JP2916183B2 - Water-decomposable and absorbent sheet - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an absorbent or water-decomposable sheet having excellent wet strength.

2. Description of the Related Art The use of fibrous carboxymethylcellulose or carboxyethylcellulose as a base material to form a water-decomposable sheet is disclosed in Japanese Patent Publication Nos.
3-1214, 48-27605, JP-A-60-139389
No. 6,139,899, U.S. Pat. No. 3,431,166, and the like. For example, in Japanese Patent Publication No. 48-27605, a papermaking material containing carboxymethylcellulose (CMC) having a degree of etherification of 0.1 to 1.0 is formed into a wet paper, and an alkali metal compound is added to the wet paper on a felt to dissolve the water. And then dried to obtain a water-disintegrable sheet.

However, such a conventional CMC-based water-disintegrable sheet has the following problems.

In production, papermaking is difficult.

The strength of the obtained sheet is not sufficient, and the sheet has high moisture absorption / release properties, so that it is difficult to process.

Poor solubility, especially in cold water.

Due to the manufacturing process, it is inevitable that a small amount of alkali will remain in the water-disintegrable sheet. Shows sex.

Storage degrades water disintegration.

In order to solve these problems, the present inventors previously added water-insoluble or poorly water-soluble inorganic powder to a carboxymethylcellulose or carboxyethylcellulose base material in order to improve the strength and facilitate the papermaking process. Proposed a water-disintegratable and absorbent sheet (Japanese Patent Application No. 1-226188)
issue).

However, there is a problem that the strength of the sheet is reduced when a large amount of water is absorbed.

Further, in Japanese Patent Publication No. 38-25159, a water-soluble paper impregnated with a fiber fleece, carboxymethylcellulose Na salt and inorganic powder is known, but the fleece is impregnated with a carboxymethylcellulose Na salt as a binder. However, there is a drawback that the solubility in cold water and the wet strength are insufficient.

Problems to be Solved by the Invention The present invention is excellent in papermaking properties, tensile strength, etc., and also has a high absorption capacity and high strength when wet, and quickly dissolves or dissolves in a large amount of water even in cold water. It is intended to provide a sheet material to be dispersed.

Constitution of the Invention The sheet-like body of the present invention comprises: (a) carboxymethylcellulose (CMC) or carboxyethylcellulose (CEC); (b) a water-insoluble or poorly water-soluble inorganic powder; and (c) a water-dispersible papermaking fiber. (A) / (b) = 80 / 20-40 / 60 ((a) +
(B)) / (c) = 100/5 to 100/50, and the sheet is absorbent or water-degradable.

 Hereinafter, the present invention will be described in more detail.

CMC or CEC used in the present invention has a structure in which a part of a hydroxyl group of cellulose is substituted with a carboxymethyl group or a carboxyethyl group, and the substitution degree suitable for the present invention (hereinafter, abbreviated as DS, glucose unit) Per degree) is in the range of 0.1 to 1.5. DS is 0.1
If it is less than 3, the obtained sheet does not show sufficient absorbency and water dissolvability. On the other hand, even if the DS exceeds 1.5, the performance does not improve even though the manufacturing cost is high due to the high DS. Preferably DS is in the range of 0.2 to 1.0.

As the water-insoluble or hardly water-soluble inorganic powder in the present invention, non-metallic inorganic substances, metals, water-insoluble (poor) -soluble salts and the like are used. Specific examples thereof include metal oxides such as aluminum oxide and titanium oxide; carbides such as silicon carbide and boron carbide; nitrides such as trisilicon tetranitride and boron nitride; and metal water such as aluminum hydroxide and magnesium hydroxide. Oxides: mica, feldspar group, silica group, clay mineral,
Silicate minerals such as synthetic zeolites and natural zeolites; titanate compounds such as potassium titanate and barium titanate; carbonate compounds such as calcium carbonate, barium carbonate, magnesium carbonate and zinc carbonate; barium sulfate, calcium sulfate and strontium sulfate And the like; silicate compounds such as zinc silicate, magnesium silicate, calcium silicate and barium silicate; phosphate compounds such as zinc phosphate; and the like, used alone or in combination of two or more.

Among the above inorganic powders, particularly preferably zeolite,
Kaolin, talc and calcium carbonate. As the zeolite, A type, X type, Y type and the like are used.

