PARTICULATE WATER-ABSORBING RESIN COMPOSITION, PRODUCTION METHOD THEREFOR, ABSORBENT OBJECT, AND ABSORBENT ARTICLE

Abstract

A particulate water-absorbing resin composition having excellent flowability is provided. The particulate water-absorbing resin composition comprises a hydrazide compound and a water-absorbing resin.

Claims

1. A particulate water-absorbing resin composition comprising: a hydrazide compound; and a water-absorbing resin.

2. The particulate water-absorbing resin composition according to claim 1, wherein the hydrazide compound is present on at least one of a surface and an inside of the water-absorbing resin composition.

3. The particulate water-absorbing resin composition according to claim 1, wherein the hydrazide compound is in particulate form.

4. The particulate water-absorbing resin composition according to claim 1, wherein a content of the hydrazide compound is 0.001 to 10 mass %.

5. The particulate water-absorbing resin composition according to claim 1, wherein an angle of spatula of the particulate water-absorbing resin composition is 20 to 38°.

6. The particulate water-absorbing resin composition according to claim 1, wherein the particulate water-absorbing resin composition has a median particle diameter of 100 to 600 μm.

7. An absorber comprising the particulate water-absorbing resin composition according to claim 1.

8. An absorbent article comprising the absorber according to claim 7 held between a liquid-permeable sheet and a liquid-impermeable sheet.

9. A method for producing a particulate water-absorbing resin composition, the method comprising mixing a water-absorbing resin that is a polymer crosslinked product of a water-soluble ethylenically unsaturated monomer, an internal-crosslinking agent, and a post-crosslinking agent, with a hydrazide compound at a temperature of 10 to 100° C.

Description

EXAMPLES

[0092] Hereinafter, the present invention will be described in detail with reference to examples and a comparative example. However, the present invention is not limited to the examples.

[0093] The particulate water-absorbing resin compositions obtained in the following examples and comparative example were evaluated in the following various tests. Hereinafter, each evaluation test method will be described.

<Median Particle Diameter>

[0094] The measurement was performed in an environment at a temperature of 25±2° C. and a humidity of 50±10%. JIS standard sieves were combined in the following order from the top: a sieve with an opening of 850 μm, a sieve with an opening of 600 μm, a sieve with an opening of 500 μm, a sieve with an opening of 425 μm, a sieve with an opening of 300 μm, a sieve with an opening of 250 μm, a sieve with an opening of 150 μm, and a receptacle.

[0095] The water-absorbing resin composition, 50 g, was placed on the uppermost sieve of the combined sieves, and shaken for 10 minutes using a rotating and tapping shaker to perform classification. After classification, the mass of the water-absorbing resin composition retained on each sieve was calculated as a mass percentage with respect to the total amount, and the particle size distribution was determined. With respect to this particle size distribution, by cumulation of the mass percentages of the retained on the sieves in descending order of particle diameter, the relationship between the opening of the sieve and the cumulative value of the mass percentage of the water-absorbing resin retained on the sieve was plotted on a logarithmic probability paper. The plotted points on the probability paper were connected with a straight line, and a particle diameter corresponding to a cumulative mass percentage of 50 mass % was defined as a median particle diameter.

<Flowability Test>

[0096] In an environment of a temperature of 25±2° C. and a humidity of 50±10%, the angle of spatula was measured using Powder Tester Model PT-X (manufactured by Hosokawa Micron Corporation), and the flowability of the particulate water-absorbing resin compositions of the examples and the comparative example was evaluated. The angle of spatula is an inclination angle of a side surface of the resin powder deposited on the spatula, and is an angle necessary for moving the powder in a stationary state, and is one of indexes of flowability. The smaller the value of the angle of spatula, the better the flowability. The measurement procedure was according to the instruction manual of the powder tester. The measured values of the angle of spatula are shown in Table 1.

<Production of Water-Absorbing Resin>

Production Example 1

[0097] A 2-L round-bottom cylindrical separable flask having an inner diameter of 11 cm and equipped with a reflux condenser, a dropping funnel, a nitrogen gas inlet tube, and a stirring blade having two stages of 4-inclined paddle blades having a blade diameter of 5 cm as a stirrer was prepared. To this flask, 293 g of n-heptane as a hydrocarbon dispersion medium and 0.736 g of a maleic anhydride-modified ethylene-propylene copolymer (Mitsui Chemicals, Inc., Hi-WAX 1105A) as a polymeric dispersant were added, the temperature was raised to 80° C. with stirring to dissolve the dispersant, and then the contents were cooled to 50° C.

[0098] On the other hand, in a beaker having an internal volume of 300 mL, 92.0 g (1.03 mol) of an 80.5 mass % aqueous acrylic acid solution as a water-soluble ethylenically unsaturated monomer was placed, 147.7 g of a 20.9 mass % aqueous sodium hydroxide solution was added dropwise while cooling with ice water to perform neutralization of 75 mol %, and then 0.092 g (Sumitomo Seika Chemicals Co., Ltd., HECAW-15F) of hydroxylethyl cellulose as a thickener, 0.0736 g (0.272 mmol) of potassium persulfate as a water-soluble radical polymerization agent, and 0.010 g (0.057 mmol) of ethylene glycol diglycidyl ether as an internal-crosslinking agent were added thereto and dissolved, thereby preparing a first-stage aqueous monomer solution.

