JPH073697A - Carbon black-containing paper - Google Patents

Abstract

PURPOSE:To obtain paper containing a large amount of carbon black, low in coming off of powder and having a high strength. CONSTITUTION:This carbon black-containing paper is characteristically produced by adding an anionic latex of a carboxy-modified polymer to a cellulose-based slurry containing carbon black dispersed therein, subsequently applying a fixation treatment thereto and making paper therefrom. This paper can be applied to an antistatic wafer material, an electromagnetic shielding material, a plane heater, etc.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a carbon black-containing paper, which is used for the purpose of imparting functions such as static electricity removal and electromagnetic wave shielding.

In recent years, many electronic devices have been manufactured and widely used due to the progress of electronics technology. Accompanying this, a lot of static electricity and electromagnetic waves are also generated, and in order to prevent these, covering with conductive paper is performed.

[0003]

The conductive paper containing carbon black is produced by a method of papermaking by mixing an aqueous dispersion of carbon black with an aqueous dispersion of cellulosic fibers such as pulp. The carbon black-containing paper obtained has problems that the strength of the paper becomes extremely small as the carbon content increases, and that the surroundings are contaminated due to desorption of carbon from the paper such as powder drop.

[0004]

As a result of investigating the structure of conventional carbon black-containing paper (hereinafter also referred to as carbon-containing paper), the present inventors have found that in conventional carbon-containing paper, carbon aggregate particles are present. It was thought that the paper was widely attached to the surface of the cellulose fibers, so that when the paper was pulled, slippage between the fibers was large, and therefore the strength of the paper was extremely reduced. Therefore, for the purpose of fixing the polymer to the fiber and entwining the fiber with carbon to improve the strength of the paper and at the same time to prevent the carbon from falling off, the polymer latex is added to the aqueous dispersion of carbon and fiber. It was found that when paper was added and fixed, the strength of the paper was significantly improved and carbon desorption could be reduced or prevented.

The present invention provides a carbon black-containing paper characterized by being produced by adding an anionic latex of a carboxy-modified polymer to a cellulosic fiber slurry in which carbon black is dispersed, fixing, and making a paper. .

As the carbon black used in the present invention, ordinary carbon black such as furnace black and carbon powder such as acetylene black, Ketjen black and graphite powder are used. These carbons can usually be used as an aqueous dispersion in addition to water, but can also be used by adding them to an aqueous dispersion of fibers as they are. On the other hand, with respect to water-floating carbon black such as acetylene black, an aqueous dispersion can be prepared and used by a method such as dispersing in an aqueous solution of a specific compound, or particularly strong stirring. The carbon black powder can be added as it is to the aqueous dispersion of 1. As the carbon black, acetylene black is particularly preferable because of its high conductivity.

The cellulosic fibers used in the present invention are wood pulp, cotton fibers, cotton, plant pulp, recovered waste paper and the like. The length and diameter of the fiber are not particularly limited, but usually the length is 0.5 to 100 mm and the thickness is 5 to 7
It is about 0 μm and is used as an aqueous dispersion, that is, a slurry.

The carboxy-modified polymer used in the present invention is selected from a carboxy-modified rubber and / or a carboxy-modified resin, and a combination of a carboxy-modified rubber and a non-carboxy-modified resin. The carboxy-modified rubber is a copolymer having a diene-based or acrylic-based polymer having a carboxyl group with a Tg of 10 ° C. or less, preferably −50 to 5 ° C. For example, diene monomers such as butadiene and isoprene, vinyl monomers such as styrene, acrylonitrile and methyl methacrylate, carboxyl group-containing monomers such as acrylic acid, methacrylic acid, itaconic acid, maleic acid and fumaric acid, and hydroxyethyl (meth) acrylate. It is a copolymer with a hydroxyl group-containing monomer such as. Ethyl acrylate, butyl acrylate instead of diene monomer, 2
-Ethylhexyl acrylate and the like are also used. Other than these, acrylamide and N-vinylpyrrolidone can be used, but not limited to these as long as they are copolymerizable vinyl monomers. Preferred are carboxy-modified styrene-butadiene rubber and carboxy-modified acrylic rubber. Carboxy-modified rubber enhances the fixing of carbon black to the fiber and is preferred.

