JP2909692B2 - Water absorbing agent - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a water-absorbing agent which is excellent in absorption characteristics and adhesion to fibers.

[0002]

2. Description of the Related Art Heretofore, a hydrophilic cross-linked polymer called a water-absorbing resin has been known as a powdery / granular water-absorbing agent having an absorbing ability for an aqueous liquid. Examples of the water-absorbent resin include starch-acrylate copolymers, cross-linked acrylates, cross-linked copolymers of acrylic acid and its salts with other monomers, isobutylene-maleic anhydride copolymers Various resins such as a crosslinked product, a polyvinyl alcohol- (meth) acrylic acid copolymer, a modified cellulose derivative, a modified polyethylene oxide, and a modified polyvinyl alcohol are known, and have been mainly used for sanitary materials such as disposable diapers and sanitary articles. .

[0003]

However, although conventional powdery water-absorbent resins have excellent absorption properties, natural fibers such as pulp, polyethylene fibers, polypropylene fibers, polyester fibers, and fibers obtained by compounding these fibers, etc. Was inadequate in terms of adhesion to synthetic fibers. In particular, as the ratio of the water-absorbent resin to the fiber increases (for example, when the weight ratio of the water-absorbent resin / fiber exceeds 30/70), the adhesiveness between the water-absorbent resin and the fiber decreases, and the sanitary material, etc. When used in water, the water-absorbent resin tends to cause problems such as migration, ubiquity, and falling off from the fiber. There is also a proposal that a water-absorbing agent in which the entire surface of a water-absorbent resin is coated with a water-soluble and / or hydrolysable thermoplastic resin has an adhesive property to fibers or the like (Japanese Patent Application Laid-Open No. 242858/1990). However, in this case, although the adhesiveness to the fiber is improved, there is a drawback that the absorption characteristics inherent to the water-absorbent resin, particularly the absorption rate and the initial absorption rate, are extremely deteriorated, and the excreted urine and menstrual blood are instantly removed. It is difficult to apply the above water-absorbing agent to sanitary materials such as disposable diapers and sanitary products that require absorption and retention performance.

[0004]

Means for Solving the Problems In view of the above problems, the present inventors have made intensive studies on a water-absorbing agent having excellent absorption characteristics (particularly, initial absorption rate) and adhesion to fibers, and as a result, have reached the present invention. did.

That is, the present invention relates to the following water-absorbent resin particles (A)
And the following heat-fusible resin powder (B), and (A) 100
A water-absorbing agent in which the amount of (B) is 1 to 20 parts by weight with respect to parts by weight. Water-absorbent resin particles (A): The absorbent capacity for physiological saline is 35 to 100 times its own weight, and 90% by weight or more is 0.1%.
Water-absorbing resin particles having a particle size distribution of ０．９0.9 mm. Heat-fusible resin powder (B): selected from the group consisting of carboxylic acid-modified polyolefin resin, olefin-acrylic acid copolymer and olefin-maleic anhydride copolymer,
A powder having a melting point of 50 to 180 ° C. and a particle diameter of at least one kind of heat-fusible resin, which does not dissolve or hydrolyze even when contacted with ordinary water for 24 hours, having a particle diameter of 300 μm or less. Absorption capacity
It is represented by the amount of absorption, and the amount of absorption is measured by the following method. Measuring method of absorption: Made of 250 mesh nylon net
1 g of a water-absorbing agent is put in a tea bag, and a large excess of 0.1 g of a water-absorbing agent is added.
Soak in 9% saline for 1 hour to absorb, then pull up
Drain for 15 minutes and measure weight gain. This value
The amount of absorption (S).

