JP2002134303A - Conductive polymer, its manufacturing method, overcurrent protection device and its manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To add an optimal amount of a surface-treatment agent so as to provide a conductive polymer which is kept stable of PTC characteristics and used as a circuit protection for various electronic apparatuses against overcurrents, and to provide an overcurrent protection device. SOLUTION: Conductive particles and a surface-treatment agent are dispersed and mixed into a crystal polymer to convert it into a conductive polymer, where the mixing weight ratio of surface treatment agent with respect to conductive particles is set at 0.1 to 1.0 wt.%.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a PTC (Posi) used as a circuit protection against overcurrent of various electronic devices.
five Temperature Coeffici
The present invention relates to a conductive polymer having characteristics (ent = having a positive temperature coefficient), a method of manufacturing the same, an overcurrent protection element, and a method of manufacturing the same.

[0002]

2. Description of the Related Art A conductive polymer having a PTC property exhibits a property in which the resistance value increases rapidly at a certain temperature, and the structure thereof is different from a crystalline polymer having a crystallinity of at least 10%.
A mixture in which conductive particles such as carbon black having a small specific surface area are dispersed. The conductive paths between the filled conductive particles are cut off due to rapid thermal expansion at the melting point of the crystalline polymer as a cause having PTC characteristics. And a PTC characteristic having a large number of digits in resistance rise can be obtained.

As a conventional conductive polymer and a method for manufacturing an overcurrent protection element using the same, the one described in Japanese Patent Publication No. 1-3322 is known.

That is, a conventional conductive polymer is composed of high-density polyethylene having a crystallinity of 70 to 90% and an average particle diameter D.
A mixture obtained by mixing carbon black having a (nm) of 20 to 150 nm and a surface area S (m ² / g) having a surface area S / D of 10 or less with two rolls heated to 150 ° C. by a heater for 20 minutes. Get.

Next, the mixture obtained in the preceding step is taken out from the two rolls into a sheet and cooled, and then cooled to 150 × 150.
Cut into mm sheets. A small piece of the sheet thus obtained was sandwiched between both sides of a 35 μm-thick nickel electrolytic foil serving as an electrode, and heated and pressed at 190 ° C. and 70 kg / cm ³ for 3 minutes to form a 0.25 mm thick flat plate with electrodes. Process.

Next, the sample is irradiated with 10 Mrad from one side in the electron beam irradiation apparatus, and then 10 Mrad from the other side.
5 after irradiation and radiation crosslinking of high density polyethylene
Cut out a sample of × 5 mm.

Finally, the sample obtained in the previous step was soldered to the nickel foil of each electrode with a lead terminal to obtain an overcurrent protection element.

[0008]

In the above-mentioned conventional structure, the role of the surface treatment agent is to uniformly disperse the mixture of the crystalline polymer and the conductive particles. If the amount is too large, excess surface treatment agent will flow out to the surface due to heat after the overcurrent protection element, and not only will the appearance as a product deteriorate, but also the characteristics such as resistance value will fluctuate and the intended purpose will not be achieved. It had problems.

The present invention solves the above-mentioned conventional problems, and provides a conductive polymer having stable characteristics by optimizing the amount of a surface treatment agent to be added, a method for manufacturing the same, an overcurrent protection element, and a method for manufacturing the same. The purpose is to do so.

[0010]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides a crystalline polymer, and a conductive polymer obtained by mixing conductive particles and a surface treating agent dispersed in the crystalline polymer. The mixing weight ratio of the surface treatment agent is set to 0.1 to 1.0% by weight with respect to the conductive particles. With this configuration, the surface treatment agent is prevented from flowing out to the surface by heat. And a conductive polymer having stable characteristics can be obtained.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The invention according to claim 1 of the present invention relates to a conductive polymer obtained by mixing a crystalline polymer, conductive particles dispersed with the crystalline polymer and a surface treating agent. The treatment agent is 0.1 to the conductive particles.
1.0% by weight of the conductive polymer,
It is possible to prevent the surface treatment agent from leaking to the surface due to the heat and causing a change in characteristics.

