Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – At least one aryl ring which is part of a fused or bridged...
Patent
1995-02-27
1997-01-07
Seccuro, Jr., Carman J.
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
At least one aryl ring which is part of a fused or bridged...
524505, 525 88, 528481, C08K 300, C08L 5300
Patent
active
055917950
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates to a polypropylene composition excellent in rigidity and heat resistance and also in impact resistance and toughness.
TECHNICAL BACKGROUND
A crystalline polypropylene is excellent in rigidity, heat resistance, surface glossiness, etc., and however, there is a problem that the polypropylene is poor in impact resistance.
On that account, there have heretofore been proposed various methods to improve the impact resistance of such a polypropylene, for example, there is known a method in which crystalline polypropylene is incorporated with modifiers such as polyethylene, rubbery substance, etc. As such a rubbery substance (rubber component), an amorphous or a low crystalline ethylene/propylene random copolymer (EPR), polyisobutylene, polybutadiene, etc. are generally used.
In order to improve the impact strength of polypropylene by incorporation of such a rubbery substance into the polypropylene, however, a large amount of the rubbery substance must be contained in the polypropylene. Although the polypropylene composition thus contained a large amount of the rubbery substance is certainly improved in impact resistance, there was such problem that the composition largely deteriorates in rigidity, heat resistance and surface hardness.
Under such circumstances, there have been proposed various polypropylene compositions which contain the rubbery substance as mentioned above together with inorganic fillers such as talc in order to impart rigidity to the compositions (see, for example, Japanese Patent L-O-P Publns. Nos. 58459/85, 60154/85, 233048/86, 36348/86, 235350/87, 122751/88, 150343/88, 149845/89, 204947/89 and 271450/89).
Such a polypropylene composition containing a large amount of the rubbery substance, however, has a limit in improving their rigidity by means of incorporation thereinto of the inorganic filler, and hence there was such a problem that it is difficult to use the composition for the purposes where a high rigidity of the composition is required.
Therefore, it has been desired to develop a polypropylene composition excellent not only in rigidity and heat resistance but also in impact resistance and toughness.
Researches conducted by the present inventors on the polypropylene composition as referred to above resulted in the finding that in the case of conventionally known polypropylene compositions formed from polypropylene and an ethylene/propylene random copolymer (rubber component), a part of the amorphous component in the polypropylene is mingled in the rubber component, and this rubber component is bound by the amorphous component of the polypropylene, with the result that no sufficient effect of the rubber component for improving the impact resistance can be exhibited.
Then, the present inventors have found that in order to obtain a polypropylene composition excellent not only in rigidity and heat resistance but also in impact resistance, it is necessary to form a polymer alloy (polypropylene composition) having a molecular composite-like structure in which the rubbery substance (rubber component) is used as a matrix and polypropylene (crystal component) is used as a dispersion phase, differing from a polymer alloy formed from polypropylene and the rubbery substance which has a generally-known structure as mentioned above. Further, the present inventors have found that when a polypropylene composition has a structure in which the polypropylene microcrystals have a specific dimension in the directions of a-, b- and c-axes and the rubber component is present around the polypropylene microcrystals as a continuous phase having a specific average thickness, such a polypropylene composition is excellent in rigidity and heat resistance and also in impact resistance. Based on these findings, the present invention has been accomplished.
Incidentally, there has been made an attempt to obtain a polypropylene composition excellent in impact resistance by mixing polypropylene with other ethylene/.alpha.-olefin copolymers in place of the aforementioned amorphous
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Hashimoto Mikio
Moriya Satoru
Nishio Takeyoshi
Nomura Takao
Mitsui Petrochemical Industries Ltd.
Seccuro, Jr. Carman J.
Toyota Jidosha & Kabushiki Kaisha
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