JPS61127612A - Production of electrically-conductive graphite material - Google Patents

Abstract

PURPOSE:To produce the titled flake-shaped graphite material of high aspect ratio by crushing the expandable graphite packed with liquid or freezed liquid into the clearances. CONSTITUTION:The expandable graphite is immersed into an aq. soln. of HCl, NaOH and methyl alcohol or the like to pack liquid into the clearances and after cooling it to freeze the liquid if necessary, it is crushed to obtain the flake-shaped graphite powder of about 0.01-1mum thickness and about 5-50mum diameter. Then after the graphite powder is subjected to the oxidizing treatment till about <=10% reduced weight of quantity of graphite at 500-1,200 deg.C in the inert gas atmosphere contg. 0.1-25% oxygen or the graphite powder is brought into contact with the organic substance (e.g.styrene) to graft-polymerize the mixture, it is extracted with a solvent to perform the chemical treatment.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing Kurofune powder with a novel shape that can impart high electrical conductivity to plastics, paints, etc.

Conventional technology and its problems Carbon is a material with excellent electrical conductivity, and graphite in particular has high electrical conductivity close to that of metal. It has been widely used as a current collector for trolleys, etc. Furthermore, in recent years, regulations regarding electromagnetic interference have been tightened, and it has become necessary to electromagnetically shield equipment such as small-sized computers and switch-shift power supplies.

Further, electronic circuits are becoming lighter and cheaper, and manufacturing processes are becoming more streamlined, and for this reason, there is a demand for new materials such as highly conductive paints. Under these circumstances, carbon powder, especially graphite powder, has come to be used as a filler or additive for imparting conductivity to conductive plastics, conductive paints, and the like.

However, the existing graphite powder used as a conductivity-imparting material is so-called colloidal graphite, and when used as a filler for plastics, for example, (a) it is necessary to use a large amount to increase conductivity. However, there are some disadvantages such as the plastic product becomes dark black, the dispersibility in 0 plastic is not good, and the impact resistance of 6Q plastic product is not satisfactory. Therefore, there is a strong desire to reduce or eliminate the above-mentioned drawbacks while taking advantage of the advantages of graphite fillers such as low cost, light weight, and good injection moldability.

Means for Solving the Problems The inventor of the present invention has conducted various experiments and researches in view of the current state of the technology as described above, and has found that when expanded graphite is crushed under specific conditions, it has a flat shape. Graphite powder with a unique shape and extremely small thickness can be obtained by using the method, and the obtained flaky graphite powder with a high aspect ratio has extremely excellent properties as a conductive material for plastics, paints, etc. etc. were found. That is, the present invention provides a method for producing thin plate graphite powder, which is characterized by pulverizing expanded graphite in a state in which the voids of the expanded graphite are filled with a liquid or in a state in which the liquid is frozen. .

Furthermore, according to the research of the present inventor, the thin graphite powder obtained by the above method is oxidized or treated with an organic t-mer.
It has been found that when the powder is subjected to oxidation treatment, oxygen or sulfur is bonded to the end of the thin plate, thereby further improving the dispersibility of the powder into plastics, paints, etc. That is, the present invention obtains thin plate-like graphite powder by crushing expanded graphite in a state in which the voids of the expanded graphite are filled with a liquid or in a state in which the liquid is frozen, and then oxidizing the powder or The present invention also provides a method for producing a thin plate-like graphite powder, which is characterized in that an organic substance is coated on the surface of the powder by chemical treatment.

The expanded graphite used in the method of the present invention is a known material, and is prepared by a chemical treatment method in which natural flaky graphite or artificial flaky graphite is immersed in a strongly oxidizing solution, washed with water, and heated, or similar scales are prepared. It is produced by an electrolytic treatment method in which graphite is anodized in a sulfuric acid electrolyte and then rapidly heated to about 800°C. According to X@ diffraction, the expanded graphite obtained in this -31+ manner has a graphite crystal structure, but it is 10 to 400 times larger in the C-axis direction than the original graphite crystal. The graphite layer has a somewhat expanded form, and a scanning electron micrograph taken from a direction parallel to the plane of the graphite layer shows that a 2-cam structure having pores with a diameter of about 20 to 100 μm is formed.

