or improved filtration ability.
W092/22604 2 i lU~99 PCI/US92/04812 The hydrophilicity or hydrophobicity of any surface is most commonly determined by measurements of the advancing and receding contact angles of distilled water droplets placed onto the horizontal surface in question. However, for purposes of the present invention, water droplet roll-off angle measurements have been found to be the preferred method for measuring high degrees of hydrophobicity. This will be further discussed below.
It has been found that lengthy exposure to radio frequency (rf) etching gas plasmas increases the hydrophobicity of porous expanded PTFE surfaces. This treatment of such a surface by rf gas plasma with most etching gases initially results in increased hydrophilicity.
This behavior is known and is in common with the treatment of non-porous PTFE surfaces. This increased hydrophilicity is generally explained in terms of chemical changes in the surface composition.
Continued gas plasma treatment results in the achievement of a peak value of hydrophilicity, still the same behavior as non-porous PTFE.
Under further treatment, non-porous PTFE remained more hydrophilic than prior to treatment Porous expanded PTFE, however, after achieving a peak value of hydrophilicity, became increasingly hydrophobic with further treatment and finally approached a maximum ~; level of hydrophobicity that substantially exceeded the degree of hydrophobicity possessed by the unmodified precursor porous expanded PTFE surface. This near-maximum level of hydrophobicity is indicated by a water droplet roll-off angle of less than about 10 degrees and will subsequently be described herein as ~highly hydrophobic." It may require more than an hour of treatment time to achieve. The treatmant time will depend primarily on the type of plasma etching gas used and on the amount of rf power applied. The gas pressure within the treatment chamber is also a factor.
While only rf gas plasma discharge has been used as the energy source to create the modified surface of the present invention, it is believed that other energy sources such as m~crowave gas plasma discharge may also be suitable. Other possible energy sources include x-rays, laser beams and ion beams. Lengthy treatment times or high energy levels may be required.
~hile many reactive gases have been found to be capable of ; increasing the hydrophobicity of a porous expanded PTFE surface, only ~:
WO 92/22604 2 1 1 ~ 4 9 ~ PCr/US92J04812 some of the reactive gases examined were capable of making the surface highly hydrophobic as indicated by a water droplet roll-off angle of less than about ten degrees.
The minimum treatment time necessary to produce this highly hydrophobic surface results in a surface appearance that is substantially indistinguishable from the surface of the untreated precursor porous expanded PTFE material when both are viewed microscopically. Continued treatment beyond the point of initial highly hydrophobic behavior results in a surface appeirance containing broken fibrils, that is, fibrils no longer having both ends connected to adjacent nodes. Still further treatment produces a surface from which the interconnecting fibrils have been removed entirely leaving the portions of the nodes closest to that surface in a freestanding condition, that is, no longer interconnected by fibrils but rather ha~ing open ~alleys disposed between these freestanding node portions.
Although the surface morphology undergoes these significant changes as indicated first by the appearance of broken fibrils and subsequently by the complete removal of fibrils, the high degree of hydrophobicity attained prior to the appearance of broken fibrils shows little if any further increase as indicated by water droplet roll-off angle measurements. The material below this modified surface, as evidenced by microscopic views of cross sections of the modified material, appears as conventional, unmodified porous expanded PTFE having a microstructure of nodes interconnected by fibri~s.
Surface modified porous expanded PTFE material, havin~ a microstructure of nodes interconnected by fibrils and further having a substantial portion of at least one sur~ace comprised of freestanding node portions with open valleys disposed between the freestanding node portions, is al50 within the scope of the present invention. This surface may or may not be highly hydrophobic depending primarily on the type of reactive gas plasma used for treatment.
The manufacture of porous expanded PTFE, the precursor material from which the present invention is made, is taught by U.S. Patents 3,953,566 and 4,18~,390.
Porous expanded PTFE having a surface according to the present invention may have many applications. For example, it may be possible to make waterproof breathable fabrics of increased performance fro,,~
WO 92/2t604 PCI /US92/0481 2 .als!~
the inventive material. Improved biocompatible porous expanded PTFE
medical implants may also be possible, such as dental implants, prosthetic ligaments, sutures, and patch and membrane materials. It may also be useful for blood-contact materials such as tubular Yascular grafts, where a material of increased hydrophobicity may prove to have increased antithrombogenic properties. A suture of cylindrical shape having a round cross section and made of porous expanded PTFE having an outer surface modified by the method of the present invention may offer enhanced knot retention. ~he surface modified porous expanded PTFE material may also prove to be a more effective filtration material in certain applications because of its increased hydrophobicity. The modified material surface may also possess enhanced bondability in comparison to unmodified precursor material. It is expected that a modified surface having increased hydrophobicity may improve the flotation characteristics of fly fishing lines having an outer surface of porous expanded PTFE. Wire insulations having an outer surface of porous expanded PTFE may also benefit from the modified surface of the present invention.
~:
BRIEF DESCRIPTION OF THE DRAWINGS
:
Figure 1 is a drawing of a device used for measuring water droplet roll-off angles for the material samples of this invention.
Figure 2 shows a pictorial representation of an enlarged cross sectional view of a precursor porous expanded PTFE material prior to plasma treatment.
Figure 2A shows a pictorial representation of an enlarged cross sectional view of the material of Figure 2 after rf gas plasma treatment with a reacti~e etching gas.
Figure 3 shows a graph of the change in water droplet roll-off angles of both non-porous P~FE and porous expanded PTFE surfaces as a ; 30 function of different treatment times by rf glow discharge gas plasma using nitrogen trifluoride (hereinafter NF3) gas.
Figure 4 shows a scanning electron photomicrograph (x500) of the surface of a porous expanded PTFE material (GORE-TEX~ Soft Tissue Patch) prior to rf gas plasma treatment.
; ::
WO 92/22604 2 i ~ O Ll ~.) 9 PCI/I S92/04812 Figure 4A shows a scanning electron photomicrograph (x500) of a perspective cross sectional view of the material of Figure 4 prior to rf gas plasma treatment.
Figure S shows a scanning electron photomicrograph (xlO00) of the surface of the same material as shown by Figure 4 after 2 minutes of rf gas plasma treatment with NF3 gas to make the surface hydrophilic.
Figure SA shows a scanning electron photomicrograph (x500) of a perspective cross sectional view of the material of Figure 4A
after 2 minutes of rf gas plasma treatment with NF3 gas to make the surface hydrophilic.
Figure 6 shows a scanning electron photomicrograph (xlO00) of the surface of the same material as shown by Figure 4 after 10 - minutes of rf gas plasma treatment with NF3 gas to make the sur~ace highly hydrophobic.
Figure 6A shows a scanning electron photomicrograph (x500) of a perspective cross sectional view of the same material as shown by Figure 4A after 10 minutes of rf gas plas~a treatment with NF3 gas to make the surface highly hydrophobic.
figure 7 shows a scanning electron photomicrograph (xlO00) of the surface of the same material as shown by Figure 4 after 15 minutes of rf gas plasma treatment with NF3 gas resulting in broken fibrils-at the material surface.
