Most vinyl caprolactam is used in the production of polycaprolactam. N-Vinyl-epsilon-caprolactam manufacturers said that about 90% of polycaprolactam is used in the production of synthetic fibers, namely polyhexanone, and 10% is used as plastics for manufacturing gears, bearings, pipes, medical equipment, electrical and insulating materials, etc. Coatings, plastics and a small amount of synthetic lysine. Mainly used to prepare caprolactam resin, fiber, artificial leather, etc. It is also used as a pharmaceutical raw material.
Preparation of caprolactam by N-Vinyl Caprolactam factory
1. Oxime method: Firstly, high-purity cyclohexanone and hydroxylamine sulfate are condensed at 80-110°C to form cyclohexanone oxime. Using fuming sulfuric acid as a catalyst, cyclohexanone oxime undergoes Beckman rearrangement reaction to produce crude caprolactam at 80-110°C. Crude caprolactam is obtained through extraction, distillation, crystallization and other processes to obtain high-purity caprolactam. Cyclohexanone is the raw material of the oxime method, and can be prepared by hydrogenation to produce cyclic alcohol and dehydrogenation. Or cyclohexane air oxidation produces cyclic alcohol and cyclohexanone, and the separated cyclic alcohol can also be produced by catalytic dehydrogenation. Hexanone
2. Toluene method: Toluene is oxidized to produce benzoic acid under the action of cobalt salt catalyst, and benzoic acid is hydrogenated on palladium carbon under the action of palladium catalyst on activated carbon to produce hexahydrobenzoic acid. In fuming sulfuric acid, hexahydrobenzoic acid reacts with nitrosyl sulfuric acid to produce caprolactam. The toluene method has a certain development prospect because of its rich toluene resources and low production cost.
3. Photonitrosation: Under the irradiation of a mercury lamp, cyclohexane reacts with nitrosyl chloride and is directly converted into cyclohexanone oxime hydrochloride. Cyclohexanone oxime hydrochloride exists in fuming sulfuric acid. It is converted to caprolactam by Beckman rearrangement.
4. Hydrogenation in the presence of a nickel catalyst to obtain cyclic alcohol, which is purified and dehydrogenated to obtain crude cyclohexanone. After purification, cyclohexanone reacts with hydroxylamine to obtain cyclohexanone oxime, which is then converted into caprolactam by Beckman reaction. The sulfuric acid in the reaction product is neutralized with ammonia to obtain the by-product ammonium sulfate. A series of chemical and physical treatments are performed on vinyl caprolactam to obtain pure caprolactam.
Vinyl monomers contain non-acrylate carbon-carbon double bonds. Vinyl monomers are typical monomers used in polymerization or copolymerization to prepare polymers, and are widely used in early light curing technology. Now it can generally be used in the fields of polymerizing monomers, crosslinking monomers, aromatic compounds, adhesives, coatings and other fields. The following are some of the main vinyl monomers.
As the first generation of UV-curable coatings, it is widely used in wood coatings. Low viscosity, strong dilution ability, but strong smell and slow curing speed. At present, St is rarely used in UV curing products.
NVP has low viscosity, strong dilution ability, high reactivity, cationic curing, low skin irritation, and can improve adhesion. It was once widely used, but was limited due to suspected carcinogenic effects. Since both NVP and its polymers are water-soluble, when the amount is large, the water resistance of the coating will be affected.
VA is also a monomer with high odor and volatility, with strong dilution ability. The use of VA will result in poor water resistance of the coating. In fact, VA is generally not used in light curing systems at present.
Vinyl Caprolactam (NVC)
NVC can be used in cationic and free radical curing systems, has excellent elasticity and adhesion, good tensile strength and excellent compatibility with acrylic oligomers.
NVI has low viscosity, strong dilution ability, high reactivity, cationic curing, and low skin irritation.