JP2002302625A - Carbon black pigment for electroconductive black paint and electroconductive black paint compounded with said carbon black pigment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a carbon black pigment suitable for forming an electroconductive coating film and an electroconductive black paint compounded with the carbon black. SOLUTION: This carbon black pigment for electroconductive black paint is prepared by chemically modifying a carbon black having a nitrogen adsorption specific surface area (N2 SA) of not larger than 110 m<2> /g and a DBP absorption of not less than 80 cm<3> /100 g through an oxidation treatment so that the value of the atomic ratio of total oxygen atoms per total carbon atoms (ratio of the intensity of oxygen bond energy to the intensity of carbon bond energy) measured by X-ray photoelectron spectrometry is not less than 0.1, and this electroconductive black paint is prepared by compounding this carbon black pigment for electroconductive black paint, a solvent, and an organic resin in the ratios of 2-20 wt.%, 70-96 wt.%, and 2-28 wt.%, respectively.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a carbon black pigment suitable for use as a conductive black paint, and a conductive black paint containing the carbon black.

[0002]

2. Description of the Related Art Carbon black is useful as a pigment for black paint. Generally, carbon black exhibits higher blackness as its particle size and structure become smaller as its basic characteristics. On the other hand, the surface properties of carbon black affect dispersibility in a solvent, blackness, fluidity, and dispersion stability.In general, the greater the amount of oxygen-containing functional groups such as carboxyl groups and hydroxyl groups, the greater the affinity with the solvent. And the dispersibility is improved.

If high conductivity can be imparted to this black paint, it is expected to be useful as a functional paint such as an electromagnetic wave shield, an IC protective material, an electronic component storage case, and a photoconductive material. Conductive paints using metal powder or metal fibers as the conductive material have also been developed, but have drawbacks such as a decrease in conductivity due to the oxidation of the metal over time and an increase in weight.

Accordingly, paints using conductive carbon such as carbon black have been developed. For example, Japanese Patent Application Laid-Open No. 60-35066 discloses a modified polyurethane prepared by mixing 100 parts by weight of conductive carbon and a polyisocyanate crosslinking agent. A conductive carbon paint comprising 170 to 350 parts by weight of a resin and an organic solvent dissolving the resin has been proposed.

[0005] The present invention is based on the finding that a paint obtained by blending a solvent-type polyurethane-modified resin with conductive carbon exhibits extremely excellent adhesion to adherends such as plastic and paper. Examples of the conductive carbon include ordinary carbon black, conductive carbon black, and the like, and indicate that the conductive material after application has an electric resistance of 10 ⁷ Ωcm or less. In the embodiment, Ketjen Black EC is used.

[0006]

However, since the surface of carbon black has very few functional groups having high wettability with a solvent or resin, its dispersibility is low, and it is extremely difficult to stably disperse it uniformly in a solvent or resin. Have difficulty.

Accordingly, the present inventors have conducted intensive studies on carbon black pigments having excellent dispersibility and conductive properties by modifying the surface of carbon black, and as a result, the carbon black was oxidized and the surface of the carbon black was modified. It has been found that carbon black suitable as a pigment for conductive black paint can be modified by chemical modification with an acidic group. That is, an object of the present invention is to blend a carbon black pigment which has a low electric resistance value of a coating film and is suitable for a conductive black paint capable of forming a conductive coating film of, for example, 10 ⁵ Ωm or less, and the carbon black pigment. An object of the present invention is to provide a conductive black paint.

[0008]

The carbon black pigment for conductive black paint according to the present invention for achieving the above object has a nitrogen adsorption specific surface area (N ₂ SA) of 110 m ² / g or less and a DB
And P absorption amount by oxidizing the above carbon black 80 cm ^3/100 g, the atomic ratio of the total oxygen atoms per total carbon atoms measured by X-ray photoelectron spectroscopy (intensity of the intensity / carbon bond energy of the oxygen binding energy) Is characterized by being chemically modified to 0.1 or more.

