JPS6262187B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing electrically conductive cellulosic materials.

BACKGROUND OF THE INVENTION Organic conductive materials obtained by imparting conductivity to organic materials having electrical insulation properties are used in antistatic materials, resistance heating elements, electromagnetic wave shielding materials, and the like. Attempts have also been made to impart electrical conductivity to paper, which is a cellulosic material, and it has been used as a base paper for antistatic wrapping paper, electrostatic recording paper, electrically conductive thermal recording paper, destructible recording paper, etc. It has been rapidly used in recent years.

Regarding conductive paper, in addition to imparting conductivity only to the surface by coating or vapor-depositing a conductive material on the paper surface, recently, conductivity has also been imparted in the volume direction. There is a growing demand for what has been done. As a method of applying it, conductive inorganic powder (e.g. carbon powder, metal powder, etc.) or conductive inorganic fiber (e.g. carbon fiber, metal fiber, etc.), which has been developed in recent years, is one of the cellulosic materials. Generally, it is mixed with wood pulp. Although such a method provides conductivity, it has the following drawbacks.

In other words, conductive inorganic materials have poor chemical affinity with wood pulp, and there is a large difference in specific gravity between the materials, requiring complicated operations when mixing, and when making paper. Since the distribution of the conductive material tends to be biased and the conductivity of the obtained paper differs between the front and back sides, a correction operation is required. Additionally, the mixed conductive material has difficulty bonding with the wood pulp and has a tendency to fall off from the paper. Naturally, it also tends to impair the original strength and texture of the paper. That is,
It is difficult to obtain good conductive paper by simply mixing such conductive materials with wood pulp.

The present inventors have discovered that if a cellulose material that has been subjected to a specific activation treatment is brought into contact with a metal complex salt solution and then subjected to a precipitation treatment, a cellulose material that has excellent conductivity both on the surface and in the volume direction can be obtained. The present invention has been achieved based on the discovery that the following can be obtained.

That is, the present invention impregnates a metal complex salt solution into a cellulose-based material that has been activated by introducing a reducing functional group through oxidation treatment, adhesion treatment with a polymeric compound having an amino group, or treatment with a silver compound. This is a method for producing a conductive cellulose-based material characterized by precipitating a conductive metal and/or a metal compound from a cellulose-based material.

This material not only has electrical conductivity, but also has a much lower specific gravity than single metal materials, has excellent moldability, and has excellent strength in molded products.
Furthermore, it is widely expected to be used in combination with other materials.

In the present invention, the metal complex salts include silver, copper,
Complex salts of cobalt, nickel and iron are preferred;
In addition, methods for depositing conductive metals or metal compounds onto cellulose materials from these complex salts include reduction treatment, sulfurization treatment, heat treatment, or a combination thereof, such as metal silver, metal copper, Copper sulfide, metallic cobalt, cobalt sulfide, metallic nickel, iron sulfide, etc. are precipitated and deposited on cellulose-based materials.

A wide variety of cellulosic materials can be used, ranging from pure cellulose to lignocellulose, and they can be in the form of sheets, films, fibers, or powders. , boards, plates, cotton cloth, etc. Film-like products include cellophane and cellulose acetate films, and fibrous products include various wood pulps ranging from bleached pulp to unbleached pulp, cotton, regenerated cellulose cotton, etc. Examples of powdered materials include microcrystalline cellulose, wood flour, and cellulose-like polysaccharides (eg, starch).

After activating these cellulose materials,
Subject to treatment with metal complex salt solution. Activation treatments include a method of introducing reducing functional groups such as aldehyde groups into the material using an oxidizing agent such as periodic acid or an oxidizing treatment such as corona discharge treatment, and a method of introducing a reducing functional group such as an aldehyde group into the material. Examples include a method of attaching imine, and a method of causing silver nitrate, silver ammonia complex salt, etc. to act on the material to generate the reduced metal as a nucleus for precipitation in the material.

In addition, when preparing a metal complex salt solution, examples of metal salts for imparting conductivity include silver salts, copper salts, cobalt salts, nickel salts, iron salts, etc. As the carboxylic acid, aliphatic carboxylic acids, aromatic carboxylic acids, aldehydes, sulfonic acids, ammonia, amines and their derivatives, aminocarboxylic acids, etc. can be used, and if necessary, an alkali such as sodium hydroxide may be used in combination.

