JP3168262B2 - Circuit protection device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric material, and more particularly, to a property of rapidly increasing electric resistance in a relatively narrow temperature range with a rise in temperature (PTC characteristic (Positive).
(Temperature Coefficient))
The present invention relates to an organic PTC composition and a circuit protection device used for a circuit breaker and the like using the same.

[0002]

2. Description of the Related Art PTC compositions have the above-mentioned PTC characteristics, and generally include a heater, a positive temperature coefficient thermistor, a thermal sensor,
It is used as a circuit protection element or the like that limits the current of a circuit when a circuit including a battery or the like is short-circuited and restores the circuit when the cause of the short-circuit is removed.

As another method of use, a circuit in which at least two electrodes are electrically connected to a PTC element made of a PTC composition is incorporated in a circuit, and the PTC element has an overcurrent or overheating function by its self-temperature control function. Circuit protection devices that prevent the

The overcurrent protection mechanism when a PTC element is used will be described below. Since the resistivity (ρ _L ) of the PTC composition at room temperature is sufficiently low, current usually flows through the circuit. However, when a high current flows through the circuit due to a short circuit accident or the like, Joule heat is generated in the PTC element due to the high current, the temperature of the element increases, and the resistivity increases.
C-characteristics), no current flows through the element, and the circuit is protected (this mechanism is called current limiting performance).

[0005] The PTC element, that is, the PTC composition must have a current-limiting performance that can be used repeatedly even under a high voltage. Further, in the PTC element, the initial resistivity (ρ _L ) is sufficiently reduced and an effective PTC
Providing a characteristic (ρ _H / ρ _L is large) improves the current limiting performance. ρ _H is the peak resistivity at a high temperature in the PTC curve.

As the PTC composition, various substances have been developed. As one of the PTC compositions, BaTiO ₃ to which a monovalent or trivalent metal oxide has been added has been known. Immediately after the PTC property is developed, NTC (Negative Temperature)
1msec. After the current was cut off in order to exhibit the characteristic (Coefficient). In the following, there is a problem that a current flows again.

For this reason, organic particles such as polyethylene (abbreviated as PE), polypropylene or ethylene-acrylic acid copolymer may be added to conductive particles such as carbon black (abbreviated as CB), carbon fiber, graphite or metal fine particles. Was developed. The PTC composition is generally produced by adding a necessary amount of conductive particles to one or more resins used as an organic polymer and kneading the resulting mixture.

When CB, carbon fiber, or graphite is used as the conductive particles, the ρ _L of the PTC element is 0.1 even when the conductive particles are closely packed in an organic polymer.
When it does not decrease to 1 Ωcm or less, and when the ρ _{L of} the PTC element decreases to 0.1 Ωcm, the ρ _H / ρ _L becomes small and shows only about 100. Therefore, the current limiting performance cannot be sufficiently improved.

On the other hand, the resistivity of the metal particles themselves is 10 ^-6 Ωc.
In the order of m, it is very low as compared with 0.05 Ωcm of CB itself. For this reason, by using metal particles such as Cu and Ni, although the ρ _L of the PTC element is expected to decrease, the metal particles are conventionally as large as CB as conductive particles for the PTC composition. not being used. One of the major reasons is that the P which contains the conventionally known metal particles
When the TC composition is used under a large current and a high voltage, an internal arc phenomenon (a minute arc is generated between conductive particles) is caused, and the composition causes electric breakdown. When the internal arc phenomenon occurs, the metal particles in the PTC composition melt and the metal particles are bonded to each other, and a conductive circuit is locally formed,
This is because a large current is concentrated on a part of the element and the element is destroyed. In addition, there is a problem in that discharge is likely to occur in a minute void portion at the interface between the composition and the electrode, and the resin in the discharge portion is degraded and decomposed, and thus the deterioration is accelerated. In particular, it was remarkable at a voltage of several tens of volts or more. Therefore, it is not used for a self-recovering overcurrent protection element.

A PTC composition containing both CB and metal particles as conductive particles is disclosed in JP-A-64-53503. The inclusion of the metal particles is for improving the thermal conductivity of the PTC composition.

