JP2001049592A - Production of bulky pulp - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing bulky pulp, by which the bulky pulp useful as a raw material for bulky sheets, bulky mats, molded articles, and so on, can be produced in simple operations in good energy efficiency, by treating pulp with an aqueous alkali solution and then reacting the treated pulp with a cross-linking agent. SOLUTION: This method for producing bulky pulp comprises immersing pulp in an aqueous alkali solution such as an aqueous sodium hydroxide solution having a concentration of 1 to 50 wt.%, preferably 3 to 30 wt.%, neutralizing and further acidifying the treated pulp with an acidic aqueous solution such as sulfuric acid having a concentration of 0.2 to 20 wt.%, preferably 0.5 to 10 wt.%, and then cross-linking the treated pulp with a cross-linking agent, such as dimethyloldihydroxyethylene urea at a temperature of 30 to 100 deg.C, preferably 50 to 90 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention is useful as a raw material for bulky sheets, mats and molded articles used for special paper, wallpaper and other building materials, vehicles, furniture, decorative articles, filter media, absorbents and the like. The present invention relates to a method for producing bulky pulp.

[0002]

2. Description of the Related Art As a method for producing a bulky pulp by crosslinking pulp, a method of reacting with a crosslinking agent in a dry state has been known for a long time. However, it is a major problem that it is difficult to defibrate into a single fiber state in order to manufacture a sheet or a mat. Originally, pulp fibers are tightly bound by hydrogen bonds caused by OH groups contained during drying and bring about excellent mechanical strength as in the case of sheets and molded products, but can be relatively easily defibrated by stirring in water . The papermaking method and the pulp mode method in which the fibers are unraveled in water and processed in a wet state are excellent processing methods utilizing this property.

[0003] However, in order to produce a bulky pulp, a pulp which has been reacted with a crosslinking agent in a dry state is bonded by hydrogen bonding, and the immobilized pulp is chemically bonded by the reaction of the crosslinking agent. It is difficult to mechanically defibrate in water, and pulp fibers are cut and short fibers and powdered. Therefore, even if bulky sheets, mats, and molded articles are manufactured using such materials, their mechanical strength is reduced, and the desired bulkiness is low.

The following proposals have been made to improve such a problem. That is, 1 pulp is immersed in a treatment liquid containing a crosslinking agent and a catalyst, squeezed,
A method in which the solvent is removed and defibrated under conditions where the crosslinking agent does not cause curing or crosslinking reaction, and then curing is performed (Japanese Patent Publication No. 49-36882). 2. A method in which pulp is immersed in a treatment liquid containing a crosslinking agent and a fibrillation aid, squeezed, and then subjected to a crosslinking reaction (Japanese Patent Publication No. 50-16442). (3) A method in which pulp is reacted in the presence of a hydrophobic fiber and a softening agent at a temperature not higher than the melting point of the hydrophobic fiber (Japanese Patent Laid-Open No. 4-1857).
92). In any of these methods, a method of performing a cross-linking reaction in a dry state is a method of slightly reducing fiber shortening, but since pulp is hardened in a dry state, it is essentially hard to be loosened, and the fundamental solution is Not be. The manufacturing process is complicated and takes a long time to process.

What is most problematic is a process requiring a great deal of energy, in which a crosslinking agent is immersed in a wet state, a crosslinking reaction is performed in a dry state, and then defibration is performed again in a wet state. It requires a great deal and is not economically favorable. If a material having excellent bulkiness can be obtained by a crosslinking reaction and fibrillation in a wet state, the pulp fiber will not be damaged, and the mechanical strength of the processed product will be maintained. Further, since the crosslinked pulp is usually considered to be used in a wet state such as wet papermaking, it is strongly desired that the crosslinked pulp can be manufactured consistently in a wet state. However,
There is no technical proposal for such a request.

[0006]

An object of the present invention is to provide a method for producing a crosslinked pulp excellent in bulkiness in a wet state.

