WO2023024497A1 - 一种聚乳酸纳米双层纤维膜滤芯及其制备方法 - Google Patents

一种聚乳酸纳米双层纤维膜滤芯及其制备方法 Download PDF

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WO2023024497A1
WO2023024497A1 PCT/CN2022/081846 CN2022081846W WO2023024497A1 WO 2023024497 A1 WO2023024497 A1 WO 2023024497A1 CN 2022081846 W CN2022081846 W CN 2022081846W WO 2023024497 A1 WO2023024497 A1 WO 2023024497A1
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mme
polylactic acid
mse
solution
fiber membrane
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PCT/CN2022/081846
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French (fr)
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张�林
赵润
徐锦龙
汪丽霞
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江苏新视界先进功能纤维创新中心有限公司
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D39/00—Filtering material for liquid or gaseous fluids
    • B01D39/14—Other self-supporting filtering material ; Other filtering material
    • B01D39/16—Other self-supporting filtering material ; Other filtering material of organic material, e.g. synthetic fibres

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  • the invention belongs to the technical field of filter elements, and relates to a polylactic acid nanometer double-layer fiber membrane filter element and a preparation method thereof.
  • the electrospinning processing technology mainly uses a high-voltage electrostatic field to charge and deform the polymer solution or melt, forming droplets at the end, and then jetting and pulling them into nanofibers under the traction of the electric field force.
  • Electrospun nanofiber membrane has excellent filtration protection performance due to its low fiber diameter and small pore size. At the same time, compared with melt-blown cloth, it does not rely on electrostatic adsorption to enhance filtration performance and maintain filtration efficiency.
  • Membrane products are reusable. Some products have been commercialized.
  • melt electrospinning and solution electrospinning both of which are commercially used in filtration and protection products, and both use non-woven fabric as the substrate support. Due to the large difference in fiber diameter, it cannot reach enhanced effect. The following characteristics exist:
  • MME Melt electrospun fiber membrane fiber
  • MSE solution electrospun fiber membrane
  • MSE has a small diameter (generally between 20 and 400nm), and can achieve ultra-high filtration efficiency at a relatively low thickness, but has the disadvantages of high filtration pressure and low strength.
  • MSE is easily separated from the protection of the non-woven fabric, and it is easily damaged by various pulling, bending and other forces during processing and use, making the entire filter membrane invalid.
  • the purpose of the present invention is to solve the above-mentioned problems existing in the prior art, and to provide a polylactic acid nano-layer fiber membrane filter element and a preparation method thereof.
  • a polylactic acid nano-layer fiber membrane filter element which is formed by bonding polylactic acid molten electrospun nanofiber membrane MME and polylactic acid solution electrospun fiber membrane MSE;
  • the ratio of the median MME fiber diameter to the median MSE fiber diameter is 1.2 to 3; the median fiber diameter is statistically determined by SEM photos in at least 5 parts of the evenly distributed part; if the ratio of the two is too large, MME Between fibers and MSE fibers, no effective entanglement can be formed, the effect of support enhancement is not obvious, and the strength advantage of MME cannot be exerted; if the ratio of the two is too small, it is easy to cause high packing density and high breathing resistance; the ratio of the two is 1.2 ⁇ 3: On the one hand, physical cross-linking and entanglement can occur between MME and MSE to improve the overall machining resistance; on the other hand, a gradation effect can be produced between MME and MSE to enhance the filtration effect and reduce the filtration pressure of MSE , improve durability;
  • the bonding position is distributed in a dot shape, and there is no large air-tight area in the filter element, which eliminates the influence on gas resistance;
  • the grammage of MSE is 0.1-0.2g/m 2 , and the grammage of MME is 10-30g/m 2 ; according to GB2626-2006, the filtration efficiency of polylactic acid nano-layer fiber membrane filter element to 0.3 ⁇ m particles is 93-99% %, suction resistance ⁇ 200Pa, after ten times of sterilization, the filtration efficiency attenuation is within 7%; the tensile strength of MSE combined with MME in the polylactic acid nano-layer fiber membrane filter element of the present invention is 7-9MPa, which is the same thickness The tensile strength of the single-layer MSE not combined with MME was measured to be 3-4 MPa after compaction. It can be seen from the comparison that the addition of MME effectively improves the strength of MSE.
  • the fiber diameter range of MME is 400-1000 nm; the fiber diameter range of MSE is 120-400 nm.
  • the present invention also provides a method for preparing a polylactic acid nano-layer fiber membrane filter core as described above. Firstly, the polylactic acid melting electrospinning nanofiber membrane MME is prepared, and then the surface of the MME is bonded with TPU nanoparticles by electrostatic spraying technology. Next, MME is used as the receiving substrate, and the surface of the TPU nanoparticle binder is used as the receiving surface to prepare the electrospun fiber membrane MSE of polylactic acid solution, and finally the method of heat treatment is used for low-pressure thermal bonding to obtain polylactic acid nanoparticles. For the double-layer fiber membrane filter element, the heat treatment temperature is 60-80°C, and the heat-bonding pressure is 10-30N.
  • the TPU nanoparticle binder partially melts, causing MSE and MME to cross-link and interact with each other. Bonding, heat treatment temperature is low, the pressure is also low, and because the size of the TPU nanoparticle binder is small, it will not produce a large area of air-tight area, eliminating the impact on gas resistance.
  • the preparation process of MME is: first, mix polylactic acid and plasticizer (acting as a viscosity reducer) evenly, then continue to mix evenly by means of melt blending, and finally spray the molten material from the spinneret , arrive at the rotating receiving roll (the receiving roll rotates continuously, and finally obtain the molten electrospun nanofiber film) to obtain MME, apply an electrostatic voltage between the spinneret and the receiving roll, and the molten material is sprayed from the spinneret under the action of an electric field A jet is generated, and the jet is stretched by an electric field to form nanofibers.
  • plasticizer is tributyl citrate (TBC), triphenyl phosphite (TPPi) or dibutyl sebacate (DBS); Polylactic acid and plasticizer
  • TBC tributyl citrate
  • TPPi triphenyl phosphite
  • DBS dibutyl sebacate
  • Polylactic acid and plasticizer The mass ratio is 100:0.2 ⁇ 3; the temperature of melt blending is 175 ⁇ 210 °C; the distance between the spinneret and the receiving roll is 10 ⁇ 20cm; the electrostatic voltage is 15 ⁇ 40kV; the present invention controls the plasticizer Addition amount, electrostatic voltage, distance between spinneret and take-up roll control fiber diameter in MME.
  • a hot air flow with a temperature of 220-260 ° C is also introduced between the spinneret and the receiving roll. If the temperature is lower than 220°C, the stretching effect will be deteriorated, and if the temperature is higher than 260°C, the stretching will be easy to fuse.
  • the process of arranging the TPU nanoparticle binder on the surface of the MME by electrostatic spraying technology is as follows: first dissolve the TPU resin (melting point 60-80°C) in a solvent to obtain a solution, and then use multi-needle electrospinning The device sprays the solution on the MME.
