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
1998-05-15
2001-01-30
Wilson, Donald R. (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...
C524S399000, C524S400000, C524S099000, C524S102000, C525S089000, C525S098000
Reexamination Certificate
active
06180709
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a thermoplastic resin composition comprising a propylene-ethylene block copolymer resin, a low crystalline ethylene-octene copolymer, a low crystalline ethylene-butene copolymer, a specific elastomer having a block structure, talc, and a specific additive admixture, which is excellent in terms of processability on injection molding and in the appearance of a molded product, has good flexural modulus, impact resistance, elongation in tension, surface hardness, and heat resistance, and is also excellent in adhesion to a paint film and improved in terms of prevention of mold contamination, and thus is particularly suited for the production of injection-molded products such as automotive interior trims.
2. Background Art
So far, numerous attempts have been made to increase the impact resistance and rigidity of polypropylene resins by the addition thereto of ethylene-propylene copolymers, various ethylene copolymers, and talc. For instance, resin compositions having excellent impact resistance are known from JP-B-63-42929, JP-A-64-150, JP-A-64-66263, and JP-A-1-204946.
However, the composition set forth in the above JP-B-63-42929 is insufficient in flexural modulus and heat resistance due to the use of a polypropylene of not so high crystallinity.
The compositions described in JP-A-64-150, JP-A-64-66263 and JP-A-1-204946, because of their low talc content, are suited for some applications, e.g., bumpers but their flexural modulus is too low for interior trims.
Furthermore, JP-A-4-159345 discloses an ethylene-&agr;-olefin copolymer composition containing a large amount of inorganic filler. This composition has a high specific gravity, and thus is not preferred in the light of weight reduction of automobiles.
In order to reduce the above drawbacks, JP-A-7-53843 has proposed a composition. This composition, however, is unsatisfactory in fluidity for use in applications requiring a higher level of fluidity where molding should be carried out at a low pressure in short cycle times.
Regarding the interior trims, they are in most cases coated with a paint to enhance the commercial value. Unfortunately, however, polypropylene materials for interior trims generally exhibit poor adhesion to a paint film, especially when fats and oils are involved. Therefore, the development of materials having higher adhesion to a paint film has been desired in the art.
On the other hand, there is the following problem with the conventional talc-containing polypropylene composite materials at the time of their molding. Thus, during the long-term continuous molding of the composite materials, bleedouts are gradually deposited on molds, whereby the resulting molded product undesirably exhibits a high gloss. This is particularly pointed out for automotive interior trims. A propylene polymer which provides a solution to this problem while maintaining the physical properties has been proposed in JP-A-5-209094 and JP-A-6-17982. However, this polymer utilizes no weathering agent. In view of the fact that stabilizers used for improving weathering resistance usually exert an adverse influence on the contamination of molds, there is still left much to be desired.
An object of the present invention is to provide a thermoplastic resin composition which has high fluidity, good physical properties and excellent moldability, can provide moldings having good adhesion to a paint film, is improved in terms of prevention of mold contamination, and is especially suited for the production of automotive interior trims such as an instrument panel.
SUMMARY OF THE INVENTION
It has now been found that the above object can be achieved by incorporating an elastomer component having specific crystallinity, an elastomer component having substantially no crystallinity, an elastomer having a block structure as a compatibilizing agent component, talc, and optionally specific additives in specific proportions into a propylene-ethylene block copolymer which contains a propylene homopolymer moiety of high fluidity and high crystallinity.
Thus, the present invention provides a thermoplastic resin composition comprising the following components (A) to (E):
component (A): 50 to 74.7% by weight of a propylene-ethylene block copolymer resin containing a propylene homopolymer moiety having a melt flow rate (MFR) of 20 to 200 g/10 min. and an isotactic pentad fraction of at least 0.98, said block copolymer having an MFR of 10 to 100 g/10 min. and a ratio of the weight average molecular weight (Mw) to the number average molecular weight (Mn), Mw/Mn, of 5 to 7,
component (B): 5 to 10% by weight of an ethylene-octene random copolymer having a melting temperature of 40 to 60° C. and an MFR of 0.5 to 15 g/10 min.,
component (C): 5 to 10% by weight of an ethylene-butene random copolymer not having a melting temperature of 35° C. or above and having an MFR of 0.5 to 15 g/10 min.,
component (D): 0.3 to 5% by weight of an elastomer, the elastomer being either one comprising a block structure represented by the following formula [I] and/or the following formula [II] and having a melting temperature of 80 to 110° C., an MFR of 0.5 to 20 g/10 min., a polyethylene crystalline moiety content of 20 to 40% by weight, and a random elastomer moiety content of 60 to 80% by weight, or one comprising a block structure represented by the following formula [III], the following formula [IV] and/or the following formula [V] and having a melt flow rate of not more than 15 g/10 min. and a polystyrene moiety content of 10 to 40% by weight and a random elastomer moiety content of 60 to 90% by weight:
polyethylene-(ethylene/butene random elastomer)-polyethylene [I]
polyethylene-(ethylene/butene random elastomer) [II]
polystyrene-(ethylene/butene random elastomer)-polystyrene [III]
polystyrene-(ethylene/propylene random elastomer)-polystyrene [IV]
polystyrene-(ethylene/propylene random elastomer) [V];
and
component (E): 15 to 25% by weight of a talc having an average particle diameter of up to 5 &mgr;m and a specific surface area of at least 3.5 m
2
/g.
According to a preferred embodiment of the present invention, the thermoplastic resin composition further comprises the following components (F) and (G):
component (F): 0.05 to 2 parts by weight, based on 100 parts by weight in total of the components (A) to (E), of a hindered amine having a structure represented by the following formula:
component (G): 0.05 to 4 parts by weight, based on 100 parts by weight in total of the components (A) to (E), of a metal salt represented by the following general formula [VI]:
(RCOO)
2
X [VI]
wherein R represents a monovalent hydrocarbon group having a molecular weight of 290 to 500 and X is zinc, magnesium, or calcium.
The thermoplastic resin composition comprising the specific components (A) to (E) in specific proportions has good moldability, can provide a molding having good appearance, has good flexural modulus, impact resistance, elongation in tension, heat resistance, and surface hardness, and is improved in adhesion to a paint film. When the thermoplastic resin composition further comprises the components (F) and (G), the weathering resistance is improved without suffering from the problem of mold contamination. Therefore, the thermoplastic resin composition of the present invention is particularly suited for the production of injection-molded automotive interior components, such as instrument panels.
DETAILED DESCRIPTION OF THE INVENTION
[I] Thermoplastic Resin Composition
(1) Components
(A) Propylene-Ethylene Block Copolymer (Component (A))
The propylene-ethylene block copolymer (component (A)) to be used in the thermoplastic resin composition of the present invention has a melt flow rate (MFR—measured at 230° C. under a load of 2.16 kg) of 10 to 100 g/10 min., preferably 20 to 80 g/10 min., and more prefer
Ishii Izumi
Iwai Hisayuki
Murayama Mitsuhiro
Nagai Takayuki
Nishio Takeyoshi
Japan Polychem Corporation
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Wilson Donald R.
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