JP2004359943A5 - - Google Patents

Description

According to the findings of the present inventor, the water-absorbent resin used for absorbent articles such as diapers, as is known so far, takes into account the particle size factor (that is, mass average particle size, and particle size). Needless to say, the ratio of powder having a diameter of less than 150 μm) is necessary, but in addition to this, it is also important to consider two entirely new parameters: total absorption capacity and absorption efficiency under pressure. According to the above-described manufacturing method, a water-absorbing resin that satisfies the above two parameters can be easily manufactured while satisfying the design criteria focusing on the particle diameter element.
That is, the method for producing a water-absorbent resin according to the present invention,
(1) a step of polymerizing a monomer component mainly containing acrylic acid and / or a salt thereof to obtain a hydrogel polymer;
Drying and pulverizing the obtained hydrogel polymer to obtain a water-absorbent resin powder having a mass average particle diameter of 300 to 600 μm and a ratio of powder having a particle diameter of less than 150 μm of 0 to 10% by weight (2);
The resulting water-absorbent resin powder has a surface cross-linking treatment agent containing a surface cross-linking agent and water as essential components, and the content of the hydrophilic organic solvent in the treatment agent is 0 to 10 mass with respect to the treatment agent. % Adding a surface cross-linking treatment agent,
Step (4) of performing a surface cross-linking treatment by heating;
Including
The time from the end of the step (3) to the start of the step (4) is within 5 minutes.

Claims (12)

(1) a step of polymerizing a monomer component mainly containing acrylic acid and / or a salt thereof to obtain a hydrogel polymer;
Drying and pulverizing the obtained hydrogel polymer to obtain a water-absorbent resin powder having a mass average particle diameter of 300 to 600 μm and a ratio of powder having a particle diameter of less than 150 μm of 0 to 10% by weight (2);
The resulting water-absorbent resin powder is a surface cross-linking agent containing a surface cross-linking agent and water as essential components, and the content of the hydrophilic organic solvent in the processing agent is 0 to 10% by mass with respect to the processing agent. (3) adding a surface cross-linking agent which is
Step (4) of performing a surface cross-linking treatment by heating;
Including
The time from the end of the step (3) to the start of the step (4) is within 5 minutes;
A method for producing a water absorbent resin.   The method for producing a water-absorbent resin according to claim 1, wherein the temperature of the water-absorbent resin powder at the time of adding the surface crosslinking agent is in the range of 40 to 80C.   The method for producing a water-absorbent resin according to claim 1 or 2, wherein the water-absorbent resin powder has an absorption capacity under no pressure of 40 g / g or more. The surface cross-linking agent essentially contains a polyhydric alcohol compound, and the amount of water in the surface cross-linking treatment agent is 0.5 to 20% by weight based on the water-absorbing resin. Method for producing a water-absorbent resin. A water-absorbent resin obtained by polymerizing / crosslinking a monomer component containing acrylic acid and / or a salt thereof as a main component, having a mass average particle diameter of 300 to 600 μm and a powder having a particle diameter of less than 150 μm. A ratio of 0 to 10% by mass with respect to the water-absorbent resin, a total absorption capacity of 70 (g / g) or more, and an absorption efficiency under pressure of 70% or more. .
However, the total absorption capacity and the absorption efficiency under pressure are defined by the following formula based on the value of 1 hour after absorbing a 0.90% by mass aqueous sodium chloride solution (25 ° C.).
Total absorption capacity (g / g) = Absorption capacity under no pressure (g / g) + Absorption capacity under single layer pressure (g / g)
Absorption efficiency under pressure (%) = Single layer absorption capacity under pressure (g / g) × 100 / absorption capacity under no pressure (g / g) The water-absorbent resin according to claim 5 , wherein the proportion of the powder having a particle diameter of less than 150 µm is 0 to 3% by mass based on the water-absorbent resin. Mass average particle diameter of 380～550Myuemu, water-absorbing resin according to claim 5 or 6. Absorption capacity without load is less than 3 3 g / g or more 80 g / g, water-absorbent resin according to any one of claims 5 to 7. The water-absorbent resin according to any one of claims 5 to 8 , wherein the particle shape is irregularly crushed. The water-absorbent resin according to any one of claims 5 to 9, wherein the logarithmic standard deviation ?? of the particle size distribution of the water-absorbent resin is in the range of 0.25 to 0.50.
However, the logarithmic standard deviation of the particle size distribution was determined by sieving the water-absorbent resin with a JIS standard sieve having openings of 850 μm, 710 μm, 600 μm, 500 μm, 425 μm, 300 μm, 212 μm, 150 μm, and 45 μm. From the results plotted in Table 1, the particle size X when R = 84.1% by mass ₁ And the particle diameter X when R = 15.9% by mass. ₂ , And these values are introduced into the following equation.
σζ = 0.5 × In (X ₂ / X ₁ ) The particle size of the water-absorbent resin is less than 850 μm and the ratio of particles having a size of 150 μm or more is 90% by weight or more of the whole and the particles of 300 μm or more is 60% by weight or more of the whole. Water absorbent resin. An absorbent article for absorbing manure and blood, comprising the water absorbent resin according to any one of claims 5 to 11 .