CN116078180A

CN116078180A - Reinforced hollow fiber porous composite membrane and preparation method thereof

Info

Publication number: CN116078180A
Application number: CN202211515886.4A
Authority: CN
Inventors: 马旭敏; 冯威; 王涛; 李勇
Original assignee: Shandong Dongyue Polymer Material Co Ltd
Current assignee: Shandong Dongyue Polymer Material Co Ltd
Priority date: 2022-11-29
Filing date: 2022-11-29
Publication date: 2023-05-09

Abstract

The invention belongs to the technical field of high polymer separation membranes, and particularly relates to an enhanced hollow fiber porous composite membrane and a preparation method thereof. The lining reinforcing material used by the porous composite membrane is a woven tube; the polymer film material used for casting the film forms a separation skin layer on the outer wall of the crochet tube, and simultaneously forms a sponge layer on the needle hole and/or the inner wall of the crochet tube, and the separation skin layer and the sponge layer form an embedded anchoring structure for the crochet tube. The preparation method of the reinforced hollow fiber porous composite membrane comprises the following steps: (1) preparing a casting solution; (2) wet spinning; (3) film yarn post-treatment. The porous composite membrane has high mechanical property, and the risk of peeling of the hollow fiber porous composite membrane in the use process is greatly avoided. The preparation method is directly operated on the existing wet spinning equipment, does not need complex pretreatment procedures such as corona, degreasing and the like on the lining reinforcing material, and does not need to carry out large-scale modification on the wet spinning equipment.

Description

Reinforced hollow fiber porous composite membrane and preparation method thereof

Technical Field

The invention belongs to the technical field of high polymer separation membranes, and particularly relates to an enhanced hollow fiber porous composite membrane and a preparation method thereof.

Background

The porous separating membrane of high molecular polymer has asymmetric structure, and the separating pore diameter can be regulated and controlled according to the formula and the production process, so that the porous separating membrane can be widely applied to the water treatment fields of industry, municipal sewage treatment, drinking water purification, reclaimed water recycling and the like. The existing mature membrane preparation methods comprise a thermal induced phase separation method (TIPS) and a non-solvent induced phase separation method (NIPS), wherein the porous membrane prepared by the TIPS method has high strength and large flux, but has no compact separation layer and low separation precision; the NIPS method has simple process, and the prepared membrane has high separation precision, good hydrophilicity and low mechanical strength, so that the membrane is easy to break when the hollow fiber membrane runs in a severe water quality environment for a long time, and the water quality of the effluent is deteriorated, the filtration efficiency is reduced and the like.

In order to solve the strength problem of the fiber membrane, more and more researches are conducted on the reinforced hollow fiber composite membrane, and the reinforced hollow fiber composite membrane is widely used. At present, a long fiber and braided fabric reinforcing method is mainly adopted, a braided tube is prepared from materials such as polyester fiber, polyamide fiber, polyolefin fiber and polyacrylonitrile fiber through a braiding process to be used as a lining reinforcing material, a casting solution is uniformly coated on the surface of the braided tube by using a spinneret plate to form a separation layer, a NIPS method is utilized to form a film, and the prepared hollow fiber porous composite film is widely applied to municipal sewage treatment MBR (membrane bioreactor) processes, immersed ultrafiltration processes and the like.

For the tensile fracture strength of the reinforced hollow fiber membrane, depending on the fracture strength of the lining reinforcing material, although the prior art adopts a woven tube as the reinforcing support tube to meet the requirement of the fracture strength, the service life of the porous membrane also depends on the interface bonding strength between the separation layer of the membrane and the support layer of the support tube to a great extent, the use stability of the fiber membrane is improved due to high bonding strength, however, the casting solution is difficult to permeate due to high weaving density of the woven tube, so that the bonding between the separation layer formed on the surface of the woven tube and the interface of the support layer of the woven tube is not firm enough, and thus the separation layer of the woven tube reinforced porous membrane is easy to peel off in the operation process, and finally the effluent is not up to standard.

In order to solve the problem of interfacial bonding force between a separation layer and a support layer of a woven tube enhanced porous membrane, the prior art adopts the following methods:

(1) The surface of the braided tube is modified in the following specific modes:

patent CN104117289a discloses a reinforced composite support hollow fiber membrane and a preparation method thereof, which is to adopt corona treatment to make the surface of a braided tube rough, and adopt NIPS method spinning after heat setting at 150-250 ℃ to increase the binding force between a transition layer and a support tube.

Patent CN101357303A discloses a preparation method of a polyvinylidene fluoride hollow fiber composite microporous membrane with strong interfacial binding force, which comprises the steps of firstly coating a braided tube with amphiphilic or neutral dilute polymer solution with concentration of 3% -10%, then drying the treated braided tube at 40-80 ℃, coating the dried braided tube with casting solution for the second time, and entering coagulation bath gel for film formation.

The patent CN102430348A and CN102512992A are used for degreasing and chemical modification treatment of the braided tube, the method needs strong alkali treatment, and the braided tube is damaged by adopting the strong alkali treatment, so that the breaking strength of the membrane wires is reduced, the service life of the membrane wires is prolonged, and the operation process is relatively complex.

The above-mentioned method of modifying the surface of the woven tube makes the preparation process of the fiber membrane relatively complex, which is not beneficial to large-scale industrialized production.

(2) The inside of the braided tube is filled with other solutions in the following specific modes:

patent CN104888621A discloses a woven tube homogeneous reinforced polyvinylidene fluoride hollow fiber membrane and a preparation method thereof, wherein a low-concentration PVDF solution is adopted to soak a woven support tube, so that PVDF permeates into the inner side of the support tube, then a high-concentration casting solution is used to coat the soaked support tube, and the high-concentration material and the low-concentration material are the same. However, in the preparation process of the fiber membrane, if the woven tube is improperly selected, the casting solution can be immersed into the hollow fiber tube to block the water passage, so that quality defects are caused.

The patent CN101254420A uses a high polymer solution with certain viscosity as a core solution to block the wall and the central hole of a woven tube, and then coats a casting solution outside the woven tube to prepare membrane wires by using an NIPS process. And the method is also relatively complex.

