JP2006173586A - Compact of temperature self-controlling nature and method of fabricating the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a compact of a temperature self-controlling nature useful as a planar or film-like temperature self-controlling heater etc. with a sharp resistance variation in the course of temperature control and a small rate of change in a resistance value (return characteristics) in repeated use, i.e., a small-retrogradation characteristic, at a high temperature. <P>SOLUTION: The compact of a temperature self-controlling nature contains a non-thermoplastic polyimide resin and an electrically conductive powder. The non-thermoplastic polyimide resin is produced by imide-converting: an ester compound derived from at least one kind of tetracarboxylic acid; and at least one kind of diamine or its derivative. The conductive powder is mixed in the non-thermoplastic polyimide resin. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a molded article having conductivity and temperature self-controllability obtained by forming a non-thermoplastic polyimide precursor composition mixed with conductive powder into a desired shape and then imide conversion.

  Polyimide resins have many excellent properties such as heat resistance, mechanical properties, chemical properties, and dimensional stability, and are commercially available in the form of films, tubes, molded products, paints, and the like. Such a polyimide resin is generally obtained by starting a polyimide precursor solution obtained by polymerizing tetracarboxylic dianhydride and diamine in a polar solvent, and casting, dipping, impregnating the precursor solution, After molding by a method such as casting, it can be obtained by heating or chemical imide conversion. Polyimide resins having excellent characteristics such as heat resistance and self-extinguishing properties are highly reliable as insulating materials in high temperature regions such as heating elements, and their applications are expanding. In recent years, a heating element capable of self-controlling the temperature has attracted attention, and a heating element capable of controlling the temperature without using a thermocouple, a thermostat, a fuse, or the like as in the conventional circuit. The development of organic thermistors has been promoted, and polyimide resin is a material that attracts attention in these fields.

  A heating element capable of self-controlling the temperature, when the temperature exceeds a specific temperature (temperature at which PTC (Positive Temperature Coefficient) characteristics are manifested) during temperature rise, the electrical resistance increases rapidly and the current value is decreased. For controlling the temperature, for example, a particle-dispersed polymer material having a positive temperature coefficient (PTC) made of a crystalline polymer material and conductive particles is not only a function as a conductive material but also a temperature self-controlling heat generation. It can also be used as a body or a self-recovery overcurrent prevention element.

  PTC characteristics are a phenomenon that occurs in the vicinity of the melting point or glass transition temperature inherent in a polymer material in a particle-dispersed polymer material, and the polymer is caused by thermal distortion, expansion, flow, etc. caused by heating the polymer material. It is considered to be a phenomenon that occurs when the conductive powder in the material is brought into contact, separated, or moved. Therefore, by selecting a polymer material having a melting point or a glass transition point within a desired set temperature control range, and combining a conductive powder suitable for the polymer material, a particle dispersion polymer material having PTC characteristics Can be manufactured. Many of such combinations are widely disclosed in literatures published in the past.

For example, Japanese Patent Laid-Open Nos. 61-39475 and 06-96843 disclose examples in which carbon black is dispersed in a polymer material. In addition, as a method for obtaining temperature self-control characteristics particularly in a high temperature region, a method of mixing spherical glassy carbon with a thermoplastic wholly aromatic polyimide resin having a glass transition point of 200 ° C. or more is disclosed (for example, patent document). 1). Further, a heater using a conductive powder having a carbon sphere surface coated with a copper layer and a thermoplastic polyimide resin is disclosed (for example, see Patent Document 2). Further, an organic positive temperature coefficient thermistor using a thermosetting resin such as an epoxy resin, a metal powder having spike-like protrusions, and a flake-like metal powder is disclosed. (For example, see Patent Document 3)
JP 11-297506 A JP 09-045466 A Japanese Patent Application Laid-Open No. 06-089802

  However, in the method disclosed in the above patent document, since a thermoplastic polyimide resin is employed, the resin is softened or aged with repeated use at high temperatures, resulting in a structure as a conductive particle-dispersed polymer material. Change characteristics and return characteristics (the rate of change in resistance value when the temperature is returned to room temperature in repeated heating and cooling. A molded body having a small rate of change with respect to the basic resistance value at room temperature is desired. ) Was not enough.

  The present invention has a PTC characteristic (rise characteristic) in which the electric resistance value sharply changes at a specific temperature, and a small change rate of the resistance value in repeated use at a high temperature, that is, self-temperature control having an excellent return characteristic An object of the present invention is to provide a molded article and a method for producing the same.

