Toluidine red is a commonly used chemical pigment, with excellent heat resistance, light resistance and solvent resistance, widely used in plastics, paints, inks and other fields. The following is the manufacturing method of Toluidine Red:
1. Toluene: Toluene is the main raw material for the preparation of Toluidine Red, which requires high purity, and industrial grade toluene is generally used.
2. o-Nitroaniline: o-Nitroaniline is another important raw material of Toluidine Red, also need high purity.
3. Hydrochloric acid: used to adjust the pH value of the reaction system, generally use industrial grade hydrochloric acid.
4. Sodium nitrite: used to generate diazonium salt, also need higher purity.
II. Manufacturing process
1. Diazotization of o-nitroaniline
Add o-nitroaniline to hydrochloric acid, stir and cool to 0-5℃, slowly add sodium nitrite solution, keep the temperature at 0-5℃, to generate diazonium salt.
2. Amination of toluene
In another reactor, toluene and sodium hydroxide are added, heated to a certain temperature, diazonium salt solution is passed through, and a coupling reaction is carried out to produce toluidine red.
3. Post-treatment
After the reaction is finished, the reaction solution is cooled to room temperature, filtered, washed and dried to obtain the finished product of Toluidine Red.
3. Precautions
1. Diazotization reaction is exothermic reaction, need to strictly control the temperature to prevent boiling and rushing materials.
2. Diazonium salt is explosive, need to be operated at low temperature, and avoid contact with organic matter and acid.
3. The amination reaction needs to control the pH value to ensure the smooth progress of the reaction.
4. In the whole manufacturing process, attention needs to be paid to environmental protection and safety to avoid harming the environment and personnel.
The above is the manufacturing method of Toluidine Red, the specific operation needs to be adjusted and optimized according to the actual situation. At the same time, in order to ensure the quality of the product and environmental protection requirements, it is necessary to strictly control the quality of raw materials and the parameters of the manufacturing process.
