Pre-processing methods for pre-shaped spandex-containing fabrics
01
In order to improve the running performance of spandex during spinning, silicone lubricants and other additives are used in the weaving process. These additives will naturally degrade over time, causing the fibers to turn yellow and the fabric’s elasticity to decrease. At the same time, spandex-containing fabrics will form “cold setting” during long-term storage, causing the fabric to produce permanent wrinkles that cannot be eliminated during post-processing.
Therefore, in addition to reducing storage time, spandex-containing knitted fabrics are more importantly opened immediately after weaving and then rolled in open width. Avoid the chance of creasing.
02
Knitted with spandex After the fabric is removed from the machine, the spandex inside the fiber has a certain amount of internal stress formed during weaving.
The purpose of preheating and setting is to eliminate stress through the relaxation process of the fabric, make the size of the fabric fully stable, and eliminate permanent creases in the fabric during post-processing. . If the loop is formed during cylinder weaving, and the second loop is to the left of the first loop, then the cloth feeding direction during preforming should also be 7% to 10% (relative width) to the left, so that it is consistent with the twist of the finished product. be consistent.
03
Therefore, the best pre-shaping scheme is: relaxation → steaming (without Rolling hot water under steaming conditions (80°C) → overfeeding and pre-shaping → (pre-processing before entering the fabric → shaping → printing).
Because most dyeing factories do not have steaming equipment, they directly squeeze water into the shape. When the temperature is below 10 degrees (winter), creases are easy to occur on the fabric. After the fabric is relaxed in the steaming box and then shaped, you will get satisfactory results. The heat setting temperature is preferably between 185 and 190°C, and the setting time is 45 to 60 seconds. If the setting temperature is too high, the fabric will turn yellow. At the same time, if the impurities and additives on the fabric are partially degraded due to the influence of baking, once the degraded substances migrate to the inside of the fiber and cause stains, these stains will be difficult to remove in subsequent processing. Oil spots inside the fiber during dyeing It will first absorb the dye, but it cannot escape in time during the heat preservation and dyeing process, forming dark spots. Even if it is stripped and re-dyed, it will still remain on the fabric. Therefore, avoid pre-shaping at high temperatures above 195°C. It will also affect the fastness of spandex.
The width during shaping is 10% to 15% wider than the blank, allowing it to fully recover during pre-processing in the dye vat and completely eliminating the internal stress of the fabric.
Pre-treatment
Knitted fabrics to be printed must also undergo pre-treatment to remove cotton stains, impurities and Grease and wax, etc., increase the whiteness of the fabric and improve the wetting and water-absorbing properties of the fabric, thereby achieving good printing effects. Pre-treatment processes can be divided into two categories, namely traditional alkali treatment and modern biological enzyme treatment. Biological enzyme treatment meets the requirements of environmentally friendly processing, but currently it is difficult to meet the requirements for fabrics with high whitening or bleaching requirements, so conventional The alkali treatment process is still widely used. It is very necessary to gradually cool down the water after washing the spandex-containing fabrics before treatment to prevent the sudden cooling from causing fiber shrinkage and creases.
Requirements for shaping of semi-finished products
The shaping of semi-finished products must be carried out according to the original design process , Generally speaking, the set width is about 3% to 5% wider than the finished product width, the meridional shrinkage is controlled within the shrinkage required by the finished product, and the elongation of the patch is equal to the enlargement ratio during tracing. If it is a single-sided knitted fabric, then paddle trimming and optimal twist control are also required to reduce the printing weft skew caused by twist. The width of the pulp edge is about 1cm, the breaking point of the pulp. It should not be too thin or too thick. If it is too thin, it will not work as it should. If it is too thick, it will affect the printing effect near the edge of the cloth.
In pigment printing, the solid pulp remaining on the cloth surface will relatively increase the square meter mass of the fabric, so under the conditions of consistent width and shrinkage, the gram mass can be lighter. </p
