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
2000-03-06
2001-05-22
Seidleck, James J. (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...
C525S098000, C525S099000
Reexamination Certificate
active
06235847
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a linear block copolymer. More particularly, the present invention is concerned with a linear block copolymer comprising at least two vinyl aromatic hydrocarbon polymer blocks (S), at least two conjugated diene polymer blocks (B) and at least one vinyl aromatic hydrocarbon/conjugated diene copolymer block (B/S); the linear block copolymer having a specific block configuration wherein both terminal polymer blocks of the linear block copolymer are S blocks, both terminal S blocks have, bonded directly to the respective inner ends thereof, B blocks, and the B blocks, which are bonded directly to the respective inner ends of both terminal polymer blocks (S), have therebetween one or two B/S blocks which is or are bonded directly to the respective inner ends of the polymer blocks (B); the linear block copolymer comprising at least two fractions having different peak molecular weights, and both terminal S blocks in total comprising at least two fractions having different peak molecular weights. The present invention is also concerned with a resin composition comprising the linear block copolymer and a styrene-containing resin in a specific amount ratio. By molding the linear block copolymer of the present invention or the resin composition containing the linear block copolymer, a shaped article retaining high transparency and having excellent rigidity and excellent impact resistance can be obtained.
2. Prior Art
A block copolymer comprising a vinyl aromatic hydrocarbon and a conjugated diene wherein the vinyl aromatic hydrocarbon content is relatively high, has various excellent characteristics, such as transparency and impact resistance, so that such a block copolymer is used for producing injection-molded products, extrusion-molded products (such as a sheet and a film) and the like. Conventionally, in an attempt to improve the mechanical properties (such as impact resistance) of a shaped article produced from a block copolymer while retaining the transparency of the shaped article, there have been proposed not only block copolymers comprising a vinyl aromatic hydrocarbon and a conjugated diene and methods for producing such block copolymers, but also resin compositions comprising such block copolymers. For example, in an attempt to improve the transparency and impact resistance of a block copolymer, Unexamined Japanese Patent Application Laid-Open Specification No. 52-58788 (corresponding to U.S. Pat. No. 4,167,545) discloses a branched block copolymer obtained by division-wise adding a catalyst to a block copolymerization system. Also, for improving the environmental stress cracking resistance of a block copolymer, Unexamined Japanese Patent Application Laid-Open Specification No. 4-277509 (corresponding to U.S. Pat. No. 5,227,419 and European Patent No. 492490) discloses a method for producing a block copolymer having gradually varied properties, which comprises division-wise adding a catalyst to a block copolymerization system. On the other hand, for obtaining a block copolymer having transparency and mechanical properties, Unexamined Japanese Patent Application Laid-Open Specification No. 63-145314 (corresponding to U.S. Pat. No. 4,939,208 and European Patent No. 270515) discloses a method for producing a block copolymer having an S
1
-B
1
-B/S-S
2
block configuration, wherein S
1
and S
2
each represent an aromatic vinyl uniform polymer block, B
1
represents a conjugated diene uniform polymer block, and B/S represents a random copolymer block. Further, with a view to improving the transparency and impact resistance of a block copolymer, Unexamined Japanese Patent Application Laid-Open Specification No. 7-97418 discloses a block copolymer which has characteristic features with respect to the vinyl aromatic hydrocarbon block ratio, the arrangement of the polymer blocks, the ratio of the conjugated diene in a segment in which a vinyl aromatic hydrocarbon and a conjugated diene are randomly copolymerized, and the like. However, the above-mentioned conventional block copolymers have problems in that when such a block copolymer is formulated into a resin composition thereof with a styrene-containing resin and molded to obtain a sheet, followed by processing to produce a shaped article, such as a cup for beverage or a cup for frozen or cold dessert, the shaped article has an unsatisfactory balance of transparency, impact resistance, rigidity and the like. Accordingly, it has been desired to produce a block copolymer which is improved so that it is capable of producing therefrom a shaped article having excellent transparency, impact resistance, rigidity and the like.
SUMMARY OF THE INVENTION
In this situation, the present inventors have made extensive and intensive studies with a view to solving the above-mentioned problems accompanying the prior art block copolymer. As a result, it has surprisingly been found that when a specific linear block copolymer is subjected to processing to obtain a shaped article, the article exhibits a good balance of transparency, rigidity and impact resistance, wherein the linear block copolymer comprises at least two vinyl aromatic hydrocarbon polymer blocks (S), at least two conjugated diene polymer blocks (B) and at least one vinyl aromatic hydrocarbon/conjugated diene copolymer block (B/S); the linear block copolymer having a specific block configuration wherein both terminal polymer blocks of the linear block copolymer are S blocks, both terminal S blocks have, bonded directly to the respective inner ends thereof, B blocks, and the B blocks, which are bonded directly to the respective inner ends of both terminal polymer blocks (S), have therebetween one or two B/S blocks which is or are bonded directly to the respective inner ends of the polymer blocks (B); the linear block copolymer comprising at least two fractions having different peak molecular weights, and both terminal S blocks in total comprising at least two fractions having different peak molecular weights. Based on this finding, the present invention has been completed.
Accordingly, it is a primary object of the present invention to provide a novel linear block copolymer having excellent transparency, impact resistance and rigidity.
It is another object of the present invention to provide a resin composition comprising the above-mentioned linear block copolymer and a styrene-containing resin, which has excellent transparency, impact resistance and rigidity.
The foregoing and other objects, features and advantages of the present invention will be apparent from the following detailed description and appended claims.
DETAILED DESCRIPTION OF THE INVENTION
In a primary aspect of the present invention, there is provided a linear block copolymer comprising:
at least two vinyl aromatic hydrocarbon polymer blocks (S);
at least two conjugated diene polymer blocks (B); and
at least one vinyl aromatic hydrocarbon/conjugated diene copolymer block (B/S),
the total amount of vinyl aromatic hydrocarbon monomer units in the linear block copolymer and the total amount of conjugated diene monomer units in the linear block copolymer being, respectively, from 65 to 90% by weight and from 35 to 10% by weight, based on the weight of the linear block copolymer,
the linear block copolymer having a block configuration wherein:
both terminal polymer blocks of the linear block copolymer are vinyl aromatic hydrocarbon polymer blocks (S),
both terminal vinyl aromatic hydrocarbon polymer blocks (S) have, bonded directly to the respective inner ends thereof, conjugated diene polymer blocks (B), and
the conjugated diene polymer blocks (B), which are bonded directly to the respective inner ends of both terminal vinyl hydrocarbon polymer blocks (S), have therebetween one or two vinyl aromatic hydrocarbon/conjugated diene copolymer blocks (B/S) which is or are bonded directly to the respective inner ends of the conjugated diene polymer blocks (B), wherein, when the polymer blocks (B) have therebetween two vinyl aromatic hydrocarbon/con
Hoshi Susumu
Yamaura Yukio
Asahi Kasei Kabushiki Kaisha
Asinovsky Olga
Birch & Stewart Kolasch & Birch, LLP
Seidleck James J.
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