JPS6227445A - Production of electrically conductive resin composition - Google Patents

Abstract

PURPOSE:To obtain a resin compsn. which has high electrical conductivity an little variation in electrical conductivity, by subjecting a slurry contg. and electrically conductive power and a polyolefin crystallized from a solvent to a solid/liquid separation treatment and reacting a radical generating agent with the resulting mixture. CONSTITUTION:A polyolefin and an electrically conductive powder are mixed with a polyolefin-dissolving solvent to dissolve the polyolefin in the solvent and to disperse uniformly the powder in the soln. The polyolefin is crystallized from said solvent contg. the polyolefin dissolved therein and the powder dispersed therein in the presence of a polyolefin-nondissolving poor solvent. A slurry contg. the crystallized polyolefin and the powder is subjected to a solid/ liquid separation treatment obtain a mixture of the polyolefin and the powder. A radical generating agent is added to the mixture. decomposed and reacted with the polyolefin to obtain the desired electrically conductive resin compsn.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for producing a conductive resin composition comprising a polyolefin and a conductive powder. Specifically, the present invention relates to a method for producing a conductive resin composition comprising a polyolefin and conductive powder that has high conductivity, small variations in conductivity, and excellent strength characteristics.

[Conventional technology]

Conventionally, so-called conductive resins, which are made by imparting conductivity to thermoplastic resins using various methods, have the characteristics of thermoplastic resins such as ease of molding, and are used as antistatic products and parts for electrical equipment. It is widely used in applications such as conductive adhesives. As a method for manufacturing the conductive resin, conductive powder,
For example carbon black or graphite! A method is known in which Q is added before and after the overlapping section and kneaded and molded using a Banbury mixer, a hot roll, or a combination thereof.

[Problem that the invention seeks to solve]

However, the conductive resin obtained by the above method has a high electrical resistance, and generally has a volume resistivity (also referred to as volume resistivity) of about 703 to 105 Ω・G, and is conductive with the resin. There is a problem in that the volume resistivity varies greatly in the same production batch due to non-uniform mixing with the bulk powder.

Ninth, in order to reduce the volume resistivity to 102Ω・α or less using the above method, it is necessary to add a larger amount of the above carbon black or graphite, that is, 50 parts by weight or more. The mixture becomes even more uneven, which not only increases the variation in the resistance value but also deteriorates the properties of the resin, that is, the moldability, making it impossible to obtain a molded product of conductive resin that is practically satisfactory. .

[Next method to solve the problem]

In view of such prior art, the inventors of the present invention have conducted extensive studies in order to produce a conductive resin composition that has high conductivity, has little variation in conductivity, and has excellent strength characteristics. By adding a conductive powder to a polyolefin solution and then adding a radical generator to the resulting mixture, it has high conductivity, has little variation in conductivity, and has excellent strength properties. The inventors have discovered that a conductive resin composition can be obtained, and have completed the present invention.

That is, the gist of the present invention is to add and mix a polyolefin and a conductive powder to a polyolefin-soluble solvent, add a polyolefin-insoluble poor solvent to this to crystallize a polyolefin, and prepare a polyolefin containing the crystallized polyolefin and a conductive powder. The slurry is solid-liquid separated, and a radical generator is added to the mixture of the obtained polyolefin and conductive powder at a rate of 0.000/~j to 10xx parts of the polyolefin.
The present invention relates to a method for producing a conductive resin composition, characterized in that the radicals are decomposed and reacted with the polyolefin.

The present invention will be explained in more detail below.

The polyolefins used in the present invention include low density polyethylene, medium density polyethylene, high density polyethylene, polybutene/, boiler methylpentene/, ethylene-propylene copolymer, ethylene-butene/copolymer, ethylene- Examples include vinyl acetate copolymers, ethylene-ac polymers, and mixtures thereof.

lc, as the conductive powder, conductive carbon black,
Examples include conductive powders such as graphite and metal powders, with conductive carbon black being particularly preferred.
CF (5uper Conductive Furn)
ace).

OF (conactive furnace),
Channel method CG (CoroLucle Cha)
nnel), acetylene black, etc.

Furthermore, the polyolefin-soluble solvent used to dissolve the above-mentioned polyolefin includes aliphatic hydrocarbons such as hexane and heptane, aromatic hydrocarbons such as benzene, toluene, and xylene, and chlorine such as trichlene, monochlorobenzene, and dichlorobenzene. Examples include hydrogenated hydrocarbons.

In the present invention, first, a polyolefin and a conductive powder are added to and mixed with the polyolefin-soluble solvent, the polyolefin is dissolved in the solvent, and the conductive powder is uniformly dispersed in the solution. There is no particular restriction on the timing of adding the polyolefin to the solvent, and it may be added before adding the conductive powder, added at the same time as the conductive powder, or added after the conductive powder, etc. You can also do it by method.

