JPH0456003A - Electroconductive sheet - Google Patents

Abstract

PURPOSE:To provide an electroconductive sheet presenting lesser fluctuation in the electric resistance even in the case of deformation by using a preparation consisting of highpolymer material such as rubber and carbon black. CONSTITUTION:Carbon black having a bulk specific gravity of 0.3g/cc or more and particle sizes over 40mum is included by 100-300 parts by weight relative to 100 parts by wt. highpolymer material, and the resultant preparation is used to make an electroconductive sheet. The highpolymer material used consists of different types of rubber or resin which are capable of being shaped into a flexible sheet.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a conductive sheet. More specifically, the present invention relates to a conductive sheet made of a polymeric material such as rubber and carbon black.

[Conventional technology]

Conventionally, carbon black, which is commercially available as a particularly conductive grade, has been used for conductive sheets made of polymer materials such as rubber and carbon black in order to obtain high conductivity. Although this grade of carbon black has a high unit price, it has a characteristic of being able to obtain high conductivity with a small amount of filling, and has a high structure.

However, although conductive sheets using such high-structure carbon black can achieve high conductivity with a small amount of compounding, because of the small amount, the number of contact points between particles is small, and when deformed, the contact points It has a large effect on the resistance value if it comes off. On the other hand, since there is a large amount of polymeric material, if the contact points shift, the polymeric material will get in between, and the resistance will increase each time deformation is applied.

Therefore, this conductive sheet may be used for applications that are stationary or where a slight change in resistance is not a problem, such as antistatic materials or EMI shielding materials (electromagnetic wave shielding materials), but it may be used for deformation. When used as a sheet heating element with a It ceases to function as a.

[Problem to be solved by the invention]

An object of the present invention is to provide a conductive sheet made of a polymeric material such as rubber and carbon black, which exhibits little change in electrical resistance even when deformed.

[Means to solve the problem]

The object of the present invention is to provide a conductive material molded from a compound containing approximately 100 to 300 parts by weight of carbon black having a bulk specific gravity of 0.3 g/cc or more and a particle size of 40 mμ or more per 100 parts by weight of a polymeric material. This is achieved by sheets.

As the polymer material, various rubber materials or various resin materials that can be molded into a flexible sheet shape are used. Specifically, for example, natural rubber, NBR, EPD
Rubber materials such as synthetic rubbers such as M, silicone rubber and fluororubber, ethylene-vinyl acetate copolymers, partially or completely saponified products thereof, and resin materials such as ethylene-acrylic acid copolymers are used.

As carbon black, the bulk specific gravity is 0.3g/cc
As mentioned above, when the particle size is 40+eμ or more, the DBP (dibutyl phthalate) oil absorption is 1. ] cc/g or less is used. Examples of such loin structure carbon black include carbon blacks such as SRF, FEF, and GPF. On the other hand, if a highly conductive furnace black, acetylene black, etc., whose bulk specific gravity or particle size is outside the above specification is used.

Changes in resistance can be seen during deformation such as bending.

Loin structure carbon black is a polymer material 1
00 parts by weight (used at a ratio of about 10 to 300 parts by weight. Carbon black needs to occupy about 30% or more by volume of the molding material containing various compounding agents,
Although it depends on the amount of the compounding agent, it is used in a proportion of about 100 parts by weight or more. On the other hand, if it is used in a proportion of about 300 parts by weight or more, the polymeric material can no longer function as a binder sufficiently and cannot be formed into a sheet.

Forming conductive sheets from such formulations.

When the polymer material is a rubber material, it is press-vulcanized using vulcanization conditions depending on the type of rubber used, and when it is a resin material, it is made into a sheet shape using a forming method such as press molding or extrusion molding. molded. The molded conductive sheet is
Generally, the thickness is about 0.1 to 2 mm, but the thickness is not limited to this range depending on the application.

Conductive sheets are generally formed directly from a compound as a single sheet, but if the compound is made into a solution in an organic solvent,
It can also be applied onto a fibrous substrate such as a woven or nonwoven fabric made of fibers resistant to the organic solvent used using a doctor knife and dried to form a sheet that is integrated with the fibrous substrate.

