JP2531277B2 - Self temperature control heater - Google Patents

Description

TECHNICAL FIELD The present invention relates to a self-temperature controllable heater used for the purpose of keeping the piping warm, preventing freezing, etc., and is particularly suitable for workability due to its good flexibility. The present invention relates to an improved self-temperature controllable heater which is excellent in oil resistance and chemical resistance.

[Prior Art] In a self-temperature controllable heater, a heating element 3 made of a composition obtained by mixing carbon black as a conductivity-imparting agent into a plastic as a base material is provided with electrodes 1 and 2 as shown in FIG. It is a long heater that is filled with a gap between the outer periphery and the outer periphery with an insulator 4 and is formed into an appropriate shape mainly according to the purpose of use, such as a flat mold, and is wound around a pipe or the like of a substance to be heated or Used by arranging vertically.

The mechanism of self-temperature control is that the conductive path is formed by the chain of carbon black blended at low temperature,
Heat is generated between the electrodes, but when the temperature rises, the plastic of the base material expands and the chain of the conductive paths is cut, resulting in a large resistance and a small heat generation. To do.

Therefore, the self-temperature controllable heater having the above configuration and mechanism is easy to maintain, easy to install,
From the viewpoint of energy saving, it has been used for heat insulation of pipes and prevention of freezing, and recently it is also used for heat insulation of chemicals, resin raw materials, heavy oil, etc., and it is expected that demand will increase in the future.

As the plastic used as the base material, a polyethylene-based material having excellent flexibility is also used in consideration of easiness of winding around a pipe, a valve or the like for a material having a relatively low output such as antifreezing. However, for those that require a large amount of heat generation at high temperature such as prevention of viscosity increase of resin raw material or heavy oil in piping, polyethylene-based materials have poor heat resistance, and therefore polyvinylidene fluoride mixed with the conductivity-imparting agent. The thing which used the thing as the heating element 3 has been widely used.

[Problems to be Solved by the Invention] However, although the above polyvinylidene fluoride has excellent heat resistance, it generally has high rigidity and hardness, so there is no problem for use in straight line installation, but thin pipes and When it is applied to a small-sized valve or the like, it has a drawback that mounting workability is deteriorated. In addition, when it is forcibly wound, the heater does not adhere to the pipe due to the repulsive force, and the thermal conductivity to the pipe is reduced. In addition, since the bending radius cannot be made small at the folded portion on the complicated pipe, there is a drawback that an extra heater is required, and its improvement is required.

The object of the present invention is to solve the above-mentioned problems of the prior art, to be able to sufficiently use it for high temperatures, to be able to use it for a long time at high output, and especially to have flexibility. The present invention is also intended to provide a novel self-temperature controllable heater which is remarkably excellent in construction workability since it also has excellent oil resistance and chemical resistance.

[Means for Solving the Problems] The present invention relates to a self-temperature controllable heater having a heating element having a positive temperature coefficient of resistance provided between electrodes, and the heating element is tetrafluoroethylene-ethylene-
A resin composition containing 0.5 parts by weight or more of an allyl type compound-based crosslinking aid based on 100 parts by weight of a fluorine-containing vinyl copolymer, and a conductivity-imparting agent, and used by crosslinking by irradiation with positive ionizing radiation. Further, instead of the tetrafluoroethylene-ethylene-fluorine-containing vinyl copolymer, a composition obtained by mixing the above-mentioned blending components in the same manner with respect to 100 parts by weight of tetrafluoroethylene-ethylene-chlorotrifluoroethylene copolymer. Is used after being crosslinked.

In the present invention, the content molar ratio of tetrafluoroethylene in the tetrafluoroethylene-ethylene-fluorine-containing vinyl copolymer is appropriately in the range of 50 to 90 mol%,
Desirably, the range of 60 to 80 mol% is more preferable.

The fluorine-containing vinyl monomer used in the present invention may be any fluorine-containing monomer copolymerizable with tetrafluoroethylene and ethylene to give a side chain to the copolymer, and the kind thereof is not limited.

