Optimization On The Preparation Of Acrylic Needle-punched Nonwoven Filter

In recent years, air pollution becomes more and more serious, causing the decline in air quality.Our government is calling for energy-saving and emission-reduction, strengthening the investmentof environmental protection industry. Acrylic needle-punched filters with excellent hydrolysisresistance and weathering ability could be widely applied in the low temperature, chemical corrosiveand damp environment instead of polyester needle-punched filters. This paper focuses on cardingprocess, uneven fiber web and low production rate. The main research is done including the structureand properties of fibers, preparation technology and finishing, to improve acrylic needle-punchedfilters.The main contents and conclusions include three aspects as follows?(1) The structure and properties of fibersStudy on two kinds of acrylic fibers including the homopolymer and copolymer acrylic fiber,compared with polyester, polypropylene, aramid and PPS fibers. Determining the fineness, crimpratio, friction coefficient, moisture regain, resistivity and mechanical properties under differentconditions. Results show that, the crimp ratio, friction coefficient, tenacity and tenacity under acidicconditions of2.32dtex homopolymer acrylic fibers are respectively2.09%,0.269,0.374,4.52cN/dtex and3.59cN/dtex. For the2.36dtex copolymer, the crimp ratio, friction coefficient,tenacity under different conditions are respectively8.64%,0.472,0.593,3.54cN/dtex and3.19cN/dtex. The1.84dtex copolymer acrylic fibers of crimp ratio, static and dynamic frictioncoefficient, tenacity are respectively4.45%,0.404,0.51and3.21cN/dtex. Under the condition withsimilar fineness, the copolymer acrylic fibers have lower initial modulus and higher frictioncoefficient, while the homopolymer fibers have higher tenacity and lower elongation at break whichis25.8%.Compared with polyester, polypropylene, aramid and PPS fibers, data show that, acrylic fibershave the highest crimp ratio and resistivity, whose friction coefficient is second to polypropylene. Due to those indexes above, static fibers are absorbed in carding machine to block the channels,causing the difficulties of carding and uneven fiber web. Besides, the highest moisture regain helpsthe fibers to wind roller. By acid treatment for120h, acrylic, polyester and polypropylene fibershave good resistance to acid.(2) Preparation technologyBy the mixture ratio, pretreatment, carding process, lapping process, needle-punched, singeing,and calendering to improve products. Optimization shows that, the best mixture ratio of2.22dtex/1.67dtex/reused material of copolymer fiber is60/30/10, pretreatment with humidifying,taking the "low speed, light weight, wide space and low speed ratio" carding principle,70g/m2acrylic plain as matrix, lapping with six kinds of speed, appropriate frequency of needle, decreasingdeep and drawing ratio, singeing and calendering with high gas volume and speed. By adjustingprocesses above and making the equipment daily maintenance, to improve the efficiency ofproduction and the quality of acrylic filters.(3) PTFE/polyacrylate (FLB) emulsion dipping finishingCombining PTFE and polyacrylate emulsion with different proportions, help to improveacrylic filters by dipping. The results show that, when the concentration ratio is3%/3%, themechanical properties, hydrolysis resistance and temperature resistance of filters are the best. Whileby150?constant temperature drying, filters with higher initial modulus are hard and red, which oflongevity should be observed in the long-term usage. In addition, in the PTFE membrane process,due to the combustion of acrylic fibers, it is more difficult to combine with PTFE film than othertype filters. Lastly, the permeability of PTFE membrane filters decreases by85%.