JPH0638362B2 - Method for producing polymer positive temperature coefficient resistor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention provides:
The property that the positive temperature coefficient rapidly increases (positive temperature coefficient characteristic)
The present invention relates to a method for producing a polymer positive temperature characteristic resistor having More specifically, the present invention is useful as a material for, for example, an overcurrent protection element or a self-temperature control heating element, has excellent positive temperature coefficient characteristics, and has a stable positive polymer temperature with a small variation in resistance value. The present invention relates to a method for manufacturing a characteristic resistor.

[Conventional technology]

Conventionally, as a material having a positive temperature coefficient characteristic, various methods, for example, a method of mixing a crystalline polymer with a carbon powder having a particle size in a specific range (Japanese Patent Publication No. 50-33707) or the carbon powder was mixed. After that, a method of cross-linking the crystalline polymer (Japanese Patent Publication No. 56-10352), or after mixing carbon black having a specific particle size into the crystalline polymer, the gel fraction is adjusted to fall within a specific range. Those obtained by a method of crosslinking the crystalline polymer (Japanese Patent Laid-Open No. 60-80201) are known.

However, these materials are usually obtained by kneading the crystalline polymer and the conductive filler with a kneading machine such as a Banbury mixer, and those obtained by such kneading means have a particularly high specific resistance. When the value is 10 Ω-cm or more, there is a problem that there is a large variation in the value of resistivity within the same batch, and even if the same operation is repeated, there is a large variation in the value of resistivity between lots. There is.

[Problems to be solved by the invention]

The present invention solves the problem in the material having such a conventional positive temperature coefficient characteristic, is excellent in the positive temperature coefficient characteristic, and is stable in the production of a polymer positive temperature characteristic resistor having a small quality variation of the resistance value. To provide a method.

[Means for solving problems]

The present inventors have conducted extensive studies to develop a polymer resistor having excellent positive temperature coefficient characteristics and stable quality, and as a result, in the presence of a conductive filler and a specific polymerization catalyst. ,
It has been found that the one obtained by polymerizing ethylene has the conductive filler dispersed extremely uniformly, and that the molded product can meet the above-mentioned object, and based on this finding, the present invention has been completed.

That is, according to the present invention, ethylene is polymerized in the presence of a polymerization catalyst composed of a catalyst component containing (A) a conductive filler and (B) (a) a transition metal, and (b) an organoaluminum compound to conduct electrical conductivity. The present invention provides a method for producing a polymer positive temperature coefficient resistor, which comprises producing a polyethylene resin composition containing 10 to 70% by volume of a filler and molding the polyethylene resin composition.

In the polyethylene resin composition according to the present invention, examples of the conductive filler used include carbon black such as thermal black, furnace black and acetylene black, graphite, metal powder, crushed carbon fiber, silicon carbide powder, boron carbide powder and the like. Is mentioned. Among these conductive fillers, the average particle size of carbon black is 0.
It is preferably less than 08 μm, preferably 0.076 μm. If the average particle size is 0.08 μm or more, the resistance value of the obtained resistor at room temperature becomes large, which is not preferable. Further, silicon carbide having a thickness of 0.5 to 100 μm is suitable.

The (a) catalyst component used for the structure of the polyethylene resin composition can be prepared by various methods. Regarding the catalyst component containing a transition metal, a higher fatty acid salt of magnesium or manganese, a higher alcohol salt, or a phosphate having a long-chain aliphatic hydrocarbon group is added to the general formula MR ¹ R ² R ³ [I] (wherein M is titanium, vanadium, zirconium or hafnium, and R ¹ , R ² and R ³ have 1 to 10 carbon atoms.
Which is an alkyl group, an alkoxy group, an acyl group, a cyclopentadienyl group, a halogen atom or a hydrogen atom) is added and reacted. At this time, the addition amount of the transition metal compound is not particularly limited, but is usually 1 mol of the above-mentioned higher fatty acid salt of magnesium or manganese, higher alcohol salt or phosphate having a long-chain aliphatic hydrocarbon group. , 0.5 mol or less, preferably 0.02 to 0.2 mol. If the amount of the transition metal compound added exceeds 0.5 mol, the catalytic activity is significantly reduced, which is not preferable.

