JPH0632281B2 - Cord-shaped heater - Google Patents

Description

TECHNICAL FIELD The present invention relates to a cord-shaped heater excellent in heat resistance, oil resistance and electric characteristics.

(Prior Art) Conventionally, as shown in the drawings, a cord-shaped heater is made of vinyl chloride resin, silicone rubber, fluororesin, etc. as an insulating layer 3 on a heating core obtained by spirally winding a metal resistance wire 2 around a galls fiber string 1. It is covered.

(Problems to be Solved by the Invention) However, vinyl chloride resin has poor heat resistance, and silicone rubber and fluororesin having excellent heat resistance have poor oil resistance and solvent resistance in the former and flexibility in the latter. It has the drawback of lacking.

On the other hand, in the field of electric wires, an insulated electric wire having a composition containing a tetrafluoroethylene-propylene-based copolymer as a main component as an insulating layer or an outer layer makes use of excellent heat resistance, oil resistance, and electric characteristics, and is suitable for automobiles and construction. It has begun to be used for machinery, generators, motor leads, etc. An insulated wire having an insulating layer or an outer layer of the composition containing the tetrafluoroethylene-propylene-based copolymer as a main component contains an allyl compound as a crosslinking aid and an organic peroxide as a crosslinking agent in the composition. After the composition is extrusion-coated on a conductor, it is heated and cross-linked with pressurized steam or a pressurized liquid so that voids are not generated in the product, or a vent type extruder is used to form a composition in the composition. A method is employed in which moisture, gas, etc. contained in a small amount are vacuum-suctioned, and then the conductor is extrusion-coated and then heat-crosslinked under normal pressure.

Therefore, it can be considered to use the composition containing the tetrafluoroethylene-propylene-based copolymer as a main component as an insulating layer or an outer layer of the cord-shaped heater. However, the cord-shaped heater is also the same manufacturing method as the insulated wire as described above, and in the case of pressure heating and crosslinking, a boiler for generating pressurized steam and a device for pressurizing a liquid are required, while When using a vent-type extruder that can be heat-crosslinked under normal pressure, it takes a considerable amount of time to set up unlike the normally used extruder, and it is necessary to always be careful so that the vacuum degree of the vacuum pump does not drop. Moreover, since the bed type extruder is a large device with a special structure that requires a large number of cylinders corresponding to it and a vacuum pump, it is not only expensive, but also requires a large installation space. A large amount of compound remains in the cylinder, resulting in high process cost and uneconomical as compared with a commonly used extruder.

The present invention has been made on the basis of such a point, and the object thereof is that it is excellent in heat resistance, oil resistance and electrical characteristics, and is heat-crosslinked under normal pressure without using a vent type extruder. Is to provide a heater on the cord that does not generate voids in the product at low cost.

(Means for Solving the Problems) In order to achieve the above object, the cord-shaped heater according to the present invention cross-links a tetrafluoroethylene-propylene-based copolymer with a methacrylic acid ester or an acrylic acid ester as a cross-linking aid. The present invention is characterized by having an insulating layer or an outer layer formed by crosslinking a mash composition containing a mixture containing an organic peroxide as an agent as a main component under normal pressure heating.

The tetrafluoroethylene-propylene-based copolymer is usually crosslinked by using an allyl compound as a cross-linking aid and an organic peroxide as a cross-linking agent and using them together. A methacrylic acid ester or an acrylic acid ester is used as an agent, and is cross-linked with an organic peroxide which is a cross-linking agent. When using a crosslinking aid such as an allyl compound, oxime compound, sulfur, maleimide compound or the like instead of the methacrylic acid ester or acrylic acid ester as a crosslinking aid, or do not use the methacrylic acid ester or acrylic acid ester together with the organic peroxide. When used alone in the above, further, when the crosslinking agent alone acts, it takes a long time for crosslinking, and at normal pressure, numerous voids are generated in the product.

Examples of the methacrylic acid ester or acrylic acid ester used as a crosslinking aid include trimethylolpropane trimethacrylate, trimethylolpropane triacrylate, ethylene dimethacrylate, polyethylene glycol dimethacrylate, polyethylene glycol diacrylate, cyclohexal methacrylate, dialkylaminoalkyl. Methacrylate, aluminum methacrylate, aluminum acrylate, zinc methacrylate, zinc acrylate and the like can be mentioned. These may be used alone or in combination of two or more. As the organic peroxide used as a cross-linking agent,
Various commonly used peroxide compounds can be used. In addition to the above-mentioned cross-linking agent and cross-linking aid, additives such as a filler, a reinforcing agent, a stabilizer, a softening agent, a lubricant, and a pigment can be used if necessary.

