US 3371667 A
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Description (OCR text may contain errors)
March 5, 1968 y E. A. vvMORSE 3,371,667
ARTICLE FOR ABSORBING BODY EXUDATES Filed June 1l, 1964 ATTORNEY United States Patent lilice :371,667- Patented Mar. 5, 1968 3,371,667 ARTICLE FOR ABSORBING BODY EXUDATES Edward A. Morse, Fanwood, NJ., assignor to Johnson & Johnson, a corporation of New Jersey Filed June 11, 1964, Ser. No. 374,487 3 Claims. (Cl. 12S-290) ABSTRACT OF THE DISCLOSURE This application discloses absorbent products which include a functional, highly porous resilient element immediately adjacent the surface of the absorbent product which is to be placed against the body and which element serves to entrap highly viscous, mucoid and gelatinous constituents of the body fluids. The open structured, porous element has interstitial Wall surfaces which are wettable so as to permit the ilu'id, low viscosity portion of body exudates to pass rapidly therethrough. Because of its porous open structured nature, the element serves to break up the low viscosity constituents of body exudates and by sheer forces exerted thereon during use render them more iluid so as to pass through the porous element and be absorbed by an absorbent core adjacent to the element.
This invention relates to absorbent products and more particularly is directed to absorbent products having irnproved fluid absorbency, improved fluid retentivity characteristics and improved shape retention and which are particularly useful for absorption of body exudates.
Absorbent products such as sanitary napkins, surgical dressings, compresses and the like, usually consist of a core of one or more layers of highly absorbent, relatively dense fibers which has a fluid permeable, soft, knitted, woven or nonwoven wrapper. The cores are conventionally made of layers of bers such as carded cotton webs, air-layered cellulosic fiber webs, comminuted wood pulp bats, tissue pulp or like materials which are highly absorbent.
Suchabsorbent products when used as intended for the absorption of body exudates, while acceptable in some instances, have not been entirely satisfactory as absorbing products in all instances. Body exudates are not at all times uniform in composition and consistency and accordingly, exhibit varying rheological properties.
It is found, for example, particularly during certain periods of the menses, that the menstrual exudate contains a large portion of high-viscosity, heavy gelatinous substances. Sanitary napkins, made as above described, are unable to absorb the gelatinous mucoid exudates at any appreciable rate because of the inability of the highly viscous exudate to be absorbed by capillarity. As a result, the gelatinous, mucoid portion of the exudates remains on the surface of the absorbent pad without penetrating into the absorbent layers and in a short time spreads out to f orm a barrier to the entrance of the low-viscosity fluid components of the exudates into the absorbent layers.
Thus, it is seen that conventional absorbent pads are not utilized to full capacity in all instances. Furthermore, instead of absorbing body exudates as intended, conventional absorbent pads in some instances actually prevent absorption of low-viscosity uids which, in the absence of high-viscosity fluids, gels and debris, would be absorbed. l
In accordance with the present' invention, an absorbent pad is provided having a highly absorbent, relatively dense core, -in conjunction with an open, porous, lowdensity structure which is both wet and dry resilient. The interstitial wall surfaces of the open, porous structure are highly wettable such that the structure permits body iluids to penetrate freely into and through the open structure while at the same time eifectively trapping the gelatinous and mucoid constituents of body exudates in thevinterstices of the structure during the prolonged time required for their absorption into the highly absorbent layer of the pad.
In addition, the open porous structure employed in conjunction with the highly absorbent layers in the absorptive products of this invention, because of its inherent resiliency in both the wet and dry states, serves another advantageous function of maintaining the absorbent pad in a desired shape.
The open, highly porous, low-density structure characterizing this invention permits low-viscosity uids to be conducted rapidly along the wettable interstitial wall surfaces thereof into the more dense absorbent layers positioned adjacent to the open structure. The highviscosity fluids, gels and debris oftentimes found in body exudates will drop by gravity into the large open interstices of the open, porous low-density structure and be held therein during the relatively long period of time required for their absorption by the relatively dense, highly absorbent material.