Here, the higher fatty acid or higher alcohol constituting the salt may be either saturated or unsaturated as long as it has 10 or more carbon atoms, and particularly preferably has 16 or more carbon atoms. Specific examples thereof include higher fatty acids such as capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, and oleic acid, and further higher alcohols such as decanol, lauric alcohol, myristyl alcohol, cetyl alcohol, and stearyl alcohol. Can be mentioned. Further, as a phosphoric acid derivative constituting a phosphate having a long-chain aliphatic hydrocarbon group, a mono- or dialkyl ester of phosphoric acid or phosphorous acid (RO
PH ₂ O ₃ , (RO) ₂ PO ₂ , ROPH ₂ O _2, etc.), mono- or dialkyl phosphoric acid or phosphorous acid (RPH ₂ O ₃ , R ₂ PHO ₂ , RPH ₂ O ₂
Etc.). The long-chain aliphatic hydrocarbon group refers to a saturated or unsaturated aliphatic hydrocarbon group having 6 or more carbon atoms, preferably 8 or more carbon atoms, and examples thereof include a hexyl group, a beptyl group, an octyl group, 2-ethyl-hexyl group, nonyl group, decyl group, lauryl group, myristyl group, palmityl group, stearyl group, oleyl group and the like can be mentioned.

These higher fatty acids, higher alcohols, or magnesium salts or manganese salts of phosphoric acid having a long-chain aliphatic hydrocarbon group may be produced by known methods, or commercially available products may be dried and used, It may be one formed by forming a double salt with another metal.

On the other hand, examples of the transition metal compound represented by the general formula [I] include tetrahalogeno titanium such as TiCl ₄ , TiBr ₄ , and TiI ₄ , Ti (OCH ₃ ) Cl ₃ , Ti (OC ₂ H ₅ ) Cl ₃ , Ti (OC ₃ H ₇ ) Cl ₃ , Ti
Trihalogenomonoalkoxy titanium such as (OC ₄ H ₉ ) Cl ₃ , Ti (OC ₂ H ₅ ) Br ₃ , Ti (OCH ₃ ) ₂ Cl ₂ , Ti (OC ₂ H ₅ ) ₂ Cl ₂ , Ti (OC ₃ H
₇ ) ₂ Cl ₂ , Ti (OC ₄ H ₉ ) ₂ Cl ₂ , Ti (OC ₂ H ₅ ) ₂ Br ₂ and other dihalogeno dialkoxy titanium, Ti (OCH ₃ ) ₃ Cl, Ti (OC ₂ H ₅ ). ₃ Cl, T
Monohalogenotrialkoxy titanium such as i (OC ₃ H ₇ ) ₃ Cl, Ti (OC ₄ H ₉ ) ₃ Cl, Ti (OC ₂ H ₅ ) ₃ Br, Ti (OCH ₃ ) ₄ , Ti (OC ₂ H ₅ )
_{4, Ti (OC 3 H 7} ) 4, tetraalkoxy titanium such as _{Ti (OC 4 H 9) 4} , Ti (OC 2 H 5) (OCOCH 3) 3, Ti (OC 2 H 5) (OCOC 4 H 9 ) ₃ , Ti
(OC ₃ H ₇ ) (OCOC ₄ H ₉ ) ₃ , Ti (OC ₃ H ₇ ) (OCOC ₁₂ H ₂₅ ) ₃ , Ti (OC
₃ H ₇ ) (OCOC ₁₇ H ₃₅ ) ₃ , Ti (OC ₄ H ₉ ) (OCOC ₁₇ H ₃₅ ) ₃ , Ti (OC ₂ H ₅ )
₂ (OCOCH ₃ ) ₂ , Ti (OC ₃ H ₇ ) ₂ (OCOC ₁₂ H ₂₅ ) ₂ , Ti (OC ₃ H ₇ ) ₂ (OCO
C ₁₇ H ₃₅ ) ₂ , Ti (OC ₂ H ₅ ) ₃ (OCOC ₄ H ₉ ), Ti (OC ₃ H ₇ ) ₃ (OCOC ₁₂ H
₂₅ ), Ti (OC ₃ H ₉ ) ₃ (OCOC ₁₇ H ₃₅ ), Ti (OCOCH ₃ ) ₄ , Ti (OCOC ₄ H
₉ ) ₄ , Ti (OCOC ₁₂ H ₂₅ ) ₄ , Ti (OCOC ₁₇ H ₃₅ ) ₄ , etc.
Titanium compound represented by (OR) _n (OCOR) _4-n , and further (cp) ₂ T
iCl ₂ ((cp) represents a cyclopentadiene group), (cp) ₂ (CH
₃ ) cyclopentadienyl titanium compounds such as ₂ Ti,
In addition, vanadium compounds such as VCl ₄ , VOCl ₃ , VO (C ₂ H ₅ ) ₃ and VO (OC ₄ H ₉ ) ₃ and zirconium such as (cp) ₂ ZrCl ₂ and (cp) ₂ (CH ₃ ) ₂ Zr. Examples thereof include compounds, hafnium compounds such as (cp) ₂ HfCl ₂ and (cp) ₂ (CH ₃ ) ₂ Hf.