The manufacturing method of the cord-shaped heater according to the present invention is the same as the atmospheric pressure heating cross-linking method in which the cost of the silicone rubber cord-shaped heater is inexpensive. That is, the composition according to the present invention is extrusion-coated on a heating core with a predetermined wall thickness, and immediately thereafter about 200
30 seconds to 5 in a heating furnace maintained at a temperature of ℃ to 300 ℃
Crosslinking is carried out by heating under atmospheric pressure for about a minute. At this time, the temperature of the cylinder and head of the extruder is preferably about 50 ° C. or lower in consideration of the fact that the composition according to the present invention is crosslinked at about 80 ° C.

(Operation) Since the cord-shaped heater of the present invention uses a tetrafluoroethylene-propylene-based copolymer as a base polymer as an auxiliary material for forming an insulating layer or an outer layer, it has excellent heat resistance, oil resistance and electric characteristics. By mixing methacrylic acid ester or acrylic acid ester, which is a cross-linking aid, and organic peroxide, which is a cross-linking agent, voids are produced in the product even when heat-crosslinked under normal pressure without using a vent-type extruder. Does not occur.

(Example) Hereinafter, the present invention will be described in more detail with reference to the drawings.
The drawing is a partially cutaway perspective view of the cord-shaped heater. In this example, the materials shown in Table 1 were kneaded with a 12-inch open roll, and the obtained composition was put into a glass fiber cord 1 having an outer diameter of about 1.0 mm and an outer diameter of 0 by an extruder for 40 mmφ rubber. ．
An insulation layer 3 is formed by extrusion-coating a heating core formed by spirally winding a metal resistance wire 2 of 18 mm to a wall thickness of 0.8 mm,
Immediately after that, in a heating furnace maintained at 200 ° C., at atmospheric pressure, 5
After heating for a minute, the insulating layer 3 was crosslinked to form a cord-shaped heater.
At this time, the temperature of the cylinder and head of the extruder is 50
℃ was made. In the composition of Table-1, siliceous filler was used as a filler, silicone oil was used as a softening agent, and sodium stearate was used as a lubricant.

Here, the test pieces obtained by cutting the cord-shaped heaters of this example and Comparative Examples 1 to 3 into predetermined lengths were used as test products, and the presence or absence of voids, tensile strength and elongation, heat resistance, and solvent resistance. A comparative test was conducted. As a test method, first, with respect to the presence or absence of a void, the test product was cut at several places and its cross section was visually confirmed. Tensile strength and elongation are J
It was measured according to IS C 3004. Regarding the heat resistance, the test product was heated in a constant temperature bath maintained at 220 ° C. for 96 hours, taken out, cooled to room temperature, and the tensile strength residual ratio and elongation residual ratio were determined according to JIS C 3004. Regarding the solvent resistance, the test product was immersed in the fuel oil C specified in JIS K 6301 at room temperature for 72 hours, then taken out, and the outer diameter was immediately measured to obtain the outer diameter change rate. The test results are shown in Table 2.

According to the test results, in Examples 1 to 4 in which the methacrylic acid ester or acrylic acid ester as the crosslinking aid and the organic peroxide as the crosslinking agent are used in combination, the process cost is low and the pressure is normal. Although voids did not occur in the test product even after heat crosslinking, Comparative Examples 1 to 3 in which other crosslinking auxiliary agents were used instead of the methacrylic acid ester or the acrylic acid ester It can be seen that a large number of voids are generated in the area and cannot be used as a cord heater.

(Effects of the Invention) As described in detail above, the cord-shaped heater according to the present invention is excellent in heat resistance, oil resistance, and electrical characteristics, and is manufactured by atmospheric pressure heating crosslinking without using a vent type extruder or the like. Therefore, it is extremely economical.

[Brief description of drawings]

 It is a partially cutaway perspective view of the cord-shaped heater of the drawing. 1 ... glass fiber string 2 ... metal resistance wire 3 ... insulating layer

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Claims (1)

[Claims] 1. A composition comprising a mixture of a tetrafluoroethylene-propylene copolymer, a methacrylic acid ester or an acrylic acid ester as a crosslinking aid, and an organic peroxide as a crosslinking agent, as a main component. A cord-shaped heater, comprising: an insulating layer or an outer layer formed by heating at normal pressure and crosslinking.