| 摘要 |
<p>A process is provided for preparing skinless liquophilic alcohol-insoluble polyamide membranes by preparing at a first temperature a solution in a polyamide solvent having a temperature coefficient of solubility within the range from about 0.01 to about 5 weight per cent per degree Centrigrade of on alcohol-insoluble polyamide resin having a ratio CH2:NHCO of methylene CH2 to amide NHCO groups within the range from about 7:1 to about 12:1; inducing nucleation of the solution by controlled addition to the solution of a nonsolvent for the polyamide resin, under controlled conditions of concentration, temperature, addition rate, and degree of agitation to obtain a visible precipitate of polyamide resin particles which may or may not thereafter partially or completely redissolve, thereby forming a casting solution; spreading the casting solution on a substrate to form a thin film thereof on the substrate; cooling the film of casting solution to a second temperature sufficiently lower than the first temperature to precipitate polyamide resin from the casting solution; contacting and diluting the film of casting solution with a nonsolvent liquid, preferably containing a substantial proportion of the solvent liquid but less than the proportion in the casting solution, to precipitate polyamide resin from the casting solution in the form of a thin skinless liquophilic membrane; and washing and drying the resulting membrane; the alcohol-insoluble polyamide membranes obtained by this process have the unusual property of being liquophilic, i.e., readily wetted by organic liquids having a surface tension below about 60 dynes/cm, while being substantially not wetted by water, have absolute particle removal capabilities of the order of 0.1 to 5 mu M or more, and are useful as filter media for liquid systems in which such organic liquids are the continuous phase, as well as for separating immiscible liquid mixtures containing such liquids and liquids having a higher surface tension such as water.</p> |
