JP3506628B2 - Manufacturing method of organic positive temperature coefficient thermistor - Google Patents

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 or an overcurrent protection element and has a PTC (positive temperature coefficient) whose resistance value increases as temperature rises.
organic positive temperature coefficient thermistor having a characteristic of resistivity.

[0002]

2. Description of the Related Art Organic positive temperature coefficient thermistors in which conductive particles are dispersed in a crystalline polymer are known in the art,
U.S. Pat. Nos. 3,243,753 and 3,351
No. 882 specification and the like. The increase in resistance is
It is considered that the crystalline polymer expands with melting and cuts the conductive path of the conductive fine particles.

The organic positive temperature coefficient thermistor can be used for a self-regulating heating element, an overcurrent protection element, a temperature sensor and the like. The characteristics required for these are that the room temperature resistance value during non-operation is sufficiently low, that the rate of change between the room temperature resistance value and the resistance value during operation is sufficiently large, and the change in resistance value due to repeated operation is small. To be

In order to satisfy such required characteristics, it has been proposed to incorporate a low molecular weight organic compound such as wax in a polymer matrix. Examples of such an organic positive temperature coefficient thermistor include polyisobutylene /
Paraffin wax / carbon black (F. Bueche, J.
Appl.Phys., 44 , 532, 1973), styrene-butadiene rubber / paraffin wax / carbon black system (F.Buech
e, J.Polymer Sci., 11 , 1319,1973), low density polyethylene / paraffin wax / carbon black system (K.Ohe et al.
al., Jpn.J.Appl.Phys., 10 , 99, 1971). Further, Japanese Patent Publication No. 62-16523, Japanese Patent Publication No. 7-109786, No. 7-48396, JP-A Nos. 62-51184, 62-51185, 62-51186, 62-511.
87, JP-A 1-231284, 3-132001, 9-27383
No. 9-69410 discloses a self-temperature control heating element using an organic positive temperature coefficient thermistor using a low molecular weight organic compound, a current limiting element, and the like. In these cases, it is considered that the resistance value increases due to the melting of the low molecular weight organic compound.

Therefore, the advantage of using a low-molecular weight organic compound is that the crystallinity is generally higher than that of a polymer, so that the rise when the resistance increases due to temperature rise becomes sharp. In addition, since a polymer is likely to be in a supercooled state, it usually exhibits a hysteresis such that the temperature at which the resistance value decreases at the time of temperature decrease becomes lower than the temperature at which the resistance value increases at the time of temperature increase. By using this, it is possible to suppress this hysteresis. Moreover,
If low molecular weight organic compounds having different melting points are used, the temperature at which the resistance increases (operating temperature) can be easily controlled. In the case of a 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 is changed, so that the sufficient PTC is obtained. The characteristics may not be obtained. This tends to be more pronounced, especially when setting the operating temperature below 100 ° C.

In the above literature, Jpn.J.Appl.Phys., 10 , 9
9,1971 shows an example in which the specific resistance value (Ω cm) is increased 10 ⁸ times. However, the resistivity at room temperature is 10 ⁴ Ω cm
It is very high, and it is not practical to use for overcurrent protection device and temperature sensor. Further, the increase in the resistance value (Ω) or the specific resistance value (Ω cm) in other documents is in the range of 10 times or less to 10 ⁴ times, and the room temperature resistance is not sufficiently low.

On the other hand, in the conventional organic positive temperature coefficient thermistor including the above-mentioned ones, carbon black and graphite have been often used as conductive particles, but when the carbon black filling amount is increased to lower the initial resistance value. There is a drawback that a sufficient resistance change rate cannot be obtained, and a low initial resistance and a large resistance change rate cannot both be achieved. In addition, although there is an example in which general metal particles are used as the conductive particles, it is similarly difficult to achieve both a low initial resistance and a large resistance change rate.

As a method for solving the above-mentioned drawbacks, a method of using conductive particles having spike-shaped protrusions is disclosed in Japanese Patent Laid-Open No. HEI 5/1993.
-47503 gazette. More specifically, it is disclosed that polyvinylidene fluoride is used as the crystalline polymer, and spike-shaped Ni powder is used as the conductive particles having spike-shaped protrusions. Further, US Pat. No. 5,378,407 also discloses a filament-shaped Ni having spike-like protrusions, and a polyolefin, an olefin-based copolymer, or a fluoropolymer.

Although these compounds improve the effect of achieving both low initial resistance and large resistance change, they have insufficient hysteresis and are not suitable for applications such as temperature sensors. Moreover, the operating temperature of these is 100 ° C. or higher. There are some operating temperatures of 60 to 90 ° C, but these are not practical because the characteristics due to repeated operation are unstable. Considering the use as a protective element for secondary batteries, electric blankets, toilet seats, heaters for vehicle seats, etc., operating temperature of 100 ° C. or higher poses a great danger to the human body. Considering safety for human body, operating temperature is 1
It must be below 00 ° C. Recently, the organic PTC thermistor is in high demand as an overcurrent protection device for mobile phones, personal computers, etc., but its operating temperature is usually 4
It is about 0 to 90 ° C, and from this aspect the operating temperature is 40 ° C.
A thermistor having a temperature of 100 ° C. or above is required.

As described above, an organic positive temperature coefficient thermistor which exhibits good characteristics at an operating temperature of less than 100 ° C. and has stable characteristics has not been obtained so far.