The catalyst component containing a transition metal in the component (a) is, as described above, a higher fatty acid salt of magnesium or manganese, a higher alcohol salt, or a phosphate having a long-chain aliphatic hydrocarbon group, added to the above general formula [ I] can be obtained by reacting a transition metal compound represented by the formula [I]. Regarding the reaction conditions at this time, for example, these compounds can be reacted at a temperature in the range of 50 ° C. or higher to the boiling point of the solvent for 10 minutes or more. Good. Of course, it is not limited to this condition, and various other conditions can be used. The higher fatty acid salt, the higher alcohol salt or the phosphate having a long-chain aliphatic hydrocarbon group and the conductive filler are mixed in a hydrocarbon solvent, and then the transition metal compound is added to react. By doing so, a catalyst component containing a transition metal may be prepared. Furthermore, in this case, in order to obtain a catalyst component containing titanium, VOCl ₃ , VO (OC ₂ H ₅ ) ₃ , VO (OC ₄ H ₉ ) ₃ and other vanadium compounds are used together with the salt and the titanium compound. It is effective for broadening the molecular weight distribution of the obtained polymer and improving the copolymerizability. Further, these transition metal-containing catalyst components may be supported on a fine carrier such as magnesium dichloride or magnesium diethoxide.

On the other hand, examples of the catalyst component containing zirconium in (a) the catalyst component include a cyclopentadienyl zirconium compound and a compound obtained by reacting this with an aluminoxane obtained by the above-mentioned known method. Examples of the cyclopentadienyl zirconium compound include dicyclopentadienyl zirconium and dimethyldicyclopentadienyl zirconium.

When these cyclopentadienyl zirconium compound or the cyclopentadienyl titanium compound and aluminoxane are used in combination, these compounds may be used as an aromatic hydrocarbon solvent such as benzene, toluene, xylene and other alkylbenzenes. Mixing in is preferred. Aliphatic hydrocarbon-based or alicyclic hydrocarbon-based solvents are not preferable because they cannot sufficiently dissolve the above transition metal compound and aluminoxane. Further, the reaction of these compounds is preferably carried out before mixing the filler when the conductive filler is treated with the catalyst component (a), but the filler is simultaneously mixed. It is also possible.

The transition metal-containing catalyst component thus obtained is an aliphatic hydrocarbon or an alicyclic hydrocarbon. It is soluble in any of the hydrocarbon solvents such as aromatic hydrocarbons.

In the present invention, (a) the catalyst component is 10 kg or more of polyethylene per 1 atm of ethylene partial pressure and 1 g of transition metal atom in low pressure polymerization of ethylene using this catalyst component and the organoaluminum compound of (b) component. Those having a high activity that can be generated are preferable. This (ii)
If the activity of the catalyst component is low, a large amount of the catalyst component must be added to the reaction system, and as a result, a deashing step is required after the polymerization reaction, and post-treatment becomes extremely complicated, which is not preferable.

In the present invention, (A) a conductive filler and (B)
(A) ethylene is polymerized in the presence of a polymerization catalyst comprising the catalyst component and (b) an organoaluminum compound,
It is preferable to pretreat the conductive filler with the catalyst component (a) and polymerize ethylene in the presence of the conductive filler to which the catalyst component has been added and (b) the organoaluminum compound.

Before being treated with the catalyst component, the conductive filler is sufficiently dried by heating under reduced pressure or azeotropic drying using a solvent, or used for treating the conductive filler (a). ) A predominant aluminum compound having 20 gram atom or less in terms of aluminum per 1 gram atom of transition metal of the catalyst component, for example, at a temperature of 50 ° C or less.
It is desirable to treat for 5 to 5 hours. Such treatment effectively prevents the activity of the catalyst component from decreasing due to the water content or the functional group in the filler. The organoaluminum compound used for this treatment may be the same as the organoaluminum compound used as the component (b),
The organoaluminum compound may be another, and examples of the organoaluminum compound include dialkylaluminum monohalides such as dimethylaluminum monochloride, diethylaluminum monochloride, diisobutylaluminum monochloride, and alkyls such as ethylaluminum dichloride and isobutylaluminum dichloride. Examples include aluminum dihalides, alkylaluminum sesquihalides such as ethylaluminum sesquichloride, trialkylaluminum, and mixtures thereof.

