Common Finishing Process

Woven fabrics, knitted fabrics and other kinds of fabrics should be dyed and processed, such as scouring, bleaching, dyeing or printing, finishing, and so on. The contents can be classified as fabric goods that are put on the market after the bleaching, dyeing and printing processes to improve and improve the quality of fabrics and give special functions to textiles. These printing and dyeing processes belong to the category of fabric finishing.

Fabric finishing can be roughly divided into the following aspects according to its finishing purposes.

(1) make the fabric door neat and stable in size and shape. This kind of finishing includes fixed width, shrink proof, wrinkle proof and heat setting.

(2) improve fabric feel. Such as stiff finishing, soft finishing. This kind of finishing can be processed by mechanical means, chemical method or two functions together to achieve the purpose of finishing.

(3) improve fabric appearance. Such as gloss, whiteness, drapability and so on. It has calender finish, whitening finish and other finishing methods to improve fabric surface properties.

(4) other performance improvements. Such as flame retardant, water repellent and hygienic finishing of cotton fabrics; hydrophilicity, antistatic and anti pilling finishing of chemical fiber fabrics.

1. Fabric finishing in general

Hand finishing

The handle of textile is related to fiber material, yarn type, fabric thickness, weight, organization structure and dyeing and finishing process. As far as fiber materials are concerned, silk fabrics feel soft, hemp fabrics are stiff, and woollen fabrics are bulky and elastic. This hand finishing only refers to stiff finishing and soft finishing.

1, hard finishing

The tough finishing is made of polymer material which can be made into film, and then is rolled and rolled onto the fabric, so that it can be attached to the surface of the fabric. After drying, it forms a film to cover the fabric surface, thereby giving the fabric a smooth, thick, plump and firm handle.

2, soft finishing

One of the soft finishing methods is to soften the feel of the fabric by mechanical action. Usually the three roll rubber blanket pre shrinking machine is used to reduce the operating temperature and pressure, and accelerate the speed of the fabric. The softer handle can be obtained. If the fabric passes through a plurality of passive square guide bars and then enters the soft rolling point of the calender, the smooth and soft handle can be obtained. However, this soft finishing method is not resistant to washing. At present, softeners are used for soft finishing.

Shape finishing

It includes two kinds of finishing, namely fixed width (amplitude) and mechanical shrinkage, which are used to eliminate the stress and strain accumulated in the preceding processes, so that the fibers in the fabric can be placed in a proper natural arrangement, thereby reducing the deformation factors of the fabric. The strain in fabric is the main cause of shrinkage, wrinkle and rough handle.

1, fixed amplitude (amplitude).

Principle:

Fixed width finishing is a kind of hydrophilic fiber made of cotton, viscose fiber, silk and wool. It has certain plasticity in damp state. The thermoplastic of synthetic fiber will widen its door width to the specified size, so as to eliminate some internal stress, adjust the form of weft in the fabric, make the fabric's door width uniform and the weft deviation be corrected. At the same time, the fabric gets a more stable size (mainly zonal) after drying and cooling, so as to meet the specification requirements of printing and dyeing products.

Effect:

The width of the fabric is pulled to the standard size, and the defects such as width unevenness, weft deviation and aurora in the printing and dyeing process are corrected.

The drawing work is based on the proper moisture content of the fabric, which is gradually widened and slowly dried by mechanical clips, thus obtaining temporary finalize.

The width of the fabric before and after the drawing should be limited, otherwise it will cause serious shrinkage.

2, mechanical shrinkage finishing

If the dry fabric after dyeing and finishing is wetted by water in the relaxed state, the warp and weft direction of the fabric will obviously shrink. This phenomenon is called shrinkage. Usually the percentage of the warp or zonal length before and after washing is measured according to the test standard, representing the percentage of the length before washing to indicate the warp or zonal shrinkage of the fabric.

