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

摘要

A spunbond method for producing non-woven fabric of natural cellulose with flame-retarding feature comprises following steps. Blend pulp and solvent of N-methylmorpholine N-oxide (NMMO) to form slurry. Evaporate water content from slurry by a Thin Film Evaporator to form dope. Extrude the dope off spin nozzles to form filament strand via spunbond method. Coagulating regenerate, water rinse, hydro-entangled needle-punch and dry the filament strand to form normal natural cellulose nonwoven, which is soaking rolled by flame retardant of N-hydroxymethyl-3-(dimethoxy-phosphate acyl) propyl amide, then orderly bake, alkaline clean, water rinse, dry and wind-up to convert it into modified natural cellulose nonwoven fabrics of long-acting flame retarding feature in coil manner. Because of cross-linking reaction between foregoing flame retardant and natural cellulose nonwoven, the flame-retarding capability thereof meet requirements of testing standards in American ASTM D6413-1999 and ASTM D2863-1995. Moreover, the wastes thereof meet environmental protection requirements.

主权项

1. A spunbond method for producing non-woven fabric of natural cellulose with flame-retarding feature comprises following process steps:
a. Prepare pulp of soft wood pulp or hard wood pulp as raw material with content cellulose over 65% and degree of polymerization (DP) in range of 450-1050; b. Blend and dissolve pulp: by putting N-methylmorpholine N-oxide (NMMO) as dissolving solvent into prepared pulp for dissolving it into slurry, and high speed blending under low temperature in range of 50-80 degrees centigrade (50-80° C.) by horizontal blending machine, wherein the concentration of the N-methylmorpholine N-oxide (NMMO) is in percentage range of 45-78%; c. Evaporate extra water content from the prepared slurry by a Thin Film Vacuum Evaporator (TFE) under temperature in range of 80-120 degrees centigrade (80-120° C.) to heat for 10 minutes for decreasing water content thereof down to 5-13% so that a homogenized mucilaginous dope is formed; d. Via 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 draw the natural cellulose filaments by 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. Coagulate and regenerate the natural filaments of fibrous strand in a coagulating liquid, next draw the natural filaments of fibrous strand by an airflow draw jet device (or airflow draw stretcher) with drawing speed thereof in range of 20-3000 m/min to become uniform fine natural cellulose filaments, then bond and lay 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 N-methylmorpholine N-oxide (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 roll the normal natural cellulose nonwoven by flame retardant of N-hydroxymethyl-3-(dimethoxy-phosphate acyl) propyl amide with concentration thereof is in range of 200-500 grams per liter (g/L); and h. Orderly bake, alkaline clean, water rinse and dry, then wind-up (coil) the soaking rolled normal natural cellulose nonwoven to produce modified natural cellulose nonwoven of long-acting flame retarding feature, wherein the bake is performed under temperature in range of 130-180 degree centigrade (130-180° C.) with baking time in range of 120-240 seconds, the alkaline clean 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 range of 2-200 meters per minute.