Process to preserve aqueous preparations of mineral materials, preserved aqueous preparations of mineral materials and use of preservative compounds in aqueous preparations of mineral materials

Abstract

The present invention refers to a process for preserving an aqueous preparation of mineral material like e.g. calcium carbonate preparations, and to the use of a composition as a preservative in an aqueous preparation of mineral materials.

Claims

1. A process for preserving an aqueous preparation of mineral material, comprising the following steps: (a) providing an aqueous preparation of mineral material at a solids content of 10 to 85% by dry weight relative to the total weight of the aqueous preparation, wherein the mineral material consists of ground calcium carbonate, precipitated calcium carbonate, dolomite, ground calcium carbonate surface treated with a fatty acid, precipitated calcium carbonate surface treated with a fatty acid, surface reacted ground calcium carbonate, surface-reacted precipitated calcium carbonate, or any mixture thereof; (b) adding to the aqueous preparation of step (a) one or more sources of lithium ions in an amount such that the total amount of lithium ions in the aqueous preparation is from 750 to less than 3000 ppm, calculated relative to the water in the preparation; (c) adding to the aqueous preparation of step a) one or more sources of sodium ions and/or potassium ions in an amount such that the total amount of sodium and/or potassium ions in the aqueous preparation is from 3000 to less than 7500 ppm, calculated relative to the water in the preparation, where steps (b) and (c) may be carried out simultaneously, or separately in any order, in order to preserve the aqueous preparation of mineral material so that the aqueous preparation so preserved has a bacterial count of less than 10.sup.4 cfu/ml.

2. The process according to claim 1, wherein the aqueous preparation has a mineral solids content of 20 to 80%, by dry weight relative to the total weight of the aqueous preparation.

3. The process according to claim 1, wherein the aqueous preparation of step (a) has a pH value of 6 to 10.5.

4. The process according to claim 1, wherein the aqueous preparation of step (a) has a pH value of 7 to 10.

5. The process according to claim 1, wherein the aqueous preparation of step (a) has a viscosity of from 50 to 800 mPa.Math.s.

6. The process according to claim 1, wherein the aqueous preparation of step (a) has a viscosity of from 80 to 600 mPa.Math.s.

7. The process according to claim 1, wherein the mineral material consists of ground calcium carbonate obtained from marble, limestone and/or chalk.

8. The process according to claim 1, wherein the mineral material consists of precipitated calcium carbonate.

9. The process according to claim 1, wherein the source of the lithium ions is a water soluble lithium compound, a lithium salt, lithium carbonate, a polymeric salt of lithium, a mixture of lithium carbonate with a polymeric salt of lithium, or a lithium salt of an acrylic homopolymer, an acrylic copolymer, a copolymer of acrylic acid and maleic acid and/or acrylamide, a polyphosphate, or any mixture thereof.

10. The process according to claim 1, wherein the source of the lithium ions is a polymeric salt of lithium selected from Li.sub.2Na.sub.2polyphosphate, lithium-sodium hexamethaphosphate, and lithium polyacrylate.

11. The process according to claim 1, wherein the source of the lithium ions is lithium carbonate.

12. The process according to claim 1, wherein the source of the lithium ions is lithium carbonate and a polymeric salt of lithium at a weight ratio of lithium carbonate:polymeric salt of lithium from 50:50 to 99.9:0.1.

13. The process according to claim 1, wherein the lithium ions are provided to the aqueous preparation of step (a) in an amount such that the total amount of lithium ions in the aqueous preparation is from 750 to 1500 ppm, calculated relative to the water in the preparation.

14. The process according to claim 1, wherein the source of the sodium and/or potassium ions is selected from the group consisting of a water soluble sodium compound, a water soluble potassium compound, sodium carbonate, potassium carbonate, sodium chloride, potassium chloride, and any mixture thereof, a mixture of one or more of sodium chloride and potassium chloride with a polymeric salt of one or more of sodium and potassium, and a mixture of one or more of sodium carbonate and potassium carbonate with a polymeric salt of one or more of sodium and potassium.

15. The process according to claim 1, wherein the source of the sodium and/or potassium ions is one or more of sodium carbonate and potassium carbonate.

16. The process according to claim 1, wherein the source of the sodium and/or potassium ions is sodium carbonate.

17. The process according to claim 1, wherein the source of sodium and/or potassium ions is provided to the aqueous preparation of step (a) in an amount such that the total amount of sodium ions in the aqueous preparation is from 5000 to 7000 ppm, calculated relative to the water in the preparation.

18. The process according to claim 1, wherein the source of the lithium ions of step (b) and the source of the sodium and/or potassium ions of step (c) are added simultaneously to the aqueous preparation of step (a).

