CN113398778B

CN113398778B - Preparation method of UPE porous membrane

Info

Publication number: CN113398778B
Application number: CN202110512965.9A
Authority: CN
Inventors: 贾建东; 陈梦泽; 庞铁生; 潘哲
Original assignee: Hangzhou Kebaite Technology Co ltd
Current assignee: Hangzhou Kebaite Technology Co ltd
Priority date: 2021-05-11
Filing date: 2021-05-11
Publication date: 2022-11-01
Anticipated expiration: 2041-05-11
Also published as: CN113398778A

Abstract

The invention provides a preparation method of a UPE porous membrane, which comprises the steps of firstly preparing a mixed material, wherein the mixed material comprises a polyethylene resin and a solvent system, and the polyethylene resin at least comprises an ultrahigh molecular weight polyethylene with the mass-average molecular weight of more than 300 ten thousand; the solvent system comprises a non-solvent compound A and a solvent compound B; then heating, melting and mixing the mixed materials to form a membrane casting solution, wherein the viscosity of the membrane casting solution is not more than 10Wcps; then extruding through a die head to form a liquid film; with the reduction of the environmental temperature, the liquid film can be split-phase and solidified to form a raw film containing a plurality of holes; then stretching the raw film to obtain a UPE porous film with a required film structure; the UPE porous membrane can be a symmetric membrane or an asymmetric membrane; the UPE porous membrane has excellent trapping performance on impurity particles with the particle size of 1-30nm, is high in trapping efficiency, can meet the requirements of practical application, and is suitable for being applied to the field of photoresist.

Description

Preparation method of UPE porous membrane

Technical Field

The invention relates to the technical field of membrane materials, in particular to a preparation method of a UPE porous membrane.

Background

The separation membrane is a membrane type material with selective permeability; generally, the separation method can be divided into a microfiltration membrane, an ultrafiltration membrane, a nanofiltration membrane, a reverse osmosis membrane, a pervaporation membrane, an ion exchange membrane and the like according to a separation mechanism and an application range; the separation membrane can be made of polymer, metal, ceramic and other materials, wherein the polymer is abundant; the existing polymers used for preparing the separation membrane mainly comprise substances such as polysulfones, polyamides, polyesters, polyolefins and the like; the polyolefin polymer mainly comprises olefins such as polyethylene, polypropylene, poly-4-methyl-1-pentene and the like, and the separation membrane has excellent physical and chemical properties, is low in price and easy to process and form, is attracted by the market, and is mainly applied to the fields of water treatment, gas separation, biomedicine and the like at present.

In recent years, many reports of polyolefin separation membranes developed by a Thermal Induced Phase Separation (TIPS) method are reported, for example, ultra-high molecular weight polyethylene (UPE for short) has a large viscosity-average molecular weight (more than 100 ten thousand), and a high melt viscosity, so that it is difficult to spin a membrane by a conventional method, and therefore, a tip method is required to prepare a polyolefin separation membrane with a corresponding pore size; however, the traditional TIPS method has certain disadvantages in the preparation of UPE separation membranes, for example, the separation membranes prepared by the method have uneven pore size distribution, which easily results in low filtration precision of the separation membranes, poor impurity particle trapping capability, and failure to meet the requirements of practical application, thus greatly limiting the development of UPE separation membranes.

Disclosure of Invention

Aiming at the defects in the prior art, the invention aims to provide a preparation method of a UPE (ultra-high molecular weight polyethylene) porous membrane, the UPE porous membrane prepared by the preparation method has excellent trapping performance on impurity particles, has high trapping efficiency and can meet the requirements of practical application; in addition, the composite material also has higher tensile strength.

In order to achieve the purpose, the invention provides the following technical scheme: a preparation method of a UPE porous membrane comprises the following steps:

s1: adding polyethylene resin into a solvent system consisting of a compound A and a compound B, stirring and mixing, and uniformly mixing to form a mixed material; wherein the polyethylene resin at least comprises an ultra-high molecular weight polyethylene with the mass average molecular weight of more than 300 ten thousand;

wherein the compound A is a non-solvent for the polyethylene resin; compound B is a solvent for the polyethylene resin; the mass fraction of the polyethylene resin in the mixed material is 8-25%;

s2: heating, melting and mixing the mixed materials at the temperature of 150-260 ℃ to form a membrane casting solution, wherein the viscosity of the membrane casting solution is not more than 10Wcps; then extruding through a die head to form a liquid film; wherein the extrusion temperature of the die head is 200-250 ℃;

s3: the liquid film is subjected to split-phase curing at the temperature of 15-120 ℃, and the split-phase curing time is 1-60S; forming a green film;

s4: then stretching the green film, and performing primary heat setting after stretching;

s5: extracting the solvent system with the extract liquid to remove the solvent system from the raw membrane to obtain an original membrane;

s6: and carrying out secondary heat setting on the original membrane to obtain the UPE porous membrane.

As a further improvement of the invention, the polyethylene treeThe bulk density of the fat is 0.2-0.35g/cm³；

The polyethylene resin and the solvent system in the S1 are stirred and mixed for 10-24 hours at the temperature of 100-130 ℃, so that a mixed material is formed;

the mass percent of the compound A in the solvent system is 60-80%, and the mass percent of the compound B is 20-40%; the boiling point of compound a is at least 50 ℃ lower than the boiling point of compound B.

In a further improvement of the present invention, the compound a is at least one of dimethyl phthalate, dioctyl adipate, ethylene glycol diacetate, dimethyl carbonate, palm oil and glycerol triacetate, and the compound B is at least one of paraffin oil, white oil, hydraulic oil, decalin, castor oil extract and castor oil.

As a further improvement of the invention, the polyethylene resin consists of 60 to 80 mass percent of ultrahigh molecular weight polyethylene with the mass-average molecular weight of more than 300 ten thousand and 20 to 40 mass percent of ultrahigh molecular weight polyethylene with the mass-average molecular weight of 100 to 200 ten thousand and the density of 0.92 to 0.98g/cm³The high-density polyethylene of (1).

As a further improvement of the invention, the mixed materials in the S2 are put into an extruder to be heated, melted and mixed for 10-30min; the extruder comprises a melting section, a mixing section, a defoaming section, a pressurizing section and an extruding section; the temperature of the melting section and the mixing section is set to be 50-90% of the highest temperature in the extruder.

As a further improvement of the invention, the length-diameter ratio of the extruder is 30-70; the pressure fluctuation at the outlet of the extruder is less than 0.1MPa; the maximum temperature in the extruder is at least 5 ℃ higher than the temperature of die extrusion.

As a further improvement of the invention, the temperature of the two sides of the liquid film is the same when S3 is subjected to split-phase solidification; after the phase separation and solidification are finished, the raw film is longitudinally stretched at the longitudinal stretching temperature of 60-150 ℃ and the longitudinal stretching multiple of 1-15 times; then, transverse stretching is carried out, wherein the transverse stretching temperature is 80-180 ℃, and the transverse stretching multiple is 1-15 times.

As a further improvement of the invention, the temperature of two sides of the liquid film is different when the S3 is subjected to split-phase solidification, wherein the temperature of one side is at least 20 ℃ higher than that of the other side, and the thickness of the green film formed in the S3 is 0.5-1.5mm.

