Method of making a gypsum slurry with modifiers and dispersants

Abstract

In a method of making a gypsum slurry, a polycarboxylate dispersant, a modifier and a hydraulic material comprising stucco are selected for use in the slurry. These components are then combined with water to form a slurry, where the modifier is added to the slurry prior to formation of a slurry phase by the water, the stucco and the dispersant. The modifier has been shown to be less effective when added after the dispersant and stucco have been contacted in an aqueous slurry. In a preferred embodiment, an amount of stucco is obtained and the modifier and dispersant are selected. A predissolved solution of a dispersant and modifier is prepared in water to form a solution prior to the addition of the stucco. After mixing the solution, the stucco is added to form the slurry. Optionally, the slurry is then shaped into a product and allowed to set.

1 . A method of making a gypsum slurry comprising: 
 obtaining an amount of dry components comprising stucco,    predissolving a modifier and a dispersant in water to form a solution, and    mixing the solution and the dry components to form a gypsum slurry.    
   
   
       2 . The method of  claim 1  wherein the modifier in said predissolving step comprises at least one of the group consisting of lime, quicklime, a silicate, a phosphate, a phosphonate and a carbonate.  
   
   
       3 . The method of  claim 2  wherein the modifier comprises at least one of the group consisting of sodium carbonate, potassium carbonate, calcium oxide and sodium silicate.  
   
   
       4 . The method of  claim 1  wherein said predissolving step comprises adding the modifier and the dispersant to the water essentially simultaneously.  
   
   
       5 . The method of  claim 1  wherein the modifier is added to the water before the dispersant in said predissolving step.  
   
   
       6 . The method of  claim 1  wherein the dispersant in said predissolving step is a polycarboxylic ether dispersant.  
   
   
       7 . The method of  claim 6  wherein the dispersant in said predissolving step comprises vinyl ether repeating units.  
   
   
       8 . The method of  claim 1  wherein said predissolving step further comprises combining the modifier with a portion of the water to form a modifier slurry, prior to predissolving the modifier slurry and dispersant in the remaining portion of water.  
   
   
       9 . The method of  claim 1  wherein the dry components comprise at least 50% stucco by weight.  
   
   
       10 . A method of making a gypsum product comprising: 
 obtaining an amount of dry components comprising stucco,    predissolving a modifier and a dispersant into water to form a solution,    mixing the solution and the dry components to form a gypsum slurry,    shaping the gypsum slurry into a product, and    allowing the slurry to set.    
   
   
       11 . The method of  claim 10  further comprising drying the product in a kiln.  
   
   
       12 . The method of  claim 10  wherein the dry components comprise at least 50% stucco by weight.  
   
   
       13 . The method of  claim 10  wherein the product is a gypsum panel.  
   
   
       14 . The method of  claim 13  wherein said shaping step further comprises sandwiching the slurry between two pieces of facing material.  
   
   
       15 . The method of  claim 13  wherein the dispersant comprises an acrylic repeating unit and a vinyl ether repeating unit.  
   
   
       16 . The method of  claim 10  wherein the dispersant comprises a polycarboxylic ether.  
   
   
       17 . The method of  claim 10  wherein the dry components further comprise at least one selected from the group consisting of strength enhancers, set accelerators, set retarders, starch, fibers and biocides.  
   
   
       18 . A method of making a gypsum slurry comprising: 
 selecting a polycarboxylate dispersant, a modifier and a hydraulic material comprising stucco; and    combining the polycarboxylate dispersant, the modifier, the hydraulic material and water together to form a slurry, wherein the modifier is added to at least one of the water, stucco and dispersant prior to formation of the slurry phase by the water, the stucco and the dispersant.    
   
   
       19 . The method of  claim 18  wherein the dispersant is in a dry form and said combining step further comprises predissolving the modifier in the water and the dispersant is added to the stucco to make a stucco-dispersant mixture, then adding the stucco-dispersant mixture to the predissolved modifier in the water.  
   
   
       20 . A product made by the method of  claim 10 .  
   
   
       21 . The product of  claim 20  wherein the product is a gypsum panel.  
   
   
       22 . The product of  claim 20  wherein the product is a floor or floor underlayment.  
   
   
       23 . The product of  claim 20  wherein the product is a cast product.