JP2003217901A - Organic positive temperature characteristic thermistor and method for manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve the characteristics stability of an organic positive temperature characteristic thermistor containing metals as conductive particles. <P>SOLUTION: An organic positive temperature characteristic thermistor is constituted of a polymeric organic matrix, conductive metal particles contained in the polymeric organic matrix, and an organic layer made of a material which is different from the material of the polymeric organic matrix, and the organic layer is placed close to the surfaces of the conductive metal particles, without their being covalently coupled to the conductive metal particles, and without having compatibility with the polymeric organic matrix at the molecular level. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is used as a temperature sensor and an overcurrent protection element, and has a PTC (positive temperature coefficient) whose resistance value increases with temperature.
organic positive temperature coefficient thermistor having a characteristic of resistivity.

[0002]

Organic positive temperature coefficient thermistors in which conductive particles are dispersed in a polymer matrix are known in the art, and are described in US Pat. Nos. 3,243,753 and 3,351.
No. 882 specification and the like.

It is considered that the increase in the resistance value is due to the expansion of the crystalline polymer as it melts, cutting the conductive path of the conductive particles.

The organic positive temperature coefficient thermistor can be used for an overcurrent / overheat protection element, a self-regulating heating element, a temperature sensor and the like. Among them, in the overcurrent / heat protection element connected in series to the electric circuit, particularly, the room temperature resistance value is sufficiently low, the room temperature resistance value and the change rate of the resistance value during operation are sufficiently large, and the resistance value of the repeated operation A small change is required as a characteristic.

Carbon-based conductive particles such as carbon black and graphite are mainly used as the conductive particles of the organic positive temperature coefficient thermistor. However, it is necessary to mix a large amount of conductive particles in order to reduce the resistance of the device. In that case, the rate of change in resistance decreases and sufficient characteristics as an overcurrent / overheat protection element cannot be obtained.

This drawback can be overcome by using metal conductive particles having a specific resistance lower than that of carbon particles.
In order to achieve both low room temperature resistance and large resistance change rate, it is disclosed to use metal conductive particles having spike-like protrusions. JP-A-5-47503 (Registration 302
2644) discloses an organic positive temperature coefficient thermistor obtained by kneading a crystalline polymer and conductive particles having spike-like protrusions therein, and US Pat. No. 5,378,407.
No. 1 is a filamentary Ni with spike-shaped protrusions.
And crystalline polyolefin, olefin copolymer,
Alternatively, conductive polymer compositions comprising fluoropolymers are disclosed.

The inventors of the present invention have also found that by using conductive particles having spike-like protrusions, both low room temperature resistance and large resistance change rate can be achieved at the same time, as disclosed in Japanese Patent Laid-Open Nos. 10-214705 and 11-168005. Open 2000-826
No. 02, 2000-200074 and the like.

However, the present inventor has confirmed that the organic positive temperature coefficient thermistor using these metal conductive particles is inferior in reliability such as long-term storage. This is that the room temperature resistance value gradually increases with the storage test time, and the degree thereof depends on the storage test conditions.

The cause of this is that the surface of the metal conductive particles is oxidized and the conductivity thereof is lowered, that the conductive particles agglomerate during storage and a part of the conductive paths are cut, and the like. Conceivable. It was found that the problem of this increase in resistance value can be solved by treating the surface of the conductive particles with an organic substance in advance.

[0010]

SUMMARY OF THE INVENTION An object of the present invention is to improve the characteristic stability of an organic PTC thermistor containing a metal as a conductive particle.

[0011]

That is, the above object is achieved by the following constitution of the present invention. (1) A polymer organic matrix and conductive metal particles contained in the polymer organic matrix, which is a material different from the polymer organic matrix in the vicinity of the surface of the conductive metal particles. Without covalent bonding
An organic positive temperature coefficient thermistor having an organic material layer that is incompatible with the polymer organic matrix at the molecular level. (2) The organic positive temperature coefficient thermistor according to (1) above, wherein the organic material is a material having no reactivity with a polymer organic matrix. (3) The organic positive temperature coefficient thermistor according to the above (1) or (2), wherein the conductive metal particles contain nickel or copper. (4) The organic positive temperature coefficient thermistor according to any one of (1) to (3), wherein the high molecular weight organic matrix is a thermoplastic polymer. (5) The above (1) including a low molecular weight organic compound
An organic positive temperature coefficient thermistor according to any one of (4). (6) The organic positive temperature coefficient thermistor according to any one of (1) to (5), wherein the conductive metal particles have spike-shaped protrusions. (7) The organic positive temperature coefficient thermistor according to any one of the above (1) to (6), wherein the organic substance is a biodegradable material. (8) A method for producing an organic positive temperature coefficient thermistor, which is obtained by previously treating the surface of a conductive metal particle with an organic substance, and mixing and dispersing the conductive metal particles with a polymer organic matrix to obtain an organic positive temperature coefficient thermistor. (9) The organic substance is a material different from the polymer organic matrix, is a material that is not covalently bonded to the conductive metal particles and is not compatible with the polymer organic matrix at the molecular level. ) A method for manufacturing an organic positive temperature coefficient thermistor. (10) The organic substance is a material having no reactivity with a polymer organic matrix (8) or (9).
For manufacturing an organic positive temperature coefficient thermistor. (11) The method for producing an organic positive temperature coefficient thermistor according to any one of the above (8) to (10), wherein the conductive metal particles contain nickel or copper. (12) The method for producing an organic positive temperature coefficient thermistor according to any one of the above (8) to (11), wherein the polymer organic matrix is a thermoplastic polymer. (13) The method for producing an organic positive temperature coefficient thermistor according to any one of (8) to (12), wherein the high molecular weight organic matrix further contains a low molecular weight organic compound. (14) The method for producing an organic positive temperature coefficient thermistor according to any one of the above (8) to (13), wherein the conductive metal particles have spike-like protrusions. (15) The method for producing an organic positive temperature coefficient thermistor according to any of (8) to (14), wherein the organic substance is a biodegradable material.