As a further improvement of the invention, the S3 liquid film is blown at least on one side of the liquid film when the split-phase solidification is carried out, and the absolute humidity is 10g H₂O/kg-30g H₂O/kg, and air flow with flow rate of 0.5-5m/s is blown to the surface of the liquid film for 1-60s.

As a further improvement of the invention, when the raw film is subjected to stretching treatment in S4, transverse stretching and longitudinal stretching are simultaneously carried out, wherein the stretching temperature is 60-150 ℃, the transverse stretching multiple is 1-10 times, the longitudinal stretching multiple is 1-10 times, the transverse stretching rate is 5%/S-100%/S, and the longitudinal stretching rate is 5%/S-100%/S.

As a further improvement of the present invention, when the green film is subjected to stretching treatment, the ratio of the longitudinal stretching magnification to the transverse stretching magnification is 0.7 to 2.

As a further improvement of the invention, the temperature for the first heat setting is 60-180 ℃ and the time is 5-120s; the temperature of the second heat setting is 5-50 ℃ higher than that of the first heat setting, and the time is 5-120s.

As a further improvement of the invention, the extract in S5 is at least one of dichloromethane, acetone, methanol, ethanol, glycerol, tetrafluoroethane and isopropanol; the extraction temperature is 5-25 ℃; the extraction time is 1-5h.

The UPE porous membrane is prepared based on a thermally induced phase separation method accompanied with liquid-liquid phase separation, and when the UPE porous membrane is prepared, firstly, a mixed material is prepared, wherein the mixed material comprises polyethylene resin and a corresponding solvent system, and the ultra-high molecular weight polyethylene is called UPE for short, is thermoplastic engineering plastic with a linear structure and excellent comprehensive performance, and the membrane prepared from the UPE has high heat resistance and wear resistance, good mechanical properties, high tensile strength and wide application range; the polyethylene resin used in the invention at least comprises an ultra-high molecular weight polyethylene with a mass-average molecular weight of more than 300 ten thousand, namely only UPE with a mass-average molecular weight of more than 300 ten thousand can be used as a film forming raw material in the invention, and the composition can also be carried out, for example, UPE with a mass-average molecular weight of more than 300 ten thousand and high density polyethylene with a mass-average molecular weight of less than 300 ten thousand are compounded to be used as film forming raw materials;

preferably, the polyethylene resin of the present invention comprises 60 to 80 mass% of an ultrahigh molecular weight polyethylene having a mass average molecular weight of 300 ten thousand or more and 20 to 40 mass% of an ultrahigh molecular weight polyethylene having a mass average molecular weight of 100 to 200 ten thousand and a density of 0.92 to 0.98g/cm³The high-density polyethylene composition of (a); compared with the method that one kind of ultra-high molecular weight polyethylene is singly selected, the polyethylene resin compounded by the ultra-high molecular weight polyethylene and the high density polyethylene is beneficial to enabling the polyethylene content in the casting solution to be higher (namely, the solid content is higher), and then the polyethylene film with smaller aperture and higher tensile strength can be obtained more easily;

the bulk density is also called volume density, and is called bulk density for short; the mass per unit volume of the particulate material (e.g., polyethylene resin particles) in a stacked state; the larger the bulk density of the resin particles is, the larger the actual mass thereof is at the same volume; the larger the bulk density of the resin particles is, the larger the volume occupied by the resin particles is under the same mass condition; the bulk density of the currently conventional polyethylene resin pellets is 0.45g/cm³On the left and right, the bulk density is higher; while the bulk density of the polyethylene resin of the present invention is 0.2 to 0.35g/cm³The smaller the bulk density of the resin particles is, the larger the specific surface area of the resin particles is, and the larger the specific surface area is, the easier the resin particles with the same mass are dissolved in the corresponding solvent system under the same conditions (at the same temperature), i.e. the polyethylene resin used in the invention can be mixed with the solvent system to form the casting solution required by the invention only in a shorter time after being melted; the common polyethylene resin can be uniformly mixed with a solvent system within a longer time or at a higher temperature, so that the chain segments of the polyethylene molecules are easy to break, the required high molecular weight polyethylene resin cannot be obtained, and the tensile strength of the finally formed UPE porous membrane is lower; in addition, the polyethylene resin in the mixed material of the invention has a mass fraction of 8-25%, i.e. a solid content of 8-25%, which is too low, resulting in a final film having a tensile strengthToo low, the mechanical strength is poor, and the requirements of practical application cannot be met; the solid content is too high, which can cause the viscosity of the subsequently obtained casting solution to be too high, the requirement on used mechanical equipment is too high, the production cost is too high, and the mass production cannot be realized;

the solvent system consists of a compound A and a compound B, wherein the compound A is a non-solvent of the polyethylene resin, and the non-solvent means that when the compound is heated to the boiling point of the compound at most, the compound can not dissolve the polyethylene resin to form a homogeneous solution and only can play a certain role in swelling the polyethylene resin; the compound A in the invention is at least one of dimethyl phthalate, dioctyl adipate, ethylene glycol diacetate, dimethyl carbonate, palm oil and glycerol triacetate; the compound B is a solvent of the polyethylene resin, and the solvent is that the compound B can completely dissolve the polyethylene resin to form a homogeneous solution when the compound B is heated to the boiling temperature of the compound B at most; the compound B is at least one of paraffin oil, white oil, hydraulic oil, decalin, castor oil extract and castor oil; compared with the method of selecting a single solvent as a solvent system, the method of the invention adopts the compounding of the solvent and the non-solvent as the corresponding solvent system, and the solvent system has the following advantages: 1. the raw film formed after the liquid film phase splitting is finished is easier to have small holes, and simultaneously more small holes are formed, the hole density is higher, the pore size distribution is more uniform, and the corresponding porosity is higher; the method is characterized in that the liquid film is subjected to liquid-liquid phase separation and solidification (phase separation and solidification are carried out by a thermal method) due to the change of temperature, and simultaneously, the diffusion exchange is carried out between the non-solvent and the solvent, so that the phase separation and solidification speed is further improved, and in addition, the content of the compound A in a solvent system is greater than that of the compound B, namely, the content of the non-solvent is greater than that of the non-solvent, so that the phase separation and solidification speed is higher, crystal nuclei are more easily separated out, small holes are more easily formed, the formed small holes are more simultaneously, the uniformity of the pore size distribution is ensured, and the interception efficiency is further ensured; 2. the fiber is easier to form, and the fiber is easier to form, so that the polyethylene film has higher tensile strength and good mechanical property, because the crystal nucleus is easier to separate out due to the acceleration of the phase separation rate, and the fiber is produced along the crystal nucleus, so that the fiber is easier to form; 3. by matching with the temperature during split-phase solidification, gradient holes are more easily formed in the final film forming process, so that an asymmetric film is formed; of course, if desired, additional substances such as antioxidants, nucleating agents, fillers and the like may be used as additives in the present invention to further enhance certain properties of the UPE porous film; in the invention, the polyethylene resin and a corresponding solvent system (comprising a compound A and a compound B) are stirred and mixed for 10 to 24 hours at the temperature of 100 to 140 ℃, thereby forming a mixed material;

