JPS6090237A - Production of heat-sensitive resistant electrically conductive material - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a heat-sensitive conductive material, and more specifically, it is possible to produce a heat-sensitive conductive material with excellent positive temperature coefficient characteristics by a simple operation of blending carbon black in a predetermined ratio with specific polyethylene and kneading it. The present invention relates to a method of manufacturing a heat-sensitive resistive conductive material.

Various methods have been known for producing materials that have positive temperature coefficient characteristics, particularly materials that have the characteristic that the positive temperature coefficient increases rapidly when the electrical resistance value reaches a specific temperature range ( Special Publication No. 36-16338,
Special Publication No. 50-33707, Special Publication No. 56-1035
Publication No. 2).

However, materials obtained by these conventional methods have the disadvantage that the rate of increase in resistance value is not very large when reaching a specific temperature range, and materials with a large rate of increase in resistance value have a large initial resistance value. There was a drawback.

The present inventors have conducted extensive research in order to eliminate the drawbacks of the conventional method described above and to produce a heat-sensitive resistive conductive material that has excellent positive temperature coefficient characteristics and has a relatively low resistance value (initial resistance value) at room temperature. Layered. As a result, they discovered that the objective could be achieved by using high-density polyethylene, which has a double bond at the end of the molecule and has a relatively large molecular weight, as a raw material, and mixed carbon black in a certain ratio and kneaded it. , we have completed the present invention.

That is, the present invention has a double bond at the end of the molecule, and has an intrinsic viscosity of 2.5 di 77 at 135°C in decalin.
Production of a heat-sensitive resistive conductive material characterized by mixing and kneading 1 carbon black with the above high-density polyethylene in a ratio of 25 to 60% by weight based on the total amount of the high-density polyethylene and carbon black. The present invention provides a method.

In the present invention, high-density polyethylene having a double bond at the molecular end is used as the raw material resin. This high-density polyethylene can be obtained by various methods, but
Generally, hexavalent chromium oxide is used as a catalyst, and the reaction temperature is 130 to 160°C.

It is obtained by polymerizing ethylene at a reaction pressure of 18 to 351 q/crn2, and has higher melt viscosity and melt elasticity than high-density polyethylene produced using a titanium-based catalyst.

In the method of the present invention, the above-mentioned molecule has a double bond at the end,
And the intrinsic viscosity at 135°C in decalin is 2.5 dt.
It is essential to use high-density polyethylene with a density of /g or more as the raw material resin, and since such high density, j-"! A conductive material is obtained.If other polyethylene or other types of synthetic resins are used instead of the high-density polyethylene mentioned above, a crosslinking reaction is required to obtain a conductive material exhibiting the desired properties. This necessitates various operations such as , which goes against the purpose of the present invention, which is to simplify the process.

Further, even if high-density polyethylene has double bonds, if the intrinsic viscosity is less than 2.5 dt/f, the rate of increase in resistance value in a specific temperature range is insufficient.

In the method of the present invention, the above-mentioned molecule has a double bond at the end, and has an intrinsic viscosity of 2.5 d at 135°C in decalin.
Carbon black is blended into high-density polyethylene of t/V or higher in a proportion of 25 to 60% by weight, preferably 35 to 55% by weight, based on the total amount of the high-density polyethylene and carbon black. If the blending ratio of carbon black is less than 25% by weight, the initial resistance value of the resulting conductive material will be large, while if it exceeds 60% by weight, the rate of increase in resistance value in a specific temperature range will decrease. Note that there are no particular restrictions on the type or average particle size of carbon black used here, and various types can be used. For example, there are various types such as Oil 7 Arness Black, Thermal Black, and Acetylene Blank, and the average particle size is 0.0.
Preferably, the diameter is about 1 to 0.1 micron.

In the method of the present invention, after or while blending carbon black with the above-mentioned high-density polyethylene, sufficient crosstalk is carried out. This crosstalk may be carried out using a normal crosstalk machine, and it is sufficient to carry out the crosstalk at 190 to 250'C for 5 minutes or more, preferably about 10 to 30 minutes.

According to the method of the present invention, a predetermined proportion of carbon black is added to a specific raw material resin, that is, high-density polyethylene having a double bond at the molecular end and having an intrinsic viscosity of 2.5 dt/fI or more at 135°C in decalin. In addition, conductive materials with the desired properties can be produced simply by kneading under normal conditions, eliminating the need for operations such as crosslinking reactions, and the process is extremely simplified.

