Low stress relaxation extrudable elastomeric composition
AssigneeShell Oil Company
InventorGlenn R. Himes
Life of this patent
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Abstract
An extrudable elastomeric composition includes an elastomeric polymer and a tackifying resin in which the extrudable elastomeric composition is adapted to form an elastic sheet having a stress relaxation or less than about 30 percent. The elastomeric polymer is a styrene-poly(ethylene-propylene)-styrene thermoplastic elastomeric block copolymer or a mixture of styrene-poly(ethylene-propylene)-styrene and styrene-poly(ethylene-butylene)-styrene elastomeric block copolymers. The extrudable elastomeric composition may also include a polyolefin and/or an extending oil.
Claims4
An elastomeric composition for extrusion into an elastic sheet having a stress relaxation of less than about 30 percent consisting of:
- (a) an elastomeric polymer selected from the group consisting of styrene-poly(ethylene-propylene)-styrene elastomeric block copolymer and a mixtrue of at least about 55 parts by weight of styrene-(ethylene-propylene)-styrene block copolymers per 100 parts by weight of elastomeric polymer and styrene-poly(ethylene-butylene)-styrene elastomeric block copolymers wherein the styrene-poly(ethylene-propylene)-styrene elastomeric block copolymer has the formula:
- ##STR3## wherein m is an integer from about 38 to about 337;
- and n is an integer from about 500 to about 1860;
- and R is selected from the group consisting of phenyl groups and substituted phenyl groups;
- and the weight ratio of polystyrene endblocks to poly-(ethylene-propylene) endblocks ranges from about 10:90 to about 25:75;
- and
- (b) no less than about 15 percent by weight and no more than abut 28 percent by weight of a tackifying resin.
An extrudable elastomeric composition for extrusion into an elastic sheet having a stress relaxation of less than about 30 percent consisting of:
- (a) from about 50 to about 80 percent by weight of an elastomeric polymer selected from the group consisting of styrene-poly(ethylene-propylene)-styrene elastomeric block copolymer and a mixture of at least about 55 parts by weight of styrene-(ethylene-propylene)-styrene block copolymers per 100 parts by weight of elastomeric polymer and styrene-poly(ethylene-butylene)-styrene elastomeric block copolymers wherein in the styrene-poly(ethylene-propylene)-styrene elastomeric block copolymer has the formula:
- ##STR4## wherein m is an integer from about 38 to about 337;
- and n is an integer from about 500 to about 1860;
- and R is selected from the group consisting of phenyl group and substituted phenyl groups;
- and the weight ratio of polystyrene endblocks to poly(ethylene-propylene) endblocks ranges from about 10:90 to about 25:75;
- (b) from about 3 to about 25 percent by weight of a polyolefin;
- (c) from about 15 to about 28 percent of a tackifying resin;
- and
- (d) from about 0 to about 15 percent by weight of an extending oil.
Dependencies are inferred from the claim text.