As a method of treating the conductive filler with the catalyst component (a), various methods can be used. For example, the filler may be added to the hydrocarbon solution containing the catalyst component of (a) as it is or as a suspension, and the mixture may be aged for a required period of time, or conversely, the filler may be added to the hydrocarbon solution. It may be added to a solvent to form a suspension, to which a hydrocarbon solution containing the catalyst component (a) is added, and after sufficient mixing, aging may be performed for a required time. The solvent used in this treatment is appropriately selected from aliphatic hydrocarbons, alicyclic hydrocarbons, aromatic hydrocarbons and the like. Further, it can be arbitrarily selected within the range of the treatment temperature or room temperature or the boiling point of the solvent used, and the aging time is usually 1 hour or more at room temperature as a guide, and the higher the temperature, the shorter the time.

Further, in the above treatment, the use ratio of the conductive filler and the catalyst component of (a) differs depending on various conditions and cannot be uniquely determined, but generally, the ethylene polymerization reaction proceeds efficiently. At the same time, a certain amount of the catalyst component (a) which does not require a deashing step after the reaction and an amount of the filler such that the content of the conductive filler in the obtained resistor is 10 to 70% by volume are provided. You can use it.

The conductive filler thus treated with the catalyst component (a) may be introduced into the reaction system as a slurry, or may be introduced after separating the solvent.

As a result, when the ethylene is polymerized, the polymer is formed on the surface of the conductive filler, so that the adhesiveness between the polymer and the filler is increased, and a resistor having good dispersibility of the filler is obtained.

Next, the organoaluminum compound which is the component (b) of the polymerization catalyst (B) is not particularly limited, but is generally represented by the general formula R ′ _m A1X ′ _3-m (II) (wherein R ′ is a carbon atom). Number 1 to 10, preferably 1 to 6 alkyl group, cycloalkyl group or aryl group, X'is a halogen atom, m is a number of 3 or less, specifically 1, 1.5,
2 or 3) Specific examples of the organoaluminum compound include trimethylaluminum, triethylaluminum, triisopropylaluminum, triisobutylaluminum,
Trialkyl aluminum such as trioctyl aluminum, diethyl aluminum monochloride, diethyl aluminum monobromide, diethyl aluminum monoiodide, diisopropyl aluminum monochloride, diisobutyl aluminum monochloride, dialkyl aluminum monohalide such as dioctyl aluminum monochloride, ethyl aluminum dichloride, Alkyl aluminum dihydrides such as ethyl aluminum dibromide, isopropyl aluminum dichloride, isobutyl aluminum dichloride, alkyl aluminum sesquihalides such as methyl aluminum sesquichloride, ethyl aluminum sesquibromide, ethyl aluminum sesquibromide, butyl aluminum sesquichloride and the like. Mixtures of al may preferably be mentioned. Particularly, a mixture of triacyl aluminum and a dialkylaluminum monohalide and a mixture of an alkylaluminum dihalide and an alkylaluminum sesquihalide are suitable when (a) a catalyst containing titanium is used.

In addition, an organolithium aluminum compound, an alkyl group-containing aluminoxane produced from trialkylaluminum and water, and the like can be used. In particular, this aluminoxane is suitable when (a) a catalyst component containing a cyclopentadienyl titanium compound or a cyclopentadienyl zirconium compound is used.

In the present invention, the polymerization catalysts (a) and (b)
Although there is no particular limitation on the proportion of these components used, it may be appropriately determined according to the conditions. Usually, (a) per (1) gram atom of transition metal in the catalyst component, (b) The amount of aluminum atoms in the component is 2-20
It is desirable to use it in a ratio of 00 gram atom, preferably 10 to 1000 gram atom.

In the present invention, ethylene is polymerized in the presence of (A) a conductive filler and (B) a polymerization catalyst comprising the above-mentioned components (a) and (b), within a range not impairing the object of the present invention. , Ethylene with small amounts of other α-olefins such as propylene, butene-1, hexene-1, octene-
It is also possible to copolymerize 1,4-methylpentene-1, decene, octadecene and the like.