The amount of polyolefin added is usually 3 to 4 parts by weight or more, preferably 3 to 4 parts by weight, per 10 parts by weight of the above solvent.
More preferably, the range is 5 to 36 parts by weight. If the amount of the polyolefin added is less than 7 parts by weight, the amount of the solvent used increases, which is not economical; if it is more than 7 parts by weight, it takes a long time to dissolve the polyolefin, and the conductivity is reduced. This method is not industrially practical because it is difficult to uniformly disperse the powder in the solution. The temperature at which the polyolefin is dissolved in the above-mentioned solvent is usually at least room temperature, preferably at least 50° C. and at most the boiling point of the solvent, and stirring is carried out for at least 30 minutes, preferably for 30 to 10 minutes.

The amount of the conductive powder added can be arbitrarily selected depending on the desired volume resistivity range of the polyolefin (109~/θ-2Ω・σ), but when the volume resistivity is set to 10Ω・α or less, is based on the weight of polyolefin 10θ,
A conductive powder such as conductive carbon black or graphite is used in an amount of 100 parts by weight or more, preferably in the range of 100 to 300 parts by weight.

In the present invention, the conductive powder obtained as described above is obtained by crystallizing the polyolefin from a mixture containing uniformly dispersed polyolefin in the presence of a polyolefin-insoluble poor solvent, and then combining the crystallized polyolefin and the conductive powder. A slurry containing powder is subjected to solid-liquid separation to obtain a mixture of polyolefin and conductive powder. Polyolefin-insoluble poor solvents are usually carbon e/~! such as methyl alcohol, ethyl alcohol, propyl alcohol, methyl alcohol, etc. Alcohols are used. The amount of the poor solvent used is usually 772 or more in terms of the weight ratio of (the poor solvent)/(polyolefin-soluble solvent), preferably //2.
~Co0//, more preferably Vi///~! Used in the range //. The method of crystallizing the polyolefin from the above mixture in the presence of the poor solvent includes a method of adding the poor solvent to the mixture to crystallize the polyolefin, or a method of adding the mixture to the poor solvent to crystallize the polyolefin. Any method of crystallizing may be used. The crystallization temperature when crystallizing the polyolefin is preferably a temperature below the boiling point of the poor solvent! It is carried out at a temperature below θ°C.

The slurry containing the polyolefin and conductive powder crystallized by K as described above is left to stand as necessary, and then
A mixture of polyolefin and conductive powder is obtained by performing solid-liquid separation using a conventional solid-liquid separation method such as filtration or centrifugation. The obtained mixture of polyolefin and conductive powder is washed with the poor solvent if necessary, and then dried.

The conductive resin composition of the present invention is obtained by further adding a radical generator to the above-described mixture of polyolefin and conductive powder, decomposing the radical generator, and reacting with the polyolefin.

The radical generator to be added to the above-mentioned mixture of polyolefin and conductive powder is preferably one with a decomposition temperature in the range of 730°C to 3θθ°C with a half-life of 7 minutes, such as dicumyl peroxide, co-! -Dimethylco,!
-di(t-butylperoxy)hexane, -1! -dimethyl-2,j-di(1-butylperoxy)hexyne-
3, α, α′-bis(1-butylbaroxyisoglobil)benzene, dibenzoyl peroxide, di-t-
Examples include butyl peroxide.

The amount of radical generator added is 100% of the above polyolefin.
selected from the range of 0.000/~j parts by weight, preferably 0.00.2~-21i parts by weight,
If this addition amount is less than O0θOθ/it part,
The effects of the present invention are not noticeable, for example, the strength properties of molded products are almost the same as those without additives, and
If the amount is more than 5 parts by weight, the added radical generator will have poor dispersibility and will locally react with the polyolefin before being uniformly dispersed, resulting in variations in the strength properties and volume resistivity of the resulting composition. This is not preferable because it increases the size.

In the present invention, the method of adding a radical generator to the mixture of the polyolefin and conductive powder, decomposing the radical generator, and reacting with the polyolefin is not particularly limited, and for example, the following method is used. It can be carried out with

(1) Using a mixing machine such as an extruder or a Banbury mixer, the mixture of the polyolefin and conductive powder and the radical generator are kneaded, pelletized, and then press-molded or compressed using the pellets. During molding, the radical generator and polyolefin are reacted.

(2) During molding, for example press molding or compression molding,
When the mixture of the polyolefin and conductive powder and the radical generator are fed simultaneously or sequentially and melt-molded, the radical generator and the polyolefin are reacted.

(3) A masterbatch containing a large amount of a radical generator (a large amount of a radical generator is added to a polyolefin at a temperature higher than the melting point of the polyolefin and at a temperature at which the reaction between the polyolefin and the radical generator is extremely slow, e.g.
High concentration (usually 2
A polyolefin masterbatch containing a radical generating agent of about 0.00 ppm -20% is prepared in advance, and this i-starbatch is blended with a mixture of the polyolefin and conductive powder, followed by press molding or compression molding.

