Woven fabrics, knitted fabrics, and other types of fabrics under the loom, subject to dyeing and finishing processes, such as practice bleaching, dyeing or printing, finishing processes, in order to become the finishing content, refers to the fabric by bleaching, dyeing, printing process to improve and enhance the quality of the fabric, giving the textile special features for the textile goods put on the market. These printing and dyeing processing processes are part of the fabric finishing category.
Fabric finishing according to its finishing purposes can be broadly divided into the following areas.
- to make the fabric width neat, size and shape stability. Belong to this kind of finishing are fixed width, shrinkage and wrinkle prevention and heat deformation, etc., called shaping finishing.
- Improve the feel of the fabric. Such as stiff finishing, soft finishing. This type of finishing can be used mechanical methods, chemical methods or both together to deal with the fabric, in order to achieve the purpose of finishing.
- Improve the appearance of the fabric. Such as gloss, whiteness, drapability, etc.. There are rolling finishing, whitening finishing and other finishing to improve the surface properties of the fabric.
- Other taking properties of the improvement. Such as cotton fabrics, flame retardant, water repellent, health finishing; chemical fiber fabrics, hydrophilic, anti-static, anti-pilling finishing.
General finishing of fabrics
The feel of the textile and fiber materials, yarn varieties, fabric thickness, weight, tissue structure, and dyeing and finishing processes are related. In terms of fiber materials, silk fabric feels soft, linen fabric stiff, tweed fabric puffy rough elastic. This section refers only to the hard and soft finishing.
A. Stiff finishing
Stiff finishing is the use of film-forming polymer substances made of finishing pulp dipped in the fabric, so that it adheres to the surface of the fabric, dried to form a film to cover the surface of the fabric, thus giving the fabric a smooth, thick, rich, stiff feel.
One of the soft finishing methods is by mechanical action to make the fabric feel softer, usually using a three-roller rubber blanket pre-shrinking machine, appropriate to reduce the operating temperature, pressure, speed up the speed, can obtain a softer feel, if the fabric through a number of the passive square guide rod, and then into the soft rolling point on the rolling machine for rolling, can also get a smooth and soft feel, but this soft finishing method is not resistant to washing, most of the current soft finishing using softener.
Including fixed-width (stenter) and mechanical pre-shrinkage two kinds of finishing, to eliminate the fabric in the previous processes in the accumulation of stress and strain, so that the fabric fiber can be in a more appropriate natural arrangement of the state, so as to reduce the deformation of the fabric factors. The strain accumulated in the fabric is the main cause of fabric shrinkage, wrinkles, and rough feel.
A. Fixed width (stretched)
Principle: fixed-width finishing is the use of cotton, viscose fiber, silk, wool, and other hygroscopic hydrophilic fibers, in the wet state with certain plasticity; synthetic fibers of thermoplastic, the door width slowly widened to the specified size, so as to eliminate part of the internal stress, adjust the warp and weft yarn in the fabric form, so that the width of the fabric is neat and uniform, weft oblique to be corrected; at the same time, the fabric by drying and cooling to obtain a more stable size (mainly refers to the weft), in order to meet the specifications of the finished printing and dyeing.
The width of the fabric is stretched to the standard size to correct the uneven width, weft slant, polarization, and other shortcomings of the fabric in the printing and dyeing processing.
Stretching project is established in the fabric contains the appropriate moisture, the use of mechanical clamps to the edge of the cloth gradually widen, and slowly dry, so as to obtain temporary stereotypes.
The width of the fabric before and after entering, there should be a certain limit, otherwise, it will cause a serious shrinkage phenomenon.
B. Mechanical pre-shrinkage finishing
After the dyeing and finishing process of the dry fabric, if in a relaxed state by the water wetting, then the fabric warp and weft will be obvious shrinkage, this phenomenon is called shrinkage. Usually, the fabric is washed according to the test standard before and after the warp or weft length difference, the percentage of the length before washing to express the fabric warp or weft shrinkage rate.
