JP3078049B2 - Manufacturing method of absorber - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing an absorber. More specifically, the present invention relates to a method for producing a thin absorbent body which is flexible and stable and does not fall off a water-absorbing polymer.

[0002]

2. Description of the Related Art Hitherto, water-absorbing polymer particles coated with hydrophilic cellulose and an absorbent containing them have been disclosed (JP-A-51-35685 and JP-A-58-5858).
163,438). Also, for the purpose of improving the wet strength of the absorber, a method of dry mixing thermoplastic fibers in the absorber (Japanese Patent Application Laid-Open No. 56-89,839).
JP-A-58-8,175 and JP-A-63-12
No. 2,452) and an absorbent in which a part of a hydrophobic fiber web is embedded in a water-absorbing polymer and an absorbent using the same are also known (Japanese Patent Application Laid-Open No. 61-62,46).
No. 3 and JP-A-1-135350).

[0003]

However, in the former case, for example, when the water-absorbing polymer coated with hydrophilic cellulose is dispersed in a hydrophilic fiber matrix, the liquid absorbing ability of the absorber obtained is Although improved compared to the case of the water-absorbing polymer alone, the wet strength after liquid absorption is insufficient,
In particular, the concentration of the water-absorbing polymer in the matrix was limited from the viewpoint of the molding strength.

[0004] On the other hand, in the latter case, although the wet stability of the web is improved by dry-blending the thermoplastic fibers, the fixation of the water-absorbing polymer is insufficient. When highly compressed, the absorbent body becomes hard, and at the same time, the absorption capacity of the absorbent body decreases because the allowable space for swelling of the water absorbent polymer in the web is reduced. It has been difficult to increase the density or increase the density. Although the wet strength and molding strength are improved by embedding a part of the fiber web in the water-absorbing polymer, swelling regulation by the fiber occurs, the absorption properties are not excellent, and the gel strength of the swollen water-absorbing polymer is low. However, there have been problems such as lowering of the manufacturing cost and time and effort for manufacturing.

Accordingly, it is an object of the present invention to provide a novel method for producing an absorber. Another object of the invention is to provide
It is an object of the present invention to provide a method for producing a thin absorbent material which is flexible and stable when wet (shape retention) and mainly exhibits a high absorbency without a water absorbent polymer falling off.

[0006]

[Means for Solving the Problems] These objects are:
(A) 100 parts by weight of water-absorbing polymer and synthetic pulp 1
(B) mixing 80 parts by weight of water in the presence of 1 to 40 parts by weight of water, and (b) mixing the mixture obtained in step (a) with 10 to 1,000 parts by weight of hydrophilic fiber per 100 parts by weight of the water-absorbing polymer. (C) air-mixing the mixture obtained in step (b) on a web, and (d) heating and compressing the web to a density of 0.1 to 1.0 g / cm ^3. This is achieved by a method for producing an absorber characterized in that:

[0007]

The basis of the present invention is that a mixture of a water-absorbing polymer and a synthetic pulp in the presence of water is dry-mixed with hydrophilic fibers,
It is a discovery that if the mixture is heated and compressed to a density of 0.1 to 1.0 g / cm ³ , it can be a thin absorber having flexibility, good shape retention and extremely excellent absorption characteristics.

[0008] The absorbent in the present invention is basically a hydrophilic fiber web in which water-absorbing polymer particles are dispersed separately and synthetic pulp is fused on the surface thereof. The water-absorbing polymer particles may be randomly dispersed, or may be those in which the fiber / water-absorbing polymer ratio is arbitrarily changed (the fiber may be a single fiber region).

The water-absorbing polymer used in the present invention may be any polymer which generally has water-absorbing properties. For example, a water-soluble polymer comprising (meth) acrylic acid or a salt thereof as a main component and optionally adding a crosslinking agent. (Crosslinked) polymers of water-soluble ethylenically unsaturated monomers, crosslinked products of polyethylene oxide, polyvinylpyrrolidone, sulfonated polystyrene and polyvinylpyridine, saponified starch-poly (meth) acrylonitrile graft copolymers, starch -Poly (meth) acrylic acid (and its salt) graft copolymer (and its crosslinked product), starch-poly (meth)
An acrylic ester graft copolymer (and a crosslinked product thereof), a hydrolyzate of a starch-poly (meth) acryl ester graft copolymer, and the like can be given. Preferably, it is a (cross-linked) polymer of a water-soluble ethylenically unsaturated monomer containing acrylic acid or acrylate as a main component, more preferably a cross-linked polymer of acrylic acid (salt). Either may be used. Further, two or more of these water absorbing polymers may be used. The water-absorbing polymer used is 5 g / g or more, preferably 20 to 80 g / g.
g, most preferably 35-60 g / g of saline, and is substantially dry particles. The water-absorbing polymer usually contains a certain amount of water due to its properties, but the term "substantially dry" as used herein refers to a state in which the particles cannot adhere to each other under a normal atmosphere. The shape of the particles may be powdery or fibrous, such as spherical, granular, irregular, foamed, etc., which may be single particles or granulated particles, A cross-link density gradient may be provided in the vicinity. In the case of powder, the particle size is 10 to 10
1,000 micron is good, preferably 100 to
It is in the range of 700 microns.

