US 2021/0198148 A1Published application

Composite gypsum board formed from high-salt stucco and related methods

AssigneeUnited States Gypsum Company

InventorsQinghua Li, Mark K. Hemphill, Brian J. Christ, Curtis B. Loring

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Abstract

Disclosed are a composite gypsum board and a method of preparing gypsum board. The board contains at least one set gypsum layer sandwiched between face and back cover sheets. The set gypsum layer is formed from at least stucco and water. The stucco material generally includes a high salt impurity content, for example, when the stucco is calcined from certain sources of low-quality synthetic gypsum. For example, in some embodiments, the salts are chloride salts, e.g., sodium chloride (NaCl), potassium chloride (KCl), magnesium chloride (MgCl2), and/or calcium chloride (CaCl2). The board and methods improve the bond between the gypsum layer(s) and at least one of the cover sheets (e.g., the back cover sheet). Also provided are methods and systems relating to drying gypsum board.

Claims20

Dependent claims

A gypsum board comprising a set gypsum core disposed between a face cover sheet and a back cover sheet, the set gypsum core formed from a slurry comprising water, stucco, and a high salt impurity content, the board comprising at least two of the following:

(a) perforations in the back cover sheet;
(b) the back cover sheet containing high absorption paper;
(c) starch included between the set gypsum core and at least one of the cover sheets;
and
(d) (i) a back skim coat layer defining first and second skim coat faces, the back skim coat layer formed from a second slurry comprising water, stucco, and a skim coat starch, the first face of the back skim coat facing the back cover sheet and the second face of the back skim coat facing the first core face, and (ii) a face skim coat layer defining first and second faces, the face skim coat layer formed from a third slurry comprising water, stucco, and optionally, the skim coat starch, the first face of the face skim coat layer facing a second face of the board core, and the second face of the face skim coat layer facing the face cover sheet, wherein the skim coat starch enhances the bond between the core and at least the back cover sheet, wherein the second and third slurries can be the same or different.

2 more elements

A method of making a gypsum board comprising:

(a) mixing at least water, stucco, and foam to form a first slurry;
(b) disposing the first slurry between a face cover sheet and a back cover sheet to form a board precursor;
(c) cutting the board precursor into a board;
(d) drying the board in a kiln containing at least one in-kiln radio-frequency moisture sensor therein, the in-kiln moisture sensor in communication with a controller outside of the kiln to produce an in-kiln moisture reading;
(e) measuring moisture content in the board upstream of the kiln using an upstream radio-frequency moisture sensor and an upstream sensor that is less influenced by high salt concentration in the slurry as compared with the radio-frequency moisture sensor, the upstream sensors in communication with the controller to produce a first upstream moisture reading and a second upstream moisture reading, respectively;
(f) correlating the moisture readings from the upstream radio-frequency moisture sensor and the upstream sensor that is less influenced by high salt concentration in the slurry as compared with the radio-frequency moisture sensor;
and
(g) biasing the in-kiln radio-frequency moisture sensor when a delta exists between the first and second moisture readings to correct for any errors in the in-kiln moisture reading.

5 more elements

Dependencies are inferred from the claim text.

Facts

Application: 16/904,779Filed 18 Jun 2020
Priority: 26 Dec 2019
Published: 1 Jul 2021
Term ends: Not estimatedThe source records don’t support an estimate.

Classification35 codes

B32B 3/266
Characterised by a particular shape of the outline of the cross-section of a continuous layer; characterised by a layer with cavities or…
C04B 28/14
Compositions of mortars, concrete or artificial stone, containing inorganic binders or the reaction product of an inorganic and an organic…
B32B 5/145
Characterised by a layer differing constitutionally or physically in different parts, e.g. denser near its faces: variation across the thickness…
B32B 5/20
Characterised by features of a layer of foamed material: foamed in situ

Family

Application62/953,764Us provisional application · filed 26 Dec 2019
US 2021/0198148 A1This patent

From the US filing history. Foreign family members aren’t listed.

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