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
2001-05-23
2002-12-24
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...
C525S216000, C525S232000, C525S240000, C525S241000, C524S424000, C524S425000, C524S426000, C524S427000, C524S445000, C524S451000, C524S500000, C524S502000, C524S505000, C524S515000, C524S543000, C524S553000, C524S556000, C524S730000
Reexamination Certificate
active
06498213
ABSTRACT:
BACKGROUND OF THE INVENTION
Field of the Invention
The present invention relates to a thermoplastic resin composition, more specifically to a thermoplastic resin composition with superior extrusion and calendar formability and directly coatable without using primer because the crosslinking density can be arranged to improve the physical and chemical properties of the composition and the solubility to the solvent is increased during the coating process by including processing oil, inorganic filler, crosslinking agent and crosslinking assistant in random polypropylene resin, highly-crystalline random polypropylene resin, highly-crystalline polyolefin resin, olefin copolymer rubber and low-density polyethylene resin. This thermoplastic resin composition may be suitable for the use as surface material of the inner parts of automobiles.
Conventionally, PVC, PVC/ ABS alloy extrusion sheet or calendar processed sheet has been widely used for the automotive inner parts like the surface material of instrument panel, door trim panel and headlining, etc. This surface material for automotive inner parts should have good physical and chemical properties, particularly superior abrasion resistance, wear resistance, chemical resistance, solvent resistance and weather resistance. The surface coating should be carried out with not so much luster in order not to hinder the vision of the driver. Also, the color should harmonize with that of other parts.
Recently, researches to replace said surface material for automotive inner parts to olefin thermoplastic elastic material (hereunder referred to as “TPO”) sheet, which is environmentally friendly and has good recyclability, lightweightness, fogging and odor, are actively being carried out. Because the TPO sheet has a nonpolar and highly-crystalline molecular structure, it has very poor adhesion property. Therefore, chlorinated polyolefin resin primer pretreatment was required to secure sufficient film adhesion property.
Processing oil is included to enhance the processing of EPDM for said olefin TPO resin. However, the processing oil greatly reduces the calendar formability and secondary formability due to the low melt tension. If the content of the processing oil is reduced and the crosslinking density of EPDM with crosslinking structure is increased to improve the calendar formability, the surface becomes rough and embo sustainability worsens during the secondary processing such as vacuum forming. And, if the crosslinking density of EPDM with crosslinking structure is reduced, processing becomes impossible due to the adhesion to roll surface during the calendar processing.
U.S. Pat. Issue No. 4,247,645 discloses a method of diluting pre-crosslinked EPDM rubber in polypropylene resin with good fluidity. However, this method does not provide sufficient crosslinking density and the elastic and mechanical properties worsen. So, it is not suitable for processing structures with complicated shape such as instrument panel and door trim panel. Also, the equipment and production cost related with the crosslinking process and diluting process are problems. Especially, high-tech equipments with excellent mixing property are required in the diluting process. Japanese Patent Publication No. Sho 48-26835 discloses a heat treatment method using peroxide after completely melting-mixing polypropylene resin and EPDM rubber. This method has a disadvantage of low calendar formability because sufficient crosslinking density and viscosity are hardly obtained during the calendar processing due to the overdecomposition of polypropylene resin and partial crosslinking of EPDM. U.S. Pat. Issue No. 4,311,528 discloses a method of completely crosslinking EPDM rubber using phenol crosslinking agent. This method provides superior elastic and mechanical properties compared with the crosslinking reaction using peroxide crosslinking agent due to the good crosslinking density and crosslinking rubber particle formation. However, the cost of the final product increases because the crosslinking agent is very expensive. U.S. Pat. Issue No. 4,212,787 discloses a non-crosslinking polyisobutylene (PIB) and butyl rubber (BR) which provide better shear effect of EPDM/polypropylene composition. Although this method provides somewhat uniform EPDM crosslinking density, the crosslinking density of the final product is insufficient for the calendar processing.
SUMMARY OF THE INVENTION
In order to solve said problems, the inventors prepared a thermoplastic resin composition by mixing processing oil with olefin copolymer rubber and then including random polypropylene resin, highly-crystalline polyolefin resin, low-density polyethylene resin, inorganic filler, peroxide crosslinking agent and crosslinking assistant.
This thermoplastic resin composition maintains the crosslinking density by using low-density polyethylene resin and random polypropylene resin during the crosslinking reaction of EPDM/polypropylene composition with peroxide. Also, by increasing the solubility to the solvent during coating so that non-crosslinking component of EPDM increases, a thermoplastic resin composition with good extrusion and calendar formability and directly coatable without primer treatment process. Therefore, the present invention was completed.
Accordingly, an object of the present invention is to provide a thermoplastic resin composition with good extrusion and calendar formability and directly coatable without primer treatment process.
DETAILED DESCRIPTION OF THE INVENTION
The present invention is characterized by a thermoplastic resin composition which comprises:
(A) 5-45wt % of random polypropylene resin;
(B) 5-80wt % of highly-crystalline polyolefin resin;
(C) 5-80wt % of olefin copolymer rubber;
(D) 5-30wt % of processing oil;
(E) 1-15wt % of low-density polyethylene resin;
(F) 2-15wt % of inorganic filler;
(G) 0.02-5 wt % of peroxide crosslinking agent to 100 wt % sum of components (A)-(F); and
(H) Less than 5 wt % of crosslinking assistant to 100 wt % sum of components.
Hereunder is given more a detailed description of the present invention.
The thermoplastic resin composition of the present invention has very good formability, physical property and chemical property. So, it is suitable for use as automotive inner parts.
Each component comprising the thermoplastic resin composition of the present invention is as follows.
(A) Random polypropylene resin
Firstly, the random polypropylene resin is an atactic polymer prepared from the propylene and a-olefin monomer block or random copolymer. For a-olefin monomer used in the copolymerization, ethylene, propylene, 1-butene, 1-pentene or 1-hexene may be used. In the present invention, the melt index (230° C., 2160 g) is recommended to be 0.1-40 g/10 min, and preferably 5-20 g/10 min. If the melt index is outside this range, the fluidity and viscosity become excessive or insufficient, so that calendar processing becomes poor. The random polypropylene resin is used in the range of 5-45 wt % to the resin composition excluding crosslinking agent and crosslinking assistant. Outside this range, the physical properties of the final product worsen.
(B) Highly-crystalline polyolefin resin
The highly-crystalline polyolefin resin is an isotactic or syntheotactic polymer prepared from crystalline propylene monopolymer or &agr;-olefin monomer and propylene block or random copolymer. For &agr;-olefin monomer used in the copolymerization, ethylene, propylene, 1-butene, 1-pentene or 1-hexene can be used. In the present invention, the melt index (230° C., 2160 g) is recommended to 0.1-60 g/10 min, and preferably 0.5-30 g/10 min. If the melt index is outside this range, the fluidity and viscosity become excessive or insufficient, so that calendar processing becomes poor. The highly-crystalline polyolefin resin is used in the range of 5-80 wt % to the resin composition excluding crosslinking agent and crosslinking assistant. Outside this range, the physical properties of the final product worsen.
(C) Olefin copolymer rubber
The olefin copolymer rubber is an amorphous random co
Jeong Kie-Youn
Lee Tae-Seung
Nam Min
Christie Parker & Hale LLP
Hyundai Motor Company
Nutter Nathan M.
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