[0011]

As described above, the PTC
As the conductive particles of the composition, the metal particles have a very low resistivity as compared with CB, and can reduce the resistivity (ρ _L ) of the PTC element at normal temperature, which is usually expected to exhibit good conductivity. However, the PTC composition containing the conventionally known metal particles, when used under a large current and high voltage, causes an internal arc phenomenon, the metal particles are melted and a conductive circuit is locally formed, There is a defect that safety and reliability are lacking, such as damage to the object and the PTC element, and the circuit cannot be repeatedly and well protected from overcurrent.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and has a low resistance and good conductivity during normal energization, and a conductive circuit is formed locally even under a large current and a high voltage. The PTC characteristics are not
PT that increases the resistance of the element and protects the circuit from overcurrent
The purpose is to obtain a C composition. That is, an object of the present invention is to obtain a PTC composition having excellent current limiting performance, high safety and reliability, and which can be favorably used as, for example, a self-recovering overcurrent protection element.

It is another object of the present invention to provide a circuit protection device which normally has good conductivity, has excellent current limiting performance even under a large current and a high voltage, and operates repeatedly and stably with high safety and reliability. .

[0014]

According to a first aspect of the circuit protection device of the present invention, an organic polymer is treated with a coupling agent.
An organic PTC element in which conductive particles having a melting point of 2,000 ° C. or higher are dispersed, and at least two electrodes electrically connected to the PTC element, wherein the ratio of overcurrent to the area of the PTC element is 50 kA / It is used under an energizing condition of 24 cm ² or more.

A second configuration of the circuit protection device according to the present invention uses the conductive particles having an average particle size of 0.01 to 50 μm in the first configuration.

According to a third configuration of the circuit protection device of the present invention, in the first or second configuration, the conductive particles are contained in an amount of 50 wt% to 99 wt% with respect to the composition.

According to a fourth aspect of the circuit protection device of the present invention, in any one of the first to third aspects, the conductive particles include metal, metal carbide, metal boride, metal silicide, and metal nitride. Particles containing at least one of them are used.

A fifth configuration of the circuit protection device according to the present invention uses tungsten as the metal in the fourth configuration.

[0019]

The sixth configuration of the circuit protection device of the present invention, the
The coupling agent in the configuration of item 1 is an aluminum type
Is a titanate type .

The seventh configuration of the circuit protection device according to the present invention
The content of the coupling agent in the configuration of 1 is 0.05 to 10% by weight based on the conductive particles.

[0022]

[0023]

BEST MODE FOR CARRYING OUT THE INVENTION The organic PTC composition according to the present invention is obtained by dispersing conductive particles having a melting point of 2000 ° C. or higher in an organic polymer.

According to the organic PTC composition of the present invention, the conductive particles have a high melting point of 2000 ° C. or more even when used under a large current and a high voltage and an internal arc is generated. Not use PT
Unlike the C composition, a conductive circuit is not locally formed in the PTC composition, that is, the element, and the PTC composition and the element do not break. When a large current flows, PT
Since the temperature of the C element rises and the resistance rises, the circuit can be protected from overcurrent.

Further, the resistivity (ρ _L ) at room temperature can be made sufficiently small, showing good conductivity during normal energization and increasing the peak resistivity (ρ _H ) at high temperatures, ie, ρ _H
/ [Rho _L can greatly be cut off reliably current when a large current flows. That is, a safe and reliable PTC composition having excellent current limiting performance is obtained, and a self-recovering type circuit protection device using a PTC element made of this PTC composition is repeatedly excellent in overcurrent protection. To work.

Note that CB is a sublimable substance having no melting point and is not included in the category of the conductive particles of the present invention.

The conductive particles have an average particle size of 0.0
It is preferable to use particles of 1 to 50 μm,
More preferably, particles of 0 μm are used. When the conductive particles having a small average particle size are filled in an organic polymer, the particle distribution becomes small and bulky, so that the filling amount cannot be increased, and the room temperature resistivity of the PTC element increases. This is because the room temperature resistivity of the PTC element increases when the amount of the polymer charged is the same. FIG. 1 is a characteristic diagram showing the relationship between the particle size of tungsten contained in the PTC element and the room temperature resistivity of the PTC element. The black circles indicate that the tungsten loading is 90 wt%, and the hollow circles indicate the tungsten loading. The case of 95 wt% is shown, and it can be seen that the normal temperature resistivity of the PTC element increases as the average particle diameter increases. By using the conductive particles having the above average particle diameter, a PTC composition having a small room temperature resistivity can be obtained, and various particles having various particle diameters can be appropriately selected according to the use and desired characteristics of the PTC composition.

