JPH0311831B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a water-soluble sheet having base neutralization ability. More specifically, the present invention is a water-soluble sheet made by impregnating or coating a water-soluble base material made of fibrous carboxymethyl cellulose with a specific acid, which has dual functions of base neutralization ability and water retention ability. Regarding water-soluble sheets. Conventionally, water-soluble paper made of fibrous carboxymethyl cellulose (hereinafter referred to as CMC-Na) has been used for writing and printing confidential documents, labels, etc., and as an industrial material that is dissolved and washed away after use, as well as for the hygiene of women and infants. It is used for lumber. On the other hand, in the fields of various industrial equipment, fine chemical industry, etc. that use alkaline liquid, there is a need for a process control material that automatically neutralizes and retains used alkaline liquid. For this reason, special neutralized timing layer polymers have been developed, but they have been difficult to manufacture and expensive. It is also possible to use so-called water-absorbing resins, but they do not have neutralizing ability and therefore do not completely satisfy the above requirements. The present inventor believes that the characteristics that the process control material should have are (a) water absorption and water retention;
Focusing on the following points: (b) it has alkali neutralization ability, and (c) it has appropriate water retention even after alkali neutralization, it is possible to use water-soluble paper as a base material for process control materials. We considered gender. As a result, the water-soluble paper was found to have the ability to be used as a base material for process control materials, since both the amount of water absorbed and the amount of water retained were more than 50 times its own weight, fully satisfying the condition (a). Therefore, the present inventor used water-soluble paper as a base material and impregnated it with acid (B).
As a result of extensive research aimed at obtaining a process control material with the characteristics of The inventors have discovered that it is possible to obtain a process control material that has all of the characteristics of , (b), and (c), and have arrived at the present invention. Conventional water-soluble paper, as disclosed in Japanese Patent Publication No. 48-27605, is made from fibrous cellulose glycolic acid (hereinafter referred to as CMC-H), and the wet paper after the press part is coated with soda carbonate, caustic soda, etc. It is manufactured by coating and impregnating an alkaline solution, ion-exchanging it to make sodium salt (CMC-Na), dehydrating it, and drying it. And its base saturation is usually 100
%. In addition, regarding water absorption and water retention, for example, a paper made using 100% CMC-H (manufactured by Nichirin Chemical Co., Ltd.) with a degree of etherification of 0.43 has a weight of approx.
The water absorption amount of 80g/ ^m2 water-soluble paper is 77g/g, and the water retention amount is
High at 52g/g, the ratio of water retention and water absorption is 67.5%
It is. The dissolution process in water involves swelling and dissolution, and the degree of swelling is indicated by the amount of water retained in the present invention. However, as the Na ⁺ ions in CMC-Na are replaced by H ⁺ ions due to acid impregnation, the base saturation decreases and the dissolution state changes from a colloidal state to a dispersed state of a fibrous gel. Change. The amount of water retained also gradually decreases. When CMC-Na is completely replaced by H ⁺ ions, the base saturation of CMC-H becomes 0% and it becomes insoluble in water, with a water retention capacity of 1 to 2 of its own weight.