Usually, a monomer represented by the formula: CH ₂ = CXRf, CF ₂ = CFRf, CF ₂ = CFORf, CH ₂ = C (Rf) ₂ [wherein, X represents hydrogen or fluorine, and Rf represents a fluoroalkyl group]. Is used, and among others, a fluorine-containing vinyl monomer represented by the formula: CH ₂ ═CXRf is preferable for the reason of copolymerizability or economic reasons. Particularly, a monomer having Rf of 1 to 8 carbon atoms is particularly preferable. Specific examples of such vinyl monomers are as follows.

1,1-dihydroperproropropene-1,1,1-dihydroperfluorobutene-1,1,1,5-trihydroper
Fluoropentene-1,1,1,7-trihydropa-fluoroheptene-1,1,1,2-trihydropa-fluorohexene-1,1,1,2-trihydroperfluorooctene-
1,2,2,3,3,4,4,5,5-octafluoropentyl vinyl ether, perfluoro (methyl vinyl ether), perfluoro (propyl vinyl ether), hexafluoropropene, perfluorobutene-1,3,3 , 3-Trifluoro-2-trifluoromethylpropene-1.

The content ratio of these modified monomers is appropriately in the range of 0.1 to 10 mol%, preferably 0.5 to 5 mol%.

On the other hand, the content molar ratio of tetrafluoroethylene in the tetrafluoroethylene-ethylene-chlorotrifluoroethylene copolymer in the present invention is 50 to 90 mol% like the above.
The range is appropriate. Further, the content ratio of chlorotrifluoroethylene is appropriately in the range of 1 to 20 mol%, preferably 2 to 10 mol%. If the amount of chlorotrifluoroethylene is too small or too large, the effect of imparting flexibility is reduced.

As the conductivity-imparting agent, it is possible to use conductive carbon black, garafite, surface-grafted carbon black, carbon black grafted with an organic polymer, and the like. The content of the conductivity-imparting agent is determined by the amount of heat generated by the heating element, and is not specified, but it is preferably in the range of 5 to 15 parts by weight per 100 parts by weight, and if less than 5 parts by weight, the electric resistance is too high. If the amount exceeds 15 parts by weight, the output becomes too large and the life tends to be shortened.

As allyl type compound crosslinking aids, triallyl isocyanurate (TAIC), triallyl cyanurate (TAIC)
C), triallyl trimellitate, triallyl trimezate, tetraallyl pyromellitate and the like, and the content thereof is preferably 0.5 to 10 parts by weight with respect to 100 parts by weight of the resin content. If the amount is less than 0.5 parts by weight, the crosslinking is insufficient, and if the amount is more than 10 parts by weight, the degree of crosslinking reaches a saturated state, and even if the amount is more than 0.5 parts by weight, the improvement in the degree of crosslinking is hardly seen.

In the present invention, other stabilizers such as calcium carbonate and processing aids may be used as necessary.

[Examples] Hereinafter, the present invention will be described with reference to Examples.

After mixing each base composition and compounding ingredients shown in Examples 1 to 3 and Comparative Example in Table 1 with a Hensil mixer,
A 40 m / m two-wheel extruder adjusted to a temperature of 0 ° C. was kneaded into pellets to obtain a heating element mixture.

Next, as shown in Fig. 1, electrodes 1 and 2 with 19 nickel-plated copper wires with an outer diameter of 0.3 mmφ twisted together (distance between electrodes 7 mm)
The heating element 3 was formed by extruding and coating the above-mentioned mixture of heating elements to a thickness of 2 mm.

Subsequently, an ethylene-tetrafluoroethylene copolymer (Tefzel 200, manufactured by DuPont) is extrusion-coated to a thickness of 0.4 mm to form an insulator 4, which is irradiated with an electron beam of 20 Mrad and crosslinked to form a heater. did.

FIG. 2 is an explanatory view showing an outline of the flexibility test apparatus for the self-temperature controllable heater manufactured as described above.
Is a sample cut to have a measurement length of 10 cm, 11 is a holding member that holds the sample 10 in a cantilever state, and 12 is a deflection amount δ.
This is a weight attached to the tip of the sample 10 in order to obtain.

