CN102580571A - Method for preparing ultra high molecular weight polyethylene micro-filtration membrane - Google Patents

Abstract

The invention relates to a preparation method of ultra-high molecular weight polyethylene microfiltration membrane, which comprises the following steps: (1) weighing 10-30 parts by weight of ultra-high molecular weight polyethylene and 67-89.4 parts by weight of diluent , 0.1-2 parts by weight of nucleating agent and 0.5-1 part by weight of antioxidant are mixed, and the gained mixture obtains a flat film through molding process or extrusion process; (2) adopt shearing process or stretching process to make nucleating agent Orientation to obtain an oriented flat film; (3) Use an extractant to remove the diluent, and form a microporous film after washing and drying; (4) Dry and anneal the microporous film to obtain an ultra-high molecular weight polyethylene microporous film. filter membrane. Compared with the prior art, the ultra-high molecular weight polyethylene microporous membrane prepared by the invention has more regular shape, more uniform pore size distribution and higher water flux. At the same time, it has outstanding mechanical properties, especially in the direction of orientation, and the elongation at break is higher.

Description

A kind of preparation method of ultrahigh molecular weight polyethylene microfiltration membrane

technical field

The invention belongs to the technical field of membrane separation, and in particular relates to the preparation of an ultrahigh molecular weight polyethylene microporous membrane. The prepared ultrahigh molecular weight polyethylene microporous membrane meets the requirements of microfiltration membrane materials in the water treatment process.

Background technique

Microfiltration is an important membrane separation process, widely used in industrial sewage treatment, drinking water preparation, food industry, medical and health, military industry and other industries. The basic element of the membrane separation process is the filter module, the core of which is the filter membrane in the module, and the microporous filter membrane and module made of organic polymer materials are the main ones. According to the average size of the membrane pores or the size of the retained particles, membrane separation can be divided into various processes. The defined pore size of microfiltration is about 0.1-100um, which mainly intercepts particles, proteins and bacteria in water. Common separation membranes include flat sheet membranes, tubular membranes, and hollow fiber membranes.

There are many methods for preparing polymer microporous membranes, such as immersion precipitation method, phase separation method, stretching method and so on. Among them, thermally induced phase separation (TIPS) is an important and widely used method. It is suitable for preparing polymers that cannot find good solvents at room temperature, especially many crystallization or polymers with hydrogen bonds; Rapid heat exchange induces phase separation of the polymer solution, and various pore structures can be obtained by controlling the process conditions. The TIPS process is briefly described as: some thermoplastic, crystalline polymers and some high-boiling diluents are first formed into a homogeneous solution at high temperature, and then the temperature of the system is lowered to induce the system to undergo solid-liquid (S-L) or liquid- The liquid (L-L) phase is separated; the polymer porous membrane can be prepared after the system is cooled and solidified, and the diluent is extracted and removed. The diluent refers to a potential solvent for polymer materials, which is a non-solvent at room temperature but a solvent at high temperature, that is, "compatibility at high temperature, phase separation at low temperature". The type and content of diluent are the most important factors in the TIPS film forming process, which have an important impact on the final film structure and film performance. The pore-forming kinetics of different polymer-diluent systems are often studied in detail by drawing polymer-diluent phase diagrams.

At present, the preparation of polymer membrane materials by TIPS method mainly focuses on high-density polyethylene (HDPE), polypropylene (PP), polyvinylidene fluoride (PVDF), etc. Due to its excellent mechanical properties, biocompatibility and chemical stability, excellent friction resistance and impact resistance, ultra-high molecular weight polyethylene makes the prepared ultra-high molecular weight polyethylene microporous membrane have high mechanical strength and is suitable for sewage treatment. Medium and long-term use performance is stable, not easy to degrade and other comprehensive characteristics. Since ultra-high molecular weight polyethylene is highly elastic when melted, it has almost no fluidity. The TIPS method provides the possibility for the preparation of ultra-high molecular weight polyethylene microporous membranes. However, the TIPS method induces phase separation of the polymer solution through rapid heat exchange, which makes the pore size distribution of the prepared microporous membrane uneven.

