CN113413684B - Polylactic acid nano double-layer fiber membrane filter element and preparation method thereof - Google Patents
Polylactic acid nano double-layer fiber membrane filter element and preparation method thereof Download PDFInfo
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Abstract
The invention relates to a polylactic acid nano double-layer fiber membrane filter core and a preparation method thereof, wherein the method comprises the following steps: firstly, preparing a polylactic acid melt electrostatic spinning nanofiber membrane MME, then arranging a TPU nanoparticle binder on the surface of the MME, then preparing a polylactic acid solution electrostatic spinning fiber membrane MSE by taking the MME as a receiving base material and the surface where the binder is located as a receiving surface, and finally performing low-pressure heat bonding in a heat treatment mode to prepare a filter element; in the prepared filter element, the ratio of the MME to the MSE fiber diameter median is 1.2-3; the gram weight of MSE is 0.1-0.2 g/m2The gram weight of the MME is 10-30 g/m2(ii) a The filtering efficiency of the filter element to 0.3 mu m particles is 93-99%, the air suction resistance is less than or equal to 200Pa, and the filtering efficiency is attenuated to be within 7% after ten times of sterilization. The method is simple, and the prepared filter element is degradable, reusable, low in gram weight and high in filtering efficiency.
Description
Technical Field
The invention belongs to the technical field of filter elements, and relates to a polylactic acid nano double-layer fiber membrane filter element and a preparation method thereof.
Background
In 2019, new coronavirus which forms a pandemic in the world is not effectively controlled, the global consumption of public safety protection products (such as masks, protective clothing and the like) is increased rapidly, and meanwhile, the recovery and treatment of waste masks become a big problem. The application of degradable materials in protective products becomes a hot point, and polylactic acid (PLA) becomes a key point of attention of technical research and development personnel in the field due to good biodegradability, biocompatibility and certain natural antibacterial performance.
The electrostatic spinning technology is mainly characterized in that a polymer solution or a melt is charged and deformed by means of a high-voltage electrostatic field, liquid drops are formed at the tail end, and then the liquid drops are sprayed and drawn into nano fibers under the drawing action of the electric field force. The electrostatic spinning nanofiber membrane has excellent filtering protection performance due to low fiber diameter and small pore diameter, and compared with melt-blown cloth, the electrostatic spinning nanofiber membrane does not depend on electrostatic adsorption to enhance the filtering performance and has filtering efficiency retention degree, so that a product adopting the electrostatic spinning fiber membrane has reusable performance. Some products have been commercialized.
The electrostatic spinning process is divided into melt electrostatic spinning and solution electrostatic spinning, the melt electrostatic spinning and the solution electrostatic spinning are commercially applied to the aspect of filtration protection products, non-woven fabrics are used as base material supports, and the enhancement effect cannot be achieved due to the large difference of fiber diameters. The following characteristics exist:
the melt electrostatic spinning fiber membrane (MME for short) has larger diameter (generally between 400 and 2000 nm), high strength, strong shape retention capacity, higher filtration efficiency (KN 95 level), obviously increased thickness and gram weight; solution electrostatic spinning fibrous membrane (MSE for short) diameter is less (generally between 20~400 nm), just can reach super high filtration efficiency at lower thickness, nevertheless has the shortcoming that filtration pressure is great, intensity is low, and when it was compound as the filter core with the non-woven fabrics in addition, MSE breaks away from the protection of non-woven fabrics easily, receives various effort such as dragging, buckling in the processing use alone, very easily damages for whole filter core membrane is invalid.
Disclosure of Invention
The invention aims to solve the problems in the prior art and provides a polylactic acid nano double-layer fiber membrane filter element and a preparation method thereof.
In order to achieve the purpose, the technical scheme adopted by the invention is as follows:
a polylactic acid nanometer double-layer fiber membrane filter core is formed by bonding a polylactic acid melt electrostatic spinning nanofiber membrane MME and a polylactic acid solution electrostatic spinning fiber membrane MSE;
the ratio of the MME fiber diameter median to the MSE fiber diameter median is 1.2-3; the median fiber diameter is determined statistically from SEM pictures of at least 5 sites in the uniformly distributed fraction; the ratio of the MME fiber to the MSE fiber is too large, so that effective entanglement cannot be formed between the MME fiber and the MSE fiber, the supporting and reinforcing effect is not obvious, and the strength advantage of the MME cannot be exerted; the ratio of the two is too small, so that the stacking density is high and the respiratory resistance is too high; when the ratio of the MME to the MSE is 1.2-3, on one hand, physical crosslinking entanglement can be generated between the MME and the MSE, so that the integral machining resistance is improved, and on the other hand, a grading effect can be generated between the MME and the MSE, so that the filtering effect is enhanced, the filtering pressure of the MSE is reduced, and the use durability is improved;
the bonding positions are distributed in a point shape, and a large-area airtight area does not exist in the filter element, so that the influence on gas resistance is avoided;
the gram weight of MSE is 0.1-0.2 g/m2The gram weight of the MME is 10-30 g/m2(ii) a The filtering efficiency of the polylactic acid nano double-layer fiber membrane filter element on 0.3 mu m particles is 93-99% according to GB2626-2006, the air suction resistance is less than or equal to 200Pa, and the filtering efficiency is attenuated to be within 7% after ten times of sterilization; the tensile strength of MSE combined with MME in the polylactic acid nano double-layer fiber membrane filter core is 7-9 MPa, and the tensile strength measured after the MSE is compacted with a single layer of MSE which has the same thickness and is not combined with MME is 3-4 MPa, and the comparison shows that the strength of MSE is effectively improved by adding MME.
