JPH03200888A - Conductive gasket material and its manufacture - Google Patents

Abstract

PURPOSE:To obtain a conductive gasket material excellent in an electromagnetic wave shielding effect, elasticity, breaking strength, etc., by mixing a specified amount of organic fibers coated with silver and those not coated with silver, forming a nonwoven fabric from the mixture, and infiltrating an elastomer into the fabric. CONSTITUTION:At least 10wt.% organic fibers (e.g. aromatic polyamide fibers) coated with silver are mixed with those not coated with silver to produce a nonwoven fabric. To coat organic fibers with silver, electroless plating, vacuum deposition, etc., are suitably utilized. A suitable coating weight of silver is 5-50wt.%. The nonwoven fabric is impregnated with an elastomer to give a conductive gasket material. As the elastomer for impregnation, a silicon rubber, an ethylene propylene rubber, a fluorosilicone rubber, etc., are suitably used. The gasket material thus obtained has high flexibility and hermetically sealing properties, is inexpensive and is excellent in versatility.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a gasket material having electrical conductivity, and more particularly to a gasket material used to ensure electromagnetic shielding of a housing fitting part. It relates to its manufacturing method.

[Conventional technology and its issues]

In order to protect the electronic circuit inside the housing from external noise radio waves, a conductive gasket material is used in the housing fitting part. Conventionally, gasket materials have been made by mixing and dispersing silver powder or silver-coated powder into rubber and forming it into a sheet, but sufficient conductivity cannot be achieved unless silver is added to the rubber base material in an amount of 70% by weight or more. The rubber elasticity is impaired because it cannot be used, and the cost is very high, so its applications are limited.

In addition to rubber materials containing silver powder, metal mesh, metal foam, metal plate springs, etc. have been conventionally used as gasket materials, but these materials are also expensive, have poor flexibility, and are not airtight. There is a problem.

[Means for solving the problem: Structure of the invention]

The present inventors investigated a gasket material that has excellent electromagnetic shielding effect, high flexibility and airtightness, is low cost, and has excellent versatility. It has been found that the conventional problems can be overcome by using a material impregnated with nidistomer.

According to the present invention, at least one silver-coated organic fiber is
A conductive gasket material is provided, which is characterized by impregnating a nonwoven fabric containing 0% by weight or more with a nidistomer.

Further, according to the present invention, after mixing at least 10% by weight of organic fibers coated with silver and organic fibers not coated with silver to form a nonwoven fabric, the nonwoven fabric is impregnated with an elastomer to form a conductive gasket material. A method of manufacturing a gasket material is provided.

The gasket material of the present invention is made from a nonwoven fabric that is a mixture of silver-coated organic fibers and ordinary organic fibers that are not coated with silver.

The organic fibers herein include natural and synthetic organic fibers, ie, fibers such as cotton, hemp, regenerated cellulose, polyamide, acrylic, polyolefin, and polyester. The thickness of the organic fiber is preferably 0.1 to 15 d (denier).
If it is thinner than 1d, a large amount of silver coating is required and the overall weight increases. Furthermore, if the thickness of the fiber is greater than 15 d, the amount of silver coating can be reduced, but the fiber becomes hard and loses its flexibility.

The silver-coated organic fibers are mixed at least 10% by weight. When the mixing amount is less than 10% by weight, the conductivity is low;
It can only be used as an electrostatic shield,
A sufficient electromagnetic shielding effect cannot be obtained.6 On the other hand, the conductivity of the gasket material can be adjusted by increasing or decreasing the amount of silver-coated organic fibers, and as the amount of silver-coated organic fibers increases, the conductivity of the gasket material also increases. .

As a method for coating with silver, an electroless plating method, a vacuum evaporation method, etc. can be applied. Of these coating methods, the electroless plating method is superior in mass productivity.

The coating amount of silver is preferably 5 to 50% by weight. If it is less than 5% by weight, the fibers cannot be sufficiently covered, the conductivity will be significantly reduced, and a satisfactory electromagnetic shielding effect cannot be obtained.
Furthermore, if the amount of silver coating is more than 50% by weight, the overall weight becomes heavy and the electrical conductivity of the silver-coated organic fiber reaches its peak.

In addition to silver, nickel and CuS are known as metals to be coated on organic fibers to impart conductivity.
It has been pointed out that nickel is allergic to the human body and carcinogenic, and nickel and CuS have poorer conductivity than silver. Therefore, silver is preferable in terms of safety, conductivity, cost, etc.

As described above, the gasket material of the present invention is imparted with electrical conductivity by containing the silver-coated organic fibers, and the electrical conductivity is adjusted by increasing or decreasing the amount of the mixture. On the other hand, there are other ways to provide conductivity.

