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
2002-01-11
2004-05-04
Sanders, Kriellion A. (Department: 1714)
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
active
06730728
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a polypropylene-based resin composition comprising a propylene/ethylene block copolymer, ethylene/octene and/or ethylene/butene copolymer, styrene-based hydrogenated block copolymer rubber, and talc, good in injection moldability, flexural modulus of elasticity, resistance to impact and tensile elongation, excellent in internal molding pressure characteristics during the molding process, and suitable for injection-molded articles, e.g., automobile exteriors.
BACKGROUND OF THE INVENTION
It is widely known that polypropylene-based resin composition, comprising a polypropylene resin incorporated with an ethylene-based thermoplastic elastomer component (e.g., ethylene/propylene or ethylene/butene copolymer) and inorganic filler (e.g., talc), has been going into automobile parts. Various polypropylene resins, rubber components and inorganic fillers have been investigated and proposed, in order to improve moldability, mechanical properties and outer appearances of the polypropylene-based resin compositions.
Automobile parts are demanded to be produced by high-cycle molding and to be thinner articles, and require the materials of higher melting flow and rigidity. Some of the attempts to improve these properties have led to development of the compositions disclosed by Japanese Patent Laid-Open Nos.53843/1995 and 20684/1996. However, materials of still higher melting flow are required for the articles to be produced by high-cycle molding at low pressure, and the above compositions are still insufficient in melting flow to meet the above requirements.
Japanese Patent Laid-Open Nos.324725/1998, 29688/1999 and 43565/1999 also disclose the materials of still higher melting flow, but are silent on internal molding pressure during the molding process. Therefore, they are still insufficient in melting flow for producing large-size molded articles, e.g., bumpers.
Moreover, it is preferable that molded articles, e.g., bumper, can be made of the same material whether it is to be painted or not, viewed from material unification, for which such a material should have as small a difference as possible between molding shrinkage and shrinkage after heating. The above patent publications are completely silent on this matter.
It is an object of the present invention to provide a resin composition high in melting flow, exhibiting good properties, excellent in moldability, shrinkage properties and mechanical properties while solving the above problems, and suitable for automobile exteriors, e.g., bumpers, rocker moldings, sidemoldings and overfenders.
DISCLOSURE OF THE INVENTION
The inventors of the present invention have found, after having extensively studied to solve the above problems, that the resin composition high in melting flow, exhibiting good properties and excellent in internal molding pressure can be obtained by incorporating a specific ethylene/&agr;-olefin copolymer elastomer, specific styrene-based hydrogenated block copolymer rubber and talc, each at a specific content, in a propylene/ethylene block copolymer having high melting flow, very high crystallinity and propylene homopolymer component, reaching the present invention.
The first invention provides a polypropylene-based resin composition comprising the following components (A) to (D), characterized by its excellent moldability and other properties.
Component (A): Propylene/ethylene block copolymer having a melt flow rate (MFR) of 100 to 200 g/10 min., its propylene homopolymer component having an MFR of 210 to 400 g/10 min. and isotactic pentad fraction (P) of 0.98 or more, and its copolymer portion containing propylene at 65 to 85% by weight; 50 to 70% by weight
Component (B): Ethylene/octene and/or ethylene/butene random copolymer, containing the comonomers at 28% by weight or more for the copolymerization and having an MFR of 0.5 to 20 g/10 min.; 10 to 25% by weight
Component (C): Styrene-based hydrogenated block copolymer rubber having the following structure, containing the segment A of polystyrene structure at 1 to 25% by weight; 4 to 9% by weight
A-B, or
A-B-A
wherein, the segment A is a polystyrene structure and segment B is an ethylene/butene or ethylene/propylene structure.
Component (D): Talc, having an average particle size of 10 &mgr;m or less, determined by the laser-aided diffractometry; 16 to 24% by weight
The second invention is the polypropylene-based resin composition of the first invention whose resin composition has the following properties; internal molding pressure: 38 MPa or less, MFR: 36 to 50 g/10 min., flexural modulus of elasticity: 1750 MPa or more, brittleness temperature: −15° C. or lower, tensile elongation: 200% or more, and difference between molding shrinkage and shrinkage after heating: {fraction (1.5/1000)} or less.
PREFERRED EMBODIMENTS OF THE INVENTION
The present invention provides the polypropylene-based resin composition, comprising (A) propylene/ethylene block copolymer, (B) ethylene/octene and/or ethylene/butene random copolymer, (C) styrene-based hydrogenated block copolymer rubber, and (D) talc. Each of these components is described in more detail.
[I] Components of the Resin Composition
(A) Propylene/Ethylene Block Copolymer (Component (A))
(1) Properties of the Propylene/Ethylene Block Copolymer
The propylene/ethylene block copolymer (Component (A)) for the polypropylene-based resin composition of the present invention has a melt flow rate (MFR at 230° C. and a load of 2.16 kg) of 100 to 200 g/10 min., preferably 105 to 170 g/10 min., more preferably 105 to 140 g/10 min. At an MFR less than 100 g/10 min., the propylene/ethylene block copolymer is insufficient in melting flow and exposed to a high internal molding pressure during the molding process for producing the thin-wall articles. This requires a molder of high clamping force, and deteriorates productivity. At an MFR more than 200 g/10 min., on the other hand, the propylene/ethylene block copolymer will have insufficient brittleness temperature and tensile elongation.
The propylene/ethylene block copolymer is preferably adjusted for its MFR during the polymerization process. When adjusted after the polymerization process with an organic peroxide, e.g., diacyl peroxide or dialkyl peroxide, the propylene/ethylene block copolymer needs a higher internal molding pressure during the molding process than the one adjusted during the polymerization process, and is unsuitable.
The propylene homopolymer component of the propylene/ethylene block copolymer has an MFR of 210 to 400 g/10 min., preferably 220 to 350 g/10 min., more preferably 250 to 300 g/10 min., and an isotactic pentad fraction (P) of 0.98 or more, preferably 0.985 or more.
The propylene homopolymer component of the propylene/ethylene block copolymer will needs a higher internal molding pressure during the molding process when its MFR is more than 400 g/10 min., and insufficient brittleness temperature and tensile elongation when its MFR is less than 210 g/10 min.
The propylene/ethylene block copolymer will have an insufficient flexural modulus of elasticity when isotactic pentad fraction (P) of its propylene homopolymer component is less than 0.98.
Isotactic pentad fraction (P) means the isotactic fraction of the pentad unit in the polypropylene molecular chain, determined by
13
C-NMR.
The copolymer portion of the propylene/ethylene block copolymer contains propylene at 65 to 85% by weight, preferably 67 to 75%. The propylene/ethylene block copolymer tends to have an insufficient tensile elongation when the propylene content is less than 65% by weight, and insufficient flexural modulus of elasticity when it is more than 85% by weight, and hence is undesirable.
(2) Production of the Propylene/Ethylene Block Copolymer
The propylene/ethylene block copolymer is produced in the presence of a catalyst of high stereoregularity. The examples of such catalysts include those produced by combining a titanium trichloride composition with an organoaluminum compound and aromatic carboxylate ester, where the titanium
Fujita Yuji
Iwai Hisayuki
Matsuda Masatoshi
Murayama Mitsuhiro
Nagai Takayuki
Japan Polychem Corporation
Sanders Kriellion A.
Westerman Hattori Daniels & Adrian LLP
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