The content of the conductive particles is preferably 50 to 99% by weight based on the PTC composition, and 70 to 9% by weight.
More preferably, it is 7 wt%. When the content of the conductive particles decreases, the room temperature resistivity increases. In addition, when the content of the conductive particles increases, the kneading torque at the time of kneading with the organic polymer increases, and kneading becomes difficult, and the obtained PTC element has low elasticity and low impact resistance. FIG. 2 is a characteristic diagram showing the relationship between the tungsten filling amount and the room temperature resistivity of the PTC element. As the tungsten filling amount decreases, FIG.
It can be seen that the room temperature resistivity of the PTC element has increased.
FIG. 3 is a characteristic diagram showing the relationship between the filling amount of tungsten and the torque during kneading. It can be seen that the torque during kneading increases as the filling amount of tungsten increases. The measurement was performed using a Labo Plastomill apparatus at 200 ° C. and 50 rpm.
Under kneading conditions.

The conductive particles have a melting point of 2,000.
C. or higher, as long as it has good electrical conductivity, thermal conductivity and melting resistance to micro-arcs as a PTC composition and can provide excellent PTC characteristics, and may be a metal, a metal carbide, or the like. , Metal boride, metal silicide, and metal nitride particles are used. PTC
Depending on the use of the composition and desired properties, a mixture of two or more of them alone can be appropriately selected and used.

For example, as the metal particles, tungsten
(W) can be used. As metal carbide, T
iC, ZrC, VC, NbC, TaC, Mo_TwoC, WC
Can be used. As metal nitrides, TiN,
ZrN, VN, NbN, TaN, Cr_TwoUsing N
Can be. As the metal silicide, TaSi_Two , Mo
Si_Two , WSi_Two Can be used. In addition, metal
As a boride, TiB _Two , ZrB_Two , NbB_Two , Ta
B_Two , CrB, MoB, and WB can be used.
(Ti: titanium, Zr: zirconium, V: vanadium
, Nb: Niobium, Ta: Tantalum, Mo: Molybdenum
, Cr: chrome)

In particular, it is preferable to use particles of tungsten and carbides, borides, silicides, and nitrides of tungsten. Tungsten is a metal having the highest melting point (3410 ° C.) among metal particles, and tungsten and a tungsten compound having a desired particle size are supplied stably and are easily available.

Examples of the organic polymer according to the present invention include polyethylene, polyethylene oxide, polybutadiene, polyethylene acrylate, ethylene-ethyl acrylate copolymer, ethylene-acrylic acid copolymer, polyester, polyamide, polyether, polycaprolactam, and fluorine. Ethylene-propylene copolymer, chlorinated polyethylene, chlorosulfonated ethylene, ethylene-vinyl acetate copolymer, polypropylene, polystyrene, styrene-acrylonitrile copolymer, polyvinyl chloride,
Polycarbonate, polyacetal, polyalkylene oxide, polyphenylene oxide, polysulfone, and fluororesin are used. These may be used alone or as a blend polymer of at least two or more selected from these. The type, composition ratio, and the like of the organic polymer may be appropriately selected according to desired performance, use, and the like.

The PTC composition comprises an organic polymer, conductive particles,
It is prepared by compounding and kneading other additives at a predetermined ratio. Compound conductive particles or both at the same time with organic polymer
It may be prepared by kneading. The mixing ratio of the organic polymer and the conductive particles may be appropriately selected according to the conductive particle content of the target composition, the type of the organic polymer, and the type of kneading machine such as a Banbury mixer, a pressure kneader, or a roll mill. Although possible, the loading of the conductive particles should not exceed the range of 50-99% by weight in the PTC composition.

In the preparation of the PTC composition, the use of conductive particles which have been previously subjected to a coupling treatment with a coupling agent can improve environmental resistance characteristics such as high temperature, high humidity and heat shock.

As the coupling agent, a titanate coupling agent and an aluminum coupling agent can be used. Monotoxy type such as isopropyl triisostearoyl titanate, isopropyl trioctanoititanate, isopropyl diisostearoyl cumyl phenyl titanate, isopropyl distearoyl methacryl titanate, isopropyl tri (dioctyl pyrophosphate) titanate, or a titanate coupling agent Tetraisopropylpyrdi (dilauryl phosphite) titanate, isostearoyl oxyacetate, isostearoyl acryloxyacetate, distearoyl ethylene titanate, dimethacrylethylene titanate can be used. Effective for improving adhesion between metal and plastic represented by rate It is possible to use all even.

The environmental resistance can be improved by adjusting the amount of the coupling agent to 0.05 to 10% by weight based on the conductive particles.

In preparing the PTC composition, various additives other than the above-mentioned organic polymer, conductive particles and coupling agent may be mixed as required. Examples of additives include flame retardants such as antimony compounds, phosphorus compounds, chlorine compounds, and bromine compounds, antioxidants, and stabilizers.

