Hyperplaty clays and their use in paper coating and filling, methods for making same, and paper products having improved brightness

Abstract

The present invention relates to a hydrous kaolin product having improved optical properties, for example, when used in the production of paper products. The present invention comprises an improved barrier coating for paper and a method of making the coated paper. The present invention also comprises an improved method from making filled and coated paper products. The present invention uses a composition comprising kaolin having a shape factor of at least about 70:1, such as at least about 80:1 or at least about 100:1.

We claim:  
     
         1 . A composition comprising kaolin having a shape factor of at least about 70:1.  
     
     
         2 . The composition according to  claim 1 , wherein the kaolin has a shape factor of at least about 80:1.  
     
     
         3 . The composition according to  claim 1 , wherein the kaolin has a shape factor of at least about 90:1  
     
     
         4 . The composition according to  claim 1 , wherein the kaolin has a shape factor of at least about 100:1  
     
     
         5 . A coating composition, comprising: 
 kaolin having a shape factor of at least about 70:1;    a binder; and    optionally a dispersant.    
     
     
         6 . The composition according to  claim 5 , further comprising an additional pigment.  
     
     
         7 . The composition according to  claim 6 , wherein the additional pigment is TiO 2 .  
     
     
         8 . The composition according to  claim 7 , wherein said composition has a ratio of kaolin to TiO 2  of less than about 85:15 parts by weight.  
     
     
         9 . A filler comprising kaolin having a shape factor of at least about 70:1.  
     
     
         10 . The filler according to  claim 9 , wherein the kaolin has a shape factor of at least about 80:1.  
     
     
         11 . The filler according to  claim 9 , wherein the kaolin has a shape factor of at least about 90:1.  
     
     
         12 . The filler according to  claim 9 , wherein the kaolin has a shape factor of at least about 100:1.  
     
     
         13 . A method of making a coated paper comprising: 
 coating a fibrous substrate with a paper coating composition comprising a filler comprising kaolin having a shape factor of at least about 70:1.    
     
     
         14 . The method according to  claim 13 , wherein the kaolin has a shape factor of at least about 80:1.  
     
     
         15 . The method according to  claim 13 , wherein the kaolin has a shape factor of at least about 90:1  
     
     
         16 . The method according to  claim 13 , wherein the kaolin has a shape factor of at least about 100:1.  
     
     
         17 . A method of making a filled paper comprising 
 providing a fibrous substrate;    adding to said substrate kaolin having a shape factor of at least about 70:1.    
     
     
         18 . The method according to  claim 17 , further comprising adding a retention aid.  
     
     
         19 . The method according to  claim 17 , wherein the kaolin has a shape factor of at least about 80:1.  
     
     
         20 . The method according to  claim 17 , wherein the kaolin has a shape factor of at least about 90:1.  
     
     
         21 . The method according to  claim 17 , wherein the kaolin has a shape factor of least about 100:1.  
     
     
         22 . A coated paper comprising: 
 a fibrous substrate; and    a coating on said substrate comprising kaolin having a shape factor of at least about 70:1.    
     
     
         23 . The method according to  claim 22 , wherein the kaolin has a shape factor of at least about 80:1.  
     
     
         24 . The method according to  claim 22 , wherein the kaolin has a shape factor of at least about 90:1.  
     
     
         25 . The method according to  claim 22 , wherein the kaolin has a shape factor of at least about 100:1.  
     
     
         26 . A method of improving barrier properties in paper comprising: 
 coating a fibrous substrate with a coating composition comprising kaolin having a shape factor of at least about 70:1.    
     
     
         27 . The method according to  claim 26 , wherein said coating further comprises a binder.  
     
     
         28 . The method according to  claim 27 , wherein said binder is a latex binder.  
     
     
         29 . The method according to  claim 27 , wherein said binder is present in an amount ranging from about 40% to about 50% by weight.  
     
     
         30 . The method according to  claim 26 , wherein the kaolin has a shape factor of at least about 80:1.  
     
     
         31 . The method according to  claim 26 , wherein the kaolin has a shape factor of at least about 90:1.  
     
     
         32 . The method according to  claim 26 , wherein the kaolin has a shape factor of at least about 100:1.  
     
     
         33 . A method of refining kaolin, comprising: 
 providing a kaolin slurry;    attrition grinding the kaolin slurry;    removing a coarse particle size fraction from the slurry by centrifugation; and    attrition grinding the coarse-particle size fraction to provide a kaolin product having a shape factor of at least about 70:1.    
     
