# US 8,785,687 B2 · For preparing surface-reacted calcium carbonate and its use > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 8,785,687 B2 - Document ID: US8785687B2 - Status: Granted - Kind: B2 - Application number: 13/378,147 - Filed: 2010-06-15 - Published: 2012-06-07 - Granted: 2014-07-22 - Earliest claimed: 2009-06-15 - Assignees: Omya International AG - Applicants: Patrick A. C. Gane; Daniel E. Gerard; Joachim Schölkopf - Inventors: Patrick A. C. Gane; Daniel E. Gerard; Joachim Schölkopf - Web page: https://patentgrep.com/patent/US8785687B2 ## CPC - C09C 1/022: {Treatment with inorganic compounds} - C01F 11/185: {After-treatment, e.g. grinding, purification, conversion of crystal morphology} - C09C 1/02: Compounds of alkaline earth metals or magnesium {(C09C1/0003, C09C1/0009, C09C1/0015, C09C1/0078 take precedence; dolomitic solids C09C1/009)} - C09C 1/021: {Calcium carbonates} - C09C 3/04: Physical treatment, e.g. grinding or treatment with ultrasonic vibrations {(C09C3/006 takes precedence)} - D21H 17/67: Water-insoluble compounds, e.g. fillers, pigments - D21H 17/69: modified, e.g. by association with other compositions prior to incorporation in the pulp or paper - C01P 2002/72: by d-values or two theta-values, e.g. as X-ray diagram - C01P 2004/61: Micrometer sized, i.e. from 1-100 micrometer - C01P 2004/62: Submicrometer sized, i.e. from 0.1-1 micrometer - C01P 2004/80: Particles consisting of a mixture of two or more inorganic phases - C01P 2006/12: Surface area - D21H 17/675: {Oxides, hydroxides or carbonates} - C09C: TREATMENT OF INORGANIC MATERIALS, OTHER THAN FIBROUS FILLERS, TO ENHANCE THEIR PIGMENTING OR FILLING PROPERTIES (treatment of materials specially adapted to enhance their filling properties in mortars, concrete or artificial stone C04B14/00, C04B18/00, C04B20/00); PREPARATION OF CARBON BLACK {; PREPARATION OF INORGANIC MATERIALS WHICH ARE NO SINGLE CHEMICAL COMPOUNDS AND WHICH ARE MAINLY USED AS PIGMENTS OR FILLERS} - C01F: COMPOUNDS OF THE METALS BERYLLIUM, MAGNESIUM, ALUMINIUM, CALCIUM, STRONTIUM, BARIUM, RADIUM, THORIUM, OR OF THE RARE-EARTH METALS (metal hydrides {monoborane, diborane or addition complexes thereof} C01B6/00; salts of oxyacids of halogens C01B11/00; peroxides, salts of peroxyacids C01B15/00; sulfides or polysulfides of magnesium, calcium, strontium, or barium C01B17/42; thiosulfates, dithionites, polythionates C01B17/64; compounds containing selenium or tellurium C01B19/00; binary compounds of nitrogen with metals C01B21/06; azides C01B21/08; {compounds other than ammonia or cyanogen containing nitrogen and non-metals and optionally metals C01B21/082; amides or imides of silicon C01B21/087}; metal {imides or} amides C01B21/092, {C01B21/0923}; nitrites C01B21/50; {compounds of noble gases C01B23/0005}; phosphides C01B25/08; salts of oxyacids of phosphorus C01B25/16; carbides C01B32/90; compounds containing silicon C01B33/00; compounds containing boron C01B35/00; compounds having molecular sieve properties but not having base-exchange properties C01B37/00; compounds having molecular sieve and base-exchange properties, e.g. crystalline zeolites, C01B39/00; cyanides C01C3/08; salts of cyanic acid C01C3/14; salts of cyanamide C01C3/16; thiocyanates C01C3/20; {double sulfates of magnesium with sodium or potassium C01D5/12; with other alkali metals C01D15/00, C01D17/00}) - D21H: PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR - C01P: INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS ## Abstract The present invention relates to an economic process for preparing surface-reacted calcium carbonate. The present invention further relates to a surface-reacted calcium carbonate having an increased specific BET surface area, and the use of a process for adjusting the specific BET surface area. ## Claims ### Claim 1 A process for preparing a surface-reacted calcium carbonate in an aqueous environment, the process comprising the following steps: a) providing a calcium carbonate; b) providing 5 wt.-% to 50 wt.-%, based on the weight of calcium carbonate, of at least one acid having a pKa of less than or equal to 2.5, wherein the corresponding acid anion is capable of forming water-insoluble calcium salts; c) providing 1 wt.-% to 20 wt.