To produce thin plate graphite powder, a honeycomb structure of expanded graphite is filled with a liquid that does not react with graphite, or the liquid is frozen and solidified and then pulverized.

Examples of the liquid for filling expanded graphite used in the present invention include the following.

! Water and aqueous solutions of the following compounds (1) Inorganic acids such as hydrochloric acid, nitric acid, phosphoric acid, sulfuric acid, silica
Aqueous solutions of organic acids such as acid, acetic acid, and f-acid. The concentration is 10r
0 (2) Aqueous solutions of alkaline substances such as sodium hydroxide, potassium hydroxide, calcium hydroxide, etc. The concentration is lO'
It is preferable that f, l/j or less be 0. (3) Aqueous solutions of metal hegenides, metal nitrates, sulfates, etc. The concentration is preferably less than 7 l/I.

■ Organic matter (1) Alkanes Butane 1 Pesitane 1 to 10 Sans to Butane 1 Octane etc.

(2) Alkenes Putesi, penten, hegyusen, heptene, etc.

(3) Alchemist species:, 11 Pescitin 1 to Beef Shishi 1 Heptishi etc. 0 (4)
Alcohols methyl alcohol, ethyl alcohol, methyl alcohol, butyl alcohol, ethylene glycol, chrysalis, etc.
benzaldehyde etc.

(6) Ketones dimethyl ketone, ethyl methyl ketone, acetophenone, propyl methyl ketone, diethyl ketone, Schifenone, benliphenone, etc. 0 (7) Carboxylic acids f-acid, acetic acid, oxalic acid, butyric acid, phosphoric acid, oxic acid, etc. .

(8) Esters Methyl f-acid, ethyl f-acid, ethyl acetate, etc.

(9) Aromatic compounds such as benzene, carbolic acid, and compounds in which a methyl group, ethyl group, sulfur, nitrogen, sulfur, etc. are added to benzene.

01 Aqueous solution of the above organic liquid soluble in water.

Filling the honeycomb with liquid is carried out by first degassing the expanded graphite under reduced pressure, bringing it into contact with saturated vapor of the liquid at an appropriate temperature, for example room temperature, to achieve saturation adsorption, and then immersing it in the liquid. is preferred. When solidifying the liquid,
This is done by cooling expanded graphite filled with a liquid to a temperature below the freezing point of the liquid. The expanded graphite filled with a liquid or its coagulated material may be pulverized using any pulverizing means such as a rotating three-wheeled spoon, a mortar, or a pulverizer. Make it. After pulverization, if a powder is obtained from which the filling liquid has been removed, the liquid is removed using a vacuum bomb while maintaining the temperature below the freezing point of the liquid. When used in a dispersed state in a liquid, it can be used as is after pulverization. Ru.

The thin plate-like graphite powder thus obtained has a unique shape in which the wall portion of the above-mentioned two-cam structure is separated at the joint, and has a thickness of about 0.01 to 18 μm, and a diameter of 5 to 50 am.
That's about it.

As is well known, graphite has a structure in which hexagonal cotton-like planes of carbon atoms are piled up in a layered manner, and various radicals can be added to the free radicals present on the end face perpendicular to the circumferential plane.

The properties of the carbon surface are modified in various ways depending on the type of radical added. Also in the present invention, by surface-treating the thin plate graphite powder obtained as described above, the dispersibility in, for example, plastics, paints, etc. can be further improved. Surface treatment can be carried out, for example, by applying thin plate graphite powder in an inert gas atmosphere containing about 0.1 to 25% oxygen, for example in air, at a temperature of about 500 to 1200°C, so that the weight loss of the graphite does not exceed 10%. This is carried out by oxidizing the graphite to a certain extent to form an oxygen complex compound having a carboxylic group, a carbonyl group, a phenyl group, etc. on the graphite surface. Alternatively, after heating and polymerizing a thin graphite powder in a state where it is in contact with a vinyl-based butadiene such as ethylene, propylene, or vinyl-based butadiene such as styrene, it can be polymerized using a solvent such as benzene. Extracted by
A surface-treated product may be obtained by heating a mixture of 1 part by weight of thin graphite and 3 parts by weight of styrene at 140°C for 5 hours as an example of using styrene in the latter. , styrene can be craft-polymerized on the carbon surface.