According to a second aspect of the present invention, there is provided the conductive polymer according to the first aspect, wherein the surface treatment agent is an aluminum-based coupling agent or a titanium-based coupling agent to stabilize characteristics. be able to.

According to a third aspect of the present invention, a surface treatment agent is dissolved in a solvent in an amount of 0.1 to 1.0% by weight based on the conductive particles, and then the conductive particles are charged and mixed. After that, the solvent is volatilized, the surface treatment agent is adsorbed on the surface of the conductive particles, and then the crystalline polymer is mixed.This is a method for producing a conductive polymer, and the surface treatment agent can be uniformly adsorbed on the conductive particles. In addition, the crystalline polymer and the conductive particles can be reliably dispersed, and a product having stable characteristics can be obtained.

According to a fourth aspect of the present invention, there is provided the method for producing a conductive polymer according to the third aspect, wherein the solvent is volatilized in a heating state of 75 to 85 ° C. A stable quality conductive polymer will be obtained.

According to a fifth aspect of the present invention, there is provided the method for producing a conductive polymer according to the third aspect, wherein the surface treatment agent is adsorbed on the conductive particles and then heated at a temperature of 85 ° C. in a vacuum. Yes, the obtained conductive polymer can be made more stable.

According to a sixth aspect of the present invention, there is provided a method for continuously performing a step of heating at a temperature of 70 ° C. to 85 ° C. in which the solvent is volatilized and heating at 85 ° C. in vacuum after the volatilization of the solvent is completed. Item 4. The method for producing a conductive polymer according to Item 3, wherein the step of volatilizing the solvent and stabilizing the conductive polymer can be performed efficiently.

According to a seventh aspect of the present invention, there is provided a conductive polymer comprising a crystalline polymer, conductive particles dispersed in the crystalline polymer, and an electrode electrically connected to the conductive polymer. In the overcurrent protection element having the above, the conductive polymer is 0.1 to 1.0% by weight based on the conductive particles.
Is an overcurrent protection element in which the surface treatment agent is mixed, and the characteristics can be stabilized.

According to the invention of claim 8 of the present invention, 0.1 to 1.0% by weight of the surface treating agent based on the conductive particles is dissolved in a solvent, and then the conductive particles are charged and mixed. Then, the solvent is volatilized, the surface treating agent is adsorbed on the surface of the conductive particles, and then the crystalline polymer is mixed and processed into a sheet. After laminating the sheet, the sheet is irradiated with an electron beam and cross-linked by radiation. This is a method for manufacturing an overcurrent protection element in which a conductive polymer element is cut to form an electrode electrically connected to the element, and an overcurrent protection element having stable characteristics can be provided.

Hereinafter, embodiments of the present invention will be described with reference to specific examples.

(Embodiment 1) An overcurrent protection element using a conductive polymer according to Embodiment 1 of the present invention will be described below.

First, 20 g of acetoalkoxy aluminum diisopropylate as an aluminum coupling agent as a surface treatment agent is dissolved in 8 kg of isopropyl alcohol, and then the specific surface area (ASTM 2414) is determined.
² kg of carbon black of 3 m ² / g are charged and mixed for 30 minutes, and then isopropyl alcohol is volatilized at 80 ° C.

Next, vacuum drying is performed at 85 ° C. for 2 hours, and acetoalkoxy aluminum aluminum
Adsorb diisopropylate.

Next, 50% by weight of high-density polyethylene having a crystallinity of 70 to 90% and 50% by weight of carbon black adsorbed with a coupling agent are mixed for 20 minutes by two rolls heated to 150 ° C. by a heater. .

Next, the mixture obtained in the preceding step was taken out from the two hot rolls into a sheet and cooled, and then cooled to 150 × 150.
Cut into mm sheets.

