JPH04159341A - Conductive composition - Google Patents

Abstract

PURPOSE:To improve processability, electrical conductivity, and mechanical strengths by compounding a rubber with a conductive carbon black, a flaky graphite, and a metal salt of a fatty acid and/or a fatty acid ester. CONSTITUTION:100 pts.wt. rubber, e.g. natural rubber or styrene-butadiene, 20-100 pts.wt. conductive carbon black, 30-150 pts.wt. flaky graphite obtd. by grinding an expanded graphite, 1-20 pts.wt. component comprising a metal salt of a fatty acid (e.g. cadmium stearate) and/or a fatty acid ester, and if necessary, a vulcanizing agent, an accelerator, an antioxidant, a filler, a process oil, etc., are compounded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a conductive composition made of rubber as a base material, which has particularly excellent processability and is suitable for use in %F antistatic flooring materials in facilities for precision electronic devices, etc. The present invention relates to a novel electrically conductive composition that can be easily processed into a sheet shape such as, and has high electrical conductivity.

[Conventional technology] In IC factories and electronic component assembly factories where problems such as dust adhesion and semiconductor destruction due to static electricity are likely to occur, conductive materials with low electrical resistance are placed on the floor to help correct the 8F electric charge caused by static electricity. Normally, the work area is covered with flexible sheets to ensure that workers can ground themselves.

In this case, the smaller the volume resistivity of the conductive sheet, the more desirable it is.For example, if the flooring material has an electrical resistance of about 1xio''Ω, static electricity accumulates in the human body on the order of several hundred volts, but the resistance is half that. It is thought that the voltage will drop to around 10 volts when the voltage drops to about 10 volts.The impact of such static electricity on semiconductor devices is naturally conceivable. In recent years, there has been an increasing demand for reducing the volumetric efficiency of the conductive sheet as much as possible.

The conventional conductive sheet mentioned above uses rubber or plastic as a base material, and adds metal powder, graphite powder,
They were manufactured by incorporating large amounts of conductive substances such as conductive carbon black or electrolytes. Among these conductive substances, carbon black, such as acetylene black or Goetjen black, which has a high degree of conductivity, has been mainly added to manufacture industrially from the viewpoint of characteristics and economy.

[Problems to be Solved by the Invention] As mentioned above, there has recently been a demand for reducing the volume resistivity of conductive sheets as much as possible.
It has become necessary to have high conductivity of Ω-C11 or less.

However, in order to obtain a high degree of conductivity with a volumetric efficiency of less than 1 Ω-CI, it is necessary to add a very large amount of conductive substance, which results in a significant increase in the viscosity of the material.
Problems have arisen in that workability is significantly impaired during kneading, extrusion, sheeting using calender rolls, and the like.

In addition, derivative drawbacks such as a significant decrease in mechanical properties, such as tensile properties, of the manufactured materials have also arisen, which has become a problem in practice.

The purpose of the present invention is to solve the problems of the prior art described above,
The object of the present invention is to provide a novel electrically conductive composition that is easy to knead, extrude, or process into sheets, and has extremely high electrical conductivity.

U Means and operation for solving the problems The gist of the present invention is to provide rubber 1. 0 parts by weight, conductive carbon black 2
The conductive composition contains 0 to 100 parts by weight of exfoliated graphite, 30 to 150 parts by weight of exfoliated graphite, and 1 to 20 parts by weight of fatty acid metal salt and/or fatty acid ester.

Rubbers include natural rubber, styrene-butadiene rubber, butadiene rubber, syndiotactic 1゜2 polybutadiene, imprene rubber, acrylonitrile-butadiene rubber, ethylene-propylene rubber, and ethylene-propylene-gentar polymer.

Halogen-free rubber such as butyl rubber, acrylic rubber, silicone rubber, polysulfide rubber, urethane rubber, chloropylene rubber, chlorosulfonated polyethylene, shrimp chloride rubber, chlorinated polyethylene, chlorinated ethylene/propylene rubber, chlorinated ethylene/propylene Examples include those containing halogen such as terpolymer, brominated butyl rubber, chlorinated butyl rubber, and fluororubber.

Types of conductive carbon black include Palkan Printex, Conductex, Denka Black, and Asahi M.
Examples include S-500, Toka Black, Mitsubishi Conductive Carbon, and Goetjen Black.

The reason why the amount added is 20 to 1001 parts by weight is because if it is less than 20 parts by weight, sufficient conductivity cannot be obtained, and if it is more than 100 parts by weight, the viscosity becomes high and processing becomes difficult.

In addition, exfoliated graphite is made by heat-treating acid-treated graphite at high temperatures and rapidly vaporizing the acid between the eyebrows to volatilize it.
At the same time, it is manufactured by crushing expanded graphite that has been expanded between the eyebrows. Commercially available products include Nippon Graphite Industries' EX
There are two grades: PP and EP. The amount added is set to 30 to 150 parts by weight because if it is less than 30 parts by weight, sufficient conductivity cannot be obtained, and if it is more than 150 parts by weight, the viscosity becomes high and it becomes difficult to process it into a sheet shape.

