Polyacrylic acid (salt) -based water-absorbent resin and a method for producing it
First Claim
1. A method for producing a polyacrylic acid (salt)-based water-absorbent resin, the method comprising:
- a preparation step in which a monomer is prepared from acrylic acid containing propionic acid;
a polymerization step in which the monomer is polymerized; and
a drying step in which the obtained hydrogel is dried, whereinFe on the basis of Fe2O3 in the monomer is 0.002 to 2 ppm by mass;
a plurality of acrylic acids having different propionic acid amounts of 1.1 to 50 times by mass with respect to the other acrylic acid are mixed to prepare the monomer;
a plurality of acrylic acids obtained by different production processes of at least one selected from plant, installation site, raw material, oxide type, and refining type are mixed to prepare the monomer;
and propionic acid is removed from polyacrylic acid (salt) during polymerization or after polymerization.
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Abstract
The purpose of the present invention is to improve the water absorption of a water-absorbent resin without sacrificing the productivity, production cost, safety, and so on. Provided is a sustainable and renewable water-absorbent resin with excellent whiteness, which is suitable for mass consumption as disposal diapers or the like, and which can dispense with excessive purification of raw material acrylic acid. Also provided is a process for the production of a water-absorbent resin, which comprises: a step of preparing acrylic monomers; a step of polymerizing the monomers; and a step of drying the obtained aqueous gel, wherein the monomers at the time of polymerization contain at least 400 ppm of propionic acid.
100 Citations
14 Claims
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1. A method for producing a polyacrylic acid (salt)-based water-absorbent resin, the method comprising:
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a preparation step in which a monomer is prepared from acrylic acid containing propionic acid; a polymerization step in which the monomer is polymerized; and a drying step in which the obtained hydrogel is dried, wherein Fe on the basis of Fe2O3 in the monomer is 0.002 to 2 ppm by mass; a plurality of acrylic acids having different propionic acid amounts of 1.1 to 50 times by mass with respect to the other acrylic acid are mixed to prepare the monomer; a plurality of acrylic acids obtained by different production processes of at least one selected from plant, installation site, raw material, oxide type, and refining type are mixed to prepare the monomer; and propionic acid is removed from polyacrylic acid (salt) during polymerization or after polymerization. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14)
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Specification