In the lower column of Table 1, the measurement length l = 10 cm, and the weight load G =
The deflection amount δ value (mm) of each of Examples 1 to 3 and Comparative Example which is a conventional example at 100 g is shown.

Furthermore, for each of the samples of Examples 1 to 3 in Table 1, the resistance value after standing for 1 hour in a thermostatic chamber maintained at each measurement temperature was measured by a Wheatstone bridge, and The relationship is plotted in FIG.

As can be seen from Table 1, Examples 1 to 3 according to the present invention
Has a sufficient amount of deflection as compared with the comparative example, which is a conventional example, and demonstrates that each has excellent flexibility.

Further, as can be seen from the temperature-resistance characteristic curve of FIG. 3, it was also proved that all of Examples 1 to 3 have good self-temperature controllability.

In addition, Table 2 shows that the base compositions and blending components of the other Examples 4 to 6 were mixed in a Hensyl mixer, and then kneaded and pelletized by a 40 m / m2 wheel extruder adjusted to a temperature of 250 ° C to generate heat. It shows the measurement results for the case of a body mixture.

Similar to the above, as shown in Fig. 1, electrodes 1 and 2 with 19 nickel-plated copper wires with an outer diameter of 0.3 mmφ twisted together (distance between electrodes: 7 m
The heating element 3 was formed by extrusion coating the above mixture of heating elements to a thickness of 2 mm on the outer periphery of m).

Subsequently, an ethylene-tetrafluoroethylene copolymer (Tefzel 200, manufactured by DuPont) is extrusion-coated to a thickness of 0.4 mm to form an insulator 4, which is irradiated with an electron beam of 20 Mrad and crosslinked to form a heater. did.

A flexibility test was conducted in the same manner as above, and the obtained deflection amount δ is shown in the lower column of Table 2.

The results of measuring the temperature-resistance characteristics of Examples 4 to 6 in the same manner as above are shown in FIG.

Similar to Examples 1 to 3 above, Examples 4 to 6 each have extremely excellent flexibility as compared with the conventional example (Comparative Example in Table 1), and all It can be said that these Table 2 and FIG. 4 clearly demonstrate that they have good temperature controllability.

[Advantages of the Invention] As described above, according to the self-temperature controllable heater of the present invention, it has extremely excellent flexibility as a high temperature heater,
Not only can the construction work be greatly facilitated, but it can also exhibit a number of excellent features such as good adhesion to the heated object and improved heating efficiency.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a cross-sectional view showing a configuration example of a self-temperature controllable heater,
FIG. 2 is an explanatory view showing the situation of the flexibility test, and FIGS. 3 and 4 are temperature-resistance characteristic diagrams of the examples. 1,2: Electrode, 3: Heating element, 4: Insulator jacket.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP 62-291882 (JP, A) JP 62-278782 (JP, A) JP 63-279589 (JP, A) JP 63- 292593 (JP, A)

Claims (2)

(57) [Claims] 1. A self-temperature controllable heater comprising a heating element having a positive temperature coefficient of resistance between electrodes, wherein the heating element is 100 parts by weight of a tetrafluoroethylene-ethylene-fluorine-containing vinyl copolymer. On the other hand, the self-temperature controllability is characterized by comprising a resin composition containing 0.5 part by weight or more of an allyl type compound-based crosslinking aid, and a conductivity-imparting agent, and being crosslinked by irradiation of ionizing radiation. heater. 2. A self-temperature controllable heater comprising a heating element having a positive temperature coefficient of resistance between electrodes, wherein the heating element is tetrafluoroethylene-ethylene-chlorotrifluoroethylene copolymer 100 wt. 0.5 parts by weight or more of an allyl type compound-based cross-linking aid for each part, and a resin composition containing a conductivity-imparting agent, self-temperature control characterized by being cross-linked by irradiation of ionizing radiation Sex heater.