Figure 7A shows a scanning electron photomicrograph (x500) of a perspective cross sectional view of the same treated material as shown by Figure 4A after 15 minutes of rf gas plasma treatment with NF3 gas resulting in broken fibrils at the material surface.
Figure 8 shows a scanning electron photomicrograph ~xS00) of the ! . i ! surface of the same material as shown by Figure 4 after 60 minutes of rf gas plasma treatment with NF3 gas resulting in removal of the fibrils from the material surface leaYing the surface comprised of a series of freestanding node portions with open valleys disposed between the freestanding node portions~
Figure 8A shows a scanning electron photomicrograph (x200) of a perspective cross sectional view of the same material as shown by Figure 4A after 60 minutes of rf gas plasma treatment with NF3 gas resulting in removal of the fibrils from the material surface 4 ~ 9 - 1 o-leaving the surface comprised of a series of freestanding node portions with open valleys disposed between the freestanding nodP
portions.
Figure 9 shows a scanning electron photomicrograph (x500) of a surface view of the same material as shown by Figure 4 after 120 minutes of rf gas plasma treatment with air resu~ting in removal of the fibrils from the material surface leaving the surface comprised of a series of freestanding node portions with open valleys disposed between the freestanding node portions.
Figure 9A shows a scanning electron photomicrograph (x200) of a perspective cross.sectional view of the same material as shown by : Figure 4A after 120 minutes of rf gas plasma treatment with air : resulting in removal of the fibrils from the material surface leaving the surface comprised of a.series of freestanding node portions with open valleys disposed between the freestanding node ~: . portions.
.~ Figure 10 shows a graph of the change in water droplet roll-off angle of a porous expanded PTFE material (GOR~-~EX Soft Tissue Patch) as a function of different treatment times by glow discharge plasma for different gases.
Figure 11 shows a scanning electron photomicrograph (xlOOO) of the luminal surface of an alternative porous expanded PTFE material (20 mm diameter GORE-TEX Vascular Graft) prior to rf gas plasma treatment.
Figure 12 shows a scanning electron photomicrograph (xlOOO) of the luminal surface of the same material as shown by Figure 10 after 30 minutes of rf gas plasma treatment with oxygen resulting in the removal of fibrils from the surface leaving the surface , I comprised of freestanding node portions having open valleys disposed between the freestanding node portions.
Figure 13 shows a scanning electron photomicrograph (xlOOO) of the luminal vascular graft surface of the same material as shown by : Figure 10 after 120 minutes of rf gas plasma treatment with : oxygen resulting in the removal of fibrils from the surface leaving the surface comprised of freestanding node portions having open valleys disposed between the freestanding node .~ .
~ portions.
WO 92/22604 PCr/US92/04~12 i' li~'l99 DE~AIL~D DESCRIPTION OF THE INVENTION
All work described herein was done using a model B12 plasma unit from Advanced Plasma Systems, lnc., St. Petersburg, Florida. Typical surface treatment times ranged fro~ about ten minutes up to as long as about two hours per sample, however, reduced times may be possible with the use of higher rf power. The preferred plasma gas has been NF3 (Air Products, Allentown, Pa.), however, similar results have been achieved with air, argon, oxygen, ammonia and Polyetch~ (Matheson Gas Products, Inc., Utica, California). Suitable gases are those eapable of producing etching or ablation of the PTFE surface. Polymerizing gases, that is gases producing a surface coating of another material, are not suitable. All surface treatments were done at a frequency of 13.56 MHz, chamber pressure of G.300 torr and 300 watts power unless noted otherwise.
2.5 x 7.5 x 0.020 centimeter samples of porous expanded PTFE
GORE-TEX Soft Tissue Patch material (W. L. Gore and Associates, Inc.
Elkton, MD) were cut and placed into a special holder that gripped the edges of the sample while leaving the surfaces of the sample exposed.
~he holder with samples was placed inside the treatment chamber of the B-12 series plasma unit. The square aluminum chamber was of 3Q.5 centimeters per side having a grounded aluminum electrode in the form of a 23 centimeter per side, square, flat~ perforated plate placed vertically in the middle of the chamber and two powered aluminum electrodes of the same size and shape placed vertically on each side of the grounded electrode with their surfaces parallel to the surface of the grounded electrode. The spacing between eleotrodes was approximately 6.5 centimeters. The samples were suspended vertically between the electrodes with the surfaces to be treated facing a powered electrode.
The chamber was evacuated to 0.020 torr pressure and the desired plasma gas was allowed to flow freely through the chamber for 5 to 10 minutes. The pressure was adjusted to 0.300 torr using a flowmeter mounted on the inlet side of the chamber. After the pressure stabilized at 0.300 torr a plasma was ignited at a 300 watt power level and maintained at these conditions during the treatment.
WO g2J22604 PCI'/US92/0481 2 Treatment times used were 1, 2, 3, 4, 5, 10, 15, 20, 30, 60 and 120 minutes. A new set of samples was used for each treatment time.
Hydrophobicity measurements were made by measuring the water droplet roll-off angle for each treated sample. At least 12 measurements of water droplet roll-off angle were taken on each sample to establish a mean value for the sample. The 12 water droplets were placed on 12 different sites on the sample surface. Readings of the roll-off angle were recorded at the moment when the droplet began to roll. The average volume of a water droplet was 0.04 cm3.
It is believed that the increased hydrophobicity resulting from rf gas plasma treatment is due to fibrils, originally lying in or very close to the level of the upper node surfaces, first being depressed ; or lowered slightly below that level. Continued treatment nextresults in breakage of some of these fibrils and finally in their complete removal from the level of the upper node surfaces and downward to some depth below that level. Still further continued treatment increases the depth of fibril removal. Prolonged treatment results in microscopically visible node ablation that appears to ultimately limit the maximum achievable depth of fibril removal. This can be explained by the assumed slower rate of fibril removal at this depth. This maximum achievable depth appears to be a function of the microstructure of the precursor material as well as of the gas plasma application parameters.
The magnified appearance of the surface from which the fibrils have been entire~y removed is thus the appearance of the portions of the nodes closest to the surface in a freestanding condition, that is, no longer having fibrils interconnecting these freestanding node portions but rather having open valleys disposed between these freestanding node portions. The valley floors, that is, the bottom of the Yalleys, are generally comprised of fibrils~ Because the surface of the microstructure has been modified only to the extent of removal of the fibrils therefrom, no apparent difference to the surface is visible to the naked eye. Magnification of the surface is required in order to make the result of the modification visible. Surfaces ; 35 modified as taught by the macrostructural techniques of U.S. Patents 4,208,745, 4,332,035 and 4,647,416 are thus not within the scope of the present invention.
