Crosslinked polyolefin foam containing a high concentration of an inorganic material and process for producing the same

Claim 2

A crosslinked foam having an expansion ratio of 25 to 60 comprising a composition containing 100 parts by weight of a resin component consisting of a non-crystalline ethylene-vinyl acetate copolymer having a vinyl acetate content in the range of 40 to 90% by weight or a mixture thereof with an amount not more than 80% by weight of a thermoplastic resin, and 50 to 500 parts by weight of an inorganic powder material which is at least one powder selected from the group consisting of aluminum hydroxide powder and magnesium hydroxide powder.

Claim 3

A crosslinked foam as claimed in claim 1, wherein said resin component consists essentially of a non-crystalline ethylene-vinyl acetate copolymer having a vinyl acetate content of 40 to 90% by weight.

Claim 4

A crosslinked foam as claimed in claim 1, wherein the thermoplastic resin is at least one ethylene polymer selected from the group consisting of polyethlene, ethylene-α-olefin copolymer, ethylene-vinyl acetate copolymer having a vinyl acetate content of 5 to 30% by weight, ethylene-vinyl acrylate copolymer, ethylene-propylene copolymer, and ethylene-vinyl acetate-vinyl chloride copolymer.

Claim 5

A crosslinked foam as claimed in claim 1, wherein said foam contains a fire retardant in an amount of 5 to 30 phr and a fire retardant synergist in an amount of 2 to 20 phr.

Claim 6

A crosslinked foam as claimed in claim 4, wherein the fire retardant has a bromine content of 40 to 80% by weight and at least two recurring units in its chemical structure.

Claim 7

A crosslinked foam as claimed in claim 1, wherein the inorganic powder material is aluminum hydroxide powder.

Claim 8

A crosslinked foam as claimed in claim 1, wherein said foam contains the resin component in an amount of less than 20 g/liter.

Claim 9

A crosslinked foam as claimed in claim 1, wherein the inorganic powder material is subjected to a surface treatment with a monoalkoxy organotitanate compound.

Claim 10

A process for producing a crosslinked foam containing a high concentration of an inorganic material and having a high expansion ratio which comprises, heating an expandable composition containing 100 parts by weight of a resin component consisting of a non-crystalline ethylene-vinyl acetate copolymer having a vinyl acetate content in the range of 40 to 90% by weight or a blend thereof with an amount of not more than 80% by weight of at least one compatible thermoplastic resin, 50 to 500 parts by weight of an inorganic powder material which is at least one powder selected from the group consisting of aluminum hydroxide powder and magnesium hydroxide powder, 5 to 50 parts by weight of a blowing agent and 0.1 to 10 parts by weight of a crosslinking agent, the water content of said expandable composition being not higher than 0.15% by weight.

Claim 11

A process for producing a crosslinked foam containing a high concentration of an inorganic material and having a high expansion ratio which comprises, heating an expandable composition containing 100 parts by weight of a resin component consisting of a non-crystalline ethylene-vinyl acetate copolymer having a vinyl acetate content in the range of 40 to 90% by weight or a blend thereof with an amount of not more than 80% by weight of at least one compatible thermoplastic resin, 50 to 500 parts by weight of an inorganic powder material which is at least one powder selected from the group consisting of aluminum hydroxide powder and magnesium hydroxide powder, 5 to 50 parts by weight of a blowing agent and 0.1 to 10 parts by weight of a crosslinking agent, the water content of said expandable composition being not higher than 0.15% by weight.

Claim 12

A process as claimed in claim 9, wherein the water content is not higher than 0.07% by weight.

Claim 13

A process as claimed in claim 9, wherein the expandable composition contains a polyfunctional monomer as a crosslinking accelerator in an amount of 0.1 to 10 parts by weight.

Claim 14

A process as claimed in claim 9, wherein said resin component consists essentially of a non-crystalline ethylene-vinyl acetate copolymer having a vinyl acetate content in the range of 40 to 90% by weight.

Claim 15

A process as claimed in claim 9, wherein the thermoplastic resin is at least one polymer selected from the group consisting of polyethylene, ethylene-α-olefin copolymer, ethylene-vinyl acetate copolymer having a vinyl acetate content of 5 to 30% by weight, ethylene-ethyl acrylate copolymer, ethylene-propylene copolymer and ethylene-vinyl acetate-vinyl chloride copolymer.

Claim 16

A process as claimed in claim 9, wherein the expandable composition is heated under normal pressure to cause crosslinking and foaming.

Claim 17

A process as claimed in claim 9, wherein the expandable composition further contains a fire retardant in an amount of 5 to 30 phr and a fire retardant synergist in an amount of 2 to 20 phr.

Claim 18

A process as claimed in claim 15, wherein the fire retardant has a bromine content of 40 to 80% by weight and at least two recurring units in the chemical structure thereof.

Claim 19

A process as claimed in claim 9, wherein the expandable composition is heated at 80° to 140° C. to reduce the water content to not higher than 0.15% by weight.

Claim 20

A process as claimed in claim 11, wherein the polyfunctional monomer is a trifunctional or a tetrafunctional acrylate or methacrylate.

Claim 21

A process for producing an ethylene-vinyl acetate copolymer foam containing an inorganic material characterized in that a composition containing 100 parts by weight of a resin component consisting of a non-crystalline ethylene-vinyl acetate copolymer having a vinyl acetate content in the range of 40 to 90% by weight or a blend thereof with an amount not more than 80% by weight of a thermoplastic resin, 50 to 500 parts by weight of an inorganic powder material which is at least one powder selected from the group consisting of aluminum hydroxide powder and magnesium hydroxide powder and 5 to 50 parts by weight of a blowing agent is molded, crosslinked by irradiation with ionizing radiation, and foamed by heating at a temperature higher than the decomposition temperature of the blowing agent.

Claim 22

A process for producing an ethylene-vinyl acetate copolymer foam containing an inorganic material characterized in that a composition containing 100 parts by weight of a resin component consisting of a non-crystalline ethylene-vinyl acetate copolymer having a vinyl acetate content in the range of 40 to 90% by weight or a blend thereof with an amount not more than 80% by weight of a thermoplastic resin, 50 to 500 parts by weight of an inorganic powder material which is at least one powder selected from the group consisting of aluminum hydroxide powder and magnesium hydroxide powder and 5 to 50 parts by weight of a blowing agent is molded, crosslinked by irradiation with ionizing radiation, and foamed by heating at a temperature higher than the decomposition temperature of the blowing agent.

Claim 23

A process for producing the foam as claimed in claim 19, wherein the thermoplastic resin is at least one ethylene polymer selected from the group consisting of polyethylene, ethylene-α-olefin copolymer, crystalline ethylene-vinyl acetate copolymer having a vinyl acetate content of 5 to 30% by weight, ethylene-vinyl acetate-vinyl chloride copolymer, ethylene-ethyl acrylate copolymer and ethylene-propylene copolymer.

Claim 24

A process as claimed in claim 19, wherein the composition further contains a fire retardant in an amount of 5 to 30 phr and a fire retardant synergist in an amount of 2 to 20 phr.

Claim 25

A process as claimed in claim 21, wherein the fire retardant has a bromine content of 40 to 80% by weight and at least two recurring units in its chemical structure.

Claim 26

A process as claimed in claim 19, wherein the expandable composition contains a metal salt of stearic acid as an additive for improving the crosslinking and foaming properties.