Lyocell Method and Device Involving the Control of the Metal Ion Content

Abstract

The invention relates to a method and a device for producing Lyocell fibers, which are extruded from a spinning mass containing water, cellulose and tertiary amine oxide. The spinning mass is obtained from cellulose in a number of process steps, wherein a treatment medium is added to the cellulose, cellulose suspension and/or cellulose solution. In order to be able to implement a stable and environmentally compatible spinning method irrespective of the type of cellulose used, according to the invention, provision is made that the content of at least one type of metal ion destabilising the cellulose suspension and/or cellulose solution is monitored in the cellulose, cellulose suspension and/or cellulose solution and adjusted below a stability limit. With the device according to the invention, the metal ion content is measured via sensors ( 23, 23′ ) and the metal ion content is adjusted using a control device ( 17 ).

1 . A method for producing a Lyocell fiber from a spinning mass containing water, cellulose and tertiary amine oxide, comprising producing the spinning mass by adding a treatment medium to a cellulose, to a cellulose suspension, cellulose solution or combination thereof, wherein the content of at least one type of destabilizing metal ions in the cellulose, cellulose suspension, cellulose solution or combination thereof is monitored and adjusted below a stability limit.  
   
   
       2 . The method according to  claim 1 , wherein the quantity of the added treatment medium is adjusted in dependence of the content of the at least one type of destabilizing metal ion.  
   
   
       3 . The method according to  claim 1 , wherein the added treatment medium is recovered in a following process step.  
   
   
       4 . The method according to  claim 3 , wherein the content of the at least one type of metal ion is reduced in the treatment medium during the recovery.  
   
   
       5 . The method according to  claim 1 , wherein a part of the treatment medium is discharged from the production process and that the quantity of the discharged treatment medium depends on the content of at least one type of destabilizing metal ion in the cellulose, cellulose suspension, cellulose solution or combination thereof.  
   
   
       6 . The method according to  claim 1 , wherein a fresh treatment medium is added simultaneously with the recovered treatment medium.  
   
   
       7 . The method according to  claim 6 , wherein the proportions of recovered and fresh treatment medium are adjusted in dependence of the content of the at least one type of metal ion.  
   
   
       8 . The method according to  claim 1 , wherein the treatment medium is dosed automatically.  
   
   
       9 . The method according to  claim 1 , wherein the treatment medium is essentially water.  
   
   
       10 . The method according to  claim 9 , wherein the recovered water is obtained by expressing the cellulose suspension.  
   
   
       11 . The method according to  claim 9 , wherein the recovered water is obtained from a spinning bath for the extruded spinning mass.  
   
   
       12 . The method according to  claim 1 , wherein the treatment medium is a tertiary amine oxide.  
   
   
       13 . The method according to  claim 12 , wherein the tertiary amine oxide is obtained from a spinning bath for the extruded spinning mass.  
   
   
       14 . The method according to  claim 1 , wherein the at least one type of destabilizing metal ion comprises iron ions.  
   
   
       15 . The method according to  claim 1 , wherein the at least one type of destabilizing metal ion comprises copper ions.  
   
   
       16 . The method according to  claim 1 , wherein the content of the at least one type of destabilizing metal ion is adjusted to below 10 mg/kg.  
   
   
       17 . The method according to  claim 1 , wherein the content of the at least one type of destabilizing metal ion is adjusted to below 0.5 mg/kg.  
   
   
       18 . The method according to  claim 1 , wherein the stability limit depends on the at least one type of destabilizing metal ion.  
   
   
       19 . The method according to  claim 1 , wherein the treatment medium is fed in a section of a shear zone.  
   
   
       20 . A device for production of Lyocell fibers, with comprising a mixing device, in which a cellulose, cellulose suspension, cellulose solution or combination thereof can be charged with a treatment medium, at least one sensor, by which the content of at least one type of metal ion in the cellulose, cellulose suspension, cellulose solution or combination thereof can be acquired and a control signal representing the content of the at least one type of metal ion can be output, and a control device, by which the content of the at least one type of metal ion in the cellulose, cellulose suspension, cellulose solution or combination thereof can be adjusted below a stability limit in dependence of the control signal.