[0012]

The organic positive temperature coefficient thermistor of the present invention is characterized in that the polymer organic matrix contains metal conductive particles whose surface is previously treated with an organic substance.

By pre-treating the surface of the conductive metal particles with an organic substance, diffusion of oxygen to the surface of the particles during long-term storage is prevented and oxidation is suppressed to stabilize the resistance value. Also,
It is considered that the surface treatment also has an effect of suppressing excessive quasi-aggregation of the conductive metal particles. Furthermore, the conductive metal particles and the polymer organic matrix can be easily separated.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION The organic positive temperature coefficient thermistor of the present invention is a polymer organic matrix which is a material whose surface is different from that of the polymer organic matrix in advance and which is not covalently bonded to the conductive metal particles. It is characterized by containing conductive metal particles treated with a material that is incompatible with the polymer organic matrix at the molecular level.

The polymer organic matrix may be either thermoplastic or thermosetting.

As the thermoplastic polymer matrix, polyolefin (for example, polyethylene), olefin copolymer (for example, ethylene-vinyl acetate copolymer, ethylene-acrylic acid copolymer), halogen-based polymer, polyamide, polystyrene, polyacrylonitrile, polyethylene oxide, polyacetal. , Thermoplastic modified cellulose, polysulfones, thermoplastic polyesters (PET, etc.), polyethyl acrylate, polymethyl methacrylate, thermoplastic elastomer and the like.

Specifically, high density polyethylene [for example, trade name HiZex 2100JP (manufactured by Mitsui Petrochemicals), trade name Marlex 6003 (manufactured by Philips), trade name HY540 (manufactured by Nippon Polychem), low density polyethylene [for example, , Trade name LC500 (manufactured by Nippon Polychem), trade name DYNH-1 (manufactured by Union Carbide Co., Ltd.)], medium density polyethylene [for example, trade name 260
4M (manufactured by Gulf Co., etc.), ethylene-ethyl acrylate copolymer [for example, trade name DPD6169 (manufactured by Union Carbide Co.)], ethylene-vinyl acetate copolymer [for example, trade name LV241 (manufactured by Nippon Polychem).
Etc.], ethylene-acrylic acid copolymer [for example, trade name EAA455 (manufactured by Dow Chemical Co., Ltd.)], ionomer [for example, trade name Himilan 1555 (manufactured by Mitsui DuPont Polychemical Co., Ltd.)], polyvinylidene fluoride [for example, trade name Kynar 461 (manufactured by Elf Atchem) and the like], vinylidene fluoride-tetrafluoroethylene-hexafluoropropylene copolymer [eg, trade name Kynar ADS (manufactured by Elf Atchem), etc.] and the like.

Of these, polyolefin is preferable, and polyethylene is particularly preferable. High-density, linear low-density, and low-density polyethylene grades can be used, with high-density and linear low-density polyethylene being preferred. Its melt viscosity (MFR) is 15.0 g /
It is preferably 10 min or less, particularly preferably 8.0 g / 10 min or less.

The thermosetting polymer matrix is not particularly limited, but epoxy resins, unsaturated polyester resins, polyimides, polyurethanes, phenol resins and silicone resins are preferably used.

The epoxy resin is obtained by curing (cross-linking) an oligomer having a reactive epoxy group at the terminal (molecular weight of several hundreds to 10,000) with various curing agents, and is a glycidyl ether type represented by bisphenol A, It is classified into glycidyl ester type, glycidyl amine type, and alicyclic type. Depending on the application, a trifunctional or higher-functional polyfunctional epoxy resin can also be used. In the present invention, of these, it is preferable to use the glycidyl ether type, especially the bisphenol A type. The epoxy equivalent of the epoxy resin used is 1
It is preferably about 00 to 500. The curing agent is classified into a polyaddition type, a catalyst type, and a condensation type according to the reaction mechanism. In the polyaddition type, the curing agent itself adds to an epoxy group or a hydroxyl group, and examples thereof include polyamine, acid anhydride, polyphenol, polymercaptan, and isocyanate. The catalyst type serves as a polymerization catalyst for epoxy groups, and examples thereof include tertiary amines and imidazoles. The condensation type cures by condensation with a hydroxyl group, and examples thereof include a phenol resin and a melamine resin.
In the present invention, as the curing agent for the bisphenol A type epoxy resin, it is preferable to use a polyaddition type, particularly a polyamine type and an acid anhydride. The curing conditions may be appropriately determined.

Such epoxy resins and curing agents are commercially available, and examples thereof include Epicoat (resin), Epicure, Epomate (curing agent) manufactured by Yuka Shell Epoxy Co., Ltd. and Araldite manufactured by Ciba Geigy.

The unsaturated polyester resin is obtained by dissolving an unsaturated dibasic acid or a polyester mainly composed of a dibasic acid and a polyhydric alcohol (a molecular weight of about 1000 to 5000) in a vinyl monomer having a function of crosslinking. It is obtained by curing an organic peroxide such as benzoyl peroxide as a polymerization initiator. If necessary, a polymerization accelerator may be used in combination for curing. As the raw material of the unsaturated polyester used in the present invention, maleic anhydride is used as the unsaturated dibasic acid,
Fumaric acid is preferable, phthalic anhydride is used as the dibasic acid,
Isophthalic acid and terephthalic acid are preferred, and propylene glycol and ethylene glycol are preferred as the polyhydric alcohol. Styrene, diallyl phthalate and vinyltoluene are preferable as the vinyl monomer. The blending amount of the vinyl monomer may be appropriately determined, but is usually about 1.0 to 3.0 mol per 1 mol of the fumaric acid residue. Also,
Known polymerization inhibitors such as quinones and hydroquinones are added for the purpose of preventing gelation in the synthesis step and controlling the curing characteristics. The curing conditions may be appropriately determined.