Contents of the invention

The object of the present invention is to provide a method for preparing an ultra-high molecular weight polyethylene microfiltration membrane with uniform pore size distribution, high water flux and excellent mechanical properties in order to overcome the above-mentioned defects in the prior art.

The object of the present invention can be achieved through the following technical scheme: a kind of preparation method of ultra-high molecular weight polyethylene microfiltration membrane, it is characterized in that, the method comprises the following steps:

(1) Take 10-30 parts by weight of ultra-high molecular weight polyethylene, 67-89.4 parts by weight of diluent, 0.1-2 parts by weight of nucleating agent and 0.5-1 parts by weight of antioxidant by parts by weight and mix the obtained mixture through Flat film obtained by molding process or extrusion process;

(2) Using a shearing process or a stretching process to orient the nucleating agent to obtain an oriented flat film;

(3) Use the extractant to remove the diluent, and form a microporous membrane after washing and drying;

(4) Drying and annealing the microporous membrane to obtain an ultra-high molecular weight polyethylene microfiltration membrane.

The molecular weight of the ultra-high molecular weight polyethylene is 1.5 to 5 million.

Described nucleating agent is silicon dioxide (SiO ₂ ), titanium dioxide (TiO ₂ ), carbon nanotube (CNT), graphene, 2,4,6-triaminopyrimidine (TP), malonylurea (BA ) or one of the sorbitol nucleating agents;

The diluent is selected from one or more of short-chain alkanes solvents or phthalates solvents;

The antioxidant is selected from any one or a combination of organotin antioxidants and/or metal soap antioxidants.

The sorbitol nucleating agent includes 1,3:2,4-dibenzylidene sorbitol (DBS), 1,3:2,4-di-p-methylbenzylidene sorbitol (MDBS) or 1,3 : 2,4-bis(3,4-dimethyl)benzylidene sorbitol (DMDBS);

Described short chain alkanes solvent comprises octane, decane, paraffin oil, solid paraffin or liquid paraffin; Described phthalates solvent comprises dimethyl phthalate, phthalic acid Diethyl phthalate, dibutyl phthalate, dihexyl phthalate, dioctyl phthalate, diisooctyl phthalate, phthalate Diisodecyl phthalate, bis(2-methylhexyl) phthalate or dicyclohexyl phthalate;

Described organotin antioxidant comprises dibutyltin dilaurate, di-n-octyltin maleate, two (monobutyl maleate) dibutyltin, two (lauryl mercaptan) dibutyltin, S, S' - two (isooctyltin thioglycolate) dibutyltin or di-n-octyltin dilaurate; the metal soap antioxidants include calcium stearate, magnesium stearate, lithium stearate, stearic acid Zinc, aluminum stearate, aluminum distearate, calcium laurate, zinc laurate, calcium ricinoleate, or zinc 2-ethylhexanoate.

The molding process described in step (1) adopts the following steps: adopt the Haake torque rheometer to directly melt the mixture, and then mold a flat film through a film pressing machine. The temperature is 160-170°C.

The extrusion process described in step (1) adopts the following steps: melting, mixing and extruding the mixture in a twin-screw extruder to obtain a film injection liquid, and then passing the film injection liquid through a T-shaped mouth film and casting it on the metal The flat film is formed on the roller, the processing temperature of the twin-screw extruder is 170-200°C, and the screw speed is 200-400rpm.

The shearing process described in step (2) adopts the following steps: heating the flat film to a shearing temperature of 125-145°C through a torque rheometer, controlling the shear rate to be 10-50s ^-1 , and the strain amplitude to be 20-100 %, to obtain an oriented flat film.

The stretching process described in step (2) adopts the following steps: the flat film is stretched and oriented by a universal electronic stretching machine with controllable stretching temperature, the stretching temperature is 40-100°C, and the stretching rate is 50-100mm/min , The tensile strain is 100-300%.

