Background and overview[1][2]
2-Mercaptobenzothiazole is an important type of thiazole rubber vulcanization accelerator. It is also an important antioxidant and anti-corrosion additive. 2-Mercaptobenzothiazole is a light yellow powder or granules with an unpleasant odor. The melting point is above 173. 0℃; the relative density is 1. 41 ~ 1. 48; it is insoluble in water and n-hexane, easily soluble in acetone, soluble in ethanol, and slightly soluble in benzene. 2-Mercaptobenzothiazole is acidic, has strong vulcanization accelerator, relatively flat vulcanization curve, and has low pollution.
This product has low toxicity, irritates the skin and mucous membranes, can cause dermatitis and difficult-to-treat skin ulcers, and can cause sensitization. Oral administration, rat, LD50, 3800mg/kg; injection, rabbit, LD50, 7940mg/kg or above. Examples of product specifications: ash content: 0.3% or less; loss on ignition: 0.3% or less; sieving residue: 0.5% or less (75 μm, powdery).
Application[2-4]
2-Mercaptobenzothiazole (MBT) is an important component of benzothiazole compounds and has wide application value in industry, agriculture and medical fields.
1) In the mineral processing industry, MBT is often used to pre-concentrate and separate precious metals and transition metal elements. It is a flotation collector for sulfide ores, pyrites, and precious metal ores. It is also used for the metal surface layer of copper and its alloys. , is an effective copper corrosion inhibitor.
2) In the analytical chemistry industry, MBT has good selective adsorption of metal ions, and all transition elements can form stable complexes M with it. It is used as a method for the determination of copper, lead, silver, gold, diamond and calcium. Important reagents are therefore effectively utilized in analytical chemistry applications and industrial water treatment.
3) In the rubber industry, MBT is a general rubber vulcanization accelerator that combines with unsaturated vulcanized polymers to form an elastic cross-linked material, referred to as vulcanization accelerator M. It has fast vulcanization acceleration and good vulcanization flatness. It has the characteristics of no early vulcanization during mixing, and is widely used in the rubber processing industry. It has a rapid acceleration effect on natural rubber and general sulfur-vulcanized synthetic rubber, and its vulcanization critical temperature is low. As an acid vulcanization accelerator, it can make rubber products have high tensile strength and hardness. By selecting different combinations of ingredients, it can also meet different performance requirements. It can be used as a plasticizer to increase the plasticity of natural rubber. But the finished product
It has a bitter taste and is not suitable for the manufacture of rubber products in contact with food. It is mainly used in the manufacture of tires, inner tubes, tapes, rubber shoes and industrial products. The rubbers that can be added are: natural rubber (NR), isoprene rubber (IR), styrene-butadiene rubber (SBR), butadiene rubber (BR), nitrile rubber (NBR), ethylene propylene diene rubber ( EPDM), butyl rubber (IIR), etc. The dosage (ph r) in rubber is 0.5 to 2.
4) In the field of agricultural products, MBT can be used as herbicides, pesticides, plant growth regulators, etc. In addition, a 2-mercaptobenzothiazole manganese-zinc compound has been researched and developed with the chemical structural formula:
Where m, n, n’ are positive integers, and m=2(n+n’), n≥n’, n:n’=1:1~9:1. Prepare materials according to the stoichiometric ratio of the target product; 2-mercaptobenzothiazole is dissolved in the sodium hydroxide solution; add the aqueous solution of the water-soluble manganese salt and the aqueous solution of the water-soluble zinc salt to the 2-mercaptobenzothiazole sodium solution in sequence, stir and mix Evenly, let stand, filter, and wash with water to obtain a filter cake; vacuum dry the filter cake to obtain 2-mercaptobenzothiazole manganese zinc. The above-mentioned 2-mercaptobenzothiazole manganese zinc can be used as an agricultural fungicide. In the present invention, zinc is complexed on the surface of 2-mercaptobenzothiazole manganese solid particles, thereby forming a stable complex of 2-mercaptobenzothiazole manganese and zinc. Tests have shown that the complex has excellent control effects against various diseases such as apple spot leaf disease, pear scab, apple ring spot, and apple anthracnose.
5) Pharmaceutical field: The US FDA has approved 2-mercaptobenzothiazole for veterinary clinical use in the treatment of pet skin infections.
Preparation [5, 6]
Method 1: 2-Mercaptobenzothiazole is mostly synthesized in industry by three methods: o-nitrochlorobenzene method, aniline method, and nitrobenzene and aniline mixed method. Among them, the o-nitrochlorobenzene method has high raw material prices and complicated production processes, so most domestic auxiliary manufacturers do not use this method; the nitrobenzene and aniline mixing method not only has low production costs, but also can make the H2S produced by the reaction higher than The aniline method reduces by 1/3, but due to the difficulty of the reaction
Because of the problems of control and high requirements on reactor materials, currently only a few domestic companies use this method for production; the aniline method for synthesizing 2-mercaptobenzothiazole is a method commonly used by various additive factories in my country. Under high temperature and high pressure, 2-mercaptobenzothiazole is produced by direct reaction of aniline plus carbon disulfide and sulfur.
The production of 2-mercaptobenzothiazole by the aniline method is characterized by stable sources of raw materials, easy operation, and low requirements for reactor materials; its disadvantage is that the crude product produced by this method has a low content of 2-mercaptobenzothiazole. (85%), the amount of tar is large and the yield is low.
In addition, there are a variety of new production methods, such as a preparation method of rubber vulcanization accelerator 2-mercaptobenzothiazole, which includes the following steps:
a. Use benzothiazole and sulfur as raw materials. The mass ratio of the added amounts of benzothiazole and sulfur is 3.5~4.0:1. First, add the weighed raw materials benzothiazole and sulfur to the reaction kettle. , directly turn on stirring or nitrogen gas.After the pressure reaches 0.4~0.6MPa, start stirring, stir and heat up to 200±5°C and start insulation. The insulation time is 200~230min. After insulation, the reaction ends and 2-mercaptobenzothiazole crude product is obtained;
b. First, add the prepared composite solvent into the reaction kettle, turn on stirring and reflux, and adjust the stirring speed to 100 to 140 rpm; then slowly add the crude 2-mercaptobenzothiazole obtained in step a to the reaction kettle. in, raise the temperature to 35~70℃ for extraction and purification, and keep it at this temperature for 2.0h;
The composite solvent is any two or three of carbon disulfide, chlorinated alkanes and chlorinated olefins; the mass volume ratio added between the crude 2-mercaptobenzothiazole and the composite solvent is 1g: (3 ~7)mL;
c. After the heat preservation is completed, the temperature is lowered to 25°C, and then solid-liquid separation is performed. The separated solid is washed with the composite solvent described in step b. After washing, a wet product is obtained, and the wet product is dried. Finally, the refined vulcanization accelerator 2-mercaptobenzothiazole is obtained;
Main reference materials
[1] 2-Mercaptobenzothiazole
[2] Experimental study on ozone oxidation of 2-mercaptobenzothiazole, an ointment containing 2-mercaptobenzothiazole and its preparation method
[3] CN201210553866.62-Mercaptobenzothiazole manganese zinc and its preparation method and application
[4] CN201610584104.0 A preparation method of rubber vulcanization accelerator 2?mercaptobenzothiazole
[5] Preparation method of CN201510649388.22-mercaptobenzothiazole
