JPH05262508A - Aqueous dispersion of carbon black and carbon black-containing paper - Google Patents

Abstract

PURPOSE:To provide the subject water-based dispersion nonfoamable because of containing no surfactant, and to provide carbon black-contg. paper excellent in electrical conductivity using the above dispersion with the carbon black therein readily adsorbable to the cellulose fibers in the paper. CONSTITUTION:The objective water-based dispersion can be obtained by dispersing (A) water-floatable carbon black in an aqueous solution containing a nonionic organic compound >=66 dyne/cm at 25 deg.C in the surface tension of its 2wt.% aqueous solution, containing at least one N and/or O atom's) (e.g. polyethyleneimine, acetamide, oxalic acid). The other objective paper can be obtained by dispersing cellulose fibers in this water-based dispersion followed by carrying out papermaking.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aqueous dispersion of water-floating carbon black and carbon black-containing paper using the same, which is used for the purpose of removing static electricity and imparting electromagnetic wave shielding function. To be done.

[0002]

2. Description of the Related Art In recent years, many electronic devices have been manufactured and widely used due to the progress of electronics technology. Along with this, a lot of static electricity and electromagnetic waves are also generated, and in order to prevent them, a conductive paint is applied or covered with a conductive paper.

As a method of imparting conductivity, a method of applying a solvent dispersion of conductive powder such as carbon black or metal powder, or a method of applying such powder or its solvent dispersion to rubber, resin,
A method is known in which paper, cement, etc. are used. For example, as a solvent dispersion of carbon black, an organic solvent dispersion and an aqueous dispersion are used, but for safety and hygiene, an aqueous dispersion is often used, and usually an aqueous dispersion containing a considerably large amount of a surfactant is used. Has been done. Conductive paper containing carbon black is produced by a method of making paper by mixing an aqueous dispersion of carbon black and an aqueous dispersion of cellulose fibers such as pulp, but it is easy to adsorb carbon black to the paper. None (see JP-A-56-68194).

[0004]

There have been some problems with conventional aqueous dispersions of carbon black.
Furnace black, which is widely used in rubber applications, is usually
Since it settles in water, the aqueous dispersion and the aqueous dispersion of cellulosic fibers can be easily mixed to make paper, but it was obtained because the yield of carbon is small and the conductivity of this carbon is small. There is a drawback that the conductivity of the paper is small. On the other hand, acetylene black, which has excellent conductivity, floats on the water surface, making it difficult to produce an aqueous dispersion.

The use of a surfactant is effective for obtaining an aqueous dispersion of acetylene black, but carbon black cannot be dispersed simply by lowering the surface tension of water, and a larger amount of surfactant is required. Become. When a surfactant is used, bubbles are likely to be generated by stirring, and when bubbles are present, carbon black is separated, which adheres to the wall of the device and the like, and the device is easily contaminated. If it is mixed with other components as it is, air bubbles remain and the strength of the generative matrix is lowered. Further, the matrix surface becomes rough, and the carbon black in the matrix becomes non-uniform. Further, since the surfactant is contained together with the carbon black, there are problems such as increased hygroscopicity and contamination of peripheral members with alkali metal ions.

When an aqueous dispersion of carbon black using a surfactant and an aqueous dispersion of fibers are mixed, air bubbles are generated, and the aggregates of fibers and carbon are separated and attached to a device wall or the like of the device, There are drawbacks such as contamination, uneven distribution of carbon black in the obtained paper, and rough surface of the paper. On the other hand, when a surfactant with almost no foaming is used, the above-mentioned problem due to the generation of bubbles does not occur, but the yield of carbon black during papermaking is poor, the conductivity of the obtained paper is small, and A large amount of carbon black is discharged and there is a problem of wastewater pollution. A fixing agent such as a polyvalent metal salt can be used to increase the yield, but the manufacturing process becomes complicated. Further, since the fixing agent remains in the paper as an impurity, there are problems such as increased hygroscopicity and contamination of the surroundings. Moreover, since a considerable amount of a surfactant is required for dispersion of acetylene black, if it is contained in the paper, it will deteriorate the physical properties of the conductive paper, such as increased hygroscopicity and contamination of the surroundings with alkali metal ions. There are problems such as.

