JPH10280291A - Production of water-soluble sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a sheet completely soluble in water, having no adhesion to wire and a blanket of a paper machine, a dryer cylindrical, etc., in a method for producing a water-soluble sheet by a wet paper making method. SOLUTION: A water-insoluble carboxymethyl cellulose having 2.0-2.5 mm number-average fiber length and 0.4-1.0 substitution degree of carboxymethyl group is mixed with inorganic powder which is slightly soluble or insoluble in water and is dissolved in an alkali solution in the weight ratio of 90:50:10-50 to give a raw material, which is made into a sheet by a wet paper making method and then treated with an alkali solution.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a method for producing a water-soluble sheet which is completely dissolved in water. More specifically, when a sheet is produced by a water-insoluble fibrous carboxymethylcellulose (hereinafter abbreviated as "CMC-H fiber") and a sheet is produced in a wet papermaking method, the inorganic powder is used in combination to make the CMC-H fiber into papermaking. Machine wires and blankets,
The present invention relates to a method for producing a water-soluble sheet which has an advantage that it does not adhere to a dryer cylinder or the like.

[0002]

2. Description of the Related Art CMC-H fibers are cellulose derivatives, and their handling is basically the same as ordinary cellulose fibers. Therefore, it can be easily formed into a sheet by a wet papermaking method, and is suitable as a material for a water-soluble sheet. The CMC-H fiber is an anionic polymer electrolyte and is hydrophilic, but is insoluble in water as it is. To make it swellable or soluble in water,
It is necessary to perform alkali solution treatment to make CMC-alkali salt fibers. In order to completely dissolve the compound in water, the degree of substitution of the carboxymethyl group must be equal to or more than a certain value. A CMC-H fiber satisfying this condition easily swells and dissolves in water to form a highly viscous aqueous solution. Utilizing such properties, CMC-H fibers are used in various fields such as emulsion stabilizers for medicines, cosmetics and foods, auxiliary agents for detergents, and thickeners for paints.

The production of a sheet soluble in water using a raw material containing CMC-H fibers is disclosed in Japanese Patent Publication Nos. 40-968, 43-1214 and 48-27.
Japanese Patent Application Laid-Open No. 605, 605, Japanese Patent Application Laid-Open No. H6-119291, Japanese Patent Application Laid-Open No. 3-180596, Japanese Patent Application Laid-Open No. 3-8897, and the like. For example, in Japanese Patent Publication Nos. 40-968 and 43-1214, a mixture of CMC-H fiber and a fibrous raw material is formed into a sheet, and then the sheet is wetted with an alkaline substance such as an alkali metal compound or ammonia. Immersed in a hydrophilic organic solvent containing
There has been proposed a method of imparting water dispersibility to the sheet by using -H fibers as alkali salts. In addition, 48
Japanese Patent Publication No. 27605 proposes a method of adding an alkali metal compound in a wet state by spraying or the like when forming a sheet using a raw material containing CMC-H fibers. Further, Japanese Patent Application Laid-Open No. 6-192991 proposes that a water-dispersible sheet can be obtained by dispersing a mixture of CMC-H fiber raw materials in an aqueous solution containing an alkali metal or ammonium carbonate or the like. However, the sheets obtained by these disclosed methods are not completely soluble in water because the fibers are only dispersed when poured into water, and the dispersed fibers do not dissolve.

[0004] In order to completely dissolve the compound in water, as described above, CMC having a carboxymethyl group substitution degree of a certain value or more is used.
It is necessary to use -H fibers. However, the CMC-H fibers having a high degree of substitution have high hydrophilicity and are easily swelled with water, so the fibers themselves have tackiness and water retention, and as a result, the sheet is hardly peeled off from the wire in the wet papermaking method, and the blanket is also used. There is a problem that the sheet adheres. Japanese Patent Application Laid-Open No. 3-180596 discloses a method for solving this problem.
When a H fiber is used as a raw material, a method of disintegrating or beating it in an aqueous solution of aluminum sulfate having a weight ratio of 0.3 to 2.5 with CMC-H fiber has been proposed. However, this method leaves a large problem in wastewater treatment and the like due to excessive addition of aluminum sulfate.

