Search Images Maps Play YouTube News Gmail Drive More »
Sign in
Screen reader users: click this link for accessible mode. Accessible mode has the same essential features but works better with your reader.

Patents

  1. Advanced Patent Search
Publication numberCA2527057 A1
Publication typeApplication
Application numberCA 2527057
Publication date2 Aug 2006
Filing date15 Nov 2005
Priority date2 Feb 2005
Also published asCA2527057C, DE602005024506D1, EP1688458A1, EP1688458B1, US7456231, US7579387, US20060173089, US20080242758
Publication numberCA 2527057, CA 2527057 A1, CA 2527057A1, CA-A1-2527057, CA2527057 A1, CA2527057A1
InventorsPeter Jackson, Marcus P. Heydrich, Karen Schnuelle
ApplicantShawcor Ltd., Peter Jackson, Marcus P. Heydrich, Karen Schnuelle
Export CitationBiBTeX, EndNote, RefMan
External Links: CIPO, Espacenet
Radiation-crosslinked polyolefin compositions
CA 2527057 A1
Abstract
An article suitable for use as an insulating or coating material comprises a radiation-crosslinked composition comprising a polyethylene, a polypropylene and optionally an ethylene-propylene elastomer. The polyethylene component is selected from high density polyethylene (HDPE), medium density polyethylene (MDPE) and linear medium density polyethylene (LMDPE) and the polypropylene component is either a homopolymer or copolymer. The composition is predominantly based on the polyethylene component and contains the polyethylene component in an amount of at least 50 percent by weight. The article is radiation-crosslinked to a sufficient degree that it possesses thermoset properties, such that when the article is heated to a temperature above the crystalline melting point of the polypropylene homopolymer or copolymer, it is softened but does not become liquid. The article is formed by first blending the polyethylene, polypropylene and optionally the ethylene-propylene elastomer, melt processing the blend to produce an article, crosslinking the article by exposing it to radiation, and optionally heating, stretching and cooling the article to impart heat shrinkability to the article.
Description  available in
Claims(25)
1. A radiation-crosslinked article comprised of a polymer composition, the polymer composition comprising:
(a) at least 50 percent by weight of a polyethylene selected from the group consisting of high density polyethylene (HDPE), medium density polyethylene (MDPE) and linear medium density polyethylene (LMDPE); and (b) from about 5 percent by weight to less than 50 percent by weight of a polypropylene selected from the group consisting of polypropylene homopolymer and polypropylene copolymers;
wherein the article is crosslinked by exposure to radiation and possesses a sufficient degree of crosslinking such that when the article is heated to a temperature above the crystalline melting point of the polypropylene, it is softened but does not become liquid.
2. The radiation-crosslinked, thermoset article according to claim 1, further comprising:
(c) up to about 40 percent by weight of an ethylene-propylene elastomer.
3. The radiation-crosslinked, thermoset article according to claim 2, wherein the ethylene-propylene elastomer comprises about 40 to 95 percent by weight ethylene monomer.
4. The radiation-crosslinked, thermoset article according to claim 2, wherein the ethylene-propylene elastomer comprises an ethylene-propylene-diene terpolymer.
5. The radiation-crosslinked, thermoset article according to claim 1, wherein the amount of the polyethylene in the composition is from about 60 to 80 percent.
6. The radiation-crosslinked, thermoset article according to claim 1, wherein the amount of the polypropylene in the composition is from about 15 to 30 percent.
7. The radiation-crosslinked, thermoset article according to claim 2, wherein the amount of the ethylene-propylene elastomer in the composition is from about to 10 percent.
8. The radiation-crosslinked, thermoset article according to claim 1, said article being heat-shrinkable.
9. The radiation-crosslinked, thermoset article according to claim 1, wherein the polypropylene comprises a copolymer of propylene and ethylene.
10. The radiation-crosslinked, thermoset article according to claim 1, wherein the polypropylene is functionalized with one or more reactive functional groups selected from the group consisting of silanes, acrylic acids, methacrylic acids, acrylates, methacrylates, glycidyl methacrylates and anhydrides.
11. The radiation-crosslinked, thermoset article according to claim 4, wherein the ethylene-propylene-diene terpolymer is polymerized using a metallocene catalyst.
12. The radiation-crosslinked, thermoset article according to claim 11, wherein the metallocene catalyst comprises a highly stereospecific, single-site, constrained geometry metallocene catalyst.
