POLYVINYLIDENE FLUORIDE HOLLOW FIBER MEMBRANE OF IN-SITU PORE-FORMING AGENT AND PREPARATION METHOD THEREFOR

Abstract

The present invention discloses a polyvinylidene fluoride hollow fiber membrane and a preparation method thereof. The hollow fiber membrane comprises 30%-50% of polyvinylidene fluoride resin, 40%-60% of inorganic molecular solution in-situ pore-forming agent and 5%-20% of organic diluent. The preparation method comprises preparing the inorganic molecular solution in-situ pore-forming agent formed from organic sol, mixing the inorganic molecular solution in-situ pore-forming agent formed from the organic sol with high-molecular polymer resin and the organic diluent to obtain a material A,extruding hollow fibers through a forming mold, stretching on line by 2-3 times to obtain hollow fiber filaments, extracting the hollow fiber filaments with an organic solvent to remove all organic matters, removing inorganic matters dispersed in the hollow fiber filaments by using an acid or alkaline solution to form a porous membrane and cleaning the porous membrane, setting and performing heat treatment to obtain the polyvinylidene fluoride hollow fiber membrane.

Claims

1. A polyvinylidene fluoride hollow fiber membrane for an in-situ pore-forming agent, comprising the following raw materials in percentage by mass: 30%-50% of polyvinylidene fluoride resin; 40%-60% of inorganic molecular solution in-situ pore-forming agent formed from organic sol calculated by mass of zinc acetate; and 5%-20% of organic diluent; the polyvinylidene fluoride resin is a homopolymer of polyvinylidene fluoride or a copolymer of polyvinylidene fluoride; the inorganic molecular solution in-situ pore-forming agent formed from organic sol adopts zinc acetate; organic solvents in the inorganic molecular solution in-situ pore-forming agent formed from organic sol are polyalcohol monoethers, polyalcohol polyethers or mono-alcohol monoethers; and the inorganic molecular solution in-situ pore-forming agent formed from organic sol is prepared by the following method: dissolving the zinc acetate in an organic solvent of ethylene glycol monomethyl ether to form a solution in the presence of a catalyst of glacial acetic acid and a stabilizer of ethanol amine, wherein the added ethanol amine and zinc acetate have an equal molar ratio; stirring at a temperature of 40-80° C. for 1-2 hours to form a transparent, homogeneous and stable complexing solution, and obtaining the inorganic molecular solution in-situ pore-forming agent formed from organic sol.

2. The polyvinylidene fluoride hollow fiber membrane for the in-situ pore-forming agent according to claim 1, wherein the polyvinylidene fluoride resin is the homopolymer of polyvinylidene fluoride.

3. The polyvinylidene fluoride hollow fiber membrane for the in-situ pore-forming agent according to claim 1, wherein the organic diluent is vegetable oil or oleate; the vegetable oil is epoxidized soybean oil; and the oleate is at least one of ethyl oleate, glyceryl monooleate and oleoyl macrogolglyceride.

4. The polyvinylidene fluoride hollow fiber membrane for the in-situ pore-forming agent according to claim 3, wherein the organic diluent is the epoxidized soybean oil or the oleoyl macrogolglyceride.

5. The polyvinylidene fluoride hollow fiber membrane for the in-situ pore-forming agent according to claim 1, wherein assistants are added into the raw materials and selected from at least one of an antioxidant, a lubricating agent, a heat stabilizer and an ultraviolet light absorber.

6. A preparation method for the polyvinylidene fluoride hollow fiber membrane for the in-situ pore-forming agent according to claim 1, comprising the following steps: a. preparing an inorganic molecular solution in-situ pore-forming agent formed from organic sol; b. mixing the inorganic molecular solution in-situ pore-forming agent formed from organic sol with high-molecular polymer resin and an organic diluent to obtain a material A; c. extruding the material A to obtain hollow fibers through a forming mold; d. stretching the hollow fibers on line by 2-3 times to obtain hollow fiber filaments; e. extracting the stretched hollow fiber filaments with an organic solvent to remove all organic matters, and removing inorganic matters dispersed in the hollow fiber filaments by using an acid or alkaline solution to form a porous membrane; and f. cleaning the porous membrane, setting and performing heat treatment to obtain the polyvinylidene fluoride hollow fiber membrane for the in-situ pore-forming agent.

7. The preparation method for the polyvinylidene fluoride hollow fiber membrane for the in-situ pore-forming agent according to claim 6, wherein in the step c, the extrusion is performed by a molding machine; and the step d of stretching the hollow fibers on line is to perform uniaxial stretching according to 50%-100% along a longitudinal direction of the hollow fiber filaments by utilizing rollers of different peripheral speeds and wind the hollow fiber filaments on a filament take-up wheel.