On the other hand, JP-A-3-8897 proposes a method of internally adding a water-insoluble or hardly water-soluble inorganic powder to a carboxymethylcellulose or carboxyethylcellulose base material in order to solve the above-mentioned problem. However, even if the sheet obtained by this method is poured into water, the inorganic powder remains in the water without being dissolved, and as a result, a sheet completely soluble in water cannot be obtained by this method.
As described above, the known method does not cause a problem such as adhesion stains at the time of manufacturing a sheet, and cannot obtain a water-soluble sheet which is completely dissolved in water at the time of use.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to solve the problems of the conventional method as described above. That is, when only a CMC-H fiber is used as a fibrous base material and a water-soluble sheet is produced by a wet papermaking method, there is no adhesion to a wire or a blanket of a paper machine, a dryer cylinder, etc. An object of the present invention is to provide a novel method for producing a water-soluble sheet that is completely soluble in water.

[0007]

According to the present invention, there is provided a water-insoluble fibrous carboxymethyl cellulose having a number average fiber length of 2.0 to 2.5 mm and a degree of substitution of a carboxymethyl group of 0.4 to 1.0. And a raw material obtained by mixing inorganic powder that is hardly soluble or insoluble in water but soluble in an alkaline solution in a weight ratio of 90 to 50:10 to 50 into a sheet by a wet papermaking method. And a method for producing a water-soluble sheet. The present invention also provides a water-insoluble fibrous carboxymethyl cellulose having a number average fiber length of 2.0 to 2.5 mm and a degree of carboxymethyl group substitution of 0.4 to 1.0, and Alternatively, when a raw material obtained by mixing an inorganic powder which is insoluble but soluble in an alkaline solution in a weight ratio of 90 to 50:10 to 50 is formed into a sheet by a wet papermaking method, the raw material is treated with an alkaline solution during the manufacturing process. A method for producing a water-soluble sheet.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The CMC-H fiber used in the present invention needs to have a number average fiber length of 2.0 to 2.5 mm. Sheet strength when wet and dry is CMC
-Depends on how the H fibers are entangled, a sufficient fiber length is required to obtain a certain strength. If it is shorter than 2.0 mm, the strength becomes insufficient, and if it exceeds 2.5 mm, the fiber length becomes insufficient. This is because skew and agglomeration of the sheets occur, and the formation of the sheet is significantly deteriorated. In addition, the number average fiber length in the present invention is a fiber length measuring instrument (FS-2 manufactured by KAJJANI).
00 type).

In order for the CMC-H fiber to completely dissolve in water, the degree of substitution of the carboxymethyl group must be 0.4 to 1.0. When the degree of substitution is less than 0.4,
After the CMC-H fiber is treated with an alkaline solution to form a CMC-alkali salt, it is not sufficiently dissolved even when poured into water, and the aqueous solution becomes cloudy and opaque. On the other hand, when the degree of substitution exceeds 1.0, the solubility in water does not improve even though the production cost is high due to the high degree of substitution. further,
As the degree of substitution increases, hydrophilicity increases and swells, resulting in stickiness and water retention, making it difficult for the sheet to peel off from the wire and causing adhesion problems to blankets and dryer cylinders. . The substitution degree means a value measured by performing nitric acid methanol treatment and methanol washing, adding caustic soda, and performing a back titration with a sulfuric acid normal solution.

Here, the alkaline solution will be described. Examples of the alkaline agent used in the alkaline solution include hydroxides such as sodium hydroxide and potassium hydroxide, carbonates such as sodium carbonate and potassium carbonate, borates such as borax, phosphates such as dibasic sodium phosphate, and the like. Silicates such as sodium silicate, and mixtures thereof are used. When only an alkaline solution is added during sheet production, water-insoluble CMC-
Since the H fiber is replaced by an alkali and becomes water-soluble during sheet production, and the CMC-alkali salt fiber is dissolved in water during production, it may be difficult to form a sheet.
It is desirable to add a mixture with a hydrophilic organic solvent such as methanol or acetone. However, depending on the method of addition and the kind of the alkaline agent, it may be simply added in the form of an aqueous solution. The amount of the alkaline agent added is determined by the CMC in the wet sheet.
The neutralization equivalent of the -H fiber is equal to or more than that, but considering the deterioration of the sheet due to aging, 1-2 times the neutralization equivalent is appropriate.

In general, when the degree of substitution of the carboxymethyl group increases, the CMC-H fiber becomes more hydrophilic and swells, and consequently has tackiness and water retention. When the degree of substitution is 0.4 or more, this tendency becomes remarkable, and when a sheet is manufactured by a wet papermaking method using such a fiber, the sheet is hardly peeled off from the wire and easily adheres to a blanket or a dryer cylinder. There are many manufacturing inconveniences. As a method for solving this problem, it is effective to add an inorganic powder that is hardly soluble or insoluble in water to CMC-H fibers. The presence of the inorganic powder evenly near the front and back surfaces of the sheet makes it possible to reduce the stickiness of the entire sheet, resulting in good peelability from the wire, and to the blanket and dryer cylinder. Adhesion can also be prevented.