It is conceivable to form the entire nonwoven fabric in advance from ordinary organic fibers not coated with silver, and then immerse the nonwoven fabric in a silver plating bath to coat the entire nonwoven fabric with silver. Even in this case, the conductivity of the gasket can be adjusted by increasing or decreasing the amount of silver coating, but the cost increases because the amount of silver coating must be at least 5% by weight of the entire nonwoven fabric.
Furthermore, the nonwoven fabric is compressed due to the application of temperature and pressure in the plating bath, resulting in poor elasticity and impregnation of the elastomer, which is not preferable.

Incidentally, as described above, the gasket material of the present invention is made using a conductive nonwoven fabric. Nonwoven fabrics are preferred because they have a higher porosity than woven fabrics, cotton, etc., and are more elastic. Furthermore, the conductivity can be easily adjusted.

Next, the gasket material of the present invention is made by impregnating a nonwoven fabric made of a mixture of the above-mentioned organic fibers with an elastomer. As the elastomer to be impregnated, sulfur-free crosslinked resins such as silicone rubber, ethylene propylene rubber, butyl rubber, fluororubber, and fluorosilicone rubber are used. When impregnating the elastomer, if the strength of the non-woven fabric is low, it is best to impregnate the hand-woven fabric with heat-fusible low melting point polyester and heat-seal it, or coat it with resin paint and bond it in advance. However, if airtightness is not required for the gasket material, it is not necessary to impregnate it with elastomer, but if complete sealing is required or if it is repeatedly opened and closed, impregnation with elastomer will improve airtightness, elasticity, and rupture. Since the strength can be improved, a product with high versatility can be obtained.

〔Effect of the invention〕

The gasket material of the present invention has a better electromagnetic shielding effect than conventional gasket materials. It also has high elasticity and breaking strength, and exhibits excellent airtightness and durability when fitted into the housing fitting part. Furthermore, the amount of silver used is small, the cost is low, and it can be used in a wide range of applications.

[Examples and comparative examples]

Examples of the present invention will be shown below along with comparative examples, but the following examples do not limit the scope of the present invention.

Aromatic polyamide fiber (manufactured by Ondai Co., Ltd.: Conex,
2dX51+*w+) by electroless plating method.
0% by weight coating. Specifically, the fibers were first immersed in a scouring agent, washed with water, and then immersed in stannous chloride 10g/ffi and hydrochloric acid 20m
After immersing in an aqueous solution containing Q/D and washing with water to impart catalytic properties to electroless silver plating, silver was coated using a predetermined amount of a plating solution having the following composition. Since all the silver ions in the plating solution are reduced and precipitated, an amount of the plating solution containing silver ions corresponding to the coating amount was used.

Electroless silver plating solution (silver log minute: liquid temperature 25°C) Tetrasodium ethylenediaminetetraacetate 200g/2 Q Sodium hydroxide 50g/2f
i formalin 100aQ
/2 Q Ammonia water 100n n This is made into a non-woven fabric with a basis weight of 50g/rrr, impregnated with silicone rubber, and heated to 200kgf/r/ at 150℃.
, After primary vulcanization under pressure to a thickness of 0.51 mil, 200℃
A test piece was prepared by secondary vulcanization for 4 hours (Example 1).

For comparison, a test piece with a thickness of 0.50 in which 80% by weight of silver powder was dispersed in the same rubber base material (specific gravity 3.8. Comparative Example 1) was prepared.
), a 0.5 mm thick test piece in which 70 wt % of glass beads coated with 10 wt % silver were dispersed (specific gravity 1.7, Comparative Example 2)
Created, the amount of silver used, breaking strength, hardness, electric field 200M1 (
Various physical properties such as electromagnetic shielding effect at z were investigated. The results are shown in Table 1.

Table 1 As is clear from the results in Table 1, the volume resistance values of Example 1 and Comparative Example 1 are the same, and therefore the electromagnetic shielding effects are also approximately the same, but the amount of silver used in Example 1 is higher than that in Comparative Example. It is much less than that, about 1/100, indicating that extremely high conductivity can be achieved with a small amount of silver used. Moreover, the breaking strength of Example 1 is about 2 to 4 times greater than that of the comparative example, and it has excellent durability. Furthermore, the hardness of Example 1 is the smallest compared to the comparative example, and it is rich in elasticity.

Claims (3)

[Claims] 1. A conductive gasket material comprising a nonwoven fabric containing at least 10% by weight of organic fibers coated with silver and impregnated with an elastomer. 2. The gasket material according to claim 1, which uses silver-coated organic fibers having a silver coating amount of 5 to 50% by weight. 3. A conductive gasket material is produced by mixing at least 10% by weight of organic fibers coated with silver and organic fibers not coated with silver to form a nonwoven fabric, and then impregnating the nonwoven fabric with an elastomer. Method of manufacturing gasket material.