Use of glycerol as an agent to improve the self-dispersing properties of a mineral material to be added to an aqueous composition

Abstract

The present disclosure relates to a method for improving the auto-dispersant characteristic in water of a mineral substance. The method includes the steps of dry-grinding, in the presence of a formulation, a mineral substance selected from a dolomite, talc, titanium dioxide, alumina, kaolin and calcium carbonate, wherein the formulation contains a polyglycerol and no glycerol.

Claims

1. A method for improving the auto-dispersant characteristic in water of a mineral substance, the method comprising dry-grinding, in the presence of a formulation, a mineral substance selected from the group consisting of a dolomite, talc, titanium dioxide, alumina, kaolin and calcium carbonate, wherein said formulation comprises a polyglycerol, no glycerol, and at least one agent, in aqueous or pure form, that is selected from the group consisting of: an organic polyacid of formula COOH(CH.sub.2).sub.nCOOH, where n is an integer between 0 and 7 inclusive, or is a mono or dialkaline salt of an organic polyacid of formula COOH(CH.sub.2).sub.nCOOH, where n is an integer between 0 and 7 inclusive, or is a polymeric organic polyacid comprising, in polymerized form at least one monomer selected from the group consisting of, in the acidic or partially or completely neutralized form, acrylic acid, methacrylic acid, maleic itaconic, an oxalic acid, a pimelic acid, and an adipic acid, and at least one cation of Group I or II of the Periodic Table of the Elements, an alkanolamine selected from the group consisting of 2-amino-2-methyl-1-propanol, 2-amino-2-ethyl-1,3-propanediol, triethanolamine, N-butyldiethanolamine and triisopropanolamine, neutralized or not, a polyethylene glycol, a polypropylene glycol or an ethylene-propylene glycol copolymer, random or block, and glucose, fructose, sucrose, starch or cellulose having a root mean square of radius of gyration of less than or equal to a modal radius of the mineral substance.

2. The method of claim 1, wherein the polyglycerol is selected from the group consisting of diglycerol, triglycerol, tetraglycerol, pentaglycerol, hexaglycerol, heptaglycerol, octaglycerol, nonaglycerol and decaglycerol and mixtures thereof.

3. The method of claim 1, wherein said formulation consists of at least one polyglycerol in the pure form and the at least one agent.

4. The method of claim 1, wherein said formulation consists of at least one aqueous polyglycerol and the at least one agent.

5. The method of claim 1, wherein said formulation consists of: 25% to 95% by weight of the polyglycerol with respect to a total weight; and the at least one agent, with the complement being constituted by water.

6. The method of claim 1, wherein said formulation comprises 100 to 5,000 ppm of the polyglycerol in relation to a dry weight of said mineral substance.

7. The method of claim 1, wherein said formulation is implemented at between 0.1 and 1 mg total dry equivalent of the polyglycerol per m.sup.2 of said mineral substance.

8. The method of claim 1, wherein said formulation comprises the polyglycerol and the at least one agent in pure form.

9. The method of claim 1, wherein said formulation further comprises a phosphoric acid.

10. The method of claim 1, wherein said formulation further comprises a mono, di or trialkaline salt of an inorganic acid.

11. The method of claim 1, wherein said formulation further comprises a mono, di or trialkaline salt of formic or citric acid.

12. The method of claim 1, wherein said agent is an organic polyacid of formula COOH(CH.sub.2).sub.nCOOH, where n is an integer between 0 and 7 inclusive, or is a mono or dialkaline salt of an organic polyacid of formula COOH(CH.sub.2).sub.nCOOH, where n is an integer between 0 and 7 inclusive, or is a polymeric organic polyacid comprising, in polymerized form at least one monomer selected from the group consisting of, in the acidic or partially or completely neutralized form, acrylic acid, methacrylic acid, maleic itaconic, an oxalic acid, a pimelic acid, and an adipic acid, and at least one cation of Group I or II of the Periodic Table of the Elements.

