The present invention relates to water-resistant gypsum compositions, methods of making such composition, as well as manufacturing methods and products comprising such compositions.
Emulsions, useful for imparting water resistance to gypsum products are disclosed. The emulsions of the invention include at least one wax, an alkyl phenol and a hydrophyllic metallic salt, preferably magnesium sulfate. The emulsions of the invention do not require the addition of a starch compound and therefore exhibit enhanced stability even at higher solids content then compared to prior art emulsions.
An emulsion comprising water as the continuous phase, a wax as the discontinuous phase, an emulsifier and a preservative having the general structure: ##STR00001## wherein R.sup.1 can be a heterocycle containing nitrogen and sulfur, such as thiazolyl, isothiazolyl, or thiadiazolyl, which can optionally be substituted with C.sub.1 C.sub.6 alkyl; R.sup.2 can be hydrogen or C.sub.1 C.sub.6 alkyl, specifically hydrogen; n is 0, 1, 2, or 3; each instance of R.sup.3 can independently be hydrogen, C.sub.1 C.sub.6 alkyl, phenoxy, C.sub.1 C.sub.6 alkoxy, halo, amino, C.sub.1 C.sub.6 alkylamino, di C.sub.1 C.sub.6 alkyl amino, imidazolyl, thiazolyl, isothiazolyl, thiadiazolyl, thienyl, furyl, pyrryl, naphthyl, phenyl, halophenyl, C.sub.1 C.sub.6 alkyl phenyl, or C.sub.1 C.sub.6 alkoxyphenyl. The preservative may be added to the emulsion after the emulsion is formed. The emulsion can be incorporated into a gypsum product such as gypsum board or gypsum wood fiber board. The gypsum product may be made by forming a slurry containing gypsum, water, and the emulsion into a solid product. A method for improving the water resistance of a lignocellulosic composite product prepared by mixing lignocellulosic material with a binder to form a mixture and solidifying the mixture in a selected configuration to form the composite product may include adding to the mixture an emulsion as described above.
A method is provided which uses an improved emulsion to imparting water-resistance to gypsum products. In one embodiment, gypsum products comprise calcium sulfate dihydrate and an emulsion which comprises a saponified wax, a nonsaponifiable wax, an alkyl phenol, a surfactant/dispersant salt of polynaphthalenesulfonic acid, and carboxymethylcellulose. Optionally, the emulsions may contain a preservative, e.g., a biocide (mildewcide, fungicide, etc.). These gypsum products resist the uptake of water and therefore resist biological infestation without addition of a preservative.
Emulsions are provided which are useful in imparting water-resistance to gypsum products. In one embodiment, the emulsions comprise at least one wax, an alkyl phenol, a salt of polynaphthalenesulfonic acid, and a complexed starch. Emulsions of this embodiment may be added to hot, even boiling, water without the emulsion separating or curdling. The emulsions of the present invention are stable for extended periods of time when stored at room temperature and do not require the addition of a bactericide. The emulsions of the present invention are pourable liquids at room temperature.