It can be seen that these methods, although improving the bonding strength between the polymer separation layer and the woven tube support layer, affect the flux of the hollow fiber membrane and the preparation process of the fiber membrane is relatively complicated.

Therefore, there is a need for an enhanced hollow fiber porous composite membrane that can ensure the strength of the composite membrane while also not affecting the permeation flux of the hollow fiber porous composite membrane.

Disclosure of Invention

The invention aims to provide a reinforced hollow fiber porous composite membrane, which adopts a woven tube as a lining reinforcing material, and a polymer membrane material for casting the membrane permeates pinholes of the lining reinforcing material woven tube or the inner wall surface of the woven tube, so that the polymer membrane material not only can form a compact separation skin layer on the outer wall of the woven tube, but also can form a loose sponge layer on the pinholes or the inner wall surface of the woven tube, and the compact separation skin layer and the loose sponge layer form an embedded anchoring structure for the woven tube, so that a bonding force with high peeling strength is formed between the separation skin layer and a supporting interface of the woven tube, and the separation skin layer is not easy to separate; meanwhile, the polymer membrane material only permeates into pinholes of the woven tube, and at most, the polymer membrane material is not blocked on the inner wall surface of the woven tube, so that the permeation flux of the composite membrane is high, and the composite membrane is suitable for industrial production.

The specific technical scheme is as follows:

the reinforced hollow fiber porous composite membrane has a hollow tubular structure, and the lining reinforcing material used by the reinforced hollow fiber porous composite membrane is a woven tube; the polymer film material used for casting the film forms a separation skin layer on the outer wall of the crochet tube, and simultaneously forms a sponge layer on the needle hole and/or the inner wall of the crochet tube, and the separation skin layer and the sponge layer form an embedded anchoring structure for the crochet tube.

The crochet pipe is a hollow fiber supporting pipe produced by a crochet process. The number of pinholes, i.e. the mesh size of the woven tube, between each bundle of fibers of the woven tube is a number due to the different weaving process, as shown in fig. 1. The woven tube plays a main role in strengthening in the composite membrane, a denser separation cortex structure formed by the polymer membrane material plays a role in separating, and a loose sponge layer structure plays a role in assisting in strengthening, and the loose sponge layer in the composite membrane is of a sponge-like hole structure unlike a large cavity or finger-like hole structure of the reinforced composite membrane in the prior art, so that the pressure resistance of the composite membrane can be improved, and the defect that a hollow fiber membrane has large holes due to improper control of a spinning process or burrs on the woven tube can be effectively reduced.

Further, the outer diameter of the woven tube in the reinforced hollow fiber porous composite membrane is 1.0-3.0mm; the mesh number of the crochet is 25-40 mesh. The mesh number of the crochet tube refers to the number of pinholes in a 25.4mm long crochet tube. The number of pinholes can reflect the crochet density of the crochet tube, and the less the number of pinholes is, the denser the crochet is.

Preferably, the outside diameter of the woven tube is 1.2-2.5mm.

Further, the woven fiber of the woven tube in the reinforced hollow fiber porous composite membrane is one selected from polyester fiber, polyamide fiber, polyolefin fiber and polyacrylonitrile fiber.

Further, the polymer membrane material used for casting the reinforced hollow fiber porous composite membrane is selected from one of polyvinylidene fluoride (PVDF), polyvinylidene fluoride-chlorotrifluoroethylene P (VDF-CTFE), polyvinyl chloride (PVC), polyacrylonitrile (PAN), polysulfone (PSF) or polyether sulfone (PES).

Further, the thickness of the casting solution coating forming the separation skin layer in the reinforced hollow fiber porous composite membrane is 40-150 mu m. The thickness herein refers only to the thickness of the coating of the casting solution on the outer wall of the woven tube.

The separation skin layer is finally formed by a polymer, such as one of polyvinylidene fluoride, polyvinylidene fluoride-chlorotrifluoroethylene, polyvinyl chloride, polyacrylonitrile, polysulfone or polyethersulfone, which is insoluble in water to form a skeleton of the separation skin layer; other additives, solvents and non-solvents mainly function to form pores, adjust the viscosity of the casting solution and the phase separation speed, wherein part of the solution enters a coagulating bath after phase inversion, and part of the solution stays in the polymer pores and gradually runs off in the use process of the film; the thickness of the final separation skin layer refers to the thickness of the dry film as shown in g in fig. 3, which is seen under an optical microscope or an electron microscope.

Further, the porosity of the reinforced hollow fiber porous composite membrane is 55% -80%; the bursting strength is 0.4-0.9MPa; the bubble point pressure of the ethanol is 0.05-0.21MPa; the pure water flux of the composite membrane under the conditions of 0.1MPa and 25 ℃ is 800-1600L/(squaremeter h). The bursting strength of the hollow fiber membrane is over 0.2MPa, the pure water flux at 0.1MPa and 25 ℃ is over 400L/(squaremeter h), and the use requirement of the water treatment field on the membrane can be met.

The size of the ethanol bubble point pressure indirectly reflects the pore size and defect number of the membrane, i.e., the larger the ethanol bubble point pressure, the smaller the pore size of the membrane. The porosity indirectly reflects the porosity of the membrane, and the flux of the fiber membrane is not only related to the compactness of the separation cortex of the fiber membrane, but also related to the porosity of the fiber membrane, and generally, the higher the porosity of the membrane is, the higher the flux of the fiber membrane is.

The invention also aims to provide a preparation method of the reinforced hollow fiber porous composite membrane, by which the embedded anchoring structure of the woven tube can be obtained directly through wet spinning without any pretreatment on the woven tube lined with the reinforced material.

The specific technical scheme is as follows:

The preparation method of the reinforced hollow fiber porous composite membrane comprises the following steps:

(1) Preparing a casting film liquid: firstly, uniformly mixing and stirring a solvent, an additive and a non-solvent, then adding a polymer film material, mixing and stirring, heating to 50-90 ℃ to dissolve the polymer film material, and uniformly stirring to form a film casting solution; vacuumizing, standing and defoaming for standby; after the polymer membrane material is stirred and swelled, the molecular chain of the polymer is relaxed and can be better dissolved.

