JPH05186728A - Heat-resistant ceramic ink - Google Patents

Abstract

PURPOSE:To provide a ceramic ink excellent in long-term heat resistance. CONSTITUTION:A heat-resistant ceramic ink obtained by dispersing a ceramic powder in a solution of a heat-resistant polymer having a glass transition temperature of 150 deg.C or higher.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat resistant ceramic ink having far infrared radiation. More specifically, in combination with a planar heating element, heat resistance suitable for use in heating devices used at high temperatures, such as industrial clean heaters, health heating appliances, household kitchen appliances, water heaters, etc. Regarding ceramic ink.

[0002]

2. Description of the Related Art It has long been known that when ceramics are heated, they emit far infrared rays. Utilizing this property, ceramics are used in various industrial heaters, heating appliances, kitchen appliances, etc. in combination with a heating source. However, conventionally, when ceramic is used for the ceramic heater, there is a drawback that the production efficiency is poor because the ceramic powder is formed into a plate shape and used. Moreover, in order to use ceramics for different kinds of appliances, it is necessary to prepare multiple molds to mold them according to the appliances, so it is widely used for cooking appliances and health and medical equipment used in home life. It was difficult to do.

In order to solve this problem, a ceramic ink obtained by dispersing ceramic powder in a polyester resin or the like has been proposed, and by applying this ink to a planar heating element, the ceramic is used in various heaters. ing. However, this ink has a drawback that its use is limited because the resin as a binder has low heat resistance.

[0004]

SUMMARY OF THE INVENTION The present invention is intended to solve the above-mentioned conventional drawbacks, and an object thereof is to provide a ceramic ink which is excellent in long-term heat resistance and can be easily applied to various heaters in a wide range. To do.

[0005]

The ceramic ink of the present invention comprises ceramic powder dispersed in a polymer solution in which a heat-resistant polymer having a glass transition temperature of 150 ° C. or higher is dissolved. Is achieved.

The heat-resistant polymer used in the present invention has a glass transition temperature of 150 ° C. or higher and is usually a polymer soluble in an organic solvent. Examples of such a polymer include polyimide, polyetherimide, polyethersulfone, and polyamideimide.
Polyamideimide is preferably used because it has excellent heat resistance and is inexpensive.

The polyamideimide suitable for the present invention is synthesized by a diamine method using an acid anhydride or acid chloride and a diamine, or an isocyanate method using an acid anhydride and an isocyanate.

Examples of the acid capable of preparing the acid chloride used in the above diamine method include terephthalic acid, isophthalic acid, 4,4'-biphenyldicarboxylic acid, pyromellitic acid, 3,3 ', 4,4'- Benzophenone tetracarboxylic acid, 3,
3 ', 4,4'-biphenylsulfone tetracarboxylic acid, 3,3',
4,4′-biphenyltetracarboxylic acid, adipic acid, sebacic acid, maleic acid, fumaric acid, dimer acid, stilbenedicarboxylic acid and the like can be mentioned. As the acid anhydride,
Trimellitic acid anhydride, benzophenone tetracarboxylic acid anhydride, diphenyl sulfone tetracarboxylic acid anhydride, biphenyl tetracarboxylic acid anhydride, pyromellitic acid anhydride, ethylene glycol dianhydrotrimellitate, propylene glycol dianhydrotrimellitate, 1,4-butanediol dianhydrotrimellitate,
Hexamethylene glycol dianhydro trimellitate, polyethylene glycol dianhydro trimellitate, polypropylene glycol dianhydro trimellitate and the like can be mentioned.

As the diamine, for example, p-phenylenediamine, m-phenylenediamine, 4,4'-diaminodiphenyl ether, 4,4'-diaminodiphenylmethane, 4,
4'-diaminodiphenyl sulfone, 4,4'-diaminobenzophenone, 2,2'-bis (aminophenyl) propane, 2,4
-Tolylenediamine, 2,6-tolylenediamine, p-xylylenediamine, isophoronediamine, hexamethylenediamine and the like.

The acid anhydride used in the isocyanate method may be the same acid anhydride used in the diamine method. As the isocyanate, for example,
Diphenylmethane diisocyanate, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 3,3'-
Examples of the isocyanate include dimethyldiphenyl-4,4'-diisocyanate, 3,3'-diethyldiphenyl-4,4'-diisocyanate, isophorone diisocyanate and hexamethylene diisocyanate.

Typical compounds used in the synthesis by the isocyanate method are trimellitic anhydride and diphenylmethane diisocyanate among the above compounds.

The solvent for dissolving the heat-resistant polymer used in the present invention is usually an organic solvent, and for example, the polymerization solvent used when synthesizing the polymer can be used as it is. As the polymerization solvent, for example, N-methyl-2
-Pyrrolidone, dimethylformamide, dimethylacetamide, γ-butyrolactone and the like. In particular, γ-butyrolactone having low hygroscopicity is suitable.