[Function] and [Effects of the Invention] The conductive sheet of the present invention, which is obtained by filling a polymer material with a large amount of loin-structured carbon black, is free from the situation where the carbon black particles shift and separate from each other due to deformation such as bending. Even when the carbon black particles become in contact with other carbon black particles, the number of conduction paths changes, but the number remains the same, and as a result, there is almost no change in the overall resistance.

Specifically, as shown in the comparison between Examples and Comparative Examples below, even if the conductive sheet of the present invention is deformed by bending, its resistance quickly returns to its original value, and when it is repeatedly folded, it becomes a highly structured carbon sheet. In the conductive sheet using black, the resistance change is accumulated, but in the sheet of the present invention, the resistance value returns to the original value even after repeated bending, indicating that the resistance stability is very good. I understand.

Furthermore, in the case of a conductive sheet integrated with a fibrous substrate, changes at the initial stage of bending are further reduced, making it more effective.

The conductive sheet of the present invention that exhibits such effects can be stably used in applications such as planar heating elements that are subject to deformation.

〔Example〕

Next, the present invention will be explained with reference to examples.

Example 1 100 parts of EPDM (Japan Synthetic Rubber Products EP22) (
weight, the same below), SRF carbon black (Chubu Carbon Products HTC#S-5; bulk specific gravity 0.5g/cc,
Particle size 50m μ, DBP oil absorption 0.74cc/g) 1
00 parts, zinc oxide 5 parts, stearic acid 1.5 parts, sulfur 1.5 parts and vulcanization accelerator (Irunai Shinko Chemical EP-9
A blend obtained by kneading 4 parts of 0) in a kneader was mixed with 180
C. for 6 minutes to obtain a conductive sheet with a thickness of 0.2 .ANG. (sheet resistance: 450 .OMEGA./hole).

This conductive sheet was cut into a size of 100 x 120 mm, and IpilOmm electrodes were attached to both ends of the long side.

It was bent 180° so that the electrode portions overlapped, and the rate of increase in resistance over time (unit: 2%) at that time was measured.

Example 2 In Example 1, the amount of SRF carbon black was changed to 150
Change to part, conductive sheet (area resistance 110Ω/hole)
I got 4.

Example 3 In Example 1, the amount of SRF carbon black was changed to 20
Change to 0 parts, conductive sheet (area resistance 60Ω/mouth)
I got it.

Comparative Example 1 In Example 1, CF carbon black, which is a conductive grade carbon black, was used instead of SRF carbon black.
A conductive sheet (sheet resistance 100 Ω/port) was obtained using 30 parts of Ketchen Black (Lion product Ketchen Black EC; bulk specific gravity 0.15 g/cc, particle size 30μ, DBP oil absorption 3.6 cc/g). Ta.

The measurement results for each of the above Examples and Comparative Examples are shown in Table 1 below.

Table 1 0 +7 1 +3 +5 +3 +5 42 0 +5 0 0 +4 0 0 +3 0 0 +3 Furthermore, for Example 2 and Comparative Example 1, increase in resistance when bending every 5 minutes while shifting the bending position The change in rate over time is shown in the graph of FIG.

Examples 4 to 6, Comparative Example 2 Each of the formulations of Examples 1 to 3 and Comparative Example 1 was dissolved in 800 parts of toluene, and the toluene solution was applied to the base fabric (Teitoron plain weave T) 1 with a doctor knife. -11
) and dried at 100℃ for 5 minutes, then
Press vulcanization was performed under the conditions of g/cd, 180° C., and 10 minutes to obtain a conductive sheet with a thickness of 0.2 mm.

The results of the bending test for this conductive sheet are shown in Table 2 below.

Table 2

[Brief explanation of drawings]

FIG. 1 is a graph showing the rate of increase in resistance over time in Example 2 and Comparative Example 1.

Claims (2)

[Claims] 1. An electrically conductive sheet formed from a compound containing approximately 100 to 300 parts by weight of carbon black having a bulk specific gravity of 0.3 g/cc or more and a particle size of 40 mμ or more per 100 parts by weight of a polymeric material. 2. The conductive sheet according to claim 1, formed on a fibrous substrate.