13. The method of claim 1, wherein said agent is an alkanolamine selected from the group consisting of 2-amino-2-methyl-1-propanol, 2-amino-2-ethyl-1,3-propanediol, triethanolamine, N-butyldiethanolamine and triisopropanolamine, neutralized or not.

14. The method of claim 1, wherein said agent is a polyethylene glycol, a polypropylene glycol or an ethylene-propylene glycol copolymer, random or block.

15. The method of claim 1, wherein said agent is selected from the group consisting of glucose, fructose, sucrose, starch and cellulose having a root mean square of radius of gyration of less than or equal to a modal radius of the mineral substance.

16. The method of claim 1, further comprising grinding said mineral substance to an average diameter measured by a Sedigraph 5100 of between 0.5 and 10 m.

17. The method of claim 1, further comprising grinding said mineral substance to obtain a percentage by weight of particles with a diameter less than 2 m, as measured by a Sedigraph 5100, ranging between 20% and 90%.

18. The method of claim 1, wherein said mineral substance is a natural calcium carbonate.

19. The method of claim 1, wherein the polyglycerol is a diglycerol, a triglycerol, or a mixture thereof.

Description

EXAMPLES

Example 1

(1) This sample illustrates the dry grinding of a natural calcium carbonate which is a Carrara marble. The grinding is performed by means of an apparatus equipped with a ball grinder and a classifier.

(2) The particle size distribution of the original calcium carbonate feeding the grinder is given in table 1.

(3) TABLE-US-00001 TABLE 1 Diameter of particles (mm) % mass .sup.4-2.5 7.25 2.5-1.6 9.73 1.6-0.8 11.44 0.8-0.5 5.57 0.5-0.2 23.73 0.2-0.1 23.18 <0.1 19.1

(4) The Carrara marble was introduced into a 5.7 m.sup.3 ball grinder using 8 tons of Cylpeb iron grinding balls in the form of cylinders with an average diameter of 16 mm, in order to obtain a ground material: with a median diameter less than or equal to 1.8 m, of which 55% by weight of the particles have a diameter less than or equal to 2 m.

(5) The dry grinding is performed continuously.

(6) On exiting the grinding chamber, the material is directed to a SELEX 6S classifier. Its speed of rotation and air flow are controlled at 5,200 rpm and 6,000 m3/h respectively in order to select the fraction of particles with an average diameter less than or equal to a given value and that will constitute the finished product. The fraction of particles remaining with an average diameter greater than this value is recycled to the ball grinder.

(7) The grinding is carried out in such a way that the feed flow of the selector is always equal to 4 tonnes/h and that the quantity of fresh product injected into the ball grinder corresponds to the quantity of selected product exiting the system.

(8) The dry crusher helper agents were introduced into the grinding system at the point of introduction of the fresh material so as to maintain a constant quantity of dry crusher helper agent in relation to the fresh material being supplied to the grinder.

(9) TABLE-US-00002 TABLE 2 Test No. 1 2 3 Type of grinding aid agent MPG PEG Glycerol Prior Art (PA)/Invention (IN) PA PA IN % of particles with a diameter <2 m 57 57 57 % of particles with a diameter <1 m 22 21 23 d50 (m) 1.8 1.8 1.7 BET Surface area (m.sup.2g) 6.3 6.9 6.9

(10) The MPG referenced grinding aid agents consist of aqueous solution containing 75% (by weight) of monopropylene glycol and were obtained from the company FLUKA.

(11) The PEG referenced grinding aid agents consist of aqueous solutions containing 75% (by weight) of polyethylene glycol with a molecular weight equal to 600 g/mole and were obtained from the company FLUKA.

(12) Glycerol designates an aqueous solution containing 75% glycerol (by weight).

(13) Each test uses 2,000 ppm of active product (i.e. 2,667 ppm of each aqueous solution).

(14) The calcium carbonates from tests No. 1 to 3 will then be tested in examples 2-4 to quantify their ability to reduce the phenomenon of foaming when dispersed in water, and their ability to be easily dispersed in an aqueous formulation.

