Water-absorbable resin powder, and method for determining elastic modulus of water-absorbable resin powder
To provide water-absorbing resin powder particularly useful for a sanitary article, water-absorbing resin powder containing a polyacrylic acid (salt)-based water-absorbing resin as a main component is surface-crosslinked, and satisfies (1) to (3) below: (1) a proportion of a water absorbent resin powder having a particle size of not less than 150 μm and less than 850 μm is not less than 90 weight %; (2) a water absorption time according to a vortex method is not more than 42 seconds; and (3) an elastic modulus index (600-500) is not less than 5500.
1. Water absorbent resin powder comprising:
a polyacrylic acid (salt)-based water-absorbing resin as a main component,
said water absorbent resin powder being surface-crosslinked and satisfying (1) to (3) below:
(1) a proportion of the water absorbent resin powder having a particle size of not less than 150 μm and less than 850 μm is not less than 90 weight %;
(2) a water absorption time according to a vortex method is not more than 42 seconds; and
(3) an elastic modulus index (600-500) is not less than 5500.
2. The water-absorbing resin powder according to claim 1 , further satisfying (4) below:
(4) an elastic modulus index (500-425) is not less than 4500.
3. The water-absorbing resin powder according to claim 2 , further satisfying (5) below:
(5) an elastic modulus index (425-300) is not less than 3500.
4. The water-absorbing resin powder according to claim 1 , wherein,
(a) a proportion of the water-absorbing resin powder having a particle size of not less than 150 μm and less than 300 μm is 5 weight % to 50 weight %;
(b) a proportion of the water-absorbing resin powder having a particle size of not less than 300 μm and less than 425 μm is 10 weight % to 60 weight %;
(c) a proportion of the water-absorbing resin powder having a particle size of not less than 425 μm and less than 500 μm is 5 weight % to 50 weight %;
(d) a proportion of the water-absorbing resin powder having a particle size of not less than 500 μm and less than 600 μm is 5 weight % to 50 weight %; and
(e) a proportion of the water-absorbing resin powder having a particle size of not less than 600 μm and less than 850 μm is 0.1 weight % to 50 weight %, and
wherein a total proportion of the water-absorbing resin powder having particle sizes, each of which is defined in (a) to (e) above, is 90 weight % to 100 weight %.
5. The water-absorbing resin powder according to claim 1 , wherein the water-absorbing resin powder has an internal gas bubble ratio of 0% to 3.7%.
6. The water-absorbing resin powder according to claim 1 , wherein the water-absorbing resin powder has a surface tension of not less than 69 mN/m.
7. The water-absorbing resin powder according to claim 1 , wherein the water-absorbing resin powder has CRC as defined in ERT 441.2-02 of 25 g/g to 50 g/g.
8. The water-absorbing resin powder according to claim 1 , wherein the water-absorbing resin powder has a weight average particle diameter (D50) of 300 μm to 500 μm and a logarithmic standard deviation (σζ) of 0.25 to 0.45.
9. An absorbent body including the water-absorbing resin powder according to claim 1 .
10. An absorbent article including the water-absorbing resin powder according to claim 1 .