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...
Reexamination Certificate
2001-06-18
2004-07-06
Mulcahy, Peter D. (Department: 1713)
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...
C524S525000, C524S528000, C525S088000, C525S089000, C525S240000
Reexamination Certificate
active
06759475
ABSTRACT:
FIELD OF THE TECHNIQUE
The present invention relates to a resin composition based on crystalline polypropylene and specifically to such a resin composition based on crystalline polypropylene which is superior in the mechanical properties and in the flowability upon injection molding and can serve for a material for producing moldings exhibiting better appearance.
BACKGROUND OF THE TECHNIQUE
For domestic electrified articles and parts for automobile made of moldings of polypropylene resin composition, a superior external appearance in favor of providing a high grade and high designing impression is requested in addition to the requisite mechanical properties. Heretofore, there have been proposed many resin compositions based on polypropylene, in which elastomers, talc, pigments and so on, are blended together with crystalline propylene block-copolymer, in order to improve the mechanical properties thereof. For example, Japanese Patent Application Kokais Sho-58-168649 A and Hei-3-172339 A (corresponding to U.S. Pat. No. 5,086,109) disclose polypropylene resin compositions, in which the balance between the rigidity and the shock resistance is improved by blending elastomers, talc, pigments and so on together with crystalline propylene block-copolymers.
When, however, such a polypropylene resin composition as above is molded by injection molding, a considerable deterioration in the appearance of the molded products may, in some cases, occur due to occurrence of “flow marks”, namely, stripes caused by repetition of high- and low-gloss regions on the surface of the molding.
In solving such a problem, Japanese Patent Application Kokais Hei-7-53828 A (corresponding to U.S. Pat. No. 5,543,454) and Hei-9-71712 A disclose each a polypropylene resin composition comprising a crystalline propylene block-copolymer which comprises a homo-polypropylene component (homo-component) having a low molecular weight and a component soluble in paraxylene of 23° C. (rubber component) having a high molecular weight. These polypropylene resin compositions do not suffer from occurrence of the flow mark and are superior in the flowability upon injection molding.
However, the above-mentioned polypropylene resin compositions may occasionally suffer from deterioration in appearance of molded product therefrom due to formation of “rashes” on the surface of the injection-molded product brought about by the formation of “polymer gel”, namely, a difficultly soluble aggregate formed from a part of the rubber component by being caused to become high molecular weight, in addition to an occasionally accompanying decrease in the impact resistance. Moreover, production of a crystalline propylene block-copolymer, in which the molecular weight of the homo-component is caused to become low molecular weight and that of the rubber-component is caused to become high molecular weight, is attained only in a low productivity at a high production cost. Thus, also for the polypropylene resin composition constituted of crystalline propylene block-copolymers in which the molecular weight of the homo-component is caused to become low molecular weight and that of the rubber-component is caused to become high molecular weight, the mechanical properties and the appearance of the molded product are not sufficiently improved and a high production cost is required.
The subject of the present invention is to provide a resin composition based on crystalline polypropylene which can bring about molded products without suffering from occurrence of flow-mark and rashes caused from formation of polymer gel and, therefore, exhibiting a superior appearance with excellent mechanical strengths, such as flexural modulus and so on, together with better flowability upon the molding and which can be obtained at a low cost by selecting starting raw materials of high productivity.
DISCLOSURE OF THE INVENTION
The present invention relates to a resin composition based on crystalline polypropylene which is to be defined as follows:
(1) A resin composition based on crystalline polypropylene, comprising
(a) 3-65% by weight of a component soluble in paraxylene of 23° C.,
(b) 35-97% by weight of a component soluble in paraxylene of 135° C. and insoluble in paraxylene of 23° C. and
(c) 0-30% by weight of a component insoluble in paraxylene of 135° C.,
wherein
the component (a) soluble in paraxylene of 23° C. is composed substantially of an elastomeric constituent (a1) having a content of styrene or its derivative in the range of 0-35% by weight and an intrinsic viscosity [&eegr;] determined in decalin at 135° C. in the range of 0.1-5 dl/g,
the component (b) soluble in paraxylene of 135° C. and insoluble in paraxylene of 23° C. is composed substantially of a crystalline polypropylene constituent (b1) having an isotactic pentad proportion (mmmm) of 97% or higher, a molecular weight distribution expressed by weight-average molecular weight
umber-average molecular weight (Mw/Mn), determined by gel permeation chromatography (GPC), of 6 or higher and a molecular weight distribution expressed by z-average molecular weight/weight-average molecular weight (Mz/Mw) of 6 or higher and
the component (c) insoluble in paraxylene of 135° C. is composed substantially of a filler (c1).
(2) A resin composition based on crystalline polypropylene, comprising
(a) 20-35% by weight of a component soluble in paraxylene of 23° C.,
(b) 43-65% by weight of a component soluble in paraxylene of 135° C. and insoluble in paraxylene of 23° C. and
(c) 15-22% by weight of a component insoluble in paraxylene of 135° C.,
wherein
the component (a) soluble in paraxylene of 23° C. is composed substantially of an elastomeric constituent (a1) having a content of styrene or its derivative in the range of 0-35% by weight and an intrinsic viscosity [&eegr;] determined in decalin at 135° C. in the range of 0.1-5 dl/g,
the component (b) soluble in paraxylene of 135° C. and insoluble in paraxylene of 23° C. is composed substantially of a crystalline polypropylene constituent (b1) having an isotactic pentad proportion (mmmm) of 98% or higher, a molecular weight distribution expressed by weight-average molecular weight
umber-average molecular weight (Mw/Mn), determined by gel permeation chromatography (GPC), of 9 or higher and a molecular weight distribution expressed by z-average molecular weight/weight-average molecular weight (Mz/Mw) of 8 or higher and
the component (c) insoluble in paraxylene of 135° C. is composed substantially of powdery talc having an average particle size in the range of 1-5 &mgr;m.
(3) A resin composition based on crystalline polypropylene as defined in above (1) or (2), wherein the elastomeric constituent (a1) comprises at least one elastomeric constituent selected from the group consisting of
(A-1) an elastomeric constituent, which may or may not be hydrogenated, based on styrene having a styrene content in the range of 10-70% by weight and a conjugated diene content in the range of 30-90% by weight;
(A-2) an ethylene/&agr;-olefin random copolymer constituent; and
(A-3) an ethylene/&agr;-olefin
on-conjugated polyene random copolymer constituent.
(4) A resin composition based on crystalline polypropylene as defined in above (1) or (2), wherein the elastomeric constituent (a1) comprises at least one elastomer selected from the group consisting of
(A-1) an elastomeric constituent, which may or may not be hydrogenated, based on styrene having 10-40% by weight of a constituent polymer block based on styrene and 60-90% by weight of a constituent polymer block based on a conjugated diene;
(A-2) an ethylene/&agr;-olefin random copolymer constituent; and
(A-3) an ethylene/&agr;-olefin
on-conjugated polyene random copolymer constituent.
(5) A resin composition based on crystalline polypropylene as defined in above (1) or (2), wherein the elastomeric constituent (a1) comprises at least one elastomeric constituent selected from the group consisting of
(A-1) an elastomeric constituent, which may or may not be hydrogenated, based on styrene having 10-70% by weight of a const
Hashimoto Mikio
Moriya Satoru
Nakagawa Hideki
Sakai Ikunori
Takaoka Tohru
Burns Doane , Swecker, Mathis LLP
Mitsui Chemicals Inc.
Mulcahy Peter D.
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