CALCIUM SULPHASE-BASED PRODUCTS

Abstract

A calcium sulphate-based product including gypsum and a shrinkage resistance additive. The shrinkage resistance additive is a metal nitrate, hydroxide, acetate or sulphate and is preferably provided in an amount greater than 4 wt % (based on the amount of additive and gypsum). The additive may be a nitrate of an alkali metal (e.g. potassium), an alkaline earth metal (e.g. magnesium or calcium), a transition metal (e.g. iron or zinc) or aluminium.

Claims

1. A calcium sulphate-based product comprising gypsum and a shrinkage resistance additive provided in an amount between 4 and 40 wt % based on the weight of gypsum and additive wherein the shrinkage resistance additive is a metal nitrate, hydroxide, acetate or sulphate.

2-7. (canceled)

8. A calcium sulphate-based product comprising gypsum and a shrinkage resistance additive wherein the product is produced by drying an aqueous slurry comprising calcined gypsum and between 4.5 and 50 wt % shrinkage resistance additive (based on the weight of gypsum and additive), the shrinkage resistance additive being a metal nitrate, hydroxide, acetate or sulphate.

9-14. (canceled)

15. A product according to claim 1 wherein the shrinkage resistance additive is a nitrate of an alkali metal, an alkaline earth metal, a transition metal or aluminium.

16. A product according to claim 1 wherein the shrinkage resistance additive is a nitrate of magnesium, aluminium, zinc, iron or copper.

17. A product according to claim 1 wherein the shrinkage resistance additive is selected from: the nitrate, hydroxide, acetate or sulphate of magnesium, aluminium or zinc; or the nitrate, hydroxide or acetate of iron.

18. A product according to claim 1 wherein the product is a building material or a mould for metal casting.

19. A product according to claim 1 wherein the product is a composite wallboard comprising a core of the gypsum and shrinkage resistance additive sandwiched between two liners.

20. A calcium sulphate-based composition for use in forming a calcium sulphate-based product by drying an aqueous slurry of the calcium sulphate-based composition, the calcium sulphate-based composition comprising calcined gypsum and between 4.5 and 50 wt % of a shrinkage resistance additive (based on the amount of gypsum and additive), wherein the shrinkage resistance additive is a metal nitrate, hydroxide, acetate or sulphate.

21-26. (canceled)

27. A composition according to claim 20 wherein the shrinkage resistance additive is a nitrate of an alkali metal, an alkaline earth metal, a transition metal or aluminium.

28. A composition according to claim 27 wherein the shrinkage resistance additive is a nitrate of magnesium, aluminium, zinc, iron or copper.

29. A composition according to claim 20 wherein the shrinkage resistance additive is selected from the nitrate, hydroxide, acetate or sulphate of magnesium, aluminium or zinc or the nitrate, hydroxide or acetate of iron.

30. A method of forming a calcium sulphate-based product by drying an aqueous slurry comprising a composition according to claim 20.

31. A method according to claim 30 wherein the product is a building material or a mould for casting metal.

32. A method according to claim 31 wherein the product is a composite wallboard and the method comprises drying the aqueous slurry between two liners.

33-48. (canceled)

49. A calcium sulphate-based product comprising gypsum and a shrinkage resistance additive provided in an amount less than 40 wt % based on the weight of gypsum and additive wherein the shrinkage resistance additive is a nitrate of an alkali metal, an alkaline earth metal, a transition metal or aluminium, the hydroxide or acetate of magnesium, aluminium, zinc or iron, or the sulphate of magnesium, aluminium or zinc.

50. A calcium sulphate-based product comprising gypsum and a shrinkage resistance additive wherein the product is produced by drying an aqueous slurry comprising calcined gypsum less than 50 wt % shrinkage resistance additive (based on the weight of gypsum and additive), the shrinkage resistance additive being a nitrate of an alkali metal, an alkaline earth metal, a transition metal or aluminium, the hydroxide or acetate of magnesium, aluminium, zinc or iron, or the sulphate of magnesium, aluminium or zinc.

51. A product according to claim 49 wherein the shrinkage resistance additive is a nitrate of magnesium, aluminium, zinc, iron or copper.

52. A product according to claim 49 wherein the product is a building material or a mould for metal casting.

53. A product according to claim 49 wherein the product is a composite wallboard comprising a core of the gypsum and shrinkage resistance additive sandwiched between two liners.