Next, by the method (2) or (3) above, the polyolefin and the radical generator are molded without sufficiently reacting, and the molded product is heat-treated at a temperature higher than the molding temperature to complete the reaction. It may also be done in the following manner.

Further, the radical generator itself may be used as it is or dissolved in a solvent.

By reacting the mixture of the above-mentioned polyolefin and conductive powder with a radical generator, the polyolefin undergoes a cross-linking reaction, cross-ring occurs between molecules, the intermolecular force increases, and a part of the polyolefin becomes gelatinous. When the product is made into a molded product such as a sheet, the impact occurs! A conductive resin composition with significantly improved strength properties such as 1 strength and tensile strength can be obtained.

The conductive resin composition of the present invention may also include antioxidants, ultraviolet absorbers, heat stabilizers, antistatic agents, etc. depending on the purpose of use.
Additives such as pigments can be added as appropriate.

〔Example〕

Examples / (a) Production of a mixture of polyolefin and carbon black
/%009) and conductive carbon black (average particle size ♂
0μ) 302, and while stirring, lower the liquid temperature to 7.20.
The temperature was raised to 'C, and to this was added high-pressure low density polyethylene (density: 0.li/L!"y/cnI, melt index: 10f/10 minutes) 70? with stirring.
After holding at 20°C for 7 hours, it was cooled at 7j'Cj, 2t of ethyl alcohol was added thereto, and the mixture was heated at 23°C for 3 hours.
The polyolefin was held for 0 minutes to crystallize on the carbon black surface. The slurry containing the crystallized polyolefin and carbon black was filtered at 23°C for solid-liquid separation, and the resulting mixture of polyolefin and carbon black was washed with ethyl alcohol/l, and then left to stand day and night. It was air-dried and further vacuum-dried at a temperature of 70 to 7JC for 70 hours to obtain a polyolefin and carbon black mixture powder 999.

(b) Manufacture and evaluation of conductive resin compositions i
i' 7.0 parts by weight of dicumyl peroxide (100 gm) of the polyolefin and carbon black mixture powder obtained in (a) was mixed in a roll, and this was press-molded at a temperature of 730°C to a thickness/wR. Made into a sheet. The obtained sheet is heat treated at a temperature of 760°C for 20 minutes or more,
It is important to complete the reaction between the unreacted radical generator and the polyolefin. The impact strength, tensile strength, volume resistivity, and variation in volume resistivity of the sheet were measured using the following methods.

In addition, the volume resistivity is at a temperature of 20°C and a humidity of 6! The volume resistivity was measured using an electrode for measuring volume resistivity (manufactured by Ando Denki, digital multimeter J% & jB type) under constant temperature conditions.

Impact strength is ASTM D //,! , 2K.

The tensile strength was determined according to J-Kotsu SK Otsu 7 Otsu θ.

The results are shown in Table/.

Example 9 The same procedure as in Example 9 was carried out except that the mixing ratio of conductive carbon black and high-pressure low density polyethylene was changed as shown in Table 9. Show the results/
Shown below.

Using the same raw materials as those used in Comparative Example/Example/, 30 parts of conductive carbon black was added to 70'N parts of high-pressure low-density polyethylene.
7.2 parts by weight was added using a roll kneader.
The process was carried out in the same manner as in Example/(b), except that the conductive resin composition was manufactured by kneading at a temperature of 0° C. for 30 minutes. The results are shown in Table/.

Comparative Example Comparative Example 1 was carried out in the same manner as Comparative Example 1, except that the mixing ratio of high-pressure low density polyethylene conductive carbon black was changed as shown in Table 1. The results are shown in Table/.

〔Effect of the invention〕

The conductive resin composition obtained by the present invention has higher conductivity than those obtained by conventional methods, has less variation in conductivity, and has excellent strength properties. Therefore, the highly conductive resin composition obtained by the method of the present invention is suitably used for battery electrodes, resistors, antistatic materials, high-voltage cables, conductive substrates, heating elements, electric field shielding materials, breaking materials, etc. be able to. Particularly when used in a resistor, since the conductor is uniformly distributed, the current flows uniformly, and there is no current runaway that is observed in conventional products, which prevents damage to the circuit, which is preferable.

Sender: Mitsubishi Chemical Industries, Ltd. Representative Patent Attorney Hase - Others/Names

Claims (1)

[Claims] (1) Polyolefin and conductive powder are added to a polyolefin-soluble solvent and mixed, a polyolefin-insoluble poor solvent is added to this to crystallize the polyolefin, and a slurry containing the crystallized polyolefin and conductive powder is converted into a solid liquid. Separating, adding 0.0001 to 5 parts by weight of a radical generator to 100 parts by weight of the polyolefin to the obtained mixture of the polyolefin and conductive powder, decomposing the radical generator and reacting with the polyolefin. A method for producing a conductive resin composition characterized by