Water absorbing agent, manufacturing method thereof, and manufacturing machine thereof

A water absorbing agent obtained by mixing and reacting a water absorbing resin containing a carboxyl group with a crosslinking agent that reacts with said carboxyl group,

• being characterized in that
• X.gtoreq.20 (g/g), and
• Y/X.gtoreq.0.90
• where X and Y respectively represent absorbency of said water absorbing agent under pressure of 50 g/cm.sup.2 before and after applying an impact force (B) to said water absorbing agent by letting said water absorbing agent collide with said water absorbing agent with a predetermined strength.

A method of manufacturing a water absorbing agent, being characterized in that it comprises the sequential steps of:

• (1) supplying a water absorbing resin containing a carboxyl group to a first area of an agitation type mixer of a continuous extruding method including at least one kind of agitating member, disposed around a rotational shaft inside a fixed cylinder, for applying a thrusting force to said water absorbing resin;
• (2) dispersing said water absorbing resin in said first area;
• (3) extruding said water absorbing resin to a second area in which said thrusting force is weaker than in said first area;
• and
• (4) mixing said water absorbing resin and an aqueous liquid in said second area.

A method of manufacturing a water absorbing agent, comprising the steps of:

• obtaining a water-containing gel-like granulation product having an average particle diameter in a range of 0.3 mm to 10 mm by mixing an aqueous liquid of 70 parts by weight to 400 parts by weight with 100 parts by weight of water absorbing resin having an average particle diameter in a range of 10 .mu.m to 150 .mu.m;
• drying and shrinking the obtained water-containing gel-like granulation product at a temperature ranging from 110.degree. C. to 300.degree. C. without grinding;
• and
• crosslinking a surface of a water absorbing resin granulation product having an average particle diameter in a range of 200 .mu.m to 800 .mu.m as obtained by drying and shrinking the water-containing gel-like granulation product.