JPH06192991A - Production of water-dispersible sheet - Google Patents

Abstract

PURPOSE:To produce a sheet having high water dispersibility simpler and more efficiently than the conventional method. CONSTITUTION:In making a water-insoluble fibrous carboxymethyl cellulose (CMC fiber) alone or a mixture of the water-insoluble fibrous carboxymethyl cellulose and a fibrous raw material into a sheet in production of a water- dispersible sheet, the water-insoluble fibrous carboxymethyl cellulose or the mixture is dispersed into an aqueous solution containing at least one (treating agent) selected from a group of a carbonate and a hydrogencarbonate of an alkali metal and ammonium to make the sheet. Since the treating agent of CMC fibers acts as a releasability improver as well as a neutralizing agent at a stage before dry part, the treating a gent hydrolyzes ester bond during the dry part and acts as the neutralizing agent for remaining carboxymethyl group, the water-dispersible sheet can be efficiently produced without requiring a complicated post-process and appearance of the objective sheet can be maintained especially by controlling esterification degree of CMC fibers.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method for producing a water-dispersible sheet, and more particularly, in a papermaking process by treating a papermaking raw material containing water-insoluble fibrous carboxymethylcellulose with a specific carbonate or hydrogencarbonate. The present invention relates to a method for improving the releasability of a wet paper web from a papermaking machine and felt of a paper machine, and producing a sheet which can be easily dispersed (hydrolyzed) in water by a simple one-step treatment.

[0002]

2. Description of the Related Art A method for producing a water-dispersible sheet using a papermaking raw material containing water-insoluble fibrous carboxymethyl cellulose (hereinafter referred to as CMC fiber) has been studied for a long time.
Development is proceeding and many methods have been reported. For example, CMC fiber alone or a mixture of CMC fiber and fibrous raw material is formed into a sheet, and then the sheet (wet paper) is
Treatment such as immersion in a hydrophilic organic solvent containing alkaline substances such as alkali metal compounds and ammonia,
Neutralize carboxymethyl cellulose to alkali salt,
Method of imparting water dispersibility (Japanese Patent Publication No. 40-968)
Japanese Patent Publication No. 43-1214), or CMC
A method is known in which a papermaking raw material containing fibers is made into a wet paper, an alkali metal compound is added to the wet paper on a felt by spraying, and then dried (see Japanese Patent Publication No. 48-27605). .

[0003]

However, these conventional methods have the following problems. 1) Since a sheet containing CMC fibers is made into a paper in the first stage and alkali treatment is performed in the next step, the manufacturing process is complicated and long. Also, the organic solvent deteriorates the working environment. 2) Even when an alkaline substance is added to wet paper to produce it in one step, it is difficult to adjust the spray pressure because the wet paper has low strength. In addition, production efficiency is poor because it is difficult to increase the papermaking speed. 3) CMC fibers generally have shorter fiber lengths and weaker strengths than fibrous raw materials such as pulp, so the strength of wet paper decreases as the blending ratio increases, and Peeling becomes difficult. In particular, when papermaking is performed using 100% CMC fibers, it is very difficult and almost impossible.

[0004]

Therefore, the present inventors have
As a result of earnest research to provide a method for improving the releasability from a paper making machine of a paper machine and producing a water-dispersible sheet in one step without requiring a post-process, CMC fibers alone or CMC When a mixture of fibers and fibrous raw materials is formed into a sheet, if the product is dispersed in an aqueous solution containing sodium hydrogen carbonate or another alkali metal or ammonium hydrogen carbonate, or an alkali metal or ammonium carbonate. It has been found that the releasability from a paper making machine of a paper machine can be improved, and a water-dispersible sheet can be obtained in a single production process. After further study, depending on the type of CMC fiber used (especially the rate of ester bond formation in the carboxymethyl group of CMC fiber), CMC fiber
It was found that the water-solubilization of the fibers made papermaking difficult, or the manufactured water-dispersible sheet had a very hard texture, which was a problem in practical use.

