Process for removing impurities from kaolin clays

Abstract

An improved process for the selective flocculation of impurities from clays is disclosed. The process comprises blunging the clay in the presence of dispersing agents, conditioning the blunged clay with aliphatic or aromatic hydroxamic acids, or salts thereof, flocculating the impurities with a high molecular weight polymeric flocculant, particularly polymers containing hydroxamate groups, and removing the flocculated impurities from the unflocculated clay. The use of hydroxamic conditioning agents improves the removal of impurities from the clay, thereby providing a clay product having high brightness and low level impurities. The hydroxamic acid conditioning agents may advantageously be used in combination with other conditioning additives and with a wide variety of polymeric flocculating agents.

We claim:  
     
         1 . A process for removing colored impurities from clay comprising the steps of: 
 a) blunging the clay with a dispersing agent, or a combination of dispersing agents, in water to form an aqueous clay dispersion;    b) forming a conditioned dispersion by treating the aqueous clay dispersion with a conditioning agent, or a mixture of conditioning agents, represented by the formula:      R−C ( =O ) N ( R″ )− OM      wherein R is linear or branched C 2 -C 18  alkyl, linear or branched C 2 -C 18  alkenyl, C 6 -C 20  aryl, substituted aryl, C 7 -C 26  aralkyl or substituted aralkyl; R″ is H, C 1 -C 12  alkyl or aralkyl; and M is hydrogen, an alkali metal or ammonium, wherein the substituted aryl or substituted aralkyl are substituted on aryl with hydroxy, C 1 -C 6  alkoxy, or C 1 -C 6  alkyl, to form a conditioned dispersion;    c) treating the conditioned dispersion with a flocculating agent comprising a water soluble or water dispersible organic polymer to flocculate the impurities; and    d) removing the flocculated impurities to form a purified clay dispersion.    
     
     
         2 . The process according to    claim 1   , wherein the clay is a kaolin clay.  
     
     
         3 . The process according to    claim 1   , wherein the dispersing agent is selected from the group consisting of sodium silicate, sodium polyacrylate, and sodium carbonate.  
     
     
         4 . The process according to    claim 1   , comprising blunging the clay with a dispersing agent, or combination of dispersing agents, and a pH modifying agent, in water.  
     
     
         5 . The process according to    claim 1   , wherein the pH modifying agent is sodium hydroxide or ammonium hydroxide.  
     
     
         6 . The process according to    claim 1   , wherein the conditioning agent is a hydroxamic acid, or salt thereof, or a mixture of hydroxamic acids, or salts thereof, represented by the formula:  
         R−C ( =O ) N ( R″ ) −OM    wherein R is an aralkyl moiety selected from the group consisting of (R′-phenyl), (R′-hydroxy-phenyl), (R′-naphthyl), or (R′-hydroxy-naphthyl), wherein R′ is linear or branched C 1 -C 12  alkyl, or linear or branched C 2 -C 12  alkenyl.    
     
     
         7 . The process according to    claim 1   , wherein the conditioning agent is a hydroxamic acid, or salt thereof, or a mixture of hydroxamic acids, or salts thereof, represented by the formula:  
         R−C ( =O ) NH−OM    wherein R is linear or branched C 8 -C 12  alkyl or linear, branched C 8 -C 12  alkenyl, C 6 -C 20  aryl, or substituted aryl, and M is hydrogen, an alkali metal or ammonium, wherein the substituted aryl is substituted with hydroxy, C 1 -C 6  alkoxy, or C 1 -C 6  alkyl.    
     
     
         8 . The process according to    claim 1   , wherein the water soluble or water dispersible organic polymer is an anionic or a non-ionic polymer having a molecular weight in the range of about 0.5 million to about 30 million.  
     
     
         9 . The process according to    claim 1   , wherein the water soluble or water dispersible organic polymer is an anionic or a non-ionic polymer having a molecular weight in the range of about 1 million to about 20 million.  
     
     
         10 . The process according to    claim 1   , wherein the water soluble or water dispersible organic polymer contains at lease one hydroxamic acid moiety, or salts thereof.  
     
     
         11 . The process according to    claim 1   , comprising forming a conditioned dispersion by treating the aqueous clay dispersion with a conditioning agent, or a mixture of conditioning agents, and at least one conditioning additive, wherein said conditioning additive is selected from the group consisting of an aliphatic alcohol, a hydrocarbon oil, a carboxylic acid ester oil, and a fatty acid having the formula:  
         R−C ( =O ) OM    wherein R is a C 10 -C 18  alkyl, C 6 -C 20  aryl, substituted aryl, C 7 -C 26  aralkyl or substituted aralkyl, and M is hydrogen, an alkali metal or ammonium, wherein the substituted aryl or substituted aralkyl are substituted on aryl with hydroxy, C 1 -C 6  alkoxy, or C 1 -C 6  alkyl.    
     