The synthetic pulp used in the present invention is a pulp made of a thermoplastic resin, and is known per se. Examples of the thermoplastic resin include polyolefin, polyester, polyacrylonitrile, and other hydrophobic thermoplastic resins. In particular, polyethylene, polypropylene, ethylene-propylene copolymer, and ethylene-1-
A polyolefin comprising one or more α-olefins such as a butene copolymer, a propylene-1-butene copolymer, and an ethylene-4-methyl-1-pentene copolymer can significantly improve the hydrophilicity. It is preferred. Methods for producing synthetic pulp from thermoplastic resins are disclosed, for example, in JP-B-47-21,898, JP-B-47-32,133 and JP-B-52-47,049.
This is, for example, SWP (manufactured by Mitsui Petrochemical Company), PU
It is available under the trade names such as LPEX (manufactured by Hercules) and PULPLUS (manufactured by DuPont).

The method for producing the absorbent of the present invention is as follows: (a) 100 parts by weight of a water-absorbing polymer and 1 to 80 parts by weight, preferably 1 to 30 parts by weight of synthetic pulp, 1 to 40 parts by weight, preferably 5 to 40 parts by weight. Mixing in the presence of 35 parts by weight of water. In this step, it is important that a specific amount of water is newly present. The mixing of the three components is, for example, (a) adding and mixing a synthetic pulp to the water-absorbing polymer particles having absorbed water. (B) A water-wet synthetic pulp is added to and mixed with the water-absorbing polymer particles. (C) After dry-blending the water-absorbing polymer particles and the synthetic pulp or simultaneously adding and mixing water. Water to be added can be in the form of an aqueous solution, droplets, water vapor, mist (fine droplets)
It can be added in various forms. If necessary, water is a polyvalent metal salt for the purpose of improving the absorption properties and flexibility of the absorber, a surfactant or a surfactant which can be a crosslinking agent for a carboxyl group-containing water-absorbing polymer such as ethylene glycol diglycidyl ether, It may contain a polyhydric alcohol or the like. For the mixing, for example, a kneader, a mixer, a fluidized bed mixer, a screw rotary mixer, or the like can be used, but is not particularly limited.

The mixture obtained in step (a) is further dry-mixed with hydrophilic fibers in step (b).
Examples of the hydrophilic fibers used in the present invention include wood pulp fibers such as mechanical pulp, chemical pulp, semi-chemical pulp, and dissolved pulp from wood, and artificial cellulose fibers such as rayon and acetate. In the present invention, these hydrophilic fibers are nylon,
It may contain some synthetic fibers such as polyester and polyolefin. An example of a preferred hydrophilic fiber is wood pulp fiber. The amount of the hydrophilic fiber used is the water-absorbing polymer 1
10 to 1,000 parts by weight, preferably 1 to 100 parts by weight
It is in the range of 0 to 200 parts by weight.

The step (b) is carried out, for example, by metering an air stream containing hydrophilic fibers and an air stream containing a mixture of the water-absorbing polymer and the synthetic pulp on a wire screen. The hydrophilic fiber and the water-absorbing polymer mixture are mixed by the turbulence generated by the two air streams. Alternatively, the mixing may have been performed in a separate mixing chamber prior to airmaking.

[0014] The mixture obtained in step (b) is formed into a web by air-papermaking in step (c). In the present invention, as the web, a usual apparatus made for air-forming a hydrophilic fibrous web can be used. A web is formed by depositing the mixture achieved in step (b) on a wire mesh screen. A desired mixed web of hydrophilic fibers and a water-absorbing polymer synthetic pulp mixture is prepared by introducing a desired amount of the water-absorbing polymer and synthetic pulp mixture into a stream of hydrophilic fibers.

[0015] webs prepared in step (c), in step (d) density of 0.1 to 1.0 g / cm ^3, preferably by being heated and compressed to 0.1 to 0.5 g / cm ³ It becomes the absorber of the present invention. By absorbing the absorbent to a density of at least 0.1 g / cm ³ , the absorption characteristics, wet stability, flexibility and absorption efficiency of the water-absorbing polymer-synthetic pulp-hydrophilic fiber matrix can be improved. Is significantly improved. Heat compression is achieved, for example, by passing between heated rolls conditioned to produce the desired density of the absorber. At this time, by using hot embossing rolls having various patterns as the hot rolls, it is possible to perform embossing simultaneously with heat compression. In addition to the hot roll, a method such as a press in an air oven, a roller press with microwave / far-infrared heating, and a hot air heat treatment after the roller press can be adopted. Heating temperature is around the softening temperature of synthetic pulp, 6
0 to 250 ° C is a standard, preferably 100 to 200 ° C.
° C. Further, the basis weight of the absorber obtained in the present invention is 0.1.
01 to 0.15 g / cm ² , especially 0.015 to 0.1 g
/ Cm ² is preferred. If necessary, a large number of linear cuts may be made in order to further increase the flexibility of the obtained absorber, as long as the absorption characteristics are not reduced.