That is, in the present invention, CMC fibers (preferably those in which 2% or more of carboxymethyl groups form an ester bond) alone or a mixture of CMC fibers (preferably the same as above) and fibrous raw material are sheeted. A method for producing a water-dispersible sheet, which comprises dispersing an aqueous solution containing at least one selected from the group consisting of carbonates and hydrogencarbonates of alkali metals or ammonium during papermaking into papermaking To do.

CM used as a papermaking raw material in the present invention
Unlike water-soluble carboxymethyl cellulose that is generally commercially available, C fiber is one in which the carboxymethyl group is partially neutralized by an alkali metal salt such as sodium, or is not neutralized at all, and is hydrophilic. However, it has the property of swelling to some extent in water. Also the degree of substitution
(Hereinafter, referred to as DS) is not particularly limited, but usually 0.2 to
Those in the range of 1.2 are suitable. If the DS is less than 0.2, the water dispersibility tends to be insufficient, and D
Even if S exceeds 1.2, the water dispersibility does not improve despite the high manufacturing cost. The neutralization rate of the carboxymethyl group with an alkali metal varies depending on the DS, but it is usually appropriate to suppress it to 90% or less (the neutralization rate is 90% or less).
If it exceeds%, in the case of CMC fibers having a high DS, the water solubility tends to be strong and papermaking tends to be difficult).

Further, regarding the ester bond of the CMC fiber, it is known that the carboxymethyl group of carboxymethyl cellulose forms an ester bond by a dehydration reaction with a hydroxyl group in the cellulose skeleton under heat treatment, coexistence with an acid catalyst or the like. . As the CMC fiber in the present invention,
The ester bond is formed by these existing methods, and the ratio of the ester bond formation (hereinafter referred to as the esterification rate) is set to 2% or more (practically 20% or less) in the carboxymethyl group. Those that have been processed are preferred. If the esterification rate is less than 2%, the water solubility of the CMC fibers tends to become strong and papermaking tends to be difficult when the below-mentioned alkali metal or ammonium carbonate is used, while the alkali metal or ammonium hydrogen carbonate is used. If so, a water-dispersible sheet can be produced, but the texture of the finished sheet tends to be hard and unsuitable for practical use.

The esterification rate was calculated as follows by utilizing the property that the ester group is reduced by sodium borohydride to produce alcohol. i) About 1 g (dry amount) of CMC fiber is treated with 100 ml of 1% sodium borohydride aqueous solution for 24 hours. ii) The treated sample is treated with about 2N sulfuric acid at room temperature for 1 hour, washed with water to completely remove the acid, and sufficiently dried. As a blank, a sample untreated with sodium borohydride is similarly treated. iii) After accurately weighing these samples and placing them in a beaker,
50 ml of 0.1N sodium hydroxide is added to neutralize the carboxymethyl group. The carboxymethyl group neutralized at this time also includes a carboxymethyl group generated by hydrolysis of the ester group. iv) The number of mols of sodium hydroxide per 1 g of the sample consumed by neutralization is determined by back titration, and the esterification rate is calculated by the following formula, using the difference from the blank as the ester amount. Esterification rate (%) = (blank-reduced sample) / blank x
100

Further, the fibrous raw material to be blended with the CMC fibers as needed is not particularly limited, and is used for ordinary wood pulp, papermaking kraft pulp, sulfite pulp, non-wood pulp, synthetic fiber. Dissolving pulp, rayon fiber, synthetic fiber (polyamide, polyester, etc.),
Inorganic fibers (glass fiber, asbestos, etc.) can be used, but biodegradable materials are preferable in view of environmental issues. In this case, the compounding ratio (weight ratio) may be selected so as to be in the range of 1 or less of CMC fiber and 4 or less of fibrous raw material. When the ratio of fibrous raw material exceeds the above range,
The water dispersibility of the sheet tends to decrease.

In the present invention, carbonates and hydrogen carbonates (hereinafter referred to as treating agents) used for treating the above papermaking raw materials include
Examples thereof include carbonates and hydrogencarbonates of alkali metals or ammonium such as Na, K and Li, and at least one of them is used.

