JPS60235385A - Method of producing ptc resistor - 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] Industrial applications The present invention relates to a method for manufacturing a PTC resistor.

Structure of the conventional example and its problems The conventional PTC resistor is a PTC resistor containing a carbon blank.
A heat generating layer is formed by the TC resistor composition layer,
The resistance value varies greatly depending on the wire manufacturing conditions during extrusion molding of the heating layer, and the manufacturing process is extremely difficult.
This is due to the following reasons. In general, polymer compositions kneaded with carbon blanks have poor resistance stability, and do not undergo heat treatment or
The electrical resistance constantly changes due to thermal history, and the resistance value varies greatly depending on the orientation and molding temperature during the molding process of this composition. This is because carbon black is a conductive material with a chain structure, so its carbon blank particles have various orientations in the polymer matrix, and even if the carbon black content in the polymer matrix is the same, give significantly different resistance values. In other words, the conductivity of the PTC resistor composition containing carbon black is caused by the channels of the carbon black conductive particles in the polymer matrix, and the increase or decrease in the number of contacts between the particles changes the resistance value. Contribute greatly. In order to actually lower the electrical resistance of a PTC resistor composition containing carbon black, it is generally necessary to add at least 20% wt of carbon black, and to obtain a composition with low resistance, it is necessary to add 40% or more. It is. However, 40%
Addition of carbon black as described above impairs the excellent moldability of the polymer itself, and there is a problem that arbitrary processing of single-stage polymers becomes impossible.

Object of the Invention The present invention overcomes these problems and significantly lowers the resistance of the PTC resistor composition particles containing a small amount of carbon black by using an affinity liquid, thereby achieving stable resistance 11t'f.
The present invention provides a method for manufacturing a PTC resistor having the following characteristics.

Discrepancies of the Invention In order to achieve the above object, the present invention employs the following method. That is, it has been found that by surface-treating the PTC resistor composition with an affinity liquid that dissolves or swells it, the electrical resistance value can be reduced by several orders of magnitude. This is because the surface of the particles of this PTC resistor composition is surface-treated with a liquid, and the polymer 71-Rinokunu is extremely softened, and the carbon black particles are oriented and aggregated to form a conductive channel. . On the other hand, polymers generally have a high viscosity even in the molded state at the molding temperature, and do not have free fluidity like membrane solvents. Therefore, the carbon particles in the polymer Matrinokunu are
In addition to being in a random arrangement, it is subjected to a large amount of flow O/strain caused by a mold during molding, and is then cooled and molded as it is. Therefore, each part of the molded body has various different resistance values. However, when this molded body is immersed in the above-mentioned liquid, the matrix polymer on the surface of the molded body is dissolved and swelled by the solvent, the viscosity decreases, and the carbon black particles near the surface become easier to move.
The carbon particles are oriented and aggregated to form a conductive channel, and after the solvent is dried and removed, the resistance value (dllll) of the surface of the molded body is uniquely lowered. The above-mentioned surface-treated PTC resistor composition is provided between the lines.

In the present invention, the particles of the PTC resistor composition containing carbon black are not formed from a solution containing a solvent such as a paint, but are manufactured by a process that does not include a solvent, such as kneading or pulverization. Use.

The present invention can be applied to compositions using various thermoplastic resins as matrix molecules, and can also be applied to crosslinked thermosetting resins.

The solvent used in the present invention is one that dissolves the matrix polymer, and if a liquid in which a doping agent is dissolved in this solvent is used, the resistance of the P'TC resistor composition particle surface is reduced and the doping agent is dissolved. can be doped with an agent. The doping agent in the present invention is PTC
Refers to polymer additives such as stabilizers, antioxidants, and rust preventive agents that are added to resistor compositions.

The polymer matrix used in the PTC resistor composition of the present invention includes polyolefins such as polyethylene, polypropylene, polyethylene-vinyl acetate copolymer, polyethylene-ethyl acrylate copolymer, and crystalline polymers such as polyamide and polyester. It shows a sharp positive temperature coefficient near the crystal transformation point of No. 4. For the film to be used in the present invention, an affinity solvent that dissolves or swells these polymers is selected.

Description of examples An embodiment of the present invention will be described below.

