The Synthesis Of Photoinitiators Applied In Pigmented UV Curing System--That Is The Synthesis Of Acylphosphine Oxide Photoinitiator

UV curing coating has been called environment -friendly coating because of its characteristics of ecology, high efficiency, economy for energy and suitable for industrial applications.The formulation of UV coating is made up of suitable photopolymerizable oligomers, suitable photopolymerizable diluting monomers, photoinitiators and other additives and addition agents such as leveling agents, fillers and stabilizers against thermal or photochemical degradation. Appropriate photoinitiators are one of the key roles for the success of this technology.It has appeared many kinds of photoinitiators applied in UV coatings available on the market, but few can be applied in UV coatings containing pigments. The curing of pigmented systems by UV or visible light has long been a major challenge.Because of its unique absorption wavelength, the absorption of acylphosphine oxides extends well into the visible part of spectrum, these compounds can even absorb sufficient light in the presence of white pigments and act as efficient photoinitiators in such formulations. An additional advantage is the disappearance of the yellow hue upon curing, a behavior not exhibited by other photoinitiators which undergo α-cleavage. Therefore, acylphosphine oxides are the most suitable photoinitiators for white lacquer applications.In this paper, two new classes of acylphosphine oxide photoinitiators(DBAPO-1 and DBAPO-2) were designed and synthesized. To find an appropriate method to synthesize bisacylphosphine oxide compounds, we took the synthesis of BAPO as an example because its raw materials is available. Their structures were characterized by 1HNMR and 31PNMR spectrum. Because some raw materials is not available on the market and few related documents are reported, we also spent much time and energy to prepare them. The main conclusions are as follows:①Synthesis of BAPO by two processes. At the same time, the raw materials in each process were synthesized and studied. The best method was found to prepare phenylphosphine, that is LiAlH4- reduced method. In addition, synthesizing bisacylphosphine oxide compounds in one pot via the intermediate phosphorus-lithium salt is the optimum method.②4,4`-biphenylenebis(dichlorophosphine) was prepared by three methods, that is one pot method, digrignard method, organic zinc agent method. Every method was all studied specifically. By analysis, the best method was found and was studied in detail. The corresponding conditional experiment was carried out.③The desired compounds (DBAPO-1) and(DBAPO-2)were synthesized and suitable separation and purification method was found. ④The initiating activities of photoinitiators synthesized in this paper and commercial monoacylphosphine oxide photoinitiator were determined. It showed that the more the photoinitiators contain acyl-phosphine oxide unit, the higher the initiating activity is. This article has five sections: IntroductionExperimentsResults and discussionConclusions and suggestionsReferences...