  • the solvent is a mixed solution of DMF and THF with a volume ratio of 1:1; the mass concentration of the solution is 7% to 9% %; the electric field spacing (that is, the distance between the nozzle and the receiving roller) during spraying is 10-13cm, and the single-needle injection rate is 0.12-0.4ml/min (the injection rate is set here to produce a large number of nano-scale TPU microchips evenly distributed on the MME ).
  • the preparation process of MSE is as follows: first dissolve polylactic acid in a solvent, add an emulsifier at the same time to obtain a solution, and use a multi-needle solution electrospinning electrode device to spray the solution on a receiving substrate to obtain MSE.
  • the solvent is more than one of NMP, DMF, DMAc, 1,4-dioxane, DMSO and acetone;
  • the emulsifier is polyvinylpyrrolidone, hexadecyltri More than one of methyl ammonium bromide, sodium dodecylbenzenesulfonate, betaine-type amphoteric surfactant, octylphenol polyoxyethylene ether and sorbitan fatty acid ester;
  • the melting temperature is 70 ⁇ 80°C;
  • the mass concentration of polylactic acid in the solution is 8% ⁇ 12%, the mass concentration of emulsifier is 0.01% ⁇ 0.04%;
  • the spinning voltage is 15 ⁇ 25kV, and the distance between the electrode and the receiving roller is 10 ⁇ 15cm, and the relative humidity of the environment is 30% to 40%.
  • the invention controls the fiber diameter in the MSE by controlling the spinning voltage, the distance between the electrode and the receiving roller, and
  • the filter elements in the prior art are mostly composed of MSE and non-woven fabrics, of which the non-woven fabric is mainly used as a supporting substrate. Because the pore size and fiber diameter distribution of the non-woven fabric is wide and difficult to control, the filtering effect on PM 0.3 particles can be ignored. Regardless, the filtration pressure of MSE is relatively high, and its durability is poor. At the same time, because it is difficult to establish an effective composite between MSE and non-woven fabrics, MSE is easy to break away from the protection of non-woven fabrics, and is subject to various pulls, pulls, and pressures during processing and use. Bending and other forces are easily damaged, making the entire filter membrane invalid. In addition, MSE also has the problem of low strength.
  • the filter element in the present invention is bonded by polylactic acid molten electrospinning nanofiber membrane MME and polylactic acid solution electrospinning fiber membrane MSE, wherein MME can not only serve as a support substrate, but also play a role of structural support. to the following effect:
  • MME average diameter ⁇ 2 ⁇ m
  • MME average diameter ⁇ 15 ⁇ m
  • MME is mainly made of filaments and has good mechanical properties. Due to the matching of MME and MSE fiber diameters, MME can produce physical cross-linking and entanglement with MSE to improve the overall mechanical processing resistance; 3) MME and MSE Effective bonding can be formed between MSEs, and the force can be shared to improve the mechanical strength of MSEs.
  • the invention solves the neglected processing strength problem of the electrospun nanofiber membrane when it is used for filtration through the rational design of the double nanofiber functional layer, and at the same time reduces the weight and weight of the filter material, and has the same performance as the traditional filter core material.
  • the SMS filter material which is a three-layer combination of non-woven fabric-melt-blown fabric-spunbonded non-woven fabric from the outside to the inside
  • the fiber diameter is also between several hundred nanometers and 1 micron.
  • the polylactic acid nano-layer fiber membrane filter element of the present invention can achieve long-term filtration efficiency maintenance without electrostatic electret and substrate, and can be reused and degraded.
  • MME can produce physical entanglement with MSE, and at the same time cooperate with a binder to significantly enhance the mechanical properties of the filter element membrane and improve the stability of use and processing ;
  • (2) the preparation method of a kind of polylactic acid nanometer double-layer fiber membrane filter element of the present invention can produce gradation effect between MME and MSE, strengthen filtration effect, alleviate the filtration pressure of MSE, improve service life;
  • the preparation method of a kind of polylactic acid nanometer double-layer fiber membrane filter core of the present invention avoids the problem that the fiber packing density that produces is big because of fiber too fine in the traditional single-layer nanofiber filter membrane preparation process (due to traditional nanofiber
  • the filter membrane only uses MSE, and the diameter of MSE is thin, which is easy to cause the problem of high packing density.
  • the present invention reasonably matches the amount of nanofibers with two diameters, thereby avoiding excessive accumulation of nanofiber membranes), and solves the scattered nanofibers at the same time, further Improve the mechanical strength of the membrane to meet the processing needs of downstream products;
  • the polylactic acid nanometer double-layer fiber membrane filter element prepared by the method of the present invention is degradable, reusable, low overall weight, and high filtration efficiency.
  • Fig. 1 is the electron micrograph of the polylactic acid nanometer double-layer fiber membrane filter element that embodiment 1 makes.
  • a preparation method of polylactic acid nano double-layer fiber membrane filter the specific steps are as follows:
  • polylactic acid is dissolved in NMP at 70°C, and polyvinylpyrrolidone is added to obtain a solution at the same time.
  • the mass concentration of polylactic acid in the solution is 8%, and the mass concentration of polyvinylpyrrolidone is 0.01%.
  • the spinning electrode equipment sprays the solution on the MME with the TPU nanoparticle binder arranged in step (2) (with the TPU nanoparticle binder as the receiving surface) to prepare the polylactic acid solution electrospun fiber membrane MSE ; Wherein, during spraying, the spinning voltage is 15kV, the distance between the electrode and the receiving roll is 10cm, and the relative humidity of the environment is 30%;
  • step (3) The product obtained in step (3) is subjected to low-pressure thermal bonding by means of heat treatment (the temperature of the heat treatment is 60° C., and the pressure of thermal bonding is 30 N) to obtain a polylactic acid nano-layer fiber membrane filter element.
  • a polylactic acid nano-layer fiber membrane filter element finally obtained is shown in Figure 1. It consists of polylactic acid melt electrospun nanofiber membrane MME (the fiber diameter range of MME is 400-1000nm) and polylactic acid solution electrospun fiber Membrane MSE (the fiber diameter of MSE ranges from 120 to 400nm) is bonded; the ratio of the median diameter of MME fibers to the median diameter of MSE fibers is 1.2; the bonding positions are distributed in dots; the grammage of MSE is 0.11 g/m 2 , the weight of MME is 23g/m 2 ; according to GB2626-2006, the filtration efficiency of the polylactic acid nano-layer fiber membrane filter element to 0.3 ⁇ m particles is 94%, the suction resistance is 120Pa, and it has been sterilized ten times After filter efficiency decay is 6%.
  • a preparation method of polylactic acid nano double-layer fiber membrane filter the specific steps are as follows:
  • step (3) The product obtained in step (3) is subjected to low-pressure thermal bonding by means of heat treatment (the temperature of the heat treatment is 63° C., and the pressure of thermal bonding is 27 N) to obtain a polylactic acid nano-layer fiber membrane filter element.
