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
2001-09-27
2003-01-28
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...
C525S191000, C525S222000
Reexamination Certificate
active
06512052
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATION
This application claims priority of Korea patent Application No. 2001-27678, filed on May 21, 2001.
BACKGROUND OF THE INVENTION
Field of the Invention
The present invention relates to a polypropylene resin composition for automobile interior covering materials capable of calender molding and high frequency welding. More particularly, the present invention relates to the polypropylene resin composition capable of calender molding and high frequency welding, which the same comprise a reactor-type polypropylene resin with excellent melt tension, an ethylene-vinyl acetate copolymer having polarity, an ethylene-glycidyl methacrylate-methyl acrylate terpolymer and a phthalate and thus useful for the automobile interior covering materials.
Core of an automobile sun visor, which absolves an impact and keeps up shape, is covered with interior covering materials for improvement in appearance and the circumference thereof is adhered by high frequency welding. The covering materials used for this purpose are supposed to have high melt tension and be manufactured into sheets by calender molding with low adhesion to a roll. And further, they are supposed to have sufficient polarity to be applicable for high frequency welding. Bead-type polypropylene foam (hereinafter referred to as “EPP FORM”) is widely used for the core and polyvinyl chloride (hereinafter referred to as “PVC”) calendaring sheet for the interior covering material. The PVC exhibits excellent melt tension and low adhesion to a roll thus, easily molded to sheet by calender molding. Further, the PVC has polarity because its is polarized to a positive charge for H and a negative charge for Cl due to H—C—Cl structure having significant difference in electronegativity between H and Cl, and thus be weldable with frictional heat generated from transition energy difference between H and Cl when high frequency is applied.
However, in recent years, it has been demanded not to use PVC resins owing to a problem of the poison of environmental hormones and a problem of the generation of a harmful dioxine gas at the time of the combustion of wastes. In Europe, it is not allowed to recover from used PVC resins by the combustion and only allowed for reclamation. And further, since the PVC resin is different class of resin from EPP FOAM used for the core and thus not incompatible, it has to be separated from the core for recycling.
Therefore, it has been highly demanded to use polypropylene resins which can be recovered by the combustion, be environmentally friend, and be recycled without separating out EPP FOAM used as the core from wastes, thus being free from the above-mentioned problems. The polypropylene resins have excellent physical characteristics such as tensile strength, modulus of bending elasticity, impact strength and chemical characteristics.
However, they have poor melt tension to be capable of being formed into sheets by calender molding and are not suitable for high frequency welding because they are structurally non-polar component. Therefore, it is necessary to secure high melt tension for calender molding and polarity for high frequency welding to use the polypropylene resins as the automobile interior covering materials such as sun visors.
SUMMARY OF THE INVENTION
Accordingly, the present invention has been made under such circumstances, and inventors have completed the present invention by obtaining a polypropylene resin composition comprising a reactor-type polypropylene resin which excellent melt tension, an ethylene-vinyl acetate compolymer having polarity and compatible with polypropylene resin, an ethylene-glycidyl methacrylate-methyl acrylate terpolymer and a phthalate for securing polarity to the surface of the sheet, from which there can be manufactured into sheets by calender molding without reducing physical characteristics and performed for high frequency welding to be applicable for automobile interior covering materials.
An object of the present invention is to provide a polypropylene resin composition for automobile interior covering materials capable of calender molding and high frequency welding.
Detailed Description of the Invention
The present invention is characterized by a polypropylene resin composition capable of calender molding and high frequency welding, which comprises:
(A) a reactor-type polypropylene resin selected from a copolymer of propylene and C
2
monomer and a copolymer of propylene and C
4
-C
10
monomer;
(B) an ethylene-glycidyl methacrylate-methyl acrylate terpolymer;
(C) an ethylene-vinyl acetate compolymer; and
(D) a phthalate.
The present invention is described in detail as set forth hereunder.
The present invention employs a reactor-type polypropylene (A) having excellent melt tension to allow a polarity to conventional polypropylene resins, wherein the polar polymer capable of being compatible with polypropylene resin is blended in an appropriate ratio to easily form sheets by calender molding and perform high frequency welding.
It is generally possible to add a reinforcing agent having high melt tension to improve the melt tension of the polypropylene resin and the most preferred method according to the present invention is use of reactor-type polypropylene resin prepared by special method. The reactor-type polypropylene resin of the present invention is a copolymer of propylene and C
2
monomer or a copolymer of propylene and C
4
-C
10
monomer having a monomer content of more than 18 wt. %. However, the reactor-type polypropylene resin is usually prepared by copolymerizing propylene with C
2
monomer or C
4
-C
10
monomer in the presence of Ziegler-Natta catalyst in the commercial polymerization reactor. At this time, the polypropylene resin has usually less than 18 wt. % of a content of monomer due to limitations of a used catalyst and a reactor and its results in being impossible to form the sheets by calender molding because the melt tension is insufficient for containing less than 18 wt. % of a monomer content.
However, the present invention uses reactor-type polypropylene resin having more than 18 wt. % of a monomer content, wherein the monomer is C
2
or C
4
-C
10
monomer. The reason to call as the reactor-type polypropylene resin is that it is prepared by using special catalyst and reactor different from the conventional catalyst and reactor.
The reactor-type polypropylene resin is preferred to have 18-30 wt. % of a monomer content and less than 1 g/10 min (230° C.) of a melt index. If the melt index is higher than 1 g/10 min, it is impossible to form sheets by calender molding due to poor melt tension. Olefins as the C
2
or C
4
-C
10
monomer are not restricted but can be ethylene, 1-butene, 4-methyl-1-pentene, 1-hexene, or 1-octene. The reactor-type polypropylene resin is preferred to be used in the range of from 44 to 55 wt. % to the total composition.
A compatibilizer is generally used to give polarity to the polypropylene resin by blending polar polymer and polypropylene resin. When a polypropylene is blended with a polar polymer having carboxylic acid, hydroxy, or epoxy group, it is preferred to use a compatibilizer to react with both the polar polymer and the polypropylene resin because non-polar polypropylene is incompatible with polar polymer. When the non-polar polypropylene is blended with the polar polymer without using a compatibilizer, there is a problem of the generation of the interfacial between non-polar polypropylene and polar polymer, thus resulting in inferior physical characteristics as sheets or even being impossible to form sheets by calender molding. However, if a polar polymer capable of being compatible with polypropylene resin is selected, it is able to be practical to obtain the polypropylene resin having polarity without using any compatibilizer and further without reducing physical characteristics.
The present invention employs an ethylene-glycidyl methacrylate-methyl acrylate terpolymer (B) and ethylene-vinyl acetate (C) having 20-30 wt. % of a vinyl acetate content to grant interior polarity for
Christie Parker & Hale LLP
Hyundai Motor Company
Nutter Nathan M.
Tran Thao
LandOfFree
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