The PTC composition obtained according to the present invention can be used for various applications. When used as a PTC element, the PTC composition is formed into a film shape, for example, and a metal foil electrode is thermocompression-bonded to the front and back of the film to form a laminate. The lead wire can be manufactured by soldering, brazing, spot welding or the like on the surface.

[0039]

EXAMPLES Hereinafter, the present invention will be described in detail with reference to Examples along with Reference Examples, but of course, the present invention is not limited by these. Reference Example 1. 10 parts by weight of high density polyethylene (abbreviated as HDPE; HJ560 manufactured by Mitsubishi Chemical Corporation) as an organic polymer, and 90 parts by weight of tungsten (W-1 manufactured by Nippon Shinmetal Co., Ltd., average particle size 0.88 μm) as conductive particles And phenolic antioxidants (Irganox 101, manufactured by Ciba-Geigy)
0) 2 parts by weight of Labo Plastomill (Toyo Seiki Co., Ltd.)
) At 200 ° C for 15 minutes. This PTC composition was formed into a 40 × 60 × 1 mm thick plate by hot pressing. In order to perform insulation at the time of interruption, a polyethylene frame was formed by injection molding around 20 mm around the plate. Next, a PTC element was produced by sandwiching the laminated body on which the frame was formed between the electrodes. FIG. 4 shows a PTC curve representing the relationship between the temperature and the resistivity of the PTC element. Room temperature resistivity (ρ _L ) is 0.01Ω
cm, peak resistivity (ρ _H ) is 10 ⁵ Ωcm, ρH / ρ
L was 10 ⁷ . When the room temperature resistance of this PTC element was 1.2 mΩ, the cutoff current with respect to an overcurrent of 300 V and 50 kA was 7.5 kA.

The relationship between the resistance of the PTC device made of this PTC composition and the current-limiting peak value (peak current at the time of overcurrent interruption: I _p ) was examined by changing the size of the device and changing the resistance. The results are shown in the characteristic diagram of FIG.

FIG. 6 is a schematic view of an optical microscope photograph showing the dispersion state of the conductive particles and tungsten particles of the PTC composition. FIG. 6 (a) is a diagram before the interruption (current limiting) test, and FIG.
Indicates after the interruption test. Even after the interruption test, there is no change from that before the test, and it can be seen that the tungsten particles 2 are uniformly dispersed in the organic polymer 1 in the same manner.

Reference Example 2 HDPE (HJ560 manufactured by Mitsubishi Chemical Corporation) 10 parts by weight,
Metallic carbide WC as conductive particles (WC-10, manufactured by Nippon Shinkin Co., Ltd., average particle size 0.7 μm, melting point 2785 ° C.) 9
0 parts by weight and 2 parts of a phenolic antioxidant (Irganox 1010, manufactured by Ciba Geigy) were kneaded at 200 ° C. for 15 minutes using a Labo Plastomill apparatus (manufactured by Toyo Seiki Co., Ltd.). This PTC composition is 40 × 60 ×
The plate was 1 mm thick. A polyethylene frame was formed by injection molding around 20 mm around the plate in order to provide insulation during interruption. Next, the laminated body on which the frame is formed
An element was manufactured. When the room temperature resistance of the PTC element was 1.5 mΩ, the cutoff current for 300 V and 50 kA was 8 kA.

Reference Example 3 HDPE (HJ560 manufactured by Mitsubishi Chemical Corporation) 10 parts by weight,
ZrN made of metal nitride as conductive particles (Nippon Shinkin Co., Ltd.)
90 parts by weight of a phenolic antioxidant (Irganox 1010 manufactured by Ciba-Geigy) at 200 ° C. using a Labo Plastomill apparatus (manufactured by Toyo Seiki Co., Ltd.) Kneaded for 15 minutes. This PTC composition was formed into a 40 × 60 × 1 mm thick plate by hot pressing. A polyethylene frame was formed by injection molding around 20 mm around the plate in order to provide insulation during interruption. Next, a PTC element was produced by sandwiching the laminated body on which the frame was formed between the electrodes. This PTC element has a cut-off current of 8.5 kA for 300 V and 50 kA when its room temperature resistance is 1.1 mΩ.
showed that.