A temperature self-controllable molded article according to the present invention is a non-thermoplastic polyimide resin obtained by imide conversion of an ester compound derived from at least one tetracarboxylic acid and at least one diamine or derivative thereof, And a conductive powder mixed in a non-thermoplastic polyimide resin.
In this temperature self-controllable molded article, the mixing molar ratio of the ester compound derived from tetracarboxylic acid and the diamine or derivative thereof, or the mixing mole of the ester compound derived from diamine or derivative thereof and tetracarboxylic acid The ratio is preferably 80: 100 to 99: 100. That is, an excess amount of diamine or a derivative thereof may be mixed with an ester compound derived from tetracarboxylic acid, or an ester compound derived from an excess amount of tetracarboxylic acid with respect to diamine or a derivative thereof. May be. The mixing molar ratio is more preferably 80: 100 to 95: 100, more preferably 80: 100 to 90: 100, and 80: 100 to 85: 100 from the viewpoint of return characteristics. More preferably it is. The mixing molar ratio is more preferably 85: 100 to 99: 100, further preferably 90: 100 to 99: 100, and 95: 100 to 99: 100 from the viewpoint of the strength of the molded body. More preferably. Further, the mixing molar ratio is more preferably 85: 100 to 95: 100, and still more preferably around 90: 100, from the viewpoint of the balance between the return characteristics and the strength of the molded body.

In this temperature self-controllable molded article, the ester compound derived from tetracarboxylic acid has the chemical formula (A) [wherein R ₁ , R ₂ , R ₃ , R ₄ are each independently —H, carbon number 1 to 8 represents a hydrocarbon group (which may have a functional group such as an aromatic ring, —O—, —CO—, —OH), or a phenyl group, and R ′ represents a chemical formula (A-1) or Chemical formula (A-2) (wherein X is —O—, —S—, —SO—, —SO ₂ —, —CH ₂ —, —C (CH ₃ ) ₂ —, —CO—, or a direct bond) Is preferred.] Is preferred.

In this temperature self-controllable molded article, the diamine or derivative thereof has the chemical formula (I) [wherein R ″ is the chemical formula (I-1) or chemical formula (I-2) (wherein Y is —O -Represents —S—, —SO—, —SO ₂ —, —CH ₂ —, —C (CH ₃ ) ₂ —, —CO—, or a direct bond).

In this temperature self-controllable molded body, the conductive powder is tantalum nitride (TaN), tantalum carbide (TaC), molybdenum trisilicide (Mo ₅ Si ₃ ), rhenium-tungsten alloy, molybdenum disilicide (MoSi ₂ ). And at least one selected from the group consisting of tungsten (W), molybdenum (Mo), tungsten carbide (WC), titanium carbide (TiC), metal powder, and carbon black.

Furthermore, the temperature self-controllable molded product according to the present invention is a temperature self-controllable molded product that is substantially composed of a non-thermoplastic polyimide resin and has electrical conductivity and positive temperature resistance characteristics. The rate of change of the electrical resistance value at 25 ± 5 ° C. after the expression of the PTC characteristic relative to the initial electrical resistance value at ° C. is within ± 10%.
And the manufacturing method of the temperature self-controllable molded object which concerns on this invention is equipped with a 1st composition preparation process, a 2nd composition preparation process, and an imide conversion process. In the first composition preparation step, a mixed molar ratio of an ester compound derived from at least one tetracarboxylic acid and at least one diamine or derivative thereof, or an ester derived from diamine or derivative thereof and tetracarboxylic acid A non-thermoplastic polyimide precursor composition having a mixing molar ratio with the compound of 80: 100 to 99: 100 is prepared. In the second composition preparation step, conductive powder is added to the non-thermoplastic polyimide precursor composition to prepare a non-thermoplastic polyimide precursor composition containing conductive powder.

  In the imide conversion step, the non-thermoplastic polyimide precursor composition containing conductive powder is developed on an insulating substrate, and then the tetracarboxylic acid ester and diamine or derivative thereof are imide converted.

  In the temperature self-controllable molded article according to the present invention, since the polyimide resin as the matrix material has a glass transition point, sharp rising characteristics can be obtained at a desired set temperature. Further, since this polyimide resin is a non-thermoplastic resin, this temperature self-controllable molded product can provide excellent return characteristics in repeated use from high temperature to room temperature. Further, in the method for producing a temperature self-controllable molded article of the present invention, the conductive powder has good dispersibility in the precursor solution, and the conductive powder can be uniformly dispersed in the precursor solution. A self-controlling shaped body is obtained. In addition, since the temperature self-controllable molded product according to the present invention is prepared using a polyimide precursor composition as a starting material, the shape thereof can be easily and inexpensively formed into a film shape, a sheet shape, a linear shape, an element shape, a round shape, etc. The shape most suitable for actual use can be obtained.

