Stabilized pressure-hydrated magnesium hydroxide slurry from burnt magnesite and process for its production

Abstract

A stabilized, pressure-hydrated magnesium hydroxide slurry and a process for its production from burnt magnesite are described. According to an embodiment of the invention, a mixture comprising burnt natural magnesite and water is pressure hydrated to provide a pressure hydrated slurry. The pressure hydrated slurry is then deagglomerated. If desired, chloride ions and cationic polymer can be added to further stabilize the slurry.

We claim: 
     
       1. A process for the production of a stabilized magnesium hydroxide slurry comprising the steps of: .Iadd.providing chloride ions to a mixture comprising burnt natural magnesite and water and then .Iaddend.pressure hydrating .[.a.]. .Iadd.the .Iaddend.mixture .[.comprising burnt natural magnesite and water.]. to provide a precursory pressure hydrated magnesium hydroxide slurry;   providing .[.chloride ions and.]. cationic polymer .Iadd.to the precursory pressure hydrated magnesium hydroxide slurry.Iaddend.; .Iadd.and .Iaddend.   deagglomerating said precursory pressure hydrated magnesium hydroxide slurry .[.in the presence of said chloride ions and cationic polymer.]. to provide a deagglomerated and stabilized magnesium hydroxide slurry comprising from 50 to 65 weight % solids. .[.2. The method of claim 1,   
     
     
        wherein said chloride ions are provided prior to pressure hydration..].3. The method of claim .[.2.]. .Iadd.1.Iaddend., wherein said chloride ions are provided in an amount ranging from 0.01 to 2.5 weight % 
     
     
        of dry MgO. 4. The method of claim .[.2.]. .Iadd.1.Iaddend., wherein said chloride ions are provided in an amount ranging from 0.2 to 0.5 weight % 
     
     
        of dry MgO. 5. The method of claim 1, wherein said chloride ions are provided from at least one member selected from the group consisting of calcium chloride, sodium chloride, aluminum chloride, potassium chloride, 
     
     
        magnesium chloride, ammonium chloride and hydrated salts thereof. 6. The method of claim 1, wherein said chloride ions are provided from calcium 
     
     
        chloride. 7. The method of claim 1, wherein at least a portion of said chloride ions are provided by anions associated with said cationic 
     
     
        polymer. 8. The method of claim 1, wherein said cationic polymer is provided in an amount ranging from 0.01 to 2.0 weight % of slurry weight. 
     
     
         . The method of claim 1, wherein said cationic polymer is provided in an 
     
     
        amount ranging from 0.1 to 0.2 weight % of slurry weight. 10. The method 
     
     
        of claim 1, wherein said cationic polymer is a polyamine. 11. The method of claim 1, wherein said pressure hydration is conducted at pressures 
     
     
        ranging from 1 to 150 psig. 12. The method of claim 1, wherein said pressure hydration is conducted at pressures ranging from 25 to 100 psig. 
     
     
         3. The method of claim 1, wherein said deagglomerated slurry comprises 
     
     
        from 57 to 62 weight % solids. 14. The method of claim 1, wherein said burnt magnesite is finely divided and capable of passing through a 20 mesh 
     
     
        screen. 15. The method of claim 1, wherein said burnt magnesite is finely 
     
     
        divided and capable of passing through a 100 mesh screen. 16. The method of claim 1, wherein exothermic heat associated with the hydrating step is recovered.