Example 2

(15) This example illustrates the effect of the dry grinding agent used on the amount of foam formed when the calcium carbonate resulting from said grinding is dispersed in water.

(16) To do this, a 40% by dry weight aqueous suspension of calcium carbonate is prepared using distilled water. 600 ml of this suspension are introduced into the equipment called the foam machine consisting of a centrifugal pump through which the suspension circulates in a loop at a flow rate of 50 l/min., of a 750 ml, 20 cm high graduated vertical glass column for introducing the suspension into the pump, and of an air supply from a pipe installed in the suspension recirculation circuit. This circulation of the suspension is carried out for 10 minutes under continuous bubbling of the air at a constant flow rate of 230-235 ml/min.

(17) At the end of the 10 minute period, the foam height is read directly from the graduations of the column.

(18) TABLE-US-00003 TABLE 3 Test No. 1 2 3 Type of grinding aid agent MPG PEG Glycerol Prior Art (PA)/Invention (IN) PA PA IN Height of foam (cm) 7 >20 3

(19) These results demonstrate that calcium carbonate dry-ground in the presence of glycerol can significantly reduce the amount of foam when the said carbonate is dispersed in water.

Example 3

(20) This example illustrates the manufacture of paints where the formulation uses 3 calcium carbonates dry-ground according to example 1. In each of the tests No. 1 (2nd.) to 3 (2nd.), a flat paint in the aqueous phase is produced by a mixture under agitation of the different constituents in the proportions in grams indicated in table 4.

(21) TABLE-US-00004 TABLE 4 Test No. Prior Art (PA)/Invention (IN) 1 (2nd.) 2 (2nd.) 3 (2nd.) PA PA IN Water 292.0 292.0 292.0 Ammonia (31% solution) 2.0 2.0 2.0 Ecodis P90 (40% solution) 4.0 4.0 4.0 Mergal K6N 2.0 2.0 2.0 Byk 034 2.0 2.0 2.0 TiO2 RL68 41.0 41.0 41.0 Durcal 2 328.0 328.0 328.0 CaCO3 dry-ground according to test No. 1 215.0 0 0 CaCO3 dry-ground according to test No. 2 0 215.0 0 CaCO3 dry-ground according to test No. 3 0 0 215.0 Acronal 290D 82.0 82.0 82.0 Monopropylene glycol 10.0 10.0 10.0 Texanol 10.0 10.0 10.0 Rheotech 3000 12.0 12.0 12.0 Total (g) 1000.0 1000.0 1000.0
Ecodis P90 designates a thickener marketed by the company COATEX,
Rheotech 3000 designates a thickener marketed by the company COATEX,
Mergal K6N designates a bactericide marketed by the company TROY,
Byk 034 designates an antifoaming agent marketed by the company BYK,
TiO2 RL68 designates a titanium dioxide powder marketed by the company Millennium,
Durcal 2 designates a calcium carbonate marketed by the company OMYA,
Acronal 290 D designates a binder marketed by the company BASF
Texanol designates a coalescent agent marketed by the company EASTMANN,

(22) For each of the tests Nos. 1 (2nd.) to 3 (2nd.), the Brookfield viscosities at 10 and 100 RPM were determined according to the methods well known to the person skilled in the art.

(23) Also measured were certain optical characteristics of the paints obtained such as the whiteness L, the 3 Hunterlab filters Sub-tone and the level of gloss at 85. The methods implemented are described specifically in document FR 2 872 815. The results are listed in tables 5 and 6.