The present inventors have proposed, in Japanese Patent Application No. 9-350108, an organic positive temperature coefficient thermistor containing a thermoplastic polymer matrix, a low molecular weight organic compound and conductive particles having spike-like protrusions. . This one has a sufficiently low room temperature specific resistance of 8 × 10 ⁻² Ωcm or less, a large resistance change rate of 10 digits or more during operation and non-operation, and has a small hysteresis of a temperature-resistance curve. Moreover, the operating temperature is 40 ° C. or higher and lower than 100 ° C.

However, this thermistor has insufficient characteristic stability, and the resistance increases remarkably under high temperature and high humidity. This is due to the low melting point and low melt viscosity of the low molecular weight organic compound, segregation of the low molecular weight organic compound of the operating substance occurs during repeated melting-solidification during operation, and the polymer matrix, low molecular weight organic compound and It is considered that the characteristics are deteriorated due to changes in the dispersed state of the conductive particles. The problem of such characteristic stability is an important problem in using a low molecular weight organic compound as an operating material.

[0013]

The object of the present invention is to obtain a sufficiently low room temperature resistance, a large rate of resistance change during operation and non-operation, to operate below 100 ° C., and to obtain a hysteresis of the temperature-resistance curve. An object of the present invention is to provide an organic positive temperature coefficient thermistor which is small, whose operating temperature can be easily adjusted, and whose characteristic stability is high.

[0014]

The above object is achieved by the present invention described below. (1) A thermoplastic polymer matrix, a low molecular weight organic compound having a melting point of 40 ° C. or higher and lower than 100 ° C., and conductive particles having spike-like protrusions are kneaded, and the kneaded product is mixed with a vinyl group or a (meth) acryloyl group. A method for producing an organic positive temperature coefficient thermistor, which is obtained by cross-linking with a silane coupling agent having an alkoxy group to obtain an organic positive temperature coefficient thermistor. (2) The method for producing an organic positive temperature coefficient thermistor according to (1), wherein the silane coupling agent is vinyltrimethoxysilane, vinyltriethoxysilane, γ-methacryloxypropylmethoxysilane or γ-methacryloxypropylethoxysilane. (3) The low molecular weight organic compound has a weight average molecular weight of 1,
The method for producing an organic positive temperature coefficient thermistor according to the above (1) or (2), which is 000 or less. (4) The method for producing an organic positive temperature coefficient thermistor according to any of (1) to (3) above, wherein the low molecular weight organic compound is a petroleum wax. (5) The method for producing an organic positive temperature coefficient thermistor according to any one of the above (1) to (4), wherein the conductive particles having the spike-like protrusions are connected in a chain. (6) The method for producing an organic positive temperature coefficient thermistor according to any one of (1) to (5) above, wherein the thermoplastic polymer matrix is a polyolefin (7) The organic positive electrode according to (6), wherein the polyolefin is a high-density polyethylene. Method of manufacturing characteristic thermistor. (8) The method for producing an organic positive temperature coefficient thermistor according to (7) above, wherein the high-density polyethylene has a melt flow rate of 3.0 g / 10 min or less. (9) The above (1) to which the operating temperature is less than 100 ° C.
8. The method for producing an organic positive temperature coefficient thermistor according to any one of (8).

[0015]

The organic positive temperature coefficient thermistor of the present invention comprises a thermoplastic polymer matrix, a low molecular weight organic compound having a melting point of 40 ° C. or higher and lower than 100 ° C., and conductive particles having spike-like protrusions. A silane coupling agent having a group or a (meth) acryloyl group and an alkoxy group is crosslinked.

In the present invention, the conductive particles having spike-like protrusions are used, so that the tunnel current easily flows due to the shape, and a lower room temperature resistance is obtained as compared with the spherical conductive particles. Further, since the distance between the conductive particles is larger than that of the spherical particles, a large resistance change can be obtained during operation.

Further, a low molecular organic compound is contained in a thermoplastic polymer matrix, preferably polyolefin,
By melting the low molecular weight organic compound, the PTC characteristic in which the resistance value increases as the temperature rises is exhibited, so that the hysteresis of the temperature-resistance curve becomes smaller than that in the case where only the polymer matrix is used. Further, as compared with the case where the operating temperature is adjusted by utilizing the change in melting point of the polymer, the operating temperature can be easily adjusted by using a low molecular weight organic compound having a different melting point. Moreover, in the present invention,
The operating temperature is set to less than 100 ° C. by using a low molecular weight organic compound having a melting point of 40 ° C. or more and less than 100 ° C. as an operating material.

Then, a mixture of a thermoplastic polymer matrix, a low molecular weight organic compound and conductive particles having spike-like protrusions is treated with a silane coupling agent having a vinyl group or a (meth) acryloyl group and an alkoxy group. By the cross-linking treatment, the stability of characteristics during storage and repeated operation is significantly improved.

By forming a cross-linking structure between the polymer matrix and the low molecular weight organic compound, the shape of the polymer matrix is maintained, and aggregation and segregation of the low molecular weight organic compound that repeatedly melts and solidifies during operation are suppressed, and the organic positive electrode is suppressed. It is considered that the characteristic stability of the characteristic thermistor is improved. Further, it is considered that the coupling agent not only crosslinks the above organic matrix but also forms a chemical bond between the organic-inorganic material and has a great effect on the modification of the interface. By treating the mixture of the thermoplastic polymer matrix, the low molecular weight organic compound and the conductive particles with the silane coupling agent, the polymer matrix-conductive particle interface, the low molecular weight organic compound-conductive particle interface, Molecular matrix
It is considered that the interface of the metal electrode and the interface of the low molecular weight organic compound-metal electrode are strengthened, and further contribute to the stable improvement of the characteristics.

