Spunbond method for producing non-woven fabric of natural cellulose with flame-retarding feature

A spunbond method for producing non-woven fabric of natural cellulose with flame-retarding feature comprises following process steps:

• a. preparing pulp of soft wood pulp or hard wood pulp as a raw material with content cellulose over 65% and degree of polymerization (DP) in range of 450-1050;
• b. blending and dissolving the pulp by putting N-methylmorpholine N-oxide (NMMO) as a dissolving solvent into the prepared pulp for dissolving it into a slurry, and high speed blending under low temperature in a range of 50-80 degrees centigrade (50-80° C.) by using a horizontal blending machine, wherein the concentration of the NMMO is in a percentage range of 45-78%;
• c. evaporating extra water content from the prepared slurry by using a Thin Film Vacuum Evaporator (TFE) under temperature in a range of 80-120 degrees centigrade (80-120° C.) and heated for 10 minutes for decreasing a water content thereof down to 5-13% so that a homogenized mucilaginous dope is formed;
• d. via a spunbond method, the dope is firstly fed into and extruded out of an extruder, henceforth the dope is fed into a spin-pack and forcedly spun out of spin nozzles by means of a gear pump, afterward external compressed quenching air is continuously blown through for cooling and preliminarily drawing the dope for converting it into natural cellulose filaments by means of air gap, latterly drawing the natural cellulose filaments by using an airflow draw jet device or airflow draw stretcher to become natural filaments of fibrous strand, wherein the ranges for distance of the air gap, temperature and relative humidity of the quenching air are 0.5-30 cm, 5-35 degrees centigrade (5-35° C.) and 60-99% respectively;
• e. coagulating and regenerating the natural filaments of fibrous strand in a coagulating liquid, and drawing the natural filaments of fibrous strand by using an airflow draw jet device or airflow draw stretcher with drawing speed thereof in a range of 20-3000 m/min to form uniform fine natural cellulose filaments, then bonding and laying these natural filaments of fibrous strand on a belt collector to form a webbed nonwoven, wherein the ranges for temperature of the coagulating liquid and concentration for existing NMMO of dissolving solvent are 5-30 degrees centigrade (5-30° C.) and 0-30 wt % respectively;
• f. after post treatments of water rinsing, hydro-entangled needle punching and drying have been orderly applied, then a normal nonwoven fabric of natural cellulose is produced from the webbed nonwoven;
• g. soaking a roll of the normal natural cellulose nonwoven in a flame retardant of N-hydroxymethyl-3-(dimethoxy-phosphate acyl) propyl amide with concentration thereof in a range of 350-500 grams per liter (g/L);
• and
• h. orderly baking, alkaline cleaning, water rinsing and drying, then winding up the soaking rolled normal natural cellulose nonwoven to produce modified natural cellulose nonwoven of long-acting flame retarding feature, wherein the baking is performed under temperature of 180 degree centigrade (180° C.) with baking time in a range of 120-240 seconds, the alkaline cleaning is performed in an alkaline solution of sodium hydroxide (NaOH) with concentration of 50 grams per liter (g/L);
• and the coiling speed is in a range of 2-200 meters per minute,
• wherein the fineness of fiber for the modified natural cellulose nonwoven produced from spunbond process in step g is greater than 15 and less than 50 μm,
• wherein the basis weight for the modified natural cellulose nonwoven produced from spunbond process in step g is in range of 100-300 g/m2, and
• wherein the modified natural cellulose nonwoven has a limit of oxygen index between 25 to 35 after 50 water rinsings.