The Preparation Of Air Filter Membrane For Melt Differential Electrospinning And The Design And Performance Of Multistage Filter Assembly

Micro-nano fiber air filter membrane has the advantages of high porosity and high specific surface area,and are currently the most widely used mining air filter material,serving as the last barrier to prevent pneumoconiosis for miners.However,due to the poor moisture absorption performance and low dust capacity of traditional air fiber filter materials,as well as the contradiction between high filtration efficiency and low filtration resistance,the surface of the filter membrane is prone to water vapor condensation and filtration performance degradation in high humidity and high dust concentration mine environments.Therefore,the preparation of mining air filtration materials with surface hydrophilicity,high efficiency,low resistance and high dust capacity has become the research focus in the coal mining industry.Melt differential electrospinning technology is one of the methods to prepare micro and nano fiber filter membranes.The principle of its fiber forming is to stretch polymer melt into fibers by using the action of high-voltage electric field force,and to make the fibers carry charges during the fiber-forming process,which improves the electrostatic adsorption capacity of the filter membrane.At the same time,the fineness of the electrospun fibers prepared by electrospinning technology can reach nanometer scale,and the electrospun membrane has the advantages of high porosity and high quality factor.Therefore,firstly in this paper,melt differential electrospinning technology was used to prepare hydrophilic polylactic acid/sodium polyacrylate（PLA/PAAS）electrospun fiber filtration membranes with stable filtration performance under high humidity environments.Secondly,the interlayer structure of the filter membrane is improved to prepare a sandwich-structure composite air filter membrane with high filtration efficiency and low filtration resistance.Finally,a multistage filter module for high concentration dust is designed,which takes polystyrene（EPS）foam particles as the coarse filter layer and composite structure filter membrane as the fine filter layer.This paper focuses on the following three aspects of research,the main research content and conclusions are as follows:（1）In order to improve the filtration performance of air filter membranes and ensure its stability of filtration performance under high humidity environments,surface-hydrophilic PLA/PAAS electrospun fiber filter membranes are prepared from the perspective of the preparation process and raw materials of the filter membrane.The experimental results show that under steady-state conditions,the filtration efficiency and quality factor of PLA/PAAS（ω=3%）electrospun fiber filter membrane with a gram weight of40 g/m²is 97.37%and 0.0353 Pa^-1,which is 1.12 times that of commercially available electret melt-blown filter membrane with the same gram weight..After 48 hours of humidity treatment,the filtration efficiency of PLA/PAAS electrospun fiber filtration membrane remains above 95%,and the filtration quality factor is 0.0206 Pa^-1,which is 1.66 times that of the commercially available electret melt-blown filtration membrane.（2）In order to alleviate the contradiction between high filtration efficiency and low filtration resistance of the fibrous air filter membrane,the interlayer structure of fibrous air filter membrane was optimized,and the sandwich-structure composite air filter membrane with electrospun fiber membrane on both sides and a yarn woven net mesh in the middle is prepared.The experimental results show that when the thickness of the woven net is 2mm,the composite structure filter membrane has the optimal filtration performance,with a filtration efficiency of 99.21%and a quality factor of0.0405 Pa-1.Based on this,when the orientation Angle of the two fiber membranes is 90°,the filtration efficiency of the composite structure filter membrane reaches 99.52%,and the quality factor reaches 0.0443 Pa-1.After48 hours of humidity pretreatment,the filtration efficiency of the composite filter membrane remains above 97%.（3）In order to solve the problems of low dust capacity and short effective service life of fibrous air filter membrane,a dust protection multistage filter component for high dust capacity was proposed by introducing polystyrene（EPS）foam particles in front of the fiber filter membrane.The component consists of a coarse filter layer of foam particles and a fine filter layer of electrospun fiber membrane.The experimental results show that when the filtration velocity is 0.2 m/s and the dust loading is 3 g,the increase of filtration resistance of the multistage filter component is 46.6%of that of the pure fiber filter membrane,and the introduction of the particle layer effectively slows down the increase of the filtration resistance of the component.Finally,based on the above experimental results,an electric fresh air multistage filtration dust mask based on the principle of multistage filtration is designed.