COPOLYMER AND GRINDING OF A MINERAL MATTER

Abstract

A polymer may have a molecular mass of less than 8,000 g/mol and a polymolecularity index PI of less than 3, produced by free radical polymerization, in water, and at a temperature higher than 50 C., of at least one anionic monomer comprising at least one polymerizable olefinic unsaturation and at least one carboxylic acid function, in the presence of phosphorus with a degree of oxidation I, phosphorus with a degree of oxidation III and a radical-generating compound. Such polymers may be produced and use for grinding mineral matter, as a detergent agent, or as an anti-scaling agent.

Claims

1. A polymer, comprising, in radically polymerized form: an anionic monomer comprising a polymerizable olefinic unsaturation and a carboxylic acid group, wherein the polymer has a molecular weight M.sub.W, measured by SEC, of less than 8,000 g/mol and a polydispersity index of less than 3, wherein the polymer is obtained by at least one radical polymerization reaction in water and at a temperature greater than 50 C. in an environment comprising: a compound (a) comprising phosphorus in an oxidation state of 1, a compound (b) in at least 5 wt. %, relative to a total weight of compounds (a) and (b), the compound (b) comprising phosphorus in an oxidation state of 3, a radical-generating compound (c) comprising hydrogen peroxide, benzoyl peroxide, acetyl peroxide, lauryl peroxide, tert-butyl hydroperoxide, cumene hydroperoxide, ammonium persulphate, an alkaline metal persulphate, and/or an azo compound, optionally comprising an Fe.sup.II, Fe.sup.III, Cu.sup.I, and/or Cu.sup.II ion.

2. The polymer of claim 1 wherein the weight-average molecular mass M.sub.W is less than 7,500 g/mol, or wherein the weight-average molecular mass M.sub.W is greater than 1,000 g/mol, or wherein the dispersity index is less than 2.8.

3. The polymer of claim 1, wherein the anionic monomer comprises one or two one carboxylic acid groups.

4. The polymer of claim 1, wherein the compound (a) is a mineral compound or is hypophosphorous acid (H.sub.3PO.sub.2) or a derivative of hypophosphorous acid.

5. The polymer of claim 1, wherein the compound (a) is present in an amount of at most 95 wt. %, relative to the total weight of compounds (a) and (b); or wherein the compound (a) is present in a range of from 0.01 to 10 wt. % relative to the amount of monomer.

6. The polymer of claim 1, wherein the compound (b) is a mineral compound or is phosphorous acid (H.sub.3PO.sub.3) or a derivative of phosphorous acid.

7. The polymer of claim 1, wherein the compound (b) is present in more than 6 wt. %, relative to the total weight of compounds (a) and (b).

8. The polymer of claim 1, wherein the compound (c) comprises hydrogen peroxide, ammonium persulfate, sodium persulfate, and/or potassium persulfate.

9. The polymer of claim 1, wherein the compound (c) is present in a range of from 0.1 to 5 wt. %, relative to the weight of monomer.

10. The polymer of claim 1, wherein the polymerization reaction is carried out in the absence of a base neutralization agent.

11. The polymer of claim 1, further comprising, in polymerized form: a further anionic monomer comprising acrylic acid, methacrylic acid, itaconic acid, and/or maleic acid, optionally as a salt; a non-ionic monomer comprising a polymerizable olefinic unsaturation.

12. The polymer of claim 1, comprising 100 wt. % of anionic monomer.

13. A method for preparing an aqueous suspension of particles of mineral material, the method comprising: mixing in water components comprising mineral material particles and the polymer of claim 1.

14. A method for preparing particles of mineral material, the method comprising: grinding, in the presence of water, components comprising a mineral material and the polymer of claim 1.

15. The method of claim 13, wherein the particles have a size of less than 50 m, or wherein an equivalent spherical diameter of the particles is in a range of from 0.05 m to 50 m.

16. The method of claim 13, wherein a single mineral material is used, or wherein the mineral material comprises alkaline-earth metal carbonate, dolomite, kaolin, titanium dioxide, talcum, lime, calcium sulphate, barium sulphate, and/or magnesium hydroxide.