As the carboxy-modified resin, the same monomer as in the carboxy-modified rubber is used, but the Tg of the polymer is
Are selected such that the ratio exceeds 10 ° C. Other carboxy-modified resins include carboxy-modified polyolefin and ethylene-acrylic acid copolymer. Polyolefins include polyethylene, polypropylene and ethylene-propylene copolymers, with polyethylene being preferred. The carboxy-modified resin is effective in fixing the carbon black to the fiber, as well as enhancing the strength of the paper and the gloss after calendering.

The non-carboxy-modified resin is a resin in which the carboxy-modified resin is not carboxy-modified, and its T
g exceeds 10 ° C. In addition to these, there are vinyl chloride (co) polymers, vinyl acetate (co) polymers, polystyrene, polymethacrylate, and the like. The use of a resin is effective in producing paper strength and gloss after calendering, and it is preferably used in combination with a carboxy-modified rubber.

As the fixing agent used for fixing the polymer latex, inorganic and organic fixing agents are used. Examples of the former include polyvalent metal salts such as aluminum salts, iron salts, zinc salts, calcium salts, among which aluminum salts and iron salts are preferable, and specifically, aluminum sulfate, alum, iron sulfate, etc. Is mentioned. As an example of the latter, a cationic latex having a charge opposite to that of the polymer latex,
Examples thereof include carboxy-containing polyacrylamide, copolymers of acrylamide and dimethylaminoethyl acrylate, modified products thereof, and cationic starch. Among these, cationic acrylamide polymers and copolymers and modified products thereof are preferable. Organic fixing agents are preferable to inorganic fixing agents because they have a smaller metal content. The fixing agent is used as it is or as an aqueous solution or dispersion. The amount of the fixing agent added varies depending on the amount of the polymer latex used, but is usually 2 to 20% with respect to the polymer in the polymer latex.

The weight composition ratio (as solid content) of the carbon black-containing paper of the present invention is usually 20 to 90/5 to 70/2 to 40 (total 100 parts by weight), preferably fiber / carbon black / polymer. 30-75 / 10-50 /
5 to 20 (total 100 parts by weight). The volume resistivity of carbon black-containing paper is usually 10 ^-1 to 10 ³ Ωc.
m, preferably 0.5 to 100 Ωcm, more preferably 0.5 to 20 Ωcm. If the amount of carbon black is less than 5 parts, the conductivity will be insufficient, and if it exceeds 70 parts, it will be difficult to produce paper. When the amount of the polymer is less than 2 parts, the effect of paper retention is insufficient and the effect of improving the strength of paper becomes small. If it exceeds 40 parts, the conductivity is lowered. The cellulosic fiber is required to be 20 parts or more for making paper, and 90 parts or less for containing carbon black and a polymer.

Various additives may be added to the aqueous dispersion of carbon black and fibers used in the present invention, if necessary. For example, various carbon fibers, iron,
Conductive materials such as fibers and powders of copper, aluminum, nickel, silver, stainless steel and glass fibers and powders coated with metal such as nickel, viscosity modifiers, dispersion stabilizers, pigments, etc. .

If necessary, various auxiliaries commonly used can be used during papermaking. For example, inorganic substances such as talc, silicon earth, silica, titanium dioxide, and zinc oxide, antioxidants, cellulose derivatives such as carboxymethyl cellulose and methyl cellulose, dyes, color pigments,
Various size agents such as polyethyleneimine and rosin, cationic, anionic or nonionic surfactants,
They can be used alone or in combination of two or more. These can be used as they are or in the form of an aqueous dispersion or emulsion.

The carbon black-containing paper of the present invention is usually mixed with an aqueous dispersion of carbon black and a cellulosic fiber while adding a polymer latex and stirring, and subsequently adding a fixing agent and mixing, and It can be easily manufactured by a papermaking method. For example, it can be produced by paper making with a normal Fourdrinier paper machine or cylinder paper machine, dehydration and drying.

