Abstract:
The present invention relates to a process for producing a cellulosic fiber, in particular a lyocell fiber which has improved opening characteristics and therefore is particularly useful for blending with feathers, in particular with down, to such a fiber fill fiber and to the use of this fiberfill fiber in mixtures for bedding and clothing.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to a method for the production of a cellulosic fiber, in particular a lyocell fiber, which, because of its improved opening performance, is especially well-suited for mixture with feathers, in particular with downs, such a filling fiber and the use of this filling fiber in mixtures, as well as bedding and clothing which are filled with these mixtures. 
       BACKGROUND OF THE INVENTION 
       [0002]    Known and widely used as filling fibers in mixture with downs and feathers are short cut fibers of melt-extruded synthetic polymers such as polyester, polylactic acid and others. 
         [0003]    Cellulosic fibers, in particular the solvent-spun fibers designated by the generic name lyocell by the BISFA (International Bureau for the Standardization of Man Made Fibers), have long been known and have for years been produced on a commercial scale. In the production of lyocell fibers, a tertiary amine oxide, in particular N-methylmorpholine-N-oxide (NMMO), is used as solvent. Ionic liquids are likewise suitable as solvents. 
         [0004]    In these methods, the solution of cellulose is usually extruded by means of a tool and is thereby formed. The formed solution goes, for example, to a so-called dry-wet spinning process through an air gap to a precipitating bath, where the formed body is obtained by precipitation. The body is washed and, optionally after additional treatment steps, dried. A method for the production of lyocell fibers is described, for example, in U.S. Pat. No. 4,246,221. 
         [0005]    It has also already been proposed to use lyocell fibers as filling fibers in the form of fleeces in quilts and as balls in cushions. Thus, for example, in WO 99/16705, crimped lyocell staple fibers are described as suitable types of filling fiber for fleeces and balls. This published source, however, makes no reference to the fiber titer, to the length of cut of the fibers or to surface treatments. Nor does WO 99/16705 go into the opening performance of the fibers and problems resulting therefrom. 
         [0006]    In WO 2004/070093 A2, lyocell fibers having a titer of 6.7 dtex and a length of cut of 11 mm are proposed as mixture participants for feathers and downs. The mixture of lyocell and feathers and downs takes place in a wet-mixing process. WO 2004/070093 A2 contains no comments of any kind concerning the opening performance of the lyocell fibers and problems associated therewith. 
         [0007]    In addition, in WO 2004/023943 are described in detail lyocell fibers in the titer range of from 0.7 to 8.0 dtex and a length of cut of from 5 to 100 mm for use as filling material for disposable quilts, which consists of pure lyocell or of mixtures with other, preferably biologically degradable, synthetic fibers. Lyocell as a mixture participant for feathers and downs is proposed only in passing, without going into the processing problems associated therewith in detail or disclosing a solution for such problems. 
         [0008]    WO 2005/007945 discloses the use of lyocell staple fibers having a numerical value of the ratio of titer (in dtex) to the length of cut (in mm) of 0.10 or more as filling fiber for blankets, cushions, pillows, mattresses or fleece for upholstered furniture. The use of such fibers for mixture with fibers of other sorts of fibers or with downs and feathers is also described there. 
         [0009]    The production of fibers known in this prior art for down mixtures takes place, for example, according to EP 797,696, in that the spun filaments, directly after spinning, are cut in the wet state to staple fibers and then are sent on as fleece to a continuous after-treatment. After a wash for the removal of residual NMMO and finishing, the fibers are dried and in a press are packed into balls, and pressures of up to 220 bar are reached. This kind of fiber production, after treatment and packing corresponds to that of similar fibers that are later employed for uses in yarns or nonwovens. For logistical and economic reasons, lower pressures cannot be used. 
         [0010]    However, down and feather processors generally do not have available the additional opening equipment otherwise customary in textile production. The synthetic fibers such as polyester, widely used as mixture fibers, can easily be opened, so that aggressive equipment need not be used for the processing of such fibers. Most downs and feathers are processed in the dry state, blowers and blow lines being used as equipment for opening, mixing and transporting. Now, if the known lyocell fibers according to the method mentioned above are used as mixture participants, the heavy pressing in balling results in incomplete opening of the fibers. At the same time, formation of large undesirable clumps of fibers may reach the following processing machinery and destroy its sensitive parts. A homogeneous mixture with downs and feathers with these fibers is not possible. WO 2005/007945 likewise does not go into the problem of the possibility of incomplete opening of fiber balls pressed in commercial fashion with the equipment present in down processing plants. 
       SUMMARY OF THE INVENTION 
       [0011]    In contrast with the known state of the art, the object of the present invention therefore consisted in making available a fiber, which, even without the use of the opening equipment customary in the textile industry, can be opened and then processed to a homogeneous mixture with downs and feathers. 
         [0012]    An additional object was to make available a method whereby a fiber, which even without the use of opening equipment customary in the textile industry, can be opened and then processed to a homogeneous mixture with downs and feathers. 
         [0013]    This object has been accomplished by a cellulosic filling fiber having an individual fiber titer of from 0.7 to 6.0 dtex, preferably of from 0.8 to 3.0 dtex, which has a crimp, produced in a stuffing box, with a count of at least 18 crimps/10 cm as well as a finishing layer. Even after heavy pressing in a commercial fiber-balling operation, these fibers have an outstanding opening performance with simple equipment, which can be demonstrated by the so-called blow box test. 
     