-%, based on the weight of calcium carbonate, of at least one water soluble non-polymeric organic and/or inorganic weak acid and/or a hydrogen salt of the at least one water soluble non-polymeric organic and/or inorganic weak acid, wherein the at least one water soluble non-polymeric organic and/or inorganic weak acid and/or hydrogen salt of the at least one water soluble non-polymeric organic and/or inorganic weak acid is selected from the group consisting of boric acid, citric acid, sodium dihydrogen citrate, potassium dihydrogen citrate, disodium hydrogen citrate, dipotassium hydrogen citrate, sodium dihydrogen borate, potassium dihydrogen borate, disodium hydrogen borate, dipotassium hydrogen borate, and any mixture thereof; and d) contacting the calcium carbonate of step a) with (i) the at least one acid having a pKa of less than or equal to 2.5 of step b), and (ii) the at least one water soluble non-polymeric organic and/or inorganic weak acid and/or hydrogen salt of the at least one water soluble non-polymeric organic and/or inorganic weak acid of step c), in an aqueous environment, in the presence of gaseous CO2, which is formed in situ or provided from an external source, to obtain a surface-reacted calcium carbonate having a BET specific surface area of at least 30 m2/g. ### Claim 2 (depends on 1) The process according to claim 1, wherein the at least one acid having a pKa of less than or equal to 2.5 is selected from the group consisting of strong acids having a pKa value of less than or equal to zero at 25° C., and medium-strong acids having a pKa value of between zero and 2.5 at 25° C. ### Claim 3 (depends on 1) The process according to claim 1, wherein the at least one acid having a pKa of less than or equal to 2.5 is selected from the group consisting of H3PO4, oxalic acid and a mixture thereof. ### Claim 4 (depends on 1) The process according to claim 1, wherein the at least one acid having a pKa of less than or equal to 2.5 is H3PO4. ### Claim 5 (depends on 1) The process according to claim 1, wherein the at least one acid having a pKa of less than or equal to 2.5 is H3PO4 in a concentration of 20% to 40% (v/v). ### Claim 6 (depends on 1) The process according to claim 1, wherein the at least one acid having a pKa of less than or equal to 2.5 is H3PO4, and the at least one water soluble non-polymeric organic and/or inorganic weak acid and/or hydrogen salt of the at least one water soluble non-polymeric organic and/or inorganic weak acid is citric acid. ### Claim 7 (depends on 1) The process according to claim 1, wherein the at least one acid having a pKa of less than or equal to 2.5 is H3PO4 in a concentration of 20% to 40% (v/v), and the at least one water soluble non-polymeric organic and/or inorganic weak acid and/or hydrogen salt of the at least one water soluble non-polymeric organic and/or inorganic weak acid is citric acid. ### Claim 8 (depends on 1) The process according to claim 1, wherein the at least one water soluble non-polymeric organic and/or inorganic weak acid and/or hydrogen salt of the at least one water soluble non-polymeric organic and/or inorganic weak acid is added in an amount between 1 wt.-% and 15 wt.-%, based on the weight of calcium carbonate. ### Claim 9 (depends on 1) The process according to claim 1, wherein the at least one water soluble non-polymeric organic and/or inorganic weak acid and/or hydrogen salt of the at least one water soluble non-polymeric organic and/or inorganic weak acid is added in an amount between 1.5 wt.-% and 10 wt.-%, based on the weight of calcium carbonate. ### Claim 10 (depends on 1) The process according to claim 1, wherein the at least one water soluble non-polymeric organic and/or inorganic weak acid and/or hydrogen salt of the at least one water soluble non-polymeric organic and/or inorganic weak acid is added in an amount between 2 wt.-% and 5 wt.-%, based on the weight of calcium carbonate. ### Claim 11 (depends on 1) The process according to claim 1, wherein the calcium carbonate is first contacted with the at least one water soluble non-polymeric organic and/or inorganic weak acid and/or hydrogen salt of the at least one water soluble non-polymeric organic and/or inorganic weak acid and then with the at least one acid having a pKa of less than or equal to 2.5. ### Claim 12 (depends on 1) The process according to claim 1, wherein the calcium carbonate is simultaneously contacted with the at least one water soluble non-polymeric organic and/or inorganic weak acid and/or hydrogen salt of the at least one water soluble non-polymeric organic and/or inorganic weak acid and the at least one acid having a pKa of less than or equal to 2.5. ### Claim 13 (depends on 1) The process according to claim 1, wherein the calcium carbonate is first contacted with the at least one acid having a pKa of less than or equal to 2.5 and during its addition, the calcium carbonate is also contacted with the at least one water soluble non-polymeric organic and/or inorganic weak acid and/or hydrogen salt of the at least one water soluble non-polymeric organic and/or inorganic weak acid. ### Claim 14 (depends on 1) The process according to claim 1, wherein the calcium carbonate is first contacted with the at least one acid having a pKa of less than or equal to 2.5 and after 5% of the total amount of the at least one acid having a pKa of less than or equal to 2.5 have been added, the calcium