secondly, the mixed materials are put into an extruder to be heated, melted and mixed under the condition that the temperature is 150-260 ℃, so that the polyethylene resin is completely melted in a corresponding solvent system, and the casting solution has uniform and stable shape; the mixed materials are put into an extruder to be heated, melted and mixed for 10-30min; the extruder comprises a melting section, a mixing section, a defoaming section, a pressurizing section and an extruding section, wherein the temperature of the melting section and the mixing section is set to be 50-90% of the highest temperature in the extruder, and the length-diameter ratio of the extruder is 30-70, so that the polymer (polyethylene resin particles) is ensured to be distributed very uniformly in a solvent system, the extrusion of a die head is facilitated, and an ideal UPE porous membrane is finally obtained; if the casting solution formed by the polymer and the solvent system contains more bubbles, more bubbles are easily formed in a liquid film extruded by the die head, and the existence of the bubbles easily causes the pore size distribution of the finally formed UPE porous film to be uneven (pores with larger pore sizes are generated), the retention efficiency of impurity particles is poor, and the tensile strength of the formed film is poor; according to the invention, the defoaming section is arranged in the extruder, and the pressure fluctuation at the outlet of the extruder is less than 0.1MPa, so that on one hand, almost no bubbles are contained in the casting solution, on the other hand, the polyethylene resin is uniformly mixed in a solvent system, and the high-quality UPE porous membrane is obtained finally; the viscosity of the casting solution is controlled to be not more than 10Wcps, because if the viscosity is further increased, the requirement on mechanical equipment is too high, the die head extrusion is not facilitated, and simultaneously a UPE porous membrane with an ideal structure cannot be obtained; then, extruding through a die head (die head forming) to form a flat liquid film, wherein the extrusion temperature of the die head is 200-250 ℃, preferably, the highest temperature in the extruder is at least 5 ℃ higher than the extrusion temperature of the die head, so that the temperatures of all areas of the liquid film are basically the same during extrusion, the subsequent split-phase solidification is facilitated, and an ideal film structure is obtained;

thirdly, the liquid film is subjected to split-phase solidification at the temperature of 15-120 ℃; at a higher temperature, a single homogeneous solution can be formed between a solvent system consisting of the compound A and the compound B and the polyethylene resin, and the homogeneous solution begins to generate liquid-liquid delamination along with the reduction of the system temperature, two liquid phases coexist, namely, one phase with high polymer content and the other phase with low polymer content occur, and then the split-phase solidification phenomenon occurs; in the invention, the solvent system is the combination of the solvent and the non-solvent, so that except for phase separation caused by temperature change, the diffusion exchange between the solvent and the non-solvent can also accelerate the solidification rate of the phase separation, thereby forming a small-pore membrane (the faster the phase separation rate is, the smaller the pore diameter of the formed pores is), namely forming the nano membrane required by the invention; the final film formation in the invention can be a symmetrical film or an asymmetrical film; if the final film is a symmetrical film, the split-phase curing speed of the two sides of the liquid film is required to be basically the same, namely the temperature of the two sides of the liquid film is the same when the split-phase curing is carried out, a certain number of holes with certain aperture are formed on the two surfaces of the raw film after the split-phase curing, and the aperture sizes of the holes on the two surfaces are basically the same, in order to further obtain the UPE porous film with the required film aperture and larger tensile strength, the raw film is stretched, the raw film with the substantially same aperture sizes of the holes on the two surfaces is longitudinally stretched at the longitudinal stretching temperature of 60-150 ℃, and the longitudinal stretching multiple is 1-15 times; then, carrying out transverse stretching at the temperature of 80-180 ℃ and at the transverse stretching multiple of 1-15 times;

if the final film is an asymmetric film, the split-phase curing rates of two sides of the liquid film are required to be different, namely one side is high and the other side is low, meanwhile, in order to further ensure that the film has higher flow rate, a certain number of larger holes are formed, the temperature difference of two sides of the liquid film is at least above 20 ℃, the small hole surface is formed on the side with low temperature, and the large hole surface is formed on the side with high temperature; when the split-phase curing is carried out, the selection of factors such as the split-phase curing temperature, the split-phase curing time and the like is very critical, and the factors determine the speed of the split-phase curing speed and whether the film with an ideal film structure and a film pore size can be finally obtained; the time of phase separation and solidification is 1-60s, and the time is relatively short, so that the UPE porous membrane with an ideal membrane structure required by people can be obtained; in order to further obtain the UPE porous membrane with the required membrane pore diameter, the invention carries out stretching treatment on the raw membrane, and the prior stretching technology firstly carries out longitudinal stretching and then transverse stretching; however, researches show that when a raw membrane is treated according to a conventional stretching technology, holes on the raw membrane are easy to partially collapse or deform, and finally a UPE porous membrane with a required membrane structure cannot be obtained, so that the raw membrane is treated by synchronous stretching, namely, the raw membrane is simultaneously stretched transversely and longitudinally, and the stretching has the advantages that the pore diameter of the membrane pores required by the invention is obtained, the tensile strength of the membrane is improved, the pores are not easy to collapse or deform, and the UPE porous membrane with the required membrane structure can be obtained finally; preferably, the ratio of longitudinal stretching multiple to transverse stretching multiple is 0.7-2, so that the uniformity of the pore diameter of the pores in the membrane is further ensured, and the interception efficiency of the membrane is further improved;

meanwhile, in order to further increase the phase separation speed of the liquid film and obtain the UPE porous membrane with the required pore size, air blowing can be carried out on at least one side of the liquid film during phase separation curing, and the absolute humidity can be 10g H₂O/kg-30g H₂Blowing air flow with the flow speed of 0.5-5m/s to the surface of the liquid film for 1-60s; if a symmetrical film is to be formed, air is blown at the two sides of the liquid film simultaneously, and the speed and the absolute humidity of air flow are the same as much as possible, so that the phase separation speeds at the two sides of the liquid film are different; if it is to be shapedThe formed UPE porous membrane is an asymmetric membrane, so that one side of a liquid membrane can be blown, or both sides can be blown, and proper air flow is selected according to the required membrane structure;

carrying out primary heat setting after the stretching is finished, wherein the primary heat setting has the function of carrying out primary setting on the stretched raw film, ensuring that film holes are basically unchanged and eliminating internal stress generated by stretching; the temperature for the first heat setting is 60-180 ℃ and the time is 5-120s; then extracting, and removing the solvent system from the raw membrane through the extract liquor to obtain an original membrane; the extract is at least one of dichloromethane, acetone, methanol, ethanol, glycerol, tetrafluoroethane and isopropanol; the extraction temperature is 5-25 ℃; the extraction time is 1-5h; by selecting proper extracting agent and extracting conditions, the solvent system is ensured to be completely removed from the raw membrane, and the time required by extraction is short; after extraction, carrying out secondary heat setting on the original membrane, wherein the temperature of the secondary heat setting is higher than that of the primary heat setting, the secondary heat setting has the functions of eliminating internal stress generated by extraction on one hand, and finally setting the membrane pores of the original membrane on the other hand, so as to ensure that the membrane pores are basically not changed, and obtain the UPE porous membrane with the required membrane pore structure, wherein the porous membrane can be a symmetric membrane or an asymmetric membrane; the finally obtained UPE porous membrane has uniform pore size distribution of holes, excellent trapping performance on impurity particles and high interception efficiency, and can meet the requirements of practical application; in addition, the composite material also has higher tensile strength and wide application range, is particularly suitable for being applied to the field of photoresist.