    
     
       DESCRIPTION OF THE DRAWINGS 
         [0014]    For a better understanding of the present invention, reference is made to the following drawings: 
           [0015]      FIG. 1  is a beaker containing exemplary fibers taken from a pressed ball in accordance with the invention; 
           [0016]      FIG. 2  depicts an exemplary blow box with a nozzle in accordance with the invention; 
           [0017]      FIG. 3  is a beaker containing exemplary fibers opened with a blow box in accordance with the invention; and 
           [0018]      FIG. 4  depicts exemplary fibers with the rating 9 for the opening value in accordance with the invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0019]    Fibers having an individual fiber titer that is distinctly less than 0.7 dtex, are too fine for the intended use as filling fiber, since, for example, they have insufficient puffability. Fibers having an individual fiber titer of substantially more than 6.0 dtex are too thick and stiff and therefore no longer result in a soft filling, as is demanded by consumers of a product with downs and/or feathers. 
         [0020]    Stuffing box crimping took place according to the method described in WO 95/24520. Surprisingly, it was found that these fibers have better opening properties than lyocell fibers that were produced by the aforementioned fleece after treatment. In particular, it was surprising that a fiber crimped in a stuffing box was opened substantially better than a fiber crimped in a fleece after treatment. 
         [0021]    At this point, it must expressly be emphasized that a fiber crimped in a stuffing box differs distinctly from a fiber crimped in a fleece after treatment. For example, permanent pinches, which are distinctly visible under the polarization microscope, are present in a fiber crimped in the fleece according to EP 797,696. While such fleece crimping is advantageous for a variety of textile and other uses, for the field of the present invention it has the disadvantage of poorer opening performance. 
         [0022]    The filling fiber according to the invention preferably has a crimp count of from 18 to 50 crimps/10 cm, especially preferably a crimp count of from 18 to 40 crimps/10 cm. A lower crimp count results in too little puffiness of the filling fiber, while counts higher than those mentioned in turn worsen the opening performance, since more bunching between individual fibers may be produced. 
         [0023]    In addition, it preferably has a finishing layer of from 0.3 to 3.0 wt. %, referred to the total mass of the finished fiber. While smaller finishing layers result in poorer sliding performance and thus in poorer opening performance, higher finishing layers are, for one thing, more costly because of the greater consumption of chemicals, leave behind too moist or wet a feel of the fibers and likewise worsen the opening and subsequent treatment performances. 
         [0024]    An amino-functionalized finishing agent is especially preferred as finishing agent for this filling fiber. The amino groups in the finishing agent contribute substantially to establishment of the sliding performance important for the filling fiber according to the invention, which makes good opening performance and the necessary puffiness possible. The type of functionalization has greater influence on sliding performance than does the basic substance of the finishing agent. 
         [0025]    All chemical compounds known therefore are possible as basic substance of the finishing agent, for example silicone oils or finishing agents on the basis of fatty acids. However, a silicone oil is preferred for the present invention, since it has the best permanence. By permanence here is meant the ability to remain on the fiber as long as possible, for example even after multiple wash operations. 
         [0026]    Staple fiber length, also called length of cut, has great influence on good opening and processing ability of the filling fiber according to the invention. Surprisingly, it has been found that filling fibers according to the invention with a staple fiber length of between 6 and 20 mm have the best properties. Too great staple fiber lengths result in more bunching and hence in deterioration of opening performance. The fiber cable crimped in the stuffing box is cut in the stretched state, i.e., under tension, by commercial cutting machinery, in which the length of cut is precisely set beforehand. 
