Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Polymers from only ethylenic monomers or processes of...
Reexamination Certificate
2000-03-28
2001-10-30
Yoon, Tae H. (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Polymers from only ethylenic monomers or processes of...
C526S216000, C526S920000, C524S504000, C525S069000, C525S080000, C525S084000
Reexamination Certificate
active
06310148
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a rubber modified styrene resin composition in which a grafted rubbery polymer is dispersed in a styrene matrix resin. More particularly, the present invention relates to a styrene resin composition that is remarkably excellent in impact resistance, in particular surface impact strength, and in addition in luster and rigidity and to a method for producing the same.
BACKGROUND ART
Rubber modified styrene resins such as HIPS (high impact polystyrene) are now widely used as thermoplastic resins having excellent impact resistance. Such rubber modified styrene resins represented by HIPS generally have a dispersed rubber particle diameter as large as 1 &mgr;m or more and as a result they have a defect that their molded products have a poor luster.
Accordingly, development of resins that have both acceptable luster and the impacts resistance of HIPS has been promoted. For example, Japanese Unexamined Patent Application, First Publication No. Hei 5-1122 discloses a technology of reducing the particle diameter of grafted rubber particles in HIPS to 0.5 to 1.0 micron to impart both luster and impact resistance thereto.
Also, Japanese Unexamined Patent Application, First Publication No. Hei 4-180907 discloses a technology of providing a resin composition that has excellent transparency, rigidity and impact resistance by graft polymerizing styrene and methyl methacrylate with a rubber component.
However, in the technology described in Japanese Unexamined Patent Application, First Publication No. Hei 5-1122, although a reduction in rubber particle diameter increases the luster to some extent, the reduction in particle diameter is accompanied by a serious decrease in impact strength, so that in order to obtain products having a decreased rubber particle diameter and high impact strength, the rubber content in the product must be higher than in common HIPS, and as a result rigidity, which is one of the characteristic features of styrene resins, is decreased. Further, use of more rubber component with smaller particle diameters has a problem regarding impact strength that the resultant composition is low in practically important surface impact strength but is high in notched Izod impact strength.
Also, the resin composition described in Japanese Unexamined Patent Application, First Publication No. Hei 4-180907 has transparency so that it has a good luster but in order to impart transparency, the particle diameter must be decreased further and as a result the resultant composition has an insufficient impact strength, thereby finding only limited applications.
DISCLOSURE OF INVENTION
A problem that the present invention is to solve is to provide a styrene resin composition that is excellent in luster, rigidity and surface impact strength.
Under the circumstances, the present inventors have carried out intensive studies and as a result have found that graft polymerization of a styrene monomer and a (meth)acrylic acid alkyl ester with a mixed rubbery polymer containing two specified rubber components dissolved therein, reduction of the median diameter on a volume basis of dispersed rubber particles, and increase in the degree of crosslinking thereof result in a composition for a molded product having excellent luster and yet having a remarkably increased rigidity and impact strength for practical use, thereby completing the present invention.
That is, the present invention relates to a styrene resin composition having a copolymer (A) of a styrene monomer and an acrylic monomer as a matrix phase and a rubber particle (B) comprising a diene rubbery polymer with which a styrene monomer and an acrylic monomer are graft copolymerized as a dispersed particle,
wherein the copolymer (A) is a copolymer of the styrene monomer and the (meth)acrylic acid alkyl ester in a proportion of the former/latter=95/5 to 50/50 on a weight basis, and
wherein the rubber particle (B) has a median diameter in the range of 0.5 to 0.9 &mgr;m on a volume basis and a value of (toluene-insoluble solids content at 25° C./toluene swelling index at 25° C.) is in the range of 1.2 to 2.5; and to a method for producing a styrene resin comprising continuously bulk polymerizing, in a continuous bulk polymerization line having incorporated therein a tubular reactor with a plurality of mixing elements that have no mobile portion fixed inside thereof, a mixed solution of
(b1) a homopolymer of a diene monomer, or (b2) a copolymer of a styrene monomer and a diene monomer, the copolymer having 15% or less on a weight basis of the styrene structure units, and (b3) a copolymer of a styrene monomer and a diene monomer, the copolymer having 20 to 50% on a weight basis of the styrene structure units,
(a1) a styrene monomer, and
(a2) a (meth)acrylic acid alkyl ester.
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patent: 0 471 550 A2 (1992-02-01), None
patent: 4-180907 (1992-06-01), None
patent: 5-1122 (1993-01-01), None
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patent: 6-16744 (1994-01-01), None
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patent: WO 96/24633 (1996-08-01), None
Fujihira Mamoru
Matsuo Jiro
Morita Tsuyoshi
Armstrong Westerman Hattori McLeland & Naughton LLP
Dainippon Ink And Chemicals, Ltd.
Yoon Tae H.
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