  • a kind of polylactic acid nano double-layer fiber membrane filter element finally made is made of polylactic acid melting electrospinning nanofiber membrane MME (the fiber diameter range of MME is 400 ⁇ 1000nm) and polylactic acid solution electrospinning fiber membrane MSE (MSE's The fiber diameter ranges from 120 to 400nm) bonded; the ratio of the median diameter of MME fibers to the median diameter of MSE fibers is 1.6; the bonding positions are distributed in dots; the weight of MSE is 0.12g/m 2 , The weight of MME is 24g/ m2 ; according to GB2626-2006, the filtration efficiency of the polylactic acid nano-layer fiber membrane filter element to 0.3 ⁇ m particles is 93%, and the suction resistance is 130Pa. After ten times of sterilization, the filtration efficiency decays as 7%.
  • a preparation method of polylactic acid nano double-layer fiber membrane filter the specific steps are as follows:
  • step (3) Polylactic acid is dissolved in DMAc at 74°C, and sodium dodecylbenzenesulfonate is added simultaneously to obtain a solution.
  • the mass concentration of polylactic acid in the solution is 10%, and the mass concentration of sodium dodecylbenzenesulfonate 0.03%, and then adopt multi-needle solution electrospinning electrode equipment to spray solution on the MME that step (2) obtains and is arranged with TPU nanoparticle binder (with the surface where the TPU nanoparticle binder is located as the receiving surface), making Obtain polylactic acid solution electrospun fiber membrane MSE; Wherein, when spraying, the spinning voltage is 20kV, the distance between the electrode and the receiving roller is 12cm, and the relative humidity of the environment is 34%;
  • step (3) The product obtained in step (3) is subjected to low-pressure thermal bonding by means of heat treatment (the temperature of the heat treatment is 66° C., and the pressure of thermal bonding is 24 N) to obtain a polylactic acid nano-layer fiber membrane filter element.
  • a kind of polylactic acid nano double-layer fiber membrane filter element finally made is made of polylactic acid melting electrospinning nanofiber membrane MME (the fiber diameter range of MME is 400 ⁇ 1000nm) and polylactic acid solution electrospinning fiber membrane MSE (MSE's The fiber diameter ranges from 120 to 400nm); the ratio of the median diameter of MME fibers to the median diameter of MSE fibers is 1.5; the bonding positions are distributed in dots; the weight of MSE is 0.13g/m 2 , The weight of MME is 26g/ m2 ; according to GB2626-2006, the filtration efficiency of the polylactic acid nano-layer fiber membrane filter element to 0.3 ⁇ m particles is 93%, and the suction resistance is 150Pa. After ten times of sterilization, the filtration efficiency decays as 6%.
  • a preparation method of polylactic acid nano double-layer fiber membrane filter the specific steps are as follows:
  • step (3) Dissolve polylactic acid in 1,4-dioxane at 76°C, and add dodecyl betaine at the same time to obtain a solution.
  • the mass concentration of polylactic acid in the solution is 11%, and dodecyl betaine The mass concentration of the solution is 0.04%, and then the multi-needle solution electrospinning electrode equipment is used to spray on the MME that is arranged with the TPU nanoparticle binder that is obtained in step (2) (the surface where the TPU nanoparticle binder is located is the receiving surface) solution, to prepare polylactic acid solution electrospun fiber membrane MSE; wherein, when spraying, the spinning voltage is 22kV, the distance between the electrode and the receiving roller is 13cm, and the relative humidity of the environment is 36%;
  • step (3) The product obtained in step (3) is subjected to low-pressure thermal bonding by means of heat treatment (the temperature of the heat treatment is 69° C., and the pressure of thermal bonding is 20 N) to obtain a polylactic acid nano-layer fiber membrane filter element.
  • a kind of polylactic acid nano double-layer fiber membrane filter element finally made is made of polylactic acid melting electrospinning nanofiber membrane MME (the fiber diameter range of MME is 400 ⁇ 1000nm) and polylactic acid solution electrospinning fiber membrane MSE (MSE's The fiber diameter ranges from 120 to 400nm) bonded; the ratio of the median diameter of MME fibers to the median diameter of MSE fibers is 2; the bonding positions are distributed in dots; the weight of MSE is 0.15g/m 2 , The weight of MME is 18g/ m2 ; according to GB2626-2006, the filtration efficiency of the polylactic acid nano-layer fiber membrane filter element to 0.3 ⁇ m particles is 96%, and the suction resistance is 150Pa. After ten times of sterilization, the filtration efficiency decays as 4%.
  • a preparation method of polylactic acid nano double-layer fiber membrane filter the specific steps are as follows:
  • step (3) The product obtained in step (3) is subjected to low-pressure thermal bonding by means of heat treatment (the temperature of the heat treatment is 72° C., and the pressure of thermal bonding is 17 N) to obtain a polylactic acid nano-layer fiber membrane filter element.
  • a kind of polylactic acid nano double-layer fiber membrane filter element finally made is made of polylactic acid melting electrospinning nanofiber membrane MME (the fiber diameter range of MME is 400 ⁇ 1000nm) and polylactic acid solution electrospinning fiber membrane MSE (MSE's The fiber diameter ranges from 120 to 400nm) bonded; the ratio of the median diameter of MME fibers to the median diameter of MSE fibers is 2.1; the bonding positions are distributed in dots; the weight of MSE is 0.12g/m 2 , The weight of MME is 20g/ m2 ; according to GB2626-2006, the filtration efficiency of the polylactic acid nano-layer fiber membrane filter element to 0.3 ⁇ m particles is 97%, and the suction resistance is 155Pa. After ten times of sterilization, the filtration efficiency decays as 3%.
  • a preparation method of polylactic acid nano double-layer fiber membrane filter the specific steps are as follows:
  • step (3) The product obtained in step (3) is subjected to low-pressure thermal bonding by means of heat treatment (the temperature of heat treatment is 76° C., and the pressure of thermal bonding is 14 N) to obtain a polylactic acid nano-layer fiber membrane filter element.
  • a kind of polylactic acid nano double-layer fiber membrane filter element finally made is made of polylactic acid melting electrospinning nanofiber membrane MME (the fiber diameter range of MME is 400 ⁇ 1000nm) and polylactic acid solution electrospinning fiber membrane MSE (MSE's The fiber diameter ranges from 120 to 400nm) bonded; the ratio of the median diameter of MME fibers to the median diameter of MSE fibers is 2.2; the bonding positions are distributed in dots; the weight of MSE is 0.14g/m 2 , The weight of MME is 16g/ m2 ; according to GB2626-2006, the filtration efficiency of the polylactic acid nano-layer fiber membrane filter element to 0.3 ⁇ m particles is 99%, and the suction resistance is 145Pa. After ten times of sterilization, the filtration efficiency decays as 4%.