19. The process according to claim 1, wherein the source of lithium ions of step (b) and source of sodium and/or potassium ions of step (c) are added separately to the aqueous preparation of step (a).

20. The process according to claim 1, wherein when the source of lithium ions is a polymeric salt, the polymeric salt of lithium is added prior to the source of sodium and/or potassium ions.

21. The process according to claim 1, wherein when the source of the sodium and/or potassium ions is a polymeric salt, the polymeric salt of one or more of sodium and/or potassium ions is added prior to the source of lithium ions.

22. The process according to claim 1, wherein no biocide other than the biocide formed by addition of lithium ions and one or more of sodium and/or potassium ions is added.

23. The process according to claim 1, wherein after step (c), the aqueous preparation is dried to obtain a dried product.

24. The process according to claim 1, wherein the mineral material consists of ground calcium carbonate surface treated with a fatty acid or precipitated calcium carbonate surface treated with a fatty acid.

25. The process according to claim 1, wherein the mineral material consists of surface reacted ground calcium carbonate or surface reacted precipitated calcium carbonate.

Description

EXAMPLES

(1) In all of the following examples, the particle size distribution characteristics are measured using a Sedigraph 5100 of Micromeritics Instrument Corporation. 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 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.

(2) All BET specific surface area measurements, quoted in m.sup.2/g, are measured according to ISO 4652.

(3) All Brookfield-viscosities are measured with a Brookfield DV-II Viscometer equipped with a LV-3 spindle at a speed of 100 rpm and room temperature (203 C.).

(4) All biocide and lithium, sodium, magnesium and potassium amounts quoted in ppm represent mg values per kilogram of water in the aqueous preparation.

(5) All quoted bacterial counts (values are in cfu/ml) in the Tables herebelow are determined after 5 days following plate-out and in accordance with counting method described in Bestimmung von aeroben mesophilen Keimen, Schweizerisches Lebensmittelbuch, chapter 56, section 7.01, edition of 1985, revised version of 1988.

Example 1: Preparation of Aqueous Mineral Preparations

(6) a) Calcium Carbonate Slurry 1

(7) Calcium carbonate slurry 1 was prepared by wet grinding, in a re-circulating, horizontal 1.4 liter attritor ball mill (Dyno-Mill), a 76.4 wt.-% suspension of north-Norwegian marble having a starting esd (equivalent spherical diameter) of about 45 m, in the presence of 0.6 wt.-%, based on the total weight of dry calcium carbonate, of a radically polymerized polyacrylic acid (MW 6000 g/Mol, polydispersity 2.6 determined by gel permeation chromatography), wherein 50 mole-% of the carboxylic acid groups are neutralized by sodium and the remaining 50 mole-% of the carboxylic acid groups are neutralized by magnesium. Following grinding, the calcium carbonate in suspension had the following particle size distribution:

(8) TABLE-US-00001 Diameter (m) wt.-% <2 91.5 <1 62.2 <0.2 17.9

(9) The Brookfield-viscosity of the slurry was determined as 180 mPa.Math.s.

(10) The total soluble magnesium content was 21 ppm and the total soluble sodium content was 927 ppm based on the weight of water in the slurry.

(11) b) Calcium Carbonate Slurry 2

(12) Calcium carbonate slurry 2 was prepared by wet grinding, in a recirculating, horizontal 1.4 liter attritor ball mill (Dyno-Mill), a 76.1 wt.-% suspension of north-Norwegian marble having a starting esd (equivalent spherical diameter) of about 45 m, in the presence of 0.6 wt.-%, based on the total weight of dry calcium carbonate, of a radically polymerized polyacrylic acid (MW 6000 g/Mol, polydispersity 2.6 determined by gel permeation chromatography), wherein 100 mole-% of the carboxylic acid groups are neutralized by lithium. Following grinding, the calcium carbonate in suspension had the following particle size distribution:

(13) TABLE-US-00002 Diameter (m) wt.-% <2 90.5 <1 60.2 <0.2 15.0

(14) The Brookfield-viscosity of the slurry was 130 mPa.Math.s. The total soluble lithium content was 800 ppm based on the weight of water in the slurry.

Example 2: Preservation Activity

(15) The preservation activity of various embodiments of the present invention and of comparison examples was determined in the tests herebelow.

(16) Tests a) Sodium and Lithium Ions

(17) 6 000 ppm of sodium ions, based on the weight of the water in the suspension, provided in the form of a 1 M solution of sodium carbonate, were introduced into 50 g samples of calcium carbonate slurry 1. In parallel, control samples of calcium carbonate slurry 1 were prepared without addition of further sodium ions.