Such unsaturated polyester resins are commercially available, for example, Epolac manufactured by Nippon Shokubai, Polyset manufactured by Hitachi Chemical, Polylite manufactured by Dainippon Ink and Chemicals, and the like.

The polyimide is roughly classified into a condensation type and an addition type depending on the production method, but a bismaleimide type polyimide of an addition polymerization type polyimide is preferable. Bismaleimide type polyimides are homopolymerized, reacted with other unsaturated bonds, subjected to Michael addition reaction with aromatic amines or with dienes.
It can be cured by using the Diels-Alder reaction. In the present invention, a bismaleimide-based polyimide resin obtained by the addition reaction of bismaleimide and aromatic diamines is particularly preferable. Examples of aromatic diamines include diaminodiphenylmethane. The synthesizing / curing conditions may be appropriately determined.

Such polyimides are commercially available,
For example, there are imidaloy manufactured by Toshiba Chemical Co., Ltd. and kelimide manufactured by Ciba Geigy.

Polyurethane is obtained by polyaddition reaction of polyisocyanate and polyol. The polyisocyanate includes an aromatic type and an aliphatic type, but an aromatic type is preferable, and 2,4- or 2,6-tolylene diisocyanate, diphenylmethane diisocyanate, naphthalene diisocyanate and the like are preferably used. Polyols include polyether polyols such as polypropylene glycol, polyester polyols and acrylic polyols, with polypropylene glycol being preferred.
The catalyst may be an amine type (a tertiary amine type such as triethylenediamine and an amine salt), but an organometallic type such as dibutyltin dilaurate or stannas octoate is preferably used. In addition, a cross-linking agent such as polyhydric alcohol and polyvalent amine may be used together as an auxiliary material. The synthesis / curing conditions may be appropriately determined.

Such polyurethane is commercially available, for example, Sumitomo Bayer Urethane Co., Ltd.
There are NP series manufactured by Mitsui Toatsu Chemicals, and Coronate manufactured by Nippon Polyurethanes.

Phenolic resins are obtained by reacting phenol with an aldehyde such as formaldehyde, and are roughly classified into novolac type and resol type depending on the synthesis conditions.
The novolac type produced under an acidic catalyst is cured by heating with a crosslinking agent such as hexamethylenetetramine, and the resol type produced under a basic catalyst is cured by itself or in the presence of an acid catalyst. Either may be used in the present invention. The synthesis / curing conditions may be appropriately determined.

Such phenolic resins are commercially available, for example, Sumicon manufactured by Sumitomo Bakelite Co., Stand Light manufactured by Hitachi Chemical, and Tecolite manufactured by Toshiba Chemical Co.

The silicone resin is composed of repeating siloxane bonds and is mainly obtained by hydrolysis or polycondensation of organohalosilane, and also alkyd-modified, polyester-modified, acrylic-modified, epoxy-modified,
Modified silicone resins such as phenol-modified, urethane-modified, melamine-modified, etc., silicone rubber obtained by crosslinking linear polydimethylsiloxane and its copolymer with organic peroxide, etc., room temperature curable (RTV) condensation and addition type There are silicone rubber and the like.

Such silicone resins are commercially available, for example, various silicone rubbers manufactured by Shin-Etsu Chemical, Toray Dow Corning, Toshiba Silicone, silicone resins and the like.

The thermosetting resin to be used can be appropriately selected according to the desired performance and application, but among them, epoxy resin and unsaturated polyester resin are preferably used. Further, it may be a polymer obtained by reacting two or more kinds with each other.

When the thermosetting polymer matrix and the thermoplastic polymer matrix are used in combination, the mass ratio of the thermosetting polymer matrix to the thermoplastic polymer matrix is 1: 5 to 9: 1, especially 1: It is preferably 4 to 8: 1. If the thermoplastic polymer matrix is larger than this, the stability of the initial resistance tends to decrease. If the amount of the thermoplastic polymer matrix is less than this, the stability under high temperature and high humidity tends to deteriorate.

Further, a low molecular weight organic compound may be used in combination. In a normal organic PTC thermistor, the element operates (the resistance value increases) due to the expansion of the polymer organic matrix. An advantage of using a low-molecular weight organic compound as an operating substance is that it generally has a higher degree of crystallinity than a polymer, and therefore the rise when the resistance value increases due to temperature rise becomes sharp. Further, by using low molecular weight organic compounds having different melting points, the temperature at which the resistance increases (operating temperature) can be easily controlled. In addition, since the polymer tends to be in a supercooled state, it exhibits hysteresis that the temperature at which the resistance value recovers when the temperature is lowered is lower than the operating temperature when the temperature is raised, but this can be suppressed by using a low-molecular organic compound. You can In the case of a crystalline polymer, the melting point and the operating temperature can be changed by the difference in the molecular weight and the degree of crystallinity, and by copolymerization with a comonomer, but at that time, the crystal state changes, which is sufficient. The PTC characteristics may not be obtained in some cases.
This tends to be more remarkable when the operating temperature is set to 100 ° C. or lower.

The low molecular weight organic compound used in the present invention has a molecular weight of up to about 2000, preferably up to about 1,000.
More preferably, it is not particularly limited as long as it is a crystalline substance of 200 to 800, but a substance which is solid at room temperature (a temperature of about 25 ° C) is preferable.

Examples of the low molecular weight organic compound include waxes (specifically, petroleum waxes such as paraffin wax and microcrystalline wax, natural waxes such as plant wax, animal wax, and mineral wax),
Fats and oils (specifically, fats or solid fats)
and so on. The components of wax and fats and oils include hydrocarbons (specifically, alkane-based straight chain hydrocarbons having 22 or more carbon atoms) and fatty acids (specifically, alkane-based straight chain hydrocarbons having 12 or more carbon atoms). Fatty acid), fatty acid ester (specifically, saturated fatty acid methyl ester obtained from saturated fatty acid having 20 or more carbon atoms and lower alcohol such as methyl alcohol), fatty acid amide (specifically, oleic acid amide, Unsaturated fatty acid amides such as erucic acid amide), aliphatic amines (specifically, aliphatic primary amines having 16 or more carbon atoms), higher alcohols (specifically, n-alkyl alcohols having 16 or more carbon atoms) ), Chlorinated paraffin, etc., which can be used alone or in combination as a low molecular weight organic compound. The low molecular weight organic compound may be appropriately selected in consideration of the polarity of the polymer matrix in order to improve the dispersion of each component.
Petroleum wax is preferred as the low molecular weight organic compound.

