Crosslinked polymer composition

An expandable polymer composition comprising:

• (a) a first polyolefin polymer;
• and
• (b) an interpenetrating network polymer comprising,
• (i) a second polyolefin polymer present in an amount of from 10 percent by weight to 80 percent by weight, based on total weight of said interpenetrating network polymer, and
• (ii) a vinyl aromatic polymer present in an amount of from 20 percent by weight to 90 percent by weight, based on total weight of said interpenetrating network polymer,
• wherein, as initially provided in said expandable polymer composition, said interpenetrating network polymer is substantially free of crosslinking;
• and
• (c) an expansion agent selected from the group consisting of physical expansion agents, chemical expansion agents and combinations thereof,
• wherein said expandable polymer composition is at least partially crosslinked.

An expanded polymer composition comprising:

• (a) a first polyolefin polymer;
• and
• (b) an interpenetrating network polymer comprising,
• (i) a second polyolefin polymer present in an amount of from 10 percent by weight to 80 percent by weight, based on total weight of said interpenetrating network polymer, and
• (ii) a vinyl aromatic polymer present in an amount of from 20 percent by weight to 90 percent by weight, based on total weight of said interpenetrating network polymer,
• wherein, as initially provided in said expanded polymer composition, said interpenetrating network polymer is substantially free of crosslinking,
• wherein said expanded polymer composition is at least partially crosslinked, and has a density of from 16 to 400 Kg/m3.

An expanded polymer composition comprising:

• (a) from 30 to 90 percent by weight based on the expanded polymer composition of a first polyolefin polymer selected from the group consisting of ethylene homopolymers, copolymers of ethylene and C3-C8 α-olefins, copolymer of ethylene and ethyl (meth)acrylate, copolymers of ethylene and vinyl acetate, and combinations thereof;
• and
• (b) from 10 to 70 percent by weight based on the expanded polymer composition of an interpenetrating network polymer comprising,
• (i) a second polyolefin polymer present in an amount of from 10 percent by weight to 80 percent by weight, based on the weight of said interpenetrating network polymer, and
• (ii) a vinyl aromatic polymer present in an amount of from 20 percent by weight to 90 percent by weight, based on the weight of said interpenetrating network polymer;
• wherein said second polyolefin is selected from the group consisting of ethylene homopolymers, copolymers of ethylene and vinyl acetate, copolymers of ethylene and C3-C8 α-olefins, copolymers of ethylene and C1-C8 linear or branched alkyl esters of (meth)acrylic acid, and combinations thereof;
• and
• wherein said vinyl aromatic polymer is selected from the group consisting of polystyrene, copolymers of styrene and C1-C8 linear or branched alkyl esters of (meth)acrylic acid, and combinations thereof;
• and
• wherein said expanded polymer composition is at least partially crosslinked and has a crosslink density of from 20 to 60 percent by weight, based on the weight of said expanded polymer composition;
• and
• wherein said expanded polymer composition has a density of from 16 to 400 Kg/m3.

A method of producing an expanded polymer composition in a shorter period of time comprising:

• forming a polymer blend by combining
• (a) a first polyolefin polymer;
• (b) an interpenetrating network polymer comprising,
• (i) a second polyolefin polymer present in an amount of from 10 percent by weight to 80 percent by weight, based on total weight of said interpenetrating network polymer, and
• (ii) a vinyl aromatic polymer present in an amount of from 20 percent by weight to 90 percent by weight, based on total weight of said interpenetrating network polymer,
• (c) one or more crosslinking agents;
• and
• (d) one or more foaming agents;
• forming a first foamed polymer composition by placing the polymer blend in a press at a temperature of from 240 to 320° F. and 250 to 2,500 psi for 20 to 90 minutes;
• and
• forming a final foamed polymer composition by placing the first foamed polymer composition in a press at a temperature of from 300 to 380° F. and 250 to 1,500 psi for 15 to 320 minutes;
• wherein the cycle time required to produce the present expanded polymer composition is at least 5% less than the time required to produce an expanded composition containing the same ingredients as the present expanded polymer composition except for the interpenetrating network polymer.