Лако-красочные материалы — производство

Indigo (57), the parent system of this group of colorants, is one of the oldest known natural dyes (see Chapter 1). The naturally occurring material is indican, the colourless glucoside of indoxyl. When subjected to a fermentation process, free indoxyl (58) is generated by enzymic hydroly­sis and this compound undergoes oxidation in air to indigo. […]

A common arrangement of the carbonyl groups in coloured molecules gives rise to a group of compounds known as quinones. These may be defined as cyclohexadienediones, i. e. compounds containing two ketone carbonyl groups and two double bonds in a six-membered ring. The simplest quinones are o — and p-benzoquinones, 49 and 50 respectively. Derivatives […]

The chemical class of colorants which is second in importance to azo dyes and pigments is characterised by the presence of a carbonyl (C=O) group, which may be regarded as the essential chromophoric unit. The vast majority of carbonyl dyes and pigments contain two or more carbonyl groups which, as illustrated in Figure 4.1, are […]

Metal complex formation has been a prominent feature of textile dyeing from very early times, since it was recognised that the technical perform­ance, including fastness to washing and light, of many natural dyes could be enhanced by treatment with certain metal ions, a process known as mordanting. Mordant dyeing is still used to a certain […]

The strategies leading to dyes with several azo groups are in essence extensions of the methods leading to disazo colorants. As the number of separate diazotisations and azo coupling reactions required for the syn­thesis of a polyazo dye increases, so does the number of potential stra­tegies. There are a number of commercial trisazo dyes, most […]

In the case of monoazo dyes and pigments, the strategy for synthesis is straightforward, involving appropriate selection of diazo and coupling components, and choice of reaction conditions in accordance with the chemical principles presented in the previous two sections of this chapter. In the case of azo colorants containing more than one azo group, the […]

Diazotisation, the first stage of azo dye and pigment synthesis, involves the treatment of a primary aromatic amine (ArNH2), which may be carbocyclic or heterocyclic, with nitrous acid to form a diazonium salt (ArN2+Cl~). Nitrous acid, HNO2, is a rather unstable substance that decomposes relatively easily by dissociation into oxides of nitrogen. It is therefore […]

Textbooks in general organic chemistry will illustrate that there are many ways of synthesising azo compounds. However, almost without excep­tion, azo dyes and pigments are made on an industrial scale by the same Scheme 3.2 The synthesis of azo colorants two-stage reaction sequence: diazotisation and azo coupling, as illus­trated in Scheme 3.2. The first stage, […]

The structural chemistry of azo compounds is complicated by the possi­bilities of isomerism. There are two types of isomerism, which may commonly be encountered with certain azo compounds: geometrical isomerism and tautomerism. Some simple azo compounds, because of restricted rotation about the (-N=N-) double bond, are capable of exhibiting geometrical isomerism. The geometrical isomerism of […]

Azo dyes and pigments constitute by far the most important chemical class of commercial organic colorant. They account for around 60-70% of the dyes used in traditional textile applications (see Chapters 7 and 8) and they occupy a similarly prominent position in the range of classical organic pigments (see Chapter 9). Azo colorants, as the […]