Synthesis And Application Of Sulfur Compounds In Ultraviolet Photoinitiators

Ultraviolet(UV)curing technology is a new technology with high efficiency,low consumption and environmental protection.It is widely used in coatings,inks,photoresists and other fields.Among them,UV-curable coatings are one of the longest research processes and mature technologies.As a key component of the system,photoinitiators determine the system whether can form a film and the performance of the film after film formation.Photoinitiators can be classified into two types,free radicals and cationics,depending on the active intermediates.In this paper,thioester compounds as free radical photoinitiators and triarylsulfonium salts as cationic photoinitiators were synthesized in different ways.(1)The first part: synthesis of the thioesters.Thiol compounds containing a benzoheterocyclic ring were synthesized by a nucleophilic substitution reaction with 2-mercaptobenzoxazole compounds and acid chloride as raw materials.The structure was characterized by 1H NMR,13 C NMR and HRMS techniques.The optimal conditions for the reaction were determined by discussion: the temperature was 60°C,the molar ratio of thiol and acid chloride was 1: 2,THF as solvent,Et3 N as base,and the yield can reach 75% after refluxing for 10 h.Subsequently,the ultraviolet absorption spectrum of the product 3 was measured with a molar concentration of 1×10-5 mol ? L of DMSO as solvent.The results showed that the absorption wavelength of the product 3 was significantly red-shifted,and the ? max of the compound 3f was close to 325 nm.Finally,the product 3 was used as a free radical photoinitiator,and compared with the commercially available photoinitiator 1-hydroxy-cyclohexyl benzophenone(Irgacure 184)and benzophenone(BP),the UV-cured coating film was tested.The results of film forming properties such as hardness and adhesion of the products 3c,3d,3e,3f,and 3g were all good.(2)The second part: synthesis of the sulfonium salts.The triarylsulfonium salts are synthesized by reacting a diaryl sulfide with a high iodide salt.First,the product 8 was synthesized under the solventless condition with Cu(OAc)2 as a catalyst,and the yield was 82%.Then the optimal reaction conditions of the products 10 and 12 were investigated: 1,1,2,2-tetrachloroethane as solvent,Cu I and Cu as catalysts,and reacting at 110°C for 3 h,the yield can reach 76%.The structures of the materials were characterized by 1H NMR,13 C NMR and HRMS techniques.The UV optical properties of the products were determined and the UV absorption intensity of the products was increased.The absorption bands of 8a and 10 a were observed at 316 nm and 294 nm,respectively.Finally,the products 8,10,and 12 were subjected to UV-curing coating film experiments as cationic photoinitiators.The results showed that most of the films were smooth and highly transparent,and the hardness and adhesion of the materials 12 a and 12 b were good.