The method for producing a water-dispersible sheet according to the present invention comprises using the above CMC fiber alone or a mixture of CMC fiber and a fibrous raw material as a papermaking raw material, and dispersing the papermaking raw material in an aqueous solution containing the above treating agent. Except that it is characterized by making paper (in this case, according to a general wet papermaking method),
It can be carried out according to conventional methods and conditions.
Hereinafter, the method procedure will be described in detail.

I) First, the papermaking raw material is appropriately disintegrated and beaten, and then dispersed in water together with the treating agent. For example, the disintegrated and beaten papermaking raw material is dispersed in water, and then the treating agent is added to prepare a complete paper stock. And Alternatively, a treating agent may be added in advance when the papermaking raw material is disintegrated or beaten. In these cases, the amount of the treating agent added can be appropriately changed according to the ratio of CMC fibers in the papermaking raw material, the freeness of the wet paper, the weight of the target sheet, and the degree of water dispersibility. , The concentration in water (concentration when making a paper with a wire part of a paper machine described later) is 0.01 to 3.0% (weight%,
The same shall apply hereinafter), preferably 0.04 to 2.0%. If the concentration is less than 0.01%, the water dispersibility of the target sheet will be insufficient, and if it exceeds 3.0%, the sheet will be discolored due to the effect of residual alkali, or the sheet will tend to deteriorate over time. is there. In addition to the treating agent, other additives (for example, oils and fats, hydrocarbons, surfactants, alcohols, disinfectants, wetting agents, preservatives, perfumes, etc.) may be added in appropriate amounts, if necessary. .

II) Next, the obtained complete stock material is appropriately diluted and made into paper by a general paper machine such as a cylinder type or a Fourdrinth type,
After forming the wet paper web on the paper making net (wire part), the wet paper web is transferred to the press part for dehydration, and then dried in the dry part to obtain the desired water-dispersible sheet.

In such a method of the present invention, although the elucidation of the action and effect of the treating agent is not sufficient, it is considered as follows. For example, when sodium hydrogen carbonate is used, the sodium hydrogen carbonate aqueous solution has the property of releasing carbon dioxide at 65 ° C. and changing to sodium carbonate. That is,
Since the wire part and the press part forming the wet paper are at room temperature, the sodium hydrogen carbonate does not change and the neutralization of the CMC fibers does not proceed so much. Further, since sodium hydrogen carbonate contained in the wet paper has some action and improves the peelability in the wire part and the press part, even when the CMC fiber having an esterification rate of less than 2% is used as the raw material, Easy to move. Then, in the dry part, sodium hydrogen carbonate is heated to 105 to 130 ° C. and changed to sodium carbonate, so that the CMC fibers are more neutralized and become water dispersible. Thus, the treating agent functions as a neutralizing agent and a peelability improving agent.

On the other hand, when attention is paid to the esterification rate of CMC fibers, a crosslinked structure is formed when ester bonds of carboxymethyl cellulose are formed between fibers. When such CMC fibers are produced in an aqueous solution of an alkali metal or ammonium carbonate, some of the unneutralized carboxymethyl groups are neutralized by the alkali metal salt or ammonium salt, but they are water-soluble due to the effect of ester crosslinking. This makes it possible to make paper.
When the wet paper thus produced is transferred to the dry part, the concentration of carbonate contained in the wet paper increases with the evaporation of water, so that the alkalinity becomes stronger and hydrolysis of the ester occurs. The resulting carboxymethyl group is neutralized with carbonate, and the water dispersibility of the dry sheet becomes good. Further, when papermaking is carried out in an aqueous solution of an alkali metal or ammonium hydrogencarbonate, the neutralization reaction of the unneutralized carboxymethyl group does not proceed as much as the carbonate, and thus the papermaking becomes easier. When the wet paper thus produced is transferred to the dry part, the hydrogen carbonate contained as an aqueous solution in the wet paper releases carbon dioxide and changes into carbonate, so that the carboxymethyl group is further neutralized.
Further, as described above, hydrolysis of the ester also occurs, so that the water dispersibility of the dried sheet becomes good. The releasability in the wire part and press part is improved because the CMC fibers that have undergone a neutralization reaction with the carbonates and hydrogen carbonates used swell to some extent, and the adhesive force between the fibers increases, and the wet paper Increased strength is also considered to be one of the causes.

