Plastic and nonmetallic article shaping or treating: processes – Direct application of electrical or wave energy to work – Reshaping – drawing or stretching
Reexamination Certificate
2001-02-14
2004-11-30
Mullis, Jeffrey (Department: 1711)
Plastic and nonmetallic article shaping or treating: processes
Direct application of electrical or wave energy to work
Reshaping, drawing or stretching
C428S461000, C428S462000, C264S483000, C525S071000
Reexamination Certificate
active
06824730
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a resin composition which has such performances as excellent rubber elasticity, favorable oil maintainability, low hardness and low compression set, has excellent adhesivity to a metal, and is well suited as a gasket material for use in a gasket integrated with a metal wherein a gasket is integrated into a metallic cover body or a metallic frame body.
In addition, the present invention pertains to a composite molded body in which a metallic sheet and a thermoplastic elastomer are integrated with each other, more particularly to a composite molded body in which a metallic sheet and a thermoplastic elastomer are integrated with each other without being subjected to surface treatment or without the use of an adhesive and which is well suited for use in a gasket fitted to a cover, etc. that is employed for housing electronic equipment and the like.
Moreover, the present invention is related to a process for producing a composite molded body of a resin and metal, for instance, a gasket integrated with a metal which has excellent adhesivity between a metallic part and a resin portion formed by injection molding of a thermoplastic elastomer composition.
Further, the present invention is concerned with a process for producing a gasket integrated with a cover having excellent gasket performance by injection molding of a thermoplastic elastomer composition.
2. Description of the Related Arts
In recent years, electronic equipment such as a computer has come to have intricate circuit constitution, accompanying the progress towards a high performance and compactification, and is prone to be readily damaged even by a slight amount of dust. Accordingly, dust prevention is increasingly required in practical application, thus making it a general practice to prevent dust penetration by the use of a gasket.
The above-mentioned gasket is, in many cases, in the form of a gasket integrated with a metal in which a gasket material composed of a thermoplastic elastomer of low hardness has been injection molded onto a metallic part such as a case lid.
The methods as described hereunder have heretofore been adopted as a method for integrating a thermoplastic elastomer of low hardness with a metallic part.
{circle around (1)} a method which comprises fixing a gasket to a cover body by means of a double-coated tape;
{circle around (2)} a method which comprises sandwiching a cover body having holes between gasket materials through the holes;
{circle around (3)} a method which comprises applying in advance, an adhesive to the surface portion of a metallic part onto which an elastomer is to be injection molded or extrusion molded; and
{circle around (4)} a method which comprises making in advance, through holes or grooves on the portion of a metallic part onto which an elastomer is to be injection molded so as to latch the injection molded portion.
However, any of the above-mentioned methods is complicated in production steps, and thus needs a high production cost. As the above-mentioned method {circle around (1)} which comprises fixing a gasket to a cover body by means of a double-coated tape, there is usually adopted a method in which a sheet-like gasket material to which a double-coated tape is adhered, is punched into a shape of gasket, and the resultant gasket is fixed to the cover body. However, the aforesaid method is involved in such problems that the production process is made intricate or troublesome, thus constituting a factor increasing the production cost, since most of the sheet-like gasket material after punching remains as waste material and besides, the gasket is fixed to the cover body after the gasket material has been punched into a shape of gasket.
In addition, in the gasket fitted to a cover body which is produced by the above-mentioned method {circle around (2)} which comprises sandwiching a cover body having holes between gasket materials through the holes, since the gasket material is exposed on the upper side of the cover body and besides is insufficiently adhered to the cover body, the gasket material exposed thereon is sometimes upturned or curled when the cover body is inserted into the space of an electronic equipment main body, which space has been narrowed accompanying the recently compactified electronic equipment part items. Thus, there is caused the problem that such upturning or curling is responsible for defective sealing properties.
Moreover, in the case where the gasket which is fitted to a cover body and which is produced by such a method is used in a hard disc drive apparatus, there is caused the problem that it is impossible to suppress the vibration due to the rotation of the hard disc.
In general, the adhesion between a thermoplastic elastomer and a metallic sheet is carried out by a method in which the metallic sheet is subjected to a surface treatment, and the treated surface is coated with an adhesive to be adhered to the thermoplastic elastomer. In order to enhance the adhesivity, there is also carried out blending of an adhesive (a pressure sensitive adhesive) material in the thermoplastic elastomer.
However, the adhesion between the thermoplastic elastomer and the metallic sheet by the use of an adhesive is involved in such problems that its production process becomes intricate and troublesome, constituting a factor increasing the production cost, since the process requires the steps of surface treatment for a metallic sheet and adhesive coating.
In the case of using, in precision electronic equipment and the like, a molded body in the form of a gasket fitted to a cover body wherein a thermoplastic elastomer is adhered to a metallic sheet, there is caused a problem of gas generation due to the surface treatment and adhesive coating, thereby making it difficult to use the precision electronic equipment. Further in the case of blending an adhesive (a pressure sensitive adhesive) material in a thermoplastic elastomer, there are caused such problems in that the tacking (pressure sensitive self adhesion) imparted to the resultant blend makes handling itself extremely difficult and also in that the blending of the adhesive (a pressure sensitive adhesive) material deteriorates the physical properties such as the compression set of a thermoplastic elastomer, whereby the elastomer no longer functions as a gasket material.
On the one hand, as a method for laminating a thermoplastic resin on a metallic sheet, there is described in Japanese Patent Application Laid Open Nos. 235783/1999 (Heisei 11) and 262978/1999 (Heisei 11), an integration method in which a polyolefin film side, that is, the resin side is subjected to a corona treatment and laminated with a metallic sheet. Methods for integrally molding a styrenic thermoplastic elastomer and poly-propylene by injection molding are described in Japanese Patent Application Laid Open Nos. 139232/1990 (Heisei 2), 99331/1996 (Heisei 8) and 266375/1995 (Heisei 7).
Nevertheless, according to single use of any of the above-stated methods, the resultant molded body does not function at all as a gasket fitted to a cover body. Saying it differently, a metallic sheet laminated with a thermoplastic resin film, even if the film thickness is extremely increased, does not function at all as a gasket by the single use of a rigid resin film. In addition, it is absolutely impossible to expect that a composite material formed by integrally injection molding a styrenic elastomer and polypropylene will function as a cover body because of the low rigidity of polypropylene as the substrate.
In the case of producing a gasket integrated with a metal by a method wherein a gasket portion is formed by injection molding or extrusion molding a thermoplastic elastomer onto the surface of a metallic cover body, the direction of the injection molding or extrusion molding for the thermoplastic elastomer has usually been the direction towards a butt contact surface on the gasket portion upon the use thereof (the surface of the gasket for the purpose of realizing hermet
Akasaka Ichiro
Imai Yasushi
Mashita Naruhiko
Nishimuro Youichi
Saito Youkou
Bridgestone Corporation
Mullis Jeffrey
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
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