| 摘要 |
PURPOSE:To obtain a film for an envelop which has waterproofness and can be dispersed or dissolved in warm water by applying a waterproofing agent to the external surface of a film made of a polyvinyl alcohol resin having a specified degree of hydrolysis and a specified average degree of polymerization. CONSTITUTION:The film is prepared by applying a waterproofing agent to at least the external surface of a film made of a polyvinyl alcohol resin having a degree of hydrolysis of 50-99mol% and an average degree of polymerization of 100 or above. Examples of the polyvinyl alcohol resins which can be applied include a polyvinyl alcohol obtained by hydrolyzing a polymer of a vinyl ester or a vinyl ether and being easily dispersible or soluble in water at 5-70 deg.C-under an atmospheric pressure and a modified polyvinyl alcohol dispersible or soluble in warm water at 40-70 deg.C. As the waterproofing agent, a urethane resin is desirable. The coating thickness is usually 1-10mum. |
