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
2001-08-13
2004-01-13
Nutter, Nathan M. (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...
C525S232000, C525S240000, C525S241000
Reexamination Certificate
active
06677403
ABSTRACT:
This application is the U.S. national phase of International Application PCT/EP00/12611, filed Dec. 12, 2000.
The present invention relates to a propylene resin composition. More specifically, it relates to a propylene resin composition having an improved performance of its properties and an excellent moldability.
A propylene resin composition made of a propylene resin and an elastic material typified by an elastomer has advantages that it is less costly, has high mechanical strengths, and is high in temperatures which can be used and excellent in chemical resistance, electrical insulating properties and the like. Thus, it is useful for a wide variety of application areas such as films, sheets, foams, blow-molded products, injection-molded products and the like. In any application, however, there are limitations in its properties. Especially, the limitations in a heat resistance, a rigidity and an impact strength are unveiled, because those of the propylene resins inferior to those of amorphous resins such as impact-resistant polystyrene, acrylonitrile-butadiene-styrene resin (ABS), polycarbonate (PC)/ABS and the like. Accordingly, the field in which it can be used is limited. Thus, it would be highly desirable to eliminate the disadvantages, some proposals have been made to date. For example, for improving the same, various polypropylene resin compositions have been proposed which are obtained by adding to polypropylene an elastic material having a low Young's modulus with which to absorb impact and by adding reinforcing materials such as inorganic fillers to enhance a heat resistance or a rigidity (Japanese Patent Laid-Open Nos. 168,649/1983 and 172,339/1991).
As the elastic material, for example, low-density polyethylene, high-density polyethylene, an ethylene-propylene copolymer rubber, an ethylene-butene copolymer rubber, a copolymer rubber of a material containing ethylene and C
2
-C
20
olefin or at least two of these C
2
-C
20
olefins, a crystalline ethylene-propylene block copolymer obtained by multi-stage polymerization, and, as a copolymer other than olefin series, a block copolymer containing an ethylene chain segment or a hydrogenated butadiene chain segment and a chain of styrene, methyl methacrylate, vinyl acetate or vinyl chloride or a chain segment of at least two types of copolymers, such as a styrene-ethylene-butylene-styrene diblock copolymer which is produced from polystyrene-block-butadiene-block-styrene), have been proposed for the purpose of the improvement of polypropylene. For example, Japanese Patent Laid-Open No. 149,845/1989 discloses a propylene resin composition made of (a) 59 to 74% by weight of a propylene-ethylene block copolymer containing 5 to 12% by weight of a boiling xylene soluble matter with an ethylene content of 20 to 60% by weight, having an ethylene content of the overall polymer of 1 to 7% by weight and having a melt flow rate of 15 to 50 g/10 minutes, (b) 35 to 20% by weight of an ethylene-propylene copolymer rubber having a propylene content of 20 to 60% by weight and having a Mooney viscosity ML
1+4
(100° C.) of 100 to 150 and (c) 3 to 6% by weight of talc having a specific surface area of 30,000 cm
2
/g or more and an average particle diameter of 0.5 to 2.0 &mgr;m. Although an impact resistance is satisfactory, an amount of an ethylene component having a low heat resistance is large. Thus, it can hardly be said that the improvement is satisfactory in view of the heat resistance and the rigidity. Moreover, when such a propylene resin composition is transformed into products by injection molding, the products sometimes have notably bad surface aspect problems which are called flow mark (tiger mark), whose tangential striped pattern is caused by alternately gloss difference repeating between high and low sections.
In order to solve the problems, Japanese Patent Laid-Open Nos. 53,838/1995 (corresponding U.S. Pat. Nos. 5,543,454) and 71,712/1997 disclose a propylene resin composition in which a molecular weight of a homopolypropylene moiety is decreased and a molecular weight of a propylene-ethylene block copolymer rubber, a p-xylene soluble fraction which is extracted from a crystalline ethylene-propylene copolymer at 23° C. is increased. Although the flow mark of this propylene resin composition is reduced, the high-molecular portion easily forms a sparingly plastic agglomerate (gel fish-eye or the like) which appears as an acne on the surface of the molded product. Consequently, not only is the appearance worsened, but also defective points in which the impact resistance is heavily decreased owing to non-uniformity by the acne are generated in some cases.
Further, Japanese Patent Laid-Open No. 189,699/1999 in which for solving the problems, an elastic material made of a styrene-ethylene-butylene-styrene (hereinafter abbreviated as “SEBS”) block copolymer for which a high molecular weight is not indispensable is used and a b-axial orientation structure of a crystalline polypropylene moiety is limited for maintaining a heat resistance and a rigidity discloses a polypropylene resin composition comprising (A) 54 to 65% by weight of a crystalline ethylene-propylene block copolymer having MFR of 60 to 120 g/10 minutes, the homopolypropylene moiety having an isotactic pentad ratio of 96% or more and MFR of 150 to 250 g/10 minutes, and the content of the ethylene-propylene copolymer moiety being 5 to 10% by weight, (B) 17 to 24% by weight of a thermoplastic elastomer comprising one or more types of styrene-ethylene-butylene-styrene block copolymers, and (C) 15 to 25% by weight of talc, the mechanical properties measured according to ASTM being as follows,
flexural modulus≧1,800 MPa
tensile yield strength≧20 MPa
23° C. Izod impact strength≧180 J/m
−30° C. Izod impact strength≧30 J/m
Rockwell hardness (R scale)≧74
heat distortion temperature (HDT 18.5 kg)≧73° C.
brittle temperature≧−20° C.
MFR=40 to 60 g/10 minutes
and the degree of b-axial orientation calculated from the differential peak intensities measured by the wide angle X-ray diffraction in the vicinity of the center of ASTM #1 dumbbell formed by injection molding being 720 or more. However, the styrene-ethylene-butylene-styrene block copolymer used to obtain the necessary impact resistance is quite expensive in comparison with olefinic elastic materials, and added in the large amount, inviting the increase in cost and the decrease in rigidity. Moreover, since the styrene.ethylene.butylene.styrene block copolymer is not so good in heat resistance, the talc content is relatively increased. Thus, the uniformity tends to decrease. Accordingly, it is hardly said that in the propylene resin composition disclosed, the heat resistance, the rigidity and the impact resistance are balanced at a high level.
Under these circumstances, the problems of the invention are to provide, at low costs, a propylene resin composition in which no flow mark is generated and no acne formed from an agglomerate of a high-molecular substance is generated, which has a uniform structure as a whole, which is therefore so excellent in moldability as to be able to provide a molded product having an excellent appearance, which is markedly improved in balance of properties compared with ordinary polypropylene materials, which is high in mechanical strengths and which is excellent in rigidity, heat resistance, impact resistance, moldability and the like.
In order to solve the problems, the present inventors have studied various elastic materials which are a constituent of the propylene resin composition of the invention and various separated micro phase structures of elastic materials intended. Consequently, they have found that a propylene resin composition excellent in rigidity, heat resistance, impact strength, moldability and the like is obtained when it is a propylene resin composition in which an elastic material present in the propylene resin composition is a component having a velocity v of sound propagated as a longitudinal wave being 3,000 m/s or less
Basell Poliolefine Italia S.p.A.
Nutter Nathan M.
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