JPS607490B2 - Absorbent manufacturing method - Google Patents

Description

[Detailed description of the invention] The present invention relates to a method for producing an absorbent material.

More specifically, when it comes into contact with water or body fluids, it exhibits a pH value that is safe for human skin, exhibits good absorption ability, safely retains the absorbed liquid, and exhibits excellent barrier properties. Conventionally, a fibrous support such as paper, cotton, or nonwoven fabric is treated with a hydrophilic polymer substance, and then used alone or in combination with other paper, cotton, nonwoven fabric, etc. It is known that absorbent materials such as sanitary napkins and disposable disposable diapers can be used as leak-proof sheets. Hydrophilic polymer materials for treating fibrous supports include, for example, Cellulose derivatives, hydrolysates of starch-acrylonitrile graft polymers, and polyvinyl alcohol are known, but none of these are satisfactory because the manufacturing process is complicated or the performance is insufficient. Other examples of such hydrophilic polymer substances include sodium polyacrylate. Sodium polyacrylate is industrially produced stably, has excellent water absorption and water retention properties, and is also suitable for food products. It is a highly safe polymeric substance for the human body that has been approved as an additive.However, sodium polyacrylate is manufactured under alkaline conditions in order to obtain it stably industrially, so it cannot be used industrially. The resulting sodium polyacrylate powder exhibits a high pH value when it comes into contact with or dissolves in water or body fluids, making it problematic to use it in absorbent materials that come into direct contact with the skin. In order to obtain a value that can be used for
Water absorption and water retention were significantly reduced, and favorable results were not obtained. Another disadvantage of sodium polyacrylate is that when it is impregnated or coated onto a support such as paper or non-woven fabric to prepare a treatment solution using water as a solvent, the viscosity becomes extremely high. be.

Therefore, a large amount of water is required to prepare the viscosity for good workability, and therefore, a large amount of energy and time is required for the evaporation of the solvent in the subsequent drying process. For example, in the invention of JP-A No. 51-40497 or the invention of Tokoku-Kekki No. 51-41295, the viscosity of the treatment liquid is reduced by using water and a hydrophilic organic solvent together, but ``even so, a large amount of solvent is still required.'' There is.
Furthermore, ``the viscosity is lowered by increasing the amount of organic solvent used to cause coagulation and precipitation of sodium polyacrylate, but with this method, the treatment liquid tends to coagulate, making it difficult to handle. In this case, "sodium polyacrylate is insoluble in the solvent, so it does not exhibit a binder effect. Therefore, it also has the disadvantage that the sodium polyacrylate tends to fall off from the support after being treated with the treatment liquid." The inventors conducted extensive research to determine the above-mentioned problems when using sodium polyacrylate, which has excellent water absorption and retention properties, as a hydrophilic polymer material for absorbent materials. It has also been discovered that all of the above problems can be solved by using a specific ratio of sodium polyacrylate and a specific polyacrylic acid and/or a crosslinked polyacrylic acid, as well as by using a specific solvent. This has led to the completion of the present invention.

Therefore, an object of the present invention is to manufacture an absorbent material by treating a fibrous support with a hydrophilic polymeric substance, and to be able to manufacture the absorbent material with good workability by using a relatively small amount of solvent. The resulting absorbent material has a pH value adjusted to a range that is harmless to the skin layer when it comes into contact with body fluids, and provides a method for producing an absorbent material that has excellent absorption, retention, and lagoon-preventing abilities for body fluids. It's about doing.

That is, in the manufacturing method of the absorbent material of the present invention, the viscosity of a 1% by weight aqueous solution of wind is determined by
Sodium polyacrylate powder (hereinafter referred to as
It is called polyacrylic acid soda powder ■.