In the present invention, the coupling agent is grafted to the thermoplastic polymer matrix and the low molecular weight organic compound through a group having a carbon double bond (C═C),
Then, it is crosslinked by dealcoholization and dehydration condensation in the presence of water. The reaction formula is shown below.

[0021]

[Chemical 1]

Other cross-linking methods include a chemical cross-linking method using an organic peroxide and a radiation cross-linking method by electron beam irradiation. However, in the chemical crosslinking method, it is necessary to perform heat treatment at a temperature higher than the melting point of the polymer matrix after molding, it is difficult to maintain the shape, and the element may be thermally deteriorated. The radiation crosslinking method requires expensive equipment,
Moreover, especially when the element is thick, it is difficult to sufficiently crosslink the inside, and it is difficult to uniformly crosslink.

It has already been proposed to carry out a silane crosslinking treatment. In a system that does not use a low molecular weight organic compound, for example, in JP-A-59-60904, 15 to 50 wt% of conductive carbon is contained in a water-crosslinked silyl-modified polyolefin having a gel fraction of 60% or more. Semi-conductive compositions that are uniformly dispersed are disclosed. Japanese Patent Laid-Open No. 4-6
In Japanese Patent No. 8501, a conductive powder is dispersed in a water-crosslinked polymer, specifically, an organosilane-modified polymer.
A resistor having TC characteristics is disclosed. Japanese Patent Laid-Open No. 4-
No. 157701 discloses a polymer (polyolefin resin) which is not water-crosslinked and a conductive powder (carbon black).
Disclosed is a resistor having PTC characteristics, which is obtained by mixing and mixing, and further adding a water-crosslinkable polymer (polyethylene having an active silane group) and mixing.

However, these do not contain low molecular weight organic compounds, the polyolefin is the working substance, and the working temperature is 10
High above 0 ° C. Further, since carbon black or the like is used for the conductive particles, the room temperature resistivity is as high as 10 ¹ Ωcm or more, the resistance change rate is about 2 to 5 digits, and the characteristics are insufficient. In these publications, there is no suggestion of stability of characteristics.

Further, Japanese Patent Publication No. 3-74481 discloses that
A heating element resin composition comprising a polyolefin-based crystalline polymer resin, a silane-based compound, an organic peroxide, a stabilizer and a conductive powder, specifically carbon is disclosed. Chemically bond a silane compound to a crystalline polymer in the presence of a stabilizer using an organic peroxide, and further form a chemical bond with a functional group on the carbon surface, or improve the affinity and unevenly distribute carbon. However, since the resistance is prevented from changing and the silane compound is chemically bonded to improve the adhesiveness with the electrode material, it is said that the stability of the characteristics is high. In JP-A-4-345785, a conductive powder is dispersed in a crystalline polymer composition to prepare a conductive composition and crosslinked, and the crosslinked product is pulverized and surface-treated with a silane coupling agent. However, a resistor having a positive temperature coefficient of resistance obtained by mixing and dispersing this in a crystalline polymer composition is disclosed. By applying a silane coupling agent to the particulate conductive composition, a chemical bond is formed between the binder polymer and the metal electrode, so that the bond becomes strong and a conductive path is formed when current is applied. In order to suppress the occurrence of cracks in the conductive powder due to the thermal expansion due to heat generation by energization, it is said that the resistance increase of the heating element can be suppressed and the life of the heating element can be extended.

However, these are only subjected to surface treatment, and the improvement in characteristic stability is small,
According to the present invention, stable characteristics can be obtained over a long period of time. Further, in both of the above publications, the initial characteristics are not shown in the examples, and it is unclear how much the test deteriorates. Further, since carbon is used as the conductive powder, the low initial resistance and the large resistance change rate are not compatible with each other as in the present invention. Further, these materials also do not contain a low molecular weight organic compound, the crystalline polymer resin is an operating substance, and the operating temperature is high at 100 ° C. or higher.

Further, it has been proposed to perform silane crosslinking treatment even in a system using a low molecular weight organic compound.

Japanese Unexamined Patent Publication (Kokai) No. 1-231284 discloses a self-temperature control type heating element which comprises a water-crosslinkable polyolefin, more specifically, an organosilane-modified polyolefin, and a conductive filler and a low molecular weight polyolefin wax. Has been done. Japanese Unexamined Patent Publication No. 9-69410 discloses a current limiting element obtained by mixing a water-crosslinkable polyolefin, specifically, an organosilane-modified polyolefin with a conductive filler and a low molecular weight polyolefin wax. However, in these, a water-crosslinked polyolefin is mixed with a low molecular weight polyolefin wax, and the polymer matrix and the low molecular weight organic compound are not in a crosslinked structure as in the present invention. Therefore, the improvement in the stability of the characteristics is very small, and the high characteristics cannot be maintained for a long period of time as much as that of the present invention. In these publications, there is no suggestion of stability of characteristics. In addition, JP-A-9-694
In JP-A-10, the conductive filler is carbon black, graphite, carbon fiber, metal powder (for example,
Ni) is used, and no mention is made of conductive particles having spike-like protrusions. Therefore, this one, but the room temperature resistivity is low as 10 ^-1 ~10 ⁰ Ω cm, the resistance change rate is 3 digits or less and small, have sufficient properties for use in over-current protection device and a temperature sensor Absent. In JP-A-1-231284, since carbon black is used as the conductive filler, the room temperature resistivity is 10
^It is as high as ¹ to 10 ² Ω cm, and the rate of resistance change is as small as about 3 digits.
It does not have sufficient characteristics. Further, these are operating substances, both of the organosilane-modified polyolefin and the low molecular weight polyolefin wax, and the operating temperature is 100 to 16 as the melting point.
Since a 0 ° C. wax is used, it is higher than that of the present invention and does not operate below 100 ° C. In the present invention, since only the low molecular weight organic compound having a melting point of 40 ° C. or higher and lower than 100 ° C. is used as the operating substance, the operating temperature can be lowered to less than 100 ° C.