These low molecular weight organic compounds are commercially available, and commercially available products can be used as they are.

In the present invention, as the low molecular weight organic compound,
Melting point mp is 40 to 200 ° C., more preferably 40 to 1
It is preferable to use one having a temperature of 00 ° C. Examples thereof include paraffin wax (for example, tetracosan C ₂₄ H ₅₀ ; mp 49 to 52 ° C., hexatriacontane C ₃₆ H ₇₄ ; mp 73 ° C., trade name HNP-10 (manufactured by Nippon Seiro Co., Ltd.); mp 75 ° C., HNP-3 (manufactured by Nippon Seiro Co., Ltd.);
mp66 ° C.), microcrystalline wax (for example, trade name Hi-Mic-1080 (manufactured by Nippon Seiro Co., Ltd.); mp83 ° C., Hi-Mic-1045 (manufactured by Nippon Seiro Co., Ltd.); mp70 ° C., Hi-Mic2045 (Japan). Seiwa Co., Ltd .; mp 64 ° C., Hi-Mic 3090 (Nippon Seiwa Co., Ltd.); mp 89 ° C., Serrata 104 (Nippon Petroleum Refining Co., Ltd.); ), Fatty acids (for example, behenic acid (manufactured by Nippon Seika); mp81 ° C, stearic acid (manufactured by Nippon Seika); mp72 ° C, palmitic acid (manufactured by Nippon Seika);
mp64 ° C, etc.), fatty acid ester (for example, arachidic acid methyl ester (manufactured by Tokyo Kasei); mp48 ° C, etc.),
There are fatty acid amides (for example, oleic acid amide (Nippon Seika); mp 76 ° C.). Further, polyethylene wax (for example, trade name Mitsui High Wax 110 (manufactured by Mitsui Petrochemical Industry Co., Ltd .; mp100 ° C.), stearic acid amide (mp109 ° C.), behenic acid amide (mp111).
C), N-N'-ethylenebislauric acid amide (mp
157 ° C), N-N'-dioleyl adipamide (mp119 ° C), N-N'-hexamethylenebis-1.
There is also 2-hydroxystearic acid amide (mp 140 ° C.) and the like. Further, a compounded wax in which resins are mixed with paraffin wax, and a microcrystalline wax is mixed with this compounded wax and has a melting point of 40 to 20.
Those at 0 ° C. can also be preferably used.

The low molecular weight organic compounds may be used alone or in combination of two or more depending on the operating temperature and the like.

The content of the low molecular weight organic compound is 0.05 to 4 of the total mass of the polymer matrix (including the curing agent etc.).
It is preferably double, particularly 0.1 to 2.5 times. If this mixing ratio becomes small and the content of the low molecular weight organic compound becomes small, it becomes difficult to obtain a sufficient resistance change rate.
On the other hand, when the mixing ratio is increased and the content of the low molecular weight organic compound is increased, the thermistor element body is largely deformed when the low molecular weight compound is melted, and it becomes difficult to mix with the conductive metal particles.

In the organic positive temperature coefficient thermistor of the present invention, endothermic peaks are observed in the vicinity of the melting point of the polymer matrix used and in the vicinity of the melting point of the low molecular weight organic compound by the differential scanning calorimetry (DSC). This is considered to have a sea-island structure in which the polymer matrix and the low-molecular weight organic compound are independently dispersed.

As the conductive metal particles, copper, aluminum, nickel, tungsten, molybdenum, silver, zinc,
Cobalt or the like is used, but nickel and copper are preferable.

As the shape, a spherical shape, a flake shape, a rod shape or the like is used. Particularly preferably used is one having spike-like protrusions on the surface. It is considered that the tunnel current easily flows due to the surface shape, and the room temperature resistance can be reduced more than that of the spherical conductive metal particles having no protrusion.

Since the spacing between the conductive metal particles is larger than that of the spherical particles, the rate of resistance change can be increased.

The conductive metal particles having spike-like protrusions that can be used in the present invention are formed of primary particles each having sharp protrusions, and each particle has a diameter of 1/3 to 1/3.
One particle has a plurality (usually 10 to 500) of conical spike-like protrusions having a height of 1/50.
The material is preferably metal, especially Ni.

Such conductive metal particles may be powders in which one and one are individually present, but the primary particles are
It is preferable that about 0 to 1000 particles are connected in a chain to form secondary particles. Some of the chain-like particles may have primary particles. An example of the former is spherical nickel powder with spike-shaped protrusions, which has the trade name INCO Type.
e 123 Nickel powder (manufactured by Inco), having an average particle size of about ³ to 7 μm, an apparent density of about 1.8 to 2.7 g / cm ³ , and a specific surface area of 0.34.
It is about 0.44 m ² / g.

As the latter example which is preferably used
Is a filamentary nickel powder, trade name INCO
  Type 210, 255, 270, 287 Nickel
It is commercially available as powder (manufactured by Inco), of which
INCO Type 210,255 is preferred. That
The average particle size of the primary particles is preferably 0.1 μm.
Or more, more preferably 0.2 μm or more and 4.0 μm or less
It is degree. Of these, the average particle size of the primary particles is 0.4
The most preferable value is 3.0 μm or less, and the average particle size
50% by mass or less of 0.1 μm or more and less than 0.4 μm
You may mix. The apparent density is 0.3 to 1.0.
g / cm³Degree, specific surface area 0.4-2.5m ²/ G
is there.

The average particle size in this case is measured by the fish subsieve method.

