Anthraquinone dyes are the general name of dyes with anthraquinone structure in the molecule, anthraquinone derivative dyes synthesized from anthraquinone as raw materials and all kinds of colloketone dyes synthesized from anthraquinone derivatives. The structural formula of anthraquinone refers to the anthracene compounds with carbonyl groups at the positions of C9 and C10, which belong to the thick cyclic organic compounds, also known as 9, 10-anthrone and 9, 10-anthraquinone. In 1835, Laurent first prepared anthraquinone by oxidizing anthraquinone with nitric acid. Anthraquinone derivatives are colored and widely exist in nature. Most of the anthraquinone compounds in natural products contain hydroxyl, which often exists in free state or combined with sugar to form glycosides. For example, the vegetable dye alizarin contains hemiflavin and hydroxyl alizarin, which are anthraquinone compounds.

In theory, there may be 10 isomers of anthraquinone, but only 1, 2-anthraquinone,1, 4-anthraquinone and 9, 10-anthraquinone, commonly known as 9, 10-anthraquinone, have been prepared to be relatively stable. Due to the special reducibility of anthraquinone, it can be reduced to 9, 10-dihydroxy-anthraquinone sodium salt in sodium disulfite alkaline solution. Anthraquinone dyes generally have good light fastness and wash fastness, and occupy a very important position in the field of synthetic dyes. Disperse dyes can be divided into three categories according to their chemical structure: anthraquinones, azo and heterocyclic. Anthraquinone is also an important intermediate in various dyes, especially in blue dyes. We should be more clear: the price of blue dyes is generally higher than that of red, yellow, etc., and bright blue dyes are generally derived from anthraquinone derivatives. It is mainly used for dyeing and printing of middle and high-grade fabrics with high price and high added value, and the price of anthraquinone dyes is generally higher, and the increase is larger than that of other dyes.

Anthraquinone dyes are important dyes because of their bright color, high color fixation rate and good color fastness. However, anthraquinone dyes are mostly aromatic compounds with stable conjugated structure, complex structure, difficult degradation and potential toxicity. Due to the special properties of dyes, the wastewater produced by dyes not only has high organic component content, is not easy to be oxidized, poor biochemical performance, high chemical oxygen demand, but also has high chroma, complex composition, and high toxicity. Dielectric barrier discharge plasma is a kind of non-equilibrium plasma under normal pressure and low temperature. Since it can be produced at or slightly above atmospheric pressure, no vacuum equipment is required and the active particles required for chemical reactions can be obtained at room temperature. In recent years, environmental scientists have applied physicochemical processes such as sound and electricity to the treatment of wastewater and exhaust gases.

History of anthraquinone dyes

In the 19th century, it was found that the natural dye alizarin used in ancient times was a compound of hydroxyl anthraquinone, and later many alizarin derivatives were synthesized and made into mordant dyes with chromium salts, aluminum salts and other metal salts. Simple derivatives of anthraquinone include anthraquinone amino compounds, anthraquinone halogen compounds and so on. Benzene-cirrhosis ketone and its derivatives were obtained by the reaction of anthraquinone with glycerol in zinc and concentrated sulfuric acid. Various VAT dyes with high molecular weight, bright color and high fastness could be prepared by condensation reaction. It is based on anthraquinone as raw material, through the sulfonic acid compounds containing amino, hydroxyl and halogen, to produce a variety of advanced acid dyes and reactive dyes. In recent years, due to the rapid development of synthetic fibers, many bright and widely used disperse dyes for synthetic fibers, especially polyester fibers, are made of anthraquinones containing hydrophilic substituents.

Production process of anthraquinone

There are four common production processes of anthraquinone:

1, anthracene gas phase catalytic oxidation method

Anthracene oxidation is a gas phase catalytic oxidation process using refined anthracene as raw material, air as oxidant and vanadium pentoxide as catalyst. There are two types of reactors: fixed bed and vulcanized bed.

2. Phthalic anhydride method

Using anhydride and benzene as raw materials and aluminum trichloride as catalyst, Friedel-Crafts reaction was carried out, and then anthraquinone was dehydrated with concentrated sulfuric acid. Anhydride process is divided into solvent method, ball milling method and gas phase shrinkage method. Most of China uses solvent method, that is, excessive benzene as solvent. This method is easy to obtain raw materials, can be started from petroleum, has the advantages of low reaction temperature, simple equipment, less side reaction and so on. The disadvantage is serious pollution, aluminum trichloride waste acid water is not easy to treat, and the production cost is high. Anhydride method is used to synthesize anthraquinone in China. Raw material consumption quota: phthalic anhydride 768kg/t, pure benzene 700kg/t, sulfuric acid (98%) 1364kg/t, aluminum trichloride 1554kg/t, fuming sulfuric acid 1000kg/t.

3. Naphthoquinone method

Anthraquinone was obtained by condensation reaction and dehydrogenation with naphthoquinone and butadiene as raw materials and cuprous chloride as catalyst. Due to the rapid development of petrochemical industry, butadiene and naphthoquinone used in this method are provided in large quantities. The naphthoquinone method has the advantages of low consumption and less waste, and has reached a considerable scale in Japan and the United States, and has a promising future. This method is used by the Kawasaki Company in Japan.

4, the styrene method

The styrene is dimerized first, then oxidized to o-benzoylbenzoic acid, and then cyclically synthesized anthraquinone. The advantages of this method are that the raw material is easy to obtain, there is no pollution problem caused by the aluminum salt wastewater of the phthalic anhydride method, and the product cost is low. However, the reaction conditions are harsh, the technology is complex, and the equipment is demanding, which is the process studied by BASF in Germany. In addition, Mitsui Chemical Company of Japan obtained a patent for the preparation of anthraquinone from toluene.

Advantages and disadvantages of anthraquinone dyes

Anthraquinone disperse dyes, acid dyes, VAT dyes, reactive dyes, etc., have been developed into a complete chromatographic, good performance of the dyes. At present, there are more than 400 varieties of anthraquinone dyes, which occupy an important position in the field of synthetic dyes. Anthraquinone disperse dyes are disperse dyes with anthraquinone structure, most of which are amino or hydroxyl groups in the alpha - position of anthraquinone nucleus. Anthraquinone dyes are insoluble in water, and the absorption coefficient is about 10000 ~ 25000, which is 1/2 ~ 1/3 of azo dyes, and the dyeing power of fibers is fundamentally worse than that of azo dyes. The following Shanghai Jingyan Chemical for you to briefly introduce the advantages and disadvantages of anthraquinone disperse dyes.

Advantages:

In the navy blue and black ranges of high concentration dyeing, anthraquinone dyes are rarely used. Anthraquinone disperse dyes are bright in color and are mostly used for red, yellow or blue dyeing. From the point of view of the color structure of anthraquinone disperse dyes, dyeing is not affected by hydrolysis reduction, so the sun fastness is good, chemical stability is good, easy to use, still occupies a very important position in disperse dyes, accounting for about 20% of disperse dyes. It is very convenient to dye, and there is no need to add additional dispersants. Formalin condensates of Lignosulfonic acid and β-naphthalene sulfonic acid can be used as dispersants, which can be easily dispersed in water to dye the colored matter.

Cons:

Anthraquinone disperse dyes have a disadvantage, which is not found in other dyes, it will react with nitrogen oxides and sulfur oxides in the atmosphere, that is, gas fading phenomenon. This phenomenon is related to the alkalinity of α-amino group. In order to overcome this shortcoming, alkyl ammonia can be replaced by aryl ammonia, and electrophilic groups such as halogen atoms, cyanide groups and nitro groups are introduced.

Article source: Xiao Xiao, dyeing and finishing encyclopedia