It decreases to twice as much. That is, the predetermined water retention amount that the water-soluble sheet of the present invention should have depends on its water-soluble property. Here, water-soluble usually refers to a state in which a solution exhibits a colloidal state when visually observed by the test method described below, but it may also be in a state in which fibrous gel is dispersed. The acid to be impregnated or applied to water-soluble paper must not interfere with water solubility; in other words, it must be a weak acid that can maintain the base saturation of CMC-Na above a certain level during impregnation or application. No. This is because as the degree of base saturation decreases, the dissolution time becomes longer, and eventually the solution becomes poorly soluble or insoluble, making it impossible to maintain a predetermined water retention amount. In the present invention, the predetermined water retention amount is set to 8 g/g or more, and the degree of base saturation that can maintain this water retention amount is set to 40% or more. In the present invention, the acid index in water (pKa) is used as an index of the acid to be selected. The acid index in water is the logarithm of the reciprocal of the dissociation constant of the electrolyte in water. The higher the acid index in water, the weaker the acid strength, and the base saturation of CMC-Na is less likely to decrease. In the present invention, the acid index in water (hereinafter referred to as acid index) is
Use an acid of 3.8 or higher. Further, even if the acid which is a constituent material of the water-soluble sheet of the present invention satisfies the above-mentioned requirements, it must not be deliquescent in nature. Since the water-soluble paper that is the base material is made of CMC-Na, its equilibrium moisture content is high at approximately 16% (20℃, 65%RH), so the moisture content in the paper is increased, and as a result, they react with each other and reduce the degree of base saturation. This is because there is a risk of deterioration. Therefore, it is necessary to use an acid that is solid at room temperature and virtually non-deliquescent;
It is desirable that CMC-Na be coated to suppress moisture absorption. The water-soluble sheet of the present invention uses water-soluble paper as a base material,
For example, the water-soluble paper is impregnated with a solution in which the specific solid acid is dissolved in an organic solvent or a mixed solvent of an organic solvent and water, and in the impregnation process, a predetermined amount of base saturation is maintained above a certain level. It is manufactured by attaching a solid acid and drying it. The seeped acid fills the mesh-like voids of the water-soluble paper and becomes a single piece. When processed into a size and shape according to the purpose of use and used as a process control material, the process control material absorbs alkaline liquid generated during the process, retains water, and automatically neutralizes it. Unless exposed to water, it will not disintegrate and maintain its shape, and there is no risk of contaminating other processes. Thus, according to the present invention, a water-soluble matrix comprising fibrous carboxymethyl cellulose or fibrous carboxymethyl cellulose and papermaking fibers is impregnated with or coated with a water-soluble solid acid or a water-soluble solid acid and a water-soluble binder. A water-soluble sheet having a characteristic base neutralizing ability and a method for producing the same are provided. The configuration of the present invention will be explained in detail below with reference to experimental examples. Experimental example 1 Using a mixed solvent of ethanol and water (1:1 parts by weight), the base material was treated with varying concentrations of acetic acid (pKa 4.756), and the relationship between base saturation and water solubility and water retention capacity of acid-treated paper was investigated. The relationship was investigated and shown in Table 1 and Figure 1. Acetic acid, which is a liquid acid, was used because it is easy to measure base saturation and water retention. As a base material, fibrous CMC-H (etherification degree
0.43, made by Nichirin Chemical Co., Ltd.), the paper is made using 100%
Water-soluble paper with a weight of 80 g/m ² manufactured by adding a soda carbonate solution was used. For acid treatment, use 50ml of acetic acid solution of each concentration.
Soak 1 g of the bone-dry sample in the water, stir for 2 hours, then separate.
The residue was washed in a conventional manner to remove residual acetic acid, and then dried under reduced pressure at 60°C. Base exchange capacity and base saturation were measured as follows. Take 0.5g of the untreated water-soluble paper and the above acid-treated sample, respectively, add 20ml of 0.5N caustic soda, stir for 2 hours, add 10ml of pure water, perform potentiometric titration with 0.5N hydrochloric acid, and calculate the titration value. Aml. As a blank test, the same operation was performed without using a sample, and the titration value was taken as Bml. The amount of base exchanged solubility and the degree of base saturation were determined using the following formula. Base exchange capacity (mg equivalent/g) =
(B-A) x 0.5 x f/1000 x 1/W x 1000 f: 0.5N HCl factor W: Sample bone dry weight (g) Base saturation (%) = base exchange capacity - exchangeable H ⁺ amount / Base exchange capacity x 100 = exchangeable base amount / exchangeable base amount + exchangeable H
⁺ Amount x 100 Water solubility was determined by putting approximately 1 g of a test piece into 300 ml of water, rotating it with a magnetic stirrer, and measuring the number of seconds it took for the test piece to dissolve. Those with small fiber lumps remaining even after 120 seconds were classified as poorly soluble, and those whose sheet form did not collapse were classified as insoluble. The water retention capacity is determined by adding 1g of bone dry sample to 200ml of water.