[0029]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below. The organic positive temperature coefficient thermistor of the present invention comprises a thermoplastic polymer matrix, a low molecular weight organic compound having a melting point of 40 ° C. or higher and lower than 100 ° C., and conductive particles having spike-shaped protrusions, and a mixture of these with a vinyl group or ( It is a product obtained by crosslinking treatment with a silane coupling agent having a (meth) acryloyl group and an alkoxy group.

The melting point of the thermoplastic polymer matrix is preferably higher than the melting point of the low molecular weight organic compound, preferably 30 ° C., in order to prevent flow of the low molecular weight organic compound due to melting during operation, deformation of the element body and the like. Or more, more preferably 3
It is preferable that the temperature is higher than 0 ° C and lower than 110 ° C. The melting point of the thermoplastic polymer matrix is usually 70 to 200 ° C.
Is preferred.

The thermoplastic polymer matrix may be crystalline or amorphous, and may be polyethylene, ethylene-vinyl acetate copolymer, polyalkyl acrylate such as polyethyl acrylate, polyalkyl (meth) acrylate such as polymethyl (meth) acrylate, or the like. Fluorine-based polymers such as polyolefin, polyvinylidene fluoride, polytetrafluoroethylene, polyhexafluoropropylene, copolymers thereof, polyvinyl chloride, polyvinylidene chloride, chlorinated polyvinyl chloride, chlorinated polyethylene, chlorinated polypropylene, etc. Examples thereof include halogen-based polymers such as chlorine-based polymers such as copolymers, polystyrene, and thermoplastic elastomers. The polyolefin may be a copolymer. Specifically, high density polyethylene [for example, trade name HiZex 2100JP
(Manufactured by Mitsui Petrochemical Co., Ltd., trade name Marlex 6003 (manufactured by Philips), etc.), low density polyethylene [eg,
Product name LC500 (manufactured by Nippon Polychem), product name DYNH
-1 (manufactured by Union Carbide Co.) and the like], medium density polyethylene [for example, product name 2604M (manufactured by Gulf Co., Ltd.)],
Ethylene-ethyl acrylate copolymer [for example, trade name DPD6169 (manufactured by Union Carbide Co.) and the like],
Ethylene-acetic acid copolymer [eg, trade name Novatec EVALV241 (manufactured by Japan Polychem), etc.], polyvinylidene fluoride [eg, trade name Kynar711 (manufactured by Elf Atchem), etc.], vinylidene fluoride-tetrafluoroethylene-hexafluoropropylene copolymer [For example, trade name KynarADS (manufactured by Elf Atchem) and the like] and the like can be mentioned. The weight average molecular weight Mw of such a thermoplastic polymer is preferably about 10,000 to 5,000,000.

Polyolefin is preferably used as the thermoplastic polymer matrix, and high density polyethylene is particularly preferably used. The high-density polyethylene refers to one having a density of 0.942 g / cm ³ or more, which is produced by coordinated anionic polymerization using a transition metal catalyst under medium or low pressure of several tens of atmospheres or less and is linear.

The melt flow rate (MFR) of high density polyethylene as defined by ASTM D1238 is 3.0 g / 10.
min or less, particularly preferably 1.5 g / 10 min or less. MF
If R is higher than this, the melt viscosity tends to be too low and the stability of properties tends to be poor. There is no particular lower limit of MFR,
Usually, it is about 0.1 g / 10 min.

The thermoplastic polymer matrix of the present invention comprises
Although only one kind may be used or two or more kinds may be used in combination, it is preferable to use only high density polyethylene having MFR of 3.0 g / 10 min or less.

The low molecular weight organic compound used in the present invention is a crystalline substance having a molecular weight of up to about 1000, preferably 200 to 800, and is not particularly limited as long as it has a melting point mp of 40 ° C. or higher and lower than 100 ° C. Those that are solid at a temperature of about 25 ° C.) are 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) ) Etc.,
These can be used alone as a low molecular weight organic compound. 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.

Since the present invention aims at a thermistor having an operating temperature of less than 100 ° C., a low molecular weight organic compound having a melting point mp of 40 ° C. or more and less than 100 ° C. is used. Examples thereof include paraffin wax (eg, tetracosane C ₂₄ H ₅₀ ; mp 49 to 52 ° C.,
Hexatriacontane C ₃₆ H ₇₄ ; mp 73 ° C, trade name H
NP-10 (manufactured by Nippon Seiro Co., Ltd.); mp75 ° C., HNP-3
(Manufactured by Nippon Seiro Co., Ltd.); mp66 ° C., etc., Microcrystalline wax (for example, trade name Hi-Mic-108)
0 (manufactured by Nippon Seiro Co., Ltd.); mp 83 ° C., Hi-Mic-10
45 (manufactured by Nippon Seiro Co., Ltd.); mp 70 ° C., Hi-Mic 20
45 (manufactured by Nippon Seiro Co., Ltd.); mp 64 ° C., Hi-Mic 30
90 (manufactured by Nippon Seiro Co., Ltd.); mp 89 ° C., serrata 104
(Nippon Petroleum Refining Co., Ltd.); mp96 ° C., 155 microwax (Nippon Petroleum Refining Co., Ltd.); mp70 ° C.), fatty acids (eg, behenic acid (Nippon Seika); mp81 ° C., stearic acid (Nippon Seika) ); Mp72 ° C., palmitic acid (Nippon Seika); mp64 ° C., etc.), fatty acid ester (eg, arachidic acid methyl ester (Tokyo Kasei);
mp48 ° C.) and fatty acid amides (eg, oleic acid amide (Nippon Seika); mp76 ° C.). Further, a blended wax obtained by blending paraffin wax with a resin and a blended wax mixed with microcrystalline wax and having a melting point of 40 ° C. or more and less than 100 ° C. can 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 conductive particles having spike-like projections used in the present invention are formed of primary particles each having a sharp projection, and have a height of 1/3 to 1/50 of the particle diameter. There are multiple cone-shaped spike-shaped protrusions of one particle (usually 1
0 to 500) exist. The material is metal,
Ni or the like is particularly preferable.

