Suede is made of island-type ultrafine polyester silk, and then after desizing, refining, relaxing, pre-shaped fiber opening, grinding and dyeing, it has a soft feel and draping texture. Good, elegant style; smooth feel, soft luster, strong suede feel, and has a good “writing effect”; good breathable and moisture-permeable properties, and good wear comfort; although the absolute strength of the monofilament is low, it has a relatively strong strength , the total strength of the wire can meet the requirements of use and has good wear resistance. In addition, it also has the characteristics of dimensional stability and washing and wearable common to chemical fiber fabrics. Therefore, suede products are very popular among consumers.
The key to obtaining a good style of suede fabric is the dyeing and finishing of the fabric, among which pretreatment is particularly important. The purpose of the pretreatment process is: 1) to wash off the oil agent of the grey cloth to prevent the color of the color and influence the finishing during dyeing; 2) to make the island-type polyester microfiber fully open and reduce the amount to facilitate the grinding of the velvet in the back. , and make the fabric have good drape and feel; 3) Make the fabric fully shrink, so that the fluff is dense, with excellent “writing effect”, fully reflecting the product style. This paper discusses the pretreatment process of suede fabrics to provide a reference for the development of a reasonable dyeing and finishing process for the development of new suede products.
1.1 The influence of temperature and NaOH concentration on the reduction rate
At the same insulation temperature, as the NaOH mass concentration increases, the reduction rate increases accordingly. This is mainly because the greater the NaOH mass concentration, the higher the chance of contact between fiber and caustic soda, which increases the chance of OH-attacking the ester bond, so the reduction rate increases. Meanwhile, at the same NaOH mass concentration, the reduction rate increases with the increase of the insulation temperature. The main reasons: First, the alkali hydrolysis of polyester is a double diffusion reaction process, that is, the reactants in the solution diffuse to the surface of the fiber, amorphous region, and the edges of the crystalline region. The hydrolysate diffuses from the fiber into the solution, the temperature increases, and the double diffusion The coefficient increases, the double diffusion rate increases, and the reduction rate increases; secondly, from the free volume theory, it can be seen that the temperature increases, the free volume fraction of the polyester increases, that is, the active space of the chain segment increases, and the number of active units of the fiber molecular chain As the increase occurs, the density of the fiber decreases, the frequency of contact reaction between carbonyl and OH- increases, and the reduction rate also increases, so the increase in temperature is conducive to the occurrence of the fibroal alkali hydrolysis reaction.
1.2 Effect of temperature and NaOH concentration on fabric shrinkage
As the increase of NaOH mass concentration, the weft shrinkage of the fabric increases, but as the concentration further increases, the degree of increase in shrinkage becomes smaller ; As the temperature increases, the weft shrinkage of the fabric also increases, but as the temperature increases further, the degree of increase in shrinkage decreases. The main reason for this change pattern of warp shrinkage in fabrics may be that as the NaOH mass concentration increases and the temperature increases, the reduction rate of fabrics increases, the space for high shrinkage wires to move, and the shrinkage rate increases. The larger the concentration and temperature, the shrinkage rate basically reaches a large value, so the degree of increase in shrinkage decreases. Another reason for the increase in fabric shrinkage is the highThe crystallinity of the shrinking filament is low. The higher the temperature, the smaller the binding force on the movement of the macromolecular segments, making it easier for the macromolecules with high orientations to de-orientate the amorphous region, thereby resulting in greater macroscopic shrinkage of the fiber.
1.3 Reasons for differences in the weft shrinkage rate of fabric
The weft shrinkage rate is much greater than the weft shrinkage rate, which is about 2.1 times the weft shrinkage rate. This is determined by the island multifilament used.
After the multifilament is opened, there are also crude fibers, which are the high-shrinkage wires in the multifilament. Highly shrinkable polyester fibers have low crystallization and high orientation supramolecular structure characteristics. At a certain temperature, due to its low crystallinity, the binding force on the movement of the macromolecule segment is small, causing macromolecules with high orientation to develop de-orientation, thereby producing high shrinkage of the macroscopic fibers. Island silk is generally combined with this high-shrinkage silk in a networked manner, so that the fabric can be fully contracted during dyeing and finishing, thus reflecting the style of the product.
1.4 Effect of treatment time on reduction rate
When reducing the amount of suede fabric alkali, when the concentration and temperature are determined, time is the decisive factor in controlling the reduction rate. As the reduction processing time is extended, the reduction rate increases, but when the time increases to a certain value (20 min), the reduction rate increases gradually. This is because as the treatment time increases, the reaction between NaOH and polyester is more sufficient, and the utilization rate of NaOH also increases accordingly, so the reduction rate increases; at the same time, the OH-concentration in the system decreases as the reaction progresses, causing the hydrolysis reaction The speed slows down and the reaction tends to equilibrium after a certain period of time.
1.5 Effect of reduction rate on fabric performance
For ordinary polyester fabrics, as the reduction rate increases, the bending stiffness, fracture strength and thickness in the weft direction should gradually decrease, and breathability Gradually increasing. The reason why the performance of suede fabrics changes with the reduction rate is different from that of ordinary polyester fabrics is mainly caused by the mixed fibers of suede fabric warp yarns of island silk and high shrinkage silk. The reduction reduces the bending stiffness, fracture strength and thickness, and increases breathability, while the contraction of the meridian mixed filament changes these properties in the opposite direction. The abnormal point of change is the result of superior performance changes caused by the shrinkage effect of mixed fibers. For small pattern suede fabrics, the performance of the fabric is better when the reduction rate is within the range of 18.9% to 21.76%.
2 Conclusion
1) At the same insulation temperature, as the NaOH mass concentration increases, the reduction rate increases accordingly; under the same NaOH mass concentration, the reduction rate increases with the increase of the insulation temperature And increase.
2) As the mass concentration of NaOH increases, the warp shrinkage of suede fabric increases, but as the concentration increases further, the degree of increase in shrinkage becomes smaller; as the temperature increases, suede, The warp shrinkage of the velvet fabric also increases, but as the temperature increases further, the degree of increase in shrinkage decreases.
3) The warp shrinkage rate of suede fabric is much greater than that of the weft shrinkage, about 2.1 times that of the weft shrinkage.
4) WithThe processing time is extended and the reduction rate increases, but after the time increases to a certain value (about 20 min), the reduction rate gradually slows down with the extension of the processing time.
5) The optimal reduction rate for achieving a more ideal suede fabric style effect is 18.9% to 21.76%.
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