Alternatively, the prepared and isolated polymer may be dissolved in the following organic solvent, or such an organic solvent may be added to the polymerization reaction system. Examples of such organic solvent include toluene, hydrocarbons such as xylene, acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, ketones such as isophorone, dioxane, ethylene glycol dimethyl ether, ethers such as tetrahydrofuran, methyl acetate,
Examples thereof include ester solvents such as ethyl acetate, butyl acetate, and cellosolve acetate. Among these, a solvent having the lowest hygroscopicity is preferable.

When the organic solvent is added to the polymerization reaction system, the organic solvent is added to the reaction system at the initial stage of the polymerization for synthesizing the heat resistant polymer, during the polymerization, or at any time after the completion of the polymerization. It doesn't matter. However, if it is added to the reaction system at the beginning and in the middle of the polymerization, the polymerization rate becomes slower. Therefore, it is preferable to add an organic solvent after completion of the polymerization or take out the produced heat-resistant polymer and dissolve it in the organic solvent. ..

The mixing ratio when the organic solvent is mixed with the above-mentioned polymerization solvent is determined by the solubility of the heat-resistant polymer and the use conditions of the ceramic ink, such as the film thickness, the drying conditions and the curing conditions.

The material of the ceramic powder used in the present invention is not particularly limited and is appropriately selected according to the application. That is, the ceramic is selected depending on whether the wavelength range of far infrared rays emitted when the ceramic is heated is suitable for the purpose of use. Generally, barium, zinc,
Examples thereof include metal oxides such as iron, nickel, cobalt, aluminum, chromium, silicon, titanium, and manganese, and one kind or a combination of two or more kinds thereof is used.

The ceramic ink of the present invention is used as an inorganic fine particle, an additive such as a leveling agent, a surfactant, a colorant, an antioxidant, and the above heat-resistant polymer in order to impart a gradation modification as required. Other than the above resins, polyester resin, acrylic resin, melamine resin, epoxy resin, etc. can be added.

As a method for dispersing the above-mentioned ceramic powder in a polymer solution in which the above-mentioned heat-resistant polymer is dissolved, an ordinary method can be adopted, for example, a high speed dissolver, a sand mill, a three-roll mill, a ball mill and the like. Can be used. Particularly, the use of a three-roll mill is preferable because of good productivity.

The ceramic ink of the present invention is applied to a heating element for use. The application method is appropriately selected depending on the shape of the heating element, and examples thereof include an impregnation method, a coating method,
A screen printing method, a spray method and the like can be mentioned. For example, in the case of a planar heating element, it is preferable to apply and cover only a necessary portion of the heating element circuit by screen printing.

[0020]

The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples.

The characteristics shown in the examples were evaluated and measured by the following methods.

(1) Logarithmic viscosity: A solution prepared by dissolving 0.5 g of a polymer in 100 ml of N-methyl-2-pyrrolidone was measured at 25 ° C. using an Ubbelohde type viscosity tube.

(2) Glass transition temperature: Measured by the TMA tensile load method at a load of 1 g and a heating rate of 5 ° C./min.

(3) Pyrolysis temperature: Using a pyrolysis measuring instrument,
The measurement was performed at a temperature rising rate of 5 ° C / min.

(4) Viscosity and degree of change: Using a B type viscometer,
It was measured at 25 ° C.

Example 1 A reaction vessel was charged with 0.8 mol of trimellitic anhydride, 0.2 mol of ethylene glycol diamine hydrotrimellitate, and 1 mol of diphenylmethane diisocyanate together with 398 g of γ-brotilactone, and the reaction system was stirred. Meanwhile, the temperature was raised to 180 ° C. in about 30 minutes. After stirring at 180 ° C. for about 3 hours, the reaction system was set to 1
The reaction was stopped by cooling to 00 ° C to obtain a polyamide.
Dissolve this polyamide in 341 g of cyclohexanone,
A uniform polymer solution having a solid content concentration of 35% and a solution viscosity of 1500 centipoise was obtained. This polymer had an inherent viscosity of 0.27 and a glass transition temperature of 263 ° C.

80 g of alumina powder having an average particle size of about 5 μm and 3 parts of silicon oxide particles were added to 100 g of the polymer solution.
g and 1 g of a leveling agent were added, and the mixture was kneaded twice with a three-roll ceramic mill. This mixture was diluted with cyclohexanone to obtain a ceramic ink having a viscosity of 740 poise and a degree of change of 2.2. The thermal decomposition temperature of the dried film of this ceramic ink was 450 ° C., indicating excellent heat resistance.

The obtained ceramic ink was screen-printed on the circuit surface of a planar heating element having a circuit formed by etching a two-layer laminate of a polyimide film having a thickness of 35 μm and an iron foil having a thickness of 20 μm to 50 μm. To form a cover layer having a thickness of. Pass current through the circuit of the sheet heating element 2
The temperature was raised to 00 ° C. and left for 10 days. The insulating property of the cover layer after leaving was almost unchanged, and the appearance was also unchanged, showing excellent long-term heat resistance.

