USO09725576B2
(12) United States Patent (10) Patent No.: US 9,725,576 B2 Sötemann (45) Date of Patent: Aug. 8, 2017
(54) PROCESS FOR MANUFACTURING WHITE B03D 2203/005; B03D 2201/02: C09C PGMENT CONTAINING PRODUCTS 1/02: C09C 1/021; C04B 14/28: C04B 16/00; C08K 3/26: C08K 5/17; C08K (71) Applicant: Omya International AG. Oftringen 5/20; C08K 2003/265; C01P 2004/51: (CH) C01P 2004/61; C01P 2006/12: C01P 2006/60; C01P 2006/80 (72) Inventor: Jörg Sötemann, Villach (AT) See application file for complete search history. (73) Assignee: Omya International AG. Oftringen (CH) (56) References Cited U.S. PATENT DOCUMENTS (*) Notice: Subject to any disclaimer, the term of this patent is extended or adjusted under 35 3,990,966 A 11/1976 Stanley et al. U.S.C. 154(b) by 169 days. 4,995,965 A 2/1991 Mehaffey et al. 5,261,539 A * 11/1993 Hancock ...... BO3D 1.01 (21) Appl. No.: 14/.414,967 209,166 5,720,873 A * 2/1998 Klingberg ...... BO3D 1 0043 209,166 (22) PCT Filed: Aug. 8, 2013 8,381,915 B2 * 2/2013 Tavakkoli ...... BO3D 1.01 209,166 (86). PCT No.: PCT/EP2013/066666 8,662,311 B2 3/2014 Gane ...... BO3D 1.01 209,166 S 371 (c)(1), 8,992,875 B2* 3/2015 Tavakkoli ...... CO1F 11/18 (2) Date: Jan. 15, 2015 423.432 2010.0040528 A1 2/2010 Tavakkoli ...... BO3D 1.01 (87) PCT Pub. No.: WO2014/029634 423 (430 2014/0048453 A1 2/2014 Birken ...... BO3D 1.01 PCT Pub. Date: Feb. 27, 2014 209,166 2014/0048454 A1 2/2014 Birken ...... BO3D 1.01 (65) Prior Publication Data 209,166 2015,0183654 A1* 7, 2015 Tavakkoli ...... CO1F 11.18 US 2015/O175775 A1 Jun. 25, 2015 428/402 2015/0273481 A1* 10/2015 Dilsky ...... BO3D 1 011 Related U.S. Application Data 209,166 (60) Provisional application No. 61/693,350, filed on Aug. 27, 2012. FOREIGN PATENT DOCUMENTS CA 1187212 A1 5, 1985 (30) Foreign Application Priority Data EP O59 1633 A1 4f1994 EP 1944088 A1 T 2008 Aug. 20, 2012 (EP) ...... 1218.1089 EP 236645.6 A1 9, 2011 WO 2007122148 A1 11 2007 (51) Int. Cl. WO 2008O84391 A1 T 2008 CSK 5/20 (2006.01) WO WO 2011, 11386.6 A1 * 9, 2011 C09C I/02 (2006.01) BO3D IMOI (2006.01) OTHER PUBLICATIONS BO3D I/004 (2006.01) C04B I4/28 (2006.01) The International Search Report, dated Sep. 19, 2013 for PCT C04B I6/00 (2006.01) Application No. PCT/EP2013/066666. C08K 3/26 (2006.01) The Written Opinion of the International Searching Authority, dated CSK 5/17 (2006.01) Sep. 19, 2013 for PCT Application No. PCT/EP2013/066666. D2 IIH (700 (2006.01) (52) U.S. Cl. * cited by examiner CPC ...... C08K 5/20 (2013.01); B03D I/0043 Primary Examiner — Anthony J Green (2013.01); B03D I/01 (2013.01); C04B I4/28 (2013.01); C04B 16/00 (2013.01); C08K 3/26 (74) Attorney, Agent, or Firm — Amster, Rothstein & (2013.01); C08K 5/17 (2013.01); C09C I/02 Ebenstein LLP (2013.01); C09C I/021 (2013.01); D21H 17/74 (2013.01); B03D 2201/02 (2013.01); (57) ABSTRACT B03D 2203/005 (2013.01); COIP 2004/51 The present invention concerns a process for manufacturing (2013.01); COIP 2004/61 (2013.01); COIP white pigment containing products. The white pigment 2006/12 (2013.01); COIP 2006/60 (2013.01); containing products are obtained from at least one white COIP 2006/80 (2013.01); C08K 2003/265 pigment and impurities containing material via froth flota (2013.01) tion. (58) Field of Classification Search CPC ...... D21H 17/74; B03D 1/0043; B03D 1701; 33 Claims, No Drawings US 9,725,576 B2 1. 2 PROCESS FOR MANUFACTURING WHITE However, conventional flotation has a significant disad PGMENT CONTAINING PRODUCTS vantage: As mentioned before, chemical treatments as col lector agents are used to render the surface of the white CROSS-REFERENCE TO RELATED pigments hydrophobic to separate these particles by gas APPLICATIONS bubbling. These collector agents are adsorbed on the surface of the white pigments and, therefore, modify the properties This application is a U.S. national phase of PCT Appli of the pigments. However, this modification may be unde cation No. PCT/EP2013/066666, filed Aug. 8, 2013, which sirable in the following use of the white pigments in paper, claims priority to European Application No. 12181108.9, paint or cosmetics. Furthermore, the direct flotation of the 10 desired white pigments is disadvantageous due to quality filed Aug. 20, 2012 and U.S. Provisional Application No. and economical reasons. 61/693,350, filed Aug. 27, 2012. Alternatively, one may consider to use reverse/indirect The present invention relates to a process for manufac froth flotation to separate the white pigments and the impu turing white pigment containing products and, more particu rities. In contrast to conventional flotation, in which the larly, relates to the field of technologies implemented in 15 desirable white pigments are directly floated and collected order to separate white pigments and impurities by froth from the produced froth, reverse (indirect) flotation aims to flotation for the manufacture of white pigment containing have the undesirable impurities preferentially floated and products. removed, leaving behind a Suspension that has been con Pigments are generally known as materials that change centrated in the desirable white pigments. Also during the color of reflected or transmitted light as the result of reverse flotation collector agents are used that render the wavelength-selective absorption. This physical process dif impurities hydrophobic. fers from fluorescence, phosphorescence, and other forms of Corresponding methods that use collector agents in luminescence, in which a material emits light. Pigments are reverse froth flotation are suggested in U.S. Pat. No. 3,990, used for coloring e.g. paint, ink, plastic, fabric, cosmetics, 966, CA 1 187212 or WO 2008/084391. However, the prior food and other materials. Most pigments used are dry 25 art methods for manufacturing products by reverse froth colorants, usually ground into a fine powder. flotation have numerous disadvantages. For example, many White pigments take a special position in the field of collector agents are formed from compounds that have high pigments due to their industrial relevance. For example, in melting points and, therefore, these compounds must be paper industries in Europe more than 10 million tons per dispersed in water using a high energy blender and/or year of white pigments are used. White pigments are also 30 heating, and then must be actively mixed so as to remain in used in paints and coatings. Especially when manufacturing Suspension. Thus, the use of Such collector agents is very dispersion paints, white pigments are the base color in the expensive. Additionally, many of the known collector agents tinting system. cause uncontrolled foaming in the reverse froth flotation White pigments occur naturally and are obtained by process. Furthermore, many of the reverse froth flotation mining. However, generally white pigments contain impu 35 processes are limited in that they are selective, i.e. a sig rities which induce discoloration Such as, for example, nificant part of the desired product is floated together with greyness or yellowness of the white pigments. Furthermore, the impurities. Also a great number of the collector agents these impurities may affect the properties of the white used so far is considered to be acquatic and environmental pigments and, thus, lead to significant disadvantages of the toxic. white pigments. A high amount of impurities such as, for 40 Therefore, there is a need for an improved method for example, silicates within the white pigments might increase producing white pigments by flotation, which method avoids the abrasion. Therefore, the impurities and the white pig or reduces the problems described above in relation to the ments have to be separated from one another to obtain a known methods. Such improved method for manufacturing white pigment containing product that is not, or merely white pigments from a white pigment and impurities con marginally, contaminated with impurities. 45 taining material should especially be an easy to handle and It is known in the prior art to separate impurities from ecological method. Also the effectiveness should be satis white minerals by physico-chemical separation. The factory. physico-chemical separation process involves firstly At least some of the foregoing object has been solved by grounding the metamorphic or sedimentary rock and then the present invention. Subjecting the resulting white pigment and impurities con 50 According to one aspect of the present invention a process taining material to conventional froth flotation in an aqueous for manufacturing white pigment containing products is environment. Conventional froth flotation is a highly versa provided, characterised in that said process comprises the tile method known in the prior art for physico-chemical following steps: separating particles based on differences in the ability of gas a) providing at least one white pigment and impurities bubbles to selectively adhere to specific surfaces in an 55 containing material aqueous suspension containing the white pigment and impu b) providing at least one collector agent selected from the rities containing material. The white pigments with attached group consisting of compounds of formula (1) air bubbles are then carried to the surface and are removed, while the impurities that remain completely wetted stay in the liquid phase. 