(24) TABLE-US-00005 TABLE 5 Test No. 1 (3.sup.rd.) 2 (3.sup.rd.) 3 (3.sup.rd.) Viscosities PA PA IN Time t = 0 .sup.B.sub.10 (mPa .Math. s) 12,400 10,000 10,700 .sup.B.sub.100 (mPa .Math. s) 3,400 2,800 3,100 Time t = .sup.B.sub.10 (mPa .Math. s) 14,200 11,900 11,700 24 hours .sup.B.sub.100 (mPa .Math. s) 4,000 3,600 3,500 Time t = .sup.B.sub.10 (mPa .Math. s) 21,400 13,900 13,600 7 days 50 C. .sup.B.sub.100 (mPa .Math. s) 5,830 4,100 4,100 Time t = .sup.B.sub.10 (mPa .Math. s) 27,500 18,100 18,100 1 month .sup.B.sub.100 (mPa .Math. s,) 7,250 5,100 5,100 50 C. .sup.B.sub.10 (mPa .Math. s): Brookfield viscosity determined at 10 RPM .sup.B.sub.100 (mPa .Math. s): Brookfield viscosity determined at 100 RPM

(25) TABLE-US-00006 TABLE 6 Test No. Prior Art (PA)/Invention (IN) 1 (3rd.) 2 (3rd.) 3 (3rd.) PA PA IN Whiteness Measurement of L 98.6 98.7 98.7 3 Hunterlab Filters Sub-tone Value of a 0 0.1 0.1 Value of b 3.0 3.0 3.1 Level of gloss 85 12.3 12.6 12.6

(26) Compared to the market reference that uses monopropylene glycol as a dry-grinding agent, we have succeeded in improving the auto-dispersant characteristic of calcium carbonate in a paint by the use of the formulation containing glycerol. Indeed, in comparison with test No. 1 (3rd.), one can observe in test No. 3 (3rd.) both a decrease in the initial viscosity, which reflects a good initial state of dispersion, and a lower by-product of this viscosity over time, reflecting a better stability. In addition, the final optical properties are not altered.

(27) Compared to calcium carbonate dry-ground with low molecular weight polyethylene glycol, the same level of performance is revealed, both at the rheological level as well as with respect to the optical properties. Glycerol is thus a solution that is as effective as low molecular weight polyethylene glycol, but is less expensive and most importantly, is derived from a renewable non-food resource that is natural and available in large quantities: It represents a VOC-free alternative that is very beneficial environmentally and for the preservation of our natural resources, which fits in perfectly with the concepts of green chemistry and of sustainable development.

Example 4

(28) This example illustrates the ability of calcium carbonate dry-ground according to the invention (with formulations containing glycerol) or according to the prior art (with a state-of-the-art dry-grinding agent) to disperse in the aqueous phase in the presence of an acrylic dispersant.

(29) For each of the tests 1 (4th.) to 3 (4th.), into a 1-liter beaker, 500 grams of calcium carbonate dry-ground according to tests 1 to 3 respectively are introduced into 175 g of water so as to obtain a 74% by weight dry extract.

(30) To the medium is then added a certain amount of acrylic dispersant (which is a homopolymer of acrylic acid, sodium/calcium 70/30% molar neutralized, with a molecular weight equal to 5,500 g/mol), it is agitated and the Brookfield viscosity is measured at 25 C. and 100 RPM.

(31) By repeating these operations for increasing additions of dispersant, one can follow the evolution of the Brookfield viscosity at 25 C. and 100 RMP (mPa.Math.s), as a function of the percentage by dry weight of dispersant with respect to the dry weight of calcium carbonate. The corresponding curves appear in FIG. 1/1 with the following symbols: black triangles for test No. 1 (4th.) with dry-ground carbonate in the presence of PEG black squares for test No. 2 (4th.) with dry-ground carbonate in the presence of MPG black circles for test No. 3 (4th.) with dry-ground carbonate in the presence of glycerol

(32) FIG. 1/1 clearly shows that at a constant dry extract level (74%), the dry-ground calcium carbonate in the presence of glycerol is the one that requires the lowest dose of dispersant to achieve a given viscosity level; in other words, it is the calcium carbonate which presents the most pronounced auto-dispersant characteristic when put in aqueous suspension in the presence of an acrylic dispersant.