Process for producing expandable thermoplastic resin beads

Claim 2

A process for producing expandable thermoplastic resin beads which comprises suspending in an aqueous medium graft copolymer beads containing from 20 to 70% by weight of a random copolymer of propylene and ethylene containing 1 to 10% by weight of ethylene and 99 to 90% by weight of propylene and 30 to 80% by weight of a vinyl aromatic monomer, and introducing a blowing agent composed of an easily volatilizable hydrocarbon or halogenated hydrocarbon into the thermoplastic resin beads.

Claim 3

The process of claim 1, wherein the amount of random copolymer in the graft copolymer is 50 to 30% by weight, and the amount of the vinyl aromatic monomer is 50 to 70% by weight.

Claim 4

The process of claim 1, wherein the vinyl aromatic monomer is at least one monomer selected from the group consisting of styrene, α-methylstyrene, ethylstyrene, chlorostyrene, bromostyrene, vinyltoluene, vinylxylene and isopropylxylene, or a mixture of at least 50% by weight of at least one of said monomers with another monomer copolymerizable therewith.

Claim 5

The process of claim 1, wherein the blowing agent is introduced into the resin beads under pressure while in the aqueous suspension.

Claim 6

The process of claim 1, wherein the blowing agent is introduced into the resin beads by dipping the beads into a liquid organic blowing agent.

Claim 7

The process of claim 1, wherein the random copolymer of propylene and ethylene is admixed with at least one other polymer selected from the group consisting of polyethylene, ethylene/vinyl acetate copolymer, ethylene/vinyl chloride copolymer, styrene/propylene rubber, polyisobutylene, butyl rubber, styrene/butadiene rubber, polybutadiene and polybutene, prior to polymerization with the vinyl aromatic monomer to prepare the graft copolymer beads.

Claim 8

A process for producing expandable thermoplastic graft copolymerized resin beads which consists essentially of suspending in an aqueous medium from 20 to 70% by weight of a random copolymer of propylene and ethylene containing 1 to 10% by weight of ethylene and 99 to 90% by weight propylene and 30 to 80% by weight of a vinyl aromatic monomer; adding a polymerization catalyst and polymerizing the vinyl aromatic monomer to form graft copolymerized thermoplastic resin beads and subsequently impregnating the graft copolymerized thermoplastic resin beads with an easily volatilizable hydrocarbon or halogenated hydrocarbon blowing agent.

Claim 9

A process for producing expandable thermoplastic graft copolymerized resin beads which consists essentially of suspending in an aqueous medium from 20 to 70% by weight of a random copolymer of propylene and ethylene containing 1 to 10% by weight of ethylene and 99 to 90% by weight propylene and 30 to 80% by weight of a vinyl aromatic monomer; adding a polymerization catalyst and polymerizing the vinyl aromatic monomer to form graft copolymerized thermoplastic resin beads and subsequently impregnating the graft copolymerized thermoplastic resin beads with an easily volatilizable hydrocarbon or halogenated hydrocarbon blowing agent.

Claim 10

In a process for producing expandable thermoplastic graft copolymerized resin beads which consists essentially of suspending in an aqueous medium containing 0.01 to 5% by weight, based on water present in the aqueous medium, of a dispersing agent selected from the group consisting of polyvinyl alcohol, methyl cellulose, calcium phosphate, magnesium pyrophosphate and calcium carbonate, from 20 to 70% by weight of a random copolymer of propylene and ethylene containing 1 to 10% by weight of ethylene and 99 to 90% by weight propylene and 30 to 80% by weight of a vinyl aromatic monomer; adding a polymerization catalyst and polymerizing the vinyl aromatic monomer to form graft copolymerized thermoplastic resin beads and subsequently impregnating the graft copolymerized thermoplastic resin beads with an easily volatilizable hydrocarbon or halogenated hydrocarbon blowing agent, the improvement comprising heating the aqueous medium to a temperature at which the vinyl aromatic monomer can be polymerized before adding the vinyl aromatic monomer and the polymerization catalyst thereto, and adding said vinyl aromatic monomer and said polymerization catalyst to the heated aqueous medium.

Claim 11

In a process for producing expandable thermoplastic graft copolymerized resin beads which consists essentially of suspending in an aqueous medium containing 0.01 to 5% by weight, based on water present in the aqueous medium, of a dispersing agent selected from the group consisting of polyvinyl alcohol, methyl cellulose, calcium phosphate, magnesium pyrophosphate and calcium carbonate, from 20 to 70% by weight of a random copolymer of propylene and ethylene containing 1 to 10% by weight of ethylene and 99 to 90% by weight propylene and 30 to 80% by weight of a vinyl aromatic monomer; adding a polymerization catalyst and polymerizing the vinyl aromatic monomer to form graft copolymerized thermoplastic resin beads and subsequently impregnating the graft copolymerized thermoplastic resin beads with an easily volatilizable hydrocarbon or halogenated hydrocarbon blowing agent, the improvement comprising heating the aqueous medium to a temperature at which the vinyl aromatic monomer can be polymerized before adding the vinyl aromatic monomer and the polymerization catalyst thereto, and adding said vinyl aromatic monomer and said polymerization catalyst to the heated aqueous medium.

Claim 12

The process of claim 8, wherein the polymerization is carried out in the further presence of a crosslinking agent.