Dry process for preparing a surface-modified alkaline earth metal carbonate-containing material

Abstract

The present invention relates to a process to modify at least part of the surface of an earth alkaline metal carbonate-containing material in a dry blending process as well as to a mineral product obtainable by the inventive process and uses thereof.

Claims

1. A process to modify at least part of a surface of an alkaline earth metal carbonate-containing material, the process comprising the following steps: (a) providing at least one alkaline earth metal carbonate-containing material; (b) providing at least one surface-modifying agent; and (c) dry blending the at least one alkaline earth metal carbonate-containing material provided in step (a) and the at least one surface-modifying agent provided in step (b) to obtain a blend; (d) dry grinding the blend in at least one grinding unit during and/or after step (c); (e) classifying the blend to obtain one or more coarse fractions, wherein the coarse fractions are optionally subjected to another dry grinding step and/or optionally subjected to another classifying step, and one or more fine fractions; wherein the at least one surface-modifying agent provided in step (b) comprises at least one of: (i) an organophosphonic acid; and (ii) derivatives of the organophosphonic acid; wherein the organophosphonic acid and/or derivatives thereof are optionally partially or fully neutralized with at least one cation comprising mono-, di-, or trivalent cations; and wherein the blend has a total moisture content of less than 2.0 wt.-%, based on the total weight of the blend.

2. The process of claim 1, wherein the alkaline earth metal carbonate-containing material provided in step (a) is a calcium-carbonate-containing material.

3. The process of claim 1, wherein the alkaline earth metal carbonate-containing material provided in step (a) comprises less than 0.1 wt.-%, based on the weight of dry mineral material, of a polycarboxylate-based dispersant.

4. The process of claim 1, wherein the organophosphonic acid is a substituted or unsubstituted alkylene diphosphonic acid.

5. The process of claim 1, wherein the organophosphonic acid comprises methylene diphosphonic acid (MDP), hydroxymethylene diphosphonic acid (FLVDP), 1-hydroxyethane-1, 1-diphosphonic acid (HEDP), hydroxycyclohexyltmethylene diphosphonic acid (HCMDP), 1-hydroxy-3-aminopropane-1, 1-diphosphonic acid (APD), amino-tris(methylene-phosphonic acid) (ATMP), diethylenetriamine penta(methylenephosphonic acid) (DTPMP), or phosphonosuccinic acid (PSA).

6. The process of claim 1, wherein the mono-, di-, and tri cations comprises: (i) Li, Na, K, or NH.sub.4.sup.+; and (ii) Mg, Ca, Mn, Co, Cu, Zn, Sr, Zr, or Sn; or (iii) Al, Cr, or Fe; wherein the organophosphonic acid and/or derivatives thereof are neutralized to a degree of from 10% to 90% based on the total number of acidic protons in the organophosphonic acid and/or derivatives thereof.

7. The process of claim 1, wherein the total amount of the at least one surface-modifying agent used in step (c) ranges from 0.01 wt.-% to 5.0 wt.-% based on the dry weight of the alkaline earth metal carbonate-containing material provided in step (a).

8. The process of claim 1, wherein the blend has a total moisture content of less than 1.0 wt,-%, based on the total weight of the blend.

9. The process of claim 1, wherein the process further comprises a step of reacting the alkaline earth metal carbonate-containing material with a hydrophobizing agent during and/or after step (c), step (d), and/or step (e).

10. The process of claim 2, wherein the calcium-carbonate containing material comprises dolomite, dolomitic and magnesitic marble, limestone, chalk, precipitated calcium carbonate, or mixtures thereof.

11. The process of claim 6, wherein the mono-, di-, and trivalent cations comprise: (i) Li, Na, or K; and (ii) Mg, Ca, or Sr; and (iii) Al.

12. The process of claim 6, wherein the mono-, di-, and trivalent cations comprise Li, Na, K, and Ca.

13. The process of claim 6, wherein the organophosphonic acid and/or derivatives thereof are neutralized to a degree of from 30% to 90%, based on the total number of acidic protons in the organophosphonic acid and/or derivatives thereof.

14. The process of claim 1, wherein the total amount of the at least one surface-modifying agent used in step (c) ranges from 0.03 wt.-% to 1.0 wt.-%, based on the dry weight of the alkaline earth metal carbonate-containing material provided in step (a).

15. The process of claim 1, wherein the blend has a total moisture content of less than 1.5 wt.-%, based on the total weight of the blend.

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) Materials

(3) Agent 1

(4) Monopropylene glycol (MPG), CAS 57-55-6, purchased from Fluka, pH of 20 wt.-% solution in water: 8.2.

(5) Agent 2

(6) Tetrasodium 1-hydroxyethane-1,1-diphosphonate (Na.sub.4HEDP), CAS 29329-71-3, purchased as Dequest 2016 from Italmatch Chemicals, 35.5 wt.-% in water, pH of 20 wt.-% solution in water: 11.76.

(7) Agent 3

(8) 1-Hydroxyethane-1,1-diphosphonic acid (HEDP), CAS 2809-21-4, purchased as Dequest 2010 from Italmatch Chemicals, also referred to as etidronic acid, 31.1 wt.-% in water, pH of 1 wt.-% solution in water: <2.0.

