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
2002-08-26
2004-12-28
Teskin, Fred (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
C525S098000, C525S316000
Reexamination Certificate
active
06835781
ABSTRACT:
TECHNICAL FIELD
This invention relates to a novel block copolymer rubber, a modifier for resin comprising the block copolymer rubber as an effective ingredient, a resin composition comprising the modifier for resin, and a process for producing the resin composition.
BACKGROUND ART
High-impact polystyrene resin (HIPS) is a modified polystyrene resin prepared by incorporating a polymer rubber such as a conjugated diene copolymer rubber as a modifier for resin in a polystyrene resin having poor impact resistance to remedy this deficiency. HIPS has good impact resistance, rigidity and processability and therefore it is widely used for electric appliances, business machines, packaging containers, miscellaneous goods and other articles.
In general, when a rubbery modifier for resin is incorporated in polystyrene resin, luster inherently possessed by the polystyrene resin tends to be deteriorated. To minimize deterioration of luster, some proposals have been made. For example, Japanese Examined Patent Publication (JP-B) No. S48-18594 (GB 1,230,507) discloses a method using a modifier for resin, comprising a butadiene-styrene block copolymer containing butadiene units having a vinyl bond content of 5 to 25% by weight. However, a resin composition made by using this modifier has a problem such that the deterioration of luster cannot be reduced to the desired extent and the luster varies within a shaped article. JP-B S60-57443 (U.S. Pat. No. 4,282,334) discloses a process for producing an impact-resistant polystyrene resin by a specific polymerization procedure using a butadiene-styrene block copolymer containing 20 to 55% by weight of styrene as a rubbery modifier. However, a resin composition obtained by this process has a problem such that the impact resistance is insufficient and, when the resin composition is injection-molded, the luster of the resulting molded article varies within the molded article.
Japanese Unexamined Patent Publication (JP-A) No. H6-220141 discloses a method using a modifier for resin, comprising an aromatic vinyl-conjugated diene block copolymer rubber having a vinyl bond content of at least 40% in the conjugated diene units and a molecular weight of 30,000 to 250,000. JP-A S57-30712 and JP-A S57-30714 disclose a method using a modifier for resin, comprising a styrene-butadiene random copolymer having a styrene content of 3 to 30% by weight and a vinyl bond content of at least 60% in the butadiene units. However, the former method has a problem such that the impact resistance of the resulting resin composition is insufficient and the luster thereof is greatly reduced. The latter method has a problem such that, when the resin composition is injection-molded, the luster of the resulting molded article is insufficient and greatly varies within the molded article, and, when a heat load is imposed on the molded article, the luster is greatly reduced.
DISCLOSURE OF THE INVENTION
A primary object of the present invention is to provide an impact-resistant aromatic vinyl resin composition having good impact resistance and luster and especially characterized in that the luster is reduced only to a minor extent even in a high-temperature environment and varies to a minimized extent within a shaped article.
Another object of the present invention is to provide a modifier for resin, used for the production of the above-mentioned impact-resistant aromatic vinyl resin composition.
To achieve the above-mentioned objects, the present inventors made extensive researches, and found that a modifier for resin, comprising an aromatic vinyl-conjugated diene block copolymer rubber having a high vinyl bond content in the conjugated diene monomer units, comprising a specific amount of aromatic vinyl monomer units with a high blocked ratio, and having a specific number average molecular weight gives a resin composition having a well-balanced luster and impact resistance, and further found that the aromatic vinyl-conjugated diene block copolymer rubber is not described in a literature and is novel. Based on these findings, the present invention has been completed.
Thus, in a first aspect of the present invention, there is provided an aromatic vinyl-conjugated diene block copolymer rubber comprising 50 to 75% by weight of conjugated diene monomer units and 25 to 50% by weight of aromatic vinyl monomer units, wherein the content of vinyl bond in the conjugated diene monomer units is at least 50% by weight, the ratio of blocked aromatic vinyl is at least 70% and the number average molecular weight of the copolymer rubber is in the range of 280,000 to 1,000,000.
In a second aspect of the present invention, there is provided a modifier for resin which comprises the above-mentioned block copolymer rubber as an effective ingredient.
In a third aspect of the present invention, there is provided a resin composition comprising 2 to 25% by weight of the above-mentioned block copolymer rubber and 98 to 75% by weight of a resin.
In a fourth aspect of the present invention, there is provided a process for producing a resin composition comprising polymerizing a monomer for forming a resin in the presence of the above-mentioned block copolymer rubber.
BEST MODE FOR CARRYING OUT THE INVENTION
[Block Copolymer Rubber]
The block copolymer rubber of the present invention comprises 50 to 75% by weight of conjugated diene monomer units and 25 to 50% by weight of aromatic vinyl monomer units, wherein the content of a vinyl bond in the conjugated diene monomer units is at least 50% by weight, the ratio of blocked aromatic vinyl is at least 70% and the number average molecular weight of the block copolymer rubber is in the range of 280,000 to 1,000,000.
Conjugated diene monomers used for the production of the above-mentioned block copolymer rubber are not particularly limited, and include, for example, 1,3-butadiene, 2-methyl-1,3-butadiene (isoprene), 2,3-dimethyl-1,3-butadiene and 1,3-pentadiene. These conjugated diene monomers may be used either alone or as a combination of at least two thereof. Of these, 1,3-butadiene and2-methyl-1,3-butadiene are preferable. 1,3-butadiene is especially preferable.
The content of the conjugated diene monomer units in the block copolymer rubber is such that the lower limit thereof is 50% by weight and preferably 55% by weight, and the upper limit thereof is 75%, preferably 73% by weight and more preferably 65% by weight. When the content of the conjugated diene monomer units is too small, the luster becomes poor. In contrast, when the content of the conjugated diene monomer units is too large, the impact resistance becomes poor.
The content of vinyl bond in the conjugated diene monomer units is such that the lower limit thereof is 50% by weight and preferably 55% by weight, and the upper limit thereof is preferably 90% by weight and more preferably 80% by weight. When the vinyl bond content is too small, the luster tends to be deteriorated, and the luster of an injection-molded article is liable to vary within a molded article. In contrast, when the luster is too large, the impact resistance tends to be reduced. By the term “vinyl bond content” herein used is meant both of the content of 1,2-vinyl bond and the content of 3,4-vinyl bond in the conjugated diene monomer units. Either or both of 1,2-vinyl bond and 3,4-vinyl bond may be present in the conjugated diene monomer units.
Aromatic vinyl monomers used for the production of the above-mentioned block copolymer rubber include, for example, styrene, 2-methylstyrene, 3-methylstyrene, 4-methylstyrene, 2,4-diisopropylstyrene, 2,4-dimethylstyrene, 4-t-butylstyrene and 5-t-butyl-2-methylstyrene. Of these, styrene is preferable.
The content of the aromatic vinyl monomer units in the block copolymer rubber is such that the lower limit thereof Is 25% by weight, preferably 27% by weight and more preferably 35% by weight, and the upper limit thereof is 50% and preferably 45% by weight. When the content of the aromatic vinyl monomer units is too small, the luster is poor. In contrast, when the content of aromatic vinyl monom
Kondou Katsuhito
Matsuda Hiroaki
Toyoshima Tetsuya
Birch & Stewart Kolasch & Birch, LLP
Teskin Fred
Zeon Corporation
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