JPS60231764A - Planar heating material filled with electrically conductive metallic fiber - Google Patents

Abstract

PURPOSE:To provide the titled material having excellent mechanical characteristics and electrical conductivity and suitable for use as a material for heaters and as a structural material for low-temperature resistant devices and melting devices, by filling a thermoplastic resin with an electrically conductive metallic fiber. CONSTITUTION:5-20vol% short metallic fiber having an average diameter of 20-120mum and an aspect ratio of 30-100, selected from among Fe, Cu, Al, Ni and their alloys, is mixed with a thermoplastic resin selected from among PP, ABS resin, nylon, polyphenylene ether and polyphenylene oxide. The mixture is molded into a desired shape to obtain a desired planar heating material having a volume resistance of 0.2-15OMEGA.cm.

Description

[Detailed Description of the Invention] [Subject of the Invention] The present invention relates to a planar heat generating material in which a resin material is filled with conductive metal short fibers. The invention relates to surface heating materials used to melt ice and snow.

[Prior art]

It is used in heating products such as sheet heating pads, heating carpets, and electric blankets, and as a material for preventing freezing of roads and water pipes. Conventional sheet heating materials include aluminum foil,
Alternatively, metal fibers (for example, silver) are deposited on a heat-resistant film, or carbon particles are mixed into a resin.

[Problems in the prior art and their technical analysis] Regarding the conventional surface heating materials, (1) When using a metal-deposited heat-resistant film as a heating element according to the shape of the product, if the radius of curvature of the product shape is small. , the heat generation efficiency of that part decreases significantly, and in the case of a film, it is necessary to use it by bonding it to a structure.
(2) The carbon particle-containing resin material is a surface heating material with a volume resistivity of around 101 Ω-cm, which contains 15 to 20 νOL% of carbon to the resin. Due to the inclusion of carbon particles in heat generating materials, the mechanical properties of the material (
(bending, tensile) decreases, making the material brittle, and also has a high volume resistivity, so when used as a heat generating material, it is necessary to apply a high voltage or shorten the length between the electrodes to reduce resistance. There is a drawback that it is necessary.

[Technical issues]

Therefore, the present invention has developed a resin composite material that has excellent mechanical properties, is low in cost, and has excellent conductivity when used as a sheet heating element in heating products and as a structural material for cold resistance and melting. This is a major issue.

[Technical means and their effects]

□ The technical measures taken to solve the above technical problems are iron, copper, aluminum, nickel, and their alloys with an average diameter of 20 to 120 μm and an aspect ratio (length/
Conductive metal short fibers having a diameter of 307,100 are used to make polypropylene (PP), acrylonitrile butadiene styrene (ABS), nylon (NY), polyphenylene ether (PPE), polyphenylene oxide (PP).
It is mixed into the thermoplastic resin (O) at 5 to 20 VOL% and molded into a product shape.

When molded by mixing conductive metal short fibers into the thermoplastic resin, it has mechanical strength suitable for a structural material, and has an extremely good volume resistivity value of 10 Ω-cm or less.

When mixing conductive metal fibers into resin, it is necessary to mix them uniformly, and the range that satisfies this and does not cause any performance problems is that the average diameter of the short fibers is 20 to 120 μm.
The aspect ratio (length/diameter) is 30 to 15'O, more preferably the average diameter is 40 to 90 μm, and the aspect ratio is preferably 0.

Table 1 shows that nylon-6 resin is coated with 60 μm conductive metal short fibers and brass fibers with an aspect ratio of -50.
vow, % mixed and carbon particles 20-30μ
Comparison of mechanical properties when m is mixed at i 5 VOL% is shown.

From Table 1 above, it can be seen that nylon resin containing brass fibers is superior.

Next, regarding the electrical resistance of the conductive metal fibers and carbon particles, the carbon particles have a diameter of 100 cm, and the conductive metal short fibers have a 10 Ω mark, which is considerably lower for the metal short fibers. Thermoplastic resins acrylonitrile, butadiene, styrene (
A-B-S resin) and brass fibers (90 μm x 3
The graph in FIG. 1 shows the relationship between the filling rate and the volume resistivity when m) is mixed. As a result, the volume resistivity can be reduced to 10-' to 10-2Ω with a small amount of mixing at a filling rate of about j5VOL%.
It can be seen that it is very low. In this way, resin mixed with 8 to 20 VOL% of conductive metal fibers has lower mechanical strength and electrical conductivity than conventional resin materials mixed with carbon particles. Table 2 shows a comparison of each electrical property when brass fibers and carbon particles are mixed into A, B, and S resins, due to carbonization of the volume resistivity (when the mixing ratio of brass fibers is changed in the resin). shows.

Table 2 As shown in Table 2, conductive short metal fibers have a low volume resistivity, so in order to obtain the same calorific value, there is a greater degree of freedom in designing the power and current used, compared to when carbon is mixed. The number of electrodes can also be reduced.If the amount of conductive metal short fibers mixed in the resin material is less than 5 VOL%, the electrical resistance will increase and a high voltage will be required, which is dangerous from a safety standpoint and dielectric breakdown of the material. However, there is a problem, and the amount of contamination is 25 VOL%.
If it is more than that, the resistance value becomes too small and the current becomes large.
When viewed as a heating element product, there are problems due to connection wires and electric capacity.

[Special effects of the present invention]

The present invention has the following unique effects; namely, the planar heating element manufactured by mixing conductive short metal fibers into the thermoplastic resin has mechanical properties that are superior to those of the planar heating element containing carbon particles. However, since the carbon particles are spherical, they are not retained well in the matrix, so surface treatment is necessary. However, since the short metal fibers are long in the lateral direction, It is easily retained and no surface treatment process is required.

(2) Compared to a planar heating element made of short metal fibers, a planar heating element made of carbon particles requires more electrodes due to its electrical conductivity when the heating element has the same area.

(3) When a planar heating element is molded by injection molding with carbon particles mixed in, carbon particles tend to be unevenly distributed and it is difficult to disperse them uniformly, but short metal fibers are easily dispersed and do not fit into the matrix. Since it is uniformly dispersed, it is easy to produce products with uniformity and properties. [Example] Hereinafter, an example showing a specific example of the above-mentioned technical means will be described.

(Example-1) 8 VOL% of brass fibers with a diameter of 60 μm x 3 dragons were mixed into a thermoplastic resin of 6-nylon as conductive short metal fibers.1.
Kneading and extrusion were performed to produce pellet materials with a length of 7IIll and a diameter of 3.

This material was molded into a flat plate of 300 x 300 x 2 mm using an in-line screw type injection molding machine.

Apply silver paste to both ends of this flat plate, measure the resistance with an electrometer to calculate the volume resistivity, and apply a voltage (
V) was applied, a current was applied, and the heat generation temperature (r) was measured, which is shown by A in the graph of FIG. Note that the volume resistivity in this case is 14.8 Ωcm.

(Example-2) Diameter of aluminum alloy fiber 90 μm as conductive short metal fiber
X 3 ++m was mixed into polypropylene, a thermoplastic resin, at a filling rate of 15 VOL%. Graph B shows the relationship between the voltage and the temperature rise in this case, which is the volume resistivity value (hereinafter referred to as R) R-2Ωcm, which was performed in the same manner as in Example-1.

(Example 3) Same as Example 2, but with a filling rate of 20 VOL%, and R=0.2 Ωcm. Graph C shows the relationship between voltage and temperature rise in this case.

(Comparative Example-1) A composite material was manufactured using Ketjenblack EC as carbon particles and in the same manner as in Example 1, with a filling rate of 15 VOL%. Graph D shows the relationship between voltage and temperature rise at R-250 Ωcm in this case.

(Comparative Example-2) A flat plate of 73 x 73 x 2 sections was cut out from the flat plate of Comparative Example-1, and the exothermic temperature was measured, as shown in the graph below. R
=250Ωcm. As a result, it can be seen that the area is approximately 1/20 of the size, or approximately the same value as Example-1.

(Comparative Example-3) A composition of conductive carbon and vinyl chloride resin (Zannomi, S-135) was measured. R = 130 Ωcm, the plate thickness was 1.31, and the strip was 81.6 x 81.6 mm. A voltage of 100V was applied to this, which is shown in F.

As a result, the area of the example was about 1/15.
It can be seen that the value is almost the same as 1.

[Brief explanation of the drawing]

Fig. 1 is a graph showing the relationship between the filling rate and the volume resistivity when the matrix of the present invention is mixed with conductive short metal fibers, and Fig. 2 is a graph showing the relationship between the voltage and the sheet heating element of the present example and the comparative example. 3 is a graph showing the relationship between surface temperature and surface temperature. Patent Applicant 1 Reio Nakai (n<→ Figure 1 y (vOLX) V Order (V)

Claims (1)

[Claims] (11 Thermoplastic resin containing 2 to 25 VO
A planar heating material containing conductive metal fibers, which is a resin composite composition filled with L% and has a volume resistivity in the range of 0.2ΩC11l to 15Ωcm. (2) The conductive metal short fibers include iron, copper, aluminum,
Average diameter 20-120μ made of nickel and its alloys
The planar heat generating material according to claim 1, having an aspect ratio of 30 to 100. (3) The planar heat-generating material according to claim 1, wherein the thermoplastic resin is polypropylene, acrylonitrile-bukdiene-styrene, nylon, polyphenylene ether, or polyphenylene oxide.