[0099] Then, the aqueous monomer solution prepared above was added to the separable flask and stirred for 10 minutes, after which a surfactant solution obtained by heating and dissolving 0.736 g of a sucrose stearate having an HLB of 3 (Mitsubishi Chemical Foods Corporation, Ryoto Sugar Ester S-370) as a surfactant in 6.62 g of n-heptane in a 20 mL-vial was further added. While stirring at a stirrer rotational speed of 550 rpm, the inside of the system was sufficiently purged with nitrogen, and then the flask was immersed in a water bath at 70° C. for 60 minutes to obtain a first-stage polymerization slurry solution.

[0100] On the other hand, in another beaker having an internal volume of 500 mL, 128.8 g (1.43 mol) of an 80.5 mass % aqueous acrylic acid solution as a water-soluble ethylenically unsaturated monomer was placed, 159.0 g of a 27 mass % aqueous sodium hydroxide solution was added dropwise while cooling with ice water to perform neutralization of 75 mol %, and then 0.103 g (0.381 mmol) of potassium persulfate as a water-soluble radical polymerization initiator and 0.0116 g (0.067 mmol) of ethylene glycol diglycidyl ether as an internal-crosslinking agent were added thereto and dissolved, thereby preparing a second-stage aqueous monomer solution.

[0101] While stirring at a stirrer rotational speed of 1000 rpm, the inside of the separable flask system was cooled to 25° C. Then the whole amount of the second-stage aqueous monomer solution was added to the first-stage polymerization slurry. After the inside of the system was purged with nitrogen for 30 minutes, the flask was immersed again in a water bath at 70° C. for 60 minutes to obtain a second-stage hydrous gel polymer.

[0102] To the hydrous gel polymer after the second-stage polymerization, 0.589 g of a 45 mass % aqueous pentasodium diethylenetriaminepentaacetate solution was added under stirring. Thereafter, the flask was immersed in an oil bath set at 125° C., and 257.7 g of water was removed to the outside of the system while refluxing n-heptane by azeotropic distillation of n-heptane and water. Then, 4.42 g (0.507 mmol) of a 2 mass % aqueous solution of ethylene glycol diglycidyl ether as a post-crosslinking agent was added to the flask, and the contents were held at 83° C. for 2 hours.

[0103] Thereafter, the contents were dried by evaporation of n-heptane at 125° C. to obtain a particulate crosslinked polymer (dry product). This particulate crosslinked polymer was passed through a sieve with an opening of 850 μm to obtain 228.0 g of a particulate water-absorbing resin. The median particle diameter of the particulate water-absorbing resin was 352 μm.

<Production of Water-Absorbing Resin Composition>

Example 1

[0104] In an environment at a temperature of 25° C., to 100 parts by mass of the particulate water-absorbing resin obtained in Production Example 1, 0.07 parts by mass of malonic acid dihydrazide as a hydrazide compound was powder-mixed to obtain a particulate water-absorbing resin composition. The angle of spatula of this particulate water-absorbing resin composition was 33.9°.

Example 2

[0105] A particulate water-absorbing resin composition was obtained in the same manner as in Example 1 except that in Example 1, the amount of malonic acid dihydrazide was changed to 0.35 parts by mass with respect to 100 parts by mass of the particulate water-absorbing resin. The angle of spatula of this particulate water-absorbing resin composition was 32.3°.

Example 3

[0106] A particulate water-absorbing resin composition was obtained in the same manner as in Example 1 except that in Example 1, the amount of malonic acid dihydrazide was changed to 0.7 parts by mass with respect to 100 parts by mass of the particulate water-absorbing resin. The angle of spatula of this particulate water-absorbing resin composition was 31.9°.

Example 4

[0107] A particulate water-absorbing resin composition was obtained in the same manner as in Example 1 except that in Example 3, malonic acid dihydrazide as a hydrazide compound was changed to adipic acid dihydrazide. The angle of spatula of this particulate water-absorbing resin composition was 31.8°.

Comparative Example 1

[0108] The particulate water-absorbing resin obtained in Production Example 1 was used as it was as the particulate water-absorbing resin of Comparative Example 1. The angle of spatula of this particulate water-absorbing resin was 40.4°.

TABLE-US-00001 TABLE 1 Flowability test Hydrazide compound Angle of Type Parts by mass spatula (°) Example 1 Malonic acid 0.07 33.9 dihydrazide Example 2 Malonic acid 0.35 32.3 dihydrazide Example 3 Malonic acid 0.7 31.9 dihydrazide Example 4 Adipic acid 0.7 31.8 dihydrazide Comparative — — 40.4 example 1