Hydrophilized substrate, dispersion, and making method

Abstract

A powder is hydrophilized by treating surfaces of particles with a hydrolyzable silyl group-containing acid anhydride compound, dispersing the surface treated particles in water, adding a base, and heating the dispersion for thereby hydrolyzing the acid anhydride moiety to open its ring and neutralizing the resultant carboxylic acid with the base. The hydrophilized powder is fully dispersible in aqueous media.

1 . A hydrophilized substrate having on its surface a surface treatment layer comprising a hydrolyzable silyl group-containing acid anhydride compound wherein carboxylic acid resulting from ring-opening of the acid anhydride moiety is partially or completely neutralized with a base, said acid anhydride compound having the general formula (1): 
     
       
         
         
             
             
         
       
     
     wherein R 1  is hydrogen or C 1 -C 6  alkyl, R 2  is each independently an organic group selected from the group consisting of C 1 -C 30  alkyl, aryl, aralkyl, and fluoroalkyl, A is a straight or branched C 2 -C 6  alkylene, a is an integer of 1 to 3, b is an integer of 0 to 2, and a+b=3. 
   
   
       2 . The hydrophilized substrate of  claim 1  wherein the acid anhydride compound has the general formula (2): 
     
       
         
         
             
             
         
       
     
     wherein R 3  is methyl or ethyl. 
   
   
       3 . The hydrophilized substrate of  claim 1  wherein the base is selected from the group consisting of NaOH, KOH, ammonia, monoethanolamine, diethanolamine, triethanolamine, and triethylamine, and mixtures thereof. 
   
   
       4 . The hydrophilized substrate of  claim 1  wherein the base is used in an equivalent amount which is 0.1 to 2 times the total equivalent amount of carboxylic acid resulting from ring-opening of the acid anhydride moiety. 
   
   
       5 . The hydrophilized substrate of  claim 1  wherein the substrate is a powder. 
   
   
       6 . The hydrophilized powder of  claim 5  wherein the powder is an inorganic powder. 
   
   
       7 . The hydrophilized powder of  claim 6  wherein the powder is zinc oxide. 
   
   
       8 . The hydrophilized powder of  claim 6  wherein the powder is titanium oxide. 
   
   
       9 . The hydrophilized powder of  claim 5 , which is obtained by treating surfaces of powder particles with the hydrolyzable silyl group-containing acid anhydride compound having the general formula (1) in an amount of 0.01 to 30 parts by weight per 100 parts by weight of the powder. 
   
   
       10 . A dispersion comprising the hydrophilized powder of  claim 5  dispersed in water, a water-soluble solvent, or a mixture of water and a water-soluble solvent. 
   
   
       11 . A method for preparing a hydrophilized substrate, comprising the steps of:
 (A) treating a surface of a substrate with a hydrolyzable silyl group-containing acid anhydride compound having the general formula (1):   
     
       
         
         
             
             
         
       
     
     wherein R 1  is hydrogen or C 1 -C 6  alkyl, R 2  is each independently an organic group selected from the group consisting of C 1 -C 30  alkyl, aryl, aralkyl, and fluoroalkyl, A is a straight or branched C 2 -C 6  alkylene, a is an integer of 1 to 3, b is an integer of 0 to 2, and a+b=3,
 (B) immersing the surface treated substrate in water or a mixture of water and a solvent, adding a base thereto, and heating the liquid for thereby hydrolyzing the acid anhydride moiety to open its ring and neutralizing the resultant carboxylic acid, and 
 (C) removing water and the solvent until the substrate is dry. 
 
   
   
       12 . The method of  claim 11  wherein the substrate is a powder. 
   
   
       13 . A method for preparing a dispersion of hydrophilized powder, comprising the steps of:
 (A) treating surfaces of powder particles with a hydrolyzable silyl group-containing acid anhydride compound having the general formula (1):   
     
       
         
         
             
             
         
       
     
     wherein R 1  is hydrogen or C 1 -C 6  alkyl, R 2  is each independently an organic group selected from the group consisting of C 1 -C 30  alkyl, aryl, aralkyl, and fluoroalkyl, A is a straight or branched C 2 -C 6  alkylene, a is an integer of 1 to 3, b is an integer of 0 to 2, and a+b=3,
 (B) immersing the surface treated powder in water or a mixture of water and a solvent, adding a base thereto, and heating the liquid for thereby hydrolyzing the acid anhydride moiety to open its ring and neutralizing the resultant carboxylic acid, and 
 (C) feeding the liquid from step (B) to a dispersing machine for finely dispersing the powder particles.