60 (1) As set out above, the basis of conventional froth flotation ,E); H is the difference in the wettabilities of the white pigments and the impurities. White pigments can either be naturally R--A1-y hydrophobic, but in general the hydrophobicity is induced (E2). by chemical treatments. Chemical treatments to render a 65 Surface hydrophobic are essentially methods for coating a particle Surface with a layer of Suitable compounds. US 9,725,576 B2 3 4 wherein agents are less toxic in comparison to known prior art R represents a hydrocarbon group containing from 6 to 30 collector agents. The white pigment containing products carbon atoms, obtained from the inventive process show good brightness A represents an alkylene group having from 1 to 6 carbon and have a low yellow index. Additionally, impurities like atoms, 5 abrasive silicates can be reduced in a better way by the E. E. and Es, are identical or different from each other, each inventive flotation process than in known prior art processes. independently chosen from among alkylene oxide groups A second aspect of the present invention relates to the use containing from 1 to 6 carbon atoms, of the white pigment bearing phase obtained by the inven n, n and n are identical or different from each other, each tive process in paper, plastics, paint, coatings, concrete, independently chosen from an integer which value is from 1 10 cement, cosmetic, water treatment and/or agriculture appli to 20, cations. The white pigment containing product is preferably p is 1, 2, 3 or 4. used in a wet end process of a paper machine, in cigarette and compounds of formula (2) paper, board, and/or coating applications, or as a Support for 15 rotogravure and/or offset and/or ink jet printing and/or continuous inkjet printing and/or flexography and/or elec (2) trophotography and/or decoration Surfaces. ?: According to a third aspect of the present invention a white pigment containing product obtained by the inventive R----,O R24 R23 process is provided. Advantageous embodiments of the present invention are wherein defined in the corresponding Sub-claims. R represents a hydrocarbon group containing from 6 to 30 According to one embodiment, the process involves an carbon atoms, indirect flotation step leading to the formation of a froth R and R2 are identical or different from each other, each 25 containing the impurities and a white pigment bearing phase independently chosen from among hydrocarbon groups con with the white pigment containing product. taining from 1 to 6 carbon atoms, According to another embodiment, the white pigment is a R represents hydrogen or a hydrocarbon group containing white mineral pigment, preferably selected from the group from 1 to 6 carbon atoms, consisting of natural calcium carbonate or ground calcium A represents an alkylene group having from 1 to 6 carbon 30 carbonate, calcium carbonate-containing mineral material, atoms, and dolomite, barite, aluminium oxide, titanium dioxide and q is 1, 2, 3 or 4 mixtures of the foregoing. and mixtures thereof According to another embodiment, the white mineral c) mixing said white pigment and impurities containing pigment is an alkaline earth metal carbonate, preferably a material of step a) and said collector agent of step b) in 35 calcium carbonate and most preferably ground calcium an aqueous environment to forman aqueous Suspension carbonate (GCC). d) passing gas through the Suspension formed in step c) According to another embodiment, the white pigment e) recovering the white pigment containing product by containing material comprises impurities selected from the removing the white pigment bearing phase from the 40 group consisting of iron Sulphides, iron oxides, graphite, aqueous Suspension obtained after step d). silicates and mixtures thereof. The silicate may be selected The inventors surprisingly found that the process for from the group consisting of quartz, a mica, an amphibolite, manufacturing white pigment containing products from at an feldspar, a clay mineral and mixtures thereof and pref least one white pigment and impurities containing material erably is quartz. and one collectoragent selected from the group consisting of 45 According to another embodiment, the silicate is a white compounds of formula (1) and compounds of formula (2) coloured silicate selected from the group consisting of and mixtures thereof wollastonite, kaolin, kaolinitic clay, calcined kaolinitic clay, montmorillonite, talc, diatomaceous earth, Sepiolite and mixtures thereof. (1) 50 According to another embodiment, the amount of white E.). H pigment in the white pigment and impurities containing R-e-r-y material of step a) is from 0.1 to 99.9 wt.-%, based on the (E1), (E) -H dry weight, preferably from 30 to 99.7 wt.-%, more prefer ably from 60 to 99.3 wt.-% and most preferably from 80 to 55 99 wt.-%, based on the dry weight. (2) According to another embodiment, the amount of white ?: pigment:impurities in the white pigment and impurities R.---N-A-,-N containing material of step a) is from 0.1: 99.9 to 99.9:0.1 O| R24 Y. 23 , based on the dry weight, preferably from 30:70 to 99.7:0.3, 60 more preferably from 60:40 to 99.3:0.7, and most preferably from 80:20 to 99:1, based on the dry weight. is advantageous because the aforementioned collector According to another embodiment, the white pigment and agents effectively bind to the surface of the impurities and impurities containing material of step a) has a weight not to the surface of the white pigments. Therefore, the median grain diameter in the range of from 1 to 1000 um, inventive flotation process is very effective in comparison to 65 preferably of from 3 to 700 um, more preferably of from 5 known prior art processes. Furthermore, the inventive flo to 500 um and most preferably of from 10 to 80 um or from tation process is very ecological since the used collector 100 to 400 um. US 9,725,576 B2 5 6 According to another embodiment, the compound of polyelectrolytes, frothers and collector agents other than the formula (1) possesses at least one of the following charac collector agents according to formula (1) or formula (2). teristics: According to another embodiment, the aqueous Suspen R represents a straight or branched hydrocarbon group sion obtained in step c) is ground during and/or after step c). containing from 6 to 30 carbon atoms, preferably from 8 to According to another embodiment, the gas in step d) is air. 26, more preferably from 12 to 22 carbon atoms, optionally According to another embodiment, the Suspension in step containing one or more insaturation(s), in the form of double d) has a temperature of between 5 and 90° C., preferably and/or triple bond(s), between 10 and 70° C., more preferably between 20 and 50° A represents a straight or branched alkylene group having C. and most preferably between 25 and 40° C. from 1 to 6 carbon atoms, preferably from 2 to 6 carbon 10 According to another embodiment, the white pigment atoms, more preferably 2, 3 or 4 carbon atoms, bearing phase obtained from step e) is dispersed and/or E. E. and Es, are identical or different from each other, each ground before and/or after step e) and preferably is dispersed independently chosen from among ethylene oxide (OE) and/or ground in the presence of at least one dispersing agent group, propylene oxide (OP) group and butylene oxide (OB) and/or at least one grinding aid agent. group, preferably among OE group and OP group, more 15 According to another embodiment, the white pigment preferably each of E. E. and E represents an OE group. containing product comprises at least 95 wt.-% white pig n, n and n are identical or different from each other, each ment, based on the dry weight, preferably of at least 98 independently chosen from an integer which value is from 1 wt.-%, more preferably of at least 99 wt.-% and most to 20, preferably from 1 to 10, and the Sum n+n+n, ranges preferably of at least 99.9 wt.-% based on the dry weight. from 3 to 9, A "pigment in the meaning of the present invention is a p is 1, 2, 3 or 4, preferably 1 or 2, and more preferably p is Solid colouring material having a defined chemical compo 1. sition and a characteristic crystalline structure. According to another embodiment, the compound of Pigments can be inorganic pigments. Pigments may be formula (2) possesses at least one of the following charac synthetic or natural pigments. Furthermore, pigments are teristics: 25 insoluble in water and, thus, resulting in a Suspension when R and R2 are identical or different from each other, each contacting them with water. independently chosen from among hydrocarbon groups con A “white pigment' in the meaning of the present inven taining from 1 to 6 carbon atoms, preferably from 1 to 4 tion is a pigment that has a white colour. carbon atoms, and more preferably are chosen from among A “white mineral pigment in the meaning of the present methyl, ethyl, propyl and butyl, 30 invention is an inorganic white pigment that may be R2 represents hydrogen, obtained naturally and specifically includes natural calcium A represents an alkylene group having 1, 2, 3 or 4 carbon carbonate or ground calcium carbonate (in particular lime atoms, and preferably A is ethylene or propylene, and more stone, chalk, marble, calcite), calcium carbonate-containing preferably propylene, mineral material (with a 70 wt.