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
2001-11-06
2004-02-10
Wu, David W. (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
C525S241000, C525S088000, C525S098000, C525S099000, C525S070000, C525S451000, C525S424000, C525S426000, C525S427000, C525S445000, C525S423000
Reexamination Certificate
active
06689841
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATION
This application claims priority of Korea patent Application No. 2001-12078, filed on Mar. 8, 2001.
FIELD OF THE INVENTION
The present invention relates to a polypropylene resin composition and more particularly, to the polypropylene resin composition comprising: (A) a propylene polymer comprising a propylene-ethylene copolymer having a certain limit viscosity alone and/or a propylene homopolymer having a certain pentad fraction (% mmmm); (B) an ethylene-&agr;-olefin copolymer rubber comprising ethylene-propylene copolymer rubber and ethylene-&agr;-olefin copolymer; (C) a styrene copolymer rubber; (D) a polypropylene modified with polar group-containing resin or a polyolefin polyol; and (E) an inorganic filler. The polypropylene resin composition provides superior in rigidity, scratch resistance, gloss, adhesion to paint to the conventional polypropylene resin compositions and further provides excellent laser scoring characteristics and improved impact strength at a low temperature thus, being useful for interior automotive parts such as instrument panels, especially an instrument panel integrally enclosing an air bag.
BACKGROUND OF THE INVENTION
Polypropylene resins have been extensively used in exterior automotive parts including automotive bumpers and interior automotive parts including instrument panels and pillars, because they are excellent in flowability, impact strength, chemical resistance, and low-cost and have low specific gravity. However, in a case of interior automotive parts such as instrument panels, especially an instrument panel integrally enclosing air bag, an air bag is mounted within the instrument panel after the portion where the air bag is stowed is cut and then concealed that portion thus, resulting in vexatious complication and poor appearance. On the other hand, when an air bag is installed integrally within the instrument panel to remove such complications, there is a possibility of no opening of the air bag in an accident. Therefore, it is required to preweaken components overlaying an air bag enclosed within the instrument panel by scoring with the use of laser beam to be properly deployed in emergency. Accordingly, the instrument panel integrally overlying an air bag is expected to have excellent physical properties and adhesion to the paint and additionally stand laser scoring for the air bag to properly open in emergency. And further, it is required to exhibit excellent impact strength at a low temperature not to form broken pieces thereof when the air bag inflates.
There have been development of polypropylene resin compositions for interior automotive parts such as an instrument panel which provide good rigidity and physical properties and thus suitable for direct painting without a pretreatment but there is no development of polypropylene resin composition suitable for an instrument panel integrally enclosing an air bag. The inventors of the present invention have disclosed the polypropylene resin composition suitable for the instrument panel having excellent physical properties and adhesion to paint in U.S. patent application Ser. No. 09/749,698. However, the polypropylene resin composition disclosed in U.S. patent application Ser. No. 09/749,698 has excellent rigidity, physical properties and adhesion but it becomes dangerous for broken pieces formed with the inflation of an air bag due to lowered impact strength at a low temperature after post-treatment with laser beam.
Therefore, it is highly demanded to develop a polypropylene resin composition having excellent physical properties, adhesion to paints and additionally superior low-temperature impact strength required for an air bag deployment opening in an automotive industry.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a polypropylene resin composition having excellent physical properties such as rigidity, scratch resistance, gloss, and adhesion to paints, laser scoring characteristics and highly reinforced low-temperature impact strength by comprising: a propylene polymer selected from the group consisting of a propylene-ethylene copolymer, and/or a propylene homopolymer; an ethylene &agr;-olefin copolymer rubber comprising an ethylene-propylene copolymer rubber and ethylene-&agr;-olefin copolymer; a styrene copolymer rubber, a polar group-containing resin, and an inorganic filler.
DETAILED DESCRIPTION OF THE INVENTION
The present invention is characterized by a polypropylene resin composition comprising;
(A) 30 to 70 wt. % of a propylene polymer comprising 0 to 30 wt. % of propylene homopolymer and 70 to 100 wt. % of propylene-ethylene copolymer;
(B) 10 to 30 wt. % of an ethylene &agr;-olefin copolymer rubber comprising 60 to 95 wt. % of ethylene-propylene copolymer rubber and 5 to 40 wt. % of ethylene &agr;-olefin copolymer;
(C) 1 to 10 wt. % of a styrene copolymer rubber comprising 10 to 50 wt. % of polymer blocks of styrene or its derivative, 50 to 90 wt. % of polymer blocks copolymerized with at least one selected from ethylene, isoprene, butylene, butadiene, and propylene;
(D) 1 to 7 wt. % of polar-group containing resin comprising a modified polypropylene grafted to 0.5 to 6.0 wt. % of graft ratio, a polyolefin polyol, or mixture thereof; and
(E) 10 to 40 wt. % of an inorganic filler selected from the group consisting from talc, barium sulfate, potassium carbonate, and wollastonite.
The polypropylene resin composition of the present invention provides an interior automotive material suitable for an instrument panel integrally enclosing air bag with an injection molding. The instrument panel integrally enclosing an air bag with excellent laser scoring property and low-temperature impact strength is prepared from the molded article by coating without primer treatment and mounting an air bag.
Hereunder is given the detailed description of each component comprising the polypropylene resin composition of the present invention.
(A) Propylene Polymer
A propylene copolymer of the present invention is a crystalline polymer comprising a propylene-ethylene copolymer containing ethylenes and/or a propylene homopolymer.
Said propylene homopolymer has higher than 96% of pentad fraction (% mmmm) measured with
13
C-NMR, preferably higher than 96.5%, and more preferably higher than 97%. If the pentad fraction is lower than 96%, the rigidity and heat resistance of the polypropylene resin composition become inferior. Also, the limit viscosity [&eegr;] of said propylene polymer of the present invention measured in 135° C. of decalin is in the range of 0.7 to 2.5 dl/g, preferably in the range of 0.85 to 2.2 dl/g, and more preferably in the range of 0.9 to 2.0 dl/g. If the limit viscosity [&eegr;] is lower than 0.7 dl/g, the impact strength of the formed polypropylene resin composition worsens, and if it exceeds 2.5 dl/g, the flowability becomes poor, so that the quality of the finally formed product worsens and the working condition becomes poor.
Said propylene-ethylene copolymer includes 3 to 20%, and preferably 5 to 15% of an ethylene content. The limit viscosity [&eegr;] of propylene-ethylene block copolymer of the present invention measured in 135° C. of decalin is in the range of 3.0 to 6.0 dl/g, preferably higher than 3.5 dl/g, and more preferably higher than 4.0 dl/g.
For a well-balanced properties of impact strength and fluidity, the composition of the propylene homopolymer and the propylene-ethylene copolymer is recommended to be in the range of 0 to 30:70 to 100 wt. %, and more preferably in the range of 0 to 20:80 to 100 wt. %. While the propylene homopolymer provides superior rigidity and heat resistance, it has poor impact strength. On the other hand, the propylene-ethylene copolymer provides improved impact strength, especially at a low temperature but it has poor formability, rigidity and heat resistance. Therefore, they can complement each other when mixed together.
The content of the propylene copolymer to the entire polypropylene resin is recommended to be in the range of 30 to 70 wt
Choi Jae-Rim
Jung Soon-Joon
Park Bong-Hyun
Christie Parker & Hale LLP
Hyundai Motor Company
Lee Rip A
Wu David W.
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