[0007]

The present inventors have conducted various studies to solve the above-mentioned problems. As a result, the pulp is immersed in an alkaline aqueous solution and then reacted with a crosslinking agent in an acidic aqueous solution to obtain a bulky material. It has been found that a crosslinked pulp excellent in the above can be produced, and the present invention has been accomplished. That is, the present invention
This is a method for producing bulky pulp, which comprises treating pulp with an aqueous alkali solution and then reacting the pulp with a crosslinking agent under acidic conditions. Even if the pulp is simply reacted with the cross-linking agent in a wet state such as an acidic aqueous solution, or simply subjected to treatment such as immersion in an alkaline aqueous solution, the bulkiness of the pulp is not significantly improved. After the pulp is immersed in an alkaline aqueous solution, the pulp is neutralized, and a cross-linking reaction is performed under acidic conditions, whereby a cross-linked pulp excellent in bulkiness can be produced for the first time.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The alkali treatment of the present invention may be carried out by immersion in an aqueous alkali solution or impregnation with an aqueous alkali solution by spraying or the like. The concentration of the alkaline aqueous solution is 1 to 50% by weight, preferably 3 to 30% by weight. Sodium,
Caustic alkalis such as potassium and calcium and water-soluble alkalis such as carbonates are used. After the treatment of the pulp with the alkaline aqueous solution, the alkaline aqueous solution can be separated from the pulp by filtration or centrifugal force and recycled if necessary. After treating the pulp with an aqueous alkaline solution, the attached alkali is neutralized using a water-soluble acidic substance, and the pulp is further adjusted to an acidic aqueous solution state. The pulp treated with an aqueous alkali solution may be immersed in an acidic aqueous solution or impregnated by spraying an acidic aqueous solution into an acidic aqueous solution. Acidic aqueous solution, sulfuric acid, hydrochloric acid, phosphoric acid, mineral acids such as nitric acid or acid salts thereof, for example, ammonium sulfate, ammonium chloride, ammonium salts such as ammonium nitrate,
A magnesium salt such as magnesium chloride or magnesium nitrate, or a zinc salt such as zinc chloride or zinc nitrate is dissolved in water, and the concentration of the aqueous solution is 0.2 to 20% by weight, preferably 0.5 to 20%.
It is adjusted to 10% by weight.

The crosslinking agent of the present invention can be used in the form of an aqueous solution,
Those having a functional group such as methylol and aldehyde having two or more bonds that react with cellulose in the molecule are exemplified. Examples include dimethylol ethylene urea,
Monomers or oligomers of methylol compounds such as dimethylol dihydroxyethylene urea, methylol acetylene diurea having 2 or more methylols, methylol urea having 2 or more methylols, methylol melamine having 2 or more methylols, mixtures thereof, and methylol thereof Is partially alkoxylated with an alcohol such as methanol, glyoxal, malonaldehyde,
Aldehyde compounds such as glutaraldehyde and their hemiacetals or partially acetalized ones may be mentioned. A mixture of two or more of the above compounds is also an object. The concentration of the crosslinking agent used in the aqueous solution is 2 to 50% by volume, preferably 5 to 20% by volume. Formalin can also be used as an effective crosslinking agent, but measures against residual formalin are important.

The crosslinking agent is reacted by adding a single aqueous solution or a mixture thereof in an acidic aqueous solution. Reaction is 30 ~
It is desirable that the heating is performed at 100 ° C, preferably 50 to 90 ° C. At a temperature of 100 ° C. or more under pressure, the reaction rate increases. After the reaction, the acidic aqueous solution containing the crosslinking agent can be separated from the pulp by filtration or centrifugal force and recycled if necessary. The pulp reacted with the cross-linking agent can be very easily dispersed as a slurry in water after filtration, sent to the next step such as papermaking or pulp mold, and used for the production of pulp bulky products. Alternatively, it is purified and dried and used as a bulky pulp in various fields.

[0011]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples. The bulkiness is evaluated by measuring the thickness of the bulky pulp produced by reacting the pulp with the crosslinking agent, washing with water and drying. The thickness was measured using a round sheet obtained by filtering and drying the pulp defibrated in water after the reaction with a glass funnel having a filtration surface of 10 cm in diameter. In the measurement, the thickness of the sample at five locations was measured, and the range of the numerical values was shown to evaluate the bulkiness.