[0016]

Embodiments will be described below with reference to embodiments.

(Performance Test) The obtained absorbent was evaluated by the following method.

1. As shown in FIG. 1, a reverse funnel 6 having an outside air suction pipe 2 mounted on a balance 1 and communicating with a 0.9% concentration saline storage section by a conduit 5 as shown in FIG. Using a device in which a glass filter 7 is attached to the top of the reverse funnel 6,
An absorber 8 was placed on the filter 7, a weight 9 was placed thereon, and an absorption amount (g / g) of the absorber under a load of 30 g / cm ² after 30 minutes was measured. In addition, what was cut out in advance into a circle having a diameter of 5.5 cm was used as the absorber.

2. Dropping Rate of Water Absorbent Polymer In a 100 cc beaker, the absorbent cut into 2 cm × 4 cm was stirred in 100 cc of physiological saline (45).
using a stirrer of 100 mm and stirring at 100 rpm). After 10 minutes of stirring, the absorbent was taken out, the weight of the water-absorbing polymer dropped into physiological saline was measured, and the amount of the water-absorbing polymer dropped was determined by the following formula.

[0020]

(Equation 1)

Reference Example 1 74.98 mol% of sodium acrylate, acrylic acid 2
Acrylate monomer 3 composed of 5 mol% and trimethylolpropane triacrylate, 0.02 mol%
4,000 parts by weight of a 7% aqueous solution was added to sodium persulfate 2.
0 parts by weight and 0.08 parts by weight of l-ascorbic acid were polymerized under stirring in a nitrogen atmosphere to obtain a gelled hydropolymer finely divided into a particle size of about 5 mm. After drying this gel-like hydropolymer with a hot air dryer at 150 ° C., it was pulverized with a hammer-type pulverizer, sieved with a 20-mesh wire mesh, and a 20-mesh passing product was collected (average particle size: 405 μm). next,
After adding and mixing 0.5 parts by weight of glycerin, 2 parts by weight of water and 2 parts by weight of ethyl alcohol to 100 parts by weight of the fractionated product, a water-absorbing polymer A whose surface was secondarily crosslinked by heating at 210 ° C. I got Its physiological saline absorption was 50 g / g.

Reference Example 2 74.95 mol% of sodium acrylate, acrylic acid 2
37% of an acrylate monomer composed of 5 mol% and 0.05 mol% of trimethylolpropane triacrylate
% Aqueous solution 4,000 parts by weight
The polymerization was carried out in a nitrogen atmosphere with stirring using 1 part by weight and 1-ascorbic acid in an amount of 0.08 part by weight to obtain a gelled hydropolymer finely divided into particles having a particle size of about 5 mm. The gel-like hydropolymer was dried with a hot air dryer at 150 ° C., pulverized with a hammer-type pulverizer, sieved with a 20-mesh wire net, and separated through a 20-mesh wire to obtain a water-absorbing polymer B (average). Particle size 3
50 microns). Its physiological saline absorption was 46 g / g.

Reference Example 3 0.5 parts by weight of glycerin, 2 parts by weight of water and 2 parts by weight of ethyl alcohol were added to 100 parts by weight of the water-absorbing polymer B obtained in Reference Example 2 and mixed, followed by heat treatment at 210 ° C. Thus, a water-absorbing polymer C in which the surface was cross-linked secondarily was obtained. Its physiological saline absorption was 43 g / g.

Reference Example 4 The water-absorbing polymer C obtained in Reference Example 3 was classified with a mesh size of 60 to 100 to obtain a water-absorbing polymer D (particle size: 250 to 149 microns). Its physiological saline absorption is 42g
/ G.

Reference Example 5 The water-absorbing polymer C obtained in Reference Example 3 was classified with a 200-mesh sieve, and the passing product (particle size: less than 74 μm) was collected to obtain a water-absorbing polymer E. Its physiological saline absorption is 3
It was 8 g / g.

Reference Example 6 A commercially available crosslinked sodium polyacrylate (trade name: AquaKeep) was classified with a mesh size of 48 to 145 to obtain a water absorbing polymer F (particle size: 297 to 105 microns). Its physiological saline absorption was 55 g / g.

