Introduction to polyamide fiber (PA) is a kind of synthetic fiber whose molecular main chain is connected by amide bond. It is the first synthetic fiber to realize industrial production in the world, and it is also one of the main varieties of chemical fiber. Nylon has many advantages, such as excellent wear resistance, high breaking strength, good resilience and fatigue resistance, good moisture absorption and so on. Therefore, nylon has a broad application in the field of textile and clothing. In the field of traditional silk stockings, nylon as a very important raw material has always occupied the vast majority of the market share. In recent years, women's underwear and all kinds of body shaping clothes are more popular in the international market. With its unique characteristics of seamless fit, body shaping, moisture permeability, fashion and beauty, the majority of domestic consumers (especially female consumers) also love it. In addition, a variety of nylon / Cotton (cotton / nylon) elastic Roman knitted fabrics are also accepted by more and more consumers, and are widely used in a variety of high-end fashion and leisure fabrics. In the field of high-grade carpet, nylon fiber also occupies a larger market share. Nylon fiber has always been the main raw material of high-grade lining. In recent years, because of its light weight, easy dyeing, high elasticity and wear resistance, tear resistance, easy finishing and other characteristics, nylon fiber has been widely used in outdoor sports, especially in the light outdoor field, such as sportswear, assault suit, quick drying clothes, cold suit, outdoor tent, sleeping bag, mountaineering bag, etc.

Introduction of nylon dyeing and finishing 2.1 pretreatment

Nylon fabric has good resilience and is easy to shrink in the process of dyeing and finishing. In order to ensure the good dimensional stability of nylon fabric in dyeing and finishing process, it is necessary to predetermine the shape before dyeing. The setting temperature depends on the specific material, generally controlled at 180 ℃ - 200 ℃. In the spinning process of polyamide fiber, certain size and oil agent will be applied (especially for spandex fabric, the introduction of oil agent will be more). The introduction of these impurities (especially oil agent) will have a greater impact on the dyeing. Improper treatment will produce color defects such as streaks and streaks in the subsequent dyeing process. Because of its good resilience, nylon fabric is easy to produce wrinkle print in the pretreatment, and it is not easy to eliminate it in the post-processing. Therefore, it is better to adopt open width treatment (such as open width pre shrinking machine or roll dyeing machine) in the pretreatment of nylon (especially polyamide) fabric, and strictly control the process conditions, so as to prevent the formation of wrinkle print which is difficult to eliminate due to sudden shrinkage at high temperature.

2.2 dyeing

2.2.1 dyeing of nylon fiber and fabric the dyeing of nylon (including polyamide) fiber and fabric can be realized by a variety of dyes. The commonly used dyes in the market are acid dyes, 1:2 metal complex dyes (neutral dyes) and disperse dyes. Disperse dyes have good levelness, excellent striping coverage, but poor color fastness. They are generally only used for light colors or varieties with low fastness requirements. At present, they are rarely used in clothing fabrics. Acid dyes with complete chromatogram, bright color, good levelness and moderate dyeing depth are the most commonly used dyes in nylon dyeing. However, their color fastness (especially the fastness to wet treatment) is poor. Increasing the fixation treatment can help to improve the wet fastness, but it is still difficult to reach a higher level. In addition, the fixation process sometimes produces fixation spots and causes losses. 1: 2 metal complex dyes have good fastness, but the color is dark and the chromatogram is incomplete. It is difficult to meet the requirements for some orders with top fastness requirements. Moreover, the environmental protection (heavy metal) problems caused by 1:2 metal complex dyes also restrict their application in the textile printing and dyeing industry, and will be more and more limited in the future.

2.2.2 dyeing of polyester / polyamide bicomponent fiber and its fabric the dyeing of polyester / Polyamide (including polyamide / polyester) bicomponent (including polyester / polyamide interweaving, polyester / polyamide composite yarn, etc.) fiber and its fabric always has the problem of fastness, which is mainly caused by the dyeing of polyamide fiber with disperse dyes. For polyester / polyamide fabrics, the traditional dyeing method is usually carried out by disperse / acid (or neutral) one bath method, but the wet treatment fastness of this method is often poor. The disperse / acid (or neutral) two bath dyeing method can help to improve the color fastness, but the improvement is limited. The two bath dyeing and finishing process is longer, the energy consumption of water, electricity and steam is more, and the sewage pressure is increased, so the sewage cost will be higher and higher.

2.2.3 dyeing of polyamide / cotton fiber and fabric the dyeing of polyamide / Cotton (including the interweaving and blending of cotton / polyamide, polyamide / rayon, rayon / polyamide) fabric is usually based on two bath method, with medium temperature reactive dyes for cotton and acid or neutral dyes for nylon. In the two bath dyeing process, the color is difficult to control and the same color is poor due to the mutual contamination of acid dyes and reactive dyes. At the same time, the low utilization rate of dyes and more floating colors (especially dark varieties) will lead to the problems of heavy pollution discharge and high production cost. The production efficiency of two bath method is also very low.

2.2.4 development trend of nylon dyeing technology in view of some of the problems mentioned above, with the improvement of people's production level, in today's environment with the theme of energy conservation and emission reduction, and under the background that the labor cost is not constantly rising, the new demand of nylon (including the components containing nylon) dyeing is reflected in the following points: the trend of high fastness requirements; the improvement of production efficiency; the trend of energy conservation and emission reduction Potential, including emissions and COD emissions. In view of these needs, the technological development of nylon dyeing has also made great progress in recent years. From the perspective of dyeing technology, it is mainly reflected in the following aspects: the application of new modified dyes with higher performance and fastness; the rapid market acceptance of short process technology; the wider use of more environmentally friendly and ecological chemicals; improving the utilization rate of chemicals and reducing the consumption of chemicals Consumption and emissions