Mainly to solve the problem of warp shrinkage, so that the fabric weft density and warp weaving shrinkage adjustment to a certain degree and make the fabric with a relaxed structure. After the mechanical pre-shrinkage of the fabric, not only “dry shaped” deformation is very small, and in the wetting, because the warp and weft still have enough space between, so it will not be caused by fiber swelling and fabric warp length shortening, that is, to eliminate the potential contraction of the fabric, so that it shrinks back in advance so that the finished product can reduce the shrinkage rate.
The main content of the appearance of the fabric finishing rolling finishing, electric finishing, rolling finishing, and bleached fabric whitening finishing. After finishing, the appearance of the fabric can be improved and beautified, such as luster increase, flatness increase, the surface rolled into a bumpy pattern.
A. Rolling, electro-glossing and rolling finishing
Mechanical finishing, rolling, electric light to enhance the luster of the fabric is the main, rolling grain can make the fabric with a three-dimensional effect of the bumpy pattern. Rolling, electric light, and rolling grain finishing is simply the use of mechanical processing, the effect is not lasting, such as the joint application with resin finishing, can obtain the effect of washable finishing.
Rolling finishing: generally can be divided into ordinary rolling, friction rolling and electric light, etc.. All through mechanical pressure, temperature, humidity, with the help of fiber plasticity, so that the surface of the fabric flattening, yarn flattening, in order to improve the surface of the fabric gloss and smooth flatness.
Electro-optical finishing: Electro-optical machine is composed of a hard steel roller with a certain angle and density of twill lines engraved on the surface and another soft roller with elasticity. The hard roller can be heated inside, in the heating and a certain moisture content conditions rolling fabric, in the fabric surface pressed parallel and neat twill money, so as to produce a regular reflection of the incident light, such as silk-like high gloss surface. Horizontal tribute satin fabric finishing more after the electric light finishing. Electric light hard roller surface slant line density varies according to the thickness of the yarn, yarn count fine fabric should be used with greater density, to 8 ~ 10 / mm slant line is the most common. The slanting direction of the engraved line should be consistent with the twist direction of the main yarns on the surface of the fabric.
Rolling finishing: similar to electro-optical finishing, rolling hard roller surface engraved with a positive pattern, the soft roller is engraved with the hard roller corresponding to the negative pattern, the two coincide with each other. The fabric is passed through the hard and soft rolls with corresponding patterns, and under the action of moisture, heat, and pressure, a bumpy pattern is produced. The hard roller is a purple copper roller for printing, and the soft roller is a nitrile rubber roller (active roller), the hard roller is engraved with a shallow pattern when copying, and the soft roller has no obvious corresponding negative pattern, the pressure is also smaller when copying, and the pattern produced on the fabric is shallow and has the feeling of the hidden flower.
B. Whitening finishing
Fabric after bleaching, often with a trace of yellow-brown color light, it is not easy to do the degree of pure white, often use the fabric whitening methods to increase the feeling of white. There are two methods of whitening.
One is on the blue whitening method: that is, a small amount of blue or purple dyes or coatings to make fabric coloring, the use of pigment color-complementary effect, so that the reflected light of the fabric in the blue-violet light is slightly heavier, the fabric looks whiteness has increased, but the brightness is reduced, slightly gray feeling, in recent years has been rarely used alone only for fluorescent whitening when the color and light adjustment.
Another is the fluorescent whitening method: fluorescent whitening agent dissolved in water is colorless, its chemical structure is similar to the dye, can dye fibers, the fluorescent whitening agent itself is colorless, but dyed fibers can be under the excitation of ultraviolet light, the blue-violet fluorescence visible to the naked eye, and the fabric itself reflects a trace of yellow-brown light mixed with complementary synthetic white light, the fabric will appear more white because the total intensity of reflection increased, the brightness increased, but in the absence of ultraviolet light source conditions slightly less effective.
Fabric resin finishing was developed with the development of polymer chemistry. The earliest formaldehyde as a finishing agent, followed by urea-formaldehyde addition product treatment of viscose fabrics, to get a good anti-wrinkle and shrinkage effect, for today’s resin finishing, laid the foundation. With the development of science and technology, cotton fabric resin finishing technology has also made great progress, which has roughly experienced wrinkle and shrinkage prevention, washable and durable pressing (D.P) finishing, and other stages of development.