As a preferred technical scheme:
according to the polylactic acid nano double-layer fiber membrane filter core, the fiber diameter range of the MME is 400-1000 nm; the MSE has a fiber diameter in the range of 120 to 400 nm.
The invention also provides a method for preparing the polylactic acid nano double-layer fiber membrane filter core, which comprises the steps of firstly preparing a polylactic acid melt electrostatic spinning nano fiber membrane MME, then arranging a TPU nano particle binder on the surface of the MME by adopting an electrostatic spray technology, then preparing a polylactic acid solution electrostatic spinning fiber membrane MSE by taking the MME as a receiving base material and the surface where the TPU nano particle binder is positioned as a receiving surface, and finally carrying out low-pressure thermal bonding by adopting a thermal treatment mode to prepare the polylactic acid nano double-layer fiber membrane filter core, wherein the temperature of the thermal treatment is 60-80 ℃, the pressure of the thermal bonding is 10-30N, in the thermal bonding process, the TPU nano particle binder is locally melted to enable the MSE and the MME to generate cross bonding and be mutually bonded, the temperature of the thermal treatment is lower, the pressure is also lower, and meanwhile, because the size of the TPU nano particle binder is smaller, a larger area of air-tight area cannot be generated, the influence on the gas resistance is avoided.
As a preferred technical scheme:
in the above method, the preparation process of the MME comprises: firstly, polylactic acid and a plasticizer (for reducing viscosity) are uniformly mixed, then the polylactic acid and the plasticizer are continuously uniformly mixed in a melt blending mode, finally, a melt material is sprayed out from a spinning nozzle and reaches a rotating receiving roller (the receiving roller continuously rotates to finally obtain a melt electrostatic spinning nanofiber membrane) to obtain MME, electrostatic voltage is applied between the spinning nozzle and the receiving roller, the melt material is sprayed out from the spinning nozzle and generates jet flow under the action of an electric field, and the jet flow is stretched by the electric field to form the nanofiber.
In the method described above, during the preparation of the MME, the plasticizer is tributyl citrate (TBC), triphenyl phosphite (TPPi), or dibutyl sebacate (DBS); the mass ratio of the polylactic acid to the plasticizer is 100: 0.2-3; the temperature of the melt blending is 175-210 ℃; the distance between the spinning nozzle and the receiving roller is 10-20 cm; the electrostatic voltage is 15-40 kV; the invention controls the fiber diameter in MME by controlling the plasticizer addition amount, electrostatic voltage, and distance between the spinneret and the receiving roller.
According to the method, in the preparation process of the MME, in order to promote the melt jet flow stretching and reduce the fiber diameter, hot air flow with the temperature of 220-260 ℃ is introduced between the spinning nozzle and the receiving roller, if the temperature of the introduced hot air flow is lower than 220 ℃, the stretching effect is poor, and if the temperature of the introduced hot air flow is higher than 260 ℃, the stretching is easy to fuse.
In the method, the process of disposing the TPU nanoparticle binder on the surface of the MME by using the electrostatic spraying technology comprises the following steps: dissolving TPU resin (melting point 60-80 ℃) in a solvent to obtain a solution, and spraying the solution on MME by using multi-needle electrostatic spinning equipment.
In the method, in the process of arranging the TPU nanoparticle binder on the surface of the MME by adopting the electrostatic spraying technology, the solvent is a mixed solution of DMF and THF in a volume ratio of 1: 1; the mass concentration of the solution is 7% -9%; the electric field distance (namely the distance between the spray head and the receiving roller) is 10-13 cm during spraying, and the single-needle injection rate is 0.12-0.4 ml/min (the injection rate is set to generate a large amount of nano-scale TPU micro-tablets which are uniformly distributed on the MME).
As described above, the MSE is prepared by the following steps: firstly, dissolving polylactic acid in a solvent, simultaneously adding an emulsifier to obtain a solution, and spraying the solution on a receiving substrate by adopting multi-needle solution electrostatic spinning electrode equipment to obtain MSE.
