JPH0130923B2 - - Google Patents

Description

[Detailed description of the invention]

"Industrial Application Field" The present invention relates to a method for producing acrylonitrile-containing fibers, particularly acrylonitrile-containing fibers that form a single or a plurality of cavities in the cross section of the fibers. ``Prior art'' ``Problems to be solved by the invention'' In general, hollow fibers are stiff, have a low apparent specific gravity, are noble, and have many characteristics such as heat retention and water absorption. . Conventionally, when producing hollow fibers, methods have been used, such as using a spinneret with a complicated structure and incorporating additives such as foaming agents into the spinning solution.
This method has the disadvantage that it is technically difficult to create fine pores due to the structure of the spinneret, and it is difficult to obtain fine pores. Further, as a result, it is difficult to increase the number of holes, and the spinneret becomes very expensive, resulting in low productivity and poor profitability. On the other hand, the method (2) has problems such as the dispersibility tends to be non-uniform due to the nature of the blowing agent, the spinning operation is unstable, and most of the fiber bundles are not hollow. "Means for Solving the Problems" In view of the above-mentioned circumstances, the inventors of the present invention have conducted intensive research to improve the drawbacks of the conventional methods as described above, and as a result, they have arrived at the present invention. That is, in the present invention, 30% by weight of acrylonitrile
The acrylonitrile copolymer containing less than 80% by weight is dissolved in an organic or inorganic solvent to obtain a spinning stock solution, and passed through a normal spinneret at a solvent concentration of 1 to 50% by weight in the first and second coagulation baths and a temperature of -10%. ~50℃,
Wet spinning was carried out under conditions of residence time of 2 to 80 seconds to form a binary structure with a skin layer and a core layer, and then 70 seconds.
The wet yarn, which has been stretched 1.1 to 5.0 times in a hot water bath at temperatures above ℃ to make the skin layer more dense, is dried at 5 to 40℃ while maintaining the binary structure, and further heat-treated at 100 to 150℃. The present invention is directed to a method for producing fibers containing acrylonitrile, which is characterized by forming a single or a plurality of cavities in the cross section of the fibers. The acrylonitrile copolymer used in the present invention is preferably a copolymer consisting of 30% by weight or more and less than 80% by weight of acrylonitrile, and is formed by copolymerizing acrylonitrile with one or more vinyl monomers. You can get it. More preferably, a copolymer containing 30% by weight or more and 60% by weight or less of acrylonitrile is desirable. That is, acrylonitrile is 60
If it exceeds % by weight, the desired binary structure tends to be difficult to develop during wet spinning. Examples of vinyl monomers include acrylic acid, methacrylic acid, vinyl chloride, vinyldene chloride, vinyl esters such as vinyl acetate, vinylpyrrolidone, vinylpyridine and its alkyl substituted products, acrylic esters, methacrylic esters, and acrylic acid. Examples include amide, methacrylic acid amide, mono- and dialkyl-substituted products thereof, styrene sulfonic acid, methallyl sulfonic acid, and metal salts and amine salts thereof. In the present invention, there is no particular requirement for copolymerizable monomers, and any common vinyl monomers that can be copolymerized with acrylonitrile can be used. This acrylonitrile copolymer is dissolved in an organic solvent such as acetone, acetonitrile, dimethylformamide, dimethylacetamide, dimethyl sulfoxide, or an inorganic solvent such as zinc chloride, nitric acid, rhodan salt, etc. to prepare a spinning stock solution. It is also possible to use organic pigments or stabilizers that are effective in preventing spinning rust, coloring, light resistance, etc., as long as they do not interfere with spinning. The conventional spinneret used in the present invention has an orifice that is circular or oval in which the ratio of the length of the major axis to the minor axis is less than 5 to 1, or a polygonal shape such as a triangle, hexagon, or diamond. Although this refers to a spinneret, an orifice having a shape close to circular or oval is suitable. The above-described spinning dope is wet-spun through the spinneret and filled with an aqueous solution containing an organic solvent or an inorganic solvent corresponding to the organic solvent or inorganic solvent present in the spinning dope, or both. Lead to the first coagulation bath. In order to form a skin layer, the concentration of the organic solvent or inorganic solvent or both in the bath is preferably 1 to 50% by weight, more preferably 5 to 30% by weight, and the temperature is preferably -10% by weight. ℃~+50℃, more preferably 0℃~+30℃. The residence time in the first coagulation bath is set depending on the above-mentioned concentration and temperature as well as the fineness, but it is preferably 2 to 80 seconds. Next, the fibers are introduced into a second coagulation bath.
In order to make the skin layer more dense and to make the difference from the core layer clearer, the concentration of the organic solvent or inorganic solvent or both in the bath should be the same as that of the first coagulation bath, more preferably the first coagulation bath. It is necessary that the concentration is lower than that of the coagulation bath, and the temperature is preferably the same as that of the first coagulation bath, and more preferably higher than that of the first coagulation bath. It is also possible to stretch the fibers in this second coagulation bath, and it is preferable to impart some physical properties by stretching, but excessive stretching will densify the core layer and destroy the binary structure. This should be avoided as it may cause The residence time in the second coagulation bath is 2 to 80 seconds, more preferably 2 to 40 seconds, including when stretching is performed. After that, the fibers are washed, and washing is usually done in two stages: in low-temperature water of about 10 to 45°C and in hot water of 70°C or higher, but in some cases, one or both may be omitted. It's okay. After passing through this washing bath, in order to develop the desired binary structure, the temperature should be 70℃ or higher, preferably 80℃ or higher.
It is necessary to stretch 1.1 to 5.0 times in hot water at 100°C or higher, but more preferably 1.5 to 5.0 times.
4.0 times is desirable. That is, if it is less than 1.1 times, the fiber physical properties will deteriorate, and if it exceeds 5.0 times, the voids in the core layer will become dense and the desired binary structure will not be maintained. Through the above process, a wet yarn with a water content of 100% by weight or less and a solvent content of 20% by weight or less is formed, and a binary structure with a dense and strong skin layer and a soft core layer with many voids is formed. can be formed.
However, heat treatment is required to form single or multiple cavities in the cross section of this fiber, but before heat treatment, low temperature drying, preferably 5 to 40°C.
It is desirable to perform low temperature drying to reduce the water content to 30% by weight or less and the solvent content to 15% by weight or less. When the drying temperature exceeds 40°C, the voids in the core layer become dense, making it difficult to maintain the binary structure. On the other hand, 5℃