The inorganic powder used in the present invention is hardly soluble or insoluble in water, but must be soluble in an alkaline solution. The water-soluble sheet produced in the present invention is characterized by being composed only of CMC-alkali salt fibers that are completely soluble in water, so that the inorganic powder needs to be dissolved when the alkaline solution is added. Because. Examples of such inorganic powders include various silicates. Particularly, amorphous silica having no specific crystal structure is preferable. The particle size of the inorganic powder is 0.01
It preferably falls within the range of 10 to 10 μm. 10μ
If it exceeds m, the distribution of the inorganic powder in the sheet becomes non-uniform, and it becomes difficult to effectively work to prevent adhesion stains during papermaking.On the other hand, if it is less than 0.01 μm, the yield of the inorganic powder deteriorates, resulting in inefficiency. Because it becomes.

The weight ratio of CMC-H fiber to inorganic powder is C
For the MC-H fibers 90 to 50, the inorganic powders need to be 10 to 50. If the amount of the inorganic powder is too small, the effect of preventing adhesion stains during papermaking is reduced, and if the amount is too large, sheet strength becomes insufficient, resulting in difficulty in sheet production.

Further, when the inorganic powder is added to the CMC-H fiber, by using a coagulant together, the yield of the inorganic powder can be improved, and the efficiency of the present invention can be improved. As coagulants, polyacrylamides,
Polymeric flocculants such as sodium polyacrylate and polyethylene glycol; inorganic flocculants such as aluminum sulfate, aluminum chloride, ferric chloride, and ferric sulfate; cationic modified starch, oxidized starch, dialdehyde starch, etc. Natural coagulants such as starch derivatives can be used. The amount of the coagulant used depends on its type and sheet-making conditions, but is preferably 0.01 to 10% by weight per solid content.

Hereinafter, the method for producing a water-soluble sheet according to the present invention will be described in detail. The water-soluble sheet of the present invention is characterized in that CMC-H fibers and inorganic powder are uniformly distributed, and for that purpose, the sheet needs to be manufactured by a wet papermaking method. . This method is superior to other methods, such as a dry papermaking method, in that a substance dispersed uniformly in water can be sheeted in a large amount while maintaining a uniform state. Further, through the dewatering process of the wet papermaking method, hydrogen bonds are generated between the CMC-H fibers, and the number-average fiber length of the CMC-H fibers is 2.0 to 2.5 mm. In addition, it is possible to provide a sheet having sufficient strength for use.

A method for producing a water-soluble sheet by a wet papermaking method is as follows. A coagulant is appropriately added to the mixture of the CMC-H fiber and the inorganic powder, and the mixture is supplied to a wire part (long net portion, round net portion) of a paper machine such as a fourdrinier paper machine or a round net paper machine to be wetted. Form the sheet in state. This sheet is sequentially transferred to a press part and a dry part, and dewatered and dried, respectively. Next, the sheet is treated with an alkaline solution in another step. In this step, since the inorganic powder is dissolved by the alkaline solution, a sheet containing only the CMC-alkali salt fibers is obtained.

Alternatively, it is possible to carry out an alkaline solution treatment during the manufacturing process. In this case, a known method such as spraying, coating, or impregnation can be adopted as a method of the alkali solution treatment. As an example, a case where a dry part is a multi-cylinder cylinder in a wet papermaking method will be described.
In this case, the cylinders are usually divided into groups, and a size press for coating or impregnating various chemicals on the paper surface is provided between the groups. Spraying, coating and impregnating methods can be adopted.

As described above, according to the present invention, the alkali solution treatment method comprises treating the dried sheet with an alkaline solution, or treating the sheet with an alkaline solution before the sheet is dried during the sheet manufacturing process, and Either method of obtaining the sheet is possible.

[0019]

The present invention will be specifically described below with reference to examples and comparative examples. All percentages shown in the examples and comparative examples mean% by weight.

Example 1 CMC-H fibers having a number average fiber length of 2.4 mm and a degree of substitution of 0.56 (trade name "Kickoreto HC-GR",
75 parts by weight of Nichirin Chemical Industry Co., Ltd.) and 25 parts by weight of amorphous silica (trade name "Fine Seal X-37", manufactured by Tokuyama Corporation; hereinafter referred to as silica 1) are dispersed in water. To obtain a slurry. As a coagulant, 5% of a cationic starch (trade name "Exel EX-3", manufactured by Nisse Chemical Co., Ltd.) was added to the above raw material. After confirming the aggregation, a band was further added to the raw material by 5%, and a sheet having a basis weight of 70 g / m2 (in terms of dry weight, the same applies hereinafter) was prepared using a Fourdrinier machine according to a conventional method.

