STRETCH BLOW MOLDING MONOVINYLIDENE AROMATIC POLYMERS
According to the present invention there are provided improved rubber modified monovinylidene aromatic polymers having the specified relatively high molecular weight and the necessary rubber levels and particles. These improved resins are specially adapted and suited for use in stretch blow molding processes. They provide improved combinations of container neck strength and toughness, wall strength and stiffness and packaging efficiency. The present invention provides the makers of stretch blow molded containers with options for improved packaging cost and efficiency.
1 . A rubber modified monovinylidene aromatic polymer composition in the form of a stretch blow molded article, the composition comprising:
(A) a monovinylidene aromatic polymer a having a weight average molecular weight (Mw) of from about 190,000 to about 350,000 g/mol;
(B) from about 3.5 to about 10 percent by weight based on the weight of components (A), (B) and (C) of a grafted, cross-linked rubber polymer;
(C) optionally up to about 5 percent by weight based on the weight of components (A), (B) and (C) of a plasticizer; and
(D) optional non-polymeric additives and stabilizers.
2 . A composition according to claim 1 wherein the plasticizer is selected from the group of: one or more mineral oil, one or more non-mineral oil, and blends of one or more mineral oil with one or more non-mineral oil.
3 . A composition according to claim 1 wherein the Mw of the monovinylidene aromatic polymer is from at least about 215,000 to less than or equal to about 260,000 g/mol.
4 . A composition according to claim 1 wherein the monovinylidene aromatic polymer is polystyrene that has been mass, bulk or solution polymerized in the presence of at least one rubber polymer.
5 . A composition according to claim 1 wherein the rubber polymer is selected from the group consisting of 1,3-butadiene homopolymer rubbers, copolymers rubbers of 1,3-butadiene with one or more copolymerizable monomer and mixtures of two or more of these.
6 . A composition according to claim 1 consisting essentially of:
(A) monovinylidene aromatic polymer a having a weight average molecular weight (Mw) of from about 220,000 to about 260,000 g/mol;
(B) from about 4 to about 6 percent by weight based on the weight of components (A), (B) and (C) of a rubber polymer in the form of grafted, cross-linked particles having a volume average rubber particle size of from about 2 to about 5 microns;
(C) from about 3 to about 4 percent by weight based on the weight of components (A), (B) and (C) of a plasticizer; and
(D) optional non-polymeric additives and stabilizers.
7 . A rubber modified monovinylidene aromatic polymer composition according to claim 1 wherein the stretch blow molded article is a container stretch blow molded from an injection molded preform.
8 . A rubber modified monovinylidene aromatic polymer composition according to claim 1 wherein the stretch blow molded article is a container stretch blow molded from a compression molded preform.
9 . A rubber modified monovinylidene aromatic polymer composition according to claim 1 wherein the stretch blow molded article is a thermoformed article.
10 . A rubber modified monovinylidene aromatic polymer composition comprising:
(A) a monovinylidene aromatic copolymer a having a weight average molecular weight (Mw) of from about 215,000 to about 350,000 g/mol;
(B) from about 3.5 to about 40 percent by weight based on the weight of components (A), (B) and (C) of a rubber polymer in the form of grafted, cross-linked particles having a volume average rubber particle size of from about 1.5 to about 10 microns;
(C) optionally up to about 5 percent by weight based on the weight of components (A), (B) and (C) of a plasticizer; and
(D) optional non-polymeric additives and stabilizers.
11 . A rubber modified monovinylidene aromatic polymer composition according to claim 10 wherein the composition has an elongation at rupture value of from about 25 to about 70%.
12 . A rubber modified monovinylidene aromatic polymer composition according to claim 10 wherein the monovinylidene aromatic polymer has a weight average molecular weight (Mw) of from about 220,000 to about 350,000 g/mol.
13 . A rubber modified monovinylidene aromatic polymer composition according to claim 10 comprising from about 1.5 to about 5 percent by weight based on the weight of components (A), (B) and (C) of a plasticizer.
14 . A rubber modified monovinylidene aromatic polymer composition according to claim 10 comprising from about 3.5 to about 10 percent by weight rubber polymer.
15 . A composition according to claim 12 wherein the Mw of the monovinylidene aromatic polymer is from about 240,000 to about 300,000 g/mol.
16 . A composition according to claim 10 wherein the monovinylidene aromatic copolymer is polystyrene-acrylonitrile) that has been mass, bulk or solution polymerized in the presence of at least one rubber polymer.
17 . A composition according to claim 10 wherein the rubber polymer is selected from the group consisting of 1,3-butadiene homopolymer rubbers, copolymers rubbers of 1,3-butadiene with one or more copolymerizable monomer and mixtures of two or more of these.
18 . (canceled)
19 . A process for preparing a stretch blow molded article comprising the steps of
A. molding a preform from a monovinylidene aromatic polymer resin according to claim 10 ;
B. heating the preform;
C. stretching the preform in a stretch blow molding apparatus;
D. blowing the preform to the stretch blow molded article shape; and
E. cooling and ejection of the stretch blow molded article from the stretch blow molding apparatus.
20 . The process for preparing a stretch blow molded article according to claim 19 wherein the preform is injection molded.
21 . The process for preparing a stretch blow molded article according to claim 19 wherein the preform is compression molded.