REDUCED MOISTURE PICKUP IN POLYOL-CONTAINING MINERAL FILLER PRODUCTS

Abstract

The present invention relates to a process for the production of a mineral filler product comprising a step of dry grinding a calcium carbonate-containing material in the presence of an agent being a polyol. The mineral filler product according to the present invention was found to have a reduced moisture pickup as compared to prior art products.

Claims

1. A process for the preparation of a mineral filler product, the process comprising the steps of: (a) providing a calcium carbonate-containing material; (b) providing at least one agent being a polyol; (c) dry grinding the calcium carbonate-containing material in a mixture comprising: (i) the calcium carbonate-containing material provided in step (a); and (ii) the at least one agent provided in step (b) in at least one grinding unit to obtain a dry ground calcium carbonate-containing material; (d) classifying the dry ground calcium carbonate-containing material of step (c) to obtain one or more coarse fractions and one or more fine fractions, wherein one or more of the coarse fractions are removed and/or subjected to dry grinding step (c) and/or subjected to classifying step (d); and (e) treating the calcium carbonate-containing material before and/or during and/or after step (c) with at least one monosubstituted succinic anhydride and, optionally, with at least one monosubstituted succinic acid and/or salts thereof to obtain a calcium carbonate-containing material having a treatment layer on at least part of the surface of said material; wherein the total amount of the at least one agent provided in step (b) ranges from 0.01 to 5.0 wt.-%, based on the total dry weight of the calcium carbonate-containing material provided in step (a); 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; the total amount of the at least one monosubstituted succinic anhydride and the optional at least one monosubstituted succinic acid and/or salts thereof in step (e) ranges from 0.01 to 5.0 wt.-%, based on the total dry weight of the calcium carbonate-containing material provided in step (a); and the temperature in step (e) is adjusted to at least 2° C. above the melting point of the at least one monosubstituted succinic anhydride.

2. The process according to claim 1, wherein the calcium carbonate-containing material provided in step (a) is selected from natural calcium carbonate sources and preferably is selected from the group consisting of calcite, marble, limestone, chalk, dolomite, and mixtures thereof.

3. The process according to claim 1, wherein the at least one agent provided in step (b) is a polyol selected from the group consisting of saccharides, glycerol, polyglycerol, ethylene glycol, propylene glycol, oligomers and polymers of ethylene glycol and/or propylene glycol, and triisopropanolamine, preferably said at least one agent is a polyol selected from glycerol and triisopropanolamine.

4. The process according to claim 1, wherein the total amount of the at least one agent provided in step (b) ranges from 0.05 to 3.0 wt.-%, preferably from 0.1 to 2.0 wt.-%, and more preferably from 0.15 to 1.5 wt.-%, based on the total dry weight of the calcium carbonate-containing material provided in step (a).

5. The process according to claim 1 any of claims 1 to ‘1, wherein the total moisture content in the mixture of step (c) is less than or equal to 2.0 wt.-%, preferably less than or equal to 1.5 wt.-%, and more preferably less than or equal to 1.0 wt.-%, based on the total weight of said mixture.

6. The process according to claim 1, wherein the at least one monosubstituted succinic anhydride of step (e) consists of succinic anhydride monosubstituted with an aliphatic group having a total amount of carbon atoms from C2 to C30, preferably from C3 to C25, and most preferably from C4 to C20.

7. The process according to claim 1, wherein the at least one monosubstituted succinic anhydride of step (e) is at least one alkyl monosubstituted succinic anhydride, preferably at least one alkyl monosubstituted succinic anhydride selected from the group consisting of ethylsuccinic anhydride, propylsuccinic anhydride, butylsuccinic anhydride, triisobutyl succinic anhydride, pentylsuccinic anhydride, hexylsuccinic anhydride, heptylsuccinic anhydride, octylsuccinic anhydride, nonylsuccinic anhydride, decyl succinic anhydride, dodecyl succinic anhydride, hexadecanyl succinic anhydride, and octadecanyl succinic anhydride.

8. The process according to claim 1, wherein the at least one monosubstituted succinic anhydride of step (e) is at least one alkenyl monosubstituted succinic anhydride, preferably at least one alkenyl monosubstituted succinic anhydride selected from the group consisting of ethenylsuccinic anhydride, propenylsuccinic anhydride, butenylsuccinic anhydride, triisobutenyl succinic anhydride, pentenylsuccinic anhydride, hexenylsuccinic anhydride, heptenylsuccinic anhydride, octenylsuccinic anhydride, nonenylsuccinic anhydride, decenyl succinic anhydride, dodecenyl succinic anhydride, hexadecenyl succinic anhydride, and octadecenyl succinic anhydride.

9. The process according to claim 1, wherein the temperature during step (e) ranges from 30° C. to 200° C., preferably from 80° C. to 150° C., and more preferably from 110° C. to 130° C.

10. The process according to claim 1, wherein the temperature in step (e) is adjusted to at least 2° C. above the melting point of the at least one monosubstituted succinic anhydride for less than 1 h, preferably less than 5 min, more preferably less than 1 min, and most preferably 1 to 10 s.

