Synthesis And Properties Of Low Migration Thioxanthpne Photoinitiator

The thioxanthone photoinitiator is an excellent photoinitiator with long absorption wavelength,strong light absorption ability and photobleaching effect,is widely used in photocurable coatings and ink formulations.The disadvantage is that such an initiator remains in the system during photopolymerization,because of its small molecular weight,it easily migrates to the surface of the article,causing odor and toxicity.At the same time,it also limits its application in food packaging materials.In recent years,low-migration photoinitiators have been rapidly developed,making the initiators safer,and greener.The purpose of this paper is to modify the thioxanthone to reduce the mobility of thioxanthone,reduce its toxicity and odor during use,increase its application range.The details are as follows.(1)In order to test the properties of the initiator,the absorbance,degradation rate and mobility of the initiator were tested by UV spectrophotometer,the light absorption ability was found to be higher than that of the commercial initiator thioxanthone(ITX).The extinction coefficient is about 1.2 times that of commercial ITX,the maximum absorption peak is around 385 nm,which indicates that the absorption peak does not shift greatly,and the light absorption capacity is improved.The photodegradation experiment of the initiator showed that the degradation rate was slightly slower than that of ITX.After 20 min photodegradation,the initiator remained 42%,ITX remained 25%,indicating that the quantum yield was lower than ITX.When the polymerization of TCM207 was initiated by using iodonium salt,the initiator was added to the system,the polymerization rate and the final conversion rate were greatly improved,indicating that the initiator has a good sensitizing effect on the iodonium salt.The UV absorption spectrum of the extract was tested and compared with the ITX initiator to find that its mobility is much lower than that of the commercial ITX initiator,indicating that the initiator will have a wider range of applications.(2)A thioxanthone photoinitiator(GTX)containing a methacrylate double bond was synthesized and its ability to initiate acrylate polymerization under different conditions was investigated by using Photo-DSC.It was found that the polymerization of ethoxyethoxyethyl acrylate(EOEOEA)was faster than that of ITX,the maximum polymerization rate was 75s earlier than that of ITX,the maximum polymerization rate was about twice that of the ITX initiator.At the same time,its light absorption capacity is better than that of ITX,and the maximum absorption peak absorbance is 1.22 times that of ITX initiator.The photodegradation rate is faster than that of ITX,indicating that the quantum yield is higher than the ITX initiator.The migration is much lower than ITX,and under the same conditions,the migration is only 0.6%of ITX.And the thermal stability of the GTX initiator is very good,the ITX initiator has evaporated completely at 300?,the main decomposition temperature of the GTX initiator is much higher than the ITX initiator at 400?,which indicates that the GTX initiator has better storage stability.It is also more stable in the system.It is an excellent low migration photoinitiator.(3)A series of macromolecular thioxanthone photoinitiators with different functionalities were synthesized.The UV absorption spectrum of these initiators was compared with the ITX initiator.The molar extinction coefficient was slightly lower than that of the ITX initiator,and the molar extinction coefficient decreased with the increase of the molecular weight,which indicated that the increase of the molecular weight produced the absorbance of the initiator.Influence,the light absorption capacity of the initiator will decrease slightly with the increase of molecular weight.Since the macromolecular initiator has a larger molecular weight,its decomposition temperature is 400?,and its thermal stability is much higher than that of the ITX initiator.When these macroinitiators initiate the polymerization of TMPTA monomers,the polymerization rate and final conversion rate are found to be the best in the trifunctional initiators compared with ITX,and the other initiators are not much different.The mobility of the initiator was tested and it was found that the mobility of the 2-functional initiator was 11%of ITX,the mobility of the 3-functional initiator was 3%of ITX,and the mobility of 4-functional initiator was 5%of ITX.The mobility of the initiator tends to decrease with increasing molecular weight,but it is also affected by the degree of polymerization of the system.The excessive molecular weight may have little effect on the mobility of the initiator.