The extractant in step (3) is selected from one or more combinations of absolute ethanol, glycerol, n-butanol or chloroform.

The drying temperature for drying and annealing for setting in step (4) is 80° C., the drying time is 3 hours, the annealing temperature is 110° C., and the annealing time is 10 hours.

In the TIPS method, adding a nucleating agent has three effects on crystalline polymers: one is to accelerate the crystallization rate of the polymer, thereby controlling the phase separation, and then affecting the kinetic process of film formation; the other is to increase the crystallinity of the polymer , help to improve the mechanical strength and heat resistance of the material, etc.; the third is to increase the density of crystal nuclei, thereby reducing the pore size of the final microporous membrane. As we all know, the reduction of the pore size of the microporous membrane is bound to be accompanied by the increase of the water flow path in the membrane, and the water flux decreases. Furthermore, nano inorganic nucleating agents are prone to agglomeration, and generally it is difficult to achieve dispersion at the primary particle level, so it is difficult to reflect the special properties of nanoparticles. Therefore, simply mixing polymer/diluent/nucleating agent not only fails to improve water flux, but also makes it more difficult to achieve good dispersion of nucleating agent. At the same time, the existing incompatible phase interface will also cause the deterioration of the mechanical properties of thin film products. Therefore, improving the dispersion of nucleating agents and preparing polymer microporous membranes with short water flow channels is one of the key technologies for preparing microporous membranes by TIPS method.

The present invention adopts organic small molecular compound, CNT and _SiO2 self-assembled into nanofibers in diluent and UHMWPE melt as nucleating agents, and at a certain temperature, the applied shear or extensional flow field makes The nucleating agent is oriented to induce the crystallization of UHMWPE, and the ultra-high molecular weight polyethylene microporous membrane is prepared by TIPS method. Nucleating agents can form homogeneous solutions in most diluents and polymer melts at elevated temperatures. After applying a shear or extensional flow field, not only the dispersion of the nucleating agent is improved, but also the nucleating agent forms an oriented structure. The oriented nucleating agent not only induces crystallization, but also makes the polymer lamellae grow vertically to the oriented direction of the nucleating agent to obtain an oriented polymer microporous membrane. Therefore, for the TIPS process of oriented ultra-high molecular weight polyethylene microporous membrane, the nucleating agent selected by the present invention and the processing technology have the following characteristics: (1) select three kinds of nucleating agents of different shapes (spherical, rod-like and fibrous) (2) For the homogeneous solution of ultra-high molecular weight polyethylene, diluent, nucleating agent and antioxidant, before the crystallization of the polymer, the applied flow field makes the nucleating agent orientate; (3) when the orientation is effectively controlled beyond Under the premise of high molecular weight polyethylene microporous membrane pore structure and membrane performance, use a small amount of nucleating agent as much as possible.

Compared with the prior art, the present invention adds a nucleating agent to the polymer and diluent, and then applies a shear or extensional flow field at high temperature to orient the nucleating agent, which not only improves the nucleating agent in the polymer/diluent The dispersed and oriented nucleating agent induces UHMWPE epitaxial crystallization to obtain a UHMWPE microporous membrane with a highly oriented surface. Compared with the UHMWPE microporous membrane without orientation, the oriented UHMWPE microporous membrane has smaller pore size distribution, higher water flux and better mechanical properties. Therefore, the microporous membrane prepared by the present invention can be used in the preparation of food, medicine and ultrapure water, meeting the requirements of separation, purification, concentration and purification.

Description of drawings

Fig. 1 is the SEM morphology diagram of the UHMWPE microporous membrane surface without orientation obtained in Comparative Example 1;

Fig. 2 is the surface SEM morphology figure of the orientation UHMWPE microporous membrane that embodiment 1 obtains;

Fig. 3 is the impact of the different nucleating agents that comparative example 1, embodiment 1 and comparative examples obtain on UHMWPE microporous membrane water flux;

Figure 4 shows the influence of different nucleating agents obtained in Comparative Example 3, Example 2, Example 4, and Example 6 on the mechanical properties of UHMWPE microporous membranes.

