A gypsum fiber board produced in a Siempelkamp dry-process, comprising 75 wt % to 90 wt % (relative to the total dry mix) of calcium sulfate hemi-hydrate and 10 wt % to 25 wt % (relative to the total dry mix) paper fibers, wherein the calcium sulfate hemi-hydrate is a mixture of α-calcium sulfate hemi-hydrate and β-calcium sulfate hemi-hydrate, wherein the content of α-calcium sulfate hemi-hydrate in the mixture is at least 5 wt % (relative to the total calcium sulfate hemi-hydrate) is disclosed. Also disclosed is a method for producing a gypsum fiber board of a thickness of 23 mm in a Siempelkamp dry-process.

The present disclosure relates more particularly to calcium sulfate-based slurries useful, for example, in making gypsum boards for building construction, as well as methods for using them, e.g., to make gypsum boards, in one aspect, the present disclosure provides a calcium sulfate slurry composition comprising calcium sulfate present substantially in the form of one or more hydrates, the calcium sulfate being present in an amount in the range of 70-99.8 wt % on a dry basis, calculated as stucco; and a cationic starch present in an amount of 0.10-10 wt % of the amount of calcium sulfate as stucco on a dry basis, the cationic starch being substituted with amine and/or ammonium groups and having a % N value in the range of 0.10 wt. % to 2 wt %, and an RVA viscosity value of at least 100 cP at 65° C. and 16 wt %; and water, in an amount sufficient to form a slurry. The disclosure also provides gypsum-based materials useful as building materials, e.g., for use as building boards in construction of walls and ceilings of buildings.

The present invention is directed to a construction chemical composition for the preparation of gypsum articles, said construction chemical composition comprising fine calcium sulfate and a dispersant being a polyarylether. Further the present invention is directed to a process for preparing said construction chemical composition as well as an article comprising said construction chemical composition.

The present invention is directed to a construction chemical composition for the preparation of gypsum articles, said construction chemical composition comprising fine calcium sulfate and a dispersant being a polyarylether. Further the present invention is directed to a process for preparing said construction chemical composition as well as an article comprising said construction chemical composition.

Disclosed is a composite gypsum board comprising a board core and a concentrated layer of substantial thickness (e.g., at least about 0.02 inches). The concentrated layer includes a higher weight percentage of an enhancing additive than the board core. The board core has a thickness greater than the thickness of the concentrated layer and forms the bulk of the board volume. The concentrated layer has a higher density (e.g., at least about 1.1 times greater) than the density of the board core. Also disclosed is a method of preparing a composite gypsum board.

A gypsum fiber board produced in a Siempelkamp dry-process, comprising 75 wt % to 90 wt % (relative to the total dry mix) of calcium sulfate hemi-hydrate and 10 wt % to 25 wt % (relative to the total dry mix) paper fibers, wherein the calcium sulfate hemi-hydrate is a mixture of -calcium sulfate hemi-hydrate and -calcium sulfate hemi-hydrate, wherein the content of -calcium sulfate hemi-hydrate in the mixture is at least 5 wt % (relative to the total calcium sulfate hemi-hydrate) is disclosed. Also disclosed is a method for producing a gypsum fiber board of a thickness of 23 mm in a Siempelkamp dry-process.

A gypsum fiber board produced in a Siempelkamp dry-process, comprising 75 wt % to 90 wt % (relative to the total dry mix) of calcium sulfate hemi-hydrate and 10 wt % to 25 wt % (relative to the total dry mix) paper fibers, wherein the calcium sulfate hemi-hydrate is a mixture of -calcium sulfate hemi-hydrate and -calcium sulfate hemi-hydrate, wherein the content of -calcium sulfate hemi-hydrate in the mixture is at least 5 wt % (relative to the total calcium sulfate hemi-hydrate) is disclosed. Also disclosed is a method for producing a gypsum fiber board of a thickness of 23 mm in a Siempelkamp dry-process.

The present application describes a process for the continuous production of alpha-calcium sulphate hemihydrate, the process comprising the steps of: providing particulate gypsum; providing water; mixing the particulate gypsum and the water to form a gypsum slurry; and maintaining said gypsum slurry under raised pressure and temperature to convert the particulate gypsum into alpha-calcium sulphate hemihydrate and provide an alpha-calcium sulphate hemihydrate slurry. Additionally, the particulate gypsum comprises a D10 value greater than or equal to 2 ?m, a D90 value smaller than or equal to 90 ?m and a D50 value smaller than or equal to 25 ?m. Particulate gypsum for use in the process is also provided.

Disclosed is a composite gypsum board comprising a board core and a concentrated layer of substantial thickness (e.g., at least about 0.02 inches). The concentrated layer includes a higher weight percentage of an enhancing additive than the board core. The board core has a thickness greater than the thickness of the concentrated layer and forms the bulk of the board volume. The concentrated layer has a higher density (e.g., at least about 1.1 times greater) than the density of the board core. Also disclosed is a method of preparing a composite gypsum board.

Disclosed is a composite gypsum board comprising a hoard core and a concentrated layer of substantial thickness (e.g., at least about 0.02 inches). The concentrated layer includes a higher weight percentage of an enhancing additive than the board core. The board core has a thickness greater than the thickness of the concentrated layer and forms the bulk of the board volume. The concentrated layer has a higher density (e.g., at least about 1.1 times greater) than the density of the board core. Also disclosed is a method of preparing a composite gypsum board.