), {B} Polyacrylic acid whose viscosity of 1% by weight aqueous solution when neutralized with sodium hydroxide is 3 pS or more as measured with a Brookfield rotational viscometer (25qo, lapm) and/ or polyacrylic acid crosslinked product (hereinafter referred to as polyacrylic acid ta} and polyacrylic acid crosslinked product 'b}, respectively), and {C) a hydrophilic organic solvent or a mixed solvent of the hydrophilic organic solvent and water (hereinafter referred to as solvent The amount of the {B} component with respect to the total amount of the system (referred to as C') and the harmful component and the 'B} component (hereinafter, the wind component and the {B} component are collectively referred to as the "polymer component"). is 10~
The present invention is characterized in that the fibrous support (D) is treated with the composition (1) in a proportion in the range of 6% by weight, and the resulting treated sheet is optionally dried. The sodium polyacrylate powder base to be used has a viscosity (hereinafter referred to as
This is called type B viscosity.

) is 300 pS or more and the particle size is 350 pS or less. If the type B viscosity is less than 300 ps, the viscosity of the resulting absorbent material when it comes into contact with liquids to be absorbed such as water or body fluids is insufficient. "Unfavorable. Also, if the particle size of the sodium polyacrylate powder exceeds 350 grains,"
Sodium polyacrylate powder style also contains polyacrylic acid {a} and/or polyacrylic acid crosslinked product 'b}' and solvent system {c
) is mixed to form a composition (early), the sodium polyacrylate powder ■ tends to precipitate, so the resulting composition (
When treating the fibrous support (D) using 1), a uniform treated sheet cannot be obtained. Furthermore, the "polymer component" is likely to fall off from the absorbent material obtained by drying such a treated sheet due to bending, making it inconvenient to use. Furthermore, when this absorbent material is used as a leak-proof sheet, it takes a long time for the polymer component attached to the fibrous support to absorb and swell to form an impermeable layer when it comes into contact with the liquid to be absorbed. During this time, the liquid to be absorbed will leak out, which is undesirable. As the sodium polyacrylate powder used in the present invention, commercially available products can be effectively used as long as they satisfy the conditions of the present invention. Examples of such commercial products include "Aqualic FH" (manufactured by Nippon Shokubai Kagaku Kogyo Co., Ltd.). ``In both cases, sodium hydroxide
It is necessary that the B type viscosity of a 1% by weight aqueous solution when made into a 00% neutralized product is 3 specific ps or more.

If the type B viscosity is less than 3 ps, the obtained absorbent material will not thicken sufficiently when the liquid to be absorbed is absorbed, and therefore the holding power of the liquid to be absorbed will be low, and when the absorbent material is put under pressure, it will not be able to thicken sufficiently. This is undesirable as it often leaks. Polyacrylic acid {a} and polyacrylic acid crosslinked product {b}' used in the present invention
It also has a strong affinity for the solvent system {C} and easily swells and thickens when mixed with the solvent system {C}.

This effectively acts to prevent the sedimentation of the sodium polyacrylate powder, which is insoluble or soluble in the solvent system. It shall be stable even in use.Also, when treating the fibrous support (b) with the resulting composition (1)...
It also has the effect of making the work easier. Moreover, in composition (1), ``polyacrylic acid {a} and/or polyacrylic acid crosslinked product {b} acts as a binder for the polyacrylic acid soda powder ■, and ``it firmly adheres to the fibrous support (rainbow)''. Therefore, even if the obtained absorbent material is bent, polyacrylic acid (a) and/or polyacrylic acid crosslinked product {
The "polymer component" does not fall off unlike when component (b) is not used. In addition, polyacrylic acid (a') and/or polyacrylic acid crosslinked material (skin-friendly) lowers the pH value when the resulting absorbent material comes into contact with water or body fluids compared to when polysodium polyacrylate is used alone. The polyacrylic acid {a} used in the present invention is obtained by polymerizing acrylic acid in water or an organic solvent using various polymerization initiators to achieve the conditions of the present invention. Alternatively, a polyacrylic acid that satisfies the conditions of the present invention may be selected from commercially available polyacrylic acids.

To produce crosslinked polyacrylic acid [b), acrylic acid and a crosslinking monomer such as divinylbenzene or hexaallyl sucrose may be copolymerized in water or an organic solvent, or polyacrylic acid and ethylene glycol may be copolymerized. Alternatively, commercially available cross-linked polyacrylic acid can be effectively used as long as the conditions of the present invention are met. Polyacrylic acid [a} or polyacrylic acid crosslinked product {Momoma, respectively, contains acrylic acid or acrylic acid and a crosslinkable monomer or other copolymerizable monomer other than polyhydric alcohol as its components. Although it may be copolymerized as ~absorbing power for the absorbed liquid.

