JPH0327667B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing peeled acrylic synthetic fibers. More specifically, an aqueous solution of an alkali metal hydroxide and/or its salt is applied to an acrylic synthetic fiber fabric, and then steamed to hydrolyze and water-solubilize the fiber molecules on the fiber surface. The present invention relates to a method for producing peeled acrylic synthetic fibers, which comprises removing the surface layer by washing with water and then contacting it with an acid solution. Conventionally, when acrylic synthetic fibers are peeled to reduce their weight, a method is known in which the surface layer is physically dissolved using a solvent for acrylic synthetic fibers. However, in the case of the solvent method, as the skin is peeled off, the eluted polymer accumulates in the solvent solution. When the concentration of the polymer exceeds 0.2% (weight%), the dissolved polymer that adheres to the fiber surface during washing with water re-solidifies and adheres to the fiber, resulting in a hard texture. There were flaws. In addition, in the case of the solvent method, a highly concentrated solvent solution is required for peeling. (For example, 65-80% for sulfuric acid,
80-100% for dimethylformamide) Therefore,
When put into practical use, there are many problems in handling, corrosion resistance, waste liquid treatment, and price. As a result of intensive research into improving the manufacturing method of peeled acrylic synthetic fibers free from such problems, the present inventors focused on a method using an aqueous solution of an alkali metal hydroxide and/or its salt. Thus, the present invention was achieved. A method of treating acrylic synthetic fibers with an aqueous solution such as caustic soda has been known for a long time. However, this method involves either partially hydrolyzing the nitrile groups on the very surface of the fibers to chemically modify the fiber surface, or using highly concentrated alkali metal water as described in JP-A-54-138693. This is a method in which the outer layer of the fiber is hydrophilically crosslinked by treatment with an oxide aqueous solution, and there is no known method that can be used to peel only the surface layer of acrylic synthetic fiber. In the present invention, an aqueous solution of an alkali metal hydroxide and/or its salt having a dissolving action on acrylic synthetic fibers is applied to an acrylic synthetic fiber fabric, and then steamed to form a surface layer of the fibers. The gist of this invention is a method for producing peeled acrylic synthetic fibers, which is characterized in that after solubilizing the fibers, the surface layer is removed by washing with water, and then the fibers are brought into contact with an acid solution. When an aqueous solution of an alkali metal hydroxide and/or its salt that has a dissolving effect on acrylic synthetic fibers is applied to acrylic synthetic fibers and then steamed, the nitrile groups in the surface layer are hydrolyzed and become water-soluble. After that, by washing with water, only the surface layer dissolves and diffuses into the water. The concentration range of the aqueous solution of the alkali metal hydroxide and/or its salt that has a dissolving effect on acrylic synthetic fibers varies depending on the type of the alkali metal hydroxide and its salt and the steaming conditions. Either saturated steam or superheated steam may be used for steaming, but steaming conditions vary depending on the type of steam used. For example, when using saturated steam, the temperature must be 80°C or higher. is preferable, and although it varies depending on the aqueous solution of the alkali metal hydroxide and/or its salt, if the temperature exceeds 120°C, the fibers tend to be hydrophilically crosslinked and become water-insoluble water-swellable fibers, making peeling difficult. . For example, in the case of sodium hydroxide, at a steaming temperature of 80 to 120°C (for saturated steam), 2
~30%, and 10-50% for sodium carbonate. The method using steaming treatment of the present invention differs from immersion heat treatment in which hydrolysis and dissolution are simultaneously performed using an alkali metal hydroxide and/or its salt, and the hydrolysis reaction reaches its peak after a certain period of time. The weight loss rate can be easily controlled simply by controlling the amount of the aqueous solution of the alkali metal hydroxide and/or its salt attached. When performing immersion heat treatment, since the alkali metal hydroxide and/or its salt are present in large excess in the aqueous solution,
Since hydrolysis and dissolution proceed linearly, time control is the only means of controlling weight loss rates. However, in the case of steaming treatment, since alkali metal hydroxide and/or its salt exists only in a limited amount on the fiber, once it is consumed in the hydrolysis reaction, the reaction will no longer proceed. It is possible to manage the weight loss rate only by controlling the amount of adhesion. In addition, in the case of the immersion method, the polymer gradually dissolves in the treatment solution, so when performing repeated weight loss processing, it is not possible to reduce the weight by simply replenishing the consumed alkali metal hydroxide and/or its salt. The weight loss rate tends to decrease, and as mentioned above, it is difficult to control the weight loss rate just by controlling the time. Therefore, the treatment solution must be constantly replaced with new solution, and in the case of the immersion method, the efficiency in using the alkali metal hydroxide and/or its salt becomes significantly lower than in the steaming method. In the present invention, only hydrolysis occurs during the steaming treatment, and the surface layer of the fiber is only made water-soluble, and the surface layer is dissolved and peeled off in the washing step after the steaming treatment. In the present invention, preferably 2 to 50% of the initial fiber weight is used.
%, more preferably 5 to 30%, and then washed with water to dissolve and diffuse. The degree of hydrolysis can be appropriately determined experimentally depending on the type and concentration of the alkali metal hydroxide and/or its salt, the amount of adhesion to the fibers, steaming temperature, and time. Such treatments are usually accompanied by yellowing of the fibers;
After the peeling process, contact with an acid solution is necessary. Acids used to remove yellowing include inorganic acids such as sulfuric acid, hydrochloric acid, nitric acid, and phosphoric acid, and organic acids such as formic acid, acetic acid, malic acid, oxalic acid, and succinic acid, but are not limited to these acids. Any acid that can control the pH to 3.5 or less is fine. Further, the treatment temperature must be 50°C or higher, preferably 80 to 100°C. If the pH is 3.5 or higher, it will take longer to remove yellowing. Appropriate pH varies depending on the type of acid, treatment temperature, and time, but generally 0.5 to 3 is good, and 1 to 2 is more preferable. In the present invention, acrylic fiber refers to acrylic synthetic fiber containing at least 40% or more of acrylonitrile units in its components. This naturally includes composite fibers made of polymers with different copolymerization components and systems with irregular cross-sections in which the cross-section of the fibers is non-circular. Also, filaments, bulky textured yarns, tows, cut cotton, slivers, rovings, spun yarns, fiber webs, nonwoven fabrics, made of acrylic fibers as defined above.
Knitted fabrics, woven fabrics, natural fibers, semi-synthetic fibers, synthesis equipment for fibers other than acrylic fibers, blends with other types of acrylic fibers, mixed weaving, mixed twisting, mixed knitting, etc. are also covered. Alkali metal hydroxides include sodium hydroxide, potassium hydroxide, lithium hydroxide, and their salts include sodium carbonate, sodium phosphate, sodium rhodanate, potassium rhodanate, and other salts of strong bases and weak acids. . The substances listed here are only examples, and any other substances that exhibit hydrolyzability to acrylic synthetic fibers can be used in the present invention, and mixtures of these substances can also be used. In the case of a mixture, one using sodium hydroxide as the main solubilizer and sodium rhodanate or potassium rhodanate has particularly high peeling efficiency. Furthermore, in this method, the concentration range that can be peeled varies depending on the scouring conditions, heat setting conditions, the history of the fibers to be treated such as the oil and sizing agent used, and the deposits, and the degree of effect obtained by peeling also differs. Thus, by treating acrylic fibers with the method of the present invention, they are given an extremely soft texture and an elegant luster. Furthermore, according to the method of the present invention, the level dyeing properties of fibers are improved and dyeing spots are improved. Although the present invention is effective for all acrylic fibers, it is particularly effective for acrylic filaments. That is, acrylic filament products have the drawbacks of being hard to the touch and prone to staining when dyed, but these drawbacks can be overcome by applying the present method, and a silk-like texture and luster can be obtained. Such an excellent modification effect is due to the fact that the surface layer of the fiber is peeled off, thereby smoothing the fiber surface and changing the physical properties of the fiber. Furthermore, peeling of the fibers constituting the textile product creates appropriate voids in the tissue, improving the feel and drape properties. EXAMPLES Next, the present invention will be explained in more detail with reference to Examples, but the scope of the present invention is not limited thereby. Note that all percentages in the description of Examples are percentages by weight. Example 1 A plain woven fabric made of Pieuron (trade name of arrylic long fiber manufactured by Asahi Kasei Industries, Ltd.) 75d/38f was immersed in a sodium hydroxide solution with the concentration listed in Table 1, and the liquid content was adjusted to 120% using a mangle. After squeezing the liquid, it was steamed at 105°C for 10 minutes. This treated cloth was thoroughly washed with hot water at 80°C to dissolve and remove the surface. The sample after washing with water is colored yellow. After dehydration, this sample was immersed in a 1% sulfuric acid aqueous solution kept at 98° C. for 10 minutes, and then washed with water and dried. This acid treatment restores the sample to a whiteness comparable to that of untreated fabric. When this sample was dyed, the DE shown in Table 1 had a luster and texture particularly similar to silk, and almost no staining occurred during dyeing.