W 0 92/22604 2 1 1 0 4 9 9 PcT~uss2to48l2 The best mode of practicing the present invention is believed to be the use of rf gas plasma discharge with NF3 gas to modify a porous expanded PTFE surface for a long enough time to create a surface comprised of freestanding node portions having open valleys disposed between the freestanding node portions. NF~ is preferred because it is read~ly available, is relatively economical, requires less etching time than other gases examined heretofore and produces a highly hydrophobic surface.
The increased hydrophobicity of the plasma treated porous expanded PTFE surfaces, as indicated by either higher water droplet contact angles or by lower water droplet roll-off angles, is believed to be a result of the water droplet resting on i reduced surface area of the modified material. It is believed that plasma treatment initially causes depression of the fibrils from the level of the upper node surfaces, followed by breakage of those fibrils and finally followed by the entire removal of fibrils from the surface. Thus it appears that when hydrophobicity of the surface modified porous ; expanded PTFE is measured by the use of a water droplet that the droplet is only in contact with the upper node surfaces and that very few, if any, of the fibrils closest to the surface are in contact with the water droplet. This is in contrast to the unmodified material wherein both the upper node surfaces and the fibrils closest to the ' ~ material surface are believed to be in contact with the water droplet.
The hydrophllicity or hydrophobicity of any surface is most commonly determined by measurements of the advancing and receding contact angles of distilled watèr droplets placed onto the horizontal s~rface in question as taught by ASTM D 724-45. Material surfaces having water droplet contact angles less than 90 degrees are considered to be hydrophilic while contact angles greater than 90 degrees indicate hydrophobicity. A typical porous expanded PTFE
surface that has not been modified according to the present invention has a water droplet contact angle of about 120 to 160 degrees while such surfaces that have been modified as taught herein have contact angles generally greater than about 170 degrees. Apparently due to the increased roughness of the modified surfaces, it is difficult to achieve consistent water droplet contact angle measurements because of increased hysteresis between the advancing and receding contact ;~ ~
WO 92/22604 PCl/US92/~)4~12 2 ~ 9 angles. Furthermore, as the contact angle approaches 180 degrees, the angle becomes more difficult to project and measure accurately due to irregularities of the surface. ~ater droplet roll-off angle measurements have been found to be the preferred method of measuring the hydrophobicity of rough surfaces and in particular surfaces modified by the present invention. Water droplet roll-off angle measurements are more easily made and the results appear to be more cons~stent than contact angle measurements for such surfaces. This has been confirmed by Y. Iriyama et al., Plasma Surface Treatment on Nylon Fabrics by Fluorocarbon Compounds, Journal of Applied Polymer Science 1990 39;249-264.
Figure 1 shows the apparatus used to measure water droplet roll-off angles for hyd~phobicity measurements. A sample 12 of material to be measured is placed onto the plane surface 11 so that the sample 12 is uniformly in contact with the plane surface 11. An adjustment knob 14 connected to a right-angle gearhead 16 is used to rotate the plane surface 11 about axis 15. Axis 15 is hori~ontally oriented, that is, perpendicular to the direction of the force of gravity. A
protractor 17 is set up adjacent and perpendicular to the plane surface 11 with its center in line with axis 15, allowing easy measurement of the angle between the plane surface 11 and the horizontal. In use, the plane surface Ll is placed into a hori~ontal position and a material sample 12 is placed onto the plane surface 11 so that it uniformly contacts the plane surface 11. A droplet of distilled water 18 is placèd onto the surface of the material sample 12. The adjustment knob L4 is turned by hand to cause slow rotation of the plane surface 1,1 about axis L5 at an angular velocity of approximately one degree per second. When the water droplet 18 begins to roll off of the surface of the material sample 1~, the roll-off angle is ~easured from the protractor as the tilt angle of the plane surface 11. Multiple individual water droplets may be placed onto a single sample if the sample is of adequate area. In measurements descr~bed herein, the data represent the average roll-off angle of at least 12 water droplets.
Water droplet roll-off angles for unmodified porous expanded PTFE
surfaces are typically greater than about 20 degrees while water droplet roll-off angles of porous expanded PTFE surfaces treated by WO 92/22604 ~ 1 1 0 ~19 9 PCl/US92/04812 the method of the present invention are typically less than about 10 degrees. The lowest water droplet roll-off angle of known porous expanded PTFE surfaces has been that of the luminal surface of GORE-TEX Vascular Graft material (W. L. Gore and Associates, Inc., Elkton, MD), which typically measures about 12 degrees.
Figure 2 is a pictorial representation of a cross sectional view of a precursor porous expanded PTFE material prior to any modification. This figure shows the microstructure of nodes 21 interconnected by fibrils ~. The surface of the material is comprised of upper node surfaces 23 and fibrils 24 closest to the surface. Figure 2A is a pictorial representation of a cross sectional view of the same material after rf gas plasma treatment to modify the - surface to the extent of removing fibrils from the surface. This - figure shows freestanding node portions 25 with open valleys 26 disposed between the freestanding node portions ~. The modified surface of the material is comprised of the freestanding node portions 25 and fibrils 24 closest to the surface. The fibrils 24 closest to the surface now form the floors of the open Yalleys 26. The microscopically visible freestanding node portions 2~ are comprised of upper node surfaces 23 and exposed vertical node surfaces 27 no longer having interconnecting fibrils attached.
Figure 3 shows a graph of the change in water droplet roll-off angle of a porous expanded PTFE material surface in comparison to a non-porous PTFE surface when samples of both materials were treated with rf gas plasma for varying amounts of time. Water droplet roll-off angle is plotted on the vertical axis against treatment time on the horizontal axis. The plasma gas used was NF3. ~he porous expanded PTFE material was GORE-TEX Soft Tissue Patch.
As shown by the graph of Figure 3, the porous expanded PTFE
surface became increasingly wettable or hydrophilic as the surface was initially treated by gas plasma discharge. A maximum water droplet roll-off angle of about 80 degrees was achieved after about two minutes of treatment. Further treatment, howe~er, resulted in a decrease in hydrophilicity. As treatment continued, the porous expanded PTFE surface surpassed the degree of hydrophobicity it possessed prior to any treatment and became increasingly hydrophobic until a maximum degree of hydrophobicity was approached after about WO 92/22604 PCI'/US92/04812 2ii3'~9 ten minutes of treatment, as indicated by a water droplet rol)-off angle of about 5 degrees. Two hours of treatment resulted in no further significant increase in hydrophobioity.
The non-porous PTFE surface also described in Figure 3 showed similar behavior in that initial gas plasma treatment made the surface more hydrophilic. Continued treatment resulted in a decrease in hydrophiliciity until a water droplet roll-off angle of slightly less than about 40 degrees was ultimately achieved and beyond which no further change was seen. Thus, unlike the porous expanded PTFE
surface, the treated non-porous PTFE surface remained more hydrophilic than the untreated precursor material.
