Process for the preparation of a mineral filler product

Abstract

A process for the preparation of a mineral filler product is disclosed, the process comprising a step of dry grinding a calcium carbonate-containing material in a mixture obtained by contacting the calcium carbonate-containing material with at least one grinding agent selected from specific styrene-maleic anhydride co-polymers and/or specific derivatives of styrene-maleic anhydride co-polymers.

Claims

1. A mineral filler product obtained by a process comprising the steps of: a) providing a calcium carbonate-containing material; b) providing at least one grinding agent; c) dry grinding the calcium carbonate-containing material in a mixture obtained by contacting: i) the calcium carbonate-containing material provided in step a), with ii) the at least one grinding agent provided in step b), in at least one grinding unit to obtain a dry ground mineral filler; d) classifying the dry ground mineral filler of step c) to obtain a coarse fraction and a fine fraction, wherein the coarse fraction is removed or subjected to dry grinding step c) and the fine fraction represents a fine mineral filler; e) optionally drying the fine mineral filler of step d) to obtain a dried mineral filler having a total moisture content of less than 1.0 wt.-%, based on the total weight of said dried mineral filler; and f) optionally treating the fine mineral filler of step d) and/or the dried mineral filler of step e) with a hydrophobizing agent to obtain a surface-treated product having a treatment layer on at least part of the surface of the product, wherein the total moisture content in the mixture of step c) is less than or equal to 10.0 wt.-%, based on the total weight of said mixture; the amount of the at least one grinding agent provided in step b) ranges from 0.05 to 150 mg/m.sup.2, based on the specific surface area of the calcium carbonate-containing material as measured by the BET nitrogen method; the temperature in step c) ranges from 65 C. to 200 C.; and the at least one grinding agent is selected from the group consisting of styrene-maleic anhydride co-polymers and derivatives of styrene-maleic anhydride co-polymers, and has a monomer unit ratio (styrene units:maleic anhydride units, S:MA) of from 1:2 to 15:1 and a molecular weight M.sub.w of from 500 to 40,000 g/mol.

2. The product according to claim 1, wherein the calcium carbonate-containing material provided in step a) is from a natural calcium carbonate source selected from the group consisting of marble, limestone, chalk, dolomite, and any mixture thereof.

3. The product according to claim 1, wherein the amount of said at least one grinding agent provided in step b) ranges from 0.1 to 100.0 mg/m.sup.2, based on the specific surface area of the calcium carbonate-containing material as measured by the BET nitrogen method.

4. The product according to claim 1, wherein the amount of said at least one grinding agent provided in step b) ranges from 0.2 to 50.0 mg/m.sup.2, based on the specific surface area of the calcium carbonate-containing material as measured by the BET nitrogen method.

5. The product according to claim 1, wherein the at least one grinding agent provided in step b) has a monomer unit ratio (S:MA) of from 1:1 to 5:1.

6. The product according to claim 1, wherein the at least one grinding agent provided in step b) has a monomer unit ratio (S:MA) of from 1:1 to 4:1.

7. The product according to claim 1, wherein the at least one grinding agent provided in step b) has a monomer unit ratio (S:MA) of from 1:1 to 3:1.

8. The product according to claim 1, wherein the at least one grinding agent provided in step b) has a molecular weight M.sub.w of from 2,000 to 30,000 g/mol.

9. The product according to claim 1, wherein the at least one grinding agent provided in step b) has a molecular weight M.sub.w of from 3,000 to 25,000 g/mol.

10. The product according to claim 1, wherein the at least one grinding agent provided in step b) is partially or fully neutralized with a cation selected from the group consisting of lithium, sodium, potassium, calcium, magnesium, ammonium, iminium, and any mixture thereof.

11. The product according to claim 1, wherein the total moisture content in the mixture of step c) is less than or equal to 5.0 wt.-%, based on the total weight of said mixture.

12. The product according to claim 1, wherein the total moisture content in the mixture of step c) is less than or equal to 1.0 wt.-%, based on the total weight of said mixture.

13. The product according to claim 1, wherein the temperature in step c) ranges from 70 C. to 180 C.

14. The product according to claim 1, wherein the fine mineral filler of step d) has a weight median particle size d.sub.50 ranging from 0.4 to 40.0 m.