(9) Agent 4

(10) Dilithium 1-hydroxyethane-1,1-diphosphonate (Li.sub.2HEDP). This agent is prepared by dissolving 36.8 g (0.1 mol) HEDP in 183.8 ml water. Thereafter, 8.39 g (0.2 mol) Li(OH).H.sub.2O are added to the solution in four portions under stirring for 2 h to form Li.sub.2HEDP. The reaction is slightly exothermic (33 C.) and a slight turbidity occurs. After 24 h, the formation of a gel is observed, the pH is 2.9, the solids content is 11.7 wt.-%. The gel is still stable after 96 h.

(11) Raw material 1: Marble

(12) Italian marble of the Pisa region, median stone size 5 to 50 cm, purity 99.5 wt.-% calcium carbonate (EDTA titration), HCl insolubles 0.5 wt.-% (mainly silicates and traces of pyrite).

Example 1

Pilot Scale

(13) This example illustrates steps (a) to (e) of the inventive process and includes dry grinding in a ball mill in combination with a step of selection by a classifier. Raw material 1, before grinding in the ball mill, is crushed in a hammer mill. The size distribution of raw material 1 is shown in Table 1.

(14) TABLE-US-00001 TABLE 1 Particle size distribution of raw material 1. Particle diameter wt.-% 1 mm-5 mm 17.0 500 m-1 mm 16.5 200-500 m 18.8 100-200 m 12.8 45-100 m 16.3 <45 m 18.4 d.sub.50 220 m Moisture content 0.15 wt.-%

(15) Raw material 1 (see Table 1) is fed into a ball mill (Hosokawa Ball Mill S.O. 80/32) using 100 kg of iron grinding beads of the type Cylpeb in barrel form at a median diameter of 25 mm. Grinding was performed in a continuous mode.

(16) The outlet of the grinding chamber at a size of 206 mm.sup.2 is connected to an Alpine Turboplex 100 ATP classifier. At an air flow of 150 m.sup.3/h, the speed of the classifier is adjusted such that a fine fraction of the desired fineness was produced. The fine fraction is removed. The coarse fraction is fed back into the inlet of the grinding chamber. The quantity of extracted fine fraction is replaced by fresh feed material at the inlet of the grinding chamber so that a total amount of 15 kg mineral is constantly in the system. The system is run for at least 2 h to stabilize the process before the fine fractions are removed for use in further steps.

(17) In Trials A-C, different agents are added continuously into the inlet of the grinding chamber and dosed relative to the amount of fine fractions extracted from the classifier. The temperature of the mineral material in the grinder after 2 h is constantly between 80 and 82 C. until to the end of each trial after 6 h.

(18) TABLE-US-00002 TABLE 2 d.sub.98 wt.-% <2 m Classifier wt.-% <1 m Agent Amount speed wt.-% <0.5 m Capacity Trial No. [ppm] [rpm] wt.-% moisture [kg/h] A 1 1500 10000 4.3 1.8 80.0 47.6 18.2 0.14 B 2 1500 10000 3.9 1.5 82.4 50.6 21.0 0.25 C 2 + 3 1350 + 150 10000 3.5 1.5 85.4 53.7 24.9 0.19

(19) The results in Table 2 show equal capacity at equal fineness in case of phosphonic acid agents (Trials B+C) when compared with MPG (Trial A).

Example 2

Suitability for Plastic Applications

(20) TABLE-US-00003 TABLE 3 Volatile onset temperatures of Trials A-C Agent Volatile onset temperature Trial No. [ C.] A 1 188 B 2 >500 C 3 >500

Example 3

Suitability of Suspension for Paper Applications

(21) TABLE-US-00004 TABLE 4 Suspension viscosity at high solids content. Agent Solids content Brookfield viscosity pH of Trial No. [wt.-%] [mPa .Math. s] suspension A 1 51.8 2048 8.01 B 2 68.3 366 10.03 C 3 75.6 448 9.46

(22) Brookfield viscosities (spindle 3) of the corresponding samples are measured 1 h after preparation. The viscosities of the inventive products are far below 1000 mPa.s which is necessary for easy pumping and also above 100 mPa.s which prevents unwanted sedimentation.

Example 4

Filler Slurry for Paint and Paper Applications

(23) This example illustrates the use of the product obtained by steps (a) to (c) of the invention. 200 g water and 300 g of a mineral product obtained as described for Trial B of Example 1are mixed in order to obtain a mixture of the mineral product. The mineral product has a final particle size distribution of 62 wt.-%<2 m, 34 wt.-%<1 m and a d.sub.50 of 1.7 m. The resulting mixture is stirred for 20 min at 30 .C. The pH value of the obtained suspension is 8.4 and the Brookfield viscosity is 696 mPa.s(spindle 3).

(24) The suspension is stirred for a further 30 min at 30 .C. The pH value now is 8.9 and the Brookfield viscosity is 582 mPa.s(spindle 3). The suspension is stored for 96 h at 23 .C and then is stirred for 5 min. The pH value now is 8.7.