Example 1 100 parts by weight of water-absorbing polymer A and synthetic pulp (trade name: SWP “UL-415”: manufactured by Mitsui Petrochemical Co., Ltd.)
25 parts by weight were mixed while adding 25 parts by weight of water. Next, the mixture was dry-mixed with 125 parts by weight of the pulverized pulp in a mixer, and air-milled on a wire screen using a batch-type air-milling apparatus, to obtain a size of 14 cm × 40 cm.
The web had a basis weight of 0.047 g / cm ² . The obtained web was compressed and heated at 150 ° C. for 10 minutes to obtain a density of 0.1
6 g / cm ³ of the absorber (1) of the present invention was obtained. Absorbent (1) of the obtained absorbent (1) with respect to physiological saline under pressure (hereinafter the same applies) was 16.5 g / g, and the water-absorbing polymer had a falling rate of 19%.
Met.

Example 2 A weight of 0.051 g was obtained in the same manner as in Example 1 except that the amount of water was changed to 32 parts by weight, the amount of synthetic pulp was changed to 17 parts by weight, and the amount of ground pulp was changed to 133 parts by weight. / Cm ² and a density of 0.13 g / cm ³ of the absorber (2) of the present invention. The absorption amount under pressure of the obtained absorbent (2) was 16.0 g /
g, the shedding rate of the water-absorbing polymer was 22%.

Example 3 To 100 parts by weight of the water-absorbing polymer A, 7 parts by weight of synthetic pulp wetted with 5 parts by weight of water was added and mixed. The mixture was dry-mixed in a mixer with 67 parts by weight of ground pulp and air-milled on a wire screen using a batch-type air-milling machine, measuring 14 cm x 40 cm,
The web had a basis weight of 0.042 g / cm ² . The obtained web was compressed and heated at 150 ° C. for 10 minutes to obtain a density of 0.2.
0 g / cm ³ of the absorber (3) of the present invention was obtained. The absorption amount under pressure of the obtained absorbent (3) was 15.8 g / g, and the falling rate of the water-absorbing polymer was 20%.

Example 4 100 parts by weight of water-absorbing polymer C and synthetic pulp (trade name: SWP "UL-415": manufactured by Mitsui Petrochemical Co., Ltd.)
13 parts by weight were mixed while adding 20 parts by weight of water. Next, the mixture was dry-mixed with 100 parts by weight of the pulverized pulp in a mixer, and air-molded on a wire screen using a batch-type air-milling apparatus to obtain a web having a size of 14 cm × 40 cm. The upper and lower surfaces of the obtained web have a basis weight of 0.00.
13 g / cm ² tissue paper, and then embossed at 150 ° C. for 1 minute to obtain a basis weight of 0.054.
g / cm ² , density 0.27 g / cm ³ of the absorber of the present invention
(4) was obtained. The absorption amount under pressure of the obtained absorber (4) is 1
4.4 g / g, the falling rate of the water-absorbing polymer was 6%.

Example 5 A basis weight of 0.044 g / cm ² and a density of 0.22 g / cm ² were obtained in the same manner as in Example 4 except that the amount of ground pulp was changed to 66 parts by weight.
cm ³ of the absorber (5) of the present invention was obtained. Obtained absorber
The absorption under pressure of (5) was 17.3 g / g, and the falling rate of the water-absorbing polymer was 7%.

Example 6 The amount of synthetic pulp was 15 parts by weight, and the amount of ground pulp was 3 parts.
The basis weight was 0.0 in the same manner as in Example 4 except that the weight was 4 parts by weight.
An absorber (6) of the present invention having a density of 29 g / cm ² and a density of 0.30 g / cm ³ was obtained. The absorption amount under pressure of the obtained absorber (6) was 16.3 g / g, and the falling rate of the water-absorbing polymer was 19%.

Example 7 100 parts by weight of water-absorbing polymer C and synthetic pulp (trade name: SWP “UL-415”: manufactured by Mitsui Petrochemical Co., Ltd.)
12 parts by weight were mixed while adding 20 parts by weight of water. Next, the mixture was dry-mixed with 131 parts by weight of the pulverized pulp in a mixer, and air-formed on a wire screen using a batch-type air-making apparatus to obtain a web having a size of 14 cm × 40 cm. The upper and lower surfaces of the obtained web have a basis weight of 0.00.
13 g / cm ² tissue paper, and then embossed at 150 ° C. for 1 minute to obtain a basis weight of 0.047.
g / cm ² and the density of 0.24 g / cm ³ of the absorber of the present invention
(7) was obtained. The absorption amount under pressure of the obtained absorber (7) is 1
2.5 g / g, and the falling off rate of the water-absorbing polymer was 8%.

Example 8 The amount of synthetic pulp was 5 parts by weight, and the amount of ground pulp was 10 parts by weight.
The basis weight was 0.0 in the same manner as in Example 7 except that the weight was 0.0 parts by weight.
An absorber (8) of the present invention having a density of 50 g / cm ² and a density of 0.25 g / cm ³ was obtained. The absorption amount under pressure of the obtained absorber (8) was 15.3 g / g, and the falling rate of the water-absorbing polymer was 13%.

