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(11) | EP 0 074 414 A1 |
| (12) | EUROPEAN PATENT APPLICATION |
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| (54) | Method for preparing spin-dyed acrylonitrile polymer filaments |
| (57) A method for spinning solution-dyed synthetic fibers from a dope of polymer dissolved
in a solvent, which comprises injecting a solution or dispersion of a colorant dissolved
or dispersed in a solvent which does not coagulate or precipitate said polymer, into
a dope at a spinneret or immediately before it, whereby the colorant is mixed with
the dope for uniform coloring. |
BACKGROUND OF THE INVENTION .
[0001] The present invention relates to an improved method for spinning solution-dyed synthetic fibers, more particularly to an improved spinning method which permits the production of solution-dyed synthetic fibers in small lots.
[0002] Hitherto, solution dyeing has been uneconomical for small-scale production because color change causes a loss of spinning solution and operating time.
[0003] The conventional solution-dyeing spinning method has been advantageous in that a small number of mixers are required because the spinning solution and the colorant are mixed in a process, e.g., spinning tank, which precedes the spinning metering pump. However, it is very difficult to clean a colored viscous spinning solution (dope). Complete cleaning requires the disassembly of piping, filter, dope feed pump, and metering pump. Color change in daily operation is carried out without such complete cleaning, and mixing of the previous color and the new color can easily happen, making color matching more difficult. Stopping the spinning machine for a long time for complete cleaning is quite uneconomical in small-lot production and is feasible only in the case where colored fibers of the same color are produced in a large quantity. The conventional method cannot meet economically the market requirements for fibers of different colors mixed together rather than fibers of a single color.
SUMMARY OF THE INVENTION
[0005] It is an object of the present invention to provide an improved spinning method which permits the production of solution-dyed synthetic fibers in small lots. It is another object of the present invention to provide a method for spinning tows of fibers of single color or fibers of different colors for each spinneret.
[0006] According to the method of the present invention for spinning the dope of a polymer dissolved in a solvent, the colorant is dissolved or dispersed uniformly in a solvent which does not coagulate or precipitate the polymer, and the colorant solution or dispersion is injected in a predetermined ratio into the passage between the spinning metering pump and the spinneret by the metering feed pump which interlocks with the spinning metering pump. The colorant injected immediately before the dope is extruded is mixed with the dope in the nozzle holder in which a mixer and a spinneret are integrated by linking the two or arranging the mixer on the line just before the nozzle. Thus, filaments or fibers containing colorants are obtained.
[0007] The nozzle holder is of a structure such that the dbpe and colorant liquid are mixed and passed as a piston flow without hold-up and need not be replaced when color change is required. Thus, the method of the present invention permits one to obtain fibers of any desired color simply by changing the colorant to be injected.
DETAILED DESCRIPTION OF THE PREFERRED - -
EMBODIMENTS OF THE INVENTION
[0008] The polymers to which the method of this invention is applied are not limited to any special ones so long as they can be formed into fibers. Those polymers which have polar groups therein are preferable when combined with 'the colorant mentioned later. Preferred examples of such polymers are acrylonitrile polymers and modacrylic polymers having acid groups (such as carboxylic acid and sulfonic acid group) in an amount of 10 to 100 mg equivalent/kg fiber. Such acrylonitrile polymers may contain 0 to 10 wt% of methyl methacrylate, methyl acrylate, and/or vinyl acetate, or up to 60 wt%, preferably notless than 10 wt%, of vinyl chloride and/or vinylidene chloride.
[0009] The colorants which can be used in the method of this invention include common cationic dyes, disperse dyes, and acid dyes, and special metal complex dyes soluble in organic solvents. These dyes are used in the form of solutions of ethylene glycol, acetic acid, water, etc. or dispersions of particle size smaller than 0.1 microns. Those dyes which have high affinity for polymers are preferable from the standpoint of spinning and color fastness. Cationic dyes should preferably be combined with acrylonitrile polymers or modacrylic polymers. Such a combination results in less dissolution of dyes in the spinning bath and provides colored raw materials having good color development and color fastness.
[0010] What is to be noted in the-coloring by injecting colorants into the dope in the spinneret or in the part just before the spinneret is the mixing ratio and viscosity of dope and colorant solution. Preferable mixing ratios of dope to colorant solution are 5:1 to 100:1 by volume. If the colorant solution is mixed in more than the upper limit of this ratio, the dope decreases in viscosity to such an extent that spinning is difficult to perform, and if the colorant solution is mixed in less than the lower limit of this ratio, the color density cannot be increased and color shading can easily happen. The dope should preferably have viscosities from 5 to 500 poise at 25°C for uniform mixing.
[0011] According to the method of this invention, it is possible to minimize the loss of colored dope resulting from color change which has been a serious drawback in solution-dyeing spinning, and to improve greatly the operating rate of the spinning machine for the production of a variety of products of different colors in small quantities. The method of the present invention can be applied to .the known conventional spinning methods, and from the standpoint of uniform coloring it is more suited to wet spinning which employs acetone, DMF, DMSO, ammonium thiocyanate, nitric acid, zinc chloride, etc. as a solvent for the dope.
[0012] In addition, the method of the present-invention makes it easy to provide solution-dyed tows of different colors from individual spinnerets, instead of mixing fibers of different colors in order to obtain a deep color tone. This eliminates the fiber blending process and makes it possible to change color easily for each spinning and provide desired color arrangement of deep tone.