Next, a small piece of the sheet thus obtained was sandwiched between both sides of a 35 μm-thick nickel electrolytic foil serving as an electrode, and heated and pressed at 190 ° C. and 70 kg / cm ³ for 3 minutes to form a sheet having a thickness of 0.1 mm. It is processed into a 25 mm flat plate with electrodes.

Next, this sample is irradiated with 10 Mrad from one side in the electron beam irradiation apparatus, and then 10 Mrad from the other side.
5 after irradiation and radiation crosslinking of high density polyethylene
Cut out a sample of × 5 mm.

Finally, the sample obtained in the previous step is soldered to the nickel foil of each electrode with a lead terminal to produce an overcurrent protection element.

The overcurrent protection device of Sample No. FIG. 1 shows the resistance temperature characteristics of No. 1 measured in a constant temperature test tank. Table 1 shows the number of digits in which the resistance value increases. By using the surface treatment agent as described above, the number of digits in which the resistance value increases can be improved.

Next, the sample No. 1
Was used as an overcurrent protection element, and a current decay characteristic, which is a dynamic characteristic, was measured. The voltage was increased from 20A to ON for 1 minute and increased to 20A at intervals of OFF for 5 minutes, but abnormalities were observed in the conductive polymer after the application of the breaking current (cracking, bleeding or ignition of the coupling agent, resistance at room temperature) Was more than doubled). The bleeding of this surface treatment agent is shown in (Table 1).

[0030]

[Table 1]

(Embodiment 2) 10 g of an aluminum-based coupling agent is dissolved in 8 kg of isopropyl alcohol, 2 kg of carbon black having a specific surface area of 38 m ² / g is added and mixed for 30 minutes, and then the isopropyl alcohol is volatilized at 80 ° C. Let it.

Next, vacuum drying is performed at 85 ° C. for 2 hours to adsorb the aluminum-based coupling agent on the surface of the carbon black.

Next, 45% by weight of high-density polyethylene having a degree of crystallinity of 70 to 90% and 55% by weight of carbon black having an aluminum-based coupling agent adsorbed thereon are prepared in the same manner as in Embodiment 1 described above. A current protection device was created. This overcurrent protection element was designated Sample No. (Table 1) shows the number of digits in which the resistance value increases as 2. By using the surface treatment agent as described above, the number of digits in which the resistance value increases can be improved.

(Comparative Example 1) This comparative example corresponds to the first embodiment.
In this example, the same conductive particles as in Example 1 were prepared without the surface treatment and in the same mixing amount.

Hereinafter, Comparative Example 1 will be described. 50% by weight of high-density polyethylene having a crystallinity of 70 to 90% and 50% by weight of carbon black having a specific surface area of 33 m ² / g
An overcurrent protection element was manufactured by the same manufacturing method as in the first embodiment. This overcurrent protection element sample No. 3
FIG. 1 shows a resistance temperature curve measured in a constant temperature test tank.
This overcurrent protection element was designated Sample No. (Table 2) shows the number of digits in which the resistance value increases as 3. The number of digits of the increase in the resistance value was reduced by about one digit as compared with the case where the surface treatment was applied to the carbon black (Sample No. 1).

[0036]

[Table 2]

Comparative Example 2 Hereinafter, Comparative Example 2 will be described. High-density polyethylene with a crystallinity of 70 to 90%
4% by weight, 46% by weight of carbon black having a specific surface area of 24 m ² / g, and 3.3% by weight of acetoalkoxy aluminum diisopropylate as an aluminum-based coupling agent were produced in the same manner as in Embodiment 1. , An overcurrent protection device was prepared. This overcurrent protection element was designated Sample No. (Table 2) shows the number of digits in which the resistance value increases as 4.

