JPH0342483B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a heat-sensitive resistive conductive material and a method for producing the same, and more specifically to a heat-sensitive resistive conductive material having a small electrical resistance value at room temperature and a large resistance increase factor in a specific temperature range, and a method thereof. Regarding the manufacturing method.

Heat-sensitive resistive conductive materials have the property of rapidly increasing their electrical resistance when reaching a specific temperature range, and various types have been known (Japanese Patent Publications No. 36-16338, No. 50). −33707, 56−
10352 etc.).

However, these conventional materials have a problem in that their resistance value at room temperature is quite high, and the resistance increase factor when a specific temperature range is reached is not sufficiently high.

The present inventors have conducted various studies to solve the above-mentioned conventional problems, and as a result, we have found that a conductive filler is a mixture of two or more types of conductive particles with different particle sizes, and the average particle size is We have discovered that by using a conductive particle mixture in a specific range, it is possible to obtain a heat-sensitive resistive conductive material that has a small electrical resistance value at room temperature and a large resistance increase ratio when reaching a specific temperature range, and we have developed this knowledge. Based on this, we have completed the present invention.

That is, the present invention firstly provides a crosslinked composition comprising a crystalline polymer and a conductive filler, in which 100 parts by weight of the crystalline polymer is added with a particle size of 10 to 35 mμ as the conductive filler. consisting of a mixture of two or more types of conductive particles with different particle sizes, including one or more types of conductive particles with a particle size of 35 to 200 mμ, and the average particle size (number average) is 15
The present invention provides a heat-sensitive, resistant, conductive material comprising 40 to 150 parts by weight of a conductive particle mixture having a particle diameter of 10 to 35 mμ to 100 parts by weight of a crystalline polymer. consisting of a mixture of two or more types of conductive particles with different particle sizes, including one or more types of conductive particles with a particle size of 35 to 200 mμ, and the average particle size (number average) is 15-50
40 to 150 parts by weight of a conductive particle mixture having mμ is blended, then kneaded at a temperature equal to or higher than the melting point of the crystalline polymer, and then the kneaded product is crosslinked. The present invention provides a method for producing synthetic materials.

The crystalline polymer used in the present invention is not particularly limited and may include various types, but usually polyolefins and olefin copolymers such as high density polyethylene, low density polyethylene, polypropylene, and ethylene-propylene polymers are used. They include various types of polyamides, polyesters, fluorine-based polymers, and modified products thereof.

Next, in the present invention, as a conductive filler,
Consisting of a mixture of two or more types of conductive particles with different particle sizes, including one or more types of conductive particles with a particle size of 10 to 35 mμ and one or more types of conductive particles with a particle size of 35 to 200 mμ, and with an average particle size A conductive particle mixture with a diameter of 15-30 mμ is used.

Various types of conductive particles can be used here. Specific examples include carbon black such as oil furnace black, thermal black, and acetylene black; graphite; metal particles; and mixtures thereof.
Particularly suitable are carbon black, graphite and mixtures thereof.

The conductive particle mixture used in the present invention consists of two or more types of conductive particles having different particle sizes, one or more types of conductive particles having a particle size of 10 to 35 mμ, preferably 16 to 30 mμ, and It consists of a mixture with one or more types of conductive particles having a diameter of 35 to 200 mμ, preferably 40 to 100 mμ. Moreover, the conductive particle mixture used in the present invention has an average particle diameter of 15 to 50 mμ,
Preferably it is 20 to 40 mμ.

Here, the average particle diameter of the conductive particle mixture is 15 mμ
If it is less than that, the resistance increase magnification of the resulting heat-sensitive resistive conductive material upon reaching a specific temperature range will not be sufficient. On the other hand, if the average particle diameter exceeds 50 mμ, the resulting heat-sensitive resistive conductive material will have a large electrical resistance value at room temperature, which is not preferable.

One or more of the above conductive particles with a particle size of 10 to 35 mμ and one of the conductive particles with a particle size of 35 to 200 mμ
There is no particular restriction on the mixing ratio of the above-mentioned conductive particles as long as the average particle diameter of the resulting conductive particle mixture is 15 to 50 mμ, but the ratio of the former to the latter is usually
A value of 0.1 to 4, preferably 0.3 to 2.5 is used.

The mixing ratio of the crystalline polymer and dielectric particle mixture is 100 parts by weight of the former and 40 parts by weight of the latter.
-150 parts by weight, preferably 45-120 parts by weight.
If the amount of the conductive particle mixture is less than the above ratio, the electrical resistance value at room temperature, that is, the initial resistance value of the resulting heat-sensitive resistive conductive material becomes large; The rate of increase in resistance value in the region decreases.