13. The radiation-crosslinked, thermoset article according to claim 4, wherein the ethylene-propylene-diene terpolymer is prepared by copolymerizing propylene with ethylene and a diene monomer selected from the group consisting of 5-ethylidene-2-norbornene, dicyclopentadiene and 1,4-hexadiene.
14. The radiation-crosslinked, thermoset article according to claim 4, wherein the ethylene-propylene-diene terpolymer comprises from about 40 to about 95 percent by weight ethylene and from about 0.5 to about 10 percent by weight diene monomer.
15. The radiation-crosslinked, thermoset article according to claim 1, further comprising one or more additional ingredients selected from the group comprising radiation sensitizers, compatibilizers, pigments, antioxidant stabilizers, heat stabilizers, ultra-violet stabilizers, mineral fillers, halogenated flame retardants and process aids.
16. The radiation-crosslinked, thermoset, article according to claim 15, wherein the compatibilizer comprises one or more members of the group consisting of:
high density polyethylene (HDPE); medium density polyethylene (MDPE); linear medium density polyethylene (LMDPE); polypropylene homopolymer and polypropylene copolymers optionally modified with reactive functional groups selected from the group consisting of silanes, acrylic acids, methacrylic acids, acrylates, methacrylates, glycidyl methacrylates and anhydrides; ethylene-propylene copolymers; ethylene-propylene diene elastomers; crystalline propylene-ethylene elastomers; thermoplastic polyolefin elastomers;
metallocene polyolefins; cyclic olefin copolymers; polyoctenamers; copolymers of ethylene with vinyl acetate, vinyl alcohol, and/or alkyl acrylates; polybutenes;
hydrogenated and non-hydrogenated polybutadienes; butyl rubber; polyolefins modified with reactive functional groups selected from the group consisting of silanes, alcohols, amines, acrylic acids, methacrylic acids, acrylates, methacrylates, glycidyl methacrylates, and anhydrides; polyolefin ionomers;
polyolefin nanocomposites; and block copolymers selected from the group consisting of styrene-butadiene, styrene-butadiene-styrene, styrene-ethylene/propylene and styrene-ethylene/butylene-styrene.
17. The radiation-crosslinked, thermoset article according to claim 1, wherein the article has a gel fraction of from about 20 to 90 percent.
18. The radiation-crosslinked, thermoset article according to claim 16, wherein the compatibilizer comprises from about 5 to about 10 percent of the composition.
19. A process for producing a radiation-crosslinked, thermoset article, comprising:
(a) forming a blend comprising at least 50 percent by weight of a polyethylene selected from the group consisting of high density polyethylene (HDPE), medium density polyethylene (MDPE) and linear medium density polyethylene (LMDPE), and from about 5 percent by weight to less than 50 percent by weight of a polypropylene selected from the group consisting of polypropylene homopolymer and polypropylene copolymers;
(b) melt processing the blend to produce a melt-processed article having a first set of dimensions; and (c) crosslinking the melt-processed article by exposure to radiation to thereby produce said radiation-crosslinked, thermoset article, wherein a dosage of said radiation is sufficient to impart thermoset characteristics to the article, such that, when the article is heated to a temperature above the crystalline melting point of the polypropylene, it is softened but does not become liquid.
20. The process of claim 19, further comprising:
(d) heating the radiation-crosslinked, thermoset article to a first temperature at which it is softened but not melted;
(e) stretching the softened article such that the article is expanded beyond the first set of dimensions; and (f) cooling the stretched article to a second temperature below the temperature at which the article is softened while holding the article in its stretched form.
21. The process of claim 19, wherein steps (a) and (b) are performed simultaneously.
22. The process of claim 19, wherein melt-mixing step (a) is performed prior to step (b) using a machine selected from the group comprising a continuous twin-screw compounder, a kneader and an internal batcher.
23. The process of claim 19, wherein melt processing step (b) comprises extruding or molding.
24. The process of claim 19, wherein crosslinking step (c) is performed in an electron beam accelerator, and wherein the radiation comprises electron beam radiation, the dosage being about 1 to 20 megarads.
25. The process of claim 24, wherein the dosage is about 5 to 10 megarads.
Classifications
International ClassificationC08J3/28
Cooperative ClassificationC08L23/00, C08L2312/06, Y10S522/906, C08L23/10, C08L23/0815, C08L23/16, C08L23/06
European ClassificationC08L23/00, C08L23/06, C08L23/08A1
Legal Events
DateCodeEventDescription
30 Sep 2008EEERExamination request
27 Dec 2016MKLALapsed
Effective date: 20161115