JPS63138685A - Manufacture of resistance paste for panel 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] For both fixed resistance type and self-temperature control type surface heating elements, if the heating element layer (film) is uneven, the heat generation will be uneven in that part, and the slight heat generation will be As the non-uniformity of the temperature gradually increases, local heating occurs, resulting in abnormally high temperatures, which can burn out the heating element and even create a fire hazard.

Conventional resistance paste for heating elements has a particle diameter of approximately θ, for example! ~
/! Graphite powder of about μ (average particle diameter approximately! μ),
A conductive material such as metal powder is added with the required amount of alumina or other ceramic material with approximately the same particle size, and a binder such as a thermoplastic synthetic resin, a flame retardant, an anti-aging agent, etc. are added. was put into a suitable organic solvent and raised to a temperature of about /θθ℃ while stirring with a centrifugal stirrer. After continuing stirring for about 7 hours, it was allowed to cool, aged at room temperature for more than 7.2 hours, and then stirred manually again. This was obtained by printing and coating on the required parts of the insulating base material using an automatic printing machine, and then heated in a firing furnace at about /♂θ℃, 3
The heating element was made by firing for 0 minutes, and the required heating element was obtained by arranging the two terminals and lead wires, but the heating element layer of these heating elements became uneven, resulting in the above drawback. easy.

In view of the above-mentioned drawbacks, the inventors conducted various studies on the method of manufacturing a resistor paste for forming a heating resistor layer, and as a result, arrived at the present invention. The present invention is directed to the particle size of a solvent-insoluble material such as a conductive material or a ceramic material that is blended into a resistance paste forming a heating resistor layer of a planar heating element. The resulting paste is obtained by adding ultrafine particles of the mixture to the solvent together with a synthetic resin binder and other soluble materials, heating and stirring the mixture, or by applying ultrasonic waves to the mixture and rapidly cooling it. The contained insoluble materials are uniformly and extremely stably dispersed, and the components do not become unevenly distributed even after a long period of time. The entire surface is heated evenly, there is no local temperature rise, and it can be used safely for a long period of time.

The present invention will be described below with reference to Examples.

A conductive material such as a carbonaceous material or a metal, which has been pulverized by an appropriate method in an appropriate solvent containing or not containing a surfactant to have an average particle size of 7 μm or less, preferably on the order of submicrons, and a conductive material such as a carbonaceous material or metal. A required amount of a material insoluble in the solvent, such as a ceramic material, a synthetic resin binder, a flame retardant, an anti-aging agent, etc., which is blended with the heat generating material to form the required heat generating layer, is added to the desired temperature, e.g. The mixture is stirred and mixed for a required period of time while heating to around 700° C., and in this state, it is rapidly cooled with water or other suitable method, or it is aged in that state for several hours to more than ten hours to obtain the required resistance paste for a heating element. In this paste, the fine powder particles present were uniformly and extremely stably dispersed, and even after a long period of time, there was no localized non-uniformity due to uneven distribution.

The obtained paste is uniformly applied to the surface of an electrically insulating base material provided with electrodes using a printing machine using a conventional method, and fired to obtain a heating element, into which terminals and lead wires are placed. Table 1 shows the results of various tests carried out on the surface heating element formed by attaching the wafer.

In the above paste manufacturing process, other ingredients are added to the solvent, heated and stirred to the required temperature, and then the mixture is heated to an appropriate frequency that is generally used for purposes such as mixing liquids and cleaning parts. A paste with even better dispersion stability can be produced by applying sound waves for a certain period of time and rapidly cooling while maintaining that state.

Furthermore, a paste with even better stability can be obtained by appropriately selecting the order of addition of other compounded raw materials added to the solvent.

The above-mentioned surfactants used in paste production are added as necessary as dispersants for fine particles that are insoluble in solvents, and the surfactants generally used for dispersion purposes are selected appropriately. It can be used in the amount /~/θ in the solvent.
In many cases, about θo ppm is sufficient.

Various solvents can be appropriately selected and used as long as the binder and the like can be dissolved therein. Examples include aromatic solvents such as toluene and xylene, as well as calpitol, methyl ethyl ketone, and the like.

Among the carbonaceous materials, graphite, carbon black, etc. can be used as the carbonaceous material, and as the metal, those used in this type of heating element can be used as appropriate. Ceramic materials include alumina, antimony oxide, and other known metal oxides used for this purpose.

Binders include cellulose resins such as ethyl cellulose, acrylic resins, polycretanes, ethylene-vinyl acetate copolymers, fluororesins, vinyl resins, etc., which can be used alone or in combination of i or more types. Furthermore, flame retardants and anti-aging agents that are blended with synthetic resins can be selected as appropriate and used. Examples of flame retardants include Fire Card (trade name of Teijin Kasei μ) and Toyoparax (trade name of Toyo Soda μ), and anti-aging agents include /, /-bis(hydroxyphenyl)-cyclohexane, ￥, 'l. '-Butylidenebis-(3-methyl-6-tert-butylphenol)
, Otsu-tert-butyl-3-methylphenol derivatives and others.

Next, examples of the present invention will be shown.

Example/ Raw material blend alumina powder (average particle size 0.2μ) Lid? (Commercial product) Antimony oxide (average particle size o, !μ) J J, &
1 (Crushed in a mortar and then separated) Ethylene-vinyl acetate copolymer JJ&#Flame retardant
4t3N anti-aging agent
g, fl xylene
/♂00g The above blended raw materials were placed in a container equipped with an electric stirrer, the temperature was raised to 700°C while stirring, the stirring process was continued for 7 hours, and while this state was continued, the mixture was rapidly cooled to room temperature, left at room temperature for 72 hours, and the required amount was A paste was obtained.