Regarding such conductive metal particles, JP-A-5-47503 and US Pat. No. 5,378,407 are applicable.
No. specification.

In addition to the conductive metal particles having spike-shaped protrusions, carbon black, graphite, carbon fiber, metal-coated carbon black, graphitized carbon can be used as conductive particles for auxiliary conductivity. Carbon-based conductive particles such as black and metal-coated carbon fiber,
Spherical, flaky, fibrous, etc. metal particles, dissimilar metal coated metal (silver coated nickel, etc.) particles, tungsten carbide,
Ceramic-based conductive particles such as titanium nitride, zirconium nitride, titanium carbide, titanium boride, molybdenum silicide,
In addition, conductive potassium titanate whiskers described in JP-A Nos. 8-31554 and 9-27383 may be added. Such conductive particles are preferably 25% by mass or less of the conductive metal particles having spike-shaped protrusions.

The content of the conductive metal particles is preferably 1.5 to 8 times the total mass of the polymer matrix and the low molecular weight organic compound (total mass of the organic components including the curing agent and the like). If this mixing ratio becomes small and the content of the conductive metal particles becomes small, it becomes impossible to sufficiently lower the room temperature resistance during non-operation. On the other hand, when the content of the conductive metal particles increases, it becomes difficult to obtain a large resistance change rate, and it becomes difficult to uniformly mix the particles, and it becomes difficult to obtain stable characteristics.

The organic substance used for the surface treatment is liquid or solid at room temperature and has a vapor pressure of 0.1 mmH at room temperature.
Any kind of non-volatile material may be used as long as it is about g or less, but it is desirable to select an organic material in consideration of affinity with the surface of the conductive metal particles. On the other hand, use of a coupling agent or the like that firmly bonds to the metal surface should be avoided because it adversely affects the conductivity of the metal particles.

Further, in order to allow the organic substance to exist on the surface of the conductive metal particles in the kneaded product, it is preferable that the compatibility with the polymer organic matrix is not so high. In the present invention, that the compatibility is not high means that it does not include those that are compatible at the molecular level, and those that undergo microphase separation and macrophase separation can be preferably used.

Materials which are active on the matrix resin should also be avoided. When the organic substance has a bond or an interaction with the matrix resin, the behavior of the conductive metal particles is limited, which adversely affects the recovery characteristics from the operation. Examples of such substances include organic acids and triazine derivatives. When using a polyolefin for the matrix resin, among organic acids, particularly long-chain saturated, when having unsaturated fatty acids, these fatty acids, the carboxyl group portion is adsorbed on the surface of the conductive metal particles,
Moreover, long-chain hydrocarbons may interact with the matrix resin. The triazine derivative may be adsorbed on the surface of the conductive metal particles, and various functional groups of the derivative may react or interact with the matrix resin.

Specific organic substances include, for example, polyhydric alcohols used as softeners and moisturizers. Specifically, ethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, diglycerin, 1,3-butylene glycol,
Examples thereof include isoprene glycol, erythritol, diethylene glycol, pentyl glycol, neopentyl glycol, polypropylene glycol, polyoxyethylene polyoxypropylene copolymer, glycerin, polyglycerin, polyoxyethylene glycerin, and polytetramethylene ether glycol.

In addition, long-chain alcohols are also preferable, and those having at least 8 carbon atoms are preferable. Examples of the long-chain alcohol having at least 8 carbon atoms include octanol, tetradecanol, undecanol, stearyl alcohol, 2-decanol, decanol, 2-dodecanol, 1,2-dodecanediol, tridecanol, hexadecanol, 1, 12-dodecanediol, 1,2-decanediol, 1,10-decanediol, 4-decanol, 2-octanol, 3
-Octanol, nonanol, 2-undecanol, 2
-Tetradecanol, 1,2-tetradecanediol,
Examples thereof include 1,14-tetradecanediol and heptadecanol.

Esters of the above alcohols and fatty acids can also be preferably used. Further, ethers such as polyoxyethylene lauryl ether and polyoxyethylene butyl ether can also be used.

Further, an aliphatic carboxylic acid amide is also preferable, and specific examples of the aliphatic carboxylic acid amide include, for example, oleic acid amide, stearic acid amide, erucic acid amide, behenic acid amide, N-oleyl palmitoamide, N. -Stearyl erucic acid amide, N, N'-ethylenebis (stearamide), N, N'-methylenebis (stearamide), methylol stearamide, ethylenebisoleic acid amide, ethylenebisbehenic acid amide, ethylenebisstearic acid amide, ethylene Bislauric acid amide, hexamethylene bisoleic acid amide, hexamethylene bisstearic acid amide,
Butylene bisstearic acid amide, N, N'-dioleyl sebacic acid amide, N, N'-dioleyl adipic acid amide, N, N'-distearyl adipic acid amide,
N, N'-distearyl sebacic acid amide, m-xylylene bisstearic acid amide, N, N'-distearyl isophthalic acid amide, N, N'-distearyl terephthalic acid amide, N-oleyl oleic acid amide, N -Stearyl oleic acid amide, N-stearyl erucic acid amide, N-oleyl stearic acid amide, N-stearyl stearic acid amide, N-butyl-N'stearyl urea, N-propyl-N'stearyl urea, N-allyl-
Examples thereof include N'stearyl urea, N-phenyl-N'stearyl urea, N-stearyl-N'stearyl urea, dimethitol oil amide, dimethyllauric acid amide, and dimethylstearic acid amide. In particular, oleic acid amide, stearic acid amide, erucic acid amide, behenic acid amide, N-oleyl palmitoamide, N-stearyl erucic acid amide and the like can be mentioned.

Many of these have biodegradability, and P
Applying this in the TC thermistor recycling process has the advantage that the matrix resin and the metal particles can be separated relatively easily by removing the organic layer covering the metal particles by biodegradation. Have.