Such conductive particles may be powders in which one particle and one particle are individually present.
It is preferable that about 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 a spherical nickel powder having spike-shaped protrusions, which has a trade name of 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.

The latter, which is preferably used, is a filamentary nickel powder, which has a trade name of IN.
It is commercially available as CO Type 210, 255, 270, 287 Nickel Powder (manufactured by Inco), and among these, INCO Type 255, 270, 287 is preferable. The average particle size of the primary particles is preferably 0.1 μm or more, more preferably 0.5 or more and 4.0 μm.
It is about m or less. Among these, the average particle size of the primary particles is most preferably 1.0 or more and 4.0 μm or less, and 50% by weight or less of particles having an average particle size of 0.1 μm or more and less than 1.0 μm may be mixed therein. The apparent density is 0.3-
About 1.0 g / cm ³ , specific surface area 0.4-2.5 m ² / g
It is a degree.

The average particle size in this case is measured by the Fish-Subsieve method.

Such conductive particles are described in JP-A-5-47503 and US Pat. No. 5,378,407.

As the conductive particles, in addition to the conductive particles having spike-like protrusions, carbon-based conductive particles such as carbon black, graphite, carbon fiber, metal-coated carbon black, graphitized carbon black, and metal-coated carbon fiber. Particles, metallic particles in the form of spheres, flakes, fibers, etc., dissimilar metal-coated metal (silver-coated nickel, etc.) particles, ceramics such as tungsten carbide, titanium nitride, zirconium nitride, titanium carbide, titanium boride, molybdenum silicide, etc. Conductive particles, and JP-A-8-31554 and JP-A-8-31554
The conductive potassium titanate whiskers described in JP-A-273383 may be added. Such conductive particles are similar to those of conductive particles having spike-shaped protrusions.
It is preferable to set the content to be not more than weight%.

The mixing ratio of the thermoplastic polymer matrix to the low molecular weight organic compound in the present invention is preferably 0.2 to 4 times the weight of the low molecular weight organic compound with respect to the thermoplastic polymer 1. If this mixing ratio becomes small and the amount of the low molecular weight organic compound becomes small, it becomes difficult to obtain a sufficient resistance change rate. On the contrary, when the amount of the low molecular weight organic compound becomes large and the amount of the low molecular weight organic compound increases, the element body is largely deformed when the low molecular weight compound is melted, and mixing with the conductive particles becomes difficult. The conductive particles are preferably 2 to 5 times the total weight of the polymer matrix and the low molecular weight organic compound. If this mixing ratio becomes small and the amount of conductive particles becomes small, it becomes impossible to sufficiently lower the room temperature resistance during non-operation. On the contrary, when the amount of the conductive particles is large, it becomes difficult to obtain a large rate of resistance change, and it becomes difficult to uniformly mix the particles, and it becomes difficult to obtain a reproducible resistance value.

The kneading may be carried out at a temperature not lower than the melting point of the thermoplastic polymer matrix (preferably melting point + 5 to 40 ° C.). Specifically, a known method may be used, and kneading may be performed for about 5 to 90 minutes with a mill or the like. Further, the thermoplastic polymer and the low molecular weight organic compound may be melt-mixed or dissolved in a solvent in advance and mixed. Then, a silane coupling agent is added to this kneaded product to perform a crosslinking treatment.

The silane-based coupling agent can be condensed by dealcoholation and dehydration and has an affinity with an alkoxy group capable of chemically bonding with an inorganic oxide and with an organic material.
It has a vinyl group or a (meth) acryloyl group chemically bonded in the molecule. As a silane coupling agent,
C = C bond-containing trialkoxysilane.

The alkoxy group preferably has a small number of carbon atoms, and a methoxy group and an ethoxy group are particularly preferable. The group containing a C = C bond is a vinyl group or a (meth) acryloyl group, and a vinyl group is preferable. These groups are directly S
Even if bonded to i, S is bonded through a carbon chain having 1 to 3 carbon atoms.
It may be bonded to i.

The silane coupling agent is preferably liquid at room temperature.

Specific examples of the silane coupling agent include vinyltrimethoxysilane, vinyltriethoxysilane, vinyltris (β-methoxyethoxy) silane, γ- (meth) acryloxypropyltrimethoxysilane, γ- ( Examples thereof include (meth) acryloxypropyltriethoxysilane, γ- (meth) acryloxypropylmethyldimethoxysilane, and γ- (meth) acryloxypropylmethyldiethoxysilane. Of these, vinyltrimethoxysilane and vinyltriethoxysilane are preferable.

