JPS6357557B2 - - Google Patents

Description

[Detailed description of the invention]

(Technical Field of the Invention) This invention relates to a method for producing conductive pulp. Specifically, this invention involves uniformly dispersing chemically inactive conductive inorganic fine powder using the colloidal properties of humic acid salts, and then chelating humic acid salts with divalent or higher metal salts. The present invention relates to a method for producing conductive pulp that can be efficiently fixed to the surface of fibers by adsorption and become insolubilized, thereby providing water resistance. (Technical Background of the Invention) Conductive pulp is a conductive paper, such as electrostatic recording paper,
Demand has increased rapidly in recent years as a raw material pulp for carbon paper, discharge recording paper, earth wrapping paper, etc., but it is also used for molded products other than flat applications such as paper. A common method for producing conductive pulp is
Conductive inorganic fine powder, such as carbon pigment, either directly or as a dispersion, is mixed with pulp slurry, formed into a sheet, dried, and made into a pulp mat with a moisture content of around 50%, but the conductivity is not achieved by internal addition. Because the carbon pigments are simply adsorbed or deposited on the fibers, when the dry pulp mat is put into water and the pulp is mechanically dispersed, the carbon pigments tend to fall off from the pulp, and as a result, the paper obtained by papermaking tends to fall off. The drawback was that the conductivity was insufficient. In addition, conductive particles such as carbon black, activated carbon, graphite, and metal powder are extremely fine particles that are electrically active but chemically inactive, so in order to fix these particles to the fiber surface, Even if a large amount of fixing agent is used, these conductive particles that flow out into the wastewater during papermaking are fine and difficult to recover, so they flow into the wastewater and cause factory wastewater pollution. (Objective of the Invention) The object of the present invention is to fix these inert conductive inorganic fine powders on the surface of cellulose fibers with a good yield to obtain a homogeneous and strong conductive pulp. Furthermore, it is an object of the present invention to provide an economical manufacturing method that uses a small amount of conductive inorganic fine powder and causes less runoff into wastewater and less pollution. (Structure of the Invention) This invention provides a method for producing conductive pulp by mixing conductive inorganic fine powder with pulp slurry and dehydrating or drying the mixture. This is a method for producing conductive pulp, which is characterized by adding a divalent or higher valent metal salt. (Pulp) Pulps used in the present invention include GP (ground wood pulp), RMP (refiner mechanical pulp),
TMP (thermomechanical pulp), CGP (chemiground pulp), SCP (semi-chemical pulp),
There are SP (sulfite pulp), KP (kraft pulp), AP (alkali pulp), waste paper pulp (deinked secondary fiber), linter pulp, etc.
These materials may be used alone or in combination. (Conductive Inorganic Fine Powder) As the conductive inorganic fine powder in the present invention, carbonaceous fine powder such as carbon black, charcoal, graphite, activated carbon, etc., and metal fine powder such as copper, nickel, aluminum, etc. are used. The amount of the conductive inorganic fine powder added may be adjusted to increase or decrease depending on the target electric resistance value of the pulp. Taking carbon pigment as an example, if the target surface resistance value is on the order of 1 x 10 ⁷ Ω, the carbon pigment should be added at a ratio of 8 to 9% to the pulp, and if the target surface resistance value is on the order of 1 x 10 ⁶ Ω, the carbon pigment should be added at a ratio of 10 to the pulp. It is appropriate to mix up to 12%. If an even lower resistance value is required, the amount of carbon pigment can be increased, but when it reaches the level of 1×10 ⁵ Ω, the amount added becomes about 16-20%, and the surface resistance value decreases even though the amount added increases. The rate of decline will be smaller. (Humate salt) In the present invention, the humate salt includes lithium salt,
In addition to alkali metal salts such as sodium salts and potassium salts or ammonium salts, alkaline earth metal salts such as magnesium salts and calcium salts are used, but sodium salts and ammonium salts are preferred. The mixing ratio of the humic acid salt and the conductive inorganic fine powder is in the range of 1:1 to 1:5, particularly preferably around 1:4. It has good fixability to pulp, and paper made from this pulp also has good electrical conductivity. (Salts of polyvalent metals) Aluminum salts, iron salts, copper salts, zinc salts, etc. are used as divalent or higher valent metal salts to chelate with humates, but those suitable for pulp fixation are aluminum sulfate or sulfuric acid. Iron, etc. (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 fine powder, but since the humate itself is ultrafine particles with a size of angstrom unit, It penetrates well into the cellulose