Rubber modified polystyrene
AssigneeThe Dow Chemical Company
InventorsDavid Schrader, Mark E. Soderquist, Mark D. Heires
Life of this patent
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Abstract
High impact polystyrene resins are provided having a surprisingly good combination of toughness and gloss characteristics. Such resins contain small (i.e., 0.1 to 0.4 micron) capsule morphology rubber particles in combination with relatively small (i.e., 0.25 to 1 micron) entanglement morphology rubber particles. It has been found that such resins are capable of providing Izod impact strength values in the range of 2.5 to 3.5 ft-lb/in (133.4 to 186.7 J/m) and higher at an overall volume average rubber size of less than 0.4 micron with corresponding gloss values in excess of 90 percent.
Claims13
A method for the preparation of a rubber-modified monovinylidene aromatic polymer composition said composition comprising, on a total composition weight basis, from about 90 to about 55 weight percent of a rigid monovinylidene aromatic polymer matrix and from about 10 to about 45 weight percent of grafted and occluded 1,3-alkadiene-based rubber particles dispersed within said matrix wherein from about 25 to about 80 weight percent of said rubber particles have a capsule particle morphology and a volume average particle size of from 0.1 to 0.4 micron and from about 75 to about 20 weight percent of said particles have an entanglement particle morphology and a volume average particle size of from about 0.25 to about 1 micron, wherein said entanglement rubber particles contain, on an entanglement particle weight basis, less than 10 percent of particles having a particle diameter in excess of 1 micron;
- said composition having a total rubber content, stated on a 1,3-alkadiene weight basis, of from about 10 to about 25 weight percent and wherein the combined volume average particle size of the capsule morphology and entanglement morphology particles is less than 0.5 micron;
- said method comprising:
- a. dissolving from about 5 to about 30 parts by weight of a 1,3-alkadiene/monovinylidene aromatic block copolymer rubber in from about 95 to about 70 parts by weight of a monovinylidene aromatic monomer, said block copolymer rubber being one which has from about 15 to about 40 weight percent of monovinylidene aromatic monomer copolymerized therein;
- b. polymerizing the resulting rubber/monomer solution at a temperature of from about 50 to about 210.degree. C., in the presence of from 0 to about 1000 parts per million by weight of a polymerization initiator and from 0 to about 2000 parts per million by weight of a chain transfer agent and under agitation conditions sufficient to provide capsule morphology and entanglement morphology rubber particles in the above-specified size ranges;
- and
- c. thereafter recovering the resulting rubber-modified monovinylidene aromatic polymer product.
A rubber-modified monovinylidene aromatic polymer composition which comprises, on a total composition weight basis, from about 90 to about 55 weight percent of a rigid monovinylidene aromatic polymer matrix and, dispersed within said matrix, from about 10 to about 45 weight percent of grafted and occluded 1,3-alkadiene-based rubber particles, said particles being composed, on a total grafted/occluded rubber particle weight basis, of:
- a. from 25 to about 80 weight percent of rubber particles having a capsule morphology and a volume average particle size of from 0.1 to 0.4 micron;
- b. from about 75 to about 20 weight percent of rubber particles having an entanglement morphology and having a volume average particle size of from about 0.25 to 1 micron, wherein said entanglement rubber particles contain, on an entanglement particle weight basis, less than 10 percent of particles having a particle diameter in excess of 1 micron and the combined volume average particle size of the capsule morphology and entanglement particle morphology particles is less than 0.5 micron;
- and
- c. from about 1 to about 25 weight percent of rubber particles having a cellular rubber particle morphology and having a volume average particle size of from about 0.6 to about 1.2 micron.
Dependencies are inferred from the claim text.