54. A calcium sulphate-based composition for use in forming a calcium sulphate-based product by drying an aqueous slurry of the calcium sulphate-based composition, the calcium sulphate-based composition comprising calcined gypsum and less than 50 wt % of a shrinkage resistance additive (based on the amount of gypsum and additive), wherein the shrinkage resistance additive is a nitrate of an alkali metal, an alkaline earth metal, a transition metal or aluminium, the hydroxide or acetate of magnesium, aluminium, zinc or iron, or the sulphate of magnesium, aluminium or zinc.

55. A composition according to claim 54 wherein the shrinkage resistance additive is a nitrate of magnesium, aluminium, zinc, iron or copper.

56. A method of forming a calcium sulphate-based product by drying an aqueous slurry comprising a composition according to claim 54.

57. A method according to claim 56 wherein the product is a building material or a mould for casting metal.

58. A method according to claim 57 wherein the product is a composite wallboard and the method comprises drying the aqueous slurry between two liners.

Description

DESCRIPTION OF THE DRAWING

[0040] FIG. 1 shows a graph of linear shrinkage for a control sample and inventive samples during heating to 1000° C.

EXPERIMENTAL

[0041] The following examples are given by way of illustration only.

Control Sample 1

[0042] 200 g of calcined gypsum was added to 140 g of water at 40° C. This was mixed by hand for 30 seconds and the resulting slurry was poured into a cylindrical silicone mould (of height 25 mm and diameter 12 mm). The sample was transferred to an oven at 40° C. and left to dry overnight (at least 12 hours).

Sample 1—Magnesium Nitrate—1% Wt:Wt Calcined Gypsum

[0043] 2 g of magnesium nitrate hexahydrate was added to 140 g of water at 40° C. 200 g of calcined gypsum was added to the solution and the resulting slurry (containing 1.0 wt % nitrate based on weight of calcined gypsum) was blended by hand for 30 seconds to form a slurry. The resulting slurry was poured into a cylindrical silicone mould (of height 25 mm and diameter 12 mm) and the sample was transferred to an oven at 40° C. and left to dry overnight (at least 12 hours).

Sample 2—Magnesium Nitrate—2.5% Wt:Wt Calcined Gypsum

[0044] 5 g of magnesium nitrate hexahydrate was added to 140 g of water at 40° C. 200 g of calcined gypsum was added to the solution and the resulting slurry (containing 2.4 wt % nitrate based on weight of dry ingredients/containing 2.5 wt % based on weight of calcined gypsum) was blended by hand for 30 seconds to form a slurry. The resulting slurry was poured into a cylindrical silicone mould (of height 25 mm and diameter 12 mm) and the sample was transferred to an oven at 40° C. and left to dry overnight (at least 12 hours).

Sample 3—Magnesium Nitrate—5% Wt:Wt Calcined Gypsum

[0045] 10 g of magnesium nitrate hexahydrate was added to 140 g of water at 40° C. 200 g of calcined gypsum was added to the solution and the resulting slurry (containing 4.8 wt % nitrate based on weight of dry ingredients/containing 5 wt % based on weight of gypsum) was blended by hand for 30 seconds to form a slurry. The resulting slurry was poured into a cylindrical silicone mould (of height 25 mm and diameter 12 mm) and the sample was transferred to an oven at 40° C. and left to dry overnight (at least 12 hours).

Sample 4—Magnesium Nitrate—10% Wt:Wt Calcined Gypsum

[0046] 20 g of magnesium nitrate hexahydrate was added to 140 g of water at 40° C. 200 g of calcined gypsum was added to the solution and the resulting slurry (containing 9.1 wt % nitrate based on weight of dry ingredients/containing 10 wt % based on weight of gypsum) was blended by hand for 30 seconds to form a slurry. The resulting slurry was poured into a cylindrical silicone mould (of height 25 mm and diameter 12 mm) and the sample was transferred to an oven at 40° C. and left to dry overnight (at least 12 hours).

Sample 5—Magnesium Nitrate—30% Wt:Wt Calcined Gypsum

[0047] 60 g of magnesium nitrate hexahydrate was added to 140 g of water at 40° C. 200 g of calcined gypsum was added to the solution and the resulting slurry (containing 23.1 wt % nitrate based on weight of dry ingredients/containing 30 wt % based on weight of gypsum) was blended by hand for 30 seconds to form a slurry. The resulting slurry was poured into a cylindrical silicone mould (of height 25 mm and diameter 12 mm) and the sample was transferred to an oven at 40° C. and left to dry overnight (at least 12 hours).