Example 1 5 g of softwood pulp was immersed in 100 g of a 20% aqueous sodium hydroxide solution for 30 minutes, and 175 g of a 20% aqueous sulfuric acid solution was added to neutralize and acidify. As a result of measurement with a pH test paper, it showed strong acidity.
Dimethylol dihydroxyethylene urea 40% aqueous solution 70 g
Was added thereto, and the mixture was reacted at 65 ° C. for 2 hours while stirring. After the reaction, the solution was suction-filtered with the above-mentioned glass funnel, then defibrated in water, and suction-filtered with the above-mentioned glass funnel. At the time of filtration, the pulp was strongly pressed with a lid of a wide-mouth bottle to separate water, and this was dried at 105 ° C. for 1 hour by a tray dryer. As a result of measuring the thickness of the obtained sheet,
It was 8.6 to 9.2 mm.

Example 2 5 g of softwood pulp was immersed in 100 g of a 5% aqueous sodium carbonate solution for 30 minutes, and the resulting mixture was poured into 150 g of an aqueous solution containing 7.5% sulfuric acid and 13.3% dimethylol dihydroxyethylene urea, followed by stirring and dispersion. As a result of measurement with a pH test paper, it showed strong acidity. This pulp dispersion aqueous solution was used in the same manner as in Example 1 for 65%.
Stirring reaction and purification were performed at 2 ° C. for 2 hours to prepare a round sheet-shaped sample. As a result of measuring the thickness of the obtained sheet, it was 8.6 to 9.4 mm. Example 3 5 g of softwood pulp was immersed in 100 g of a 5% aqueous solution of caustic soda for 30 minutes, then suctioned and filtered with a glass funnel to separate the alkali-treated pulp. Next, it was added to 200 g of an aqueous solution containing 4% sulfuric acid and 10% dimethylol dihydroxyethylene urea, and was dispersed by stirring. This pulp dispersion aqueous solution was reacted and purified in the same manner as in Example 1 to prepare a round sheet-shaped sample. As a result of measuring the thickness of the obtained sheet, 8.1 to 8.6
mm.

Example 4 5 g of softwood pulp was immersed in 100 g of a 20% aqueous solution of caustic soda for 30 minutes, and 245 g of an aqueous solution containing 14% sulfuric acid and 10% glyoxal was added thereto and dispersed by stirring. The pH of this aqueous solution was strongly acidic. This pulp dispersion aqueous solution was reacted and purified in the same manner as in Example 1 to prepare a round sheet-shaped sample. As a result of measuring the thickness of the obtained sheet, 8.0 to 8.6
mm. Comparative Example 1 Softwood pulp (5 g) was defibrated in water, filtered and dried in the same manner as in Example 1 to prepare a round sheet sample. As a result of measuring the thickness, it was 2.7 to 3.2 mm. Comparative Example 2 Softwood pulp, 5 g, was immersed in 100 g of a 20% aqueous sodium hydroxide solution for 30 minutes, filtered under suction, dispersed and neutralized in water, filtered and dried in the same manner as in Example 1 to prepare a Matsui sheet-shaped sample. did. As a result of measuring the thickness, it was 4.5 to 5.2 mm. The improvement in bulkiness is far less than that of the embodiment by using only the alkali aqueous solution treatment.

Comparative Example 3 5 g of softwood pulp was dispersed in 245 g of an aqueous solution containing 5% of sulfuric acid and 10% of glyoxal, and the aqueous pulp dispersion was reacted and purified in the same manner as in Example 1 to prepare a round sheet sample. As a result of measuring the thickness of the obtained sheet,
It was 3.9 to 4.3 mm. Only by reacting with a crosslinking agent in an acidic aqueous solution, the improvement in bulkiness was far less than in the examples.

[0016]

According to the present invention, a method for performing a pulp crosslinking reaction in a wet state has been found. This has made it possible to produce a crosslinked pulp excellent in bulkiness by a simple operation without shortening the pulp fiber and by a method with extremely high energy efficiency.

Claims (1)

[Claims] After treating the pulp with an aqueous alkaline solution,
A method for producing bulky pulp, which comprises reacting with a crosslinking agent under acidic conditions.