JPS6159701A - Method of producing polymer positive temperature coefficientresistor - 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 manufacturing a polymeric positive temperature characteristic resistor, and more specifically, the present invention relates to a method for manufacturing a polymeric positive temperature characteristic resistor, which has a high adhesive strength between a positive temperature characteristic material and a metal electrode, and
This invention relates to a method for manufacturing a polymeric positive temperature characteristic resistor that has a long life, is free from warping or deformation, and has stable quality.

A composition in which conductive particles such as carbon black are blended into a crystalline polymer has positive temperature characteristics such that its electrical resistance value increases rapidly when it reaches a specific temperature range.

Various attempts have been made to detect and control temperature using these characteristics (Japanese Patent Publication No. 36-16338, No. 4).
2-23288 etc.).

However, these positive temperature characteristic resistors are used with electrodes attached, but if a metal electrode is simply crimped onto a crystalline polymer composition, the adhesive strength between the two is low, and it may peel off easily. However, when used repeatedly for a long period of time, the resistance value gradually increases, resulting in a short lifespan. In addition, it is easy to cause warping and deformation,
It was extremely unsatisfactory in practice, with inconsistent quality.

It is an object of the present invention to solve the above-mentioned conventional problems and to provide a method for manufacturing a polymeric positive temperature characteristic resistor that has a long life, is free from warping or deformation, and has stable quality. .

That is, in the present invention, when manufacturing a polymer positive temperature characteristic resistor by attaching a metal electrode to a positive temperature characteristic material consisting of a crystalline polymer and conductive particles, the positive temperature characteristic material is a crystalline polymer. After heating and melting the positive temperature characteristic material to a temperature higher than the melting point of The present invention provides a method for manufacturing a polymer positive temperature characteristic resistor, which is characterized by cooling in a pressurized state.

The crystalline polymer used in the present invention is not particularly limited and can include various types, but usually polyolefins such as polyethylene and polypropylene, olefin copolymers, various polyamides, polyesters, and fluorine polymers. etc. are used.

Next, various types of conductive particles can be used. Specific examples include carbon black, graphite, metal particles, and mixtures thereof, with carbon black, graphite, and mixtures thereof being particularly preferred. These usually have an average particle size of 5 mp" 1 .mu., preferably 10 m.mu. to 100 .mu.m.

The positive temperature characteristic material of the present invention is composed of the above-mentioned crystalline polymer and conductive particles, but this material may be further crosslinked. This can be done by adding a cross-linking agent such as, or by irradiating energy rays such as radiation.

The blending amount of each component is not particularly limited and varies depending on the desired physical properties, etc., and cannot be unambiguously determined, but it is usually 40 to 85% by weight of the crystalline polymer.

Conductive particles 60-15% by weight, preferably crystalline polymer 45-65% by weight, conductive particles 55-35% by weight
It is.

The positive temperature characteristic material of the present invention is produced by adding a predetermined amount of conductive particles to a crystalline polymer and then thoroughly kneading the mixture. This kneading may be carried out using a normal mixing machine such as a Banbury mixer, and is usually 120 to 25
It may be carried out at 0°C for 5 to 40 minutes.

Note that the positive temperature characteristic material may be formed into a sealing film or the like, or may be in the form of a powder.

In the method of the present invention, the heating time for heating and melting the positive temperature characteristic material thus obtained above the melting point of the crystalline polymer may generally be within 20 minutes.

Next, the heated and melted positive temperature characteristic material and the metal electrode are pressed together.

Here, as the metal electrode, metal foil, metal plate, metal wire, metal net, etc. are used. Further, as for the type of metal, any metal having good conductivity may be used, and various metals can be used. In particular, as the metal foil, electrolytic copper foil, electrolytic nickel foil, etc. are preferably used.

Further, the pressure-bonding of the positive temperature characteristic material and the metal electrode can be carried out by various methods, and although there are no particular limitations, it may be carried out usually by hot press, pressure roll, etc. When carrying out this pressure bonding, it is preferable to simultaneously press the metal electrodes on both the front and back surfaces of the positive temperature characteristic material because the adhesive force becomes uniform and no warpage or deformation occurs.

In this case, it is preferable to use a positive temperature characteristic material whose surface to which the metal electrode is pressed has been oxidized in advance. The oxidation treatment of the surface of the positive temperature characteristic material to which the metal electrode is pressed is performed using, for example, ozone, oxygen, nitrogen oxide, hydrogen peroxide, or the like. Here, the ozone treatment is usually carried out by contact treatment with an ozone-containing gas having a concentration of about 1 to 209A.

The conditions for oxidation treatment vary depending on the type of oxidation treatment, the desired physical properties, the type of crystalline polymer used, etc., and cannot be determined unambiguously, but they are usually carried out at a temperature of 20 to 80°C for 10 minutes or more. It is 6 hours.