Sample 6—Aluminium Nitrate—2.5% Wt:Wt Calcined Gypsum

[0048] 5 g of aluminium nitrate nonahydrate was added to 140 g of water at 40° C. 200 g of calcined gypsum was added to the solution and the resulting slurry (containing 2.4 wt % nitrate based on weight of dry ingredients/containing 2.5 wt % based on weight of calcined gypsum) was blended by hand for 30 seconds to form a slurry. The resulting slurry was poured into a cylindrical silicone mould (of height 25 mm and diameter 12 mm) and the sample was transferred to an oven at 40° C. and left to dry overnight (at least 12 hours).

Sample 7—Aluminium Nitrate—5% Wt:Wt Calcined Gypsum

[0049] 10 g of aluminium nitrate nonahydrate was added to 140 g of water at 40° C. 200 g of calcined gypsum was added to the solution and the resulting slurry (containing 4.8 wt % nitrate based on weight of dry ingredients/containing 5 wt % based on weight of gypsum) was blended by hand for 30 seconds to form a slurry. The resulting slurry was poured into a cylindrical silicone mould (of height 25 mm and diameter 12 mm) and the sample was transferred to an oven at 40° C. and left to dry overnight (at least 12 hours).

Sample 8—Aluminium Nitrate—10% Wt:Wt Calcined Gypsum

[0050] 20 g of aluminium nitrate nonahydrate was added to 140 g of water at 40° C. 200 g of calcined gypsum was added to the solution and the resulting slurry (containing 9.1 wt % nitrate based on weight of dry ingredients/containing 10 wt % based on weight of gypsum) was blended by hand for 30 seconds to form a slurry. The resulting slurry was poured into a cylindrical silicone mould (of height 25 mm and diameter 12 mm) and the sample was transferred to an oven at 40° C. and left to dry overnight (at least 12 hours).

Sample 9—Zinc Nitrate—2.5% Wt:Wt Calcined Gypsum

[0051] 5 g of zinc nitrate hexahydrate was added to 140 g of water at 40° C. 200 g of calcined gypsum was added to the solution and the resulting slurry (containing 2.4 wt % nitrate based on weight of dry ingredients/containing 2.5 wt % based on weight of calcined gypsum) was blended by hand for 30 seconds to form a slurry. The resulting slurry was poured into a cylindrical silicone mould (of height 25 mm and diameter 12 mm) and the sample was transferred to an oven at 40° C. and left to dry overnight (at least 12 hours).

Sample 10—Zinc Nitrate—5% Wt:Wt Calcined Gypsum

[0052] 10 g of zinc nitrate hexahydrate was added to 140 g of water at 40° C. 200 g of calcined gypsum was added to the solution and the resulting slurry (containing 4.8 wt % nitrate based on weight of dry ingredients/containing 5 wt % based on weight of gypsum) was blended by hand for 30 seconds to form a slurry. The resulting slurry was poured into a cylindrical silicone mould (of height 25 mm and diameter 12 mm) and the sample was transferred to an oven at 40° C. and left to dry overnight (at least 12 hours).

Sample 11—Zinc Nitrate—10% Wt:Wt Calcined Gypsum

[0053] 20 g of zinc nitrate hexahydrate was added to 140 g of water at 40° C. 200 g of calcined gypsum was added to the solution and the resulting slurry (containing 9.1 wt % nitrate based on weight of dry ingredients/containing 10 wt % based on weight of gypsum) was blended by hand for 30 seconds to form a slurry. The resulting slurry was poured into a cylindrical silicone mould (of height 25 mm and diameter 12 mm) and the sample was transferred to an oven at 40° C. and left to dry overnight (at least 12 hours).

Sample 12—Iron Nitrate—2.5% Wt:Wt Calcined Gypsum

[0054] 5 g of iron (Ill) nitrate nonahydrate was added to 140 g of water at 40° C. 200 g of calcined gypsum was added to the solution and the resulting slurry (containing 2.4 wt % nitrate based on weight of dry ingredients/containing 2.5 wt % based on weight of calcined gypsum) was blended by hand for 30 seconds to form a slurry. The resulting slurry was poured into a cylindrical silicone mould (of height 25 mm and diameter 12 mm) and the sample was transferred to an oven at 40° C. and left to dry overnight (at least 12 hours).