From the viewpoint of retention, it is preferable to contain acrylic acid in an amount of 9% by weight or more. In the present invention, the usage ratio of sodium polyacrylate powder ■ and polyacrylic acid {a} and/or polyacrylic acid crosslinked product {b} is determined as follows: The amount of {a} and/or polyacrylic acid crosslinked product {b} is 10 to 6% by weight
It is necessary that the ratio is within the range of .

When mixed with polyacrylic acid 'a} and/or polyacrylic acid crosslinked product (in the solvent system if the amount of b; is less than 1% by weight), the degree of thickening is small, and polyacrylic acid salt
The anti-sedimentation effect against dust powder becomes insufficient, and the resulting composition becomes unstable. Even if the fibrous support (b) is treated with such an unstable composition, the binder effect of the polyacrylic acid {a} and the crosslinked polyacrylic acid 'b) is small, and the resulting absorption "Polymer component" tends to fall off from the material, which is "unfavorable."
} in the solvent system if the amount exceeds 6% by weight.
When mixed with tC, the degree of viscosity increase becomes too large, and unless the amount of the solvent system tC} is increased, workability deteriorates, which is economically disadvantageous. Furthermore, the absorbent material obtained using such a composition is not preferable because its pH value becomes too low when it comes into contact with the liquid to be absorbed.In the present invention, a hydrophilic organic solvent is used as a component of the solvent system [C' By using the composition (1
) is made stable even with a relatively small amount of solvent, and workability during processing on the fibrous support (0) is made easy.

Examples of such hydrophilic organic solvents used in the present invention include methanol, ethanol, and fluoride. Lopyl alcohol, isof. lopyl alcohol, h-butanol, acetone,
Examples include dioxane, ethylene glycol, diethylene glycol, propylene glycol, and glycerin. As the solvent system, one type or a mixture of two or more of these hydrophilic organic solvents may be used, or a mixed solvent of these hydrophilic organic solvents and water may be used.However, When used in combination with water, the sodium polyacrylate powder tends to partially dissolve and aggregate, so it is necessary to suppress the amount of water used to an extent that does not cause aggregation.Based on the present invention, the composition ( To obtain 1),
Solvent total C}, polyacrylic acid soda powder ■ ~ polyacrylic acid (a} and/or polyacrylic acid crosslinked product, etc. mixed)
However, these components may be mixed in any order.

In addition, polyacrylic acid (a) and/or polyacrylic acid crosslinked product (b'') may be used as they are in powder form. It is also possible to use a mixture that has been previously melted or dispersed.As for the mixing method, ordinary means for mixing powder and liquid can be used.The present invention is not limited by such mixing order or method. In addition, the composition (1) obtained may be in the form of a dispersion or a paste.
The present invention is not limited by this state. The fibrous supports (rainbow) used in the present invention include non-woven fabrics, Japanese paper, pulp paper, gauze, cotton, rayon paper, etc., which can withstand mechanical tension during processing and drying according to composition (1). However, it is not particularly limited.

However, when the absorbent material according to the present invention is used as an absorbent part of a sanitary napkin or as a moat prevention sheet, a water-dispersible fibrous support is required as the fibrous support (b) from the viewpoint of disposal in a flush toilet. It is appropriate to use Fibrous support (
To treat the fibrous substrate (D) with composition (1), the composition (edge) may be applied or sprayed onto the fibrous support (D).

Alternatively, the fibrous support (b) may be impregnated with the composition (1). The present invention is not limited by these processing methods. In the production method of the present invention, the treated sheet obtained by treating the fibrous support (b) with the composition (1) is used as an absorbent as it is or by drying if necessary.