In the present invention, the water-absorbent resin particles (A) are usually hydrophilic cross-linked polymers capable of absorbing water of 30 times or more to about 1000 times their own weight, and a carboxylic acid ( Salt) group [refers to carboxylic acid and / or carboxylic acid base. Hereinafter, the same description is used. ], A water-absorbing resin having a hydrophilic group such as a sulfonic acid (salt) group, a phosphoric acid (salt) group, a tertiary amino group, a quaternary ammonium base, a hydroxyl group, and a polyethylene oxide group. The manufacturing method is not particularly limited. Examples of the water-absorbing resin which can be preferably used in the present invention include starch-acrylic acid (salt) copolymers described in JP-B-53-46199 and JP-B-53-46200, and JP-B-54-46200. No. 30710, JP-A-56-26909, crosslinked or self-crosslinked polyacrylates by the reversed-phase suspension polymerization method, and JP-A-55-1334.
No. 13, JP-A-52-14689, JP-A-52-27, crosslinked polyacrylic acid (salt) obtained by aqueous solution polymerization (adiabatic polymerization, thin-film polymerization, spray polymerization, etc.)
No. 455, and the like. Saponified copolymers of vinyl esters and unsaturated carboxylic acids or derivatives thereof described in JP-A Nos. 455-455 and sulfonic acids described in JP-A Nos. 58-2312 and 61-36309. Salt) group-containing water-absorbing resin, cross-linked isobutylene-maleic anhydride copolymer, starch
Examples include a hydrolyzate of an acrylonitrile copolymer, a crosslinked carboxymethyl derivative, a crosslinked polyethylene oxide derivative, a crosslinked polyvinyl alcohol derivative, and a partial hydrolyzate of polyacrylamide. Further, a water-absorbing resin obtained by further surface-cross-linking the above-mentioned water-absorbing resin can also be used. Two or more of the above water-absorbing resins may be used in combination.

The absorption capacity of the water-absorbent resin for physiological saline (0.9% aqueous sodium chloride solution) is usually 3% of its own weight.
It is 5 to 100 times, preferably 40 to 80 times. Absorption capacity
Is represented by an absorption amount and is measured by a measurement method described later.

The shape of the water-absorbent resin particles (A) is not particularly limited as long as it is in the form of powder, and may be any of granular, granular, granulated, scaly, massive, pearl, fine powder and the like. It may be in the form of a particle, but is preferably a granular, granular, granulated, scaly or massive particle. Also, (A)
Usually has a particle size distribution of 0.1 to 0.9 mm at 90% by weight or more.

Among the heat-fusible resins in the heat-fusible resin powder (B) of the present invention, examples of the carboxylic acid-modified polyolefin resin include maleic acid-modified polyethylene and maleic acid-modified polypropylene. Is preferably 1 to 30% by weight. Examples of the olefin-acrylic acid copolymer include an ethylene-acrylic acid copolymer and a propylene-acrylic acid copolymer, and those having an acrylic acid content of 1 to 30% by weight are preferred. Examples of the olefin-maleic anhydride copolymer include an ethylene-maleic anhydride copolymer, a propylene-maleic anhydride copolymer, an isobutylene-maleic anhydride copolymer, and a maleic anhydride content of 1 to 30. % By weight is preferred.

The melting point of (B) is 50 to 180 ° C.,
Preferably it is 60-160 degreeC. When the melting point is less than 50 ° C., problems tend to occur such as blocking during storage or use of the water absorbing agent, and fusion of the water absorbing agents. On the other hand, when the melting point exceeds 180 ° C., a high temperature is required for fixing to the fiber, and a large amount of heat energy is required, which is not economical, and a treatment at a high temperature causes a decrease in absorption performance or a coloring phenomenon. Is not preferred.

The particle size of (B) is usually not more than 300 microns, preferably 1 to 250 microns, more preferably 10 to 200 microns. When the particle size exceeds 300 microns, the mixed state with the water-absorbent resin (A) becomes uneven, and the fixation to the fiber is reduced, and the initial absorption of the water-absorbing agent is reduced. Further, there is a problem that due to the uneven mixing state, phase separation between (A) and (B) occurs during storage, transportation or use of the water absorbing agent.

The resin (B) is a resin particle which does not dissolve or hydrolyze even when it is brought into contact with ordinary water for at least about 24 hours. The reason for this is that when the water absorbing agent of the present invention is applied to sanitary materials such as disposable diapers and sanitary articles, it is possible to maintain a certain degree of adhesiveness during the wearing period even after absorbing urine or menstrual blood. Conversely, in the case of a resin that dissolves in water in a short time or becomes water-soluble by hydrolysis, even if there is no problem in fixing to the fiber in a dry state, the resin dissolves after absorbing urine or menstrual blood. This may cause a slimy feeling, and may cause problems such as gel migration or falling off after water absorption.