11. The process according to claim 1, wherein the total amount of the at least one monosubstituted succinic anhydride and the optional at least one monosubstituted succinic acid and/or salts thereof in step (e) ranges from 0.05 to 3.0 wt.-%, preferably from 0.1 to 2.0 wt.-%, and more preferably from 0.15 to 1.5 wt.-%, based on the total dry weight of the calcium carbonate-containing material provided in step (a).

12. The process according to claim 1, wherein said treatment layer of step (e) comprises the at least one monosubstituted succinic anhydride and/or reaction product(s) thereof and the optional at least one monosubstituted succinic acid and/or salts thereof and/or reaction product(s) thereof in a total amount of from 0.01 to 2.0 wt.-%, preferably from 0.05 to 1.5 wt.-%, and more preferably from 0.1 to 1.0 wt.-%, based on the total dry weight of the calcium carbonate-containing material.

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

14. The mineral filler product according to claim 13, wherein the mineral filler product has a weight median particle size d.sub.50 ranging from 0.3 to 25.0 μm, preferably from 0.5 to 10.0 μm, more preferably from 1.0 to 8.0 μm, and most preferably from 1.2 to 5.0 μm.

15. The mineral filler product according to claim 13, wherein the mineral filler product has a specific surface area ranging from 0.5 to 20.0 m.sup.2/g, preferably from 1.0 to 10.0 m.sup.2/g, and more preferably from 2.0 to 8.0 m.sup.2/g as measured by the BET nitrogen method.

Description

EXAMPLES

[0225] 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.

Example 1

[0226] Marble from Carrara, Italy was wet ground at 25 wt.-% solids content in tap water in a horizontal ball mill (Dynomill) and spray dried. The obtained calcium carbonate-containing material features a d.sub.50 of approximately 1.7 μm, a topcut (d.sub.98) of 5.0 μm, a specific surface area (BET) of 4.1 m.sup.2/g, and a total moisture content of 0.06 wt.-%.

[0227] This dry calcium carbonate was used to demonstrate the effect of a monosubstituted succinic anhydride on the moisture pickup of a mineral filler product. In order to simulate dry grinding in the presence of glycerol, the dry calcium carbonate was treated with 0.6 wt.-% of glycerol in a MTI mixer (MTI Mischtechnik International GmbH). The contents of the mixer were mixed at 120° C. under a stirring speed of 3,000 rpm for a period of 10 min.

[0228] The glycerol-containing calcium carbonate was subsequently divided in several aliquots and surface-treated with either stearic acid or alkenylsuccinic anhydride (HYDRORES AS 1000, commercially available from Kemira Oyj, Vaasa, Finland) in the MTI mixer. The glycerol-containing calcium carbonate was activated for 10 min at 120° C. and 3,000 rpm. Subsequently, the treatment agent was added and the blend was further mixed at 120° C. at a stirring speed of 3,000 rpm fair a period of 10 min. The results are given in Table 1 below.

TABLE-US-00001 TABLE 1 Moisture pickup of dry ground calcium carbonate (n/d = not determined). Moisture pickup susceptibility [mg/g] Treatment agent Stearic acid Succinic anhydride [wt.-%] (prior art) (inventive) 0.0 7.5 0.3 6.2 6.3 0.4 n/d 6.4 0.5 6.6 6.1 0.6 n/d 5.7 0.8 6.3 4.8 1.0 6.0 4.4

Example 2

[0229] The effect of a reduced moisture pick is also observed in cases where the calcium carbonate contains more than one polyol.

[0230] Marble from Carrara, Italy was dry ground in a ball mill equipped with a classifier to produce a dry ground calcium carbonate with d.sub.50 of 2 μm, a topcut (d.sub.98) of 10 μm, and wherein 60 wt.-% of the particles have a particle size of below 2 μm. The total moisture content was 0.3 wt %. For the dry grinding process, 1,500 ppm of a blend (weight ratio 80:20) of glycerol and triisopropanolamine was used as dry grinding agent.

[0231] The dry ground calcium carbonate was subsequently divided in several aliquots and surface-treated with either stearic acid or alkenylsuccinic anhydride (HYDRORES AS 1000, commercially available from Kemira Oyj, Vaasa, Finland) in a MTI mixer (MTI Mischtechnik International GmbH). The dry ground calcium carbonate was activated for 10 min at 120° C., and 3,000 rpm. Subsequently, the treatment agent was added and the blend was further mixed at 120° C. at a stirring speed of 3,000 rpm for a period of 10 min. The results are given in Table 2 below.

TABLE-US-00002 TABLE 2 Moisture pickup of dry ground calcium carbonate. Moisture pickup susceptibility [mg/g] Treatment agent Stearic acid Succinic anhydride [wt.-%] (prior art) (inventive) 0.0 5.52 0.6 2.72 2.25 0.8 2.57 2.05

[0232] In both examples, a reduced moisture pickup as compared to prior art treatment methods using stearic acid can he observed while using glycerol as an agent being suitable to increase the grinding efficiency and throughput.