-% minimum content of q is 1 or 2, and preferably 1. 35 CaCO, based on the weight of the mineral), dolomite, According to another embodiment, the collector agent of barite, aluminium oxide, titanium dioxide and mixtures of step b) consists of one or more compounds of formula (1) or the foregoing. consist of one or more compounds of formula (2). An “alkaline earth metal carbonate' in the meaning of the According to another embodiment, the aqueous Suspen present invention is a carbonate that comprises at least one sion obtained in step c) has a pH from 7 to 12, preferably 40 alkaline earth metal cation. The alkaline earth metals accord from 7.5 to 11 and more preferably from 8.5 to 9.5. ing to the present invention are beryllium Be", magnesium According to another embodiment, the collecting agent is Mg", calcium Ca", strontium Sr*., barium Bat and added in step c) in an amount of from 5 to 5000 ppm based radium Ra". on the total dry weight of the white pigment and impurities “Calcium carbonate” in the meaning of the present inven containing material of step a), preferably in an amount of 45 tion includes natural calcium carbonate and may be a ground from 20 to 2000 ppm, more preferably in an amount of from calcium carbonate (GCC). 30 to 1000 ppm, and most preferably in an amount of from “Natural calcium carbonate' in the meaning of the present 50 to 800 ppm based on the total dry weight of said white invention is a calcium carbonate (calcite) obtained from pigment and impurities containing material of step a). natural sources, such as marble, limestone, or chalk. According to another embodiment, the aqueous Suspen 50 “Ground calcium carbonate” (GCC) in the meaning of the sion obtained in step c) has a solids content of between 5 and present invention is a natural calcium carbonate that is 80 wt.-% based on the total weight of the solids in the processed through a wet and/or dry treatment such as suspension, preferably of between 10 and 70 wt.-%, more grinding, screening and/or fractionating, for example by a preferably of between 20 and 60 wt.-% and most preferably cyclone or classifier. of between 25 and 55 wt.-% based on the total weight of the 55 “Impurities’ in the meaning of the present invention are Solids in the Suspension. substances that differ from the chemical composition of the According to another embodiment, the collecting agent is desired white pigment. present in the aqueous Suspension obtained in step c) in an A “collector agent' in the meaning of the present inven amount of from 0.01 to 10 wt.-% based on the total weight tion is a chemical compound that is adsorbed by the envis of the solids in the suspension, preferably from 0.05 to 5 60 aged particles either by chemisorption or by physisorption. wt.-%, more preferably from 0.1 to 3.0 wt.-%, and most The collector agent renders the surface of the impurities preferably from 0.2 to 2.0 wt.-%, based on the total weight more hydrophobic. of the Solids in the Suspension. A "gas' in the meaning of the present invention is a According to another embodiment, one or more additives Substance in a physical state in which it does not resist are added to the aqueous Suspension prior to, during or after 65 change of shape and will expand indefinitely. The gas is step c), wherein the additives are selected from the group composed of molecules that are in constant random motion. comprising pH-adjusting agents, solvents, depressants, According to the present invention the compound has to be US 9,725,576 B2 7 8 in a gaseous state at room temperature (20+2' C.) and at ground calcium carbonate (in particular limestone, chalk, standard pressure (101325 Pa or 101325 bar). marble, calcite), calcium carbonate-containing mineral A “suspension” or “slurry' in the meaning of the present material (with a 70 wt.-% minimum content of CaCO, invention comprises insoluble Solids and water, and option based on the weight of the mineral), dolomite, barite, ally further additives, and usually contains large amounts of 5 aluminium oxide, titanium dioxide and mixtures of the Solids and, thus, is more viscous and can be of higher density foregoing. than the liquid from which it is formed. White pigments may be white mineral pigments. White Throughout the present document, the “weight grain mineral pigments in the meaning of the present invention are diameter of a white pigment and impurities containing inorganic white pigments that may be obtained naturally. material is described by its distribution of particle sizes. The 10 value d represents the diameter relative to which X % by Beside the above mentioned natural calcium carbonate or weight of the particles have diameters less than dy. This ground calcium carbonate (in particular limestone, chalk, means that the do value is the weight grain diameter at marble, calcite), calcium carbonate-containing mineral which 20 wt.-% of all particles are smaller, and the dis value material (with a 70 wt.-% minimum content of CaCO, is the weight grain diameter at which 75 wt.-% of all 15 based on the weight of the mineral), dolomite, barite, and particles are smaller. The do value is thus the “weight mixtures of the foregoing, the white mineral pigments median grain diameter, i.e. 50 wt.-% of all grains are bigger include aluminium oxide Al-O containing minerals, for or Smaller than this particle size. For determining the weight example Y-Al-O having a cubic structure and C-Al-O median grain diameter do value, a Sedigraph 5120 device having a rhomboedral (trigonal) structure. Additionally, the from the company Micromeritics, USA or a Mastersizer aluminium oxide containing minerals may comprise other 2000 from Malvern company, GB can be used. elements such as for example sodium in NaO. 11 Al-O. A “specific surface area (SSA) of a calcium carbonate commonly known as diaoyudaoit. Other inventive white product in the meaning of the present invention is defined as mineral pigments are titanium dioxide TiO, containing min the surface area of the mineral particle divided by the mass erals, for example rutile, anatase or brookite. Further white of the mineral particle. As used herein the specific surface 25 mineral pigments are white oxide minerals such as barium area is measured by adsorption using the BET isotherm (ISO sulphate (BaSO4), zinc oxide (ZnO), zirconium dioxide 92.77:1995) and is specified in m/g. (ZrO2), or tin dioxide (SnO), or white sulphate minerals A “conventional flotation process' or a “direct flotation and white sulphide minerals such as zinc sulphide (ZnS) or process in the meaning of the present invention is a lead carbonate (PbCO). flotation process in which the desirable white pigments are 30 Preferably, the white mineral pigment is an alkaline earth directly floated and collected from the produced froth leav metal carbonate. ing behind a suspension containing the impurities. Alkaline earth metal carbonates in the meaning of the A “reverse flotation process” or “indirect flotation pro present invention are carbonates that comprise at least one cess' in the meaning of the present invention is a flotation alkaline earth metal cation. The alkaline earth metals accord process in which the impurities are directly floated and 35 ing to the present invention are beryllium Be", magnesium collected from the produced froth leaving behind a suspen Mg", calcium Ca", strontium Sr", barium Ba" and sion containing the desired white pigments. radium Ra" and, preferably, magnesium and calcium. The The inventive process for manufacturing white pigment alkaline earth metal carbonates in the meaning of the present containing products involves the provision of at least one invention are, for example, beryllium carbonate, magnesium “white pigment and impurities containing material” and at 40 carbonate, calcium carbonate, strontium carbonate, barium least one inventive collector agent. Said white pigment and carbonate or radium carbonate. impurities containing material and said collector agent are According to one embodiment of the present invention, mixed in an aqueous environment to form an aqueous the alkaline earth metal carbonate consist of only one Suspension. Afterwards or during mixing a gas is passed alkaline earth metal, for example, calcium. The alkaline through the obtained aqueous Suspension and the white 45 earth metal carbonate may alternatively consist of a mixture pigment containing product is recovered by removing the of two alkaline earth metals as for example calcium and white pigment bearing phase from the aqueous Suspension magnesium and, thus, the alkaline earth metal carbonate obtained after passing the gas through the Suspension. may be a calcium magnesium carbonate, e.g., dolomite. The In the following, details and preferred embodiments of the alkaline earth metal carbonate may comprise a mixture of process for manufacturing white pigment containing prod 50 two or more alkaline earth metals. ucts will be set out in more detail. It is to be understood that Additionally, the alkaline earth metal carbonate may these embodiments or details apply also for the white comprise further cations as for example sodium in gaylussit pigments containing product obtained by the inventive pro (sodium calcium carbonate). cess and for the inventive use of the white pigment bearing The white pigment may comprise more than one alkaline phase also obtained by the inventive process. 