(2) Wet spinning: firstly, co-extruding a lining reinforcing material crocheted pipe and the casting film liquid prepared in the step (1) through a spinneret plate in wet spinning equipment to obtain primary film yarns, wherein the viscosity of the casting film liquid is controlled to be 20000-100000 mPa.s; then the primary membrane silk vertically enters a coagulating bath after passing through an air section, and the water depth of the primary membrane silk in the coagulating bath is 60-180cm; the primary film yarn enters a rinsing tank for rinsing after reaching the water inlet depth, and is collected and cut by a winding machine after rinsing; the cut film yarn is soaked in pure water.

The water depth refers to the distance between the water surface of the coagulating bath and the first godet wheel after the nascent film yarn enters the coagulating bath. The water depth can be adjusted and controlled by moving a guide rod connected with the first godet wheel up and down.

(3) Film yarn post-treatment: firstly, taking out and draining the membrane filaments soaked in pure water in the step (2), and then taking out and airing the drained membrane filaments after soaking in a protective solution to obtain the reinforced hollow fiber porous composite membrane.

Firstly, the lining reinforcing material selected by the invention is a woven pipe, and the woven pipe is different from the woven pipe in that: the woven tube has high weaving density, and the woven tube has high porosity, so that the seepage of the woven tube is extremely easy to be overlarge, and the water producing channel inside the woven tube is blocked. In order to solve the problem of serious seepage of the woven tube, the prior art means firstly greatly improves the viscosity of the casting solution, generally the viscosity of the casting solution is 60000-120000 mPa.s during spinning, and reduces the seepage by increasing the viscosity of the casting solution, thereby avoiding blocking the water producing channel of the woven tube, and greatly limiting the range of the available casting solution; in addition, by increasing the polymer content to increase the viscosity of the casting solution, not only the cost of film production increases, but also the adhesiveness between the casting solution and the woven tube decreases, and peeling is easy; the porosity of the hollow fiber membrane is reduced and the flux is reduced.

The other prior art means is to pre-treat the woven tube, firstly fill part of surface holes of the woven tube by soaking solution, reduce the porosity to reduce the infiltration of the material, thereby avoiding the blockage of the water producing channel of the woven tube caused by serious infiltration in the subsequent wet spinning process, and the process of the fiber membrane is relatively complex like the weaving of the tube.

The invention does not need any pretreatment on the woven tube, and directly regulates and controls the degree of the polymer film material penetrating into the woven tube through the cooperative matching between the viscosity of the casting solution and the water inlet depth in the wet spinning process of the existing wet spinning equipment, so as to ensure that the polymer film material penetrates into pinholes of the woven tube or slightly penetrates into the surface of the inner wall of the woven tube, and the phenomenon that a fiber film cannot be used due to blockage of water producing holes is avoided. Therefore, the invention is still carried out according to the necessary working procedures of the existing wet spinning, and other working procedures are not required to be additionally added, so that the production cost including the production time cost, the labor cost, the raw material cost and the like cannot be increased. Meanwhile, the viscosity of the casting solution is not limited to be high, and the problem of serious seepage can be avoided by adopting the casting solution with low viscosity, so that the variety or type of the available casting solution is enlarged.

More unexpected, through the synergistic effect that the viscosity of casting solution and the depth of entering water are properly distinguished, the polymer film material can form a separation skin layer on the outer wall of the crochet tube, and simultaneously a sponge layer is formed on the needle hole and/or the inner wall of the crochet tube, and the separation skin layer and the sponge layer just form an embedded anchoring structure to the crochet tube, thereby realizing the structure of the composite film with the polymer film material anchoring crochet tube, and solving the problem of weak bonding force between the separation layer and the supporting interface.

Further, in the step (1) of the preparation method of the reinforced hollow fiber porous composite membrane, the solvent contained in the casting solution is 51-73.5 wt%, the additive is 10-30 wt%, the non-solvent is 0.5-4 wt% and the polymer membrane material is 15-25 wt%.

Further, in the step (1) of the preparation method of the reinforced hollow fiber porous composite membrane, the solvent is one of N, N-dimethylacetamide (DMAc), N-Dimethylformamide (DMF), dimethyl sulfoxide (DMSO) and N-methyl pyrrolidone (NMP);

the additive is at least composed of polyethylene glycol (PEG), tween and polyvinylpyrrolidone (PVP). The membrane silk after the coagulation bath, the rinsing tank, the pure water soaking and the protection treatment by the protection liquid also contains most PVP, a little PEG and tween.

Preferably, the polyethylene glycol has a number average molecular weight of 200-20000; more preferably, the polyethylene glycol is at least one of PEG400, PEG1000, PEG2000 and PEG 8000.

Preferably, the tween is tween 80.

Preferably, the polyvinylpyrrolidone has a number average molecular weight of 10000-650000; more preferably, the polyvinylpyrrolidone is at least one of PVPK17, PVPK30 and PVPK 90. The molecular weight of PVPK90 is typically 630000.

The non-solvent is glycerol or deionized water;

further, in the step (2) of the preparation method of the reinforced hollow fiber porous composite membrane, the viscosity of the casting solution is controlled to 25000-50000 mPa.s.

The spinning temperature through the spinneret plate in the step (2) is 50-75 ℃; the spinning speed is 15-35m/min. The spinning speed comprehensively considers the membrane pore structure and the yield, not only ensures a certain yield, but also ensures that the membrane is completely formed into a required pore structure in the coagulation bath.

The spinning speed and the spinning temperature are mutually matched technological parameters, the spinning temperature is low, the viscosity of the casting solution is high, the speed is required to be slow, or else the casting solution is difficult to infiltrate into the needle holes of the crochet tube; the spinning temperature is high, the viscosity of the casting solution is low, so that the casting solution is easier to permeate into pinholes, and the spinning speed can be relatively high.

