Methods for treating an inorganic slurry

Abstract

A method for treating an inorganic slurry to preserve the slurry against bacterial contamination, including (I) providing a slurry in a substantially homogeneous phase, and then (II) adding to the slurry an effective amount of a composition containing: (a) a tetrakis(hydroxyorgano)phosphonium salt selected from the group consisting of tetrakis (hydroxymethyl) phosphonium sulphate, tetrakis (hydroxymethyl) phosphonium chloride, tetrakis (hydroxymethyl) phosphonium phosphate, tetrakis (hydroxymethyl) phosphonium nitrate and tetrakis (hydroxymethyl) phosphonium oxalate; and (b) a dispersant selected from the group consisting of (i) a phosphonated compound containing at least one tertiary nitrogen atom and (ii) a homopolymer of an unsaturated acid; and (III) preserving the slurry against bacterial contamination, whilst avoiding instantaneous heterogeneous thickening of the slurry due to the tetrakis (hydroxyorgano) phosphonium salt.

1 . A method for treating an inorganic slurry to preserve the slurry against bacterial contamination, comprising the steps of:
 (I) providing a slurry in a substantially homogeneous phase, and then   (II) adding to the slurry an effective amount of a composition comprising:   (a) a tetrakis(hydroxyorgano)phosphonium salt selected from the group consisting of   
       tetrakis (hydroxymethyl) phosphonium sulphate, 
       tetrakis (hydroxymethyl) phosphonium chloride, 
       tetrakis (hydroxymethyl) phosphonium phosphate, 
       tetrakis (hydroxymethyl) phosphonium nitrate and 
       tetrakis (hydroxymethyl) phosphonium oxalate; and
 (b) a dispersant selected from the group consisting of (i) a phosphonated compound containing at least one tertiary nitrogen atom and (ii) a homopolymer of an unsaturated acid; and 
 (III) preserving the slurry against bacterial contamination, whilst avoiding instantaneous heterogeneous thickening of the slurry due to the tetrakis(hydroxyorgano)phosphonium salt. 
 
     
     
         2 . The method according to  claim 1 , wherein the tetrakis (hydroxyorgano)phosphonium salt is tetrakis(hydroxymethyl) phosphonium sulphate. 
     
     
         3 . The method according to  claim 1 , wherein the tetrakis (hydroxyorgano)phosphonium salt is tetrakis(hydroxymethyl) phosphonium chloride, phosphate, nitrate or oxalate. 
     
     
         4 . The method according to  claim 1 , wherein the dispersant (b(i)) is a phosphonated compound containing one tertiary nitrogen atom. 
     
     
         5 . The method according to  claim 4 , wherein the dispersant (b(i)) is a sodium salt of nitrilo-tris(methylene phosphonate). 
     
     
         6 . The method according to  claim 5 , wherein the salt is the tetra-sodium salt. 
     
     
         7 . The method according to  claim 1 , wherein the dispersant (b(ii)) is a homopolymer of acrylic acid. 
     
     
         8 . The method according to  claim 7 , wherein the homopolymer has a molecular weight in the range 2000 to 5000. 
     
     
         9 . The method according to  claim 1 , wherein the ratio of the tetrakis(hydroxyorgano)phosphonium salt to the dispersant in the composition is about 2:1, as active ingredients. 
     
     
         10 . The method according to  claim 1 , wherein the composition is added to the slurry in an amount in the range 10 ppm to 1000 ppm, by weight of the slurry. 
     
     
         11 . The method according to  claim 1 , wherein the composition is added to the slurry in an amount of about 750 ppm, by weight of the slurry. 
     
     
         12 . The method according to  claim 1 , wherein the slurry comprises a calcium carbonate-based slurry. 
     
     
         13 . The method according to  claim 1 , wherein the slurry comprises a pigment slurry, a clay slurry or a cement slurry. 
     
     
         14 . The method of  claim 1 , wherein the slurry being provided contains 70 to 80% by weight of undissolved suspended solids. 
     
     
         15 . The method of  claim 1 , wherein the slurry being provided comprises a calcium carbonate slurry that contains 70 to 80% or more, by weight, of undissolved suspended solids. 
     
     
         16 . The method of  claim 15 , wherein the dispersant is selected from the group consisting of (b)(i) a sodium salt of nitrilo-tris(methylene phosphonate) and (b)(ii) a homopolymer of acrylic acid having a molecular weight in the range of 2,000 to 5,000. 
     
     
         17 . The method of  claim 16 , wherein the composition is added to the slurry in an amount in the range 10 ppm to 1000 ppm, by weight of the slurry. 
     
     
         18 . A method for treating an inorganic slurry to preserve the slurry against bacterial contamination, comprising the steps of:
 (I) providing a slurry in a substantially homogeneous phase, and then   (II) adding to the slurry an effective amount of a composition comprising:   (a) a tetrakis (hydroxyorgano) phosphonium salt selected from the group consisting of   
       tetrakis (hydroxymethyl) phosphonium sulphate, 
       tetrakis (hydroxymethyl) phosphonium chloride, 
       tetrakis (hydroxymethyl) phosphonium phosphate, 
       tetrakis (hydroxymethyl) phosphonium nitrate and 
       tetrakis (hydroxymethyl) phosphonium oxalate; and
 (b) a dispersant which is the tetra sodium salt of nitrilo-tris (methylene phosphonate); and 
 (III) preserving the slurry against bacterial contamination, whilst avoiding instantaneous heterogeneous thickening of the slurry due to the tetrakis (hydroxyorgano) phosphonium salt. 
 
     
     
         19 . A method for treating an inorganic slurry to preserve the slurry against bacterial contamination, comprising the steps of:
 (I) providing a slurry in a substantially homogeneous phase, and then   (II) adding to the slurry an effective amount of a composition comprising:   (a) a tetrakis (hydroxyorgano) phosphonium salt selected from the group consisting of   
       tetrakis (hydroxymethyl) phosphonium sulphate, 
       tetrakis (hydroxymethyl) phosphonium chloride, 
       tetrakis (hydroxymethyl) phosphonium phosphate, 
       tetrakis (hydroxymethyl) phosphonium nitrate and 
       tetrakis (hydroxymethyl) phosphonium oxalate; and
 (b) a dispersant which is a homopolymer of acrylic acid, the homopolymer having a molecular weight in the range of 2,000 to 5,000, and 
 (III) preserving the slurry against bacterial contamination, whilst avoiding instantaneous heterogeneous thickening of the slurry due to the tetrakis (hydroxyorgano) phosphonium salt.