The first heat-sensitive resistive conductive material of the present invention is a crosslinked composition comprising the above-mentioned crystalline polymer and a conductive filler.

Although the first heat-sensitive resistive conductive material of the present invention as described above can be manufactured by various methods,
The second aspect of the present invention is to provide a particularly suitable manufacturing method.

That is, first, 100 parts by weight of a crystalline polymer is made of a mixture of one or more types of conductive particles with a particle size of 10 to 35 mμ and one or more types of conductive particles with a particle size of 35 to 200 mμ, and the average particle size is 40 to 150 parts by weight of a conductive particle mixture having a particle diameter of 15 to 50 mμ is blended.

Next, this blend is heated at a temperature equal to or higher than the melting point of the crystalline polymer, preferably at a temperature higher than the melting point by 30°C or more, more preferably at a temperature of 35 to 150°C higher than the melting point.
Knead at a high temperature. Specifically, the temperature is usually about 140 to 200°C, although it varies depending on the type of crystalline polymer used and cannot be unambiguously determined. If the kneading temperature is outside the above range,
This is not preferable because the electrical resistance value at room temperature becomes large.

Further, as for the kneading time, it is sufficient if the kneading time is 5 minutes or more after reaching the above-mentioned kneading temperature, that is, a temperature equal to or higher than the melting point of the crystalline polymer used. This kneading is done using a Banbury mixer,
This may be carried out using a kneader such as a mixing roll.

After this kneading, the kneaded product is crosslinked. The crosslinking treatment can be carried out by various means, such as a method of adding a crosslinking agent such as an organic peroxide, a method of using ozone, and a method of irradiating with active energy rays such as electron beams. Here, the organic peroxides include benzoyl peroxide, t-butyl peroxybenzoate, dicumyl peroxide, t-butylcumyl peroxide, t-butyl peroxide, 2,5-dimethyl-2,5-di(t -butylperoxy)hexyne-3 and the like.

The degree of crosslinking mentioned above is such that the gel fraction is 20 to 55% by weight, preferably based on the crystalline polymer used.
It should be adjusted within a range of 30 to 50% by weight. If the gel fraction is less than 20% by weight, the resulting heat-sensitive resistive conductive material will not have sufficient positive temperature coefficient characteristics, and if it exceeds 55% by weight, the rate of increase in resistance value in a specific temperature range will decrease. I don't like it.

In this way, the degree of crosslinking of the crystalline polymer can be adjusted within the above-mentioned range by appropriately determining the temperature, time, amount of crosslinking agent, etc. used during the crosslinking reaction. For example, when organic peroxide is used as a crosslinking agent for high-density polyethylene, the amount of organic peroxide used is 0.05 to 0.30% relative to the high-density polyethylene.
By weight%, kneading at a temperature of 160 to 180°C for about 0.5 to 5 minutes, and heating at around 190°C for about 5 to 15 minutes during molding will advance crosslinking to the desired range.

Note that when crosslinking is performed using organic peroxide, the temperature difference between the ignition point of the organic peroxide and the kneading temperature of the resin composition containing the conductive filler is small, so the organic peroxide is likely to ignite. Therefore, organic peroxide is added to the resin composition by mixing the organic peroxide with a portion of a crystalline polymer such as polyethylene in advance at room temperature and feeding the mixture to a kneader. It is preferable. Further, it is preferable to introduce an inert gas such as nitrogen gas, argon gas, or carbon dioxide gas into the kneading machine to keep the O ₂ concentration at 10% or less. In this way, when using a crosslinking agent such as an organic peroxide, it is preferable to use a mixture of the crosslinking agent and a part of the crystalline polymer in advance, and furthermore, it is carried out in the presence of an inert gas. It is more preferable.

In addition, when crosslinking is performed using ozone, after exposure to a gas containing 0.5 to 20% by volume of ozone for 0.5 to 8 hours, a crosslinking aid such as divinylbenzene is added at a concentration of 0.5 to 10% by volume per 100 parts by weight of high density polyethylene. Crosslinking progresses by adding parts by weight, preferably 1 to 5 parts by weight, and kneading.

Further, when crosslinking is performed using an electron beam, high density polyethylene may be irradiated with a dose of about 2 to 15 megarads.

The heat-sensitive resistive conductive material of the present invention obtained by the above-described operation has a low electrical resistance value at room temperature.

Moreover, the heat-sensitive resistive conductive material of the present invention has a large resistance increase factor when reaching a specific temperature range,
It exhibits extremely advantageous properties as a heat-sensitive resistive conductive material.

Further, according to the method of the present invention, a heat-sensitive resistive conductive material having the above-mentioned characteristics can be efficiently produced.

Therefore, the present invention can be effectively utilized in heat-sensitive resistance elements, self-temperature control heating elements, and the like.

