Abstract:
In the manufacture of cellulose ester fibers, a dope is extruded into filaments. Extrusion occurs in an elongated cabinet having an outlet for the filaments. The filaments are taken up after exiting the outlet. The filaments are lubricated at the outlet of the cabinet.

Description:
FIELD OF THE INVENTION 
     The present invention is directed to the manufacture of cellulose ester filaments. 
     BACKGROUND OF THE INVENTION 
     Conventionally, in the manufacture of cellulose esters filaments, the filaments are not lubricated until after they leave the spinning cabinet. One reason for this practice is to avoid the contamination of the solvent used in the extrusion of the cellulose ester filaments with the lubricant. 
     Conventionally, in the manufacture of cellulose ester filaments, the cellulose ester polymer is dissolved into a solvent, that solution is known as dope. The dope is pumped to a die (or jet or spinneret) having a plurality of holes therethrough. The die is typically located at the upper end of a spinning cabinet. When the dope exits the die, the solvent flashes from the dope and the filaments begin to solidify. While the filaments travel downwardly through the cabinet, the solvent is captured within the cabinet for reuse. At the bottom of the cabinet, there is an outlet through which the filaments exit the cabinet. Typically, the filaments are guided from their downward (or vertical) travel to a generally horizontal direction (including angles below the horizontal) of travel at the outlet of the cabinet. The guide may be any conventional guide device, but it does not lubricate the filaments as their direction is changed. Thereafter, the filaments exit the cabinet. After exit, the filaments are lubricated by a lubricator, for example, a kiss roll. This lubricator is typically located about 6-12 inches (15-30 cm) from the exit of the cabinet. Then, the filaments are drawn away by a feed roll. 
     It is believed that the filaments are damaged as they pass over the non-lubricated guide. This damage causes variability in the filament. 
     There is a need to make a more uniform and more robust filament product. 
     Japanese Application No. 2003-020952 (Publication No. 2004-232124) discloses a method for manufacturing cellulose acetate tow where finish (oil) is metered on to filaments of the tow band at the point where the various thread lines from the cabinets are converged. The point of convergence is away from the cabinet exit. 
     U.S. Publication Nos. 2005/0202179 and 2005/0202993 disclose a finish for improving plug making that is applied, through existing fiber finish applicators, as the filaments exit the spinning cabinet. These publications do not mention the problem solved in the instant application. 
     SUMMARY OF THE INVENTION 
     In the manufacture of cellulose ester fibers, a dope is extruded into filaments. Extrusion occurs in an elongated cabinet having an outlet for the filaments. The filaments are taken up after exiting the outlet. The filaments are lubricated at the outlet of the cabinet. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
       For the purpose of illustrating the invention, there is shown in the drawings a form that is presently preferred; it being understood, however, that this invention is not limited to the precise arrangements and instrumentalities shown. 
         FIG. 1  is a schematic illustration of the present invention. 
         FIG. 2  is an isometric illustration of an embodiment of a lubricator. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Cellulose ester filaments, as used herein, refers to, but is not limited to, cellulose acetates, cellulose propionates, cellulose butyrates, cellulose valerates, cellulose formates, and co-polymers thereof. Co-polymers include, but are not limited to, acetates-propionates or butyrates or valerates or formates and the like. Cellulose acetate refers to a cellulose acetate polymer having a typically degree of substitution between 2.1 and 2.7. For the following discussion of the invention, reference will be made to cellulose acetate, but the invention is not so limited. 
     Referring to  FIG. 1 , there is shown a cellulose acetate spinning operation  10 . For simplicity, only one spinning operation  10  is shown, but the skilled person will understand that there may be a plurality of spinning operations joined together (e.g., a métier). A dope supply  12  is connected to a die  16 , via manifold  14 . Die  16  is located at the upper end of cabinet  18 . Cabinet  18  is an elongated enclosure that is used to capture the solvent (e.g., acetone when forming cellulose acetate filaments) for re-use. Cabinet  18  has an outlet  20  (typically a door or opening through the cabinet wall) through which filaments  22  exit the cabinet. A lubricant applicator  24  is located at the lowermost end of the cabinet. The placement of applicator  24  with relation to outlet  20  will be discussed in greater detail below. Applicator  24  is used to apply lubricant (discussed below) to the filaments and change the direction of travel of the filaments. After lubrication, the filaments exit the cabinet  18  via outlet  20 . Filaments  22  are drawn from the cabinet  18  by feed roll  32  (or take up roll). Between outlet  20  and feed roll  32 , there is a lubricator  30  which is conventional, e.g., a kiss roll. While spinning operation  10  is illustrated with filaments exiting on a side of cabinet  18 , spinning operation  10  may also be a ‘pass through’ spinning operation where filaments exit through the bottom end of the cabinet  18 . 
     The applicator  24  is located at the lowermost end of the cabinet and in the vicinity of outlet  20 . ‘In the vicinity of outlet  20 ’ means from about six inches (15.25 cm) before to about six inches (15.25 cm) after the outlet  20 , and before the lubricator  30 . In one embodiment, applicator  24  is located within the cabinet before the outlet or at the outlet but in the cabinet. 
     Lubricant, discussed in greater detail below, is supplied to applicator  24  from a lubricant supply  26  via metering pump  28 . In one embodiment, pump  28  is a peristaltic pump. 
     Lubricant application rates are less than 40 cc/min (when the filaments number 80-620 filaments per cabinet) to avoid excess lubricant for subsequent processing of the tow. Preferably, the rate is less than 20 cc/min, and most preferably, the rate is 5-10 cc/min. 
     Lubricant may be selected from the group consisting of water, oil-in-water emulsions, and oils. Typically, oils are mineral oils, as is well known in the art. The oil-in-water emulsions are well known and may include emulsifiers, anti-stats, and the like. 
     The applicator  24  may be any type of applicator including cylindrical applicators, channel applicators, spray applicators, dip tank applicators, or brush applicators. In  FIG. 2 , applicator  60  is a channel-type applicator. Applicator  60  may be an inverted U with a flat surface  62 . Flat surface  62  is the filament contact surface. Lubricant is introduced via inlet  64  and wets the filaments on surface  62 . 
     EXAMPLES 
     The foregoing invention is further illustrated in the following non-limiting examples. 
     The following examples illustrate the improvement in filament properties obtained by lubrication at the outlet of the cabinet. In each of the examples, the applicator  24  (referred to as the FCPL in the Table) is located at the inside of the outlet  20 . The FCPL applicator was a channel-type applicator (see  FIG. 2 ). ‘Control-1’ refers to the use of a non-rotating ceramic roll with a concave surface. “Control-2’ refers to the use of a ceramic channel guide with a flat surface (see  FIG. 2 ). The ‘kiss roll’ refers to the conventional lubricator  30 . For lubricant, ‘Nothing’ means no lubricant; ‘H2O’ means water; and ‘EMUL’ means an oil-in-water emulsion. Improvement in filament properties is illustrated by the coeffiecent of variation for elongation at break (% Eb CV) and tensile factor (TE 1/2 ). All physical properties set forth in the table below are measured in a conventional manner. 
     
