JPS62291882A - Temperature self-control heater - 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 3. Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a self-temperature control heater used for purposes such as keeping pipes warm and preventing freezing.

[Prior Art] Self-temperature-controlling heaters consisting of heating elements with a positive temperature coefficient of resistance have been used to keep pipes warm and prevent freezing from the viewpoint of being maintenance-free, easy to install, and energy-saving. It is also used to insulate chemicals, resin raw materials, heavy oil, etc., and demand is expected to increase in the future.

Conventional self-temperature control heaters generally have a heating element made of a mixture of polyethylene and a conductivity imparting agent, and because of their excellent flexibility, they are suitable for use in thin pipes. Widely used for pipes of all sizes and sizes.

However, depending on the application, there are some that require high heating temperatures, and polyethylene-based materials have low output, so they have the disadvantage that the length of the laying strip must be increased to increase the temperature of the object to be heated.

If an attempt is made to raise the heating temperature by increasing the output in order to solve this problem, the heating temperature will rise to the crystal melting point of polyethylene due to heat generation, and there is a risk that the life of the heater itself will be extremely shortened. Furthermore, although polyethylene has excellent water resistance, it has the disadvantage of poor oil resistance. As a countermeasure to this problem, some products use polyurethane, which has good oil resistance, as an insulator to prevent oil from entering from the outside, but this alone is not a perfect solution. For example, if the terminal seal part is incomplete during installation, or if the insulation is cracked due to external trauma, oil may seep in from this part.
The heating element swells and its electrical resistance increases, resulting in almost no heat generation.

On the other hand, fluororesin has a higher crystal melting point than polyethylene and has excellent oil and chemical resistance, so a self-temperature-controlling heater using a mixture of fluororesin and a conductivity agent as a heating element has been proposed. has been done.

[Problems to be solved by the invention] However, since fluororesin is generally very rigid and hard, it cannot be used in applications where it is installed in a straight line, but it is not suitable for applications such as thin pipes and small-sized valves. However, the installation has the disadvantage of poor workability. Moreover, if the heater is wrapped forcibly, the heater will not come into close contact with the pipe due to repulsive force, and the thermal conductivity to the pipe will decrease. In addition, there are other drawbacks, such as the need for an extra heater because the bending radius cannot be made small in the folded portion of a complicated pipe.

The present invention has been made in order to solve the problems of the prior art described above, and can be used for a long time with high output, has flexibility, has excellent construction workability, and is oil resistant. The purpose of this invention is to provide a self-temperature control heater with excellent chemical resistance.

[Means for Solving the Problems] The self-temperature control heater of the present invention is a self-temperature control heater comprising a heating element having a positive temperature coefficient of resistance between electrodes, wherein the heating element is made of ethylene. - 0.05 to 1 part by weight of neodymium oxide per 100 parts by weight of a resin containing 95 to 70 parts by weight of a tetrafluoroethylene copolymer and 5 to 30 parts by weight of a tetrafluoroethylene-propylene copolymer
0 parts by weight, 0.5 parts by weight or more of an allyl type compound crosslinking aid, and a conductivity imparting agent, and is characterized by being crosslinked by irradiation with ionizing radiation. be.

In the present invention, an ethylene-tetrafluoroethylene copolymer and a tetrafluoroethylene-propylene copolymer are used as the resin component forming the heating element. In addition to tetrafluoroethylene and propylene, components copolymerizable with these, such as ethylene, butene-1, isobutyne, acrylic acid and its alkyl esters, methacrylic acid and its alkyl esters, vinyl butene, vinylidene butene, hexafluoride, etc. It may contain a suitable amount of fluoropropene, chloroethyl vinyl ether, glycidyl vinyl ether, chlorotrifluoroerylene, perfluoroalkyl vinyl ether, or the like. In such a copolymer, the molar ratio of tetrafluoroethylene/propylene is 9515 to 30/70, particularly 90/10 to 4.
It is preferable to select from the range of 5155 from the viewpoint of heat resistance, moldability, etc., and the content of components other than the main component, which may be added as appropriate, is usually selected from the range of 50 mol% or less, particularly 30 mol% or less. It is preferable to do so.

Ethylene-tetrafluoroethylene copolymer and tetrafluoroethylene-propylene copolymer are 5 to 30 parts by weight of tetrafluoroethylene-propylene copolymer to 95 to 70 parts by weight of ethylene-tetrafluoroethylene copolymer. If the content of the ethylene-tetrafluoroethylene copolymer exceeds 95 parts by weight,
If the flexibility of the heating element obtained is insufficient and the amount is less than 70 parts by weight, the self-temperature control function will not be exhibited due to the reduced crystal content.

