PURPOSE: To obtain titled composite membrane having an extremely thin effective thickness and used in reverse osmosis, by forming a specific unsymmetrically structured crosslinked ultrathin film functional layer on a porous supporting membrane.
CONSTITUTION: Onto a porous supporting membrane is coated a solution containing a polyamene which has primary or secondary amino groups (a) and quanternary ammonium salt groups (b) in an eq. ratio of 10/1W1/10 and a sum of (a) and (b) of 0.7W20meq./g and which is soluble (more than 0.5wt%) in a solvent such as a water-miscible alcohol or ether having a b.p. of below 120°C. After drying, the coated film is contacted at a temperature of below 100°C, with a solution-type or gaseous polyfunctional compound having at least two functional groups readily reactive with (a), and then heat-treated to form an unsymmetrically structured selectively permeable layer having a crosslinked ultrathin film functional layer wherein 0.5W20meq./g of at least one nitrogen-crosslinking structure derived from (a) and selected from the groups shown (c) and (b) are present, and the ratio of (b) to (c) is 2.1W2:2:1.9.
MINEMATSU HIROMASA
HAYASHI YUZURU
HARA SHIGEYOSHI