carbonate is contacted with the at least one water soluble non-polymeric organic and/or inorganic weak acid and/or hydrogen salt of the at least one water soluble non-polymeric organic and/or inorganic weak acid. ### Claim 15 (depends on 1) The process according to claim 1, wherein the calcium carbonate is first contacted with the at least one acid having a pKa of less than or equal to 2.5 and after 10% of the total amount of the at least one acid having a pKa of less than or equal to 2.5 have been added, the calcium carbonate is contacted with the at least one water soluble non-polymeric organic and/or inorganic weak acid and/or hydrogen salt of the at least one water soluble non-polymeric organic and/or inorganic weak acid. ### Claim 16 (depends on 1) The process according to claim 1, wherein the calcium carbonate is first contacted with the at least one acid having a pKa of less than or equal to 2.5 and after 20% of the total amount of the at least one acid having a pKa of less than or equal to 2.5 have been added, the calcium carbonate is contacted with the at least one water soluble non-polymeric organic and/or inorganic weak acid and/or hydrogen salt of the at least one water soluble non-polymeric organic and/or inorganic weak acid. ### Claim 17 (depends on 1) The process according to claim 1, wherein the calcium carbonate is first contacted with the at least one acid having a pKa of less than or equal to 2.5 and after 30% of the total amount of the at least one acid having a pKa of less than or equal to 2.5 have been added, the calcium carbonate is contacted with the at least one water soluble non-polymeric organic and/or inorganic weak acid and/or hydrogen salt of the at least one water soluble non-polymeric organic and/or inorganic weak acid. ### Claim 18 (depends on 1) The process according to claim 1, wherein the calcium carbonate is first contacted with the at least one acid having a pKa of less than or equal to 2.5 and after 50% of the total amount of the at least one acid having a pKa of less than or equal to 2.5 have been added, the calcium carbonate is contacted with the at least one water soluble non-polymeric organic and/or inorganic weak acid and/or hydrogen salt of the at least one water soluble non-polymeric organic and/or inorganic weak acid. ### Claim 19 (depends on 1) The process according to claim 1, wherein the calcium carbonate is first contacted with the at least one acid having a pKa of less than or equal to 2.5 and after 80% of the total amount of the at least one acid having a pKa of less than or equal to 2.5 have been added, the calcium carbonate is contacted with the at least one water soluble non-polymeric organic and/or inorganic weak acid and/or hydrogen salt of the at least one water soluble non-polymeric organic and/or inorganic weak acid. ### Claim 20 (depends on 1) The process according to claim 1, wherein the at least one acid having a pKa of less than or equal to 2.5 is provided in the form of: (i) at least one H3O+-ion provider having a pKa of less than or equal to 2.5, wherein the corresponding acid anion is capable of forming a water-soluble calcium salt, and (ii) at least one anion, provided in the form of a water-soluble salt or hydrogen salt, wherein the corresponding acid of this at least one anion has a pKa of less than or equal to 2.5 and wherein the anion is capable of forming water-insoluble calcium salts. ### Claim 21 (depends on 1) The process according to claim 1, wherein the calcium carbonate is further contacted with a compound selected from the group consisting of a sodium silicate, a potassium silicate, a lithium silicate, an aluminium silicate, a synthetic silica, a calcium silicate, an aluminium hydroxide, a sodium aluminate, a potassium aluminate, and any mixture thereof. ### Claim 22 (depends on 1) The process according to claim 1, wherein the surface-reacted calcium carbonate obtained by the process has a BET specific surface area of at least 40 m2/g. ### Claim 23 (depends on 1) The process according to claim 1, wherein the surface-reacted calcium carbonate obtained by the process has a BET specific surface area of at least 50 m2/g. ### Claim 24 (depends on 1) The process according to claim 1, wherein the surface-reacted calcium carbonate obtained by the process has a BET specific surface area of at least 60 m2/g. ### Claim 25 (depends on 1) The process according to claim 1, wherein the surface-reacted calcium carbonate obtained by the process has a BET specific surface area of at least 70 m2/g. ### Claim 26 (depends on 1) The process according to claim 1, wherein the surface-reacted calcium carbonate obtained by the process has a BET specific surface area of at least 80 m2/g. ### Claim 27 (depends on 1) The process according to claim 1, wherein the aqueous suspension obtained after step d) is dried.