The polymerization method and conditions are not particularly limited, and slurry polymerization, gas phase polymerization, or the like is possible, and either continuous polymerization or discontinuous polymerization is possible. Usually, the ethylene pressure of the reaction system is atmospheric pressure to 50 kg / cm ² , and the reaction temperature is 2.
It is selected in the range of 0 to 100 ° C, preferably 50 to 90 ° C. In the polymerization, the molecular weight can be adjusted by a known means such as hydrogen. The weight average molecular weight of the polymer is preferably about 50,000 to 400,000.

In the present invention, in order to uniformize the heat generation inside the resistor due to energization, if desired, powders of alumina, mica, magnesium oxide, clay, talc and the like are added to the reaction system to polymerize ethylene. You can go.

After carrying out the polymerization reaction in this manner, for example, in the case of slurry polymerization, the polymer is taken out by means such as flashing or centrifugation, and the solvent is removed by further drying, and then this polyethylene resin composition is publicly known. The desired resistor is obtained by forming into a desired shape by the above method. During this molding process, if desired, a lubricant, an antioxidant, various stabilizers and the like may be added in a usual amount, or an organic peroxide may be further added as a crosslinking agent for crosslinking. Good.

Examples of the organic peroxide of the cross-linking agent include benzoyl peroxide, t-butylperoxybenzoate, dicumyl peroxide, t-butylcumyl peroxide, t-butyl peroxide and 2,5-di (t-butylperoxide). Oxy) hexyne-3 and the like. The degree of crosslinking is such that the gel fraction with respect to the polymer is 10 to 50% by weight,
Preferably, it is desirable to adjust the content in the range of 15 to 40% by weight. By this cross-linking, more excellent positive temperature coefficient characteristics can be obtained. Regarding the crosslinking conditions, usually, the organic peroxide is added in the range of 0.1 to 3% by weight with respect to the polymer, and the mixture is kneaded at a temperature of 145 to 200 ° C. for about 0.5 to 5 minutes. By heating at a temperature for about 5 to 15 minutes, a desired degree of crosslinking can be obtained.
Of course, it is not limited to this condition.

In addition to the method of using an organic peroxide, crosslinking can be performed by, for example, a method of using ozone or a method of irradiating active energy rays such as ultraviolet rays and electron beams.
When crosslinking is performed using ozone, for example, ozone 0.5
After exposure to a gas containing ˜20% by volume for about 0.5 to 8 hours, 0.5 to 10 parts by weight, preferably 1 to 5 parts by weight, of a crosslinking aid such as divinylbenzene is added to the polymer and kneaded. As a result, crosslinking proceeds. Furthermore, when crosslinking is performed using an electron beam, the polymer is
Irradiation with a dose of about 15 megarads is sufficient.

The content of the conductive filler in the resistor thus obtained must be within the range of 10 to 70% by volume. If this amount is less than 10% by volume, sufficient conductivity cannot be obtained, while if it exceeds 70% by volume, the positive temperature coefficient characteristic is not sufficiently exhibited.

EXAMPLES Next, the present invention will be described in more detail with reference to Examples.
The invention is in no way limited by these examples.

Example 1 In a 500 ml flask purged with argon, 100 ml of dehydrated n-heptane and 10.0 g of magnesium stearate (17
Mmol) and titanium tetrachloride 0.33 g (1.7 mmol)
Then, the temperature was raised and the mixture was reacted under reflux for 2 hours to obtain a solution of a viscous titanium-containing catalyst component.

Next, in a 500 ml flask whose atmosphere was replaced with argon, n-
100 ml of Xanthan and well dried average particle size 43 mμ
Carbon black [manufactured by Mitsubishi Kasei Co., Ltd., Diab
rack E] 20 g, and then the titanium-containing catalyst
Add 0.02 mmol of component and treat at 40 ℃ for 1 hour
The carbon black and the catalyst component.
A rally-like contact treatment product was obtained.

Next, the whole amount of the contact-treated product was put into an autoclave 1 having been replaced with argon, and n-hexane was added to make the total amount 400 ml. Next, 1 mmol each of triethylaluminum and diethylaluminum monochloride was added thereto, and the temperature was raised to 90 ° C., and then hydrogen was added at an internal pressure of 4 kg / cm ²
-G is supplied until ethylene is further introduced and the total pressure is continuously supplied so as to maintain 9 kg / cm ² -G,
A polymerization reaction was carried out for 40 minutes. As a result, 80 g of a carbon black-containing polyethylene composition was obtained. The composition ratio of this product was 15.1% by volume of carbon black and 84.9% by volume of polyethylene.

