Reactive dyes (Reactive Dyes) refers to dye molecules with active groups in a class of water-soluble dyes, its molecular structure is often composed of two parts of the dye matrix and the active group, the dye precursor in the reaction process through the reaction of reactive dyes and fibers Covalent bond, to obtain a stable "dye-fiber" colored compound as a whole, so that the dyed product has good wash fastness and fastness to rubbing. The active dye has a bright color. Chromatography is complete. The price is low. The dyeing process is simple. Good leveling and other advantages, mainly used for the dyeing of cotton fibers and textiles. Printing. Can also be used for hemp. Wool. Silk and some synthetic fiber dyeing, is an important dye in the dye industry.
Reactive dyes, if classified according to the structure of the dye matrix, are classified as azo-type, quinoid-type, quinoid-type, etc. However, reactive dyes are usually classified according to the structure of their active groups. For example, trichlorocyano groups are often referred to as homotriazoles. Benzene (or s-triazine) reactive dyes; vinylsulfone-based reactive dyes known as vinyl sulfone. With the development of production technology, the types of reactive groups are increasing, and the variety of reactive dyes is also increasing. .
The dyeing mechanism of reactive dyes includes two processes: color absorption and color fixation. The color absorption is both the dye and the water molecules enter the fiber at the same time and is absorbed by the fiber. Therefore, the reactive dye molecules all contain hydrophilic groups and have good water solubility. Fixation is not only the reactive group in the dye molecule reacts with the group in the fiber molecule, but also forms a new covalent bond and is stained.
Due to the excellent performance of reactive dyes, the expanding range of applications, and the continuous emergence of new products, in today's development trends, the concentrated performance is: the development of high fixation rate. High color fastness. Suitable for low salt, low water, low energy dyeing requirements In order to meet the requirements of environmental protection, new dyestuffs are developed. The development of new varieties in the dye matrix is ​​to develop highly direct reactive dye color bodies, mainly bis-azo type color bodies, and more is the development of new active groups. The new active groups that have been put into production are: monofluorotriazine, nicotinic acid triazine, trichloropyrimidine, difluoromonochloropyrimidine, dichloroquinoline, a-bromoacrylamide, etc. These new active groups The introduction of dyestuffs has greatly improved the brightness, fastness, fixing rate and other aspects of dyes. Dyes containing complex reactive groups have been developed due to excellent application performance and low price.
Currently put into production: KE type with two monochlorotriazine groups; M type with one chloro-s-triazinyl group and one vinylsulfone group, among which there is a chloro-s-triazine and meta-ester Mixed ME type (or B type); chloro-triazine type and EF type with para-ester, and some new varieties containing three active groups. The production of these new varieties has accelerated the green process of reactive dyes. From the perspective of development trends, reactive dyes are gradually replacing reducing, direct, vulcanized, and ice-dyeing dyes, becoming the main varieties of cellulose fiber dyes, and are being applied to the dyeing of protein fibers and synthetic fibers.
X type ------ dichloro-s-triazine type
K------monochlorotriazine
Type KN----vinylsulfone type
M type------monochlorotriazine, vinylsulfone double active base type
KE type ----- double chlorotriazine type direct dye (DIRECT DYES) is a type of dye that can directly dye cellulose fibers in neutral or slightly alkaline media, usually without mordant, dyeing The bath can be dyed simply by adding salt or Yuan Ming powder and boiled. He usually uses the hydrogen bond between cellulose and dye and Van der Waals force to combine, so it is washable. The light fastness is poor. The light fastness is Above level 5 is called direct lightfast dye.
The direct dye has a very complete spectrum from yellow to black, and has a simple production process, low price, and easy use. Therefore, it is widely used in knitting, silk, cotton, ribbon, leather, wool, papermaking and other industries. It is also used in viscose fiber. The dyeing.
Direct dye molecules are usually larger than other types of dye molecules, and are dominated by a variety of diamine-derived azo and polyazo structures, the earliest being biphenyldiamines and stilbenes. Due to biphenyl The carcinogenic effect of amine compounds has been banned by various countries in the world. Some novel structural dyes have been developed and applied, such as urea type, benzoylaniline type, melamine type, benzimidazole type, thiazole type, and diazines. Types of copper cerium type and polyazo type. In order to improve the fastness and fastness to washing of direct dyes, copper complex-type direct dyes have also been developed and used, and fixing agents have been used in the dyeing process. A variety of fixing agents are available.
In particular, melamine-type direct dyes should be proposed. Due to the incorporation of a triazine ring group, their light fastness, wash fastness is better than that of benzidine-type direct dyes, and such dyes have good high-temperature stability and are dyed. The rate is high, the pH value of the bath is wide, and it is suitable for dyeing in the same bath as disperse dyes. It is less stained on polyester and has received attention from various countries. It has formed a separate series, collectively referred to as D-type direct-blend dyes.
Another new discovery of direct dyes is the appearance of reactive direct dyes (or direct-crosslinking dyes). This is a copper-complexed polyazo direct dye that must be used with specific fixing agents for dyeing. Most of these fixing agents are cationic macromolecular compounds that, when fixed, can produce covalent bonds with dyes and cellulose molecules, ionic bonds or coordination bonds, etc., thereby greatly improving the dyeing and fastness of dyes. Degree of fixation and fixation rate, suitable for one-step dyeing of polyester/cotton fabrics. Disadvantages are all copper complexes that make the dyed fabric shaded dark.
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