The particle size of the water-insoluble or poorly water-soluble inorganic powder is preferably 30 μm or less, more preferably in the range of 0.01 to 10 μm. If the particle size is too large, dispersibility with CMC or CEC is not sufficient, and if the particle size is too small, the yield of inorganic powder is not enough, and the aqueous property at the time of papermaking is poor, and in both cases, a sufficient sheet Cannot be made.

The water-dispersible papermaking fiber in the present invention is not particularly limited as long as it is a fiber material having a dispersibility in water essentially. Specific examples include wood pulp fiber, non-wood vegetable fiber, rayon fiber and the like. Depending on the use of the sheet, for example, kraft pulp or sulfite pulp for papermaking, dissolved pulp for synthetic fiber, etc. are preferably used, but plant fibers such as straw pulp, hemp pulp, cotton pulp, polyamide, and polyester. Synthetic fibers such as glass fiber, asbestos, rock wool, slag wool, silica wool, silica alumina wool and the like can also be used.

The fiber length of the water-dispersible papermaking fiber in the present invention is generally about 40 mm or less, preferably about 30 mm or less, and particularly preferably 20 mm or less.
A fiber length of less than mm is optimal. If the length of the fiber is longer than about 40 mm and exists in a considerable amount in the sheet, the fiber will disperse in water and fall apart, but the length tends to form a fiber "line". , Worsening fluidity. On the other hand, when the fiber length is shorter than 1 mm, the effect of improving the wet strength of the obtained sheet is reduced.

The inorganic powder is mixed and mixed such that the weight ratio of (b) the inorganic powder to (a) CMC or CEC is (a) / (b) = 80/20 to 40/60. If this ratio exceeds 40/60 and the amount of inorganic powder increases, papermaking becomes difficult, and the strength becomes weak, making it difficult to use as a sheet. On the other hand, the above weight ratio is 80
If it is less than / 20, the effect of adding the inorganic powder is not sufficiently exhibited, and it becomes difficult to peel off the wire during papermaking, and
The resulting sheet is slightly hard.

The mixing amount of the water-dispersible papermaking fiber is preferably not more than 50% by weight of the total amount of (b) the inorganic powder and (a) CMC or CEC. This is because if it exceeds 50% by weight, bundling of fibers in water tends to occur. On the other hand, if the amount of the fiber is too small, the effect of improving the wet strength cannot be sufficiently obtained. Therefore, the water-dispersible papermaking fiber is 5 to 5 parts by weight based on 100 parts by weight of the mixture of (b) the inorganic powder and (a) CMC or CEC.
It is preferable to add 0 parts by weight, and most preferably 20 parts by weight or less.

Further, in mixing CMC or CEC with inorganic powder and papermaking fibers, coexistence of a coagulant can further improve papermaking properties.

Examples of the flocculant include polymeric flocculants such as polyacrylamides, sodium polyacrylate, and polyethylene glycols; inorganic flocculants such as aluminum sulfate, aluminum chloride, ferric chloride, and ferric sulfate; and cation-modified. Natural coagulants such as starch, oxidized starch and starch derivatives such as dialdehyde starch are used. The amount of the coagulant used for the solid component is determined by the type of the coagulant and the papermaking conditions, but is preferably about 0.01 to 10% by weight.

The sheet of the present invention is, for example, a fibrous CMC or CEC in a water-insoluble or poorly water-soluble state and an inorganic powder and a papermaking fiber, or a coagulant is evenly mixed to obtain a papermaking raw material. The wet paper web is manufactured by dehydrating the wet paper web as required, and then subjecting the wet paper web to a water-decomposable treatment. Further, it is also manufactured by drying the wet paper and then subjecting it to a water-decomposable treatment. The production method itself is not particularly limited, and for example, except that the inorganic powder and papermaking fibers are mixed into a papermaking raw material, and then mixed and formed into a sheet, the method described in JP-B-48-27605 described above. Can be applied as it is.

Examples of CMC or CEC in a water-insoluble (poorly) soluble state include CMC-H in the form of a free acid, CEC-H, and various other salts such as aluminum salts (CMC-Al, CEC-Al) and barium salts (CMC-CMC-H).
Ba, CEC-Ba), zinc salt (CMC-Zn, CEC-Zn), tin salt (C
MC-Sn, CEC-Sn) and manganese salts (CMC-Mn, CEC-Mn) can be used, and these can be used alone or in combination of two or more.

A fibrous CMC or CEC in a water-insoluble state such as CMC-H;
Inorganic powder and papermaking fibers, or other additives such as a flocculant, if necessary, are dispersed in water to obtain a papermaking raw material.

