Hydrophilic modified PVDF and PU mixed taper hole ultrafilteration membrane and preparation method thereof

Abstract

The invention provides a hydrophilic modified PVDF (polyvinylidene fluoride) and PU (polyurethane) mixed taper hole ultrafilteration membrane and a preparation method thereof. The taper hole ultrafilteration membrane is prepared by the following steps: taking PVDF as a base material, PU as a reinforced additive and polyvinylpyrrolidone as a hydrophilic additive; adding diluents-DMAC (dimethylacetamide) and polyethylene glycol 600, and processing to obtain a membrane preparation raw material solution; extruding the membrane preparation raw material solution and an inner coagulating solution-DMAC solution with the temperature difference of 8-15 DEG C through a concentric spinneret to obtain hollow fibers; and soaking, reaming, dehydrating and airing. The hydrophilicity and the stretching strength of a PVDF base membrane are improved; and by changing the coagulating bath composition and the wire drawing process, micropores in a flow guide layer are controlled to be 0.12-0.18 mu m, micropores in a filter layer are controlled to be 0.05-0.09 mu m, pores in the membrane form a 'cone funnel shape', small particles can be effectively intercepted, the recovery rate of a backwardly washed and chemically washed membrane is increased, and the blocking rate of the membrane in the running process is increased.

Description

technical field [0001] The invention relates to a hydrophilic modified PVDF and PU blended cone-pore ultrafiltration membrane and a preparation method thereof, in particular to a tapered-pore hydrophilic modified membrane prepared with polyvinylidene fluoride (PVDF) and polyurethane (PU) as substrates. Hollow fiber ultrafiltration membrane and its preparation method. Background technique [0002] At present, PVDF ultrafiltration membrane modules on the domestic and foreign markets have been widely used in industry, especially in submerged ultrafiltration for advanced treatment of slightly polluted water sources, membrane bioreactors in sewage treatment, and pressure type for reclaimed water reuse. Ultrafiltration is widely used. However, the current ultrafiltration membrane elements have the following disadvantages: First, the micropores of the PDVF ultrafiltration membrane elements in the domestic and foreign markets have a symmetrical or asymmetric structure, and the memb...

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Problems solved by technology

However, the current ultrafiltration membrane elements have the following disadvantages: First, the micropores of the PDVF ultrafiltration membrane elements in the domestic and foreign markets have a symmetrical or asymmetric structure, and the membrane is prone to clogging of the retentate membrane pores during operation. After the membrane has been used for a certain period of time, the chemical cleaning rate is high, and the entire membrane element is often replaced, so that the replacement rate of the membrane is high and the operating cost of the equipment is high; the second is that the matrix of the membrane material of the PDVF ultrafiltration membrane is currently used Polyvinylidene fluoride (PVDF), PVDF is a crystalline polymer with good mechanical strength, outstanding anti-ultraviolet and weather aging characteristics, but a single PVDF hollow fiber ultrafiltration membrane has affinity Poor water quality and easy to pollute. Although it has undergone hydrophilic modification during the membrane making process, its tensile strength is not high. Especially equipped with air-washed structural membrane modules, the membrane will break and age during operation. Shorten the service life of the ultrafiltration membrane and affect the use effect of the ultrafiltration membrane

However, due to the difference in structure between PVDF and PU, it is difficult to achieve molecular-level mixing, and even the compatibility is not good, and the prepared membrane has low strength and large pore size.

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