  When a predetermined voltage is applied to the temperature self-controllable molded body, the temperature of the temperature self-controllable molded body gradually increases, and when reaching a predetermined temperature, the resistance value of the temperature self-controllable molded body increases rapidly. . At this time, the temperature self-controllable molded article develops so-called PTC characteristics that control the current flowing through itself and the temperature of itself. The temperature self-controllable molded body according to the present invention is in a high temperature region in which the temperature at which the PTC characteristic is expressed exceeds 200 ° C. In such a temperature self-controllable molded article, it is preferable that the rate of change of the electrical resistance value at 25 ± 5 ° C. after the development of the PTC characteristic with respect to the initial electrical resistance value at 25 ± 5 ° C. is within ± 10%. More preferably, it is within ± 5%, and further preferably within ± 3%. It can be called a highly accurate temperature self-controllable molded article having a superior resistance return characteristic as the change rate is smaller.

  Further, the material constitution of the temperature self-controllable molded body is an ester compound derived from at least one tetracarboxylic acid (hereinafter referred to as a tetracarboxylic acid ester compound) and a diamine or a derivative thereof (hereinafter referred to as a diamine compound). And a polar solvent, and further a conductive powder (hereinafter referred to as a non-thermoplastic polyimide precursor composition). In addition, the mixing molar ratio of the tetracarboxylic acid ester compound and the diamine compound or the mixing molar ratio of the diamine compound and the tetracarboxylic acid ester compound will determine the molecular weight of the imidized polyimide resin, improving the return characteristics. In order to make it, it is preferable that it is 80: 100-99: 100. That is, the mixing molar ratio may be determined so that either the tetracarboxylic acid ester compound or the diamine compound increases. The more preferable mixing molar ratio of the tetracarboxylic acid ester compound and the diamine compound is 85: 100 to 95: 100, and the preferable mixing molar ratio of the tetracarboxylic acid ester compound and the diamine compound is around 90: 100. is there.

  Usually, after preparing a polyamic acid solution that is a precursor by reacting tetracarboxylic dianhydride and diamine in a polar solvent, the polyimide is molded and dried by a method such as casting, Subsequently, it can obtain by making it heat imidize at the temperature of 300-400 degreeC. Among such polyimides, non-thermoplastic materials do not melt and flow even when the molecular chain is rigid and exhibits a glass transition temperature. Therefore, a temperature self-controllable molded body obtained by mixing and dispersing conductive powder in such polyimide exhibits PTC characteristics and high shape stability.

In the present invention, the tetracarboxylic acid ester compound and the diamine compound are mixed at a specific molar ratio to reduce the molecular weight of the non-thermoplastic polyimide resin. A self-controlling molded body could be obtained.
When the mixing molar ratio of the tetracarboxylic acid ester compound and the diamine compound is 80: 100 or less, the molecular weight of the polyimide is lowered, and at the same time, the strength as a molded body is remarkably lowered, and the molded body is contracted at the time of heating imidization. It becomes impossible to endure, and cracks and cracks occur in the molded body. On the other hand, when the mixing molar ratio is 99: 100 or more, the polyimide becomes rigid and the rate of change in resistance value at room temperature increases, which is not preferable. In a preferred embodiment of the present invention, the mixing molar ratio of tetracarboxylic acid and diamine compound is 90: 100.

In the present invention, a preferable raw material composition is that the tetracarboxylic acid ester compound is represented by the following chemical formula (A): wherein R ₁ , R ₂ , R ₃ and R ₄ are each independently —H and having 1 to 8 carbon atoms. It represents a hydrocarbon group (which may have a functional group such as an aromatic ring, —O—, —CO—, —OH) or a phenyl group, and R ′ represents a chemical formula (A-1) or a chemical formula (A-2). (Wherein X represents —O—, —S—, —SO—, —SO ₂ —, —CH ₂ —, —C (CH ₃ ) ₂ —, —CO—, or a direct bond). ] An ester compound derived from a tetracarboxylic acid represented by the formula:

In addition, diamine or a derivative thereof may be represented by the following chemical formula (I) [wherein R ″ is the chemical formula (I-1) or chemical formula (I-2) (where Y is —O—, —S—, — _{SO -, - SO 2 -,} - CH 2 -, - C (CH 3) 2 -, - CO-, or a diamine or a derivative represented by direct binding represents a) represent].

