Study On The Synthesis Of New UV Photoinitiator

With the development of UV-curing system, photoinitiator plays a very important role in the curing system, although it accounts for a very small proportion. This paper explored the new photoinitiators, such as the free radical photoinitiator, triaryl sulfonium salt, free radicals, cationic hybrid photoinitiator, etc, then studied the performance of products with initiator groups. On the basis of analyzing and summarizing a large number of literatures, this paper aimed at doing the following three aspectsFirstly, the benzoyl-based compounds were readily prepared by the reaction of benzoyl chloride and a nucleophilic reagent under the alkaline conditions, or by the Friedel-Crafts acylation reaction of benzoyl chloride with an aromatic compound. Otherwise, the enonecompounds were synthesised by acrylic acid chloride and a nucleophilic reagent or by the aldol condensation reaction. The reaction time, solvent, temperature, reactant molar ratio in the reaction of benzoyl chloride and benzimidazole were optimized. The suitable experimental conditions are in THF solvent with the reaction time of12h and n(nucleophile):n(halogensubstituting the compound)=1:2. The target products and some intermediates were characterizated by ultraviolet (UV) spectroscopy, nuclear magnetic resonance hydrogen (1HNMR) and carbon (13CNMR) spectrum etc. By testing performance as free radical photoinitiator, Six compounds,2-(p-toly lthio)-1-pheny lethanone(1),(benzoimidazol-1-yl)(pheny1) methanone(4a),(benzothiophen-yl)(phenyl)methanone(5a),(5-methyl-3-phenyl-benzothiophen-2-yl)(phenyl) methanone(5b),(4-chloro-phenyl)(phenyl)methanone(6),(4-(benzoyl-)-4’-methyl-diphenyl sulfide(7b) were screened out. Among of the above six compounds,5b has better reactivity, surface curing ability and solubility in the UV-curing system.Secondly, a series of S-aryl sulfonium salts were sythesised by diaryliodonium trifluoromethanesulfonate and benzothiophene or benzothiazole compounds and their derivatives with copper catalyst. The reaction time, temperature, catalyst content in the reaction of benzo-thiophene and adiphenyliodine trifluoromethanesulfonate were discussed, the appropriate experimental conditions were confirmed: n(benzofive-memberedheterocyclic):n(diaryl iodonium salt):n (Cu(OAc)2) is1:1.3:0.1, the reaction time is1h, the reaction temperature is130℃. The target products were characterizated by ultraviolet (UV) spectroscopy, nuclear magnetic resonance hydrogen (1HNMR) and carbon (13CNMR) spectrum, etc. By testing performance as triaryl sulfonium salt photoinitiators, Six compounds were screened out as follows: Diphenylene iodonium trifluoromethane sulfonate(14a),4,4--dimethyl iodonium trifluoromethanesulfonate(14e), S-phenyl benzothienyl salt(15a), S-(4-methyl) phenyl-benzothiophen salt(15e),S-phenyl-(5-methyl-phenyl)-benzothiophene salt(16a),S-(4-methyl) phenyl-(5-methyl-phenyl)-benzothiophene salt(16e). The coating performance results need further discussion.Thirdly, the hybrid compounds containing radicals and cationic were synthesised by diaryliodonium tri-fluoromethanesulfonate and sulfide sulfur compounds with the synthesis of chlorinated diphenyl-ketone and thiocresol under the catalysis of copper. The synthesis methods and reactant molar ratio in the reaction of the above sulfide sulfur and diphenyliodine trifluoromethane-sulfonate were discussed, the appropriate experimental conditions were confirmed. The target products were characterizated by ultraviolet (UV) spectroscopy, nuclear magnetic resonance hydrogen (1HNMR) and carbon (13CNMR) spectrum etc. By testing performance as free radicals-cationic hybrid photoinitiators, two compounds were screened out as follows:(4-benzophenoneyl)-p-tolyl phenyl sulfonium salt(20a),(4-benzophenoneyl)-p-tolyl sulfonium salt(20b). The coating performance was different on the different materials.