Reference Example 4 HDPE (HJ560 manufactured by Mitsubishi Chemical Corporation) 10 parts by weight,
As conductive particles, 90 parts by weight of metal silicide WSi ₂ (manufactured by Nippon Shinkin Co., Ltd., average particle size 1 μm, melting point 2160 ° C.) and a phenolic antioxidant (manufactured by Ciba Geigy,
Two parts of Irganox 1010) were kneaded at 200 ° C. for 15 minutes using a Labo Plastomill apparatus (manufactured by Toyo Seiki Co., Ltd.). This PTC composition is 40 × 60 × 1 mm in a hot press.
It was a thick plate. A polyethylene frame was formed by injection molding around 20 mm around the plate in order to provide insulation during interruption. Next, a frame is formed, and the obtained laminate is sandwiched between electrodes to form a PT.
C element was produced. When the room temperature resistance of the PTC element was 1.3 mΩ, the cutoff current with respect to 300 V and 50 kA was 8 kA.

Reference Example 5 HDPE (Mitsubishi Chemical Co., Ltd. HJ560) and polypropylene (Mitsubishi Chemical Co., Ltd. MA03) were added in equal amounts to give 1
0 parts by weight, WB of metal boride as conductive particles (manufactured by Nippon Shinkin Co., Ltd., average particle size 1 μm, melting point 3700 ° C.) 90
Parts by weight and 2 parts of a phenolic antioxidant (Irganox 1010, manufactured by Ciba Geigy) were kneaded at 200 ° C. for 15 minutes using a Labo Plastomill apparatus (manufactured by Toyo Seiki Co., Ltd.). This PTC composition is heated to 40 × 60 × 1 by hot pressing.
It was a plate having a thickness of mm. A polyethylene frame was formed by injection molding around 20 mm around the plate in order to provide insulation during interruption. Next, a PTC element was produced by sandwiching the laminate obtained by forming a frame in this manner between electrodes. When the room temperature resistance of this PTC element was 1.2 mΩ, the breaking current for 300 V and 50 kA was 8 kA. In addition, instead of a mixture of high-density polyethylene and polypropylene, a PTC element similarly formed with the above composition using a high-density polyethylene alone, a polypropylene alone, or a copolymer of polyethylene and polypropylene has the same PTC characteristics. Indicated.

Reference Example 6 10 parts by weight of polypropylene (MA03, manufactured by Mitsubishi Chemical Corporation), 90 parts by weight of tungsten (W-1, manufactured by Nippon Shinkin Co., Ltd., average particle size: 0.88 μm) as conductive particles, and a phenolic antioxidant (manufactured by Ciba Geigy) Two parts of Irganox 1010) were kneaded at 200 ° C. for 15 minutes using a Labo Plastomill apparatus (manufactured by Toyo Seiki Co., Ltd.). This P
The TC composition was pressed into a 40 × 60 × 1 mm thick plate by hot pressing. A polyethylene frame was formed by injection molding around 20 mm around the plate in order to provide insulation during interruption. Next, a PTC element was produced by sandwiching the laminate obtained by forming a frame in this manner between electrodes. Figure PTC curve of Example 1 in this case 4
Was the same as Room temperature resistivity (ρ _L ) is 0.01Ωc
m, peak resistivity (ρ _H ) was 10 ⁵ Ωcm, and ρ _H / ρ _L was 10 ⁷ . When the room temperature resistance of this PTC element was 1.2 mΩ, the cutoff current with respect to an overcurrent of 300 and 50 kA was 7.5 kA.

Embodiment 1 Titanate-based coupling agent (KRT manufactured by Ajinomoto Co., Inc.)
TS) To a solution obtained by dissolving 1 part by weight of isopropyl alcohol in 28 parts by weight of isopropyl alcohol, 100 parts by weight of tungsten (W-1 manufactured by Nippon Shinkin Co., Ltd., average particle size 0.88 μm) was added and mixed for 10 minutes. . Then, after filtering the isopropyl alcohol solvent, the composition on the filter paper was vacuum-dried all day and night.

90 parts by weight of the composition after drying (coupling-treated tungsten), 10 parts by weight of HDPE (HJ560 manufactured by Mitsubishi Chemical Corporation), and 2 parts by weight of a phenolic antioxidant (Irganox 1010 manufactured by Ciba Geigy) With a lab plast mill (manufactured by Toyo Seiki)
Kneaded at 150C for 15 minutes. This PTC composition was formed into a 40 × 60 × 1 mm thick plate by hot pressing. 20m around this board
A polyethylene frame was made by injection molding in order to insulate the circuit at m. Next, a PTC element was produced by sandwiching the PTC composition plate on which the frame was formed between electrodes. Room temperature resistivity (ρ _L ) is 0.01 Ωcm, peak resistivity (ρ _H ) is 1
0 ⁵ Ωcm and ρ _H / ρ _L were 10 ⁷ . This PTC element has a resistance of 300, 50 when its room temperature resistance is 1.2 mΩ.
The current limiting peak value for the overcurrent of kA was 7.5 kA.

