Finishing of cotton fabrics
1. Tentering
Tentering is based on the fact that cotton fibers have certain plasticity in a humid state. The state of the warp and weft yarns in the fabric is adjusted under slow drying, and the fabric width is stretched to a predetermined size to achieve uniformity. Form stabilizing effect.
Cotton fabrics are often tentered with clip tenters, while wool fabrics, silk fabrics and chemical fiber fabrics are often tented with clip tenters.
The front end of the tenter is often equipped with a padding machine and a drum drying device, so tenter finishing is often combined with certain additive finishing (such as softening, whitening, etc.).
2. Calendering and electro-optical finishing (jackingfinishing)
And embossed finishing. Calendering and electro-optical finishing can increase the luster of the fabric, while embossed finishing causes the surface of the fabric to be pressed into a three-dimensional, concave and convex pattern.
These finishings are accomplished by using the plasticity of cotton fibers in a hot and humid state and through roller rolling to varying degrees.
3. Hard finishing (hard finishing)
Hard finishing is commonly known as Sizing finishing is the use of slurry made of polymer substances (wet starch or chemical slurry) with a certain viscosity to pad and roll on the fabric to form a thin film, so that the fabric can obtain various smooth, stiff, thick, and plump handles, and improve the fabric’s texture. Strong and wear-resistant, extending service life.
4. Softening (softening)
In addition to In addition to obtaining a softer feel through calendering, mechanical shrinking and other processing, soft finishing can also be achieved by adding softeners.
There are many types of softeners. The varieties with short-lasting effects include paraffin emulsion, “mercerizing paste”, “red oil”, etc.; the varieties with long-lasting effects are mostly reactive softeners, such as Softener Vs, waterproofing agent Pf, rc and reactive silicone emulsion, etc.
Softening finishing usually uses padding finishing liquid and then heat treatment, which is often combined with hot air tenter finishing.
5. Whitening (whitening)
Fluorescent whitening agent (Fluorescent whitening agent) can absorb invisible ultraviolet rays in sunlight and convert it into bright blue-violet visible light and radiate it, which mixes with the original yellow light on the fabric to form white light, thus greatly improving the whiteness of the fabric. Fluorescent whitening agents have affinity for fibers and can be dyed like dyes. Therefore, dip dyeing or hot air tenter drying after padding can be used for whitening.
The commonly used fluorescent whitening agents for cotton include VBl, VBu, etc.; for silk fibers, Bsl, Ws, Wg, etc. are commonly used, and VBl can also be used; for polyester whitening, whitening agents are often used. dt.
6. Anti-shrinkage and anti-wrinkle finishing
Fabrics that have been dried after dyeing and finishing will shrink significantly in the warp and weft directions when they are re-wetted in a relaxed state. This phenomenon is called shrinkage. Mechanical pre-shrinking and chemical finishing methods are often used in dyeing and finishing to solve the problem of excessive fabric shrinkage.
A. Mechanical shrinking and finishing
Mechanical shrinking and finishing can be carried out by a variety of equipment. Commonly used ones include super-speed cloth feeding needle tenter, blanket or rubber blanket shrinking and finishing machine, etc. When feeding the tent at an overspeed, the linear speed of the fabric fed into the clip chain is slightly greater than the running speed of the clip chain. Therefore, during the tenter process, the fabric is in a tension-free state in the warp direction and can freely retract, increasing the warp shrinkage. Improve shrinkage. When the blanket or rubber blanket is pre-shrunk, the retraction effect of the blanket or rubber blanket when it relaxes after stretching is used to cause the fabric that fits it to shrink synchronously in the warp direction, thereby eliminating potential shrinkage.
B. Chemical anti-shrinkage and anti-wrinkle finishing
Some fibers, such as viscose, have a low degree of molecular polymerization and are more prone to swelling and elongation than cotton shrinkage. The dimensional stability of the fabric is poor, not only High shrinkage and easy to wrinkle. For this type of fabric, if mechanical preshrinking is used, the antishrinking effect will be poor, and chemical finishing must be used. In production, chemical finishing is rarely used for anti-shrinkage purposes alone, but is often combined with anti-wrinkle, because while anti-wrinkle finishing is carried out, the fabric also obtains anti-shrinkage effect, and the two are inseparable.
The currently commonly used anti-wrinkle and anti-shrink finishing method is a chemical finishing process that uses compounds with cross-linking polymerization ability to treat fabrics to cross-link with fibers and polymerize and deposit within the fibers. Commonly known as resin finishing.
There are many types of resins used for anti-wrinkle finishing, such as urea-formaldehyde resin (uf), cyanoformaldehyde resin (tMM), dimethylol dihydroxyethylene urea resin (2d), etc. Although these resins have good finishing effects, their applications are limited because most of them are aldehyde-containing compounds that release free formaldehyde that is harmful to the human body and the environment. In recent years, low-formaldehyde and formaldehyde-free varieties have been gradually developed, such as polycarboxylic acid (Btca), glyoxal derivatives, tetraoxane, epoxy compounds and thermoplastic resins.
The basic method of resin finishing is:
The fabric is padded with a finishing solution containing resin monomer or primary shrinkage body, and then Perform dry heat treatment.
At �On the basis of the above-mentioned finishing technology, non-iron finishing that can improve the anti-wrinkle performance of fabrics in a wet state and more demanding durable press finishing technology for clothing have been developed. </p