30 g of the composition thus obtained was melted and kneaded for 3 minutes using a kneading roll at 180 ° C., and then a sheet was molded by a hot press molding machine. Then, electrolytic nickel foil having a thickness of 20 μm was thermocompression bonded to both surfaces of this sheet to obtain a laminate having a thickness of 1 mm. Sixteen 1 cm square test pieces were cut out from this laminate. For all these test pieces, the resistance value between the upper and lower nickel foils at 25 ° C. was measured, and the value converted into the specific resistance was within the range of 100 to 135 Ω-cm, and the average value was 120 Ω-cm. there were. The resistance increase ratio when the test piece was heated to 135 ° C was 25
It was 10 ^6.0 times the value at ° C.

Example 2 Instead of the carbon black used in Example 1, silicon carbide powder [GC # 20 manufactured by Fujimi Abrasives Co., Ltd.]
[00] Example 1 except that 15 g of the same carbon black used in Example 1 was added prior to contact treatment with the titanium-containing catalyst component as in Example 1 and introducing hydrogen in the autoclave. 60 g of a polyethylene composition was obtained in the same manner as in. The composition ratio of this product was 28.4% by volume of silicon carbide, 24.9% by volume of carbon black, and 46.7% by volume of polyethylene.

Using 30 g of this polyethylene composition, 16 test pieces were prepared in the same manner as in Example 1, and the resistance value at 25 ° C. was measured and converted to a specific resistance within the range of 91 to 100 Ω-cm. And their average value was 96 Ω-cm. Further, the resistance increase ratio when the temperature of this test piece was raised to 135 ° C. was 10 ^6.0 times the value at 25 ° C.

Comparative Example 1 18.6 parts by volume of high-density polyethylene [Idemitsu Petrochemical Co., Ltd., Idemitsu Polyethylene 440M] and 81.4 parts by volume of carbon black used in Example 1 were used at 170 ° C. in a Labo Plastomill.
It was kneaded for 10 minutes.

Using this composition, 16 test pieces were prepared in the same manner as in Example 1, the resistance value at 25 ° C. was measured, and the value converted into the specific resistance was in the range of 75 to 165 Ω-cm. Value is 1
It was 25 Ω-cm. The resistance increase ratio at 135 ° C was 10 ^7.0 times the value at 25 ° C.

Comparative Example 2 High density polyethylene (same as that used in Comparative Example 1) 5
3.7 parts by volume, silicon carbide powder (identical to that used in Example 2) 27.2 parts by volume and carbon black powder (identical to that used in Example 1) 19.1 parts by volume were added to a Labo Plus Mill at 170 ° C. for 10 Kneaded for minutes.

Using this composition, 16 test pieces were prepared in the same manner as in Example 1, and the resistance value at 25 ° C. was measured and converted to a specific resistance in the range of 80 to 105 Ω-cm. The average value was 92 Ω-cm. The resistance increase ratio at 135 ° C. was 10 ^6.5 times the value at 25 ° C.

As can be seen by comparing Example 1 and Comparative Example 1 and Example 2 and Comparative Example 2, in the Comparative Example, the variation in the value converted into the specific resistance is considerably larger than that in the Example.

〔The invention's effect〕

The polymer positive temperature coefficient resistor obtained by the manufacturing method of the present invention has excellent positive temperature coefficient characteristics such that the rising ratio of the resistance value reaches 10 ⁶ , and the resistance value of the resistance value is higher than that of the conventional one. It has a stable quality with little variation, and is useful as a material for, for example, an overcurrent protection element, a temperature detector, and a self-temperature control heating element.

Claims (2)

[Claims] 1. Conductivity is obtained by polymerizing ethylene in the presence of a polymerization catalyst comprising (A) a conductive filler and (B) a transition metal-containing catalyst component and (B) an organoaluminum compound. A method for producing a polymer positive temperature coefficient resistor, comprising producing a polyethylene resin composition containing 10 to 70% by volume of a filler and molding the polyethylene resin composition. 2. Ethylene, (A) conductive filler (A)
A polyethylene resin composition containing 10 to 70% by volume of a conductive filler is polymerized in the presence of (b) an organoaluminum compound treated with a catalyst component containing a transition metal. 2. A method for producing a polymer positive temperature coefficient resistor according to item 1.