Metal soaps are usually various metal higher fatty acid salts represented by M(OOCR)n, and their properties vary depending on not only the type of metal but also the chain length, degree of unsaturation, substituents, etc. of the fatty acid. Specifically, cadmium stearate, cadmium laurate, cadmium ricinoleate, cadmium naphthenate, 2
- Cadmium ethylhexoylate, barium stearate, barium laurate, barium ricinoleate, barium naphthenate, barium 2-ethylhexoylate, calcium stearate, calcium laurate, calcium ricinoleate, strontium stearate, zinc stearate, laurine zinc acid, zinc ricinoleate, 2
- Zinc ethylhexoate, lead stearate, dibasic lead stearate, lead naphthenate, tin stearate, aluminum stearate, magnesium stearate, zinc oleate, copper oleate, magnesium oleate, nickel oleate, Examples include iron oleate, aluminum oleate, lead oleate, chromium oleate, and calcium oleate.

In addition, fatty acid esters are compounds of long-chain fatty acids and alcohols. Fatty acids include long-chain saturated and unsaturated monocarboxylic acids, dicarboxylic acids, and oxycarboxylic acids, and alcohols include butanol, octatool, etc. There are alcohols and polyhydric alcohols such as ethyl glycol, glycerin, pentaerythritol, and sorbitol, and many types of fatty acid esters can be produced. Hydrophilic types include emulsion-like types.

There are various types of these metal soaps and fatty acid esters, such as individual ones, composites with other compounding agents, mixtures of both, and even mixtures of the two with other compounding agents. Can be mentioned.

Further, when adding to the conductive material, each may be used alone, but the effect will be further enhanced if two or more of them are used in combination. The amount of these added was 1 to 20 parts by weight.
This is because if the amount is less than 20 parts by weight, sufficient processability cannot be obtained, and if it is more than 20 parts by weight, a part of the sheet oozes out to the surface after being processed into a sheet (bleed or bloom phenomenon).

In the present invention, in addition to the above compounding agents, a vulcanizing agent, a vulcanization accelerator, an antioxidant, a filler, an operating oil, a pigment, etc. may be added.

As a method for crosslinking the composition of the present invention, a method using a sulfur-based vulcanizing agent is generally used, but depending on the application, methods such as crosslinking using an organic peroxide, crosslinking using electron beam irradiation, and silane graft water crosslinking may also be used. You can choose. As the crosslinking agent used for crosslinking with an organic peroxide, dicumyl peroxide, 3-bis(t-butylperoxyisopropyl)benzene, etc. are suitable. In addition, as a crosslinking aid in crosslinking by electron beam irradiation, reactive monomers such as trimethylolpropane trimellitate and triallyl isocyanurate are generally used.

U example] Preferred embodiments of the present invention will be described below with reference to the accompanying drawings.

Mix various ingredients according to the proportions shown in Table 1, and make approximately 8.
The material was placed in a 6-inch roll maintained at 0° C. to perform roll cross-wiring. After kneading, heat the mixture at 160°C using a steam heating press.
Vulcanize for 10 minutes to obtain a 1ms thick sheet.

The evaluation results for each side are shown in the lower column of Table 1. The evaluation method is as follows.

Workability 2 Measured by appearance during roll kneading and motor load. Regarding the motor load, it is acceptable if it is less than IOA.

Electrical characteristics: As shown in Figure 1, 20X100Xll
Silver paint 2.2 was applied to both ends 10cm of sample 1 of ll, and after leaving it for one day, the resistance (R) was measured using resistance measuring device 4 using the Wheatstone bridge method, and the volume resistivity (ρ) was calculated using the following formula. .

Breed, bloom: inn thick unvulcanized sheet and vulcanized sheet room temperature (6 hours), room temperature → 100℃ (6h), 100℃ (6h), 100 ℃ → Always! <6h) as one cycle7 Visually evaluate appearance after cycle exposure Cases where there was no change were considered good.

, l g As is clear from Table 1, Examples 1 to 4 all have excellent roll workability, exhibit high conductivity with a volume resistivity of 1 Ω-cn or less, and exhibit no bloom or bleed phenomena. .

On the other hand, both Comparative Example 1, in which no metal soap or fatty acid ester was added, and Comparative Example 2, in which a large amount of Ketchen Black EC was added, had poor roll processability. Comparative Example 3 of exfoliated graphite alone and Ketchen Black E
C. Comparative Example 5, in which the amount of exfoliated graphite added was small, had a high volume resistivity. Comparative Example 4, in which the total amount of metal soap and fatty acid ester exceeds 20 parts by weight, exhibits blooming and bleeding phenomena and is inferior.

From the above results, by combining conductive carbon black and exfoliated graphite within the scope of the present invention, and adding metal soap and fatty acid ester within the scope of the present invention, it is possible to improve processability, improve electrical properties and sheet appearance. This shows that it is possible to obtain materials that are the best in terms of performance and can be processed into conductive sheets and the like to achieve excellent results.

The metal soap and fatty acid ester used in the present invention have the effect of lowering the viscosity of the compound, increasing the glabellar slipperiness of the st material during processing of caentalol, reducing the load on the roll, and suppressing roll stickiness. This combination improves processability overall.

E. Effects of the Invention As described above, according to the composition of the present invention, it is possible to provide a conductive composition that maintains high S conductivity and has improved workability and mechanical strength, and is It can appropriately meet modern demands in the industry, and its industrial value is extremely large.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing an example of measuring the volume resistivity of a conductive composition obtained according to the present invention and a ratio of ¥1 FIAJ. In the figure, 1 is a sample, 2 is silver paint, and 3 is a resistance measuring device. Figure 1

Claims (1)

[Claims] 1. 100 parts by weight of rubber, 20 parts by weight of conductive carbon black
1. A conductive composition comprising: 100 parts by weight of exfoliated graphite, 30 to 150 parts by weight of exfoliated graphite, and 1 to 20 parts by weight of a fatty acid metal salt and/or a fatty acid ester.