Drying conditions vary depending on the type of solvent to be evaporated and dried, but any ordinary drying method can be used.The scope of the present invention is not affected by such drying methods. Based on the invention, it has ``imitation absorption ability, retention ability, and leak-proofing ability for absorbed liquids such as water and body fluids,'' and has a pH value that does not affect the skin when it comes into contact with absorbed liquids. This excellent absorbent material can be manufactured with good workability using a relatively small amount of solvent.

Furthermore. As mentioned above, the absorbent material obtained by the present invention has excellent absorbency for liquids to be absorbed. It has a holding power G and has barrier properties.If this absorbent material is used as an absorbent material for sanitary napkins, leak-proof sheets, or disposable disposable diapers, it can be used even when a large amount of body fluid is discharged or when external pressure is applied. It does not leak and stain clothes.Also, conventional sanitary napkins use films such as polyethylene, completely saponified polyvinyl alcohol, or waterproof paper to prevent menstrual blood from leaking. When a dispersible film is used, there is a drawback that the outside of the water-washable toy cannot be disposed of.However, in the absorbent material obtained based on the present invention, the leakage prevention is achieved by using a water-dispersible film as the fibrous support (D). When used as a sheet, it has excellent t-absorption capacity and is also extremely effective in preventing leakage, and it also has the advantage of being easily dispersed and dissolved with a large amount of water when disposed of in a flush toilet. .Hereinafter, the present invention will be explained in more detail with reference to Examples and Comparative Examples.

However, it goes without saying that the present invention is not limited to these Examples. In addition, in Examples and Comparative Examples, "part" means "part by weight" and "%" means percent by weight. Example 1 PoIJ sodium acrylate powder (1% aqueous solution B type viscosity 1500 ps) Particle size less than 74 mm (Nippon Shokubai Kagaku Kogyo Co., Ltd. "Aqualic FH")
8-anchor polyacrylic acid crosslinked product (B-type viscosity of 1% aqueous solution when 100% neutralized with sodium hydroxide 8000 ps) (
BF.

Also manufactured by Goodrich is 'Power Scream Bopol 934''))
2 Akebono B methanol
By mixing each of the above components, the composition (
1} was obtained. This composition {1} was coated with a brush on one side of washi paper (basis weight 40 J-J) to obtain a treated sheet, and then air-dried to form an absorbent material {1}. Even though the absorbent material had a high viscosity, there were no aggregates.Although the workability was good during coating, a uniform treated layer was formed on the Japanese paper. It did not fall off. Comparative Example 1 In Example 1 ~ No crosslinked polyacrylic acid was used ~
A comparative composition 'li was prepared in the same manner as in Example 1, except that 100 parts of sodium polyacrylate powder was used.

Comparative composition '1} produced a precipitate when mixing was stopped. or,
Comparative composition '1} was applied to Japanese paper in the same manner as in Example 1, but a uniform treated layer was not obtained. Furthermore, in the comparative absorbent material m obtained after air drying, the "polymer component" easily fell off when bent. Example 2 In Example 1, sodium hydroxide was used instead of the cross-linked polyacrylic acid.
B type viscosity of 1% aqueous solution when made into 0% neutralized product is 9 ratio p
Composition (2') was prepared in the same manner as in Example 1, except that polyacrylic acid s was used.

Composition (1) had a moderate viscosity and no agglomerates. When Japanese paper was treated using this composition (1) in the same manner as in Example 1, a treated sheet having a uniform treated layer was obtained. This treated sheet was air-dried to obtain an absorbent material (2). The "polymer component" of the absorbent material (■) did not fall off when bent. Comparative Example 2 Substituted for the crosslinked polyacrylic acid in Example 1 Comparative composition (2) was prepared in the same manner as in Example 1, except that DL-malic acid was used.

Comparative composition [A bifurcated precipitate was produced, and this comparative composition
The "polymer component" easily fell off from the comparative absorbent material '2' obtained in the same manner as in Example 1 by bending. Example 3 The absorption capacity and pH value when dispersed in water of each absorbent material and untreated Japanese paper obtained in Examples 1 and 2 and Comparative Examples 1 and 2 were measured.