fiber structure, reacts with divalent or higher valent metal salts mixed in later, and chelates and adsorbs onto the fiber surface. Moreover, since this chelate reaction product becomes water-insoluble, the obtained pulp has improved water resistance. Pulp with carbon particles fixed with humates and metal salts of divalent or higher valence can be made into sheets with a moisture content of 50 to 55% using a pulp sheet machine, but it can also be made into sheets or disintegrated pulp by going through a drying process. However, dried sheet-like pulp or disintegrated pulp tends to have somewhat poor redispersibility in water and takes a long time for dispersion. Even if mechanical stirring is used for redispersion, the carbon fine particles fixed to the fiber surface will not fall off and the conductivity will not be impaired. Unlike conventional conductive pulp, which exhibits conductivity through the adsorption or deposition of carbon particles on the fiber surface, the conductive pulp of the present invention exhibits conductivity by chemically adsorbing ions onto the fibers. Since it is firmly fixed, when it is redispersed in water, there is almost no dropout of the carbon fine particles, and therefore, there is almost no decrease in conductive performance in conductive paper or molded products made from the conductive pulp of the present invention. do not have. This fact is considered to be the result of the metal chelate of humic acid salt and aluminum sulfate entrapping carbon fine particles and penetrating into the pulp fiber surface or inside the tissue and fixing them. The effects of this invention are as follows. (i) A chelate of a salt of humic acid and a metal salt with a valence of 2 or more is uniformly fixed to the pulp fiber surface or inside the tissue together with the conductive inorganic fine powder and exhibits conductivity, so a small amount of the conductive inorganic fine powder Demonstrates effective conductive performance in the body. (ii) Chelates of humates and divalent or higher metal salts envelop conductive inorganic fine particles, penetrate into the pulp fiber structure, and stick to the structure. After drying, they become insoluble in water and the fixation is stabilized. Therefore, the conductive inorganic fine powder hardly falls off from the pulp during redispersion in water or mechanical disintegration. (iii) The conductive pulp of the present invention has very little influence on surface resistivity and volume resistivity due to moisture absorption and desorption peculiar to pulp. (iv) Chelates of humic acid salts and divalent or higher valent metal salts envelop the conductive inorganic fine powder and penetrate into the pulp fiber surface or inside the tissue, thereby fixing the conductive inorganic fine powder. The yield is very high, there is little runoff into the wastewater, and there is little pollution of the wastewater. (Examples) In order to make the present invention easier to understand, Examples are described below, but the present invention is not limited to the following Examples. Example 1 Unbleached kraft pulp was defibrated to prepare a pulp slurry having a concentration of 2%. Add sodium humate (manufactured by Ternite Co., Ltd., CHA humic acid) and carbon black (manufactured by Gearbot Co., Ltd., CHA humic acid) to this pulp slurry.
VULCAN XC-72) mixed solution (mixing ratio 1:
4) was added to the pulp at 9%, 12%, 16%, and 20%, and after stirring for 5 minutes, aluminum sulfate was added at 2.5% to the pulp, and the pulp was heated to a moisture content of 60 to 65% using a pulp sheet machine. Mats was manufactured and used as a conductive pulp material. After storing this conductive pulp for two months, it was redispersed with water to form a pulp slurry, which was then used to make paper by a conventional method to obtain conductive paper. Table 1 shows the surface resistivity values of this conductive paper.

[Table] Surface resistivity measurement: Measurement example 2 using pressure applying electrode Unbleached kraft pulp was defibrated to prepare a pulp slurry with a concentration of 2%. Add humic acid ammonium salt (manufactured by Ternite Co., Ltd.) to this pulp slurry.
CH-07) and carbon black (manufactured by Gearbot Co., Ltd., VULCAN death,
Made into wet mats with a moisture content of 62% using a pulp sheet machine,
Thereafter, the wet mat was made into a cotton-like material using a fibrillator and dried in a dry air dryer at 105°C for 5 minutes to obtain a conductive pulp material. After storing this conductive pulp for one month, it was molded into a mat shape, sprayed with a small amount of water, and hot pressed.
Pressurized at 180℃, 35Kg/cm ² for 2 minutes to a thickness of approximately 1m/cm.
I created a board of m. The volume resistivity of this sample is shown in Table 2.

[Table] Volume resistivity measurement: Measurement using pressurized electrodes

Claims (1)

[Claims] 1 A method for producing conductive pulp by mixing conductive inorganic fine powder with pulp slurry and dehydrating or drying the mixture, in which a solution of a humic acid salt and a salt of a divalent or higher valent metal are added to the pulp slurry. A method for producing conductive pulp characterized by the following.