Next, the sample No. of Comparative Example 2 was used. 4 was measured as a current decay characteristic, which is a dynamic characteristic when used as an overcurrent protection element. ON for 1 minute from 20A, OFF for 5 minutes
When the voltage was increased by 20 A at intervals of 200 A to 200 A, bleeding of the surface treatment agent was observed in the conductive polymer after the application of the breaking current. The bleeding of the surface treatment agent is shown in (Table 2).

It has been confirmed by experiments that the surface treatment agent has an effect of increasing the resistance value even when the content is 0.1% by weight with respect to the conductive particles. Bleeding of the surface treating agent was observed on the surface of the conductive polymer.

In the present embodiment, the type of coupling agent to be added is described for an aluminum-based coupling agent.
There was an effect of increasing the resistance value at 0 ° C.

As the crystalline polymer, high-density polyethylene was used in the present embodiment. However, any crystalline polymer other than polyethylene, such as EVA, polypropylene, or polyvinylidene fluoride, may be used. Melting point.

[0042]

As described above, according to the present invention, 0.1 to 1.0% by weight of the surface treating agent based on the conductive particles is dissolved in a solvent, and then the conductive particles are charged and stirred. Is used after the surface treatment agent is adsorbed on the surface of the conductive particles by volatilization, so that even if the mixed weight of the conductive particles is the same as the conventional amount, the rise resistance value is large, and excess surface treatment agent due to heat causes the surface It exhibits excellent properties without flowing out into the product and deteriorating the appearance of the product or changing its properties such as resistance value.

[Brief description of the drawings]

FIG. 1 is a diagram showing resistance-temperature characteristics of an overcurrent protection element according to a first embodiment and a comparative example 2 of the present invention.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Hideki Tanaka 1006 Kazuma Kadoma, Kadoma-shi, Osaka Matsushita Electric Industrial Co., Ltd. F-term (reference) 5E034 AC10 AC19 DA02 DC02 DC05

Claims (8)

[Claims] In a conductive polymer obtained by mixing a crystalline polymer, conductive particles dispersed in the crystalline polymer, and a surface treating agent, the mixing weight ratio of the surface treating agent to the conductive particles is Conductive polymer with 0.1-1.0% by weight. 2. The conductive polymer according to claim 1, wherein the surface treatment agent is an aluminum-based coupling agent or a titanium-based coupling agent. 3. A method of dissolving a surface treatment agent in an amount of 0.1 to 1.0% by weight based on the conductive particles, adding the conductive particles and stirring, and then volatilizing the solvent to remove the conductive particles. A method for producing a conductive polymer, comprising mixing a crystalline polymer after adsorbing a surface treatment agent on the surface. 4. The method for producing a conductive polymer according to claim 3, wherein the solvent is volatilized in a heated state at 75 ° C. to 85 ° C. 5. The method for producing a conductive polymer according to claim 3, wherein the surface treatment agent is adsorbed on the conductive particles, and then heated at a temperature of 85 ° C. in a vacuum. 6. The process for producing a conductive polymer according to claim 3, wherein the step of heating at a temperature of 85 ° C. in a vacuum after the completion of the volatilization of the solvent is continuously performed from a heating state of 70 to 85 ° C. for volatilizing the solvent. Method. 7. An overcurrent protection element having a crystalline polymer, a conductive polymer composed of conductive particles dispersed in the crystalline polymer, and an electrode electrically connected to the conductive polymer. An overcurrent protection element in which 0.1 to 1.0% by weight of a surface treatment agent is mixed with respect to particles. 8. A conductive agent is dissolved by dissolving 0.1 to 1.0% by weight of a surface treating agent in a solvent with respect to the conductive particles, and then mixed by adding the conductive particles. After being adsorbed, the crystalline polymer is mixed and processed into a sheet, and after laminating the sheet, an electron beam is irradiated and cross-linked by radiation to be cut into individual pieces to obtain a conductive polymer element. Manufacturing method of an overcurrent protection element for forming an electrode electrically connected to an overcurrent protection element.