JP-7856626-B2 - Method for producing superabsorbent polymer particles

Inventors

• 岡澤 志保

Assignees

• 住友精化株式会社

Dates

Publication Date

20260511

Application Date

20220217

Priority Date

20210225

Claims (4)

1. A method for producing water-absorbing resin particles containing polymer particles, wherein the method is The process includes a step of crosslinking the polymer with the surface crosslinking agent by reacting the polymer with the surface crosslinking agent in a mixture of polymer particle powder containing the polymer and a crosslinking agent solution containing a surface crosslinking agent and water. The aforementioned crosslinking agent solution contains a monohydric alcohol, The surface crosslinking agent comprises alkylene carbonate, The amount (mass) of the surface crosslinking agent used is 0.00045 or more and 0.00110 or less with respect to 1 mass of the total solid content of the polymer particles. A method wherein the amount (mass) of alkylene carbonate in the crosslinking agent solution is 0.009 or more and 0.027 or less per unit mass of water.
2. The method according to claim 1, wherein the amount (mass) of the surface crosslinking agent used is 0.00050 or more and 0.00110 or less with respect to 1 mass of the total amount of solids of the polymer particles.
3. The method according to claim 1 or 2 , wherein the alkylene carbonate is ethylene carbonate.
4. A method for suppressing the decrease in centrifugal retention capacity of water-absorbent resin particles containing polymer particles and for improving the absorption amount of the water-absorbent resin particles under pressure, wherein the method is The method includes crosslinking the polymer with the surface crosslinking agent by reacting the polymer with the surface crosslinking agent in a mixture of polymer particle powder containing the polymer and a crosslinking agent solution containing a surface crosslinking agent and water. The surface crosslinking agent comprises alkylene carbonate, The amount (mass) of the surface crosslinking agent used is 0.00045 or more and 0.00110 or less with respect to 1 mass of the total solid content of the polymer particles. A method wherein the amount (mass) of alkylene carbonate in the crosslinking agent solution is 0.009 or more and 0.027 or less per unit mass of water.

Description

The present invention relates to a method for producing water-absorbent resin particles. Patent Document 1 discloses a method for producing surface-crosslinked water-absorbent resin particles that can be used in absorbent articles such as sanitary products. Special Publication No. 2020-516753 This is a cross-sectional view showing one embodiment of an absorbent article.This is a schematic diagram showing a device for measuring water absorption under load. Several embodiments of the present invention will be described in detail below. However, the present invention is not limited to the following embodiments. In this specification, "(meth)acrylic" means both acrylic and methacrylic. Similarly, "acrylate" and "methacrylate" are also written as "(meth)acrylate." The same applies to other similar terms. "(poly)" means both with and without the prefix "poly." In the numerical ranges described stepwise in this specification, the upper or lower limit of one step in the numerical range can be arbitrarily combined with the upper or lower limit of another step in the numerical range. In the numerical ranges described in this specification, the upper or lower limit of that numerical range may be replaced with the values shown in the examples. "Water-soluble" means solubility of 5% by mass or more in water at 25°C. The materials exemplified in this specification may be used individually or in combination of two or more. "Physiological saline" means a 0.9% by mass aqueous solution of sodium chloride. "Room temperature" means 25°C. One embodiment of a method for producing superabsorbent polymer particles includes a step of crosslinking the polymer with a surface crosslinking agent by reacting the polymer with a surface crosslinking agent in a mixture of polymer particle powder containing the polymer and a crosslinking agent solution containing a surface crosslinking agent and water. The polymer forming the polymer particles only needs to be capable of imparting water absorption to the polymer particles. The monomers constituting the polymer may be ethylenically unsaturated monomers. The polymer may also be a crosslinked polymer. The ethylenically unsaturated monomers constituting the polymer may include, for example, at least one compound selected from the group consisting of (meth)acrylic acid and its salts, 2-(meth)acrylamide-2-methylpropanesulfonic acid and its salts, (meth)acrylamide, N,N-dimethyl(meth)acrylamide, 2-hydroxyethyl(meth)acrylate, N-methylol(meth)acrylamide, polyethylene glycol mono(meth)acrylate, N,N-diethylaminoethyl(meth)acrylate, N,N-diethylaminopropyl(meth)acrylate, and diethylaminopropyl(meth)acrylamide. If the ethylenically unsaturated monomer contains an amino group, the amino group may be quaternized. The ethylenically unsaturated monomers constituting the polymer may include at least one compound selected from the group consisting of acrylic acid and its salts, methacrylic acid and its salts, acrylamide, methacrylamide, and N,N-dimethylacrylamide; at least one compound selected from the group consisting of acrylic acid and its salts, methacrylic acid and its salts, and acrylamide; or at least one compound selected from the group consisting of acrylic acid and its salts, and methacrylic acid and its salts. The polymer forming the polymer particles may have functional groups that react with the crosslinking agent. These functional groups may be, for example, carboxyl groups, amino groups, or combinations thereof. The carboxyl groups may be, for example, groups derived from acrylic acid, methacrylic acid, or salts thereof. The polymer may contain monomer units derived from monomers other than ethylenically unsaturated monomers. The proportion of monomer units derived from ethylenically unsaturated monomers (particularly (meth)acrylic acid and its salts) in the polymer may be 70 to 100 mol% of the total amount of monomers. Polymer particles can be obtained by polymerization methods selected from, for example, reverse-phase suspension polymerization, aqueous solution polymerization, bulk polymerization, and precipitation polymerization. Polymer particles containing crosslinked polymers (crosslinked polymer particles) can be obtained through self-crosslinking during polymerization, reaction with an internal crosslinking agent, or a combination thereof. One example of a method for obtaining polymer particles by aqueous solution polymerization includes polymerizing an ethylenically unsaturated monomer in an aqueous monomer aqueous solution containing an ethylenically unsaturated monomer, a radical polymerization initiator, and water to form a bulk, water-containing gel-like polymer containing the polymer and water; roughly crushing the water-containing gel-like polymer to form a crushed product; drying the crushed product to obtain a dried product; and grinding the dried product to obtain polymer particles. The polymer particles powder after grinding may be classified by sieving or the like. The radica