As a further improvement of the invention, the thickness of the UPE porous membrane is 1-50um; the porosity of the UPE porous membrane is 20% -60%;

under the conditions that the positive pressure is 0.03MPa and the temperature is 20 ℃, the time required for 50ml of water to pass through a porous membrane with the diameter of 47mm is 400-5000s;

the tensile strength of the UPE porous membrane is 20-100MPa, and the elongation at break is 200% -800%;

the UPE porous membrane is used in the field of photoresist.

The thickness of the film can be measured by using a scanning electron microscope to perform morphology characterization on the film structure, and then using computer software (such as Matlab, NIS-Elements and the like) or manually measuring and then calculating; of course, the skilled person can also obtain the above parameters by other measuring means, and the above measuring means is only used for reference; when the thickness of the film is too small, the mechanical strength of the film is low; meanwhile, as the filtering time is too short, effective filtering cannot be carried out; when the thickness of the membrane is too large, the filtration time is too long, and the time cost is too large; the thickness of the UPE porous membrane is 1-50 μm, preferably 10-40 μm, so that the UPE porous membrane has high mechanical strength, can perform effective filtration, has high filtration efficiency, short filtration time and low time cost, and is suitable for the field of photoresist;

the porosity of the membrane is the proportion of the volume of membrane pores of the filter membrane to the total volume, and the membrane pores comprise open pores and closed pores; the commonly used porosity test methods are mercury intrusion method, density method and dry-wet film weighing method; of course, the skilled person can also obtain the above parameters by other measuring means, and the above measuring means is only used for reference; when the porosity of the membrane is too high, the tensile strength of the membrane is too low, the mechanical property is poor, the industrial practical value is low, and the market demand cannot be met; when the porosity of the membrane is too low, on one hand, the flow rate of the membrane is influenced, so that the filtering speed of the membrane is low, the filtering time is long, and the time cost is high; on the other hand, the pollution capacity of the membrane is too low, the service life is too short, the membrane needs to be replaced in a short time, and the economic cost is greatly improved; the porosity of the UPE porous membrane is 20-60%, and 25-55% is preferred; therefore, the UPE porous membrane not only has higher tensile strength, but also has higher filtering speed, high flow rate, higher pollutant carrying capacity, long service life and lower economic cost, and can retain more impurity particles.

By testing the flow rate of the UPE porous membrane, the time required for 50ml of water to pass through the porous membrane with the diameter of 47mm is 400-5000s under the conditions that the pressure is 0.03MPa and the temperature is 20 ℃; the UPE porous membrane has the advantages of large flow rate, short time for fluid to pass through the membrane, low time cost and high economic benefit, and the UPE porous membrane is suitable for being applied to the field of photoresist;

important indexes for evaluating the mechanical strength of the film are the tensile strength and the elongation at break of the film; under certain conditions, the greater the tensile strength of the film, the better the mechanical strength of the film is said to be; tensile strength refers to the ability of a film to withstand parallel stretching; when the film is tested under a certain condition, the film sample is acted by a tensile load until the film sample is damaged, and the tensile strength and the elongation at break of the film can be calculated according to the maximum tensile load corresponding to the damage of the film sample, the change of the size (length) of the film sample and the like; tensile strength, elongation at break, can be measured by a universal tensile tester, tensile strength testing methods are well known in the art, for example, tensile strength testing procedures are explained in detail in ASTM D790 or ISO 178; the tensile strength of the UPE porous membrane is 20-100MPa, and the elongation at break is 200-800%; the UPE porous membrane has higher tensile strength and elongation at break, better mechanical property and higher industrial practical value, and can completely meet the market demand;

in addition, the UPE porous membrane is tested for the retention efficiency, and the retention efficiency of the UPE porous membrane on impurity particles with the particle size of 1-30nm is found to be more than 95% (preferably, the retention efficiency of the UPE porous membrane on standard gold particle impurities with the particle size of 1-30nm is more than 95%), the filtration precision is high, the requirements of practical application can be met, and the UPE porous membrane has a high economic value;

the invention has the beneficial effects that: the invention provides a preparation method of a UPE porous membrane, which comprises the steps of firstly preparing a mixed material, wherein the mixed material comprises a polyethylene resin and a solvent system, and the polyethylene resin at least comprises an ultrahigh molecular weight polyethylene with the mass-average molecular weight of more than 300 ten thousand; the solvent system comprises a compound A and a compound B, wherein the compound A is a non-solvent of the polyethylene resin; compound B is a solvent for the polyethylene resin; then heating, melting and mixing the mixed materials to form a membrane casting solution, wherein the viscosity of the membrane casting solution is not more than 10Wcps; then extruding through a die head to form a liquid film; with the reduction of the environmental temperature, the liquid film can be split-phase and solidified to form a raw film containing a plurality of holes; stretching the raw membrane, and then carrying out primary heat setting, extraction and secondary heat setting to obtain the UPE porous membrane with the required membrane structure; the preparation method is convenient, rapid and effective, and is suitable for large-scale production; the finally prepared UPE porous membrane can be a symmetrical membrane or an asymmetrical membrane; the UPE porous membrane has excellent trapping performance on impurity particles with the particle size of 1-30nm, has high interception efficiency, and can meet the requirements of practical application; in addition, the high-tensile-strength photoresist has high tensile strength, and is particularly suitable for the field of photoresist.

Drawings

FIG. 1 is a Scanning Electron Microscope (SEM) image of a first outer surface of a UPE porous membrane prepared according to example 5 at 10K ×;

FIG. 2 is a further enlarged Scanning Electron Microscope (SEM) image of a first outer surface of a UPE porous membrane prepared in example 5 at a magnification of 50K;

FIG. 3 is a Scanning Electron Microscope (SEM) image of a second outer surface of a UPE porous membrane prepared according to example 5 at a magnification of 10K ×;

FIG. 4 is a further enlarged Scanning Electron Microscope (SEM) image of the second outer surface of the UPE porous membrane prepared in example 5 at 50K;

FIG. 5 is a schematic view of the apparatus for flow rate testing of a UPE porous membrane in accordance with the present invention;

fig. 6 is a schematic diagram of the filtration accuracy (retention efficiency) testing device of the UPE porous membrane of the present invention.

Detailed Description

In order to more clearly explain the overall concept of the present application, the following detailed description is given by way of example. In the following description, numerous specific details are set forth in order to provide a more thorough understanding of the present application. It will be apparent, however, to one skilled in the art, that the present application may be practiced without one or more of these specific details. In other instances, well-known features of the art have not been described in order to avoid obscuring the present application.

In the following examples, raw materials and equipment for preparing the UPE porous film were commercially available, unless otherwise specified. The structural morphology of the UPE porous membrane is characterized by adopting a scanning electron microscope with the model number of S-5500 provided by Hitachi company.

