Improvements relating to the cold-alkali process for the production of regenerated cellulosic fibers

Abstract

A method and a production facility for producing regenerated cellulosic fibers. A spinning solution is extruded into a coagulation bath which contains a salt and preferably an alkali. The spinning solution comprises cellulose dissolved in an aqueous solvent comprising NaOH and ZnO and the coagulation bath has a pH-value of at least seven. The processing facility comprises a cutter to cut the fiber tow in an undried state into cut fibers, a fleece-forming device for suspending the cut fibers and collecting them in form of a non-woven fiber layer, and at least on pressing device for pressing the non-woven fiber layer, thereby imposing a natural crimp on the fibers.

1 . A method for producing regenerated cellulosic fibers including extruding a spinning solution into a coagulation bath which contains a salt and preferably an alkali to produce a fiber tow, the spinning solution comprising cellulose dissolved in an aqueous solvent comprising NaOH and ZnO, the coagulation bath having a pH-value of at least seven, the method comprising the following steps of:
 cutting the fiber tow in an undried state into cut fibers;   suspending the cut fibers and collecting them in form of a non-woven fiber layer, and   pressing the non-woven fiber layer, thereby imposing a natural crimp on the fibers.   
     
     
         2 . The method according to  claim 1 , further comprising the steps of:
 stretching the fibers in the fiber tow to a final cellulose specific diameter, and   orienting the fibers in the fiber tow to a final state before being cut in an undried state.   
     
     
         3 . The method according to  claim 1 , further comprising the steps of:
 after leaving the coagulation bath, routing the fiber tow into at least one conditioning bath, the conditioning bath comprising between about 10 percent and about 30 percent per weight a salt to facilitate a further coagulation of the spinning solution, the conditioning bath preferably being fluidly separated from a downstream washing line; and   stretching the fibers in the fiber tow to a final cellulose specific diameter and orienting the fibers in the fiber towy to a final state in the at least one conditioning bath.   
     
     
         4 . The method according to  claim 3 , wherein the coagulation bath and the conditioning bath are fluidly connected and wherein a temperature of the coagulation bath and a temperature of the conditioning bath are independently controlled. 
     
     
         5 . The method according to  claim 3 , further comprising the steps of:
 routing the fiber tow through a washing line, the washing line comprising at least one washing step and being configured downstream of the at least one conditioning bath; and   keeping a tension of the fiber tow and a cellulose specific diameter of the fibers constant in the washing line.   
     
     
         6 . The method according to  claim 1 , further comprising at least one of the following steps:
 washing the fiber tow or the non-woven fiber layer;   neutralizing the fiber tow or the non-woven fiber layer with an acidic liquid, wherein the acidic liquid is one of diluted acetic acid, lactic acid, and sulphuric acid;   bleaching the fiber tow or the non-woven fiber layer;   applying a crosslinking agent to the fiber tow or the non-woven fiber layer;   applying a finishing agent onto the fiber tow or the non-woven fiber layer;   drying the non-woven fiber layer; and   pressing the fiber tow or the non-woven fiber layer before and/or after any other processing step.   
     
     
         7 . The method according to  claim 1 , further comprising at least one of opening the non-woven fiber layer to loosen up and/or at least partially separate the fibers. 
     
     
         8 . A processing facility for producing regenerated cellulosic fibers including a spinneret for extruding a spinning solution into a coagulation bath which contains a salt and preferably an alkali to produce a fiber tow, the spinning solution comprising cellulose dissolved in an aqueous solvent comprising NaOH and ZnO, the coagulation bath having a pH-value of at least seven, the processing facility comprising:
 a cutter configured to cut the fiber tow in an undried state into cut fibers;   a fleece-forming device configured to suspend the cut fibers and collect the cut fibers in a non-woven fiber layer; and   at least once pressing device configured to squeeze the non-woven fiber layer to pose a natural crimp on the cut fibers.   
     
     
         9 . The processing facility according to  claim 8 , wherein the processing facility further comprises at least one stretching device for configured to stretch the fibers in the fiber tow to a final cellulose specific diameter and orient cellulose in the fibers to a final state. 
     
