1 Relaxation of spandex knitted fabrics
During the weaving process, spandex knitted fabrics are stretched and deformed due to the action of tension. The upper part of the spandex knitted fabric must be folded by placing the cloth on the knitting machine. During assembly, the gray fabric has been relaxed, but there is still considerable residual stress, which changes the width and weight of the gray fabric, making it difficult to control and affecting the quality indicators of the dyeing and finishing process. The purpose of the relaxation project is to make the fabric fully Pre-shrinking eliminates internal residual stress, allowing the maximum weight and minimum amplitude to be controlled. The data after relaxation can be provided as a guide to the organizer.
Methods for relaxing:
① Resting and relaxing: The original method is to relax the gray fabric in the cloth cart and let it sit for a while. Leave it for more than 8-12 hours to allow the residual tension in the cloth to release itself, but of course the effect will be poor.
②Steam relaxation: For example, open-width fabrics can be steam-relaxed through a steam box, and cylindrical fabrics can be relaxed through a tension-free cylindrical steam setting machine, using the amount of steam and Speed control conditions to obtain maximum retraction and weight.
③Hot water relaxation: It can be pre-cooked in a dye vat or processed by an open-width washing machine.
2 Pre-shaping of spandex knitted fabrics
Purpose:
After the spandex knitted fabric is fully relaxed, the next step is heat setting treatment. This can stabilize the fabric size, reduce shrinkage, and prevent the fabric from wrinkling during the wet treatment process.
The most important factors in heat setting are temperature, time and amplitude settings.
1. Setting temperature
The setting effect of fabric depends on the amount of heat received by the fabric. and the actual temperature. The heat setting temperature is generally 185-195 degrees Celsius (except for low-temperature functional spandex), and the softening point of spandex is 170-190 degrees Celsius. The speed depends on the length of the setting machine, usually 20-60 seconds and 24-40 meters. Temperature can also be used as one of the methods to control the elasticity of fabrics. If you want low elasticity, you can increase the temperature to 195 degrees Celsius to reduce the count of spandex and the elastic modulus. To control the warp and weft of elastic fabrics, just stabilize the spandex to a certain level. The degree can control its elasticity, so the setting temperature is very important.
2. Amplitude setting
3 Refining Engineering
Purpose:
Eliminate the oil in spandex fibers or impurities in cotton yarn.
During the refining process, the water quality must be absolutely soft. Poor water quality will lead to poor refining effect. The refining degree needs to be adjusted according to the changes in the material of the interwoven material, the structure of the cloth, and the spandex content. Refining Formula and temperature, time setting.
4 Bleaching Project
For the bleaching treatment of spandex, it is generally not possible to The use of chlorine (except spandex with anti-chlorine function) will reduce the elasticity and stretch of spandex. Generally, reduction bleaching agent is used to interweave cotton fabrics, and alkali is used as little as possible. Bleaching is done with hydrogen peroxide and sodium perborate at normal pressure, or with insurance powder bleaching agent. If extra whiteness is required, a fluorescent whitening agent can be used after bleaching.
5 Dyeing Project
Equipment for dyeing spandex fabrics must be considered To ensure that the cloth surface is flat and the tension is reduced, the dyeing machine is best equipped with tension-free cloth feeding and folding devices to maintain the elasticity and recovery properties of the fabric.
Spandex and cotton interwoven fabrics can be dyed in the same way as cotton fabrics. Cotton fabrics are usually dyed with direct dyes or reactive dyes. The spandex will not be colored and may appear white on the surface of the fabric. , so choose bright spandex to avoid this problem.
For spandex and polyester interwoven fabrics, the biggest problem is how to solve the dyeing reproducibility and color fastness. It is necessary to pay attention to the changes in dyeing conditions, temperature, and PH.
Due to fear of embrittlement of spandex fiber, polyester is mostly dyed at around 120 degrees Celsius. However, this method makes high-temperature dyeing disperse dyes insufficient for polyester dyeing, resulting in dyeing recurrence. Bad sex.
Some scholars advocate taking the following three measures:
① Inhibit the contamination of spandex components by disperse dyes to make the dyes more effective Ground dyed polyester component.
② When using disperse dyes, both dyeing reproducibility and dyeing fastness should be taken into consideration.
③In the reduction cleaning, the disperse dye stained on the spandex component is effectively removed.
For the dyeing of spandex and nylon interwoven fabrics, acid dyes are mostly used, and the general color fastness will be very good.
6 Dry cloth engineering
Spandex open-width fabric can be used in Overfeed the dry cloth on the chain tenter and do not exceed the minimum heat requirement. Spandex cylinder fabric can be dried in a drum dryer, and the drying temperature is 120-135 degrees Celsius.
7 Finishing Project
Spandex Fabric Considering that spandex has no obvious melting point, and factors such as the opponent’s material and the type of setting machine, its thermal efficiency is also different. The general benchmark is set at 190 degrees Celsius. High temperatures may cause color changes and strong strength.��low.
Spandex fabrics can be mechanically finished with ordinary cotton fabrics, and tension-free steam calendering is suitable for spandex cylindrical knitted fabrics to stabilize the dimensions. To improve the smoothness and waterproofness of spandex fabrics, softeners can be used to finish them. Most of them will not affect the performance of spandex, but attention must be paid to the PH value of the treatment.
8 Mercerization Project
Spandex circular braid can also be mercerized In the process, mercerization is divided into single mercerization and double mercerization.
1. Single mercerization means that the yarn has not been mercerized. After weaving, the gray cloth undergoes a mercerization process. If the gray cloth is single-mercerized, the gray cloth is generally singed first. For example, in a cylindrical fabric singeing machine, after the induction pull, the speed and tension must be well controlled. Otherwise, the heat during singeing will affect the change of spandex and the tension on the cloth surface will be uneven, and the specifications of the cloth surface after singeing will also be inconsistent. Stablize. In the case of single mercerization, the gray cloth is directly mercerized without any singeing treatment.
2. Double mercerization means that the yarn has been singed and mercerized, and then the gray cloth is mercerized after weaving.
The mercerizing process is generally at a temperature of 15-23 degrees Celsius, a speed of 8-12 meters/minute, a time of 0.5-1 minutes, a concentration of 28 degrees Be, and penetration needs to be added agent. After mercerization, neutralize with acetic acid and wash with water before dyeing.
To set the mercerizing width, generally take a piece of gray fabric and process it in a mercerizing liquid, measure its final width, and then order the adjustment number of the large silk rack. Such as double mercerization, it usually depends on the yarn. The thread has been mercerized and will not shrink too much.
The brightness of mercerization is unstable due to the characteristics of spandex fabric. Unlike other fabrics that are subject to strong tension during mercerization, there is less shrinkage after mercerization and the brightness of the cloth surface is good. However, after mercerization of spandex fabric, the shrinkage rate is large, which affects the brightness of the cloth surface. In addition, the cloth structure also has an impact. Generally, smooth tissue has better brightness than unsmooth tissue.
Spandex fabric production flow chart:
Weaving – opening – gray fabric shaping – scouring – dyeing – dehydration – drying Cloth – styling. </p