       
         
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
             
           
               
                   
                 TABLE 
               
               
                   
                   
               
               
                   
                   
                   
                   
                 Elongation 
                   
                   
               
               
                   
                   
                 Kiss 
                 Tenacity 
                 at Break 
                 % Eb 
               
               
                   
                 FCPL 
                 Roll 
                 (g/denier) 
                 (Eb %) 
                 CV 
                 TE½ 
               
               
                   
                   
               
             
             
               
                   
               
             
          
           
               
                 Control-1 
                 Nothing 
                 EMUL 
                 1.03 
                 22.13 
                 7.50 
                 4.83 
               
               
                 Control-2 
                 Nothing 
                 EMUL 
                 1.03 
                 21.40 
                 4.63 
                 4.79 
               
               
                 Invention 
                 H20 
                 EMUL 
                 1.07 
                 22.69 
                 5.60 
                 5.09 
               
               
                 Invention 
                 EMUL 
                 EMUL 
                 1.05 
                 22.22 
                 5.09 
                 4.95 
               
               
                 Invention 
                 EMUL 
                 Nothing 
                 1.02 
                 21.06 
                 6.70 
                 4.70 
               
               
                 Control-1 
                 Nothing 
                 EMUL 
                 1.12 
                 17.57 
                 13.49 
                 4.72 
               
               
                 Control-2 
                 Nothing 
                 EMUL 
                 1.13 
                 18.15 
                 11.02 
                 4.82 
               
               
                 Invention 
                 H2O 
                 EMUL 
                 1.27 
                 21.86 
                 2.15 
                 5.92 
               
               
                 Invention 
                 EMUL 
                 EMUL 
                 1.26 
                 22.95 
                 4.97 
                 6.04 
               
               
                 Invention 
                 EMUL 
                 Nothing 
                 1.22 
                 22.17 
                 3.88 
                 5.75 
               
               
                 Control-1 
                 Nothing 
                 EMUL 
                 1.06 
                 16.64 
                 21.54 
                 4.37 
               
               
                 Control-2 
                 Nothing 
                 EMUL 
                 1.10 
                 17.88 
                 18.35 
                 4.69 
               
               
                 Invention 
                 H2O 
                 EMUL 
                 0.75 
                 24.31 
                 7.08 
                 3.70 
               
               
                 Invention 
                 EMUL 
                 EMUL 
                 1.05 
                 21.17 
                 3.35 
                 4.84 
               
               
                 Invention 
                 EMUL 
                 Nothing 
                 1.03 
                 21.59 
                 5.05 
                 4.77 
               
               
                 Control-2 
                 Nothing 
                 EMUL 
                 1.11 
                 15.28 
                 16.36 
                 4.35 
               
               
                 Invention 
                 H20 
                 EMUL 
                 1.15 
                 19.17 
                 5.53 
                 5.02 
               
               
                   
               
             
          
         
       
     
     The present invention may be embodied in other forms without departing from the spirit and the essential attributes thereof, and, accordingly, reference should be made to the appended claims, rather than to the foregoing specification, as indicated the scope of the invention.