Processability improver for foam molding and vinyl chloride resin composition containing same

1. A processability improver for foam molding, comprising:

a (meth)acrylic polymer powder with a weight average molecular weight of 2,000,000 to 7,000,000,

wherein the (meth)acrylic polymer powder comprises 1 to 20% by weight of a (meth)acrylic polymer (A) with a weight average molecular weight of 10,000 to 300,000, and 80 to 99% by weight of a (meth)acrylic polymer (B) with a weight average molecular weight of greater than 2,000,000 to 7,000,000, and

the (meth)acrylic polymer powder comprises a primary particle having a multilayer structure, and the primary particle comprises an inner layer containing the (meth)acrylic polymer (A) and an outer layer containing the (meth)acrylic polymer (B).

2. The processability improver for foam molding according to claim 1 ,

wherein the (meth)acrylic polymer is obtained by emulsion polymerization of 75 to 100% by weight of methyl methacrylate, 0 to 25% by weight of a (meth)acrylic ester other than the methyl methacrylate, and 0 to 5% by weight of other monomers copolymerizable with the methyl methacrylate and the (meth)acrylic ester.

3. The processability improver for foam molding according to claim 2 ,

wherein the (meth)acrylic polymer (B) is obtained by emulsion polymerization of a monomer mixture (B), the monomer mixture (B) comprising 75 to 100% by weight of methyl methacrylate, 0 to 25% by weight of a (meth)acrylic ester other than the methyl methacrylate, and 0 to 5% by weight of other monomers copolymerizable with the methyl methacrylate and the (meth)acrylic ester.

4. The processability improver for foam molding according to claim 2 ,

wherein the (meth)acrylic polymer (B) is obtained by emulsion polymerization of a monomer mixture (B), the monomer mixture (B) comprising 75 to 99.999999% by weight of methyl methacrylate, 0 to 25% by weight of a (meth)acrylic ester other than the methyl methacrylate, and 0.000001 to 0.01% by weight (0.01 to 100 ppm by weight) of a multifunctional monomer.

5. The processability improver for foam molding according to claim 2 ,

wherein the (meth)acrylic polymer (A) is obtained by emulsion polymerization of a monomer mixture (A), the monomer mixture (A) comprising 10 to 100% by weight of methyl methacrylate, 0 to 90% by weight of a (meth)acrylic ester other than the methyl methacrylate, and 0 to 5% by weight of other monomers copolymerizable with the methyl methacrylate and the (meth)acrylic ester.

6. The processability improver for foam molding according to claim 2 ,

which is obtained by emulsion polymerization of 80 to 99 parts by weight of the monomer mixture (B) in the presence of a latex of the (meth)acrylic polymer (A) obtained by emulsion polymerization of 1 to 20 parts by weight of the monomer mixture (A).

7. The processability improver for foam molding according to claim 6 ,

wherein an emulsifier to be used in the emulsion polymerization is one or more salts selected from the group consisting of alkylbenzene sulfonates, alkyldiphenyl ether disulfonates and alkyl sarcosinates.

8. The processability improver for foam molding according to claim 6 , further comprising

0.2 to 4.0% by weight of the emulsifier based on 100% by weight of the processability improver for foam molding.

9. The processability improver for foam molding according to claim 6 ,

wherein the (meth)acrylic polymer powder has a volume average particle diameter of 50 to 300 μm, and

a particle in the powder is a porous aggregate formed by fusion sticking of primary particles having a volume average primary particle diameter of 0.12 to 0.70 μm in an immature-melt state at a position contacting with each other.

10. The processability improver for foam molding according to claim 9 ,

wherein the (meth)acrylic polymer powder is obtained by spray-drying a polymer latex obtained by the emulsion polymerization.

11. A vinyl chloride resin composition, comprising:

100 parts by weight of a vinyl chloride resin; and

1 to 30 parts by weight of the processability improver for foam molding comprising: a (meth)acrylic polymer powder with a weight average molecular weight of 2,000,000 to 7,000,000, wherein the (meth)acrylic polymer powder comprises 1 to 20% by weight of a (meth)acrylic polymer (A) with a weight average molecular weight of 10,000 to 300,000, and 80 to 99% by weight of a (meth)acrylic polymer (B) with a weight average molecular weight of greater than 2,000,000 to 7,000,000, and the (meth)acrylic polymer powder comprises a primary particle having a multilayer structure, and the primary particle comprises an inner layer containing the (meth)acrylic polymer (A) and an outer layer containing the (meth)acrylic polymer (B).