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
2000-02-22
2002-05-28
Mullis, Jeffrey (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
Reexamination Certificate
active
06395829
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to amorphous polyolefin resin compositions which are excellent in the balance of the impact resistance with the surface glossiness and, further, the balance of the impact resistance with the transparency.
BACKGROUND OF THE INVENTION
In recent years, cyclic olefin polymers (including copolymers) have attracted public attention, among amorphous polyolefins, as plastics being excellent in moldability, dimensional stability, transparency and water vapour barrier property. However, these polymers are insufficient in impact strength and, therefore, attempts have been made to improve the impact resistance. Namely, it has been required to improve the impact resistance of cyclic olefin polymers while sustaining their excellent transparency.
In general, it is known that the impact strength of a brittle thermoplastic resin can be improved by alloying it with a non-compatible rubber component. This method is also effective on cyclic olefin polymers.
JP-A-1-256548 discloses a method for improving the impact resistance of a cyclic olefin copolymer by alloying the cyclic olefin copolymer with commercially available block copolymers as rubber components (SBS, SEBS and SIS) as well as the thus obtained compositions (the term “JP-A” as used herein means an “unexamined published Japanese patent application”). However, this document states nothing about the transparency of the compositions or the surface conditions of molded articles obtained from these compositions. Even if the impact strength can be improved by using these block copolymers, this method suffers from a problem that the decrease in the transparency arising simultaneously cannot be prevented.
As another method for improving the impact-toughness of cyclic olefin copolymers, JP-A-7-278402 discloses a method of using a core-shell type elastomer and a block copolymer. In this document, it is disclosed that a method for improving the impact resistance of a brittle polymer by using a core-shell type elastomer together with a block copolymer had been known (Polymer. Vol. 28, 1703 (1987)) and that this method is also effective on cyclic olefin copolymers. It is described therein that the impact resistance of a cyclic olefin copolymer can be improved by the above method without the experimental optimization of the core-shell particles to be employed.
So long as judged from the Examples in the above document, an effect of improving the impact resistance could be found. However, the addition of the block copolymers was scarcely effective in improving the impact resistance (impact toughness). Thus, the effect is not always satisfactory and there remains room for improvement.
Based on the prior art, it might be considered to optimize the core-shell type elastomer so as to improve the impact resistance of a cyclic olefin copolymer. However, JP-A-7-278402 neither suggests any method or idea of optimizing the core-shell type elastomer to elevate the impact resistance nor describes the mechanism of improving the impact resistance with the combined use of the core-shell type elastomer and the block copolymer.
Core-shell type elastomers have been frequently used in improving the impact resistance of typical polymers to be improved in the impact resistance, for example, brittle polymers such as PVC and PMMA (PMMA is an amorphous substance similar to cyclic olefin polymers). Such a core-shell type elastomer has a core made of a rubber component (flexible component) and a graft polymer (i.e., a shell layer) formed on the surface of the core. The graft polymer is usually made of a polymer system highly compatible with the polymer which is to be improved in the impact resistance. Therefore, the core-shell type elastomer can be easily dispersed, while maintaining the primary particle size thereof, in the polymer which is to be improved in the impact resistance. Thus, it is considered that the size needed for improving the impact resistance can be easily and stably maintained and sufficient interfacial adhesion can be established, thereby ensuring the considerable improvement in the impact resistance of the polymer which is to be improved in the impact resistance. It is generally considered that the effect of improving the impact resistance of the matrix polymer cannot be sufficiently achieved unless the core-shell type elastomer is dispersed while maintaining the primary particle diameter thereof.
Therefore, it seems that the following two points are particularly important in optimizing a core-shell type elastomer.
The first point resides in that, as the graft polymer (i.e., the shell layer) of the core-shell type elastomer, a component sufficiently compatible with the polymer which is to be improved in the impact resistance should be selected so as to achieve a sufficient interfacial adhesion between the core-shell type elastomer and the polymer which is to be improved in the impact resistance (i.e., the-amorphous polyolefin in the present invention). The second point resides in that the particle size (primary particle diameter) of the core-shell type elastomer should be regulated to the optimum level that can most effectively give the impact resistance to the polymer which is to be improved in the impact resistance.
With respect to the first point as described above, the compatibility and adhesion between phases thus achieved can generally be evaluated depending on the solubility parameter (delta), as stated in JP-A-7-278402. According to JP-A-7-278402, the solubility parameter (delta) of a cyclic olefin copolymer is about 13.5
1/2
cm
3/2
which is significantly lower than that of a typical polymer to be improved in the impact resistance.
This fact means that a core-shell type elastomer for a typical polymer which is to be improved in the impact resistance can hardly achieve a sufficient compatibility with a cyclic olefin copolymer, thereby hardly establishing interfacial adhesion. That is to say, it can be hardly expected to achieve the effect of improving the impact resistance as observed in the case of the combination of a typical polymer having improved impact resistance with a core-shell type elastomer developed exclusively therefor.
With respect to the second point, it is generally known that the optimum primary particle diameter of a core-shell type elastomer optimum for improving the impact resistance of a brittle polymer depends on the entanglement density (n
e
) of the polymer (S. Wu, Polymer International, 29(1992), p.229-247) and the validity of this relation is supported by experimental data (Polym. Eng. Sci., Vol. 31, 213 (1991) and J. Appl. Polym. Sci., Vol. 48, 75(1993)). Also, JP-A-7-233301 discloses this fact. From this viewpoint, it is also stated in this document that, to improve the impact resistance of a cyclic olefin copolymer, it is considered that a core-shell type elastomer should have a particle diameter of 1 to 3 &mgr;m.
Therefore, it might be considered based on the prior art that a core-shell type elastomer can be optimized, as a means for improving the method described in JP-A-7-278402, by using a graft polymer which is excellent in the compatibility (interfacial adhesion) with a cyclic olefin copolymer as the shell layer and regulating the primary particle diameter of the core-shell type elastomer to 1 to 3 &mgr;m.
As a means for improving the interfacial adhesion between the core-shell type elastomer and the cyclic olefin copolymer as discussed above, JP-A-7-300540 discloses a technique wherein a cyclic alkyl (meth)acrylate is inserted as a graft polymer (a shell layer). In the Examples given in this document, the impact resistance was improved thereby, which suggests that a compatibility would be thus achieved in a certain extent.
However, cyclic alkyl (meth)acrylates are very special monomers from an industrial viewpoint. These monomers are not only expensive but also hardly soluble in water. It is therefore considered that these cyclic alkyl (meth)acrylates would bring about difficulties in emulsion polymerization or seed polymerization usually employed in industrially pr
Kawai Hideki
Miyamoto Masahiro
Takaki Akira
Armstrong Westerman & Hattori, LLP
Kaneka Corporation
Mullis Jeffrey
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