A particular advantage is obtained when the absorbent product made in accordance with the present invention is a sanitary napkin. During dynamic use of the sanitary napkin, i.e., during walking, crossing of the legs, etc., the pores or interstices of the open, highly porous, lowdensity structure are caused to open and close or to vary in size. In effect, this action creates local pumps which aid in forcing the highly viscous constituents of menstrual exudates downwardly into the more dense absorbent mass below. In addition, this pumping action being a form of work causes those highly viscous constituents of the menstrual eXudates Whose viscosities are greatly reduced by shear or other forms or physical work to flow more freely.
Different constituents in body exudates exhibit different rheological properties ranging from those of the lowviscosity uids to those of the highly viscous mucoid materials. By the use of the open, highly porous, low-density Y structure of the present invention, the rapid conduction of the low-viscosity fluids along the wettable interstitial wall surfaces aids in pulling the high-viscosity, gelatinous and mucoid constituents of the body exudates into the open interstices. In other words, the low-viscosity fluids act as a transport medium for the higher viscosity gelatinous mass into the open, highly porous, low-density structure.
These and other attendant advantages will be apparent from the description hereinafter contained when taken in conjunction with the accompanying drawings, in which:
FIGURE l is a perspective view of an absorbent pad such as a sanitary napkin which is shown partially open to illustrate the incorporation of the invention,
FIGURE 2 is a section taken along line 2 2 of FIG- URE 1 and discloses a layer of highly absorbent material with one embodiment of a highly porous, low-density structure positioned with respect to the highly absorbent layer in accordance with the present invention,
FIGURE 3 is a section similar to FIGURE 2 showing another embodiment of the absorbent product of the present invention,
FIGURE 4 is a section similar to that illustrated in FIGURES 2 and 3 but showing the incorporation of another embodiment of the open, highly porous, low-density structure employed in accordance with the present invention,
FIGURE 5 is a greatly enlarged section taken through the open, highly porous, low-density structure illustrated in FIGURES 2 and 3 showing the details of its components and construction, and
FIGURE 6 is similarly a greatly enlarged section through the open, highly porous, low-density structure illustrated in FIGURE 4.
Referring now to FIGURE 1, a sanitary napkin'10 incorporating the invention is shown completely assembled but with parts broken away to expose the interior components. The napkin 10 comprises generaly a two component core covered with a foraminous, liquid pervious wrapper 12. Within the wrapper 12 the uppermost layer, i.e., that layer which is to be positioned against the body surface in use, is an open, highly porous, lowdensity structure 14. The lower layer 16 which can itself be composed of one or a plurality of layers of fibrous materials is a highly absorbent, dense material such as cotton or terminated wood pulp, tissue pulp and the like. The whole assembly is held together by the outside foraminous cover 12 which has tabs 18 extending beyond the ends of the core assembly for securing the napkin in position on the body of the wearer.
The open, porous, low-density structure 14 of the ernbodiment shown in FIGURES 1, 2, 3 and 5 is a fibrous web, preferably formed of hydrophobic fibers 20` of a synthetic material. However, the fibrous web 14 can also be formed from absorbent fibers such as rayon but must be rendered hydrophobic in character by treatment with a resin or the like. By selection of a synthetic fiber or an absorbent fiber which is treated to obtain a hydrophobic coating, absorption of fluids into the fiber is prevented, thereby also preventing Wet collapse of the individual fibers in the web made therefrom.
Suitable materials from which the fibers 20 of the open, highly porous, low-density web 14 can be made include cellulose acetate, polyvinyl chloride, polyvinylidene chloride, acrylic resins, polyvinyl acetates, non-soluble polyvinyl alcohols, polyethylenes, polypropylenes, polyamides and polyesters. Other materials can also be used as long as the fibers 20 made therefrom are hydrophobic and exhibit an inherent wet and dry resilience. Similarly, ab-
sorbent fibers 20 such as rayon or wool which have been coated with materials of the above type can also be used to form the open structured web 14.
The open structured web 14 is made of fibers 20 which are individually both Wet and dry resilient because of 'their hydrophobic character which prevents absorbency of fluids into the interior of the fiber itself. The fibers 20 forming the open structured web 14 of the embodiment shown in FIGURES 1, 2, 3 and 5 are arranged haphazardly in intertwined relationship in all directions so as to define a three-dimensional, springy, open mat.
