Methods for reclaiming gypsum panels that contain hydrophobic materials and use thereof
A method for making a gypsum board including: combining a first plurality of particles including at least about 50 wt. % calcium sulfate dihydrate and about 0.05 wt. % to about 10 wt. % hydrophobic material and having a D50 particle size of about 200 μm to about 800 μm with a second plurality of particles including calcium sulfate hemihydrate to form a combined mixture of calcium sulfate; adding water to the combined mixture of calcium sulfate to make an aqueous gypsum slurry; depositing a core layer including the aqueous gypsum slurry over a forming surface; and allowing the core layer to set, thereby forming a set gypsum core.
1. A method for making a gypsum board comprising:
depositing a core layer comprising an aqueous gypsum slurry over a forming surface;
wherein non-calcined reclaimed gypsum particles in the aqueous gypsum slurry consist of non-calcined reclaimed gypsum particles with a D50 particle size of about 200 μm to about 800 μm, and wherein the non-calcined reclaimed gypsum particles comprise at least about 50 wt. % calcium sulfate dihydrate and about 0.05 wt. % to about 10 wt. % hydrophobic material;
wherein the aqueous gypsum slurry is made by combining
water, and
the non-calcined reclaimed gypsum particles and
calcined gypsum particles comprising calcium sulfate hemihydrate; and
allowing the core layer to set, thereby forming a set gypsum core.
2. The method of claim 1 , wherein the non-calcined reclaimed gypsum particles are combined with the calcined gypsum particles to form a combined dry mixture and
the water is added to the combined dry mixture to make the aqueous gypsum slurry.
3. The method of claim 1 , wherein the aqueous gypsum slurry does not include alpha-sulfo fatty acid di salts.
4. The method of claim 1 , wherein the hydrophobic material comprises one or more of siloxane, wax, and resin,
wherein the gypsum board is a drywall gypsum board,
wherein the method further comprises placing a first facer sheet on the forming surface, wherein the core layer is deposited on the first facer sheet, and further comprising placing a second facer sheet over the deposited core layer such that the core layer sets between the first and second facer sheet, thereby forming the gypsum board to comprise the set gypsum core, the first facer sheet and the seconds facer sheet, wherein each said facer sheet is selected from the group consisting of a glass mat facer sheet and a paper facer sheet.
5. The method of claim 1 , wherein the non-calcined reclaimed gypsum particles have a D50 particle size of about 300 μm to about 500 μm.
6. The method of claim 1 , further comprising subjecting a gypsum waste comprising a gypsum feed material to a size reduction process to generate the non-calcined particles, the gypsum feed material comprising:
A) at least about 50 wt. % calcium sulfate dihydrate and
B) hydrophobic material,
wherein the gypsum feed material comprises gypsum board comprising a gypsum layer and at least one facer sheet, wherein the gypsum layer comprises at least about 50 wt. % calcium sulfate dihydrate and about 0.05 wt. % to about 10 wt. % hydrophobic material.
7. The method of claim 6 , wherein the at least one facer sheet comprises at least one of a glass mat facer sheet and a paper facer sheet.
8. The method of claim 6 , wherein the size reduction process at least partially removes the at least one facer sheet from the gypsum layer.
9. The method of claim 1 , wherein the set gypsum core comprises air bubbles, wherein the air bubbles have an average cross-section diameter of less than 1.5 mm.
10. The method of claim 1 , wherein the depositing the core layer over the forming surface comprises:
depositing a first portion of the aqueous gypsum slurry on the forming surface as a skim layer; and
depositing a second portion of the aqueous gypsum slurry on the skim layer as a primary gypsum layer; and
allowing the skim layer and the primary gypsum layer to dry, thereby forming the set gypsum core comprising a set primary gypsum layer and a set skim layer.
11. The method of claim 1 , wherein the aqueous gypsum slurry comprises about 0.1 wt. % to about 20 wt. % of the non-calcined reclaimed gypsum particles based on a combined dry weight of the non-calcined reclaimed gypsum particles and the calcined gypsum particles.
12. The method of claim 1 , wherein the hydrophobic material comprises siloxane and wherein the non-calcined reclaimed gypsum particles comprises about 0.05 wt. % to about 5 wt. %, of said siloxane.
