WATER-ABSORBENT RESIN PARTICLES
FIG1 is a schematic view illustrating a device for measuring a swelling force 
Using a device in FIG1, a swelling force test of the water-absorbent resin particles was performed. An acrylic resin-made cylinder 2 with an inner diameter of 20 mm and a height of 50 mm, which had openings at both ends and had a nylon mesh 1 (255 mesh) installed at one of the openings was prepared. 0.1 g of water-absorbent resin particles 3 were uniformly spread onto the nylon mesh 1 of the cylinder 2 in a state where the cylinder 2 was left to stand vertically in such a direction that the opening of the side having the nylon mesh 1 installed was positioned below. An acrylic resin-made cylindrical jig (weight) 4 with a diameter of 19.5 mm, a height of 59 mm, and a mass of 20.5 g was inserted.
schematic view
5
dish
9
load cell
2
cylinder
6
glass filter
10
pressure-sensitive part
3
water-absorbent resin particles
['1. Water-absorbent resin particles comprising a crosslinked polymer comprising a monomer unit derived from a water-soluble ethylenically unsaturated monomer, wherein an initial swelling force of the water-absorbent resin particles as measured according to a swelling force test conducted in the following order of i), ii), iii), iv), and v) is 8 N or more, and a ratio of particles having a particle diameter of more than 250 µm and 850 µm or less is 70% by mass or more and a ratio of particles having a particle diameter of 250 µm or less is 20% by mass or less, with respect to the total amount of the water-absorbent resin particles: i) preparing a cylinder with an inner diameter of 20 mm, which has openings at both ends and has a nylon mesh installed in one of the openings, spreading 0.1 g of the water-absorbent resin particles uniformly on the nylon mesh in the cylinder in the state where the cylinder is left to stand vertically in such a direction that a side having the nylon mesh installed thereon is positioned below, and placing a cylindrical jig with a diameter of 19.5 mm on the water-absorbent resin particles, ii) placing a glass filter with a thickness of 5 mm in a horizontally installed Petri dish and infiltrating physiological saline into the grass filter up to a position slightly below an upper surface of the glass filter, iii) placing a liquid-impermeable sheet on the upper surface of the glass filter having the physiological saline infiltrated thereinto and standing the cylinder containing the water-absorbent resin particles  vertically on the liquid-impermeable sheet in a direction such that the nylon mesh is positioned below, iv) removing the liquid-impermeable sheet to initiate water absorption by the water-absorbent resin particles, and v) measuring a force to push up the cylindrical jig generated by the swelling of the water-absorbent resin particles at a time point of 10 seconds after the removal of the liquid-impermeable sheet with a load cell and recording it as an initial swelling force.']