English Views: 2 Author: Site Editor Publish Time: 2021-09-01 Origin: Site
During the weaving process, the spandex knitted fabric is stretched and deformed due to tension. When the fabric is folded and folded on the knitting machine, the original fabric has been relaxed, but there is still considerable residual stress. Amplitude and weight change, which is difficult to control. The quality indicator of the dyeing and finishing process is affected. The purpose of the relaxation project is to fully pre-shrink the fabric, eliminate internal residual stress, and control its maximum weight and minimum amplitude. The information can be provided with the organizer as a pointer.
(1) Stay and relax: The original method is to loosen the cloth in the cloth car and let it stand for more than 8-12 hours to release the residual tension in the cloth by itself. Of course, the effect is poor.
(2) Steam relaxation: For example, open-width fabrics can pass through a steam box for steam relaxation, and cylindrical fabrics can be passed through a tension-free cylindrical steam setting machine, using steam volume and speed control conditions to obtain the maximum retraction and weight.
(3) Hot water relaxation: pre-cooking and smelting can be carried out through the dyeing vat, or the open-width washing machine can be used for treatment.
After the spandex knitted fabric is sufficiently relaxed, the next step is heat setting treatment, which can stabilize the size of the fabric, reduce the shrinkage rate, and prevent the fabric from wrinkling and wagging during the wet treatment process.
The most important thing for heat setting is temperature, time and amplitude setting.
The effect of fabric setting depends on how much heat the fabric receives 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. The general time is 20-60 seconds and the speed is 24-40 meters. Temperature can also be used as one of the methods to control the elasticity of the fabric. If the elasticity is small, the temperature can be increased to 195 degrees Celsius to reduce the spandex count and elastic modulus. The warp and weft direction of the elastic fabric can be controlled, as long as the spandex is stabilized. The degree of flexibility can be controlled, so the setting temperature is very important.
The original fabric that has been relaxed earlier still has residual stress, so the heat setting range must be 5-15% larger than the expected range.
Setting the setting temperature and range, the fabric sample after relaxation can be boiled for 30 minutes, and alkali oil can be added during the boil.
And scouring agent, dried after scouring, this time is the smallest width after the fabric shrinks. This data can be used to calculate the width of the fabric and heat setting efficiency.
Set cloth width = (relaxed cloth pattern cloth width-cloth pattern cloth width after cooking)/2
Heat setting efficiency = (Fabric-like width after cooking/Fabric-like relaxation width)*100
Precautions: During the heat setting process of the green fabric, pay attention to the oil in the cloth, such as spinning oil, wax, and lubricating machine lubricating agent. After heat setting, it may not be removed during the dyeing or bleaching process. , Or discoloration or yellowing. Nowadays, there are special lubricants for looms for weaving spandex, which can volatilize by itself during heat setting.
Purpose: Eliminate the oil of spandex fiber or the impurities of cotton yarn.
During the refining process, the water quality must be absolutely soft water. Poor water quality results in poor refining effect. The degree of refining needs to be adjusted according to the changes in the material of the opponent, the organization of the cloth, and the content of spandex. The refining formula, temperature and time setting.
For the bleaching treatment of spandex, chlorine generally cannot be used (except spandex with chlorine resistance). Chlorine will reduce the elasticity and elongation of spandex. Generally use reducing bleaching agent, mixed with cotton fabric, use as little alkali as possible, bleach with hydrogen peroxide sodium perborate at normal pressure, or bleach with sodium sulfonate bleaching agent. If extra white is required, fluorescent brightener can be used after bleaching.
In the equipment for dyeing spandex fabrics, it is necessary to consider the smoothness of the cloth surface and reduce the tension used. The dyeing machine is best equipped with tension-free feeding and folding devices to maintain the elasticity and recovery performance of the fabric.
Spandex and cotton blended fabrics can be dyed in the same way as cotton. Cotton fabrics are usually dyed with direct dyes or reactive dyes. Spandex will not be colored and may appear white on the surface of the fabric, so choose the light spandex to avoid this problem.
The biggest problem with spandex and polyester blended fabric is how to solve the dyeing reproducibility and color fastness. It is necessary to pay attention to the changes of dyeing conditions, temperature and pH.
For fear of embrittlement of spandex fiber, dyeing is usually performed at around 120 degrees Celsius, but this makes high-temperature dyeing disperse dyes insufficient for dyeing polyester, resulting in poor dyeing reproducibility.
Some scholars advocate the following three measures:
(1) Suppress disperse dyes from staining the spandex component, so that the dye can effectively dye the polyester component.
(2) The disperse dyes used should take into account the reproducibility of dyeing and the fastness of dyeing.
(3) In reduction cleaning, effectively remove disperse dyes contaminated on spandex components.
The dyeing of spandex and nylon interwoven fabrics mostly uses acid dyes, and the general color fastness will be very good.
Spandex open-width fabrics can be dried on a needle chain tenter with overfeed, and the heat should not exceed the minimum heat requirement. The spandex cylindrical fabric can be dried with a tumble dryer at a temperature of 120-135 degrees Celsius.
The thermal efficiency of spandex fabric is different due to the fact that spandex has no obvious melting point, the material of the opponent, the type of setting machine and other factors. The general benchmark is set at 190 degrees Celsius. High temperature may cause color change and decrease in strength.
Spandex fabrics can be mechanically finished with ordinary cotton fabrics, and the tension-free steam calendering is suitable for spandex circular knitted fabrics to stabilize the size. For spandex fabrics, the fabric surface is smooth and waterproof, and it can be finished with softeners. Most of them will not affect the performance of spandex, but it is necessary to pay attention to the pH value of the treatment.
Spandex circular knit fabrics can also be used for mercerizing, which can be divided into single mercerizing and double mercerizing.
After weaving, the embryonic fabric is mercerized. If the embryonic fabric is mono-mererized, the embryonic fabric is generally singed first, such as the cylindrical embryo singeing machine, and then the broaching machine. , The speed and tension must be well controlled, otherwise the heat during singeing will affect the changes of spandex, and the fabric surface tension will be uneven, and the fabric surface specifications will be unstable after singeing. When there is mono-satin, the fabric is mercerized directly without singeing.
The process of mercerizing is generally at a temperature of 15-23 degrees Celsius, a speed of 8-12 m/min, a time of 0.5-1 minute, a concentration of 28 degrees Be, and a penetrant must be added. After mercerizing, it is neutralized with acetic acid and dyed after washing.
For setting mercerizing range, generally take a piece of fabric and treat it with mercerizing liquid, measure its final range, and then order the adjustment data of the large cargo frame. For example, double mercerizing is generally because the yarn has been mercerized, and its shrinkage will not be too large.
Mercerized brightness is unstable due to the characteristics of spandex fabric. Unlike other fabrics that are subject to strong tension when mercerized, there is less shrinkage after mercerizing, and the fabric surface has good brightness. However, after the spandex fabric is mercerized, the shrinkage rate is large, which affects the brightness of the cloth surface. In addition, the cloth structure also has an impact. Generally, the smooth structure has better brightness than the non-smooth structure.
Spandex fabric production process technology table:
Weaving-open width-embryo setting-scouring-dyeing-dehydration-dry cloth-setting.