Next, the present invention will be explained by examples.

Example 1 100 parts by weight of high-density polyethylene (manufactured by Idemitsu Petrochemical Co., Ltd., Idemitsu Polyethylene 550B) with a melting point of 128°C was used as a crystalline polymer, and carbon black (manufactured by Mitsubishi Kasei Co., Ltd.) with a particle size of 21 mμ was used as a conductive filler. Manufactured by Kogyo Co., Ltd., Diablack I) 49 parts by weight and particle size 80
Using a mixture (number average particle size 21.7 mμ) with 33 parts by weight of carbon black (manufactured by Mitsubishi Chemical Industries, Ltd., Dia Black G) of 170 Kneading was carried out at ℃ for 20 minutes, and further 0.5 parts by weight of 2,5-dimethyl-2,5-di(t-butylperoxy)hexyne-3 was added as a crosslinking agent, and the mixture was kneaded for 2 minutes to perform a crosslinking treatment. Summer.

The obtained composition was formed into a sheet using a hot press molding machine, and copper foil was crimped on both sides of the sheet to give a thickness of 1 mm.
I got a sheet of A square test piece with a side of 1 cm was cut out from this sheet, and the electrical resistance value at 25°C and the resistance increase ratio (multiplier relative to the resistance value at 25°C) when the temperature was raised to 150°C were measured.
The results are shown in Table 1.

Example 2 In Example 1, as the conductive filler, the particle size
27 parts by weight of carbon black of 21 mμ (same as in Example 1) and carbon black of particle size 76 mμ (manufactured by Asahi Carbon Co., Ltd., Asahi Carbon HS-500)
A composition was obtained and measured in the same manner as in Example 1, except that a mixture with 40 parts by weight (number average particle diameter: 22.7 mμ) was used. The results are shown in Table 1.

Example 3 In Example 1, as the conductive filler, the particle size
Except that a mixture (number average particle diameter 22.6 mμ) of 37 parts by weight of 21 mμ carbon black (same as in Example 1) and 55 parts by weight of carbon black with particle size 80 mμ (same as in Example 1) was used. A composition was obtained and measured in the same manner as in Example 1. The results are shown in Table 1.

Example 4 In Example 1, as the conductive filler, the particle size
A mixture of 29 parts by weight of 21 mμ carbon black (same as in Example 1) and 43 parts by weight of carbon black (manufactured by Mitsubishi Chemical Industries, Ltd., Diamond Black E) with a particle size of 43 mμ (number average particle size 24.3 mμ) A composition was obtained in the same manner as in Example 1 except that
Measurement was carried out. The results are shown in Table 1.

Example 5 In Example 1, as the conductive filler, the particle size
A mixture (number average particle size 38.6
A composition was obtained and measured in the same manner as in Example 1, except that mμ) was used. The results are shown in Table 1.

Comparative Example 1 In Example 1, as the conductive filler, the particle size
Example 1 except that 67 parts by weight of 21 mμ carbon black (same as Example 1) was used alone.
A composition was obtained and measured in the same manner as above. The results are shown in Table 1.

Comparative Example 2 In Example 1, as the conductive filler, the particle size
Example 1 except that 82 parts by weight of 80 mμ carbon black (same as in Example 1) was used alone.
A composition was obtained and measured in the same manner as above. The results are shown in Table 1.

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Claims (1)

[Scope of Claims] 1. A crosslinked composition comprising a crystalline polymer and a conductive filler, the composition comprising:
To 100 parts by weight, add particle size 10 as the conductive filler.
-One or more types of conductive particles of ~35mμ and particle size of 35~
Consisting of one or more types of conductive particles of 200 mμ and a mixture of two or more types of conductive particles with different particle sizes,
A heat-sensitive resistive conductive material comprising 40 to 150 parts by weight of a conductive particle mixture having an average particle diameter of 15 to 50 mμ. 2. The heat-sensitive resistive conductive material according to claim 1, wherein the conductive particles are carbon black or graphite. 3 100 parts by weight of crystalline polymer, particle size 10
-One or more types of conductive particles of ~35mμ and particle size of 35~
Consisting of one or more types of conductive particles of 200 mμ and a mixture of two or more types of conductive particles with different particle sizes,
40 to 150 parts by weight of a conductive particle mixture having an average particle diameter of 15 to 50 mμ is blended, and then kneaded at a temperature equal to or higher than the melting point of the crystalline polymer, and then the kneaded product is subjected to a crosslinking treatment. A manufacturing method for a characteristic heat-sensitive resistive conductive material. 4 The kneading temperature is 30° below the melting point of the crystalline polymer.
The manufacturing method according to claim 3, wherein the temperature is higher than ℃.