When an environmental test (high temperature and high humidity: 85 ° C., 85%) was performed, the one having an initial resistivity of 0.02 Ωcm was 1
It was 0.1 Ωcm after 000 hours. On the other hand, Reference Example 1
In the case where the coupling treatment was not performed, the one having an initial resistivity of 0.02 Ωcm was changed to 960 after 1000 hours.
It greatly increased to Ωcm.

The environmental test (heat shock: -25)
Cycle test of 30 ° C. for 30 minutes and 85 ° C. for 30 minutes).
It was 0.2 Ωcm after 00 cycles. On the other hand, a reference example
In the case where the coupling treatment shown in No. 1 was not performed, the one having the initial resistivity of 0.02 Ωcm was changed to the one after 300 cycles.
It greatly increased to 00 Ωcm.

Embodiment 2 FIG . Aluminum-based coupling agent (AL-AL manufactured by Ajinomoto Co., Inc.)
M) A solution of 1 part by weight in 28 parts by weight of an isopropyl alcohol solvent was added with tungsten carbide (WC-10, manufactured by Nippon Shinkin Co., Ltd., average particle size 0.7 μm) 100
Parts by weight were added and mixed for 10 minutes. Then, after filtering the isopropyl alcohol solvent, the composition on the filter paper was vacuum-dried all day and night.

90 parts by weight of the dried composition (coupling-treated tungsten carbide), 10 parts by weight of HDPE (HJ560 manufactured by Mitsubishi Chemical Corporation), and a phenolic antioxidant (Irganox 101 manufactured by Ciba-Geigy)
0) 2 parts by weight were kneaded at 200 ° C. for 15 minutes using a Labo Plastomill (manufactured by Toyo Seiki). This PTC composition was formed into a 40 × 60 × 1 mm thick plate by hot pressing. A polyethylene frame for insulation at the time of interruption was formed at a distance of 20 mm around the plate by injection molding. Next, the PT
A PTC element was produced by sandwiching a plate of the C composition between electrodes. Room temperature resistivity (ρ _L ) is 0.01 Ωcm, peak resistivity (ρ _L )
_H ) was 10 ⁵ Ωcm, and ρ _H / ρ _L was 10 ⁷ . This PTC element has a resistance of 30 m when its room temperature resistance is 1.2 mΩ.
The current limiting peak value for an overcurrent of 0 and 50 kA was 8 kA.

When an environmental test (high temperature and high humidity: 85 ° C., 85%) was performed, the one having an initial resistivity of 0.02 Ωcm was 1
After 000 hours, the value was 0.03 Ωcm. On the other hand, a reference example
In the case where the coupling treatment shown in FIG. 2 was not performed, the one having the initial resistivity of 0.02 Ωcm was 11 hours after 1000 hours.
It greatly increased to 5 Ωcm.

The environmental test (heat shock: -25)
Cycle test of 30 ° C. for 30 minutes and 85 ° C. for 30 minutes).
It was 0.15 Ωcm after 00 cycles. Meanwhile, reference
In the case where the coupling treatment shown in Example 2 was not performed, the sample having an initial resistivity of 0.02 Ωcm greatly increased to 1.6 Ωcm after 300 cycles.

Embodiments 3 to 27. The above examples were prepared by changing the types of the polymer, filler and coupling agent of the PTC composition as shown in Tables 1 and 2.
PTC elements were manufactured in the same manner as in Examples 1 and 2, and the environmental resistance characteristics were measured. The results are shown together with Examples 1 and 2 . As is clear from Tables 1 and 2, by performing the coupling treatment, the current-limiting peak value was not changed, and good results were obtained for the environmental test.

[0056]

[Table 1]

[0057]

[Table 2]

In the above embodiment, the case where only one type of metal or metal composite is used as the conductive particles has been described. However, two or more types may be used in combination.