In the present invention, the amount of (B) is usually 1 to 20 parts by weight, preferably 3 to 100 parts by weight of (A).
１５15 parts by weight. When the amount of (B) exceeds 20 parts by weight, the fixing property to the fiber is improved, but (B) is changed to (A).
Because most of the surface (for example, 80% or more) is covered, the absorption performance, absorption rate, and initial absorption rate of the water absorbing agent are reduced. On the other hand, if it is less than 1 part by weight, the adhesion to the fiber becomes insufficient.

The method for producing the water-absorbing agent of the present invention includes (A)
And (B) are the simplest and most economical method. Further, at the time of or after mixing (A) and (B), the mixture is treated at a temperature equal to or higher than the melting point of (B) to partially fix (B) to the surface of (A).
And (B) can be improved in uniform mixing properties and adhesion to fibers. Further, (B) was converted to (A) by a mechanical operation such as a hybridization method and a coatmizer method.
It is also possible to partially adhere to the surface of. The term “partial” as used herein means that the surface of (A) is not covered with (B), and for example, an area of about 80% or less of the surface of (A), preferably 60 to 10% Means that the area is fixed at (B). When the surface of (A) is covered with (B), the absorption rate and the initial absorption of the water absorbing agent are extremely reduced.

As a device for mixing (A) and (B), a conventional powder mixing device may be used, such as a conical blender, a Nauter mixer, a V-type mixer, a fluidized-bed mixer,
Examples include a turbulizer, a screw type line blending device, and a honeycomb type static mixer. Examples of an apparatus for performing heat treatment after mixing (A) and (B) include, for example, a hot air heater, a Nauter type heater,
Paddle dryers, fluidized bed heaters, infrared heaters, high-frequency heaters and the like can be mentioned. Examples of an apparatus that heat-treats (A) and (B) simultaneously with mixing include a Nauter-type heater, a paddle dryer, and a fluidized-bed heater.

The initial absorption of the water-absorbing agent obtained by the method of the present invention is usually 40% or more. It becomes 50% or more by selection of preferable conditions. If the initial absorption rate is less than 40%, it is unsuitable for application to sanitary materials such as disposable diapers and sanitary products which require the ability to instantly absorb and retain excreted urine and menstrual blood. It is not where to do.
Note that the initial absorption rate is a value measured by a method described later.

The fixing rate of the water-absorbing agent obtained by the method of the present invention to the fiber is usually 40% or more, and can be 60% or more by selecting preferable conditions. Here, the sticking rate is a sticking rate to fibers when a water absorbing agent is dispersed in the fiber layer and heat-treated at a temperature equal to or higher than the melting point of (B), as described later. If the rate of fixation to fibers is less than 40%, when applied to sanitary materials such as disposable diapers and sanitary goods, the water absorbing agent may move or be ubiquitous in the process of storing and transporting these products.

The water-absorbing agent of the present invention may optionally include a bulking agent,
As additives, organic powders (eg, pulp powder, cellulose derivatives, natural polysaccharides, etc.), inorganic powders (eg, zeolite, silica, alumina, bentonite, activated carbon, etc.), antioxidants, preservatives, bactericides, surfactants, Coloring agents, fragrances and the like can be blended. These amounts are usually 10% by weight or less based on the weight of the water absorbing agent.

[0019]

The present invention will be further described with reference to the following examples and comparative examples, but the present invention is not limited to these examples. The absorption amount, initial absorption rate, and sticking rate to fiber (pulp or synthetic fiber) were measured by the following methods. Hereinafter, unless otherwise specified,% indicates% by weight.