The tetracarboxylic acid ester compound used in the present invention can be obtained very simply by esterifying the corresponding tetracarboxylic dianhydride with an alcohol. The esterification is preferably performed at a temperature of 50 ° C to 150 ° C.
Tetracarboxylic dianhydrides for inducing formation of tetracarboxylic acid ester compounds include 3,4,3 ′, 4′-benzophenonetetracarboxylic dianhydride, pyromellitic anhydride, 3,4,3 ′, 4 '-Biphenyltetracarboxylic dianhydride, 3,4,3', 4'-diphenyl sulfoxide tetracarboxylic dianhydride, 2,3,3 ', 4'-diphenyl ether tetracarboxylic dianhydride, 3,4 , 3 ′, 4′-diphenylsulfide tetracarboxylic dianhydride, 2,3,3 ′, 4′-biphenyltetracarboxylic dianhydride, 2,3,3 ′, 4′-diphenylmethanetetracarboxylic dianhydride 3,4,3 ′, 4′-diphenyl (2,2-isopropylidene) tetracarboxylic dianhydride, 2,3,3 ′, 4′-diphenyl sulfoxide tetracarboxylic dianhydride, 3,4 , 3 ', 4'-diphenyl ether tetracarboxylic dianhydride, 3,4,3', 4'-diphenylsulfone tetracarboxylic dianhydride, 2,3,3 ', 4'-diphenylsulfone tetracarboxylic dianhydride 2,3,3 ′, 4′-diphenylsulfide tetracarboxylic dianhydride, 3,4,3 ′, 4′-diphenylsulfone methanetetracarboxylic dianhydride, 2,3,3 ′, 4′- Examples include benzophenone tetracarboxylic dianhydride, 2,3,3 ′, 4′-diphenyl (2,2-isopropylidene) tetracarboxylic dianhydride, and these may be used alone or in combination of two or more. Can do.

  Examples of the alcohol for inducing formation of the tetracarboxylic acid ester compound include methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, 2-methyl-1-propanol, and 2-methyl-2- Propanol, 1-pentanol, 2-pentanol, 3-pentanol, 2-methyl-1-butanol, 3-methyl-1-butanol, 2-methyl-2-butanol, 3-methyl-2-butanol, 2 , 2-dimethyl-1-propanol, 1-hexanol, 2-methyl-1-pentanol, 4-methyl-2-pentanol, 2-ethyl-1-butanol, cyclohexanol, 2-methoxyethanol, 2-ethoxy Ethanol, 2- (methoxymethoxy) ethanol, 2-isopropoxyethanol, 2- Toxiethanol, phenol, 1-hydroxy-2-propanone, 4-hydroxy-2-butanone, 3-hydroxy-2-butanone, 1-hydroxy-2-butanone, 2-phenylethanol, 1-phenyl-1-hydroxyethane 2-phenoxyethanol and the like, and 1,2-ethanediol, 1,2-propanediol, 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, 2,3-butane Diol, 1,5-pentanediol, 2-methyl-2,4-pentanediol, glycerol, 2-ethyl-2- (hydroxymethyl) -1,3-propanediol, 1,2,6-hexanetriol, 2 , 2′-dihydroxydiethyl ether, 2- (2-methoxyethoxy) ethanol, 2- ( 2-ethoxyethoxy) ethanol, 3,6-dioxaoctane-1,8-diol, 1-methoxy-2-propanol, 1-ethoxy-2-propanol, dipropylene glycol, and other polyhydric alcohols can also be used. . These may be used alone or in combination of two or more.

Tetracarboxylic acid ester compounds can also be produced by other methods, for example by direct esterification of tetracarboxylic acid.
Examples of the diamine of the present invention include 4,4′-diaminodiphenylmethane, 4,4′-diaminodiphenylsulfone, 4,4′-diaminodiphenyl ether, 1,4-diaminobenzene, 1,3-diaminobenzene, 2, 2′-dimethyl-4,4′-diaminobiphenyl, 2,4-diaminotoluene, 3,4′-biphenyldiamine, 3,4′-diaminodiphenyl sulfoxide, 2,2-bis (3-aminophenyl) propane, 4,4′-diaminobenzophenone, 3,3′-biphenyldiamine, 3,4′-diaminodiphenyl ether, 2,6-diaminotoluene, 4,4′-biphenyldiamine, 3,3′-diaminodiphenylsulfone, 3, 4′-diaminodiphenylmethane, 3,3′-diaminodiphenyl ether, 4,4′-bis (4-aminophenyl) Nyl) sulfide, 3,3′-diaminodiphenylmethane, 2,2-bis (4-aminophenyl) propane, 2,2- (3-aminophenyl) (4-aminophenyl) propane, 3,3′-diaminobenzophenone 3,3′-dimethyl-4,4′-diaminobiphenyl, 3,3′-bis (4-aminophenyl) sulfide, 4,4′-diaminodiphenyl sulfoxide, 3,4′-diaminobenzophenone, 3,3 '-Diaminodiphenyl sulfoxide, 3,4'-diaminodiphenyl sulfone, 2,5-diaminotoluene, 3,3'-diaminodiphenyl ether, 4,4'-bis (4-aminophenyl) sulfide, 3,3'-diamino Diphenylmethane, 2,2-bis (4-aminophenyl) propane, 2,2- (3-aminophenyl) (4-amino) Phenyl) propane, 3,3′-diaminobenzophenone, 3,3′-dimethyl-4,4′-diaminobiphenyl, 2,2′-dimethyl-4,4′-diaminobiphenyl, 3,4′-bis (4 -Aminophenyl) sulfide, 3,3'-bis (4-aminophenyl) sulfide, 4,4'-diaminodiphenyl sulfoxide, 3,4'-diaminobenzophenone, 3,3'-diaminodiphenyl sulfoxide, 3,4 ' -Diaminodiphenyl sulfone, 2,5-diaminotoluene, 3,3'-hydroxy-4,4'-diaminobiphenyl may be mentioned, and these may be used alone or in combination of two or more.