Detailed ways

The present invention will be described in detail below in conjunction with the accompanying drawings and specific embodiments.

Comparative example 1

(1) by Haake torque rheometer the antioxidant dibutyltin maleate of the ultra-high molecular weight polyethylene of 10% weight fraction, the DBS of 0.1% weight fraction, the liquid paraffin of 89.4% weight fraction, 0.5% weight fraction Melt mixing to obtain ultra-high molecular weight polyethylene mixture. The melt mixing temperature of the Haake torque rheometer is 160° C., the melt mixing time is 12 min, and the rotor speed is 80 rpm.

(2) Then the ultra-high molecular weight polyethylene mixture is formed into a flat film on a laminator. The film thickness is controlled at 200um, the molding temperature is 160°C, and the molding time is 5min.

(3) Then use absolute ethanol to extract the liquid paraffin, wash it repeatedly with deionized water, and form a microporous membrane after drying.

(4) Finally, an oven is used to dry and anneal the microporous membrane to obtain an ultra-high molecular weight polyethylene microfiltration membrane. The drying temperature is 80°C, the drying time is 3 hours, the annealing temperature is 110°C, and the annealing time is 10 hours.

Comparative example 2

(1) by Haake torque rheometer, the antioxidant dibutyltin maleate of the ultra-high molecular weight polyethylene of 20% weight fraction, the CNT of 1% weight fraction, the liquid paraffin of 78% weight fraction, 1% weight fraction Melt mixing to obtain ultra-high molecular weight polyethylene mixture. The melt mixing temperature is 170° C., the melt mixing time is 12 min, and the rotor speed is 80 rpm.

(2) Molding the ultra-high molecular weight polyethylene mixture into a flat film. The film thickness is controlled at 200um, the molding temperature is 170°C, the molding time is 5min, and the pressure is 5MPa.

(3) Next, the liquid paraffin is extracted with absolute ethanol, washed with deionized water, and dried to form a microporous membrane.

(4) Finally, an oven is used to dry and anneal the microporous membrane to obtain an ultra-high molecular weight polyethylene microfiltration membrane. The drying temperature is 80°C, the drying time is 3 hours, the annealing temperature is 110°C, and the annealing time is 10 hours.

Comparative example 3

(1) by Haake torque rheometer, the ultra-high molecular weight polyethylene of 30% by weight, the SiO of 2% by weight ₂ , the liquid paraffin of 67% by weight, the antioxidant maleic acid two of 1% by weight Butyl tin is melt mixed to obtain ultra-high molecular weight polyethylene mixture. The melt mixing temperature is 170° C., the melt mixing time is 12 min, and the rotor speed is 80 rpm.

(2) Molding the ultra-high molecular weight polyethylene mixture into a flat film. The film thickness is controlled at 200um, the molding temperature is 170°C, the molding time is 5min, and the pressure is 5MPa.

(3) Next, the liquid paraffin is extracted with absolute ethanol, washed with deionized water, and dried to form a microporous membrane.

(4) Finally, an oven is used to dry and anneal the microporous membrane to obtain an ultra-high molecular weight polyethylene microfiltration membrane. The drying temperature is 80°C, the drying time is 3 hours, the annealing temperature is 110°C, and the annealing time is 10 hours.

Example 1

(1) by Haake torque rheometer, the ultra-high molecular weight polyethylene of 10% weight fraction, the DBS of 0.1% weight fraction, the liquid paraffin of 89.4% weight fraction, the antioxidant dibutyltin maleate of 0.5% weight fraction Melt mixing to obtain ultra-high molecular weight polyethylene mixture. The melt mixing temperature is 170° C., the melt mixing time is 16 min, and the rotor speed is 80 rpm.

(2) Molding the ultra-high molecular weight polyethylene mixture into a flat film. The film thickness is controlled at 200um, the pressure is 5MPa, the molding temperature is 170°C, and the molding time is 6min.

