This paper discusses the classification and characteristics of woven grey cloth for dyeing and finishing. To clarify the requirements of grey cloth for different dyeing and finishing products; The influence of grey cloth on dyeing and finishing products is analyzed, and the ways to improve the quality of dyeing and finishing products from raw materials are discussed.

The concept of grey cloth

Grey cloth refers to the semi-finished products without dyeing and finishing after the fiber is spun into fabric. Dyeing and finishing enterprises often will not be boiled, desizing grey cloth called raw grey cloth.

After scouring and desizing, the grey cloth is called cooked grey cloth.

The main factors that affect the quality of dyeing and finishing products are raw materials, technology, equipment, operation and environment, among which grey cloth has a great influence on the quality of dyeing and finishing products.

1618966638230478.jpg

01

The relation between the classification and characteristics of dyeing and finishing grey cloth and dyeing and finishing products

Classified by fabric structure

According to the different forms of warp and weft yarns, the grey fabric forms different structures, so that the fabric has different appearance and physical and mechanical properties. Commonly used fabrics can be divided into five categories.

A) plain texture

Plain weave structure is close, the surface is smooth, the warp and weft yarn coverage probability is basically the same, the tightness is not different. Yarn sliver, cotton knot impurity, diameter and cross weft in grey cloth have obvious effect on dyeing and finishing products. Because the general spinning part of a tube will be concentrated in a section of the door, the fabric quality is very sensitive to the weft requirements should be paid more attention to. For dyeing and finishing products with higher quality requirements, the warp and weft yarn should be separated from cotton, and the raw material and process should be taken care of, especially for the poplin fabric with high warp density and low weft density.

B) Twill tissue

The surface of the twill structure has oblique lines formed by the continuous connection of the floating long points or the weft floating long points. The warp and weft intersections of this organization are less than the plain weave organization, therefore, the weaving density is generally higher than the plain weave organization, the fabric tightness is greater than the plain weave organization, and the warp density is generally higher than the weft density.

The fabric has two up, two down, three up and one down.

The two upper and lower cloth surface is symmetrical, and the warp and weft yarn is basically the same.

Three up and down the front of the fabric warp more exposed, the warp appearance defects are easy to be exposed in the cloth. The filling, however, can be concealed because it is less exposed.

Therefore, we must pay more attention to the quality of grey warp yarn from the consideration of dyeing and finishing products. Defects are caused by the weave error of the twill fabric due to the lack of roots (equivalent to the thin weft of plain weave fabric). Twill fabrics include khaki, gaberdine and serge. Khaki has greater fabric tightness than gaberdine. The greater the general tightness, the greater the difficulty of weaving, and the more easy to produce defects.

C) Satin weave

It is characterized by the satin texture formation, interweaving point spacing is longer, less interweaving point, so the weaving density can be higher. Fabric. The surface is smooth and shiny, and the feel is soft. After dyeing and finishing with resin and electric light calendering, it is full of dazzling brilliance. There are two kinds of satin weave fabrics: horizontal and straight. The front side of the crosscut fabric is mainly formed by the weft, while the front side of the crosscut fabric is mainly formed by the warp, with the weft showing less than the warp. Generally speaking, satin products belong to middle and high grade products, and the requirements for yarn defects are higher.

Classified by the fibers that make up the fabric

Generally, it can be divided into three categories: pure natural fiber fabric, pure chemical fiber fabric and blended fabric.

Blended fabrics are of two kinds or. Fabrics blended or interwoven with more than two kinds of fibers, including chemical and natural fibers, different natural fibers and different chemical fibers blended and interwoven.

Blended fabric must grasp the composite fiber proportion to meet the requirements of regulations or standards; Blended fiber is mixed evenly, otherwise it will form color flower or strip shadow or even color difference.

Different mixing methods of spinning, such as bale mixing, multi-bin mixing and sliver mixing, can achieve different mixing effects, and high requirements can be put forward according to the final dyeing and finishing results. Single dyed blending or interwoven products to strictly control the dye selection and dyeing process, so that the color and color of the two fiber consistent.

Synthetic fibers, such as polyester, polypropylene and vinylon, are prone to static electricity when spinning, and the phenomenon of "three winding" often occurs, such as winding the roller, winding the roller and winding the leather ring, resulting in pressure failure and broken end of the drafting device, resulting in yarn defects such as slub and coarse weft. Attention should be paid to this kind of yarn defects during the acceptance of grey fabric.

If polyester/cotton blended fabric is blended with several different boiling water shrinkage rates of polyester, "skirt crepe" defects will occur after dyeing and finishing. Because of the electrostatic adhesion in polyester/cotton blending, white polyester/cotton yarn is easy to form "coal ash yarn".