After stirring for a second, the sample was transferred to a polyester cloth bag of known weight, dehydrated for 1 minute at 770 ^G using a centrifuge, and the weight was determined and expressed as the weight per 1 g of the bone-dried sample.

[Table] According to Table 1, when the base saturation is 53% or higher, the water solubility is the same as that of untreated water-soluble paper, and when it is lower than that, the dissolution rate is slightly slower. The lower the degree of base saturation, the more pronounced the dispersion of fibrous gel in the solution. The amount of water retained was reduced to almost the same level as paper treated with 0.5M hydrochloric acid with a base saturation of 0% for papers with a water retention capacity of 35.3% or less. According to FIG. 1, which illustrates the results of Table 1, the water retention amount is almost the lowest when the degree of base saturation is 40% or less, so in the present invention, the water retention amount is
8 g/g or more, and the base saturation that can maintain this is 40% or more. Example 2 In order to specify the acid used in the present invention, 80 g of paper was made using 100% fibrous cellulose glycolic acid (hereinafter referred to as CMC-H) with a degree of etherification of 0.43, and a soda carbonate solution was added. /m ² water-soluble paper was used as the base material, and various acids with different acid indices were dissolved in ethanol to prepare a 15% by weight solution as an impregnating liquid. Approximately a certain amount of water-soluble paper is added to each acid solution.
A test sample was prepared by immersing it for 10 seconds, dehydrating it under pressure, and drying it at 80°C. Test items and test results are shown in the second
It was as shown in the table. In the table, the acid index indicates pKa ₁ for acids of dibasic acid or higher. In addition, a sample cut to a size of 3 cm x 5 cm was prepared using 0.1N caustic potassium solution 25
ml and stirred for 5 minutes, the remaining caustic potassium was titrated using 0.1N hydrochloric acid, the amount of neutralization of caustic potassium was determined from the data, and this was taken as the base neutralization ability. The water retention amount was measured according to Experimental Example 1, and the displayed value was the water retention amount per 1 g of water-soluble paper as the base material, so that it could be compared with Table 1.

[Table] According to Table 2, water solubility differs depending on the acid index, but the water solubility of acids with high acid indexes is no different from that of untreated water-soluble paper. Glycolic acid (pKa 3.831) slows down the dissolution time, and acids below malic acid (pKa 3.460) become insoluble. A clear branching point was also observed for water retention, with acids below malic acid reaching 2g/g or less. Although the amount of acid adhering varied depending on the sample, it had little effect on the above trend. Therefore, applying to Figure 1 above, it is found that in this experiment, by using an acid of glycolic acid (pKa 3.831) or higher, a water-soluble sheet of the present invention with a base saturation of 40% or higher can be obtained. . Furthermore, since measuring the degree of base saturation by dissolving and removing adhering solid acids from the water-soluble sheet of the present invention requires complicated experimental operations, this can be easily estimated by measuring the amount of water retained. be able to. From the above results, the acid used in the present invention has a pKa of
A solid acid of 3.831 or higher is preferred, but CMC-H with an etherification degree of 0.25 to 0.65 is usually used for water-soluble paper, and CMC-H with a degree of 0.43 was used in this experiment.
Considering that the higher the degree of etherification, the greater the water retention capacity and the higher the acid resistance, it can be said that the acid that can be used in the present invention is a solid acid with an acid index of 3.8 or more. Further, an inorganic acid may be used as long as it satisfies the above requirements. In this experiment, lactic acid (liquid acid) was also tested (it has already been explained that liquid acid is inappropriate for achieving the purpose of the present invention), and the amount of adhesion was 8g/m ² (substrate The maximum base neutralization ability was only 0.17 equivalent/m ² ). Therefore, it is desirable for the water-soluble sheet of the present invention to have a solid acid adhesion of 10% by weight or more of the base material, and a practical base neutralization ability of 0.15 g equivalent/m ² or more. In addition, the pH of the dissolving solution during the dissolution test of the water-soluble sheet of the present invention was all 3 or less. The relationship between the adhesion amount and base neutralization ability will be described later. The water-soluble paper used as the base material of the present invention is composed of short fibers of fibrous carboxymethyl cellulose, that is, a monovalent metal salt such as sodium or potassium of cellulose glycolate. Usually, the sodium salt (CMC-Na) is used. The water-soluble paper made of CMC-Na may contain other known fiber raw materials and is produced by a known method. For example, as disclosed in Special Publication No. 48-27605,
Paper is made from a mixed paper stock of 100% CMC-H or CMC-H and 40% by weight or less of bleached kraft pulp, and an alkaline aqueous solution is added to the wet paper web on the press felt.
