Super Absorbent Polymer and Method for Producing Same

Abstract

The present invention relates to an olefin polymer and a method for producing the same. The super absorbent polymer can exhibit excellent absorbent properties even in a swollen state and thus exhibit excellent anti-rewetting effects. Accordingly, when the super absorbent polymer is used, it is possible to provide a sanitary material such as a diaper or a sanitary napkin which can give a smooth touch feeling even after the body fluid is discharged.

1 . A method for producing a super absorbent polymer comprising the steps of:
 carrying out a crosslinking polymerization of a monomer mixture including a water-soluble ethylenically unsaturated monomer having at least partially neutralized acidic groups in the presence of an internal crosslinking agent to form a hydrogel polymer;   drying, pulverizing and classifying the hydrogel polymer to form a base polymer powder; and   subjecting the surface of the base polymer powder to a first crosslinking in the presence of an epoxy-based surface crosslinking agent and then subjecting the surface of the first cross-linked base polymer powder to a second crosslinking in the presence of a non-epoxy-based surface crosslinking agent to form a surface crosslinked layer, wherein a GBP change ratio of the super absorbent polymer calculated by the following Formula 1 is 0.90 or less.   
       
         
           
             
               
                 
                   
                     
                       
                         0.3 
                          
                         
                             
                         
                          
                         GBP 
                       
                       - 
                       
                         0.3 
                          
                         
                             
                         
                          
                         AGBP 
                       
                     
                     
                       0.3 
                        
                       
                           
                       
                        
                       GBP 
                     
                   
                 
                 
                   
                     [ 
                     
                       Formula 
                        
                       
                           
                       
                        
                       1 
                     
                     ] 
                   
                 
               
             
           
         
         in Formula 1, 
         0.3 GBP is a gel bed permeability (GBP) under 0.3 psi for a physiological saline solution of a super absorbent polymer, 
         0.3 AGBP is a gel bed permeability (GBP) under 0.3 psi for a physiological saline solution of a super absorbent polymer having a particle size from 300 to 600 μm after swelling and drying which is obtained by a process of adding 5 g of the super absorbent polymer to 125 g of distilled water, stirring the resultant for 1 minute, drying the swollen super absorbent polymer at 100° C. for 3 hours, and then classifying the dried polymer through a U.S. standard 30 mesh screen and a U.S. standard 50 mesh screen. 
       
     
     
         2 . The method for producing a super absorbent polymer of  claim 1 , wherein the epoxy-based surface crosslinking agent include at least one polyglycidyl ether selected from the group consisting of ethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, butanediol diglycidyl ether, hexanediol diglycidyl ether, diethylene glycol diglycidyl ether, triethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, dipropylene glycol diglycidyl ether, tripropylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, and glycerol triglycidyl ether. 
     
     
         3 . The method for producing a super absorbent polymer of  claim 1 , wherein, in the step of forming the surface crosslinked layer, the surface of the base polymer powder is subjected to a first surface crosslinking at a temperature of 120 to 160° C. for 5 to 40 minutes using an epoxy-based surface crosslinking agent. 
     
     
         4 . The method for producing a super absorbent polymer of  claim 1 , wherein the non-epoxy-based surface crosslinking agent includes a polyol, a carbonate-based compound or a mixture thereof. 
     
     
         5 . The method for producing a super absorbent polymer of  claim 4 , wherein the polyol includes at least one selected from the group consisting of ethylene glycol, propylene glycol, 1,4-butanediol, 1,6-hexanediol, 1,2-hexanediol, 1,3-hexanediol, 2-methyl-1,3-propanediol, 2,5-hexanediol, 2-methyl-1,3-pentanediol, 2-methyl-2,4-pentanediol, tripropylene glycol and glycerol. 
     
     
         6 . The method for producing a super absorbent polymer of  claim 4 , wherein the carbonate-based compound includes at least one selected from the group consisting of ethylene carbonate and propylene carbonate. 
     
     
         7 . The method for producing a super absorbent polymer of  claim 3 , wherein, in the step of forming the surface crosslinked layer, the surface of the first surface cross-linked powder is subjected to a second surface crosslinking at a temperature of 170 to 210° C. for 5 to 40 minutes using a non-epoxy-based surface crosslinking agent.