(3) A torque rheometer is used to apply a shear flow field to the formed flat film. The shear temperature is 125°C, the shear rate is 50s ^-1 , and the strain amplitude is 100%.

(4) Next, the liquid paraffin is extracted with absolute ethanol, washed with deionized water, and dried to form a microporous membrane.

(5) Finally, an oven is used to dry and anneal the microporous membrane to obtain an ultra-high molecular weight polyethylene microfiltration membrane. The drying temperature is 80°C, the drying time is 3 hours, the annealing temperature is 110°C, and the annealing time is 10 hours.

Example 2

(1) by Haake torque rheometer the antioxidant dibutyltin maleate of the ultra-high molecular weight polyethylene of 30% weight fraction, the DMDBS of 1% weight fraction, the liquid paraffin of 68% weight fraction, 1% weight fraction Melt mixing to obtain ultra-high molecular weight polyethylene mixture. The melt mixing temperature is 170° C., the melt mixing time is 16 min, and the rotor speed is 80 rpm.

(2) Molding the ultra-high molecular weight polyethylene mixture into a flat film. The film thickness is controlled at 200um, the pressure is 5MPa, the molding temperature is 170°C, and the molding time is 6min.

(3) An electronic universal tensile testing machine is used to apply a tensile flow field to the formed flat film. The stretching temperature was 40° C., the stretching rate was 100 mm/min, and the stretching strain was 300%.

(4) Next, the liquid paraffin is extracted with absolute ethanol, washed with deionized water, and dried to form a microporous membrane.

(5) Finally, an oven is used to dry and anneal the microporous membrane to obtain an ultra-high molecular weight polyethylene microfiltration membrane. The drying temperature is 80°C, the drying time is 3 hours, the annealing temperature is 110°C, and the annealing time is 10 hours.

Example 3

(1) by Haake torque rheometer, the ultra-high molecular weight polyethylene of 10% weight fraction, the CNT of 0.5% weight fraction, the liquid paraffin of 89% weight fraction, the antioxidant dibutyltin maleate of 0.5% weight fraction Melt mixing to obtain ultra-high molecular weight polyethylene mixture. The melt mixing temperature is 170° C., the melt mixing time is 16 min, and the rotor speed is 80 rpm.

(2) Molding the ultra-high molecular weight polyethylene mixture into a flat film. The film thickness is controlled at 200um, the pressure is 5MPa, the molding temperature is 170°C, and the molding time is 6min.

(3) A torque rheometer is used to apply a shear flow field to the formed flat film. The shear temperature is 130°C, the shear rate is 50s ^-1 , and the strain amplitude is 100%.

(4) Next, the liquid paraffin is extracted with absolute ethanol, washed with deionized water, and dried to form a microporous membrane.

(5) Finally, an oven is used to dry and anneal the microporous membrane to obtain an ultra-high molecular weight polyethylene microfiltration membrane. The drying temperature is 80°C, the drying time is 3 hours, the annealing temperature is 110°C, and the annealing time is 10 hours.

Example 4

(1) by Haake torque rheometer the antioxidant dibutyltin maleate of the ultra-high molecular weight polyethylene of 30% weight fraction, the CNT of 2% weight fraction, the liquid paraffin of 67% weight fraction, 1% weight fraction Melt mixing to obtain ultra-high molecular weight polyethylene mixture. The melt mixing temperature is 170° C., the melt mixing time is 16 min, and the rotor speed is 80 rpm.

(2) Molding the ultra-high molecular weight polyethylene mixture into a flat film. The film thickness is controlled at 200um, the pressure is 5MPa, the molding temperature is 170°C, and the molding time is 6min.

(3) An electronic universal tensile testing machine is used to apply a tensile flow field to the formed flat film. The stretching temperature was 40° C., the stretching rate was 100 mm/min, and the stretching strain was 300%.

(4) Next, the liquid paraffin is extracted with absolute ethanol, washed with deionized water, and dried to form a microporous membrane.

(5) Finally, an oven is used to dry and anneal the microporous membrane to obtain an ultra-high molecular weight polyethylene microfiltration membrane. The drying temperature is 80°C, the drying time is 3 hours, the annealing temperature is 110°C, and the annealing time is 10 hours.