The carbon black-containing paper produced by papermaking can be rolled at room temperature to 100 ° C., if necessary. By rolling, physical properties of paper such as paper strength and conductivity can be improved. Carbon-containing paper made with a polymer latex having a softening point or melting point higher than room temperature is subjected to a gloss calendering treatment at a softening point or melting point or higher, so that the paper strength is high, there is no carbon desorption, and it is glossy. It is particularly preferable because a carbon-containing paper can be obtained. In the case of gloss calendar, usually 100 ~
Perform at 140 ° C.

[0017]

EXAMPLES The present invention will be described in more detail with reference to examples of the present invention, but the invention described in the claims is not limited by the examples in any sense.
The analysis and measurement in the examples were carried out by the following methods. (1) Carbon content: Carbon black-containing paper was analyzed with a thermogravimetric analyzer. (2) Resistance value: Cut the test paper into 1 cm width and 10 cm length,
It was measured at both ends in the length direction. Volume resistivity is measured value ×
It was calculated by width × thickness ÷ length. (3) Tensile strength: Measured by pulling a test paper having a width of 2 cm and a length of 10 cm in the length direction. (4) Powder desorption: The surface of the test paper was lightly rubbed with a tissue paper, and the degree of adhesion of carbon black to the tissue paper was visually observed. (5) Gloss: Observed with the naked eye.

Examples 1 to 3 A predetermined amount of cotton linter pulp described in Table 1 was added to 1000 ml of water, and the mixture was stirred for 10 minutes with a disintegrator to prepare an aqueous dispersion. On the other hand, a predetermined amount described in Table 1 of acetylene black (manufactured by Denki Kagaku Kogyo KK, hereinafter abbreviated as AB) was added to 200 ml of water, and a mixer equipped with a high-speed rotary blade (manufactured by Dynamic Corporation, Waring Blender 7010, Model 31BL91). , And the internal volume was adjusted to 1 liter) to prepare an aqueous dispersion.

Both aqueous dispersions were mixed, and carboxy-modified styrene-butadiene resin latex (manufactured by Japan Synthetic Rubber Co., Ltd., JSR-0693, using an anionic emulsifier, polymer Tg: 20 ° C., solid content concentration 48. 5%)
The predetermined amount described in Table 1 was added and stirred for 5 minutes. Then, a cation-modified polyacrylamide derivative aqueous solution (manufactured by Mitsui Toatsu Chemicals, Inc., Euramine P5600,
A solid content concentration of 31.4%) was added and the mixture was further stirred for 5 minutes. This mixed solution was added to a paper machine equipped with a 150-mesh wire net and containing water. Further, water was added to adjust the total amount of the mixture to 5 liters, and then papermaking was performed. After peeling the paper from the wire mesh and compressing and dehydrating with a roll and press,
It was dried with hot air at 130 ° C.

The volume resistivity and the tensile strength of the obtained paper were measured. Further, the obtained paper is nipped at a pressure of 50 kg.
/ Cm, a temperature of 112 ℃
The same measurement was performed on the paper after the calendar treatment. The results are shown in Table 1. From the comparison with the comparative example,
It can be seen that the tensile strength of the paper was improved by using the polymer. In addition, gloss calendering produced luster, almost no detachment of carbon powder, and a significant improvement in tensile strength. The carbon black-containing paper obtained using the polymer had sufficient tensile strength even after being immersed in water.

Example 4 Example 4 was repeated except that the cotton-linter pulp was replaced with wood pulp. Examples 5 to 7 Carboxy-modified styrene-butadiene rubber latex (manufactured by Japan Synthetic Rubber Co., Ltd., JSR-0695, using anionic emulsifier, Tg of polymer: -5 ° C, solid content concentration 5)
2.4%) and using the amount shown in Table 1,
It carried out like Example 1. The use of rubber latex is
The effect of increasing the paper yield was recognized as compared to the use of resin latex.

Example 8 A polymer latex was used as a carboxy-modified polyethylene emulsion (manufactured by Toho Chemical Industry Co., Ltd., Hitec E-4A,
The procedure of Example 1 was repeated, except that the anionic emulsifier was used and the solid content concentration was 35%), and the amount shown in Table 1 was used.

