Plastic and nonmetallic article shaping or treating: processes – Forming electrical articles by shaping electroconductive...
Reexamination Certificate
2000-06-08
2001-08-14
Ortiz, Angela (Department: 1732)
Plastic and nonmetallic article shaping or treating: processes
Forming electrical articles by shaping electroconductive...
C264S254000, C264S328180
Reexamination Certificate
active
06274070
ABSTRACT:
The present application corresponds to Japanese Application No. 09(1997)-41145, filed Feb. 25, 1997, the entire content of which is incorporated herein by reference.
FIELD OF THE INVENTION
The present invention generally relates to resin compositions and to methods for producing such compositions. More particularly, the present invention pertains to resin moldings composed of conductive parts and insulating parts, and to methods for producing such resin moldings.
BACKGROUND OF INVENTION
The production of resin moldings of the type having conductive parts typically involves the use of high-conductive plastics. These high-conductive plastics contain, as a conductive filler, short metal fibers of copper, stainless steel or the like. For example, the Journal of the Plastic Molding Engineering Society of Japan (Molding, '93), pp. 143-144, describes a conductive resin composition containing a conductive filler of Pb—Sn solder powder (e.g., Pb: 70%, Sn: 30%). Also, Japanese Patent Publication (JP-B) 07-49491 describes a conductive resin composition containing a combination of conductive fibers and low melting point metal consisting essentially of Pb—Sn.
One general method for producing resin moldings having conductive parts is disclosed in Japanese Laid Open Patent Application (JP-A) 63-50482 and 01-207989. The method involves forming a primary molding for the backbone from a plastic molding material capable of being easily plated by chemical plating (i.e., an easily platable material), injecting a plastic molding material that is hardly platable by chemical plating (i.e., a hardly platable material) into the area of the outer surface of the primary molding that is not to be plated, and integrating these to produce a secondary molding. Thereafter, the exposed area of the easily platable material of the secondary molding is plated.
The conventional method of forming the conductive parts through plating is illustrated in FIG.
6
. As illustrated therein, a filler and a base resin (for example, a thermoplastic resin) are first formulated in a predetermined ratio, kneaded and then pelletized into easily platable resin pellets (conductive material). Next, the resin pellets are formed into a primary molding to be the backbone through injection molding. The surface of this primary molding is etched and activated by catalytic treatment to facilitate the plating thereover. Next, the primary molding is subjected to secondary molding. Finally, the activated area of the surface is plated to form conductive parts. This method thereby produces a resin molding having conductive parts.
However, the conventional conductive composition comprising the conductive fibers and low melting point metal that consists essentially of Sn—Pb has a negative impact on the environment in that it contains lead, which is a harmful material. Substitutes for this material are presently needed.
In addition, the conventional method of producing resin moldings which have conductive parts requires an additional plating step for forming the conductive parts. This additional plating step undesirably increases the production costs associated with the method.
SUMMARY OF THE INVENTION
To avoid or conspicuously ameliorate the problems associated with the related art, it is an object of the present invention to provide a novel resin composition in which negative impacts on the environment is greatly reduced. It is a further object of the invention to provide resin moldings having conductive parts of the inventive resin composition and insulating parts. It is a further object of the invention to provide methods of producing the inventive resin composition and resin moldings. Through the invention, production costs for the resin moldings can be minimized.
In accordance with one aspect of the invention, a conductive resin composition is provided. The conductive resin composition is prepared by kneading a thermoplastic or thermosetting resin with a low melting point alloy, which is moldable along with the resin being molded and which consists essentially of tin but does not contain lead. Such a composition greatly reduces the negative environmental impact in comparison with conventional compositions.
Preferably, the low melting point alloy comprises an Sn—Cu base. Depending on the alloying ratio, the alloy may have a lowered melting point and may be in melt during molding of the composition, resulting in a composition which is easy to mold.
In accordance with a second aspect of the invention, provided is a resin molding composed of conductive parts of a conductive resin composition, and insulating parts of a thermoplastic or thermosetting resin. The conductive resin composition is prepared by kneading a thermoplastic or thermosetting resin with a low melting point alloy, which is moldable along with the resin being molded and which consists essentially of tin but does not contain lead.
According to this aspect of the invention, a primary molding for conductive parts is formed in the primal molding step and is integrated with insulating parts in the secondary molding step. The resulting resin molding thus composed of the conductive parts and the insulating parts has few negative influences on the environment.
In accordance with a third aspect of the invention, a method for producing a resin molding is provided. The method comprises a step of kneading a conductive filler with a base resin, a step of pelletizing the resulting resin mixture to give a conductive material where the base resin is a thermoplastic resin, or directly forming it into a conductive material where the base resin is a thermosetting resin, a step of molding a thermoplastic or thermosetting resin into a body through primary molding, and a step of integrating the resulting body with conductive parts of the conductive material through secondary molding.
According to the third aspect of the invention, the insulating resin body is formed through primary molding and is integrated with conductive parts in the secondary molding step. The resin molding thus produced is comprised of conductive parts and insulating parts. Accordingly, a plating step is not required and the production costs associated with this method are less than conventional methods.
In accordance with a fourth aspect of the invention, a further method for producing a resin molding is provided. The method comprises a step of kneading a conductive filler with a base resin, a step of pelletizing the resulting resin mixture to give a conductive material where the base resin is a thermoplastic resin, or directly forming it into a conductive material where the base resin is a thermosetting resin, a step of molding the conductive material into conductive parts through primary molding, and a step of forming a body of a thermoplastic or thermosetting resin integrated with the conductive parts through secondary molding.
In accordance with this aspect of the invention, the conductive parts are formed through primary molding and are integrated with an insulating resin body in the secondary molding step. The resin molding thus produced is comprised of conductive parts and insulating parts. Accordingly, a plating step is not required, and the production costs associated therewith are not as high as those of conventional methods.
Preferably, a dispersing aid is used in the kneading step to improve dispersion of the resin mixture to be pelletized. Using a uniform dispersion of the resin mixture improves the quality of the resin moldings formed.
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patent: 2 1
Izawa Shogo
Kohama Tadahiko
Matsumoto Akikazu
Tanigaki Tsuyoshi
Aisin Seiki Kabushiki Kaisha
Burns Doane , Swecker, Mathis LLP
Ortiz Angela
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