Process for manufacturing white pigment containing products

Abstract

The present invention concerns a process for manufacturing white pigment containing products. The white pigment containing products are obtained from at least one white pigment and impurities containing material via froth flotation.

Claims

1. A process for manufacturing a white pigment containing product comprising the following steps: a) providing at least one white pigment and impurities containing material, b) providing at least one collector agent selected from the group consisting of compounds of formula (1), ##STR00006## wherein R.sub.1 represents a hydrocarbon group containing from 6 to 30 carbon atoms, A.sub.1 represents an alkylene group having from 1 to 6 carbon atoms, E.sub.1, E.sub.2 and E.sub.3, are identical or different from each other, each independently chosen from among alkylene oxide groups containing from 1 to 6 carbon atoms, n.sub.1, n.sub.2 and n.sub.3, are identical or different from each other, each independently chosen from an integer which value is from 1 to 20, p is 1, 2, 3 or 4, and compounds of formula (2) ##STR00007## wherein R.sub.21 represents a hydrocarbon group containing from 6 to 30 carbon atoms, R.sub.22 and R.sub.23 are identical or different from each other, each independently chosen from among hydrocarbon groups containing from 1 to 6 carbon atoms, R.sub.24 represents hydrogen or a hydrocarbon group containing from 1 to 6 carbon atoms, A.sub.2 represents an alkylene group having from 1 to 6 carbon atoms, and q is 1, 2, 3 or 4, and mixtures of compounds (1) and (2), c) mixing the white pigment and impurities containing material of step a) and the collector agent of step b) in an aqueous environment to form an aqueous suspension, d) passing gas through the suspension formed in step c), and e) recovering the white pigment containing product by removing a white pigment bearing phase from the aqueous suspension obtained after step d).

2. The process according to claim 1, wherein step d) results in the formation of a froth containing the impurities and a white pigment bearing phase with the white pigment containing product.

3. The process according to claim 1, wherein the white pigment is selected from the group consisting of a white mineral pigment, natural calcium carbonate, ground calcium carbonate, calcium carbonate-containing mineral material, dolomite, barite, aluminium oxide, titanium dioxide, and any mixture thereof.

4. The process according to claim 1, wherein the white mineral pigment is an alkaline earth metal carbonate, a calcium carbonate, or ground calcium carbonate (GCC).

5. The process according to claim 1, wherein the white pigment containing material comprises impurities selected from the group consisting of iron sulphides, iron oxides, graphite, silicates, and any mixture thereof.

6. The process according to claim 5, wherein the silicates are selected from the group consisting of quartz, a mica, an amphibolite, an feldspar, a clay mineral and any mixture thereon.

7. The process according to claim 5, wherein the silicate is a white coloured silicate selected from the group consisting of wollastonite, kaolin, kaolinitic clay, calcined kaolinitic clay, montmorillonite, talc, diatomaceous earth, sepiolite, and any mixture thereof.

8. The process according to claim 1, wherein the white pigment is present in the white pigment and impurities containing material of step a) in an amount from 30 to 99.6 wt.-%, based on the dry weight of the white pigment and impurities containing material, and the impurities are present in the white pigment and impurities containing material of step a) in an amount from 0.4 to 60 wt.-%, based on the dry weight of the white pigment and impurities containing material.

9. The process according to claim 1, wherein the white pigment is present in the white pigment and impurities containing material of step a) in an amount from 60 to 99.3 wt.-%, based on the dry weight of the white pigment and impurities containing material, and the impurities are present in the white pigment and impurities containing material of step a) in an amount from 0.7 to 40 wt.-%, based on the dry weight of the white pigment and impurities containing material.

10. The process according to claim 1, wherein the white pigment is present in the white pigment and impurities containing material of step a) in an amount from 80 to 99 wt.-%, based on the dry weight of the white pigment and impurities containing material, and the impurities are present in the white pigment and impurities containing material of step a) in an amount from 1 to 20 wt.-%, based on the dry weight of the white pigment and impurities containing material.

11. The process according to claim 1, wherein the white pigment and impurities containing material of step a) has a weight median grain diameter in the range of from 1 to 1000 μm.

12. The process according to claim 1, wherein the white pigment and impurities containing material of step a) has a weight median grain diameter in the range of from 5 to 500 μm.

13. The process according to claim 1, wherein the white pigment and impurities containing material of step a) has a weight median grain diameter in the range of from 10 to 80 μm.

