Gypsum slurries with linear polycarboxylate dispersants

A gypsum board comprising:

• a gypsum core material comprising
• calcium sulfate dihydrate and
• a linear polycarboxylate anionic dispersant comprising a first monomeric repeating unit A and a second monomeric repeating unit B, and an absence of polyvinyl acetate monomeric units;
• wherein the first monomeric repeating unit A is at least one carboxylic acid functional group containing olefinic moiety of formula I:
• wherein R is selected from the group consisting of —CH3, and —CH2—C(O)—OH, or a Na, K, or NH4+ salt thereof, wherein linear polycarboxylate anionic dispersant has an absence of acrylic acid monomer;
• and
• wherein the second monomeric repeating unit B is at least one vinyl sulfonate according to formula II:
• wherein X is NH or O;
• R1 is H or —CH3;
• R2 is a linear or branched alkylene group having the formula —(CnH2n)—, wherein n=2 to 6;
• M=H, Na, K, or NH4+;
• wherein the molar ratio of the first repeating unit A to the second repeating unit B is A is between 1:9 and 9:1;
• wherein the weight average molecular weight of the linear polycarboxylate anionic dispersant is 3000 to 100000 Daltons;
• wherein the gypsum core material has a total void volume of 10 to 92 volume percent,
• wherein the gypsum core material was made from a slurry comprising a mixture of the water, the linear polycarboxylate anionic dispersant, and a hydraulic component comprising hydraulic material, wherein the hydraulic material of the slurry comprises at least 80% calcium sulfate hemihydrate by weight based on the dry weight of the hydraulic component, wherein calcium sulfate anhydrite, synthetic gypsum or landplaster is less than 20% of the hydraulic material;
• wherein weight ratio of water to calcium sulfate hemihydrate of the slurry from which the gypsum core material was 0.2-1.5:1;
• wherein the board comprises the gypsum core sandwiched between cover sheets, wherein the dispersant is present in the slurry in an amount of from about 0.01% to about 2% by weight of the dry dispersant calculated as a percentage of the calcium sulfate hemihydrate.