It is produced by neutralizing CMC-H, then dehydrating and drying it. CHC-H can have an etherification degree of 0.2 to 1.0, but it is usually 0.25 to 0.65.
A value between 0.40 and 0.60 is most commonly used. If the value is 0.65 or more, the fibers will swell significantly and become difficult to form into paper, but depending on the type of acid to be treated, the base material used in the present invention may have a value of 0.65 to 1.0 to increase acid resistance. CMC-H of 0.25 or less is easy to make, but
The product has poor water solubility. There are no particular restrictions on the type of papermaking fibers other than CMC-H, and general cellulosic pulp, semi-synthetic fibers such as rayon, synthetic pulps such as polyethylene, synthetic fibers such as acrylonitrile, etc. can be used, but the present invention For this purpose, materials with water absorption and water retention properties are preferred, and cellulose pulps such as bleached kraft pulp, bleached sulfite pulp, and dissolving pulp, and rayon are usually used. The purpose of this is to improve paper-making properties, increase the strength of the water-soluble sheet of the present invention, increase air permeability, and speed up water absorption. However, since the amount of water retained is usually less than 1 times its own weight, it is preferable not to use it frequently. No, only 50% by weight or less of CMC-H is replaced. The acid solution used in the present invention can be prepared by dissolving a predetermined amount of a solid acid in various organic solvents or a mixed solvent of water and an organic solvent that is compatible with water, or by adding fine particles obtained by pulverizing a solid acid to a sparsely soluble or It is prepared by dispersing it in an insoluble organic solvent and adding a small amount of binder therein. Examples of organic solvents that can dissolve solid acids include alcohols such as methyl alcohol, ethyl alcohol, butyl alcohol, and propyl alcohol, ketones such as acetone, ethyl methyl ketone, and methyl propyl ketone, and ethers such as ethyl ether and isopropyl ether. can be used. Organic solvents that are compatible with water include methyl alcohol, ethyl alcohol,
Alcohols such as butyl alcohol and propyl alcohol, and ketones such as acetone, ethyl methyl ketone and methyl propyl ketone can be used. And usually from the point of view of manufacturing costs,
A 50% by weight mixed water solvent such as methyl alcohol and ethyl alcohol is used. As the fine particles of the pulverized solid acid, for example, a powder that has passed through a standard sieve of 250 mesh is used. Organic solvents for dispersing this include aromatic hydrocarbons such as benzene, toluene, and xylene, aliphatic hydrocarbons such as heptane and hexane, esters such as ethyl acetate and n-butyl acetate, chloroform, and methylene chloride. , n-butyl chloride and the like can be used. Note that alcohols such as methanol, ethanol, and n-propanol, and ketones such as acetone and ethyl methyl ketone may be added to these. The binder added to the dispersion solution of fine solid acid particles must be soluble in an organic solvent that does not dissolve the solid acid and the base material, and must also be soluble in water and aqueous alkaline solutions. If this requirement is not met, it will remain in the form of a film, impeding water solubility and base neutralization. Examples of suitable binders include polyvinylpyrrolidone, carboxy-modified vinyl acetate polymers, and styrene-maleic anhydride copolymers. The amount of binder added is in the range of 5 to 15% based on the acid, for the same purpose as above. In addition to the cases where solid acids are used in the form of solutions or dispersions mentioned above, solid acids with a melting point of 200°C or lower, such as azelaic acid (106.5°C), adipic acid (153°C),
In the case of succinic acid (185°C), glutaric acid (97°C), etc., it can also be produced by impregnating the base material with the melt and cooling it. In order to apply the above-mentioned acid solution, dispersion, or melt to the substrate, a conventional impregnation machine or coating machine having an impregnation tank, a coating roll, etc. is used. The higher the concentration of the acid solution, the better. Even if the base material is impregnated with a methanol-water (1:1 parts by weight) mixed solution of azelaic acid having a concentration of 10% by weight, the excess is scraped off with a doctor.