In accordance with the present invention the open structured web 14 made from hydrophobic fibers 20 must also exhibit both wet and dry resilience, i.e., form stability. Thus, it is essential that the fibers 20 from which it is made be stabilized. Stabilization of the fibrous web is preferably accomplished by bonding the fibers at their points of intersection 22 with a resin in a manner to be described hereinafter.
Suitable resins are copolymers of polyvinyl acetates and acrylic resins or non-solublepolyvinyl alcohols and acrylic resins, ethylene-ethyl acrylates and ethylene-ethyl acetates. Also suitable are acrylic polymers, polyethylene, polypropylene, polyvinyl chlorides, rubber latex and polyvinylidene chloride. Particularly suitable is a resin emulsion designated Karamul 154, a solids content emulsion of polyvinyl acetate and acrylic ester produced and marketed by Refined Products Company. Also suitable are resin emulsions designated Nos. 33,820 and 2802, products of National Starch Company which are emulsions of copolymers of non-soluble polyvinyl alcohols and polyvinyl acetates with acrylic resins respectively.
Because it is essential that the open fibrous structure 14 exhibit both wet and dry resilience for which the fibers 20 are bonded to one another at their points of intersection 22 (FIGURE 5), it is preferred that the individual fibers 20 range from about 3/4 of an inch to 2 inches in length, thus assuring bonding of fibers to one another at least at two points along their lengths. Generally, it will be preferred to use the fibers falling in the upper range of lengths when they are made of hydrophobic synthetic materials. The shorter fibers are more advantageously used when the fibers are inherently absorbent fibers but which are coated with resins to render them hydrophobic.
The weight of the fibers employed in the open structured web ranges from about 5 to about 50 denier. More preferred is a range from about l0 to about 25 denier, While most preferred is the use of fibers of about l5 denier.
As described above, the open structured fibrous web y'14 can also be made of individual fibers 20 which are inherently absorbent such as rayon or wool but which are coated with resins of the above type bonding agents to render them hydrophobic. In such instances, it is preferred to select an absorbent fiber of about 5 to 10 denier which, subsequent to the application of a resin coating, becomes a coated fiber of about 15 to 2() denier.
Another feature of the open, porous, low-density structure 14 characterizing the products of this invention is that its interstitial Wall surfaces are wettable.
When the open structured web is of the fibrous form shown in FIGURES 2, 3, and 5, the interstitial wall surfaces are, in fact, the surfaces of the fibers 20. Since the fibers selected for forming the open structured web 14 are hydrophobic and will not absorb fluids into their interiors, their surfaces as formed are also hydrophobic. In order that the interstitial walls of the open structured web are rendered hydrophilic, it is required that the hydrophobic fibers be treated with a wetting agent. By treatment with the wetting agent, only the surfaces of the fibers exhibit hydrophilic characteristics while the fiber itself remains hydrophobic as above described.
Suitable wetting agents or surface-active agents can include any anionic and nonionic surface-active agents as are generally well known. Such agents are set out, for example, in a detailed listing in Detergents and Emulsifiers-Up to Date 1963 by John W. McCutcheon, Incorporated.
While cationic surface-active agents can be suitable for preparing the open fibrous web 14 used in accordance with the present invention, they are not generally preferred as they are known to have sometimes an irritating effect on the skin.
Among the more preferred surface-active agents are the anionic and nonionic agents recognized in the art as wetting agents, detergents, or emul'sifiers. Among anionic surface-active agents, preferred ones are alkali metal or amine salts of alkyl benzene sulfonic acids such as dodecylbenzene sulfonic acid, sodium lauryl sulfate, alkyl naphthalene sulfonates, sodium N-methyl-N- oleoyltaurate, oleic acid ester of sodium isethionate, dioctyl sodium sulfosuccinate, sodium dodecyldiphenyloxide disulfonate and reaction products of aliphatic alcohols with orthophosphoric acid with or without ethylene oxide linkages, a family of anionic wetting agents known as Hostaphats made by Farbwerke Hoechst A.G. of Frankfurt am Main-Hochst, Germany, and marketed in the United States by Hostachem Corporation of Mountainside, NJ. Among nonionic agents, preferred members are alkyl phenoxy poly(ethyleneoxy)ethanols such as nonyl phenol adducts with ethylene oxide; trimethyl nonyl polyethylene glycol ethers, polyethylene oxide adducts of fatty and rosin acids and long chain alkylmercaptan adducts with ethylene oxide.