Further, in the step (2) of the preparation method of the reinforced hollow fiber porous composite membrane, the height of the air section through which the primary membrane filaments pass is 10-30cm. The height of the air segment affects the open cell content of the film surface according to the mechanism of solvent evaporation pore formation.

Further, in the step (2) of the preparation method of the reinforced hollow fiber porous composite membrane, the coagulating bath is water or solvent aqueous solution with the mass fraction of less than or equal to 50%, wherein the solvent is the same as that of the casting solution. According to a solvent phase inversion (NIPS) film-making mechanism, the coagulating bath and the casting film liquid are mutually cooperated to jointly regulate and control the pore structure and the permeation separation performance of the composite film.

Further, the temperature of the solidifying bath in the step (2) of the preparation method of the reinforced hollow fiber porous composite membrane is 35-60 ℃.

Further, the rinsing liquid of the rinsing tank in the step (2) of the preparation method of the enhanced hollow fiber porous composite membrane is pure water; the temperature of the rinsing liquid in the rinsing tank is 30-45 ℃.

Further, the protective solution for membrane filament aftertreatment in the step (3) of the preparation method of the enhanced hollow fiber porous composite membrane comprises the following components: water; 15-35% of glycerin and 50-100ppm of bactericide kathon.

The beneficial effects of the invention are as follows:

the reinforced hollow fiber porous composite membrane adopts the woven tube as the lining reinforcing material, so that the mechanical property of the composite membrane is greatly improved, the bursting strength reaches 0.9MPa, the density of the woven tube is lower than that of the woven tube, and the reinforced hollow fiber porous composite membrane is beneficial to energy conservation and consumption reduction in the use process of water treatment. The polymer membrane material has an embedded anchoring effect on the woven tube, so that the binding force of the two materials is greatly improved, the bursting strength of the membrane wires is high, and the risk of peeling of the hollow fiber porous composite membrane in the use process is greatly avoided.

Meanwhile, the hollow fiber porous composite membrane has large permeation flux, the pure water flux at 0.1MPa and 25 ℃ can reach 1600L/square meter h, and the use requirement of the hollow fiber porous composite membrane is improved by 2-4 times compared with that of a water treatment fiber membrane.

The preparation method of the hollow fiber porous composite membrane is directly operated on the existing wet spinning equipment, does not need complex pretreatment procedures such as corona, degreasing and the like for lining reinforcing materials, and does not need large-scale modification for the wet spinning equipment. Reduces the pretreatment cost and simplifies the spinning process.

According to the preparation method, through perfect matching of the water inlet depth of the nascent membrane filaments in the coagulating bath and the viscosity of the casting solution, the balance relation between the hydrostatic pressure and the phase separation speed is regulated, the depth of the casting solution penetrating into the woven tube and the thickness of the casting solution coated on the outer wall of the woven tube are accurately controlled, the effect that the penetration flux of the hollow fiber membrane and the coating thickness of the casting solution are not influenced while the polymer membrane material anchoring woven tube structure is formed is achieved, and the large-scale continuous production is facilitated.

Drawings

FIG. 1 is a schematic view of the internal structure of the woven tube of the present invention.

Fig. 2 is a diagram of a wet spinning process apparatus used in an embodiment of the present invention.

FIG. 3 is an electron microscopic image of the whole cross section of the PVDF ultrafiltration membrane based on the woven tube prepared in example 1 of the present invention.

FIG. 4 is a partial profile electron microscope image of the membrane cross section of the PVDF ultrafiltration membrane of example 1 of the present invention.

FIG. 5 is a film section overall morphology electron microscopy image of a woven tube-based PVDF ultrafiltration film of comparative example 2 of the present invention.

FIG. 6 is a partial profile electron microscopy image of the membrane cross section of a woven tube-based PVDF ultrafiltration membrane of comparative example 3 of the present invention.

Wherein, 1 is a woven pipe, 2 is a spinneret plate, 3 is a metering pump, 4 is a casting solution container, 5 is an air section, 6 is a water inlet depth, 7 is a guide wheel, 8 is a guide screw, 9 is a coagulation bath, 10 is a rinsing tank, 11 is a winding machine, and 12 is a hollow fiber porous composite membrane.

Detailed Description

The technical scheme of the invention is described in detail below with reference to the accompanying drawings.

1. The method for testing the porosity of the hollow fiber porous composite membrane comprises the following steps: determining pore volume V of the membrane by weighing based on the change in weight of the wetted water of the membrane _Hole(s) The method comprises the steps of carrying out a first treatment on the surface of the The membrane skeleton volume V _{Membrane framework} Obtainable by film raw material density and dry film weight, the film has a porosity of ε=V _Hole(s) /(V _Hole(s) +V _{Membrane framework} )。

2. Ethanol bubble point pressure test method: placing the prepared reinforced hollow fiber porous composite membrane in absolute ethyl alcohol, and soaking for 10 minutes at the temperature of 25 ℃; and placing the pre-infiltrated sample in a tester of a bubble point pressure-flow tester, infiltrating the membrane wire in absolute ethyl alcohol, adjusting the pressure of the tester, stopping boosting when the first and continuous bubbles appear in the tester, and recording the pressure value at the moment as the bubble point pressure of the alcohol.

3. Thickness of dry film separation skin: the thickness of the dry film separation skin layer was tested using an optical microscope.

4. The test method of the pure water flux of the composite porous membrane comprises the following steps: when the pure water flux is measured, pure water passes through the porous membrane at the pressure of 0.1MPa and the temperature of 25 ℃, and the total volume of the pure water passing through the porous membrane in unit area per unit time is measured by adopting a bubble point pressure-flow tester.

Pure water flux was calculated according to the formula j=q/a·t.

Wherein J-fluid flux, L/-square meter h; q-sample test flux, L; a-area of sample, m ² The method comprises the steps of carrying out a first treatment on the surface of the t-test time, h.

5. The method for testing the burst pressure of the membrane wires comprises the following steps: the burst pressure of the membrane wire is measured by adopting an internal pressure dead-end filtering mode, and the burst pressure of the membrane wire is measured by reversely pumping high-pressure gas.

