Process for preparing a hydrogel
AssigneeNippon Oil Co., Ltd.
InventorMasao Nambu
Life of this patent
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Abstract
A hydrogel which has a water content of 20 to 92 weight % and which is stable and superior in mechanical properties is obtained by preparing a 3 to 25 weight % aqueous solution of a polyvinyl alcohol having a degree of hydrolysis not less than 95 mol % and a viscosity-average polymerization degree of not less than 1,500, then pouring the aqueous polyvinyl alcohol solution into a desired shape of a vessel or a mold, then freeze-molding the aqueous polyvinyl alcohol solution at a temperature lower than -6.degree. C., thereafter dehydrating the molded article without thawing it until the dehydration percentage reaches 5 weight % or more and, if required, immersing the dehydrated product in water.
Claims12
A process for preparing a water-insoluble hydrogel which comprises the steps:
- preparing a 3 to 25 weight % aqueous solution of a polyvinyl alcohol having a degree of hydrolysis not less than 95 mol % and a viscosity-average polymerization degree of not less than 1,500, pouring said aqueous polyvinyl alcohol solution into a desired shape of a vessel or a mold, freeze-molding said poured aqueous polyvinyl alochol solution at a temperature lower than -6.degree. C., vacuum-dehydrating the resulting molded article without thawing it to a dehydration percentage not lower than 5 weight %, and thawing said dehydrated article to provide a water-insoluble hydrogel having a water content of 20 to 92% by weight.
Dependencies are inferred from the claim text.