  Polar organic solvents useful in the present invention include, for example, N, N-dimethylformamide, N, N-dimethylacetamide, N, N-diethylacetamide, N-methyl-2-pyrrolidone, 1,3-dimethyl-2-imidazo Lidinone, N-methylcaprolactam, hexamethylphosphoric triamide, 1,2-dimethoxyethane, diglyme, triglyme, tetrahydrofuran, 1,4-dioxane, γ-butyrolactone, dimethyl carbonate, diethyl carbonate, ethylene carbonate, propylene carbonate, Examples include diethoxyethane, dimethyl sulfoxide, and sulfolane. A preferred solvent is N-methyl-2-pyrrolidone (NMP). These solvents can be used alone or as a mixture or mixed with other solvents such as toluene, xylene, ie, aromatic hydrocarbon, methanol, ethanol, ie, alcohol.

  In a preferred embodiment, the non-thermoplastic polyimide precursor composition which is a precursor composition of the temperature self-controllable molded article of the present invention is represented by the following chemical formula (A-3) as an aromatic tetracarboxylic dianhydride. 3,4,3 ′, 4′-benzophenonetetracarboxylic dianhydride (BTDA) is employed, which is 50 in alcohol, preferably ethanol and a polar solvent, preferably N-methyl-2-pyrrolidone. A solution of tetracarboxylic acid ester compound is obtained by heating and stirring at a temperature of from 150 ° C. to 150 ° C. Next, in this solution, 4, 4 of the following chemical formula (I-3) is used so that the mixing molar ratio of the tetracarboxylic acid component and the diamine component is 80: 100 to 99: 100, more preferably 90: 100. '-Diaminodiphenylmethane (MDA) is added and stirred at room temperature to 150 ° C. to prepare a polyimide precursor solution. Finally, conductive powder is added to the polyimide precursor solution.

  In order to facilitate handling of the polyimide precursor solution, the solid concentration in the solution is preferably 30 to 80% by weight, and more preferably 40 to 70% by weight. When the solid content concentration decreases, the viscosity of the polyimide precursor solution becomes extremely low, and the mixed and dispersed conductive powder settles, making it difficult to obtain a temperature self-controllable molded product with stable rise and return characteristics. Become. On the other hand, when the solid content concentration is too high, the fluidity of the polyimide precursor solution is remarkably lost, and further, it becomes a glassy solid, and it becomes extremely difficult to mix and disperse the conductive powder and to mold the composition.

The polyimide precursor solution of the present invention may contain an additive such as an antioxidant and a heat conductive material such as boron nitride as long as the PTC characteristics are not adversely affected.
The conductive powder used in the present invention is tantalum nitride (TaN), tantalum carbide (TaC), molybdenum trisilicide (Mo ₅ Si ₃ ), rhenium-tungsten alloy, molybdenum disilicide (MoSi ₂ ), tungsten (W), molybdenum It is preferably at least one selected from the group consisting of (Mo), tungsten carbide (WC), titanium carbide (TiC), metal powder, and carbon black. Tungsten carbide is one of the more preferred conductive powders. Although the compounding quantity of electroconductive powder changes with selection of electroconductive powder material, 20 to 90 weight% is common with respect to the solid content density | concentration of a polyimide precursor solution.

  The temperature self-controllable molded product according to the present invention is obtained by spreading a non-thermoplastic polyimide precursor composition on an insulating substrate and heating imidization treatment. In a preferred embodiment, the planar temperature self-controllable molded body is a known method such as bar coating or screen printing of a non-thermoplastic polyimide precursor composition in which conductive powder is mixed and dispersed on the surface of a ceramic substrate or the like. Molded with. Thereafter, the molded product is heated stepwise in an oven or the like to remove the polar solvent and to convert the polyimide precursor to imide sequentially or simultaneously.

  In a more preferred embodiment, the temperature self-controllable molded body made of non-thermoplastic polyimide resin is developed by spreading the non-thermoplastic polyimide precursor composition on the surface of the substrate and drying at a temperature of 80 to 120 ° C. for 30 to 120 minutes. The temperature is then raised to 200 ° C. and heated at this temperature for 10-180 minutes, then the temperature is further raised to 250-400 ° C. and heated at this temperature for 30-120 minutes to complete the imide conversion. Can be obtained. In addition, the temperature self-controllable molded body can be formed with an electrode for detecting the amount of current flow or resistance change with a conductive paint such as silver paste.