8. The preparation method for the polyvinylidene fluoride hollow fiber membrane for the in-situ pore-forming agent according to claim 6, wherein in the step e, the organic solvent extraction treatment is performed by an organic solvent extraction agent and the organic solvent extraction agent is selected from chlorinated hydrocarbon or alcohol of low molecular weight.

9. The preparation method for the polyvinylidene fluoride hollow fiber membrane for the in-situ pore-forming agent according to claim 8, wherein the the organic solvent extraction agent is chlorinated hydrocarbon.

10. The preparation method for the polyvinylidene fluoride hollow fiber membrane for the in-situ pore-forming agent according to claim 9, wherein the chlorinated hydrocarbon is dichloromethane.

11. The preparation method for the polyvinylidene fluoride hollow fiber membrane for the in-situ pore-forming agent according to claim 6, wherein the acid is hydrochloric acid or sulfuric acid, and the alkali is sodium hydroxide or potassium hydroxide.

12. The preparation method for the polyvinylidene fluoride hollow fiber membrane for the in-situ pore-forming agent according to claim 6, wherein in the step f, the cleaning is performed with water, and a heat treatment temperature is 120° C-140° C.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0028] FIG. 1 is a section scanning electron-microscope photo of a polyvinylidene fluoride hollow fiber membrane for an inorganic molecular solution in-situ pore-forming agent formed by utilizing organic sol prepared in embodiments.

[0029] FIG. 2 is an outer surface scanning electron-microscope photo of a polyvinylidene fluoride hollow fiber membrane for an inorganic molecular solution in-situ pore-forming agent formed by utilizing organic sol prepared in embodiments.

DETAILED DESCRIPTION OF THE INVENTION

[0030] The present invention is further described below in combination with drawings through embodiments.

[0031] A ratio of each raw material is mass percentage if not defined.

Embodiment 1

[0032] The preparation method comprises the following steps:

[0033] 1) dissolving a certain amount of zinc acetate in ethylene glycol monomethyl ether in an in-situ pore-forming agent, adding an ethanol amine solution with an equal molar ratio to the zinc acetate, stirring at a temperature of 65° C. under catalysis of a little glacial acetic acid, and finally preparing a homogeneous and transparent solution with a zinc ion concentration of 10%-30%; and

[0034] 2) mixing 40% of a polyvinylidene fluoride resin PVDF, 6.5% of oleoyl macrogolglyceride, 3.5% of epoxidized soybean oil and 50% of a zinc molecular solution in-situ pore-forming agent formed by organic sol prepared in the step 1) in a high-speed mixer at high speed, uniformly dispersing polyvinylidene fluoride resin solids in a uniform organic phase, performing 170 mixing by using a screw extruder, extruding hollow fiber filaments by a hollow fiber mold, solidifying with cooling water in a cooling tank, performing uniaxial stretching by 80%, and winding the hollow fiber filaments on a filament take-up wheel; discharging the hollow fiber filaments from the wheel, then soaking with dichloromethane twice at a room temperature for 1 hour to remove all organic matters, soaking once in 10% of sulfuric acid solution for 30 minutes to remove all inorganic matters, and finally repeatedly flushing with pure water, airing and performing heat setting in a drying oven at a temperature of 140° C. for 3 hours to obtain the final product. Performance test data of hollow fiber membrane samples is shown in Table 1, and sections and outer surfaces of the membrane filaments are shown in FIG. 1 and FIG. 2.

Embodiment 2

[0035] 1) A preparation method of an in-situ pore-forming agent adopts the same formulation as that in the step 1) of embodiment 1.

[0036] 2) Processes of preparing the hollow fiber membrane are the same as those in embodiment 1, while the difference is that: 50% of polyvinylidene fluoride resin, 6.5% of oleoyl macrogolglyceride, 3.5% of epoxidized soybean oil and 40% of zinc molecular solution in-situ pore-forming agent formed by organic sol prepared in the step 1) are mixed to obtain the final product. Performance test data of hollow fiber membrane samples is shown in Table 1.

TABLE-US-00001 TABLE 1 Membrane sample performance parameters Tensile Outer Inner Membrane strength Tensile Compressive Embod- diameter diameter pore size Porosity Flux at break elongnation strength iments (mm) (mm) (μm) (%) (L/m2*h) (MPa) at break (MPa) 1 1.25 0.62 0.1 70 1350 8.5 85 >1 2 1.21 0.58 0.06 63 780 9.7 90 >1

[0037] The inorganic molecular solution formed from organic sol in the present invention, that is, the stable molecular complexing solution, has excellent compatibility with the high-molecular polymer, high dispersity and uniformity. The prepared hollow fiber membrane remains original due characteristics of membrane filaments prepared by the thermally induced phase separation process and further has a uniform meshed structure in a three-dimensional space, so that distribution of membrane pores is more uniform. The hollow fiber membrane is applicable to multiple wastewater treatment MBRs.