High-impact polystyrene and process for the production thereof

Claim 2

A high impact polystyrene composition with improved physical properties, comprising a blend of: a. from about 50 to 85% by weight of a diene rubber-modified polystyrene graft copolymer, produced by a mass-suspension polymerization process, having a small rubber particle size S of from about 0.2 to 0.9 microns and a superstrate to substrate ratio of from about 65-125:100; and, b. from about 15 to 50% by weight of a diene rubber-modified polystyrene graft copolymer, produced by a mass-suspension polymerization process, having a larger rubber particle size L of at least about 0.9 microns and a superstrate to substrate ratio of from about 140-180:100, L being at least 1.5 times S.

Claim 3

The high-impact polystyrene composition of claim 1, wherein said polystyrene graft copolymer having said small rubber particle size S has a rubber particle size of from about 0.5 to 0.9 microns.

Claim 4

The high-impact polystyrene composition of claim 1, wherein said polystyrene graft copolymer having said small rubber particle size S has a rubber particle size of about 0.6 microns.

Claim 5

The high-impact polystyrene composition of claim 1, wherein said polystyrene graft copolymer having said larger rubber particle size L has a rubber particle size of from about 2 to 5 microns.

Claim 6

The high-impact polystyrene composition of claim 1, wherein said polystyrene graft copolymer having said larger rubber particle size L has a rubber particle size of 5 microns.

Claim 7

The high-impact polystyrene composition of claim 1, wherein the rubber in each of said graft copolymers comprises polybutadiene.

Claim 8

The high-impact polystyrene composition of claim 1, wherein said composition has a total rubber content of from about 2% to 12% by weight of said composition.

Claim 9

The high-impact polystyrene composition of claim 1, wherein said composition has a total rubber content of from about 5.6% to about 10.5% by weight of said composition.

Claim 10

The high-impact polystyrene composition of claim 1, wherein said graft copolymer having said small rubber particle size S comprises from about 65 to 85% by weight of said composition, and said graft copolymer having said larger rubber particle size L comprises from about 15 to 35% by weight of said composition.

Claim 11

The high-impact polystyrene composition of claim 1, wherein said blend further comprises crystal polystyrene.

Claim 12

A high-impact polystyrene composition with improved physical properties, comprising a blend of: a. from about 50 to 85% by weight of a diene rubber-modified polystyrene graft copolymer, produced by a mass-suspension polymerization process, having a small rubber particle size S of from about 0.5 to 0.9 microns and a superstrate to substrate ratio of from about 65-125:100; and, b. from about 15 to 50% by weight of a diene rubber-modified polystyrene graft copolymer produced by a mass-suspension polymerization process, having a larger rubber particle size L of from about 2 to 5 microns and a superstrate to substrate ratio of from about 140-180:100, said composition having a total rubber content of from about 2% to 12% by weight.

Claim 13

A high-impact polystyrene composition with improved physical properties, comprising a blend of: a. from about 50 to 85% by weight of a diene rubber-modified polystyrene graft copolymer, produced by a mass-suspension polymerization process, having a small rubber particle size S of from about 0.5 to 0.9 microns and a superstrate to substrate ratio of from about 65-125:100; and, b. from about 15 to 50% by weight of a diene rubber-modified polystyrene graft copolymer produced by a mass-suspension polymerization process, having a larger rubber particle size L of from about 2 to 5 microns and a superstrate to substrate ratio of from about 140-180:100, said composition having a total rubber content of from about 2% to 12% by weight.

Claim 14

The high-impact polystyrene composition of claim 11, wherein said blend further comprises crystal polystyrene.

Claim 15

The high-impact polystyrene composition of claim 11, wherein the rubber in each of said graft copolymers comprises polybutadiene.

Claim 16

The high-impact polystyrene composition of claim 11, wherein said composition has a total rubber content of from about 5.6% to about 10.5% by weight of said composition.

Claim 17

The high-impact polystyrene composition of claim 11, wherein said graft copolymer having said small rubber particle size S comprises from about 65 to 85% by weight of said composition, and said graft copolymer having said larger rubber particle size L comprises from about 15 to 35% by weight of said composition.

Claim 18

A process for preparing a polystyrene composition having improved physical properties, comprising the steps of: a. preparing a diene rubber-modified polystyrene graft copolymer having a small rubber particle size S of from about 0.2 to 0.9 microns and a superstrate to substrate ratio of from about 65-125:100 by a mass-suspension polymerization process; b. preparing a diene rubber-modified polystyrene graft copolymer having a larger rubber particle size L of at least about 0.9 microns and a superstrate to substrate ratio of from about 140-180:100, L being at least 1.5 times S, by a mass-suspension polymerization process; and, c. mechanically blending from about 50 to 85 parts by weight of said graft copolymer having said small rubber particle size with from about 15 to 85 parts by weight of said graft copolymer having said larger rubber particle size.

Claim 19

A process for preparing a polystyrene composition having improved physical properties, comprising the steps of: a. preparing a diene rubber-modified polystyrene graft copolymer having a small rubber particle size S of from about 0.2 to 0.9 microns and a superstrate to substrate ratio of from about 65-125:100 by a mass-suspension polymerization process; b. preparing a diene rubber-modified polystyrene graft copolymer having a larger rubber particle size L of at least about 0.9 microns and a superstrate to substrate ratio of from about 140-180:100, L being at least 1.5 times S, by a mass-suspension polymerization process; and, c. mechanically blending from about 50 to 85 parts by weight of said graft copolymer having said small rubber particle size with from about 15 to 85 parts by weight of said graft copolymer having said larger rubber particle size.

Claim 20

The process of claim 16, further comprising the step of mechanically blending crystal polystyrene with said graft copolymers in an amount sufficient to produce a polystyrene composition having a total rubber content of between about 2 to 12% by weight.

Claim 21

The process of claim 16, further comprising the step of mechanically blending crystal polystyrene with said graft copolymers in an amount sufficient to produce a polystyrene composition having a total rubber content of between about 5.6% to about 10.5% by weight.

Claim 22

The process of claim 16, wherein said polystyrene graft copolymer having said small rubber particle size S has a rubber particle size of from about 0.5 to 0.9 microns.

Claim 23

The process of claim 16, wherein said polystyrene graft copolymer having said small rubber particle size S has a rubber particle size of about 0.6 microns.

Claim 24

The process of claim 16, wherein said polystyrene graft copolymer having said larger rubber particle size L has a rubber particle size of from about 2 to 5 microns.

Claim 25

The process of claim 16, wherein said polystyrene graft copolymer having said larger rubber particle size L has a rubber particle size of 5 microns.

Claim 26

The process of claim 16, wherein the rubber in each of said graft copolymers comprises polybutadiene.

Claim 27

The process of claim 16, wherein from about 65 to 85 parts by weight of said graft copolymer having said small rubber particle size is mechanically blended with from about 15 to 35 parts by weight of said graft copolymer having said larger rubber particle size.