     
         34 . The method according to  claim 33 , wherein the kaolin slurry comprises whole crude kaolin or a blend of whole crude and coarse-particle size fractions from a centrifuge.  
     
     
         35 . The method according to  claim 33 , wherein the kaolin product has a shape factor ranging from about 70:1 to about 140:1.  
     
     
         36 . The method according to  claim 33 , wherein the kaolin product has a shape factor ranging from about 80:1 to about 100:1.  
     
     
         37 . The method according to  claim 33 , wherein the kaolin slurry is beneficiated prior to the attrition grinding.  
     
     
         38 . The method according to  claim 33 , wherein the kaolin slurry is degritted prior to the attrition grinding.  
     
     
         39 . The method according to  claim 33 , wherein the kaolin slurry comprises a blunged-degritted-brightness beneficiated slurry.  
     
     
         40 . The method according to  claim 33 , wherein the coarse particle size fraction that is removed comprises kaolin particles comprising from 80% to 95% by weight of the particles having an esd of less than 2 μm.  
     
     
         41 . The method according to  claim 33 , wherein the kaolin product resulting from attrition grinding the coarse particle size fraction comprises particles having an esd ranging from 0.2 μm to 1.7 μm.  
     
     
         42 . The method according to  claim 33 , wherein the kaolin product resulting from attrition grinding the coarse particle size fraction comprises particles having a shape factor value ranging from 80:1 to 110:1.  
     
     
         43 . The method according to  claim 33 , wherein the kaolin product has a shape factor of at least about 80:1.  
     
     
         44 . The method according to  claim 33 , wherein the kaolin product has a shape factor of at least about 90:1.  
     
     
         45 . The method according to  claim 33 , wherein the kaolin product has a shape factor of at least about 100:1.  
     
     
         46 . An extender for paint comprising kaolin, prepared by a method comprising: 
 providing a kaolin slurry comprising whole crude kaolin or a blend of whole crude and coarse-particle size fractions from a centrifuge;    attrition grinding the kaolin slurry;    removing a coarse particle size fraction from the slurry by centrifugation; and    attrition grinding the coarse-particle size fraction to provide a kaolin product having a shape factor of at least about 70:1.    
     
     
         47 . The extender according to  claim 46 , wherein the kaolin product has a d 50  ranging from 0.1 μm to 2.0 μm.  
     
     
         48 . The extender according to  claim 46 , wherein the kaolin product has a d 50  ranging from 0.5 μm to 1.5 μm.  
     
     
         49 . The extender according to  claim 46 , wherein the kaolin product has a shape factor ranging from about 80:1 to about 100:1.  
     
     
         50 . The extender according to  claim 46 , wherein the kaolin product has a shape factor of at least about 80:1.  
     
     
         51 . The extender according to  claim 46 , wherein the kaolin product has a shape factor of at least about 90:1.  
     
     
         52 . The extender according to  claim 46 , wherein the kaolin product has a shape factor of at least about 100:1.  
     
     
         53 . A barrier coating composition, comprising a slurry comprising kaolin having a shape factor of at least about 70:1, the solids content of the slurry ranging from about 45% to about 70%.  
     
     
         54 . The barrier coating composition according to  claim 53 , wherein the kaolin has a shape factor of at least about 80:1.  
     
     
         55 . The barrier coating composition according to  claim 53 , wherein the kaolin has a shape factor of at least about 90:1.  
     
     
         56 . The barrier coating composition according to  claim 53 , wherein the kaolin has a shape factor of at least about 100:1.  
     
     
         57 . A slurry comprising kaolin having a shape factor of greater than 70:1 and a stabilizing agent.  
     
     
         58 . The slurry according to  claim 57 , wherein said stabilizing agent comprises carboxymethylcellulose.  
     
     
         59 . The slurry according to  claim 57 , wherein said stabilizing agent comprises a smectite clay.  
     
     
         60 . The slurry according to  claim 57 , wherein said stabilizing agent comprises bentonite.  
     
     
         61 . The slurry according to  claim 57 , wherein said stabilizing agent comprises hectorite.  
     
     
         62 . The slurry according to  claim 57 , wherein said stabilizing agent is present in the slurry in an amount ranging from about 4 pounds per dry tonne kaolin to about 10 lbs per dry tonne kaolin.  
     
     
         63 . The slurry according to  claim 57 , wherein said slurry has a solids content of greater than about 45%.  
     
     
         64 . The slurry according to  claim 57 , wherein said slurry has a solids content ranging from about 50% to about 60%.