Anti-fouling agent and method for producing the same

Abstract

Disclosed is an anti-fouling agent which is superior in viscosity stability, water resistance of its film and ability of preventing a scale from depositing on the inner wall of a polymerization reactor and which can prevent the contamination of foreign substances into a polymeric product caused by exfoliation of a scale depositing on the inner wall of a polymerization reactor and exfoliation of the anti-fouling agent itself, the anti-fouling agent comprising an aqueous solution containing a polyvinyl alcohol that is obtained through saponification of a polyvinyl ester that contains monomer units having a specific silyl group and that satisfies the following formulae (I) and (II): 370< P×S<9000   (I) wherein P indicates the viscosity-average degree of polymerization of the polyvinyl alcohol, and S indicates the content (mole %) of the monomer units having a silyl group of formula (1) in the polyvinyl alcohol; 0.2/100 ≦( A−B )/( B )≦ 75/100   (II) wherein A indicates the content (ppm) of silicon atoms in the polyvinyl alcohol, and B indicates the content (ppm) of silicon atoms in the polyvinyl alcohol that was washed with sodium hydroxide-containing methanol and then washed with methanol by Soxhlet extraction.

1 . An anti-fouling agent comprising an aqueous solution containing a polyvinyl alcohol obtained through saponification of a polyvinyl ester that contains monomer units having a silyl group of formula (1):  
       
         
           
           
               
               
           
         
       
       wherein R 1  represents an alkyl group having from 1 to 5 carbon atoms; R 2  represents an alkoxyl or acyloxyl group optionally having an oxygen-containing substituent; and m indicates an integer of from 0 to 2,  
       wherein the polyvinyl alcohol satisfies the following formulae (I) and (II):  
         370< P×S< 9000  (I)  
       wherein 
 P indicates the viscosity-average degree of polymerization of the polyvinyl alcohol,  
 and S indicates the content (mole %) of the monomer units having a silyl group of formula (1) in the polyvinyl alcohol;  
   0.2/100≦( A−B )/( B )≦75/100  (II)  
 wherein  
 A indicates the content (ppm) of silicon atoms in the polyvinyl alcohol,  
 and B indicates the content (ppm) of silicon atoms in the polyvinyl alcohol that was washed with sodium hydroxide-containing methanol and then washed with methanol by Soxhlet extraction, wherein A and B are measured by ICP emission spectrometry after ashing of a sample.  
 
     
     
         2 . The anti-fouling agent according to  claim 1  wherein the aqueous solution has a pH of from 10 to 14.  
     
     
         3 . The anti-fouling agent according to  claim 1  wherein the content of the polyvinyl alcohol is from 0.1 to 10% by weight.  
     
     
         4 . A method for producing an anti-fouling agent wherein the method comprises obtaining a polyvinyl alcohol satisfying formulae (I) and (II) defined below by saponifying a polyvinyl ester that contains monomer units having a silyl group of formula (1):  
       
         
           
           
               
               
           
         
       
       wherein R 1  represents an alkyl group having from 1 to 5 carbon atoms; R 2  represents an alkoxyl or acyloxyl group optionally having an oxygen-containing substituent; and m indicates an integer of from 0 to 2,  
       and then preparing an aqueous solution by dissolving the polyvinyl alcohol in water:  
         370< P×S< 9000  (I)  
       wherein 
 P indicates the viscosity-average degree of polymerization of the polyvinyl alcohol,  
 and S indicates the content (mole %) of the monomer units having a silyl group of formula (1) in the polyvinyl alcohol;  
   0.2/100≦( A−B )/( B )≦75/100  (II)  
 wherein  
 A indicates the content (ppm) of silicon atoms in the polyvinyl alcohol,  
 and B indicates the content (ppm) of silicon atoms in the polyvinyl alcohol that was washed with sodium hydroxide-containing methanol and then washed with methanol by Soxhlet extraction, wherein A and B are measured by ICP emission spectrometry after ashing of a sample.  
 
     
     
         5 . The method for producing an anti-fouling agent according to  claim 4 , wherein said polyvinyl alcohol is obtained by saponifying said polyvinyl ester, subsequently neutralizing a remaining saponification catalyst, and then subjecting to a heat treatment in an organic solvent.  
     
     
         6 . The method for producing an anti-fouling agent according to  claim 5  wherein said organic solvent is used in an amount of from 1 to 20 times the weight of polyvinyl alcohol during the heat treatment.  
     
     
         7 . The method for producing an anti-fouling agent according to  claim 5  wherein said organic solvent is a mixed solvent of a lower alcohol and a lower fatty acid ester.  
     
     
         8 . The method for producing an anti-fouling agent according to  claim 5  wherein the treatment temperature is from 40° C. to 100° C. and the treatment time is from 30 minutes to 10 hours in said heat treatment.  
     
     
         9 . The method for producing an anti-fouling agent according to  claim 4  wherein said polyvinyl alcohol and a base are dissolved in water.  
     
     
         10 . A method for producing a polymer wherein polymerization is conducted using a polymerization reactor having an inner wall covered with the anti-fouling agent according to  claim 1 .  
     
     
         11 . The method for producing a polymer according to  claim 10  wherein the polymerization is suspension polymerization or emulsion polymerization.  
     
     
         12 . The method for producing a polymer according to  claim 10  wherein the polymer is polyvinyl chloride.  
     
     
         13 . A polyvinyl alcohol for anti-fouling agents wherein said polyvinyl alcohol is obtained through saponification of a polyvinyl ester having monomer units that contains monomer units having a silyl group of formula (1):  
       
         
           
           
               
               
           
         
       
       wherein R 1  represents an alkyl group having from 1 to 5 carbon atoms; R 2  represents an alkoxyl or acyloxyl group optionally having an oxygen-containing substituent; and m indicates an integer of from 0 to 2,  
       and wherein the polyvinyl alcohol satisfies the following formulae (I) and (II):  
         370< P×S< 9000  (I)  
       wherein 
 P indicates the viscosity-average degree of polymerization of the polyvinyl alcohol,  
 and S indicates the content (mole %) of the monomer units having a silyl group of formula (1) in the polyvinyl alcohol;  
   0.2/100≦( A−B )/( B )≦75/100  (II),  
 wherein  
 A indicates the content (ppm) of silicon atoms in the polyvinyl alcohol,  
 and B indicates the content (ppm) of silicon atoms in the polyvinyl alcohol that was washed with sodium hydroxide-containing methanol and then washed with methanol by Soxhlet extraction, wherein A and B are measured by ICP emission spectrometry after ashing of a sample.