An activated cellulose-based material is immersed in a solution of a metal complex salt formed from these ligands and a metal salt. Metals are preferentially deposited. For example, in the case of complex salts of silver, copper, cobalt, and nickel, there are reducing agents such as formalin, paraformaldehyde, sulfite water, hydrosulfite, hydrazine, sodium hypophosphite, sodium borohydride, and carbon powder. of,
Adding heat before or after dipping will preferentially deposit metal into the material. In addition, in the case of complex salts of copper, cobalt, and iron, for example, hydrogen sulfide gas is blown into the solution, or ammonium sulfide, ammonium polysulfide, sodium sulfide, thiourea, thioglycolic acid, etc. are added and heated. , metal sulfides precipitate. Similarly, when a metal complex solution is impregnated in a cellulose material and heated, brought into contact with a reducing gas such as sulfur dioxide or hydrogen, or brought into contact with a sulfide gas such as hydrogen sulfide, the material A metal or metal compound having electrical conductivity is deposited.

The metal or metal compound deposited on the cellulosic material by any of these precipitation treatments or a combination thereof is in good adhesion to the material;
Since it does not fall off when washed with water, substances that are undesirable for use can be removed by washing thoroughly with water. When dried after washing with water, a conductive cellulose material with excellent moisture resistance and weather resistance is obtained.

The amount of metal or metal compound deposited on the cellulose material can be varied from 1 to several hundred percent by weight, and the electrical resistance value of the cellulose material can be freely controlled depending on the amount deposited.

However, from the point of view of economic efficiency and maintaining the original performance of cellulose-based materials, excluding the electrical resistance value, it depends on the type of metal and metal compound, but the weight ratio is about 1 to 50%, and the capacity ratio is at 0.2
It is appropriate to suppress the electrical resistance value of the cellulose material to about 10 ¹³ to 10 ¹ within this range.
It can be changed to Ω.

Next, the present invention will be explained in more detail with reference to Examples.

Example 1 Bleached softwood pulp was beaten to a freeness of 450 ml to prepare a 2% slurry. While stirring this slurry, an aqueous silver nitrate solution was added to the slurry to give a silver content of 1% based on the weight of the pulp. After dehydrating and washing the activated pulp in this way, copper chloride,
When dispersed in a liquid consisting of formalin, tartaric acid, and caustic soda, copper precipitates on the surface of the pulp. After washing this pulp with water, it is made into paper and dried in a conventional manner to obtain conductive paper. The electrical resistance values of this conductive paper were a surface resistivity of 1.1×10 ² Ω and a volume resistivity of 4.3×10 ³ Ω·cm when the copper adhesion rate was 60%.

The measurement conditions are as follows.

Sample: Basis weight 80g/m ² , thickness 105μ Electrical resistance value measuring device: Kawaguchi Electric Manufacturing Co., Ltd.
MODEL-505 Example 2 Softwood bleached pulp was beaten to a freeness of 480 ml, 0.2% of cationic paper strength enhancer was added to the pulp, and unsized paper was made in a conventional manner, and corona discharge treatment was performed to remove aldehyde from the paper. increase group. When this activated paper is immersed in Fehling's solution containing formalin and held at 50°C for 30 minutes, pink metallic copper is deposited on the paper. When this copper-deposited paper was washed with water and dried with a cylinder dryer, it turned dark brown, but when this dried paper was run on a hot calender roll, a conductive paper with a copper luster was obtained. The electrical resistance of this conductive paper was 1.3 x 10 ² Ω on the surface and 6.4 x 10 ³ Ω cm in volume when the adhesion rate of copper metal was 54% of the weight of the paper. .