(18) The total sodium amounts listed in the Table below were calculated as the amount of sodium ions added as sodium carbonate to calcium carbonate slurry 1, plus the amount of soluble sodium ions added via the polyacrylic acid as mentioned above.

(19) To the indicated samples, lithium ions were provided in the form of lithium carbonate, which was added in the form of a powder and mixed with the suspension in the amounts indicated in the Table below.

(20) Thereafter, half of the samples of calcium carbonate slurry 1 were inoculated with either 1 mL of Pseudomonas species or 1 mL of Pseudomonas species that are resistant glutaraldehyde-isothiazoline mixtures (said mixtures being in the form of aqueous solutions of 21 weight % glutaraldehyde, 0.25 weight % methylisothiazoline, and 0.75 weight % chloromethylisothiazoline). Each of the samples was incubated at 30 C. for 72 hours. Thereafter, a 1:10 dilution in phosphate buffered saline (PBS) was plated on plate count agar (PCA). These plates were incubated at 30 C. and analysed after 5 days.

(21) TABLE-US-00003 Resistant Pseudomonas Pseudomonas sp. species Na (ppm 1 350 ppm 750 ppm Slurry on water) No lithium lithium No lithium lithium Calcium 927 ppm >10.sup.4 >10.sup.4 >10.sup.4 >10.sup.4 carbonate slurry 1 Calcium 6 927 ppm >10.sup.4 <10.sup.2 >10.sup.4 <10.sup.2 carbonate slurry 1

(22) The results of the above table confirm that it is only when sodium is implemented in combination with lithium in the appropriate amount that the bacterial count of the suspension falls to below 10.sup.4 cfu/ml.

(23) Tests b) Potassium and Lithium Ions

(24) 6 000 ppm of potassium ions, based on the weight of the weight of water in the suspension, provided in the form of a 1 M solution of potassium carbonate, was introduced into 50 g samples of calcium carbonate slurry 1. In parallel, control samples of calcium carbonate slurry 1 were prepared in absence of any sodium.

(25) To the indicated samples, lithium ions were provided in the form of lithium carbonate, which was added in the form of a powder and mixed with the suspension in the amounts indicated in the Table below.

(26) Thereafter, half of the samples of calcium carbonate slurry 1 were inoculated with either 1 mL of Pseudomonas species or 1 mL of Pseudomonas species that are resistant glutaraldehyde-isothiazoline mixtures (said mixtures being in the form of aqueous solutions of 21 weight % glutaraldehyde, 0.25 weight % methylisothiazoline, and 0.75 weight % chloromethylisothiazoline). Each of the samples was incubated at 30 C. for 72 hours. Thereafter, a 1:10 dilution in phosphate buffered saline (PBS) was plated on plate count agar (PCA). These plates were incubated at 30 C. and analysed after 5 days.

(27) TABLE-US-00004 Resistant Pseudomonas Pseudomonas sp. species K (ppm on 1700 ppm 1050 ppm Slurry water) No lithium lithium No lithium lithium Calcium 0 ppm >10.sup.4 >10.sup.4 >10.sup.4 >10.sup.4 carbonate slurry 1 Calcium 6 000 ppm >10.sup.4 <10.sup.2 >10.sup.4 <10.sup.2 carbonate slurry 1

(28) The results of the above table confirm that it is only when potassium is implemented in combination with lithium in the appropriate amount that the bacterial count of the suspension falls to below 10.sup.4 cfu/ml.

(29) Tests c) Sodium and Lithium Ions

(30) 2 250 ppm of sodium ions, based on the weight of the weight of water in the suspension, provided in the form of a 1 M solution of sodium carbonate, was introduced into 50 g samples of calcium carbonate slurry 1.

(31) The total sodium amounts listed in the Table below were calculated as the amount of sodium ions added as sodium carbonate to calcium carbonate slurry 1, plus the amount of soluble sodium ions added via the polyacrylic acid as mentioned above.

(32) To the indicated samples, lithium ions were provided in the form of lithium carbonate, which was added in the form of a powder and mixed with the suspension in the amounts indicated in the Table below.

(33) All of samples were then inoculated with 1 mL of Pseudomonas species. After inoculation, the samples were incubated at 30 C. for 72 hours. Thereafter, a 1:10 dilution in phosphate buffered saline (PBS) was plated on plate count agar (PCA). These plates were incubated at 30 C. and analysed after 5 days.

(34) TABLE-US-00005 Pseudomonas sp. Na (ppm 2 250 ppm Slurry on water) No lithium lithium Calcium 3 177 ppm >10.sup.4 <10.sup.2 carbonate slurry 1

(35) The results of the above table confirm that it is only when sodium is implemented in combination with lithium in the appropriate amount that the bacterial count of the suspension falls to below 10.sup.4 cfu/ml.

