This article discusses the classification and characteristics of woven gray fabrics for dyeing and finishing; clarifies the requirements for gray fabrics for different dyeing and finishing products; analyzes the impact of gray fabrics on dyeing and finishing products, and explores ways to improve the quality of dyeing and finishing products in terms of raw materials.
The concept of gray cloth
Grey cloth refers to the semi-finished product that has not been dyed or finished after the fibers have been woven into fabric. Dyeing and finishing companies often refer to gray fabrics that have not been scoured and desized as green fabrics. The gray cloth after scouring and desizing is called cooked gray cloth.
The main factors that affect the quality of dyeing and finishing products include raw materials, technology, equipment, operations, and environment. Among them, gray fabrics have a great influence on the quality of dyeing and finishing products.
The classification, characteristics and relationship between dyeing and finishing gray fabrics and dyeing and finishing products
1. Classification according to fabric structure
Grey fabrics are classified according to warp and weft Different interweaving forms of yarns form different structures, giving the fabrics different appearance forms and physical and mechanical properties. Commonly used fabric tissues can be divided into five major categories.
a) Plain weave plain weave has a tight structure and a smooth surface. The coverage probability of warp and weft yarns is basically the same, and the tightness is not much different. Yarn slubs, neps, thick diameters, and wrong wefts in gray fabrics all have very obvious reflections on the dyeing and finishing products. Since generally one bobbin in the spinning department will be concentrated on a section of width, it is very sensitive to the quality of the gray fabric, and more attention should be paid to the weft yarn requirements. For dyeing and finishing products with higher quality requirements, the warp and weft yarns should be mixed with cotton separately, and care should be taken in terms of raw materials and technology, especially for poplin fabrics with high warp density and low weft density.
b) Twill weave The surface of the twill weave has a diagonal pattern formed by continuous floating points or weft floating points. The intersection points of warp and weft of this kind of weave are less than that of plain weave, so its weaving density is generally higher than that of plain weave, the fabric tightness is greater than that of plain weave, and the warp density is generally higher than the weft density.
Fabric weaves include two up and two down, and three up and one down. The front and back of the two upper and lower cloths are symmetrical, and the warp and weft yarns are basically the same. Three up and one down will expose more warp threads on the front of the fabric, and warp appearance defects will be easily exposed on the fabric surface. The weft can be concealed because it shows less.
For this reason, when considering dyeing and finishing products, we must focus on the quality of gray fabric warp yarns. Defects in twill fabrics are caused by fabric weave errors caused by missing weft threads (equivalent to the thin weft of plain weave fabrics). There are three types of twill fabrics: khaki, gabardine, and twill. Among them, the fabric tightness of khaki is greater than that of gabardine, and the tightness of khaki is the largest. Generally, the greater the tightness, the more difficult it is to weave, and weaving defects are more likely to occur.
c) Satin weave is characterized by a satin weave with longer interlacing point spacing and fewer interweaving points, so the weaving density can be higher. The fabric has a smooth and shiny surface and a soft hand feel. It has a dazzling luster after being dyed, finished, resin-finished and electro-calendered. Satin fabrics are divided into two types: Henggong and Zhigong. The front side of the Henggong fabric is mainly formed by weft yarns, while the front side of Zhigong fabric is mainly formed by warp yarns, with the weft yarns showing less than the warp yarns. Generally speaking, satin products are mid- to high-end products and have higher requirements for yarn weaving defects.
2. Classification according to the fibers that make up the fabric
Generally, it can be divided into three categories: pure natural fiber fabrics, pure fiber fabrics and blended fabrics.
Blended fabrics are fabrics in which two or more fibers are blended or interwoven, including the blending and interweaving of chemical fibers and natural fibers, different natural fibers, and different chemical fibers.
Blended fabrics must ensure that the proportion of combined fibers meets regulations or standard requirements; the blended fibers must be mixed evenly, otherwise colored flowers or streaks or even color differences will form.
Different mixing methods in the spinning department, such as cotton bale mixing, multi-silo mixing, and sliver mixing, achieve different mixing effects. The best requirements can be put forward based on the final finished product effect of dyeing and finishing. Single-dyed blended or interwoven products must strictly control the dye selection and dyeing process to ensure that the color and hue of the two fibers are consistent.