[0007]

It is considered that the acetylene black powdery product has a low bulk specific gravity and its agglomerate particles contain a large amount of air so that they are difficult to disperse in water. The present inventors have conducted extensive studies on obtaining an aqueous dispersion of a water-floating carbon black such as acetylene black by a method that does not use a surfactant, and as a result, water containing a specific nonionic organic compound. It was found that an aqueous dispersion of acetylene black can be easily obtained by using. Furthermore, when this aqueous dispersion and an aqueous dispersion of natural pulp were mixed and made into paper, the yield of carbon black was large even without the use of a fixing agent, the dispersion of carbon black was uniform, and the conductivity was high. It has been found that a good conductive paper can be obtained, and the present invention has been completed.

The first aspect of the present invention is a nonionic organic compound containing at least one N atom and / or O atom and having 2 or more carbon atoms, wherein the organic compound is an N atom-containing compound ( O atom is not contained), the ratio N / C of the number of N atoms and the number of C atoms is 1/3 or more and 3/4 or less,
When the compound is an O atom-containing compound (N atom is not contained), O
A polycarboxylic acid having a ratio of the number of atoms to the number of C atoms of O / C of 1 or more and 2 or less, and a cyclic ether having an O / C of 1/3 or more and less than 1 and having 4 or more carbon atoms, an aromatic phenol and a polyol. In the case of a compound containing both N and O atoms, those selected from amino alcohols having (N + O) / C of less than 1, amides or imides of carboxylic acids, and urea derivatives having one or more alkyl substituents. And the surface tension of the aqueous solution is not less than 66 dynes / cm at 25 ° C. and 2% by weight, or 6 at 0.5% by weight.
Provided is an aqueous carbon black dispersion, which comprises dispersing a water-floating carbon black in an aqueous solution containing a nonionic organic compound having a dying rate of 9 dynes / cm or more. A second aspect of the present invention is a carbon black-containing paper produced by making a mixture of the aqueous dispersion of carbon black of the first aspect and an aqueous dispersion of fibers.

The N atom-containing compound (not containing O atom) used in the present invention has a ratio N / C of N atoms to C atoms of 1/3.
The above is 3/4 or less. For example, H (NHCH ₂ CH
₂ ) _n NH ₂ (n = 2 to 10), polyethyleneimine,
There are phenylenediamine and triaminobenzene, and polyethyleneimine is particularly preferable. Ethylenediamine and methylamine are out of range.

The O atom-containing compound (not containing N atom) used in the present invention is a polycarboxylic acid having a ratio O / C of the number of O atoms to the number of C atoms of 1 or more and 2 or less, such as oxalic acid or succinic acid. , Maleic acid, citric acid and the like. Glycolic acid and glyoxalic acid are out of range. In addition, O / C is 1/3 or more and less than 1, and is a cyclic ether having 4 or more C atoms, aromatic phenols and polyols, such as 1,4-dioxane, resorcin, pyrogallol,
_{1,4-butanediol, HO (CH 2 CH 2 O} ) n H
(N = 2, 3, 4) and so on. ethylene glycol,
Propylene glycol and glycerin are out of range.

The compounds containing both N and O atoms used in the present invention are amino alcohols having (N + O) / C of less than 1, amides or imides of carboxylic acids, and urea derivatives having one or more alkyl substituents. is there. For example,
2- (2-aminoethoxy) ethanol, acetamide, N-methylformamide, N, N-dimethylacetamide, N, N-dimethylformamide, N-methylpyrrolidone, succinimide, maleic imide, 1,3
-Such as dimethylurea. Monoethanolamine, formamide, urea are out of range.

The nonionic organic compound used in the present invention contains a carboxylic acid, but the carboxylic acid salt is ionic and thus out of range. Amino acids are also considered ionic in water and are out of range. The nonionic organic compound has a surface tension of an aqueous solution of 25 deg.
m or more, preferably 67 dynes / cm or more, and up to 2% by weight of a compound having no water solubility, it is 69 dynes / cm or more in a 0.5% by weight solution.