     
         12 . The process according to    claim 11   , wherein the aliphatic alcohol is decanol or dodecanol.  
     
     
         13 . The process according to    claim 1   , further comprising the step of treating the aqueous clay dispersion with a salt containing a polyvalent metal cation.  
     
     
         14 . The process according to    claim 13   , wherein the salt is calcium chloride.  
     
     
         15 . A process for removing colored impurities from clay comprising the steps of: 
 a) blunging the clay with a dispersing agent, or a combination of dispersing agents, in water to form an aqueous clay dispersion;    b) treating the aqueous clay dispersion with a conditioning composition comprising at least one conditioning agent and at least one conditioning additive, wherein 
 (i) the at least one conditioning agent is represented by the formula:  
 R−C( =O ) N ( R″ )− OM    
   
   wherein R is linear or branched C 2 -C 18  alkyl, linear or branched C 2 -C 18  alkenyl, C 6 -C 20  aryl, substituted aryl, C 7 -C 26  aralkyl or substituted aralkyl; R″ is H, C 1 -C 12  alkyl or aralkyl; and M is hydrogen, an alkali metal or ammonium, wherein the substituted aryl or substituted aralkyl are substituted on aryl with hydroxy, C 1 -C 6  alkoxy, or C 1 -C 6  alkyl, to form a conditioned dispersion; and 
 (ii) the at least one conditioning additive is a fatty acid represented by the formula:  
   R−C ( =O ) OM    
   wherein R is a C 10 -C 18  alkyl, C 6 -C 20  aryl, substituted aryl, C 7 -C 26  aralkyl or substituted aralkyl, and M is hydrogen, an alkali metal or ammonium, wherein the substituted aryl or substituted aralkyl are substituted on aryl with hydroxy, C 1 -C 6  alkoxy, or C 1 -C 6  alkyl, to form a conditioned clay dispersion;    c) flocculating the conditioned clay dispersion by treatment with a flocculating agent comprising a water dispersible organic polymer, to form flocculated impurities; and    d) removing the flocculated impurities to form a purified clay dispersion.    
     
     
         16 . The process according to    claim 15   , wherein the clay is a kaolin clay.  
     
     
         17 . The process according to    claim 15   , wherein the dispersing agent is selected from the group consisting of sodium silicate, sodium polyacrylate, and sodium carbonate.  
     
     
         18 . The process according to    claim 15   , comprising blunging the clay with a dispersing agent, or combination of dispersing agents, and a pH modifying agent, in water.  
     
     
         19 . The process according to    claim 15   , wherein the pH modifying agent is sodium hydroxide or ammonium hydroxide.  
     
     
         20 . The process according to    claim 15   , wherein the conditioning agent is a hydroxamic acid, or salt thereof, or a mixture of hydroxamic acids, or salts thereof, represented by the formula:  
         R−C ( =O ) N ( R″ ) −OM    wherein R is an aralkyl moiety selected from the group consisting of (R′-phenyl), (R′-hydroxy-phenyl), (R′-naphthyl), or (R′-hydroxy-naphthyl), wherein R′ is linear or branched C 1 -C 12  alkyl, or linear or branched C 2 -C 12  alkenyl.    
     
     
         21 . The process according to    claim 15   , wherein the conditioning agent is a hydroxamic acid, or salt thereof, or a mixture of hydroxamic acids, or salts thereof, represented by the formula:  
         R−C ( =O ) NH−OM    wherein R is linear or branched C 8 -C 12  alkyl or linear, branched C 8 -C 12  alkenyl, C 6 -C 20  aryl, or substituted aryl, and M is hydrogen, an alkali metal or ammonium, wherein the substituted aryl is substituted with hydroxy, C 1 -C 6  alkoxy, or C 1 -C 6  alkyl.    
     
     
         22 . The process according to    claim 15   , wherein the fatty acid is a compound represented by the formula:  
         R−C ( =O ) OM    wherein R is a C 16 -C 18  alkyl, C 6 -C 20  aryl, substituted aryl, C 7 -C 26  aralkyl or substituted aralkyl, and M is hydrogen, an alkali metal or ammonium, wherein the substituted aryl or substituted aralkyl are substituted on aryl with hydroxy, C 1 -C 6  alkoxy, or C 1 -C 6  alkyl.    
     
     
         23 . The process according to    claim 15   , wherein the fatty acid is oleic acid.  
     
     
         24 . The process according to    claim 15   , comprising treating the aqueous clay dispersion with at least two conditioning additives, wherein the second conditioning additive is selected from the group consisting of an aliphatic alcohol, a hydrocarbon oil and a carboxylic acid ester oil.  
     
     
         25 . The process according to    claim 24   , wherein the aliphatic alcohol is decanol or dodecanol.  
     
     
         26 . The process according to    claim 15   , further comprising the step of treating the aqueous clay dispersion with a salt containing a polyvalent metal cation.  
     
