What Is Water-Soluble Fiber?
Water-soluble fiber, namely water-soluble polyvinyl alcohol (PVA), is a valuable functional differentiated fiber. There are two types of water-soluble PVA fibers: filament and staple fiber.
Characteristics Of Water-Soluble Fiber
Water-soluble PVA fiber not only has ideal water solubility temperature, strength and elongation, but also has good acid resistance, alkali resistance and dry heat resistance. It is also tasteless and non-toxic after being dissolved in water. The aqueous solution is colorless and transparent. In a short time It can decompose naturally and does not cause any pollution to the environment. It is a 100% green product. In addition, according to recent research results, PVA is the only biodegradable material in a large variety of synthetic polymers. It is the unique water-soluble properties of PVA fibers that the development of water-soluble PVA fibers with different properties and the development of broadening their application scope are still ongoing.
Weaving Method of Water-Soluble Fiber
1. Wet Spinning
The PVA aqueous solution is sprayed into a high-concentration Na2SO4 solution for coagulation, and the coagulated fiber is drawn and dried under moist heat, and then drawn by dry heat and heat treated.
Advantages: high output, low cost, the use of modified PVA is also conducive to the modification of ordinary PVA in the original solution.
Disadvantages: The process is difficult, Na2SO4 enters the fiber surface, it is difficult to produce PVA fiber that does not contain Na2SO4 salt and can be dissolved in water below 80°C, and the surface and internal structure of the fiber are irregular due to the direct removal of the solvent from the coagulation solution. Strength improvement is limited.
2. Dry Spinning
The high-concentration PVA fiber solution is sprayed into hot air to evaporate the solvent and solidify into filaments, which are then obtained by dry heat drawing and heat treatment.
Advantages: The spinning process is simple, which is suitable for the production of various water-soluble filaments, especially suitable for the production of water-soluble fibers at room temperature.
Disadvantages: low fiber tow size, low output, and high cost.
3. Melt and Semi-Melt Spinning
Add a certain amount of water to plasticize the PVA, then make it into a semi-melted state at a low temperature (120℃～150℃), press it out of the spinneret with a great pressure, and then cool it in the air solidification. This method can be used to spin monofilament or multifilament, but it has not been widely used in industrial production so far.
4. Boric Acid Gel Spinning
The PVA gel solution to which boric acid has been added is squeezed into the NaOH and Na2SO4 solution for forming and cross-linking. The cross-linked fiber is made by drawing, neutralization, water washing, drying, dry heat drawing, and heat treatment under humid and hot conditions. The cross-linking of this kind of fiber can make the water-soluble PVA fiber have better stability in the atmosphere of moderate humidity, and will be hydrolyzed and detached quickly in water, so its water solubility will not be affected.
5. Frozen Rubber Spinning
The new type of frozen glue yarn method newly developed by Kuraray Japan is to dissolve PVA with an organic solvent with very good solubility as the spinning dope, squeeze it into the coagulation liquid of the organic solvent from the spinneret, and quickly cool it into a gel to make the dope. The trickle forms a stable structure before the solvent is removed, and the coagulated fiber has a uniform circular cross-sectional structure. This method can obtain PVA fiber with low alcoholysis degree, high strength, low shrinkage and not easy to be glued.
Application Of Water-Soluble Fiber in Textile Industry
1. With Spinning and Weaving
The water-soluble PVA fiber is blended with other fibers as the intermediate fiber, and the water-soluble fiber is dissolved out after spinning to obtain high-count high-end textiles. In theory, water-soluble PVA fiber can be applied to any spinning system, and its role is defined as improving the spinnability and weaveability of the fiber more appropriately.
According to the International Wool Bureau, the output of wool with an average diameter of less than 19μm only accounts for 5.44% of the total output of Australian wool, while the output of wool with 20-30μm accounts for 66.6% of the total output. The price difference between the two is more than 50%. Therefore, the use of companion spinning can solve the dual problems of raw material resources and price constraints. There is no need to emphasize the fineness level of the wool. The medium and coarse wool can be used to spin higher-grade wool fabrics, and increase the space between the wool fibers, so that the wool fabrics are lighter, softer, and bulkier and warmer.
The blending of water-soluble fiber and natural fibers such as cotton and hemp can change the internal structure of the yarn, increase the gap between the fibers and the capillary pores in the yarn, thereby changing the air permeability of the fabric; the reduced twist makes the yarn soft and fluffy, and the fabric feels softer. The drape is further improved, the fabric is lighter and thinner, moisture wicking, and the clothes are more comfortable. Spinning high-count yarns in this way changes the traditional combed spinning process and shortens the process flow. High-count yarns can be spun with ordinary raw materials, which greatly saves raw material costs.