Next, the obtained sheet is dried with a cylinder drier at 120 ° C., and then impregnated with a 50% aqueous solution of methyl alcohol containing 5% of sodium hydroxide in a CMC-H contained in the wet paper. The impregnation was performed while adjusting the amount to one and a half times the sum of the equivalents, followed by drying at 90 ° C. to obtain a desired water-soluble sheet.

Example 2 75 parts by weight of CMC-H fiber (same as above) having a number average fiber length of 2.4 mm and a degree of substitution of 0.56, and 25 parts of silica 1
The slurry was obtained by dispersing parts by weight in water. As a coagulant, 5% of a cationic starch (same as above) was added to the above raw materials. After confirming the aggregation, a band was further added at 5% to the raw material.

When a sheet (basis weight 70 g / m 2) is manufactured using a fourdrinier according to a conventional method, when the sheet is transferred from a wire to a press in this forming step, the sheet contains 5% of sodium hydroxide. % Methyl alcohol aqueous solution as the neutralization equivalent of CMC-H fiber contained in the wet paper of 1.
The solution prepared so as to have a 5-fold volume was sprayed uniformly. At this time, the water content of the sheet was 92%. Then, drying was performed at 90 ° C. to obtain a desired water-soluble sheet.

Example 3 A water-soluble sheet was obtained in the same manner as in Example 1 except that the number average fiber length was 2.2 mm.

Example 4 The type of amorphous silica was changed (trade name "Mizukasil P").
-510 ", manufactured by Mizusawa Chemical Industry Co., Ltd .; hereinafter, silica 2
), And a water-soluble sheet was obtained in the same manner as in Example 1.

Example 5 A water-soluble sheet was obtained in the same manner as in Example 1, except that 80 parts by weight of the CMC-H fiber and 20 parts by weight of the silica 1 were used.

Comparative Example 1 A sheet was prepared in the same manner as in Example 1 except that the number average fiber length was 1.9 mm. However, peeling from the wire became poor, and a water-soluble sheet was not obtained.

Comparative Example 2 A sheet was prepared in the same manner as in Example 1 except that the number average fiber length was 2.7 mm. However, adhesion occurred by pressing and no water-soluble sheet was obtained.

Comparative Example 3 A water-soluble sheet was obtained in the same manner as in Example 1 except that the substitution degree of the CMC-H fiber was 0.32. However, after dissolution in water, residues of CMC fibers were observed.

Comparative Example 4 Example 1 except that the substitution degree of CMC-H fiber was 1.2.
A sheet was prepared in the same manner as described above, but peeling from the wire became poor due to swelling of the CMC fiber, and a water-soluble sheet was not obtained.

Comparative Example 5 A water-soluble sheet was obtained in the same manner as in Example 1, except that kaolin (trade name "HT Kaolin", manufactured by Engelhard Co., Ltd.) was used as the inorganic powder. However, after being dissolved in water, inorganic powder (kaolin) was recognized as a residue.

Comparative Example 6 A sheet was prepared in the same manner as in Example 1 except that 95 parts by weight of CMC-H fiber and 5 parts by weight of silica 1 were used. Peeling from the wire became worse, and no water-soluble sheet was obtained.

Comparative Example 7 A sheet was prepared in the same manner as in Example 1 except that the CMC-H fiber was used in an amount of 45 parts by weight and the silica 1 was used in an amount of 55 parts by weight. The sheet strength was insufficient, and no water-soluble sheet was obtained.

Table 1 shows the evaluation results of the sheets obtained in the examples and comparative examples. The evaluation method was as follows. Evaluation of "Suitability for Papermaking" Sensory evaluation was performed on the degree of adhesion of the sheet to a wire or a cylinder dryer during sheetmaking. In particular, no adhesion was observed, and there was no inconvenience in papermaking, which was indicated by ○. When adhesion occurred, the location where the adhesion occurred was noted.

Evaluation of “Solubility” From the sheet obtained above, a 2.5 mm × 2.5 mm piece of paper was taken, put into 300 ml of water, and stirred with a stirrer. After stirring for 10 minutes, the dissolved state of the sheet was observed. The case where there was no residue and the water after dissolution was transparent was indicated by ○. When there was a residue, it was indicated by x. In addition, when papermaking was not possible as a sheet, it was shown by-.

