Different from natural fibers, nylon or polyester fibers are synthetic fibers. Their basic characteristics are that they have a very tight molecular structure, little or no water absorption, and the fiber surface is very smooth. Therefore, the pigment printing slurry cannot penetrate into the fiber, but only adheres to the surface of the fabric fiber. Its fastness depends entirely on the adhesion of the adhesive (resin) to the fiber surface and the mechanical properties of the resin film itself. Therefore, the printing fastness of nylon or polyester fabrics is far less than that of natural fibers.
People usually confuse the waterproofness and water repellency of fabrics in their lives. In fact, in dyeing and finishing technology, the two are two different concepts that are both related and different. The so-called water repellency is non-stick The meaning of water is that water can form rolling water drops on a lotus leaf, which shows that the lotus leaf has strong water repellency. If the nylon cloth is treated with water repellency, it will have a lotus-like effect. Water-repellent like leaves. The so-called waterproof means impermeable. For example, a nylon poncho coated on one side cannot be water-permeable even in heavy rain. A multi-functional product that is water-repellent, waterproof, windproof and warm. Usually, the printing of waterproof nylon cloth is not printed on the rubberized side, but on the non-glued side. Therefore, the waterproofness is crucial to the printing. The fastness has little or no effect. It is the water repellency that affects the adhesion of the printing slurry to the fiber surface. The greater the water repellency, the greater the impact. In dyeing and finishing, organic water-repellent finishing agents are often used. Silicon compound is also a release agent used to process release transfer printing paper. It can be imagined how difficult it is to print fastness due to the water repellency of printed nylon or polyester cloth. . In nylon fabric printing, due to the different types of nylon, some are only waterproof, some are only water-repellent, some are both waterproof and water-repellent, and some are neither waterproof nor waterproof during dyeing and finishing. No water repellency. Therefore, before printing, it is necessary to conduct actual identification in order to treat it differently, and determine the selection of printing slurry and process technology conditions according to the strength of the fabric’s water repellency.
Currently, there are two main types of slurry used for printing nylon or polyester fabrics: water-based printing emulsion and solvent-based printing ink. As far as their resin components are concerned, they are mainly polyacrylate and polyurethane. This Two types of resins can be made into either water-based magma or solvent-based ink. In terms of process application, they are divided into single-component and two-component. . Regarding the printing fastness, solvent-based ink is better than water-based magma, polyurethane is better than polyacrylate, and two-component solvent-based polyurethane ink is better than single-component. . Of course, in actual production, labor protection and environmental issues must also be considered. Therefore, the selection of printing paste should be as practical and feasible as possible.
Cross-linking agents, also known as bridging agents, are usually divided into two categories: water-based and oil-based. They can be mixed with water-based magma or solvent-based ink respectively. But in practical applications, it is not very strict. For example, put oily The combination of cross-linking agent and water-based magma is also feasible and effective. In the printing process, the cross-linking agent can cross-link itself or react with the printing resin to form a huge network structure, thus strengthening the adhesion to the fabric fibers. , and improve the mechanical properties of the resin film The mechanical properties greatly improve the printing fastness. The one-component printing slurry can be used directly for printing or can be used together with a cross-linking agent, while the two-component printing slurry must be used together with a cross-linking agent. It should be pointed out that the amount of cross-linking agent should be mixed. It should not be too large, otherwise it will affect the feel and will not be good for the fastness. When using oil-based cross-linking agents, the prepared printing ink should be used up immediately. If time passes, the properties will deteriorate and even coagulate and fail.
Most of the production characteristics of the printing industry are small batches, multiple varieties, and multiple colors, especially some special printings with relatively complex products. There is still a lack of unified industry standards. For the printing fastness of nylon fabrics, manual printing is generally used. Test by scrubbing and non-drying tape method. Hand scrubbing includes dry scrubbing and wet scrubbing (regularly immerse the cloth in water or soap, and then perform destructive scrubbing) to observe whether the resin film is broken and the number of scrubbings it can tolerate.Currently, in the production of the general printing industry, the drying processes after printing mainly include natural drying, low-temperature hot air drying, and high-temperature baking or pressing after drying or drying. Among these three processes, the drying process of drying or drying and then high-temperature baking or pressing has better printing fastness, because high-temperature treatment can volatilize the water or solvent cleanly, and at the same time make each component in the printing paste ink The full reaction can also make the resin film and fabric fibers bond more closely, which plays an extremely important role in improving the fastness, especially the fastness to washing. It should be pointed out that when performing high temperature treatment, the temperature and time must be strictly controlled. If the temperature is too high or the treatment time is too long, it will cause the yellowing of white fabrics or the thermal migration of dyes on colored fabrics to cause pan-coloring, causing damage to the resin film, reducing the fastness, and even shrinking or shrinking the fabric. coking. Therefore, various practical tests must be conducted before formal production to optimize the printing paste and ink and determine reasonable process and technical conditions. In addition, during the printing operation, the shape, hardness and pressure of the platen, screen and scraper used for printing not only affect the surface effect of the flower shape, but also have a certain impact on the fastness. The key is to control the appropriate amount of pulp ink. To prevent the resin film formed on the surface of the fabric from being too thick and affecting the scrubbing fastness.
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