Figure 4 shows a scanning electron photomicrograph (x500) of the surface of the untreated precursor porous expanded PTFE material (GORE-TEX Soft Tissue Patch) which had a water droplet roll-off angle of 29 degrees as indicated by the graph of Figure 3. Figure 4~ shows ~i a photomicrograph (xSOO) of a perspective cross section of the,same untreated precursor material. The foreground material in the lower portion of the photom~crograph is the cross sectional view while the material shown in the upper part of the photomicrograph is the surface of the material shown in perspective. This presentation is typical of all perspective cross sections shown herein. Figures 5 (xlOOO) and SA
(x500) show surface and perspective cross sectional views respectively of the same material that has been gas plasma treated for 2 minutes as described by the graph of Figure 3. While the plasma treated surface shown by Figures 5 and 5A is much more hydrophilic than the unmodified surface shown by Figures 4 and 4A, the magnified treated and untreated surfaces do not appear to be visually distinguishable. Figures 6 (xlOOO) and 6A (xSOO~ show surface and perspective cross sectional views respectively of the same material that has been gas plasma treated for 10 minutes as described by the graph of Figure 3.
Although the plasma treated surface of Figures 6 and 6A was much more hydrophobic than the unmodified surface of Figures 4 and 4A, the magnified treated and untreated surfaces appear to be visually indistinguishable. While it is not visually apparent under microscopy, it is believed that the highly hydrophobic behavior of the ~ 10 minute NF3 plasma treated sample shown by Figures 6 and 6A is the :
WO 92~22604 PCr/US92/04812 result of the fibrils nearest the material surface being lowered or depressed downward away from the material surface.
Figures 7 (xl000) and 7A (xS00) are photomicrographs of the same porous expanded PTFE surface and perspective cross section that has been NF3 gas plasma treated, this time for 15 minutes, as described by the graph of Figure 3. The broken fibrils of the plasma treated surface of Figures 7 and ~A are apparent. Figures 7 and 7A show also the upper node surfaces to be somewhat elevated above the adjacent interconnecting fibrils as a probable result of the removal by etching of some surface fibrils. The photomicrograph of Figure 7 suggests subjectively that about 20 percent of the fibrils comprising the ; surface have been broken. Typical precursor materials do not appear to contain more than about l percent of broken fibrils out of the ; total number of fibrils visible at their surface. It is believed that a surface containing more than about 5 percent visible broken fibrils within the surface is unique to the highly hydrophobic material of the present ~nvention.
F1gures 8 (xS00) and 8A (x200) show a surface and perspective cross sectional view of the same material that has been NF3 gas plasma treated even longer, this time for 60 minutes as described by the graph of Figure 3. Figures 9 (xS00) and 9A (x200) show a surface and perspective cross sections of the same material that has been exposed to gas plasma treatment with air for a period of l20 minutes. These figures all show a surface from which the fibrils ha~e been entirely removed from between the node portions closest to the surface so that the sur~ace morphology is now comprised of freestanding node portions having open valleys disp~sed between the freestanding node portions.
The valley floors are oomprised of fibrils closest to the surface As w,ith the sample surface shown by Figures 7 and 7A, the surfaces of' Figures 8 and 8A are highly hydrophobic but only very slightly more than the sample surface shown by Figure 6. The comparative water droplet roll-off angle data is ~hown by the graph of Figure 3~ The surfaces shown by Figures 9 and 9A are not highly hydrophobic, having a water drbplet roll-off angle of about 18 degrees.
Figure l0 is a graph of water droplet roll-off angle versus treatment time for surface treatment of porous expanded PTFE (GORE-TEX
Soft Tissue Patch) for different types of gases. Air, NF3, argon, WO 92/22~i04 PCI'/US92/04812 ~liO~99 oxygen, ammonia and Polyetch are shown. All treatments shown ultimately produced increased hydrophobicity and a surface comprised of freestanding node portions having open valleys disposed between the freestanding node portions. However, some gases did not produce S highly hydrophobic surfaces as indicated by those surfaces ha~ing water droplet roll-off angles greater than about ten degrees. Very little difference was seen to result from the use of different gases as long as the chosen gas was a reactive etching gas. ~he primary difference seen between the different gases shown by Figure 10 was in the length of treatment time required to produce the surface comprised of freestanding node portions.
Figure 1I shows a scanning electron photomicrograph ~xlOOO) of an alternative porous expanded PTFE surface prior to any surface treatment. The material shown is a commercially available 20 mm GORE-TEX Vascular Graft. The surface shown is the tuminal surface of thevascular graft.
Figure 12 depicts a scanning electron photomicrograph (xlOOO) of the luminal surface of another sample of the same GORE-TEX Vascular Graft material after lengthy treatment by glow discharge plasma using oxygen as the plasma gas. The treatment time was 30 minutes. The removal of the fibrils that normally interconnect the nodes is apparent. No modification to the nodes appears to take place other than some ablation. Figure 13 (xlOOO) shows another sample of the same material surface after having been exposed to the same treatment for 120 minutes.
Claims (48)
1. Porous expanded polytetrafluoroethylene having a microstructure of nodes interconnected by fibrils, comprising a three dimensional material having surfaces and having a water droplet roll-off angle of less than about 10 degrees on at least a portion of at least one surface.
2. Porous expanded polytetrafluoroethylene according to claim 1 wherein the water droplet roll-off angle is less than about 8 degrees.
3. Porous expanded polytetrafluoroethylene according to claim 1 wherein the water droplet roll-off angle is less than about 6 degrees.
4. Porous expanded polytetrafluoroethylene according to claim 1 wherein the water droplet roll-off angle is less than about 5 degrees.
5. Porous expanded polytetrafluoroethylene according to claim 1 wherein the water droplet roll-off angle is less than about 4 degrees.
6. Porous expanded polytetrafluoroethylene according to claim 1 wherein the water droplet roll-off angle is less than about 3 degrees.
7. Porous expanded polytetrafluoroethylene according to claim 1 wherein the three dimensional material is in the form of a tubular shape having an inner surface and an outer surface and the at least one surface comprises the inner surface of the tubular shape.
8. Porous expanded polytetrafluoroethylene according to claim 7 wherein the tubular shape is a vascular graft.
9. Porous expanded polytetrafluoroethylene according to claim 7 wherein the tubular shape is a filter.
10. Porous expanded polytetrafluoroethylene according to claim 7 wherein the tubular shape is a wire insulation.
11. Porous expanded polytetrafluoroethylene according to claim 1 wherein the three dimensional material is in the form of a tubular shape having an inner surface and an outer surface and the at least one surface comprises the outer surface of the tubular shape.