17. An aqueous composition, comprising: particles of ground mineral material; and the polymer of claim 1.

18. The composition of claim 17, further comprising: an admixture.

19. (canceled)

20. A method of producing paper, the method comprising: contacting the composition of claim 17 with a paper precursor.

21. A washing method, comprising: applying the polymer of claim 1 to an object to be washed.

22. A detergent or scale-inhibiting composition, comprising: the polymer of claim 1.

Description

EXAMPLE 1

Preparation of Neutralised Polymers According to the Invention

[0117] A mixture (R) of water, calcium phosphite hydrate and sodium hypophosphite hydrate is injected into a tank reactor. Then, mixture 1 (M1), mixture 2 (M2) and mixture 3 (M3) are prepared from water, acrylic acid (AA), sodium persulphate, and sodium hypophosphite hydrate. The reactor is then heated so as to reach the polymerisation temperature T (972 C.) and mixtures 1, 2 and 3 are simultaneously injected into the reactor. Finally, the reactor is cooled and the polymer is neutralised using an aqueous solution of sodium hydroxide at 50%, while injecting the pre-prepared neutralisation mixture (NM).

[0118] Neutralisation is carried out to achieve a polymeric solution with a pH greater than 6, typically a pH of from 8 to 9. The amounts of reagents (in g), the reaction conditions, the concentration by weight of phosphite (dry/dry) relative to the total amount of phosphite and hypophosphite as well as the characteristics of the polymers (molecular mass M.sub.W and polymolecularity index (PI)) are shown in Table 1.

TABLE-US-00001 TABLE 1 Example: 1-1 1-2 1-3 1-4 1-5 1-6 R Water 326.87 326.87 790 790 790 326.87 CaHPO.sub.3 2.59 5.18 15.02 18.00 23.93 12.94 NaH.sub.2PO.sub.2 2.37 2.11 12.43 12.41 12.38 5.26 M1 Acrylic acid 508.41 508.41 1223.88 1227.04 1223.40 508.41 Water 37.66 37.66 37.66 M2 Sodium persulphate 4.23 4.23 10.23 10.22 10.19 4.23 Water 112.28 112.28 100.00 100.00 100.00 112.28 M3 NaH.sub.2PO.sub.2 21.32 18.95 37.30 37.25 37.14 15.79 Water 93.9 93.9 200.0 200.0 200.0 93.9 NM NaOH at 50% in water qsp pH 8-9 [CaHPO.sub.3] (ppm) 98,554 197,408 231,969 266,036 325,800 380,700 Mw (g/mol) 5,225 6,140 5,435 5,555 5,450 5,515 PI 2.2 2.4 2.2 2.3 2.3 2.3

[0119] It can be seen that the reaction conditions implemented according to the invention make it possible to prepare polymers whose molecular mass and polymolecularity index are well-controlled.

[0120] Polymers can be used as a natural calcium carbonate grinding aid agent.

EXAMPLE 2

Grinding Calcium Carbonate with an ESD of Less than 1 m Equal to 80% by Weight:

[0121] Aqueous suspensions of natural calcium carbonate are prepared with a solid content by weight of 76%1% for an ESD of less than 1 m equal to 80% by weight. They are prepared in the presence of an amount of 1.07% by dry weight of an aqueous polymer solution, as a grinding aid, relative to the solid content in calcium carbonate used in this grinding operation in order to obtain the desired particle size. The polymer solutions have a concentration of 35%1% in active ingredient and a pH of 8.50.5. The raw material used to prepare these aqueous suspensions is an aqueous suspension of coarse-grain calcium carbonate with a solids content of 75%1% by weight. The calcium carbonate is a coarse marble (commercial name Omyacarb 10 AV Omya) from the Carrare region in Italy. The grinding conditions are adapted so as to obtain a suspension of mineral particles of which 80.0%0.5% by weight of its population has an equivalent spherical diameter of less than 1 m (ESD <1 m=80.0%0.5%).

[0122] The suspensions according to the invention are then analysed and characterised using Brookfield viscosity measurements (mPa.Math.s) after the grinding operation (VB0), then after eight days at rest (VB8) at 25 C. The results are shown in Table 2.

TABLE-US-00002 TABLE 2 Suspension Polymer VB0 VB8 S1-1 1-1 313 649 S1-2 1-2 323 707 S1-3 1-3 296 601 S1-4 1-4 327 692 S1-5 1-5 320 702 S1-6 1-6 324 781

[0123] The use of a grinding aid agent according to the invention makes it possible to prepare low-density suspensions of ground calcium carbonate. The viscosity of these suspensions changes slowly over a period of eight days. The suspension prepared according to the invention has a lower viscosity than that of the suspensions in the prior art. It is therefore more stable during storage.