Resin energy-curable

In approaching the development of an energy-curable resin system, we have attempted to solve a number of problems with which the ultimate user of these types of materials is faced, namely ... 

Oxygen inhibition of cure which exists in many energy-curable resins necessitating the use of inert blanketing. 

Much has already been published concerning the composition of energy-curable resin systems for use In coatings and Inks, and the basic approach to the development of such vehicles Is well known (Refs. 1, 2, 3). A typical formulation contains an oligomer, which may or may not contain reactive functional groups (e.g., double bonds), a cross-linking agent, a reactive diluent (for viscosity control), and a photosensitizer or photolnltlator. 

The Uvimers comprise a useful new group of energy-curable resins suitable for a wide variety of applications. Special features which should be of interest to potential users include ... 

The chemistry involved in LfV-curable resin systems has been extensively investigated and thoroughly surveyed [88-94]. LfV-radiation polymerization, is in principle, completely analogous to the conventional addition polymerization. A photoinitiator is used in UV polymerization. Its function is the same as the free-radical initiator. A conventional initiator possesses a thermally labile bond which is cleaved to form free-radical species, but the photoinitiator has a bond which breaks upon absorption of radiant energy. Benzoin ethers, benzyldialkyl ketals, benzophenone, and acetophenone derivatives are the important LfV-photoinitiators [95-99]. 

Caul, Lawrence D. and Forsyth, Paul F. (to Caiboran-dum Abrasives), Resin Systems for High Energy Electron Curable Resin Coated Webs, U.S. Patent 4,588,419, May 13, 1986. 

Some polysiloxanes are curable with lead monoxide, with a consequent reduction in both curing time and temperature. High-frequency electrical energy vulcanizes in one case at least. Zirconium naphthenate imparts improved resistance to high temperatures. Barium salts are said to prevent blooming. Sulfur dichloride is also used. Some resins are solidified by pressure vulcanization, using di-f-butyl peroxide. Improvements are to be found in lower condensation temperatures and shorter times of treatment... 

The primary resins used in this market are the radiation-curable epoxy acrylates, accounting for 60% of the resins used. A small amoimt of cycloaliphatic epoxies are also used in UV-curable inks and resists. Phenol and cresol epoxy no-volacs, and bisphenol A based epoxies are used in thermally cured formulations. The epoxy novolacs are used where higher heat resistance is needed such as in solder masks. Both free-radical and cationic-curable UV inks and colored base coats have grown rapidly because of the needs for higher line speeds, faster cleanup or line turnaround, less energy consumption, less capital for a new hne, and fewer emissions. 

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