  In addition, in the molded body with the electrodes attached, by applying a polyimide precursor solution not containing conductive powder in a well-known manner in a state where a part of both electrodes is left on both electrodes, an imide conversion treatment is performed, An insulating protective film can be formed on both electrodes. The insulating protective film can also be formed by coating a material such as a fluororesin dispersion on the surface of the heating element and baking it.

The present invention will be specifically described below based on examples. Various characteristics of the polyimide precursor composition and the temperature self-controllable molded body produced in each Example and Comparative Example were measured by the following measuring methods.
(1) Measurement of electric resistance value Electric resistance was measured using a digital multimeter Model 7562 manufactured by Yokogawa Electric Corporation.

(A) Preparation of polyimide precursor solution A 500 mL three-necked flask was equipped with a stirring rod equipped with a stirring blade made of polytetrafluoroethylene to prepare a synthesis container. Then, in the synthesis container, 3,4,3 ′, 4′-benzophenone tetracarboxylic dianhydride (BTDA) manufactured by ALLCO as an acid component so that the solid content of the polyimide precursor solution is 55 mass%. 667 g (0.1014 mol) as a solvent, 30.326 g of N-methyl-2-pyrrolidone (NMP) manufactured by Mitsubishi Gas Chemical Co., Ltd. and 14.674 g (0.3041 mol) of ethanol manufactured by Wako Pure Chemical Industries as an esterifying agent. ), And heated to 60 ° C. and stirred for 2 hours to obtain an ester compound of BTDA. Thereafter, 21.052 g (0.1126 mol) of 4,4′-diaminodiphenylmethane (MDA) manufactured by Ciba-Geigy was added so that the number of moles of the tetracarboxylic acid component was 0.9 times the number of moles of the diamine component. Furthermore, it stirred at 60 degreeC for 1 hour, and obtained the polyimide precursor solution.

(B) Blending of conductive powder Next, 277 parts by weight of tungsten carbide powder (WC10 manufactured by Allied Material Co., Ltd.) as a conductive powder was blended with respect to 100 parts by weight of the solid content of the polyimide precursor solution, and stirred with an ultrasonic wave. The mixture was stirred for 30 minutes and mixed to obtain a polyimide precursor composition in which tungsten carbide was uniformly mixed and dispersed. This polyimide precursor composition was pasty.

(C) Production of Temperature Self-Controlling Heating Element As shown in FIG. 1, the silver conductive ink is 20 μm thick with a spacing of 3 mm parallel to the width direction of the ceramic substrate 1 having a width of 20 mm, a length of 300 mm and a thickness of 3 mm. The electrode 2 was formed on both ends of the substrate by coating at 150 ° C. for 10 minutes and baking at 600 ° C. for 20 minutes. Thereafter, the polyimide precursor composition was uniformly coated on the electrodes in a rectangular shape having a width of 7 mm and a length of 220 mm with a thickness of 20 μm (based on solid content) by leaving a part of these electrodes. The molded article is then placed in an oven for 20 minutes at 80 ° C., then 30 minutes at 110 ° C., 30 minutes at 120 ° C., 20 minutes at 150 ° C., 20 minutes at 200 ° C., then 1 hour at 300 ° C. The temperature was maintained at 400 ° C. for 20 minutes to complete the imidization reaction, and a temperature self-control heating element 3 was obtained. Furthermore, a polyimide varnish (RC5019 manufactured by IST Co., Ltd.) is applied so as to cover the entire substrate except for a part of the electrode portion thereon, and is heated to imidize to form a polyimide insulating coating layer 4 having a thickness of 20 μm. A temperature self-control exothermic test body 5 was obtained. The electric resistance value at 23 ° C. was 25Ω.

(D) Temperature-resistance curve Take the lead wires from both electrodes of the temperature self-control exothermic test body prepared in (c) and insert it into the thermostatic layer. The change in resistance value was measured. FIG. 3 shows the temperature-resistance curve. The change in resistance value with increasing temperature rose very sharply around 250 ° C., and the resistance value at 350 ° C. increased to 15 times the resistance value at room temperature. In addition, the resistance value after repeating the temperature raising / cooling operation from room temperature to 350 ° C. 10 times is 25.5Ω at 23 ° C., the rate of change of the resistance value is + 2%, and a very stable return characteristic is obtained. It was.

(E) Voltage application characteristics
Lead wires were taken from both electrodes of the temperature self-control exothermic test body prepared in (c), and a DC voltage was gradually applied to the sample while a thermocouple was provided on the surface of the central portion of the exothermic body and the temperature was measured. The surface temperature of the heating element was controlled at 290 ° C. and became constant, and the temperature did not rise above 290 ° C. Thereafter, the voltage was gradually lowered to return the surface temperature of the test body to room temperature. The resistance value at room temperature after repeating this operation 10 times was measured to determine the rate of change. The rate of change in the resistance value was + 2.3%, and the change in the resistance value was very small, and a stable temperature self-control heating element excellent in return characteristics could be obtained.