Example 1

The adopted lining reinforcing material is selected from the following crochet pipes: a polyester fiber woven tube with the outer diameter of 1.30mm and 32 meshes of pinholes is selected.

(1) Preparing a casting film liquid: first 3025g (60.5 wt%) of solvent NMP, additives (19 wt%) consisting of 250g PEG400, 150g PEG2000, 500g PVPK17 and 50g Tween 80, and 75g (1.5 wt%) of non-solvent deionized water were sequentially added to a 10L stirring vessel, stirred for 15min, then 950g (19 wt%) of polymer film material PVDF powder was added and stirred for 30min, then the heating switch of the stirring vessel was turned on, the heating temperature was set to 80℃and stirred and dissolved until a uniform solution was formed. Reducing the stirring speed, vacuumizing, standing, preserving heat and defoaming to obtain the casting solution for later use.

(2) Wet spinning:

first, the parameters were set as follows: the spinneret plate heating sleeve is set to 70 ℃ (controlled by a circulating water heating sleeve outside the spinneret plate); the viscosity of the casting solution at this temperature was 41000 mPa.s; the coagulation bath was a 50wt% NMP solution, the temperature was set at 40 ℃; the spinning speed is set to be 20m/min, the height of an air section is adjusted to be 15cm, the water inlet depth is set to be 120cm, the rinsing liquid in the rinsing water tank is pure water, and the temperature is 40 ℃;

then, after the setting of each parameter is completed and the setting condition is reached, opening a valve and a metering pump for spinning:

co-extruding the crochet hook tube and the casting solution to obtain a primary membrane wire;

the primary membrane yarn vertically enters into a coagulating bath after passing through an air section;

the primary membrane filaments enter a rinsing tank for rinsing after reaching the water entering depth;

after rinsing, collecting and cutting the filaments by a winding machine; the wound and cut film yarn was rinsed in pure water at 35 ℃ for 24 hours.

(3) Film yarn post-treatment: firstly, taking out and draining membrane filaments soaked in pure water; and then soaking the drained membrane filaments in an aqueous solution consisting of 20wt% of glycerol and 50ppm of kathon for 4 hours, wherein the temperature of the protective solution is 35 ℃, taking out the membrane filaments after the soaking is finished, and airing the membrane filaments to obtain the hollow fiber porous composite membrane.

As shown in fig. 3 and 4, a is a hollow fiber porous composite membrane obtained in this embodiment, b is a conductive adhesive for fixing the hollow fiber membrane when an electron microscope photograph is taken, c is a polymer coating formed by a casting solution after being co-extruded with a woven tube and sequentially subjected to immersion and air drying of a coagulation bath, a rinsing bath, a winding machine and an immersion liquid, d is a woven tube, e is a woven fiber, f is a pinhole of the woven tube, and g is a thickness of a dry film separation skin layer.

Example 2

The adopted lining reinforcing material is selected from the following crochet pipes: a polyamide fiber woven tube with an outer diameter of 1.45mm and a pinhole number of 25 meshes is selected.

(1) Preparing a casting film liquid: 2975g (51.7 wt%) of solvent DMAc, additive (30 wt%) composed of 1000g PEG1000, 600g PVPK30, 50g PVPK90 and 75g Tween 80, and 150g (2.6 wt%) of non-solvent glycerin were sequentially added to a 10L stirring kettle, stirred for 15min, then 900g (15.7 wt%) of polymer film material PVDF powder was added and stirred for 30min, then a heating switch of the stirring kettle was turned on, the heating temperature was set to 80 ℃, and stirring and dissolution were carried out until a uniform solution was formed. Reducing the stirring speed, vacuumizing, standing, preserving heat and defoaming to obtain the casting solution for later use.

(2) Wet spinning:

first, the parameters were set as follows: the spinneret plate heating sleeve is set to 60 ℃ (controlled by a circulating water heating sleeve outside the spinneret plate); the viscosity of the casting solution at this temperature was 38500 mPa.s; the coagulation bath was a 30wt% DMAc solution, the temperature was set at 45 ℃; the spinning speed is set to 25m/min, the height of the air section is adjusted to 10cm, the water inlet depth is set to 180cm, the rinsing liquid in the rinsing water tank is pure water, and the temperature is 40 ℃;

(3) Film yarn post-treatment: firstly, taking out and draining membrane filaments soaked in pure water; and then soaking the drained membrane filaments in an aqueous solution consisting of 15wt% of glycerol and 100ppm of kathon for 4 hours, wherein the temperature of the protective solution is 35 ℃, and taking out and airing after the soaking is finished, thus obtaining the hollow fiber porous composite membrane.

Example 3

The adopted lining reinforcing material is selected from the following crochet pipes: the polyolefin fiber woven tube with the outer diameter of 2.5mm and the pinhole number of 35 meshes is selected.

(1) Preparing a casting film liquid: 3275g (65.5 wt%) of solvent DMAc, additive (15.5 wt%) composed of 250g PEG400, 200g PEG8000, 250g PVPK30 and 75g Tween 80 and 100g (2.0 wt%) of non-solvent glycerine were added into 10L stirring kettle in turn, after stirring for 15min, 850g (17.0 wt%) of polymer film material P (VDF-CTFE) powder was added and stirred for 30min, then the heating switch of stirring kettle was turned on, the heating temperature was set to 80 deg.C, and stirring was carried out until a uniform solution was formed. Reducing the stirring speed, vacuumizing, standing, preserving heat and defoaming to obtain the casting solution for later use.

(2) Wet spinning:

first, the parameters were set as follows: the spinneret plate heating sleeve is set to 55 ℃ (controlled by a circulating water heating sleeve outside the spinneret plate); the viscosity of the casting solution at this temperature was 25500 mPa.s; the coagulation bath was a 40wt% DMAc solution, the temperature was set at 45 ℃; the spinning speed is set to be 15m/min, the height of the air section is adjusted to be 20cm, the water inlet depth is set to be 150cm, the rinsing liquid in the rinsing water tank is pure water, and the temperature is 40 ℃;

(3) Film yarn post-treatment: firstly, taking out and draining membrane filaments soaked in pure water; and then soaking the drained membrane filaments in an aqueous solution consisting of 25wt% of glycerol and 60ppm of kathon for 4 hours, wherein the temperature of the protective solution is 35 ℃, and taking out and airing after the soaking is finished, thus obtaining the hollow fiber porous composite membrane.