A particularly suitable wetting agent is one designated Tween 20, a nonionic family of emulsifers produced and marketed by Atlas Chemical Company.
The open fibrous web 14 is manufactured from the fibers above described by using conventional web forming equipment and techniques. Subsequent to the formation of the fibrous web 14, it is then subjected to bonding and surface wetting of the fibers. This is accomplished preferably by mist spraying techniques wherein a mixture of a resin emulsion and wetting agents are sprayed into the fibrous web preferably from both sides. Alternatively, the fibrous web 14 can be bonded and the surfaces of the fibers rendered hydrophilic by dipping the pre-formed web 14 into a liquid bath containing the resin emulsion and wetting agent mixture. Subsequent to passing through the bath, the excess resin and bonding agent can be squeezed or otherwise driven out of the web 14. However, mist spraying techniques are preferred as collapse of the fibrous web 14..is prevented, there is a more even penetration of the treating agents into the web 14, and the amount of treating agents applied thereto is more easily and readily controlled.
Following treatment of the fibrous web with a resin emulsion and wetting agent, it is air-dried and then cut into forms suitable for use in absorbent products as hereafter described.
The foregoing description has presented, for the purpose of illustration only, one form of the open structured member 14 which can be used in accordance with the present invention. Another such illustrative form is shown in FIGURES 4 and 6-, where the open structured member 14 consists of a web of highly porous foam material 24. It can be seen that the pores 26 in the foam web 24 can be considerably smaller than the interporous connections defined by the earlier described fibrous structure14. However, because of the inherent resilience of the foam structure 24 employed in accordance with this invention, the pores 26 will lbe caused to open up during use. Accordingly, it is found that the foam structure 24, while having smaller irregularly shaped interconnecting pores 26 than the fibrous open structured member 14, the inherent characteristics of foam during use in products of the invention provide equivalent results.
Suitable materials from which the foam structured member 24 can be made are generally any of the polymeric materials listed above from which the fibrous structured web 14 is made and with which it is bonded. Also suitable are conventional polyurethane, polyethylene foams and wet crosslinked cellulosic foams. Cellulosic foams which have been wet crosslinked by conventional procedures obtain increased wet resilience and are accordingly preferred.
The density of the foam structured web 24 preferably ranges from about 1.0 to 3 pounds per cubic foot while most preferred is about 2 pounds per cubic foot. The average pore size 26 in t-he foam structure preferably ranges from about 1/le-inch diameter to about Vs-inch diameter with the preferred pore size 26 being 1i-inch in diameter.
The interstitial wall surfaces of the foam structured web 24 must also be rendered hydrophilic since the foam materials used are hydrophobic to maintain the foam web 24 resilient in both the wet and dry state. However, since the foam web 24 is inherently resilient and form retentive, treatment with a bonding agent is not required.
To obtain hydrophilic interstitial wall surfaces in the foam structured web 24, it is sprayed with the above listed wetting or surface-active agents used in connection with the fibrous web 14. Mist spraying techniques are preferred but the foam web can similarly be dipped into the liquid wetting agent and subsequently squeezed dry.
The thickness of the open structured web in both fibrous 14 and foam 24 form, when used in sanitary napkins ranges from about 1z-inch to 1A of an inch. The thickness of the web when used in other absorbent products can be varied within wide ranges according to the requirements desired. Generally, however, the ratio by volume of the open structured web to the highly absorbent fibrous core portion in products of the present invention will range from about 1:1 to about 1:50.
Referring now to FIGURES l, 2, 3 and 4, there is illustrated a sanitary napkin embodying the above described' op'en structured member 14 or 24. The open structured member 14 or 24 occupies a position in the absorbent product between and immediately adjacent to the dense absorbent core material 16 and a cover 12. The open structured web 14 or 24 is positioned within the napkin 10 on the side thereof adapted to be worn against the body and is located immediately beneath the fluid permeable wrapper or cover 12. The cover 12 can be any iiuid permeable, soft, knitted, woven, or non-woven material, and it is preferred that the cover material exhibit a balance of hydrophobic and hydrophilic characteristics. That is to say, thecover 12 should be sufficiently hydrophobic that uids will not wick therein and suliiciently hydrophilic to provide a low enough contact angle with fluids to permit them to permeate the Wrapper 12. Conventional Wrapper materials include cotton or rayon acetate and are generally suitable as wrapper materials used for the absorbent products of the present invention.