Dry at 100℃. With this method, up to 100% by weight of the substrate can be deposited. If it exceeds 100% by weight, powder will fall off significantly and the water absorption rate will be slow. The solid acid dispersion is applied to the substrate using a coating machine. With the coating method, it is possible to deposit up to 150% by weight, and with the melting method, it is possible to deposit up to 120% by weight. Next, in order to understand the relationship between the amount of acid attached (g/m ² ) and the base neutralization ability, samples were prepared and compared using the solution impregnation method, coating method, and melt impregnation method. . The water-soluble paper used as the base material was made of 100% CMC-Na with a weight of about 120 g and a degree of etherification of 0.43. In the solution impregnation method, azelaic acid and adivic acid were each mixed in an ethanol-water mixed solvent (1:1
A 10% strength by weight solution was used. In the coating method, 100 parts by weight of succinic acid was pulverized to pass through a 250-mesh standard sieve, and a solution was prepared by dissolving 10 parts by weight of polyvinylpyrrolidone in 150 parts by weight of chloroform as a binder. Dispersed in solution. Furthermore, in the melt impregnation method, a melt of azelaic acid was used. In all of these methods, samples were prepared by impregnation or coating one or more times. The amount of acid attached was determined by the difference in weight of the sample before and after impregnation and coating, and the base neutralization ability was measured by the method described above. The results are shown in Figure 2. In the figure, 1 is data for the azelaic acid solution impregnation method, 2 is the adipic acid solution impregnation method, 3 is the succinic acid coating method, and 4 is the data for the azelaic acid melt impregnation method. It should be noted that each sample had satisfactory solubility and water retention. According to FIG. ² , there is a proportional relationship between the amount of acid attached and the base neutralization ability. , 75g/according to the azelaic acid solution impregnation method.
m ² deposited, and according to the same melt impregnation method 68
g/m ² , and according to the succinic acid coating method, it is sufficient to apply 75 g/m ² . The straight lines of adipic acid and azelaic acid shown in the figure as an example of the solution impregnation method are parallel if the method of attachment is the same, and the difference in the height of the straight lines is the difference in molecular weight in the case of the above dibasic acid. It can be seen that adipic acid, which has a smaller molecular weight, requires a smaller amount of adhesion to obtain the same base neutralization ability. In this experiment, the measured moisture content of the sample (20
℃, 65%RH) is minimum 6.8% and maximum 10.8%,
It was thought that the base material was coated with the solid acid, resulting in a moisture-proofing effect. As explained above, the water-soluble sheet of the present invention requires specific conditions, that is, using a specific acid and This is a new water-soluble sheet that can be manufactured by balancing the reaction between CMC-Na polymer salt and acid by selecting the application method to the base material, and the manufacturing method is also new. be. The water-soluble sheet of the present invention is usually 0.1N to
It is used as a process control material for the purpose of treating alkaline solutions of about 1N, but is not limited to concentrations within this range, and can also be used for alkaline solutions such as all inorganic bases, organic bases, and salts of weak acids and strong bases. It can also be widely used for In addition, the water-soluble sheet of the present invention can be laminated and fixed on ordinary pulp, paper, plastic film, etc., and used as a so-called neutralization timing layer, as well as used alone as a process control material. You can also do it. The present invention will be explained in more detail with reference to Examples below, but the present invention is not limited thereto. In addition, in Examples, examples in which other papermaking fibers were blended with the base material were also listed, but the solubility in this case was expressed as dissolution and dispersibility. We also gave an example of the water retention capacity using a 1N-NaOH solution, but unlike when using water, it becomes a complete gel that does not contain fibrous gels and cannot be measured using the centrifugal dehydration method. I obeyed. That is, after putting 0.5 g of an absolutely dry sample into 100 g of a specified alkaline solution and stirring for 30 seconds,
The mixture was poured onto a Buchner funnel lined with polyester cloth, and the mixture was suctioned at 6.7 mmHg, and the water retention amount was calculated according to the formula: Water retention amount by suction method g/g = 100 - weight of liquid/absolutely dry weight of sample. Example 1 Etherification 0.43 CMC-H (manufactured by Nichirin Chemical Co., Ltd.)