  Biphenyltetracarboxylic dianhydride (BPDA) 28.384 g (0.0965 mol) as the acid component, NMP 35.727 g as the solvent, and 9.273 g (0.2894 mol) of methanol as the esterifying agent were used at 80 ° C. for 2 hours. Stirring to prepare a tetracarboxylic acid ester compound, 26.616 g (0.1072 mol) of 4,4′-diaminodiphenylsulfone (44DDS) so that the mixing molar ratio of the ester compound component and the diamine component is 90: 100. A polyimide precursor solution was synthesized in the same manner as in Example 1 except that the reaction temperature was 80 ° C. Next, 277 parts by weight of tungsten carbide powder was blended with respect to 100 parts by weight of the solid content of the polyimide precursor solution, and a temperature self-control exothermic test body was produced under the same conditions as in Example 1. Thereafter, the characteristics of the exothermic test body were evaluated in the same manner as in Example 1. In the temperature-resistance characteristics of this specimen, the resistance value sharply rises in the vicinity of 280 ° C., and PTC characteristics are obtained. In addition, the voltage applied from the electrode of the specimen is raised to 280 ° C., and the temperature is further returned to room temperature. The change rate of the resistance value of the test body after 5 repetitions was −3%, and a temperature self-control heating element having a stable resistance value in a repeated test from room temperature to a high temperature region could be obtained.

  438 parts by weight of tantalum carbide powder (Wako Grade 1) is blended with 100 parts by weight of the solid content of the polyimide precursor solution prepared in Example 1, and a temperature self-control exothermic test body is prepared under the same conditions as in Example 1. When the change in the electrical resistance value accompanying the temperature rise was measured, the resistance value sharply rose in the vicinity of 200 ° C., and the resistance value increased to 2.5 times by 265 ° C. Further, the change rate of the resistance value of the test specimen at this time was + 10% (see FIG. 4).

  51.5 parts by weight of filamentous nickel powder (Type 210 manufactured by INCO) is blended with 100 parts by weight of the solid content of the polyimide precursor solution prepared in Example 1, and temperature self-controlled heat generation is performed under the same conditions as in Example 1. A test specimen was prepared and the change in the electrical resistance value accompanying a temperature rise was measured. The resistance value sharply rose in the vicinity of 300 ° C., and the resistance value increased to 2.2 times by 350 ° C. Further, the change rate of the resistance value of the test specimen at this time was −3% (see FIG. 5).

  29.627 g (0.0922 mol) of BTDA as an acid component, 43.408 g of NMP as a solvent and 6.292 g (0.1014 mol) of ethylene glycol as an esterifying agent were stirred at 60 ° C. for 2 hours to obtain a tetracarboxylic acid ester compound. A polyimide precursor solution was synthesized in the same manner as in Example 1 except that 20.303 g (0.102 mol) of MDA was used so that the mixing molar ratio of the ester compound component and the diamine component was 90: 100. 189 parts by weight of titanium carbide powder (OP10 manufactured by Allied Material) was blended with 100 parts by weight of the solid content of this polyimide precursor solution, and a temperature self-control exothermic test body was produced under the same conditions as in Example 1. When the change in the electrical resistance value accompanying the temperature rise of the temperature self-control exothermic test piece was measured, the resistance value sharply rose in the vicinity of 250 ° C., and the resistance value increased to 33 times by 300 ° C. Further, the change rate of the resistance value of the test specimen at this time was + 2% (see FIG. 6).

  BTDA 32.180 g (0.0999 mol) as an acid component, NMP 43.181 g as a solvent, and ethylene glycol 6.819 g (0.1099 mol) as an esterifying agent were stirred at 60 ° C. for 2 hours to obtain a tetracarboxylic acid ester compound. A polyimide precursor solution was synthesized in the same manner as in Example 1 except that 17.820 g (0.0899 mol) of MDA was used so that the mixing molar ratio of the ester compound component and the diamine component was 100: 90. 151 parts by weight of titanium carbide powder was blended with 100 parts by weight of the solid content of this polyimide precursor solution, and a temperature self-control exothermic test body was produced under the same conditions as in Example 1. When the change in the electrical resistance value accompanying the temperature rise of this temperature self-control exothermic test body was measured, the resistance value sharply rose in the vicinity of 250 ° C., and the resistance value increased to 17 times by 300 ° C. Further, the change rate of the resistance value of the test specimen at this time was −5% (see FIG. 7).

