The Preparation And Properties Of Air Filter Materials With High Filtering Efficiency And Low Filtering Resistance

Among the filter materials used in high temperature dust removal applications, the conventionaland frequently used needle-punched filter material barriers the dust by inertial collision, interceptionand diffusion with lower filtering efficiency, and due to frequent cleaning, the service life is short.The filter material laminated with a PTFE micro-porous membrane intercepts the dust by themicroporous structure of the membrane.The dust can be easily cleared because of the unstickyproperties of the PTFE.The filter materials laminated with a membrane have a high filteringefficiency and filtering resistance with less cleaning requirements and longer life, but it has adisadvantage which the fast moving dust in the high temperature smoke can easily damage themembrane and lower the filtering efficiency. Gradient filter materials intercept the dust by small gapof the superfine fiber layer.And also because of this, this kind of filter materials can achive a highfiltering efficiency and a low filtering resistance, but we have to waste more raw materials withhigher cost.In this paper, the effects of needling density and needling depth to the permeability and tensilestrength of needle-punched PPS were studied, and the filtering resistance and filtering efficiencyunder best processing conditions were tested; then, a micro-porous PTFE membrane laminatedfiltering material was prepared based on the above needle-punched PPS nonwoven, and theinfluences of adhesive dosage, temperature and tension on the permeability of the filter materialswere investigated and the best conditions were optimized. At last, a foam coated needle-punchedfiltering material was prepared, the effects of the foaming agent, stable agent, curing time, PTFEemulsion on the permeability of the filter material were studied, and the formula of the coatingprocess was optimized, and the filtering efficiency and resistance of foam coated filtering materials were compared with the above two filtering materials. Through SEM observation, DSC and FTIRmeasurements, the physical and chemical properties of the foam coating latexwere analyzed.The experimental results are as follows：In terms of strength and air permeability for the conventional needle punched filter, theoptimized processing conditions are: the punch density is93.8punches/cm~2, the penetration depth is15mm in the pre-needling; the punch density is500punches/cm~2, the penetration depth is8mm inthe second needling；the punch density is500punches/cm~2, the penetration depth is4.5mm in thelast needling. Under these conditions, the average filtering efficiency of the conventional filtermaterial is about44.4%, and the average filtering resistance is36.36Pa (American DOP0.3μmefficiency)When the temperature of the roller is270°C, the speed of the roller is4m/min, the pressure of theroller is3kg/cm~2, the best air permeability for the PTFE micro-porous membrane laminated filtermaterials has been achieved. Under these conditions, the average filtering efficiency of the laminatedfilter materials is about92.4%, and the average filtering resistance is362.1Pa (American DOP0.3μm efficiency)When the concentration of the polytetrafluoroethylene(PTFE) emulsion is25%, theconcentration of the hydroxyethyl cellulose is1%, the concentration of the hydroxypropyl methylcellulose is0.3%, the concentration of the sodium dodecyl sulfate is2%, the concentration of theorgansilicone-modified acrylates is25%, the curing temperature is140°C and the curing time is300sin the curing process, the air permeability of the foam coated fabrics is the biggest which almostamounts to95L/m~2.s. The average filtering efficiency of the foam coated filter materials is almost64.8%(American DOP0.3μm efficiency (%)) and filtering resistance is96Pa. The melting point ofthe foam coated film almost gets to350℃and the filter materials have high temperature resistance.Compared with conventional needle punched filter material and micro-porous PTFE membranelaminated filer material, foam coated filter material has the advantage of higher filtering efficiencyand lower filtering resistance.The results of this paper may help to develop new type filter materials with high filteringefficiency and low filtering resistance and expand the market of the foam coated filter materials.