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
2001-11-28
2003-10-21
Nutter, Nathan M. (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...
C525S216000, C525S222000, C525S232000, C525S240000
Reexamination Certificate
active
06635713
ABSTRACT:
TECHNICAL FIELD
This invention relates to a rubber composition used as an effective ingredient of a resin modifier, a resin modifier comprising the rubber composition, and a resin composition comprising the resin modifier.
BACKGROUND ART
A high-impact polystyrene resin (HIPS) is a modified resin made by incorporating a rubbery polymer such as a conjugated diene copolymer as a resin modifier in a polystyrene resin. The high-polystyrene resin has good impact resistance, gloss, rigidity and processability and is inexpensive, and thus, is widely used for electrical equipments, office appliances, packaging containers and miscellaneous good.
Among high-impact polystyrene resins, most of those exhibiting a higher impact strength have poor gloss. As a high-impact polystyrene resin having improved gloss, high-impact polystyrene resins having incorporated therein a styrene-butadiene block copolymer as a resin modifier have been proposed, for example, in Japanese Examined Patent Publication No. S48-18594 and ibid. S60-57443. These proposed high-impact polystyrene resins have a problem such that their use is limited because of poor impact resistance.
As methods for improving impact strength without deterioration of gloss, a method of using as a resin modifier a rubber composition comprising polybutadiene having a cis-1,4-bond content of 25 to 40% by weight, and a styrene-butadiene block copolymer, both of which are prepared by polymerization using an organic alkali metal, has been proposed, for example, in Unexamined Japanese Patent Publication No. H2-34611 and ibid. H2-34612. Further, it is taught in these patent publications that, when the polybutadiene is subjected to coupling, impact strength is further improved. However, these high-impact polystyrene resins are still to be poor in impact strength or, when the impact strength is highly improved, they become poor in gloss. Further, a problem arises in that the gloss of high-impact polystyrene resins tends to be reduced in a high-temperature environment.
DISCLOSURE OF THE INVENTION
An object of the present invention is to provide an impact-resistant aromatic vinyl resin composition having well balanced impact resistance and gloss and being less apt to deteriorate in gloss in a high-temperature environment.
Another object of the present invention is to provide a rubber composition used as an effective ingredient in a resin modifier capable of providing the above-mentioned impact-resistant aromatic vinyl resin composition.
The present inventors made extensive research to develop an impact-resistant aromatic vinyl resin composition having well balanced impact resistance and gloss and being less apt to deteriorate in gloss in a high-temperature environment, and found that an impact-resistant aromatic vinyl resin having satisfactory characteristics can be obtained from a rubber composition comprising (A) a specific amount of a conjugated diene polymer selected from (A1) a conjugated diene polymer having a specific vinyl bond content and (A2) a conjugated diene polymer having a specific vinyl bond content in the conjugated diene monomer units and a specific coupling ratio, and (B) an aromatic vinyl-conjugated diene copolymer having a specific aromatic vinyl monomer unit content.
Thus, in one aspect of the present invention, there is provided a rubber composition comprising (A) 2% to 40% by weight of a conjugated diene polymer selected from (A1) a conjugated diene polymer having a vinyl bond content of at least 60% by weight in the conjugated diene monomer units and (A2) a conjugated diene polymer having a vinyl bond content of at least 30% by weight in the conjugated diene monomer units and a coupling ratio of at least 75% by weight, and (B) 98% to 60% by weight of an aromatic vinyl-conjugated diene copolymer having an aromatic vinyl monomer unit content of 25% to 50% by weight.
In another aspect of the present invention, there is provided a resin modifier comprising as an effective ingredient the above-mentioned rubber composition.
In still another aspect of the present invention, there is provided a resin composition comprising the above-mentioned resin modifier.
