Fabricating method for spunbond nonwoven from natural cellulose fiber blended with nano silver

A fabricating method for spunbond nonwoven from natural cellulose fiber blended with nano silver comprises following steps:

• (a) Put partially alkalized polyvinyl alcohol (PVA) power together with silver nitrate (AgNO3) solution as precursor thereof into pure water for agitating to form polyvinyl alcohol (PVA) solution in gel state such that the alkalization degree and the molecular weight of partially alkalized polyvinyl alcohol (PVA) power added is 86-89 mole % and 14,700-98,000 respectively while the weight percentage of polyvinyl alcohol (PVA) solution is 5-12 wt %, and the silver nitrate (AgNO3) solution is created by dissolving the silver nitrate (AgNO3) crystal into pure water;
• (b) Put sodium borohydride (NaBH4) into the gel state polyvinyl alcohol (PVA) solution for reduction titration by agitating to form nano silver colloidal sol such that the reduction titration is performed by sodium borohydride (NaBH4) with mole ratio in range of 1:4-1:8, titration speed in range of 5-15 ml/min, agitating frequency about 200 rpm, and titration time in range of 10-20 minutes, and the concentration of produced nano silver sol is in range of 500-20,000 ppm while the diameter of the nano silver particle is in range of 10-150 nm;
• (c) Put the nano silver colloidal sol into a mixing cellulose serum of wood pulp raw material and N-methylmorpholine N-oxide (NMMO) solvent for blending process to prepare blending mucilage such that the blending process is performed by putting raw material of chipped wood pulp, solvent of N-methylmorpholine N-oxide (NMMO), and stabilizer together into an expansion dissolving tank with constant temperature in range of 60-80 degrees centigrade (° C.) for blending agitation, and in association of dehydration in a vacuum condensing equipment with vacuum about 933 micro-Pa. Wherein, the raw material wood pulp is a mixture of soft wood and hard wood with blending weight ratio thereof in range of 0:100-100:0, and the content of α-cellulose is over 85% while the polymerization degree for the cellulose of wood pulp thereof is in range of 500-1200, and the weight percentage for the nano silver sol in the prepared blending mucilage is in range of 5-35 wt % while the concentration of the nano silver particle therein is in range of 100-5000 ppm, as well as the chemical structures of the N-methylmorpholine N-oxide (NMMO) and pulp cellulose used here are shown as in FIGS. 3 and 4 respectively;
• (d) Evaporate water contained in the blending mucilage of nano silver colloidal sol and natural cellulose of wood pulp to form spinning dope by heating via a Thin Film Evaporator (TFE) under vacuum in range of 939-926 micro-Pa, heating temperature in range of 80-130 degrees centigrade (° C.) to dehydrate water down to range of 9-18% in time range of 5-10 minutes so that the wood cellulose is dissolved into spinning dope such that the percentage of water (H2O) is in range of 9-18%, the percentage of N-methylmorpholine N-oxide (NMMO) is in range of 75-87%, and the percentage of cellulose is in range of 6-11%;
• (e) Spin the spinning dope via “spunbond spinning method” by means of firstly conveying the spinning dope via boosted pressure to a continuous polymer filter (CPF) for filtration and defoaming treatment, secondly feeding the spinning dope into a spinning block for heating to melt the spinning dope by means of constantly blowing hot air into the spinning block, and finally spunbond extruding the melted spinning dope out of spinnerets to form into molten filament tow by means of jetting chilly quenching air through conical-frustum shell-shaped air gaps sheathing the spinnerets for quenched stretching process;
• (f) By means of coagulation bath, feed the molten filament tow in a coagulation liquid for coagulation, regeneration, and water rinse such that the concentration of the coagulation liquid is in range of 2.5-7.0%, and the residual quantity percentage of the N-methylmorpholine N-oxide (NMMO) solvent is less than 0.1% while the residual quantity percentage of the polyvinyl alcohol (PVA) solution is less than 0.2%, both of which become leftover mixture of residual N-methylmorpholine N-oxide (NMMO) solvent and residual polyvinyl alcohol (PVA) solution;
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• (g) By means of airflow draw stretcher, lay and stack the molten filament tow out of coagulation bath onto a collecting net to form a fibrous web of nonwoven substrate for high-speed stretching process under high pressure condition, and after post treatments of hydro-entangled needle punching, drying, winding-up processes have been orderly applied on the fibrous web of nonwoven substrate, then the spunbond nonwoven of natural cellulose fiber blended with nano silver is fabricated completely.