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
2001-05-29
2003-03-18
Dawson, Robert (Department: 1712)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
C525S102000, C525S431000, C525S446000, C524S268000, C528S026000, C528S042000
Reexamination Certificate
active
06534594
ABSTRACT:
TECHNICAL FIELD
The present invention relates to an elastomer composition useful as an impact modifier and a thermoplastic resin composition excellent in impact resistance. More specifically, the invention relates to an elastomer composition comprising (a) a block copolymer containing a methacrylate polymer and a siloxane polymer and (b) a graft copolymer containing a polymer component whose glass transition temperature is lower than 25° C. and a polymer component whose glass transition temperature is at least 25° C., and to a thermoplastic resin composition comprising the elastomer composition and (c) a thermoplastic resin.
BACKGROUND ART
Generally, thermoplastic resins are used in various fields and attempts are made regarding methods of use in combination with other resins and the like when sufficient performance cannot be achieved by the uniform resin. Particularly, a polymer material with elastomer characteristics is used in combination therewith in most cases for improving impact resistance. The polymer material used for such purposes is referred to as an impact modifier.
There are proposed compositions obtained by combining, for example, a vinyl chloride resin with chlorinated polyethylene, ethylene-vinyl acetate copolymer, methyl methacrylate-butadiene-styrene copolymer (hereinafter referred to as MBS resin) acrylonitrile-butadiene-styrene copolymer (hereinafter referred to as ABS resin), butyl acrylate-methyl methacrylate copolymer or the like; a methacrylate resin with butyl acrylate-styrene-methyl methacrylate copolymer or the like; a polycarbonate resin with ABS resin, butyl acrylate-methyl methacrylate copolymer or the like; a poly(butylene terephthalate) resin with ABS resin, epoxy modified ethylene-propylene copolymer or the like, and many of these compositions are for industrial use. Among these impact modifiers, MBS resin, ABS resin and butyl acrylate-methyl methacrylate copolymer are copolymers obtained by graft copolymerizing a vinyl monomer (forming a shell) in the presence of cross-linked rubber particles (forming a core), which are called a core-shell graft copolymer based on the particle structure, and useful as an impact modifier. MBS resin and ABS resin obtained by copolymerizing butadiene have a problem with weatherability among these core-shell graft copolymers, because unsaturated double bond remains in the main chain of the polymer. Therefore, butyl acrylate-methyl methacrylate copolymer is selected very frequently when weatherability is required. It is pointed out, however, that these core-shell graft copolymers have problems with molding flowability because of the cross-linked structure though they are useful as an impact modifier.
Also it is known that a block copolymer obtained by combining a hard segment and a soft segment (rubber component) can be used by combining them with a thermoplastic resin. Examples of these block copolymers are styrene-butadiene copolymers, styrene-isoprene copolymers and hydrogenated copolymers thereof (referred to as a styrene-ethylene-butylene copolymer and a styrene-ethylene-propylene copolymer, respectively) and they are widely used. Generally, use of these block copolymers enables to obtain a composition having excellent balance in impact resistance, rigidity and molding flowability, but limits the kinds of combined thermoplastic resins to low polarity resins such as polystyrene resins, polyolefin resins and poly(phenylene ether) resins.
An object of the present invention is to provide an elastomer composition useful as an impact modifier and a thermoplastic resin composition having improved impact resistance.
DISCLOSURE OF INVENTION
The present invention was completed based on the findings by the inventors that an elastomer composition comprising (a) a block copolymer containing a methacrylate polymer and a siloxane polymer, and (b) a graft copolymer containing a polymer component whose glass transition temperature is lower than 25° C. and a polymer component whose glass transition temperature is at least 25° C., functions as an excellent impact modifier, surprisingly showing a higher improvement effect on impact resistance than when (a) or (b) is used alone, and that combination of the elastomer composition and a thermoplastic resin (c) leads to a thermoplastic resin composition excellent in impact resistance.
That is, the present invention relates to an elastomer composition comprising (a) a block copolymer containing a methacrylate polymer and a siloxane polymer and (b) a graft copolymer containing a polymer component whose glass transition temperature is lower than 25° C. and a polymer component whose glass transition temperature is at least 25° C.
The present invention also relates to a thermoplastic resin composition comprising the elastomer composition and (c) a thermoplastic resin.
BEST MODE FOR CARRYING OUT THE INVENTION
The block copolymer (a) useful in the present invention is a block copolymer having at least one of (A) a methacrylate polymer containing a methacrylic monomer as a main component and at least one of (B) a siloxane polymer containing a siloxane monomer as a main component, respectively. The component (A) functions to improve dispersability and interface adhesion with the thermoplastic resin, while the component (B) functions to improve impact resistance.
The above block copolymer (a) is at least one block copolymer selected from the group consisting of A-B type di-block copolymer, A-B-A type tri-block copolymer, B-A-B type tri-block copolymer and (A-B)
n
type multi-block copolymer. Among them, the A-B di-block copolymer, the A-B-A tri-block copolymer and a mixture thereof are preferable from the viewpoint of impact resistance.
The structure of the above block copolymer (a) may be linear, branched (star-shaped) or a mixed structure thereof. The structures of these block copolymer may be selected and used properly depending on necessary characteristics including processability or mechanical properties of the thermoplastic resin composition.
The number average molecular weight of the block copolymer (a) is not particularly limited, and is usually 30,000 to 500,000, preferably 50,000 to 400,000. It can be determined according to the processability required, since a small number average molecular weight tends to cause low viscosity and large number average molecular weight high viscosity.
The ratio of weight average molecular weight (Mw) to number average molecular weight (Mn) measured by gel permeation chromatography is not particularly limited, and is preferably at most 1.8, more preferably at most 1.5. When Mw/Mn is larger than 1.8, uniformity of the block copolymer tends to decrease.
The composition ratio of the methacrylic polymer block (A) and the siloxane polymer block (B) constituting the above block copolymer (a) is preferably 5 to 90% by weight of component (A) and 95 to 10% by weight of component (B), more preferably 10 to 80% by weight of component (A) and 90 to 20% by weight of component (B) and most preferably 20 to 50% by weight of component (A) and 80 to 50% by weight of component (B). When the component (A) is less than 5% by weight, compatibility with the thermoplastic resin tends to decrease. When the component (B) is less than 10% by weight, impact resistance of the thermoplastic resin tends to decrease. In order to impart transparency to the thermoplastic resin composition, the ratio of the component (A) and (B) may be selected in such a way that the refraction index of the block copolymer matches the refraction index of the thermoplastic resin to be combined.
The methacrylic polymer block (A) which constitutes the block copolymer (a) is a block obtained by polymerizing a monomer having a methacrylate ester as a main component, and a vinyl monomer copolymerizable therewith may be copolymerized within the range in which properties of the methacrylate ester polymer are not lost for the purpose of adjusting refraction index, glass transition temperature, compatibility with the thermoplastic resin and the like. The methacrylic polymer block (A) comprises, preferably, 50 t
Aoyama Taizo
Kimura Katsuhiko
Armstrong Westerman & Hattori, LLP
Dawson Robert
Kaneka Corporation
Zimmer Marc S
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