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. Process to modify at least part of the 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; 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 may be partially or fully neutralized with at least one cation selected from mono-, di-, and trivalent cations; and wherein said blend has a total moisture content of less than 2.0 wt.-%, based on the total weight of said blend.

2. The process according to claim 1, characterized in that said process further comprises at least one of the following steps: (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.

3. The process according to claim 1, characterized in that the alkaline earth metal carbonate-containing material provided in step (a) is a calcium-carbonate-containing material, and preferably is selected from the group consisting of dolomite, dolomitic and magnesitic marble, limestone, chalk, and precipitated calcium carbonate.

4. The process according to claim 1, characterized in that 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.

5. The process according to claim 1, characterized in that the organophosphonic acid is a substituted or unsubstituted alkylene diphosphonic acid.

6. The process according to claim 1, characterized in that the organophosphonic acid is selected from methylene diphosphonic acid (MDP), hydroxymethylene diphosphonic acid (HMDP), 1-hydroxyethane-1,1-diphosphonic acid (HEDP), hydroxycyclohexylmethylene diphosphonic acid (HCMDP), 1-hydroxy-3-aminopropane-1,1-diphosphonic acid (APD), amino-tris(methylenephosphonic acid) (ATMP), diethylenetriamine penta(methylenephosphonic acid) (DTPMP), and phosphonosuccinic acid (PSA).

7. The process according to claim 1, characterized in that the mono-, di-, and trivalent cations are selected from: (i) Li, Na, K, NH.sub.4.sup.+, preferably Li, Na, K; and (ii) Mg, Ca, Mn, Co, Cu, Zn, Sr, Zr, Sn, preferably Mg, Ca, Sr; and (iii) Al, Cr, Fe, preferably Al; wherein the organophosphonic acid and/or derivatives thereof are preferably neutralized to a degree of from 10 to 90%, more preferably from 30 to 80%, and most preferably from 40 to 60%, based on the total number of acidic protons in the organophosphonic acid and/or derivatives thereof.

8. The process according to claim 1, characterized in that the total amount of the at least one surface-modifying agent used in step (c) ranges from 0.01 to 5.0 wt.-%, preferably from 0.03 to 1.0 wt-%, and more preferably from 0.05 to 0.7 wt.-%, based on the dry weight of the alkaline earth metal carbonate-containing material provided in step (a).

9. The process according to claim 1, characterized in that the blend has a total moisture content of less than 2.0 wt.-%, preferably less than 1.5 wt.-%, more preferably less than 1.0 wt.-%, even more preferably less than 0.5 wt.-%, and most preferably from 0.03 to 0.2 wt.-%, based on the total weight of said blend.

10. The process according to claim 1, characterized in that 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).

11. A mineral product obtainable by a process according to claim 1.

12. The mineral product according to claim 11, characterized in that the mineral product has a total moisture content of less than 2.0 wt.-%, preferably less than 1.5 wt.-%, more preferably less than 1.0 wt.-%, even more preferably less than 0.5 wt.-%, and most preferably from 0.03 to 0.2 wt.-%, based on the total weight of said mineral product.

13. The mineral product according to claim 11, characterized in that the mineral product has a weight median particle size d.sub.50 of from 0.2 to 45 μm, preferably from 0.5 to 15 μm, and more preferably from 0.7 to 2 μm.

14. The mineral product according to claim 11, characterized in that the mineral product has a specific surface area of from 0.5 to 60 m.sup.2/g, more preferably from 2 to 15 m.sup.2/g, and most preferably from 3 to 10 m.sup.2/g, as measured by the BET nitrogen method.

15. Paper, plastic, sealant, paint, concrete, cosmetic, polyolefin product, film, fiber or breathable film comprising the mineral product according to claim 11.

Description

EXAMPLES

[0175] 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.

Materials

[0176] Agent 1
Monopropylene glycol (MPG), CAS 57-55-6, purchased from Fluka, pH of 20 wt.-% solution in water: 8.2. [0177] Agent 2
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. [0178] Agent 3
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. [0179] Agent 4
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. [0180] Raw material 1: Marble
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

[0181] 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.

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

[0182] 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.

[0183] The outlet of the grinding chamber at a size of 20×6 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.

[0184] 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.

TABLE-US-00002 TABLE 2 d.sub.98 wt.-% <2 μm Classifier wt.-% <1 μm Agent Amount speed wt.-% <0.5 μm Capacity Trial No. [ppm] [rpm] wt.-% moisture [kg/h] A 1 1500 10′000 4.3 1.8 80.0 47.6 18.2 0.14 B 2 1500 10′000 3.9 1.5 82.4 50.6 21.0 0.25 C 2 + 3 1350 + 150 10′000 3.5 1.5 85.4 53.7 24.9 0.19

[0185] 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

[0186]

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