Example: Pour the respective amounts of xylene and ethylene-vinyl acetate copolymer into a container equipped with an electric stirrer, and lower the temperature to 7°C while stirring.
A flame retardant that is melted at 00℃ and then maintained in that state.
Processing was carried out in almost the same manner as in Example/, except that each compounded amount of anti-aging agent was sequentially added and dissolved, and then xylene-insoluble fine particles of graphite, alumina, antimony oxide, etc. were added in the respective compounded amounts in this order. to obtain the required paste.

Example 3 In Example 2, ultrasonic waves (30 kilocycles) were applied for 70 minutes to the mixed solution in which insoluble particulate material was added to xylene and stirred for 7 hours while maintaining the temperature/θ0℃, and the state was maintained. A paste was obtained in the same manner as in the previous example except that the paste was rapidly cooled.

Example: Surfactant (nonionic) 0. /? The ethylene-vinyl acetate copolymer was added to the xylene to which the ethylene-vinyl acetate copolymer was added, heated and stirred to raise the temperature to 700°C to dissolve, then flame retardants and anti-aging agents were added while stirring, and graphite, alumina,
After sequentially adding each fine powder of antimony oxide, the temperature was 700°C.
The mixture was stirred at .degree. C. for 7 hours, then subjected to ultrasonic waves for 70 minutes, and rapidly cooled to room temperature while continuing to do so.

example! 11f of each fine powder of graphite, alumina, and antimony oxide was first added to xylene containing a surfactant (nonionic), and after applying ultrasonic waves for 70 minutes while stirring, ethylene-vinyl acetate copolymer, #1 refractory, It is almost the same as Example G except that the anti-aging agent was added and the temperature was raised to 100℃/time with stirring, and then ultrasonic waves were applied again for 70 minutes, and the state was maintained and rapidly cooled (= processed and paste was Obtained.

Example 6 A paste was obtained in substantially the same manner as in Example j, except that xylene with surfactant/2 added was used.

Comparative Example The graphite (particle diameter θ, ta~/μ, average particle diameter jμ), alumina, and antimony oxide in the blended raw materials were those conventionally used in the production of resistance pastes for heating elements. The same raw materials as in Example / were mixed in the same amount and put into a container with an electric stirrer, and after being treated at a temperature of 700℃ for 7 hours with stirring, they were left to cool and matured at room temperature for more than 1 hour, and then further heated (with two manual stirrings). and got a paste.

The pastes obtained in the above Examples/~B and Comparative Example (=) The results of the following tests were as shown in the @/ table.

(1) Pot life measurement The paste was placed in a constant temperature bath at 0° C. and θ° C., and the presence or absence of a change in the state of the paste was examined (visually observed).

(2) Surface condition Homogeneity was observed visually and with a microscope.

(3) Temperature distribution test (surface temperature difference) Measured using a thermal imager probe eye.

(4) Overload test (rupture test) (3) A test heating element formed similarly to the test heating element used in the temperature distribution test! A voltage of 0θV was applied, and the state of the heating element was examined 70 minutes later.

(5) Durability test A voltage of 10θV was continuously applied to the test heating element prepared in the same manner as used in the temperature distribution test (3) above, and the initial characteristics (resistance value and surface temperature) and / Changes in characteristics over the course of several months were investigated, and durability time was estimated from the degree of change.

In addition, each test of (1) to (5) was carried out on each side and in the comparative example with /θ
This is the average value or the result estimated from the average value of the tests conducted on each sample.

Table 1 From the results shown in Table 1 above, it is clear that the resistance paste for surface heating elements produced according to the present invention has extremely excellent effects.

Claims (1)

[Claims] 1. A conductive material such as carbon or metal, a fine powder of a ceramic material, a synthetic resin binder, and other compounding agents are added to a solvent and mixed with stirring to produce a resistance paste for a surface heating element. A method for producing a resistance paste for a surface heating element, characterized in that the conductive material and a material insoluble in a solvent, such as a ceramic material, are added in the form of ultrafine particles, heated, stirred and mixed, and then cooled. 2. When manufacturing a resistance paste for a surface heating element using a solvent, fine powder of conductive material and ceramic material, synthetic resin binder, and other compounding agents, the conductive material and ceramic material, etc. A method for producing a resistance paste for a surface heating element, characterized by adding a material insoluble in a solvent in the form of ultrafine particles, and cooling the mixture by applying ultrasonic waves. 3 Fine powder of conductive material and ceramic material in solvent,
When manufacturing a resistance paste for a surface heating element by blending a synthetic resin binder and others, the conductive material and a solvent-insoluble material such as a ceramic material are sequentially added and mixed into ultrafine particles and subjected to ultrasonic waves. A method for manufacturing a resistance paste for a surface heating element, which comprises applying a binder and other mixed raw materials to the paste, dissolving it, applying superheat waves, and cooling it. 4. A method for producing a resistance paste for a surface heating element according to claim 1, 2 or 3, wherein the solvent contains or does not contain a surfactant. 5. The aspect of claim 1, 2, or 3, wherein the synthetic resin binder is one or more of fluorine resin, polyurethane, ethyl cellulose, and ethylene-vinyl acetate copolymer. A method for manufacturing a heat generating resistor paste.