A water-soluble paper having a weight of 130 g/m ² was produced by a known method using a paper stock consisting of 80 parts by weight of dissolving pulp and 20 parts by weight of dissolving pulp. As a solid acid, azelaic acid (pKa 4.523) was dissolved in ethanol to prepare a 10% by weight solution. This was transferred to an impregnating tank of an impregnation machine, passed through water-soluble paper, and then dried with hot air at 70°C. By changing the impregnation time in the impregnation step and the nip pressure of the press rolls, three types of water-soluble papers of the present invention with different amounts of acid adhesion were manufactured. Table 3 shows the respective characteristic values.

[Table] According to Table 3, the water-soluble sheet of the present invention impregnated with an ethanol solution of azelaic acid is similar to general white impregnated paper in terms of weight, thickness, density and appearance. The amount of acid attached was 29 to 60% by weight. In this range of coating weight, there was almost no difference in dissolution and dispersion time in water and in 0.1N-NaOH solution, and dissolution and dispersion occurred quickly in both cases. Also, the water retention amount is 17-29g/g
It was found that this decreases when the amount of acid adhesion increases significantly. However, according to FIG. 1, it can be seen that the base saturation of CMC-Na in the water-soluble sheet of the present invention is maintained at 50%. 0.1N−
The water retention capacity of the NaOH solution was almost the same as that of water. In the test using 1N-NaOH solution, the dissolution and dispersion time was almost the same as that of water and 0.1N-NaOH solution, but it completely gelled and swelled significantly, and the water retention amount by suction method was 24g/g in both cases. It was hot. A wide range of base neutralization abilities could be obtained, ranging from 0.32 to 0.90 g equivalent/m ² . In addition, these water-soluble sheets have a sheet moisture content (20℃, 65%RH) of 7.
~10%, which is a sharp decrease compared to 16% for the base material.
This indicates that waxy azelaic acid coated the base material, which has the effect of preventing a decrease in base saturation due to moisture absorption, that is, a decrease in dissolution and dispersion method and water retention. Example 2 A water-soluble paper having a weight of 130 g/m ² was produced in the same manner as in Example 1 except that 20 parts by weight of rayon was used instead of the dissolving pulp of Example 1. The water-soluble sheet of the present invention is produced by a melt impregnation method with azelaic acid (pKa 4.523, melting point 106.5°C).
After passing the paper through the azelaic acid melt heated to 115℃ in the heated impregnation tank of the impregnation machine, it was left to cool and solidify.
A water-soluble paper of the present invention having a weight of 197.3 g/m ² and a coating weight of 67.3 g/m ² was obtained. This product had a thickness of 224 μm, a density of 0.881 g/cm ³ , and a base neutralization capacity of 0.92 g equivalent/m ² . The dissolution and dispersion time in water is 39 seconds and 0.1N.
It took 44 seconds in NaOH solution. The reason why the dissolution and dispersion time is long is thought to be that in the melt impregnation method, the sheet density was considerably higher than in the solution impregnation method of Example 1, so that it was difficult for the liquid to penetrate. However, the water retention capacity is 18
g/g, and the water retention amount of the 1N-NaOH solution by suction filtration method was 24 g/g, the same as in Example 1. Example 3 Produced in the same manner as Example 1, weighing 130 g/m ²
The water-soluble sheet of the present invention is produced by a coating method using succinic acid (pKa 4.207) using an aqueous solution of as a base material.