Comparative Example 1 90 parts by weight of silver particles (Novamet, melting point 960.5 ° C.) as conductive particles, HDPE1
0 parts by weight and 2 parts by weight of a phenolic antioxidant (manufactured by Ciba Geigy, Irganox 1010) were added at 200 ° C. using a Labo Plastomill apparatus (manufactured by Toyo Seiki Co., Ltd.) at 15 ° C.
Kneaded for minutes. This PTC composition was hot pressed to 40 × 6
It was made into a plate of 0 × 1 mm thickness. A polyethylene frame was formed by injection molding around 20 mm around the plate in order to provide insulation during interruption. Next, a PTC element was produced by sandwiching the laminate obtained by forming the frame between the electrodes. The PTC element having a room temperature resistance of 1 mΩ could not be cut off even when a high voltage and a large current of 300 V and 50 kA flowed. The reason why the interruption was impossible was that the PTC composition of this comparative example was filled with silver particles having a low melting point, and when used under a large current and a high voltage, an internal arc phenomenon (between conductive particles) occurred. It is considered that a small arc was generated, and the PTC composition caused electrical breakdown. It is considered that when the internal arc phenomenon occurs, the silver particles in the PTC composition are melted by the heat, and then the silver particles are bonded to each other, a large current flows in the bonded portion, and the composition is considered to be electrically damaged.

Comparative Example 2 Copper (melting point 108) as conductive particles
85 ° C., 15 parts by weight of HDPE and a phenolic antioxidant (Irganox 101, manufactured by Ciba-Geigy) at 3 ° C., Fukuda Metal Tomari Kogyo, average particle size 1.0 μm)
0) 2 parts by weight of Labo Plastomill (Toyo Seiki Co., Ltd.)
Kneading at 200 ° C. for 15 minutes. Around this board 2
A polyethylene frame was made by injection molding to provide insulation at the time of interruption to 0 mm. Next, the obtained laminate was sandwiched between electrodes. The PTC element having a room temperature resistance of 3 mΩ could not be cut off even when a high voltage and a large current of 300 V and 50 kA flowed. As in Comparative Example 1, it is considered that the copper particles in the PTC composition were melted and a conductive circuit was locally formed.

Comparative Example 3 85 parts by weight of nickel particles (melting point: 1452 ° C., Novamet) as conductive particles, HD
15 parts by weight of PE and 2 parts by weight of a phenolic antioxidant (Irganox 1010, manufactured by Ciba Geigy Co., Ltd.) were heated at 200 ° C. using a Labo Plastomill apparatus (manufactured by Toyo Seiki Co., Ltd.).
And kneaded for 15 minutes. A polyethylene frame was formed by injection molding around 20 mm around the plate in order to provide insulation during interruption. Next, the obtained laminate was sandwiched between electrodes. This P
When the TC element has a room temperature resistance of 1 mΩ,
Even if a high voltage and a large current of kA flowed, it could not be cut off. As in Comparative Examples 1 and 2, it is considered that the nickel particles in the PTC composition were melted and a conductive circuit was locally formed.

FIG. 7 is a schematic view of an optical microscope photograph showing a dispersion state of nickel particles of the PTC composition. FIG. 7 (a) shows a device before a blocking (current limiting) test, and FIG. 7 (b) shows a device after a blocking test. Indicates a state of destruction. Before the shut-off test, the nickel particles 3 are uniformly dispersed in the organic polymer 1. However, after the shut-off test, the nickel particles 3 are melted and the nickel particles 3 are bonded to each other to form a nickel particle bonding portion 3a. . P
Since the nickel particles 3 in the TC composition were melted and the nickel particle bonding portions 3a (that is, conductive circuits) were formed, the overcurrent could not be cut off as in Comparative Examples 1 and 2, and the element was destroyed. it is conceivable that.

[0063]

According to the first configuration of the circuit protection device of the present invention, an organic PTC in which conductive particles having a melting point of 2000 ° C. or more treated with a coupling agent are dispersed in an organic polymer.
An element and at least two electrodes electrically connected to the PTC element, and used under an energizing condition in which a ratio of an overcurrent to the area of the PTC element is 50 kA / 24 cm ² or more. Low resistance during normal energization,
The conductivity becomes good, and even under a large current and a high voltage, the conductive particles do not melt and a conductive circuit is not formed locally,
The effect of increasing the resistance due to the development of the PTC characteristic and protecting the circuit from overcurrent and the effect of treating the conductive particles with a coupling agent.
This has the effect of improving the environmental resistance characteristics .

According to a second configuration of the circuit protection device of the present invention, in the first configuration, the average particle diameter is 0.01 to 50.
The use of the conductive particles of μm has an effect that an organic PTC element having a small resistivity at normal temperature can be obtained .

In the third configuration of the circuit protection device according to the present invention, in the first or second configuration, the conductive particles are contained in the composition in an amount of 50 wt% to 99 wt% with respect to the composition, so that the room temperature resistivity is small, There is an effect that an organic PTC element more suitable for practical use can be obtained .