55 earth metal carbonate. For example, the white pigment may The White Pigment and Impurities Containing Material comprise one magnesium carbonate and one calcium car Step a) of the process of the invention refers to the bonate. Alternatively, the white pigment may consist of only provision of at least one white pigment and impurities one alkaline earth metal carbonate. containing mineral. The white pigment may comprise a mixture of two or A white pigment in the meaning of the present invention 60 more white mineral pigments. For example the white pig is a pigment that has a white colour. The white colour of the ment may comprise one alkaline earth metal carbonate and white pigments is predominately based on the relatively low an inorganic white pigment that is selected from the group light absorption in combination with an unselective light consisting of aluminium dioxide, titanium dioxide, barium scattering of the visual light at the pigments. The white Sulphate, Zinc oxid, Zirconium dioxide, or tin dioxide, white pigments according to the present invention are inorganic 65 Sulphate or Sulphide minerals. white pigments that may be obtained naturally and syntheti Preferably, the alkaline earth metal carbonate may be a cally and specifically include natural calcium carbonate or calcium carbonate. US 9,725,576 B2 10 Calcium carbonate or natural calcium carbonate is under removed or reduced have a white colour but have different stood to be a naturally occurring form of calcium carbonate, physical properties than the white pigments and, therefore, mined from sedimentary rocks such as limestone or chalk, or adversely affect the white pigments. from metamorphic marble rocks. Calcium carbonate is According to a preferred embodiment the starting mate known to exist as three types of crystal polymorphs: calcite, rial, e.g., the white pigment and impurities containing mate aragonite and Vaterite. Calcite, the most common crystal rial may comprise impurities selected from iron Sulphides. polymorph, is considered to be the most stable crystal form Iron Sulphides or iron Sulfides in the meaning of the of calcium carbonate. Less common is aragonite, which has present invention are understood to be chemical compounds a discrete or clustered needle orthorhombic crystal structure. of iron and Sulphur comprising a wide range of stochiomet Vaterite is the rarest calcium carbonate polymorph and is 10 ric formulae and different crystalline structures. For example generally unstable. Calcium carbonate is almost exclusively the iron sulphide can be iron(II) sulphide FeS (magnetopy of the calcitic polymorph, which is said to be trigonal rite) or pyrrhotite FeS whereinx is from 0 to 0.2. The iron rhombohedral and represents the most stable of the calcium sulphide can also be a iron(II) disulphide FeS (pyrite or carbonate polymorphs. The term “source of the calcium marcasite). The iron Sulphides can also contain other ele carbonate in the meaning of the present application refers to 15 ments then iron and Sulphur as for example nickel in the the naturally occurring mineral material from which the form of mackinawite (Fe,Ni)S whereinx is from 0 to 0.1. calcium carbonate is obtained. The source of the calcium The impurities in the white pigment and impurities con carbonate may comprise further naturally occurring compo taining material may also be iron oxides. nents such as magnesium carbonate, aluminium oxide etc. Iron oxides in the meaning of the present invention are The source of calcium carbonate may be selected from understood to be chemical compounds composed of iron and marble, chalk, calcite, dolomite, limestone, or mixtures oxide. Iron oxide comprises, for example iron(II) oxide FeC), thereof. Preferably, the source of calcium carbonate may be also known as wistite, iron(III) oxides FeO, also known selected from marble. as magnetite and iron(III) oxide Fe-O. The iron oxides Preferably, the alkaline earth metal carbonate may be a include also iron hydroxides and iron oxyhydroxides that ground calcium carbonate (GCC). Ground calcium carbon 25 contain beneath the elements iron and oxygen, the additional ate (GCC) is understood to be obtained by grinding the element hydrogen. Iron hydroxide comprises, for example calcium carbonate either dry or alternatively wet followed iron(II) hydroxide Fe(OH) and iron(III) hydroxide Fe(OH) by a Subsequent drying step. , also known as bernalite. Iron oxyhydroxide comprises, for In general, the grinding step can be carried out with any example O.-FeCOH also known as goethite forming pris conventional grinding device, for example, under conditions 30 matic needle-like crystals, Y-FeCOH also known as lepido Such that refinement predominantly results from impacts crocite forming orthorhombic crystal structures, 8-FeOOH with a secondary body, i.e. in one or more of a ball mill, a also known as feroxyhyte crystallizing in the hexagonal rod mill, a vibrating mill, a roll crusher, a centrifugal impact system and ferrihydrite Fe0OH.0.4H2O. The iron oxides mill, a vertical bead mill, an attrition mill, a pin mill, a can also contain additional elements as, for example, Sulphur hammer mill or other such equipment known to the skilled 35 in FesO(OH) (SO).nH2O also known as Schwertmannite man. In case calcium carbonate containing mineral powder or chloride in FeC(OH,Cl) also known as akaganeite. comprises a wet ground calcium carbonate containing min The white pigment and impurities containing material eral material, the grinding step may be performed under may comprise impurities that are selected from graphite. conditions such that autogenous grinding takes place and/or Graphite in the meaning of the present invention is by horizontal ball milling, and/or other Such processes 40 understood to be an allotrope of carbon. There are three known to the skilled man. The wet processed ground cal principal types of natural graphite: Crystalline flake graph cium carbonate containing mineral material thus obtained ite, amorphous graphite and lump graphite. Crystalline flake may be dewatered by well known processes, e.g. by filtra graphite (or flake graphite for short) occurs as isolated, flat, tion, centrifugation or forced evaporation prior to dewater plate-like particles with hexagonal edges if unbroken and, ing. An additional step of drying may be carried out in a 45 when broken, the edges can be irregular or angular. Amor single step Such as spray drying, or in at least two steps. phous graphite occurs as fine particles and is the result of Preferably, the white pigment may consist of only one thermal metamorphism of coal, the last stage of coalifica ground calcium carbonate. Alternatively, the white pigment tion, and is sometimes called meta-anthracite. Very fine flake may consist of a mixture of two ground calcium carbonates graphite is sometimes called amorphous in the trade. Lump selected from different Sources of ground calcium carbonate. 50 graphite (also called vein graphite) occurs in fissure veins or The white pigment may also comprise a mixture of two or fractures and appears as massive platy intergrowths of more ground calcium carbonates selected from different fibrous or acicular crystalline aggregates. Sources of ground calcium carbonate. For example, the Alternatively the impurities in the white pigment and white pigment may comprise one GCC selected from dolo impurities containing material may be silicates. The silicates mite and one GCC selected from calcite marble. Addition 55 may be colouring or abrasive. ally to the GCC the white pigment may comprise further Silicates or silicate minerals in the meaning of the present white mineral pigments. invention are understood to be compounds that comprise The white pigment and impurities containing material will silicon and oxygen. Additionally, the silicates can comprises contain white pigments as defined above and impurities. further ions such as for example aluminium ions, magne Impurities in the meaning of the present invention are 60 sium ions, iron ions or calcium ions. The silicates and substances that differ from the chemical composition of the silicate minerals can be selected from neosilicates, Sorosili white pigment and, therefore, are no white pigments. cates, cyclosilicates, inosilicates, phyllosilicates, and tecto The impurities to be removed or reduced by the process silicates and amorphous silicates. Neosilicates are silicate according to the present invention are compounds that have, minerals in which the SiO4 tetrahedra are isolated and have for example a grey, black, brown, red, or yellow colour or 65 metal ions as neighbours. Commonly known neosilicates are any other colour affecting the white appearance of the white Zircon, willemite, olivine, mullite, forsterite, aluminosili pigment material. Alternatively, the impurities to be cates or fayalite. Sorosilicates are silicate minerals which US 9,725,576 B2 11 12 have isolated double tetrahedral groups with a silicon to The total amount of the white pigment and the impurities oxygen ratio of 2:7. Commonly known Sorosilicates are in the white pigment and impurities containing material of ilavite, gehlenite, epidote or kornerupine. Cyclosilicates are step a) may represent at least 90 wt.