Classified by the yarn counts of the fabric

According to the yarn count (special count) of the fabric, it is generally divided into four categories: low count (coarse) fabric, medium count (medium and special count) fabric, fine count (fine and special count) fabric and high count (extra and special count) fabric.

The general division is as follows:

Low count (coarse) fabric: 32tex or more (18 or less);

Middle (middle and special) fabric: weft and longitude count 20~30tex(19~29);

Fine count fabric: 9~19tex(30~60);

High count (extra fine) fabric: the warp and weft count below 9tex (more than 60).

Low - count fabrics are commonly used as coarse, flannelette, interlining, etc. Medium and fine count fabrics are the most widely used varieties in daily use. High - count fabric is often processed into high-grade fine cloth, poplin, khaki, voile, down cloth. High count fabric is generally made of combed yarn by spinning combing process, and more thread fabrics, more than 60 pieces of long staple cotton or fine denier, super fine denier chemical fiber spinning system. The higher the count, the higher the quality requirement.

When high count yarn is spinning, the interval between doffing and falling is long, which is easy to produce coal ash yarn. High yarn twist is high and easy to wrinkle, the weft usually needs to be fixed twist treatment, otherwise it will form weft shrinkage and small braid yarn defects; The high-count poplin and down cloth with higher weft density can easily produce yellow and white yarn. The requirement of thin and dense "voile" grey cloth dryness is particularly high; Special attention should be paid to the inspection of dyed and finished grey cloth.

Classified according to the density or tightness of warp and weft yarns

Generally sparse fabrics, the warp and weft yarn density is low, small tightness, such as mull, voile, gauze, mosquito net cloth, mesh cloth and other light and thin fabrics. Medium dense fabric refers to the fabric commonly used. Compact fabrics refer to fabrics with higher density and tightness, such as corduroy cloth, plain flannelette, rainproof cloth, down cloth, high count poplin, etc. There is no quantitative regulation of classification at present.

General sparse fabric warp and weft yarn cover is small, exposed more, on the dry unevenness, thick knot, details, all kinds of defects at a glance, so the higher requirements. High tightness of tight fabric (generally about 90%), weaving is difficult, the most easy to produce three jump (jump flower, jump yarn, star jump) and other defects; The cloth surface requires smooth, smooth and clean, dry, miscellaneous also have higher requirements. Because the filling color contrast of compact fabric is enhanced, the occurrence probability of yellow and white yarn is also increased correspondingly.

Fabrics are classified according to their elasticity

Stretch fabrics are very popular in the current market. Because it is comfortable to wear, it can fully reflect the beauty of human body, and is favored by men, women and children. Stretch fabrics have warp stretch, weft stretch and warp and weft stretch, of which weft stretch is the most. A stretch fabric obtains its elasticity from a stretch yarn. The appearance defects of elastic fabric include broken silk, dewy silk and missing silk, which will cause uneven local elasticity, wrinkling, blistering and color defects after dyeing and finishing. Special attention should be paid to these defects.

Classified by fabric raising products

The dyeing and finishing products of grey cloth are mainly flannelette, corduroy, velveteen, etc.

The general flannelette has bleached flannelette, printed double-sided flannelette, serge flannelette and so on. It is made of medium and low count yarns. Most of the flannelette is weft drawn, so the weft twist is on the low side. After weft drawing, the strength of the fabric is reduced by nearly half, so the weft should have a higher strength. Tight-twist yarn should be avoided in spinning defects, especially instantaneous twist caused by spinning joint operation. The weft shrinkage rate of flannelette blank is larger, generally 11% ~ 16%, so the width of grey fabric door should be enlarged than that of general fabric. Considering the effect of wool, the general use of coarse cotton and other raw materials.

The fabric structure of corduroy includes two parts: velvet fabric and ground fabric. The fabric may have weft or warp. Generally to velvet weft in the majority. Wool or weft cutting machine to form a wick.

Corduroys are characterized by high tightness, generally small warp density and large weft density, about 1:2.5~3 in this case. Therefore, warp yarns should have high strength and wear resistance. Weft yarns should be even and less cotton impurities, so as to achieve fullness and smoothness of suede surface. Due to the high tightness, we should strengthen the management of mixed cotton to prevent yellow and white yarn.

The surface of velveteen fabric is covered with even and smooth fluff, which has soft luster, soft texture and elasticity.

Velvet is classified as either weft cutting or warp cutting. Its warp and weft density is relatively high, the weft density of cut velveteen is 3~5 times higher than the warp density, to ensure the fabric fastness and prevent de-fleeting. The warp direction of fabric tightness is 55% ~ 60%, and the weft direction is 160% ~ 220%, so it is difficult to weave, and the probability of weaving defects is high, so special looms are often used for weaving. Velvet is a high-grade product, warp and weft yarn commonly used high strength combed strand such as J14X2, J10X2.