[0036]

[Table 1]

The following has been found by comparing the example with the comparative example. (1) The replacement of the CMC-H fiber with an alkaline solution is performed by forming a sheet by a wet papermaking method and then treating with an alkaline solution as in Examples 1 and 2, or by treating with an alkaline solution during the sheet manufacturing process by the wet papermaking method. It is possible to adopt either of the methods. That is, a sheet containing only the desired CMC-alkali salt fibers can be obtained by either method.

(2) The number average fiber length is from 2.0 to
It needs to be 2.5 mm. In Comparative Example 1, since the fibers were short, adhesion occurred with a wire, and a sheet could not be produced. When the fibers are long as in Comparative Example 2, there is no wire adhesion, but adhesion is observed by pressing, and the sheet formation is significantly deteriorated.

(3) The degree of substitution of the CMC-H fiber is 0.4
However, Comparative Examples 3 and 4 greatly deviate from this range. Comparative Example 3 has suitability for papermaking but has poor solubility. On the other hand, when the degree of substitution is high as in Comparative Example 4, peeling from the wire becomes poor due to swelling of the fiber, and as a result, sheet making becomes difficult.

(4) Inorganic powders that are hardly soluble or insoluble in water, such as amorphous silica, but are soluble in alkali solutions, are hardly soluble in water. Alternatively, since the sheet is insoluble but is dissolved in an alkaline solution, a sheet containing only CMC-alkali salt fibers can be produced. In Comparative Example 5, the sheet was produced using kaolin. However, since kaolin is insoluble in an alkaline solution, kaolin remains and a sheet completely soluble in water cannot be obtained. However, if an inorganic powder soluble in an alkaline solution is selected as in Examples 1 to 5, a sheet completely soluble in water can be obtained.

(5) The weight ratio of the CMC-H fiber to the inorganic powder must be 10 to 50 parts by weight of the inorganic powder to 90 to 50 parts by weight of the CMC-H fiber. As in Comparative Example 6, when the amount of the inorganic powder is small, peeling from the wire is deteriorated, and sheet forming cannot be performed. Conversely, when the amount of the inorganic powder exceeds a certain amount as in Comparative Example 7, the sheet strength becomes insufficient, and the paper cannot be formed.

[0042]

As described above, according to the method for producing a water-soluble sheet of the present invention, the number average fiber length is 2.0 to 2.5.
mm, and the degree of substitution is 0.4 to 1.0.
Fibers, raw materials obtained by mixing inorganic powders that are hardly soluble or insoluble in water but are soluble in an alkaline solution, and then treated with an alkali solution after forming a sheet by a wet papermaking method, or a sheet by a wet papermaking method In any of the methods of treating with an alkaline solution during the production process, the inorganic powder can be easily produced without adhering to a wire, a blanket, a dryer cylinder, etc. of a paper machine. By dissolving the inorganic powder at the time of alkali solution treatment, the sheet containing only CMC-alkali salt fibers is obtained, and a sheet completely soluble in water can be produced.

The water-soluble sheet obtained in the present invention has various uses such as a packaging material by utilizing the above characteristics. For example, when used for packing laundry detergents and bathing agents, it is very convenient because only the required amount can be carried on a trip or the like, and when used, it is sufficient to put it in water as it is. Also, the handling of chemicals, detergents, etc., which are not preferably handled directly by hand, can be easily handled by packaging the water-soluble sheet.

Claims (4)

[Claims] 1. A water-insoluble fibrous carboxymethyl cellulose having a number average fiber length of 2.0 to 2.5 mm and a degree of carboxymethyl group substitution of 0.4 to 1.0, and a poorly soluble in water Alternatively, a raw material obtained by mixing inorganic powders that are insoluble but soluble in an alkali solution in a weight ratio of 90 to 50:10 to 50 is formed into a sheet by a wet papermaking method, and then treated with an alkali solution. A method for producing a water-soluble sheet. 2. A water-insoluble fibrous carboxymethyl cellulose having a number average fiber length of 2.0 to 2.5 mm and a degree of carboxymethyl group substitution of 0.4 to 1.0, and a poorly soluble in water Alternatively, when a raw material obtained by mixing an inorganic powder which is insoluble but soluble in an alkaline solution in a weight ratio of 90 to 50:10 to 50 is formed into a sheet by a wet papermaking method, the raw material is treated with an alkaline solution during the manufacturing process. A method for producing a water-soluble sheet. 3. The method for producing a water-soluble sheet according to claim 1, wherein the particle size of the inorganic powder is 0.01 to 10 μm. 4. The method for producing a water-soluble sheet according to claim 1, wherein the inorganic powder is amorphous silica.