In the method, during the preparation process of MSE, the solvent is more than one of NMP, DMF, DMAc, 1, 4-dioxane, DMSO and acetone; the emulsifier is more than one of polyvinylpyrrolidone, cetyl trimethyl ammonium bromide, sodium dodecyl benzene sulfonate, betaine amphoteric surfactant, octyl phenol polyoxyethylene ether and sorbitan fatty acid ester; the dissolving temperature is 70-80 ℃; the mass concentration of polylactic acid in the solution is 8-12%, and the mass concentration of the emulsifier is 0.01-0.04%; during spraying, the spinning voltage is 15-25 kV, the distance between an electrode and a receiving roller is 10-15 cm, and the relative humidity of the environment is 30% -40%; the invention controls the fiber diameter in MSE by controlling the spinning voltage, the spacing between the electrode and the receiving roller and the relative humidity of the environment.
The principle of the invention is as follows:
the filter element in the prior art mostly consists of MSE and non-woven fabrics, wherein the non-woven fabrics are mainly used as supporting base materials, the pore diameter and the fiber diameter distribution of the non-woven fabrics are wide and difficult to control, and PM is treated0.3The filter effect of granule can be ignored, MSE's filtration pressure is great, uses the durability relatively poor, simultaneously because of being difficult to establish effectual complex between MSE and the non-woven fabrics, MSE breaks away from the protection of non-woven fabrics easily, receives in the processing use alone various effort such as dragging, buckling, very easily damaged for whole filter element membrane inefficacy, in addition, MSE still has the problem that intensity is low.
The filter element is formed by bonding a polylactic acid melt electrostatic spinning nanofiber membrane MME and a polylactic acid solution electrostatic spinning fiber membrane MSE, wherein the MME not only serves as a support base material and plays a role in structural support, but also can play the following roles:
1) the fiber diameter (the average diameter is less than or equal to 2 mu m) of the MME is far smaller than that of the non-woven fabric (the average diameter is more than or equal to 15 mu m), grading effect can be generated between the MME and the MSE, the filtering effect is enhanced, the filtering pressure of the MSE is reduced, and the use durability is improved; 2) the MME is mainly made of filaments and has better mechanical property, and due to the matching of the diameters of the MME and the MSE fibers, the MME can be physically cross-linked and entangled with the MSE, so that the integral machining resistance is improved; 3) effective bonding can be formed between the MME and the MSE, common stress is applied, and the mechanical strength of the MSE is improved.
The invention solves the problem of processing strength of neglected electrostatic spinning nanofiber membrane when used for filtration by reasonable design of double nanofiber functional layers, simultaneously reduces weight and decrement of the filter material by more than 60% compared with the weight of a traditional filter core material (namely an SMS filter material which is a three-layer combination of non-woven fabric-melt-blown fabric-spun-bonded non-woven fabric from outside to inside) with the same efficiency, and can design a thinner and lighter filtration protection product (on one hand, the MME (mobility management entity) gram weight is lower than that of the traditional non-woven fabric (more than 35 g/m)2) (ii) a On the other hand, as the MME has certain stable filtering efficiency and takes the MME as a substrate, the MSE amount can be obviously reduced under the condition of achieving the same filtering efficiency); the MME has relatively good strength and certain original filtering efficiency, the fiber diameter is between hundreds of nanometers and 1 micron, only a layer of thin MSE needs to be added, and then a common rolling and fixing mode of non-woven fabrics is adopted to obtain a light, thin and practical filter element membrane; the polylactic acid nano double-layer fiber membrane filter core can realize long-term filtration efficiency maintenance without electrostatic electret and base materials, and can be repeatedly used and degraded.
Has the advantages that:
(1) according to the preparation method of the polylactic acid nano double-layer fiber membrane filter element, the MME can be physically entangled with MSE, and meanwhile, the mechanical property of the filter element membrane is obviously enhanced by matching with a binder, so that the use and processing stability is improved;
(2) according to the preparation method of the polylactic acid nano double-layer fiber membrane filter element, the grading effect can be generated between the MME and the MSE, the filtering effect is enhanced, the filtering pressure of the MSE is reduced, and the use durability is improved;
(3) the preparation method of the polylactic acid nano double-layer fiber membrane filter element avoids the problem of high fiber stacking density caused by too thin fibers in the preparation process of the traditional single-layer nanofiber filter membrane (the problem of high stacking density caused by the fact that the traditional nanofiber filter membrane only uses MSE and the MSE has thin diameter is solved, the quantity of the nanofibers with two diameters is reasonably matched, so that excessive stacking of the nanofiber membrane can be avoided), and meanwhile, the scattering of the nanofiber fibers is solved, the mechanical strength of the membrane is further improved, and the processing requirement of downstream products is met;
(4) the polylactic acid nano double-layer fiber membrane filter element prepared by the method is degradable, can be repeatedly used, and has low gram weight and high filtering efficiency.
Drawings
Fig. 1 is an electron microscope image of the polylactic acid nano double-layer fiber membrane filter element prepared in example 1.
Detailed Description
The invention will be further illustrated with reference to specific embodiments. It should be understood that these examples are for illustrative purposes only and are not intended to limit the scope of the present invention. Further, it should be understood that various changes or modifications of the present invention may be made by those skilled in the art after reading the teaching of the present invention, and such equivalents may fall within the scope of the present invention as defined in the appended claims.