Example 5

(1) by Haake torque rheometer, the ultra-high molecular weight polyethylene of 10% weight fraction, the SiO of 0.5% weight fraction ₂ , the liquid paraffin of 89% weight fraction, the antioxidant maleic acid two of 0.5% weight fraction Butyl tin is melt mixed to obtain ultra-high molecular weight polyethylene mixture. The melt mixing temperature is 170° C., the melt mixing time is 16 min, and the rotor speed is 80 rpm.

(2) Molding the ultra-high molecular weight polyethylene mixture into a flat film. The film thickness is controlled at 200um, the pressure is 5MPa, the molding temperature is 170°C, and the molding time is 6min.

(3) A torque rheometer is used to apply a shear flow field to the formed flat film. The shear temperature is 130°C, the shear rate is 50s ^-1 , and the strain amplitude is 100%.

(4) Next, the liquid paraffin is extracted with absolute ethanol, washed with deionized water, and dried to form a microporous membrane.

(5) Finally, an oven is used to dry and anneal the microporous membrane to obtain an ultra-high molecular weight polyethylene microfiltration membrane. The drying temperature is 80°C, the drying time is 3 hours, the annealing temperature is 110°C, and the annealing time is 10 hours.

Example 6

(1) by Haake torque rheometer, the ultra-high molecular weight polyethylene of 30% by weight, the SiO of 2% by weight ₂ , the liquid paraffin of 67% by weight, the antioxidant maleic acid two of 1% by weight Butyl tin is melt mixed to obtain ultra-high molecular weight polyethylene mixture. The melt mixing temperature is 170° C., the melt mixing time is 16 min, and the rotor speed is 80 rpm.

(2) Molding the ultra-high molecular weight polyethylene mixture into a flat film. The film thickness is controlled at 200um, the pressure is 5MPa, the molding temperature is 170°C, and the molding time is 6min.

(3) An electronic universal tensile testing machine is used to apply a tensile flow field to the formed flat film. The stretching temperature was 40°C, the stretching rate was 100mm/min, and the stretching strain was 300%.

(4) Next, the liquid paraffin is extracted with absolute ethanol, washed with deionized water, and dried to form a microporous membrane.

(5) Finally, an oven is used to dry and anneal the microporous membrane to obtain an ultra-high molecular weight polyethylene microfiltration membrane. The drying temperature is 80°C, the drying time is 3 hours, the annealing temperature is 110°C, and the annealing time is 10 hours.

Example 7

(1) First utilize twin-screw extruder extrusion process to melt mix 15% by weight of ultra-high molecular weight polyethylene, 0.5% by weight of MDBS, 84% by weight of dioctyl phthalate, 0.5% by weight Antioxidant dibutyltin maleate in weight fraction to obtain film injection solution. The extrusion temperature of the screw is 170-190° C., and the rotational speed of the screw is 350 rpm.

(2) Make the film injection liquid pass through a T-shaped mouth film under pressure, and cast it on a metal roller to form a flat film. The die temperature is 130-140°C, and the metal roller temperature is 25-35°C.

(3) A torque rheometer is used to apply a shear flow field to the formed flat film. The shear temperature is 130°C, the shear rate is 50s ^-1 , and the strain amplitude is 100%.

(4) Then use absolute ethanol to extract dioctyl phthalate, wash properly with deionized water, and form a microporous membrane after drying.

(5) Finally, an oven is used to dry and anneal the microporous membrane to obtain an ultra-high molecular weight polyethylene microfiltration membrane. The drying temperature is 80°C, the drying time is 3 hours, the annealing temperature is 110°C, and the annealing time is 10 hours.

Example 8

(1) Firstly utilize twin-screw extruder extrusion process to melt mix 20% by weight of ultra-high molecular weight polyethylene, 1% by weight of CNT, 78% by weight of dioctyl phthalate, 1% Antioxidant dibutyltin maleate in weight fraction to obtain film injection solution. The extrusion temperature of the screw is 170-190° C., and the rotational speed of the screw is 350 rpm.

