Foam Prevention In The Reverse Flotation Process For Purifying Calcium Carbonate

1 . A composition, comprising

A) at least one quaternary ammonium compound which is a collector for the reverse flotation of magnesium minerals from calcium carbonate,

B) at least one antifoam agent, and

C) at least one solvent.

2 . The composition according to claim 1 , wherein the quaternary ammonium compound corresponds to formula (8)

[R 1 R 2 R 3 R 4 N] + X −   (8)

wherein

R 1 , R 2 , R 3 and R 4 independently from each other are hydrocarbon groups containing 1 to 30 carbon atoms, with the proviso that at least one of R 1 , R 2 , R 3 and R 4 contains between 6 and 20 carbon atoms, and

X is selected from the group consisting of chloride, carbonate, bicarbonate, nitrate, bromide, acetate or carboxylate.

3 . The composition according to claim 2 , wherein the total number of carbon atoms contained in R 1 , R 2 , R 3 and R 4 is from 9 to 35.

4 . The composition according to claim 2 , wherein the quaternary ammonium compound corresponds to formula (9)

[R 1 (CH 3 ) 3 N] + X −   (9)

wherein R 1 is a C 6 -C 20 hydrocarbon group.

5 . The composition according to claim 2 , wherein the quaternary ammonium compound corresponds to formula (10)

[R 1 R 2 (CH 3 ) 2 N] + X −   (10)

wherein both R 1 and R 2 are C 6 -C 20 hydrocarbon groups.

6 . The composition according to claim 2 , wherein the quaternary ammonium compound corresponds to formula (11)

[R 1 R 2 (CH 3 ) 2 N] + X −   (11)

wherein R 1 is a benzyl group and R 2 is a linear C 10 to C 20 hydrocarbon group.

7 . The composition according to claim 2 , wherein the quaternary ammonium compound corresponds to formula (12)

[R 1 R 2 N(CH 3 )((CH 2 CH 2 O) n H)] + X −   (12)

wherein both R 1 and R 2 are independently a C 6 -C 20 hydrocarbon group, and n is an integer from 1 to 5.

8 . The composition according to claim 2 , wherein the quaternary ammonium compound corresponds to formula (13)

[R 1 R 2 R 3 (CH 3 )N] + X −   (13)

wherein R 1 , R 2 and R 3 independently are linear or branched C 6 -C 20 saturated or unsaturated hydrocarbon groups.

9 . The composition according to claim 1 , wherein X is chloride.

10 . The composition according to claim 1 , wherein the amount of component A is from 20 to 60 wt.-%.

11 . The composition position according to claim 1 , wherein the amount of component B is from 5 to 25 wt. %.

12 . The composition according to claim 1 , wherein the amount of component C is from 15 to 75 wt.-%.

13 . The composition according to claim 1 , wherein the solvent is selected from the group consisting of water, ethanol, isopropanol, 2-ethylhexanol and paraffin, or mixtures thereof.

14 . The composition according to claim 1 , wherein the antifoam agent comprises at least one component selected from the group consisting of insoluble paraffinic and naphthenic mineral oils, vegetable oils, residues from the oxo alcohol synthesis, alkylbenzenes, and crude oils from the low-temperature carbonization of brown coal or other bituminous materials.

15 . The composition according to claim 1 , wherein the antifoam agent comprises at least one component selected from the group consisting of the compounds according to the formulae 1 to 5

wherein

R 1 and R 2 are independently from each other hydrocarbon groups having from 1 to 30, particularly from 2 to 10 carbon atoms.

16 . The composition according to claim 1 , wherein the antifoam agent comprises at least one dimethylpolysiloxane having 2 to 2000 siloxane groups.

17 . The composition according to claim 1 , wherein the antifoam agent comprises at least one hydrophobic silica.

18 . The composition according to claim 1 , wherein the antifoam agent comprises at least one hydrophobic fat or wax selected from the group consisting of fatty acid esters of monofunctional and polyfunctional alcohols;

fatty acid amides and sulfonamides;

paraffinic hydrocarbon waxes, ozokerite, and montan wax;

phosphoric acid mono-, di-, and triesters of short- and long-chain fatty alcohols;

short- and long-chain natural or synthetic fatty alcohols;

water-insoluble soaps of long-chain fatty acids; and

perfluorinated fatty alcohols.

19 . The composition according to claim 1 , wherein the antifoam agent comprises at least one water-insoluble polymer selected from the group consisting of fatty acid modified alkyd resins; novolak resins; copolymers of vinyl acetate and long-chain maleic and fumaric acid diesters; methyl methacrylate-vinylpyrrolidone copolymers; poly(propylene glycols); propylene oxide adducts to glycerol, trimethylolpropane, (1,1,1-tris(hydroxymethyl)propane), pentaerythritol, triethanolamine, dipentaerythritol, and polyglycerol.

20 . The composition according to claim 1 , wherein the antifoam agent comprises at least one ethoxylated alcohol corresponding to the formulae (6) and (7)

R—O-(A-O) n —H  (6)

R—O-(A-O) n —(B—O) m —H  (7)

wherein

n is a number from 1 to 30

m is a number from 1 to 30

A is a C 2 - to C 4 -alkylene group

B is a C 2 - to C 4 -alkylene group

R is a C 6 - to C 30 -hydrocarbon group.

21 . The composition according to claim 20 , wherein n and m independently are numbers from 2 to 10.

22 . The composition according to claim 10 , wherein R is selected from the group consisting of alkyl and alkenyl groups.

23 . The composition according to claim 20 , wherein formula (6) denotes a polyoxyalkylene homopolymer or a polyoxyalkylene random copolymer.

24 . The composition according to claim 20 , wherein formula (7) denotes a polyoxyalkylene block copolymer.

25 . The composition according to claim 20 , wherein A is a C 2 -alkylene group and B is a C 3 - or C 4 -alkylene group.

26 . (canceled)

27 . A process for reversely flotating magnesium silicate minerals from calcium carbonate ore, the process comprising adding the composition according to claim 1 , to a flotation cell containing magnesium silicate minerals and calcium carbonate ore, subsequently flowing air through the flotation cell and removing the magnesium silicate minerals with the foam so generated.