12. Porous expanded polytetrafluoroethylene according to claim 11 wherein the tubular shape is a vascular graft.
13. Porous expanded polytetrafluoroethylene according to claim 11 wherein the tubular shape is a filter.
14. Porous expanded polytetrafluoroethylene according to claim 11 wherein the tubular shape is a wire insulation.
15. Porous expanded polytetrafluoroethylene according to claim 11 wherein the tubular shape is a fly line outer surface.
16. Porous expanded polytetrafluoroethylene according to claim 1 wherein the three dimensional material is in the form of a flat sheet.
17. Porous expanded polytetrafluoroethylene according to claim 16 wherein the flat sheet is a filter.
18. Porous expanded polytetrafluoroethylene according to claim 16 wherein the flat sheet is a layer of a garment material.
19. Porous expanded polytetrafluoroethylene according to claim 16 wherein the flat sheet is an implantable patch.
20. Porous expanded polytetrafluoroethylene according to claim 16 wherein the flat sheet is an implantable membrane.
21. Porous expanded polytetrafluoroethylene according to claim 1 wherein the three dimensional material is in the form of a cylindrical shape having a curved outer surface and the at least one surface comprises the curved outer surface.
22. Porous expanded polytetrafluoroethylene according to claim 21 wherein the cylindrical shape is a suture.
23. Porous expanded polytetrafluoroethylene having a microstructure comprised of nodes interconnected by fibrils, said porous expanded polytetrafluoroethylene comprising a three dimensional material having at least one surface wherein at least a portion of the at least one surface is comprised of freestanding node portions with open valleys disposed between the freestanding node portions.
24. Porous expanded polytetrafluoroethylene according to claim 23 wherein the porous expanded polytetrafluoroethylene has a water droplet roll-off angle of less than about 10 degrees.
25. Porous expanded polytetrafluoroethylene according to claim 23 wherein the porous expanded polytetrafluoroethylene has a water droplet roll-off angle of less than about 8 degrees.
26. Porous expanded polytetrafluoroethylene according to claim 23 wherein the porous expanded polytetrafluoroethylene has a water droplet roll-off angle of less than about 6 degrees.
27. Porous expanded polytetrafluoroethylene according to claim 23 wherein the porous expanded polytetrafluoroethylene has a water droplet roll-off angle of less than about 4 degrees.
28. Porous expanded polytetrafluoroethylene according to claim 23 wherein the three dimensional material is in the form of a tubular shape having an inner surface and an outer surface and the at least one surface comprises the inner surface of the tubular shape.
29. Porous expanded polytetrafluoroethylene according to claim 28 wherein the tubular shape is a vascular graft.
30. Porous expanded polytetrafluoroethylene according to claim 28 wherein the tubular shape is a filter.
31. Porous expanded polytetrafluoroethylene according to claim 28 wherein the tubular shape is a wire insulation.
32. Porous expanded polytetrafluoroethylene according to claim 23 wherein the three dimensional material is in the form of a tubular shape having an inner surface and an outer surface and the at least one surface comprises the outer surface of the tubular shape.
33. Porous expanded polytetrafluoroethylene according to claim 32 wherein the tubular shape is a vascular graft.
34. Porous expanded polytetrafluoroethylene according to claim 32 wherein the tubular shape is a filter.
35. Porous expanded polytetrafluoroethylene according to claim 32 wherein the tubular shape is a wire insulation.
36. Porous expanded polytetrafluoroethylene according to claim 32 wherein the tubular shape is a fly line outer surface.
37. Porous expanded polytetrafluoroethylene according to claim 23 wherein the three dimensional material is in the form of a flat sheet.
38. Porous expanded polytetrafluoroethylene according to claim 37 wherein the flat sheet is a filter.
39. Porous expanded polytetrafluoroethylene according to claim 37 wherein the flat sheet is a layer of a garment material.
40. Porous expanded polytetrafluoroethylene according to claim 37 wherein the flat sheet is an implantable patch.
41. Porous expanded polytetrafluoroethylene according to claim 37 wherein the flat sheet is an implantable membrane.
42. Porous expanded polytetrafluoroethylene according to claim 23 wherein the three dimensional material is in the form of a cylindrical shape having a curved outer surface and the at least one surface comprises the curved outer surface.
43. Porous expanded polytetrafluoroethylene according to claim 42 wherein the cylindrical shape is a suture.
44. A method of modifying a surface of a porous expanded polytetrafluoroethylene material, said porous expanded polytetrafluoroethylene material having a microstructure of nodes interconnected by fibrils, said method comprising exposing the surface to a radio frequency gas plasma discharge with a reactive etching gas until at least a portion of the surface has a water droplet roll-off angle of less than about 10 degrees.
45. A method according to claim 44 wherein at least a substantial portion of the surface has a water droplet roll-off angle of less than about 8 degrees.
46. A method according to claim 44 wherein at least a substantial portion of the surface has a water droplet roll-off angle of less than about 6 degrees.
47. A method according to claim 44 wherein at least a substantial portion of the surface has a water droplet roll-off angle of less than about 4 degrees.
48. A method of modifying a surface of a porous expanded polytetrafluoroethylene material said porous expanded polytetrafluoroethylene material having a microstructure of nodes interconnected by fibrils, said method comprising exposing the surface to a reactive gas plasma discharge until the fibrils are removed from at least a portion of the surface and the surface is comprised of freestanding node portions with open valleys disposed between the freestanding node portions.
