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

Abstract

The present invention relates to a gypsum composition comprising recycled gypsum and a foam former comprising at least one alpha-sulfo fatty acid disalt, to a process for production thereof and to an article comprising the gypsum composition of the invention. The present invention further relates to the use of a foam former comprising at least one alpha-sulfo fatty acid disalt for reducing the wet density of an aqueous gypsum composition having a recycled gypsum content of at least 0.5% by weight.

Claims

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.sup.1CH(SO.sub.3M.sup.1)COOM.sup.2  (I), wherein R.sup.1 is a linear or branched alkyl or alkylene radical having 6 to 16 carbon atoms, and wherein M.sup.1 and M.sup.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.sup.1 is a saturated linear alkyl radical having 8 to 16 carbon atoms.

5. The aqueous gypsum composition of claim 3, where wherein M.sup.1 and M.sup.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.sup.1CH(SO.sub.3M.sup.1)COOM.sup.2  (I), wherein R.sup.1 is a linear or branched alkyl or alkylene radical having 6 to 16 carbon atoms, and wherein M.sup.1 and M.sup.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.sup.1 is a saturated linear alkyl radical having 8 to 16 carbon atoms.

17. The method of claim 15, wherein M.sup.1 and M.sup.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.

Description

EXAMPLES

(1) 1) Methods

(2) Wet Density

(3) To determine the wet density of the gypsum compositions, the ratio between weight and volume was determined by introducing the respective composition into a beaker of known volume and then weighing.

(4) Foam Density

(5) To determine the foam density, the ratio between weight and volume was determined by introducing the respective foam into a beaker of known volume and then weighing.

(6) 2) Production of Recycled Gypsum

(7) For production of a gypsum slurry, 300 g of beta-hemihydrate (obtained from flue gas desulfurization) were introduced into 201.0 g of water containing 3.0 g of siloxane (Silres BS 94, from Wacker Chemie) and left to soak for 15 seconds. Subsequently, the mixture was sheared at 285 rpm for 30 seconds and poured into a mold. After 15 minutes, the sample was taken from the mold and subjected to thermal treatment at 150° C. in a saturated steam atmosphere for one hour. Thereafter, the samples were stored at 40° C. until constant mass was attained.

(8) For further processing, the samples were ground with a ball mill to a d.sub.50 of about 10 μm and then calcined at 150° C. for 5 hours. After cooling to room temperature, the recycled gypsum was usable for the application tests.

(9) 3) Compositions Based on Fatty Alkyl Ether Sulfate Surfactants

(10) First of all, a foam based on fatty alkyl ether sulfate was produced.

(11) For this purpose, a 0.40% surfactant solution (Vinapor GYP 2680, BASF) was converted to foam by means of a foam generator based on a rotor/stator system with addition of compressed air. The foam density established was 75 g/L.

(12) Reference Mixture R1

(13) For production of the gypsum slurry, 350 g of beta-hemihydrate (obtained from flue gas desulfurization) were homogenized with 0.035 g of retardant (Plastretard) and 3.3 g of finely ground dihydrate and then introduced into 234.2 g of water that contained 1.05 g of beta-naphthalene plasticizer and left to soak for 15 seconds. Subsequently, the mixture was sheared at 1600 rpm for 30 seconds. During that time, the fatty alkyl ether sulfate-based foam (18.2 g with a density of 75 g/L) was added. The resulting fresh density of reference mixture 1 was 1050 kg/m.sup.3.

(14) Reference Mixture R2

(15) Reference mixture R2 was produced analogously to reference mixture R1, except that 5% beta-hemihydrate was replaced by siloxane-containing recycled gypsum. The wet density of reference mixture R2 rose to 1380 kg/m.sup.3.

(16) 4) Compositions Based on Alpha-Sulfo Fatty Acid Disalt Surfactants

(17) First of all, a foam based on an alpha-sulfo fatty acid disalt was produced.

(18) For this purpose, a 0.40% surfactant solution based on C12/14-alpha-sulfo fatty acid Na disalt was converted to foam by means of a foam generator based on a rotor/stator system with addition of compressed air. The foam density established was 75 g/L.

(19) Reference mixture R3 For production of the gypsum slurry, 350 g of beta-hemihydrate (obtained from flue gas desulfurization) were homogenized with 0.035 g of retardant (Plastretard) and 3.3 g of finely ground dihydrate and then introduced into 234.2 g of water that contained 1.05 g of beta-naphthalene plasticizer and left to soak for 15 seconds. Subsequently, the mixture was sheared at 1600 rpm for 30 seconds. During that time, the alpha-sulfo fatty acid disalt-based foam (18.2 g with a density of 75 g/L) was added. The resulting fresh density of reference mixture 1 was 1110 kg/m.sup.3.

Example E1 (Inventive)

(20) Example E1 was produced analogously to reference mixture R3 except that 5% beta-hemihydrate was replaced by siloxane-containing recycled gypsum. The wet density of the inventive example rose to only 1170 kg/m.sup.3.

(21) The compositions and properties of the reference mixtures and of the inventive example are collated in table 1.

(22) TABLE-US-00001 TABLE 1 Composition and properties of the gypsum compositions R1 R2 R3 E1 Beta-hemihydrate [g] 350.0 346.5 350.0 346.5 Recycled gypsum [g] 3.5 3.5 Finely ground [g] 3.3 3.3 3.3 3.3 dihydrate Wet density [kg/m.sup.3] 1050 1380 1110 1170 Rise in wet density [%] — 31.4 — 5.4

(23) The results show that the recycled gypsum-containing compositions have an only slightly higher wet density using alpha-sulfo fatty acid disalt-based foams than the reference mixtures that do not contain any recycled gypsum, whereas a distinct rise in wet density is observed for recycled gypsum-containing compositions with fatty alkyl ether sulfate-based foams.