Next, pressurization and depressurization are intermittently repeated on the crimped body of the positive temperature characteristic material and the metal electrode obtained in this way. Here, the pressure during pressurization is usually 50 to 200 kg /
am'', and the number of repetitions of pressurization and depressurization is usually about 2 to 20 times, although it is difficult to unambiguously determine it depending on the pressurization conditions, the type of crystalline polymer, etc.

By carrying out this pressurization/depressurization operation, the air can be sufficiently degassed. If this pressurization/depressurization operation is not performed, gas will be contained between the crimped positive temperature characteristic material and the metal electrode, making it impossible to obtain sufficient crimping strength and making it difficult to maintain long-term durability. It becomes unbearable after repeated use.

Furthermore, in the present invention, the crimped body that has been repeatedly subjected to pressurization and depressurization operations as described above is cooled in a pressurized state. The conditions for this operation are usually 50 to 200 kg.
/am''. By performing cooling under pressure in this manner, molding distortion can be prevented.

If the resistor is cooled without applying pressure, the resultant positive temperature characteristic resistor may warp or the metal electrode may easily peel off, which is not preferable.

As described above, the desired polymer positive temperature characteristic resistor can be manufactured.

The polymer positive temperature characteristic resistor obtained by the method of the present invention has a high adhesive strength between the positive temperature characteristic material and the metal electrode, and therefore is difficult to peel off and has no risk of increasing electrical resistance even after repeated use over a long period of time. It can be used for a long period of time.

Moreover, the polymer positive temperature characteristic resistor obtained by the method of the present invention is free from warpage and deformation and has extremely stable quality.

Therefore, the present invention can be effectively utilized for manufacturing a positive temperature characteristic resistor used for the heating element of the heat-sensitive resistance element 1, etc.

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

Example 1 High-density polyethylene with a melting point of 135°C (manufactured by Idemitsu Petrochemical Co., Ltd., Idemitsu Polyethylene 52) as a crystalline polymer
0B) 75 parts by weight of carbon black (manufactured by Mitsubishi Chemical Industries, Ltd., Diablack E) having an average particle size of 43 mμ was blended with 100 parts by weight, and the mixture was kneaded for 20 minutes at 160 to 165°C using a Banbury mixer. Later, 0.5 parts by weight of 2.5-dimethyl-2.5-di(t-butylperoxy)hexyne-3 was added as a crosslinking agent to obtain a positive temperature characteristic material.Next, this material was heated By press molding machine,
It was pressed at 190° C. for 5 minutes to form a sheet with a wall thickness of III+.

The obtained sheet was cut into a square with a side of 30 cm, electrolytic copper foil with a thickness of 35 μm was layered on both the front and back sides of this sheet, and the sheet was placed in a press molding machine and held at 190° C. for 10 minutes to melt the sheet. .

Next, this laminate was pressed at a pressure of 150 kg/cm", held for 2 minutes, and then rapidly depressurized. After repeating this pressurization/depressurization operation 10 times, a pressure of 150 kg/cm" was applied.
It was cooled to room temperature under pressure.

A square test piece of 1.50 mm on a side was cut out from the laminated sheet thus obtained, and the specific resistance value at 25°C and the resistance increase magnification relative to the electrical resistance value at 25°C when the temperature was raised to 130°C were measured. Furthermore, the rate of change in specific resistance after being maintained at 120° C. for a long time was measured.

Further, the above laminated sheet was cut into strips having a width of 15 mm, and a 180° peeling test of electrolytic copper foil was conducted in accordance with JIS-6854. The above results are shown in Table 1.

Comparative Example 1 The same procedure as in Example 1 was conducted except that the pressurization and depressurization operations were not repeated. The results are shown in Table 1.

Comparative Example 2 The same procedure as in Example 1 was carried out except that the pressurization upon cooling to room temperature was not performed. The results are shown in Table 1.

Claims (6)

[Claims] (1) When manufacturing a polymer positive temperature characteristic resistor by attaching a metal electrode to a positive temperature characteristic material consisting of a crystalline polymer and conductive particles, the positive temperature characteristic material is used at the melting point of the crystalline polymer. After heating and melting as described above, the positive temperature characteristic material and the metal electrode are crimped, and then pressure is applied and depressurized intermittently to the crimped body obtained in this way, and then the crimped body is pressurized. 1. A method for producing a polymer positive temperature characteristic resistor characterized by cooling in a state. (2) The manufacturing method according to claim 1, wherein the positive temperature characteristic material is a sheet of a kneaded product of a crystalline polymer and conductive particles. (3) The manufacturing method according to claim 1, wherein the positive temperature characteristic material is a powder consisting of a crystalline polymer and conductive particles. (4) The manufacturing method according to claim 1, wherein metal electrodes are simultaneously pressed onto both the front and back surfaces of the positive temperature characteristic material. (5) The manufacturing method according to claim 1, which uses a positive temperature characteristic material whose surface to which the metal electrode is pressed has been oxidized in advance. (6) The manufacturing method according to claim 1, wherein the metal electrode is made of electrolytic steel foil or electrolytic nickel foil.