JPH087648A - Conductive resin composition - Google Patents

Abstract

PURPOSE:To provide a conductive resin composition useful for obtaining a conductive resin mold whose electric resistance is low and on which the ratio of the layer direction (the perpendicular direction to a plane) of volume specific resistance to the plane direction (the parallel direction to the plane) is further brought close to 1. CONSTITUTION:This conductive resin composition is formed by dispersing graphite and carbon black, on which a layer interval of a carbon six member ring network plane of the graphite is larger than a particle diameter of the carbon black, in a high polymer matrix.

Description

Detailed Description of the Invention

[0001]

The present invention relates to a contact switch,
Materials such as interconnectors, touch sensors, high-frequency shielding packing, waveguide gaskets, electronic device housings, electronic component packaging containers, sheet heating elements, electrode substrates, etc. The present invention relates to a conductive resin composition which is useful for obtaining a conductive resin molded product having a ratio of the surface direction (direction perpendicular to the surface) to the surface direction (direction parallel to the surface) close to 1.

[0002]

2. Description of the Related Art Conductive fillers such as graphite, carbon black, carbon fibers, metal powders and metal fibers are dispersed in various polymer matrices such as rubber, elastomers, thermoplastic resins and thermosetting resins to improve conductivity. The applied composite conductive material is widely used in the field of the above electric / electronic devices. Among them, those that use carbonaceous materials such as graphite, carbon black, and carbon fibers as conductive fillers are chemically stable and do not oxidize or sulfide, so high temperature atmosphere, high humidity atmosphere, sulfurous acid gas atmosphere, hydrogen sulfide gas atmosphere, etc. It is widely used because its volume resistivity does not deteriorate with time even under severe environmental conditions. It is also well known that, in order to achieve even lower resistance, graphite having a low volume resistivity and carbon black having a high structure (higher order chain structure) are combined and graphite particles are connected to each other by carbon black. Has been.

Graphite is roughly divided into natural graphite and artificial graphite. Natural graphite is further
Depending on the particle shape, it is divided into flake (scale-like) graphite, vane (scale-like) graphite, and amorphous (earth-like) graphite. Although these graphites remove impurities by flotation and chemical treatment, especially flake graphite and bain graphite can increase the fixed carbon content to 98 to 99% or more and have a high crystallinity. Is widely used as. On the other hand, amorphous graphite has a fixed carbon content of about 75% and low crystallinity, and is not suitable as a conductive filler, and artificial graphite has a high temperature when coke is mixed with petroleum tar or petroleum pitch as a binder. Since it is a fired product, it requires a crushing process, and thus has a drawback of being slightly expensive. By the way, in the crystal structure of these graphites, mesh planes in which a large number of six-membered conjugated carbon rings are condensed overlap each other at an interval of 3.35Å, and the volume resistivity due to π electron conjugation in the parallel direction to this plane is 1 × 10 ^-5 Ω.・ C
Although it is extremely low as m, the volume resistivity in the direction perpendicular to this plane is as large as 1 × 10 ^-3 Ω · cm, indicating electrical anisotropy.

[0004]

Due to this crystal structure, graphite powder is always flat, and a conductive resin composition in which the flat powder is dispersed in a polymer matrix is subjected to calender roll processing and T-die extrusion processing. When a conductive resin molded body is formed by injection molding processing, coating processing, etc., the flat surface of the graphite powder is almost uniformly oriented in the flow direction of the conductive resin composition. Are arranged substantially parallel to the sheet plane. In the case of blending graphite alone, the ratio of the volume resistivity of the compact to the layer direction and the plane direction (hereinafter referred to as the layer: plane ratio) is 100: 1, which means that high structure such as acetylene black or special oil furnace black is used. Even when carbon black was combined and graphite particles were connected by a carbon black structure to achieve low resistance, there was a drawback that the layer: face ratio was only 10: 1 or more. Further, the volume resistivity of graphite powder is 5 × 10 ⁻³ Ω · cm, although the volume resistivity in the direction perpendicular to the plane of the carbon six-membered ring network is the rate-determining factor.
In the case of a conductive resin composition containing only graphite particles,
The volume resistance in the surface direction is 1 × 10 ⁰ Ω · cm or more, and the volume resistance in the surface direction is 5 × 10 ^{-2 in} the case of a conductive resin composition in which graphite particles and high structure carbon black are compounded and compounded.
Ω · cm or more. At this time, the volume resistivity in the layer direction is
Indicates a value of 10 to 100 times. Therefore, the object of the present invention is to
Layer direction with low electrical resistance and volume resistivity (perpendicular to the plane)
Another object of the present invention is to provide a conductive resin composition which is useful for obtaining a conductive resin molded body having a ratio of the surface direction (direction parallel to the surface) close to 1.