Example 1
A preparation method of a polylactic acid nano double-layer fiber membrane filter core comprises the following specific steps:
(1) firstly, uniformly mixing polylactic acid and tributyl citrate in a mass ratio of 100:0.2, then continuously and uniformly mixing at 175 ℃ in a melt blending mode, finally spraying a molten material from a spinning nozzle, and under the applied electrostatic voltage of 15kV, enabling the molten material to reach a rotating receiving roller to prepare a polylactic acid melt electrostatic spinning nanofiber membrane MME; wherein the distance between the spinneret and the receiving roller is 10 m;
(2) dissolving TPU resin in a mixed solution of DMF and THF in a volume ratio of 1:1 to obtain a solution with a mass concentration of 7%, and spraying the solution on the MME prepared in the step (1) by adopting multi-needle electrostatic spinning equipment to prepare the MME with the TPU nanoparticle binder arranged on one surface; wherein, the electric field distance is 10cm during spraying, and the single-needle injection rate in the multi-needle electrostatic spinning equipment is 0.12 ml/min;
(3) dissolving polylactic acid in NMP at 70 ℃, simultaneously adding polyvinylpyrrolidone to obtain a solution, wherein the mass concentration of the polylactic acid in the solution is 8%, and the mass concentration of the polyvinylpyrrolidone in the solution is 0.01%, and then spraying the solution on the MME (the surface where the TPU nanoparticle binder is located is the receiving surface) with the TPU nanoparticle binder obtained in the step (2) by adopting a multi-needle solution electrostatic spinning electrode device to prepare a polylactic acid solution electrostatic spinning fiber membrane MSE; wherein, during spraying, the spinning voltage is 15kV, the distance between an electrode and a receiving roller is 10cm, and the relative humidity of the environment is 30 percent;
(4) and (3) carrying out low-pressure thermal bonding (the temperature of the thermal treatment is 60 ℃, and the pressure of the thermal bonding is 30N) on the product obtained in the step (3) by adopting a thermal treatment mode to obtain the polylactic acid nano double-layer fiber membrane filter element.
The finally prepared polylactic acid nano double-layer fiber membrane filter element is shown in figure 1 and is formed by bonding a polylactic acid melt electrostatic spinning nano fiber membrane MME (the fiber diameter range of MME is 400-1000 nm) and a polylactic acid solution electrostatic spinning fiber membrane MSE (the fiber diameter range of MSE is 120-400 nm); the ratio of the median of MME fiber diameter to the median of MSE fiber diameter is 1.2; the bonding positions are distributed in a point shape; the gram weight of MSE was 0.11g/m2The gram weight of the MME is 23g/m2(ii) a According to GB2626-2006, the filtration efficiency of the polylactic acid nano double-layer fiber membrane filter core on 0.3 mu m particles is 94%, the air suction resistance is 120Pa, and the attenuation of the filtration efficiency after ten times of sterilization is 6%.
Example 2
A preparation method of a polylactic acid nano double-layer fiber membrane filter core comprises the following specific steps:
(1) firstly, uniformly mixing polylactic acid and triphenyl phosphite in a mass ratio of 100:0.6, then continuously and uniformly mixing at the temperature of 180 ℃ in a melt blending mode, finally spraying a molten material from a spinning nozzle, and under the applied electrostatic voltage of 20kV, enabling the molten material to reach a rotating receiving roller to prepare a polylactic acid melt electrostatic spinning nanofiber membrane MME; wherein the distance between the spinneret and the receiving roller is 12 m;
(2) dissolving TPU resin in a mixed solution of DMF and THF in a volume ratio of 1:1 to obtain a solution with the mass concentration of 8%, and spraying the solution on the MME prepared in the step (1) by adopting multi-needle electrostatic spinning equipment to prepare the MME with the TPU nanoparticle binder arranged on one surface; wherein, the electric field distance is 11cm during spraying, and the single-needle injection rate in the multi-needle electrostatic spinning equipment is 0.2 ml/min;
(3) dissolving polylactic acid in DMF at 72 ℃, simultaneously adding cetyl trimethyl ammonium bromide to obtain a solution, wherein the mass concentration of the polylactic acid in the solution is 9%, and the mass concentration of the cetyl trimethyl ammonium bromide is 0.02%, and then spraying the solution on the MME (the surface where the TPU nanoparticle binder is located is the receiving surface) with the TPU nanoparticle binder obtained in the step (2) by adopting multi-needle solution electrostatic spinning electrode equipment to prepare a polylactic acid solution electrostatic spinning fiber membrane MSE; wherein, during spraying, the spinning voltage is 18kV, the distance between an electrode and a receiving roller is 11cm, and the relative humidity of the environment is 32%;
(4) and (3) carrying out low-pressure thermal bonding (the temperature of the thermal treatment is 63 ℃, and the pressure of the thermal bonding is 27N) on the product obtained in the step (3) by adopting a thermal treatment mode to prepare the polylactic acid nano double-layer fiber membrane filter element.