Example 4

The adopted lining reinforcing material is selected from the following crochet pipes: the polyacrylonitrile fiber woven tube with the outer diameter of 1.8mm and the pinhole number of 30 meshes is selected.

(1) Preparing a casting film liquid: first 3025g (60.5 wt%) of solvent DMF, additive (19.0 wt%) composed of 250g PEG400, 400g PEG2000, 250g PVPK30 and 50g Tween 80, and 25g (0.5 wt%) of non-solvent deionized water were sequentially added to a 10L stirred tank, stirred for 15min, then 1000g (20.0 wt%) of polymer film material PAN powder was added and stirred for 30min, then the heated switch of the stirred tank was turned on, the heating temperature was set to 80℃and stirred and dissolved until a uniform solution was formed. Reducing the stirring speed, vacuumizing, standing, preserving heat and defoaming to obtain the casting solution for later use.

(2) Wet spinning:

first, the parameters were set as follows: the spinneret plate heating sleeve is set to 60 ℃ (controlled by a circulating water heating sleeve outside the spinneret plate); the viscosity of the casting solution at this temperature was 32000 mPa.s; the coagulation bath is a 40wt% DMF solution, and the temperature is set to 45 ℃; the spinning speed is set to be 20m/min, the height of the air section is adjusted to be 25cm, the water inlet depth is set to be 80cm, the rinsing liquid in the rinsing water tank is pure water, and the temperature is 40 ℃;

Because the crochet tube and the coating material are the same, the combination of the polymer and the crochet tube is tighter, and the bursting pressure is greatly improved.

Example 5

(1) Preparing a casting film liquid: firstly, 3100g (62 wt%) of solvent DMSO, additive (18.0 wt%) consisting of 250g of PEG400, 500g of PVPK17, 50g of PVPK90 and 100g of Tween 80 and 50g (1.0 wt%) of non-solvent deionized water are added into a 10L stirring kettle in sequence, after stirring for 15min, 950g (19.0 wt%) of polymer film material PVC powder is added and stirred for 30min, then a heating switch of the stirring kettle is started, the heating temperature is set to 80 ℃, and stirring and dissolving are carried out until a uniform solution is formed. Reducing the stirring speed, vacuumizing, standing, preserving heat and defoaming to obtain the casting solution for later use.

(2) Wet spinning:

first, the parameters were set as follows: the spinneret plate heating sleeve is set to be 50 ℃ (controlled by a circulating water heating sleeve outside the spinneret plate); the viscosity of the casting solution at this temperature was 35400 mPa.s; the coagulation bath is a 35wt% DMSO solution, and the temperature is set to 55 ℃; the spinning speed is set to 25m/min, the height of the air section is adjusted to 20cm, the water inlet depth is set to 170cm, the rinsing liquid in the rinsing water tank is pure water, and the temperature is 40 ℃;

(3) Film yarn post-treatment: firstly, taking out and draining membrane filaments soaked in pure water; and then soaking the drained membrane filaments in an aqueous solution consisting of 30wt% of glycerol and 75ppm of kathon for 4 hours, wherein the temperature of the protective solution is 35 ℃, and taking out and airing after the soaking is finished, thus obtaining the hollow fiber porous composite membrane.

Example 6

The adopted lining reinforcing material is selected from the following crochet pipes: the polyester fiber woven tube with the outer diameter of 1.5mm and the pinhole number of 40 meshes is selected.

(1) Preparing a casting film liquid: 2700g (54 wt%) of solvent DMAc, 400g of PEG400, 150g of PEG8000, 350g of PVPK30 and 100g of Tween 80 (20.0 wt%) and 150g (3.0 wt%) of non-solvent deionized water are sequentially added into a 10L stirring kettle, after stirring for 15min, 1150g (23.0 wt%) of polymer film material PS powder is added and stirred for 30min, then a heating switch of the stirring kettle is started, the heating temperature is set to 80 ℃, and stirring and dissolving are carried out until a uniform solution is formed. Reducing the stirring speed, vacuumizing, standing, preserving heat and defoaming to obtain the casting solution for later use.

(2) Wet spinning:

first, the parameters were set as follows: the spinneret plate heating sleeve is set to be 50 ℃ (controlled by a circulating water heating sleeve outside the spinneret plate); the viscosity of the casting solution at this temperature was 21500 mPas; the coagulating bath is pure water, and the temperature is set to 45 ℃; the spinning speed is set to be 30m/min, the height of the air section is adjusted to be 15cm, the water inlet depth is set to be 60cm, the rinsing liquid in the rinsing water tank is pure water, and the temperature is 40 ℃;

(3) Film yarn post-treatment: firstly, taking out and draining membrane filaments soaked in pure water; and then soaking the drained membrane filaments in an aqueous solution consisting of 20wt% of glycerol and 75ppm of kathon for 4 hours, wherein the temperature of the protective solution is 35 ℃, and taking out and airing after the soaking is finished, thus obtaining the hollow fiber porous composite membrane.

Example 7

The adopted lining reinforcing material is selected from the following crochet pipes: a polyamide fiber woven tube with an outer diameter of 1.3mm and a pinhole number of 35 meshes is selected.

(1) Preparing a casting film liquid: 3000g (58.8 wt%) of solvent DMAc, an additive (19.6 wt%) consisting of 500g PEG400, 250g PEG8000, 200g PVPK30 and 50g Tween 80, and 150g (2.9 wt%) of non-solvent glycerol were added sequentially to a 10L stirred tank, stirred for 15min, 950g (18.6 wt%) of polymer film material PES powder was added and stirred for 30min, and then the stirred tank heating switch was turned on, the heating temperature was set to 80℃and stirred and dissolved until a uniform solution was formed. Reducing the stirring speed, vacuumizing, standing, preserving heat and defoaming to obtain the casting solution for later use.