15. The product according to claim 1, wherein the fine mineral filler of step d) has a weight median particle size d.sub.50 ranging from 0.6 to 20.0 m.

16. The product according to claim 1, wherein the fine mineral filler of step d) has a weight median particle size d.sub.50 ranging from 0.7 to 10.0 m.

17. The product according to claim 1, wherein step e) takes place.

18. The product according to claim 1, wherein step f) takes place.

19. The product according to claim 1, having a moisture pick up susceptibility of less than or equal to 0.9 mg/g.

20. The product according to claim 1, having a moisture pick up susceptibility of less than or equal to 0.8 mg/g.

21. The product according to claim 1, having a moisture pick up susceptibility of less than or equal to 0.7 mg/g.

22. The product according to claim 1, having a moisture pick up susceptibility of from 0.2 to 0.6 mg/g.

23. The product according to claim 1, having a volatile onset temperature of at least or equal to 200 C.

24. The product according to claim 1, having a volatile onset temperature of at least or equal to 230 C.

25. The product according to claim 1, having a volatile onset temperature of at least or equal to 250 C.

26. A polymer composition, paper, paper coating, agricultural product, paint, adhesive, sealant, construction product or cosmetic comprising the product according to claim 1.

27. A polymer composition comprising at least one polymeric resin and from 0.1 to 90.0 wt.-%, based on the total weight of said polymer composition, of the product according to claim 1.

28. A polymer composition comprising at least one polymeric resin and from 2.0 to 45.0 wt.-%, based on the total weight of said polymer composition, of the product according to claim 1.

Description

EXAMPLES

(1) The scope and interest of the invention may be better understood on basis of the following examples which are intended to illustrate embodiments of the present invention. However, they are not to be construed to limit the scope of the claims in any manner whatsoever.

(2) Weight Average Molecular Weight M.sub.W

(3) The weight average molecular weight M.sub.W as used herein may be determined using GPC (SEC) as follows:

(4) A sample corresponding to 90 mg of dry polymer is introduced into a 10 ml flask and at least 1 ml of 5 M aqueous NaOH is added until the pH value does change by not more than 0.3 pH units within 48 hours. Mobile phase with an additional 0.04 wt.-% of dimethylformamide is added until a total mass of 10 g is reached. The composition of the mobile phase at pH 9 is as follows: 0.05 M NaHCO.sub.3, 0.1 M NaNO.sub.3, 0.02 M triethanolamine, 0.03 wt.-% of NaN.sub.3.

(5) The SEC equipment is consisting of an isocratic Waters 515 type pump, the flow rate of which is set to 0.8 ml/min, a Waters0 717+ sample changer, a kiln containing a precolumn type Guard Column Ultrahydrogel Waters which is 6 cm in length and has an internal diameter of 40 mm, followed by a linear column type Ultrahydrogel Waters which is 30 cm in length and has an internal diameter of 7.8 mm.

(6) Detection is accomplished by means of a Waters 410 differential refractometer. The kiln is heated to a temperature of 60 C. and the refractometer is heated to a temperature of 45 C.

(7) The SEC is calibrated with a series of sodium polyacrylate standards supplied by Polymer Standard Service having maximum molecular weight of between 2'000 and 1.10.sup.6 g/mol and a polydispersity index of between 1.4 and 1.7 and further with a sodium polyacrylate of average weight molecular weight of 5'600 g/mol and a polydispersity index equal to 2.4.

(8) The calibration graph is of the linear type and takes account of the correction obtained using the flow rate marker (dimethylformamide).

(9) Measurement of Volatiles

(10) For the purpose of the present application, the total volatiles associated with mineral fillers and evolved over a temperature range of 25 C. to 350 C. is characterized by % of mass loss of a mineral filler sample over a temperature range as read on a thermogravimetric (TGA) curve.

(11) TGA analytical methods provide information regarding losses of mass and volatile onset temperatures with great accuracy. The methods are well-known to the skilled person and described in, for example, Principles of Instrumental analysis, 5.sup.th edition, Skoog Holler Nieman, 1998, chapter 31, pp. 798-800. In the present invention, thermogravimetric analysis (TGA) is performed using a Mettler Toledo TGA 851 based on a sample of 50050 mg and scanning temperatures of from 25 C. to 350 C. at a rate of 20 C./min under an air flow of 70 ml/min.