         [0027]    Surprisingly, it has turned out that it can be determined by the so-called blow box test whether a fiber is suitable for use as filling fiber with good opening performance. This is of great importance in product quality assurance. Poor opening performance results in complaints from customers, since the latter, as already described above, are able to open the fiber balls only insufficiently or not at all with their existing equipment and therefore cannot process fiber supplied with poor opening performance. Poorly opened fibers may also result in damage to the sensitive processing machinery of the filling fiber processor and thus in claims for damages against the fiber producer. 
         [0028]    The greater the blow box height ratio, the more easily the fiber opens with the machinery that filling fiber processors generally have. Therefore, the filling fibers according to the invention preferably have a blow box height ratio of between 4 and 15, especially preferably between 6 and 14. 
         [0029]    The additional object is accomplished by a method for the production of a cellulosic filling fiber having an individual fiber titer of from 0.7 to 6.0 dtex, preferably of from 0.8 to 3.0 dtex, consisting of the steps 
         [0030]    a. production of a cellulose-containing spinning solution, 
         [0031]    b. spinning of the spinning solution into a fiber cable, 
         [0032]    c. cable after-treatment by washing, drying, crimping and finishing, where the cable is crimped in a stuffing box to a crimp count of at least 18 crimps/10 cm and is then cut, and the cut filling fiber has a blow box height ratio between 4 and 15, preferably between 6 and 14. 
         [0033]    An amino-functionalized finishing agent preferably is used in the method according to the invention. 
         [0034]    The finishing agent used in the method according to the invention preferably is a silicone oil. 
         [0035]    Also important for the opening and subsequent processing properties of the filling fiber is its finishing layer. It should be between 0.3 and 3.0 wt. %, referred to the total mass of the finished fiber. 
         [0036]    The fibers preferably are spun in a dry-wet spinning process, for example one of the known lyocell processes, with aqueous amine oxides or ionic liquids as solvent for the cellulose. 
         [0037]    The object is also accomplished by the use of a cellulosic filling fiber having an individual fiber titer of from 0.7 to 6.0 dtex, preferably of from 0.8 to 3.0 dtex, which has a crimp produced in a stuffing box with a crimp count of at least 18 crimps/10 cm as well as a finishing layer, as filling material in bedding and clothing. 
         [0038]    The cellulosic filling fiber used for this preferably has a blow box height ratio of between 4 and 15, preferably between 6 and 14. 
         [0039]    It may be used in mixture with downs and/or feathers or alternatively in mixture with polyester, polylactic acid and/or polypropylene. Use in mixture with natural fibers such as kapok or poplar down is also possible. 
       Determination of Crimp Count: 
       [0040]    The crimp count is determined by the method described in WO 95/24520. 
       Blow Box Test: 
       [0041]    The opening properties relevant to practice for use as filling fiber in mixture with downs and feathers may be examined on a laboratory scale by the method described below, the so-called blow box test: 
         [0042]    The blow box is a rectangular metal receptacle which is open on the underside and covered with an air-permeable screen on the upper side. The dimensions of the blow box are 20×15×20 cm (length×width×height, i.e., 6 L volume). On the surface is found an air-permeable metal screen with a mesh size of about 0.8 mm. A constant stream of air, which stirs up the fiber, is brought in through the screen by means of a nozzle. The excess air likewise escapes through the screen. 
         [0043]    Determination of the opening properties is performed as follows, where, for determining reliable results, the average of two tests in each instance is always used: 
       Determination of Starting Height: 
       [0044]    5 g of a fiber taken by hand from a pressed ball, i.e., not mechanically opened, first are conditioned according to BISFA&#39;s directions (BISFA Booklet “Testing methods viscose, modal, lyocell and acetate, staple fibers and tows,” 2004 edition) in standard atmosphere (20° C., 65% relative humidity) and then carefully transferred to a 3000-ml beaker with a diameter of 14.5 cm and the fill height measured ( FIG. 1 ). 
