Discuss the classification and characteristics of woven gray fabrics for dyeing and finishing; clarify the requirements of different dyeing and finishing products for gray fabrics; analyze the impact of gray fabrics on dyeing and finishing products, and explore ways to improve the quality of dyeing and finishing products in terms of raw materials.
Grey fabric 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.
01 Classification and characteristics of dyeing and finishing gray fabrics and characteristics of dyeing and finishing products Relationship
Classification by fabric organization
Grey fabrics form different organizations according to the different interweaving forms of warp and weft yarns, making the fabrics have different appearance and physical and mechanical properties. Commonly used fabric tissues can be divided into five major categories.
a) Plain weave structure
Plain weave structure is tight and the surface is smooth , 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 warp relief A diagonal pattern formed by continuous connection of long 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.
The fabric structure has two up and two down, three up and one down.
The two upper and two lower cloth surfaces are symmetrical, and the warp and weft yarns are basically the same.
Three up and down will reveal 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
It is characterized by satin The grain structure is formed, the spacing between interweaving points is longer, and there are 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.
Classification according to the fibers that make up the fabric
Generally, it can be divided into pure There are three categories: 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 be formed.
Different mixing methods in the spinning department, such as cotton bale mixing, multi-silo mixing, and sliver mixing, achieve different mixing effects. They can be proposed based on the final finished product effect of dyeing and finishing. Best request. 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., because they are prone to the influence of static electricity, they often produce “three windings” of winding top rollers, winding rollers, and winding apron. phenomenon, leading to pressure 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 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”.
Classified by the yarn count that makes up the fabric
According to the yarn used in the fabric Different counts (number of specials) are generally divided into four categories: low count (coarse count) fabrics, medium count (medium count) fabrics, fine count (fine count) fabrics, and high count (extra fine count) fabrics.
The general classification is as follows:
Low count (coarse) fabrics: warp and weft count 32tex and above (18 count and below) ;
Medium count (medium special) fabric: warp and weft count 20~30tex (19~29);
Fine count (Extra fine) fabric: warp and weft count 9~19tex (30~60 count);
High count (extra fine) fabric: warp and weft count 9tex or less (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 made of thread fabrics.� Shilin colors, snow cyan, beige, etc. are very sensitive to the appearance of streaks on gray fabrics.
Printed gray fabric
Printed gray fabric has the first priority due to the visual impact of the pattern, so Relatively speaking, it has less impact on evenness, neps, impurities and spinning and weaving defects, but it has less impact on some prominent defects on the cloth surface, such as crossbars, slubs, thin wefts, hundreds of feet, wrong wefts, weft shrinkage, and jumps. Flowers still need attention.
It must be pointed out that dyeing and printing gray fabrics must not mix wrong fibers (foreign fibers), which 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.
Resin-finished gray fabrics
Resin-finished fabrics can improve the wrinkle resistance and wrinkle recovery properties of fabrics, making them easy to iron and shrink-proof. , to improve the feel and drape. 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.
03 Strengthen the management of gray cloth and make good use of gray cloth
Dyeing and finishing enterprises It is necessary to designate departments to be responsible for the management of gray fabrics, maintain contact with fabric suppliers, communicate information in a timely manner, and advocate the development of one-stop cooperation and research activities in spinning, weaving, and dyeing. The key points should be done in the following points.
a) The gray fabrics entering the factory must be inspected and accepted. According to the principle of exclusive use of special fabrics and first-in-first-out, they are stacked separately according to the type, batch number, and package number of the supplying factory. If there are major changes in the raw materials and processes supplied to the cloth factory, they need to be modified.
b) 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.
c) 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.
d) Identification marks should be made when sewing the gray fabric. When sewing the ends, the edges of the fabric should be aligned, evenly flattened and straightened without wrinkles. For sparse fabrics, the requirements should be consistent. Seams are added on both sides to prevent the hems from unraveling.
e) It is recommended to implement an “instruction manual” system for gray fabrics for reference by dyeing and finishing enterprises.
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