In a fourth configuration of the circuit protection device according to the present invention, in any one of the first to third configurations, the conductive particles may include metal, metal carbide, metal boride, metal silicide, and metal nitride. By using particles containing at least one of the above, there is an effect that an organic PTC element having excellent PTC characteristics and current limiting performance can be obtained .

In the fifth configuration of the circuit protection device according to the present invention, by using tungsten as the metal in the fourth configuration, a safer and more reliable PTC characteristic can be obtained.
There is an effect that an organic PTC element having excellent current limiting performance can be obtained .

In the sixth or seventh configuration of the circuit protection device of the present invention, the effect of improving the environmental resistance characteristics is obtained by treating the conductive particles with the coupling agent.

[0069]

[Brief description of the drawings]

FIG. 1 is a characteristic diagram showing the relationship between the particle size of conductive particles (tungsten) according to the present invention and the room temperature resistivity of a PTC element.

FIG. 2 is a characteristic diagram showing a relationship between a filling amount of conductive particles (tungsten) according to the present invention and a normal temperature resistivity of a PTC element.

FIG. 3 is a characteristic diagram showing a relationship between a filling amount of conductive particles (tungsten) according to the present invention and a torque during kneading.

FIG. 4 is a characteristic diagram showing a PTC curve representing the relationship between the temperature and the resistivity of the PTC element according to the first embodiment of the present invention.

FIG. 5 is a characteristic diagram showing a relationship between a resistance of a PTC element and a peak current (I _p ) at the time of overcurrent interruption according to Embodiment 1 of the present invention.

FIG. 6 is a schematic diagram of optical micrographs before and after a current-limiting test showing a dispersion state of conductive particles and tungsten particles of the PTC composition of Reference Example 1 of the present invention.

FIG. 7 is a schematic diagram of optical micrographs before and after a current-limiting test showing a dispersion state of conductive particles and nickel particles of the PTC composition of Comparative Example 1 of the present invention.

[Explanation of symbols]

1 Organic polymer, 2 Tungsten particles, 3 Nickel particles, 3a Nickel particle bonding part.

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Osamu Hiroi 2-3-2 Marunouchi, Chiyoda-ku, Tokyo Inside Mitsubishi Electric Corporation (72) Inventor Sadajiro Mori 2-3-2 Marunouchi, Chiyoda-ku, Tokyo Mitsubishi Electric (72) Inventor Tatsuya Hayashi 2-3-2 Marunouchi, Chiyoda-ku, Tokyo Mitsubishi Electric Corporation (72) Inventor Tomoe Takahashi 2-3-2 Marunouchi, Chiyoda-ku, Tokyo Mitsubishi Electric Corporation ( 72) Inventor Shiro Murata 2-3-2 Marunouchi, Chiyoda-ku, Tokyo Inside Mitsubishi Electric Corporation (72) Inventor Kenichi Nishina 2-3-2 Marunouchi 2-chome, Chiyoda-ku, Tokyo Inside Mitsubishi Electric Corporation (72) Inventor Manabu Sogabe 2-3-2 Marunouchi, Chiyoda-ku, Tokyo Inside Mitsubishi Electric Corporation (72) Inventor Masahiro Ishikawa Marunouchi, Chiyoda-ku, Tokyo Chome No. 2 No. 3 Mitsubishi Electric in Co., Ltd. (56) references PCT National flat 5-508055 (JP, A) (58 ) investigated the field (Int.Cl. ^7, DB name) H01C 7/00 - 7/22

Claims (7)

(57) [Claims] An organic polymer is treated with a coupling agent.
An organic PTC element in which conductive particles having a melting point of 2,000 ° C. or higher are dispersed, and at least two electrodes electrically connected to the PTC element.
A circuit protection device characterized in that it is used under a current-carrying condition having a ratio to an element area of 50 kA / 24 cm ² or more. 2. The conductive particles have an average particle size of 0.01 to 50 μm.
The circuit protection device according to claim 1, wherein m is m. 3. The circuit protection device according to claim 1, wherein the conductive particles are contained in the composition in an amount of 50 wt% to 99 wt%. 4. The circuit protection according to claim 1, wherein the conductive particles are particles containing at least one of a metal, a metal carbide, a metal boride, a metal silicide, and a metal nitride. apparatus. 5. The circuit protection device according to claim 4, wherein the metal is tungsten. 6. The method according to claim 1, wherein the coupling agent is aluminum or
The circuit protection device according to claim 1, wherein the circuit protection device is a titanate type . 7. The content of the coupling agent is in relation to the conductive particles.
From 0.05 to 10% by weight
Item 2. The circuit protection device according to Item 1 .