Application in textile printing and dyeing industry

Due to the presence of lactam structures in PVP molecules, there is a strong binding force between them and hydroxyl, amino, and carboxyl groups, which are often present in dyes. Therefore, PVP has a strong affinity for general organic dyes, sometimes even exceeding the binding force between dyes and fibers. Therefore, PVP is known as "liquid fiber". By utilizing the property of PVP, the affinity between hydrophobic fibers and dyes can be increased, thereby improving the dyeability of such fibers. For example, adding an appropriate amount of PVP during the synthetic fiber process can evenly dye the synthetic fibers, increase coloring power and dyeing depth. For polypropylene fibers that are difficult to dye, adding about 7.5% NVP/styrene copolymer can increase the dyeing depth of acidic dyes by about 10 times and disperse dyes by about 5 times. In the process of blending PVP, making it evenly distributed in the fibers can greatly reduce the color difference of the dyed fabric and improve the adhesion of the dye on the fabric. Obtain textile dyes with uniform color, light and heat resistance, and resistance to fading.

In addition to improving the dyeability of certain fibers, PVP can also enhance their moisture absorption, sun protection, and other properties, greatly improving the quality and grade of synthetic fibers. For example, polyamide fibers, polyester fibers, and other synthetic fibers are popular for their high strength, high fineness, friction resistance, thermal plasticity, good luster, and vivid dyeing. However, their moisture absorption is worse than natural fibers, which often results in a layer of water vapor from the air adhering to the surface of clothing when used as clothing, affecting the comfort of wearing. Especially in hot and humid weather in summer, clothing with poor moisture absorption is easily soaked by body sweat or high humidity air and adheres tightly to the skin, even causing irritation to the skin. One of the methods to solve this problem is to add 4% -8% PVP to the melt melted polyamide before spinning, and then perform melt spinning in a low oxygen environment. The PVPK value added should be between 30-70, and the residual monomer content should be less than 0.1%. In this way, synthetic fibers such as polyamide fibers and polyester fibers have high moisture absorption, washing resistance, and thermal plasticity. As mentioned earlier, the addition of PVP can also improve some dyeing properties, and controlling the spinning speed can obtain fibers of different fineness. It is worth mentioning that if the PVPK value added is less than 30, due to the poor chelating ability between low molecular weight PVP and polyamide, some PVP will dissolve in water during the water treatment process and high moisture absorption fibers will not be obtained. On the other hand, if the added PVP molecular weight is greater than 70, the viscosity of the molten system increases during spinning, making it difficult to spin silk and affecting production efficiency. Moreover, if the PVP molecular weight is too large, the resulting fiber hardness is too high and cannot meet the requirements for softness and comfort of synthetic fibers. The moisture absorption rate of polyester fibers improved by PVP-K60 can reach up to 20% of the weight of the fibers themselves. The influence of PVP on the moisture absorption and dyeing properties of synthetic fibers is shown in the table:

注：

（1）Yellowness refers to the degree of yellowing of fibers spun without dye after adding PVP, and a degree below 10 is considered qualified.

（2）There are two factors that lead to low production efficiency: one is an increase in PVP dissolution rate, and the other is a slow silk output speed.

（3）The dissolution rate data in the table represents the dissolution rate of PVP when synthetic fibers are treated in boiling water for 30 minutes.

The binding ability of PVP with different dyes varies. By utilizing this property, PVP can be used as a local anti dye agent for anti dyeing printing of polyamide fibers and polypropylene fibers, resulting in printed fabrics with distinct patterns and clear contours. In the production process of printed fabrics, after printing, the fabric also needs to be washed and desilted to remove the uncured dye and other printing and dyeing auxiliaries, and obtain printed fabric products. In order to achieve desilting without contaminating the pattern and ensuring product quality, the choice of detergent is very important. Research has shown that industrial detergents mainly composed of PVP and sodium aluminosilicate have significantly higher cleaning ability than detergents without PVP, and can prevent color transfer or white ground contamination during the cleaning process.