Gypsum compositions with enhanced resistance to permanent deformation
A composition and gypsum technology, applied in the field of gypsum composition, can solve problems such as poor dimensional stability
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Embodiment 1
[0078] Resistance to permanent deformation (sagging resistance of laboratory plasterboard)
[0079] In the laboratory, samples containing gypsum board were prepared according to the present invention and compared to the resistance to permanent deformation of sample boards prepared using methods and compositions outside the scope of the present invention.
[0080] Prepare the sample by mixing the mixture in a 5 liter WARING mixer at low speed for 10 seconds: 1.5 kg beta calcium sulfate hemihydrate; Heating as described in Patent 3,573,947, the disclosure of which is incorporated herein by reference; 2 liters of tap water; and 0 g of additive (control sample), 1.5 g of organic polyphosphonic acid compound, or 1.5 g of other additive. The resulting slurry was cast into pans to prepare gypsum slab samples, each approximately 6 x 24 x 1 / 2 inches in size. After the calcium sulfate hemihydrate had set into gypsum (calcium sulfate dihydrate), the boards were dried in an oven ...
Embodiment 2
[0089] This example illustrates the use of sorborite as a reinforcing material suitable for improving the sag resistance of gypsum boards. The resistance to permanent deformation was determined as described in Example 1 using sorborite as an additive by itself and ground with a coagulant comprising finely ground particles of calcium sulfate dihydrate as described above.
[0090] In addition, the beneficial effect of using sorbite is also demonstrated in the presence of high levels of chloride salt impurities. Gypsum boards were prepared as described in Example 1 except that chloride ions were introduced into the mixture along with the sodium borite additive. Sag deviation was tested following the ASTM C 473-95 procedure above for laboratory prepared panels.
[0091] In these examples, the sodium borite was added to the aqueous calcined gypsum slurry in an amount of about 0.05 wt.% of the calcined gypsum by addition in a ground mixture with the coagulant material. In the last...
Embodiment 3
[0095] Post coagulation treatment of calcium sulfate dihydrate
[0096] In some preferred embodiments of the invention, the calcium sulfate dihydrate cast body is treated with an aqueous solution of reinforcing material to improve the permanent deformation resistance (eg, sag resistance) and dimensional stability of the set gypsum-containing article after drying. More specifically, it has been found that treatment of calcium sulfate dihydrate with various reinforcing materials according to the present invention improves permanent deformation resistance (eg, sag resistance) and dimensional stability. Accordingly, embodiments incorporating set gypsum reinforcement provide new compositions and methods for making improved gypsum products including, but not limited to, boards, panels, gypsum, tile, gypsum / cellulose fiber composites, and the like. Accordingly, any gypsum-based article requiring tight control over sag resistance would benefit from embodiments of the p...
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Abstract
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