JPH01259044A - Rubber composition of ptc behavior - Google Patents

Abstract

PURPOSE:To obtain the subject composition useful as conductor constituting material for self-controlling type electric heating wire requiring accurate temperature control, having excellent flexibility and showing high degree of PTC behavior, comprising a specific polyisoprene and specific amount of electric conducting carbon black. CONSTITUTION:100pts.wt. polyisoprene having trans 1,4 bonding and 20-60wt.%, preferably 30-50wt.% crystallinity is mixed with 10-100pts.wt., preferably 30-70pts.wt. electrically conducting carbon black (preferably oil absorption of >=50cc/100g) to afford the aimed composition.

Description

[Detailed Description of the Invention] The present invention is based on the present invention.
It relates to a rubber composition exhibiting co-efficient behavior.

As is well known in the field, PTC behavior is a behavior in which the electrical resistance of a material increases greatly as the temperature rises in a specific temperature range, and it is characterized by a low electrical resistance near room temperature. PTC behavior materials exhibiting resistance find use as conductors in self-regulating heating wires, which are often used in heating cloaks and the like.

It is known that conductive compositions made by mixing conductive carbon black with organic polymers exhibit PTC behavior, but in some self-regulating heating wires, it is necessary to precisely control the temperature. The development of materials that exhibit a high degree of PTC behavior, that is, a property in which the electrical resistance of the material increases rapidly above a certain temperature, and that also has excellent flexibility has become an important issue.

- The present invention for divination is a means for solving the above problems.
Crystallinity with trans 1.4 bonds is 20-60% by weight
and 10 to 100 parts by weight of conductive carbon black per 100 parts by weight of the polyisoprene.

Matasato Zaiho The organic polymers used as the base of the composition include trans-l,
Polyisoprene having 4 bonds and a specific crystallinity is used, and by making the polyisoprene conductive with a specific amount of conductive carbon black, it has excellent flexibility and a high degree of PTC behavior. What you show is what you get.

As the polyisoprene having trans 1.4 bonds, which is the base of the composition of the present invention, one having a crystallinity of 20 to 60% by weight as measured by the density method is used. If the degree of crystallinity is less than 20% by weight, the desired high p 'r c behavior is not achieved, while if the degree of crystallinity is greater than 60% by weight, there is a problem of reduced flexibility due to the admixture of conductive carbon black. be. Therefore, those having a crystallinity of 25 to 55% by weight, particularly 30 to 50% by weight are preferred. The above-mentioned polyisoprene used in the present invention is manufactured by Kuraray Co., Ltd. under the trade name Tarare Transpolyisoprene TP-30.
1. Product name: TRA manufactured by Polysar
Examples include NS-PIF, especially ML. 4
．． Particularly preferred are those having a Mouni viscosity of 10 to 50 at 100°C.

The above polyisoprene may be used alone, but other low to highly crystalline organic polymers having good compatibility with the polyisoprene may be used, such as polyethylene, ethylene-vinyl acetate copolymer, ethylene-ethyl acrylate copolymer,
Syndiotactic 1゜2 polybutadiene, ethylene-propylene-diene terpolymer, ethylene-propylene copolymer, etc., or in small amounts with various rubbers, may be used or blended. The amount of the organic polymer used varies depending on the magnitude of the required PTC behavior, but in general, it is appropriate to use about 10 to 100 parts by weight per 100 parts by weight of the polyisoprene.

Examples of conductive carbon black include MT and FT.

SRF, GPF, HMF, FEFSFF, HAF.

Furnace or thermal blacks such as rsAF, SAF, acetylene black, CC, MPC.

Any of RPC channel blacks, lamp blacks such as HML, high structure blacks such as Ketchen Black EC, or other carbon blacks used in PTC behavior organic polymer compositions can be used, but the above high structure Blanks,
Particularly preferred is one with an oil absorption of 50 cc/100 g or more.

These conductive carbon blacks may be used alone or in combination of two or more. The amount of conductive carbon black mixed is per 100 parts by weight of the above polyisoprene,
The amount is approximately 10 to 100 parts by weight. When the amount is less than 10 parts by weight, it is difficult to obtain a composition having the desired conductivity, and when it is more than 100 parts by weight, there is a problem that the flexibility of the composition is reduced. Therefore, the amount of conductive carbon black mixed is preferably about 15 to 90 parts by weight, particularly about 30 to 70 parts by weight, per 100 parts by weight of the polyisoprene.

The composition of the present invention may contain various compounding agents, such as antioxidants, processing aids, fillers, flame retardants, etc., in normal amounts, as required. Although necessary, crosslinking can be carried out by a chemical crosslinking method using sulfur, thierams, or peroxide, a radiation crosslinking method, or the like.

EXAMPLES Below, the present invention will be explained in more detail with reference to Examples and Comparative Examples.

Examples 1 to 7, Comparative Example 1 The compositions of Examples 1 to 7 and Comparative Example 1 shown in Table 1 were mixed and prepared using two rolls, and then press-crosslinked at 170 t' for 20 minutes to form a 1 mm thick film. A crosslinked sheet was created.

For each stretched sheet obtained, 5 to 140
The electrical resistance-temperature characteristics between degrees Celsius and flexibility were evaluated.

The results are shown in the same table.

Method for Measuring Electrical Resistance-Temperature Characteristics: The volume resistivity of each crosslinked test piece of 1 mm thickness, 30 mm width, and 110 mm length was measured at each temperature in accordance with ASTM D991-68.

Flexibility evaluation method: Each 1 mm thick test piece (20 mm width x 100 mm length) was
Those with bending cracks or cuts were marked as ×, and those with no cracks or cuts were marked as O. .

25I and the composition of the present invention have excellent flexibility and exhibit a high degree of PTC behavior. Therefore, the composition of the present invention can be used as a conductor for self-regulating heating 'g1 line which requires precise temperature control. It is suitable as a constituent material.

Patent applicant: Mitsubishi Cable Industries, Ltd.

Claims (1)

[Claims] 1. A PTC behavior rubber composition comprising polyisoprene having a trans-1,4 bond and a crystallinity of 20 to 60% by weight, and 10 to 100 parts by weight of conductive carbon black per 100 parts by weight of the polyisoprene. .