[0013] The present invention will be described in detail with reference to the examples that follow. In the examples parts or percent means by weight unless otherwise specified.
Example 1
[0014] A dope containing 25% polymer, 50 poise at 25°C, was prepared by dissolving in acetone a resin consisting of 48 parts by weight of acrylonitrile, 51.2 parts by weight of vinyl chloride, and 0.8 parts by weight of sodium methallylsulfonate (sulfonic acid group in an amount of 50.7 mg equivalent/kg resin). A 7.5% coloring solution was prepared by diluting with acetone Cathilon Yellow RLH liquid, (aqueous solution of a cationic dye; made by Hodogaya Chemical Co., Ltd. ) The dope was supplied by a gear pump at a rate of 200 ml/min, and the coloring soultion was supplied by a constant rate pump at a rate of 20 ml/min. The mixing of the dope and coloring solution was accomplished by a mixing unit installed immediately before the nozzle holder. The dope was extruded from a spinneret having 6000 holes, each having a diameter of 0.08 mm, followed by coagulation in an acetone/water coagulating bath. The colored, extruded fibers underwent drying, drawing, and heat treatment so that the final fineness of single yarn was 3 denier or the fineness of tow was 18000 denier. Nonuniformity of coloring was not observed in the resulting colored tow, and the coloring concentration was 3% o.w.f.
Example 2
[0015] Three kinds of tows colored in yellow, red, and blue were prepared as in Example 1 by switching the colorants in the order of A, B, and C as shown in Table 1.
[0016] It is to be noted that complete color change took only 5 minutes from coloring concentration as high as 2% o.w.f. to coloring concentration as low as 0.2% o.w.f., and switching from low concentration to high concentration took only 2 minutes.
Example 3
[0017] A dope containing 23% polymer, 200 poise at 25°C, was prepared by dissolving in dimethylformamide a resin con- - - sisting of 93.0 parts by weight of acrylonitrile, 5.9 parts by weight of vinyl acetate, and 1.1 parts by weight of sodium methallylsulfonate (sulfonic acid group in an amount of 69.7 mg equivalent/kg resin). A 8.0% coloring solution was prepared by diluting Basacryl Red GL (liquid, made by BASF) with dimethylformamide. The dope was supplied by a gear pump at a rate of 200 ml/min, and the coloring solution was supplied at a rate of 15 ml/min. The mixing of the dope and coloring solution was accomplished by a mixing unit installed immediately before the nozzle holder. The dope was extruded from a spinneret having 6000 holes, each having a diameter of 0.08 mm, followed by coagulation and 400% drawing in a dimethylformamide/water coagulating bath. The colored, extruded fibers underwent drying and heat treatment so that the final fineness of single yarn was 3 denier or the fineness of tow was 18000 denier. Nonuniformity of coloring was not observed in the resulting colored tow, and the coloring concentration was 2.5% o.w.f. No contamination occurred in the spinning bath.
Example 4
[0018] A dope containing 25% acetate was prepared by dissolving acetate flakes (acetyl content is 54.8%) in acetone. A 1% coloring solution was prepared by dissolving in acetone Kayalon Fast Orange GR (disperse dye made by Nihon Kayaku Co., Ltd.). The dope was supplied by a gear pump at a rate of 95 ml/min, and the coloring solution was supplied by a constant rate pump at a rate of 9.6 ml/min. The mixing of the dope and coloring solution was accomplished by a mixing unit installed immediately before the nozzle holder. Spinning was performed to obtain a colored tow having a final fineness of 5 denier for single yarn. Nonuniformity of coloring was not observed in the resulting colored tow, and the coloring concentration was 0.4% o.w.f.
Example 5
[0019] A dope containing 22.5 polymer was prepared by dissolving in dimethylformamide a copolymer consisting of acrylonitrile 95% and methyl acrylate 5%. A 5% coloring solution was prepared by diluting with dimethylformamide Spilon Blue GNH (made by Hodocaya Chemical Co., Ltd.). Colored tows were prepared from the dope and coloring solution as in Example 3 using a dimethylformanide/water coagulating bath.
[0020] The resulting colored tows have a deep color tone which is characteristic of metal complex dyes and different from the bright color tone obtained by dyeing acrylic fibers with a cationic dye. Also, the resulting tows exhibited good lightfastness, class 6, which is one of the characteristics of metal complex dyes.
1. A method for spinning solution-dyed synthetic fibers from a dope of polymer dissolved
in a solvent, which comprises injecting. a solution or dispersion of a colorant dissolved
or dispersed in a solvent which does not coagulate or precipitate said polymer, into
a dope at a spinneret or immediately before it, whereby the colorant is mixed with
the dope for uniform coloring.
2. A method as claimed in Claim 1 in which at least two spinnerets are used for the
same dope and different colorants are injected for respective spinnerets, whereby
tows containing dyed fibers of different colors can be obtained from the same dope.
3. A method as claimed in Claim 1 or 2 in which the colorant is a dye.
4. A method as claimed in Claim 1 or 2 in which the colorant is a cationic dye.
5. A method as claimed in Claim 1 or 2 in which the polymer is acrylonitrile polymer
or copolymer having acid groups.