JPH0129889B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) This invention relates to a method for producing acrylic fibers that are free from sticking and have good splitting properties. (Prior Art) Methods for preventing acrylic fibers from sticking during wet spinning include increasing the polymer concentration in the spinning dope as high as possible and lowering the solvent concentration in the coagulation bath. However, if the polymer concentration in the spinning dope is increased, the anti-sticking property becomes better, but the increase in the viscosity of the spinning dope significantly reduces the spinnability. In the case of sulfoxide (hereinafter abbreviated as DMSO), the polymer concentration in the spinning dope is at most 25% by weight. For this reason, wet spinning is generally performed by lowering the solvent concentration in the coagulation bath to a level that does not cause agglutination. For example, if an aqueous solution of an organic solvent such as DMF, DMSO, dimethylacetamide, or acetone is used as a coagulation bath, a 60 to 65% by weight aqueous solution of an organic solvent may be used as a coagulation bath for a thick denier such as 15 denier, which has good fibrillation properties. In the case of a fine denier such as 1.5 denier, which requires easy spinning and good splitting properties, a 50-60% by weight organic solvent aqueous solution must be used. Furthermore, since fibers with a flat or triangular fiber cross section change from point contact to surface contact, and stickiness is extremely likely to occur, it is essential to further reduce the concentration of the organic solvent in the coagulation bath to 45 to 55% by weight.
However, when recovering the solvent from the coagulation bath, the lower the solvent concentration in the coagulation bath, the greater the recovery cost and uneconomical effect, which is a major disadvantage. When spinning fibers, especially when the concentration of the coagulation bath is low, it is difficult to obtain fibers that retain the shape of the spinneret, making it difficult to obtain the desired quality. (Problems to be Solved by the Invention) The present invention addresses the drawbacks of the prior art, namely, that when wet spinning acrylic fibers, the solvent concentration in the coagulation bath is controlled by the brand of the fiber being spun, especially its splitting property. This is an attempt to solve the drawback that it is not possible to achieve a high concentration that is industrially advantageous. The purpose of the present invention is to industrially advantageously produce acrylic fibers with improved splitting properties, and to produce acrylic fibers with a flat or triangular fiber cross section that have good splitting properties and a fiber cross section. The object of the present invention is to provide a method that maintains the shape of the base as it is.
Further objects of the invention will become apparent from the description below. (Means for Solving the Problems) The present invention has been made by focusing on the above-mentioned problems of the conventional art. When the tow is stacked and taken off, it is characterized in that water or an aqueous solution is applied in advance before stacking so that the center of the stacked tow contains the water or aqueous solution. Generally, the die used to produce acrylic fibers has 10,000 to 150,000 holes, so by combining multiple spindles, a tow of 200,000 to 1,000,000 deniers is usually formed, but when the tow is stacked, the concentration is slightly higher than the coagulation bath concentration. An aqueous solution with a solvent concentration is trapped between the tows, causing the tows to stick together due to the pulling force and nip roller pressure. When the solvent concentration of the solution adhering to the tow was reduced, sticking was also significantly improved. The acrylic polymer in the present invention is not particularly limited, but preferably contains 80% by weight or more of acrylonitrile (hereinafter abbreviated as AN).
AN polymer or 40 to 80% by weight of AN, 20 to 60% by weight of a vinyl monomer containing a halogen element such as vinyl chloride, vinylidene chloride, or vinyl bromide.
It is a flame-retardant acrylic polymer consisting of In addition, solvents used for acrylic polymer solutions include organic solvents such as DMF, DMSO, dimethylacetamide, ethylene carbonate, and acetone, and inorganic solvents such as nitric acid aqueous solution, zinc chloride aqueous solution, and Rodan salt aqueous solution. Anything you can do is fine. The coagulation bath used in wet spinning is also an aqueous solution of organic solvents such as DMF, DMSO, dimethylacetamide, ethylene carbonate, and acetone, and any one of these is used in the solvent that dissolves the acrylic polymer, or in wet spinning. It is more advantageous to use inorganic solvents in coagulation baths than inorganic solvents in terms of solvent recovery costs and corrosion. The more tows that rise from the coagulation bath of wet spinning, the higher the total denier and the better the productivity, so usually 2 to 10 tows are piled up.
Applying water or an aqueous solution in advance to lowering the solvent concentration between the tows before stacking the tows together is significantly effective in preventing sticking. Water alone has a significantly good anti-sticking effect, but an aqueous solution may also be used.
A preferred aqueous solution is one that has the same components as the coagulation bath for wet spinning, and has a higher water content than the coagulation bath. Furthermore, the temperature of water or aqueous solution is not particularly limited, but is preferably 30°C or lower. Methods for applying water or aqueous solutions include dipping, spraying,
There are shower methods, and either method is effective. However, spraying and showering methods are convenient and preferred. (Function) When the acrylic fiber tow obtained by wet spinning as in the present invention is pulled up from the coagulation bath and collected in layers, water or an aqueous solution is applied in advance to remove the solvent aqueous solution adhering to the surface of the acrylic fiber tow. Not only does the decrease in the solvent concentration further promote coagulation and make it difficult to stick together, but the decrease in the solvent concentration on the surface of the acrylic fiber tow also reduces the dissolving power, making it even more difficult to stick together. The present invention does not involve washing each spun yarn individually, but instead contains water or an aqueous solution in the center of the stacked tow to prevent fibers from sticking together due to an increase in solvent concentration in the center of the tow. It is something. Therefore, there is no need for a large amount of water or aqueous solution to be applied to wash the tow, and only a relatively small amount of water or aqueous solution is needed to achieve coagulation balance. (Example) The present invention will be described in detail below with reference to Examples. Example 1 24 parts of an acrylic polymer with a molecular weight of 50,000 and a composition of AN: methyl acrylate: sodium methallylsulfonate = 91.4:8.0:0.6% by weight are dissolved in a mixed solution of 74 parts of DMF and 2 parts of water, and mixed with DMF/water. =60/40% by weight,
When four acrylic fiber tows spun through a 100,000-hole (diameter 0.45 mmφ) spinneret in a coagulation bath at 25°C are collected, water or an aqueous solution is applied to each tow by a shower method (as shown in Table 1). 5/min) and then stretched 6 times in a second bath. Thereafter, washing with water, oiling, drying, oiling, crimping, heat treatment, and drying were performed to obtain a fiber of 1.5 denier. This was cut into a length of 51 m/m, and after opening, the number of defective yarns in 15 g was counted visually using a card machine of a Schare mini spinning machine manufactured by Platt.

