Stock material or miscellaneous articles – Web or sheet containing structurally defined element or... – Composite having voids in a component
Reexamination Certificate
2000-03-31
2003-03-18
Dunn, Tom (Department: 1725)
Stock material or miscellaneous articles
Web or sheet containing structurally defined element or...
Composite having voids in a component
Reexamination Certificate
active
06534167
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a polymer composition for powder molding and a powder, a foamed article obtained by using said polymer composition, a producing method of the foamed article and a molded article. More specifically, the present invention relates to a polymer composition for powder molding containing a peroxide-crosslinkable olefin-based copolymer as a polymer component, wherein the composition is excellent in the storage stability of an uncrosslinked article and provides a foamed article having a high expansion ratio, an excellent heat stability and elasticity and an excellent surface skin and hardly having a skin lack of hiding and a powder of said polymer composition, a foamed article, a method for producing said foamed article, and a molded article containing said foamed article.
BACKGROUND ARTS
Interior parts such as an instrument panel, a headrest, an armrest, a door trim and the like of an automobile have had a remarkable tendency to be a soft type from a conventional hard type. These parts are constituted by multi-layers composed of a skin layer with embossing, a foamed layer as a cushion layer and a base material layer.
Hitherto, a method of separately making a skin layer and a base material layer, then inserting them into a mold, injecting an urethane between the skin layer and the base material layer, and foaming it to integrate, has been applied as a method for obtaining such multi-layer parts. In this case, the skin layer is prepared by a slush molding using a vinyl chloride resin powder, and the base material layer is prepared by an injection molding using a polyolefin (e.g. polypropylene, polyethylene), an ABS resin (an acrylonitrile-butadiene-styrene copolymer) or the like. In case of applying production method composed of such three steps, there is a problem that its cost is high.
According to the investigation by the present inventors, a multi-layer molded article can be obtained by two steps of laminating a resin of the base material layer on the surface of a foamed layer by means of a press molding, injection molding, adhesion or the like after a two-layer molded article of a skin layer and a foamed layer is obtained. When the skin layer and the base material layer are laminated, it is required that the surface of the foamed layer is smooth.
In order to obtain a two-layer molded article by a powder slush molding, for example, the two-layer molded article composed of a non-foamed skin layer and a foamed layer is formed by heating a mold which may have a complicated pattern on a molding face above a melting temperature of a resin powder for the skin layer, then feeding the above-mentioned resin powder for the skin layer on the molding face of said mold, removing an extra powder which did not melt after obtaining an sheet-like melted article on said molding face by mutually heat-fusing the powders, successively feeding a peroxide-crosslinkable and expandable olefin-based resin composition powder (hereinafter, referred to as “powder for crosslinking-foaming”) on the sheet-like melted article, removing the extra powder which did not melt after obtaining the sheet-like melted article on said molding face by heat-fusing the powders each other, then further heating it thereby crosslinking and foaming, and cooling the mold.
The powder for crosslinking-foaming used in such step is subject to a remarkable thermal history since the feed of the powder on a heat melted resin and the removal of said unmelted powder therefrom are repeatedly carried out. Further, when the powder for crosslinking-foaming is stored for a long time in a hot period of summer till using it from preparation, the powder is also subject to a remarkable thermal history. When the powder for crosslinking-foaming containing a crosslinking agent induces an early crosslinking (hereinafter, referred to as “scorch”) according to such thermal history, the melt flow property of the powder becomes poor , and a foamed article having a smooth surface skin can not be obtained, therefore the storage stability of the powder for crosslinking-foaming is an important subject.
Further, when a balance between the crosslinking rate of the powder for crosslinking-foaming and the decomposition rate of a foaming agent is broken, a gas is stored in an interface between the skin layer of non-crosslinked layer and the foamed layer, and accordingly, the skin layer becomes partially thin and a phenomena in which the part of foamed layer is seen through (hereinafter, referred to as “skin lack of hiding”) occurs. When a molded article of two-layer structure is obtained by a powder slush molding, a powder composition for foaming excellent in the storage stability of an uncrosslinked powder and further providing a molded article having no skin lack of hiding and a smooth surface skin of the foamed layer, has not been found yet.
As a method for obtaining a foamed molded article, for example, a method for obtaining a foamed molded article by adding a foaming agent to a partially crosslinked matter of a composition of an ethylene-&agr;-olefin copolymer rubber and a polyolefin-based resin, is disclosed (Japanese Patent Publication (Kokai) Hei No. 4-345637). Although this process has characteristics that a foamed article having a high expansion ratio, homogeneous cells and the like, can be obtained, a melt flow property is remarkably inferior, and therefore, a powder slush molding cannot be adopted.
Further, a method for obtaining a foamed article by adding a carboxylic acid having 2 or more of carboxyl groups and a thermal decomposition type foaming agent to an ethylene-based copolymer containing a glycidyl group, is disclosed (Japanese Patent Publication (Kokai) Hei No. 7-228720). However, although the method is superior in the surface skin of the foamed article obtained and the homogeneity of cells, the composition used in the method induces a scorch during a short time storage, and therefore has a problem that the storage stability is remarkably inferior.
DISCLOSURE OF THE INVENTION
Under these circumstances, the subject to be solved by the present invention is to provide a polymer composition for powder molding containing a peroxide-crosslinkable olefin-based copolymer as a polymer component, a polymer composition for powder molding having an excellent storage stability of an uncrosslinked powder and being capable of providing a foamed article having homogeneous cells and an excellent surface skin, and hardly having a skin lack of hiding, a powder of said polymer composition, a foamed article, a method for producing said foamed article, and a molded article.
The present invention relates to a polymer composition for powder molding containing (A)-(E) described below:
(A) a peroxide-crosslinkable olefin-based copolymer having a melt flow rate measured under the conditions of a load of 2.16 kgf and a temperature of 190° C. according to JIS K7210 of 1 g/10 min. or more;
(B) 0.01 to 10 parts by weight of a peroxide having a temperature for obtaining a half life of 10 hours of 100° C. or more, per 100 parts by weight of (A);
(C) 0.1 to 7 parts by weight of a crosslinking aid per 100 parts by weight of (A);
(D) 0.1 to 20 parts by weight of a thermal decomposition type foaming agent per 100 parts by weight of (A); and
(E) 0.1 to 10 parts by weight of a foaming aid per 100 parts by weight of (A).
Further, the present invention relates to a powder prepared from the above-mentioned polymer composition, a method for producing a foamed article comprising crosslinking-foaming said powder, and a molded article obtained by the method.
Moreover, the present invention relates to a two-layer molded article obtained by laminating a non-foamed layer composed of a thermoplastic elastomer or vinyl chloride-based resin composition on a foamed layer composed of the above-mentioned foamed article, a multi-layer molded article obtained by laminating a reinforcing layer composed of a thermoplastic resin composition or a thermoplastic elastomer composition on the foamed layer side of said two-layer molded article, and further, a
Iketani Kohichi
Nakatsuji Yoshihiro
Ohtani Kohsuke
Dunn Tom
Johnson Jonathan
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