Specifically, by crushing or crushing the resin matrix containing the metal powder and treating it with a batch layer containing microorganisms, enzymes, etc., the organic layer existing around the metal powder is decomposed. Then, the matrix and the metal powder are separated. After that, the matrix and the metal powder can be easily separated by applying a difference in specific gravity or the like.

As a treatment method for decomposing by a usual biological treatment, a microorganism suspension method such as an activated sludge method, an anaerobic nitrification method or a sponge carrier method, a biological filtration method, an immersion filter method,
A biofilm method such as a fluidized bed method, a rotating disk method or a sprinkling filter method or a self-granulation method can be used. These treatments may be continuous or batch type. It may be either aerobic or anaerobic or a combination thereof. For activated sludge method, see Japanese Patent Publication No.55-4955
No. 9 and No. 51-12943 are also disclosed. Further, a degrading enzyme may be used instead of the microorganism, or both may be combined.

In addition to the above organic substances, phenol compounds and hydrophilic polymers can be used.

More specifically, P-phenolsulfonic acid, 2,6-dibutyl-P-cresol, 2,2'-methylenebis (4-methyl-6-t-butylphenol), 4,4'-butylidenebis ( 3-methyl-6-t
-Butylphenol), polyvinyl alcohol, polyvinylpyrrolidone, polyacrylamide, polyacrylic acid and salts thereof, polyvinyl methyl ether and the like.

As a treatment method, a solution is prepared by dissolving an organic substance in a solvent, and the conductive metal particles are dispersed in the solution, and then the solvent is evaporated. Alternatively, the solution is applied to the conductive metal particles by spraying or the like. There is a method of evaporating the solvent, and the like.

Examples of the solvent include water, ethanol, methanol, acetone, toluene, hexane and the like.

The treatment amount depends on the specific surface area / specific gravity of the conductive metal particles and the size / molecular weight of the organic molecule, but it is preferable to treat with 0.1 to 5 mass% of the organic substance of the conductive metal particles. If the treatment amount is lower than this, the characteristic improving effect is not sufficient, and if the treatment amount is higher than this, it tends to be difficult to sufficiently reduce the resistance value of the element.

Next, a method of manufacturing the organic positive temperature coefficient thermistor of the present invention will be described.

The kneading of the thermoplastic polymer matrix, the low molecular weight organic compound and the conductive metal particles may be carried out by a known method, and the temperature is equal to or higher than the melting point of the polymer having the highest melting point in the material, preferably 5 to 40 ° C. The kneading may be performed at a high temperature for about 5 to 90 minutes using a known mill or roll. In order to prevent thermal deterioration, the temperature may be higher than the melting point of the polymer, but the kneading may be performed at the lowest possible temperature. Also,
The polymer matrix and the low molecular weight organic compound may be melt-mixed in advance, or may be dissolved and mixed in a solvent.

When the polymer matrix, the low molecular weight organic compound and the conductive metal particles are mixed by the solution method, the polymer matrix and a solvent in which at least one low molecular weight organic compound is dissolved are used, and the remaining polymer matrix is used. , And the low molecular weight organic compound and the conductive metal particles may be dispersed in this solution.

The kneaded product is press-molded into a sheet having a predetermined thickness. The molding may be performed by an injection method, an extrusion method, or the like. Further, an extrusion method in which the kneading and the sheet forming are performed in one step can also be used. After molding, a crosslinking treatment may be carried out if necessary. The cross-linking method includes radiation cross-linking, chemical cross-linking with an organic peroxide, water cross-linking in which a silane coupling agent is grafted and a silanol group is condensed and reacted, and radiation cross-linking is preferable. Finally, C
A metal electrode such as u or Ni is thermocompression bonded or a conductive paste or the like is applied to form a thermistor element. Also, press molding and electrode formation may be performed simultaneously.

When the thermosetting polymer matrix is used, a predetermined amount of the thermosetting resin before curing and the conductive metal particles are mixed and dispersed to form a paint. Mixing / dispersion may be performed by a known method, and various stirrers, dispersers, roll machines for paints, etc. can be used. If air bubbles are mixed in during mixing, vacuum degassing is performed. Aromatic hydrocarbons for adjusting viscosity,
Various solvents such as ketones and alcohols can also be used. This is poured between metal foil electrodes of nickel, copper or the like, or formed into a sheet by coating such as screen printing, and cured under a predetermined heat treatment condition of a thermosetting resin. There is also a method of performing pre-curing at a relatively low temperature and then performing main curing at a high temperature. The electrode may be formed by applying a conductive paste or the like to a sheet in which only the mixture is cured. The obtained sheet molded body is punched into a desired shape to form a thermistor element.

An antioxidant may be mixed in order to prevent thermal deterioration of the polymer matrix and the low molecular weight organic compound, and phenols, organic sulfurs, phosphites and the like are used.

Further, as a good thermal conductive additive, Japanese Patent Laid-Open No.
7-12061, silicon nitride, silica, alumina, clay (mica, talc, etc.), Japanese Patent Publication No. 7-
Silicon, silicon carbide, silicon nitride, beryllia, selenium described in Japanese Patent No. 77161, JP-A-5-217
Inorganic nitrides, magnesium oxide and the like described in Japanese Patent No. 711 may be added.

To improve durability, Japanese Patent Laid-Open No. 5-2261
Titanium oxide, iron oxide, zinc oxide, silica, magnesium oxide, alumina, chromium oxide, barium sulfate, calcium carbonate, calcium hydroxide, lead oxide described in JP-A-6-68963. Inorganic solid having a high relative dielectric constant, specifically, barium titanate, strontium titanate, potassium niobate or the like may be added.

To improve the withstand voltage, Japanese Patent Laid-Open No. 7438/1992.
Boron carbide and the like described in Japanese Patent Publication No. 3 may be added.

In order to improve the strength, JP-A-5-74603 is used.
The hydrated alkali titanate described in JP-A-8-17563 and the titanium oxide, iron oxide, zinc oxide, silica and the like described in JP-A-8-17563 may be added.

