Hydrophobised calcium carbonate particles

Abstract

The present invention relates to a process for the reduction of pitch in an aqueous medium generated in a papermaking or pulping process, comprising the following steps: a) providing an aqueous medium comprising pitch generated in a papermaking or pulping process; b) providing a ground calcium carbonate and/or a precipitated calcium carbonate; c) providing a hydrophobising agent selected from an aliphatic carboxylic acid having between 5 and 24 carbon atoms; d) contacting the ground calcium carbonate and/or the precipitated calcium carbonate of step b) with the hydrophobising agent of step c) for obtaining a hydrophobised ground calcium carbonate and/or a hydrophobised precipitated calcium carbonate; and e) contacting the aqueous medium provided in step a) with the hydrophobised ground calcium carbonate and/or the hydrophobised precipitated calcium carbonate obtained in step d), to the use of a hydrophobised ground calcium carbonate and/or a hydrophobised ground calcium carbonate for reducing the amount of pitch in an aqueous medium as well as to a hydrophobised ground calcium carbonate and/or a hydrophobised ground calcium carbonate and a composite of hydrophobised ground calcium carbonate and/or hydrophobised ground calcium carbonate and pitch.

1 . A hydrophobised ground calcium carbonate and/or a hydrophobised precipitated calcium carbonate, wherein between 10% and 19% of the specific surface area of the ground calcium carbonate and/or the precipitated calcium carbonate is covered by a coating consisting of an aliphatic carboxylic acid having between 5 and 24 carbon atoms and reaction products thereof. 
     
     
         2 . The hydrophobised ground calcium carbonate and/or the hydrophobised precipitated calcium carbonate according to  claim 1 , wherein between 10% and 19% of the specific surface area of the ground calcium carbonate and/or the precipitated calcium carbonate is covered by a coating consisting of stearic acid and reaction products thereof. 
     
     
         3 . The hydrophobised ground calcium carbonate and/or the hydrophobised precipitated calcium carbonate according to  claim 1 , wherein between 13% and 17% of the specific surface area of the ground calcium carbonate and/or the precipitated calcium carbonate is covered by a coating consisting of an aliphatic carboxylic acid having between 5 and 24 carbon atoms and reaction products thereof. 
     
     
         4 . The hydrophobised ground calcium carbonate and/or the hydrophobised precipitated calcium carbonate according to  claim 1 , wherein between 13% and 17% of the specific surface area of the ground calcium carbonate and/or the precipitated calcium carbonate is covered by a coating consisting of stearic acid and reaction products thereof. 
     
     
         5 . The hydrophobised ground calcium carbonate and/or the hydrophobised precipitated calcium carbonate according to  claim 1 , wherein ground calcium carbonate (GCC) is selected from marble, chalk, calcite, dolomite, limestone, and any mixture thereof and/or the precipitated calcium carbonate (PCC) is selected from one or more of the aragonitic, vateritic and calcitic mineralogical crystal forms. 
     
     
         6 . The hydrophobised ground calcium carbonate and/or the hydrophobised precipitated calcium carbonate according to  claim 1 , wherein the ground calcium carbonate particles and/or the precipitated calcium carbonate particles have a weight median particle diameter d 50  value of from 0.1 to 50 μm, measured according to the sedimentation method. 
     
     
         7 . The hydrophobised ground calcium carbonate and/or the hydrophobised precipitated calcium carbonate according to  claim 1 , wherein the ground calcium carbonate particles and/or the precipitated calcium carbonate particles have a weight median particle diameter d 50  value of from 0.1 to 15 μm, measured according to the sedimentation method. 
     
     
         8 . The hydrophobised ground calcium carbonate and/or the hydrophobised precipitated calcium carbonate according to  claim 1 , wherein the ground calcium carbonate particles and/or the precipitated calcium carbonate particles have a weight median particle diameter d 50  value of from 0.5 to 5 μm, measured according to the sedimentation method. 
     
     
         9 . The hydrophobised ground calcium carbonate and/or the hydrophobised precipitated calcium carbonate according to  claim 1 , wherein the ground calcium carbonate particles and/or the precipitated calcium carbonate particles have a specific surface area of from 0.5 m 2 /g to 25 m 2 /g, measured using nitrogen and the BET method. 
     
     
         10 . The hydrophobised ground calcium carbonate and/or the hydrophobised precipitated calcium carbonate according to  claim 1 , wherein the ground calcium carbonate particles and/or the precipitated calcium carbonate particles have a specific surface area of from 0.5 m 2 /g to 11 m 2 /g, measured using nitrogen and the BET method. 
     
     
         11 . The hydrophobised ground calcium carbonate and/or the hydrophobised precipitated calcium carbonate according to  claim 1 , wherein the hydrophobised ground calcium carbonate and/or the hydrophobised precipitated calcium carbonate is in powder form or in the form of granules or in the form of slurry. 
     
     
         12 . The hydrophobised ground calcium carbonate and/or the hydrophobised precipitated calcium carbonate according to  claim 1 , which is hydrophobised ground calcium carbonate. 
     
     
         13 . The hydrophobised ground calcium carbonate and/or the hydrophobised precipitated calcium carbonate according to  claim 1 , which is hydrophobised precipitated calcium carbonate. 
     
     
         14 . A composite comprising the hydrophobised ground calcium carbonate and/or the hydrophobised precipitated calcium carbonate according to  claim 1  and pitch. 
     
     
         15 . A composite comprising hydrophobised ground calcium carbonate and/or the hydrophobised precipitated calcium carbonate and adsorbed pitch, that is obtained by a process comprising the following steps:
 a) providing an aqueous medium comprising pitch from paper pulp, wherein the pitch is natural resin from the paper pulp, wherein the paper pulp is selected from the group consisting of mechanical pulp, ground wood, TMP (thermo mechanical pulp), chemithermomechanical pulp (CTMP), chemical pulp, and kraft or sulphate pulp, and wherein the pulp is not recycled pulp;   b) contacting the aqueous medium provided in step a) with calcium carbonate consisting of a partially hydrophobised ground calcium carbonate and/or partially hydrophobised precipitated calcium carbonate so that the calcium carbonate adsorbs pitch in the aqueous medium to form a composite comprising the hydrophobised ground calcium carbonate and/or the hydrophobised precipitated calcium carbonate and adsorbed pitch, wherein the aqueous medium is contacted with 0.05 to 20 wt.-% of the partially hydrophobised ground calcium carbonate and/or the partially hydrophobised precipitated calcium carbonate, based on the total weight of the aqueous medium, wherein the adsorbed pitch is natural resin from the paper pulp, and wherein the partially hydrophobised ground calcium carbonate and/or a partially hydrophobised precipitated calcium carbonate is ground calcium carbonate and/or precipitated calcium carbonate that has been mixed with a hydrophobising agent selected from the group consisting of one or more aliphatic carboxylic acids having between 5 and 24 carbon atoms at a temperature of at least 50° C. such that the hydrophobising agent is in a liquid or molten state and less than 20% of the specific surface area of the ground calcium carbonate and/or the precipitated calcium carbonate is covered by a coating consisting of the hydrophobising agent and reaction products thereof; and   c) separating the composite comprising the hydrophobised ground calcium carbonate and/or the hydrophobised precipitated calcium carbonate and adsorbed pitch from the aqueous medium.