| 摘要 |
The invention relates to a method of preparation of semi-permeable diaphragms, especially for use in inverse osmosis and enabling substantially pure water to be extracted from aqueous solutions of dissolved substances of low molecular weight, such as sodium chloride, saccharose, etc. The diaphragms for inverse osmosis essentially consist of a film-producing polymer having a sufficient number of mobile hydrogen groups to give, after reticulation, compounds which are insoluble in water. The method covers the preparation of ultra-thin layers which can be employed for hyper-filtration purposes, and also includes the superficial reticulation of a dry film of polymers which include, inter alia, the polyvinyl alcohols and polyvinyl pyrrolidone. The reticulation agent is preferably chosen from the di-isocyanates and may comprise a solvent for a swelling agent for the polymer and a catalyst for the reticulation reaction. An important feature of the invention is that the degree of reticulation of such diaphragms varies progressively throughout the thickness of the film, the most highly reticulated layer being a very thin superficial layer of the diaphragm. |
