JP2606392B2 - Conductive gasket material and manufacturing method thereof - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gasket material having conductivity, and more particularly to a gasket material used for reliably performing electromagnetic shielding of a housing fitting portion. It relates to the manufacturing method.

[Conventional technology and its problems]

In order to protect the electronic circuit inside the housing from external noise radio waves, a conductive gasket material is used for the housing fitting portion. Conventionally, as a gasket material, silver powder or silver-coated powder is mixed and dispersed in rubber to form a sheet. However, sufficient conductivity is obtained unless silver is added to the rubber substrate in an amount of 70% by weight or more. Because of this, rubber elasticity is impaired, and the cost is extremely high, so that its use is limited. In addition to silver powder-containing rubber materials, metal meshes, metal foams, metal leaf springs, and the like have been conventionally used as gasket materials, but these materials are also expensive, have poor flexibility, and lack airtightness. There is a problem.

[Means for Solving the Problems: Structure of the Invention]

The present inventors have studied a gasket material having excellent electromagnetic shielding effect, high flexibility and airtightness, low cost and excellent versatility, and a nonwoven fabric comprising a mixture of silver-coated organic fibers and ordinary organic fibers. It has been found that the conventional problem can be overcome by using a material impregnated with an elastomer.

According to the present invention, the organic fiber coated with silver is at least
There is provided a conductive gasket material characterized in that a nonwoven fabric containing 10% by weight or more is impregnated with an elastomer.

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

The gasket material of the present invention is made of a non-woven fabric in which silver-coated organic fibers and ordinary organic fibers not coated with silver are mixed. Here, the organic fiber is a natural or synthetic organic fiber, that is, a fiber such as cotton, hemp, regenerated cellulose, polyamide, acryl, polyolefin, or polyether. The thickness of the organic fiber is preferably from 0.1 to 15 d (denier), and if it is smaller than 0.1 d, a large amount of silver is required, and the overall weight increases. If the thickness of the fiber is larger than 15d, the silver coverage can be reduced, but the fiber becomes hard and loses flexibility.

The silver-coated organic fibers are mixed in at least 10% by weight or more. If the mixing amount is less than 10% by weight, the conductivity is small,
It can only be used for applications of the order of an electrostatic shield,
A sufficient electromagnetic wave shielding effect cannot be obtained. On the other hand, the conductivity of the gasket material can be adjusted by increasing or decreasing the amount of the silver-coated organic fiber, and the conductivity of the gasket material increases as the amount of the silver-coated organic fiber increases.

As a method for coating silver, an electroless plating method, a vacuum evaporation method, or the like can be applied. Among these coating methods, the electroless Mecca method is excellent in mass productivity. Silver coverage is 5-50
% By weight is preferred. If the amount is less than 5% by weight, the fiber cannot be sufficiently coated, the conductivity is greatly reduced, and a satisfactory electromagnetic wave shielding effect cannot be obtained. On the other hand, if the silver coating amount is more than 50% by weight, the overall weight becomes heavy and the conductivity of the silver-coated organic fiber also reaches a plateau.

Incidentally, as the metal to be coated on the organic fibers to impart conductivity, in addition to silver, nickel and CuS are known,
It has been pointed out that nickel is allergic to humans and carcinogenic. Nickel and CuS are inferior in conductivity to silver. Therefore, silver is preferred in view of safety, degree of conductivity, cost, and the like.

As described above, the gasket material of the present invention is provided with conductivity by containing the silver-coated organic fiber, and the conductivity is adjusted by increasing or decreasing the mixing amount. On the other hand, as another method for imparting conductivity, it is conceivable to form the entire nonwoven fabric with ordinary organic fibers not previously coated with silver, and then immerse the nonwoven fabric in a silver plating bath to apply silver coating to the entire nonwoven fabric. In this case as well, the conductivity of the gasket can be adjusted by increasing or decreasing the amount of silver coating. However, the cost is high because the silver coating amount is required to be at least 5% by weight of the entire nonwoven fabric. Since the temperature and pressure are applied in the bath, the nonwoven fabric is compressed, the elasticity becomes poor, and the elastomer is hardly impregnated.

As described above, the gasket material of the present invention is manufactured using a conductive nonwoven fabric. Non-woven fabrics are preferred because they have a higher porosity than woven fabrics and cotton and are rich in elasticity. Also, the conductivity is easily adjusted.