If it is less than that, the drying efficiency will decrease and the drying time will become longer, causing problems in terms of productivity. The heat treatment referred to in the present invention includes all methods such as general dry heat treatment using hot air, moist heat treatment using steam, etc., or heat treatment using a constant temperature bath using organic compounds such as polyethylene glycol, glycerin, etc. The object can be achieved using one or more of these methods. The heat treatment temperature is preferably 100 to 150℃, and the higher the temperature, the better the cavities will be formed.
Heat treatment at 130°C or higher is not preferable because excessive shrinkage may occur and the fibers may be cut. According to the method of the present invention, there are differences in the shape of the cavities formed depending on the type of heat treatment method, but when manufacturing fibers, the shape of the fibers obtained differs depending on the heat treatment method. This is normal, and the most appropriate method should be selected depending on the purpose. In this way, it is possible to obtain a fiber having a single or multiple cavities in the cross section of the fiber, but the void ratio obtained by the method of the present invention, including single and multiple cavities, is 5 to 40%. It shows. The void ratio was calculated using the following method. Projecting a cross-sectional photograph of the fiber onto paper of uniform thickness,
Total weight of fiber cross section (Sw + Cw) and weight of hollow part
The ratio of Cw was determined according to the following formula. Cavity ratio [%] = [Cw/(Sw+Cw)] x 100 (Cw: weight of cavity portion, Sw: weight of non-void portion) In addition, the above-mentioned water content and solvent content were calculated by the following measurement method. That is, the fibers to be measured are immersed in pure water and boiled to elute the solvent, etc. in the fibers, and the concentration of the organic or inorganic solvent in the solution is measured by gas chromatography, etc., while the fibers are immersed. Take out the fiber 115-120
After drying at ℃ for 3 hours, the weight was measured. When the weight of pure water is W ₁ , the weight of the fiber before soaking is W ₂ , the weight of the fiber after drying is W ₃ , and the concentration of the organic or inorganic solvent is C, the solvent content is calculated by the following formula. . Solvent ratio S [%] = {C [W ₁ + W ₂ )-W ₃ ]/W ₃ }×100 Further, the water content is calculated by the following formula. Moisture content [%] = [(W ₂ - W ₃ )/W ₃ ] x 100-S (%) "Example" The present invention will be explained in detail by giving Examples and Comparative Examples. is not limited in any way by these. Example 1 30% by weight of acrylonitrile copolymer consisting of acrylonitrile/sodium styrene sulfonate/vinyl chloride = 49.5/1.0/49.5 in acetone
The spinning stock solution containing 45 to 55℃ is
30% by weight of acetone in water through a spinneret with a circular orifice with 100 0.25mm holes.
wet-spinning into a first coagulation bath containing 25° C. and maintained at 25°C, and then a second
It was passed through a coagulation bath where it was stretched twice. At this time, the first bath residence time was 80 seconds, and the second bath residence time was 20 seconds.
It was hot in seconds. After further passing through a 30℃ water bath, 90℃
It was stretched 2.5 times by passing it through a hot water bath at ℃. At this stage, the moisture content is 74.4% by weight, and the acetone content is
It was 16.5% by weight. Next, by performing low temperature drying at 30° C. for 6 minutes, the moisture content was reduced to 19.1% by weight and the acetone content was reduced to 12.2% by weight. After that
It was allowed to stay in the drying process at 145°C for 5 minutes. The fiber obtained through the above steps had a fineness of 29.7 denier and was a hollow fiber having a single cavity. A cross-sectional photograph (scanning electron microscope) of this fiber is shown in FIG. Example 2 The same spinning dope as in Example 1 was prepared using a pore size of 0.14 mm.
Wet spinning was carried out through a spinneret with a circular orifice of 300 holes into a first coagulation bath similar to that in Example 1, and then the spinning was carried out using water containing 20% by weight of acetone at 25°C.
The film was then passed through a second coagulation bath maintained at a temperature of 100 mL, where it was stretched twice. At this time, the first bath residence time was 25 seconds, and the second bath residence time was 10 seconds. Furthermore, the water washing bath was omitted and the film was passed through a hot water bath at 90°C to perform stretching 2.5 times.
At this stage, the water content was 95% by weight and the acetone content was 7.9% by weight. Next, by performing low temperature drying at 25° C. for 5 minutes, the water content was reduced to 28% by weight and the acetone content was reduced to 5.9% by weight. After that
It was kept in a glycerin bath maintained at 130°C for 2 minutes. The fineness of the fiber obtained through the above process is
It was 6.8 denier, and its cross-sectional photograph is shown in FIG. 2, which is structurally almost identical to that of Example 1 (FIG. 1). Example 3 The same spinning dope as in Example 1 was prepared with a pore diameter of 0.5 mm and a number of holes.
Wet spinning was carried out through a spinneret having a circular orifice of 50 mm into a first coagulation bath containing 40% by weight of acetone in water and maintained at 45°C, and then a coagulation bath containing 30% by weight of acetone in water and heated to 25°C. held second
It passed through a coagulation bath, where it was stretched 1.4 times. At this time, the first bath residence time was 90 seconds, and the second bath residence time was
It was hot in 20 seconds. After further passing through a 30℃ water bath, 90℃
It was stretched 3.6 times by passing it through a hot water bath at ℃. At this stage, the moisture content is 81.8% by weight, and the acetone content is
It was 16.9% by weight. Next, low-temperature drying at 30° C. was performed for 5 minutes to reduce the water content to 23.2% by weight and the acetone content to 12.2% by weight. Thereafter, it was allowed to remain in a moist heat treatment process at 125°C for 10 minutes. The fiber obtained through the above steps had a fineness of 56.5 denier and was a hollow fiber having a plurality of cavities as shown in FIG. Comparative Example 1 Using the same spinning solution as in Example 1, the pore size was 0.25.
Wet-spinning into a first coagulation bath containing 30% by weight of acetone in water and maintained at 25°C through a spinneret having a circular orifice with 100 mm holes;
Next, the film was passed through a second coagulation bath having the same bath conditions as the first coagulation bath, where it was stretched twice. At this time, the first bath residence time was 80 seconds and the second bath residence time was 20 seconds. The film was further passed through a washing bath at 30°C, and then passed through a hot water bath at 90°C to be stretched 2.5 times. Next, after drying at 80°C for 6 minutes, it was kept in a dry heat treatment step at 145°C for 5 minutes. The fiber obtained through the above process had a fineness of 30 denier and no cavities were formed at all. Table 1 shows the shape characteristics of the fibers obtained in the above Examples and Comparative Examples.