The water-floating carbon black used in the present invention means a material that floats on the water surface when carbon is added to water, or when water is stirred with water, or partially floated.
The rest is what exists below the water surface and near the water surface.
A typical example is acetylene black.

The carbon black aqueous dispersion of the present invention means a state in which carbon black is added to water in which a specific nonionic organic compound is dissolved, and the carbon black is mixed as it is or by stirring or shaking. Means that carbon black is uniformly dispersed in water, is precipitated below the water surface, or is not precipitated but is separated and suspended below the water surface. Even if it precipitates or is free in water, carbon black that has been uniformly dispersed once is dispersed evenly by stirring lightly.

The action of the nonionic organic compound used in the present invention is to increase the leakability of water with respect to carbon by dissolving the organic compound in water, and to increase the water-floating carbon black aggregate structure containing air. It is considered that water easily enters the carbon black and the carbon black easily mixes with water. The concentration at which the effects of these nonionic organic compounds appear and the surface tension at that time vary depending on the type of compound. However, it is preferable that the amount of addition is as small as possible in order to reduce mixing in waste water and increase in manufacturing cost.

The content of the nonionic organic compound of the present invention in water is usually 0.005 to 2% by weight, preferably 0.01 to 1% by weight, more preferably 0.03 to 0.
It is 5% by weight. If it is less than 0.005% by weight, the effect of addition does not appear, and if it is more than 2% by weight, there is a problem that not only the cost increases but also the treatment of waste water becomes difficult.

In the present invention, the water-floating carbon black aqueous dispersion can be prepared by adding the water-floating carbon black to an aqueous solution of a nonionic organic compound and stirring the mixture as it is or by stirring. As one of preferred methods for producing an aqueous dispersion of carbon black, a nonionic organic compound aqueous solution having a concentration capable of dispersing carbon black is mixed with carbon black and kneaded to form a putty or a paste. , A method of preparing an aqueous dispersion having a predetermined carbon concentration by adding only water.

The concentration of the carbon black aqueous dispersion of the present invention is 25% by weight or less, preferably 15% by weight or less. If it exceeds 25% by weight, it will be scattered and hard to harden. Further, the properties of the carbon black aqueous dispersion change depending on the concentration. A concentration of about 1% by weight or less is a free-flowing aqueous dispersion, and a concentration of more than 1.5% by weight causes a stickiness, and a concentration of 2.0% by weight causes a remarkable stickiness. At 3% by weight, it flows slowly, and at 3.5% by weight, it hardly flows. When it is 3.5% by weight or more, it is in a paste form, when 10% by weight or more, it is a putty form, and when it is 20% by weight, it is a hard putty form. It is easy to dilute a paste or putty-like dispersion with water to obtain a lower concentration dispersion.

Various additives may be added to the carbon black aqueous dispersion of the present invention as required. For example, carbon black such as ordinary furnace black, Ketjen black, graphite powder, carbon materials such as various carbon fibers and iron, copper, aluminum, nickel,
Examples include conductive materials such as fibers and powders of silver and glass fibers and powders coated with metals such as nickel, viscosity modifiers, dispersion stabilizers, and pigments.

The second aspect of the present invention is a carbon black-containing paper produced by using the carbon black aqueous dispersion of the first aspect of the present invention. The fiber used in the second aspect of the present invention may be one that can be easily dispersed uniformly in water. For example, natural fibers represented by cellulose fibers, inorganic fibers such as glass fibers and rock wool, polyvinyl alcohol fibers, nylon fibers, polyester fibers, polypropylene fibers,
Polyacrylonitrile fibers, aromatic polyamide fibers such as Kevlar, and synthetic fibers such as ceramic fibers can be used alone or in combination. Cellulose fibers are particularly preferred, and more specifically 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.
Those having a thickness of 5 to 100 mm and a thickness of 5 to 70 μm are used.

