JPS6040560B2 - Method for manufacturing conductive base material - Google Patents

Description

[Detailed description of the invention] (Technical field of invention) The present invention relates to a method for manufacturing a conductive base material.

Specifically, the present invention involves uniformly dispersing a chemically inactive conductive inorganic powder using the colloidal properties of humic acid salts, and then coating or combining it on the surface of a fibrous base material mainly composed of cellulose. The present invention relates to a method for manufacturing a conductive base material that is efficiently fixed on the surface or inside of a fibrous base material by soaking, and the humic acid salt becomes immovable by drying, thereby making the conductive base material water resistant. (Technical Background of the Invention) Conductive substrates are widely used in various industrial fields such as electrically-related conductive paper and earth wrapping paper, and demand has been rapidly increasing in recent years.

A common method for producing conductive substrates, such as conductive paper (carbon-coated paper), is to use a coating liquid in which carbon-like powder such as carbon black is dispersed in a water-soluble adhesive such as starch, casein, or glue. Coating on paper base material (Patent No. 1726)
No. 36), but since the cellulose fibers and carbonaceous powder are bonded together with a water-soluble adhesive, they are not water resistant and have the disadvantage of easily falling off in an atmosphere containing moisture or moisture. .

In order to improve adhesion and water resistance, it is common practice to use synthetic polymer latex such as styrene-butadiene latex as an adhesive instead of the water-soluble adhesive described above. Although this method improved the shedding of carbon particles from the conductive substrate, it had the disadvantage that the electrical resistance value increased during the process. (Object of the invention) This invention provides chemically inert conductive inorganic powder,
The purpose is to obtain a homogeneous and strong conductive base material by fixing it on the surface of a fibrous base material mainly composed of cellulose or on the surface of its constituent fibers.

A further object of the present invention is to provide an economical method for producing a conductive base material that has improved water resistance and prevents conductive inorganic fine powder from falling off.

(Structure of the Invention) This invention provides a conductive material characterized by coating or impregnating at least one side of a fibrous base material mainly composed of cellulose with a mixed solution of a salt of humic acid and a conductive inorganic powder. This is a method for manufacturing a base material.

Below, the constituent elements of the present invention will be individually explained in detail.
(Salt of Humic Acid) In the present invention, in addition to alkali metal salts such as lithium salts, sodium salts, potassium salts, or ammonium salts, alkali metal salts such as magnesium salts and calcium salts are used as humic acid salts. However, preferred are the sodium and ammonium salts.

(Fibrous base material) As the fibrous base material mainly composed of cellulose in the present invention, cellulose pulp paper such as wood-free paper, kraft paper, newsprint paper, etc. is used. However, it is not necessarily limited to the above, but mainly consists of cellulose pulp, natural fibers such as cotton, rayon,
The base material may include chemical fibers such as polypynyl alcohol fibers, polyester, and polyacrylonitrile, synthetic pulps such as polyethylene and polypropylene, and inorganic fibers such as asbestos, rock wool, and glass fibers.

The substrate may be in the form of paper (including paperboard and cardboard), nonwoven fabric, or cloth. It is preferable that these materials are preliminarily supported on a base material by internally adding, coating, or impregnating a divalent or higher-valent metal salt during production. In addition, when the conductive base material in the present invention is paper-like, the electrical resistance value can be further reduced by calendering to make the surface smooth.

(Salt of polyvalent metal) Examples of metal salts of divalent or higher valence that are chelated with the humate contained in the base material include aluminum salt,
Iron salts, copper salts, zinc salts, etc. are used, but aluminum sulfate, iron sulfate, etc. are preferable for paper making.

(Conductive Inorganic Fine Powder) Carbon black, charcoal, graphite, activated carbon, metal powder, etc. are used as the conductive inorganic powder in the present invention.

The mixing ratio of the humate and the conductive inorganic powder is in the range of 1:1 to 1:5, particularly preferably 1:4.
It's nearby.

(Mixed liquid) In the present invention, the conductive inorganic powder and the humic acid salt are dispersed in water, and the thus obtained dispersion (mixed liquid)
is used for coating or impregnation.

The solid content concentration in the liquid mixture is suitably about 1 to 1% by weight. The above-mentioned liquid mixture is applied or impregnated onto at least one side of a fibrous base material mainly composed of cellulose in an amount of about 0.5 g to about 100 g (in terms of solid content), and dried.

In the above range, the adhesion of the conductive inorganic powder onto the textile base material is good and the tendency of the conductive inorganic powder to fall off is the lowest. In addition, if more complete adhesion and prevention of falling off are required, add water-repellent polyolefin resin emulsion, modified SBR emulsion, EUA resin emulsion, acrylic resin emulsion, etc. to the above mixture to an extent that does not impair conductivity. May be mixed. (Operations and Effects of the Invention) Since the humate used in the present invention has colloidal properties, it facilitates the dispersion of the conductive inorganic powder into water, but the humate itself is made up of ultrafine particles with a size of angstrom unit. Therefore, it penetrates well into the cellulose fiber structure, reacts with the active groups of cellulose fibers through ionic bonding, reacts with internally added divalent or higher metal salts, and adsorbs the chelate, and at the same time, it also absorbs the conductive layer inorganic powder. It is thought that it is fixed on the fiber surface.

