JPH0229764B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing acetate fibers.
More specifically, the present invention relates to a method for producing acetate fibers using a dry spinning method from a spinning stock solution in which cellulose diacetate is dissolved in a mixture of methylene chloride and methanol. Diacetate fibers are generally produced by dry spinning from a spinning stock solution using acetone or a mixture of acetone and water as the solvent, whereas triacetate fibers are produced using methylene chloride or a mixture of methylene chloride and methanol as the solvent. It is manufactured using the dry spinning method from spinning dope. Factories that manufacture these two types of acetate fibers often have separate spinning buildings and solvent recovery equipment in order to prevent the vapors of each solvent from mixing and recover them separately. It is also possible to produce these two types of acetate fibers in the same spinning building and solvent recovery equipment, but in this case, unless the recovered solvent is precisely distilled, problems may occur during the spinning process due to the spinning dope containing the recovered solvent. will occur frequently. When diacetate fibers are produced by a dry spinning method from a spinning stock solution using methylene chloride or a mixture of methylene chloride and methanol as a solvent, diacetate fibers and triacetate fibers are manufactured in a common building and a solvent recovery device. However, this method has the disadvantage that yarn breakage occurs frequently in the spinning process. The present inventor has devised a method for producing acetate fibers using a dry spinning method from a spinning dope in which cellulose diacetate is dissolved in a mixture of methylene chloride and methanol. As a result of intensive studies aimed at making it possible to manufacture fibers and triacetate fibers in the same building, we have determined the mixing ratio of methylene chloride and methanol used as solvents (hereinafter referred to as the solvent mixing ratio) and the spinning dope. Two factors, the concentration of cellulose diacetate in the fiber (hereinafter referred to as the concentration of the stock solution), have a large effect on the incidence of yarn breakage in the spinning process, and when these two factors are within a certain limited optimum range, found that the occurrence of yarn breakage during the spinning process was reduced, and after further investigation, they arrived at the present invention. Cellulose diacetate is dissolved in an organic solvent consisting of a mixture of methylene chloride and methanol in which the proportion of methanol in the mixture is 8 to 15% by weight so that the concentration of cellulose diacetate is 21 to 24% by weight. After heating this spinning dope to 70 to 80°C, V _T /V _E (where V _E is the discharge speed of the spinning dope from the spinning nozzle, and V _T is the take-up speed of the yarn). A method for producing acetate fiber, which comprises dry spinning under conditions such that the fiber is 0.85 to 0.80. The solvent mixing ratio has a great influence on the incidence of yarn breakage in the spinning process and the physical properties of the spun yarn. When the proportion of methanol is less than 8% by weight, as the proportion of methanol decreases, the occurrence of yarn breakage in the spinning process increases, and in the area where the proportion of methanol exceeds 15%, the proportion of spun yarn increases as the proportion of methanol increases. strength and elongation are reduced. From this, the proportion of methanol is 8% by weight or more and
A suitable content is 15% by weight or less. The concentration of the stock solution also has a large effect on the incidence of yarn breakage during the spinning process and on the physical properties of the spun yarn. Regarding the concentration of the stock solution, the higher the concentration, the higher the productivity of the stock solution preparation process and the lower the cost required for solvent recovery.From the viewpoint of manufacturing costs, it is desirable that the concentration of the stock solution is as high as possible.
If it exceeds % by weight, the incidence of yarn breakage in the spinning process will suddenly increase and the elongation of the spun yarn will decrease. If the concentration of the stock solution is less than 21%, the production cost will be high and the proportion of single fibers with abnormal fiber cross-sectional shapes in the spun yarn will be high. From this, it is appropriate that the concentration of the stock solution is in the range of 21% by weight or more and 24% by weight or less. In carrying out the present invention, the spinning stock solution is
It is preferable to discharge it from a spinning nozzle after heating it to a temperature of 70° C. or higher and 80° C. or lower. The higher the temperature of the spinning dope, the higher the elongation of the spun yarn, so it is desirable to keep the temperature high within a range that does not increase the incidence of yarn breakage in the spinning process. In the case of the method of the present invention, if the spinning dope is heated above 80°C, the incidence of yarn breakage will be extremely high;
If the temperature is less than 70°C, the elongation of the spun yarn will be low, so it is preferably in the range of 70°C or higher and 80°C or lower. Furthermore, in the present invention, if the ratio V _T /V _E of the speed V _E at which the spinning dope is discharged from the spinning nozzle and the take-up speed V _T of the yarn exceeds 0.85, the occurrence of yarn breakage in the spinning speed process is reduced. If it is less than 0.80, the incidence of abnormal cross section will be high, so V _T /V _E 0.85 ~
A value of 0.80 is desirable. This speed ratio V _T /V _E
is expressed by the formula (1) using the fineness (D denier) and number of filaments (F) of the yarn to be spun, the concentration (C weight %) and density (Pg/cm ³ ) of the spinning dope, and the nozzle hole radius (rcm). ), the _nozzle hole radius r should be determined so that V _T /V _E is 0.85 to 0.80. V _T /V _E =A·C·P r ² F/D (1) (However, A is a constant.) The present invention will be described in more detail below with reference to Examples. Example 1 A solution in which a predetermined amount of cellulose diacetate was dissolved in a mixture of methylene chloride and methanol mixed in the ratio shown in Table 1 was passed in the usual manner to obtain a spinning stock solution. After heating to ℃, it is discharged from a spinning nozzle selected so that V _T /V _E is 0.85 or less and 0.80 or more, dried in the usual manner, and taken off at a speed of 800 m/min to produce 100 denier 27 filament acetate. Fibers were obtained and the results are shown in Table 1. In Table 1, the stock solution concentration is the weight concentration (%) of the proportion of cellulose diacetate contained in the spinning stock solution, and the methanol ratio is the proportion of methanol contained in the mixture of methylene chloride and methanol. The value is expressed as weight concentration (%), and the yarn breakage rate is calculated based on the yarn breakage rate per day in the spinning process.
This value indicates the number of times yarn breakage occurs per 100 spindles, the elongation is the dry elongation measured according to the method specified by JIS, and the abnormal cross-section incidence rate indicates that the cross-sectional shape of the fiber is abnormal. This is a value indicating the proportion (%) of filaments. In order to determine whether the fiber cross section is abnormal, the fiber cross section was observed under a microscope, and a filament with three or less concave portions and three or less convex portions was determined to be a filament with an abnormal fiber cross section.