01、Commonly used resins for fabric finishing
There are several major types of resins used for fabric finishing, but N-hydroxymethyl amide compounds are still the most used. The commonly used resin primary shrinkage is briefly described below.
A. Urea-formaldehyde resin (UF resin)
Viscose fiber fabric with urea-formaldehyde resin finishing, the fabric feels rich, shrinkage rate reduced, dry and wet strength increased significantly, wrinkle resistance improved. Urea resin is prepared with urea and formaldehyde, a wide source of raw materials, convenient preparation, low cost, but can not be used for cotton fabrics, because cotton fabrics with urea resin finishing, strength drop too much, the amount of free formaldehyde is high.
B. Melamine formaldehyde resin (MF resin)
MF resin’s initial shrinkage properties are similar to those of UF resin. Due to the larger molecular weight of MF resin, the washing resistance is better than UF resin, so it can be used for cotton fabric finishing, which not only can get better shrinkage and wrinkle resistance, but also has smaller strength loss than UF resin. However, after finishing with MF resin, the fabric has a yellowing phenomenon, so it cannot be used for resin finishing of the bleached fabric. The stability of MF resin can also be improved by etherifying the initial shrinkage of MF resin with methanol.
C. Dihydroxymethyl dihydroxyvinyl urea resin (DMDHEU or 2D resin)
2D resin is a class of resins currently used in China, the performance is better than UF and MF resin, after finishing fabric washing resistance, not easy to hydrolyze, resin initial shrinkage itself is less reactive, placed not easy to generate polymer condensate, can be stored for a longer period of time, only in use conditions and fiber chemistry, the odor is small, direct dyes and reactive dyes have less impact on the sun fastness, applied to durable pressing (D. P) finishing is very suitable. P) finishing is very suitable, but the chlorine resistance is poor.
In addition to the textile articles used in general daily life, after some special finishing process, it can also improve its application range, such as water repellent, flame retardant, anti-static, anti-fouling, etc. These properties are not generally available in textiles but are obtained through special finishing methods, which are called special finishing methods.
According to the different processing methods can be divided into two categories: one is to use the coating method to apply a layer of water-insoluble continuity film on the surface of the fabric, this product and impervious to water, but also not breathable, should not be used as general clothing items, but suitable for making rainproof tarpaulin, umbrellas, etc. Another type of finishing method lies in changing the fiber surface properties, so that the fiber surface is hydrophilic into hydrophobic, while the fabric between the fibers and yarns still retain a large number of pores, so that the fabric can maintain breathability, but also not easy to be water wetting, suitable for the production of weatherproof clothing fabrics. This breathable waterproof whole water is also known as water-repellent finishing. Water repellent finishing mainly has the following methods.
Clothes due to friction with static electricity, often make the skirt cling to the legs, outerwear tightly absorbed in the underwear, in some explosive places will also lead to explosive accidents due to electrostatic sparks.
Printing and dyeing finishing process is often used in the durability, external application type static electricity prevention agent. This type of electrostatic preventive agent requires a durable anti-static effect, does not affect the fabric style, does not affect the color and light of the dyeing and printing fabric and the fastness of the dyeing, and other additives have compatibility, no odor, non-toxic to human skin, etc. Commonly used polymer surfactants, including anionic, non-ionic. Cationic type. The above antistatic properties are all used to increase the moisture absorption of the fiber surface to inhibit the accumulation of electric charges.
03、Flame retardant finishing
After finishing the fabric by flame retardant, and can not reach the degree of non-combustible such as asbestos, but can deter the spread of flame, when the fire source removed no longer burning and does not occur residual flame negative combustion. Flame-retardant finishing fabrics can be used in the military sector, industrial transportation sector, civilian products, such as carpets, curtains, curtains, work clothes, bedding, and children’s clothing.
When selecting flame retardants, in addition to the flame retardant effect and durability, we must also pay attention to the strength, feel, appearance, fabric dye color, and colorfastness of the fabric has no adverse effects; whether there is irritation to human skin, flame retardants in the fabric when the heat of combustion has no toxic gas generation, and other finishing agents co-tolerance.