The carbon black-containing paper of the present invention has a carbon black content of 0.3 to 400 parts by weight, preferably 0.5 to 300 parts by weight, based on 100 parts by weight of fibers. When the carbon black content is less than 0.3 part by weight, the dielectric property of paper is insufficient. Again 400
If it is larger than the weight part, the strength of the paper is not sufficient, the loss of carbon black at the time of papermaking is large, and the pollution of the waste water becomes severe. Since the carbon black aqueous dispersion used in the present invention has excellent dispersibility and is easily mixed with the aqueous fiber dispersion, it is possible to easily make paper without adding an auxiliary agent.

However, various auxiliaries which are usually used can be used as needed at the time of papermaking. For example, inorganic substances such as talc, diatomaceous earth, silica, titanium dioxide, barium sulfate, calcium carbonate, aluminum sulfate, magnesium carbonate, alum and the like, aqueous dispersions of organic polymers, further antioxidants, carboxymethyl cellulose, methyl cellulose, etc. Cellulose derivatives, dyes, color pigments, starch, starch derivatives, waxes, acrylamide copolymers and their derivatives, crosslinking agents such as melamine formaldehyde resin, urea aldehyde resin, epoxy compounds, and fixing agents, etc., alone or in combination of two or more. Can be used. These can be used as they are or in the form of an aqueous dispersion or emulsion.

Aqueous dispersions of the above organic polymers include styrene-butadiene copolymers, styrene-butadiene- (meth) acrylic acid ester copolymers, acrylonitrile-
Butadiene copolymer, styrene-based polymer, (meth) acrylic acid ester (co) polymer, polyolefin-based polymer (polyethylene or polypropylene), and their carboxy-modified products, ethylene-acrylic acid copolymer,
It is a latex or emulsion of a vinyl acetate polymer, a vinyl chloride polymer or the like. These are alone or 2
Used as a mixture of more than one species. Of these, styrene-
Butadiene copolymer, styrene-butadiene- (meth)
Acrylic acid ester copolymers, (meth) acrylic acid ester (co) polymers, polyolefin polymers, and anionic latexes or emulsions of these carboxy-modified products are preferable. By using an aqueous dispersion of these organic polymers in combination with a fixing agent for an organic polymer or an inorganic substance such as polyacrylamide and its derivatives or a sulfuric acid band, the paper strength is increased without lowering the conductivity of the paper. be able to. In particular, a combination of a vinyl monomer containing a carboxyl group or a hydroxyl group with a conjugated diene or a styrene copolymer copolymer latex (anionic) and a cation fixing agent is preferable.

The carbon black-containing paper of the present invention can usually be easily produced by a conventional papermaking method after mixing the carbon black aqueous dispersion of the present invention with fibers, particularly an aqueous dispersion of cellulosic fibers. it can. For example, paper making with a normal Fourdrinier or cylinder paper machine,
It can be produced by dehydration and drying. Further, the nonionic compound of the present invention can be added to an aqueous dispersion of fibers to prepare an aqueous mixture of carbon and fibers all at once. As the carbon black aqueous dispersion, it is possible to use one having a carbon black content of several% by weight or less, or a paste or putty having a high concentration.

[0025]

EXAMPLES The present invention will be described in more detail with reference to the examples of the present invention, but the invention described in the claims is not limited by the examples in any sense.
In the following, "surface tension" means Kyowa Welhelmy type (CVBP type), surface tension meter (Kyowa Scientific Co., Ltd.).
"Dispersibility of carbon black in water" was measured by the following method.

