Method for preparing alloy flat-sheet membrane by using low-temperature thermal induced phase separation method

Abstract

The invention discloses a method for preparing an alloy flat-sheet membrane by using a low-temperature thermal induced phase separation method. The method comprises the steps of blending polyvinylidene fluoride and polysulfone; mixing under stirring at a temperature of 60-150 DEG C, by using polyethylene glycol and polyvinyl pyrrolidone as additives and a normal temperature solvent of N,N-dimethyl formamide and a high temperature solvent of dibutyl phthalate as diluents; then desorbing to obtain a membrane-casting solution; and then scraping the membrane-casting solution on a non-woven fabric with a flat-sheet membrane scraper to obtain the alloy flat-sheet membrane.

Description

technical field [0001] The invention belongs to the technical field of membrane preparation, and in particular relates to a method for preparing an alloy flat membrane by using a low-temperature thermotropic phase. Background technique [0002] In the field of separation membranes, there are many types of membranes, such as hollow fiber membranes, capillary fiber membranes, tubular membranes, and flat membranes. Among them, the flat membrane is valued because of its anti-pollution, easy cleaning, long service life, and easy use in the separation field with harsh conditions. The flat film prepared by the common non-solvent-induced phase separation method has low crystallinity of the polymer after film formation, resulting in poor strength of the flat film, which is not resistant to cleaning and has a short service life. The preparation of porous membranes by thermally induced phase separation can effectively solve the shortcomings of non-solvent induced phase separation. At ...

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Problems solved by technology

However, this method is rarely used in the field of flat film preparation. This is because the thermally induced phase separation method involves high-temperature dissolution, and the temperature is generally above 180°C. Some materials even need to be dissolved at a temperature above 300°C. rapid phase separation

Therefore, the thermally induced phase separation method is used to prepare flat membranes. The scraping equipment requires heating and heat preservation above 180°C. The requirements for equipment are high, the process conditions are complex and difficult to control, so thermally induced phase separation is rarely used to prepare flat membranes.

At the same time, due to the high temperature of the casting solution, the thermally induced phase separation method also requires a special non-woven substrate to cooperate, which also increases the difficulty and cost of membrane production, and the prepared membrane has the problem of excessively large pore size. , so that its field of application is limited

[0003] In the Chinese patent CN100478389C, an alloy flat membrane is prepared by blending polyvinylidene fluoride and polysulfone, and the flat membrane is directly prepared on a glass plate by a non-solvent-induced phase separation method. The non-solvent-induced phase separation method causes poor pressure resistance of the membrane and usually The amount is also slightly low, and without the use of non-woven substrates, it is difficult to mass-produce and practically use

Chinese patent CN101138708A adopts thermally induced phase separation to prepare polyvinylidene fluoride flat film. Although a mixed diluent is used, the mixed diluent is a high-temperature solvent of oil, resulting in a scraping film temperature of 180-260 ° C. For equipment The requirements are high, continuous production is difficult and the cost of film production is high. This method does not effectively reduce the temperature of the casting solution

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