Methods of preparing gypsum wallboards containing styrene butadiene latex additive

1. A method of making a gypsum wallboard, the method comprising:

forming a slurry comprising calcium sulfate hemihydrate, water, and a functionalized styrene butadiene latex polymer; crosslinked by dimethacrylate having from 2 to 30 ethoxy units between methacrylate functionalities mixing the slurry;

depositing the slurry onto a first cover sheet; and

applying a second cover sheet atop the deposited slurry.

2. The method of claim 1 , wherein the functionalized styrene butadiene latex polymer includes at least about 0.25 percent by weight of a monomer that conveys ionic character to the functionalized styrene butadiene latex polymer.

3. The method of claim 2 , wherein the monomer is selected from the group consisting of 2-acrylamido -2-methyl propanesulfonic acid salt, styrene sulfate salt, styrene sulfonate salt, allyl sulfonate salt, 3-sulfopropyl acrylate salt, 3-sulfopropyl methacrylate salt, 2-sulfoethyl acrylate salt, 2-sulfoethyl methacrylate salt, maleic acid, salts of maleic acid, itaconic acid, salts of itaconic acid, and mixtures thereof.

4. The method of claim 2 , wherein the monomer is a metal salt of 2-acrylamido-2-methyl propanesulfonic acid.

5. The method of claim 2 , wherein the monomer is a sodium salt of 2-acrylamido-2-methyl propanesulfonic acid.

6. The method of claim 1 , wherein the functionalized styrene butadiene latex polymer is prepared by aqueous emulsion polymerization of a monomeric mixture comprising styrene and butadiene in the presence of a seed polymer prepared by aqueous polymerization of styrene and a salt of 2-acrylamido-2-methyl propanesulfonic acid.

7. The method of claim 1 , wherein the median particle diameter of the functionalized styrene butadiene latex polymer is about 170 nanometers to about 190 nanometers.

8. The method of claim 1 , wherein the styrene butadiene latex polymer has a gel content of about 50%.