The coupling treatment is carried out in the kneaded product of the thermoplastic polymer matrix, the low molecular weight organic compound and the conductive particles, with 0.1 to 5% by weight of silane based on the total weight of the thermoplastic polymer and the low molecular weight organic compound. Drop the system coupling agent,
After mixing well, it is water-crosslinked. When the amount of the coupling agent is smaller than that, the effect of the crosslinking treatment becomes small, and when the amount of the coupling agent is large, no change is observed in the effect. When using a silane coupling agent having a vinyl group, 5 to 20% by weight of the coupling agent of an organic peroxide, for example,
2,2-di- (t-butylperoxy) butane, dicumyl peroxide, 1,1-di-t-butylperoxy-3,3,5-trimethylcyclohexane, etc. were mixed together and the vinyl group was added. Then, the organic substance, that is, the thermoplastic polymer and the low molecular weight organic compound are grafted. The silane coupling agent is added after the thermoplastic polymer, the low molecular weight organic compound, and the conductive particles are sufficiently and uniformly kneaded.

The kneaded product is press-molded into a sheet having a predetermined thickness and subjected to a crosslinking treatment in the presence of water. Specifically, a metal carboxylate such as dibutyltin dilaurate, dioctyltin dilaurate, tin acetate, tin octoate, or zinc octoate is used as a catalyst, and the compact is immersed in warm water for 6 to 8 hours. It is also possible to knead the catalyst in the thermistor body and carry out crosslinking under high temperature and high humidity. Among them, dibutyltin dilaurate is preferably used as the catalyst. The crosslinking temperature is preferably below the melting point of the low molecular weight organic compound in order to enhance the stability of characteristics such as repeated operation. And after the cross-linking treatment,
The molded body is dried, and a metal electrode such as Cu or Ni is thermocompression bonded to obtain a thermistor element.

The organic positive temperature coefficient thermistor of the present invention has a low initial resistance when not in operation, and its room temperature specific resistance value is 10%.
^-2 is about to 10 ⁰ Omega cm, a steep rise in resistance at the time of operation, the rate of resistance change over the operation from during non-operation is as large as 6 digits or more. Also, 80 ° C 80% RH
After 500 hours (20 years or more in Tokyo, 10 years or more in Naha), its characteristics hardly deteriorate.

Further, the organic thermistor of the present invention may be mixed with an antioxidant in order to prevent thermal deterioration of the polymer matrix and the low molecular weight organic compound, such as phenols, organic sulfurs and phosphites ( Organophosphorus) or the like is 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 halide, melamine resin described in JP-A-6-76511, benzoic acid, dibenzylidene sorbitol, metal benzoate described in JP-A-6-76511, and JP-A-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 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 inhibitor, 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,
It is preferably 25% by weight or less based on the total weight of the low molecular weight organic compound and the conductive particles.

[0066]

EXAMPLES Examples of the present invention will be shown below together with comparative examples to specifically describe the present invention. <Example 1> High-density polyethylene as a polymer matrix (manufactured by Nippon Polychem, trade name HY540; MFR1.
0g / 10min, melting point 135 ℃, as a low molecular weight organic compound microcrystalline wax (Nippon Seiwa Co., Ltd., H
i-Mic-1080; melting point 83 ° C.), and filamentous nickel powder (manufactured by INCO, trade name Type 255 nickel powder) was used as the conductive particles. The average particle diameter of the conductive particles is 2.2 to 2.8 μm, the apparent density is 0.5 to 0.65 g / cm ³ , and the specific surface area is 0.68 m ² / g.

High-density polyethylene and 4 times its weight of nickel powder were kneaded in a mill at 150 ° C. for 5 minutes.
Then, 1.5 times the weight of the high-density polyethylene wax and 4 times the weight of the nickel powder were further added and kneaded. As a silane coupling agent, 1.0% by weight of the total weight of polyethylene and wax is vinyltriethoxysilane (manufactured by Shin-Etsu Chemical Co., Ltd., product name KBE10.
03) and 20% by weight of vinyltriethoxysilane as an organic peroxide, 2,2-di- (t-butylperoxy) butane (manufactured by Kayaku Akzo, product name Trigonox D-
T50) was added dropwise to the kneaded product and kneaded for 60 minutes.

This kneaded product was formed into a sheet having a thickness of 1.1 mm at 150 ° C. by a hot press machine. Then, this sheet was immersed in 20% by weight of dibutyltin dilaurate (manufactured by Tokyo Kasei) in an emulsion water solution and subjected to a crosslinking treatment at 65 ° C. for 8 hours.

After the crosslinked sheet was dried, both sides were sandwiched by Ni foil electrodes having a thickness of 30 μm, and the Ni foil was pressure-bonded to the sheet at 150 ° C. by using a heat press machine to form a molded product having a thickness of 1 mm. Obtained. Then, this was punched into a disk shape having a diameter of 10 mm to obtain a thermistor element. A cross-sectional view of this thermistor element is shown in FIG. As shown in FIG. 1, the thermistor element has a thermistor element body 12, which is a kneading molded sheet containing a low molecular weight organic compound, a polymer matrix and conductive particles, sandwiched between electrodes 11 formed of Ni foil. Is.

This element was heated and cooled in a constant temperature bath, and the resistance value was measured by the 4-terminal method at a predetermined temperature to obtain a temperature-resistance curve. The result is shown in FIG.

Room temperature (25 ° C.) resistance value is 2.0 × 10 ⁻³ Ω
At (1.6 × 10 ^-2 Ω cm), a sharp increase in resistance was observed around 75 ° C., and the maximum resistance value was 1.6 × 10 ⁵ Ω (1.
3 × 10 ⁶ Ωcm), and the resistance change rate was 7.9 digits.