-% relative to the total ring silicates that contain rings of linked SiO4 tetrahedra weight of the white pigment and impurities containing wherein the silicon to oxygen ratio is 1:3. Commonly known material, preferably at least 95 wt.-%, more preferably at cyclosilicates are benitonite, beryl or tourmaline. Inosili least 98 wt.-%, and most preferably at least 99 wt.-% relative cates or chain silicates are silicate minerals which have to the total weight of the white pigment and impurities interlocking chains of silicate tetrahedra with either SiO in containing material. a 1:3 ratio for single chains or SiO in a 4:11 ratio for double chains. Commonly known inosilicates are enstatite, 10 As set out before, in a preferred embodiment the impurity wollastonite, rhodenite, diopside or amphibolite as for in the white pigment and impurities containing material may example grunerite, cummingtonite, actinolithe or horn consist of a silicate. In this case, the total amount of the blende. Phyllosilicates are sheet silicates that form parallel white pigment and the silicate in the white pigment and sheets of silicate tetrahedra with SiOs or a silicon oxygen impurities containing material of step a) represents at least ration of 2:5. Commonly known phyllosilicates are clay 15 90 wt.-% relative to the total weight of the white pigment minerals, for example talc, kaoline, kaolinitic clay, calcined and impurities containing material, preferably at least 95 kaolinitic clay, halloysite, dickite, Vermiculite, nontronite, wt.-%, more preferably at least 98 wt.-%, and most prefer Sepiolite or montmorillonite, mica minerals, for example, ably for at least 99 wt.-%. biotite, muscovite, phlogopite, lepidolite or glauconite, or a Alternatively, the white pigment and impurities contain chlorite mineral, for example clinochlore. Tectosilicates or framework silicates have a three-dimensional framework of ing material may consist of white pigment and silicate. silicate tetrahedra with SiO, tetrahedra or a silicon oxygen Preferably, the white pigment and impurities containing ration of 1:2. Commonly known tectosilicates are quartz material may consist of white pigment and quartz. Alterna minerals as for example quartz, tridymite and cristobalite, tively, the white pigment and impurities containing material feldspar minerals as for example potassium feldspars com 25 may consist of white pigment and a white colored silicate prising orthoclase and microline, Sodium or calcium feld that is selected from the group consisting of wollastonite, spars comprising plagioclase, albite and andesine or Scapo kaolin, kaolinitic clay, calcines kaolinitic clay, montmoril lite and Zeolithe. Amorphous silicates are for example lonite, talc, diatomaceous earth or sepiolite. diatomaceous earth or opale. The white pigment and impurities containing material of The silicate may be selected from the group consisting of 30 step a) may have a weight median grain diameter in the quartz, a mica, an amphibolite, an feldspar, a clay mineral range of from 1 to 1000 um, preferably of from 3 to 700 um, and mixtures thereof and, preferably, may be quartz. The inventive process is especially contemplated for more preferably of from 5 to 500 um and most preferably of separating white pigments from impurities that consist of from 10 to 80 um or from 100 to 400 um. quartz and/or additional silicates. 35 In another preferred embodiment the white pigment and Preferably the impurity in the white pigments and impu impurities containing material of step a) may have a weight rities containing material consist only of quartz. median grain diameter in the range of from 1 to 1000 um, Alternatively, the impurity or impurities in the white preferably of from 3 to 500 um, more preferably of from 5 pigment and impurities containing material may comprise to 100 um and most preferably of from 10 to 80 um if the silicates that have a white colour. For example, the impuri 40 Subsequent flotation process is a standard flotation process. ties may comprise silicates such as wollastonite, kaolin, A standard flotation process in the meaning of the present kaolinitic clay, calcined kaolinitic clay, montmorillonite, invention is a flotation process that is performed after talc, diatomaceous earth or sepiolite. In a preferred embodi grinding and/or classification of the white pigment and ment of the invention, the impurity consists of silicates that impurities containing material. have a white colour and more preferably the impurity 45 consists of only one white coloured silicate. For example, In another preferred embodiment the white pigment and the impurity may consist only of wollastonite, kaolin, kao impurities containing material of step a) may have a weight linitic clay, calcines kaolinitic clay, montmorillonite, talc, median grain diameter in the range of from 1 to 1000 um, diatomaceous earth or sepiolite. These impurities obtained preferably of from 10 to 700 um, more preferably of from 50 and separated according to the inventive flotation method 50 to 500 um and most preferably of from 100 to 400 m if the may be further processed and used in Suitable applications. Subsequent flotation process is a coarse flotation process. A The impurities containing only white coloured silicates and, coarse flotation process in the meaning of the present preferably containing only one white coloured silicate invention is a flotation process that is performed within the obtained by the inventive process may be used in the same first grinding loop of the white pigment and impurities way than the white pigment containing product. 55 containing material. In a preferred embodiment, the amount of white pigment in the white pigment and impurities containing material of The Collector Agent step a) may be from 0.1 to 99.9 wt.-%, based on the dry Step b) of the process of the present invention refers to the weight, preferably from 30 to 99.7 wt.-%, more preferably provision of at least one collector agent. from 60 to 99.3 wt.-% and most preferably from 80 to 99 60 A collector agent in the meaning of the present invention wt.-%, based on the dry weight. is a chemical compound that is adsorbed by the envisaged In another preferred embodiment, the weight ratio of particles either by chemisorptions or by physisorption. The white pigment:impurities in the white pigment and impuri collector agent is an organic collector compound that con ties containing material of step a) may be from 0.1: 99.9 to tains at least one amino group. The collector agent according 99.9:0.1, based on the dry weight, preferably from 30:70 to 65 to the present invention is selected from the group consisting 99.7:0.3, more preferably from 60:40 to 99.3:0.7, and most of compounds of formula (1) and compounds of formula (2) preferably from 80:20 to 99:1, based on the dry weight. and mixtures thereof US 9,725,576 B2 13 14 nitrogen atom via their sp2 carbon atom. Preferably E. E. (1) and E may be chosen from ethylene oxide —(CH-CH O)—, and propylene oxide —(CH-CH(CH)—O)— and/ ,E); H or -(CH(CH) CH-O)—. More preferably from 70 R-t-Ary mol % to 100 mol% of all the alkylene oxide groups present (E1), (E) -H in the compound of formula (1), are ethylene oxide groups and Omol % to 30 mol % are propylene oxide groups. Still more preferably E. E. and E are identical radicals and are (2) chosen from among ethylene oxide and propylene oxide, ?: 10 even more preferably all E. E. and E are identical radicals R.