The finally prepared polylactic acid nano double-layer fiber membrane filter core is formed by bonding a polylactic acid melt electrostatic spinning nanofiber membrane MME (the fiber diameter range of MME is 400-1000 nm) and a polylactic acid solution electrostatic spinning fiber membrane MSE (the fiber diameter range of MSE is 120-400 nm); the ratio of the median of MME fiber diameter to the median of MSE fiber diameter is 1.6; the bonding positions are distributed in a point shape; the gram weight of MSE was 0.12g/m2The gram weight of MME is 24g/m2(ii) a According to GB2626-2006, the filtration efficiency of the polylactic acid nano double-layer fiber membrane filter element on 0.3 mu m particles is 93%, the air suction resistance is 130Pa, and the filtration efficiency attenuation is 7% after ten times of sterilization.
Example 3
A preparation method of a polylactic acid nano double-layer fiber membrane filter core comprises the following specific steps:
(1) firstly, uniformly mixing polylactic acid and dibutyl sebacate in a mass ratio of 100:1, then continuously and uniformly mixing at 185 ℃ in a melt blending mode, finally spraying molten materials from a spinning nozzle, and under the applied electrostatic voltage of 25kV, enabling the molten materials to reach a rotating receiving roller to prepare a polylactic acid melt electrostatic spinning nanofiber membrane MME; wherein the distance between the spinneret and the receiving roller is 14 m;
(2) dissolving TPU resin in a mixed solution of DMF and THF in a volume ratio of 1:1 to obtain a solution with the mass concentration of 9%, and spraying the solution on the MME prepared in the step (1) by adopting multi-needle electrostatic spinning equipment to prepare the MME with the TPU nanoparticle binder arranged on one surface; wherein, the electric field distance is 12cm during spraying, and the single-needle injection rate in the multi-needle electrostatic spinning equipment is 0.24 ml/min;
(3) dissolving polylactic acid in DMAc at 74 ℃, simultaneously adding sodium dodecyl benzene sulfonate to obtain a solution, wherein the mass concentration of the polylactic acid in the solution is 10%, and the mass concentration of the sodium dodecyl benzene sulfonate is 0.03%, and then spraying the solution on the MME (the surface where the TPU nanoparticle binder is located is the receiving surface) with the TPU nanoparticle binder obtained in the step (2) by adopting multi-needle solution electrostatic spinning electrode equipment to prepare a polylactic acid solution electrostatic spinning fiber membrane MSE; wherein, during spraying, the spinning voltage is 20kV, the distance between an electrode and a receiving roller is 12cm, and the relative humidity of the environment is 34 percent;
(4) and (3) carrying out low-pressure thermal bonding (the temperature of the thermal treatment is 66 ℃, and the pressure of the thermal bonding is 24N) on the product obtained in the step (3) by adopting a thermal treatment mode to obtain the polylactic acid nano double-layer fiber membrane filter element.
The finally prepared polylactic acid nano double-layer fiber membrane filter core is formed by bonding a polylactic acid melt electrostatic spinning nanofiber membrane MME (the fiber diameter range of MME is 400-1000 nm) and a polylactic acid solution electrostatic spinning fiber membrane MSE (the fiber diameter range of MSE is 120-400 nm); the ratio of the median of MME fiber diameter to the median of MSE fiber diameter is 1.5; the bonding positions are distributed in a point shape; the gram weight of MSE was 0.13g/m2The gram weight of the MME is 26g/m2(ii) a The filtering efficiency of the polylactic acid nano double-layer fiber membrane filter element on 0.3 mu m particles is measured according to GB2626-200693 percent, the air suction resistance is 150Pa, and the filtration efficiency is attenuated to 6 percent after ten times of sterilization.
Example 4
A preparation method of a polylactic acid nano double-layer fiber membrane filter core comprises the following specific steps:
(1) firstly, uniformly mixing polylactic acid and tributyl citrate in a mass ratio of 100:1.4, then continuously and uniformly mixing at 190 ℃ by adopting a melt blending mode, finally spraying a molten material from a spinning nozzle, and under the applied electrostatic voltage of 30kV, passing through hot air flow at 220 ℃ and then reaching a rotating receiving roller to prepare a polylactic acid melt electrostatic spinning nanofiber membrane MME; wherein the distance between the spinneret and the receiving roller is 16 m;
(2) dissolving TPU resin in a mixed solution of DMF and THF in a volume ratio of 1:1 to obtain a solution with a mass concentration of 7%, and spraying the solution on the MME prepared in the step (1) by adopting multi-needle electrostatic spinning equipment to prepare the MME with the TPU nanoparticle binder arranged on one surface; wherein, the electric field distance is 13cm during spraying, and the single-needle injection rate in the multi-needle electrostatic spinning equipment is 0.28 ml/min;
(3) dissolving polylactic acid in 1, 4-dioxane at 76 ℃, simultaneously adding dodecyl betaine to obtain a solution, wherein the mass concentration of the polylactic acid in the solution is 11%, and the mass concentration of the dodecyl betaine is 0.04%, and then spraying the solution on the MME (the surface where the TPU nanoparticle binder is located is a receiving surface) with the TPU nanoparticle binder obtained in the step (2) by adopting multi-needle solution electrostatic spinning electrode equipment to prepare a polylactic acid solution electrostatic spinning fibrous membrane MSE; wherein, during spraying, the spinning voltage is 22kV, the distance between an electrode and a receiving roller is 13cm, and the relative humidity of the environment is 36%;
(4) and (3) carrying out low-pressure thermal bonding (the temperature of the thermal treatment is 69 ℃, and the pressure of the thermal bonding is 20N) on the product obtained in the step (3) by adopting a thermal treatment mode to obtain the polylactic acid nano double-layer fiber membrane filter element.