(12) The volatile onset temperature can be determined as follows by analysis of the TGA curve: The first derivative of the TGA curve is obtained and the inflection points thereon between 150 C. and 350 C. are identified. Among these inflection points having a tangential slope value of greater than 45 relative to a horizontal line, the one having the lowest associated temperature above 200 C. is identified. The temperature associated with this lowest inflection point of the first derivative curve is the volatile onset temperature.

(13) Particle Size Distribution

(14) For the purpose of the present application, particle sizes being lower than 100 m, the weight median particle size d.sub.50 and further granulometric characteristics are determined based on measurements made by using a Sedigraph 5100 instrument of Micromeritics Instrument Corporation. The method and the instrument are known to the skilled person and are commonly used to determine the particle size of fillers and pigments. The measurement is carried out in an aqueous solution of 0.1 wt.-% Na.sub.4P.sub.2O.sub.7. The samples are dispersed using a high speed stirrer and supersonics. In case of surface-treated products, additional 0.5 g of a surfactant (Photo-Flo 200 from Kodak) were added to 50 ml of the solution of 0.1 wt.-% Na.sub.4P.sub.2O.sub.7 before dispersing the treated carbonate sample.

(15) In case of particle sizes being greater than 100 m, fractional sieving is used to determine granulometric characteristics.

(16) BET Specific Surface Area of a Material

(17) Throughout the present document, the specific surface area (expressed in m.sup.2/g) of a mineral filler is determined using the BET method (using nitrogen as adsorbing gas), which is well known to the skilled person (ISO 9277:1995). The total surface area (in m.sup.2) of the mineral filler can be obtained by multiplication of the specific surface area (in m.sup.2/g) and the mass (in g) of the mineral filler.

(18) Moisture Pick Up Susceptibility

(19) The moisture pick up susceptibility of a material as referred to herein is determined in mg moisture/g after exposure to an atmosphere of 10 and 85% relative humidity, respectively, for 2.5 hours at a temperature of +23 C. (2 C.). For this purpose, the sample is first kept at an atmosphere of 10% relative humidity for 2.5 hours, then the atmosphere is changed to 85% relative humidity at which the sample is kept for another 2.5 hours. The weight increase between 10 and 85% relative humidity is then used to calculate the moisture pick-up in mg moisture/g of sample.

(20) The moisture pick up susceptibility in mg/g divided by the specific surface area in m.sup.2 (BET method) corresponds to the normalized moisture pick up susceptibility expressed in mg/m.sup.2 of sample.

(21) Total Moisture Content

(22) The total moisture content as used herein is measured according to the Karl Fischer coulometric titration method, desorbing the moisture in an oven at 220 C. for 10 min and passing it continuously into a KF coulometer (Mettler Toledo coulometric KF Titrator C30, combined with Mettler oven DO 0337) using dry nitrogen at 100 ml/min for 10 min. A calibration curve using water has to be recorded and a blank of 10 min nitrogen flow without a sample has to be taken into account.

(23) Materials Grinding agent A

(24) MPG=monopropylene glycol. Grinding agent B

(25) Cray Valley SMA 1000HNa=aqueous solution of hydrolyzed styrene-maleic anhydride co-polymer, 100% sodium neutralized, commercially available from Cray Valley LLC, USA; approx. molecular weight M.sub.W=5'000 g/mol; monomer unit ratio (S:MA)=1:1; 40.4 wt.-% grinding agent content; pH=8.5. Grinding agent C

(26) Cray Valley SMA 1000=powdered styrene-maleic anhydride co-polymer, commercially available from Cray Valley LLC, USA; approx. molecular weight M.sub.W=5'000 g/mol; monomer unit ratio (S:MA)=1:1. Grinding agent D

(27) Cray Valley SMA 3000HNa=aqueous solution of hydrolyzed styrene-maleic anhydride co-polymer, 100% sodium neutralized, commercially available from Cray Valley LLC, USA; approx. molecular weight M.sub.W=9'500 g/mol; monomer unit ratio (S:MA)=3:1; 24.4 wt.-% grinding agent content; pH=8.6. Grinding agent E