This papermaking raw material (paper material) is supplied to a wire part (long net portion, circular net portion) of a paper machine such as a fourdrinier paper machine or a round net paper machine to form a wet paper. The wet paper web is then sequentially transferred to a press part (pressing part) and a dry part (drying part) to be dehydrated and dried to form a sheet.

However, if the wet paper is directly formed into a sheet, the obtained sheet does not show sufficient absorbency and water dissolvability. Therefore, at an appropriate stage, the wet paper is made water-disintegrable by adding an alkali agent by spraying, coating or the like.

Examples of the alkaline agent 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 sodium silicate. Silicates and mixtures thereof are used. These alkaline agents are
In order to prevent the breakage of the wet paper, it is preferable to add it in the form of an aqueous solution containing an 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 such that the wet paper is CMC-H or CEC-H.
When the composition is mainly composed of, the neutralization equivalent of the CMC-H or CEC-H contained in the wet paper is equal to or greater than the neutralization equivalent, preferably, considering the deterioration of the water-disintegratable sheet due to aging. 1 to 2 times the amount is appropriate. Further, when the paper is mainly composed of a metal salt such as CMC-Al, the pH of the paper after drying the wet paper is adjusted to be in the range of 8 to 12, preferably 8 to 10. desirable. By drying after the alkali treatment, when the wet paper is mainly composed of CMC-H or CEC-H, CMC-H or CEC-H is changed to an alkali salt, and a metal salt such as CMC-Al is removed. When it is constituted as a main component, the alkaline agent adheres to the surface and between the fibers, and a sheet having high absorbency or water-decomposability is obtained.

Since such a sheet-like body shows excellent absorbability to water, physiological saline, menstrual blood, etc., utilizing this property,
It can be used as a highly absorbent sheet with excellent wet strength. Further, since the sheet is dissolved or dispersed in water in a large amount of water, it can be used as a water-disintegrable sheet.

The sheet-shaped body of the present invention has a large liquid absorption capacity (g / g), and is preferably about 10 to 100 g / g with water. What is the absorption capacity?
This is an amount that can hold the liquid without dissolving or dispersing the sheet in water. The liquid absorption ratio can be adjusted by controlling the amount of inorganic powder, papermaking fiber, and alkali agent used.

Furthermore, the above-mentioned sheet-like body can preserve the water-decomposability for a long time even in the presence of an acidic or alkaline substance.

Therefore, the sheet body of the present invention can be applied to a wide range of fields requiring high absorbency or water dissolvability. For example, water-absorbing paper mainly as an absorbent sheet; sanitary and medical supplies such as disposable diapers, sanitary napkins, disposable diapers, bandages;
Vegetables and other freshness preserving materials; water retention materials and the like can be suitably used for applications requiring liquid retention in the agriculture and forestry and civil engineering fields.

Also, toilet cleaning paper, mainly as a water-disintegrable sheet; an individual packaging body for packaging and using an alkaline substance such as a detergent for clothing, a bleaching agent, and sodium polyacrylate;
It can be used for individual packaging of fertilizer; individual packaging of pesticides such as insecticides, fungicides, herbicides, etc .;

Effects of the Invention According to the present invention, by mixing CMC or CEC with water-insoluble or poorly water-soluble inorganic powder and water-dispersible papermaking fiber, papermaking properties are improved, tensile strength is excellent, and wetness is improved. It is possible to obtain a sheet having high strength, high water absorption capacity, and hydrolyzed by a large amount of water.

Hereinafter, the present invention will be described more specifically with reference to examples. Prior to this, the evaluation method employed in the examples will be described.

(1) Liquid absorption ratio A sheet-like material cut into a size of about 6 cm x 17 cm is weighed (W ₀ ), wrapped in a 40-mesh stainless steel wire mesh, poured into distilled water, quickly taken out, and left in the air for 3 minutes. The weight after absorption (W ₁ ) after weighing and removing the weight of the wire mesh and the above W ₀
From the difference, the liquid absorption ratio of the sheet was determined.

(2) Water decomposability The sheet was cut into 2 × 2 cm, placed in a water tank containing 10 ° C. water 1, allowed to stand for 1 minute, and then rotated at 100 to 200 rpm using a 3 cm stirrer. Those which were hydrolyzed or dissolved by lightly stirring at were evaluated as “good in hydrolyzability”.

