HUMIDITY CONTROL AGENT

PURPOSE:To obtain a humidity control agent having a wide humidity control range, excellent in the keeping stability of objective humidity and having a high moisture absorbing and releasing speed, by containing water in a composition, which consists of a saponified vinyl acetate/unsaturated dicarboxylic acid copolymer and deliquescent salts, up to the equilibrium water content at the relative humidity of an atmosphere. CONSTITUTION:A saponified copolymer prepared by saponifying 70mol% or more of the vinyl acetate component of a copolymer consisting of 50-99.8mol% of vinyl acetate and 50-0.2mol% of unsaturated dicarboxylic acid such as a saponified vinyl acetate/monomethyl maleate copolymer is used as an A- component an a deliquescent salt such as calcium chloride is used as a B- component and the powder of the A-component is mixed with the aqueous solution of the B-component by impregnation to form a composition X. Next, water is infiltrated in the composition X in quality corresponding to the equilibrium water content of the composition X at the relative humidity of an atmosphere to be subjected to moisture control to obtain a humidity control agent which is, in turn, adapted to an objective atmosphere.