Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Reexamination Certificate
2000-03-30
2003-03-04
Mullis, Jeffrey (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
C083S085000
Reexamination Certificate
active
06528583
ABSTRACT:
The invention concerns a thermoplastic molding composition and more particularly a composition, which contains grafted rubber having a bimodal size distribution.
SUMMARY OF THE INVENTION
A thermoplastic molding composition which features improved dimensional stability and low gloss is disclosed. The composition which contains (A) a first grafted rubber having a weight average particle size of 0.05 to 0.30 microns, (B) a second grafted rubber having a weight average particle size of 0.31 to 1.00 microns, (C) vinyl chloride (co) polymer, and, optionally, (D) styrene copolymer is especially suitable for extruding profiles. In a preferred embodiment, at least one of the grafted rubbers is characterized in that its substrate features a core-shell structure, wherein the core contain at least one crosslinked vinylaromatic polymer, and the shell is elastomeric.
BACKGROUND OF THE INVENTION
It has long been known that thermoplastically processable styrene/acrylonitrile copolymers (SAN) may be imparted improved impact properties by the incorporation of rubbers. In ABS polymers, diene polymers are used as the rubbers for toughening, most notably at low temperatures; however, the relatively poor weathering and aging resistance make these materials less favored in more demanding applications. In some such applications, use has successfully been made of crosslinked acrylic acid ester polymers; these are the well-known ASA copolymers. Such copolymers have been described in U.S. Pat. No. 3,055,859 and in German Patents 1,260,135 and 1,911,882. Accordingly, the preferably crosslinked, rubbery acrylic acid ester polymer which serves as the grafting base (substrate) is first prepared by emulsion polymerization and the latex thus prepared is then grafted, preferably by emulsion, with a mixture of styrene and acrylonitrile. The art thus has long-recognized that improved impact strength, notched Izod and greater hardness are associated with ASA products which have, as a grafting base, a polyacrylate latex having a mean particle diameter of about 150 to 800 nm and a narrow particle size distribution. Also, noted is U.S. Pat. No. 4,224,419 which disclosed an ASA based composition that contains two different graft copolymers of SAN onto crosslinked acrylates, and a hard copolymeric SAN component. U.S. Pat. No. 5,157,076 is noted for its disclosure of a thermoplastic elastomer having improved abrasion resistance, the composition containing a (co)polymer of vinyl chloride and ASA as an impact modifier.
The art refers to “hard” and “soft” segments in terms of the relative position of their glass transition temperature vis a vis room temperature. “Hard” means T
g
above room temperature and “soft” means below room temperature. Multi-phase structured emulsion copolymers, including hard-soft and hard morphologies have been disclosed in EP 534,212 and in the documents referenced therein. Accordingly, graft copolymers having a hard core of polystyrene, a first butyl acrylate shell and an outer SAN shell are known. Significantly, the '212 document disclosed a monomodal system containing particles having a styrene core and measuring less than 0.2 microns. Also presently relevant is U.S. Pat. No. 5,932,655 that disclosed grafted rubbers having core/shell structures, the rubbers having bimodal size distribution, of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
The inventive thermoplastic composition comprises:
(A) a first grafted rubber having a weight average particle size of 0.05 to 0.30, preferably 0.10 to 0.25 microns, and
(B) a second grafted rubber having a weight average particle size of 0.31 to 1.00, preferably 0.32 to 0.60 microns, and
(C) a (co)polymer of vinyl chloride, and optionally
(D) a styrene copolymer,
wherein rubber content is 15 to 25, preferably 17 to 23 percent relative to the total weight of (A), (B), (C) and (D).
Preferably the total amount of (A) and (B) is about 25 to 50 percent, the amount of (C) is about 25 to 75 percent and (D) may be present in a positive amount of up to 20 percent, the percents being relative to the total of A, B, C and D. Components A and B may be present at a weight ratio of 9/1 to 1/9 therebetween.