Absorption: 1 g of a water-absorbing agent was placed in a 250-mesh nylon net tea bag, immersed in a large excess of 0.9% saline for 1 hour, absorbed, and drained for 15 minutes. Measure the weight gain. This value was taken as the absorption amount (S). Initial absorption: 1 g of a water-absorbing agent was placed in a 250 mesh nylon net tea bag, and the excess was 0.9%.
Soak in saline for 10 minutes to absorb, then pull up to 1
Drain for 5 minutes and measure weight gain. Set this value to 1
The absorption amount after 0 minutes (S10). Initial absorption rate = (S10 / S) × 100 Fixing rate to fiber: A layer of fluff pulp or synthetic fiber (ES fiber EA; manufactured by Chisso Corporation) of 200 g / m ² was cut into a circular shape having a diameter of 15 cm. While sucking from the lower surface of the layer, 2 g of the water-absorbing agent is evenly dispersed on this. Next, after a heat treatment at a temperature about 10 ° C. higher than the melting point of (B) for 2 minutes, the mixture is cooled to room temperature, and the water-absorbing agent that is not fixed is shaken off, and the weight (W) is measured. Adhesion rate to fiber = [(2-W) / 2] × 100

Example 1 Crosslinked sodium acrylate-based water-absorbent resin ("Sunwet IM-5000D" manufactured by Sanyo Chemical Industries, Ltd .; granular) 9
3 parts and maleic acid-modified polyethylene having a particle size of 50 to 100 microns ("UMEX 2" manufactured by Sanyo Chemical Industries, Ltd.)
000P "; melting point 108 ° C) in a V-type mixer and mixed for 20 minutes to obtain a water-absorbing agent (a) of the present invention. Table 1 shows the measurement results of the absorption amount, initial absorption rate, and fixing rate of the water absorbing agent (a) to the fiber.

Examples 2 and 3 "Sunwet IM-5000D" and "UMEX 2"
Water absorbing agents (b) and (c) were obtained in the same manner as in Example 1 except that the mixing ratio of “000P” was changed as follows. Table 1 shows the performance measurement results of these water absorbing agents. Water absorbing agent (b): "Sun wet IM-5000D" / "UMEX 2
000P "= 98/2 water-absorbing agent (c):" Sunwet IM-5000D "/" UMEX 2
000P "= 80/20

Examples 4 and 5 Water absorbing agents (d) and (e) were obtained in the same manner as in Example 1 except that the particle size of the maleic acid-modified polyethylene was changed as follows. Table 1 shows the performance measurement results of these water absorbing agents. Water-absorbing agent (d): particle size of 10 to 50 microns Water-absorbing agent (e): particle size of 150 to 200 microns

Example 6 The water-absorbing agent (a) obtained in Example 1 was further treated with hot air at 130 ° C. for 30 seconds, so that the maleic acid-modified polyethylene powder partially adhered to the surface of the water-absorbing resin particles. Agent (f) was obtained. Table 1 shows the performance measurement results of the water absorbing agent (f).
Shown in

Examples 7 and 8 Water-absorbing agents (g) and (h) were obtained in the same manner as in Example 6 except that the following water-absorbing resin was used instead of "Sunwet IM-5000D". Table 1 shows the performance measurement results of these water absorbing agents. Water-absorbing agent (g): Saponified vinyl acetate-methyl acrylate copolymer (“Sumikagel S-5” manufactured by Sumitomo Chemical Co., Ltd.)
0; pearl) Water-absorbing agent (h): Starch-acrylate graft polymer (“Sanwet IM-100” manufactured by Sanyo Chemical Industries, Ltd.)
0 "; scaly)

Comparative Examples 1-3 Commercially available water-absorbing resins, a crosslinked sodium acrylate-based water-absorbing resin, a saponified vinyl acetate-methyl acrylate copolymer and a starch-acrylate graft polymer were each used as a comparative water-absorbing agent (a). ) To (c), and these absorption amounts,
Table 1 shows the results of measurement of the initial absorption rate and the fixation rate to the fiber.

Comparative Example 4 In Example 1, "Sunwet IM-5000D"
Comparative water-absorbing agent (d) in the same manner as in Example 1 except that the mixing ratio between “Umex 2000P” and “UMEX 2000P” was changed to 60/40.
I got Table 1 shows the performance measurement results of this comparative water absorbing agent.

Comparative Example 5 Example 1 described in JP-A-2-242858
In the same manner as in the above, a comparative water-absorbing agent (e) in which the surface of the water-absorbing resin was covered with the thermoplastic resin was obtained. Table 1 shows the performance measurement results of the comparative water absorbing agent (e).