The main problem is to solve the problem of warp shrinkage, so that weft density and warp knitted fabric can be adjusted to a certain extent to make the fabric have a slack structure. After mechanical shrinkage, the fabric is not only "dry setting" but has little deformation, and after wetting, there is enough room between the warp and weft, so that the warp length of the fabric will not be shortened due to the swelling of the fiber, that is, the potential shrinkage of the fabric will be eliminated, so that it can be retracted in advance, so that the shrinkage of the finished product can be reduced.

Appearance finishing

The main contents of fabric appearance finishing include calender finishing, electro optic finishing, grain finishing and bleaching fabric finishing. After finishing, the appearance of the fabric can be improved and beautified, such as gloss increase, smoothness and surface embossing.

1. Calendering, electro optic and grain finishing.

Mechanical finishing, calendering, electro-optic to enhance the fabric lustre, rolling grain can make the fabric have concave and convex pattern of three-dimensional effect. Calendering, electro optic and rolling finishing are simply made use of mechanical processing, and the effect is not durable. If combined with resin finishing, the finishing effect of washable can be obtained.

Calendering finishing: General calendering, friction calendering and electro-optic. By means of mechanical pressure, temperature and humidity, the fabric surface is flatten and the yarn is flattened by means of the plasticity of the fiber, so as to enhance the gloss and smoothness of the fabric surface.

Electro optic finishing: electro optic machine is a hard steel roller with a certain surface and density twill line and another elastic soft roll. The inside of the hard roll can be heated. Under heating and certain humidity conditions, the fabric is pressed and parallel and neat twill is pressed on the fabric surface, resulting in regular reflection on the incident light and obtaining a high glossy surface like silk. The finishing of satin satin fabric is done by electro optic finishing. The density of the surface of the electric roller is different from that of the yarn. The fabric with fine yarn is suitable for larger density, and the 8~10 /mm slash is the most common. The skew of the lines should be consistent with the twist of the main yarns on the fabric surface.

Stripe finishing: similar to electro optic finishing, the surface of hardened roller is carved with Yang pattern, and the soft roller has the shade pattern corresponding to the hard roll, which coincides with each other. The fabric produces concave and convex patterns through the soft and hard rolls with corresponding patterns, under the action of moisture, heat and pressure. The light rolling machine is also known as the "flower machine", the hard roller is the copper roller for printing, the soft roller is the nitrile rubber roller (active roller), the hard roll is lighter when the flower is copied, the soft roller has no obvious corresponding shade pattern, the pressure is smaller when copying flowers, and the degree of concave and convex pattern produced on the fabric is also shallow, and there is a sense of hidden flowers.

2. Whitening finish

After bleaching, fabrics often have a trace of yellowish brown color. It is not easy to achieve pure white degree. Fabric whitening is often used to increase the white feeling. There are two ways to whiten.

One is the blue and white method: a small amount of blue or purple dyes or paints will make the fabric coloring. The complementary effect of pigment and color will make the blue violet light of the fabric slightly heavier. The fabric appears to have improved whiteness, but the brightness will be reduced and slightly darker. In recent years, it has been rarely used alone for the color adjustment of fluorescent whitening.

The other is fluorescent whitening method: fluorescent whitening agent is soluble in water, colorless, its chemical structure is similar to dyes, it can dye the fiber, fluorescent whitening agent itself is colorless, but after dyeing with fiber, it can give out visible blue purple fluorescence under ultraviolet light, mixed with the micro yellow brown light reflected from the fabric to make the white light, and the fabric will become more white. Because the total intensity of reflection increases, the brightness increases, but the effect is slightly worse under the condition of lacking ultraviolet light source.

Two. Resin finishing

Resin finishing is developed with the development of polymer chemistry. Formaldehyde was used as finishing agent, and then the addition product of urea formaldehyde was used to treat viscose fabric, which had good anti wrinkle and shrink proof effect, and laid the foundation for today's resin finishing. With the development of science and technology, the resin finishing technology of cotton fabric has made great progress. It has gone through several development stages, such as wrinkle prevention, shrink proof, washable and durable press finishing (D.P).

