Лако-красочные материалы — производство

2.3.1. Acylated Oxazine Leuco Dyes Benzoyl leuco Basic Blue 3 (2) is a typical cyan leuco oxazine used in carbonless copy paper. To satisfy the requirements of new applications such as electrolytic recording and Color Dry Silver, new oxazine leucos have beendeveloped that can offer colors other than cyan such as red, purple, and blue […]

The thiazine dyes used in the preparation of this type of leuco are obtained through oxidative coupling of phenothiazine with an active methylene compound or an aniline. The reduction of the dye 23 with zinc powder in acetic acid is straightforward.9 Treatment of the leuco 24 with acetic anhydride at 40°C yields a more air […]

Methylene Violet, which is a well-known phenothiazinone dye, is also reduced and acylated in one step by refluxing with zinc powder in an acid anhydride. Synthetic Method 3: 6-dimethylamino-3-acetoxy-10-acetylphenothiazine (11a) (procedure from US. Patent 4,604,458)? Under a nitrogen atmos­phere, a mixture of 5.0 g of 7-dimethylaminophenothiazin-3-one (Methylene Violet), 75.0ml of acetic anhydride, 5.0ml of pyridine, […]

The standard procedure for the synthesis of leuco dyes related to benzoyl leuco Methylene Blue is straightforward. The one-pot synthesis is carried out in a two-phase water-toluene system. Methylene Blue is first dissolved in the aqueous phase and reduced with sodium dithionite under nitrogen and with stirring. The yellowish leuco is extracted into the organic […]

These leuco dyes are stable enough to be isolated without the need for acylation. Some are more resistant than others to air oxidation depending on their redox potential.9 As shown in Table 1, the introduction of an electron-withdrawing group raises the redox potential and stabilizes the leuco against air oxida­tion. In one extreme case, this […]

The leucos 11a-d are claimed to give blue gray images in electrolytic recording instead of the purple color of Methylene Violet from which they are derived.7 As in the case of the leucos Azure A and B, the exocyclic acyl group is not eliminated on oxidation, resulting in a Methylene Blue-type cationic dye. The color […]

When Methylene Blue is reduced, the yellowish leuco cannot be isolated due to instant air oxidation. Benzoylation of the leuco form provides stabilization. There are also leuco thiazine dyes stable enough to be isolated without the need for aroylation. 3.2.1. Acylated Leuco Thiazine Dyes There are cationic thiazine dyes (3 to 5) and neutral thiazinone […]

TRAN VAN THIEN 3.1. INTRODUCTION Benzoyl leuco Methylene Blue (1), which is a phenothiazine leuco dye, has been known since 1900. The material was developed to extend the range of hues and colors obtainable in such applications as pressure-sensitive carbonless paper and to complement other classes of leuco dyes such as triarylmethanes, crystal violet lactone, […]

Leuco naphthazarins have been well studied as hair dyes.25 Human hair has been colored purplish red from dye solutions in aqueous benzyl alcohol. For example, 33 has been oxidized on hair during the drying process. Although leuco quinones have been studied as color formers, their use in color-forming recording media has not been studied extensively […]

It is well known that quinizarin (22) is alkylaminated in air to give a mixture of 1-alkylamino-4-hydroxyanthraquinone (23), 1,4-bis(alkylamino)- anthraquinone (24), and 2-alkylaminoquinizarin (25) (Scheme 7). The reac­tion conditions affect the ratio of these products. In a nitrogen atmosphere, or in the presence of sodium dithionite as reducing agent, the main amination product is 24. […]