Nonviscous aqueous dispersion compositions of water-swellable layered silicates and the method of producing the same

Abstract

Concentrated suspensions of smectite clays are obtained as either relatively “thin” or highly shear-thinning slurries that are easy to pump, by adding one or more of certain cationic polymers whose weight average molecular weight, Mw, is 50,000 or higher. It was found during the course of the invention that a cationic polymer with an Mw of 10,000 did not work, while the same polymer with a bimodal Mw of 50,000 and 30,000 worked satisfactorily. To achieve the full advantage of the present invention, the cationic polymer preferably has 1 to 10 milliequivalents of cationic charge per gram of the polymer, and more preferably 5 to 10 milliequivalents of cationic charge per gram of the polymer, and most preferably 6 to 8 milliequivalents of cationic charge per gram of the polymer.

1 . An aqueous suspension comprising a sodium smectite clay, and at least one water-soluble, cationic polymer with a weight average molecular weight of at least 50,000, wherein the amount of sodium smectite clay exceeds 20 weight percent based on the total weight of the aqueous suspension, and wherein the aqueous suspension has a Brookfield RV viscosity, at 10 rpm, less than 6,000 cps, when measured at 38% sodium smectite clay, based on the total weight of clay and water.  
   
   
       2 . The suspension of  claim 1  wherein the layered silicate is selected from the group consisting of smectite clays, lithium magnesium silicate (laponite), and a mixture thereof.  
   
   
       3 . (canceled)  
   
   
       4 . The suspension of  claim 1  wherein the amount of sodium smectite clay is from greater than 20 weight percent to 50 weight percent based on the total weight of the suspension.  
   
   
       5 . The suspension of  claim 4  wherein the amount of sodium smectite clay is from 25 weight percent to 50 weight percent based on the total weight of the suspension.  
   
   
       6 . The suspension of  claim 5  wherein the amount of sodium smectite clay is from 25 weight percent to 45 weight percent based on the total weight of the suspension.  
   
   
       7 . The suspension of  claim 1  wherein the weight ratio of sodium smectite clay to the cationic polymer is 2:1 to 1000:1.  
   
   
       8 . The suspension of  claim 7  wherein the amount of cationic polymer in the suspension is in the range of 0.1% to 50% based on the dry weight of sodium smectite clay.  
   
   
       9 . The suspension of  claim 8  wherein the amount of cationic polymer in the suspension is in the range of 8% to 30% based on the dry weight of sodium smectite clay.  
   
   
       10 . The suspension of  claim 9  wherein the amount of cationic polymer in the suspension is in the range of 10% to 25% based on the dry weight of sodium smectite clay.  
   
   
       11 . The suspension of  claim 1  wherein the cationic polymer has 1 to 10 milliequivalents of cationic charge per gram of the polymer.  
   
   
       12 . The suspension of  claim 11  wherein the cationic polymer has 5 to 10 milliequivalents of cationic charge per gram of the polymer.  
   
   
       13 . The suspension of  claim 12  wherein the cationic polymer has 6 to 8 milliequivalents of cationic charge per gram of the polymer.  
   
   
       14 . The suspension of  claim 1  wherein the suspension contains a mixture of a lower molecular weight cationic polymer and a higher molecular weight cationic polymer, at least one of which has a weight average molecular weight of at least 50,000.  
   
   
       15 . The suspension of  claim 14 , wherein the weight ratio of the lower molecular weight cationic polymer to the higher molecular weight cationic polymer is in the range of 10:1 to 1:10.  
   
   
       16 . The suspension of  claim 15 , wherein the weight ratio of the lower molecular weight cationic polymer to the higher molecular weight cationic polymer is in the range of 7:1 to 1:7.  
   
   
       17 . The suspension of  claim 16 , wherein the weight ratio of the lower molecular weight cationic polymer to the higher molecular weight cationic polymer is in the range of 1:1 to 1:7.  
   
   
       18 . A method of clarifying a wastewater containing suspended matter comprising adding to said wastewater an effective amount of the aqueous suspension of  claim 1  to flocculate or coagulate the suspended matter.  
   
   
       19 . The method of  claim 18 , comprising adding to said wastewater the sodium smectite clay and cationic polymer at a combined dry weight of 1 ppm to 10,000 ppm, based on the weight of the wastewater treated.  
   
   
       20 . The method of  claim 19 , comprising adding to said wastewater the sodium smectite clay and cationic polymer at a combined dry weight of 10 ppm to 1,000 ppm, based on the weight of the wastewater treated.  
   
   
       21 . The method of  claim 20 , comprising adding to said wastewater the sodium smectite clay and cationic polymer at a combined dry weight of 10 ppm to 500 ppm, based on the weight of the wastewater treated.  
   
   
       22 .- 26 . (canceled)  
   
   
       27 . A method of softening a fabric comprising contacting said fabric with an effective amount of the aqueous suspension of  claim 1 .  
   
   
       28 . The method of  claim 27 , wherein the aqueous suspension is diluted with water during fabric softening such that the concentration of sodium smectite clay and cationic polymer in said water is in the range of 0.001% to 5% by weight, based on the total weight of water.  
   
   
       29 . The method of  claim 28 , wherein the aqueous suspension is diluted with water such that the concentration of sodium smectite clay and cationic polymer in said water is in the range of 0.005% to 3.0% by weight, based on the total weight of water.  
   
   
       30 . The method of  claim 29 , wherein the aqueous suspension is diluted with water such that the concentration of sodium smectite clay and cationic polymer in said water is in the range of 0.1% to 2.5% by weight, based on the total weight of water.  
   
   
       31 . The method of  claim 30 , wherein the aqueous suspension is diluted with water such that the concentration of sodium smectite clay and cationic polymer in said water is in the range of 0.3% to 1.0% by weight, based on the total weight of water.  
   
   
       32 . A method of reducing the viscosity of an aqueous suspension of a having greater than 20 weight percent sodium smectite clay comprising shearing said suspension with a cationic polymer having a weight average molecular weight of at least 50,000, such that the aqueos suspension has a Brookfield RV viscosity, at 10 μm, less than 6,000 cps, when measured at 38% sodium smectite clay, based on the total weight of clay and water.