As a crystal nucleating agent, JP-B-59-10553
Alkali halides, melamine resins described in Japanese Patent Publication No. 6-76511, benzoic acid, dibenzylidene sorbitol, metal benzoates described in Japanese Patent Publication No. 6-76511, and Japanese Patent Application Laid-Open No. 7-6864. Talc, zeolite, dibenzylidene sorbitol, sorbitol derivative (gelling agent) described in JP-A-7-263127, asphalt, and bis (4-t-butylphenyl) sodium phosphate are added. Good.

As an arc control agent, Japanese Patent Publication No. 4-2
Alumina, magnesia hydrate described in Japanese Patent No. 8744, metal hydrate described in JP-A No. 61-250058, silicon carbide and the like may be added.

As a metal damage preventing agent, JP-A-7-6864 is known.
Irganox MD1024 described in Japanese Patent Publication No.
(Manufactured by Ciba Geigy) or the like may be added.

Further, as a flame retardant, JP-A-61-239
Diantimony trioxide and aluminum hydroxide described in Japanese Patent No. 581, magnesium hydroxide described in JP-A-5-74603, and further 2,2-bis (4-hydroxy-3,5-). Organic compounds (including polymers) containing halogen such as dibromophenyl) propane and polyvinylidene fluoride (PVDF), phosphorus-based compounds such as ammonium phosphate and the like may be added.

In addition to these, zinc sulfide, basic magnesium carbonate, aluminum oxide, calcium silicate, magnesium silicate, aluminosilicate clay (mica, talc, kaolinite, montmorillonite, etc.), glass powder, glass flakes, glass fiber , Calcium sulfate, etc. may be added.

These additives are a polymer matrix,
2 of the total weight of the low molecular weight organic compound and the conductive metal particles
It is preferably 5% by weight or less.

The organic positive temperature coefficient thermistor of the present invention has a low initial resistance when it is not operating, and its room temperature specific resistance value is 10.
It is about ⁻³ to 10 ⁻¹ Ω · cm, the rise of resistance during operation is steep, and the rate of resistance change from non-operation to operation is as large as 6 digits or more.

FIG. 1 shows an example of the structure of the organic positive temperature coefficient thermistor of the present invention. In the organic positive temperature coefficient thermistor of the present invention, a thermistor body 2 having at least a thermoplastic polymer matrix and conductive metal particles, and a pair of electrodes 3 are arranged so as to sandwich the thermistor body 2. . The illustrated example shows an example of the sectional shape of the thermistor, and various modifications can be made without departing from the spirit of the present invention. The plane shape may be a circle, a quadrangle, or any other optimum shape depending on the required characteristics and specifications.

[0085]

EXAMPLES Example 1 Filamentous nickel powder (I
NCO Co., Ltd., type 210 nickel powder, average particle size 0.5 to 1.0 μm, apparent density 0.8 g / cm ³ , specific surface area 1.5 to ^2.5 m ² / g) are used as conductive metal particles. I was there.

The nickel powder was dispersed and stirred in a 0.25% ethanol solution containing 0.5% by weight of polyethylene glycol (manufactured by Junsei Chemical Co., Ltd., molecular weight: 200) to form a slurry, and ethanol was evaporated by an evaporator. ,
The remaining surface-treated nickel powder was vacuum dried. TEM photographs of the nickel powder before and after the treatment are shown in FIGS.

Linear low density polyethylene as a high molecular organic matrix (Mitsui Chemicals, trade name Evolue 252
0, MFR = 1.7 g / 10 min, melting point 121 ° C.), the surface-treated filamentary nickel powder, and paraffin wax (trade name Poly Wax655, manufactured by Baker Petrolite, melting point 99 ° C.) as a working substance in volume ratio. 44:
It was used at a ratio of 26:30. These were put into a mill set at 150 ° C. and kneaded for 30 minutes.

The obtained kneaded product was sandwiched between Ni foil electrodes, and the foil was thermocompression bonded at 150 ° C. with a heat press machine to make the whole 0.35 mm.
And Both sides of the obtained electrode-attached sheet were irradiated with an electron beam of 20 Mrad for cross-linking treatment and punched into a disc shape having a diameter of 10 mm to obtain a thermistor element.

Example 2 A thermistor element was produced in the same manner as in Example 1 except that the polyethylene glycol of Example 1 was changed to polyglycerin (Nippon Yushi-Seiyaku, trade name Uniguri G-2).

[Example 3] The polyethylene glycol of Example 1 was replaced with tetradecanol (manufactured by NOF CORPORATION, trade name NAA).
A thermistor element was prepared in the same manner as in Example 1 except that the temperature was changed to −43, melting point 38 ° C.).

[Example 4] A thermistor element was prepared in the same manner as in Example 1 except that the polyethylene glycol of Example 1 was changed to erucic acid amide (Nippon Seika, trade name Neutron S, melting point 78 ° C). .

[Example 5] The surface treatment of nickel powder was performed in the same manner as in Example 1. The nickel powder used is filamentary nickel powder (trade name: Type 255 nickel powder, manufactured by INCO, average particle size 2.2 to 2.8 μm, apparent density 0.5 to 0.65 g / cm ³ , specific surface area 0.68 m). ² / g
).

20 g of bisphenol A type epoxy resin (trade name Shrimp Coat 801 manufactured by Yuka Shell Epoxy Co., Ltd.),
Modified amine curing agent (Okaka Shell Epoxy Co., trade name Epomate B002) 10 g, paraffin wax (Ba
Made by ker Petrolite, product name Poly Wax655, melting point 99
15 ° C.), 180 g of the surface-treated nickel powder, and 20 ml of toluene were mixed for 20 minutes by a centrifugal disperser. The obtained slurry-like kneaded product is applied to one side of a Ni foil, the applied surface is sandwiched by another Ni electrode, and the upper and lower sides thereof are sandwiched by a brass plate with a spacer having a thickness of 0.4 mm, and the temperature is 90 ° C. Curing was carried out for 3 hours under pressure using the set heat press machine. The obtained sheet with an electrode having a thickness of 0.4 mm was punched out in the same manner as in Example 1 to obtain a thermistor element. The resistance values of the five obtained samples before the thermal shock test were as follows. (1) 0.006Ω, (2) 0.006Ω, (3) 0.006Ω, (4) 0.007Ω, (5) 0.0
07Ω From the above results, it can be seen that the aggregation of the metal particles is suppressed and the variation of the sample is reduced.

