Polyacrylic acid (salt)-type water absorbent resin and method for producing of same
First Claim
1. A method for producing a polyacrylic acid (salt) water absorbent resin, comprising steps of:
- preparing an aqueous monomer solution of acrylic acid (salt),polymerizing the aqueous monomer solution,finely shredding a hydrous gel-like crosslinked polymer during or after polymerization,drying the obtained particulate hydrous gel-like crosslinked polymer,crushing the dried polymer,classifying the dried polymer,heating and surface-crosslinking the dried polymer after the classification, andcooling after the surface-crosslinking, whereinthe inner surface area of a cooling apparatus to be used in the cooling step is 0.25 to 0.95 times as large as the inner surface area of a heating apparatus to be used in the heating and surface-crosslinking step.
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Abstract
Disclosed is a method for producing a water absorbent resin, by which a surface-crosslinked water absorbent resin having excellent physical properties can be efficiently obtained at low cost, while assuring high productivity. When the production scale is increased to a continuous production on a huge scale (for example, 1 t/hr or more), the physical properties are improved and stabilized (for example, standard deviation of the physical properties is reduced) by a surface-crosslinking treatment, and the absorption against pressure (AAP) and liquid permeability (SFC) are further improved. Specifically disclosed is a method for continuously producing a polyacrylic acid (salt)-type water absorbent resin powder, which comprises: a step of preparing an aqueous monomer solution using an acrylic acid (salt); a step of polymerizing the aqueous monomer solution; a shredding step of a hydrous gel-like crosslinked polymer during or after the polymerization; a step of drying the thus-obtained particulate hydrous gel-like crosslinked polymer; a step of crushing and classifying the dried product; a step of heating and surface-crosslinking after the classification; and a step of cooling after the surface-crosslinking. In the method for producing a polyacrylic acid (salt)-type water absorbent resin, the internal area of the cooling device that is used in the cooling step is 0.25-0.95 times the internal area of the heating device that is used in the surface-crosslinking step.
96 Citations
16 Claims
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1. A method for producing a polyacrylic acid (salt) water absorbent resin, comprising steps of:
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preparing an aqueous monomer solution of acrylic acid (salt), polymerizing the aqueous monomer solution, finely shredding a hydrous gel-like crosslinked polymer during or after polymerization, drying the obtained particulate hydrous gel-like crosslinked polymer, crushing the dried polymer, classifying the dried polymer, heating and surface-crosslinking the dried polymer after the classification, and cooling after the surface-crosslinking, wherein the inner surface area of a cooling apparatus to be used in the cooling step is 0.25 to 0.95 times as large as the inner surface area of a heating apparatus to be used in the heating and surface-crosslinking step. - View Dependent Claims (3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16)
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2. A method for producing a polyacrylic acid water absorbent resin, comprising steps of:
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preparing an aqueous monomer solution of acrylic acid (salt), polymerizing the aqueous monomer solution, finely shredding a hydrous gel-like crosslinked polymer during or after polymerization, drying the obtained particulate hydrous gel-like crosslinked polymer, crushing the dried polymer, classifying the dried polymer, heating and surface-crosslinking the dried polymer after the classification, and cooling after the surface-crosslinking, wherein the inner volume of a cooling apparatus to be used in the cooling step is 0.25 to 0.95 times as large as the inner volume of a heating apparatus to be used in the heating and surface-crosslinking step.
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Specification