Example 9 The amount of synthetic pulp was 23 parts by weight and the amount of ground pulp was 1
Except that the weight was set to 33 parts by weight, the basis weight was set to 0.1 in the same manner as in Example 7.
An absorbent (9) of the present invention having a density of 060 g / cm ² and a density of 0.30 g / cm ³ was obtained. The absorption amount under pressure of the obtained absorber (9) was 13.5 g / g, and the falling rate of the water-absorbing polymer was 12%.

Example 10 The amount of synthetic pulp was 24 parts by weight, and the amount of ground pulp was 1
A basis weight of 0.1 was used in the same manner as in Example 7 except that the weight was 67 parts by weight.
An absorber (10) of the present invention having a density of 070 g / cm ² and a density of 0.35 g / cm ³ was obtained. The obtained absorbent (10) had an absorption amount under pressure of 12.3 g / g, and the falling rate of the water-absorbing polymer was 15%.

Example 11 A basis weight of 0.044 g / cm ² and a density of 0.33 g / cm ² were obtained in the same manner as in Example 9 except that the amount of ground pulp was changed to 67 parts by weight.
cm ³ of the absorber (11) of the present invention was obtained. The obtained absorber (1
The absorption under pressure of 1) was 14.2 g / g, and the falling rate of the water-absorbing polymer was 10%.

Example 12 100 parts by weight of water-absorbing polymer D and synthetic pulp (trade name: SWP “UL-415”: manufactured by Mitsui Petrochemical Co., Ltd.)
13 parts by weight were mixed while adding 20 parts by weight of a 30% by weight aqueous solution of polyaluminum chloride. The mixture is then
The mixture was dry-mixed with 00 parts by weight of the pulverized pulp in a mixer, and air-formed on a wire screen using a batch-type air-making apparatus to form a web having a size of 14 cm × 40 cm. The upper and lower surfaces of the obtained web are sandwiched between tissue papers having a basis weight of 0.0013 g / cm ² and then embossed at 150 ° C. for 1 minute to obtain a basis weight of 0.042 g / cm ² and a density of 0.21 g / cm ^3. Of the present invention (12) was obtained. The obtained absorbent (12) had an absorption amount under pressure of 13.2 g / g, and the water-absorbing polymer had a falling rate of 5%.

Example 13 100 parts by weight of water-absorbing polymer B and synthetic pulp (trade name: SWP “UL-415”: manufactured by Mitsui Petrochemical Co., Ltd.)
13 parts by weight were mixed while adding 20 parts by weight of a 1% by weight aqueous solution of ethylene glycol diglycidyl ether (manufactured by Nagase Kasei KK: Denacol EX-810). Next, the mixture was dry-mixed with 67 parts by weight of the pulverized pulp in a mixer, and air-molded on a wire screen using a batch-type air-milling apparatus to obtain a web having a size of 14 cm × 40 cm. The upper and lower surfaces of the obtained web are weighed 0.0013 g / c.
m ² tissue paper, and then embossed at 150 ° C. for 1 minute to obtain a basis weight of 0.047 g / c.
An absorber (13) of the present invention having m ² and a density of 0.23 g / cm ³ was obtained. The obtained absorbent (13) had an absorption amount under pressure of 13.7 g.
/ G, the shedding rate of the water-absorbing polymer was 3%.

Example 14 The procedure of Example 8 was repeated, except that the amount of the synthetic pulp was changed to 7 parts by weight, to obtain a basis weight of 0.043 g / cm ² .
An absorber (14) of the present invention having a density of 0.22 g / cm ³ was obtained.
The absorption amount under pressure of the obtained absorber (14) was 15.3 g / g,
The shedding rate of the water-absorbing polymer was 14%.

Example 15 100 parts by weight of water-absorbing polymer C and synthetic pulp (trade name: SWP “UL-415”: manufactured by Mitsui Petrochemical Co., Ltd.)
13 parts by weight were mixed while adding 20 parts by weight of water. Next, the mixture was dry-mixed with 100 parts by weight of the pulverized pulp in a mixer, and air-molded on a wire screen using a batch-type air-milling apparatus to obtain a web having a size of 14 cm × 40 cm. The upper and lower surfaces of the obtained web have a basis weight of 0.00.
2g / cm ² tissue paper, then 2
Emboss press at 00 ° C for 10 seconds to obtain a basis weight of 0.052
g / cm ² , density 0.26 g / cm ³ of the absorber of the present invention
(15) was obtained. The absorption amount under pressure of the obtained absorber (15) is 1
4.5 g / g, and the shedding rate of the water-absorbing polymer was 11%.