Example 1

A preparation method of a UPE porous membrane comprises the following steps:

s1: adding polyethylene resin into a solvent system consisting of a compound A and a compound B, stirring and mixing, and uniformly mixing to form a mixed material; wherein the polyethylene resin is an ultra-high molecular weight polyethylene with the mass-average molecular weight of 400 ten thousand; bulk density of polyethylene resin 0.26g/cm³(ii) a The compound A is a non-solvent of the polyethylene resin; compound B is a solvent for the polyethylene resin; the compound A is dioctyl adipate, and the compound B is paraffin oil;

the mixed material comprises the following substances in parts by weight: polyethylene resin: 14 parts of (1); a compound A:58 parts of a solvent; compound B:28 parts of a binder;

s2: putting the mixed material into an extruder at the temperature of 160-250 ℃, heating, melting and mixing for 20min to form a membrane casting solution, and then extruding through a die head to form a liquid membrane; wherein the die extrusion temperature is 235 ℃; the extruder comprises a melting section, a mixing section, a defoaming section, a pressurizing section and an extruding section; the length-diameter ratio of the extruder is 60;

s3: the liquid film is subjected to split-phase curing at the temperature of 30 ℃ on one side and 70 ℃ on the other side for 20s, and a green film is formed after the split-phase curing is finished; the thickness of the green film is 1.0mm;

s4: then stretching the raw film, and simultaneously carrying out transverse stretching and longitudinal stretching on the raw film, wherein the temperature of the transverse stretching and the longitudinal stretching is 120 ℃, the transverse stretching multiple and the longitudinal stretching multiple are both 5 times, and the stretching speed of the transverse stretching and the longitudinal stretching is both 60%/s; carrying out primary heat setting after the stretching is finished, wherein the temperature during the primary heat setting is 130 ℃ and the time is 60s;

s5: extracting the solvent system with extraction liquid dichloromethane to remove the solvent system from the raw membrane to obtain an original membrane; the extraction temperature is 15 ℃; the extraction time is 3h;

s6: and (3) carrying out secondary heat setting on the original membrane, wherein the temperature of the secondary heat setting is 140 ℃ and the time is 70s, and obtaining the UPE porous membrane.

Example 2

A preparation method of a UPE porous membrane comprises the following steps:

s1: adding polyethylene resin into a solvent system consisting of a compound A and a compound B, stirring and mixing, and uniformly mixing to form a mixed material; the compound A is a non-solvent of the polyethylene resin; compound B is a solvent for the polyethylene resin; the compound A is dimethyl phthalate; the compound B is white oil; the polyethylene resin is prepared from 75 mass percent of ultrahigh molecular weight polyethylene with the mass-average molecular weight of 450 ten thousand and 25 mass percent of ultrahigh molecular weight polyethylene with the mass-average molecular weight of 150 ten thousand and the density of 0.92-0.98g/cm³High-density polyethylene composition of (a); bulk density of polyethylene resin 0.22g/cm³；

The mixed material comprises the following substances in parts by weight: polyethylene resin: 20 parts of (1); a compound A:53 parts of a mixture; compound B:27 parts of (1);

s2: heating, melting and mixing the mixed material for 28min at the temperature of 180-260 ℃ to form a membrane casting solution, and then extruding the membrane casting solution through a die head to form a liquid membrane; the extrusion temperature of a die head is 250 ℃; the extruder comprises a melting section, a mixing section, a defoaming section, a pressurizing section and an extruding section; the length-diameter ratio of the extruder is 50;

s3: the liquid film is subjected to split-phase curing in an environment with the temperature of one side set to be 20 ℃ and the temperature of the other side set to be 45 ℃, the split-phase curing time is 5s, and a green film is formed after the split-phase curing is finished; the thickness of the green film is 0.7mm;

s4: then stretching the raw film, and simultaneously carrying out transverse stretching and longitudinal stretching on the raw film, wherein the temperature of the transverse stretching and the longitudinal stretching is 80 ℃, the longitudinal stretching multiple is 1.5 times, the transverse stretching multiple is 2 times, the longitudinal stretching speed is 60%/s, and the transverse stretching speed is 80%/s; carrying out first heat setting after the stretching is finished, wherein the temperature of the first heat setting is 100 ℃, and the time is 50s;

s5: extracting the solvent system with isopropanol of the extraction liquid to remove the solvent system from the raw membrane to obtain a raw membrane; the extraction temperature is 20 ℃; the extraction time is 2.5h;

s6: and (3) carrying out secondary heat setting on the original membrane, wherein the temperature of the secondary heat setting is 120 ℃ and the time is 60s, and obtaining the UPE porous membrane.

Example 3

A preparation method of a UPE porous membrane comprises the following steps:

s1: adding polyethylene resin into a solvent system consisting of a compound A and a compound B, stirring and mixing, and uniformly mixing to form a mixed material; the polyethylene resin is prepared from 75 mass percent of ultrahigh molecular weight polyethylene with the mass-average molecular weight of 400 ten thousand and 25 mass percent of ultrahigh molecular weight polyethylene with the mass-average molecular weight of 120 ten thousand and the density of 0.92-0.98g/cm³The high-density polyethylene composition of (a); bulk density of polyethylene resin 0.24g/cm³(ii) a The compound A is a non-solvent of the polyethylene resin; compound B is a solvent for the polyethylene resin; the compound A is dimethyl carbonate, and the compound B is decalin;

the mixed material comprises the following substances in parts by weight: polyethylene resin: 16 parts of a mixture; a compound A:59 parts of a base; compound B:25 parts of (1);

s2: heating, melting and mixing the mixed materials at 165-250 ℃ for 24min to form a membrane casting solution, and then extruding the membrane casting solution through a die head to form a liquid membrane; the extrusion temperature of the die head is 240 ℃; the extruder comprises a melting section, a mixing section, a defoaming section, a pressurizing section and an extruding section; the length-diameter ratio of the extruder is 55;

s3: the liquid film is subjected to split-phase solidification under the environment that the temperature of one side of the liquid film is set to be 28 ℃ and the temperature of the other side of the liquid film is set to be 60 ℃, the split-phase solidification time is 15s, and a green film is formed after the split-phase solidification is finished; the thickness of the green film is 0.9mm;

s4: then stretching the raw film, and simultaneously performing transverse stretching and longitudinal stretching on the raw film, wherein the temperature during the transverse stretching and the longitudinal stretching is 110 ℃, the longitudinal stretching multiple is 5 times, the transverse stretching multiple is 3 times, the longitudinal stretching speed is 75%/s, and the transverse stretching speed is 45%/s; carrying out first heat setting after the stretching is finished, wherein the temperature of the first heat setting is 125 ℃ and the time is 50s;

s5: extracting the solvent system with extraction liquid glycerol to remove the solvent system from the raw membrane to obtain a raw membrane; the extraction temperature is 10 ℃; the extraction time is 4h;

s6: and (3) carrying out secondary heat setting on the original membrane, wherein the temperature of the secondary heat setting is 140 ℃ and the time is 80s, and obtaining the UPE porous membrane.