(28) Cray Valley SMA EF-30=powdered styrene-maleic anhydride co-polymer, commercially available from Cray Valley LLC, USA; approx. molecular weight M.sub.W=9'500 g/mol; monomer unit ratio (S:MA)=3:1. Grinding agent F

(29) Cray Valley SMA EF-40=solution in acetone prepared from styrene-maleic anhydride co-polymer, commercially available from Cray Valley LLC, USA; approx. molecular weight M.sub.W=11'000 g/mol; monomer unit ratio (S:MA)=4:1; 33.0 wt.-% grinding agent content. Grinding agent G

(30) Cray Valley SMA 17352=partially esterified styrene-maleic anhydride co-polymer in powdered form, commercially available from Cray Valley LLC, USA; approx. molecular weight M.sub.W=7'000 g/mol; acid value: 270 mg KOH/g. Grinding agent H

(31) Cray Valley SMA 1440=partially esterified styrene-maleic anhydride co-polymer in powdered form, commercially available from Cray Valley LLC, USA; approx. molecular weight M.sub.W=7'000 g/mol; acid value: 185 mg KOH/g.

(32) General Procedure

(33) Italian marble having an average diameter of approx. 5 cm was crushed using a hammer mill. The size distribution of the crushed material was determined by sieving and is given in Table 1 herein below.

(34) The crushed material was contacted with one of the grinding agents summarized above immediately before grinding and mixed in a concrete mixer for at least 10 min.

(35) The obtained material was then transferred into a ball mill (Hosokawa Ball Mill S.O. 80/32) using 100 kg of cylindrically shaped iron grinding balls, having an average diameter of 16 mm in order to obtain a ground material having a weight median particle size d.sub.50 of less than or equal to 1.0 m.

(36) The outlet of the grinding chamber was equipped with an opening of 205 mm discharging to an Alpine Turboplex 100 ATP classifier. The classifier was adjusted in order to recover the fine fraction having a desired weight median particle size d.sub.50. The remaining coarse material having a weight median particle size d.sub.50 being higher than said desired value is sent back to the mill feed.

(37) The dry grinding was performed in a continuous fashion, wherein approx. 15 kg of material were constantly present in the system. Thus, the mill feed was continuously fed with a quantity of crushed material and/or coarse fraction material resulting from the classifying step material which was equal to the quantity of the fine fraction leaving the system.

(38) The system was operated until constant amounts of material having a suitable quality could be recovered by monitoring the grinding capacity and the grinding energy. The grinding chamber is heated to a constant temperature of 80 C.

(39) TABLE-US-00001 TABLE 1 Particle size distribution of crushed marble. Particle size fraction wt.-% >1 mm 28.3 0.5 to 1 mm 8.7 200 to 500 m 18.3 100 to 200 m 18.1 50 to 100 m 11.6 <50 m 15.0

(40) TABLE-US-00002 TABLE 2 Process throughput and particle sizes after grinding. Particle size Grinding Grinding distribution Example agent agent Throughput d.sub.10 d.sub.50 d.sub.98 no. type [ppm] [kg/h] [m] [m] [m] 1 A 1500 1.6 0.34 1.02 3.4 2 B 1500 2.3 0.30 0.92 5.3 3 C 1500 2.6 0.31 0.93 3.6 4 D 1500 2.5 0.32 0.92 3.1 5 E 1500 2.2 0.34 1.00 3.4 6 F 1500 2.7 0.35 1.03 3.1 7 B 7500 3.2 0.34 1.11 3.5 8 G 1500 2.9 0.31 0.93 2.14 9 H 1500 3.2 0.31 0.95 2.10

(41) TABLE-US-00003 TABLE 3 Volatile onset temperatures. Example Grinding agent Final product no. Grinding agent type [ppm] Volatile onset [ C.] 1 A 1500 178 2 B 1500 336 3 C 1500 337 4 D 1500 341 5 E 1500 383 6 F 1500 380 7 B 7500 320 8 G 1500 359 9 H 1500 381

(42) These examples illustrate the improved grinding capacities (i.e. an increased throughput) in a process according to the present invention as compared to a process carried out in the absence of grinding agent or using a conventional grinding agent.