---N-A-,-N and are ethylene oxide groups. It should also be understood O| R24 Y. 23 s that each of E. E. and E may comprise two or more different alkylene oxides groups that may be arranged in block or random distribution. wherein 15 The values n, n and n, may be identical or different, and R represents a hydrocarbon group containing from 6 to 30 independently may represent an integer from 1 to 10, more carbon atoms, preferably from 1 to 5, and still more preferably from 1 to A represents an alkylene group having from 1 to 6 carbon 3. Preference may also given to compounds of formula (1) atoms, wherein the Sum of n+n+n is strictly less than 10. E. E. and E, are identical or different from each other, each Alternatively if the collector agent comprises compounds independently chosen from among alkylene oxide groups of formula (1) and additionally compounds of formula (2) containing from 1 to 6 carbon atoms, the values n, n and n may be identical or different, and n, n and n, are identical or different from each other, each independently may represent an integer from 3 to 20, independently chosen from an integer which value is from 1 preferably from 3 to 10. In this case preference may also to 20, 25 given to compounds of formula (1) wherein the Sum n+n+ p is 1, 2, 3 or 4. n3 ranges from 10 to 40, preferably from 10 to 30. R represents a hydrocarbon group containing from 6 to 30 The value p may be preferably 1 or 2, and more preferably carbon atoms, 1. R and R2 are identical or different from each other, each According to a preferred embodiment, the compound of independently chosen from among hydrocarbon groups con 30 formula (1) possesses at least one of the following charac taining from 1 to 6 carbon atoms, teristics: R represents hydrogen or a hydrocarbon group containing R represents a straight or branched hydrocarbon group from 1 to 6 carbon atoms, containing from 6 to 30 carbon atoms, preferably from 8 to A represents an alkylene group having from 1 to 6 carbon 26, more preferably from 12 to 22 carbon atoms, optionally atoms, 35 containing one or more insaturation(s), in the form of double q is 1, 2, 3 or 4. and/or triple bond(s), The compounds of formula (1) and (2) may also be used A represents a straight or branched alkylene group having in the form of their addition salts with one or more acid(s), from 1 to 6 carbon atoms, preferably from 2 to 6 carbon said acid(s) being chosen from among mineral and organic atoms, more preferably 2, 3 or 4 carbon atoms, acids, including, but not limited to, hydrochloric acid, acetic 40 E. E. and E, are identical or different from each other, each acid, phosphoric acid, Sulphuric acid, alkane (e.g. methane) independently chosen from among ethylene oxide (OE) Sulphonic acid, toluene Sulphonic acid, and the like. group, propylene oxide (OP) group and butylene oxide (OB) According to one embodiment of the present invention the group, preferably among OE group and OP group, more compounds of formula (1) and/or formula (2) may have preferably each of E. E. and E. represents an OE group, various R and/or R radicals and therefore may comprise 45 n, n and n are identical or different from each other, each a mixture of different compounds of formula (1) and/or independently chosen from an integer which value is from 1 formula (2). For example, the mixture will comprise com to 20, preferably from 1 to 10, and the sum pounds of formula (1) and/or formula (2) wherein the n+n+n, ranges from 3 to 9, various R and/or R radicals contain from 16 to 18 carbon p is 1, 2, 3 or 4, preferably 1 or 2, and more preferably p is atOmS. 50 1. The R radical in the compounds of formula (1) and the Alternatively, if the collector agent comprises compounds R radical in the compounds of formula (2) may be a of formula (1) and, additionally, compounds of formula (2), straight, cyclic or branched, saturated or unsaturated hydro the compounds of formula (1) may possess at least one of the carbon group having from 6 to 30, preferably from 8 to 26, following characteristics: more preferably from 12 to 22 carbon atoms, said group 55 R represents a straight or branched hydrocarbon group optionally containing one or more rings. containing from 6 to 30 carbon atoms, preferably from 8 to The A radical may represents an alkylene group having 26, more preferably from 12 to 22 carbon atoms, optionally from 1 to 6 carbon atoms, preferably from 2 to 6 carbon containing one or more insaturation(s), in the form of double atoms, more preferably 2, 3 or 4 carbon atoms. Preferred and/or triple bond(s), compounds of formula (1) are those wherein A represents 60 A represents a straight or branched alkylene group having propylene. from 1 to 6 carbon atoms, preferably from 2 to 6 carbon The radicals E, E, and E may be chosen from methylene atoms, more preferably 2, 3 or 4 carbon atoms, oxide —(CH-O)—, ethylene oxide —(CH-CH E. E. and E, are identical or different from each other, each O)—, propylene oxide —(CH-CH(CH)—O)— and/or independently chosen from among ethylene oxide (OE) —(CH(CH)—CH2—O)—, and butylene oxide —(CH 65 group, propylene oxide (OP) group and butylene oxide (OB) (CH CH)—CH2—O)— and/or —(CH CH(CH group, preferably among OE group and OP group, more CH)—O)—. E. E. and E are linked to the respective preferably each of E. E. and E. represents an OE group, US 9,725,576 B2 15 16 n, n and n are identical or different from each other, each For example, compounds of formula (1) may be easily independently chosen from an integer which value is from 1 obtained by condensation of a fatty polyamine with alkylene to 20, preferably from 1 to 10, and the Sum n+n+n, ranges oxide(s). A typical example of a compound of formula (1) is from 3 to 40, and preferably from 3 to 30, an ethoxylated tallow diamine, for example a tallow diamine p is 1, 2, 3 or 4, preferably 1 or 2, and more preferably p is reacted with 3 molecules of ethylene oxide, typically N',N', 1. N'-tri-hydroxyethyl-N-tallow (or arachidyl or behenyl) pro According to a further preferred embodiment, the above pylene diamine (tallow or arachidyl or behenyl diamine with compound of formula (1) may possess at least one of the 3 moles ethylene oxide), having CAS RN 61790-85-0. This following characteristics or may possess all of the following compound is of particular interest as it is liquid at room characteristics: 10 temperature, easy to handle, readily dispersible in water, and R represents a straight alkyl group containing from 8 to 26, being biodegradable. and more preferably from 12 to 22 carbon atoms, As other compounds of formula (1), mention may be A represents a straight alkylene group having from 2 to 4 made of various alkoxylated propylene diamine compounds, carbon atoms, for example a —(CH)— (propylene) group, 15 among which mention may be made of for example, N,N', E. E. and Es, are identical or different from each other, each N'-tri-hydroxyethyl-N-oleyl propylene diamine (CAS Reg independently chosen from among OE group and OP group, istry Number 103625-43-0), N,N',N'-tri-hydroxyethyl-N- more preferably each of E, E, and E. represents an OE lauryl propylene diamine (CAS RN 25725-44-4), grOup, propoxylated N-tallow alkyl trimethylene diamines (CAS n, n and n are identical or different from each other, each RN 68603-75-8), and the like. independently chosen from an integer which value is from 1 Compounds of formula (2) may be easily obtained by to 5, preferably from 1 to 3 and the Sum n+n+n, ranges condensation of an unsaturated fatty acid (rapeseed oil, tall from 3 to 9, for example the sum n+n+n is 3. oil) with an amine compound of formula (2): p is 1 or 2, and is preferably 1. Alternatively if the collector agent comprises compounds 25 of formula (1) and additionally compounds of formula (2), (2) the compounds of formula (1) may possess at least one of the R22 following characteristics or may possess all of the following H-e-N-A \ characteristics: R24---, R23 R represents a straight alkyl group containing from 8 to 26, 30 and more preferably from 12 to 22 carbon atoms, A represents a straight alkylene group having from 2 to 4 wherein R. R. R. A. and q are as defined above. carbon atoms, for example a —(CH)— (propylene) group, The condensation product of dimethyl amino propyl E. E. and Es, are identical or different from each other, each amine with a C-Cls unsaturated fatty acid, such as from independently chosen from among OE group and OP group, 35 rapeseed oil (CAS RN 85408-42-0), or from tall oil (CAS more preferably each of E. E. and E represents an OE RN 68650-79-3) are of particular interest as they are liquid grOup, at room temperature (easy to handle), readily dispersible in n, n and n are identical or different from each other, each water and provide the further advantage of being biodegrad independently chosen from an integer which value is from 3 able. to 20, preferably from 3 to 10 or alternatively the sum 40 Other examples of compounds of formula (2) are the n+n+n, ranges from 10 to 40, and preferably from 10 to condensation products of dimethylamino propylamine with 30, a coco, palm, tallow, and/or oleic fatty acid, and/or with a p is 1 or 2, and is preferably 1. C (e.g. lauric) fatty acid, and/or with a C (e.g. ricinoleic) The compounds of formula (1) may be chosen from fatty acid, and/or with Co-C fatty acid, and/or the like. alkoxylated Co-Co alkyl fatty polyamines, and preferably 45 Other examples of compounds of formula (2) are those with may be chosen from C-C alkyl ethoxylated or propoxy the following Registry CAS numbers: 68188-30-7, 69278 lated fatty diamines. “Polyamine' in the meaning of the 64-4, 691400-76-7, 165586-99-2, 226994-25-8, 97.552-95-9 present invention intends a compound comprising two or which are the