Before flower printing on fabric velvet, it is necessar […]
Before flower printing on fabric velvet, it is necessary to pre-process the knitted fabric grey fabric to remove impurities and bleach to improve its wearability and appearance quality, and prepare for the subsequent printing process. A good pre-processing is knitted fabric rotary screen printing. Foundation. It can be said that all the good properties of knitted fabrics are obtained in the pre-treatment process. The pretreatment of knitted fabric is mainly composed of three parts: alkali shrinkage mererization, scouring and bleaching whitening. Alkali shrinkage is a process in which cotton knitted fabrics are dipped in a caustic soda solution and stacked in an open width cylinder and tension-free state, and then washed to remove alkali. Through alkali shrinkage, the fabric shrinks, increases the density, elasticity and gloss, improves the smooth feel, reduces the shrinkage rate, and improves the dimensional stability of the finished product.
In recent years, the use of mercerizing technology for knitted fabrics has gradually increased, and the quality of mercerized products is much higher than that of alkaline shrink products. The effect and principle of scouring and bleaching of knitted fabrics are the same as that of woven fabrics, but because of its loose structure, the processing conditions mainly the concentration of working fluid are lower than that of woven fabrics. The scouring and bleaching processing methods are intermittent. , Continuous type, intermittent type generally uses cloth boiling pot or in overflow dyeing machine, continuous type generally uses J box or crawler box open width steaming. Knitted printing semi-products require uniform cooking, consistent whiteness, small weft skew, and gram weight to meet the requirements. The quality problems caused by improper pretreatment and processing have the same problems as the processing of woven fabrics, such as uneven scouring, uneven bleaching, insufficient whiteness, etc., during the printing process, it will often cause color difference, background color difference or At the same time, some unique quality problems will occur, which should be paid attention to during processing.
The bad hair effect will cause uneven coloring of the printed block surface. In severe cases, there will be a phenomenon of "showing the bottom" or the depth cannot be increased. Pay special attention to the pattern of dark large blocks. In addition to the usual lack of scouring, the reasons for this are more often due to the special softening process of the pre-treatment of knitted fabrics, which is different from the softening of conventional bleaching and dyeing varieties. After the softening of knitted semi-products for printing It needs to be printed again. At this time, the finishing process of bleaching and dyeing cannot be simply applied. The softener should be carefully selected and formulated reasonably. While improving the feel of the fabric, it also takes into account the wool effect of the knitted semi-finished product. Affect the smooth progress of the printing process or affect the color fastness of the product after printing. For some finished products that need to be washed with water or enzyme washing, the semi-printed products should not be softened, and the softening treatment should be combined with water washing or enzyme washing, which is more conducive to printing and also has an effect on improving fastness. benefit.
The square meter weight of the finished printed knitted fabric is one of the important indicators of customer quality requirements and must be guaranteed if it exceeds too much, it will increase production costs. Therefore, under the premise of guaranteeing the square meter weight of the finished product, it is very important to control the weight of the rough fabric. In the pre-treatment and printing process, there are factors that reduce the weight, such as the removal of impurities in the pre-treatment, the elongation of the fabric after a certain tension during the printing process, the brushing of velvet fabrics, etc., which also increase the weight. Factors such as the shrinkage of the fabric during pretreatment, the amount of paint and auxiliary agents added to the fabric during printing, etc. However, due to the difference in the tension of the processing equipment, the different process flow, and the different pattern printing area, the weight of the fabric is different. It is difficult to calculate the weight of the rough fabric from the weight of the finished product by simple calculation. When the yield rate does not meet the requirements, except for the products that the customer returns and remakes, the pioneer samples are generally required, with a certain amount and go through the same process as the mass production. The processing equipment obtains the result of the change in the weight of the knitted fabric, and then formulates or revises the weight index of the rough fabric in mass production, so that the final weight of the printed knitted fabric can be grasped.