         [0045]    These fibers are then placed in the blow box. Through a nozzle, the head of which is set at an angle of 45° placed 6 cm from the right edge in the direction of the center of the blow box ( FIG. 2 ), air is blown in through the screen with a cross section of 4 mm at a distance of 1 cm, as a result of which the fibers are stirred up and opened. The quantity of compressed air flow-through is set at 8.4 Nm3/h; the nozzle cross section must be 4 mm. The blowing time per use is 60 sec. 
       Calculation of Blow Box Height: 
       [0046]    The fibers previously opened with the blow box are then again carefully transferred to the 3000-ml beaker with a diameter of 14.5 cm and the fill height measured anew ( FIG. 3 ). 
       Determination of Blow Box Height Ratio: 
       [0047]    The blow box height ratio is the quotient of blow box height and starting height. 
         [0048]    In addition, the opening value of the fibers is assessed visually by the following rating key: 
         [0049]    Rating 1: No opening 
         [0050]    Rating 5: Half of the fibers are open 
         [0051]    Rating 10: All fibers are open 
         [0052]      FIG. 4 , for example, shows fibers with the rating 9 for the opening value. 
       EXAMPLES 
     Example 1 
     Comparison 
       [0053]    Lyocell fibers having an individual fiber titer of 1.7 dtex were formed according to the known method by extrusion of a solution of cellulose in aqueous amine oxide, coagulated in a dry-wet spinning process and cut, washed, dried and finished in a fleece after-treatment according to the prior art so that they had a finishing layer of between 0.8 and 1.2 wt. %. A single value cannot be indicated for these parameters, since even with careful application of the finishing agent, the layer in the fiber fleece fluctuates within certain limits. The fibers were pressed into balls in a commercial Autefa ball press on a production scale. Samples were then taken according to the method described above. 
       Examples 2 and 3 According to the Invention 
       [0054]    Lyocell fibers having an individual fiber titer of 1.7 dtex were formed according to a known method by extrusion of a solution of cellulose in aqueous amine oxide, coagulated in a dry-wet spinning process and washed, dried in a cable after treatment, crimped in a stuffing box crimping operation and finished with an amino-functionalized silicone oil, type Wacker Finish CT96E, so that they had a finishing layer of between 0.7 and 0.9 wt. %. Only then was the cable cut. The fibers were pressed into bales in a commercial Autefa baling press on a production scale. Samples were then taken according to the method described above. 
         [0055]    The fibers produced according to the method according to the invention exhibit a substantially better opening performance than do those of the prior art. 
         [0000]    
       
         
               
               
             
               
               
               
               
             
               
               
               
               
             
           
               
                   
                   
               
               
                   
                 Example 
               
             
          
           
               
                   
                 1 
                 2 
                 3 
               
               
                   
                   
               
             
          
           
               
                 Production 
                 Fleece 
                 Cable crimped 
                 Cable crimped 
               
               
                 Length of cut [mm] 
                 11  
                 12 
                 20 
               
               
                 Crimp count 
                 — 
                 20-25 
                 20-25 
               
               
                 Blow box rating 
                 2 
                  6 
                  6 
               
               
                 Starting height [cm] 
                 2 
                  2 
                  2 
               
               
                 Blow box height [cm] 
                 6 
                 23 
                 24 
               
               
                 Blow box height ratio 
                 3 
                   11.5 
                 12