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US71832491A | 1991-06-14 | 1991-06-14 | |
US07/718,324 | 1991-06-14 |
Publications (2)
Publication Number | Publication Date |
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CA2110499A1 CA2110499A1 (en) | 1992-12-23 |
CA2110499C true CA2110499C (en) | 1998-06-23 |
Family
ID=24885684
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
CA002110499A Expired - Lifetime CA2110499C (en) | 1991-06-14 | 1992-06-08 | Surface modified porous expanded polytetrafluoroethylene and process for making |
Country Status (6)
Country | Link |
---|---|
US (1) | US5437900A (en) |
EP (1) | EP0646151B1 (en) |
JP (1) | JPH07500122A (en) |
CA (1) | CA2110499C (en) |
DE (1) | DE69223065T2 (en) |
WO (1) | WO1992022604A1 (en) |
Families Citing this family (113)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JPH06506713A (en) * | 1991-04-15 | 1994-07-28 | レイクスユニベルシテイト・グロニンゲン | Method for modifying fluorine-containing plastics, modified plastics and biomaterials containing the plastics |
US5773098A (en) * | 1991-06-20 | 1998-06-30 | British Technology Group, Ltd. | Applying a fluoropolymer film to a body |
US5443743A (en) * | 1991-09-11 | 1995-08-22 | Pall Corporation | Gas plasma treated porous medium and method of separation using same |
US20030168157A1 (en) * | 1992-01-06 | 2003-09-11 | Kuenzel Kenneth J. | Fluoropolymer composite tube and method of preparation |
US6517657B1 (en) * | 1992-01-06 | 2003-02-11 | Pilot Industries, Inc. | Fluoropolymer composite tube and method of preparation |
GB9325567D0 (en) * | 1993-12-14 | 1994-02-16 | Gore W L & Ass Uk | Fibrillated ptfe surface |
US5584876A (en) * | 1994-04-29 | 1996-12-17 | W. L. Gore & Associates, Inc. | Cell excluding sheath for vascular grafts |
US5519172A (en) * | 1994-09-13 | 1996-05-21 | W. L. Gore & Associates, Inc. | Jacket material for protection of electrical conductors |
US5814405A (en) * | 1995-08-04 | 1998-09-29 | W. L. Gore & Associates, Inc. | Strong, air permeable membranes of polytetrafluoroethylene |
US5620669A (en) * | 1995-08-15 | 1997-04-15 | W. L. Gore & Associates, Inc. | Catalytic filter material and method of making same |
US5800512A (en) * | 1996-01-22 | 1998-09-01 | Meadox Medicals, Inc. | PTFE vascular graft |
US6428571B1 (en) | 1996-01-22 | 2002-08-06 | Scimed Life Systems, Inc. | Self-sealing PTFE vascular graft and manufacturing methods |
JP3273735B2 (en) * | 1996-05-17 | 2002-04-15 | 日東電工株式会社 | Polytetrafluoroethylene porous membrane and method for producing the same, sheet-like polytetrafluoroethylene molded article, and filter medium for air filter |
AUPO071896A0 (en) * | 1996-06-28 | 1996-07-25 | Cortronix Pty Ltd | Bio compatible material and method |
US20010002412A1 (en) * | 1996-11-07 | 2001-05-31 | John P. Kolarik | Decorative structurally enhanced impregnated porous stone product |
DE19745294A1 (en) * | 1997-10-14 | 1999-04-15 | Biotronik Mess & Therapieg | Process for the production of fine-structured medical technology implants |
US6395019B2 (en) | 1998-02-09 | 2002-05-28 | Trivascular, Inc. | Endovascular graft |
US6321483B1 (en) | 1998-04-20 | 2001-11-27 | 3M Innovative Properties Company | Fly fishing line and method for manufacturing of same |
US6432175B1 (en) * | 1998-07-02 | 2002-08-13 | 3M Innovative Properties Company | Fluorinated electret |
US6167650B1 (en) * | 1998-09-25 | 2001-01-02 | The Orvis Company, Inc. | Coated fly fishing line and a method and apparatus for coating a fly fishing line |
JP2000255015A (en) * | 1999-03-10 | 2000-09-19 | Mitsubishi Polyester Film Copp | Cover film for dry film resist |
US6235479B1 (en) | 1999-04-13 | 2001-05-22 | Bio Merieux, Inc. | Methods and devices for performing analysis of a nucleic acid sample |
US6780497B1 (en) * | 1999-08-05 | 2004-08-24 | Gore Enterprise Holdings, Inc. | Surface modified expanded polytetrafluoroethylene devices and methods of producing the same |
US6342294B1 (en) * | 1999-08-12 | 2002-01-29 | Bruce G. Ruefer | Composite PTFE article and method of manufacture |
US6573311B1 (en) * | 1999-09-22 | 2003-06-03 | Atrium Medical Corporation | Method for treating polymer materials and products produced therefrom |
US6419871B1 (en) | 2000-05-25 | 2002-07-16 | Transweb, Llc. | Plasma treatment of filter media |
US6704604B2 (en) * | 2000-12-28 | 2004-03-09 | Medtronic, Inc. | System and method for promoting selective tissue in-growth for an implantable medical device |
US6605116B2 (en) | 2001-04-03 | 2003-08-12 | Mentor Corporation | Reinforced radius mammary prostheses and soft tissue expanders |
US7396582B2 (en) | 2001-04-06 | 2008-07-08 | Advanced Cardiovascular Systems, Inc. | Medical device chemically modified by plasma polymerization |
GB0115374D0 (en) * | 2001-06-22 | 2001-08-15 | Isis Innovation | Machining polymers |
US6716239B2 (en) | 2001-07-03 | 2004-04-06 | Scimed Life Systems, Inc. | ePTFE graft with axial elongation properties |
US7887889B2 (en) * | 2001-12-14 | 2011-02-15 | 3M Innovative Properties Company | Plasma fluorination treatment of porous materials |
US7147661B2 (en) | 2001-12-20 | 2006-12-12 | Boston Scientific Santa Rosa Corp. | Radially expandable stent |
US20030216758A1 (en) * | 2001-12-28 | 2003-11-20 | Angiotech Pharmaceuticals, Inc. | Coated surgical patches |
EP1466020B1 (en) * | 2002-01-15 | 2010-07-21 | Conciaricerca Italia S.r.l. | Method for the processing of leather |
GB0206930D0 (en) * | 2002-03-23 | 2002-05-08 | Univ Durham | Method and apparatus for the formation of hydrophobic surfaces |
JP4398860B2 (en) * | 2002-07-11 | 2010-01-13 | ポール・コーポレーション | UV-treated film |
US7141063B2 (en) * | 2002-08-06 | 2006-11-28 | Icon Medical Corp. | Stent with micro-latching hinge joints |
AU2003254111A1 (en) * | 2002-08-14 | 2004-03-03 | Pall Corporation | Fluoropolymer membrane |
US6939321B2 (en) | 2002-09-26 | 2005-09-06 | Advanced Cardiovascular Systems, Inc. | Catheter balloon having improved balloon bonding |
US20060121080A1 (en) * | 2002-11-13 | 2006-06-08 | Lye Whye K | Medical devices having nanoporous layers and methods for making the same |
US7172575B2 (en) * | 2003-03-05 | 2007-02-06 | Advanced Cardiovascular Systems, Inc. | Catheter balloon having a lubricious coating |