Example 16 100 parts by weight of water-absorbent polymer C and synthetic pulp (trade name: SWP “UL-415”: manufactured by Mitsui Petrochemical Co., Ltd.)
10 parts by weight were mixed while adding 20 parts by weight of water. Next, the mixture was dry-mixed with 133 parts by weight of the pulverized pulp in a mixer, and air-formed on a wire screen using a batch-type air-making apparatus to obtain a web having a size of 14 cm × 40 cm. The upper and lower surfaces of the obtained web have a basis weight of 0.00.
2g / cm ² tissue paper, then 1
Embossing press at 50 ° C for 10 minutes, basis weight 0.092
g / cm ² , density 0.23 g / cm ³ of the absorber of the present invention
(16) was obtained. The absorption amount under pressure of the obtained absorber (16) is 1
3.5 g / g, and the shedding rate of the water-absorbing polymer was 29%.

Example 17 100 parts by weight of the water-absorbing polymer A and 8 parts by weight of synthetic pulp were mixed while adding 20 parts by weight of water. Mix 70
A part by weight of the pulverized pulp was dry-mixed in a mixer, and then air-milled on a wire mesh screen to form a web. Separately, 35 parts by weight of ground pulp and 0.1 part of synthetic pulp.
A web consisting of 7 parts by weight was prepared, and the two webs sandwiched both sides of the web to obtain a web having a size of 14 cm × 40 cm and a basis weight of 0.046 g / cm ² . The obtained web was sandwiched between embossing hot presses and heated at 150 ° C. for 1 minute to obtain an absorber (17) of the present invention having a density of 0.23 g / cm ³ . The amount of the absorbent (17) obtained under pressure was 13.5 g.
/ G, the shedding rate of the water-absorbing polymer was 20%.

Example 18 100 parts by weight of the water-absorbing polymer D and 20 parts by weight of synthetic pulp were mixed while adding 20 parts by weight of water. The mixture was dry-blended with 18 parts by weight of ground pulp and then air-machined on a wire mesh screen to form a web. This was sandwiched between tissues having a basis weight of 0.0013 / cm ² and then embossed at 150 ° C. for 1 minute to obtain a basis weight of 0.013 / cm ^2.
An absorber (18) of the present invention having a density of 19 g / cm ² and a density of 0.25 g / cm ³ was obtained. The amount of the absorbent (18) obtained under pressure was 18.0 g / g, and the falling rate of the absorbent polymer was 35%.

Example 19 100 parts by weight of water-absorbing polymer C and synthetic pulp (trade name: SWP “UL-415”: manufactured by Mitsui Petrochemical Co., Ltd.)
20 parts by weight were mixed while adding 20 parts by weight of water. Next, the mixture was dry-mixed with 60 parts by weight of the pulverized pulp in a mixer, and air-molded on a wire screen using a batch-type air-milling apparatus to obtain a web having a size of 14 cm × 40 cm. Next, a web consisting of 30 parts by weight of the pulverized pulp is placed on one side of the web, and the upper and lower surfaces of the obtained web are sandwiched between tissues having a basis weight of 0.0013 g / cm ² , and the web passes between heat rollers. The resultant was heated at 200 ° C. for 20 seconds to obtain an absorbent (19) of the present invention having a basis weight of 0.048 g / cm ² and a density of 0.16 g / cm ³ . The obtained absorbent (19) had an absorption amount under pressure of 12.2 g / g, and the shedding rate of the water-absorbing polymer was 14%.

Example 20 100 parts by weight of water-absorbing polymer E and synthetic pulp (trade name: SWP "UL-415": manufactured by Mitsui Petrochemical Co., Ltd.)
13 parts by weight were mixed while adding 20 parts by weight of a 30% by weight aqueous solution of polyaluminum chloride. The mixture is then
The dry pulp was mixed with 00 parts by weight in a mixer in a mixer and air-formed on a wire screen using a batch-type air-sheeting apparatus to obtain a web having a size of 14 cm × 40 cm. The upper and lower surfaces of the obtained web are sandwiched between tissue papers having a basis weight of 0.0013 g / cm ² and then embossed at 150 ° C. for 1 minute to obtain a basis weight of 0.042 g / cm ² and a density of 0.21 g / cm ^3. Of the present invention (20) was obtained. The obtained absorbent (20) had an absorption amount under pressure of 12.1 g / g, and the falling rate of the absorbent polymer was 12%.

Example 21 In the same manner as in Example 20, except that the water-absorbing polymer F was used instead of the water-absorbing polymer E, the basis weight was 0.049 g / cm ² and the density was 0.24 g. / Cm ³ of the absorber (21) of the present invention was obtained. The resulting absorbent (21) had an absorption under pressure of 13.9 g / g, and the water-absorbing polymer had a falling rate of 17%.
Met.