Further, the conductive black paint of the present invention comprises 2 to 20 wt.
%, A solvent of 70 to 96 wt%, and an organic resin of 2 to 28 wt%.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION As the carbon black targeted in the present invention, various carbon blacks such as furnace black, channel black, thermal black, and acetylene black can be used. Absent.

However, the carbon black pigment for conductive black paint of the present invention has a nitrogen adsorption specific surface area (N ₂ SA) of 110.
m ² / g or less, DBP absorption amount include the 80 cm ^3/100 g or more properties used. The higher the nitrogen adsorption specific surface area (N ₂ SA), the higher the conductivity and the higher the blackness, but the viscosity of the carbon black dispersion increases, and it is difficult to maintain a constant viscosity. When the nitrogen adsorption specific surface area (N ₂ SA) exceeds 110 m ² / g, the coating film becomes uneven due to the variation in the viscosity of the prepared coating material, and as a result, the variation in the electric resistance value becomes large. Also, the smaller the DBP absorption, the higher the blackness, but the smaller the structure,
Since the network between the carbon black particles is insufficient, the conductivity is low.

In general, the surface properties of carbon black greatly affect the dispersibility, flowability, blackness, etc., when preparing a paint. adsorption specific surface area (N ₂ SA) of 110m ² / g or less, as a target carbon black DBP absorption has a 80 cm ^3/100 g or more properties by oxidation, high wettability with the solvent or resin on the surface thereof It is a product of an acidic functional group. That is, functional groups such as ＯO, —COOH, and —OH are formed on the surface of the oxidized carbon black, and the carbon black pigment for conductive black paint of the present invention has X as the amount of these functional groups. It modifies the value of the atomic ratio of total oxygen atoms per carbon atom (intensity of oxygen binding energy / intensity of carbon binding energy) measured by line photoelectron spectroscopy to 0.1 or more.

That is, the value of the intensity ratio (atomic ratio) of (oxygen bond energy / carbon bond energy) measured by X-ray photoelectron spectroscopy is related to the formation amount of acidic functional groups such as carboxyl groups and hydroxyl groups. , This value is 0.1
When the amount is less than the above, the amount of the carboxyl group or the hydroxyl group formed is small, so that the dispersing performance in a solvent or a resin is reduced, and the conductivity is also low. In a normal furnace black, the value of the intensity ratio (the intensity of the oxygen binding energy / the intensity of the carbon binding energy) is 0.002 to 0.002.
It is about 0.003.

The oxidation treatment of carbon black can be performed, for example, by
Wet oxidation treatment in which carbon black is added to an aqueous solution of an oxidizing agent, such as an alkali metal salt such as perchlorate, persulfate, perborate, percarbonate, or perphosphate, or an ammonium salt, followed by stirring and mixing. In gas phase oxidation such as ozone oxidation and air oxidation, it is difficult to chemically modify the intensity ratio of (oxygen binding energy intensity / carbon binding energy intensity) to 0.1 or more. The wet oxidation treatment appropriately controls oxidation reaction conditions such as the concentration of the oxidizing agent aqueous solution, the amount of carbon black added, the reaction temperature, and the reaction time, so that the atomic ratio of all oxygen atoms to all carbon atoms (oxygen bond energy (Strength / carbon bonding energy strength) of 0.1 or more.

The wet-oxidized carbon black dispersion is separated and purified by electrodialysis or a separation membrane (reverse osmosis membrane, ultrafiltration membrane, loose RO, etc.). In this case, the residual salt concentration in the carbon black dispersion was 0.2 s / m 2 with the carbon black content being 20 wt%.
It is preferred to purify so as to be less than.

When a conductive black paint is prepared using oxidized carbon black, the solvent has a low surface tension.
Polar solvents having a low viscosity, such as water, ethanol, N-methyl-2-pyrrolidone, 2-pyrrolidone, N, N-dimethylformamide, dimethylacetamide, dimethylsulfoxide, and hexamethylphosphamide, are preferred. Also, a mixed solution of water with ethanol, ethylene glycol, diethylene glycol, ethylene glycol butyl ether, diethylene glycol butyl ether, or the like can be preferably used.

The organic resin used for preparing the conductive black paint includes, for example, a phenol resin, a melamine resin, a xylene resin, a diallyl phthalate resin, a gliptal resin, an epoxy resin, an alkylbenzene resin, a polyimide resin, an acrylic resin, and a polyvinyl resin. Various resins can be used as long as heat resistance, flowability, and dispersibility of carbon black such as alcohol and polyester resin are not affected.

The conductive black paint of the present invention is prepared such that the carbon black pigment for the conductive black paint is 2 to 20 wt%, the solvent is 70 to 96 wt%, and the organic resin is 2 to 28 wt%. It is prepared by blending these components. If the compounding ratio of the carbon black pigment is less than 2% by weight, the electric resistance increases, for example, it is difficult to form a coating film of 10 ⁵ Ωm or less, while if it exceeds 20% by weight, the electric resistance decreases. This is because carbon black particles fall off from the coating film.

If the compounding ratio of the organic resin is less than 2% by weight, the strength of the coating film is lowered and the film may be peeled off. On the other hand, if it exceeds 28% by weight, the viscosity of the coating material is increased. It becomes difficult to control the film thickness, the film thickness becomes non-uniform, and the variation in the electric resistance value increases. If the blending ratio of the solvent is less than 70 wt%, the viscosity of the paint increases and the fluidity deteriorates, so that it becomes difficult to control the thickness of the coating film, and the variation in the electric resistance value increases. This is because the electric resistance value increases and it becomes difficult to form a coating film of, for example, 10 ⁵ Ωm or less.

Hereinafter, examples of the present invention will be specifically described in comparison with comparative examples.

Examples 1 to 3 and Comparative Examples 1 to 3 Using carbon blacks having different nitrogen adsorption specific surface areas (N ₂ SA) and DBP absorption amounts, 100 g of carbon black was added to sodium persulfate having a concentration of 1.0 mol / dm ^3. The solution was added to ³ dm ³ of the aqueous solution, and oxidized under the conditions of a reaction temperature of 60 ° C., a reaction time of 10 hours, and a stirring speed of 500 rpm. After the oxidation treatment, an ultrafiltration membrane (AHP-1010, molecular weight cut off 500
After the salt remaining in the reaction solution was separated by
After drying at ℃, a carbon black sample modified by an oxidation treatment was prepared.

Comparative Examples 4 to 6 The same carbon black as in Examples 1 to 3 was used, and a carbon black sample was used without oxidation treatment.

For these carbon black samples,
Surface Science Instruments S-Probe ESCA 2803
The oxygen binding energy intensity and the carbon binding energy intensity were measured using a mold, and the atomic ratio of all oxygen atoms per all carbon atoms was determined. The measurement was performed by performing wide scan measurement (qualitative analysis) on the surface of the sample in a tangible state, and performing high-resolution measurement (state analysis) of the detected element. The binding energy was normalized by setting CC and CH to 284.6 eV. The results obtained are shown in Table 1.

[0024]

[Table 1]

Next, using these carbon black samples, 10% by weight of carbon black, 73% by weight of ion-purified water
%, One-component curing type water-based epoxy resin (manufactured by Asahi Denka Co., Ltd., EM-043
4) A black paint was prepared by blending at a ratio of 17 wt% and dispersing with a homogenizer (manufactured by Nippon Seiki) at an output of 200 μA for 3 minutes.

Comparative Examples 7 to 9 Using an oxidized carbon black sample treated in the same manner as in Examples 1 to 3, 1% by weight of carbon black, 98% by weight of ion-purified water, and a one-part curing type water-based epoxy resin (manufactured by Asahi Denka Co., Ltd.) , EM-0434) at a ratio of 1 wt% and dispersed with a homogenizer (manufactured by Nippon Seiki) at an output of 200 μA for 3 minutes to prepare a black paint.

The viscosity and surface tension of the black paint thus prepared were measured by the following methods, and the measurement results are shown in Table 2 together with the composition of the black paint. Viscosity; rotational vibration type viscometer (VM-100A-L, manufactured by Yamaichi Denki)
Was used to measure the viscosity at a temperature of 25 ° C. Surface tension: The surface tension at a temperature of 25 ° C. was measured by a surface tension measuring device (manufactured by Shimadzu Corporation, DN).

Next, these black paints were dip-coated on a transparent quartz plate having a length and width of 5 cm and a thickness of 2 mm.
Heat treatment was performed for 0 minutes to form a coating film. The properties of the formed coating film were measured by the following methods, and the measurement results are shown in Table 3. Film thickness: The film thickness of the cross section of the coating film was measured with a microscope. Electric resistance value; Surface resistance meter (Mitsubishi Yuka, Loresta) and 4-probe method resistance calculation software (Mitsubishi Yuka, Re
siCalc). Adhesion test: Adhere a cellophane adhesive tape to the surface of the paint film, then peel off the tape instantaneously in the vertical direction, visually observe the condition of the paint film attached to the adhesive surface, and adhere according to the following criteria The sex was evaluated. ○… No carbon fallout. ×: Carbon dropped out. Pencil hardness: Measured according to JIS K5400 “Pencil scratch value”.

[0029]

[Table 2] Note: * 1 Carbon black

[0030]

[Table 3] Note: * 2 No coating film can be formed.

From the results in Tables 1 to 3, the following can be understood. (1) The coating films of Examples 1 to 3 have low electric resistance values and small variations in film thickness and electric resistance value. Also, the adhesion of the coating film is good and the coating film strength is high. (2) Comparative Examples 1 to 3 using carbon black having a nitrogen adsorption specific surface area (N ₂ SA) and a DBP absorption amount outside the requirements of the present invention.
The coating film No. 3 has large variations in the film thickness and the electric resistance value. Further, the adhesion of the coating film is poor, the carbon black particles easily fall off from the coating film, and the strength is low. (3) On the other hand, even if the nitrogen adsorption specific surface area (N ₂ SA) and the DBP absorption amount satisfy the requirements of the present invention, the coating films of Comparative Examples 4 to 6 using carbon black that is not subjected to the oxidation treatment were added to the solvent. The formation of a coating film is substantially impossible due to the remarkable deterioration of dispersibility. (4) Further, the coating films of Comparative Examples 7 to 9 formed by using a black paint having a low blending ratio of carbon black and a resin component have extremely high electric resistance and can form a conductive coating film. And the adhesion of the coating film was also poor.

[0032]

As described above, the nitrogen adsorption specific surface area (N ₂ SA)
110m ² / g or less, and DBP absorption amount by oxidizing the above carbon black 80 cm ^3/100 g, the atomic ratio of the total oxygen atoms per total carbon atoms measured by X-ray photoelectron spectroscopy (oxygen binding energy intensity / Strength of carbon binding energy)
2 to 20% by weight of the carbon black pigment for conductive black paint of the present invention chemically modified to a value of 0.1 or more, and 70% of a solvent.
According to the conductive black paint of the present invention in which an organic resin is blended in a proportion of about 96 wt% and an organic resin in a proportion of 2 to 28 wt%, a conductive paint film having a low electric resistance value of, for example, 10 ⁵ Ωm or less can be formed. In addition, the dispersion of the coating film and the electric resistance value is small, and the coating film strength is high.
It is extremely useful as a functional paint such as a C protective material, an electronic component storage case, and a photoconductive material.

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Claims (2)

[Claims] 1. A nitrogen adsorption specific surface area (N ₂ SA) 110m ² / g or less, and DBP absorption amount by oxidizing the above carbon black 80 cm ^3/100 g, total carbon atoms measured by X-ray photoelectron spectroscopy The value of the atomic ratio of total oxygen atoms per unit (strength of oxygen binding energy / strength of carbon binding energy) is 0.1
A carbon black pigment for a conductive black paint, characterized by being chemically modified as described above. 2. A conductive black, comprising 2 to 20% by weight of the carbon black pigment for conductive black paint according to claim 1, 70 to 96% by weight of a solvent, and 2 to 28% by weight of an organic resin. paint.