JPH0336927B2 - - Google Patents

Description

[Detailed description of the invention]

[Technical Field] The present invention relates to a method for producing acetate yarn having complex irregularities on the fiber surface. [Prior art and problems] Acetate fiber has characteristics such as excellent color development and dry texture, and has been developing unique applications that take advantage of these characteristics, and has established itself as a fashion material. There is. In recent years, there has been a strong demand for diversification and individualization of fashion materials, and even for acetate fibers, materials with stronger individuality and more distinctive characteristics are being sought. Conventionally, synthetic fibers, especially nylon and polyester, have been treated with alkali on the surface, or by mixing fine particles that are soluble in water or organic liquid in advance, spinning them, and then treating them with water or organic liquid. A method for imparting complex irregularities has been introduced and put into practical use. Also, several methods have been proposed for acetate fibers. For example, a method of dry spinning in a steam atmosphere to generate voids on the fiber surface (Japanese Patent Application Laid-Open No. 1983-6918), and a method of immersing acetate fiber after dry spinning in an acetate-soluble solvent for a very short time. A method of destroying only the surface layer to create unevenness (Japanese Patent Application Laid-Open No. 55-93814) has been introduced. However, the former has a marked decrease in strength and elongation,
Furthermore, the latter method requires complicated equipment and is difficult to put into practical use. The present invention solves these conventional problems and provides a method for easily creating complex irregularities on the surface of acetate fibers without impairing their physical properties as threads. [Means for Solving the Problems] The present invention is a method for producing acetate yarn, which is characterized in that an acetate yarn that has been dry-spun under conditions that satisfy the following formulas [] and [] is subsequently drawn by 3 to 20%. []: 0.15<V _F /V _J <0.60 []: V _J <2400V _F /V _J +600 [In the formula, V _J = Linear velocity of spinning dope from the nozzle (m/
(min), V _F = Take-up speed of spun yarn (m/min)] V _F /V _J is usually called spinning draft, and V _J is (discharge amount of spinning dope) / (total amount of spinneret). pore area). In general, dry spinning of acetate fibers involves dissolving flakes to prepare a spinning stock solution, which is then discharged into heated air from a small-pore spinneret to evaporate the solvent and form yarn. When the filament is discharged from the spinneret, a considerable amount of the solvent on the surface layer evaporates in a very short period of time, forming a skin layer.As the filament continues to dry, the solvent diffuses from inside the filament, and as the solvent is lost from inside. As a result, the internal volume decreases, the internal pressure becomes negative, and the fiber surface shrinks, but under normal spinning conditions (region B in Figure 1), this shrinkage is limited to the radial direction, resulting in a so-called "chrysanthemum-shaped" It has a cross-sectional shape of , and is very smooth in the longitudinal direction as shown in FIG. This is considered to be because, as shown in FIG. 1, the spinning draft is relatively high, and the yarn remains in a tensioned state in the longitudinal direction during the yarn formation process (drying shrinkage process). The present inventors have conducted extensive studies on the relationship between the surface formation situation, the spinning draft, and furthermore the discharge speed, and have arrived at the present invention. First, regarding the first requirement of the present invention, that is, regarding the area from the spinning nozzle to the first take-up roller, first, by reducing the spinning draft to 0.60 or less, the surface shape of the yarn can be changed to a complex shape as shown in Figure 3. It was found that this caused unevenness. This is thought to be due to shrinkage occurring in the longitudinal direction of the yarn by relaxing the constraints in the longitudinal direction of the yarn during the drying shrinkage process after spinning, and by further lowering the spinning draft, these wrinkles can be eliminated. The surface becomes finer and more complex. However, if the spinning draft is set too low, the yarn will be loosened more than the shrinkage caused by evaporation, which will cause the yarn to slack in the drying cylinder, and as a result, yarn breakage, fuzz, loops, etc. will tend to occur more easily. . Furthermore, the occurrence of such complex irregularities is not determined solely by the spinning draft, but also largely depends on the linear discharge speed of the spinning. That is, as the ejection linear velocity increases, the degree of unevenness increases. The exact reason for this is unknown, but even if the draft is the same, in areas where the dope delivery speed is high, the difference between the dope speed immediately after delivery and the transaction speed becomes large, so there is no substantial draft down. It is thought that this leads to a more pronounced effect and more unevenness. Therefore, increasing the discharge linear velocity and lowering the spinning draft are ways to increase the unevenness of the yarn, but it is difficult to avoid yarn slack in the dry cylinder, and the resulting yarn defects, especially loops, become relatively noticeable. . Therefore, in the present invention, as shown in FIG. 2, the second requirement is to carry out stretching of at least 3% or more and 20% or less between the first take-up roller 4 and the second take-up roller 5. It is said that That is, as mentioned above, as the unevenness effect becomes more pronounced, the yarn sways within the drying cylinder becomes more pronounced, making it easier for the yarn to become slack, but if you try to forcefully control this with guides, etc. The slack in the thread is squeezed out by the guide, etc., and the thread defects are further exacerbated.
For this reason, the first take-up roller 4 avoids such lengths and picks up in a somewhat disordered state; Light stretching is performed between the first take-up roller 4 and the second take-up roller 5 to remove slack. In this case, very slight stretching is sufficient, but stretching of about 3% or more is necessary to completely prevent yarn defects. As mentioned above, the yarn stretched in this region is spun under extremely relaxed conditions, so the elongation of the yarn is about twice that of normal acetate filament. This stretching action does not cause any fatal loss of yarn physical properties, but the complexity of the unevenness caused by the stretching is slightly reduced. or,
Excessive stretching of about 20% or more is undesirable because it may cause a decrease in yarn elongation, crack-like defects on the surface of the yarn, and breakage of single fibers. Also, since this stretching is relatively slight, it is not necessary to provide a second pulling roller.
It is also effective to perform stretching between winding devices as shown in the figure. Explanations will be added below using examples. [Example] Cellulose acetate flakes with an acetylation degree of 61.3% were dissolved in a mixed solution of methylene chloride and methanol, and the cells were spun at a linear speed from a spinning nozzle using the apparatus shown in Figure 2.
The fibers were spun at 980 m/min, taken off at a take-off speed of 300 m/min, and then stretched as shown in the table below.

〔Effect of the invention〕

As described above, the present invention has a unique and complex uneven surface morphology that is completely different from the surface morphology of conventional dry acetate yarns, and has an unprecedented dry texture effect and unique luster for acetate. Furthermore, an acetate material that exhibits good coloring properties is provided, and its value is extremely great.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing the spinning condition range of the present invention;
FIG. 2 is a partially longitudinal side view showing an example of the apparatus used to carry out the present invention, FIG. 3 is an enlarged surface view of the yarn obtained by the present invention, and FIG. 4 is a yarn obtained by conventional methods. FIG. 3 is an enlarged surface view of the acetate yarn. 1: spinning nozzle, 2: spinning tube, 3: spun yarn,
4: First take-up roll, 5: Second take-up roll, 6:
Winding machine.

Claims (1)

[Claims] 1. A method for producing acetate yarn, characterized in that acetate yarn dry-spun under conditions satisfying the following formulas [] and [] is subsequently stretched by 3 to 20%. []: 0.15<V _F /V _J <0.60 []: V _J <2400V _F /V _J +600 [In the formula, V _J = Linear velocity of spinning dope from the nozzle (m/
min), V _F = take-up speed of spun yarn (m/min)]