Water-absorptive composite and process for producing the same

A process for producing a water-absorptive composite which comprises a fibrous substrate bearing water-absorptive polymer particles, said water-absorptive composite having the following physical characteristics (1) to (4):

• (1) a porosity of a substrate of 50 to 99.5%;
• (2) a primary particle diameter of said polymer particles of 50 to 1000 .mu.m;
• (3) an amount of said polymer particles of 10 to 500 g per m.sup.2 of said substrate;
• and
• (4) a percentage retention (A) of said polymer particles, defined by the following equation, of not less than 60%:
• ##EQU4## wherein W.sub.0 represents the dry weight (g) of a water-absorptive polymer in the following sample, and w represents the dry weight (g) of a water-absorptive polymer fallen from said sample,
• w being measured by a method wherein physiological saline is absorbed into a sheet sample, having a size of 60 mm.times.300 mm and a thickness of 0.5 to 20 mm, of a water-absorptive composite until the absorption reaches the saturation, the sample is then put on a stone table;
• in iron roller with a smooth surface, having a diameter of 105 mm, a width of 60 mm and a weight of 4 kg, is reciprocated on said sample five times at a speed of 10 cm/sec, and the weight, after drying, of a water-absorptive polymer fallen from said sample is measured as the w value
• comprising the steps of:
• allowing first and second liquids to collide against each other in a gas phase, thereby preparing a reaction mixture;
• applying the resultant reaction mixture, which is in the course of polymerization, dropwise onto a fibrous substrate;
• and
• allowing said polymerization to proceed and finish on said substrate,
• wherein the degree of polymerization when said reaction mixture reaches said substrate is 3-90%
• wherein said first liquid comprises an aqueous polymerizable monomer solution containing either one of an oxidizing agent and a reducing agent which together constitute a redox polymerization initiator;
• and
• said second liquid comprises an aqueous solution containing the other one of said oxidizing and reducing agents and optionally a polymerizable monomer.