[0029]

[Table 1]

[0030]

The water absorbing agent of the present invention has the following features and effects. Has excellent absorption performance, absorption rate and initial absorption rate. Fiber substrates (eg, fluff pulp, synthetic fiber webs, synthetic fiber filaments, nonwoven fabrics,
Excellent adhesion to fabrics, fabrics, paper, etc.) Even when left in a high-humidity atmosphere, there is no blocking unlike a conventional water-absorbent resin. It can be manufactured by a simple operation of mixing (A) and (B). By applying the water-absorbing agent of the present invention to a fiber base material containing heat-fusible fibers, an absorber having excellent shape retention after absorption can be obtained.

Because of the above effects, the water-absorbing agent of the present invention is useful for various sanitary materials such as disposable diapers, sanitary products, puerperal mats, and medical underpads. Especially,
It is useful for thin paper diapers and thin sanitary articles having a high ratio of water-absorbent resin / fiber (pulp and / or heat-adherable fiber). In addition, freshness preserving material for fruits and vegetables, drip absorbing material,
It is also useful when producing sheet or tape-shaped water-absorbing materials such as moisture or humidity control sheets, dew condensation preventing materials, seedling raising sheets for rice, concrete curing sheets, and waterproof materials for communication cables and optical fiber cables.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-3-95211 (JP, A) JP-A-1-252669 (JP, A) JP-A-4-119154 (JP, A) 501494 (JP, A) (58) Field surveyed (Int. Cl. ⁶ , DB name) C08L 1/00-101/14 B01J 20/26

Claims (4)

(57) [Claims] 1. A water-absorbing agent comprising the following water-absorbing resin particles (A) and the following heat-fusible resin powder (B), wherein the amount of (B) is 1 to 20 parts by weight based on 100 parts by weight of (A). Water-absorbent resin particles (A): The absorbent capacity for physiological saline is 35 to 100 times its own weight, and 90% by weight or more is 0.1%.
Water-absorbing resin particles having a particle size distribution of ０．９0.9 mm. Heat-fusible resin powder (B): selected from the group consisting of carboxylic acid-modified polyolefin resin, olefin-acrylic acid copolymer and olefin-maleic anhydride copolymer,
A powder having a melting point of 50 to 180 ° C. and a particle diameter of at least one kind of heat-fusible resin, which does not dissolve or hydrolyze even when contacted with ordinary water for 24 hours, having a particle diameter of 300 μm or less. Absorption capacity
It is represented by the amount of absorption, and the amount of absorption is measured by the following method. Measuring method of absorption: Made of 250 mesh nylon net
1 g of a water-absorbing agent is put in a tea bag, and a large excess of 0.1 g of a water-absorbing agent is added.
Soak in 9% saline for 1 hour to absorb, then pull up
Drain for 15 minutes and measure weight gain. This value
The amount of absorption (S). 2. The initial absorption rate in physiological saline is 40%.
The water-absorbing material according to claim 1, which is as described above. Initial absorption rate measurement method: 250 mesh nylon net
1 g of a water-absorbing agent in a tea bag made of
Soak in 0.9% saline for 10 minutes to absorb, then pull
Raise and drain for 15 minutes and measure weight gain. This
Is the absorption amount after 10 minutes (S10). Initial absorption rate = (S10 / S) × 100 3. A mixture of (A) and (B).
The heat treatment is performed at a temperature equal to or higher than the melting point of (B) during or after mixing (A) and (B), and (B) is partially fixed to the surface of (A). Or the water-absorbing agent according to 2. 4. When the water-absorbing agent is sprinkled on the fiber layer and heat-treated at a temperature not lower than the melting point of (B), the fixation rate to the fiber is 40%.
The water absorbing agent according to any one of claims 1 to 3, which is the above. Method for measuring sticking rate to fiber: 200 g / m ² fluff
Pulp or synthetic fiber (ES fiber EA; Chisso Corporation)
Made into a circle with a diameter of 15 cm, and the lower surface of the fiber layer
2g of water-absorbing agent is uniformly dispersed on this
I do. Then at a temperature about 10 ° C. higher than the melting point of (B) for 2 minutes
After heat treatment for a while, cool to room temperature and remove
The water absorbing agent is shaken off and the weight (W) is measured. Adhesion rate to fiber = [(2-W) / 2] × 100