Production of pcc

Abstract

The present invention is directed to a process for producing an aqueous suspension of precipitated calcium carbonate, wherein a milk of lime is prepared by mixing water, a calcium oxide containing material, at least one water-soluble polymer having a molecular weight Mw in the range from 200 to 6500 g/mol, and at least one slaking additive, and subsequently, the milk of lime is carbonated to form an aqueous suspension of precipitated calcium carbonate.

1 . An aqueous suspension of precipitated calcium carbonate obtained by a process comprising the steps of:
 i) providing a calcium oxide containing material,   ii) providing at least one water-soluble polymer having a molecular weight M w  in the range from 200 to 6500 g/mol, wherein the at least one polymer has the chemical structure of formula (I):   
       
         
           
           
               
               
           
         
         wherein n, m, and p are integers and at least one of n, m, or p is greater than zero and n+m+p is less than or equal to 70, 
         R 1  is H or CH 3 , 
         R 2  is H or CH 3 , 
         R 3  is —C(═O)—O—R 4  or —C(═O)—NH—R 4 , wherein R 4  is a C 1  to C 20  alkyl group, a C 3  to C 20  cycloalkyl group and/or a C 6  to C 30  aryl group, being optionally substituted with one or more sulfonate groups, and wherein the cycloalkyl group and/or the aryl group comprises one ring or several rings, which are linked to each other, 
         R 5  is H or CH 3 , 
         R 6  is H or CH 3 , and 
         X is H and/or M, wherein M is Na, K, Li, Mg, and/or Ca, and 
       
       wherein the structural units 
       
         
           
           
               
               
           
         
       
       are arranged randomly, regularly and/or in blocks,
 iii) providing at least one slaking additive, wherein the at least one slaking additive is selected from the group consisting of organic acids, organic acid salts, sugar alcohols, monosaccharides, disaccharides, polysaccharides, gluconates, phosphonates, lignosulfonates, and mixtures thereof, 
 iv) preparing a milk of lime by mixing water, the calcium oxide containing material of step i), the at least one polymer of step ii), and the at least one slaking additive of step iii), wherein the calcium oxide containing material and the water are mixed in a weight ratio from 1:1 to 1:12, and 
 v) carbonating the milk of lime obtained from step iv) to form an aqueous suspension of precipitated calcium carbonate. 
 
     
     
         2 . The aqueous suspension of precipitated calcium carbonate of  claim 1 , wherein the at least one polymer has the chemical structure of formula (II): 
       
         
           
           
               
               
           
         
         wherein n, m, and p are integers and at least one of n, m, or p is greater than zero and n+m+p is less than or equal to 70, 
         R 1  is H or CH 3 , 
         R 2  is H or CH 3 ; 
         R 3  is —C(═O)—O—R 4  or —C(═O)—NH—R 4 , wherein R 4  is a C 1  to C 20  alkyl group, a C 3  to C 20  cycloalkyl group and/or a C 6  to C 30  aryl group, being optionally substituted with one or more sulfonate groups, and wherein the cycloalkyl group and/or the aryl group comprises one ring or several rings, which are linked to each other, and 
         X is H and/or M, wherein M is Na, K, Li, Mg, and/or Ca, and 
       
       wherein the structural units 
       
         
           
           
               
               
           
         
       
       are arranged randomly, regularly and/or in blocks. 
     
     
         3 . The aqueous suspension of precipitated calcium carbonate of  claim 1 , wherein R 1  is H and R 5  is H. 
     
     
         4 . The aqueous suspension of precipitated calcium carbonate of  claim 1 , wherein in step iv) the calcium oxide containing material and the water are mixed in a weight ratio from 1:1 to 1:9. 
     
     
         5 . The aqueous suspension of precipitated calcium carbonate of  claim 1 , wherein in step iv) the calcium oxide containing material and the water are mixed in a weight ratio from 1:3 to 1:5. 
     
     
         6 . The aqueous suspension of precipitated calcium carbonate of  claim 1 , wherein the at least one slaking additive is selected from the group consisting of sodium citrate, potassium citrate, calcium citrate, magnesium citrate, monosaccharides, disaccharides, polysaccharides, sucrose, sugar alcohols, meritol, citric acid, sorbitol, sodium salt of diethylene triamine pentaacetic acid, gluconates, phosphonates, sodium tartrate, sodium lignosulfonate, calcium lignosulfonate, and any mixture thereof. 
     
     
         7 . The aqueous suspension of precipitated calcium carbonate of  claim 1 , wherein the at least one slaking additive is sodium citrate and/or saccharose. 
     
     
         8 . The aqueous suspension of precipitated calcium carbonate of  claim 1 , wherein the milk of lime of step iv) has a Brookfield viscosity from 1 to 1000 mPa·s at 25° C. 
     
     
         9 . The aqueous suspension of precipitated calcium carbonate of  claim 1 , wherein the suspension of PCC of step v) has a Brookfield viscosity of less than or equal to 1000 mPa·s at 25° C. 
     
     
         10 . The aqueous suspension of precipitated calcium carbonate of  claim 1 , wherein the suspension of PCC of step v) has a Brookfield viscosity of less than or equal to 800 mPa·s at 25° C. 
     
     
         11 . The aqueous suspension of precipitated calcium carbonate of  claim 1 , wherein the suspension of PCC of step v) has a Brookfield viscosity of less than or equal to 600 mPa·s at 25° C. 
     