Example 4

A preparation method of a UPE porous membrane comprises the following steps:

s1: adding polyethylene resin into a solvent system consisting of a compound A and a compound B, stirring and mixing, and uniformly mixing to form a mixed material; wherein the polyethylene resin is prepared from 80% by mass of ultrahigh molecular weight polyethylene with a mass-average molecular weight of 350 ten thousand and 20% by mass of ultrahigh molecular weight polyethylene with a mass-average molecular weight of 120 ten thousand and a density of 0.92-0.98g/cm³The high-density polyethylene composition of (a); bulk density of polyethylene resin 0.30g/cm³；

The compound A is a non-solvent of the polyethylene resin; compound B is a solvent for the polyethylene resin; the compound A is glycerol triacetate, and the compound B is castor oil;

the mixed material comprises the following substances in parts by weight: polyethylene resin: 12 parts of (a); a compound A:65 parts of (1); compound B:23 parts;

s2: heating, melting and mixing the mixed material for 18min at the temperature of 155-245 ℃ to form a membrane casting solution, and then extruding the membrane casting solution through a die head to form a liquid membrane; the extrusion temperature of the die head is 235 ℃; the extruder comprises a melting section, a mixing section, a defoaming section, a pressurizing section and an extruding section; the length-diameter ratio of the extruder is 45;

s3: the liquid film is subjected to split-phase solidification under the environment that the temperature of one side of the liquid film is set to be 40 ℃ and the temperature of the other side of the liquid film is set to be 85 ℃, the split-phase solidification time is 40s, and a green film is formed after the split-phase solidification is finished; the thickness of the green film is 1.2mm;

s4: then stretching the green film, and simultaneously carrying out transverse stretching and longitudinal stretching on the green film, wherein the temperature of the transverse stretching and the longitudinal stretching is 130 ℃, the transverse stretching multiple and the longitudinal stretching multiple are both 7 times, and the stretching speed of the transverse stretching and the longitudinal stretching is both 40%/s; performing first heat setting after the stretching is finished, wherein the temperature during the first heat setting is 135 ℃ and the time is 45s;

s5: extracting the solvent system with extraction liquid dichloromethane to remove the solvent system from the raw membrane to obtain an original membrane; the extraction temperature is 18 ℃; the extraction time is 3.5h;

s6: and (3) carrying out secondary heat setting on the original membrane, wherein the temperature of the secondary heat setting is 140 ℃ and the time is 60s, and obtaining the UPE porous membrane.

Example 5

A preparation method of a UPE porous membrane comprises the following steps:

s1: adding polyethylene resin into a solvent system consisting of a compound A and a compound B, stirring and mixing, and uniformly mixing to form a mixed material; wherein the polyethylene resin is an ultra-high molecular weight polyethylene with the mass-average molecular weight of 350 ten thousand; bulk density of polyethylene resin 0.34g/cm³(ii) a The compound A is a non-solvent of the polyethylene resin; compound B is a solvent for the polyethylene resin; the compound A is palm oil, and the compound B is hydraulic oil;

the mixed material comprises the following substances in parts by weight: polyethylene resin: 10 parts of a binder; a compound A:60 parts; compound B:30 parts of (1);

s2: heating, melting and mixing the mixed materials at the temperature of 150-240 ℃ for 15min to form a membrane casting solution, and then extruding the membrane casting solution through a die head to form a liquid membrane; the die head extrusion temperature is 230 ℃; the extruder comprises a melting section, a mixing section, a defoaming section, a pressurizing section and an extruding section; the length-diameter ratio of the extruder is 40;

s3: the liquid film is subjected to split-phase curing in an environment with the temperature of one side set to be 60 ℃ and the temperature of the other side set to be 110 ℃, the split-phase curing time is 60s, and a green film is formed after the split-phase curing is finished; the thickness of the green film is 1.4mm;

s4: then stretching the green film, and simultaneously carrying out transverse stretching and longitudinal stretching on the green film, wherein the temperature during the transverse stretching and the longitudinal stretching is 145 ℃, the transverse stretching multiple and the longitudinal stretching multiple are both 9 times, and the stretching speed of the transverse stretching and the longitudinal stretching is both 30%/s; carrying out first heat setting after the stretching is finished, wherein the temperature of the first heat setting is 150 ℃ and the time is 30s;

s5: extracting the solvent system with extract liquor ethanol to remove the solvent system from the raw membrane to obtain a raw membrane; the extraction temperature is 8 ℃; the extraction time is 5h;

s6: and (3) carrying out secondary heat setting on the original membrane, wherein the temperature of the secondary heat setting is 160 ℃ and the time is 45s, and obtaining the UPE porous membrane.

Example 6

A preparation method of a UPE porous membrane comprises the following steps:

s1: adding polyethylene resin into a solvent system consisting of a compound A and a compound B, stirring and mixing, and uniformly mixing to form a mixed material; the polyethylene resin is prepared from 67 mass percent of ultrahigh molecular weight polyethylene with the mass-average molecular weight of 400 ten thousand and 33 mass percent of ultrahigh molecular weight polyethylene with the mass-average molecular weight of 180 ten thousand and the density of 0.92-0.98g/cm³High-density polyethylene composition of (a); bulk density of polyethylene resin 0.23g/cm³；

The compound A is a non-solvent of polyethylene resin; compound B is a solvent for the polyethylene resin; the compound A is ethylene glycol diacetate, and the compound B is castor oil extract;

the mixed material comprises the following substances in parts by weight: polyethylene resin: 18 parts of a binder; a compound A:52 parts of (1); compound B:30 parts of (1);

s2: heating, melting and mixing the mixed material for 22min at the temperature of 170-255 ℃ to form a membrane casting solution, and then extruding the membrane casting solution through a die head to form a liquid membrane; the extrusion temperature of the die head is 240 ℃; the extruder comprises a melting section, a mixing section, a defoaming section, a pressurizing section and an extruding section; the length-diameter ratio of the extruder is 54;

s3: the liquid film is subjected to split-phase solidification in an environment with the temperature of one side set to be 25 ℃ and the temperature of the other side set to be 50 ℃, and the split-phase solidification time is 10s; blowing air to the liquid film at 25 deg.C with absolute humidity of 20g H₂O/kg, the flow rate is 2m/s, and the duration is 10s; after the phase separation solidification is finished, a green film is formed; the above-mentionedThe thickness of the green film is 0.8mm;

s4: then stretching the raw film, and simultaneously performing transverse stretching and longitudinal stretching on the raw film, wherein the temperature during the transverse stretching and the longitudinal stretching is 90 ℃, the longitudinal stretching multiple is 4 times, the transverse stretching multiple is 2 times, the longitudinal stretching speed is 80%/s, and the transverse stretching speed is 40%/s; carrying out first heat setting after the stretching is finished, wherein the temperature of the first heat setting is 110 ℃, and the time is 50s;

s5: extracting the solvent system with acetone to remove the solvent system from the raw membrane to obtain a raw membrane; wherein the extraction temperature is 17 ℃; the extraction time is 2.5h;

s6: and (3) carrying out secondary heat setting on the original membrane, wherein the temperature of the secondary heat setting is 125 ℃ and the time is 75s, and obtaining the UPE porous membrane.