US20050055085A1 (en) * | 2003-09-04 | 2005-03-10 | Rivron Nicolas C. | Implantable medical devices having recesses |
US20050086850A1 (en) * | 2003-10-23 | 2005-04-28 | Clough Norman E. | Fishing line and methods for making the same |
JP2007512102A (en) | 2003-11-20 | 2007-05-17 | ザ ヘンリー エム. ジャクソン ファウンデーション フォー ザ アドヴァンスメント オブ ミリタリー メディシン, インク. | Portable manual pump for fluid suction |
US20050124256A1 (en) * | 2003-12-09 | 2005-06-09 | Vanessa Mason | Synthetic insulation with microporous membrane |
ITPD20030312A1 (en) * | 2003-12-30 | 2005-06-30 | Geox Spa | BREATHABLE AND WATER RESISTANT SOLE FOR FOOTWEAR |
US20050158609A1 (en) * | 2004-01-16 | 2005-07-21 | Gennadi Finkelshtain | Hydride-based fuel cell designed for the elimination of hydrogen formed therein |
US7418464B2 (en) * | 2004-01-27 | 2008-08-26 | International Business Machines Corporation | Method, system, and program for storing data for retrieval and transfer |
US7803178B2 (en) | 2004-01-30 | 2010-09-28 | Trivascular, Inc. | Inflatable porous implants and methods for drug delivery |
US7213309B2 (en) * | 2004-02-24 | 2007-05-08 | Yunzhang Wang | Treated textile substrate and method for making a textile substrate |
AU2005237985B2 (en) | 2004-04-20 | 2010-10-21 | Genzyme Corporation | Surgical mesh-like implant |
US20050260481A1 (en) * | 2004-05-20 | 2005-11-24 | Gennadi Finkelshtain | Disposable fuel cell with and without cartridge and method of making and using the fuel cell and cartridge |
US20060047311A1 (en) * | 2004-08-26 | 2006-03-02 | Lutz David I | Expanded PTFE articles and method of making same |
US7406797B2 (en) * | 2004-09-09 | 2008-08-05 | Rio Products Intl., Inc. | Super high floating line |
US20060057435A1 (en) * | 2004-09-15 | 2006-03-16 | Medis Technologies Ltd | Method and apparatus for preventing fuel decomposition in a direct liquid fuel cell |
US20060058890A1 (en) * | 2004-09-16 | 2006-03-16 | Lesh Michael D | Methods for soft tissue augmentation |
US7244270B2 (en) | 2004-09-16 | 2007-07-17 | Evera Medical | Systems and devices for soft tissue augmentation |
US7641688B2 (en) | 2004-09-16 | 2010-01-05 | Evera Medical, Inc. | Tissue augmentation device |
US8337475B2 (en) | 2004-10-12 | 2012-12-25 | C. R. Bard, Inc. | Corporeal drainage system |
JP4678830B2 (en) * | 2005-02-07 | 2011-04-27 | 本田技研工業株式会社 | Fuel cell stack |
US20060199265A1 (en) * | 2005-03-02 | 2006-09-07 | Wolf Michael F | Seeding implantable medical devices with cells |
US7759120B2 (en) * | 2005-03-02 | 2010-07-20 | Kps Bay Medical, Inc. | Seeding implantable medical devices with cells |
US20060233991A1 (en) | 2005-04-13 | 2006-10-19 | Trivascular, Inc. | PTFE layers and methods of manufacturing |
US20060233990A1 (en) | 2005-04-13 | 2006-10-19 | Trivascular, Inc. | PTFE layers and methods of manufacturing |
US20070005024A1 (en) * | 2005-06-10 | 2007-01-04 | Jan Weber | Medical devices having superhydrophobic surfaces, superhydrophilic surfaces, or both |
US7597924B2 (en) * | 2005-08-18 | 2009-10-06 | Boston Scientific Scimed, Inc. | Surface modification of ePTFE and implants using the same |
WO2007038643A1 (en) | 2005-09-26 | 2007-04-05 | C.R. Bard, Inc. | Catheter connection systems |
WO2007087900A1 (en) * | 2006-02-02 | 2007-08-09 | The European Community, Represented By The European Commission | Process for controlling surface wettability |
US20070275174A1 (en) * | 2006-05-24 | 2007-11-29 | Hanson Eric L | Fishing fly and fly fishing line with fluorocarbon coating |
JP4323535B2 (en) * | 2007-04-26 | 2009-09-02 | クロリンエンジニアズ株式会社 | Water electrolysis equipment |
WO2008154403A2 (en) * | 2007-06-08 | 2008-12-18 | 3M Innovative Properties Company | Lines having shaped surface and method of making |
US7785363B2 (en) * | 2007-08-15 | 2010-08-31 | Boston Scientific Scimed, Inc. | Skewed nodal-fibril ePTFE structure |
US8066755B2 (en) | 2007-09-26 | 2011-11-29 | Trivascular, Inc. | System and method of pivoted stent deployment |
US8226701B2 (en) | 2007-09-26 | 2012-07-24 | Trivascular, Inc. | Stent and delivery system for deployment thereof |
US8663309B2 (en) | 2007-09-26 | 2014-03-04 | Trivascular, Inc. | Asymmetric stent apparatus and method |
JP2010540190A (en) | 2007-10-04 | 2010-12-24 | トリバスキュラー・インコーポレイテッド | Modular vascular graft for low profile transdermal delivery |
US8328861B2 (en) | 2007-11-16 | 2012-12-11 | Trivascular, Inc. | Delivery system and method for bifurcated graft |
US8083789B2 (en) | 2007-11-16 | 2011-12-27 | Trivascular, Inc. | Securement assembly and method for expandable endovascular device |
US20090198329A1 (en) | 2008-02-01 | 2009-08-06 | Kesten Randy J | Breast implant with internal flow dampening |
US11786036B2 (en) | 2008-06-27 | 2023-10-17 | Ssw Advanced Technologies, Llc | Spill containing refrigerator shelf assembly |
US8286561B2 (en) | 2008-06-27 | 2012-10-16 | Ssw Holding Company, Inc. | Spill containing refrigerator shelf assembly |
ES2654377T3 (en) | 2008-10-07 | 2018-02-13 | Ross Technology Corporation | Spill resistant surfaces with hydrophobic and oleophobic boundaries |
SG176834A1 (en) * | 2009-07-10 | 2012-01-30 | Sumitomo Elec Fine Polymer Inc | Filtration purpose flat-membrane element, flat-membrane-type separation membrane module, and filtration apparatus |
EP2496886B1 (en) | 2009-11-04 | 2016-12-21 | SSW Holding Company, Inc. | Cooking appliance surfaces having spill containment pattern and methods of making the same |
EP2359876A1 (en) * | 2010-02-12 | 2011-08-24 | Aesculap AG | Medical device comprising a porous article of ePTFE exhibiting improved cellular tissue ingrowth |
JP5858441B2 (en) | 2010-03-15 | 2016-02-10 | ロス テクノロジー コーポレーション.Ross Technology Corporation | Plunger and method for obtaining a hydrophobic surface |
AU2012220798B2 (en) | 2011-02-21 | 2016-04-28 | Ross Technology Corporation | Superhydrophobic and oleophobic coatings with low VOC binder systems |
US8965499B2 (en) | 2011-04-29 | 2015-02-24 | Cyberonics, Inc. | Overwrap for nerve stimulation system |
DE102011085428A1 (en) | 2011-10-28 | 2013-05-02 | Schott Ag | shelf |
EP2791255B1 (en) | 2011-12-15 | 2017-11-01 | Ross Technology Corporation | Composition and coating for superhydrophobic performance |
WO2015157202A1 (en) | 2014-04-09 | 2015-10-15 | Corning Incorporated | Device modified substrate article and methods for making |