To measure the absorption capacity, the absorbent material is made of 15 bases x 8 arcs, placed on a 5-mesh wire mesh of known weight, and water in the vat or 0.5%
The absorbent material was soaked in an aqueous NaCI solution, taken out after 1 minute, and the difference in weight between the absorbent material before and after soaking was measured.

In addition, the pH value when dispersing in water is 15 skins x 8 absorbers for 5
The pH value of the liquid dispersed in 0 cc of water was measured. The results are shown in Table 1. Table 1 (Note 1) Weight of polymer sword coated with 15 x 8 x absorbent material.

As the results are shown in Table 1, it is clear that the absorbent materials {1} and ■ obtained based on the present invention have excellent absorption ability and exhibit a pH value that is safe for the skin. .

Example 4 The composition {1} obtained in Example 1 was made into pulp paper (basis weight 329'
The resulting treated sheet was impregnated with
The absorbent material {4} was obtained by drying with warm air of 0 for 2 hours.

This absorbent material {4} was cut into a size of 16 x 6.5 to form a leak-proof sheet. The leak-proof sheet is a commercially available sanitary napkin (hereinafter referred to as commercial product 'C').

), a sanitary napkin style was obtained by replacing it with a polyvinyl alcohol leakproof sheet. In addition, a comparative sanitary napkin (B-) was obtained using untreated pulp paper in the same manner. A leakage test was conducted.

The results are shown in Table 2. Also, leak-proof sheet, commercial product 'C}
An underwater dispersion test was conducted on polypynyl alcohol-based leak-proof sheets and untreated pulp paper used in . 3rd result
Shown in the table. The methods for the leakage prevention test and underwater dispersion test are as follows. S. Leak proof test Absorber test was carried out by placing the surface to be used facing up on a piece of oven paper spread out on a glass slope, and placing a buret containing a solution of 0.2 parts Congo Red and 100 parts water in the center. When the tip was lightly touched and one drop was allowed to flow down at a rate of 5 to 10 drops per minute, it was allowed to stand still for 1 minute, and a load was applied to the dripping area using a bell with a diameter of 5 mm and a weight of 3 k9. Observe the leakage of the Congo red solution onto the furnace paper.

S Underwater dispersion test: Put 2 leak-proof sheets (16 arcs x 6.5 strips) into the water.
Observe the state of dispersion using a magnetic stirrer.

As shown in Table 2 and Table 3, the absorbent material obtained according to the present invention exhibits excellent leak-proofing properties as a leak-proof sheet.
As shown in the table, it is clear that the dispersibility in water is also excellent.

Example 5 The absorption amount of the sanitary napkin ■ obtained in Example 4 and the commercial product {C} was measured.

To measure, place a sanitary napkin with the side to be used facing up on a 5-mesh wire mesh with a known weight, gently pour water over the entire surface of the napkin with a beaker until the entire sanitary napkin absorbs water, and then pour water until it overflows. After leaving it for 1 minute, the water was drained off with an incline, and the weight was measured. In addition, the amount of absorption was also measured after applying 25 degrees of pressure to the sanitary napkin that had absorbed water. The results are shown in Table 4.
Table 4 As the results are shown in Table 4, the sanitary napkin style using the absorbent material obtained based on the present invention has superior absorbency compared to commercially available products, and can be pressurized. It is clear that it maintains excellent absorbency even at times.

Claims (1)

[Claims] 1 (A) The viscosity of a 1% by weight aqueous solution is 300 as measured with a Bruckfield rotational viscometer (25°C, 12 rpm).
Sodium polyacrylate powder having a particle size of 0 cps or more and a particle size of 350 μ or less, (B) The viscosity of a 1% by weight aqueous solution when 100% neutralized with sodium hydroxide was measured using a Bruckfield rotational viscometer (25°C , 12 rpm)
Polyacrylic acid and /
or a polyacrylic acid crosslinked product, and (C) a hydrophilic organic solvent or a mixed solvent of the hydrophilic organic solvent and water,
and a composition in which the amount of component (B) is in the range of 10 to 60% by weight with respect to the total amount of components (A) and (B) (
A method for producing an absorbent material, which comprises treating a fibrous support (II) using I) and drying the resulting treated sheet, if necessary.