[0005]

This conductive resin composition comprises a polymer matrix in which graphite and carbon black having a carbon six-membered ring network plane spacing of graphite larger than the particle size of carbon black are dispersed. It is characterized by being done. Explaining this, the present inventor has conducted various studies for solving the above-mentioned problems, and when the spacing between the carbon six-membered ring network planes of graphite is wide, if the particle diameter of the high structure carbon black is smaller than this, High structure carbon black can penetrate between layers to form a pseudo intercalation compound and form a strong electrical connection state. For example, in a Li-ion secondary battery, Li ions of the positive electrode active material are graphite of the negative electrode active material. The graphite intercalation compound Li _x C ₆ is formed between the two layers, and when the carbon of the high structure carbon black is Bk and the carbon of graphite is C, the graphite intercalation compound in this case is Bk _x C ₆
The present invention has been achieved by finding out that a product represented by

As described above, the high-structure carbon black is effective as the carbon black in the present invention. Examples of such carbon black include acetylene black and conductive oil furnace black (Ketjenblack ^R).
EC, Vulcan ^R XC-72, etc.) and the like. The particle size of acetylene black is 50 ~ 950Å (50% particle size 420Å), the particle size of Ketjenblack ^R EC is 200 ~ 300Å, Vulcan
The 50% particle size of ^R XC-72 is 300Å. Among them Ketjenblack ^R EC the nitrogen specific surface area 900~1000m ² / g, DBP oil absorption of 350 cm ^3/100 g, has the physical properties of the volatile content 0.8%, etc., are known to have the most developed structure,
In addition, it is preferable to use Ketjen Black ^R EC in view of the relationship between the interlayer distance and the particle size of graphite, which will be described later.

Expanded graphite powder is an example of graphite in which the plane spacing of the carbon six-member ring network plane is larger than the particle size of carbon black. Expanded graphite is obtained by adding strong acids such as sulfuric acid and nitric acid to natural graphite to stabilize it as an intercalation compound, gasifying it in a firing furnace at 900 to 1000 ° C, and expanding the intercalation 100 to 300 times. Specifically, scaly natural graphite is immersed in a solution of concentrated sulfuric acid and an oxidizing agent to form a graphite intercalation compound, diluted, washed with water, dried, and then expanded. This intercalation compound is
It is made up of 1 layer in 12 layers, and the chemical formula is C _n HSO ₄ · 2H ₂ SO.
₄ (n is 24 in the first stage and 48 in the second stage ...
.. Therefore, it will be 288 in the 12th stage. ) Is indicated. Since such a graphite intercalation compound expands, an electron micrograph of expanded graphite can be observed as an irregular lantern shape. The expanded graphite powder can be obtained by directly crushing caterpillar-like expanded graphite, or by compression-molding expanded graphite into a sheet and then crushing it. If the particle size of the expanded graphite powder is too large, the surface becomes rough when a conductive resin molded body is used, and if the particle size is too small, it takes time to pulverize and it is expensive.
It is preferably in the range of ˜500 μm, particularly in the range of 1˜100 μm.

The layer spacing of the plane of the carbon six-membered ring network of the expanded graphite powder is 3.35 layer of natural graphite.
Since Å is expanded 100 to 300 times,
It is 1005Å. Therefore, as mentioned above, acetylene black, Ketjenblack ^R EC, Vulcan ^R XC-72, etc. can be optionally used, but considering the case where the expansion coefficient is 100 times the minimum, the particle size of 200 ~ 300 Å Most preferably, Ketjen Black ^R EC is used. The blending ratio of carbon black to 100 parts by weight of the above graphite is
If it is too small, it becomes difficult to connect the graphite to each other, and if it is too large, it is easy to impede the development of the low resistance characteristic of graphite, so the range is 10 to 150 parts by weight, especially 30 to 100 parts by weight. Is preferred.