condensation products of dimethyl amino more amine groups, the amine groups possibly being Sub propylamine with Soya oil, castor oil, peanut oil, almond oil, stituted, i.e. the two or more amine groups may be identical 50 avocado oil, fish oil, respectively. or different and be primary, secondary or tertiary amine The collector agent may be selected from the group groups. consisting of compounds of formula (1) and compounds of Preferred compounds of formula (2) may possess at least formula (2) and mixtures thereof. For example, the collector one of the following characteristics: agent may consist of one compound of formula (1) and at R and R2 are identical or different from each other, each 55 least one compound of formula (2) or may consist of one independently chosen from among hydrocarbon groups con compound of formula (2) and at least one compound of taining from 1 to 6 carbon atoms, preferably from 1 to 4 formula (1). In a preferred embodiment the collector agent carbon atoms, and more preferably are chosen from among may consist of only one compound of formula (1) and only methyl, ethyl, propyl and butyl, one compound of formula (2). R2 represents hydrogen, 60 The weight ratio of compound(s) of formula (1) to com A represents an alkylene group having 1, 2, 3 or 4 carbon pound(s) of formula (2) in the collector agent may vary in atoms, and preferably A is ethylene or propylene, and more great proportions, without any specific limitation. According preferably propylene, to a preferred embodiment, this weight ratio ranges from q is 1 or 2, and preferably 1. 1:99 to 99:1, more preferably from 20:80 to 80:20, even The compounds of formula (1) and (2) are commercially 65 more preferably from 40:60 to 60:40, based on dry weight available or may be prepared according to known prepara of the compounds of formula (1) and (2). Particularly tions techniques. satisfactory results are obtained with a 50:50 weight ratio US 9,725,576 B2 17 18 mixture of at least one compound of formula (1) and at least wt.-% and most preferably of between 25 and 55 wt.-%, one compound of formula (2), and typically with a 50:50 based on the total weight of the Solids in the Suspension. weight ratio mixture consists of one compound of formula The aqueous Suspension obtained in step c) may have a (1) and one compound of formula (2). pH from 7 to 12, preferably from 7.5 to 11 and more Alternatively, the collector agent may consist only of one 5 preferably from 8.5 to 9.5. or more compounds of formula (1) or may consist only of The inventive collecting agent(s) may be added in step c) one or more compounds of formula (2). in an amount of from 5 to 5000 ppm, based on the total dry The collector agent may be substantially free, and more weight of the mineral material of step a), preferably in an preferably may be totally free, from any quaternary ammo amount of from 20 to 2000 ppm, more preferably in an nium-containing compound. 10 amount of from 30 to 1000 ppm, and most preferably in an Step c) of the Process of the Invention amount of from 50 to 800 ppm, based on the total dry weight Step c) of the process of the invention refers to mixing of the mineral material of step a). said white pigment and impurities containing material of The amount of the inventive collecting agent may be step a) and said collector agent of step b), in an aqueous adjusted by considering the specific Surface area of the environment to form an aqueous Suspension. 15 impurities. According to one embodiment, the inventive According to one embodiment of the present invention the collecting agent may be added in step c) in an amount of at least one white pigment and impurities containing mate from 1 to 100 mg perm of impurities in said white pigment rial of step a) may be mixed, in a first step, with water, and containing material of step a), preferably in an amount of then, the obtained suspension may be mixed with the col from 5 to 50 mg per m of impurities in said white pigment lector agent of step b) to form an aqueous Suspension. containing material of step a), and most preferably of from The collectoragent of step b) may be mixed, in a first step, 10 to 45 mg per m of impurities in said white pigment with water, and then, the obtained Suspension may be mixed containing material of step a). The specific Surface area of with the at least one white pigment and impurities contain the impurities is measured as described in the Examples ing material of step a) to form an aqueous Suspension. section hereafter. According to another embodiment of the present inven 25 The inventive collecting agent(s) may be present in the tion, the at least one white pigment and impurities contain aqueous Suspension obtained in step c) in an amount of from ing material of step a) and the collector agent of step b) may 0.01 to 10 wt.-%, based on the total weight of the solids in be mixed in one step with water to form an aqueous the suspension, preferably from 0.05 to 5 wt.-%, more Suspension. preferably from 0.1 to 3.0 wt.-%, and most preferably from Preferably, mixing may be carried out using a wet mill, a 30 0.2 to 2.0 wt.-%, based on the total weight of the solids in mixing tank or a flotation agitator for mixing the collector the Suspension. into the aqueous suspension. Additionally to the white pigment and impurities contain The mixing may be carried out at room temperature, i.e. ing material a) and the collectoragent b), one or more further at 20° C.2°C., or at other temperatures. According to one additives may be present in the aqueous Suspension. Pos embodiment the mixing may be carried out at a temperature 35 sible additives are, for example pH-adjusting agents, Sol from 5 to 90° C., preferably from 10 to 80° C. and most vents (water, organic solvent(s) and mixtures thereof); preferably from 20° C. to 60° C., or at other temperatures. depressants, such as starch, quebracho, tannin, dextrin and Heat may be introduced by internal shear or by an external guar gum, and polyelectrolytes, such as polyphosphates and Source or a combination thereof. water glass, which have a dispersant effect, often combined The water of step c) may be preheated before it is mixed 40 with a depressant effect. Other conventional additives that with the white pigment and impurities containing material of are known in the art of flotation are frothers (foaming step a) and the collector agent of step b). agents). Such as methyl isobutyl carbinol, triethoxybutane, Mixing may be carried out for at least 1 s, preferably for pine oil, terpineol and polypropylene oxide and its alkyl at least 1 min, e.g. for at least 15 min, 30 min, 1 hour, 2 ethers, among which methyl isobutyl carbinol, triethoxy hours, 4 hours, 6 hours, 8 hours, or 10 hours. 45 butane, pine oil, terpineol, are preferred frothers. By way of The solids content of the aqueous Suspension obtained by non limiting examples, preferred conventional additives are the inventive method can be adjusted by the methods known generally frothers, among which terpineol is the most com to the skilled person. To adjust the solids content of an monly used. aqueous white pigments and impurities containing material Furthermore, one or more other conventional collector comprising Suspension, the Suspension may be partially or 50 agents known in the art of flotation, and preferably one or fully dewatered by a filtration, centrifugation or thermal more conventional cationic collector agents may be in the separation process. For example, the Suspension may be aqueous Suspension formed in step c). Preferred conven partially or fully dewatered by a filtration process such as tional cationic collector agents are those containing no filtration or a thermal separation process Such as an evapo Sulphur atoms, and most preferred are those containing only ration process. Alternatively, water may be added to the 55 carbon, nitrogen and hydrogen atoms and optionally oxygen white pigment and impurities containing material until the atoms. Conventional cationic collectoragents, in the form of desired solids content is obtained. Additionally or alterna their addition salts with acids, may however contain Sulphur tively, a Suspension having an appropriate lower content of atom(s), when the Salifying acid itself comprises Sulphur a white pigment and impurities containing material may be atom(s), e.g. Sulphuric, Sulphonic or alkane Sulphonic acid. added to the aqueous Suspension until the desired solid 60 Examples of conventional cationic collector agents that content is obtained. may be present in the Suspension obtained from step c) may According to a preferred embodiment, of the present include, but are not limited to fatty amines and their salts, as invention the aqueous Suspension obtained in step c) has a well as their alkoxylated derivatives, fatty poly(alkylene Solids content measured as described in the Examples sec amines) and their salts, e.g. poly(ethylene amines), polypro tion hereafter of between 5 and 80 wt.-% based on the total 65 pylene amines) and their salts, as well as their alkoxylated weight of the solids in the suspension, preferably of between derivatives, fatty amidopolyamines, and their salts, as well 10 and 70 wt.