(2) Make the film injection liquid pass through a T-shaped mouth film under pressure, and cast it on a metal roller to form a flat film. The die temperature is 130-140°C, and the metal roller temperature is 25-35°C.

(3) An electronic universal tensile testing machine is used to apply a tensile flow field to the formed flat film. The stretching temperature was 40°C, the stretching rate was 100mm/min, and the stretching strain was 300%.

(4) Then use absolute ethanol to extract dioctyl phthalate, wash properly with deionized water, and dry to form a microporous membrane.

(5) Finally, an oven is used to dry and anneal the microporous membrane to obtain an ultra-high molecular weight polyethylene microfiltration membrane. The drying temperature is 80°C, the drying time is 3 hours, the annealing temperature is 110°C, and the annealing time is 10 hours.

Example 9

(1) First utilize twin-screw extruder extrusion process to melt mix 20% by weight of ultra-high molecular weight polyethylene, 1% by weight of SiO ₂ , 78% by weight of dioctyl phthalate, 1 % weight fraction of the antioxidant dibutyltin maleate to obtain a film injection solution. The extrusion temperature of the screw is 170-190° C., and the rotational speed of the screw is 350 rpm.

(2) Make the film injection liquid pass through a T-shaped mouth film under pressure, and cast it on a metal roller to form a flat film. The die temperature is 130-140°C, and the metal roller temperature is 25-35°C.

(3) An electronic universal tensile testing machine is used to apply a tensile flow field to the formed flat film. The stretching temperature was 40° C., the stretching rate was 100 mm/min, and the stretching strain was 300%.

(4) Then use absolute ethanol to extract dioctyl phthalate, wash properly with deionized water, and dry to form a microporous membrane.

(5) Finally, an oven is used to dry and anneal the microporous membrane to obtain an ultra-high molecular weight polyethylene microfiltration membrane. The drying temperature is 80°C, the drying time is 3 hours, the annealing temperature is 110°C, and the annealing time is 10 hours.

The ultra-high molecular weight polyethylene microfiltration membrane of the present invention can also be prepared under the following conditions: using the same steps as in Examples 1 to 9, the difference lies in different shearing or stretching conditions, and the specific processing process is shown in Table 1-2 :

Table 1

Table 2

Figures 1 and 2 are SEM photos of the surface of the 10% UHMWPE microporous membrane obtained in Comparative Example 1 and Example 1, respectively. It can be seen from the photos that in Example 1, due to the orientation of the DBS fibers to induce the epigenetic crystallization of UHMWPE, an anisotropic UHMWPE microporous membrane with a more uniform pore size distribution was obtained.

Figure 3 is for 10% UHMWPE, no orientation and the effect of orientation on water flux of UHMWPE microporous membrane. It can be clearly seen from the figure that the water flux of the oriented film is increased by 3 to 4 times.

Figure 4 is for 30% UHMWPE, no orientation and the influence of orientation on the mechanical properties of the orientation direction of UHMWPE microporous membrane. For oriented films, both stress and strain increase to some extent along the orientation direction.

Claims (10)