(2) Wet spinning:

first, the parameters were set as follows: the spinneret plate heating sleeve is set to 65 ℃ (controlled by a circulating water heating sleeve outside the spinneret plate); the viscosity of the casting solution at this temperature was 24500 mPa.s; the coagulation bath is 30% DMAc solution, and the temperature is set to 55 ℃; the spinning speed is set to 25m/min, the height of the air section is adjusted to 15cm, the water inlet depth is set to 90cm, the rinsing liquid in the rinsing water tank is pure water, and the temperature is 40 ℃;

(3) Film yarn post-treatment: firstly, taking out and draining membrane filaments soaked in pure water; and then soaking the drained membrane filaments in an aqueous solution consisting of 25wt% of glycerol and 75ppm of kathon for 4 hours, wherein the temperature of the protective solution is 35 ℃, and taking out and airing after the soaking is finished, thus obtaining the hollow fiber porous composite membrane.

Comparative example 1

(1) Preparing a casting solution (without non-solvent): firstly, 3200g (64 wt%) of solvent NMP, 250g of PEG400, 150g of PEG2000, 500g of PVPK17 and 50g of Tween 80 (19 wt%) are added into a 10L stirring kettle in turn, after stirring for 15min, 850g (17 wt%) of polymer film material PVDF powder is added, stirring is carried out for 30min, then a heating switch of the stirring kettle is started, the heating temperature is set to 80 ℃, and stirring and dissolving are carried out until a uniform solution is formed. Reducing the stirring speed, vacuumizing, standing, preserving heat and defoaming to obtain the casting solution for later use.

(2) Wet spinning:

first, the parameters were set as follows: the spinneret plate heating sleeve is set to 70 ℃ (controlled by a circulating water heating sleeve outside the spinneret plate); the viscosity of the casting solution at the temperature is 40500 mPa.s; the coagulation bath was a 50wt% NMP solution, the temperature was set at 40 ℃; the spinning speed is set to be 20m/min, the height of an air section is adjusted to be 15cm, the water inlet depth is set to be 105cm, the rinsing liquid in the rinsing water tank is pure water, and the temperature is 40 ℃;

Comparative example 2

This comparative example 2 is different from example 1 in that: an unmodified braided tube braided by polyester fibers is used as a lining reinforcing material.

Other than in example 1, the recipe and process parameter settings including the film wire were the same as in example 1.

As can be seen from fig. 5, the polymer membrane material of the hollow fiber membrane obtained in comparative example 2 was substantially at the outer wall of the woven tube, and did not form an anchoring structure with the woven tube.

Comparative example 3

This comparative example 3 differs from example 2 in that: an unmodified braided tube braided with polyamide fibers is used as a lining reinforcing material.

Other than in example 2, the recipe and process parameter settings including the film wire were the same as in example 2.

As is apparent from fig. 6, the membrane wire cross-section polymer and the woven tube of the hollow fiber membrane of comparative example 3 do not form an anchoring structure, the woven tube has a high woven density, and the polymer coating is substantially outside the woven tube, resulting in a poor flux and burst strength compared with the woven tube, further showing that the hollow fiber porous membrane of the present invention has the advantage of high membrane flux and burst pressure.

Comparative example 4

This comparative example 4 differs from example 3 in that: the depth of water was 210cm.

Other than in example 3, the recipe and process parameter settings including the film wire were the same as in example 3.

When the water depth is 210cm, normal membrane wires cannot be prepared, all the inside of the woven pipe is blocked by seepage, and the pure water flux is 0.

Comparative example 5

This comparative example 5 differs from example 5 in that: the depth of water is 50cm.

Other than in example 5, the recipe and process parameter settings including the film wire were the same as in example 5.

Compared with example 5, the casting solution has less penetration into the woven tube gaps due to the small water penetration depth, so that the bonding strength is not high, and the bursting strength is reduced compared with that of the woven tube.

The water inlet depth mainly influences the static pressure of the coagulating liquid in the coagulating bath, when the primary membrane yarn is too deep in the coagulating bath or contacts with the guide wheel before being solidified, serious seepage occurs, so that water producing holes of the hollow fibers are blocked, spinning fails, the phase separation speed and the water inlet depth of a formula system are controlled, and the phenomenon that the seepage blocks the water producing holes can be effectively prevented.

Comparative example 6

(1) Preparing a casting film liquid: first, 3212.5g (64.25 wt%) of solvent NMP, additive (19 wt%) composed of 250g PEG400, 150g PEG2000, 500g PVPK17 and 50g Tween 80, and 12.5g (0.25 wt%) of non-solvent deionized water were sequentially added to a 10L stirring vessel, stirred for 15min, then 825g (16.5 wt%) of polymer film material PVDF powder was added and stirred for 30min, then a heating switch of the stirring vessel was turned on, the heating temperature was set to 70℃and stirred and dissolved until a uniform solution was formed. Reducing the stirring speed, vacuumizing, standing, preserving heat and defoaming to obtain the casting solution for later use.

(2) Wet spinning:

first, the parameters were set as follows: the spinneret plate heating sleeve is set to 70 ℃ (controlled by a circulating water heating sleeve outside the spinneret plate); the viscosity of the casting solution at this temperature was 19000 mPa.s; the coagulation bath was a 50wt% NMP solution, the temperature was set at 40 ℃; the spinning speed is set to be 20m/min, the height of an air section is adjusted to be 15cm, the water inlet depth is set to be 120cm, the rinsing liquid in the rinsing water tank is pure water, and the temperature is 40 ℃;

Compared with example 1, the membrane silk ethanol bubble point pressure, pure water flux and bursting strength of comparative example 6 are all reduced, and it is seen that when the polymer content is too low, the viscosity of the casting solution is too low, and the non-solvent content in the formula is too low, the phase separation speed of the casting solution is slow, the coating under the spinning condition is thinner, thicker polymer cannot be coated, the seepage is serious, and spinning cannot be performed.