When spinning synthetic fibers such as polyester, polypropylene, vinylon, etc., due to the easy generation of static electricity, the “three winding” phenomenon of winding top rollers, winding rollers, and winding aprons often occurs, resulting in pressurization failure of the drafting device and End breakage, resulting in yarn defects such as slubs and thick wefts. When checking and accepting gray fabrics, you should focus on this type of yarn defects.
If polyester-cotton blended fabrics are made of several types of polyester blends with large differences in boiling water shrinkage, “skirt crepe” defects will occur after dyeing and finishing. Due to the electrostatic adhesion during polyester-cotton blending, the white polyester-cotton yarn easily forms “soot yarn”.
3. Classification according to the yarn count of the fabric
According to the different yarn count (special number) used in the fabric, it is generally divided into low count (thick special) There are four categories: fabrics, medium count (medium special) fabrics, fine count (fine special) fabrics, and high count (extra fine special) fabrics.
The general classification is as follows: low-count (thick and special) fabrics: warp and weft counts 32tex and above (18 and below); medium-count (medium special) fabrics: warp and weft counts 20~30tex (19~29) count); fine (fine) fabrics: warp and weft counts 9 to 19 tex (30 to 60 counts); high count (extra fine) fabrics: warp and weft counts below 9 tex (60 or more).
Low-count fabrics are often used as coarse cloths, flannelettes, interlinings, etc. with lower requirements. Medium and fine count fabrics are the most widely used varieties in daily life. High-count fabrics are often processed into high-grade muslin, poplin, khaki, voile, and down cloth. High-count fabrics generally use spinning and combing processes to make combed yarn, and most of them are thread fabrics. Above 60 counts, they need to be spun from long-staple cotton or fine-denier or ultra-fine-denier chemical fibers. The higher the count, the higher the quality requirements.
When spinning high-count yarns, the time between doffing and doffing is long, and soot yarn is easily produced; high-count yarns have high twist and are prone to wrinkles, and the weft yarns generally need to be twisted, otherwise they will form Weft shrinkage and small braid yarn defects; weft(D) is mixed in, it will cause very conspicuous defects. Recently, polypropylene packaging cloth is often mixed in the cleaning process of the spinning department, causing adverse effects. The mixing of foreign fibers in the warp direction will have a greater impact. In order to prevent foreign fibers from being mixed in, dyeing and finishing gray fabrics can be inspected with an ultraviolet lamp (commonly known as a black light lamp) before use, which is very effective in identifying the confusion between natural fibers and chemical fibers.
4. Resin-finished gray fabric
Resin-finished fabric can improve the wrinkle resistance and wrinkle recovery properties of the fabric, achieve iron-free and anti-shrinkage, and improve the feel and drape. Effect. However, the strength of the fabric will be significantly reduced after resin finishing. Therefore, gray fabrics treated with resin require higher strength, especially high-count fabrics and voile fabrics, which have low strength due to their high count. Therefore, we must focus on the change in strength after resin finishing. Ensure taking requirements.
Strengthen the management of gray cloth and make good use of gray cloth
Dyeing and finishing enterprises must designate departments responsible for the management of gray cloth, maintain contact with cloth suppliers, communicate information in a timely manner, and advocate Carry out one-stop cooperation and research activities in spinning, weaving and dyeing.
The following points should be focused on:
1. The gray fabric entering the factory must be inspected and accepted according to the principle of exclusive use of special fabrics and first-in-first-out. Package numbers are stacked separately for collection. If there are major changes in the raw materials and processes supplied to the cloth factory, they need to be modified.
2. The quality of gray fabrics must be randomly inspected, and the general inspection rate should reach 3%. It is necessary to inspect the width, warp density, and weft density of the gray fabric; inspect appearance defects according to the key requirements of the gray fabric; and test the fabric strength index if the strength of the gray fabric is high.
3. If quality problems with gray fabrics are found, the fabric supplier is required to send personnel to check and correct them in a timely manner. When sudden or major quality problems occur, production must be stopped to investigate the cause and trace the responsibility.
4. Identification marks should be made when sewing the gray fabric. When sewing, the edges of the fabric should be aligned, evenly flattened, and straightened without wrinkles. Sparse fabrics are required to add seams on both sides to prevent Curl and excuse.
5. It is recommended to implement the “instruction manual” system for gray fabrics for reference by dyeing and finishing enterprises. </p