According to the thin plate graphite powder of the present invention, the following remarkable effects can be achieved.

(1) Since the orientation of the powder particles when molded or applied is much higher, the conductivity of plastic products, coatings, etc. can be significantly increased by using a small amount compared to colloidal graphite. (2) Therefore, since the amount of gold used can be reduced, dark black coloring of plastic products, paint films, etc. can be avoided.

(3) Good dispersibility in plastics, especially those with surface modification.0 (4) Significantly increases the impact resistance of plastic products.0 (5) Even in paints, thin plate-like Because of its morphology, sedimentation is extremely low compared to colloidal graphite.

(6) Even in the coating film, it has excellent adhesion to the coated surface and does not cause sorbeito cracks even when thickly coated.

The features of the present invention will be further clarified by the following examples.

Example 1 Natural flaky graphite powder from Madagascar (average diameter approximately 500 mm)
ams thickness about 50 am, purity 99%) 5V to 1
After repeating electrolytic oxidation treatment and electrolytic reduction treatment three times under the conditions shown in Table 1 below in a 5V Nyl/l sulfuric acid electrolyte (20 l) to form a residual compound of sulfuric acid between the graphite layers, By washing with water, drying, and then rapidly heating to 850° C., expanded graphite having a volumetric expansion coefficient of 300 times was obtained.

Table 1 Next, the expanded graphite obtained above was placed in a glass container and degassed using a vacuum pump.Ethyl alcohol vapor at saturated pressure was introduced into the container and left to stand for 12 hours. Ethyl alcohol was saturated and adsorbed into the pores. Then,
The expanded Kurofune was immersed in 10-proof ethyl alcohol, and then pulverized at room temperature for 4 hours at a rotation speed of 500Qr7m using a mill equipped with four blades in the diameter direction around the rotating shaft. After the grinding was completed, the shape of the graphite powder dispersed in ethyl alcohol and kneaded was observed using a scanning and transmission electron microscope.
As shown in (10x), it was confirmed that the graphite powder was a thin plate-shaped graphite powder with a thickness of 0.05 to 1.0 #m and a diameter of 10 to 150 μm. Further, a powder was easily obtained by removing the ethyl alcohol using a vacuum bomb.

Example 2 Expanded graphite prepared in the same manner as in Example 1 was filled with ethyl alcohol in the same manner as in the example, and then cooled with liquid nitrogen (-179°C) to remove the ethyl alcohol present in the pores. The ethyl alcohol was freeze-solidified and ground in a mortar for 5 minutes to obtain a thin graphite powder. After leaving the obtained thin graphite powder at room temperature to melt the ethyl alcohol, the shape of the graphite powder in the dispersion was observed using a scanning and transmission electron microscope. Micrograph, 2
X I O' times) VC as shown (, thickness i 0.01 ~ O
, l atn-i2- M is flat thin plate graphite with a diameter of 10 to 50 μm
It was ordered.

When compared with the electron micrograph of colloidal graphite at the same magnification shown in FIG. 3, the unique shape of the product of the present invention becomes clear.

Further, by removing the ethyl alcohol in the dispersion obtained above using a vacuum pump, thin plate graphite could be obtained as a powder.

Example 3 Expanded graphite 5f prepared in the same manner as in Example 1 was placed in a glass container and degassed using a vacuum pump. Steam at saturated pressure was introduced into the container and left for 12 hours to dissolve the expanded graphite. Water was saturated and adsorbed into the pores, and then immersed in IO- water and cooled with liquid nitrogen to freeze and solidify the water filled in the pores. After pulverizing the frozen material in a mortar for 5 minutes, it was left at room temperature to melt the ice, and a 40 μm sample was collected from the aqueous dispersion of graphite powder, with a width Q of 15ffi and a length of 2.8 as.
injected into a plastic frame and allowed to dry. The electrical resistance of the ribbon graphite obtained after drying was measured by a voltage drop method and was found to be 6×10 Ω·1.