The finally prepared polylactic acid nano double-layer fiber membrane filter core is prepared by melting and electrostatically spinning a polylactic acid nano fiber membrane MME (fiber alignment of MME)Diameter range of 400-1000 nm) and polylactic acid solution electrostatic spinning fiber film MSE (MSE fiber diameter range of 120-400 nm); the ratio of the median of the MME fiber diameter to the median of the MSE fiber diameter is 2; the bonding positions are distributed in a point shape; the gram weight of MSE is 0.15g/m2The gram weight of MME is 18g/m2(ii) a According to GB2626-2006, the filtration efficiency of the polylactic acid nano double-layer fiber membrane filter core on 0.3 mu m particles is 96%, the air suction resistance is 150Pa, and the attenuation of the filtration efficiency after ten times of sterilization is 4%.
Example 5
A preparation method of a polylactic acid nano double-layer fiber membrane filter core comprises the following specific steps:
(1) firstly, uniformly mixing polylactic acid and triphenyl phosphite in a mass ratio of 100:1.8, then continuously and uniformly mixing at the temperature of 195 ℃ by adopting a melt blending mode, finally spraying a molten material from a spinning nozzle, and under the applied electrostatic voltage of 35kV, passing through hot air flow at the temperature of 230 ℃ and then reaching a rotating receiving roller to prepare a polylactic acid melt electrostatic spinning nanofiber membrane MME; wherein the distance between the spinneret and the receiving roller is 18 m;
(2) dissolving TPU resin in a mixed solution of DMF and THF in a volume ratio of 1:1 to obtain a solution with the mass concentration of 8%, and spraying the solution on the MME prepared in the step (1) by adopting multi-needle electrostatic spinning equipment to prepare the MME with the TPU nanoparticle binder arranged on one surface; wherein, the electric field distance is 10cm during spraying, and the single-needle injection rate in the multi-needle electrostatic spinning equipment is 0.32 ml/min;
(3) dissolving polylactic acid in DMSO (dimethyl sulfoxide) at 78 ℃, simultaneously adding octylphenol polyoxyethylene ether to obtain a solution, wherein the mass concentration of the polylactic acid in the solution is 12%, and the mass concentration of the octylphenol polyoxyethylene ether in the solution is 0.01%, and then spraying the solution on the MME (the surface where the TPU nanoparticle binder is located is the receiving surface) with the TPU nanoparticle binder obtained in the step (2) by adopting multi-needle solution electrostatic spinning electrode equipment to prepare a polylactic acid solution electrostatic spinning fiber membrane MSE; wherein, during spraying, the spinning voltage is 23kV, the distance between an electrode and a receiving roller is 14cm, and the relative humidity of the environment is 38%;
(4) and (3) carrying out low-pressure thermal bonding (the temperature of the thermal treatment is 72 ℃, and the pressure of the thermal bonding is 17N) on the product obtained in the step (3) by adopting a thermal treatment mode to obtain the polylactic acid nano double-layer fiber membrane filter element.
The finally prepared polylactic acid nano double-layer fiber membrane filter core is formed by bonding a polylactic acid melt electrostatic spinning nanofiber membrane MME (the fiber diameter range of MME is 400-1000 nm) and a polylactic acid solution electrostatic spinning fiber membrane MSE (the fiber diameter range of MSE is 120-400 nm); the ratio of the median of MME fiber diameter to the median of MSE fiber diameter is 2.1; the bonding positions are distributed in a point shape; the gram weight of MSE was 0.12g/m2The gram weight of MME is 20g/m2(ii) a According to GB2626-2006, the filtration efficiency of the polylactic acid nano double-layer fiber membrane filter core on 0.3 mu m particles is 97%, the air suction resistance is 155Pa, and the attenuation of the filtration efficiency after ten times of sterilization is 3%.