[Table] △... Same as untreated ×... Harder than untreated Example 2 Plain woven fabric using 48 count single yarn of Cashmilon (trade name of acrylic short fiber manufactured by Asahi Kasei Industries, Ltd.) spun yarn
It was immersed in a 15% sodium hydroxide solution, squeezed with a mangle to a liquid content of 150%, and then steamed at 100°C for 15 minutes. When this treated cloth was washed with water and treated with acid in the same manner as in Example 1, the weight decreased by 28%. It was observed that this treated fabric had a much better feel than the untreated fabric and was dyed evenly. Example 3 A plain woven fabric made of Pieuron (trade name of acrylic long fiber manufactured by Asahi Kasei Industries, Ltd.) 75D/38F was soaked in a 15% sodium hydroxide solution, and the liquid content was 120 with a mangle.
%, and then steamed for 15 minutes under the temperature conditions listed in Table 2. This treated cloth was washed with water and treated with acid in the same manner as in Example 1.

[Table] △...Same level as untreated ×...Harder than untreated.
Samples C and D shown in Table 2 above had particularly silk-like luster and texture, and almost no staining decontamination spots occurred. Example 4 A blended yarn fabric consisting of 70% acrylic fiber (trade name: Cashmilon, manufactured by Asahi Kasei Industries, Ltd.) and 30% polyester fiber was subjected to the same treatment as in Example 2.
This treatment reduced the fabric by 25%, giving it a soft texture.

Claims (1)

[Claims] 1. An aqueous solution of an alkali metal hydroxide and/or its salt that has a dissolving effect on acrylic synthetic fibers is applied to an acrylic synthetic fiber fabric, and then steamed to make only the surface layer of this fiber solubilized in water. After that, the surface layer is removed by washing with water, and then
A method for producing a peeled acrylic synthetic fiber, characterized by contacting it with an acid solution.