In a cylindrical glass container with an outer diameter of 25 mm and a height of 55 mm (internal volume of about 20 ml) was placed 10 g of water or an aqueous solution of a nonionic organic compound, and then about 0.03 g of carbon black, which settled. After determining whether or not to do it, the mixture was lightly stirred with a glass rod. The container is covered, shaken up and down 30 times, and then left standing. The behavior of carbon black after standing for 30 seconds was visually determined. Excellent: Carbon black is uniformly dispersed or precipitated in water. Good: Carbon black is separated and suspended in water, and the floating layer is dispersed as a layer with a thickness of 1/2 or more of the water depth. Possible: Carbon black is separated and suspended in water. However, the floating layer becomes a layer having a thickness of 1/2 to 1/4 of the water depth and cannot be dispersed: Carbon black floats on the water surface and / or is separated and floated in water, and the floating layer is 1/4 of the water depth. Dispersed as a layer with the following thickness

Examples 1 to 21 and Comparative Examples 2 to 21 As the water-floating carbon black, acetylene black (abbreviated as AB, manufactured by Denki Kagaku Kogyo Co., Ltd.) powder was used. AB of 0.03 g was added to 10 g of an aqueous solution of various compounds, shaken up and down 30 times, and allowed to stand still, and the dispersibility of AB was visually determined. The results are summarized in Tables 1 and 2. For reference, the surface tension of a 2% by weight aqueous solution of each compound was measured and recorded in the table. The aqueous solution concentrations of the compounds of Comparative Examples for surface tension measurement are shown in Table 2.

Comparative Example 1 When 0.03 g of acetylene black was added to 10 g of water, it remained floating on the water surface, and even when stirred with a glass rod. After shaking it up and down 30 times, when it is left standing, carbon black immediately begins to separate,
Almost all of them collected in seconds on the surface of water and the upper part of water layer.
The layer of carbon black is 1/5 of the whole, and the surface thereof is a muddy shape rising on the water surface.

Example 22 This example is an example in which a high concentration aqueous dispersion of acetylene black (AB) was first prepared and then diluted with water to prepare a low concentration aqueous dispersion. In a 200 ml plastic cup, 1.05 g of AB was added, 20 g of an aqueous solution of 1.0% by weight triethylenetetramine (including 0.2 g of triethylenetetramine) was added, and the mixture was covered and shaken, then stirred with a spatula to paste. Was prepared (the concentration of AB is 5.0% by weight). Then water 8
When 0 g was added, an aqueous dispersion of acetylene black was obtained. At this time, the concentration of triethylenetetramine in water was 0.2% by weight, and the dispersibility of the dispersion was “good”.

Examples 23 to 29 After mixing the acetylene black (AB) aqueous dispersion and the cotton linter pulp aqueous dispersion, papermaking was carried out to produce a carbon black-containing paper. As shown in Table 3,
A predetermined amount of AB of Example 1 was added to an aqueous solution containing various organic compounds and stirred to prepare an AB aqueous dispersion.
A predetermined amount of cotton linter pulp was added to 1000 ml of water, and the mixture was stirred for 10 minutes with a disintegrator to prepare an aqueous dispersion of pulp.

Next, the both were mixed and stirred for 5 minutes with a mixer, and then a wire mesh of 150 mesh was attached and added to a paper machine containing water. Further, water was added to adjust the total amount of the mixture to 5 liters, and then paper was made. Peel the paper from the wire mesh,
After compression dehydration with a roll and a press, hot air drying was performed at 130 ° C. The volume resistivity and the tensile strength of the obtained paper were measured. The results are shown in Table 3.

Example 30 This example is an example using a polymer latex and a polymer fixing agent. A mixture of pulp and AB was prepared in the same manner as in Example 23 using a predetermined amount of AB of Example 24 and a predetermined amount of linter pulp of cotton, and then anionic system of carboxy-modified styrene-butadiene-methacrylic acid ester copolymer. 2 g of a solution of latex (solid content 25%) was added and stirred for 5 minutes. Next, 4 g of a 1% solution of the cation-modified polyacrylamide derivative was added, and the mixture was stirred for 5 minutes, and then paper was made in the same manner as in Example 23.

Comparative Example 22 Instead of the N, N-dimethylacetamide of Example 23,
Sodium dodecyl sulfate, which is a surfactant, was used.
When the aqueous dispersion of AB and the aqueous dispersion of pulp were mixed and stirred, foaming became violent and almost overflowed from the container. Therefore, a silicone antifoaming agent and a higher alcohol antifoaming agent were added to defoam. .. The effluent after papermaking was black and contaminated. The paper yield and the content of AB in the paper were low, and the volume resistivity was large. Further, it was confirmed that the carbon density was uneven on the surface of the paper, and the carbon dispersion was non-uniform.