This device was left in a constant temperature and constant humidity chamber set at 80 ° C. and 80% RH for an acceleration test. FIG. 3 shows the room temperature resistance and the resistance change rate at each standing time. After 500 hours, the room temperature (25 ° C.) resistance value is 5.3 × 10 ⁻³ Ω (4.2
× 10 ^-2 Ω cm), resistance change rate is 7.2 digits, room temperature resistance value, resistance change rate is almost unchanged
The characteristics were retained.

The accelerated test at 80 ° C. and 80% RH for 500 hours was converted to absolute humidity in Tokyo for 20 years or more and in Naha as 1
Equivalent to a humidity life of 0 years or more. Regarding absolute humidity conversion, from life at 80 ° C and 80% RH, 25 ° C and 60%
The calculation of the life under the RH condition will be described as an example. 80
Absolute humidity of ℃ 80% RH 232.5g / m ³ , 25 ℃
The absolute humidity at 60% RH is 13.8 g / m ³ . The acceleration constant is set to 2 and is calculated by the following calculation formula. (232.5 / 13.8) ² ≈ 283.85 In this case, the life under conditions of 80 ° C and 80% RH is 500 hours.
Then, the life under the condition of 25 ° C. and 60% RH is 500 hr × 283.85 = 141925 hr≈5914 days≈16.2 years. Regarding the humidity in Tokyo and Naha, the monthly average relative humidity was converted into absolute humidity, and the total was taken as the annual humidity.

Example 2 Paraffin wax (manufactured by Nippon Seiro Co., Ltd., trade name HNP) as a low molecular weight non-water-soluble organic compound
A thermistor element was obtained in the same manner as in Example 1 except that -10, melting point 75 ° C) was used. Then, in the same manner as in Example 1, a temperature-resistance curve was obtained and an acceleration test was performed.

The room temperature (25 ° C.) resistance value of this element is 2.0.
At × 10 ^-3 Ω (1.6 × 10 ^-2 Ω cm), a sharp increase in resistance was observed around 75 ° C, and the maximum resistance value was 7.7 × 10
^It becomes ⁶ Ω (6.0 × 10 ⁷ Ω cm), and the resistance change rate is 9.
It was 6 digits.

In the 80 ° C. 80% RH acceleration test, the room temperature resistance value after 500 hours was 6.2 × 10 ⁻³ Ω (4.9 × 10 ^−2).
Ω cm), resistance change rate is 8.7 digits, room temperature resistance value,
The rate of resistance change hardly changed, and sufficient PTC characteristics were maintained.

Example 3 High-density polyethylene (manufactured by Nippon Polychem, trade name HY42) as a polymer matrix
0: MFR 0.4 g / 10 min, melting point 134 ° C.) was used to obtain a thermistor element in the same manner as in Example 1. Then, in the same manner as in Example 1, a temperature-resistance curve was obtained and an acceleration test was performed.

The room temperature (25 ° C.) resistance value of this element is 4.0.
At × 10 ^-3 Ω (3.1 × 10 ^-2 Ω cm), a sharp increase in resistance was observed at around 75 ° C, and the maximum resistance value was 6.0 × 10.
⁴ Ω (4.7 × 10 ⁵ Ω cm), and the resistance change rate was 7.
It was two digits.

In the 80 ° C. 80% RH accelerated test, the room temperature resistance value after 500 hours was 7.5 × 10 ⁻³ Ω (5.9 × 10 ^−2).
Ω cm), resistance change rate is 6.5 digits, room temperature resistance value,
The rate of resistance change hardly changed, and sufficient PTC characteristics were maintained.

Comparative Example 1 A thermistor element was obtained in the same manner as in Example 1 except that the silane coupling agent and the organic peroxide were not added and the crosslinking treatment was not performed.

The temperature-resistance curve of this sample was obtained in the same manner as in Example 1. The resistance value of this element at room temperature (25 ° C) is 3.0 x 10 ^-3 Ω (2.4 x 10 ^-2 Ω cm) and 75 ℃.
A sharp rise in resistance was seen in the vicinity, and the maximum resistance value was 8.2.
It was × 10 ⁴ Ω (6.4 × 10 ⁵ Ωcm), and the resistance change rate was 7.4 digits.

In the same manner as in Example 1, 80 ° C. 80% RH
Then, the acceleration test of this device was performed. FIG. 4 shows the room temperature resistance and the resistance change rate at each standing time. After 500 hours, the room temperature resistance value was 3.4 × 10 ⁻² Ω (2.7 × 10 ⁻¹ Ω cm), which was more than 10 times the initial value, and the resistance change rate decreased to 5.4 digits.

Comparative Example 2 A thermistor element was obtained in the same manner as in Example 2 except that the silane coupling agent and the organic peroxide were not added and the crosslinking treatment was not performed. Then, in the same manner as in Example 1, a temperature-resistance curve was obtained and an acceleration test was performed.

The room temperature (25 ° C.) resistance value of this element is 2.0.
At × 10 ^-3 Ω (1.6 × 10 ^-2 Ω cm), a sharp increase in resistance was observed at around 75 ° C, and the maximum resistance value was 8.0 × 10.
^It becomes ⁷ Ω (6.3 × 10 ⁸ Ω cm), and the resistance change rate is 1
It was 0.6 digit.

In the 80 ° C. 80% RH acceleration test, the room temperature resistance value after 500 hours was 7.7 Ω (60.5 Ω cm), and the resistance change rate was 7.1 digits. Both the room temperature resistance value and the resistance change rate were remarkable. Deterioration was seen.

Comparative Example 3 Low density polyethylene (manufactured by Nippon Polychem, trade name LC50) as a polymer matrix
0; MFR 4.0 g / 10 min, melting point 106 ° C.) was used to obtain a thermistor element in the same manner as in Example 1. Then, in the same manner as in Example 1, a temperature-resistance curve was obtained and an acceleration test was performed.