Example 2 Trimellitic anhydride 0.5
Mol, ethylene glycol dianhydrotrimellitate 0.5 mol, diphenylmethane diisocyanate 1 mol and γ-butyrolactone 463 g were used to polymerize under the same conditions as in Example 1 to obtain a polyamide, which was dissolved in cyclohexanone, A polymer solution having a solution viscosity of 1150 centipoise and a solid content concentration of 35% was obtained. This polymer has an inherent viscosity of 0.22 and a glass transition temperature of 2
It was 32 ° C.

Example 1 was conducted using the obtained polymer solution.
A ceramic ink was obtained in the same manner as in. The obtained ceramic ink had a viscosity of 570 poise and a degree of fluctuation of 1.8. The thermal decomposition temperature of the dried film of this ceramic ink was 430 ° C., which was excellent in heat resistance.

This ceramic ink was screen-printed on the circuit surface of the same planar heating element used in Example 1 to form a cover layer having a thickness of 45 μm, and the same test as in Example 1 was conducted. As a result, the insulating property of the cover layer was almost unchanged, and the appearance was also unchanged, showing excellent long-term heat resistance.

Example 3 A reaction vessel was charged with 1 mol of trimellitic anhydride and 1 mol of diphenylmethane diisocyanate together with 354 g of N-methyl-2-pyrrolidone, and the reaction system was heated to 100 ° C. and stirred for 5 hours. It was made to react. To this, 303 g of cyclohexanone was added to obtain a polymer solution having a solid content concentration of 35% and a solution viscosity of 1750 centipoise. This polymer had an inherent viscosity of 0.45 and a glass transition temperature of 295 ° C.

Example 1 was conducted using the obtained polymer solution.
A ceramic ink was obtained in the same manner as in. The obtained ceramic ink had a viscosity of 800 poise and a degree of fluctuation of 2.1. The decomposition temperature of the dry film of this ceramic ink is 4
It was 65 ° C. and was excellent in heat resistance.

This ceramic ink was screen-printed on the circuit surface of the same planar heating element used in Example 1 to form a cover layer having a thickness of 55 μm, and the same test as in Example 1 was conducted. As a result, the insulating property of the cover layer was almost unchanged, and the appearance was also unchanged, showing excellent long-term heat resistance.

(Example 4) 20 g of polyether sulfone [Victrex PES (glass transition temperature: 225
C): ICI Co.] 20 g of N-methyl-2-pyrrolidone 80
g to give a polymer solution. This polymer solution 1
To 00 g, 55 g of alumina powder having an average particle size of about 5 μm,
3 g of silicon oxide fine particles and 1 g of a leveling agent were added, and the mixture was kneaded twice with a three-roll ceramic mill. This mixture was diluted with N-methyl-2-pyrrolidone to obtain a ceramic ink. The viscosity of the obtained ceramic ink is 3
The poise was 50 poise and the fluctuation degree was 1.6. The decomposition temperature of the dry coating of this ceramic ink was 530 ° C., which was excellent in heat resistance.

This ceramic ink was screen-printed on the circuit surface of the same planar heating element used in Example 1 to form a cover layer having a thickness of 38 μm, and tested in the same manner as in Example 1. As a result, the insulating property of the cover layer was almost unchanged, and the appearance was also unchanged, showing excellent long-term heat resistance.

Comparative Example 0.5 mol of terephthalic acid, 0.5 mol of isophthalic acid, 0.5 mol of ethylene glycol,
Further, 30 g of a copolymerized polyester resin having a glass transition temperature of 70 ° C. and obtained by polymerizing 0.5 mol of neopentyl glycol was dissolved in 70 g of methyl ethyl ketone / cyclohexanone (50/50 weight ratio) to obtain a polymer solution.

In 100 g of this polymer solution, 69 g of alumina powder having an average particle size of about 5 μm, 3 g of silicon oxide fine particles,
Then, 1 g of a leveling agent was added, and the mixture was kneaded twice with a three-roll ceramic mill. This polymer solution was diluted with cyclohexanone to obtain a ceramic ink. The viscosity of this ceramic ink is 180 poise and the degree of fluctuation is 1.9.
Met. The thermal decomposition temperature of the dried film of this ceramic ink was 310 ° C.

This ceramic ink was screen-printed on the circuit surface of the same planar heating element used in Example 1 to form a cover layer having a thickness of 45 μm, and the same test was conducted. As a result, the ink layer is significantly discolored and brittle,
It was easily peeled off from the circuit surface.

[0040]

According to the present invention, a heat-resistant ceramic ink having excellent heat resistance and capable of sustaining its effect for a long period of time is provided. This ceramic ink is easily applied to various heating elements and can be used for various purposes such as household heating equipment and protection of printed substrates.

Claims (1)

[Claims] 1. A heat-resistant ceramic ink obtained by dispersing ceramic powder in a polymer solution in which a heat-resistant polymer having a glass transition temperature of 150 ° C. or higher is dissolved.