1618966681780713.jpg

02

Requirements of grey cloth for different dyeing and finishing processes

Different dyeing and finishing processes have different requirements for grey cloth. For different objects and different treatments, the effect of more, faster, better and less can be obtained.

Bleaching cloth

The grey cloth after scouring and bleaching, the cloth surface is clear and white, and the remaining colored defects on the grey cloth will be exposed to the world. Therefore, special attention should be paid to the oil defects and color defects of the grey cloth, such as oil warp, oil weft, color warp, color weft, coal ash yarn, hemp yarn, hair yarn, grass yarn (called three silk) and other defects. Chemical fiber blends, pure spinning products because of their high whiteness, higher requirements for the above defects. Compared with dyed grey cloth, bleached grey cloth has lower requirements on dryness, netting impurities, yarn defects and so on.

Dyeing cloth

Dyed grey cloth is divided into variegated grey and dark grey. Processing similar to no. 190 shilin blue cloth and lighter color cloth is variously colored billet, darker than no. 190 shilin blue cloth is dark billet.

Dark grey cloth: because of the darker dyeing, the contrast with grey fabric is stronger. In order to prevent the color difference caused by uneven dyeing, the uneven density of the fiber, the impact of dye penetration difference defects, such as cotton knot, tight warp, loose warp, tight twist yarn, loose twist yarn, wrong weft, thin weft, foot, slubby and other textile defects have higher requirements.

The problem of white star in dark billet is a particularly prominent quality key, which is mainly caused by the failure of dye coloring caused by low mature fibers such as raw cotton mid-border flap, soft seed surface and dead fiber, which must be paid attention to.

Variegated or medium-light color billet is similar to bleached billet, which has higher requirements for oil and color defects, and slightly higher requirements for general yarn defects such as slit, cross tight road and cross stop than dark billet. Different colors of grey cloth will have different visual effects on grey cloth. According to my experience, the color of shilin, snow blue and beige are very sensitive to the appearance of grey cloth.

Printed fabric

Printed grey fabric has the most important effect on vision because of the pattern, so relatively speaking, it has less impact on strip dry, knot impurity and spinning and weaving defects. However, attention should be paid to some prominent defects on the fabric, such as cross stop, slubby, thin weft, foot, wrong weft, weft shrinkage and jump.

It must be pointed out that no wrong fibres (foreign fibres) should be mixed into the dyeing and printing greys, which will cause very noticeable defects. Recently polypropylene packaging cloth is often mixed in the spinning department in the process of opening and cleaning cotton, resulting in adverse effects. The influence is greater when the meridional foreign fiber is mixed. In order to prevent the mixing of different fibers, the dyeing and finishing grey cloth can be tested by ultraviolet lamp (commonly known as black light lamp) before use, which has a considerable effect on identifying the confusion between natural fibers and chemical fibers.

Resin finish grey cloth

Resin finishing can improve the fabric crease resistance, crease recovery, to achieve ironing, shrinkage, improve the feel and drape effect. But the resin finishing will make the fabric strength decreased significantly, so the resin finishing grey cloth, the requirement of high strength, especially such as high count fabric, Barry yarn fabric, itself due to high strength low, we must pay attention to the resin finishing strength change, to ensure the requirements of taking.

03

Strengthen the management of grey cloth and make good use of grey cloth

Dyeing and finishing enterprises must designate departments to be responsible for grey cloth management, keep in touch with cloth suppliers, communicate information in time, and advocate to carry out one-stop cooperation and tackle key problems in spinning, weaving and dyeing. The key to do the following points.

A) The incoming grey cloth shall be checked and accepted. According to the principle of special use and first-in-first-use, the incoming grey cloth shall be stacked and used respectively according to the blank type, batch number and package number of the supplying factory. For cloth factory raw materials, process changes need to be changed.

B) Sampling inspection should be carried out on the quality of grey cloth, and the general sampling inspection rate should reach 3%. To check the width, warp density and weft of the grey cloth; Inspection the appearance defects according to the key requirements of grey cloth; The strength index of grey fabric should be tested if the strength requirement of grey fabric is high.

C) If the quality problem of grey cloth is found, it shall be checked and corrected by the cloth manufacturer. Any sudden or large quality problem must be stopped to investigate the cause and trace the responsibility.

D) The identification of grey cloth stitching should be done well. When stitching, the cloth edge should be aligned, evenly flattened and straightened, and there should be no creases. For sparse fabrics, measures should be taken to add stitching on both sides to prevent unwinding of edges.

E) It is suggested to carry out the "operation manual" system of grey cloth for the reference of dyeing and finishing enterprises.