JPH0757854A - Panel heater - Google Patents

Abstract

PURPOSE:To use a specified thermoplastic resin and provide stable heating and excellent durability. CONSTITUTION:As a heating element 1, a thermoplastic polyester or its elastomer is used. An insulating plastic resin such as low density polyethylene, high density polyethylene, or polypropylene is sandwich molded on the element 1 by use of a press molding machine to form a cover layer 2. To stabilize the resistance of the element 1, annealing is carried out, specified wires are connected to one-side ends of two electrode lines 3 as lead wires 5 by use of crimping sleeves 4. The layer 2 is thermoplastic, and has a volume resistance value of 10<10>OMEGAcm or more and a softening point lower than 160 deg.C. Such a panel heater has an output change ratio lower than 10% at a temperature difference of 100 deg.C, the element 1 contains 5-50wt.% of a conductive material having a volume resistance value less than 10<-1>OMEGAcm, and is formed by molding a conductive resin composite having a volume resistance value of 10-10<4>OMEGAcm into a panel. Thus, the temperature dependency of electric resistance value is minimized, and stable heating can be provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a railroad turnout, a roof, snow melting and freezing prevention on a road surface, agricultural soil, freezing prevention and heating of tank contents, and output change due to temperature used for indoor floor heating. Regarding less panel heaters.

[0002]

2. Description of the Related Art Electric heaters coated with nichrome wire have been widely used. This heating element is inexpensive and has a constant output even when the temperature changes. However, since the heating temperature is high, the nichrome wire and the covering material are prone to deterioration due to heat, and the durability is poor. On the other hand, there is a heating element used for a planar heating element using carbon black as a conductive material, but there is a PTC characteristic that the resistance value decreases as the temperature rises, and it is difficult to always obtain a constant amount of heat generation. is there.

[0003]

DISCLOSURE OF THE INVENTION The present invention has a drawback that the nichrome wire has a disadvantage that the heat generation temperature is inevitably high because the fine wire having a small heat generation area is used to generate heat when a constant heat generation amount is obtained. By increasing the heat generation area by using the molded heat generating element, the heat generation temperature is lowered to suppress the deterioration of the used material due to heat, and the output greatly fluctuates depending on the temperature as seen in the plastic sheet heating element. It is intended to provide a heater with suppressed characteristics.

[0004]

The present invention uses a thermoplastic polyester resin as a base resin and has a volume resistance value of 10 ^-1 Ω.
cm to 50% by weight of a conductive material and having a volume resistance value of 10 ¹ to 10 ⁴ Ω · cm and having a conductivity, the resin composition is molded into a panel shape, and a metal stranded wire as electrodes at both ends thereof,
A heating element having a metal braid or a metal rod is covered with a thermoplastic resin having a volume resistance value of 10 ¹⁰ Ω · cm or more and a softening point of 160 ° C. or less as a covering material.
The present invention relates to a panel heater having an output change rate of 10% or less at a temperature difference of 100 ° C.

The panel heater of the present invention is manufactured by the following steps. Thermoplastic polyester and its elastomer are used for the conductive resin composition which is a raw material of a heating element. The reason for this is that thermoplastic polyester has a smaller linear expansion coefficient than other thermoplastic resins and the resistance change with temperature when used as a heating element is small, and the softening temperature is 1
Since the temperature is 80 ° C. or higher, it is possible to withstand the temperature and pressure at the time of molding the coating layer, and it is possible to knead the conductive material at a high concentration in the polyester elastomer. As the conductive material, carbon black, graphite, metal powder, metal fiber, carbon fiber or the like which has a volume resistance value of 10 ⁻¹ Ω · cm or less and is generally used as a conductive material for plastics may be used.

When the content of the conductive material is less than 5% by weight, the resistance value is too large and a sufficient output cannot be obtained as a heating element. On the other hand, if it exceeds 50% by weight, the physical strength of the heat generating element is significantly lowered, and thus neither is suitable. The melt-kneading of the base resin and the conductive material is performed by a single-screw or twin-screw extruder, FCM,
It is desirable to pelletize using a continuous kneader such as a cokneader. The pelletized resin composition is 3 at 120 ° C.
After drying for about an hour, a panel-shaped heating element is molded by injection molding, extrusion molding, press molding, or the like. In addition, a method may be adopted in which a twisted metal wire, a metal braided wire, and a metal rod are previously installed as electrode wires at both ends in the mold at the time of molding, and the electrode wires instantly adhere to each other at the time of molding.

From one end and both ends of the obtained heating element,
Connect the end of the electrode wire and the lead wire. Further, this heating element is sandwich-molded with an insulating thermoplastic resin by a press molding machine or an injection molding machine to form a coating layer. The resin used as the coating layer has a volume resistance value of 10 ¹⁰ Ω · cm.
As described above, the softening point is 160 ° C. or lower, and examples thereof include low-density polyethylene, high-density polyethylene, polypropylene and its elastomers, ionomers, and acid-modified products.

[0008]

EXAMPLES The present invention will be described in more detail based on the following examples. In the examples,% means% by weight. Example 1 56.5% of a polyester elastomer (Hytrel 7247 manufactured by Toray-Dyupon Co., Ltd.) and 43.5% of graphite having an average particle diameter of 20 μ were used, and a cylinder bore diameter was 30 mm and L / D = 3.
The mixture was melt-kneaded at 250 ° C. with a twin screw extruder No. 2 to obtain pellets. Next, the pellets are heated with a hot air dryer to 120
After drying at ℃ for 3 hours, it was used as a raw material for molding.

This raw material is tin-plated with a cross-sectional area of 2 mm ² at both ends in the longitudinal direction of the inner surface of the mold so that a panel-shaped molded product of 50 × 170 × 4.5 mm can be obtained by an injection molding machine with a clamping pressure of 100 t. After arranging in parallel with the copper stranded wire, injection molding was performed to obtain a heating element having a predetermined shape. The obtained heating element was annealed at 120 ° C. for 12 hours in order to stabilize the resistance value. The resistance after annealing is 130
It was Ω. Further, a Lycal electric wire as a lead wire was connected to one end of each of the two electrode wires using a crimp sleeve.

Next, at 190 ° C. on the upper and lower surfaces of this heating element,
It was sandwiched between sheets of maleic acid-modified high-density polyethylene having a thickness of 1.5 mm with an MFR at 2.16 kgf of 1 g / min, preheated sufficiently by a hot press at 160 ° C, and then 10
A coating layer was provided by pressurizing with a pressure of 0 kg / cm ² for 2 minutes to obtain a panel heater.

[0011]

By using the thermoplastic polyester resin, the present invention can provide a panel heater having a small temperature dependence of the electric resistance value and constantly generating heat.

[Brief description of drawings]

FIG. 1 shows a general view of the present invention.

[Explanation of symbols]

 1: Heating element 2: Coating layer 3: Electrode wire 4: Crimping sleeve 5: Lead wire

Claims (1)

[Claims] 1. A thermoplastic polyester resin as a base resin
However, the volume resistance value is 10 ^-15 to 5 conductive material of Ω · cm or less
Contains 0% by weight and has a volume resistance value of 10¹-10^FourΩ · cm
The resin composition having conductivity of is molded into a panel shape,
Install metal strands, metal braids, or metal rods on both ends as electrodes.
Volume resistance value due to thermoplasticity as a covering material for the placed heating element
Is 10^TenFor resin with Ω · cm or higher and softening point of 160 ° C or lower
Covers the periphery of the heat generating element more and changes the output at a temperature difference of 100 ° C.
A panel-shaped heater whose conversion rate is 10% or less.