Example 7

A preparation method of a UPE porous membrane comprises the following steps:

s1: adding polyethylene resin into a solvent system consisting of a compound A and a compound B, stirring and mixing, and uniformly mixing to form a mixed material; wherein the polyethylene resin comprises 60 mass% of ultra-high molecular weight polyethylene with a mass average molecular weight of 450 ten thousand and 40 mass% of polyethylene with a mass average molecular weight of 180 ten thousand and a density of 0.92-0.98g/cm³The high-density polyethylene composition of (a); bulk density of polyethylene resin 0.27g/cm³；

The compound A is a non-solvent of the polyethylene resin; compound B is a solvent for the polyethylene resin; the compound A is dioctyl adipate, and the compound B is castor oil extract;

the mixed material comprises the following substances in parts by weight: polyethylene resin: 13 parts of (1); a compound A:62 parts of a binder; compound B:25 parts of (1);

s2: heating, melting and mixing the mixed material for 25min at the temperature of 165-240 ℃ to form a membrane casting solution, and then extruding the membrane casting solution through a die head to form a liquid membrane; the die head extrusion temperature is 230 ℃; the extruder comprises a melting section, a mixing section, a defoaming section, a pressurizing section and an extruding section; the length-diameter ratio of the extruder was 58;

s3: the liquid film is subjected to split-phase solidification in an environment with the temperature of one side set to 35 ℃ and the temperature of the other side set to 35 ℃, and the split-phase solidification time is 38s; after the phase separation solidification is finished, a green film is formed; the thickness of the green film is 1.1mm;

s4: then stretching the raw film, namely longitudinally stretching the raw film at the longitudinal stretching temperature of 80 ℃ by 6 times; then performing transverse stretching at the temperature of 120 ℃ by 8 times; performing first heat setting after the stretching is finished, wherein the temperature during the first heat setting is 135 ℃ and the time is 50s;

s5: extracting the solvent system with extraction liquid dichloromethane to remove the solvent system from the raw membrane to obtain an original membrane; wherein the extraction temperature is 16 ℃; the extraction time is 3h;

s6: and (3) carrying out secondary heat setting on the original membrane, wherein the temperature of the secondary heat setting is 150 ℃ and the time is 60s, and obtaining the UPE porous membrane.

Comparative example 1

A preparation method of a UPE porous membrane comprises the following steps:

s1: adding the polyethylene resin into the compound B, stirring and mixing, and uniformly mixing to form a mixed material; wherein the polyethylene resin is an ultra-high molecular weight polyethylene with a mass average molecular weight of 400 ten thousand; bulk density of polyethylene resin 0.45g/cm³(ii) a Compound B is a solvent for the polyethylene resin; the compound B is paraffin oil;

the mixed material comprises the following substances in parts by weight: polyethylene resin: 14 parts of a binder; compound B:86 parts of a binder;

s3: the liquid film is subjected to split-phase curing in an environment with the temperature of one side being 20 ℃ and the temperature of the other side being 60 ℃, the split-phase curing time is 30s, and a green film is formed after the split-phase curing is finished; the thickness of the green film is 1.0mm;

s4: then stretching the raw film, and simultaneously carrying out transverse stretching and longitudinal stretching on the raw film, wherein the temperature of the transverse stretching and the longitudinal stretching is 120 ℃, the transverse stretching multiple and the longitudinal stretching multiple are both 5 times, and the stretching speed of the transverse stretching and the longitudinal stretching is both 60%/s; carrying out first heat setting after the stretching is finished, wherein the temperature of the first heat setting is 130 ℃ and the time is 60s;

s5: extracting the solvent system by using extraction liquid dichloromethane, so that the solvent system is removed from the raw membrane to obtain an original membrane; the extraction temperature is 15 ℃; the extraction time is 3h;

Comparative example 2

A preparation method of a UPE porous membrane comprises the following steps:

s1: adding polyethylene resin into a solvent system consisting of a compound A and a compound B, stirring and mixing, and uniformly mixing to form a mixed material; wherein the polyethylene resin is an ultra-high molecular weight polyethylene with the mass-average molecular weight of 350 ten thousand; bulk density of polyethylene resin 0.45g/cm³(ii) a The compound A is a non-solvent of the polyethylene resin; compound B is a solvent for the polyethylene resin; the compound A is glycerol triacetate, and the compound B is castor oil;

the mixed material comprises the following substances in parts by weight: polyethylene resin: 12 parts of (1); a compound A:65 parts of (1); compound B:23 parts;

s4: then stretching the raw film, wherein the raw film is longitudinally stretched at the temperature of 130 ℃, the longitudinal stretching multiple is 7 times, and the stretching rate is 40%/s; after the longitudinal stretching is finished, transverse stretching is carried out, wherein the transverse stretching temperature is 130 ℃, the transverse stretching multiple is 7 times, and the stretching speed is 40%/s; carrying out first heat setting after transverse stretching is finished, wherein the temperature during the first heat setting is 135 ℃ and the time is 45s;

Firstly, the method comprises the following steps: structural characterization

The UPE porous films prepared in examples 1-7 and comparative examples 1-2 were subjected to various performance tests, and the results were as follows:

as can be seen from the above table, the UPE porous membranes prepared in examples 1-7 of the present invention have suitable membrane thickness and high porosity; the ratio of the initial bubble point of the porous membrane IPA to the complete bubble point of the IPA is larger and is more than 0.75, which indicates that the pore diameter distribution of the pores in the porous membrane is uniform and no extra large pores exist, so that the porous membrane has higher interception efficiency and stronger trapping capacity for impurity particles; in contrast to example 1, the solvent system of comparative example 1 has only solvent and no non-solvent, which results in less occurrence of pores during phase separation, resulting in lower porosity of the film; compared with example 4, due to the asynchronous stretching after the phase separation in comparative example 2, the pores collapse, although the average pore diameter of the membrane does not change greatly, the membrane pores become very uneven, and the difference of pore diameters in the membrane is large, so that the impurity particle capturing capability of the porous membrane is poor, and the requirement of practical application cannot be met.

The viscosity of the casting solution in examples 1 to 7 was measured with a viscometer and was less than 10Wcps, thus ensuring the normal operation of the mechanical equipment and facilitating mass production.

Water flow rate test (test device as figure 5)

Experimental procedure

The method comprises the following steps: and (3) mounting the sample to be tested after the IPA is wetted on a support for decompression and filtration, closing a valve 2 on a decompression and filtration frame, opening a valve 1, starting a vacuum pump, adjusting the pressure to 0.03MPa, and closing the valve 1.

Step two: 50ml of test solution (water) is filled into a plastic measuring cylinder of a bracket for reduced pressure filtration, a valve 2 is opened, timing is started from one scale, and timing is stopped from the other scale;

step three: after the test, the value indicated by the stopwatch was recorded, and when all the test solution passed through the UPE porous membrane, the valve 2 on the holder was closed and the sample was taken out.