Furthermore, since the chelate reaction product is insoluble in water, the obtained base material is imparted with water resistance and the conductive inorganic powder is prevented from falling off. Furthermore, since humates permeate and disperse into the cellulose fiber structure and become fixed through metal chelation, the bonds between the cellulose fibers become stronger, and at the same time, the spaces in the fiber structure are filled, thereby increasing the paper's tightness. Increases elasticity and strengthens the waist (also improves tensile strength).

Since the conductive base material of the present invention has humic acid metal salts uniformly dispersed and fixed on the fiber surface, it is impervious to water and has improved water resistance.

Therefore, the electrical resistance value is stable with little variation due to the influence of moisture absorption and desorption. In addition, when the present invention is carried out using a nonwoven fabric, the conductive substrate of the present invention has a coarse fiber composition, so there are many voids, and the impregnating liquid is evenly distributed and fixed over the front and back, so the conductivity between the front and back is high. That is, the volume resistivity value is low. Generally, conventional products coated with conductive inorganic powder require a large amount of adhesive to prevent them from falling off during use, so most have a surface resistivity of 1 x 1070 or more. Therefore, it is difficult to obtain a low surface resistivity value. However, with the use of the humic acid salt of the present invention, coated products with a surface resistivity of about 1 x 1 x ○ can be manufactured without using an adhesive, and coated products with a surface resistivity of about 1 x 1 x ○ or less can be manufactured without using an adhesive. The present invention is an economical manufacturing method because a small amount of adhesive is required to prevent falling off even when the product is of high quality. Furthermore, the present invention has the following effects.

■ Since humic acid salts also act as dispersants and fixing agents, pigments can be prepared and produced using conductive inorganic fine powder using a simple process, and it is the most economical method as it requires no or a small amount of adhesive. This is a great method.

■ In addition, humic acid salts contain carbon and adhere to the fiber surface, making it impervious to water, improving the water resistance of the product and reducing fluctuations in electrical resistance due to moisture absorption and desorption, making it more stable. be.

(Examples) Examples are shown below to explain the present invention in more detail, but the following examples do not limit the present invention.

Example 1 Ammonium salt of humic acid (C manufactured by Ternite Co., Ltd.)
HA-07) is diluted with water, carbon black powder (XC-72 manufactured by Cabot Corporation) is added thereto, and the mixture is stirred and kneaded.

The mixing ratio of humate and carbon black at this time is
A mixed solution was prepared such that the weight ratio was 1:4 and the total amount of humate and carbon black was 5% by weight of the mixed solution, and this was used as a carbon pigment stock solution.
Using a bar coater, apply the above carbon pigment stock solution uniformly onto one side of bleached kraft paper with a basis weight of 7 female/final, place it in a 60 qo hot air dryer, and dry for about 1 minute. It was dried and made into a product.

A sample for comparison was prepared in the same manner as above except that humate was not used. The surface resistivity values of the products obtained by the above treatment were measured, and the results shown in Table 1 were obtained. [Table 1] (Note 1) Measurement using voltage-applying electrodes was used.

(Note 2) Sample 1 is a comparison sample, and samples 2 and 4 are products according to the present invention. Example 2 Sodium salt of humisic acid (CH-02 manufactured by Ternite Co., Ltd.) is diluted with water, carbon black powder (XC-72 manufactured by Cabot Corporation) is added thereto, and the mixture is kneaded.

At this time, the mixing ratio of humic acid salt and carbon black should be 1:4 by weight, and the total amount of humic acid salt and carbon black should be 1% by weight of the mixed liquid. A mixed solution was prepared. Using this preparation liquid, the basis weight is 80g/
Apply impregnation to both sides of that bleached kraft paper and apply it to 60qo.
The product was placed in a constant temperature hot air dryer and dried for about 1 minute to obtain a product. A sample for comparison was prepared in the same manner as above except that humate was not used.

The surface resistivity values of the products obtained by the above treatment were measured, and the results shown in Table 2 were obtained. Table 2 Note] Electrical resistance measurement method: Measurement example using voltage applied electrode 3 Ammonium salt of humic acid (CH-
A 10% aqueous solution of 07) was further diluted with water, and carbon black powder (Cabot XC-72 95
A mixture of 5 parts by weight of Ketjen Black EC manufactured by Nippon EC Co., Ltd.) was added and kneaded to prepare a mixed solution.

In this mixed solution, the weight ratio of humic acid ammonium salt and carbon black was 1:4, and the concentration of carbon black was 1% by weight. This mixed solution was further mixed with a solution of Zychsen-A (polyolefin resin emulsion manufactured by Tetsuko Kagaku Co., Ltd.) to adjust the solution concentration to 1% by weight to obtain an impregnating solution. Zaichsen-A in this impregnation solution
The blending ratio was 3 parts by weight per 10 parts by weight of carbon pigment (solid content). A wet non-woven fabric (rayon non-woven fabric manufactured by Kunimitsu Paper Co., Ltd.) was immersed in the above impregnating liquid, then pulled up, squeezed with a rubber roll, placed in a constant temperature hot air dryer at 60:00, and dried for about 1 minute to form a product. .

The test results for this product are shown in Table 3. Table 3

Claims (1)

[Claims] 1. Production of a conductive base material characterized by coating or impregnating at least one side of a fibrous base material mainly made of cellulose with a liquid mixture in which a salt of humic acid and a conductive inorganic fine powder are dispersed in water. Method.