BEST MODE FOR CARRYING OUT THE INVENTION
Conjugated Diene Polymer (A)
The conjugated diene polymer (A) used in the present invention is selected from (A1) a conjugated diene polymer having a vinyl bond content of at least 60% by weight in the conjugated diene monomer units, and (A2) a conjugated diene polymer having a vinyl bond content of at least 30% by weight in the conjugated diene monomer units and a coupling ratio of at least 75% by weight.
As specific examples of a conjugated diene monomer used for the production of the conjugated diene polymer (A), there can be mentioned 1,3-butadiene, 2-methyl-1,3-butadiene, 2,3-dimethyl-1,3-butadiene, 2-chloro-1,3-butadiene and 1,3-pentadiene. Of these, 1,3-butadiene and 2-methyl-1,3-butadiene are preferable. 1,3-Butadiene is most preferable. These conjugated diene monomers may be used either alone or as a combination of at least two thereof.
The conjugated diene polymer (A) may be a copolymer of a conjugated diene monomer with other copolymerizable monomer. The copolymerizable monomer includes, aromatic vinyl monomers, olefin monomers, non-conjugated diene monomers and acrylic acid ester monomers. Of these, aromatic vinyl monomers are preferable.
As specific examples of the aromatic vinyl monomers, styrene, &agr;-methylstyrene, 2-methylstyrene, 3-methylstyrene, 4-methylstyrene, 2,4-diisopropylstyrene, 2,4-dimethylstyrene, 4-t-butylstyrene, 5-t-butyl-2-methylstyrene, monochlorostyrene, dichlorostyrene and monofluorostyrene. Of these, styrene is preferable. As specific examples of the olefin monomers, there can be mentioned ethylene, propylene, 1-butene, cyclopentene and 2-norbornene. As specific examples of the non-conjugated diene monomers, there can be mentioned 1,5-hexadiene, 1,6-heptadiene, 1,7-octadiene, dicyclopentadiene and 5-ethylidene-2-norbornene. As specific examples of the acrylic acid ester monomers, there can be mentioned methyl acrylate and methyl methacrylate. These copolymerizable monomers may be used either alone or as a combination of at least two thereof.
The lower limit of the conjugated diene monomer units in the conjugated diene polymer (A) is preferably 55% by weight, and more preferably 75% by weight. If the amount of the conjugated diene monomer units is too small, the resulting resin modifier tends to exhibit reduced resin-modifying effect, i.e., reduced impact strength-improving effect.
The lower limit of the vinyl bond content in the conjugated diene monomer units in the conjugated diene polymer (A1) is 60%, preferably 65% and more preferably 70%. The upper limit thereof is preferably 85% and more preferably 80%. If the vinyl bond content is too small, the resulting resin composition has poor gloss and heat stability of gloss. In contrast, the vinyl bond content is too large, the resulting resin composition tends to exhibit reduced impact strength, especially reduced impact strength at a low temperature. The type of bond in the conjugated diene monomer units is classified into a vinyl bond including a 1,2-vinyl bond unit and 3,4-vinyl bond unit, and a 1,4-bond including 1,4-cis bond unit and 1,4-trans bond.
The lower limit of viscosity of a 5% by weight solution in styrene of the conjugated diene polymer (A1) is preferably 3 cps and more preferably 10 cps. The upper limit thereof is preferably 1,000 cps and more preferably 200 cps. If the solution viscosity is too low, the resulting resin composition tends to have reduced impact strength. In contrast, when the solution viscosity is too high, the resulting resin composition tends to have reduced gloss and heat stability of gloss.
The conjugated diene polymer (A1) may have been subjected to a coupling treatment. In the case of a coupling-treated conjugated diene polymer, the coupling ratio is preferably smaller than 75% by weight and more preferably less than 65% by weight. If the coupling ratio is large, a long time is required for conducting the coupling trea
Kondou Katsuhito
Matsuda Hiroaki
Toyoshima Tetsuya
Armstrong Westerman & Hattori, LLP.
Nutter Nathan M.
Zeon Corporation
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