The performance indexes of the hollow fiber porous composite membranes obtained in each example and each comparative example are summarized in table 1 below.

Table 1 Performance index of each hollow fiber porous composite film

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(1) Comparative example 1 the pure water flux of the porous membrane of comparative example 1 was reduced by 7.5% and the burst strength was reduced by 19.0% as compared with example 1.

(2) Comparative example 2 the pure water flux of the porous membrane of comparative example 2 was reduced by 12.3% and the burst strength was reduced by 30.2% as compared with example 1.

(3) Comparative example 3 the pure water flux of the porous membrane of comparative example 3 was reduced by 10.4% and the burst strength was reduced by 17.7% as compared with example 2.

(4) Comparative example 5 the pure water flux of the porous membrane of comparative example 5 was reduced by 33.5% and the burst strength was reduced by 32.8% as compared with example 5.

(5) Comparative example 6 the pure water flux of the porous membrane of comparative example 6 was reduced by 28.5% and the burst strength was reduced by 33.3% as compared with example 1.

Claims

1. The reinforced hollow fiber porous composite membrane has a hollow tubular structure and is characterized in that a lining reinforcing material used for the reinforced hollow fiber porous composite membrane is a woven tube; the polymer film material used for casting the film forms a separation skin layer on the outer wall of the crochet tube, and simultaneously forms a sponge layer on the needle hole and/or the inner wall of the crochet tube, and the separation skin layer and the sponge layer form an embedded anchoring structure for the crochet tube.

2. The reinforced hollow fiber porous composite membrane of claim 1, wherein the woven tube has an outer diameter of 1.0-3.0mm; the mesh number of the crochet hook tube is 25-40 meshes;

preferably, the outside diameter of the woven tube is 1.2-2.5mm.

3. The reinforced hollow fiber porous composite membrane of claim 1, wherein the crocheted fibers of the crocheted tube are selected from one of polyester fibers, polyamide fibers, polyolefin fibers, or polyacrylonitrile fibers.

4. The reinforced hollow fiber porous composite membrane of claim 1, wherein the polymer membrane material is selected from one of polyvinylidene fluoride, polyvinylidene fluoride-chlorotrifluoroethylene, polyvinyl chloride, polyacrylonitrile, polysulfone, or polyethersulfone.

5. The reinforced hollow fiber porous composite membrane of claim 1, wherein the thickness of the dope forming the separation skin layer is 40-150 μm.

6. The reinforced hollow fiber porous composite membrane of any one of claims 1-5, wherein the composite membrane has a porosity of 55% to 80%; the bursting strength is 0.4-0.9MPa; the bubble point pressure of the ethanol is 0.05-0.21MPa; the pure water flux of the composite membrane under the conditions of 0.1MPa and 25 ℃ is 800-1600L/(squaremeter h).

7. The method for preparing the reinforced hollow fiber porous composite membrane according to any one of claims 1 to 5, comprising the steps of:

(1) Preparing a casting film liquid: firstly, uniformly mixing and stirring a solvent, an additive and a non-solvent, then adding a polymer film material, mixing and stirring, heating to 50-90 ℃ to dissolve the polymer film material, and uniformly stirring to form a film casting solution; vacuumizing, standing and defoaming for standby;

(2) Wet spinning: firstly, co-extruding a lining reinforcing material crocheted pipe and the casting solution prepared in the step (1) through a spinneret plate in wet spinning equipment to obtain primary film yarns, wherein the viscosity of the casting solution is controlled to be 20000-100000 mPa.s;

then, the primary membrane silk vertically enters a coagulating bath after passing through an air section, and the water inlet depth of the primary membrane silk in the coagulating bath is 60-180cm;

the primary film yarn enters a rinsing tank for rinsing after reaching the water inlet depth, and is collected and cut by a winding machine after rinsing; soaking the cut film yarns in pure water;

(3) Film yarn post-treatment: firstly, taking out and draining membrane filaments soaked in pure water in the step (2); and then soaking the drained membrane filaments in a protective solution, taking out and airing to obtain the reinforced hollow fiber porous composite membrane.

8. The method for preparing a reinforced hollow fiber porous composite membrane according to claim 7, wherein the solvent contained in the casting solution in the step (1) is 51-73.5 wt%, the additive is 10-30 wt%, the non-solvent is 0.5-4 wt%, and the polymer membrane material is 15-25 wt%;

the solvent is one of N, N-dimethylacetamide, N-dimethylformamide, dimethyl sulfoxide and N-methyl pyrrolidone;

the additive at least comprises polyethylene glycol, tween and polyvinylpyrrolidone;

preferably, the polyethylene glycol has a number average molecular weight of 200-20000;

more preferably, the polyethylene glycol is at least one of PEG400, PEG1000, PEG2000 and PEG 8000;

preferably, the tween is tween 80;

preferably, the polyvinylpyrrolidone has a number average molecular weight of 10000-650000;

more preferably, the polyvinylpyrrolidone is at least one of PVPK17, PVPK30 and PVPK 90;

the non-solvent is glycerol or deionized water.

9. The method for producing a reinforced hollow fiber porous composite membrane according to claim 7, wherein the viscosity of the casting solution in the step (2) is controlled to 25000 to 50000 mPa-s;

the spinning temperature through the spinneret plate in the step (2) is 50-75 ℃; the spinning speed is 15-35m/min.

10. The method for preparing an enhanced hollow fiber porous composite membrane according to claim 7, wherein the height of the air section through which the primary membrane filaments pass in the step (2) is 10-30cm;

the coagulating liquid in the coagulating bath in the step (2) is water or solvent aqueous solution with the mass fraction less than or equal to 50%, wherein the solvent is the same as that of the casting film liquid;

the temperature of the solidification bath in the step (2) is 35-60 ℃;

the rinsing liquid of the rinsing tank in the step (2) is pure water; the temperature of the rinsing liquid in the rinsing tank is 30-45 ℃;

the protective solution for membrane filament post-treatment in the step (3) comprises the following components: water; 15-35% of glycerin and 50-100ppm of bactericide kathon.