1. a preparation method of ultra-high molecular weight polyethylene microfiltration membrane, is characterized in that, the method may further comprise the steps: (1) Take 10-30 parts by weight of ultra-high molecular weight polyethylene, 67-89.4 parts by weight of diluent, 0.1-2 parts by weight of nucleating agent and 0.5-1 parts by weight of antioxidant by parts by weight and mix the obtained mixture through Molding process or extrusion process to obtain flat film; (2) Using a shearing process or a stretching process to orient the nucleating agent to obtain an oriented flat film; (3) Use the extractant to remove the diluent, and form a microporous membrane after washing and drying; (4) Drying and annealing the microporous membrane to obtain an ultra-high molecular weight polyethylene microfiltration membrane. 2. The method for preparing an ultra-high molecular weight polyethylene microfiltration membrane according to claim 1, wherein the molecular weight of the ultra-high molecular weight polyethylene is 1.5 to 5 million. 3. the preparation method of a kind of ultra-high molecular weight polyethylene microfiltration membrane according to claim 1, is characterized in that, described nucleating agent is silicon dioxide, titanium dioxide, carbon nanotube, graphene, 2,4 , one of 6-triaminopyrimidine, malonylurea or sorbitol nucleating agents; The diluent is selected from one or more of short-chain alkanes solvents or phthalates solvents; The antioxidant is selected from any one or a combination of organotin antioxidants and/or metal soap antioxidants. 4. the preparation method of a kind of ultra-high molecular weight polyethylene microfiltration membrane according to claim 3 is characterized in that, described sorbitol nucleating agent comprises 1,3:2,4-dibenzylidene sorbitol , 1,3:2,4-di-p-methylbenzylidene sorbitol or 1,3:2,4-di(3,4-dimethyl)benzylidene sorbitol; Described short chain alkanes solvent comprises octane, decane, paraffin oil, solid paraffin or liquid paraffin; Described phthalates solvent comprises dimethyl phthalate, phthalic acid Diethyl phthalate, dibutyl phthalate, dihexyl phthalate, dioctyl phthalate, diisooctyl phthalate, phthalate Diisodecyl phthalate, bis(2-methylhexyl) phthalate or dicyclohexyl phthalate; Described organotin antioxidant comprises dibutyltin dilaurate, di-n-octyltin maleate, two (monobutyl maleate) dibutyltin, two (lauryl mercaptan) dibutyltin, S, S' - two (isooctyltin thioglycolate) dibutyltin or di-n-octyltin dilaurate; the metal soap antioxidants include calcium stearate, magnesium stearate, lithium stearate, stearic acid Zinc, aluminum stearate, aluminum distearate, calcium laurate, zinc laurate, calcium ricinoleate, or zinc 2-ethylhexanoate. 5. the preparation method of a kind of ultra-high molecular weight polyethylene microfiltration membrane according to claim 1 is characterized in that, the molding process described in step (1) adopts the following steps: adopt Haake torque rheometer direct melting mixture , and then molded into a flat film by a film laminator, the melt mixing temperature of Haake torque rheometer is 160-180°C, and the molding temperature is 160-170°C. 6. the preparation method of a kind of ultra-high molecular weight polyethylene microfiltration membrane according to claim 1, is characterized in that, the extrusion process described in step (1) adopts the following steps: the mixture is mixed in a twin-screw extruder Melt, mix and extrude to obtain the film injection liquid, then pass the film injection liquid through the T-shaped mouth film, and cast it on the metal roller to form a flat film. The processing temperature of the twin-screw extruder is 170-200 °C, and the screw speed is 200～400rpm. 7. the preparation method of a kind of ultra-high molecular weight polyethylene microfiltration membrane according to claim 1, is characterized in that, the shear process described in step (2) adopts the following steps: by torque rheometer by flat film Heating to a shearing temperature of 125-145°C, controlling the shearing rate to be 10-50s ^-1 , and the strain range to be 20-100%, to obtain an oriented flat film. 8. the preparation method of a kind of ultra-high molecular weight polyethylene microfiltration membrane according to claim 1 is characterized in that, the stretching process described in step (2) adopts the following steps: The stretching machine stretches and orients the flat film, the stretching temperature is 40-100°C, the stretching rate is 50-100mm/min, and the stretching strain is 100-300%. 9. the preparation method of a kind of ultrahigh molecular weight polyethylene microfiltration membrane according to claim 1 is characterized in that, the extractant described in step (3) is selected from dehydrated alcohol, glycerol, n-butyl alcohol or chloroform one or a combination of several. 10. the preparation method of a kind of ultra-high molecular weight polyethylene microfiltration membrane according to claim 1 is characterized in that, the drying temperature described in step (4) drying and annealing setting is 80 ℃, and drying time is 3h, The annealing temperature is 110°C, and the annealing time is 10h.

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