  • a preparation method of polylactic acid nano double-layer fiber membrane filter the specific steps are as follows:
  • step (3) The product obtained in step (3) is subjected to low-pressure thermal bonding by heat treatment (the temperature of heat treatment is 80° C., and the pressure of thermal bonding is 10 N) to obtain a polylactic acid nano-layer fiber membrane filter element.
  • a kind of polylactic acid nano double-layer fiber membrane filter element finally made is made of polylactic acid melting electrospinning nanofiber membrane MME (the fiber diameter range of MME is 400 ⁇ 1000nm) and polylactic acid solution electrospinning fiber membrane MSE (MSE's The fiber diameter ranges from 120 to 400nm) bonded; the ratio of the median diameter of MME fibers to the median diameter of MSE fibers is 2.1; the bonding positions are distributed in dots; the weight of MSE is 0.18g/m 2 , The weight of MME is 17g/ m2 ; according to GB2626-2006, the filtration efficiency of the polylactic acid nano-layer fiber membrane filter element to 0.3 ⁇ m particles is 98%, and the suction resistance is 156Pa. After ten times of sterilization, the filtration efficiency decays as 2%.

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  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Nonwoven Fabrics (AREA)
  • Filtering Materials (AREA)
  • Spinning Methods And Devices For Manufacturing Artificial Fibers (AREA)

Abstract

一种聚乳酸纳米双层纤维膜滤芯及其制备方法。制备方法为：首先制备聚乳酸熔融静电纺丝纳米纤维膜MME，然后在MME的表面布置TPU纳米颗粒粘结剂，接着以MME为接收基材，以粘结剂所在面为接收面，制备聚乳酸溶液静电纺丝纤维膜MSE，最后采用热处理的方式进行低压热粘合，制得滤芯；制得的滤芯中，MME与MSE纤维直径中位数的比值为1.2～3；MSE的克重为0.1～0.2g/m2，MME的克重为10～30g/m2；滤芯对0.3μm颗粒物的过滤效率为93～99％，吸气阻力≤200Pa，经过十次杀菌后过滤效率衰减在7％以内。制得的滤芯可降解，可重复使用。

Description

一种聚乳酸纳米双层纤维膜滤芯及其制备方法 技术领域
本发明属于滤芯技术领域，涉及一种聚乳酸纳米双层纤维膜滤芯及其制备方法。
背景技术
2019年底开始在全球形成大流行的新冠病毒尚未得到有效控制，全球对于公共安全防护类产品(如口罩、防护服等)的消耗激增，同时废旧口罩的回收处理成为大问题。可降解材料在防护类产品中的应用成为热点，聚乳酸(PLA)因其具有良好的生物可降解性、生物相容性和一定的天然抗菌性能，成为领域内技术研发人员关注的重点。
静电纺丝加工技术主要是借助于高压静电场使聚合物溶液或熔体带电并产生形变，在末端处形成液滴，后在电场力的牵引作用下，喷射牵引成纳米纤维。静电纺丝纳米纤维膜因其纤维直径低，孔径小，具有优异的过滤防护性能，同时与熔喷布相比，不依靠静电吸附作用增强过滤性能，过滤效率保持度，使采用静电纺丝纤维膜的产品具有可重复使用的性能。已有部分产品商业化。
静电纺丝工艺分为熔体静电纺丝和溶液静电纺丝两种，均有在过滤防护产品方面商业化应用，均采用无纺布作为基材支撑，由于纤维直径差别太大，达不到增强的效果。存在以下特点：
熔体静电纺丝纤维膜纤维(简称MME)直径较大(一般在400～2000nm间)，纤维膜强度高形状保持能力强，但要达到较高的过滤效率(KN95级)，厚度和克重明显增加；溶液静电纺丝纤维膜(简称MSE)直径较小(一般20～400nm间)，在较低的厚度就能达到超高的过滤效率，但存在过滤压力较大、强度低的缺点，此外当其与无纺布复合作为滤芯时，MSE容易脱离无纺布的保护，单独受到加工使用过程中各种拉扯、弯折等作用力，极易破损，使得整个滤芯膜失效。
发明内容
本发明的目的是解决现有技术存在的上述问题，提供一种聚乳酸纳米双层纤维膜滤芯及其制备方法。
为达到上述目的，本发明所采用的技术方案为：
一种聚乳酸纳米双层纤维膜滤芯，由聚乳酸熔融静电纺丝纳米纤维膜MME和聚乳酸溶液静电纺丝纤维膜MSE粘结而成；
MME纤维直径中位数与MSE纤维直径中位数的比值为1.2～3；纤维直径中位数是通过在均匀分布部分至少5个部位的SEM照片统计确定的；二者的比值过大，MME纤维与MSE纤维间，无法形成有效缠结，支撑增强效果不明显，发挥不出MME的强度优势；二者的比值过小，容易造成堆积密度大，呼吸阻力过高；二者的比值为1.2～3时，一方面MME与MSE之间能够产生物理交联缠结，提高整体的 耐机械加工性能，另一方面MME与MSE之间能够产生级配效果，增强过滤效果，减轻MSE的过滤压力，提高使用耐久度；