(36) Tests d) Sodium or Potassium and Lithium IonsMultiple Inoculations of Pseudomonas Species

(37) The indicated amount of sodium or potassium ions, based on the weight of the weight of water in the suspension, as listed in the Tables below, provided in the form of a 1 M solutions of sodium or potassium carbonate, was introduced into 50 g samples of calcium carbonate slurry 2. In parallel, control samples of calcium carbonate slurry 1 were prepared in absence of any sodium or potassium.

(38) All of samples were then inoculated three times with 1 mL of Pseudomonas species. After each inoculation, the samples were incubated at 30 C. for 72 hours. Thereafter, a 1:10 dilution in phosphate buffered saline (PBS) was plated on plate count agar (PCA). These plates were incubated at 30 C. and analysed after 5 days.

(39) TABLE-US-00006 Calcium Calcium Calcium Calcium carbonate carbonate carbonate carbonate slurry 2 slurry 2 slurry 2 slurry 2 Na (ppm on 0 3 000 4 500 6 000 water) Li (ppm on 800 800 800 800 water) Inoculation 1 >10.sup.4 <10.sup.2 <10.sup.2 <10.sup.2 Inoculation 2 >10.sup.4 10.sup.3 <10.sup.2 <10.sup.2 Inoculation 3 >10.sup.4 >10.sup.4 <10.sup.2 <10.sup.2

(40) TABLE-US-00007 Calcium Calcium Calcium carbonate carbonate carbonate slurry 2 slurry 2 slurry 2 K (ppm on 0 4 500 6 000 water) Li (ppm on 800 800 800 water) Inoculation 1 >10.sup.4 <10.sup.2 <10.sup.2 Inoculation 2 >10.sup.4 <10.sup.3 <10.sup.2 Inoculation 3 >10.sup.4 >10.sup.4 <10.sup.2

(41) The results of the above tables confirm that it is only when sodium or potassium is implemented in combination with lithium in the appropriate amount that the bacterial count of the suspension falls to below 10.sup.4 cfu/ml following at least one innoculation.

(42) Tests e) Sodium or Potassium and Lithium IonsMultiple Inoculations of biocide-Resistant Pseudomonas Species

(43) The indicated amount of sodium or potassium ions, based on the weight of the weight of water in the suspension, as listed in the Tables below, provided in the form of a 1 M solutions of sodium or potassium carbonate, was introduced into 50 g samples of calcium carbonate slurry 2. In parallel, control samples of calcium carbonate slurry 1 were prepared in absence of any sodium or potassium.

(44) All of samples were then inoculated three times with 1 mL of Pseudomonas species that are resistant glutaraldehyde-isothiazoline mixtures (said mixtures being in the form of aqueous solutions of 21 weight % glutaraldehyde, 0.25 weight % methylisothiazoline, and 0.75 weight % chloromethylisothiazoline). After each inoculation, the samples were incubated at 30 C. for 72 hours. Thereafter, a 1:10 dilution in phosphate buffered saline (PBS) was plated on plate count agar (PCA). These plates were incubated at 30 C. and analysed after 5 days.

(45) TABLE-US-00008 Calcium Calcium Calcium Calcium carbonate carbonate carbonate carbonate slurry 2 slurry 2 slurry 2 slurry 2 Na 0 3 000 4 500 6 000 (ppm on water) Li 800 800 800 800 (ppm on water) Inoculation 1 >10.sup.4 <10.sup.3 <10.sup.2 <10.sup.2 Inoculation 2 >10.sup.4 >10.sup.4 <10.sup.3 <10.sup.2 Inoculation 3 >10.sup.4 >10.sup.4 >10.sup.4 <10.sup.2

(46) TABLE-US-00009 Calcium Calcium Calcium Calcium carbonate carbonate carbonate carbonate slurry 2 slurry 2 slurry 2 slurry 2 K (ppm on 0 3 000 4 500 6 000 water) Li (ppm on 800 800 800 800 water) Inoculation 1 >10.sup.4 <10.sup.3 <10.sup.3 <10.sup.2 Inoculation 2 >10.sup.4 >10.sup.4 >10.sup.4 >10.sup.4 Inoculation 3 >10.sup.4 >10.sup.4 >10.sup.4 >10.sup.4

(47) The results of the above tables confirm that it is only when sodium or potassium is implemented in combination with lithium in the appropriate amount that the bacterial count of the suspension falls to below 10.sup.4 cfu/ml following at least one innoculation.