Methods for reclaiming gypsum panels that contain hydrophobic materials and use thereof

Patent metadata

Field	Value
Publication number	US-2021331978-A1
Application number	US-202117210789-A
Country	US
Kind code	A1
Filing date	Mar 24, 2021
Priority date	Apr 28, 2020
Publication date	Oct 28, 2021
Grant date	—

Abstract

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.

First claim

We claim:

1 . 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, the first plurality of particles having a D50 particle size of about 200 μm to about 800 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.

2 . The method of claim 1 , wherein the first plurality of particles is combined with the second plurality of particles to form a combined mixture of calcium sulfate, and
the water is added to the combined mixture of calcium sulfate to make the aqueous gypsum slurry.

3 . The method of claim 1 , wherein the first plurality of particles is combined with the second plurality of particles to form a combined dry mixture of calcium sulfate and the water is added to the combined dry mixture of calcium sulfate to make the aqueous gypsum slurry.

4 . The method of claim 1 , wherein the hydrophobic material comprises siloxane.

5 . The method of claim 1 , wherein the hydrophobic material comprises one or more of siloxane, wax, and resin.

6 . The method of claim 1 , wherein the first plurality of particles have a D50 particle size of about 300 μm to about 500 μm.

7 . The method of claim 1 , further comprising subjecting a gypsum waste comprising a gypsum feed material to a size reduction process to generate the first plurality of 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 a gypsum layer and optionally 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, wherein the gypsum feed material comprises gypsum board comprising at least one facer sheet.

8 . The method of claim 7 , wherein the at least one facer sheet comprises at least one of a glass mat facer sheet and a paper facer sheet.

9 . The method of claim 7 , wherein the size reduction process at least partially removes the at least one facer sheet from the gypsum layer.

10 . 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.

11 . 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 a set gypsum core comprising a set primary gypsum layer and a set skim layer.

12 . The method of claim 1 , wherein the aqueous gypsum slurry comprises about 0.1 wt. % to about 20 wt. % of the first plurality of particles based on a combined dry weight of the first plurality of particles and second plurality of particles.

13 . The method of claim 1 , wherein the hydrophobic material comprises siloxane and wherein the first plurality of particles comprises about 0.05 wt. % to about 5 wt. %, of said siloxane.

14 . The method of claim 1 , wherein the hydrophobic material comprises wax and wherein the first plurality of particles comprises about 0.5 wt. % to about 10 wt. % of said wax.

15 . The method of claim 1 , wherein the aqueous gypsum slurry comprises about 1 wt. % to about 10 wt. % of the first plurality of particles based on a combined dry weight of the first plurality of particles and second plurality of particles.

16 . The method of claim 1 , further comprising adding air to the aqueous gypsum slurry prior to depositing it.

17 . The method of claim 1 , wherein the set gypsum core has a total air volume of about 30 vol. % to about 90 vol. %.

18 . The method of claim 19 , wherein the total air volume of the set gypsum core is about 45 vol. % to about 80 vol. %.

19 . 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.

Assignees

• United States Gypsum Co

Inventors

• Schermann Rudy A
• Vilinska Annamaria
• Li Alfred
• Walker Blair C
• Lau Te Hua
• Erickson Stephen P
• Carrazco Jose Luis
• Rueda Angel Arturo

Classifications

• B28B19/0092

  to webs, sheets or the like, e.g. of paper, cardboard · CPC title

• C04B28/145

  Calcium sulfate hemi-hydrate with a specific crystal form · CPC title

• Y02W30/91

  Use of waste materials as fillers for mortars or concrete · CPC title

• C04B28/14 Primary

  containing calcium sulfate cements {(gypsum-paper plates E04C)} · CPC title

• C04B2111/0062

  Gypsum-paper board like materials · CPC title