粘结位置呈点状分布，滤芯中不存在较大面积的不透气区域，杜绝了对气体阻力的影响；
MSE的克重为0.1～0.2g/m 2，MME的克重为10～30g/m 2；按GB2626-2006测得聚乳酸纳米双层纤维膜滤芯对0.3μm颗粒物的过滤效率为93～99％，吸气阻力≤200Pa，经过十次杀菌后过滤效率衰减在7％以内；本发明的聚乳酸纳米双层纤维膜滤芯中与MME结合的MSE的拉伸强度为7～9MPa，与其相同厚度的未与MME结合的单层MSE压实后测得拉伸强度为3～4MPa，对比可以看出，MME的加入有效提高了MSE的强度。
作为优选的技术方案：
如上所述的一种聚乳酸纳米双层纤维膜滤芯，MME的纤维直径范围为400～1000nm；MSE的纤维直径范围为120～400nm。
本发明还提供制备如上所述的一种聚乳酸纳米双层纤维膜滤芯的方法，首先制备聚乳酸熔融静电纺丝纳米纤维膜MME，然后在MME的表面采用静电喷雾技术布置TPU纳米颗粒粘结剂，接着以MME为接收基材，以TPU纳米颗粒粘结剂所在面为接收面，制备聚乳酸溶液静电纺丝纤维膜MSE，最后采用热处理的方式进行低压热粘合，制得聚乳酸纳米双层纤维膜滤芯，热处理的温度为60～80℃，热粘合的压力为10～30N，热粘合的过程中，TPU纳米颗粒粘结剂局部熔化，使MSE与MME产生交联，相互粘结，热处理的温度较低，压力也较低，同时因为TPU纳米颗粒粘结剂的尺寸较小，不会产生较大面积的不透气区域，杜绝了对气体阻力的影响。
作为优选的技术方案：
如上所述的方法，MME的制备过程为：首先将聚乳酸与增塑剂(作用为降粘)混合均匀，然后采用熔融共混的方式继续混合均匀，最后将熔融料从喷丝头喷出，到达旋转的接收辊(接收辊不断旋转，最终得到熔融静电纺丝纳米纤维膜)得到MME，喷丝头和接收辊之间施加静电电压，熔融料从喷丝头喷出后在电场作用下产生射流，射流经过电场的拉伸后，形成纳米纤维。
如上所述的方法，MME的制备过程中，增塑剂为柠檬酸三丁酯(TBC)、亚磷酸三苯酯(TPPi)或癸二酸二丁酯(DBS)；聚乳酸与增塑剂的质量比为100:0.2～3；熔融共混的温度为175～210℃；喷丝头和接收辊之间的距离为10～20cm；静电电压为15～40kV；本发明通过控制增塑剂添加量、静电电压、喷丝头和接收辊之间的距离控制MME中的纤维直径。
如上所述的方法，MME的制备过程中，为促进熔体射流拉伸，降低纤维直径，在喷丝头和接收辊之间还引入温度为220～260℃的热气流，若引入的热气流的温度低于220℃，会使得拉伸效果变差，高于260℃，则拉伸易熔断。
如上所述的方法，在MME的表面采用静电喷雾技术布置TPU纳米颗粒粘结剂的过程为：先将TPU树脂(熔点60～80℃)溶解在溶剂中得到溶液，再采用多针头静电纺丝设备将溶液喷射在MME上。
如上所述的方法，在MME的表面采用静电喷雾技术布置TPU纳米颗粒粘结剂的过程中，溶剂为体积比为1:1的DMF与THF的混合液；溶液的质量浓度为7％～9％；喷射时电场间距(即喷头与接收辊的距离)为10～13cm，单针头注射速率为0.12～0.4ml/min(注射速率设置于此将产生大量纳米级TPU微片均匀分布在MME上)。
如上所述的方法，MSE的制备过程为：先将聚乳酸溶解在溶剂中，同时加入乳化剂得到溶液，采用多针头溶液静电纺丝电极设备将溶液喷射在接收基材上得到MSE。
如上所述的方法，MSE的制备过程中，溶剂为NMP、DMF、DMAc、1,4-二氧六环、DMSO和丙酮中的一种以上；乳化剂为聚乙烯吡咯烷酮、十六烷基三甲基溴化铵、十二烷基苯磺酸钠、甜菜碱型两性表面活性剂、辛基酚聚氧乙烯醚和失水山梨糖醇脂肪酸酯中的一种以上；溶解的温度为70～80℃；溶液中聚乳酸的质量浓度为8％～12％，乳化剂的质量浓度为0.01％～0.04％；喷射时，纺丝电压为15～25kV，电极与接收辊的间距为10～15cm，环境相对湿度为30％～40％；本发明通过控制纺丝电压、电极与接收辊的间距、环境相对湿度控制MSE中的纤维直径。
本发明的原理如下：
现有技术中的滤芯多由MSE和无纺布组成，其中无纺布主要作为支撑基材，因无纺布的孔径和纤维直径分布较宽难控制，对于PM 0.3的颗粒的过滤效果可以忽略不计，MSE的过滤压力较大，使用耐久度较差，同时因MSE和无纺布之间难以建立起有效的复合，MSE容易脱离无纺布的保护，单独受到加工使用过程中各种拉扯、弯折等作用力，极易破损，使得整个滤芯膜失效，此外，MSE还存在强度低的问题。
本发明中的滤芯由聚乳酸熔融静电纺丝纳米纤维膜MME和聚乳酸溶液静电纺丝纤维膜MSE粘结而成，其中MME除了作为支撑基材，起到结构支撑的作用外，还能够起到如下作用：
1)MME的纤维直径(平均直径≤2μm)远小于无纺布(平均直径≥15μm)，MME与MSE之间能够产生级配效果，增强过滤效果，减轻MSE的过滤压力，提高使用耐久度；2)MME以长丝为主，具有较好的机械性能，因MME与MSE纤维直径的匹配，MME可以与MSE之间产生物理交联缠结，提高整体的耐机械加工性能；3)MME与MSE之间能够形成有效粘结，共同受力，提高MSE的机械强度。
本发明通过双纳米纤维功能层的合理设计，解决了被忽视的静电纺丝纳米纤维膜在用于过滤的时候的加工强度问题，同时使滤材减重，减量，同效能比传统滤芯材(即SMS滤材，从外到内为无纺布-熔喷布-纺粘无纺布的三层组合)减重60％以上，可设计更轻薄的过滤防护产品(一方面因为MME克重低于传统无纺布(超过35g/m 2)；另一方面因为MME具有一定的稳定过滤效能，以MME作为基材，在 达到同等过滤效能的情况下，MSE的量可明显降低)；MME具有相对好的强度，同时具有一定的原始过滤效率，纤维直径也在几百纳米到1微米之间，只需要添加一层薄薄的MSE，之后采用无纺布常用的轧合固定方式就可以得到既轻薄又实用的滤芯膜；本发明的聚乳酸纳米双层纤维膜滤芯不用静电驻极、不用基材就能实现长久的过滤效率保持，可重复使用，可降解。
有益效果：