Examples of the polymer matrix used in the present invention include polyethylene, polypropylene, polyvinyl chloride, polyvinyl acetate, vinyl chloride-vinyl acetate copolymer, ethylene-vinyl acetate copolymer, chlorinated polyethylene, polyamide, polybutylene terephthalate. , Polystyrene, polyurethane, ABS resin, natural rubber, isoprene rubber, butadiene rubber, nitrile rubber,
Examples thereof include chloroprene rubber, butyl rubber, urethane rubber, acrylic rubber, silicone rubber, silicone acrylic rubber, and fluororubber. These polymer matrices 1
The blending ratio of graphite and carbon black with respect to 00 parts by weight is 10 to 150 parts by weight in order to obtain high conductivity or to improve workability without deteriorating flowability and avoid brittleness of the obtained molded product. It is preferably in the range of 30 parts by weight, particularly 30 to 100 parts by weight.

[0010]

EXAMPLES The present invention will be described more specifically below with reference to Examples and Comparative Examples. (Example) Chlorinated polyethylene having a chlorine content of 30%: Daisolac ^R N130 (manufactured by Daiso Co., Ltd.) 100 parts by weight, 50% particle size by laser diffraction method, particle size 7.2 μm, 10
105 parts by weight of expanded graphite powder (produced by Chuetsu Graphite Industry Co., Ltd., trade name) having a% particle size of 2.8 μm and 90% particle size of 18.6 μm, and 35 parts by weight of Ketjen Black ^R EC (produced by Lion, trade name) A conductive resin composition was prepared by dispersing and blending with a two-roll kneading, and this was calendered into a sheet, which was then heated and cooled at 150 ° C and 50 kgf / cm ²
After hot-pressing for 15 minutes and cooling, a conductive sheet having a thickness of 1 mm was obtained. The volume resistivity in the surface direction of this conductive sheet was measured by Loresta ^R AP (trade name, manufactured by Mitsubishi Petrochemical Co., Ltd.) and found to be 9.5 × 10 ^-3 Ω · cm, and the volume resistivity in the layer direction was 10 mm mercury column. Was 1.6 × 10 ^-2 Ω · cm as measured by contacting both sides of the conductive sheet. Therefore, the molded product made of this conductive resin composition had a low volume specific resistance in the plane direction, and the layer: plane ratio was a very small value of 1.7: 1.

(Comparative Example) 100 parts by weight of chlorinated polyethylene similar to the above was added to flake graphite BF having a particle size by laser diffraction of 50% particle size of 7.6 μm, 10% particle size of 3.0 μm and 90% particle size of 16.3 μm. -8H and (Chuetsu graphite Industries, Ltd., trade name) 105 parts by weight of Ketjen black ^R EC and (Lion Corporation, trade name) 35 parts by weight, and kneaded and dispersed and blended under the same conditions as the sheet Then, it was heated and cooled and pressed to obtain a conductive sheet having a thickness of 1 mm. The volume resistivity in the surface direction of this conductive sheet is calculated by Loresta ^R AP (manufactured by Mitsubishi Petrochemical Co., Ltd.,
It was 9.0 × 10 ^-2 Ω · cm when measured by the product name), and the volume resistivity in the direction perpendicular to the plane was 1.2 × 10 ⁰ Ω · cm measured by the above method. Therefore, the molded product made of this conductive resin composition had a volume resistivity in the plane direction higher by one digit and a layer: plane ratio of 13: 1, which was a considerably large value.

[0012]

^Industrial Applicability According to the present invention, graphite particles having a low volume resistivity on the order of 10 ⁻³ Ω · cm are connected with high structure carbon black to obtain a conductive material having a volume resistivity lower than that of graphite alone. By advancing the conventional method of obtaining a resin composition, by combining graphite in which the layer spacing of the carbon six-member ring network plane is expanded and high structure carbon black with a particle size smaller than this layer spacing, the carbon between the graphite layers is Black is made to enter and graphite is connected. For this reason, the conductive resin composition in which these are dispersed and mixed can have a volume resistivity much lower than that by the conventional method, and the conductive resin molded body obtained from this has a layer: area ratio of The volume resistivity is closer to 1.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Internal reference number FI Technical indication location H01B 5/16 (72) Inventor Yoshiaki Nishijima 1-1406 Yoshino-cho, Omiya-shi, Saitama 1 Shin-Etsu Polymer Product Research Institute Co., Ltd.

Claims (1)

[Claims] 1. A conductive resin composition comprising graphite and carbon black dispersed in a polymer matrix, the graphite having a carbon six-membered ring network plane spacing larger than the particle size of carbon black. Stuff.