-%, more preferably of between 20 and 60 as their alkoxylated derivatives, fatty amidopoly(alkyle US 9,725,576 B2 19 20 namines), and their salts, as well as their alkoxylated deriva duced via entry ports located on an agitation device in said tives, fatty imidazolines and their salts, as well as their vessel. The gas then naturally rises upwards through the alkoxylated derivatives, N-fatty alkylamino carboxylic acid Suspension. and their salts, e.g. N-fatty alkyl amino propionic acid and Preferably the gas in the present invention may be air. their salts, alkyl ether amines and alkyl ether diamines and The gas may have a bubble size in the Suspension of their salts, quaternary ammonium compounds, e.g. fatty between 0.01 and 10 mm, preferably of between 0.05 and 5 quaternary ammonium compounds, mono (fatty alkyl) qua mm and most preferably between 0.1 and 2 mm. The gas ternary ammonium compounds, di(fatty alkyl) quaternary flow rate in step d) may be adjusted, e.g. between 0.1 and 30 ammonium compounds, such as those described in WO dm/min, preferably between 1 and 10 dm/min and more 10 preferably between 3 and 7dm/min in a 4 dm flotation cell. 2007/122148, and the like. According to a preferred embodiment of the invention, A "polyamine' in the meaning of the present invention is step d) may implement an agitation cell and/or a flotation a compound comprising two or more amine groups, the column and/or a pneumatic flotation device and/or a flota amine groups possibly being Substituted, i.e. the two or more tion device featuring a gas injection. amine groups may be identical or different and be primary, 15 According to a preferred embodiment of the present secondary or tertiary amine groups. invention, the aqueous Suspension in step d) may have a Specific examples of conventional cationic collector temperature of between 5 and 90°C., preferably between 10 agents that may be present in the Suspension obtained from and 70° C., more preferably of between 20 and 50° C. and step c) may include, without any limitation, dicoco-dimethyl most preferably between 25 and 40° C. ammonium chloride (CAS RN 61789-77-3), coco-dimeth Step d) may be preferably performed under agitation. Furthermore, step d) may be continuous or discontinuous. ylbenzyl ammonium chloride (CAS RN 61789-71-7), tallow According to a preferred embodiment, step d) is per dimethylbenzyl ammonium chloride (CAS RN 61789-75 formed until no more foam is formed or can be visually 1), ethoxylated tallow monoamine, 1,3-propanediamine-N- observed or until no more impurities can be collected in the tallow diacetate (CAS RN 68911-78-4), N,N',N'-tri-hy 25 foam. droxyethyl N-tallow propylene diamine (CAS RN 61790 Step e) of the Process of the Invention 85-0), N,N',N'-tri-hydroxyethyl N-oleyl propylene diamine Stepe) of the process of the invention refers to recovering (CAS RN 103625-43-0), N,N',N'-tri-hydroxyethyl N-lauryl the white pigment containing product by removing the white propylene diamine (CAS RN 25725-44-4), fatty alkyl imi pigment bearing phase from the aqueous Suspension dazoline obtained by condensation of diethylenetriamine 30 obtained after step d). and oleic fatty acid (CAS RN 162774-14-3), N,N',N'-tri The inventive process comprises at least one indirect hydroxyethyl N-behenyl-propylene diamine (CAS RN flotation step. In contrast to conventional flotation, in which 91001-82-0), isodecyloxypropyl-1,3-diaminopropane (CAS the desirable white pigments are directly floated and col RN 72.162-46-0), N,N-di(tallow carboxyethyl)-N-hydroxy lected from the produced froth, reverse or indirect flotation 35 aims to have the undesirable impurities preferentially floated ethyl-N-methyl ammonium methylsulphate (CAS RN and removed, leaving behind a Suspension that has been 91995-81-2), N-coco-f-aminopropionic acid (CAS RN concentrated in the desirable white pigments. According to 84812-94-2), N-lauryl-3-aminopropionic acid (CAS RN the present invention, the inventive process leads to the 1462-54-0), N-myristyl-3-aminopropionic acid (CAS RN formation of a froth containing the impurities and a white 14960-08-8), their addition salts with acid(s), sodium salt of 40 pigment bearing phase with the white pigment containing N-lauryl-3-aminopropionic acid (CAS RN 3546-96-1), tri product. The hydrophobised impurities are migrating to the ethanolamine salt of N-lauryl-3-aminopropionic acid (CAS Surface of the Suspension and are concentrated in a Super RN 14171-00-7), triethanolamine salt of N-myristyl-3- natant foam or froth at the surface. This foam can be aminopropionic acid (CAS RN 61791-98-8), as well as collected by skimming it off the Surface, using for example 45 a scraper, or simply by allowing an overflowing of the foam, mixtures of two or more of the above compounds, in all and passing the foam into a separate collection container. proportions, and the like. After collecting the foam, the white pigment bearing phase “Etheramines' and “etherdiamines' in the meaning of the containing the non-floated white pigment containing product present invention are compounds comprising at least one will remain. The white pigment containing product remain ether group and respectively a NH2 terminal group and a 50 ing in the aqueous Suspension can be collected by filtration NH terminal group as well as another primary, secondary or to remove the aqueous phase, by decantation or by other tertiary amine group. means commonly employed in the art to separate liquids If there are additives and/or conventional collector agents from solids. in the Suspension, the collector agent of the present inven The collected white pigment containing product can be 55 subjected to one or more further steps of froth flotation, tion may be present from 1 wt.-% to 100 wt.-%, more according to the invention or according to prior art froth preferably from 10 wt.-% 100 wt.-%, typically from 20 flotation methods. wt.-% to 100 wt.-%, and advantageously from 1 wt.-% to 99 According to a preferred embodiment, the white pigment wt.-%, more preferably from 10 wt.-% to 99 wt.-%, typically bearing phase obtained from step e) may be ground before from 20 wt.-% to 99 wt.-% relative to the total amount of the 60 and/or after step e). collector agent and the further additives. The grinding step can be carried out with any conven Step d) of the Process of the Invention tional grinding device, for example by e.g. using a ball mill, Step d) of the process of the invention refers to passing a a hammer mill, a rod mill, a vibrating mill, a roll crusher, a gas through the Suspension formed in Step c). centrifugal impact mill, a vertical bead mill, an attrition mill, The gas may be generally introduced in the vessel of step 65 a pin mill, a hammer mill. However, any other device that is d) via one or more entry ports located in the lower half of the able to grind the white pigment containing product recov vessel. Alternatively or additionally, the gas may be intro ered during method step e) may be used. US 9,725,576 B2 21 22 Step e) of the inventive process may be followed by at The scope and interest of the invention will be better least one grinding or classification step for example by wet understood based on the following examples which are grinding and screening to achieve a fine ground product intended to illustrate certain embodiments of the invention slurry and/or at least one other treatment step. and are non-limitative. The hydrophobised impurities obtained by the inventive process and, preferably the hydrophobised silicates that are EXAMPLES contained in the foam can be collected as already set out above. In a preferred embodiment of the invention, the 1. Measurement Methods hydrophobised impurities may comprise silicates that have a 10 pH Measurement white colour as for example wollastonite, kaolin, kaolinitic The pH was measured at 25° C. using a Mettler Toledo clay, calcines kaolinitic clay, montmorillonite, talc, diato Seven Easy pH meter and a Mettler Toledo InLab(R) Expert maceous earth or sepiolite. More preferably, the hydropho Pro pH electrode. A three point calibration (according to the bised impurity consists of silicates that have a white colour segment method) of the instrument was first made using and more preferably the impurity consists of only one white 15 commercially available buffer solutions having pH values of coloured silicate. For example, the impurity may consist 4, 7 and 10 at 20°C. (from Aldrich). The reported pH values only of wollastonite or kaolin or kaolinitic clay or calcines were the endpoint values detected by the instrument (the kaolinitic clay or montmorillonite or talc or diatomaceous endpoint was when the measured signal differs by less than earth or sepiolite. These impurities obtained and separated 0.1 mV from the average over the last 6 seconds). from the white pigments according to the inventive flotation Particle Size Distribution (Mass % Particles with a method may be further processed and used in suitable Diameter