A mixture consisting of 18% carbon black, 81% polyethylene-vinyl acetate copolymer, and 1% pheno-)V light stabilizer was kneaded for 20 minutes using heated rolls, and then taken out in the form of a sheet. This is crushed into approximately 10 to 200 μm using a rotary pulverizer.
It was ground into particles (5). The particles (8) were placed in a fluidized coating device, and surface-treated by spraying toluene to obtain particles (B). After partially air-drying the particles (B), they were molded into three layers of the PTC resistor composition shown in FIG. 1 using an extruder in the following steps. That is, as a PTC resistor, as shown in Fig. 1, aramid fiber (1500De) is used as a core
and using particles (8), CB) on it, m] PT
A C resistor composition layer was coated with a thickness of 0.4 mm. Each of the two types of wires made in this way has an outer winding of 2.2'.
Two copper wires each having a diameter Q of 3 mm were sized, and as the insulating jacket 4, polyvinyl chloride copolymer was sized 0 and 5 mm.
It was coated with a thickness of mm. Then, the PTC resistor shown in Fig. 1 was cut into 1 m length each, and the PTC resistor was not subjected to the solvent warming process.
Characteristics were measured while comparing with a conventional one using resistor composition particles.

The results are shown in FIGS. 2 and 3. The PTC resistor using particles (A) is shown as A), and the PTC resistor using particles (B) is shown as B.

That is, A is the conventional example. As is clear from FIGS. 2 and 3, compared to the conventional example A, B has more resistance variation, PT
Both C characteristics are excellent.

In addition, in this example, PT containing carbon blank
As a method for bringing an affinity liquid into contact with a group of particles of the C resistor composition, there are the following methods. (1) Immersion method, 2) Liquid spraying method, Exposure to G solvent vapor, ■Liquid pouring method.

Further, methods for removing the liquid include (1) vacuum drying method, 2) heat drying method, and drying method using circulating gas. This drying step is mainly performed after forming the PTC resistor composition 3. When applying chemical crosslinking or electronic crosslinking to the PTC resistor composition 3, it is effective to carry out the process after forming three layers of the PTC resistor composition. In this example, molding m
Since the particle surface has a low resistance and is stabilized in the particle state of J, the resistance value of the three layers of the PTC resistor composition is less likely to be destabilized by extrusion strain. It goes without saying that the finer the particles in this example, the better.

In this way, the resistance of the three layers of the PTC resistor composition containing carbon black is reduced, and the present invention is not limited to this. Furthermore, the low resistance layer thus formed has a uniform resistance value throughout the molded body. It has been found that the non-uniform resistance distribution as before the method of this embodiment disappears. According to this example, even if the resistance value is in the range of 105 to 108 Ω, cm, which is extremely difficult to manufacture with a PTC resistor composition using carbon, it is possible to easily show a uniform resistance distribution. You can make it.

Effect of the invention The effects of the present invention can be summarized as follows.

(1) Conventionally, stabilizing the resistance of a PTC resistor composition has been a very big problem, but according to the present invention, a stable PTC resistor with little resistance variation in each part can be obtained. .

2) Since resistance is lowered by solvent treatment, a PTC resistor composition with low carbon content and excellent mechanical properties can be formed.

3) During the extrusion process of the PTC resistor composition using an extruder,
The resistance value was greatly affected by the extrusion speed, and in order to maintain a constant resistance value, it was necessary to extrude at a constant speed.
In the present invention, there is little need for this, and productivity is high.

[Brief explanation of the drawing]

Fig. 1 is a perspective view showing an embodiment of the present invention, Fig. 2 is a characteristic diagram showing resistance fluctuations within a 1 m length of the product of this embodiment and a conventional example, and Fig. 3 is a characteristic diagram of the product of this embodiment. The figure shows the resistance-temperature characteristics per 1 m length of the conventional example product. 1. Core yarn, 2.2'. Copper wire (conductor traces), 3
,,, - PTC resistor composition. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure 2 Figure 3 Crush 47 (σC)

Claims (1)

[Claims] (1) After pulverizing and pulverizing a PTC resistor composition containing carbon black and having a large positive temperature coefficient of resistance (hereinafter abbreviated as PTC), the surface of the particles is A PTC formed by processing and molding with a molding machine and disposed between at least a pair of electrodes.
Method of manufacturing a resistor. 2. The method for producing a PTC resistor according to claim 1, wherein the PTC resistor composition is made of IJ (polymer matrix containing polyolefin as a main component) and the affinity liquid contains an aromatic solvent. ■ Aromatic agents include benzene, toluene, xylene,
The method for manufacturing a PTC resistor according to claim 2, wherein the PTC resistor is selected from naphthalene or its derivatives. 4) The method for manufacturing a PTC resistor according to any one of claims 1 to 3, wherein the surface treatment is performed by a fluid coating method. 6. The method for manufacturing a PTC resistor according to claim 1, wherein the molding machine is an extrusion molding machine.