DEVELOPMENT OF NEW PHOTOINITIATORS

清泥

INTRODUCTION
The most commonly used photoinitiators were developed more than 20 years ago, but they are still the bases of the energy curing technology for their performances, low costs and flexibility in the formulations.
However the development of the technology needs more and more demanding characteristics to satisfy the requirements of new applications.
One of the critical issues in energy curing is the undesirable odour and release of photoinitiator or of its photodecomosition products from the cured formulation. There is therefore a demand for products with limited release of the parent compound or of its photodecomposition products from the cured formulations.
This is important in general in UV curable formulations such as conventional coatings and inks, but in particular in development of applications for food packaging or child use.
Of course this hold true both for radical and cationic energy curing.
In radical systems the conventional photoinitiators suffer the problem of their low molecular weight that is responsible for their migration from the cured formulation and for the release of volatile, and in some cases odorous, photodecomposition products. This behaviour is more important for Type I compounds which generate radicals through cleavage mechanisms. On the contrary Type II photoinitiators have a more favourable profile because the ketyl radical generated by hydrogen transfer either is re-oxidised back to ketone or it gives rise to recombination products with formation of higher molecular weight derivatives with a lower volatility than parent compounds.
In cationic systems the conventional sulfonium salt gives rise both to odorous photodecomposition products of diphenylsulfide type and to volatile toxic derivatives 1.
For these reasons we developed new classes of radical and cationic photoinitiators which combine fast cure with the absence of volatile, odorous, toxic by-products when the active species are generated during the curing process.

Hans

这类新光引发剂有特点，固化反应没有光分解产物迁移问题。不错不错。