PURPOSE: To improve the mechanical property of a gypsum-based material by mixing polyethers and water, and polyurethane, polyurethane-urea and/or another polymer if necessary and, adding a unhardened gypsum so as to execute molding and hardening.
CONSTITUTION: One or more kinds of polyethers expressed by formulas I-IV ((a) is 17-23, (b) is 3-6, (c) is 1-6, (d) is 17-23, (e) is 3-15, (f) and (g) are 2-30, St and St' are each a glyceric molecule including a fatty acid radial of 2.5-0C and (n) and n' are each 0.5-3) is mixed with water. The polyurethane including a hydrophilic group, the polyurethane-urea and/or the aqueous dispersion of another polymer such as a vinyl acetate-ethyrene copolyme, etc., are additionally mixed as necessary. Then, the unfixed gypsum is added to the mixture so as to be stirred and the reaction mixture is injected to a mold so as to be left for a prescribed time. It is taken-out from the mold after hardening so as to obtain a gypsum hardened object containing 0.02-5 wt.% polyether and, as necessary, 0.02-50 wt.% polyurethan and polyurethan-urea and/or another polymer is obtained.
YAN MATSUANEKU
URURITSUHI FUON GITSUIKI