Particularly suitable as a wrapper 12 because of their recognized softness and large pore size are materials produced in accordance with U.S. Patent No. 2,862,251, issued to F. Kalwaites on December 2, 1958. By the use of such materials, the relatively large openings therein assure that a large area of the low-density open structured member 14 or 24 will be exposed directly to the body exudates during use.
The highly absorbent portion 16 of the core as shown in FIGURES 2, 3, and 4 consists of a single layer of conventional highly absorbent fibers which can be carded cotton webs, air-layered cellulosic fiber webs, terminated wood pulp bats, tissue paper or like materials. While the principles of the invention are illustrated in its simplest form, it is to be understood that the highly absorbent portion 16 of the core can consist of one or more layers. For example, the highly absorbent portion 16 may include as shown in FIGURES 1 and 2, a partial covering of polyethylene film 28 between the highly absorbent core member 16 and the outer soft cover 12 which partial covering 28 extends across the bottom of the absorbent core 16 on the side opposite the location of the lowdensity open structured member 14 and up the lateral edges of the core 16 terminating short of the upper lateral edges of the open structured member 14. This polyethylene film 28 serves the function of preventing strike through of body exudates absorbed by the absorbent products of the present invention. Also, the highly absorbent core portion 16, can include a centrally located polyethylene film extending laterally and longitudinally across the napkin and strips of polyethylene covering the lateral edges of the core 16 immediately under the wrapper 12 (not shown) when a so-called two-way napkin is desired. In this'instance, it would be desirable to employ the open structured member 14 or 24 on both the upper and lower surfaces of the highly absorbent core portion 16 immediately under and in juxtaposition to the outer wrapper 12.
As shown in FIGURES 2 and 4, the open structured member 14 or 24 terminates short of the width of the highly absorbent core portion 16. The highly absorbent core portion 16- extends upwardly to ll the longitudinally extending gaps 30 between the lateral edges of the open structured member 14 or 24 and the lateral edges defined by the inner surfaces of the outer wrapper 12. In this form, particularly when the absorbent product is a sanitary napkin 10', any harshness that might result from the use of the low-density open structured member 14 or 24 is eliminated and a highly absorbent core portion 32 provides an absorbent mechanism for any fluids which might have a tendency to migrate to the lateral edges of the napkin 10.
While the illustrations and descriptions herein contained have related principally to sanitary napkins, it is to be expressly understood that the principles of the invention described therewith are equally adaptable to all absorbent products which are conventionally employed for the absorption of body exudates. Various changes can be made in the processes and the products herein described as the preferred embodiments without departing from the principles and scope of the invention as defined in the appended claims.
1. An absorbent product for absorbing body exudates, said product having at least one side adapted to be placed adjacent to the body for absorbing said exudates and comprising a relatively dense, highly absorbent core having relatively high uid retentivity, a foraminous and uid permeable cover on said side readily and easily permeable by said exudates, and an open structured, highly porous member of a foamed material of relatively low-density disposed between and in juxtaposition to said core and said cover, said open structured foamed member being wet and dry resilient and having interstitial walls the surfaces of which are wettable to permit rapid penetration of the low-viscosity uid portion of said eXudates through said open structured foamed member into said absorbent core while entrapping the highly-viscosity uid, gel and debris portion of said exudates within said interstitial walls.
2. The invention as defined in claim 1 wherein said foamed material is a polymeric resin.
3. The invention as defined in claim 1 wherein said interstitial wall surfaces are coated with a surface-active agent.
References Cited UNITED STATES PATENTS 3,230,955 1/1966 Joa et al. 128-290 3,113,568 12/1963 Robins 12S- 296 3,111,948 11/1963 Burgeni 128-290 3,105,491 10/1963 Harwood 128-290 3,094,494 `6/ 1963 Hopkins et al 128-290 3,046,986 7/1962 Harwood 128-290 3,029,817 4/1962 Harwood et al. 128-290 FOREIGN PATENTS v 814,498 6/ 1959 Great Britain.
RICHARD A. GAUDET, Primary Examiner.
C. F. ROSENBAUM, Examiner.