14. The process according to claim 1, wherein the compound of formula (1) possesses the following characteristics: R.sub.1 represents a straight or branched hydrocarbon group containing from 8 to 26 carbon atoms, optionally containing one or more insaturation(s), in the form of double and/or triple bond(s), A.sub.1 represents a straight or branched alkylene group having from 2 to 6 carbon atoms, E.sub.1, E.sub.2 and E.sub.3, are identical or different from each other, each independently chosen from among ethylene oxide (OE) group, propylene oxide (OP) group and butylene oxide (OB) group, n.sub.1, n.sub.2 and n.sub.3, are identical or different from each other, each independently chosen from an integer which value is from 1 to 10, and the sum n.sub.1+n.sub.2+n.sub.3 ranges from 3 to 9, and p is 1 or 2.

15. The process according to claim 1, wherein the compound of formula (1) possesses the following characteristics: R.sub.1 represents a straight or branched hydrocarbon group containing from 12 to 22 carbon atoms, optionally containing one or more insaturation(s), in the form of double and/or triple bond(s), A.sub.1 represents a straight or branched alkylene group having from 2, 3 or 4 carbon atoms, E.sub.1, E.sub.2 and E.sub.3, are identical or different from each other, each independently chosen from among an OE group and an OP group, n.sub.1, n.sub.2 and n.sub.3, are identical or different from each other, each independently chosen from an integer which value is from 1 to 10, and the sum n.sub.1+n.sub.2+n.sub.3 ranges from 3 to 9, and p is 1.

16. The process according to claim 1, wherein the compound of formula (2) possesses the following characteristics: R.sub.22 and R.sub.23 are identical or different from each other, each independently chosen from among hydrocarbon groups containing from 1 to 4 carbon atoms, R.sub.24 represents hydrogen, A.sub.2 represents an alkylene group having 1, 2, 3 or 4 carbon atoms, and q is 1 or 2.

17. The process according to claim 1, wherein the compound of formula (2) possesses the following characteristics: R.sub.22 and R.sub.23 are identical or different from each other, each independently chosen from among methyl, ethyl, propyl and butyl, R.sub.24 represents hydrogen, A.sub.2 is ethylene or propylene, and q is 1.

18. The process according to claim 1, wherein the collector agent of step b) consists of one or more compounds of formula (1) or consist of one or more compounds of formula (2).

19. The process according to claim 1, wherein the aqueous suspension obtained in step c) has a pH from 7 to 12.

20. The process according to claim 1, wherein the aqueous suspension obtained in step c) has a pH from 7.5 to 11.

21. The process according to claim 1, wherein the aqueous suspension obtained in step c) has a pH from 8.5 to 9.5.

22. The process according to claim 1, wherein the collecting agent is added in step c) in an amount of from 5 to 5000 ppm based on the total dry weight of the white pigment and impurities containing material of step a).

23. The process according to claim 1, wherein the collecting agent is added in step c) in an amount of from 30 to 1000 ppm, based on the total dry weight of the white pigment and impurities containing material of step a).

24. The process according to claim 1, wherein the aqueous suspension obtained in step c) has a solids content of between 5 and 80 wt.-%, based on the total weight of the solids in the suspension.

25. The process according to claim 1, wherein the aqueous suspension obtained in step c) has a solids content of between 20 and 60 wt.-%, based on the total weight of the solids in the suspension.

26. The process according to claim 1, wherein the collecting agent is present in the aqueous suspension obtained in step c) in an amount of from 0.01 to 10 wt.-%, based on the total weight of the solids in the suspension.

27. The process according to claim 1, wherein the collecting agent is present in the aqueous suspension obtained in step c) in an amount of from 0.1 to 3 wt.-%, based on the total weight of the solids in the suspension.

28. The process according to claim 1, wherein one or more additives are added to the aqueous suspension prior to, during or after step c), wherein the additives are selected from the group consisting of pH-adjusting agents, solvents, depressants, polyelectrolytes, frothers and collector agents other than the collector agents according to formula (1) or formula (2).

29. The process according to claim 1, wherein the aqueous suspension obtained in step c) is ground during and/or after step c).