(1)本发明的一种聚乳酸纳米双层纤维膜滤芯的制备方法，MME可以与MSE之间产生物理缠结，同时配合粘结剂，明显增强滤芯膜机械性能，提升使用及加工稳定性；
(2)本发明的一种聚乳酸纳米双层纤维膜滤芯的制备方法，MME与MSE之间能够产生级配效果，增强过滤效果，减轻MSE的过滤压力，提高使用耐久度；
(3)本发明的一种聚乳酸纳米双层纤维膜滤芯的制备方法，规避了传统单层纳米纤维滤膜制备过程中因纤维过细，而产生的纤维堆积密度大的问题(因传统纳米纤维滤膜只用MSE，MSE直径细，易产生堆积密度大的问题，本发明合理匹配了两种直径纳米纤维的量，因而能避免纳米纤维膜过度堆积)，同时解决纳米纤维丝的零散，进一步提高膜的力学强度，满足下游产品加工需求；
(4)本发明的方法制得的聚乳酸纳米双层纤维膜滤芯，可降解，可重复使用，整体低克重，高滤效。
附图说明
图1为实施例1制得的聚乳酸纳米双层纤维膜滤芯的电镜图。
具体实施方式
下面结合具体实施方式，进一步阐述本发明。应理解，这些实施例仅用于说明本发明而不用于限制本发明的范围。此外应理解，在阅读了本发明讲授的内容之后，本领域技术人员可以对本发明作各种改动或修改，这些等价形式同样落于本申请所附权利要求书所限定的范围。
实施例1
一种聚乳酸纳米双层纤维膜滤芯的制备方法，具体步骤如下：
(1)首先将质量比为100:0.2的聚乳酸与柠檬酸三丁酯混合均匀，然后采用熔融共混的方式，在温度为175℃下继续混合均匀，最后将熔融料从喷丝头喷出，在施加的15kV的静电电压下，到达旋转的接收辊，制得聚乳酸熔融静电纺丝纳米纤维膜MME；其中，喷丝头和接收辊之间的距离为10m；
(2)将TPU树脂溶解在体积比为1:1的DMF与THF的混合液中，得到质量浓度为7％的溶液，再采用多针头静电纺丝设备将溶液喷射在步骤(1)制得的MME上，制得到一面布置有TPU纳米颗粒粘结剂的MME；其中，喷射时电场间距为10cm，多针头静电纺丝设备中的单针头注射速率为0.12ml/min；
(3)将聚乳酸在70℃下溶解在NMP中，同时加入聚乙烯吡咯烷酮得到溶液，溶液中聚乳酸的质量浓度为8％，聚乙烯吡咯烷酮的质量浓度为0.01％，然后采用多针头溶液静电纺丝电极设备在步骤(2)得到的布置有TPU纳米颗粒粘结剂的MME上(以TPU纳米颗粒粘结剂所在面为接收面)喷射溶液，制得聚乳酸溶液静电纺丝纤维膜MSE；其中，喷射时，纺丝电压为15kV，电极与接收辊的间距为10cm，环境相对湿度为30％；
(4)采用热处理的方式对步骤(3)得到的产品进行低压热粘合(热处理的温度为60℃，热粘合的压力为30N)，制得聚乳酸纳米双层纤维膜滤芯。
最终制得的一种聚乳酸纳米双层纤维膜滤芯如图1所示，由聚乳酸熔融静电纺丝纳米纤维膜MME(MME的纤维直径范围为400～1000nm)和聚乳酸溶液静电纺丝纤维膜MSE(MSE的纤维直径范围为120～400nm)粘结而成；MME纤维直径中位数与MSE纤维直径中位数的比值为1.2；粘结位置呈点状分布；MSE的克重为0.11g/m 2，MME的克重为23g/m 2；按GB2626-2006测得聚乳酸纳米双层纤维膜滤芯对0.3μm颗粒物的过滤效率为94％，吸气阻力为120Pa，经过十次杀菌后过滤效率衰减为6％。
实施例2
一种聚乳酸纳米双层纤维膜滤芯的制备方法，具体步骤如下：
(1)首先将质量比为100:0.6的聚乳酸与亚磷酸三苯酯混合均匀，然后采用熔融共混的方式，在温度为180℃下继续混合均匀，最后将熔融料从喷丝头喷出，在施加的20kV的静电电压下，到达旋转的接收辊，制得聚乳酸熔融静电纺丝纳米纤维膜MME；其中，喷丝头和接收辊之间的距离为12m；
(2)将TPU树脂溶解在体积比为1:1的DMF与THF的混合液中，得到质量浓度为8％的溶液，再采用多针头静电纺丝设备将溶液喷射在步骤(1)制得的MME上，制得到一面布置有TPU纳米颗粒粘结剂的MME；其中，喷射时电场间距为11cm，多针头静电纺丝设备中的单针头注射速率为0.2ml/min；
(3)将聚乳酸在72℃下溶解在DMF中，同时加入十六烷基三甲基溴化铵得到溶液，溶液中聚乳酸的质量浓度为9％，十六烷基三甲基溴化铵的质量浓度为0.02％，然后采用多针头溶液静电纺丝电极设备在步骤(2)得到的布置有TPU纳米颗粒粘结剂的MME上(以TPU纳米颗粒粘结剂所在面为接收面)喷射溶液，制得聚乳酸溶液静电纺丝纤维膜MSE；其中，喷射时，纺丝电压为18kV，电极与接收辊的间距为11cm，环境相对湿度为32％；
(4)采用热处理的方式对步骤(3)得到的产品进行低压热粘合(热处理的温度为63℃，热粘合的压力为27N)，制得聚乳酸纳米双层纤维膜滤芯。
最终制得的一种聚乳酸纳米双层纤维膜滤芯，由聚乳酸熔融静电纺丝纳米纤维膜MME(MME的纤维直径范围为400～1000nm)和聚乳酸溶液静电纺丝纤维膜MSE(MSE的纤维直径范围为120～400nm)粘结而成；MME纤维直径中位数与MSE纤维直径中位数的比值为1.6；粘结位置呈点状分布；MSE的克 重为0.12g/m 2，MME的克重为24g/m 2；按GB2626-2006测得聚乳酸纳米双层纤维膜滤芯对0.3μm颗粒物的过滤效率为93％，吸气阻力为130Pa，经过十次杀菌后过滤效率衰减为7％。
实施例3
一种聚乳酸纳米双层纤维膜滤芯的制备方法，具体步骤如下：
(1)首先将质量比为100:1的聚乳酸与癸二酸二丁酯混合均匀，然后采用熔融共混的方式，在温度为185℃下继续混合均匀，最后将熔融料从喷丝头喷出，在施加的25kV的静电电压下，到达旋转的接收辊，制得聚乳酸熔融静电纺丝纳米纤维膜MME；其中，喷丝头和接收辊之间的距离为14m；
(2)将TPU树脂溶解在体积比为1:1的DMF与THF的混合液中，得到质量浓度为9％的溶液，再采用多针头静电纺丝设备将溶液喷射在步骤(1)制得的MME上，制得到一面布置有TPU纳米颗粒粘结剂的MME；其中，喷射时电场间距为12cm，多针头静电纺丝设备中的单针头注射速率为0.24ml/min；
(3)将聚乳酸在74℃下溶解在DMAc中，同时加入十二烷基苯磺酸钠得到溶液，溶液中聚乳酸的质量浓度为10％，十二烷基苯磺酸钠的质量浓度为0.03％，然后采用多针头溶液静电纺丝电极设备在步骤(2)得到的布置有TPU纳米颗粒粘结剂的MME上(以TPU纳米颗粒粘结剂所在面为接收面)喷射溶液，制得聚乳酸溶液静电纺丝纤维膜MSE；其中，喷射时，纺丝电压为20kV，电极与接收辊的间距为12cm，环境相对湿度为34％；
