Dyeing project is the machining process using dyestuff on fiber to causing some physical or chemical changes on fabric or using chemical methods on fiber and textile products to causing some dyestuff effects and make fiber or textile products become colored objects. Dyed products not only requires uniform color, and must have good color fastness . In order to meet the environmental requirements, the project must to be environmental-friendly and clean.
Because of the objects and dyeing apparatus difference ,dyeing methods have many different kinds. Generally,there are divided into fabric dyeing, yarn dyeing and loose fiber dyeing . Among these three,fabric dyeing is the most widely applied,fabric dyeing methods including tie dyeing , jig dyeing , overflow dyeing , jet dyeing and etc .Tie dye is a continuous dyeing process . Loose fiber dyeing and yarn dyeing are mostly intermittent impregnation , such as reciprocating swing hank dyeing , high temperature and high pressure dyeing, double box flow dyeing , jet dyeing , cheese dyeing , beam dyeing and etc., these ways are suitable for knitting&yarn-dyed like industries . Continuous yarn dyeing is to round yarns on big scrolls into piece of yarns or balls shape, then rounded on beams after padding, such as continuous indigo dyeing . Loose fiber dyeing mainly used in the wool industry .

Dyeing workers should be familiar with the properties of various dyestuffs , only the correct selection of dyestuffs and dyeing formulation can get high quality products. Dyeing theory involves theories of chemistry , physical chemistry and high polymer chemistry and the various disciplines of other subjects, according to modern theories of dyeing,the reason why dyestuffs is able to dye fibers and cause a certain fastness between the fibers is due to the gravity of the fiber molecules and dyestuff molecules. But due to different characteristics of different dyestuffs and fibers, its dyeing principles and dyeing process is also different. In terms of its dyeing process,it can be divided into three stages.
◆ adsorption . When the fiber put into the dye solution , the dyestuffs gradually transferred from the solution to the fiber surface , this process was called adsorption .
◆ spread. The dyestuffs adsorbed on the fiber surface diffusion inside the fiber , until the dyestuff concentration of fiber comes to consistency in various parts .
◆ fixation . Fixation is the combining process of the fiber and dyestuffs, due to the difference of dyestuffs and fibers , its binding modes also different. In general , the dyeing fixation can be divided into chemical fixation and physical chemical fixation .

According to the structure of dyestuffs,it can be divided into : azo dyestuffs, anthraquinone dyestuffs, indigoid dyestuffs, sulfur dyestuffs, phthalocyanine dyestuffs, nitroso dyestuffs, nitro dyestuffs , aromatic dyestuffs, acridine dyestuffs,azine dyestuffs, evil oxazine dyestuffs, thiazole dyestuffs , thiazine dyestuffs, and cyanine dyestuffs and etc. According to its appliance ,it can be divided into : direct dyestuffs, sulfur dyestuffs, reactive dyestuffs, vat dyestuffs , azoic dyestuffs , disperse dyestuffs , cationic dyestuffs, acid dyestuffs, Mordant dyestuffs, neutral dyestuffs , alkaline dyestuffs , solubilised vat dyestuffs, phthalocyanine dyestuffs, polyester indanthrene dyestuffs,polycondesation dyes,etc. The basic characteristics of different kinds of dyes various ,so there have different affinities to the fiber,some dyestuffs can dye kinds of fibers, but with different color fastness. Some dyestuffs only have a good affinity to one kind of the fibers,if so there need to use special methods to dye the other kinds of fibers. Until now some fibers still can not dyed (e.g. polypropylene ) , but after modifying the fiber`surface,then can be dyed use some kinds of dyestuffs. For some kinds of fibers,by modifying the fiber’s surface, can also be dyed with another kinds of dyestuffs , to producing multicolored effects. In recent years , with the advances in science and technology, new types of dyeing methods are developed, such as no solvent dyeing, low temperature plasma treatment dyeing , supercritical carbon dioxide dyeing , ultrasonic treatment dyeing , new pigment dyeing and other kinds dyeing keep on appearing, and are gradually extended and used . New fibers and dyestuffs` research&development have created more conditions for the development of printing and dyeing industry, but also lay a good foundation for the “green” production.

Currently,the textile products become more fine finishing,further processing,high-grade,diversification,fashionable,decorative and functional,and by increasing textile products` high added value to improve economic benefits. Dyeing process should be small amount,multi-species,automation,and efficient and consider clean production as the major premise,to be energy saving,water conservation,labor saving.

Printing is a process to use printing paste transfer function to dye or paint flower patterns on the fabric.Thickener plays roles of making printing paste be thicker, adhesive and fix dyes,and maintain clear outlines of flowers,to overcome infiltration of dyes to be extended.Substantially printing process is the same as dyeing,it is also dyed on fibers,fixed,and requires a certain degree of fastness,except that printings are multi- color patterns,it can also be seen as a partial dyeing process.

According to equipments,methods of printing can be divided into screen printing,roller printing,transfer printing,electrostatic printing,photosensitive printing, trichromatic printing,ink jet printing, pouring and dyeing printing,etc. according to different processes,printing can be divided into direct printing,discharge printing,resist printing and anti- dyeing printing. With the development of science and technology,the printing equipment and processes develop rapidly,printing products innovation changed quickly. Since the 20th century,many kinds of printings come out,such as foam printing,gold and silver powder printing,micro-capsules printing,penetration printing and other various special printings,with the invention of ink-jet printing and electrostatic printing,photographic printing and other new technologies,printing products become more charming and textile products more colorful.The develop trends of printing products is to pay more attention to ecological environment,improve efficiency, improve the reproducibility of calico,develop digital ink jet printing and other advanced technologies.

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