A fine succinic acid powder that passed through a 250 mesh standard sieve was prepared. Further, a solution was prepared by dissolving 10 parts by weight of polyvinylpyrrolidone in 150 parts by weight of chloroform, and 100 parts by weight of the above-mentioned fine succinic acid powder was added to the solution to prepare a coating dispersion. This dispersion was applied to a substrate using an applicator bar and dried with hot air at 75°C to obtain two types of water-soluble sheets of the present invention with different amounts of adhesion. Its physical properties are shown in Table 4.

[Table] According to Table 4, by selecting the organic solvent and binder when applying the fine particle dispersion of succinic acid to the substrate, water and 0.1N-NaOH
It is possible to obtain a material whose dissolution and dispersion time in a solution is completely the same as that of the base material. Therefore, the coating method is suitable for processes that require rapid base neutralization. In addition, the water retention capacity of these items is 17~
It was 18g/g. Example 4 Aqueous paper with a weight of 130 g/m ² manufactured using 100% CMC-H (manufactured by Nichirin Chemical Co., Ltd.) with a degree of etherification of 0.65 was used as the base material, and 15% of adipic acid (pKa 4.430) was used as the impregnating liquid. % ethanol solution was used. Transfer this to the impregnating tank of the impregnating machine and impregnate at a speed of 2 m/
After passing through water-soluble paper for min., dry with hot air at 70℃ and weigh.
A water-soluble paper of the present invention weighing 160.4 g/m ² was obtained. Adipic acid adhesion amount 30g/m ² , base neutralization ability 0.60g equivalent/m ² ,
Solubility is 27 seconds in water and 22 seconds in 0.1N NaOH solution.
Second, the water retention amount was 28 g/g, and the water retention amount by suction filtration method of 1N-NaOH solution was 28 g. The moisture content was set at 10.8%, so there is no risk of the product deteriorating in quality while in stock.

[Brief explanation of the drawing]

FIG. 1 is a chart showing the relationship between water retention amount and base saturation degree, and FIG. 2 is a chart showing the relationship between acid adhesion amount and base neutralization ability. In FIG. 2, 1 shows the azelaic acid solution impregnation method, 2 the adipic acid solution impregnation method, 3 the succinic acid coating method, and 4 the azelaic acid melt impregnation method.

Claims (1)

[Scope of Claims] 1 A water-soluble matrix formed from fibrous carboxymethyl cellulose or fibrous carboxymethyl cellulose and papermaking fibers is impregnated with or coated with a water-soluble solid acid or a water-soluble solid acid and a water-soluble binder. A water-soluble sheet having base neutralizing ability, characterized by: 2. The water-soluble sheet having base neutralization ability according to claim 1, wherein the water-soluble solid acid has an acid index in water of 3.8 or more. 3. The water-soluble sheet having a base neutralizing ability according to claim 1 or 2, which has a base neutralizing ability of 0.15 g equivalent/m ² or more. 4 The base material is water-soluble paper made of fibrous carboxymethyl cellulose or water-soluble paper made of fibrous carboxymethyl cellulose mixed with papermaking fibers,
This is impregnated or coated with a water-soluble solid acid having a water acid index of 3.8 or higher and virtually non-deliquescent, and the degree of base saturation of the fibrous carboxymethylcellulose in the impregnated or coated paper web is maintained at 40% or higher. At the same time, the water-soluble solid acid was added to the base material as a dry substance for 10 minutes.
A method for producing a water-soluble sheet having a base neutralizing ability, characterized by adhering the base in an amount of at least % by weight. 5. The method for producing a water-soluble sheet having base neutralization ability according to claim 4, which comprises impregnating or coating a water-soluble solid acid in the form of a solution dissolved in an organic solvent or a mixed solvent of an organic solvent and water. 6. A method for producing a water-soluble sheet having base neutralization ability according to claim 4, which comprises impregnating or coating a water-soluble solid acid in the form of a melt. 7. A method for producing a water-soluble sheet having base neutralization ability according to claim 4, which comprises impregnating or coating a water-soluble solid acid in the form of a dispersion in an organic solvent together with water and an alkali-soluble binder.