13. The method of claim 1 , wherein the hydrophobic material comprises wax and wherein the non-calcined reclaimed gypsum particles comprises about 0.5 wt. % to about 10 wt. % of said wax.
14. The method of claim 1 , wherein the aqueous gypsum slurry comprises about 1 wt. % to about 10 wt. % of the non-calcined reclaimed gypsum particles based on a combined dry weight of the non-calcined reclaimed gypsum particles and the calcined gypsum particles.
15. The method of claim 1 , further comprising adding air to the aqueous gypsum slurry prior to depositing it.
16. The method of claim 1 , wherein the set gypsum core has a total air volume of about 30 vol. % to about 90 vol. %.
17. The method of claim 1 , further comprising adding to the aqueous gypsum slurry prior to depositing the aqueous slurry at least one additive selected from the group consisting of retarders, accelerators, foaming agents, wet strength enhancing materials, biocides, sag resistant ingredients, cellulosic fibers, glass fibers, fire retarding materials, binders, water repellency ingredients, dust mitigators, and starches.
18. A method for making a gypsum board comprising:
combining
water, and
non-calcined reclaimed gypsum particles comprising at least about 50 wt. % calcium sulfate dihydrate and about 0.05 wt. % to about 10 wt. % hydrophobic material, the non-calcined reclaimed gypsum particles having a D50 particle size of about 200 μm to about 800 μm, and
calcined gypsum particles comprising calcium sulfate hemihydrate to make an aqueous gypsum slurry;
depositing a core layer comprising the aqueous gypsum slurry over a forming surface; and
allowing the core layer to set, thereby forming a set gypsum core;
wherein the non-calcined reclaimed gypsum particles and the calcined gypsum particles are fed as separate streams to a slurry mixer to mix with water to make the aqueous gypsum slurry, wherein the calcined particles are non-reclaimed.
19. A method for making a gypsum board comprising:
combining
water, and
a first plurality of non-calcined reclaimed gypsum particles comprising at least about 50 wt. % calcium sulfate dihydrate and about 0.05 wt. % to about 10 wt. % hydrophobic material, the first plurality of particles having a D50 particle size of about 200 μm to about 800 μm and
a second plurality of calcined gypsum particles comprising calcium sulfate hemihydrate to make an aqueous gypsum slurry;
depositing a core layer comprising the aqueous gypsum slurry over a forming surface; and
allowing the core layer to set, thereby forming a set gypsum core,
wherein total air volume of the set gypsum core is about 45 vol. % to about 80 vol. %.
20. A method for making a gypsum board comprising:
combining
water,
a first plurality of particles comprising at least about 50 wt. % calcium sulfate dihydrate and about 0.05 wt. % to about 10 wt. % hydrophobic material and at least about 98 wt. % of the first plurality of particles have a particle size of about 100 μm to about 3000 μm, and
a second plurality of particles comprising calcium sulfate hemihydrate to make an aqueous gypsum slurry;
depositing a core layer comprising the aqueous gypsum slurry over a forming surface; and
allowing the core layer to set, thereby forming a set gypsum core.
21. A method for making a gypsum board comprising:
combining
water, and
a first plurality of non-calcined reclaimed gypsum particles comprising at least about 50 wt. % calcium sulfate dihydrate and about 0.05 wt. % to about 10 wt. % hydrophobic material, the first plurality of particles having a D50 particle size of about 200 μm to about 800 μm and
a second plurality of calcined gypsum particles comprising calcium sulfate hemihydrate to make an aqueous gypsum slurry;
depositing a core layer comprising the aqueous gypsum slurry over a forming surface; and
allowing the core layer to set, thereby forming a set gypsum core,
wherein the water is combined with particles consisting of:
the first plurality of non-calcined reclaimed gypsum particles comprising at least about 50 wt. % calcium sulfate dihydrate and about 0.05 wt. % to about 10 wt. % hydrophobic material, the first plurality of particles having the D50 particle size of about 200 μm to about 800 μm and
the second plurality of calcined gypsum particles comprising calcium sulfate hemihydrate to make the aqueous gypsum slurry.