30. The process according to claim 1, wherein the gas in step d) is air.

31. The process according to claim 1, wherein the suspension in step d) has a temperature of between 5 and 90° C.

32. The process according to claim 1, wherein the suspension in step d) has a temperature of between 20 and 50° C.

33. The process according to claim 1, wherein the white pigment bearing phase obtained from step e) is dispersed and/or ground before and/or after step e), optionally in the present of at least one dispersing agent and/or at least one grinding aid agent.

Description

EXAMPLES

1. Measurement Methods

(1) pH Measurement

(2) The pH was measured at 25° C. using a Mettler Toledo Seven Easy pH meter and a Mettler Toledo InLab® Expert Pro pH electrode. A three point calibration (according to the segment method) of the instrument was first made using commercially available buffer solutions having pH values of 4, 7 and 10 at 20° C. (from Aldrich). The reported pH values were the endpoint values detected by the instrument (the endpoint was when the measured signal differs by less than 0.1 mV from the average over the last 6 seconds).

(3) Particle Size Distribution (Mass % Particles with a Diameter<X) and Weight Median Grain Diameter (d.sub.50) of Particulate Material Using Sedigraph™ 5120

(4) Weight median grain diameter and grain diameter mass distribution of a particulate material were determined via the sedimentation method, i.e. an analysis of sedimentation behaviour in a gravimetric field. The measurement was made with a Sedigraph™ 5120.

(5) The method and the instrument are known to the skilled person and are commonly used to determine grain size of fillers and pigments. The measurement was carried out in an aqueous solution of 0.1% by weight of Na.sub.4P.sub.2O.sub.7. The samples were dispersed using a high speed stirrer and ultrasonic.

(6) Median Grain Diameter d.sub.50 of Particulate Material Using Malvern Mastersizer 2000

(7) Median grain diameter, d.sub.50 was determined using a Malvern Mastersizer 2000 Laser Diffraction System, with a defined RI of 1.57 and iRI of 0.005, Malvern Application Software 5.60. The measurement was performed on an aqueous dispersion. The samples were dispersed using a high-speed stirrer. In this respect, the d.sub.50 values define the diameters, at which 50 vol.% of the particles measured, have a diameter smaller than d.sub.50 value, respectively.

(8) Weight Solids (Wt.-%) of a Material in Suspension

(9) The weight solids were determined by dividing the weight of the solid material by the total weight of the aqueous suspension. The weight of the solid material is determined by weighing the solid material obtained by evaporating the aqueous phase of suspension and drying the obtained material to a constant weight.

(10) Specific Surface (BET) Measurement

(11) The specific surface area (in m.sup.2/g) of the white pigment or of the impurities was determined using nitrogen and the BET method, which is well known to the skilled man (ISO 9277:1995). The total surface area (in m.sup.2) of the white pigment or of the impurities was then obtained by multiplication of the specific surface area and the mass (in g) of the white pigment or of the impurities. The method and the instrument are known to the skilled person and are commonly used to determine specific surface of white pigments or of the impurities.

(12) Carbon Fraction Determination (% by Weight)

(13) 10 g of the white pigment and impurities containing material or of the white pigment containing product is dissolved in 150 g of an aqueous solution of 10% active content hydrochloric acid under heating at between 95 and 100° C. Following complete dissolution, the solution is allowed to cool to room temperature and, thereafter, is filtered and washed on a 0.2 μm membrane filter. The collected material, including the filter, is then dried in an oven at 105° C. to constant weight. The so-dried material (“insoluble material”) is then allowed to cool to room temperature and weighed, correcting the weight by subtracting the filter weight (hereafter the “insoluble weight”). This insoluble weight value is subtracted from 10 g, and the resulting figure is then multiplied by 100% and divided by 10 g, to give the carbonate fraction. The carbonate fraction is a measure for the amount of impurities in the white pigment and impurities containing material or of the white pigment containing product.

(14) Brightness Measurement

(15) The samples from the flotation process were ground either dry or wet to a defined product fineness (e.g. d.sub.50=5 d.sub.50=1.5 μm or d.sub.50=0.7 μm). If the samples were wet ground they were dried by use of microwave.

(16) The obtained dry powders were prepared in a powder press to get a flat surface and Tappi brightness (R457 ISO brightness) is measured according to ISO 2469 and yellow-index according to DIN 6167 using an ELREPHO 3000 from the company Datacolor. The results for the Tappi brightness are given as percentage in comparison to a calibration standard. The yellow index is calculated from the reflexion values (R.sub.i=(R.sub.x−R.sub.z)/R.sub.y).