Next, the gasket material of the present invention is produced by impregnating a non-woven fabric made of a mixture of the organic fibers with an elastomer. As the elastomer to be impregnated, a sulfur-free cross-linked resin such as silicone rubber, ethylene propylene rubber, butyl rubber, fluorine rubber, fluorosilicone rubber or the like is used. When the strength of the nonwoven fabric is low when the elastomer is impregnated, the nonwoven fabric may be impregnated with a heat-fusible low-melting polyester or the like and heat-sealed, or may be coated with a resin paint and bonded in advance. If the gasket material does not require airtightness, it is not necessary to impregnate with an elastomer.However, if complete sealing is required, or if the gasket material is repeatedly opened and closed, the airtightness, elasticity, and breaking strength are obtained by impregnation of the elastomer. Can be improved, so that a highly versatile product can be obtained.

〔The invention's effect〕

The gasket material of the present invention has a better electromagnetic wave shielding effect than the conventional gasket material. It also has high elasticity and breaking strength, and exhibits excellent airtightness and durability when fitted to the housing fitting portion. Further, the amount of silver used is small and the cost is low, so that it can be used for a wide range of applications.

[Examples and Comparative Examples]

Examples of the present invention are shown below together with comparative examples. In addition, the following examples do not limit the scope of the present invention.

30% by weight of silver on an aromatic polyamide fiber (manufactured by Teijin Limited: Conex, 2d × 51mm) by electroless plating
Coated. Specifically, the fiber was first immersed in a scouring agent, washed with water, immersed in an aqueous solution containing stannous chloride 10 g / l, and hydrochloric acid 20 ml / l, washed with water, and provided with a catalytic property for electroless silver plating. Thereafter, silver was coated using a predetermined amount of a plating solution having the following composition. Since all silver ions in the plating solution were reduced and precipitated, an amount of the plating solution containing silver ions corresponding to the coating amount was used.

Electroless silver plating solution (for 10g silver: solution temperature 25 ° C) Tetrasodium ethylenediaminetetraacetate 200g / 2l Sodium hydroxide 50g / 2l Formalin 100ml / 2l Dissolve in silver nitrate 31.6g 1ml and add dropwise ammonia water 100ml〃 This was made into a nonwoven fabric with a basis weight of 50 g / m ² , impregnated with silicone rubber, pressurized at 150 ° C to 200 kgf / m ² , and pressed to a thickness of 0.5 mm for primary vulcanization, followed by secondary vulcanization at 200 ° C for 4 hours. To prepare a test piece (Example 1).

For comparison, a 0.5 mm-thick test piece (specific gravity: 3.8, Comparative Example 1) in which 80% by weight of silver powder was dispersed in the same rubber base material, silver
Thickness with 70% by weight of 10% by weight coated glass beads dispersed.
A 5 mm test piece (specific gravity 1.7, Comparative Example 2) was prepared, and various physical properties such as the breaking strength, hardness, and electromagnetic wave shielding effect at an electric field of 200 MHz were examined. Table 1 shows the results.

As is clear from the results in Table 1, Example 1 and Comparative Example 1
Have the same volume resistance value, and therefore have substantially the same electromagnetic shielding effect. However, the amount of silver used in Example 1 is remarkably smaller than that of Comparative Example 1 and is about 1/100, and extremely high conductivity is obtained with a small amount of silver used. It has achieved the nature. The breaking strength of Example 1 is about 2 to 4 times larger than that of Comparative Example,
Has excellent durability. Further, the hardness of Example 1 is the smallest and rich in elasticity as compared with the comparative example.

 ──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-59-140281 (JP, A) JP-A 62-59387 (JP, U) JP-A 63-102299 (JP, U) JP-A 61-140 137693 (JP, U)

Claims (3)

(57) [Claims] 1. A conductive gasket material comprising an elastomer impregnated in a nonwoven fabric containing at least 10% by weight or more of organic fibers coated with silver. 2. The gasket material according to claim 1, wherein silver-coated organic fibers having a silver coverage of 5 to 50% by weight are used. 3. A conductive gasket material is produced by mixing at least 10% by weight or more of organic fibers coated with silver and organic fibers not coated with silver to form a nonwoven fabric, and impregnating the nonwoven fabric with an elastomer. A method for producing a gasket material, comprising: