reactive dye

New water-soluble dyes

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Reactive dyes Reactive dye It is a new type of water-soluble dye that appeared in the 1950s. Reactive dye molecules contain hydroxyl and Protein fibre The reactive group that reacts with the amino group in the, when dyeing, forms a covalent bond with the fiber to form a "dye fiber" compound. Reactive dyes are characterized by bright colors, good dyeing uniformity, simple dyeing methods, high color fastness, complete color spectrum and low cost. They are mainly used for dyeing and printing of cotton, linen, viscose, silk, wool and other fibers and their blends.^[1]

Chinese name: reactive dye
Foreign name: reaction dye

Also called: Reactive dye
Meaning: Chemically active Group

catalog

nine Acid dye
ten Structural characteristics

definition

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Reactive dyes are also called reactive dyes. Chemically active Group , can aqueous solution A dye that reacts with cotton, wool and other fibers to form a common bond. High washing resistance fastness

classification

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formula

According to the different reactive groups, reactive dyes can be divided into two main categories. The general formula of symmetrical triazine type is:

Where D is the parent dye. In this kind of reactive dyes chemical property More lively. When dyeing, the chlorine atom is Cellulosic fibre Replace, become leave Group leave. The reaction between dye and cellulose fiber belongs to Bimolecular nucleophilic substitution reaction (See Substitution reaction ）。

Vinyl sulfone The active group contained in this type of reactive dyes is ethylene Sulfonyl (D-SO2CH=CH2) or β -Sulfate ester of hydroxyethyl sulfone group. When dyeing, β -Hydroxyethylsulfonyl sulfate was treated by Elimination reaction Produce vinyl sulfone group, and then combine with cellulose fiber Addition reaction , forming covalent bond 。

The above two types of reactive dyes are the main reactive dyes with the largest output in the world. In order to improve the Fixation rate In recent years, two activities have been introduced into dye molecules Group , called dual reactive dye. Reactive dye removal Cellulosic fibre In addition to the varieties used, it has also developed Protein fibre (such as silk, wool and other fibers).^[2]

technology

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Dyeing method of reactive dyes; Dyeing cotton with reactive dyes, the most commonly used dyeing methods are: Impregnation method , plus Pad dyeing Materials. Dip dyeing method: dip dyeing method can be divided into three dyeing methods: one bath one step method, one bath two step method and two bath method. A: One bath one step method: Dyeing is carried out in alkaline bath, that is, color fixation is carried out at the same time as dyeing. This method is simple in process, short in dyeing time and convenient in operation. However, since adsorption and color fixation are carried out at the same time, the dye cannot be diffused after color fixation, so the levelness and penetration are poor. When dyeing under alkaline conditions, the dye in the dyeing bath is more stable and hydrolyzed. B: One bath two-step method: Dye in neutral bath first Dyeing When approaching balance, add in the dye bath Alkaline agent Adjust the PH value to the specified PH value for color fixation (generally 11), then the dye and fiber achieve covalent combination to achieve the purpose of color fixation. One bath two-step method is a more reasonable dyeing method in reactive dye dip dyeing, which can not only obtain higher Dye uptake and Fixation rate 。 And it has good level dyeing effect, so this method is commonly used for cotton knitted fabric dyeing.

advantage

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Reactive dyes are composed of parent dyes, linkers and reactive groups, so that they can form firm covalent bond Combined with a series of other Cellulosic fibre The incomparable characteristics of dyes have established their position as the focus of development and use of dyes for cellulose fibers, which is highlighted in the following four aspects:

(1) Reactive dyes are used to replace prohibited dyes and other types of cellulose dyes such as Sulfur dye 、 Ice dye and Vat dye One of the best choices.

(2) Reactive dyes can use economical dyeing process and simple dyeing operation to obtain high level of various fastness properties, especially wet fastness 。

(3) Reactive dyes have wide color spectrum, bright color, excellent performance and strong applicability. Their color phase and performance basically meet the requirements of the market for fibers and clothing materials.

(4) Reactive dyes are suitable for new types Cellulosic fibre Products such as Lyocell fiber And other printing and dyeing needs.

shortcoming

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However, the main technical problems of reactive dyes are as follows:

(1) The utilization rate is not high enough, generally 60%~70%, which produces a large amount of colored sewage with a chromaticity of more than a few thousand times, and the COD value is generally between 8000 and 30000 ppm waste water The COD value of is more than 50000 ppm.

(2) In order to restrain the charge on the fiber surface, reactive dyes need to use a considerable amount of electrolyte, which not only increases the labor intensity, but also causes Chloride ion The concentration is up to 100000 ppm, which greatly increases the difficulty of treating reactive dye dyeing wastewater.

(3) Some Color fastness Can not meet market requirements, such as sweat, sunlight fastness, wet Rubbing fastness as well as Azo The light fastness of B type red dye and azo type blue dye in light color.

(4) It can replace vulcanized materials and Vat dye There are fewer dark varieties.

Functional purpose

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Reactive dyes, which are composed of parent dyes, linkers and reactive groups, can form strong covalent bonds with fibers when used, and have a series of characteristics that other cellulose fiber dyes cannot match. Their position as the development and use focus of cellulose fiber dyes has been established, which is highlighted in the following four aspects:

(1) Reactive dyes are used to replace prohibited dyes and other types of cellulose dyes such as Sulfur dye 、 Ice dye and Vat dye One of the best choices.

(2) Reactive dyes can use economical dyeing process and simple dyeing operation to obtain high level of various fastness properties, especially wet fastness 。

(4) Reactive dyes are suitable for printing and dyeing of new cellulosic fiber products such as Lyocell fiber.

Main technologies

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There are four points as follows:

(4) There are few dark colors that can replace vulcanized materials and vat dyes.

The main way to solve the technical problems of reactive dyes is to improve their absorption and fixation rate Triazine Base and Vinyl sulfone Base. For the New reactive dyes In addition to the characteristics of various active groups, such as low acidity hydrolysis High acid hydrolysis bond breaking stability, excellent washability, good items fastness In addition to the smaller difference between the absorption rate and the fixation rate, it also has new characteristics resulting from the addition and interaction between two different active groups, such as better ability to resist acid hydrolysis and peroxide washing, higher fixation rate, wider dyeing temperature range, better dyeing reproducibility and suitable for medium temperature dyeing Low temperature dyeing , short-time dyeing, high RFT dyeing, etc., so the output of this kind of reactive dyes has accounted for two-thirds of all reactive dyes used for dyeing, and has become a cotton fabric Pad dyeing With dip dyed main dye.^[3]

matters needing attention

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Pay attention to the following points when using dyes:

1. The selection of basic three primary colors is important, and their solubility, directness, diffusibility, compatibility, sensitivity under normal fluctuation of dyeing conditions, fixation action and washability should be fully considered to ensure that the balance between directness and diffusivity of dyes can be achieved quickly The fixation behavior and washability can be reasonably balanced.

2. Especially light color when dyeing light medium color, because Azo Sunshine of type I red dye and azo blue dye fastness Poor, unable to meet the market demand, needs careful choice. As for the use of light fastness enhancers, experiments are required, generally speaking UV absorber The method to improve the light fastness of reactive dyes has no obvious effect.

3. Wet of many varieties when dyeing deep and thick colors Rubbing fastness Poor, unable to meet the market requirements, and needs careful use. The key to improving the wet rubbing fastness of reactive dyes lies in the basic dyeability of cotton, namely Cotton fibre yes Surface texture , surface texture, smoothness, rough hardness, etc., which are directly related to the quality of raw cotton and cotton yarn and the pretreatment of cotton fiber.

4. For those proposed in the market textile Requirements for complex fastness, such as sweat sunlight fastness and alkaline wet sunlight fading Color fastness , alkaline wet light fading fastness containing peroxide, etc. There are still some problems with this kind of reactive dyes, which need to be selected through experiments. These problems are also the focus of research and development of dyes containing heterogeneous double reactive groups.

Acid dye

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Acid dyes are characterized by complete color spectrum and bright color. They are mainly used for dyeing and printing of protein fibers and polyamide fibers such as wool and silk, as well as for coloring of leather, paper, cosmetics and inks, and a few are also used for manufacturing food pigments and lake pigments. Because acid dyes have low directness to cellulose fibers, acid dyes are generally not used to dye cellulose fibers.

Structural characteristics

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Acid dyes are mostly aromatic sulfonic sodium salts in structure, and azo and anthraquinone account for a large proportion in the chromophore structure. In addition, there are various chromophores such as triarylmethane, acrazine, xanthan, indigo, quinoline, phthalocyanine and nitroimine. Among various structures, azo acid dyes rank first in variety and yield, especially single azo and double azo dyes, including yellow, orange, red, navy blue and black. Anthraquinones have good light fastness and bright color, mainly some purple, blue and green dyes, especially blue. Some acid dyes with anthraquinone structure can play a role in brightening the dyeing of acid mordant dyes. Triarylmethane mainly consists of red, purple, blue and green. Generally, the light fastness is poor. Some bright blue varieties are not resistant to oxygen bleaching, but the color is very bright, and the wet treatment fastness is good. The color and application performance of xanthene acid dyes are similar to those of triarylmethane, and they are not used alone. They are mainly used for color matching and brightening of acid mordant dyes.^[4]

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