     
         10 . The processing facility according to  claim 8 , further comprising:
 at least one conditioning bath downstream of the coagulation bath, the conditioning bath being fluidly separated from a downstream washing line; and   at least one stretching device configured to stretch the fibers in the fiber tow to a final cellulose specific diameter and orient cellulose in the fibers to a final state within the at least one conditioning bath.   
     
     
         11 . The processing facility according to  claim 10 , wherein the coagulation bath and the conditioning bath are fluidly connected and wherein a temperature of the coagulation bath and a temperature of the conditioning bath independently controlled. 
     
     
         12 . The processing facility according to  claim 8 , further comprising a washing line through which the fiber tow is routed, the washing line comprising at least one washing step, wherein the washing line is configured downstream of at least one conditioning bath, and wherein a tension of the fiber tow and a cellulose specific diameter of the fibers are preferably kept essentially-constant in the washing line. 
     
     
         13 . The processing facility according to  claim 8 , further comprising at least one treatment facility comprising at least one of:
 at least one washing device configured to wash the fiber tow or the non-woven fiber layer;   at least one further pressing device configured to the fiber tow or the non-woven fiber layer;   a neutralizer configured to neutralize the cut or uncut fibers with an acidic liquid;   a bleaching facility configured to bleach the cut or uncut fibers;   a crosslinking facility configured to apply a crosslinking agent to the cut or uncut fibers,   a finishing facility configured to apply a finishing agent; to the cut or uncut fibers,   an opener configured to open the non-woven fiber layer to loosen up and/or at least partially separate the cut fibers; and   a dryer, configured to dry the cut fibers.   
     
     
         14 . A regenerated cellulosic fiber, produced in a processing facility including a spinneret for extruding a spinning solution into a coagulation bath which contains a salt and preferably an alkali to produce a fiber tow, the spinning solution comprising cellulose dissolved in an aqueous solvent comprising NaOH and ZnO, the coagulation bath having a pH-value of at least seven, the processing facility further comprising a cutter configured to cut the fiber tow in dried state into cut fibers; a fleece-forming device configured to s be cut fibers and collect them in form of a non-woven fiber layer and at least one pressing device configured to squeeze the non-woven fiber layer to impose a natural crimp on the cut fibers. 
     
     
         15 . A product comprising a regenerated cellulosic fiber produced in a processing facility including a spinneret for extruding a spinning solution into a coagulation bath which contains a salt and preferably an alkali to produce a fiber tow, the spinng solution comprising cellulose dissolved in an aqueous solvent comprising NaOH and ZnO, the coagulation bath having a pH-value of at least seven the processing facility further comprising a cutter configured to cut the fiber tow in an undried state into cut fibers; a fleece-forming device configured to suspend the cut fibers and collect them in form of a non-woven fiber layer; and at least one pressing device configured to squeeze the non-woven fiber layer to impose a natural crimp on the cut fibers. 
     
     
         16 . The product according to  claim 15 , wherein the product is selected from a list consisting of: yarns, fabrics, textiles, home textiles, garments, nonwovens, hygiene products, upholstery, or technical applications. 
     
     
         17 . A regenerated cellulosic fiber, produced by a method including extruding a spinning solution into a coagulation bath which contains a salt and preferably an alkali to produce a fiber tow, the spinning solution comprising cellulose dissolved in an aqueous solvent comprising NaOH and ZnO, the coagulation bath having a pH-value of at least seven, the method further comprising the steps of cutting the fiber tow in an undried state into cut fibers; suspending the cut fibers and collecting them in form of a non-woven fiber layer; and pressing the non-woven fiber layer, thereby imposing a natural crimp on the fibers. 
     
     
         18 . A product comprising a regenerated cellulosic fiber produced by a method including extruding a spinning solution into a coagulation bath which contains a salt and preferably an alkali to produce a fiber tow, the spinning solution comprising cellulose dissolved in an aqueous solvent comprising NaOH and ZnO, the coagulation bath having a pH-value of at least seven, the method further comprising cutting the fiber tow in an undried state into cut fibers; suspending the cut fibers and collecting them in form of a non-woven fiber layer; and pressing the non-woven fiber layer, thereby imposing a natural crimp on the fibers. 
     
     
         19 . The product according to  claim 18 , wherein the product is selected from a list comprising yarns, fabrics, textiles, home textiles, garments, nonwovens, hygiene products, upholstery, and technical applications.