(Comparative example)
6.903 g (0.0348 mol) of MDA as a diamine component and 83.0 g of NMP as a polymerization solvent were added so that the solid content of the polyimide precursor solution was 17% by mass, and after the MDA was completely dissolved in NMP, the acid component BTDA 10.097 g (0.0313 mol) was added as a bifunctional acid anhydride over 5 minutes as a bifunctional acid anhydride so that the mixing molar ratio of the diamine component and the diamine component was 100: 90, and allowed to react at room temperature for 12 hours. A body solution was obtained. Thereafter, 277 parts by weight of tungsten carbide powder was blended with respect to 100 parts by weight of the solid content of the polyimide precursor solution, and an attempt was made to produce a temperature self-control heating element under the same conditions as in Example 1, but cracking occurred during heating imidization. It occurred and could not be used as a specimen. That is, the polyimide composition prepared by setting the mixing ratio of the acid component and the diamine component to 90: 100 in a state where the tetracarboxylic dianhydride was not esterified was brittle and could not be produced as a molded product.

  The temperature self-controllable molded product according to the present invention has excellent PTC characteristics (rise characteristics) and return characteristics, and is a self-recovery overcurrent control element, a sheet-like or film-like heater, an on-demand fixing method. Is useful as a heating element or an organic thermistor incorporated in a laser beam printer or a copying machine in which is used.

It is the schematic from the upper surface of a temperature self-control property molded object, and a side surface cross section. It is the schematic of the cross section of the width direction of the temperature self-control property molded object shown in FIG. It is a figure which shows the temperature and resistance characteristic of the heat generating body shown by Example 1. FIG. It is a figure which shows the temperature and resistance characteristic of the heat generating body shown by Example 3. FIG. It is a figure which shows the temperature and resistance characteristic of the heat generating body shown by Example 4. FIG. It is a figure which shows the temperature and resistance characteristic of the heat generating body shown by Example 5. FIG. It is a figure which shows the temperature and resistance characteristic of the heat generating body shown by Example 6. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Ceramic substrate 2 Electrode 3 Temperature self-control molding part 4 Protective layer 5 Temperature self-control exothermic test body

Claims (7)

A non-thermoplastic polyimide resin obtained by imide conversion of an ester compound derived from at least one tetracarboxylic acid and at least one diamine or derivative thereof;
Conductive powder mixed in the non-thermoplastic polyimide resin;
A temperature self-controllable molded article containing The mixing molar ratio of the ester compound derived from the tetracarboxylic acid and the diamine or derivative thereof, or the mixing molar ratio of the ester compound derived from the diamine or derivative thereof and the tetracarboxylic acid is from 80: 100 to 99: 100,
The temperature self-controllable molded article according to claim 1. The ester compound derived from the tetracarboxylic acid has the chemical formula (A) [wherein R ₁ , R ₂ , R ₃ , R ₄ are each independently —H, a hydrocarbon group having 1 to 8 carbon atoms (aromatic A ring, a functional group such as —O—, —CO—, and —OH), or a phenyl group, and R ′ represents a chemical formula (A-1) or a chemical formula (A-2) (wherein X is -O -, - S -, - SO -, - SO 2 -, - CH 2 -, - C (CH 3) 2 -, - CO-, or represented by a direct bond represents a) represents a]
The temperature self-controllable molded article according to claim 1 or 2.

The diamine or derivative thereof has the chemical formula (I) [wherein R ″ is the chemical formula (I-1) or the chemical formula (I-2) (where Y is —O—, —S—, —SO—, _{-SO 2 -, - CH 2 -} , - C (CH 3) 2 -, - CO-, or represented by a direct bond represents a) represents a]
The temperature self-controllable molded article according to any one of claims 1 to 3.

The conductive powder includes tantalum nitride (TaN), tantalum carbide (TaC), molybdenum trisilicide (Mo ₅ Si ₃ ), rhenium-tungsten alloy, molybdenum disilicide (MoSi ₂ ), tungsten (W), molybdenum (Mo). , At least one selected from the group consisting of tungsten carbide (WC), titanium carbide (TiC), metal powder, and carbon black.
The temperature self-controllable molded article according to any one of claims 1 to 4. A temperature self-controllable molded body having a non-thermoplastic polyimide resin as a main component and having conductive and positive temperature resistance characteristics,
The rate of change of the electrical resistance value at 25 ± 5 ° C. after the expression of the PTC characteristic relative to the initial electrical resistance value at 25 ± 5 ° C. is within ± 10%.
Temperature self-control molded body. Mixing molar ratio of an ester compound derived from at least one tetracarboxylic acid and at least one diamine or a derivative thereof, or a mixing mole of an ester compound derived from the diamine or a derivative thereof and the tetracarboxylic acid ester A first composition preparation step of preparing a non-thermoplastic polyimide precursor composition having a ratio of 80: 100 to 99: 100;
A second composition preparation step of preparing a non-thermoplastic polyimide precursor composition containing conductive powder by adding conductive powder to the non-thermoplastic polyimide precursor composition;
An imide conversion step in which the tetracarboxylic acid ester and the diamine or derivative thereof are imide-converted after the conductive powder-containing non-thermoplastic polyimide precursor composition is developed on an insulating substrate;
A method for producing a temperature self-controllable molded article.

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