| 摘要 |
PURPOSE:To reduce saturation moisture content and improve mechanical strengths and stabilities, by treating a solution of PVA of a specific degree of polymerization at a low temp. to form a gel, drying the resulting gel, and then treating it at a high temp. CONSTITUTION:1-30wt.% PVA with a degree of polymerization of 1200 or more and a degree of saponification of pref. 95mol% or more is dissolved in 99-70wt.% solvent mixture comprising water and a water-miscible org. solvent in a ratio of water to said org. solvent of (5:95)-(30:70) to give a PVA solution, which is caused to gel by cooling below room temp., pref. below 0 deg.C. The resulting gel is dehydrated, then dried to a moisture content of 3wt.% or less, and heat-treated at 100 deg.C or higher, pref. 120-160 deg.C, for 5min to 10hr, pref., in a vacuum or in an inert-gas stream or in an inert solvent to give a polyvinyl alcohol hydrogel with a saturation moisture content of 40wt.% or less. |