US8992595B2 (en) | 2012-04-04 | 2015-03-31 | Trivascular, Inc. | Durable stent graft with tapered struts and stable delivery methods and devices |
US9498363B2 (en) | 2012-04-06 | 2016-11-22 | Trivascular, Inc. | Delivery catheter for endovascular device |
MX2015000119A (en) | 2012-06-25 | 2015-04-14 | Ross Technology Corp | Elastomeric coatings having hydrophobic and/or oleophobic properties. |
CN106030686A (en) * | 2012-12-13 | 2016-10-12 | 康宁股份有限公司 | Glass and methods of making glass articles |
US10014177B2 (en) | 2012-12-13 | 2018-07-03 | Corning Incorporated | Methods for processing electronic devices |
TWI617437B (en) | 2012-12-13 | 2018-03-11 | 康寧公司 | Facilitated processing for controlling bonding between sheet and carrier |
US9340443B2 (en) | 2012-12-13 | 2016-05-17 | Corning Incorporated | Bulk annealing of glass sheets |
US10086584B2 (en) | 2012-12-13 | 2018-10-02 | Corning Incorporated | Glass articles and methods for controlled bonding of glass sheets with carriers |
US10510576B2 (en) | 2013-10-14 | 2019-12-17 | Corning Incorporated | Carrier-bonding methods and articles for semiconductor and interposer processing |
CN107635769B (en) | 2015-05-19 | 2020-09-15 | 康宁股份有限公司 | Article and method for bonding sheet to carrier |
EP3313799B1 (en) | 2015-06-26 | 2022-09-07 | Corning Incorporated | Methods and articles including a sheet and a carrier |
AU2017238143B2 (en) | 2016-03-22 | 2022-06-30 | Scientific Anglers Llc | Fly fishing line and method for manufacturing same |
AU2017299466B2 (en) | 2016-07-18 | 2022-07-14 | Merit Medical Systems, Inc. | Inflatable radial artery compression device |
CN109922871B (en) | 2016-08-16 | 2022-01-04 | 唐纳森公司 | Hydrocarbon fluid-water separation |
TW201825623A (en) | 2016-08-30 | 2018-07-16 | 美商康寧公司 | Siloxane plasma polymers for sheet bonding |
TWI821867B (en) | 2016-08-31 | 2023-11-11 | 美商康寧公司 | Articles of controllably bonded sheets and methods for making same |
US11331692B2 (en) | 2017-12-15 | 2022-05-17 | Corning Incorporated | Methods for treating a substrate and method for making articles comprising bonded sheets |
CA3089266A1 (en) * | 2018-02-15 | 2019-08-22 | Donaldson Company, Inc. | Filter element configurations |
KR102131101B1 (en) * | 2018-04-06 | 2020-07-09 | 서울대학교 산학협력단 | Method for preparation of ePTFE-based artificial vessels with enhanced hemocompatibility via selective plasma etching |
EP3970762A4 (en) * | 2019-05-15 | 2022-12-14 | Seoul National University R&DB Foundation | Method for manufacturing eptfe artificial blood vessels having improved hemocompatibility via selective plasma etching |
CN110772662A (en) * | 2019-11-30 | 2020-02-11 | 山东百多安医疗器械有限公司 | Antibacterial expanded polytetrafluoroethylene facial implant material and preparation process thereof |
Family Cites Families (17)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
SE392582B (en) * | 1970-05-21 | 1977-04-04 | Gore & Ass | PROCEDURE FOR THE PREPARATION OF A POROST MATERIAL, BY EXPANDING AND STRETCHING A TETRAFLUORETENE POLYMER PREPARED IN AN PASTE-FORMING EXTENSION PROCEDURE |
JPS51125455A (en) * | 1975-04-14 | 1976-11-01 | Jiyunkichi Nakai | Method of surface treatment of molded article |
US4208745A (en) * | 1976-01-21 | 1980-06-24 | Sumitomo Electric Industries, Ltd. | Vascular prostheses composed of polytetrafluoroethylene and process for their production |
CA1147109A (en) * | 1978-11-30 | 1983-05-31 | Hiroshi Mano | Porous structure of polytetrafluoroethylene and process for production thereof |
US4647416A (en) * | 1983-08-03 | 1987-03-03 | Shiley Incorporated | Method of preparing a vascular graft prosthesis |
US4657544A (en) * | 1984-04-18 | 1987-04-14 | Cordis Corporation | Cardiovascular graft and method of forming same |
US4718907A (en) * | 1985-06-20 | 1988-01-12 | Atrium Medical Corporation | Vascular prosthesis having fluorinated coating with varying F/C ratio |
US4919659A (en) * | 1985-12-16 | 1990-04-24 | The Board Of Regents For The University Of Washington | Radio frequency plasma deposited polymers that enhance cell growth |
US4767418A (en) * | 1986-02-13 | 1988-08-30 | California Institute Of Technology | Luminal surface fabrication for cardiovascular prostheses |
US4869714A (en) * | 1986-02-13 | 1989-09-26 | California Institute Of Technology | Luminal surface fabrication for cardiovascular prostheses |
US5002572A (en) * | 1986-09-11 | 1991-03-26 | Picha George J | Biological implant with textured surface |
US4933060A (en) * | 1987-03-02 | 1990-06-12 | The Standard Oil Company | Surface modification of fluoropolymers by reactive gas plasmas |
GB2211190A (en) * | 1987-10-19 | 1989-06-28 | Gore & Ass | Rapid recoverable ptfe and a process for its manufacture |
US4955909A (en) * | 1989-01-31 | 1990-09-11 | Bioplasty, Inc. | Textured silicone implant prosthesis |
US4946903A (en) * | 1989-03-27 | 1990-08-07 | The Research Foundation Of State University Of Ny | Oxyfluoropolymers having chemically reactive surface functionality and increased surface energies |
US5118524A (en) * | 1990-09-14 | 1992-06-02 | The Toronto Hospital | Vascular biomaterial |
JPH06506713A (en) * | 1991-04-15 | 1994-07-28 | レイクスユニベルシテイト・グロニンゲン | Method for modifying fluorine-containing plastics, modified plastics and biomaterials containing the plastics |
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1992
- 1992-06-08 WO PCT/US1992/004812 patent/WO1992022604A1/en active IP Right Grant
- 1992-06-08 EP EP92914071A patent/EP0646151B1/en not_active Expired - Lifetime
- 1992-06-08 CA CA002110499A patent/CA2110499C/en not_active Expired - Lifetime
- 1992-06-08 JP JP5500960A patent/JPH07500122A/en active Pending
- 1992-06-08 DE DE69223065T patent/DE69223065T2/en not_active Expired - Lifetime
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1993
- 1993-12-01 US US08/161,184 patent/US5437900A/en not_active Expired - Lifetime
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CA2110499A1 (en) | 1992-12-23 |
US5437900A (en) | 1995-08-01 |
DE69223065D1 (en) | 1997-12-11 |
EP0646151B1 (en) | 1997-11-05 |
JPH07500122A (en) | 1995-01-05 |
WO1992022604A1 (en) | 1992-12-23 |
EP0646151A1 (en) | 1995-04-05 |
DE69223065T2 (en) | 1998-04-09 |
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