Comparative Example 1 A thermistor element was prepared in the same manner as in Example 1 except that the nickel powder was not surface-treated.

[Comparative Example 2] Example 2 was repeated except that the nickel powder was not surface-treated in advance as in Example 1, and polyethylene glycol was mixed with polyethylene paraffin wax and nickel powder at the same time when polyethylene glycol was mixed. A thermistor element was prepared in the same manner as in 1.

Comparative Example 3 A thermistor element was prepared in the same manner as in Example 5 except that the nickel powder was not surface-treated. The resistance values of the five obtained samples before the thermal shock test were as follows. (31) 0.005Ω, (32) 0.008Ω, (33) 0.011Ω, (34) 0.012Ω, (3
5) 0.015Ω From the above results, it is understood that the dispersion of the resistance value is increased due to the aggregation of the metal particles.

[Comparative Example 4] 0.5 wt% of the silane coupling agent (vinyltriethoxysilane, manufactured by Shin-Etsu Chemical Co., Ltd., trade name KBE1) with respect to the nickel powder used in Example 1.
003) was dissolved in a 1: 1 water / ethanol mixed solvent, and 1 wt% acetic acid (99.7%) of the whole solution was added.
Nickel powder was added to this solution and stirred for 5 hours. This is filtered, after washing the nickel powder on the filter paper with ethanol,
It dried at 60 degreeC all day and night.

A thermistor element was manufactured in the same manner as in Example 1 except that the obtained nickel powder after coupling treatment was used.

With respect to these devices, a temperature cycle of holding at -40 ° C. for 30 minutes and then at 85 ° C. for 30 minutes was set to 1 cycle.
The thermal shock test as a cycle was performed for 200 cycles. The results are shown in the table below.

[0100]

[Table 1]

Compared with Comparative Example 1 in which no surface treatment was performed,
The effects of the surface treatments of Examples 1 to 4 are clear.
In addition, Examples 1 to 4 in which the surface treatment is performed are more effective than Comparative Example 2 in which the conductive powder is not mixed in advance and simply mixed. In addition, a large effect of surface treatment appeared even when the polymer organic matrix was a thermosetting epoxy resin (Example 5, Comparative Example 3). Further, it was found that by coating the surface of the metal particles with an organic material that is incompatible with the organic matrix, excessive aggregation of the conductive metal particles was suppressed and the dispersibility was improved, so that the initial resistance was stable.
In addition, when a polymer matrix or a coupling agent capable of firmly bonding to the metal surface was used, the characteristics were deteriorated in comparison with the untreated one (Comparative Example 4).

[0102]

As described above, according to the present invention, it is possible to improve the characteristic stability of an organic positive temperature coefficient thermistor containing a metal as a conductive particle.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing the basic structure of an organic positive temperature coefficient thermistor of the present invention.

FIG. 2 is a drawing-substituting TEM photograph showing a state of nickel powder before organic matter treatment in an example.

FIG. 3 is a drawing-substituting TEM photograph showing a state of nickel powder after organic matter treatment in Examples.

[Explanation of symbols]

2 Thermistor body 3 electrodes

Claims (15)

[Claims] 1. A polymer organic matrix, and conductive metal particles contained in the polymer organic matrix, the material being different from the polymer organic matrix in the vicinity of the surface of the conductive metal particles. An organic positive temperature coefficient thermistor having an organic material layer which is not covalently bonded to particles and is incompatible with the polymer organic matrix at a molecular level. 2. The organic positive temperature coefficient thermistor according to claim 1, wherein the organic substance is a material having no reactivity with a polymer organic matrix. 3. The organic positive temperature coefficient thermistor according to claim 1, wherein the conductive metal particles contain nickel or copper. 4. The organic positive temperature coefficient thermistor according to claim 1, wherein the high molecular weight organic matrix is a thermoplastic polymer. 5. The method according to claim 1, further comprising a low molecular weight organic compound.
An organic positive temperature coefficient thermistor of any one of to 4. 6. The organic positive temperature coefficient thermistor according to claim 1, wherein the conductive metal particles have spike-shaped protrusions. 7. The organic positive temperature coefficient thermistor according to claim 1, wherein the organic substance is a material having biodegradability. 8. A method for producing an organic positive temperature coefficient thermistor, which is obtained by previously treating the surface of a conductive metal particle with an organic substance, and mixing and dispersing the conductive metal particle with a polymer organic matrix to obtain an organic positive temperature coefficient thermistor. 9. The organic material is a material different from the polymer organic matrix, and is a material that is not covalently bonded to the conductive metal particles and is incompatible with the polymer organic matrix at the molecular level. Item 9. A method for manufacturing an organic positive temperature coefficient thermistor according to item 8. 10. The method for producing an organic positive temperature coefficient thermistor according to claim 8, wherein the organic substance is a material having no reactivity with a polymer organic matrix. 11. The method for manufacturing an organic positive temperature coefficient thermistor according to claim 8, wherein the conductive metal particles contain nickel or copper. 12. The method for producing an organic positive temperature coefficient thermistor according to claim 8, wherein the high molecular weight organic matrix is a thermoplastic polymer. 13. The method for producing an organic positive temperature coefficient thermistor according to claim 8, wherein the high molecular weight organic matrix further contains a low molecular weight organic compound. 14. The method for manufacturing an organic positive temperature coefficient thermistor according to claim 8, wherein the conductive metal particles have spike-shaped protrusions. 15. The method for manufacturing an organic positive temperature coefficient thermistor according to claim 8, wherein the organic substance is a material having biodegradability.