(4)采用热处理的方式对步骤(3)得到的产品进行低压热粘合(热处理的温度为66℃，热粘合的压力为24N)，制得聚乳酸纳米双层纤维膜滤芯。
最终制得的一种聚乳酸纳米双层纤维膜滤芯，由聚乳酸熔融静电纺丝纳米纤维膜MME(MME的纤维直径范围为400～1000nm)和聚乳酸溶液静电纺丝纤维膜MSE(MSE的纤维直径范围为120～400nm)粘结而成；MME纤维直径中位数与MSE纤维直径中位数的比值为1.5；粘结位置呈点状分布；MSE的克重为0.13g/m 2，MME的克重为26g/m 2；按GB2626-2006测得聚乳酸纳米双层纤维膜滤芯对0.3μm颗粒物的过滤效率为93％，吸气阻力为150Pa，经过十次杀菌后过滤效率衰减为6％。
实施例4
一种聚乳酸纳米双层纤维膜滤芯的制备方法，具体步骤如下：
(1)首先将质量比为100:1.4的聚乳酸与柠檬酸三丁酯混合均匀，然后采用熔融共混的方式，在温度为190℃下继续混合均匀，最后将熔融料从喷丝头喷出，在施加的30kV的静电电压下，经过温度为220℃的热气流后，到达旋转的接收辊，制得聚乳酸熔融静电纺丝纳米纤维膜MME；其中，喷丝头和接收辊之间的距离为16m；
(2)将TPU树脂溶解在体积比为1:1的DMF与THF的混合液中，得到质量浓度为7％的溶液，再采用多针头静电纺丝设备将溶液喷射在步骤(1)制得的MME上，制得到一面布置有TPU纳米颗粒粘结剂的MME；其中，喷射时电场间距为13cm，多针头静电纺丝设备中的单针头注射速率为0.28ml/min；
(3)将聚乳酸在76℃下溶解在1,4-二氧六环中，同时加入十二烷基甜菜碱得到溶液，溶液中聚乳酸的质量浓度为11％，十二烷基甜菜碱的质量浓度为0.04％，然后采用多针头溶液静电纺丝电极设备在步骤(2)得到的布置有TPU纳米颗粒粘结剂的MME上(以TPU纳米颗粒粘结剂所在面为接收面)喷射溶液，制得聚乳酸溶液静电纺丝纤维膜MSE；其中，喷射时，纺丝电压为22kV，电极与接收辊的间距为13cm，环境相对湿度为36％；
(4)采用热处理的方式对步骤(3)得到的产品进行低压热粘合(热处理的温度为69℃，热粘合的压力为20N)，制得聚乳酸纳米双层纤维膜滤芯。
最终制得的一种聚乳酸纳米双层纤维膜滤芯，由聚乳酸熔融静电纺丝纳米纤维膜MME(MME的纤维直径范围为400～1000nm)和聚乳酸溶液静电纺丝纤维膜MSE(MSE的纤维直径范围为120～400nm)粘结而成；MME纤维直径中位数与MSE纤维直径中位数的比值为2；粘结位置呈点状分布；MSE的克重为0.15g/m 2，MME的克重为18g/m 2；按GB2626-2006测得聚乳酸纳米双层纤维膜滤芯对0.3μm颗粒物的过滤效率为96％，吸气阻力为150Pa，经过十次杀菌后过滤效率衰减为4％。
实施例5
一种聚乳酸纳米双层纤维膜滤芯的制备方法，具体步骤如下：
(1)首先将质量比为100:1.8的聚乳酸与亚磷酸三苯酯混合均匀，然后采用熔融共混的方式，在温度为195℃下继续混合均匀，最后将熔融料从喷丝头喷出，在施加的35kV的静电电压下，经过温度为230℃的热气流后，到达旋转的接收辊，制得聚乳酸熔融静电纺丝纳米纤维膜MME；其中，喷丝头和接收辊之间的距离为18m；
(2)将TPU树脂溶解在体积比为1:1的DMF与THF的混合液中，得到质量浓度为8％的溶液，再采用多针头静电纺丝设备将溶液喷射在步骤(1)制得的MME上，制得到一面布置有TPU纳米颗粒粘结剂的MME；其中，喷射时电场间距为10cm，多针头静电纺丝设备中的单针头注射速率为0.32ml/min；
(3)将聚乳酸在78℃下溶解在DMSO中，同时加入辛基酚聚氧乙烯醚得到溶液，溶液中聚乳酸的质量浓度为12％，辛基酚聚氧乙烯醚的质量浓度为0.01％，然后采用多针头溶液静电纺丝电极设备在步骤(2)得到的布置有TPU纳米颗粒粘结剂的MME上(以TPU纳米颗粒粘结剂所在面为接收面)喷射溶液，制得聚乳酸溶液静电纺丝纤维膜MSE；其中，喷射时，纺丝电压为23kV，电极与接收辊的间距为14cm，环境相对湿度为38％；
(4)采用热处理的方式对步骤(3)得到的产品进行低压热粘合(热处理的温度为72℃，热粘合的压力为17N)，制得聚乳酸纳米双层纤维膜滤芯。
最终制得的一种聚乳酸纳米双层纤维膜滤芯，由聚乳酸熔融静电纺丝纳米纤维膜MME(MME的纤维直径范围为400～1000nm)和聚乳酸溶液静电纺丝纤维膜MSE(MSE的纤维直径范围为120～400nm)粘结而成；MME纤维直径中位数与MSE纤维直径中位数的比值为2.1；粘结位置呈点状分布；MSE的克重为0.12g/m 2，MME的克重为20g/m 2；按GB2626-2006测得聚乳酸纳米双层纤维膜滤芯对0.3μm颗粒物的过滤效率为97％，吸气阻力为155Pa，经过十次杀菌后过滤效率衰减为3％。
实施例6
一种聚乳酸纳米双层纤维膜滤芯的制备方法，具体步骤如下：
(1)首先将质量比为100:2.2的聚乳酸与癸二酸二丁酯混合均匀，然后采用熔融共混的方式，在温度为200℃下继续混合均匀，最后将熔融料从喷丝头喷出，在施加的40kV的静电电压下，经过温度为245℃的热气流后，到达旋转的接收辊，制得聚乳酸熔融静电纺丝纳米纤维膜MME；其中，喷丝头和接收辊之间的距离为19m；
(2)将TPU树脂溶解在体积比为1:1的DMF与THF的混合液中，得到质量浓度为9％的溶液，再采用多针头静电纺丝设备将溶液喷射在步骤(1)制得的MME上，制得到一面布置有TPU纳米颗粒粘结剂的MME；其中，喷射时电场间距为11cm，多针头静电纺丝设备中的单针头注射速率为0.35ml/min；
(3)将聚乳酸在79℃下溶解在丙酮中，同时加入SPAN-80得到溶液，溶液中聚乳酸的质量浓度为8％，SPAN-80的质量浓度为0.02％，然后采用多针头溶液静电纺丝电极设备在步骤(2)得到的布置有TPU纳米颗粒粘结剂的MME上(以TPU纳米颗粒粘结剂所在面为接收面)喷射溶液，制得聚乳酸溶液静电纺丝纤维膜MSE；其中，喷射时，纺丝电压为24kV，电极与接收辊的间距为15cm，环境相对湿度为39％；
(4)采用热处理的方式对步骤(3)得到的产品进行低压热粘合(热处理的温度为76℃，热粘合的压力为14N)，制得聚乳酸纳米双层纤维膜滤芯。