[0016]

EXAMPLES The present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited thereto. Example 1 DS0.43 CMC fiber and wood pulp (NBKP)
Is beaten to 700 ml csf and mixed and dispersed in water at a predetermined mixing ratio. Next, sodium hydrogencarbonate was added so as to have a predetermined concentration to adjust the complete stock, and after paper making and drying, a water-dispersible paper weighing 80 g was obtained. The water dispersibility evaluation method is as follows. (Water dispersibility evaluation method) Water dispersible paper 20 mm wide, 120 mm long
When cut into strips of mm, one side of the piece of paper is dipped in 40 mm of water and lifted after 5 seconds, the torn pieces are judged to have good water dispersibility. The results are shown in Table 1.

[0017]

[Table 1]

Example 2 and Comparative Example 1 650 mlcs of CMC fiber of DS0.50 and NBKP.
It is beaten into f and the releasability from the paper making net when the operation of making a water-dispersible paper is performed in the same manner as in Example 1 is examined. At the same time, comparison is made with the case where sodium hydrogen carbonate is not added. The results are shown in Table 2.

[0019]

[Table 2]

Example 3 CMC having a DS of 0.42, a neutralization rate of 0% and an esterification rate of 6%
The fiber and NBKP are beaten to 680 mlcsf, and mixed and dispersed in water at a predetermined mixing ratio. Next, sodium hydrogen carbonate and sodium carbonate were added so as to have a predetermined concentration to adjust the complete stock, and after paper making and drying, a weight of 60 g of water dispersibility was obtained. The water dispersibility evaluation method is as follows. (Water dispersibility evaluation method) Cut water dispersible paper into 5 cm x 5 cm,
1 liter of water is put and the piece of paper is put into a beaker stirred at 500 rpm, and the time until it collapses is measured. The results are shown in Table 3.

[0021]

[Table 3]

Example 4 CM with DS 0.42, neutralization rate 70%, esterification rate 6%
C fiber and NBKP are beaten to 680 mlcsf to prepare a water dispersible paper in the same manner as in Example 3. The results are shown in Table 4.

[0023]

[Table 4]

Example 5 and Comparative Example 2 DS 0.52, C with a neutralization rate of 60% and a different esterification rate
MC fiber and NBKP are mixed at a ratio of 90:10 to 700 m
After beating into lcsf, a water dispersible paper is made as in Example 3. At this time, the peelability from the paper making net and the texture of the dried paper are also examined. The results are shown in Table 5.

[0025]

[Table 5]

[0026]

According to the method of the present invention having the above constitution, a water-dispersible sheet can be easily prepared without requiring a complicated post-process, and the peelability in the wire part and the press part can be improved. Therefore, it is possible to efficiently manufacture a sheet having a high water dispersibility and containing a high proportion of CMC fibers. The resulting water-dispersible sheets are sanitary paper, sanitary napkin absorbers, absorbent diaper absorbent pads, hospital underpads, sanitized rags, confidential document paper, office paper including label base paper, wrapping paper, etc. Can be used in various fields.

Claims (3)

[Claims] 1. When a water-insoluble fibrous carboxymethyl cellulose alone or a mixture of a water-insoluble fibrous carboxymethyl cellulose and a fibrous raw material is formed into a sheet, it is selected from the group of alkali metal or ammonium carbonates and hydrogen carbonates. A method for producing a water-dispersible sheet, which comprises dispersing in an aqueous solution containing at least one kind to produce a paper. 2. The method according to claim 1, wherein the concentration of at least one selected from the group of carbonates and hydrogencarbonates of alkali metals or ammonium in the aqueous solution is 0.01 to 3.0% by weight. 3. The production method according to claim 1, wherein the water-insoluble fibrous carboxymethyl cellulose has 2% or more of carboxymethyl groups formed with an ester bond.