Common resins for fabric finishing

There are several kinds of resins used for fabric finishing, but N- hydroxymethyl amide compounds are the most widely used. The commonly used resins are first outlined below.

1. urea formaldehyde resin (UF resin) viscose fabric finished with urea formaldehyde resin, the fabric feels full, shrinkage rate decreases, dry and wet strength increases significantly and wrinkle resistance increases. Urea formaldehyde resin is prepared from urea and formaldehyde, which has wide sources of raw materials, convenient preparation and low cost, but it can not be used for cotton fabrics. Cotton fabric is strongly reduced after using urea formaldehyde resin, and its free formaldehyde content is high.

2. the melamine formaldehyde resin (MF resin) MF resin has the properties of initial shrinkage near UF resin. Because MF resin has larger molecular weight and washability is better than UF resin, it can be used for finishing cotton fabric. It can not only get better shrink proof and crease resistance, but also lose more strength than UF resin. However, the fabric is yellowed after finishing with MF resin, so it can not be used for resin finishing of bleached fabrics. After the etherification of MF resin with methanol, it can also improve its stability.

3. dimethoxylated two hydroxyethylene urea resin (DMDHEU or 2D resin) 2D resin is a kind of resin which is widely used in China. Its performance is better than that of UF and MF resin. After finishing, the fabric has good washability and is not easy to hydrolyze, and its resin reactivity is low. It is not easy to form polymer condensates when placed. It can be stored for a long time, only when it is used. It has little odor, and has little effect on the fastness of direct dyes and reactive dyes. It is suitable for durable press finishing (D.P), but its chlorine resistance is poor.

Three. Special finishing

In addition to ordinary daily life, textile products can also improve their application range after special finishing, such as water repellency, flame retardancy, antistatic and antifouling. These properties are not available in general textiles, but are obtained through special finishing methods. This kind of finishing method is called special finishing.

Waterproof finishing

According to the different processing methods, they can be divided into two categories: one is to apply a coating of continuous film on the surface of the fabric, which is impermeable to water but not breathable. It is not suitable for general clothing, but also suitable for making rainproof tarpaulins and umbrellas. Another method of sorting is to change the surface properties of fibers, so that the hydrophilicity of the fiber surface can be changed to hydrophobic, and there are still a large number of pores between the fibers and yarns. The fabric can maintain breathability and is not easily wetted by water, making it suitable for making raincoat fabrics. This kind of breathable waterproof water is also called water repellent finishing.

Antistatic finishing

When the clothes are rubbed with static electricity, they often attach the skirt to their legs, and the outer garment is tightly absorbed on the underwear. In some explosive places, the explosion caused by electrostatic sparks will also happen.

Durability and external application of electrostatic inhibitor are often used in dyeing and finishing process. This kind of electrostatic preventive agent requires durable antistatic effect, does not affect the fabric style, does not affect the dyed and dyed fabric's dyed fastness and dyeing fastness, is compatible with other auxiliaries, has no odor, and is harmless to human skin. Commonly used polymer surfactants, including anionic, non-ionic. Cationic type. The above antistatic properties are used to increase the hygroscopicity of the fiber surface in order to suppress the charge accumulation.

Flame retardant finishing

After flame retardant finishing, the fabric can not reach the non combustible degree of asbestos, but it can stop the spread of flame, no longer burn when the fire source is removed, and no residual flame smoldering. Flame retardant finishing fabrics can be used in military departments, industrial transportation departments, and civilian products, such as carpets, curtains, curtain, work clothes, bedding and children's clothing.

In addition to the importance of flame retardancy and durability, flame retardant must also be taken care of whether there is any adverse effect on fabric strength, handle, appearance, fabric dyestuff and color fastness, whether there is any irritation on human skin, and the presence of non-toxic gas in the fabric when heated, and the compatibility with other finishing agents.