Sample 13—Iron Nitrate—5% Wt:Wt Calcined Gypsum

[0055] 10 g of iron (III) nitrate nonahydrate was added to 140 g of water at 40° C. 200 g of calcined gypsum was added to the solution and the resulting slurry (containing 4.8 wt % nitrate based on weight of dry ingredients/containing 5 wt % based on weight of gypsum) was blended by hand for 30 seconds to form a slurry. The resulting slurry was poured into a cylindrical silicone mould (of height 25 mm and diameter 12 mm) and the sample was transferred to an oven at 40° C. and left to dry overnight (at least 12 hours).

Sample 14—Iron Nitrate—10% Wt:Wt Calcined Gypsum

[0056] 20 g of iron (Ill) nitrate nonahydrate was added to 140 g of water at 40° C. 200 g of calcined gypsum was added to the solution and the resulting slurry (containing 9.1 wt % nitrate based on weight of dry ingredients/containing 10 wt % based on weight of gypsum) was blended by hand for 30 seconds to form a slurry. The resulting slurry was poured into a cylindrical silicone mould (of height 25 mm and diameter 12 mm) and the sample was transferred to an oven at 40° C. and left to dry overnight (at least 12 hours).

Sample 15—Potassium Nitrate—10% Wt:Wt Calcined Gypsum

[0057] 20 g of potassium nitrate was added to 140 g of water at 40° C. 200 g of calcined gypsum was added to the solution and the resulting slurry (containing 9.1 wt % nitrate based on weight of dry ingredients/containing 10 wt % based on weight of gypsum) was blended by hand for 30 seconds to form a slurry. The resulting slurry was poured into a cylindrical silicone mould (of height 25 mm and diameter 12 mm) and the sample was transferred to an oven at 40° C. and left to dry overnight (at least 12 hours).

Sample 16—Copper Nitrate—8% Wt:Wt Calcined Gypsum

[0058] 16 g of copper nitrate tetrahydrate was added to 140 g of water at 40° C. 200 g of calcined gypsum was added to the solution and the resulting slurry (containing 7.4 wt % nitrate based on weight of dry ingredients/containing 5 wt % based on weight of gypsum) was blended by hand for 30 seconds to form a slurry. The resulting slurry was poured into a cylindrical silicone mould (of height 25 mm and diameter 12 mm) and the sample was transferred to an oven at 40° C. and left to dry overnight (at least 12 hours).

Sample 17—Calcium Nitrate—9% Wt:Wt Calcined Gypsum

[0059] 18 g of calcium nitrate tetrahydrate was added to 140 g of water at 40° C. 200 g of calcined gypsum was added to the solution and the resulting slurry (containing 8.3 wt % nitrate based on weight of dry ingredients/containing 9 wt % based on weight of gypsum) was blended by hand for 30 seconds to form a slurry. The resulting slurry was poured into a cylindrical silicone mould (of height 25 mm and diameter 12 mm) and the sample was transferred to an oven at 40° C. and left to dry overnight (at least 12 hours).

Sample 18—Magnesium Hydroxide—10% Wt:Wt Calcined Gypsum

[0060] 20 g of magnesium hydroxide was added to 140 g of water at 40° C. 200 g of calcined gypsum was added to the solution and the resulting slurry (containing 9.1 wt % hydroxide based on weight of dry ingredients/containing 7.8 wt % based on weight of gypsum) was blended by hand for 30 seconds to form a slurry. The resulting slurry was poured into a cylindrical silicone mould (of height 25 mm and diameter 12 mm) and the sample was transferred to an oven at 40° C. and left to dry overnight (at least 12 hours).

Sample 19—Magnesium Acetate—10% Wt:Wt Calcined Gypsum

[0061] 20 g of magnesium acetate tetrahydrate was added to 140 g of water at 40° C. 200 g of calcined gypsum was added to the solution and the resulting slurry (containing 9.1 wt % acetate based on weight of dry ingredients/containing 7.8 wt % based on weight of gypsum) was blended by hand for 30 seconds to form a slurry. The resulting slurry was poured into a cylindrical silicone mould (of height 25 mm and diameter 12 mm) and the sample was transferred to an oven at 40° C. and left to dry overnight (at least 12 hours).