     
         27 . The process according to    claim 26   , wherein the salt is calcium chloride.  
     
     
         28 . The process according to    claim 15   , wherein the water soluble or water dispersible organic polymer is an anionic or a non-ionic polymer having a molecular weight in the range of about 0.5 million to about 30 million.  
     
     
         29 . The process according to    claim 15   , wherein the water soluble or water dispersible organic polymer is an anionic or a non-ionic polymer having a molecular weight in the range of about 1 million to about 20 million.  
     
     
         30 . The process according to    claim 15   , wherein the water soluble or water dispersible organic polymer contains at lease one hydroxamic acid moiety, or salts thereof.  
     
     
         31 . A process for removing colored impurities from clay comprising the steps of: 
 a) blunging the clay with a dispersing agent, or a combination of dispersing agents, in water to form an aqueous clay dispersion;    b) treating the aqueous clay dispersion with a conditioning agent represented by the formula:      R−C ( =O ) OM      wherein R is C 10 -C 18  alkyl, C 6 -C 20  aryl, substituted aryl, C 7 -C 26  aralkyl or substituted aralkyl, and M is hydrogen, an alkali metal or ammonium, wherein the substituted aryl or substituted aralkyl are substituted on aryl with hydroxy, C 1 -C 6  alkoxy, or C 1 -C 6  alkyl;    c) flocculating the conditioned clay dispersion by treatment with a flocculating agent comprising a water soluble or water dispersible organic polymer containing hydroxamic acid groups or salts thereof, to form flocculated impurities; and    d) removing the flocculated impurities to form a purified clay dispersion.    
     
     
         32 . The process according to    claim 31   , wherein the clay is a kaolin clay.  
     
     
         33 . The process according to    claim 31   , wherein the dispersing agent is selected from sodium silicate, sodium polyacrylate, and sodium carbonate.  
     
     
         34 . The process according to    claim 31   , wherein the water soluble or water dispersible flocculant is an organic polymer containing hydroxamic acid groups or salts thereof having a molecular weight in the range of about 0.5 million to about 30 million.  
     
     
         35 . The process according to    claim 31   , wherein the water soluble or water dispersible flocculant is an organic polymer containing hydroxamic acid groups or salts thereof having a molecular weight in the range of about 1 million to about 20 million.  
     
     
         36 . The process according to    claim 31   , further comprising treating the clay dispersion with at least one conditioning additive selected from the group consisting of an aliphatic alcohol, a hydrocarbon oil and a carboxylic acid ester oil.  
     
     
         37 . The process according to    claim 31   , wherein the additive is decanol or dodecanol.  
     
     
         38 . The process according to    claim 31   , further comprising the step of treating the aqueous clay dispersion with a salt containing a polyvalent metal cation.  
     
     
         39 . The process according to    claim 31   , wherein the salt containing a polyvalent metal cation is calcium chloride.  
     
     
         40 . A process for removing colored impurities from clay comprising the following steps: 
 a) blunging the clay with sodium silicate and sodium polyacrylate in water to form an aqueous clay dispersion;    b) treating the aqueous clay dispersion with a oleic acid fatty acid and calcium chloride,    c) flocculating the conditioned clay dispersion by treatment with hydroxamated polyacrylamide of molecular weight of about 10-20 million, to form flocculated impurities; and    d) removing the flocculated impurities to form a purified clay dispersion.    
     
     
         41 . The process according to    claim 40   , wherein the conditioning agent further comprises an additive selected from aliphatic alcohol, hydrocarbon oil or a carboxylic acid ester oil.  
     
     
         42 . The process according to    claim 41   , wherein the additive is decanol or dodecanol.  
     
     
         43 . The process according to    claim 40   , further comprising the step of treating the aqueous clay dispersion with a salt containing a polyvalent metal cation.  
     
     
         44 . The process according to    claim 43   , wherein the salt containing a polyvalent metal cation is calcium chloride.  
     
     
         45 . A process for removing colored impurities from kaolin clay comprising the following steps: 
 a) blunging the clay with sodium silicate and sodium polyacrylate in water to form an aqueous clay dispersion;    b) treating the aqueous clay dispersion with a mixture of C 8 -C 10  hydroxamic acid and C 12  alcohol;    c) flocculating the conditioned clay dispersion by treatment with hydroxamated polyacrylamide of molecular weight of about 10-20 million, to form flocculated impurities; and    d) removing the flocculated impurities to form a purified clay dispersion.    
     
     
         46 . The process according to    claim 45   , further comprising blunging the clay with sodium hydroxide or ammonium hydroxide.  
     
     
         47 . The process according to    claim 45   , further comprising treating the aqueous clay dispersion with oleic acid.  
     
     
         48 . The process according to    claim 45   , further comprising treating the aqueous clay dispersion with calcium chloride.