Neodymium oxide is added to suppress the chemical reaction between the ethylene-tetrafluoroethylene copolymer and the crosslinking aid to increase the crosslinking efficiency, and the amount of neodymium oxide added is 0.00 parts by weight per 100 parts by weight of the resin. 05 to 10 parts by weight, preferably 0.2 to 2 parts by weight. If it is less than 0.05 parts by weight, the effect of suppressing the above chemical reaction is not sufficient and the extruded appearance tends to be poor, and if it exceeds 10 parts by weight, neodymium oxide agglomerates and stubble is likely to occur.

As the allyl type compound crosslinking aid, triallyl isocyanurate (TAIC), triallyl cyanurate (T
AC) ,) Reallyl trimellitate, triallyl trimezate, tetraallyl pyromellitate, etc.
Its content must be 0.5 parts by weight or more based on 100 parts by weight of the resin consisting of the ethylene-tetrafluoroethylene copolymer and the tetrafluoroethylene-propylene copolymer; less than this will result in cross-linking. As a result, a heater having self-temperature control and good mechanical properties in a high-temperature atmosphere cannot be obtained.

There is no particular upper limit, but if it exceeds 10 parts by weight, the degree of crosslinking will reach a saturated state, and even if more is added, there will be little improvement in the degree of crosslinking.

As the conductivity imparting agent, conductive carbon black, graphite, surface-grafted carbon black, carbon black grafted with an organic polymer, etc. can be used. The content of the conductivity imparting agent is determined by the calorific value of the heating element, so it is not particularly specified, but it is based on 100 parts by weight of the resin consisting of ethylene-tetrafluoroethylene copolymer and tetrafluoroethylene-propylene copolymer. against 5-1
The range of 5 parts by weight is preferable; if it is less than 5 parts by weight, the electrical resistance tends to be too high and it will not function as a heating element;
If it exceeds 5 parts by weight, the output tends to be too large and the life tends to be shortened.

In the present invention, other stabilizers, flame retardants, processing aids, etc. may be used as necessary.

[Example 1 of the invention (1) 95 parts by weight of ethylene-tetrafluoroethylene copolymer (Afron C0PC-88APM, manufactured by Asahi Glass Co., Ltd.) (2) 95 parts by weight of ethylene-tetrafluoroethylene-propylene copolymer (Awalas 150E, manufactured by Asahi Glass Co., Ltd.) (manufactured by Cabot Corporation) 5 parts by weight (3) Triallylisocyanurate (TA I C, manufactured by Shikoku Kasei Co., Ltd.) 10 parts by weight (4) Neodymium oxide 7 parts by weight (5) Conductive carbon black (XC-72, manufactured by Cabot Corporation)
After mixing 14 parts by weight with a Henshil mixer, 3 parts by weight
The mixture was kneaded and pelletized using a 40 m/m twin-screw extruder adjusted to a temperature of 20°C to obtain a heating element mixture.

Next, as shown in Figure 1, electrode 1.2 (interelectrode distance 7 m
A heating element 3 was formed by extrusion coating the above heating element mixture on the outer periphery of the heating element 3 to a thickness of 2 mm.

Next, an insulator 4 was formed by extrusion coating an ethylene-tetrafluoroethylene copolymer (Tefcel 200, manufactured by DuPont) to a thickness Q of 4 mm, and the heater was turned on by irradiating it with an electron beam of 20 M r a d. Created.

Example 2 (1) 80 parts by weight of ethylene-tetrafluoroethylene copolymer (Aflon COPC-138APM, manufactured by Asahi Glass Co., Ltd.) (2) 20 parts by weight of ethylene-tetrafluoroethylene-propylene copolymer (Aflon 150E, manufactured by Asahi Glass Co., Ltd.) (3) Triallylisocyanurate (TA I C, manufactured by Shikoku Kasei Co., Ltd.)
10 parts by weight (4) Neodymium oxide 7 parts by weight (5) Conductive carbon black (XC-72, manufactured by Cabot)
A heater was produced in the same manner as in Example 1 using 14 parts by weight.

Example 3 (1) 70 parts by weight of ethylene-tetrafluoroethylene copolymer (Afron COPC-88APM, manufactured by Asahi Glass Co., Ltd.) (2) 30 parts by weight of ethylene-tetrafluoroethylene-propylene copolymer (Awalas 150E, manufactured by Asahi Glass Co., Ltd.) (3) Triallyl isocyanurate (TAIC, manufactured by Shikoku Kasei Co., Ltd.)
10 parts by weight (4) Neodymium oxide 7 parts by weight (5) Conductive carbon black (XC-72, manufactured by Cabot)
A heater was produced in the same manner as in Example 1 using 14 parts by weight.

Comparative Example 1 (1) 100 parts by weight of ethylene-tetrafluoroethylene copolymer (Aflon COPC-88APM, manufactured by Asahi Glass Co., Ltd.) (2) 10 parts by weight (3
) Neodymium oxide 7 parts by weight (4) Conductive carbon black (XC-72, manufactured by Cabot)
A heater was produced in the same manner as in Example 1 using 14 parts by weight.

