Before the bulk fabrics are sent to the garment factory for garment production, we often encounter various problems with the fabrics sent to the factory, such as edge differences, cylinder differences, step differences and other color differences. Among them, differences are the problem There are many reasons. It depends on how to predict and minimize the possibility of problems during the production process. When a problem occurs, how to find the problem as soon as possible and solve the problem so as not to affect the garment production plan of the garment factory. In this article, we focus on the problem of fabric color difference, how to improve it and the inspection standards.
01 Defect characteristics
Dyeing products have different shades of color , there is a difference in color and light.
A. Color difference in the same batch: In the same batch of products, the color difference between boxes and boxes, pieces and pieces, packages and packages, and matches of a color number There is color difference between them. B. Color difference of the same piece: Products of the same piece have color difference on the left center, front and back, or front and back. Color difference is one of the common defects and multiple defects in dyeing and finishing factories, which seriously affects the quality of dyed finished products.
02 Causes
The fiber composition of various types of fabrics is different, and the types of dyes used in dyeing are different. Different processes and equipment, as well as different requirements and characteristics in dyeing and processing, result in different causes and manifestations of defects. Color differences vary in appearance, but the main causes are as follows.
A. The dye is unevenly distributed on the fabric in advance: before the dye is fixed, if the dye is unevenly distributed in various parts of the fabric, color difference will inevitably form after the dye is fixed. The main reasons for this phenomenon are:
① Fabric factors: Due to different fiber properties or insufficient uniformity of pre-treatment, boiling, bleaching and mercerization, the permeability of the semi-finished products before dyeing is Unevenness causes differences in dye absorption.
②Liquid absorption factors: Due to mechanical structure reasons or improper operation, the liquid pick-up rate of various parts of the fabric is inconsistent, thus causing color difference. Uneven roller pressure, uneven addition of dyeing materials, etc. will cause the fabric to absorb dye unevenly.
③Pre-baking factors: When pre-baking after padding the dyeing solution, due to the inconsistent drying rate and degree, the dye will migrate to varying degrees, causing the dye to migrate on the fabric. Uneven distribution.
B. The degree of dye fixation on the fabric is different: Although the dye is uniformly distributed on the fabric in advance, during the fixation process. If the conditions are not properly controlled (such as temperature, time, dye concentration, etc.), the dye in some parts of the fabric is not fully fixed and will be removed during post-processing and soaping. This results in color difference. For example, inconsistent hot melt temperatures of disperse dyes on both sides or front and back, insufficient partial reduction or oxidation of vat dyes, poor steaming conditions of reactive dyes, etc. will all cause color differences on the front, back, or left sides of the fabric.
C. Variation of dye shade: This difference is not caused by uneven distribution of dyes on the fabric, but due to certain reasons that cause the shade of some dyes on the fabric to change. , generally there are the following reasons:
① Factors before dyeing:
The whiteness of the semi-finished product is uneven or the pH value is different. Large differences often result in color and light differences after dyeing.
②Dyeing factors:
For example, the hot melt temperature of disperse dyes is too high, which makes the color of some dyes dim; Excessive reduction of vat dyes will also cause differences in color and light.
③Post-dyeing factors:
During the finishing process. Such as resin finishing, high temperature tentering and different pH values on the fabric, etc., will cause the dye shade to change to varying degrees.
④Soaping:
If soaping is not sufficient, the hair color will be insufficient and the color will be inaccurate.
03 Overcoming methods
1 .Improve roll uniformity. For those who use ordinary pad car dyeing, the surface of the roll should be ground into an olive-shaped roll with a slightly larger diameter in the middle and a slightly smaller diameter at both ends; the hardness of the rubber roll should be reasonably selected.
2. Use uniform rolling. When producing products of a single variety and color, it is a feasible method to use an olive-shaped roller to solve the color difference in the middle side or the left middle. However, when producing small batches, multiple varieties, and multi-color varieties, there are many factors to consider, and the rollers often need to be replaced frequently, which brings trouble to the use process. Using uniform rolling is a good way to solve the color difference between the sides and the left, middle and right colors.
3. Choose appropriate equipment and improve the condition of the equipment so that the dyed objects can be dyed evenly during the entire dyeing process.
4. Improve the uniformity of fabric drying.
After the fabric enters the hot air dryer, the wind speed of the air outlet and the temperature have different effects on the speed of water evaporation. In areas with high wind speed and high temperature, water evaporates quickly, causing the dye liquor to migrate to areas with fast evaporation, causing color difference. When processing thick fabrics, the temperature difference within 10°C will have little effect on color difference, while when processing thin fabrics, there will be significant color difference if the temperature difference is greater than 5°C.
The wind speed difference between left, middle and right is within 4m/s, which has little effect on thick fabrics. When the wind speed difference is 2m/s, thin fabrics will have obvious color differences. Therefore, we must take it seriously, strictly adjust the wind speed, and make the cloth surface temperature and heating rate consistent so that the fabric can be dried uniformly without causing color difference.
The hot air part adopts the horizontal guide roller threading method, which is more beneficial to prevent the color difference between the front and back sides. Because the hot air blowing to both sides of the fabric comes from the same air duct. If you use a hot air dryer that passes fabric vertically, the equipment must be modified so that it canWhen the materials are returned to the company, the time of arrival and departure from the factory should be noted in the report, and the person in charge of the factory should be asked to sign on the work schedule. Before leaving the factory, check whether all samples, documents and related things have been brought back.
05 Fabric Shrinkage Analysis
1. Fabric shrinkage
Fabric shrinkage refers to the percentage of fabric shrinkage after being soaked in water or washed. Fabrics with the largest shrinkage rates are synthetic fibers and their blended fabrics, and the largest ones are viscose fiber, rayon, and artificial wool fabrics, followed by wool fabrics, linen fabrics, and cotton fabrics in the middle.
2. Factors of production shrinkage
Density:
Different fabric densities have different shrinkage rates. Fabrics with a high warp density will shrink in the warp direction. Conversely, fabrics with a weft density greater than the warp density will shrink in the weft direction.
Thread count:
The fabric yarn count is different in thickness and shrinkage rate Also different. Fabrics with a thicker yarn count will have a greater shrinkage rate, while fabrics with a finer yarn count will have a smaller shrinkage rate.
Raw materials:
Different raw materials of fabrics have different shrinkage rates. Fibers with high hygroscopicity will expand and shorten in length after soaking in water, resulting in a large shrinkage rate. The water absorption rate of viscose fiber is as high as 13%, while synthetic fiber fabrics have poor hygroscopicity and their shrinkage rate is small.
Technology:
Different fabric processes have different shrinkage rates. During the weaving, dyeing and finishing process of fabrics, due to the multiple stretching of fibers and long processing time, the shrinkage of fabrics with greater tension will be greater, and vice versa. </p
