JPH0676511B2 - Conductive resin composition - Google Patents

Description

TECHNICAL FIELD The present invention relates to a carbon-based conductive resin composition having a positive temperature coefficient in which resistance is stable for a long time and heat generation temperature is uniform.

2. Description of the Related Art Most of the conventional carbon-based conductive resin compositions having this type of positive temperature coefficient are formed by mixing carbon powder into an organic polymer binder having crystallinity to make contact with a carbon structure or a simple contact with carbon. And so on.
The temperature is controlled by changing the expansion or contraction of the crystalline organic polymer conjugate, separating the carbon contact point by changing the spherulite, and performing the contact appropriately to automatically change the resistance. It is a mechanism that indicates the temperature of.

Problems to be Solved by the Invention However, since the conductive resin composition having a positive temperature coefficient of this kind is mainly composed of a crystalline organic polymer, the operating temperature,
The spherulite of the crystalline organic polymer grows with the passage of time, the number of carbon contact points decreases, the current path length increases, and the phenomenon of increased resistance appears. As a result, the temperature of the conductive resin composition rises and it is endangered as a resistor. Therefore, the present invention intends to obtain a conductive resin composition having such a carbon-based positive temperature coefficient that resistance changes little even after long-term use and has stable temperature characteristics. Is.

Therefore, the technical means of the present invention for solving these problems is that an organic binder having crystallinity, carbon powder, and a structural formula are used. (However, R is H, CH ₃ , C ₂ H ₅ , and M is Al, Na, K, Ca) 0.1 wt% or more and less than 5 wt% is added, and the organic binder having the crystallinity is formed. The nucleating agent shown in the above structural formula for refining the spherulites is added to suppress the growth of spherulites under normal use conditions, reduce the change in carbon contact points, and stabilize the resistance to ensure long-term use. It is intended to obtain a composition having a stable and constant temperature even in a state.

Operation The effects of this technical means are as follows. That is, in a carbon-based conductive resin composition using a crystalline organic polymer, a spherulite of the crystalline organic polymer grows due to use conditions, time passage, etc., and a current path distance due to partial separation of carbon contact points. Becomes longer, resulting in an increase in resistance and a rise in temperature. In order to eliminate such a phenomenon, expansion of spherulites is suppressed, and a nucleating agent substance having a uniform refining effect is added to suppress change in resistance and change in temperature due to separation of carbon contact points. As a result, it is possible to obtain a carbon-based conductive resin composition which has a small change in carbon contact point, a constant resistance value, and a stable positive temperature coefficient over a long period of time.

Example Hereinafter, an example of the present invention will be described with reference to the drawings.

[Examples 1 to 5] A vinylsilane 0.5% solution was added to carbon powder, and after aging with stirring, vinylsilane-treated carbon powder was obtained.

A resin composition containing carbon by kneading this carbon powder with polyethylene modified with an organic acid as a first organic binder and benzoic acid (C ₆ H ₅ COOH) as a nucleating agent according to the composition in the table at 150 to 180 ° C. and 75 rpm for 10 to 15 minutes. I got a thing.

After crushing this composition, an olefin elastomer is added as a second organic binder, and the final carbon content is
Adjusted to be 30wt%. A copper electrode was formed on the conductive resin composition thus obtained, and after annealing, the performance of resistance to time was evaluated. The results are shown in the figure.

[Examples 6 to 10] Similar to Examples 1 to 5, the action is shown as a nucleating agent. Dibenzylidene sorbitol (Gel-ol MD; Shin Nippon Rika) C ₂₂ H
₂₆ O ₆ was added instead of benzoic acid and similar results as shown in the figure were obtained.

Although benzoic acid and dibenzylidene sorbitol were used as nucleating agents in the present application, aluminum benzoate, potassium benzoate, calcium benzoate, sodium benzoate, sodium β-naphthoate, sodium cyclohexanecarboxylate, etc. may be used. It has been confirmed that the same effect as the present invention can be obtained. Further, in the present example, the maximum effect was obtained by adding the nucleating agent to 0.3 wt%, but if it was less than 5 wt%, a sufficient effect was obtained. However, if it is added in an amount of 5 wt% or more, the cost becomes high and the economical effect cannot be obtained.

As described above, according to the present invention, in a conductive composition containing a crystalline resin, the spherulites of the crystalline resin grow and expand with age and use conditions such as temperature, and it is difficult to cut the contact point of the conductive material to reduce resistance. There is an increasing phenomenon. However, as in the present application, by adding a substance for making the spherulites fine and uniform, the growth is eliminated, the carbon contact points are not separated, and the resistance is made uniform over a long period of time.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a graph showing changes in resistance value of the composition shown in one example of the present invention.

Claims (1)

[Claims] 1. A crystalline organic binder, carbon powder and structural formula (Wherein, R represents _{H, CH 3, C 2 H} 5, M is Al, Na, K, Ca) compound a conductive resin composition obtained by adding less than 0.1 wt% or more 5 wt% represented by.