초록 ▼

A flexible thermoplastic article is formed from a blend comprising from about 2 to about 15 weight percent of a styrene-elastomer block copolymer; from about 60 to about 90 weight percent polyolefin; from about 4 to about 15 weight percent plasticizer oil, and optionally from about 0 to about 3 weig

A flexible thermoplastic article is formed from a blend comprising from about 2 to about 15 weight percent of a styrene-elastomer block copolymer; from about 60 to about 90 weight percent polyolefin; from about 4 to about 15 weight percent plasticizer oil, and optionally from about 0 to about 3 weight percent of at least one additive. The additives are typically present in a concentration of from 0.05 to about 3 weigh percent and can include those additives conventionally used in polyolefin foam compositions, including antioxidants and stabilizers, processing aids, etc. The styrene-elastomer block copolymer is preferably a tri-block copolymer structure which includes styrene end-blocks and a mid-block of a saturated olefin elastomer. A particularly suitable styrene elastomer block copolymer is a styrene-ethylene/butylene-styrene (SEBS) block copolymer. In one embodiment of the present invention, the styrene-ethylene/butylene-styrene block copolymer has a styrene/rubber ratio of from 30 to 70 with an Average Molecular Weight (Mn) in the range of 50,000 to 300,000. The polyolefin is preferably predominately a polyethylene and desirably comprises from 85 to 100 weight percent polyethylene and from 0 to 15 weight percent polypropylene, more preferably from 95 to 100 weight percent polyethylene and from 0 to 5 weight percent polypropylene. Particularly suitable for inclusion in the foam composition of the present invention are those polyolefins which are produced with a single-site catalyst and are generally referred to in the industry as metallocene polyethylene. The polyolefin component can also include a blend of linear low density polyethylene and high density polyethylene. The plasticizer oil preferably has a molecular weight of from 200 to 1,000, and most desirably around 400.

대표청구항 ▼

1. A flexible thermoplastic article having a foamed structure and comprising: a) from about 2 to about 15 percent by weight styrene-elastomer block copolymer; b) from about 60 to about 90 percent by weight polyolefin; c) from about 4 to about 15 percent by weight plasticizer oil; and d) from a

1. A flexible thermoplastic article having a foamed structure and comprising: a) from about 2 to about 15 percent by weight styrene-elastomer block copolymer; b) from about 60 to about 90 percent by weight polyolefin; c) from about 4 to about 15 percent by weight plasticizer oil; and d) from about 0 to about 3 percent by weight of at least one additive. 2. The article of claim 1, wherein said styrene-elastomer block copolymer is a tri-block copolymer structure that includes styrene end-blocks and a mid-block of a saturated olefin elastomer. 3. The article of claim 1, wherein said styrene-elastomer block copolymer is a styrene-ethylene/butylene-styrene (SEBS) block copolymer. 4. The article of claim 3, wherein said styrene-ethylene/butylene-styrene (SEBS) block copolymer is predominately a linear tri-block copolymer structure. 5. The article of claim 3, wherein said styrene-ethylene/butylene-styrene block copolymer has a styrene/rubber ratio of from 30 to 70 with an Average Molecular Weight (Mn) in the range of 50,000 to 300,000. 6. The article of claim 1, wherein said polyolefin comprises from 85 to 100 weight percent polyethylene and from 0 to 15 weight percent polypropylene. 7. The article of claim 1, wherein said polyolefin comprises metallocene polyethylene. 8. The article of claim 1, wherein said polyolefin comprises a blend of linear low density polyethylene and high density polyethylene. 9. The article of claim 1, wherein said plasticizer oil comprises a hydrocarbon oil having a molecular weight of from 200 to 1000. 10. The article of claim 1, which has a uniform closed cell structure, and wherein the article will withstand elevated temperatures of 110° C. for 96 hours without rupture or collapse of the foam cells. 11. The article of claim 1, having an electrical dissipation factor at 2 Ghz in the range of 30 to 200 microradians. 12. A flexible thermoplastic foam having a closed cell foam structure and comprising: a) from about 2 to about 15 percent by weight styrene-ethylene/butylene-styrene (SEBS) block copolymer; b) from about 60 to about 90 percent by weight low density polyethylene; c) from about 4 to about 15 percent by weight plasticizer oil; and d) from about 0 to about 3 percent by weight of at least one additive. 13. Hollow tubular pipe insulation made from the foam of claim 1. 14. A coaxial cable comprising a dielectric formed of the thermoplastic foam of claim 1. 15. A composition for producing a flexible thermoplastic foam, said composition consisting essentially of: a) from about 2 to about 15 percent by weight styrene-elastomer block copolymer; b) from about 60 to about 90 percent by weight polyolefin; c) from about 4 to about 15 percent by weight plasticizer oil; d) at least one blowing agent in an amount sufficient to produce a foam structure; and e) from about 0 to about 3 percent by weight of at least one additive. 16. The composition of claim 15, wherein said styrene-elastomer block copolymer is a styrene-ethylene/butylene-styrene (SEBS) block copolymer. 17. The composition of claim 16, wherein said styrene-ethylene/butylene-styrene (SEBS) block copolymer is predominately a linear tri-block copolymer structure. 18. The composition of claim 17, wherein said styrene-ethylene/butylene-styrene block copolymer has a styrene to rubber ratio of from about 25 to about 75. 19. The composition of claim 15, wherein said blowing agent is selected from the group consisting of fluorinated aliphatic hydrocarbons, aliphatic hydrocarbons, or chemical blowing agents. 20. The composition of claim 15, wherein said blowing agent is a chemical blowing agent comprising at least one member selected from the group consisting of azodicarbonamide, sodium bicarbonate, sodium carbonate, ammonium carbonate, and citric acid.