【table】

[Table] Example 2 A solution of cellulose diacetate dissolved in a mixture of methylene chloride and methanol with a methanol ratio of 12% by weight to a concentration of 22% by weight was filtered as usual to obtain a spinning stock solution. After heating this spinning stock solution to the temperature shown in Table 2, it was discharged from a spinning nozzle selected so that the V _T /V _E ratio was 0.85 or less and 0.80 or more, and dried in the usual manner at 800 m/min. The results are shown in Table 2.

[Table] Example 3 A solution of cellulose diacetate dissolved in a mixture of methylene chloride and methanol with a methanol ratio of 12% by weight to a concentration of 22% by weight was filtered as usual to obtain a spinning stock solution. , this spinning stock solution is applied to a nozzle hole with a diameter of 37μ to 41μ.
It is spun out from a spinning nozzle, dried as usual, and taken up at a speed of 800 m/min to produce 100 denier 27
Filament acetate fibers were obtained and the results are shown in Table 3.

【table】

Claims (1)

[Claims] 1 Cellulose diacetate is dissolved in an organic solvent consisting of a mixture of methylene chloride and methanol in which the proportion of methanol in the mixture is 8 to 15% by weight so that the concentration of cellulose diacetate is 21 to 24% by weight. After heating this spinning stock solution to 70-80℃, V _T /V _E (however, V _E
1. A method for producing acetate fibers, which comprises performing dry spinning under conditions such that a spinning dope is discharged from a spinning nozzle at a speed of 0.85 to 0.80 ( _VT is a yarn take-up speed).