JPS61101554A - Preparation of electrically conductive resin composition - Google Patents

Abstract

PURPOSE:To obtain an electrically conductive resin compsn. which has excellent electrical conductivity and does not cause changes in electrical conductivity even when subjected to a heat cycle, by mixing electrically conductive oil furnace black having specified oil absorption and surface area with a thermoplastic resin. CONSTITUTION:Oil furnace black (e.g. Toka Black #4500, a product of Tokai Carbo K.K.) having DBP absorption of 130 to 200ml/100g (JIS K6221-1970) and a BET surface area (N2) of less than 100m<2>/g is used. Said carbon black is mixed with a thermoplastic resin such as polyethylene, ethylene/vinyl acetate copolymer or ethylene/propylene rubber to obtain the desired electrically conductive compsn. The compsn. does not cause lowering in electrical conductivity even when high a mechanical shearing force is applied thereto during kneading or extrusion coating.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) This invention relates to a method for preparing a conductive resin composition using a thermoplastic rubber or plastic composition.

(Prior art) Conventionally, in order to impart desired conductivity to thermoplastic resin, 4
What is meant by mechanically adding conductive carbon black, such as conductive furnace black, acetylene black, etc., in a fairly large amount, approximately 40 to 80 parts by weight, to 100 parts by weight of the thermoplastic resin base material. It was common to knead the mixture immediately.

(Problems to be Solved by the Invention) Such conventional conductive resin mixtures are
l! l! Because no special consideration has been given to the conductive carbon black, it is difficult to use when the wires are mixed mechanically with large shearing forces, such as in a Banbury mixer, or when the wires are later extruded into cables, etc. using an extruder. When doing so, there was a problem in that the connections (straftures) between carbon black particles were broken, resulting in a decrease in the desired conductive brightness.

For this purpose, a larger amount of carbon black must be blended, which, on the other hand, inevitably causes other problems such as significantly lowering the moldability of the semiconductive mixture.

(Means for Solving the Problems) The inventors hereby propose that the above problems can be solved by using a specific carbon black that has been carefully selected as a result of intensive studies to solve the problems. Heading completed this invention.

That is, in the present invention, when a conductive carbon black is mixed with a thermo-i plastic resin to obtain a conductive resin composition, JIS K6221-1970 is used as the conductive carbon black.
DBP oil absorption amount of 130m17100g or more20
Less than 0 m171G”O'g, BET surface area (N,)
This is a method for preparing a conductive resin composition, which comprises blending an oil furnace black having a particle diameter of less than 100 n'/g.

In this invention, thermoplastic resins (generally thermoplastic rubbers or plastics used for this type of purpose) are widely used as the base material, specifically low, medium, and high density polyethylene, ethylene, etc. Thermoplastic resins such as vinyl acetate copolymer, ethylene-acrylic acid copolymer, chlorinated polyethylene, polyvinyl chloride, polyethylene, rubber elastic bodies such as ethylene butetrapyrene rubber, chlorosulfonated polyethylene, etc. alone or mixed in amounts of 2g1 or more It includes things.

And as the conductive carbon black to be blended, JI
DBP oil absorption by S K6221-1970 is 13
-Oml/100g or more 200ml less than 7100g,
An oil furnace black having a BET surface area (N2) of less than 100 m'/g is selected and used.

A specific example of such specified oil furnace black is Toka Black #4500 (trade name, manufactured by Tokai Carbon Co., Ltd.).

As mentioned above, the conductive carbon black used in this development has a DBP oil absorption of 130 ml/100 g, or more than 2
Less than 00ml/100g, BET surface area (N2) is
The reason for limiting the amount of oil furnace black Iζ to less than 100 ml is that by using carbon black within this range, the conductivity of the composition will hardly decrease during kneading and extrusion coating due to the above-mentioned large mechanical shearing force. This is because it is not recognized.

The above DBP oil absorption of conductive carbon black is 130m
If less than 1/100 g, carbon black particles 5
On the other hand, when the DBP oil absorption amount exceeds 200*j/100g, although one link of the carbon black particles is developed, the conductivity is also poor. When subjected to large mechanical shear forces, the strutures tend to break, which significantly reduces the conductivity, and furthermore, the ET surface area (N2) decreases to 100rn'/
The carbon black has a large i7i property when the composition is extruded, which causes foaming and the like during extrusion molding of the composition, making it impossible to achieve the object of the present invention.

In this invention, the desired conductivity is determined by the mixing side 41 of the conductive carbon black with respect to the base resin. ``Additionally, appropriate amounts of other antioxidants, lubricants, and organic peroxides may be added at any time depending on the purpose of use.

(Example) Next, this invention will be explained in detail with reference to specific examples. A conductive atM resin composition was obtained by mixing conductive carbon black in a resin using a conventional method using the formulation shown in the following table. .

Regarding these conductive resin compositions, the characteristics of molded products and coated molded products of <y were investigated and the results are shown in the same table.

According to the results in the above table, all of the example products mixed with the above-mentioned specific conductive carbon black gave good results with the above-mentioned characteristics being well balanced, whereas the comparative example products had the following characteristics: For example, Comparative Example 1 had a large specific resistance after extrusion molding, and Comparative Examples 2 to 4 had poor extruded appearance.

(Effects of the Invention) As is clear from the above explanation and the results of the examples, the conductive resin composition produced by the method of the present invention has a low volume resistivity,
In other words, it has good conductivity and is practically excellent in that the conductivity does not change even when subjected to heat cycles, etc., and its industrial use effect is great.

Claims (1)

[Claims] When mixing conductive carbon black with a thermoplastic resin to obtain a conductive resin composition, DBP according to JIS K6221-1970 is used as the conductive carbon black.
Oil absorption amount is 130ml/100g or more 200ml/100
Less than g, BET surface area (N_2) is 100m^2/g
1. A method for preparing a conductive resin composition, which comprises blending an oil furnace black having a content of less than 10%.