Due to the characteristics of knitted fabrics, the operations in the printing production process must be quite different from the operations in the printing production process of woven fabrics. Reasonable and correct printing operations are the key to ensuring and improving the quality and output of knitted fabric printing.
01 seam
In order to prevent weft skew defects in woven fabrics, the more effective way to operate the seams is to tear off the seams. However, the structure of knitted fabrics is different from that of woven fabrics, so it is impossible to use the tear-off seams operation method.
In order to prevent the weft skew caused by improper seam head of knitted fabrics, the work to be done before the seam head is: to see the fabric grain clearly, and if necessary, cut the two cloth heads along the cloth grain. It is necessary to distinguish the front and back sides of the fabric, so that the front is facing the front, overlap the cut ends of the fabric along the edge of the fabric, and then sew, and make sure the seams are firm and straight.
02 Sectional width and seam allowance
The incoming embryos of woven fabrics produced by textile mills are all in the shape of open width, so there is no need to perform slitting and hemming during the printing and dyeing production process. However, knitted fabrics are different. The incoming embryos produced by knitting factories are mostly cylindrical. .
In the production process of knitted fabrics, some processing and production processes require the fabric to be carried out in open width, such as tenter setting, printing, steaming, etc. Some processing steps require the fabric to be carried out in a cylindrical shape, such as knitted fabric pre-treatment, dyeing, post-printing flat washing, etc., in order to reduce and prevent knitted fabric yarns from being damaged, resulting in detachment and crimping, and the edges of the fabric being difficult to hold.
For this reason, according to the needs of knitted fabric production and processing, it is necessary to cut the cylindrical knitted fabric into a flat-width shape in a timely manner; sometimes the flat-width knitted fabric or seam must be cut into a cylindrical shape to facilitate smooth production. Slitting of knitted fabrics is done on a slitting machine.
03 Glue edge and trimmed edge
Some varieties and specifications of knitted fabrics are prone to curling after cutting. The occurrence of curling will seriously affect the quality of knitted fabric printing products and affect the smooth progress of printing production. For this reason, it is necessary to pay attention to the sizing and trimming of knitted fabrics, mainly for those knitted fabrics that are prone to curling during the production process. Woven fabrics also have curling. For example, cotton gauze and cotton-span elastic fabrics are more likely to curl when exposed to strong alkali, humidity, and heat. Generally, this can be solved by improving fabric edges, pre-shaping, and clamping. .
However, the above method for producing hems on knitted fabrics does not work during the production process. Instead, it is necessary to adopt the method of sizing the edges and cutting off a small amount of useless edges outside the sizing edges to ensure uniform fabric width and meet the needs of printing production. Generally, non-water-soluble slurry is used for the slurry edge. The width of the pulp edge is about 1cm, and the hardness of the pulp edge should be moderate. If it is too hard, the sizing will be too thick, which will cause a thickness difference between the edge of the cloth and the cloth surface, which will affect the contact surface between the flower net and the cloth surface and make the printing color yield uneven. The hardness can be controlled by not curling the edges of the knitted fabric when it is put on the rotary screen printing machine, and it should not be too thick.
04 Preparation before printing
Preparation before knitted fabric printing includes two parts:
1. Pre-treatment of knitted fabric printing fabric
Remove natural and artificial impurities on knitted fabric printing fabrics through pre-printing treatment to provide qualified printed semi-finished products for knitted fabric printing;
2. In order to ensure the quality of printed products and the smooth progress of the printing process, the processing content that must be carried out before printing is:
⑴ Knitted fabric pre-treatment, different fiber components adopt different pre-treatment processes.
Synthetic fibers, man-made regenerated fibers. Such as polyester, nylon, acrylic, viscose, modal, etc. The fiber texture itself is relatively clean and does not need to be boiled, rinsed or bleached. What needs to be removed and washed are man-made impurities; such as oil stains, dust, stains, etc. on the fabric. . Natural fibers such as cotton, linen, silk, etc., the symbiotic organisms that grow along with the fibers during the growth process will affect the printing and dyeing processing of these fibers and the wearing properties of knitted fabrics made of these fibers. These symbiotic organisms are natural Impurities must be removed.
For cotton knitted fabrics, the most important pre-treatment process in the current traditional pre-treatment process is scouring. Knitted fabrics do not need to be sized during weaving, so there is no desizing process before knitted fabrics are bleached. Most cotton knitted fabrics do not undergo singeing and mercerization.
With the improvement of consumer quality requirements for knitted fabrics and the development of technological production, the production of high-end knitted products has become a trend. Nowadays, yarn singeing and mercerization are used, and then knitted fabrics are singed and mercerized during the printing and dyeing process. , in order to improve the gloss and color quantity of knitted fabrics and improve the grade of knitted finished products, production batches have been formed. In order to improve the smoothness of the fabric and reduce the lint of the fabric, some companies without singeing equipment use cellulase to treat lint.
⑵ Preparation work before knitted fabric printing
On the basis of pre-treatment, knitted fabric printing semi-finished products areThe processing technology and equipment, whether the fabric has been mercerized, tentered, pre-shrunk, etc., still need to be explored, summarized, improved and improved in practice.
2. Measures and methods to overcome the large shrinkage rate of cotton knitted fabrics
To overcome the problem of large shrinkage of cotton knitted fabrics, the following measures and methods can be taken based on the characteristics of knitted fabric printing in the open-width state:
⑴ Loose processing.
Minimize the tension in each process during the printing and dyeing production process, try to avoid plastic deformation of the fabric in the wet state, and avoid fabric and fiber elongation. This is the most ideal way to prevent fabric shrinkage.
In fact, printing companies have adopted many loose processing methods in the dyeing and finishing of knitted fabrics. Regardless of the current selection of knitted fabric printing and pre-treatment and post-finishing equipment, many effective loose processing methods have been taken into consideration. Good way to process. It is believed that with the development of knitted fabric printing and knitted printing equipment, knitted fabric loose processing will continue to be improved and improved. In addition, shortening the printing process has also attracted attention in production and been put into production practice. The adoption of the above measures will definitely reduce the plastic deformation of knitted fabrics in the wet state and will inevitably prevent the elongation of fabrics and fibers. , which is of great benefit in reducing fabric shrinkage.
⑵ Overfeeding and drying.
That is to say, it is necessary to achieve relaxation and drying, reduce the tension effect, and bring the fabric to a fully balanced state. Before knitted fabric printing, overfeeding and drying can be combined with the pre-printing stenter and shaping process to control overfeeding in a timely manner and dry the fabric to achieve the purpose of reducing fabric shrinkage.
⑶ Mechanical pre-shrinking.
It is carried out using special mechanical shrinking equipment. First, the fabric is over-fed to allow room for pre-shrinking when the fabric is in a relaxed state in the longitudinal direction. Then the fabric is steam-humidified to enhance the plasticity of the fabric in the relaxed state and relax the internal stress of the fabric. Then the fabric is stretched longitudinally through diffusion. Shrinkage, transverse expansion, or longitudinal extrusion causes the longitudinal elongation of the fabric to retract during weaving or dyeing and finishing. Make the fabric have a relaxed structure and dry it loosely in this state to achieve the effect and purpose of pre-shrinking. Mechanical pre-shrinking is one of the effective measures to overcome the large shrinkage rate of knitted fabrics. At present, knitted fabric preshrinking machines are designed for cylindrical knitted fabrics and open-width knitted fabrics. Knitted fabric printing generally only uses pre-shrinking machines that perform split-width printing.
</p
