JPH0342482B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a polymer positive temperature characteristic resistor, and more specifically, the present invention relates to a method for manufacturing a polymer positive temperature characteristic resistor, and more specifically, it has high adhesive strength between a positive temperature characteristic material and a metal electrode, has a long life, is free from warping or deformation, and has high quality. This invention relates to a method for producing a stable polymeric positive temperature characteristic resistor.

A composition in which conductive particles such as carbon black are blended with a crystalline polymer has positive temperature characteristics in which its electrical resistance value increases rapidly when it reaches a specific temperature range. Various attempts have been made to detect and control temperature using such characteristics (Japanese Patent Publications No. 36-16338, No. 42-23288, etc.).

However, these positive temperature characteristic resistors are used with electrodes attached to them, but if the metal electrodes are simply crimped onto the crystalline polymer composition, the adhesive strength between the two is low, and as a result, they easily peel off. In addition, there was a problem that the resistance value gradually increased due to repeated use over a long period of time, resulting in a short lifespan. Furthermore, it was extremely unsatisfactory for practical use, as it was prone to warping and deformation, and its quality was inconsistent.

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

The crystalline polymer used in the present invention is not particularly limited and may include various materials, but usually polyolefins such as polyethylene and polypropylene, olefin copolymers, various polyamides, polyesters, and fluorine polymers. Combination 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 5mμ to 1μ, preferably 10m
It is μ~100mμ.

The positive temperature characteristic material of the present invention is composed of the above-mentioned crystalline high molecular weight polymer and conductive particles, but this material may be further subjected to a crosslinking treatment. Crosslinking is carried out by a commonly used method such as adding a crosslinking agent such as an organic peroxide, or by irradiating energy rays such as radiation.

The amount of each component is not particularly limited and varies depending on the desired physical properties, etc., and cannot be determined unambiguously, but it is usually 40 to 85% by weight of crystalline polymer and 60 to 15% by weight of conductive particles. , preferably 45 to 65% by weight of the crystalline polymer and 55 to 35% by weight of the conductive particles.

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 conventional kneading machine such as a Banbury mixer, and is usually carried out at 120 to 250°C for 5 to 40 minutes.

The positive temperature characteristic material may be formed into a sheet, 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 performing this crimping, if metal electrodes are crimped on both the front and back sides of the positive temperature characteristic material at the same time,
This is preferable 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. The ozone treatment is usually carried out by contact treatment with an ozone-containing gas having a concentration of about 1 to 20%.

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 unambiguously determined, but they are usually 10 minutes at a temperature of 20 to 80°C. It is 6 hours.

Next, pressurization and depressurization are intermittently repeated on the thus obtained crimped body of the positive temperature characteristic material and the metal electrode. Here, the pressure during pressurization is usually 50~
The number of repetitions of pressurization and depressurization is ^about 200Kg/cm2, and although it is difficult to unambiguously determine the number of repetitions of pressurization and depressurization depending on the pressurization conditions and the type of crystalline polymer, it is usually about 200Kg/cm2.
~20 times. 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 cooling under a pressure of 50 to 200 kg/cm ² . By performing cooling under pressure in this manner, molding distortion can be prevented.

If it is cooled without applying pressure, warping may occur in the resulting positive temperature characteristic resistor and 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 positive temperature characteristic resistors used in heat-sensitive resistance elements, heating elements, and the like.

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

Example 1 For 100 parts by weight of high-density polyethylene (manufactured by Idemitsu Petrochemical Co., Ltd., Idemitsu Polyethylene 520B) with a melting point of 135°C as a crystalline polymer, an average particle size of 43 mμ was used.
75 parts by weight of carbon black (Dia Black E, manufactured by Mitsubishi Chemical Industries, Ltd.) were blended and kneaded for 20 minutes at 160 to 165°C using a Banbury mixer. Di(t-
A positive temperature characteristic material was obtained by adding 0.5 part by weight of (butylperoxy)hexyne-3. Next, this material was pressed using a hot press molding machine at 190°C for 5 minutes to form a sheet with a wall thickness of 1 mm.

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 ² and held for 2 minutes, and then the pressure was rapidly released. After repeating this pressurization/depressurization operation 10 times, the mixture was cooled to room temperature while being pressurized to 150 Kg/cm ² .

One side of the laminated sheet obtained in this way
A 1.5 cm square test piece was cut out, 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 was measured after being kept at 120°C for a long time. Further, the laminated sheet was cut into strips having a width of 15 mm, and a 180° peel test of electrolytic copper foil was conducted in accordance with JIS-K-6854. The above results are shown in Table 1.

Comparative Example 1 The same procedure as in Example 1 was carried out 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 was not performed when cooling to room temperature. The results are shown in Table 1.

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Claims (1)

[Claims] 1. In 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 polymer to a temperature higher than its melting point, the positive temperature characteristic material and the metal electrode are crimped together, and then pressure is intermittently applied and depressurized to the crimped body thus obtained, and then the crimped material is melted. A method for producing a polymer positive temperature characteristic resistor, which is characterized by cooling the body under pressure. 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. Claim 1, wherein the positive temperature characteristic material is a powder consisting of a crystalline polymer and conductive particles.
Manufacturing method described in section. 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, in which the surface of the positive temperature characteristic material 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 copper foil or electrolytic nickel foil.