[Table] "Action""Effects of the Invention" The present invention has the following advantages: (1) It does not require a spinneret with a complicated structure;
Since a spinneret having a normal orifice can be used, unnecessary expenses are not required and there is no decrease in productivity.Furthermore, since the spinneret is a normal spinneret, products with fine fineness can be easily obtained. (2) Since no additives such as foaming agents are required, stable spinning operation can be maintained and a certain controlled cavity can be formed. (3) The process used to carry out the present invention is a normal process for manufacturing fibers and is no different from the conventional process, so it is possible to produce the fibers with high productivity and at low cost. It is possible. Furthermore, the fibers obtained according to the present invention are suitable for the following uses. That is, it has a suitable stiffness and a dull feel, making it suitable for pile applications, and its heat retention and water absorption properties make it suitable for use in carpets, futons, and other applications.

[Brief explanation of drawings]

1 to 3 are cross-sectional micrographs showing the shapes of the fibers obtained in Examples 1 to 3.

Claims (1)

[Claims] 1. An acrylonitrile copolymer containing 30% by weight or more and less than 80% by weight of acrylonitrile is dissolved in an organic or inorganic solvent to obtain a spinning source solution, and the solvent concentration of the first and second coagulation baths is 1 to 1 through a normal spinneret. 50% by weight, temperature -10~50℃, residence time 2~80
Wet-spun the fibers under conditions of 2 seconds to form a binary structure with a skin layer and a core layer, and then stretched 1.1 to 5.0 times in a hot water bath at 70°C or higher to make the skin layer more dense. 5~ with the yarn maintaining its binary structure.
A method for producing fibers containing acrylonitrile, which comprises drying at 40°C and further heat-treating at 100 to 150°C to form single or multiple cavities in the cross section of the fibers.