Examples 9 and 10 In Example 9, AB was HAF carbon black (manufactured by Mitsubishi Kasei Kogyo KK, ASTM N330, Diamond Black H), and in Example 10, AB was Ketjen Black EC.
The procedure of Example 5 was repeated, except that DJ-500 (sold by Lion Akzo Co., Ltd., abbreviated as KB hereinafter) was used, and the amounts described in Table 1 were used. The aqueous dispersions of these carbons were prepared by simply adding carbon to water and stirring. When KB of conductive carbon black was used, a conductive paper having a small volume resistivity and a large tensile strength was obtained. In the case of HAF, which is a typical carbon black for rubber, it was also possible to fix it by using a polymer latex to obtain a conductive paper. However, its resistance value was 10 times or more higher than that of AB or KB.

Examples 11 to 14 In Examples 11, 12, and 14, the resin latex used in Example 1 and the rubber latex used in Example 5 were used in combination as the carboxy-modified polymer. In Example 13, only resin latex was used. Other conditions were the same as in Example 1 except for those described in Tables 1 and 2. It was observed that the simultaneous use of both the rubber / resin polymer increased the yield of paper and the tensile strength.

Comparative Example 1 This is an example in which only cotton-linter pulp is made into paper. Comparative Examples 2 to 4 Examples in which the polymer latex and the cationic fixing agent were not used in Examples 1, 4 and 7. Comparative Examples 5 and 6 In Examples 9 and 10, the polymer latex and the cationic fixing agent were not used.

[0026]

[Table 1]

[0027]

[Table 2]

Application Example of Carbon Black-Containing Paper (1) Cement / Silica sand (No. 7) /Water=60.8/60.8/2
5.4 (weight ratio) of raw mortar was prepared and height 1
cm, width 1 cm, length 10 cm, first filled with about 1/3, carbon black containing paper (Example 1, AB24
%, Thickness 0.3 mm, width 1 cm, length 10 cm, without gloss calendering), and then filled with fresh mortar to fill the mold. The surface was covered with a polyethylene film, left at room temperature for 48 hours, and then demolded to obtain a rod-shaped cured product. As a result of measuring the resistance value of the carbon black-containing paper protruding from both ends of the rod, it was 2.0 kΩ, which was almost the same level as the resistance value of 2.1 kΩ before mortar filling.

Application Example of Carbon Black-Containing Paper (2) A liquid epoxy resin was used in place of the mortar of Application Example (1) to prepare an epoxy resin cured product sandwiching the same carbon black-containing paper as in Application Example (1). . The resistance value between the carbon black-containing papers on both ends was 2.2 kΩ.

Application Example of Carbon Black-Containing Paper (3) The resin latex used in Example 1 was added to the pigment containing clay and calcium carbonate as the main components to prepare a color composition for paper coating, and an applicator was used. Apply to one side of carbon black containing paper [same as application example (1)],
It was dried at 0 ° C. for 3 minutes, further applied on the other surface of the paper in the same manner, and dried to prepare a carbon black-containing paper sandwiched with an insulating layer. A test piece with a width of 1 cm and a length of 10 cm was cut out and the resistance value at both ends was measured and found to be 2.6 kΩ.

[0031]

The carbon black-containing paper of the present invention has high strength, less desorption of powder, good water resistance, and excellent conductivity. Since this paper has excellent conductivity, it can be usefully used for the purpose of preventing static electricity and shielding electromagnetic waves. Further, it can be used for applications such as sheet-like electric discharge recording paper and ground wrapping paper.

The carbon black-containing paper is a liquid curable resin, thermosetting resin or thermoplastic resin solution,
Furthermore, a sheet or board can be molded by impregnating with an aqueous mixture of a water-curable inorganic compound such as cement or green mortar and then curing. The resin-impregnated cured product can be carbonized at a high temperature to form a carbon / carbon composite, which is useful as a battery material such as a separator for a fuel cell.

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Claims (1)

[Claims] 1. A carbon black-containing paper, which is produced by adding an anionic latex of a carboxy-modified polymer to a cellulosic fiber slurry in which carbon black is dispersed, fixing, and making a paper.