The preparation method of 2-isopropylthioxanthone

Abstract

The invention relates to a preparation method of 2-isopropyl thioxanthone. The preparation method comprises the following steps: chlorobenzonitrile is used as a raw material to react with 4-isopropylthiophenol to obtain an intermediate of 2-(4-isopropylthiophenol)cyanophenyl with good solubleness under an alkaline condition; the intermediate is subjected to cyclization reaction under the catalysis of sulphuric acid to obtain 2-isopropyl thioxanthone. The preparation method of 2-isopropyl thioxanthone is a technical method, and has the advantages that the raw material is cheap and highly available, the reaction temperature is low, the solubleness of the reaction intermediate is good, the reaction yield is high, the operation is simple and convenient, and the preparation method is suitable for industrial production.

Description

technical field [0001] The invention relates to a preparation method of a photoinitiator 2-isopropylthioxanthone, in particular to an intermediate with good solubility prepared from o-chlorobenzonitrile and 4-isopropylthiophenol as raw materials body, under the catalysis of sulfuric acid to generate 2-isopropylthioxanthone. Background technique [0002] 2-Isopropylthioxanthone is a high-efficiency free radical type II photoinitiator, suitable for photocurable materials composed of unsaturated polyester and acrylic monomers, and can be used for colorless or colored UV curable inks, wood Furniture, decorative coatings, adhesives, automotive metal parts coatings, optical fiber manufacturing, printed luminescent materials, etc. It acts as a sensitizer when used together with a cationic photoinitiator, and can also be used as a photosensitizer to enhance the curing performance of photoinitiator 907. In recent years, the research on thioxanthone photoinitiators tends to be in t...

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Problems solved by technology

The disadvantages of this method are: the amount of concentrated sulfuric acid used is large (more than 10 times the quality of dithiodiphenylformic acid), so a large amount of waste acid is produced; the yield of the product obtained is not high (the yield is only about 75%); The product is a mixture of 2-isopropylthioxanthone and 4-isopropylthioxanthone, which cannot be separated, thus reducing its photoinitiation efficiency

The method also has the disadvantages of the above method: use a large amount of excessive volatile, irritating, highly corrosive sulfur oxychloride; the product yield obtained is low (yield 69%); the product obtained is 2- Mixture of isopropylthioxanthone and 4-isopropylthioxanthone

[0016] The process of method 3 requires a very high reaction temperature of about 200°C, all of which pass through the intermediate 2-(4-isopropylthiophenolyl)benzoic acid. The inventors of the present invention have found that 2-(4-isopropylphenylthio) Phenyl)benzoic acid (or salt) has particularly poor solubility, and is slightly soluble or insoluble in many solvents at room temperature, which increases the difficulty of post-processing, or needs to be acidified at high temperature (about 90°C) to obtain 2-(4- isopropylthiophenolyl)benzoic acid solution (2-(4-isopropylthiophenolyl)benzoic acid is dissolved in some solvents at high temperature), and then separated at a higher temperature; or at room temperature The acidification reaction is carried out first, and the intermediate 2-(4-isopropylthiophenolyl)benzoic acid is precipitated in the acid water, and the next step reaction can only be carried out after suction filtration and drying, and the total yield of the two-step reaction is not ideal

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