2. White Pigments and Collector Agents

(17) In the following examples, the impurities identified have the following corresponding chemical formula:

(18) TABLE-US-00001 TABLE 1 Impurities and the corresponding chemical formulas Impurities name Chemical Formula Silicates (non-exhaustive list) Quartz SiO.sub.2 Muskovite KAl.sub.2(Si.sub.3Al)O.sub.10(OH, F).sub.2 Biotite K(Mg, Fe).sub.3(AlSi.sub.3)O.sub.10(OH, F).sub.2 Chlorite Na.sub.0.5Al.sub.4Mg.sub.2Si.sub.7AlO.sub.18(OH).sub.12•5(H.sub.2O) Plagioclase (Na, Ca)[(Si, Al)AlSi.sub.2O.sub.8] Orthoclase KAlSi.sub.3O.sub.8 Montmorrilonite Na.sub.0.3Fe.sub.2Si.sub.3AlO.sub.10(OH).sub.2•4(H.sub.2O) Amphibole NaCa2Fe.sup.II4Fe.sup.III[(OH).sub.2Al.sub.2Si.sub.6O.sub.22] Talc Mg.sub.3Si.sub.4O.sub.10(OH).sub.2 Non-silicates (non-exhaustive list) Graphite C Pyrite FeS.sub.2 Magnetite Fe.sub.3O.sub.4

(19) In the following examples, the collector agents identified have the following corresponding chemical formula:

(20) Reagent PX 5274 (Inventive)

(21) N,N′,N′-tri-hydroxyethyl N-tallow propylene diamine (CAS RN 61790-85-0)

(22) Reagent PX 5275 (Inventive)

(23) mixture of N,N′,N′-tri-hydroxyethyl N-tallow propylene diamine (CAS RN 61790-85-0) and rapeseed-oil, N-(3-(dimethyl amino)-propyl))amide, (CAS RN 85408-42-0) in a weight ratio 50/50

(24) Reagent PX 5276 (Inventive)

(25) mixture of N,N′,N′-tri-hydroxyethyl N-tallow propylene diamine (CAS RN 61790-85-0) and terpineol in a weight ratio 90/10

(26) Reagent Lupromin FP 18 AS (Comparative)

(27) Polymeric Esterquat

(28) Commercial available from BASF

3. Examples

(29) All froth flotation trials were performed at room temperature (20±2° C.) in an Outotec laboratory flotation cell, equipped with a conical gassing agitator under agitation of 1600 rpm under use of a 4 dm.sup.3 capacity glass cell. The solids content of the aqueous white pigment and impurities containing material suspension added to the flotation machine was of 33% by dry weight, said white pigment and impurities containing material being sourced from sedimentary marble rock deposits with different origins, running already a flotation process. The used water was original tab water from each local flotation process.

(30) 80% a typical practiced dosage of the flotation agent were given in the beginning of the trial and mixed within a 2 min conditioning time. A second dosage was added depending on the achieved froth product and visual seen impurities in the cell.

(31) A flotation gas, consisting of air, was then introduced via orifices situated along the axis of the agitator at a rate of approximately 3 dm.sup.3/min.

(32) The foam created at the surface of the suspension was separated from the suspension by overflow and skimming until no more foam could be collected, and both the remaining suspension and the collected foam were dewatered and dried in order to form two concentrates for mass balance and quality analyses like carbon fraction determination.

(33) Comparative Examples are marked with a “C” after the Example number.

Examples 1 to 3

(34) For Examples 1 to 3 a white pigment and impurities containing material from Gummern marble deposit in Autria is selected. The material contains 3.21 wt.-% of impurities determined by carbon fraction determination. The material is crushed and pre ground to a median grinding size d.sub.50 of 20 μm. The material is treated according to the above mentioned process. The test data are summarized in the following table 2.

(35) TABLE-US-00002 TABLE 2 Examples 1 to 3 Flotation data Amount of White pigment containing product Test Collector Collector Impurities Tappi- Yellow- No. agent agent [ppm] [wt.-%] brightness index 1 PX 5274 500 0.21 93.7 2.5 2 PX 5275 500 0.12 93.5 2.6 3 PX 5276 300 0.44 92.1 2.6

(36) As can be seen from Examples 1 to 3 the inventive process for manufacturing white pigment containing products shows good results (low amount of impurities in the white pigment containing product, high values for Tappi-brightness and low values for yellow-indes) even at low amounts of collector agent (Example 3: 300 ppm) within the aqueous suspension.