[Table] Example 2 AN: 24 parts of an acrylic polymer with a molecular weight of 55,000 and a composition of vinylidene chloride:sodium allylsulfonate = 58:40:2% by weight are dissolved in a mixed solution of 72 parts of DMSO and 2 parts of water. /Water concentration (20℃) is the second
0.55mm x 0.055 in the coagulation bath (25℃) changed as shown in the table.
When four tows of acrylic fibers spun through a spinneret with a slit-shaped cross section of mm are stacked and taken off, a 10% by weight DMSO aqueous solution (20°C) is applied in advance by a spraying method for 2.5 minutes, and then a second bath is applied. The film was stretched 6 times. Thereafter, the fibers were passed through the same steps as in Example 1 to obtain flat fibers of 15 denier. A sample without spraying was also spun under the same conditions as a reference example. (EXP−
7, 9, 11, 13)

[Table] As shown in Table 2, when the coagulation bath concentration is low, the fiber splitting property is good, but the cross-sectional shape of the product is poor, whereas when the coagulation bath concentration is high, the cross-sectional shape is good, but many fibers with poor fiber splitting result. However, when an aqueous solution was sprayed as in this example, a product that satisfied both the cross-sectional shape and the fiber splitting quality was obtained. (Effect of the invention) This invention reduces the solvent concentration inside the tow by applying water or an aqueous solution in advance when stacking and pulling a plurality of tows made of acrylic fibers obtained by wet spinning an acrylic polymer solution. At the same time, by promoting coagulation, sticking can be prevented even if the solvent concentration in the coagulation bath is increased, and acrylic fibers with improved splitting properties can be industrially advantageously produced.

Claims (1)

[Claims] 1. When multiple tows made of acrylic fibers obtained by wet spinning an acrylic polymer solution are stacked and taken off, water or an aqueous solution is applied in advance to the center of the stacked tows before stacking. 1. A method for producing an acrylic fiber with improved splitting properties, the method comprising: