# US 2021/0331978 A1 · Methods for reclaiming gypsum panels that contain hydrophobic materials and use thereof

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- Number: US 2021/0331978 A1
- Document ID: US20210331978A1
- Status: Published application
- Kind: A1
- Application number: 17/210,789
- Filed: 2021-03-24
- Published: 2021-10-28
- Earliest claimed: 2020-04-28
- Assignees: Knauf Gips KG
- Applicants: United States Gypsum Company
- Inventors: Rudy A. Schermann; Annamaria Vilinska; Alfred Li; Blair C. Walker; Te Hua Lau; Stephen P. Erickson; Jose Luis Carrazco; Angel Arturo Rueda
- Web page: https://patentgrep.com/patent/US20210331978A1

## CPC

- C04B 28/14: containing calcium sulfate cements {(gypsum-paper plates E04C)}
- B28B 19/0092: {to webs, sheets or the like, e.g. of paper, cardboard}
- C04B 18/167: Recycled materials, i.e. waste materials reused in the production of the same materials
- C04B 24/42: Organo-silicon compounds
- C04B 28/145: {Calcium sulfate hemi-hydrate with a specific crystal form}
- C04B 38/10: by using foaming agents (C04B38/02 takes precedence){or by using mechanical means, e.g. adding preformed foam}
- C04B 2111/0062: {Gypsum-paper board like materials}
- Y02W 30/91: Use of waste materials as fillers for mortars or concrete
- C04B: LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE {(roofing granules E04D7/005)}; CERAMICS (devitrified glass-ceramics C03C10/00); REFRACTORIES; TREATMENT OF NATURAL STONE
- B28B: SHAPING CLAY OR OTHER CERAMIC COMPOSITIONS; SHAPING SLAG; SHAPING MIXTURES CONTAINING CEMENTITIOUS MATERIAL, e.g. PLASTER (foundry moulding B22C; working stone or stone-like material B28D; shaping of substances in a plastic state, in general B29C; making layered products not composed wholly of these substances B32B)
- Y02W: CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT

## 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.

## Claims

### 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.

### Claim 2 (depends on 1)

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.

### Claim 3 (depends on 1)

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.

### Claim 4 (depends on 1)

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

### Claim 5 (depends on 1)

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

### Claim 6 (depends on 1)

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

### Claim 7 (depends on 1)

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.

### Claim 8 (depends on 7)

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.

### Claim 9 (depends on 7)

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

### Claim 10 (depends on 1)

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.

### Claim 11 (depends on 1)

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.

### Claim 12 (depends on 1)

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.

### Claim 13 (depends on 1)

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.

### Claim 14 (depends on 1)

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.

### Claim 15 (depends on 1)

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.

### Claim 16 (depends on 1)

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

### Claim 17 (depends on 1)

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

### Claim 18 (depends on 19)

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

### Claim 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.