Comparative Example 2 (1) 50 parts by weight of ethylene-tetrafluoroethylene copolymer (Aflon COPC-88APM, manufactured by Asahi Glass Co., Ltd.) (2) 50 parts by weight of ethylene-tetrafluoroethylene-propylene copolymer (Aflon 150 E, manufactured by Asahi Glass Co., Ltd.) Part (3) Triallylisocyanurate (TAIC, manufactured by Shikoku Kasei Co., Ltd.) 10 parts by weight (4) Neodymium oxide 7 parts by weight (5) Conductive carbon black (XC-72, manufactured by Capot Co., Ltd.)
A heater was produced in the same manner as in Example 1 using 14 parts by weight.

Conventional example (1) Polyvinylidene buttonide (Kynar 901, manufactured by Pennwalt Co., Ltd.) 100 parts by weight (2) Triallyl cyanurate (TAC, manufactured by Shikoku Kasei Co., Ltd.)
5 parts by weight (3) Surface-treated calcium carbonate (Msi-v, manufactured by Maruo Seifun Co., Ltd.
5 parts by weight (4) Conductive carbon black (XC
-72, manufactured by Cabot) 12
A heater was produced in the same manner as in Example 1 using parts by weight.

Table 1 shows test results for self-temperature control heaters manufactured in Examples, Comparative Examples, and Conventional Examples.

The test was conducted based on the following.

(1) Hardness of heating element: The hardness of heating element 3 was measured according to JIS-6301. In addition, Shore D was used as a hardness tester.

(2) Resistance: After being left in a constant temperature bath at 20° C. for 1 hour, CI was determined using a Wheatstone bridge.

(3) It was installed in a straight line on a pipe with an inner diameter of 1 inch, and the top was covered with a glass wool insulation material with a thickness of 30 Ωm. Next, pour water at 20℃ into the pipe, and then
Apply an AC voltage of 00V.

The current value was read 30 minutes after energization in the circuit connected as shown in FIG. 3, and the output was calculated using the following formula.

In FIG. 3, 5 is a sample, 6 is an ammeter, 7 is a power source, and 8 is a voltmeter.

(4) Operating temperature - Measure the surface temperature of the heater when placing a heater with a sample length of 1 m in a constant temperature bath at 20°C and applying 200 V between the electrodes.The temperature at which the temperature is saturated is defined as the operating temperature. did.

(5) Self-temperature controllability: A resistance-temperature curve as shown in FIG. 2 was obtained, and a heater with a large positive temperature coefficient (PTC) of resistance was determined to have good self-temperature controllability.

(4) Degradation life due to charging: A sample with a length of 1 m was connected to a power charging device wired as shown in FIG. 3 and charged with power in an atmosphere at room temperature. The applied voltage is 500, which is 2.5 times the normal voltage (200V).
As V, the resistance value between the electrodes was measured at regular intervals, a curve change in resistance was plotted, and the time when the value became twice the rate of change with respect to the initial value was defined as the energization life.

[Effects of the Invention] As explained above, the present invention consists of 95 to 70 parts by weight of ethylene-tetrafluoroethylene copolymer and 5 to 30 parts by weight of tetrafluoroethylene-propylene copolymer, and oxidation The heating element is formed from a composition containing neodymium, an allyl-type compound crosslinking aid, and a conductivity imparting agent, and the output per unit length is higher than when conventional vinylidene butoxide is used alone. It is extremely large, has a high operating temperature, and can realize a high-temperature, high-output self-temperature-controlling heater.

In addition, the lifespan due to electrical deterioration is greatly improved, and because of its excellent flexibility, workability and adhesion when attaching to piping, etc. are improved, and thermal conductivity is also significantly improved.

Furthermore, it has the excellent heat resistance, oil resistance, and flame retardancy of fluororesin, and its industrial value is extremely large.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram of an embodiment of the self-temperature control heater of the present invention, Fig. '7A2 is an explanatory diagram showing the resistance-temperature curves of heaters of the embodiment, comparative example, and conventional example, and Fig. 3 is an illustration of output measurement. FIG. 2 is a wiring diagram of a device for a charging deterioration test.

Claims (1)

[Claims] (1) In a self-temperature-controlling heater comprising a heating element having a positive temperature coefficient of resistance between electrodes, the heating element is made of ethylene-tetrafluoroethylene copolymer 95
0.05 to 10 parts by weight of neodymium oxide and 0.05 to 10 parts by weight of an allyl type compound crosslinking aid per 100 parts by weight of the resin containing ~70 parts by weight and 5 to 30 parts by weight of the tetrafluoroethylene-propylene copolymer. 1. A self-temperature-controlling heater comprising a resin composition containing 5 parts by weight or more and a conductivity imparting agent, and crosslinked by irradiation with ionizing radiation.