Preparation method of superabsorbent polymer

1 . A method for preparing a superabsorbent polymer, comprising:

forming a water-containing gel polymer, by a crosslinking-polymerization of a water-soluble ethylenically unsaturated monomer having acidic groups and an internal crosslinking agent;

preparing a primary pulverized water-containing gel polymer by performing a primary water-containing gel pulverization of the water-containing gel polymer in the presence of a surfactant;

preparing a primary dry water-containing gel polymer by a primary drying by moving the primary pulverized water-containing gel polymer;

preparing a secondary pulverized water-containing gel polymer by performing a secondary water-containing gel pulverization of the primary dry water-containing gel polymer;

preparing a secondary dry water-containing gel polymer by a secondary drying by moving the secondary pulverized water-containing gel polymer;

and preparing superabsorbent polymer particles by pulverizing the secondary dry water-containing gel polymer,

wherein the primary drying is performed such that a ratio of a water content of the primary dry water-containing gel polymer to a water content of the water-containing gel polymer formed during the forming step is 45% to 80%.

2 . The method for preparing a superabsorbent polymer according to claim 1 , wherein the primary drying is performed such that the ratio of the water content of the primary dry water-containing gel polymer to the water content of the water-containing gel polymer is 47% to 78%.

3 . The method for preparing a superabsorbent polymer according to claim 1 , wherein the primary drying is performed at 100° C. to 300° C. for 5 minutes to 20 minutes.

4 . The method for preparing a superabsorbent polymer according to claim 1 , wherein the water content of the primary dry water-containing gel polymer is 20% by weight to 50% by weight with respect to a total weight of the primary dry water-containing gel polymer.

5 . The method for preparing a superabsorbent polymer according to claim 1 , wherein the secondary drying is performed at 100° C. to 250° C. for 20 minutes to 60 minutes.

6 . The method for preparing a superabsorbent polymer according to claim 1 , wherein the primary drying and the secondary drying are performed using a horizontal mixer dryer, a rotary kiln, a paddle dryer, or a steam tube dryer, respectively.

7 . The method for preparing a superabsorbent polymer according to claim 1 , wherein the secondary dry water-containing gel polymer has an average particle diameter of 900 μm to 1500 μm, and a content of the secondary dry water-containing gel polymer having a particle size of 1400 μm or more is 25% by weight or less with respect to a total weight of the secondary dry water-containing gel polymer.

8 . The method for preparing a superabsorbent polymer according to claim 1 , wherein the primary water-containing gel pulverization and the secondary water-containing gel pulverization are performed using a first micronizer and a second micronizer, respectively,

the first micronizer and the second micronizer each including

a body part comprising a transfer space through which the water-containing gel polymer is transferred;

a screw member which is rotatably installed inside the transfer space to transfer the water-containing gel polymer;

a driving motor providing a rotational driving force for the screw member;

a cutter member which is installed in the body part to pulverize the water-containing gel polymer; and

a perforated plate having a plurality of holes formed therein, which discharges the water-containing gel polymer pulverized by the cutter member to an outside of the body part.

9 . The method for preparing a superabsorbent polymer according to claim 8 , wherein a size of holes in the perforated plate of the second micronizer is smaller than a size of holes provided in the perforated plate of the first micronizer.

10 . The method for preparing a superabsorbent polymer according to claim 9 , wherein the size of holes in the perforated plate of the first micronizer is 1 mm to 10 mm, and

the size of holes in the perforated plate of the second micronizer is 0.5 mm to 6 mm.

11 . The method for preparing a superabsorbent polymer according to claim 1 , wherein the surfactant includes a compound represented by Chemical Formula 2 or a salt thereof:

wherein, in Chemical Formula 2,

A 1 , A 2 and A 3 are each independently a single bond, carbonyl,

wherein m1, m2 and m3 are each independently an integer of 1 to 8

is linked to an adjacent oxygen atom, is linked to adjacent R 1 , R 2 , or R 3 , provided that one or more thereof are carbonyl or

R 1 , R 2 and R 3 are each independently hydrogen, a linear or branched alkyl having 6 to 18 carbon atoms, or a linear or branched alkenyl having 6 to 18 carbon atoms, and

n is an integer of 1 to 9.

12 . The method for preparing a superabsorbent polymer according to claim 1 , wherein the forming the water-containing gel polymer comprises:

neutralizing at least part of the acidic groups of the water-soluble ethylenically unsaturated monomer, and

polymerization of a monomer composition including the water-soluble ethylenically unsaturated monomer having at least partially neutralized acidic groups, an internal crosslinking agent, and a polymerization initiator.

13 . The method for preparing a superabsorbent polymer according to claim 1 , wherein the water content of the water-containing gel polymer is 30% by weight to 80% by weight with respect to a total weight of the water-containing gel polymer.

14 . The method for preparing a superabsorbent polymer according to claim 1 , further comprising the step of classifying the superabsorbent polymer particles according to the particle size, after the step of preparing the superabsorbent polymer particles.

15 . The method for preparing a superabsorbent polymer according to claim 1 , further comprising the step of forming a surface-crosslinked layer on at least part of the surface of the superabsorbent polymer particles, after the step of preparing the superabsorbent polymer particles.

16 . The method for preparing a superabsorbent polymer according to claim 1 , wherein the forming the water-containing gel polymer comprises:

polymerization of a monomer composition including the water-soluble ethylenically unsaturated monomer having acidic groups, the internal crosslinking agent, and a polymerization initiator to form a polymer in which the water-soluble ethylenically unsaturated monomer having acidic groups and the internal crosslinking agent are crosslinking-polymerized; and

neutralizing at least part of the acidic groups of the polymer to form the water-containing gel polymer.