Examples 4 to 7

(37) For Examples 4 to 7 a white pigment and impurities containing material from Styria was selected, wherein the white pigment was marble and the impurities were silicate minerals. The material contains 0.74 wt.-% of impurities determined by carbon fraction determination. The white pigment and impurities containing material had a low amount of silicate minerals in the feed. The material was crushed and pre ground to a median grinding size d.sub.50 of 11 μm. The material was treated according to the above mentioned process. The test data are summarized in the following table 3.

(38) TABLE-US-00003 TABLE 3 Examples 4 to 7 Flotation data Amount of White pigment containing product Test Collector Collector Impurities Tappi- Yellow- No. agent agent [ppm] [wt.-%] brightness index 4 PX 5274 400 0.09 94.5 1.5 5 PX 5275 400 0.10 93.9 2.0 6C Lupromin 450 0.21 93.9 1.9 18AS 7C Lupromin 450 0.30 92.3 1.9 18AS

(39) The results show clearly that the inventive process for manufacturing white pigment containing products (Examples 4 and 5) is advantageous compared to prior art flotation processes (Examples 6C and 7C). The amount of impurities in the white pigment containing products obtained by the inventive process is much lower than the amount of impurities in the white pigment containing products obtained by a comparative process. This good result is achievable even if the amount of collector agent in the inventive process is around 12% lower than the amount of collector agent in the comparative process.

Examples 8 to 11

(40) For Examples 8 to 11 a white pigment and impurities containing material from a Swedish deposit was selected, wherein the white pigment was marble and the impurities were silicate minerals. The material contains 0.74 wt.-% of impurities determined by carbon fraction determination. The white pigment and impurities containing material had a high amount of silicate minerals in the feed. The material was crushed and pre ground to a median grinding size d.sub.50 of 35 μm. The material was treated according to the above mentioned process. The test data are summarized in the following table 4.

(41) TABLE-US-00004 TABLE 4 Examples 8 to 11 Flotation data Amount of White pigment containing product Test Collector Collector Impurities Tappi- Yellow- No. agent agent [ppm] [wt.-%] brightness index  8 PX 5274 400 0.09 94.5 1.5  9 PX 5275 400 0.10 93.9 2.0 10C Lupromin 450 0.21 93.9 1.9 18AS 11C Lupromin 400 0.30 92.3 1.9 18AS

(42) The results show clearly that the inventive process for manufacturing white pigment containing products (Examples 8 and 9) is advantageous compared to prior art flotation processes (Examples 10C and 11C). The amount of impurities in the white pigment containing products obtained by the inventive process is much lower than the amount of impurities in the white pigment containing products obtained by a comparative process. This good result is achievable even if the amount of collector agent in the inventive process is around 12% lower than the amount of collector agent in the comparative process.

Example 12 to 14

(43) For Examples 12 to 14 a white pigment and impurities containing material from a Spanish deposit was selected, wherein the white pigment was marble and the impurities were silicate minerals. The material contains 0.34 wt.-% of impurities determined by carbon fraction determination. The white pigment and impurities containing material had a low amount of silicate minerals in the feed. The material was crushed and pre ground to a median grinding size d.sub.50 of 15 μm. The material was treated according to the above mentioned process. The test data are summarized in the following table 5.

(44) TABLE-US-00005 TABLE 5 Examples 12 to 14 Flotation data Amount of White pigment containing product Test Collector Collector Impurities Tappi- Yellow- No. agent agent [ppm] [wt.-%] brightness index 12C Lupromin 100 0.04 93.2 3.0 18 AS 13 PX 5274 100 0.03 94.4 2.4 14 PX 5275 100 0.03 93.8 2.6

(45) The results show clearly that the inventive process for manufacturing white pigment containing products (Examples 13 and 14) is advantageous compared to prior art flotation processes (Example 12C). The amount of impurities in the white pigment containing products obtained by the inventive process is comparable to the amount of impurities in the white pigment containing product obtained by a comparative process if the amount of collector agents in both processes is the same (100 ppm). However, the Tappi-brightness of the white pigment containing product obtained by the inventive process is superior to the Tappi-brightness of the white pigment containing product obtained by the comparative process. Also the yellow-index of the white pigment containing product obtained by the inventive process is much lower than the yellow-index of the white pigment containing product obtained by the comparative process.