COMPARATIVE EXAMPLE 23 Instead of N, N-dimethylacetamide of Example 23, a condensed sodium naphthalenesulfonate as a surfactant having a small amount of foam generation was used. No bubbles were generated when the aqueous carbon / pulp dispersion mixture was stirred. However, the wastewater at the time of papermaking was black, and a large amount of carbon outflow was observed. Further, the yield of paper and the amount of carbon in the paper were extremely small, and the volume resistivity of the paper was also large.

Comparative Example 24 In place of AB of Example 23, non-water floating property (easy water dispersibility)
Using HAF carbon black [ASTM N330, manufactured by Mitsubishi Kasei Kogyo Co., Ltd., Diamond Black H], which is a furnace black of carbon black, and using an aqueous dispersion obtained by directly dispersing this in water, the same conditions as in Example 23 were used. Made paper. The carbon yield of the obtained paper was low and the volume resistivity was large.

[0036]

[Table 1]

[0037]

[Table 2]

[0038]

[Table 3]

[0039]

The carbon black aqueous dispersion of the present invention is stable and does not generate bubbles and remain after stirring, so that it is easy to manufacture and easy to handle. Further, since no bubbles remain, there is no trouble due to bubbles in the field of use, and handling is easy. Moreover, excellent conductivity can be given to a product obtained by using the same. Further, most of the organic compounds of the present invention can be removed by drying, and the adverse effect caused by remaining with carbon black can be prevented.

The carbon black aqueous dispersion of the present invention comprises:
Although it is mixed with a binder such as a water-soluble polymer or a polymer emulsion, it can be used as a conductive paint or a colored paint by adding it to a paint composition such as a polymer emulsion. It can be added as a thickening agent to various aqueous dispersions (for example, coal slurry). Further, the carbon black aqueous dispersion of the present invention can be mixed with a material to be an inorganic or organic matrix, or an aqueous dispersion thereof to impart conductivity or colorability. For example, carbon black-containing paper having good conductivity can be obtained by making paper from an aqueous dispersion of cellulose fibers. This paper has excellent conductivity, so for the purpose of preventing static electricity and shielding electromagnetic waves,
Further, it can be usefully used for earth wrapping paper, discharge recording paper, sheet heating element and the like. Furthermore, it can be used for applications such as a sheet heating element and discharge recording 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 hydraulic 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 fuel cell separator.

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[Procedure amendment]

[Submission date] July 22, 1991

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0038

[Correction method] Change

[Correction content]

[0038]

[Table 3]

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Claims (2)

[Claims] 1. A nonionic organic compound containing at least one N atom and / or O atom and having 2 or more carbon atoms, wherein the organic compound is an N atom-containing compound (O
When the atom is not contained), the ratio N / C of the number of N atoms and the number of C atoms is 1/3 or more and 3/4 or less, and when the compound is an O atom-containing compound (N atom is not contained), Polycarboxylic acid having a ratio of the number of O atoms to the number of C atoms of O / C of 1 or more and 2 or less, and a cyclic ether having an O / C of 1/3 or more and less than 1 and having 4 or more carbon atoms, aromatic phenols and polyols And in the case of a compound containing both N and O atoms,
(N + O) / C is selected from aminoalcohols less than 1, amides or imides of carboxylic acids, and urea derivatives having one or more alkyl substituents, and the surface tension of the aqueous solution is 25 ° C., 2 wt. 66 dynes /%
cm or more, or 69 dynes / cm at 0.5% by weight
An aqueous dispersion of carbon black, wherein the water-floating carbon black is dispersed in an aqueous solution containing the above nonionic organic compound. 2. A carbon black-containing paper, characterized in that a mixed liquid of the carbon black aqueous dispersion according to claim 1 and an aqueous fiber dispersion is made into paper.