In addition, Kuraray is studying new composite materials of “Kuraron K-Ⅱ” easily water-soluble fiber and high-performance fibers such as polyamide fiber, fluorine fiber, and carbon fiber. Although these high-performance fibers have some special excellent properties, due to the crimping, strength, oil and other reasons of these fibers, there will be some difficulties in spinning, weaving and other processes, which can be improved by compounding. . At the same time, the composite hollow cotton yarn of “Kuraron K-Ⅱ” water-soluble fiber and cotton fiber jointly developed by Kuraray Company and Kola Spin Company has been successful, and it has been sold under the trade name of “SPINAIR”.
It is appropriate that the proportion of water-soluble PVA fiber in the accompanying spinning is 10%-20%. If the ratio is too small, the yarn count will not increase much after de-tightening, and the effect will not be obvious; the larger the ratio, the more the number of fibers in the yarn section, and the lower the count of the accompanying spinning yarn, which is beneficial to spinning production, but in order to make The fabric after de-dimensionalization still has a certain degree of yarn tightness, and a larger fabric tightness must be selected, which increases the difficulty of weaving. At the same time, the water-soluble fiber must be completely dissolved in the finishing process. The greater the proportion of its associated spinning, the more difficult it is to retreat, and the higher the product cost. Therefore, when choosing the ratio of associated spinning, comprehensive consideration should be given to production, quality, and cost.
On the other hand, based on the practical experience of “longer in short, thinner in thicker”, a small amount of water-soluble PVA fiber can be mixed into the raw material to improve the spinnability of the fiber and the mechanical and physical properties of the yarn, thereby improving the yarn’s performance. Weaving and fabric performance. At this time, the mixing amount is small, and a part of it can be naturally dissolved in the sizing and fabric finishing. Even if there is a small amount of residue, it will have little effect on the wearability of the fabric and will not cause any harm to the human body.
2. Production of Ultra-Fine Fibers
The water-soluble PVA and nylon, polyester, polyethylene, polypropylene, etc. are made into composite fibers. After being stretched, the PVA is washed with water to obtain ultrafine fibers below 0.1 dtex. As long as the appropriate mixing ratio is selected, ultra-fine fibers of any size can be produced.
3. Application in Embroidery Base Fabric
Embroidered base fabric is mainly used as a skeleton material for embroidery in the clothing industry. It can be embroidered alone or used as a lining with other clothing fabrics. After embroidering the desired pattern on the fabric and the non-woven base fabric made from it, the PVA component is dissolved to make the fabric obtain a beautiful pattern. After embroidering, the water-soluble non-woven fabric is removed to make lace, which has made a breakthrough in the traditional lace manufacturing industry.
4. Knitwear Tailoring
Using water-soluble fiber filaments as split yarns in knitting can achieve bladeless cutting. For example, in the process of knitting socks, using water-soluble fiber at the joint of two socks can not only ensure the continuity of weaving, but also can separate the connected socks by hot water treatment after weaving.
5. Development of Non-Twisted Fabrics
Ply the water-soluble PVA fiber with other single yarns and reverse twist, or adopt the wrapping yarn production technology, use the water-soluble PVA fiber as the wrapping fiber to wrap the short fiber yarn, weave it into a fabric and dissolve the water-soluble PVA fiber part to obtain the fabric Untwisted effect of medium yarn. It not only satisfies the strength required by the weaving process, but also enables the retained fibers in the yarn to be in a single fiber, untwisted or weakly twisted state after de-twisting, and the gaps between the fibers are enlarged, and the luster, softness and warmth retention of the resulting product are greatly improved. The water absorption performance has also been improved. It can manufacture untwisted towels, bath towels, baby products, hotel products, sporting goods, etc., and its application prospects are broad.
6. Uniform Sizing
Wrap the water-soluble PVA fiber on the surface of the yarn or use 2%~5% of the water-soluble PVA fiber to blend with other fibers, and then treat it at a certain water temperature. The yarn surface forms a complete adhesion layer, which is uniform. Sizing effect, while improving the abrasion resistance of the fabric, preventing fluffing and pilling. The sizing process has always been the most intensive process of energy and material consumption in traditional textile production and processing.
It is a key process for textile enterprises to cause environmental pollution. To achieve cleaner production and green manufacturing, the yarn sizing technology must be updated or even eliminated, although no sizing The concept of the process has been proposed earlier, but under the current state of the art, it is not feasible to realize it. The “wrapping or blending-dissolving” sizing technology of water-soluble PVA fibers has a certain promotion significance at present.