Polypropylene-based resin molded article and process for producing the same

Abstract

The present invention provides a crystalline polypropylene-based resin molded article having an excellent impact resistance, in particular a remarkably high Izod impact strength, and a process for producing the molded article. A polypropylene-based resin molded article with an excellent impact resistance in which the β crystals of the polypropylene-based resin are unoriented can be produced by a process comprising the steps of: adding 0.01 to 0.1 parts by weight of at least one amide compound to 100 parts by weight of a polypropylene-based resin; kneading the resulting mixture at a temperature not lower than the dissolution temperature of the amide compound in the molten polypropylene-based resin until the compound dissolves in the molten polypropylene-based resin; and injecting and / or extruding the resulting melt in such a state that the amide compound has dissolved in the molten polypropylene-based resin.

Description

CROSS REFERENCE TO RELATED APPLICATION [0001] This application is a continuation of Ser. No. 10 / 485,814, filed Feb. 10, 2004, which is a 35 U.S.C. 371 application of international application No. PCT / JP02 / 08909 filed Sep. 3, 2002, which is based on Japanese Application No. 2001-276964 filed Sep. 12, 2001.TECHNICAL FIELD [0002] The present invention relates to a crystalline polypropylene-based resin molded article having an excellent impact resistance, in particular, having a remarkably high Izod impact strength, and a process for producing the same. BACKGROUND ART [0003] Crystalline polypropylene has been widely used in recent years in a variety of molding materials, owing to its excellent mechanical properties and high recyclability. Crystalline polypropylene has α, β and γ forms, and it is broadly known that the β form (hereinafter referred to as “β crystals”) has interesting properties, such as a lower melting point, a higher heat distortion temperature, and a higher impact resis...

AI Technical Summary

Benefits of technology

[0006] An object of the present invention is to provide a crystalline propylene-based resin molded article free of the above problems and having an excellent impact resistance, in particular, having a remarkably high Izod impact strength, and a process for producing the molded article.

[0007] The present inventors carried out extensive research to achieve the above object. As a result, the inventors found that, when a crystalline polypropylene-based resin composition containing a specific proportion of a specific amide compound is molded under specific conditions, unoriented β crystals of the polypropylene-based resin are formed, thereby greatly improving the Izod impact value of the resulting molded article.

Problems solved by technology

However, the molded articles thus obtained are liable to vary in characteristics, especially in impact resistance, and do not necessarily have satisfactory impact strength.

Specifically, some of the molded articles exhibit a high impact resistance in a planar impact test, such as the DuPont impact test, but show a poor impact resistance in a linear impact test, such as the Charpy impact test or the Izod impact test.

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