Example 6
A preparation method of a polylactic acid nano double-layer fiber membrane filter core comprises the following specific steps:
(1) firstly, uniformly mixing polylactic acid and dibutyl sebacate in a mass ratio of 100:2.2, then continuously and uniformly mixing at the temperature of 200 ℃ by adopting a melt blending mode, finally spraying a molten material from a spinning nozzle, and under the applied electrostatic voltage of 40kV, passing through hot air flow at the temperature of 245 ℃ to reach a rotating receiving roller to prepare a polylactic acid melt electrostatic spinning nanofiber membrane MME; wherein the distance between the spinneret and the receiving roller is 19 m;
(2) dissolving TPU resin in a mixed solution of DMF and THF in a volume ratio of 1:1 to obtain a solution with the mass concentration of 9%, and spraying the solution on the MME prepared in the step (1) by adopting multi-needle electrostatic spinning equipment to prepare the MME with the TPU nanoparticle binder arranged on one surface; wherein, the electric field distance is 11cm during spraying, and the single-needle injection rate in the multi-needle electrostatic spinning equipment is 0.35 ml/min;
(3) dissolving polylactic acid in acetone at 79 ℃, simultaneously adding SPAN-80 to obtain a solution, wherein the mass concentration of the polylactic acid in the solution is 8%, and the mass concentration of the SPAN-80 in the solution is 0.02%, and then spraying the solution on the MME (the surface where the TPU nanoparticle binder is located is the receiving surface) with the TPU nanoparticle binder obtained in the step (2) by adopting multi-needle solution electrostatic spinning electrode equipment to prepare a polylactic acid solution electrostatic spinning fiber membrane MSE; wherein, during spraying, the spinning voltage is 24kV, the distance between an electrode and a receiving roller is 15cm, and the relative humidity of the environment is 39%;
(4) and (3) carrying out low-pressure thermal bonding (the temperature of the thermal treatment is 76 ℃, and the pressure of the thermal bonding is 14N) on the product obtained in the step (3) by adopting a thermal treatment mode to obtain the polylactic acid nano double-layer fiber membrane filter element.
The finally prepared polylactic acid nano double-layer fiber membrane filter core is formed by bonding a polylactic acid melt electrostatic spinning nanofiber membrane MME (the fiber diameter range of MME is 400-1000 nm) and a polylactic acid solution electrostatic spinning fiber membrane MSE (the fiber diameter range of MSE is 120-400 nm); the ratio of the median of MME fiber diameter to the median of MSE fiber diameter is 2.2; the bonding positions are distributed in a point shape; the gram weight of MSE was 0.14g/m2The gram weight of MME is 16g/m2(ii) a According to GB2626-2006, the filtration efficiency of the polylactic acid nano double-layer fiber membrane filter core on 0.3 mu m particles is 99%, the air suction resistance is 145Pa, and the filtration efficiency attenuation is 4% after ten times of sterilization.
Example 7
A preparation method of a polylactic acid nano double-layer fiber membrane filter core comprises the following specific steps:
(1) firstly, uniformly mixing polylactic acid and tributyl citrate in a mass ratio of 100:3, then continuously and uniformly mixing at 210 ℃ in a melt blending mode, finally spraying a molten material from a spinning nozzle, and under the applied electrostatic voltage of 40kV, passing through hot air flow at 260 ℃ and then reaching a rotating receiving roller to prepare a polylactic acid melt electrostatic spinning nanofiber membrane MME; wherein the distance between the spinneret and the receiving roller is 20 m;
(2) dissolving TPU resin in a mixed solution of DMF and THF in a volume ratio of 1:1 to obtain a solution with a mass concentration of 7%, and spraying the solution on the MME prepared in the step (1) by adopting multi-needle electrostatic spinning equipment to prepare the MME with the TPU nanoparticle binder arranged on one surface; wherein, the electric field distance is 12cm during spraying, and the single-needle injection rate in the multi-needle electrostatic spinning equipment is 0.4 ml/min;
(3) dissolving polylactic acid in a mixture of NMP and DMF at a mass ratio of 1:1 at 80 ℃, simultaneously adding a mixture of polyvinylpyrrolidone and cetyltrimethylammonium bromide at a mass ratio of 1:1 to obtain a solution, wherein the mass concentration of the polylactic acid in the solution is 9%, and the mass concentration of the mixture of polyvinylpyrrolidone and cetyltrimethylammonium bromide is 0.03%, and then spraying the solution on the MME (the surface where the TPU nanoparticle binder is located is a receiving surface) with the TPU nanoparticle binder obtained in the step (2) by adopting multi-needle solution electrostatic spinning electrode equipment to prepare a polylactic acid solution electrostatic spinning fiber membrane MSE; wherein, during spraying, the spinning voltage is 25kV, the distance between an electrode and a receiving roller is 15cm, and the relative humidity of the environment is 40%;
(4) and (3) carrying out low-pressure thermal bonding (the temperature of the thermal treatment is 80 ℃, and the pressure of the thermal bonding is 10N) on the product obtained in the step (3) by adopting a thermal treatment mode to prepare the polylactic acid nano double-layer fiber membrane filter element.