Example 3 When beech wood flour (80 mesh pass) is suspended in a 0.5% periodic acid aqueous solution and oxidized for 5 minutes, 30 mmol of aldehyde groups are produced per 100 g of wood flour. After washing this treated wood flour with water, it is suspended in a cuprous nitrate/ammonia complex salt solution, and stirring is continued for 30 minutes. Then, when hydrogen sulfide gas is blown into the suspension, almost all of the copper ions are precipitated into the wood flour as cuprous sulfide, giving the wood a black edge color.
Conductive wood flour is obtained by heating and drying after washing with water, and the electrical resistance value of the conductive wood flour obtained by adding copper ions to the wood flour at 25% by weight is 2.0×10 ² Ω.
It was hot.

Similarly, conductive wood flour was prepared by adding 40% by weight of copper ions to the wood flour and performing the same precipitation treatment.
A resin board was made by mixing epoxy resin with 17% by weight of resin and 83% by weight of conductive wood powder. When we measured its volumetric specific electrical resistance value, it was 2.4×10 ⁶ Ω・cm
A conductive resin plate was obtained. An epoxy resin board made by mixing non-conductively treated wood flour with resin at the same ratio showed an electrical resistance value of 10 ¹² Ω·cm or more.

Example 4 Ordinary cellophane (23μ thick) was immersed in a 1% polyethyleneimine aqueous solution for 10 minutes to undergo activation treatment. When this treated cellophane is immersed in a nickel complex salt solution prepared with nickel sulfate, aqueous ammonia, caustic soda, sodium citrate, and sodium hypophosphite, heated to 80°C and held for 10 minutes, nickel precipitates into the cellophane. It's coming. The electrical resistance values of nickel precipitated at 30% based on the weight of cellophane were 1.8×10 ² Ω in surface resistivity and 1.0×10 ³ Ω·cm in volume resistivity.

Example 5 Cotton linter cotton is degreased, oxidized in a nitrogen dioxide atmosphere, and immersed in a complex salt solution prepared with cuprous chloride, ammonia, and polyethyleneimine. After thoroughly soaking the cotton with the liquid, remove the liquid. The copper complex salt solution is contained in an amount of about 125% by weight of the cotton. When this wet cotton is exposed to a hydrogen sulfide gas atmosphere, cuprous sulfide precipitates instantaneously, giving it a dark brown color. After heat treating this dark brown cotton with hot air, impurities were removed by washing with water to obtain conductive cotton. Its electrical resistance value is 10 ² Ω・
cm of conductive cotton contained 8 to 10% by weight of cuprous sulfide based on the weight of the cotton. This conductive cotton is
It is dark brown when wet, but grass-colored when dry.

Comparative Example 1 The same pulp as in Example 1 was subjected to no activation treatment with silver nitrate, and copper was precipitated in the same manner as in Example 1. After washing this pulp with water, paper was made in a conventional manner. At this time, it was observed that a large amount of copper particles were washed away from between the paper screens. The electrical resistance value of the pulp sheet was 10 ¹⁰ Ω or more. When this pulp sheet was observed under an optical microscope, it was found that the pulp fibers had become fibrillated due to beating, and there were some copper particles present in the parts, but this formed a copper network that exhibited electrical conductivity as a pulp sheet. had not yet reached that point.

Comparative Example 2 Copper sulfide precipitation treatment was performed in the same manner as in Example 3 except that beech wood flour was not subjected to activation treatment. The electric resistance value of the wood flour obtained by treating the wood flour so that the content of copper ions was 25% by weight was 10 ¹⁰ Ω or more.

Comparative Example 3 Same as Example 4, ordinary cellophane (23μ thickness)
was immersed in 0.01 mol of palladium chloride/solution. Nickel was deposited on the treated cellophane in the same manner as in Example 4. Although 30% of nickel was precipitated based on the weight of cellophane, the surface resistivity was 2.4 x 10 ² Ω and the volume resistivity was 1.5 x 10 ³ Ω cm, and this example was activated with polyethyleneimine. A product inferior to 4 was obtained.

Claims (1)

[Claims] 1. A cellulose-based material that has been activated by introducing a reducing functional group through oxidation treatment, adhesion treatment with a polymer compound having an amino group, or treatment with a silver compound is impregnated with a metal complex salt solution.
A method for producing a conductive cellulose-based material, characterized in that conductivity is imparted by precipitating a metal and/or a metal compound having conductivity.