The room temperature (25 ° C.) resistance value of this element is 3.0.
At × 10 ^-3 Ω (2.4 × 10 ^-2 Ω cm), a sharp increase in resistance was observed around 80 ° C, and the maximum resistance value was 1.0 × 10
^{It was 9} Ω (7.8 × 10 ⁹ Ω cm) or more, and the resistance change rate was 11 digits or more.

In the 80 ° C. 80% RH acceleration test, the maximum resistance value after 100 hours was 1.0 × 10 ⁹ Ω or more.
The room temperature resistance value was 7.0 × 10 ⁻¹ Ω (5.5 Ω cm), which was a remarkable increase.

<Comparative Example 4> High density polyethylene (manufactured by Nippon Polychem, trade name HJ36 as a polymer matrix
0; MFR 6.0 g / 10 min, melting point 131 ° C.) was used to obtain a thermistor element in the same manner as in Example 1. Then, in the same manner as in Example 1, a temperature-resistance curve was obtained and an acceleration test was performed.

The room temperature (25 ° C.) resistance value of this element was 3.8.
At × 10 ^-3 Ω (3.0 × 10 ^-2 Ω cm), a sharp increase in resistance was observed at around 75 ° C, and the maximum resistance value was 8.0 × 10.
^It becomes ⁶ Ω (6.3 × 10 ⁷ Ω cm), and the resistance change rate is 9.
It was three digits.

In the 80 ° C. 80% RH accelerated test, the room temperature resistance value after 500 hours was 6.4 × 10 ⁻³ Ω (5.0 × 10 ^−2).
Ω cm) did not change so much, but the resistance value increased with temperature, but the clear transition point of the resistance value seen in the early stage was not recognized, and the resistance value at 75 ° C was 1.3 x 10
^The rate of change from room temperature to ^-1 Ω was 1.3 digits.

Table 1 shows the room temperature resistance values and resistance change rates before and after the acceleration test of Examples 1 to 3 and Comparative Examples 1 to 4. In addition,
Polymer matrix melt flow rate (MFR),
The melting point mp of the low molecular weight organic compound is also shown.

[0093]

[Table 1]

In Examples 1 to 3, even when vinyltrimethoxysilane was used as the silane coupling agent, the same results as in Examples 1 to 3 using vinyltriethoxysilane were obtained. The same effect was obtained by using γ-methacryloxypropyltrimethoxysilane and γ-methacryloxypropyltriethoxysilane.

[0095]

According to the present invention, a sufficiently low room temperature resistance can be obtained, and the rate of change in resistance during operation and non-operation is large.
It is possible to provide an organic positive temperature coefficient thermistor which operates at a temperature of less than ° C, has a small hysteresis of the temperature-resistance curve, is easy to adjust the operating temperature, and has high characteristic stability.

[Brief description of drawings]

FIG. 1 is a schematic sectional view of an organic positive temperature coefficient thermistor element.

2 is a temperature-resistance curve of the thermistor element of Example 1. FIG.

FIG. 3 is a thermistor element of Example 1 at 80 ° C. and 80% RH.
The room temperature resistance and the rate of resistance change at each standing time in the acceleration test.

FIG. 4 is a thermistor element of Comparative Example 1 at 80 ° C. and 80% RH.
The room temperature resistance and the rate of resistance change at each standing time in the acceleration test.

[Explanation of symbols]

11 electrodes 12 Thermistor body

─────────────────────────────────────────────────── --- Continuation of the front page (56) References JP-A-9-69410 (JP, A) JP-A-5-47503 (JP, A) JP-A-10-116702 (JP, A) JP-A-7- 263202 (JP, A) JP 2-156502 (JP, A) JP 62-51184 (JP, A) JP 1-231284 (JP, A) JP 3-132001 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) H01C ^7/ 02-7/22

Claims (9)

(57) [Claims] 1. A thermoplastic polymer matrix having a melting point of 4
A silane coupling agent having a vinyl group or a (meth) acryloyl group and an alkoxy group is obtained by kneading a low-molecular organic compound having a temperature of 0 ° C. or more and less than 100 ° C. and conductive particles having spike-like protrusions. A method for producing an organic positive temperature coefficient thermistor, which is obtained by cross-linking with an organic positive temperature coefficient thermistor. 2. The silane coupling agent is vinyltrimethoxysilane or vinyltriethoxysilane, γ
A method for producing an organic positive temperature coefficient thermistor according to claim 1, which is -methacryloxypropylmethoxysilane or γ-methacryloxypropylethoxysilane. 3. The method for producing an organic positive temperature coefficient thermistor according to claim 1, wherein the low molecular weight organic compound has a weight average molecular weight of 1,000 or less. 4. The method for producing an organic positive temperature coefficient thermistor according to claim 1, wherein the low molecular weight organic compound is a petroleum wax. 5. The method for producing an organic positive temperature coefficient thermistor according to claim 1, wherein the conductive particles having the spike-shaped protrusions are connected in a chain. 6. The method for producing an organic positive temperature coefficient thermistor according to claim 1, wherein the thermoplastic polymer matrix is polyolefin. 7. The method for manufacturing an organic positive temperature coefficient thermistor according to claim 6, wherein the polyolefin is high density polyethylene. 8. The method for manufacturing an organic positive temperature coefficient thermistor according to claim 7, wherein the high-density polyethylene has a melt flow rate of 3.0 g / 10 min or less. 9. The operating temperature is less than 100 ° C.
[8] A method for manufacturing an organic positive temperature coefficient thermistor.