The finally prepared polylactic acid nano double-layer fiber membrane filter core is formed by bonding a polylactic acid melt electrostatic spinning nanofiber membrane MME (the fiber diameter range of MME is 400-1000 nm) and a polylactic acid solution electrostatic spinning fiber membrane MSE (the fiber diameter range of MSE is 120-400 nm); the ratio of the median of MME fiber diameter to the median of MSE fiber diameter is 2.1; the bonding positions are distributed in a point shape; the gram weight of MSE is 0.18g/m2The gram weight of MME is 17g/m2(ii) a The filtering efficiency of the polylactic acid nano double-layer fiber membrane filter element on 0.3 mu m particles is 98 percent and the air suction resistance is 156Pa according to GB2626-2006, and the filtering efficiency is attenuated to 2 percent after ten times of sterilization.
Claims (10)
1. A polylactic acid nano double-layer fiber membrane filter core is characterized in that a polylactic acid melt electrostatic spinning nano fiber membrane MME and a polylactic acid solution electrostatic spinning fiber membrane MSE are bonded through a TPU nanoparticle binder;
the ratio of the MME fiber diameter median to the MSE fiber diameter median is 1.2-3;
the MME fiber consists of polylactic acid and a plasticizer; the MSE fiber consists of polylactic acid and an emulsifier;
the bonding positions are distributed in a point shape;
the gram weight of MSE is 0.1-0.2 g/m2The gram weight of the MME is 10-30 g/m2(ii) a The filtering efficiency of the polylactic acid nano double-layer fiber membrane filter element on 0.3 mu m particles is 93-99% measured according to GB2626-2006, the air suction resistance is less than or equal to 200Pa, and the filtering efficiency is attenuated within 7% after ten times of sterilization.
2. The polylactic acid nano double-layer fiber membrane filter element according to claim 1, wherein the fiber diameter of MME is 400-1000 nm; the MSE has a fiber diameter in the range of 120 to 400 nm.
3. The preparation method of the polylactic acid nanometer double-layer fiber membrane filter element as claimed in claim 1 or 2, characterized in that, firstly, a polylactic acid melt electrostatic spinning nanometer fiber membrane MME is prepared, then a TPU nanometer particle binder is arranged on the surface of the MME by adopting an electrostatic spraying technology, then the MME is used as a receiving base material, the surface where the TPU nanometer particle binder is located is used as a receiving surface, a polylactic acid solution electrostatic spinning fiber membrane MSE is prepared, and finally, a heat treatment mode is adopted for low-pressure heat bonding, so that the polylactic acid nanometer double-layer fiber membrane filter element is prepared, wherein the heat treatment temperature is 60-80 ℃, and the heat bonding pressure is 10-30N.
4. The method of claim 3, wherein the MME is prepared by: firstly, uniformly mixing polylactic acid and a plasticizer, then continuously and uniformly mixing in a melt blending mode, finally, spraying a molten material from a spinning nozzle to a rotating receiving roller to obtain MME, and applying electrostatic voltage between the spinning nozzle and the receiving roller.
5. The method of claim 4, wherein during the preparation of the MME, the plasticizer is tributyl citrate, triphenyl phosphite or dibutyl sebacate; the mass ratio of the polylactic acid to the plasticizer is 100: 0.2-3; the temperature of the melt blending is 175-210 ℃; the distance between the spinning nozzle and the receiving roller is 10-20 cm; the electrostatic voltage is 15-40 kV.
6. The method according to claim 4, wherein during the preparation of MME, hot air with the temperature of 220-260 ℃ is introduced between the spinneret and the receiving roller.
7. The method of claim 3, wherein the disposing of the TPU nanoparticle binder on the surface of the MME by the electrostatic spraying technique comprises: dissolving TPU resin in a solvent to obtain a solution, and spraying the solution on the MME by adopting multi-needle electrostatic spinning equipment.
8. The method as claimed in claim 7, wherein in the process of disposing the TPU nanoparticle binder on the surface of the MME by using the electrostatic spraying technology, the solvent is a mixed solution of DMF and THF in a volume ratio of 1: 1; the mass concentration of the solution is 7-9%; the electric field distance is 10-13 cm during spraying, and the single-needle injection rate is 0.12-0.4 ml/min.
9. The method of claim 3, wherein the MSE is prepared by: firstly, dissolving polylactic acid in a solvent, simultaneously adding an emulsifier to obtain a solution, and spraying the solution on a receiving substrate by adopting multi-needle solution electrostatic spinning electrode equipment to obtain MSE.
10. The method of claim 9, wherein during the preparation of MSE, the solvent is one or more of NMP, DMF, DMAc, 1, 4-dioxane, DMSO, and acetone; the emulsifier is more than one of polyvinylpyrrolidone, cetyl trimethyl ammonium bromide, sodium dodecyl benzene sulfonate, betaine amphoteric surfactant, octyl phenol polyoxyethylene ether and sorbitan fatty acid ester; the dissolving temperature is 70-80 ℃; the mass concentration of the polylactic acid in the solution is 8-12 percent, and the mass concentration of the emulsifier is 0.01-0.04 percent; and during spraying, the spinning voltage is 15-25 kV, the distance between an electrode and a receiving roller is 10-15 cm, and the relative humidity of the environment is 30% -40%.
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