The grafted rubber, in both component (A) and (B), contains a grafted phase and a substrate, the weight ratio therebetween preferably ranges from 0.3 to 1, preferably 0.5 to 0.9. In the preferred embodiments, the substrate of at least one of (A) and (B) has a core-shell structure. The grafted phase contains a copolymer of at least one monomer selected from a first group consisting of styrene, &agr;-methyl styrene, ring-halogenated styrene and ring-alkylated styrene and at least one monomer selected from a second group consisting of (meth)acrylonitrile and methyl methacrylate. The weight ratio between said monomer(s) of said first group to said monomer(s) of said second group ranges between 80:20 to about 65:35.
The substrate of (A) and/or (B) comprises the crosslinked polymerization product of at least one member selected from the group consisting of C
2-8
-alkyl acrylate, vinyl acetate, hydrogenated diene and diene. In a preferred embodiment, the substrate comprises a core/shell structure in at least one of (A) and (B). In these embodiments, the substrate contains about 2 to 40, preferably 5 to 30% relative to the weight of the substrate, of a core containing at least one, preferably crosslinked, vinylaromatic polymer, and about 60 to 98, preferably 70 to 95% relative to the weight of the substrate, of a shell containing the crosslinked polymerization product of at least one member selected from the group consisting of C
2-8
-alkyl acrylate, vinyl acetate, hydrogenated diene and diene.
The (co)polymer of vinyl chloride, component (C) includes polyvinyl chloride homopolymer and vinyl chloride copolymers of at least one of: esters of vinyl alcohol containing 1 to 20 carbon atoms in the acid portion used to make the ester such as vinyl stearate, vinyl epoxystearate, vinyl benzoate, and vinyl acetate; acrylates and methacrylates containing 1 to 20, preferably 2 to 10 carbon atoms in the alcohol group that is used to make the ester such as ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate; acrylonitrile, methacrylonitrile, and derivatives thereof; esters of unsaturated dicarboxylic acids such as maleates, fumarates, and itaconates; carbon monoxide; olefins containing 2 to 20, preferably 2 to 6 carbon atoms such as ethylene, propylene and isobutylene; diolefins containing 4 to 20, preferably 4 to 8 carbon atoms such as butadiene, isoprene and halogen derivatives thereof such as chloroprene; alkyl vinyl ethers such as vinyl isobutyl ether and cetyl vinyl ether; vinyl aromatics containing 8 to 30, preferably 8 to 16 carbon atoms such as styrene, alpha-methyl styrene, and halogenated derivatives thereof such as para-chlorostyrene; vinyl organometallics such as monovinyldiethyl tin laurate, trialkyl tin acrylate and methacrylate, trialkylvinyl tin, unsaturated trihydrocarbon phosphate esters, vinyl phosphonic acid, N-chloroph-thalimide, poly-N-allyl substituted aminotriazine, N-substituted maleimide, vinyl pyridine, vinyl imidazole; alkenyl halides such as vinylidene chloride, vinyl bromide and fluoride, halogenated propenes, vinylidenechloro-fluoride, dichloroethylene; allyl clycidyl ether; allyl esters of hydroxy-alkanoic acids; dimethyl dicrotonate; chloroalydene; isopropenyl chloride; tetrafluoroethylene; norbornene acrylate; (cyanoethoxy) ethyl acrylate; and isopropenyl acetate.
PVC resins useful in the practice of this invention include copolymers of vinyl chloride containing up to 90 and preferably up to 70, and especially 30 to 60 weight percent of copolymerizable monomers. Methods for preparing the PVC polymers are also well known and such resins are widely available commercially in a variety of molding and extrusion grades.
The optional styrene copolymer, component (D) contains a copolymer of at least one monomer selected from a first group consisting of styrene, &agr;-methyl styrene, ring-halogenated styrene and ring-alkylated styrene and at l
Chen Chuan-Ju
Gage Marc E.
Bayer Corporation
Gil Joseph C.
Mullis Jeffrey
Preis Aron
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