Example 22 100 parts by weight of water-absorbing polymer C and synthetic pulp (trade name: SWP “UL-415”: manufactured by Mitsui Petrochemical Co., Ltd.)
33 parts by weight were mixed while adding 20 parts by weight of water. Next, the mixture was dry-mixed with 100 parts by weight of the pulverized pulp in a mixer, and air-molded on a wire screen using a batch-type air-milling apparatus to obtain a web having a size of 14 cm × 40 cm. The upper and lower surfaces of the obtained web have a basis weight of 0.00.
13 g / cm ² tissue paper, and then embossed at 150 ° C. for 1 minute to obtain a basis weight of 0.048 g.
/ Cm ² and a density of 0.24 g / cm ³ of the absorber (2
2) was obtained. The amount of the absorbent (22) obtained under pressure was 10.
2 g / g, and the shedding rate of the water-absorbing polymer was 17%.

Example 23 100 parts by weight of water-absorbing polymer C and synthetic pulp (trade name: SWP "UL-415": manufactured by Mitsui Petrochemical Co., Ltd.)
66 parts by weight were mixed while adding 20 parts by weight of water. Next, the mixture was dry-mixed with 100 parts by weight of the pulverized pulp in a mixer, and air-molded on a wire screen using a batch-type air-milling apparatus to obtain a web having a size of 14 cm × 40 cm. The upper and lower surfaces of the obtained web have a basis weight of 0.00.
13 g / cm ² of tissue paper and then embossed at 150 ° C. for 1 minute to obtain a basis weight of 0.056
g / cm ² and density of 0.28 g / cm ³ of the absorber of the present invention
(23) was obtained. The amount of the absorbent (23) obtained under pressure was 8.
8 g / g, and the falling rate of the water-absorbing polymer was 5%.

Example 24 The absorber (4) obtained by the method of Example 4 was further subjected to a 5 mm length × 0.5 mm width at intervals of 7 mm × 10 mm.
A notch was cut in a linear form with a cutter having a basis weight of 0.1 mm.
Absorbent having a density of 054 g / cm ^{2 and a} density of 0.27 g / cm ³ (24)
I got The absorption amount of the obtained absorber (24) under pressure was 14.2.
g / g, and the shedding rate of the water-absorbing polymer was 10%. The Gurley rigidity test value (JIS-L-1)
096) is 1.5 (mg) before making the cut.
f), after making the cut, 0.5 (mg)
f) (when the cut is perpendicular to the bending direction) and 1.
0 (mgf) (when the cut was parallel to the bending direction).

Comparative Example 1 100 parts by weight of the water-absorbing polymer C and 100 parts by weight of the pulverized pulp were dry-mixed in a mixer, and then air-molded on a wire screen using a batch-type air-papermaking apparatus to obtain a size of 14 cm × 40 cm. Web. The upper and lower surfaces of the obtained web are sandwiched between tissue papers having a basis weight of 0.0013 g / cm ² and then embossed at 150 ° C. for 1 minute to obtain a basis weight of 0.043 g / cm ² and a density of 0.17.
g / cm ³ of the comparative absorber (1) was obtained. The absorbency under pressure of the obtained comparative absorbent (1) was 12.3 g / g, and the falling rate of the water-absorbing polymer was 76%.

Comparative Example 2 100 parts by weight of water-absorbing polymer C, synthetic pulp ("UL41
5)) 13 parts by weight and 100 parts by weight of the pulverized pulp were dry-mixed in a mixer, and then air-milled on a wire screen using a batch-type air-milling machine to obtain a size 1
The web was 4 cm × 40 cm. The resulting upper and lower surfaces of the web was nipped with a tissue paper having a basis weight of 0.0013 g / cm ^2, and 1 minute embossing press Thereafter 0.99 ° C., basis weight 0.049 g / cm ^2, density of 0.25 g / cm
^Thus , Comparative Absorbent (2) was obtained. The absorption amount under pressure of the obtained comparative absorbent (2) was 10.9 g / g, and the falling rate of the water-absorbing polymer was 53%.

Comparative Example 3 100 parts by weight of water-absorbing polymer C and synthetic pulp ("UL
415 ") 25 parts by weight were mixed while adding 60 parts by weight of water. Next, the mixture was dry-mixed with 100 parts by weight of the pulverized pulp in a mixer, air-formed on a wire screen using a batch-type air-making apparatus, and the size was 14 cm ×
The web had a size of 40 cm and a basis weight of 0.048 g / cm ² .
The obtained web was hot-pressed at 150 ° C. for 3 minutes to obtain a comparative absorbent (3) having a density of 0.25 g / cm ³ . The absorbency under pressure of the obtained comparative absorbent (3) was 9.9 g / g, and the falling rate of the water-absorbing polymer was 30%.