Furthermore, the heat-sensitive resistive conductive material produced by the method of the present invention has excellent positive temperature coefficient characteristics, and the resistance value rise multiplier reaches 108 or more, which is far superior to the conventional value of about 104. be.

Furthermore, although this conductive material has a large resistance value rise multiplier, its initial resistance value is relatively small, and exhibits extremely advantageous characteristics as a heat-sensitive resistive material.

Therefore, the heat-sensitive resistive conductive material produced by the method of the present invention can be effectively used in temperature detectors, self-temperature-controlled heating elements, and the like.

Next, the method of the present invention will be explained in more detail with reference to Examples.

Example 1 It has a double bond at the end of the molecule and has an intrinsic viscosity of 3.04 dt/f at 135°C in decalin and a melt index of 0.
01r/10 min high density polyethylene (Showa Denko K.K.)
After melting, 100 parts by weight of Niziyorex 4250I-LM (manufactured by Niziyorex 4250I-LM) was placed in a laboplasto mill maintained at 190°C, and stirred for 9 minutes after melting. Dia black E)
67 parts by weight were gradually added, and then 2 parts by weight were added at 220°C.
The mixture was kneaded for 0 minutes. The resulting kneaded product was molded at a temperature of 190°C.

Hot press molding was performed at a molding pressure of 100 lq/crn2G, diameter 17.5 mm, wall thickness III+++1
Obtained a disc.

Silver paste was applied to both sides of this disk, dried, and the temperature and electrical resistance (by the four-terminal method) were measured.

As a result, the specific resistance at 25°C is 7.6Ω・Cm, and the PTC resistance increase factor at 138°C (ratio of increasing resistance value to resistance value at 25°C) is approximately 2.5×10
It was 9 (109.4).

Example 2 - A disk was obtained in the same manner as in Example 1, except that 100 parts by weight of carbon black (manufactured by Mitsubishi Chemical Industries, Ltd.: Diablack G) having an average particle size of 0.08 μm was used as the carbon black. The specific resistance of this product at 25℃ is 9.3
ΩΦCrrL, and the PTC resistance increase factor at 150° C. was approximately 3.2×108 (108·5).

Comparative Example 1 Intrinsic viscosity at 135°C in decalin as polyethylene: 2.18 dt/ff, melt index: 0.9S
'/10 minutes and has no double bonds (manufactured by Idemitsu Petrochemical Co., Ltd.: Idemitsu Polyethylene 4
40M), 67 parts by weight of carbon black (manufactured by Mitsubishi Chemical Industries, Ltd.: Diablack E) with an average 'JH of 10,043μ was blended, and the mixture was placed in a Lavogelasto mill maintained at 150°C, and the kneading temperature was set to 180°C. A disk was obtained in the same manner as in Example 1 except for the above. The specific resistance of this product at 25°C is 3.9Ω・cm, and the PTC resistance increase factor at 134°C is approximately 2.5 x 102 (102
・It was 4).

Comparative Example 2 Polyethylene has a double bond at the end of the molecule, and has an intrinsic viscosity of 2.03 dt/f/ at 135°C in decalin.
High-density polyethylene with a melt index of 0.17r710 (manufactured by Showa Denko K.K., Shorex 6002H)
) 100 parts by weight was placed in a laboplasto mill maintained at 165°C, and after melting and stirring for about 7 minutes, the average particle size was 0.04.
A disk was obtained in the same manner as in Example 1, except that 67 parts by weight of 3 μm carbon black (Diablack E, manufactured by Mitsubishi Chemical Industries, Ltd.) was gradually added and kneaded at 180° C. for 20 minutes. The specific resistance of this product at 25℃ is 4.2Ω・c
m, and the PTC resistance increase factor at 136°C is approximately 9
．． It was 0×103 (103·95).

Claims (1)

[Claims] 1. Has a double bond at the end of the molecule and contains 135 in decalin
It is characterized by mixing and kneading carbon black into high-density polyethylene having an intrinsic viscosity of 2.5 dt/g or more at °C in a proportion of 25 to 60% by weight based on the total amount of the high-density polyethylene and carbon black. A method for producing a heat-sensitive resistive conductive material.