Sample 20—Magnesium Sulphate—10% Wt:Wt Calcined Gypsum

[0062] 20 g of magnesium sulphate heptahydrate was added to 140 g of water at 40° C. 200 g of calcined gypsum was added to the solution and the resulting slurry (containing 9.1 wt % sulphate based on weight of dry ingredients/containing 7.8 wt % based on weight of gypsum) was blended by hand for 30 seconds to form a slurry. The resulting slurry was poured into a cylindrical silicone mould (of height 25 mm and diameter 12 mm) and the sample was transferred to an oven at 40° C. and left to dry overnight (at least 12 hours).

[0063] A summary of all sample formulations is shown in Table 1 below.

TABLE-US-00001 Nitrate % wt:wt stucco Wt % in slurry Wt % in product Mg 1 1 1.0 0.8 2 2.5 2.4 2.0 3 5 4.8 4.0 4 10 9.1 7.8 5 30 23.1 20.2 Al 6 2.5 2.4 2.0 7 5 4.8 4.1 8 10 9.1 7.8 Zn 9 2.5 2.4 2.0 10 5 4.8 4.1 11 10 9.1 7.8 Fe 12 2.5 2.4 2.0 13 5 4.8 4.0 14 10 9.1 7.8 K 15 10 9.1 7.8 Cu 16 8 7.4 6.3 Ca 17 9 8.3 7.1 Mg(OH).sub.2 18 10 9.1 7.8 Mg(C.sub.2H.sub.3O.sub.2).sub.2 19 10 9.1 7.8 MgSO.sub.4 20 10 9.1 7.8

Linear Shrinkage

[0064] The linear shrinkage of the samples was measured using a Netzsch dilatometer with a ceramic rod attached to a linear displacement transducer having a resolution of 8 nm. The samples were supported by other ceramic rods and the heated in a furnace to 1000° C. at a rate of 5° C./min. The results are shown in FIGS. 1 and 2 and Table 2 below.

TABLE-US-00002 Linear Shrinkage (%) Formulation 500° C. 750° C. 900° C. 950° C. 1000° C. Control −1.8 −3.6 −7.1 −18.0 Off scale Mg nitrate 1 −0.8 −0.7 −1.3 −10.6 −12.3 2 −0.3 −0.1 0.0 −4.4 −12.1 3 −0.3 −0.3 −0.5 −7.0 −12.1 4 −0.0 −0.1 0.2 −2.8 −6.5 5 −0.5 0.1 0.2 −0.5 −1.9 Al nitrate 6 −0.7 −2.0 −5.6 −11.7 −16.7 7 −0.8 −1.4 −5.3 −10.4 −15.7 8 −0.7 −0.4 −0.4 −0.9 −3.5 Zn nitrate 9 −0.9 −1.1 −7.4 −17.8 Off-scale 10 −0.4 −0.8 −7.6 −17.3 Off-scale 11 −0.2 −0.3 −1.8 −6.5 −9.7 Fe nitrate 12 −0.9 −1.6 −4.7 −15.9 −17.0 13 −0.3 −0.7 −2.9 −9.0 −15.9 14 −0.6 −0.7 −3.6 −7.7 −12.3 K nitrate 15 −0.9 −2.8 −16.4 −17.4 Off-scale Cu nitrate 16 −0.2 −1.5 −12.9 Off-scale Off-scale Ca nitrate 17 −0.3 −2.8 −9.1 −9.1 Off-scale Mg hydroxide 18 −1.4 −3.2 −5.8 −8.0 −9.9 Mg acetate 19 −0.7 −3.5 −5.3 −9.7 −12.7 Mg sulphate 20 −1.4 −3.2 −5.1 −7.4 −11.1

[0065] It can be seen that: [0066] a) linear shrinkage is reduced at 500° C. and 750° C. for all samples; [0067] b) linear shrinkage is reduced at all temperatures for all magnesium and aluminium salt samples; [0068] c) linear shrinkage at 900° C. is reduced to less than around 1% for all samples containing magnesium nitrate; and [0069] d) linear shrinkage reduction is greater at addition levels greater than 4 wt % (based on amount of additive/gypsum in product) and especially at addition levels greater than 7 wt %.