Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Polymers from only ethylenic monomers or processes of...
Patent
1998-03-30
2000-12-19
Wu, David W.
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Polymers from only ethylenic monomers or processes of...
5263481, 525240, 524451, 524570, 524584, 428364, 428523, C08F 1006, C08L 2312
Patent
active
061628875
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a highly crystalline polypropylene, to a resin which contains this highly crystalline polypropylene, and to molded products made from them. In more detail, the present invention relates to a highly crystalline polypropylene having a high degree of crystallinity and having a specific spherulite structure, to a resin which contains this polypropylene resin, and to molded products having a high rigidity which are molded from these resins.
BACKGROUND ART
Crystalline polypropylene is an excellent material in extensive use which has comparatively good mechanical and thermal characteristics. It is known that mechanical characteristics and thermal characteristics are closely related to the degree of crystallinity, and research to increase the crystallinity of crystalline polypropylene is proceeding.
In general, with the goal of improving mechanical and thermal properties of polypropylene, control of the stereoregularity, molecular weight, and molecular weight distribution (for example, Japanese Patent Application, First Publication, No. 62-195007), the addition of crystal nucleating agents (for example, Japanese Patent Application, First Publication, No. 62-209151), the addition of various filling agents such as fiber (for example, Japanese Patent Application, First Publication, No. 61-160359), the carrying out heat treatments after molding (for example, Japanese Patent Application, First Publication, No. 62-256837), and the like have been attempted. However, when crystalline polypropylenes have been obtained by crystallization under normally used molding conditions, the degree of crystallinity of the polypropylene is not sufficiently increased because the rate of crystallization of the polypropylene is slow.
Polypropylenes are crystalline high polymers, and when crystallized without orientation, spherulites are formed. These spherulites are formed from lath like crystals called lamella, but in situations of polypropylene spherulites of a normal monoclinic crystal (.alpha.-crystal), it is known that they comprise lamellae which extend radiating from the center of the spherulite (herein after referred to as R-lamella) and lamellae which extend at angle of approximately 80 degrees 40 minutes from the R-lamella (hereinafter referred to as T-lamella).
Because of the presence of this type of spherulite structure, it has not been possible to improve the degree of crystallinity and, as a result, it has not been possible to improve rigidity. In addition, because the lamella thickness of the T-lamella is thin compared with the thickness of the R-lamella, the melting point is low and, therefore, the heat distortion temperature is also low.
SUMMARY OF THE INVENTION
The first object of the present invention is the provision of a highly crystalline polypropylene for which the degree of crystallinity is sufficiently high and which is superior in mechanical and thermal characteristics, and a resin composition which contains this highly crystalline polypropylene.
The second object of the present invention is the provision of molded products which are superior in mechanical and thermal characteristics and which comprise a highly crystalline polypropylene or a resin composition which contains this highly crystalline polypropylene.
The highly crystalline polypropylene of the present invention is characterized by a degree of crystallinity of at least 50.5% calculated from the heat of fusion; and by a relationship between the proportion of R-lamella f(R) with respect to spherulites calculated using the following formula (I) and the weight-average molecular weight Mw, wherein the relationship satisfies the following Formula (II), and wherein the proportion of R-lamella f(R) with respect to spherulites is calculated using the following Formula (I) from the birefringence .DELTA.n of crystallized spherulites which were obtained by melting the highly crystalline polypropylene at 230.degree. C. for 5 minutes, cooling it to 132.degree. C. at a cooling rate of 20.degree. C./minute, and t
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International Search Report.
Iwasaki Yoshiharu
Yamada Koji
Japan Polyolefins Co., Ltd.
Rabago R.
Wu David W.
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