最终制得的一种聚乳酸纳米双层纤维膜滤芯，由聚乳酸熔融静电纺丝纳米纤维膜MME(MME的纤维直径范围为400～1000nm)和聚乳酸溶液静电纺丝纤维膜MSE(MSE的纤维直径范围为120～400nm)粘结而成；MME纤维直径中位数与MSE纤维直径中位数的比值为2.2；粘结位置呈点状分布；MSE的克重为0.14g/m 2，MME的克重为16g/m 2；按GB2626-2006测得聚乳酸纳米双层纤维膜滤芯对0.3μm颗粒物的过滤效率为99％，吸气阻力为145Pa，经过十次杀菌后过滤效率衰减为4％。
实施例7
一种聚乳酸纳米双层纤维膜滤芯的制备方法，具体步骤如下：
(1)首先将质量比为100:3的聚乳酸与柠檬酸三丁酯混合均匀，然后采用熔融共混的方式，在温度为210℃下继续混合均匀，最后将熔融料从喷丝头喷出，在施加的40kV的静电电压下，经过温度为260℃的热气流后，到达旋转的接收辊，制得聚乳酸熔融静电纺丝纳米纤维膜MME；其中，喷丝头和接收辊之间的距离为20m；
(2)将TPU树脂溶解在体积比为1:1的DMF与THF的混合液中，得到质量浓度为7％的溶液，再采用多针头静电纺丝设备将溶液喷射在步骤(1)制得的MME上，制得到一面布置有TPU纳米颗粒粘结剂的MME；其中，喷射时电场间距为12cm，多针头静电纺丝设备中的单针头注射速率为0.4ml/min；
(3)将聚乳酸在80℃下溶解在质量比为1:1的NMP和DMF的混合物中，同时加入质量比为1:1的聚乙烯吡咯烷酮和十六烷基三甲基溴化铵的混合物得到溶液，溶液中聚乳酸的质量浓度为9％，聚乙烯吡咯烷酮和十六烷基三甲基溴化铵的混合物的质量浓度为0.03％，然后采用多针头溶液静电纺丝电极设备在步骤(2)得到的布置有TPU纳米颗粒粘结剂的MME上(以TPU纳米颗粒粘结剂所在面为接收面)喷射溶液，制得聚乳酸溶液静电纺丝纤维膜MSE；其中，喷射时，纺丝电压为25kV，电极与接收辊的间距为15cm，环境相对湿度为40％；
(4)采用热处理的方式对步骤(3)得到的产品进行低压热粘合(热处理的温度为80℃，热粘合的压力为10N)，制得聚乳酸纳米双层纤维膜滤芯。
最终制得的一种聚乳酸纳米双层纤维膜滤芯，由聚乳酸熔融静电纺丝纳米纤维膜MME(MME的纤维直径范围为400～1000nm)和聚乳酸溶液静电纺丝纤维膜MSE(MSE的纤维直径范围为120～400nm)粘结而成；MME纤维直径中位数与MSE纤维直径中位数的比值为2.1；粘结位置呈点状分布；MSE的克重为0.18g/m 2，MME的克重为17g/m 2；按GB2626-2006测得聚乳酸纳米双层纤维膜滤芯对0.3μm颗粒物的过滤效率为98％，吸气阻力为156Pa，经过十次杀菌后过滤效率衰减为2％。

Claims (10)

  1. 一种聚乳酸纳米双层纤维膜滤芯，其特征在于，由聚乳酸熔融静电纺丝纳米纤维膜MME和聚乳酸溶液静电纺丝纤维膜MSE通过TPU纳米颗粒粘结剂粘结而成；
    MME纤维直径中位数与MSE纤维直径中位数的比值为1.2～3；
    MME纤维由聚乳酸和增塑剂组成；MSE纤维由聚乳酸和乳化剂组成；
    粘结位置呈点状分布；
    MSE的克重为0.1～0.2g/m 2，MME的克重为10～30g/m 2；按GB2626-2006测得聚乳酸纳米双层纤维膜滤芯对0.3μm颗粒物的过滤效率为93～99％，吸气阻力≤200Pa，经过十次杀菌后过滤效率衰减在7％以内。
  2. 根据权利要求1所述的一种聚乳酸纳米双层纤维膜滤芯，其特征在于，MME的纤维直径范围为400～1000nm；MSE的纤维直径范围为120～400nm。
  3. 制备如权利要求1或2所述的一种聚乳酸纳米双层纤维膜滤芯的方法，其特征在于，首先制备聚乳酸熔融静电纺丝纳米纤维膜MME，然后在MME的表面采用静电喷雾技术布置TPU纳米颗粒粘结剂，接着以MME为接收基材，以TPU纳米颗粒粘结剂所在面为接收面，制备聚乳酸溶液静电纺丝纤维膜MSE，最后采用热处理的方式进行低压热粘合，制得聚乳酸纳米双层纤维膜滤芯，热处理的温度为60～80℃，热粘合的压力为10～30N。
  4. 根据权利要求3所述的方法，其特征在于，MME的制备过程为：首先将聚乳酸与增塑剂混合均匀，然后采用熔融共混的方式继续混合均匀，最后将熔融料从喷丝头喷出，到达旋转的接收辊得到MME，喷丝头和接收辊之间施加静电电压。
  5. 根据权利要求4所述的方法，其特征在于，MME的制备过程中，增塑剂为柠檬酸三丁酯、亚磷酸三苯酯或癸二酸二丁酯；聚乳酸与增塑剂的质量比为100:0.2～3；熔融共混的温度为175～210℃；喷丝头和接收辊之间的距离为10～20cm；静电电压为15～40kV。
  6. 根据权利要求4所述的方法，其特征在于，MME的制备过程中，在喷丝头和接收辊之间还引入温度为220～260℃的热气流。
  7. 根据权利要求3所述的方法，其特征在于，在MME的表面采用静电喷雾技术布置TPU纳米颗粒粘结剂的过程为：先将TPU树脂溶解在溶剂中得到溶液，再采用多针头静电纺丝设备将溶液喷射在MME上。
  8. 根据权利要求7所述的方法，其特征在于，在MME的表面采用静电喷雾技术布置TPU纳米颗粒粘结剂的过程中，溶剂为体积比为1:1的DMF与THF的混合液；溶液的质量浓度为7％～9％；喷射时电场间距为10～13cm，单针头注射速率为0.12～0.4ml/min。
  9. 根据权利要求3所述的方法，其特征在于，MSE的制备过程为：先将聚乳酸溶解在溶剂 中，同时加入乳化剂得到溶液，采用多针头溶液静电纺丝电极设备将溶液喷射在接收基材上得到MSE。
  10. 根据权利要求9所述的方法，其特征在于，MSE的制备过程中，溶剂为NMP、DMF、DMAc、1,4-二氧六环、DMSO和丙酮中的一种以上；乳化剂为聚乙烯吡咯烷酮、十六烷基三甲基溴化铵、十二烷基苯磺酸钠、甜菜碱型两性表面活性剂、辛基酚聚氧乙烯醚和失水山梨糖醇脂肪酸酯中的一种以上；溶解的温度为70～80℃；溶液中聚乳酸的质量浓度为8％～12％，乳化剂的质量浓度为0.01％～0.04％；喷射时，纺丝电压为15～25kV，电极与接收辊的间距为10～15cm，环境相对湿度为30％～40％。
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