Disalt as robust primary surfactant for calcium sulfate mixtures containing recycled gypsum

1. An aqueous gypsum composition, comprising:

at least 40.0% by weight of gypsum, and

at least 0.002% by weight of a foam former comprising at least one alpha-sulfo fatty acid disalt, each weight percentage based on the total weight of the aqueous gypsum composition, and

wherein the gypsum has a recycled gypsum content of at least 0.5% by weight, based on the total weight of gypsum.

2. The aqueous gypsum composition of claim 1 , wherein the recycled gypsum is comprises siloxane.

3. The aqueous gypsum composition of claim 1 , wherein the at least one alpha-sulfo fatty acid disalt is a compound of formula (I):

R 1 CH(SO 3 M 1 )COOM 2   (I),

wherein R 1 is a linear or branched alkyl or alkylene radical having 6 to 16 carbon atoms, and

wherein M 1 and M 2 are each independently selected from the group consisting of H, Li, Na, K, Ca, Mg, ammonium, and alkanolamine.

4. The aqueous gypsum composition of claim 3 , wherein R 1 is a saturated linear alkyl radical having 8 to 16 carbon atoms.

5. The aqueous gypsum composition of claim 3 , where wherein M 1 and M 2 are Na.

6. The aqueous gypsum composition of claim 1 , further comprising at least 0.001% by weight of at least one cosurfactant other than an alpha-sulfo fatty acid disalt, relative to the total weight of the aqueous gypsum composition.

7. The aqueous gypsum composition of claim 6 , wherein the at least one cosurfactant is at least one selected from the group consisting of alkyl polyglycosides, alkylamido betaines, glutamates, sulfo ketones, sulfates, isethionates, N-acylamino acid compounds, sulfoacetates, sulfonates, sulfosuccinates, taurates, betaines, amphosurfactants, alkanolamides, amine oxides, carboxylates, alkyl ethoxylates, cationic surfactants, cationic polymers, protein hydrolyzates, silicones, fatty alcohols, protein derivatives, bleaches of disalts, and nonionic surfactants.

8. The aqueous gypsum composition of claim 1 , further comprising at least one solvent.

9. The aqueous gypsum composition of claim 1 , further comprising one or more additives selected from the group consisting of cellulose ethers, slaked lime, starch, modified starch, hydrophobizing agents, mineral additives, low-density aggregates, fibers, accelerators, thickeners, retardants, air pore formers, foaming agents, swelling agents, fillers, polyacrylates, dispersants, plasticizers, superabsorbents, and stabilizers.

10. The aqueous gypsum composition of claim 1 , further comprising 0.0001% to 1.0% by weight of a retardant and/or 0.01% to 2.0% by weight of a plasticizer, each weight percentage relative to the total weight of the aqueous gypsum composition.

11. An article comprising the aqueous gypsum composition of claim 1 .

12. The article of claim 11 , further comprising at least one selected from the group consisting of stucco gypsums, mortar gypsums, machine gypsum plasters, plastering gypsums, bonding gypsums, jointing gypsums, filling gypsums, insulating gypsums, flooring gypsums, ready-mixed plaster gypsums, imitation marbles, gypsum-containing ready-made structural components, gypsum plasterboard panels, gypsum fiberboard panels, gypsum-containing wallboard panels, fleece-lined gypsum panels, and gypsum-containing moldings.

13. A process for producing an aqueous gypsum composition, comprising:

providing a foam comprising a foam former, the foam former comprising at least one alpha-sulfo fatty acid disalt;

providing a composition comprising water and gypsum, and optionally comprising additives; and

allowing shear forces to act on the composition with addition of the foam;

wherein the gypsum has a recycled gypsum content of at least 0.5% by weight, based on the total weight of gypsum.

14. A method of using a foam former comprising at least one alpha-sulfo fatty acid disalt, the method comprising:

reducing the wet density of an aqueous gypsum composition,

wherein the aqueous gypsum composition has a recycled gypsum content of at least 0.5% by weight, based on the total weight of gypsum.

15. The method of claim 14 , wherein the at least one alpha-sulfo fatty acid disalt is a compound of formula (I):

R 1 CH(SO 3 M 1 )COOM 2   (I),

wherein R 1 is a linear or branched alkyl or alkylene radical having 6 to 16 carbon atoms, and

wherein M 1 and M 2 are each independently selected from the group consisting of H, Li, Na, K, Ca, Mg, ammonium, and alkanolamine.

16. The method of claim 15 , wherein R 1 is a saturated linear alkyl radical having 8 to 16 carbon atoms.

17. The method of claim 15 , wherein M 1 and M 2 are Na.

18. The method of claim 15 , wherein the aqueous gypsum composition further comprises at least 0.001% by weight of at least one cosurfactant other than an alpha-sulfo fatty acid disalt, relative to the total weight of the aqueous gypsum composition.

19. A process for producing a gypsum board comprising the steps of

providing a foam comprising a foam former, the foam former comprising at least one alpha-sulfo fatty acid disalt;

providing a composition comprising water and gypsum, and optionally comprising additives;

allowing shear forces to act on the composition with addition of the foam; and

drying the obtained composition thermally;

wherein the gypsum has a recycled gypsum content of at least 0.5% by weight, based on the total weight of gypsum.

20. A gypsum board obtained by thermally drying an aqueous gypsum composition comprising:

at least 40.0% by weight of gypsum, and

at least 0.002% by weight of a foam former comprising at least one alpha-sulfo fatty acid disalt, each weight percentage based on the total weight of the aqueous gypsum composition, and

wherein the gypsum has a recycled gypsum content of at least 0.5% by weight, based on the total weight of gypsum.