Testing the tensile strength and the elongation at break of each sample by using a universal tensile testing machine;

as can be seen from the above table, the UPE porous membranes prepared in examples 1-7 of the present invention have a large filtration rate, a short time required for a fluid to pass through the UPE porous membrane, a low time cost, and a high economic benefit per unit time; meanwhile, the composite material has higher tensile strength, is convenient for various processing treatments, and meets the requirements of practical application. The UPE porous membrane prepared by the comparative examples 1-2 has low flow rate and poor tensile strength, and cannot meet the actual industrial requirements.

And (3) testing the filtering precision: the UPE porous membranes from each example were tested for interception efficiency.

Experimental equipment: a Tianjin Rougen particle counter KB-3; preparation of the experiment: the experimental set-up was assembled as per fig. 6, ensuring the set-up was clean, and the set-up was rinsed with ultra pure water; a sample with the diameter of 47mm is taken and is arranged in a butterfly filter, so that the air tightness of the assembled filter is ensured to be good.

The experimental steps are as follows:

the challenge was poured into a tank, the butterfly filter was vented, pressurized to 10kPa, and the butterfly downstream filtrate was taken using a clean bottle.

The number of particles in the filtrate and stock solutions was measured using a particle counter.

Intercepting efficiency:

in the formula:

eta-type-interception efficiency,%;

n 0-m-number of particles in the stock solution, average of 5 sets of counts;

n 1-number of particles in filtrate, average of 5 sets of counts.

The interception efficiency test results for each example are as follows:

as can be seen from the above table, the UPE porous membranes prepared in embodiments 1 to 7 of the present invention have a relatively high filtration accuracy, a retention efficiency of 95% or more, a relatively high trapping ability for impurity particles (e.g., standard gold particle impurities), and are particularly suitable for application in the field of photoresists; the UPE porous membrane prepared by the comparative examples 1-2 has poor interception efficiency and weak impurity particle trapping performance, and cannot meet the actual industrial requirements.

After the UPE porous membrane prepared in the embodiments 1 to 7 is placed for 1 hour at the temperature of 120 ℃, the shrinkage rate is less than 5 percent, which shows that the UPE porous membrane has high thermal stability, and the membrane pores are not easy to shrink or deform at high temperature, so that the membrane has high retention efficiency for a long time, the flow rate change is small in the use process, the service life is long, the application range is very wide, and the UPE porous membrane is particularly suitable for being applied to the field of photoresist.

The above description is only a preferred embodiment of the present invention, and the protection scope of the present invention is not limited to the above embodiments, and all technical solutions belonging to the idea of the present invention belong to the protection scope of the present invention. It should be noted that modifications and embellishments within the scope of the invention may occur to those skilled in the art without departing from the principle of the invention, and are considered to be within the scope of the invention.

Claims

1. A preparation method of a UPE porous membrane is characterized by comprising the following steps: the method comprises the following steps:

s1: adding polyethylene resin into a solvent system consisting of a compound A and a compound B, stirring and mixing, and uniformly mixing to form a mixed material; wherein the polyethylene resin at least comprises an ultrahigh molecular weight polyethylene with the mass-average molecular weight of more than 300 ten thousand;

s3: the liquid film is subjected to split-phase curing at the temperature of 15-120 ℃, the split-phase curing time is 1-60S,

forming a green film;

2. The method of claim 1 for preparing a UPE porous membrane, wherein: the bulk density of the polyethylene resin is 0.2-0.35g/cm³；

3. The method of claim 1 for preparing a UPE porous membrane, wherein: the compound A is at least one of dimethyl phthalate, dioctyl adipate, ethylene glycol diacetate, dimethyl carbonate, palm oil and triacetin, and the compound B is at least one of paraffin oil, white oil, hydraulic oil, decalin, a castor oil extract and castor oil.

4. The method of claim 1 for preparing a UPE porous membrane, wherein: the polyethylene resin comprises 60-80% by mass of ultrahigh molecular weight polyethylene with mass average molecular weight of more than 300 ten thousand and 20-40% by mass of ultrahigh molecular weight polyethylene with mass average molecular weight of 100-200 ten thousand and density of 0.92-0.98g/cm³The high-density polyethylene of (1).

5. The method of claim 1 for preparing a UPE porous membrane, wherein: s2, putting the mixed materials into an extruder to be heated, melted and mixed for 10-30min; the extruder comprises a melting section, a mixing section, a defoaming section, a pressurizing section and an extruding section; the temperature of the melting section and the mixing section is set to be 50-90% of the highest temperature in the extruder.

6. The method for preparing a UPE porous membrane according to claim 5, wherein: the length-diameter ratio of the extruder is 30-70;

the pressure fluctuation at the outlet of the extruder is less than 0.1MPa;

the maximum temperature in the extruder is at least 5 ℃ higher than the temperature of die extrusion.

7. The method of claim 1 for preparing a UPE porous membrane, wherein: s3, the temperatures of the two sides of the liquid film are the same when the split-phase solidification is carried out; after the phase separation and solidification are finished, the raw film is longitudinally stretched at the longitudinal stretching temperature of 60-150 ℃ and the longitudinal stretching multiple of 1-15 times; then, transverse stretching is carried out, wherein the transverse stretching temperature is 80-180 ℃, and the transverse stretching multiple is 1-15 times.

8. The method of claim 1 for preparing a UPE porous membrane, wherein: and (3) when the split-phase solidification is carried out, the temperatures of two sides of the liquid film are different, wherein the temperature of one side is at least 20 ℃ higher than that of the other side, and the thickness of the green film formed in the step (3) is 0.5-1.5mm.

9. The method of claim 1 for preparing a UPE porous membrane, wherein: s3, blowing air to at least one side of the liquid film when the liquid film is subjected to split-phase solidification, wherein the absolute humidity is 10g H₂O/kg-30g H₂O/kg, and air flow with flow rate of 0.5-5m/s is blown to the surface of the liquid film for 1-60s.

10. The method of claim 8 for making a UPE porous membrane, wherein: and S4, when the raw film is subjected to stretching treatment, simultaneously performing transverse stretching and longitudinal stretching, wherein the stretching temperature is 60-150 ℃, the transverse stretching multiple is 1-10 times, the longitudinal stretching multiple is 1-10 times, the transverse stretching speed is 5%/S-100%/S, and the longitudinal stretching speed is 5%/S-100%/S.

11. The method of claim 10 for making a UPE porous membrane, wherein the method comprises: when the raw film is subjected to stretching treatment, the ratio of the longitudinal stretching ratio to the transverse stretching ratio is 0.7-2.

12. The method of claim 1 for preparing a UPE porous membrane, wherein: the temperature for the first heat setting is 60-180 ℃ and the time is 5-120s; the temperature of the second heat setting is 5-50 ℃ higher than that of the first heat setting, and the time is 5-120s.

13. The method of claim 1 for preparing a UPE porous membrane, wherein: the extraction liquid in the S5 is at least one of dichloromethane, acetone, methanol, ethanol, glycerol, tetrafluoroethane and isopropanol; the extraction temperature is 5-25 ℃; the extraction time is 1-5h.

14. The method of claim 1 for preparing a UPE porous membrane, wherein: the thickness of the UPE porous membrane is 1-50um; the porosity of the UPE porous membrane is 20% -60%;

the UPE porous membrane is used in the field of photoresist.