Comparative Example 4 100 parts by weight of water-absorbing polymer C and synthetic pulp (“UL
415 ") 25 parts by weight were mixed while adding 0.5 parts by weight of water. Then, the mixture was dry-mixed with 100 parts by weight of the pulverized pulp in a mixer, air-molded on a wire screen using a batch-type air-milling machine, and dimensioned to 14 cm.
A web having a size of × 40 cm and a basis weight of 0.048 g / cm ² was obtained. The obtained web was hot pressed at 150 ° C. for 1 minute,
A comparative absorber (4) having a density of 0.25 g / cm ³ was obtained. The absorption amount under pressure of the obtained comparative absorber (4) was 11.9 g / g,
The shedding rate of the water-absorbing polymer was 60%.

Example 25 Absorbent (1) of the present invention cut into liquid-permeable polypropylene top sheet, two tissues, and 9 cm × 35 cm
A disposable diaper consisting of a liquid impermeable polyethylene backsheet (weight 15 g), leg gathers and two tape fasteners was assembled manually by fastening the individual components with double-sided tape. The total weight of the diaper was 33 g.

The obtained diaper was 1 year old (weight 10 kg)
Diapers currently on the market (total weight 50g)
As compared with the diaper, the diaper using the absorbent of the present invention was remarkably excellent in shape retention after urine absorption, and had little leak.

[0057]

The absorber obtained by the present invention has the following features.

(1) The obtained absorbent has high strength when dry and wet and is flexible.

(2) The concentration of the water-absorbing polymer in the obtained absorber can be raised to a range which has not been possible conventionally without reducing the absorption efficiency of the water-absorbing polymer. Therefore, it is possible to provide an ultra-thin absorber.

(3) Since the fusion of thermoplastic fibers occurs at the surface of the water-absorbing polymer particles dispersed separately, gel blocking between the water-absorbing polymers at the time of liquid absorption can be prevented and swelled. The gel strength of the water-absorbing polymer particles can be increased.

(4) The wicking performance, absorption amount and elasticity of the obtained absorber can be remarkably improved.

(5) An absorbent article using the absorbent of the present invention can provide a manufacturer with reduced transportation costs and management costs,
Comfort can be provided to the user.

In the present invention, an absorber having the above characteristics can be manufactured by a simple and inexpensive method. Therefore, the absorbent of the present invention is most suitable as an absorbent in absorbent articles in the fields of medical and sanitary materials such as sanitary napkins, disposable diapers, incontinence pads, breast milk pads and medical pads. Also freshness preserving material,
It can be used for various uses that require water retention and water absorption, such as agricultural and horticultural water retention materials and industrial water absorption materials.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of an apparatus for measuring an absorption amount under pressure used in the present invention.

──────────────────────────────────────────────────続 き Continuation of the front page (51) Int.Cl. ⁷ Identification code FI A61F 13/49 A41B 13/02 S 13/53 A61F 13/18 307A A61L 15/60 (56) References Japanese Patent Publication 8-19610 (JP, B2) (58) Fields investigated (Int. Cl. ⁷ , DB name) D04H 1/00-1/74

Claims (8)

(57) [Claims] (A) a weight average particle diameter of 100 to 700;
100 parts by weight of a water-absorbing polymer having a cross-linking density gradient near the particle surface, which can absorb 35 to 60 g / g of physiological saline, and 1 to 80 parts by weight of synthetic pulp,
Mixing in the presence of 40 parts by weight of water, (b) mixing the mixture obtained in step (a) with the water-absorbing polymer 1
Dry mixing with 10 to 1,000 parts by weight of hydrophilic fiber per 100 parts by weight, (c) air-mixing the mixture obtained in step (b) on a web, and (d) density of the web at 0. 1-1.0
A method for producing an absorber, comprising a step of heating and compressing the absorbent to g / cm ³ . 2. The method according to claim 1, wherein the water-absorbing polymer is a crosslinked polymer of a water-soluble ethylenic monomer containing acrylic acid or acrylate as a main component. 3. The method according to claim 1, wherein the amount of the synthetic pulp is in the range of 1 to 30 parts by weight based on 100 parts by weight of the water-absorbing polymer. 4. The method according to claim 1, wherein the amount of the hydrophilic fiber is in the range of 10 to 200 parts by weight per 100 parts by weight of the water-absorbing polymer. 5. The method for producing an absorbent body according to claim 1, wherein the heating temperature is in the range of 60 to 250 ° C. 6. The method according to claim 1, wherein the basis weight is 0.01 to 0.15 g / cm ² . 7. The method according to claim 1, wherein the synthetic pulp is a pulp-like thermoplastic resin. 8. A water-absorbing polymer 10 having a weight average particle diameter of 100 to 700 microns and capable of absorbing physiological saline in an amount of 35 to 60 g / g and having a crosslink density gradient near the particle surface.
Density obtained by mixing 1 to 80 parts by weight of synthetic pulp, 1 to 40 parts by weight of water and 10 to 1,000 parts by weight of hydrophilic fiber with respect to 0 parts by weight and 100 parts by weight of the water-absorbing polymer.
A web-like absorber heated and compressed to 1 to 1.0 g / cm ³ .