On the other hand, ribbon graphite was prepared using the same amount of colloidal graphite powder, and its electrical resistance was measured.
The damage was 0''Ω.

It is clear that the electrical resistance of the graphite powder of the present invention is extremely low.

Example 4 10F of flaky artificial graphite (beef graphite) was dissolved in 50 ml of 18 mol sulfuric acid and 5 g of potassium perchlorate. After the obtained expanded graphite powder was saturated with benzene adsorption, it was immersed in benzene, then cooled with liquid nitrogen, and the frozen material was pulverized. After centrifuging the pulverized material at room temperature, the graphite powder and styrene salt were mixed at a weight ratio of d (1:3).
The ratio to the surface area determined from the 5-pole crosstalk at 40°C is calculated by heating for a period of time before treatment to craft styryl on the surface of the graphite powder, then extracting with benzene to give a 90-degree shape.
After adding and mixing 2f of thin plate graphite powder, which was freeze-dried at 5°C to completely remove benzene, to 8f of the EVO+Si group-containing compound, it was polymerized to create an EVO+Si resin molded body of 5M11 x 20fi x 50gm1. The electrical resistance of the obtained molded body was measured by the voltage drop method and was found to be 3×10 Ω.
・It was 1.

In addition, the electric resistance of a similar Evo + Shi resin molded product obtained by using Shitshu graphite as an additive instead of thin plate graphite powder is 9 × 1
00・It was a scratch@Example 5 The thin plate graphite powder obtained in the same manner as in Example 2 was heated to an oxygen partial pressure of 3.
The sample was heated at 850° C. for 10 minutes in an inert gas atmosphere to form an oxygen complex compound on its surface. The weight reduction rate in this case was 0.8%.

Surface area determined from crosstalk such as water adsorption and nitrogen gas absorption 0.25
After the treatment, the value increased to 0.45, indicating that hydrophilic oxides were generated on the surface of the thin graphite powder.

The powder after the surface treatment obtained above and the oil for paint are mixed in 1 part
After applying the mixture to a thickness of 0.021111 on paper and leaving it at room temperature for 48 hours, a conductive thin film was obtained.The electrical resistance of the obtained thin film was measured by the DC voltage drop method. When measured, it was found to be 8×10”Ω·1, which revealed that the thin film had extremely excellent conductivity.

[Brief explanation of the drawing]

Figures 1 and 2 show transmission electron micrographs (2X10x magnification) of laminar graphite powder according to the present invention, and Figure 3 shows a similar picture of a known colloidal graphite powder. ) Figure 1 Figure 2 Figure 3 Procedural amendment (method) % formula % 1. Indication of the case 1982 Patent Application No. 249934 2. Name of the invention Method for manufacturing conductive graphite material 3. Person making the amendment Relationship to the incident Patent applicant address 1-3-1 Kasumigaseki, Chiyoda-ku, Tokyo Name (114) Director of the Agency of Industrial Science and Technology 4 Designated agent address 1-8-31 Midorigaoka, Ikeda-shi, Osaka 6. Item ``Inventor other than the above'' in the application to be amended and Item 7 ``Brief explanation of the drawings'' in the specification, Contents of amendment 1 copy of the resident card proving the exact address of the inventor Rokube Fujii Attached as
, Contents of Amendment A 1 The statement ``Figures 1 and 2 show old photographs'' in Lines 13 to 16 of Specification No. 17 is corrected as follows. Figures 1 and 2 show transmission electron micrographs (2XlO' magnification) of the particle structure of the thin plate graphite powder according to the present invention, and Figure 3 shows the transmission electron micrograph of the particle structure of the known colloidal graphite powder. A type electron micrograph (2 x 104x) is shown.''(That's all)

Claims (2)

[Claims] (1) A method for producing a conductive graphite material, which comprises pulverizing expanded graphite in a state in which the voids of the expanded graphite are filled with a liquid or in a state in which the liquid is frozen. (2) After obtaining a thin plate-like graphite powder by crushing the expanded graphite with a liquid filled in the voids of the expanded graphite or with the liquid frozen, the surface of the powder is oxidized or A method for producing a conductive graphite material, which comprises grafting an organic substance onto the surface of the powder by chemical treatment.