Rubber modified monovinylidene aromatic polymers and fabricated articles prepared therefrom
View Patent ↗The present invention is a rubber modified monovinylidene aromatic polymer composition which can be used in conventional thermoforming or other highly orienting forming or shaping processes to produce tough, cost effective, transparent containers or other packaging materials.
1. A film having a total thickness of up to about 0.25 mm produced from a rubber modified monovinylidene aromatic polymer composition comprising:
a) a monovinylidene aromatic polymer matrix;
b) from about 1.5 to about 8 percent by weight rubber (based on total diene content in the composition) dispersed as crosslinked rubber particles having primarily a core/shell morphology and a volume average particle size of from about 0.1 to about 1.5 microns; where from about 40 to about 90 volume percent of the rubber particles have diameters of less than about 0.4 microns and from about 10 to about 60 volume percent of the rubber particles have diameters between about 0.4 and about 2.5 microns and the rubber is a blend comprising a conjugated diene block copolymer rubber comprising from about 15 to about 60 percent by weight monovinylidene aromatic monomer block with from about 2 to about 25 weight percent of conjugated diene homopolymer rubber based on the total weight of rubber in the composition; and
c) optionally from 0.1 to 4 weight percent mineral oil.
2. A film according to claim 1 having a total thickness of from 0.012 to 0.20 mm.
3. A film according to claim 1 wherein the rubber modified monovinylidene aromatic polymer composition comprises from about 2 to about 6 percent by weight rubber.
4. A film according to claim 1 wherein the rubber modified monovinylidene aromatic polymer composition, at least about 70 percent of the rubber particles have core/shell morphology and the volume average rubber particle size is from about 0.2 to about 1 micron.
5. A film according to claim 1 where, in the rubber modified monovinylidene aromatic polymer composition, from about 50 to about 80 volume percent of the rubber particles have diameters of less than about 0.4 microns and from about 20 to 50 volume percent of the rubber particles have diameters of from about 0.4 to about 1.2 microns.
6. A film according to claim 1 where, in the rubber modified monovinylidene aromatic polymer composition, the monovinylidene aromatic matrix polymer is polystyrene.
7. A film according to claim 1 where, in the rubber modified monovinylidene aromatic polymer composition, at least 90 percent of the total rubber particles have core/shell morphology and the volume average particle size of the rubber particles is from 0.2 to 0.6 micron.