(3) Storage stability After the sheet (10 × 10 cm) was left under the conditions of 35 ° C. and a relative humidity of 85% for 40 days, the water disintegration was evaluated by the method of the above (2).

(4) Wet strength The sheet-like body cut into a size of about 6 cm x 6 cm was wrapped in a 40-mesh stainless steel wire mesh, poured into distilled water and quickly taken out, and the wet strength of the sheet-like body was evaluated according to the following criteria.

；: Those that sufficiently maintain the shape of the sheet-shaped ×: those that do not maintain the shape of the original sheet-shaped (5) Flexibility A sensory test was performed on the flexibility and texture of the sheet-shaped material, Evaluation was made according to the following criteria.

：: Soft and good texture △: Soft but slightly bad texture or good texture but slightly hard ×: Hard and poor texture (6) Tensile strength A test specimen of a 25 mm wide sheet is gripped 150 mm wide. The breaking strength at the time of tearing at a tensile speed of 300 mm / min was defined as the value of tensile strength.

(7) Papermaking properties When using a mixed papermaking raw material consisting of fibrous CMC-H, inorganic powder, and papermaking fibers, when making a handmade sheet with a sheet machine under each condition, it is peeled off from the papermaking wire to form a sheet. The difficulty of papermaking when obtaining the product was evaluated according to the following criteria.

；: Easy to peel from wire and possible to form a sheet △: Peeling from wire is somewhat difficult but possible to form a sheet ×: Difficult to peel from wire and impossible to form a sheet Example 1 Fibrous CMC-H (degree of etherification) DS = 0.65, Nichirin Chemical Co., 80 parts by weight, zeolite (A type, Na ₂ O.2SiO ₂ .Al ₂₎
O ₃ · 4.5H ₂ O, average particle size 5 µ, manufactured by Mizusawa Chemical Co., Ltd.) A mixed papermaking raw material comprising 20 parts by weight and 20 parts by weight of NBKP pulp having a fiber length of 3 to 20 mm was made into a 1% slurry solution, and sufficiently stirred and dispersed. Thereafter, a 10% by weight aqueous solution of a sulfuric acid band as a flocculant was added in an amount of 5% by weight based on the raw material under stirring at 150 rpm by a Suriwan motor, followed by stirring for 3 minutes, and then a 0.1% anionic polyacrylamide solution (Hiholder, (Kurita Kogyo Co., Ltd.) was added at 0.02% by weight based on the raw material, and the mixture was stirred for 3 minutes.
It was diluted with a 5% slurry solution, and a hand-made sheet (weighing about 120 g / m ² ) was prepared using a square sheet machine (manufactured by Kumagaya Riki Kogyo Co., Ltd.).

The obtained sheet was dried into a sheet by a roll rotating drier at 120 ° C., and then impregnated with a 50% methyl alcohol solution containing 3% by weight of sodium hydroxide.
It dried at ℃, and prepared the sheet-shaped body of sample No. 1 of Table-1.

Hereinafter, the sheet-like bodies of Sample Nos. 1 to 17 were obtained by changing the manufacturing conditions of the sheet-like bodies as shown in Table 1.

 These were evaluated for characteristics and are shown in Table 2.

 Details of the inorganic powder and the like shown in the table are as follows.

Zeolite: Type A, Mizusawa Chemical Kaolin: HI-WHITE, Nissei Kyoiku Kuruta: MgO ・ SiO ₂ , Nippon Mistron Heavy Carbonate: Softon 2200, Shiraishi Calcium Synthetic Silicate: ZnO ・ SiO ₂・ Al ₂ O ₃ , Mizusawa Chemical Activated clay: Galleon Earth, Mizusawa Chemical Anionic polyacrylamide: High holder, Kurita Kogyo Cationic polyacrylamide: Accurac 185, Mitsui Cyanamid

Claims (3)

(57) [Claims] (1) A weight ratio of (a) / (b) = 80 / (b) water-insoluble or poorly water-soluble inorganic powder and (c) water-dispersible papermaking fiber to (a) carboxymethylcellulose or carboxyethylcellulose. 20-40 / 60 ((a) +
(B)) An absorbent or water-decomposable sheet-like material which is mixed in the range of (c) = 100/5 to 100/50. 2. The sheet according to claim 1, which is mixed in the presence of a coagulant. 3. The sheet according to claim 1, wherein the fiber length of the water-dispersible papermaking fiber is 1 to 40 mm.