     
         12 . The aqueous suspension of precipitated calcium carbonate of  claim 1 , wherein the suspension of PCC of step v) has a solids content of at least 20 wt.-%, based on the total weight of the suspension. 
     
     
         13 . The aqueous suspension of precipitated calcium carbonate of  claim 1 , wherein the suspension of PCC of step v) has a solids content of from 20 to 50 wt.-%, based on the total weight of the suspension. 
     
     
         14 . The aqueous suspension of precipitated calcium carbonate of  claim 1 , wherein the suspension of PCC of step v) has a solids content of from 30 to 40 wt.-%, based on the total weight of the suspension. 
     
     
         15 . The aqueous suspension of precipitated calcium carbonate of  claim 1 , wherein the at least one slaking additive is added in an amount from 0.01 to 2 wt.-%, based on the total amount of calcium oxide containing material. 
     
     
         16 . The aqueous suspension of precipitated calcium carbonate of  claim 1 , wherein the at least one slaking additive is added in an amount from 0.05 to 1 wt.-%, based on the total amount of calcium oxide containing material. 
     
     
         17 . The aqueous suspension of precipitated calcium carbonate of  claim 1 , wherein the at least one slaking additive is added in an amount from 0.06 to 0.8 wt.-%, based on the total amount of calcium oxide containing material. 
     
     
         18 . The aqueous suspension of precipitated calcium carbonate of  claim 1 , wherein the at least one slaking additive is added in an amount from 0.07 to 0.5 wt.-%, based on the total amount of calcium oxide containing material. 
     
     
         19 . The aqueous suspension of precipitated calcium carbonate of  claim 1 , wherein the water used in mixing step iv) has a temperature that is adjusted to be in the range from more than 0° C. and less than 100° C. 
     
     
         20 . The aqueous suspension of precipitated calcium carbonate of  claim 1 , wherein the water used in mixing step iv) has a temperature that is adjusted to be in the range from 1° C. to 70° C. 
     
     
         21 . The aqueous suspension of precipitated calcium carbonate of  claim 1 , wherein the milk of lime obtained from step iv), which is employed in step v), has a temperature that is adjusted to be in the range from 20° C. to 60° C. 
     
     
         22 . The aqueous suspension of precipitated calcium carbonate of  claim 1 , wherein the milk of lime is screened after step iv) and before step v). 
     
     
         23 . Precipitated calcium carbonate obtained by a process comprising the steps of:
 i) providing a calcium oxide containing material,   ii) providing at least one water-soluble polymer having a molecular weight M w  in the range from 200 to 6500 g/mol, wherein the at least one polymer has the chemical structure of formula (I):   
       
         
           
           
               
               
           
         
         wherein n, m, and p are integers and at least one of n, m, or p is greater than zero and n+m+p is less than or equal to 70, 
         R 1  is H or CH 3 , 
         R 2  is H or CH 3 , 
         R 3  is —C(═O)—O—R 4  or —C(═O)—NH—R 4 , wherein R 4  is a C 1  to C 20  alkyl group, a C 3  to C 20  cycloalkyl group and/or a C 6  to C 30  aryl group, being optionally substituted with one or more sulfonate groups, and wherein the cycloalkyl group and/or the aryl group comprises one ring or several rings, which are linked to each other, 
         R 5  is H or CH 3 , 
         R 6  is H or CH 3 , and 
         X is H and/or M, wherein M is Na, K, Li, Mg, and/or Ca, and 
       
       wherein the structural units 
       
         
           
           
               
               
           
         
       
       are arranged randomly, regularly and/or in blocks,
 iii) providing at least one slaking additive, wherein the at least one slaking additive is selected from the group consisting of organic acids, organic acid salts, sugar alcohols, monosaccharides, disaccharides, polysaccharides, gluconates, phosphonates, lignosulfonates, and mixtures thereof, 
 iv) preparing a milk of lime by mixing water, the calcium oxide containing material of step i), the at least one polymer of step ii), and the at least one slaking additive of step iii), wherein the calcium oxide containing material and the water are mixed in a weight ratio from 1:1 to 1:12, 
 v) carbonating the milk of lime obtained from step iv) to form an aqueous suspension of precipitated calcium carbonate, 
 vi) separating the precipitated calcium carbonate from the aqueous suspension obtained from step v), and 
 vii) optionally drying the separated precipitated calcium carbonate obtained from step vi). 
 
     
     
         24 . The precipitated calcium carbonate of  claim 23 , wherein step vii) is performed to obtain dried precipitated calcium carbonate in the form of a powder. 
     
     
         25 . A product comprising the aqueous suspension of precipitated calcium carbonate of  claim 1 . 
     
     
         26 . A product comprising the precipitated calcium carbonate of  claim 23 . 
     
     
         27 . A product comprising the precipitated calcium carbonate of  claim 24 . 
     
     
         28 . The product of  claim 26 , which is a paper, a paper product, an ink, a paint, a coating, a plastic, a polymer composition, an adhesive, a building product, a foodstuff, an agricultural product, a cosmetic product or a pharmaceutical product. 
     
     
         29 . The product of  claim 27 , which is a paper, a paper product, an ink, a paint, a coating, a plastic, a polymer composition, an adhesive, a building product, a foodstuff, an agricultural product, a cosmetic product or a pharmaceutical product. 
     
     
         30 . The product of  claim 27 , which is a plastic or a polymer composition.