Light curable coatings

The extension of blsmaleimlde photoaddltlon to polystyrene crossllnklng represents a practical application of photopoly-merlzatlon with potential in the area of light curable coatings. Initial crossllnklng experiments have been concerned with the effect of both aliphatic and aromatic blsmaleimldes on gelation times of polystyrene solutions. A commercial atactic polystyrene with number average molecular weight of 270,000 was used for this work. 

Photosensitized Epoxides as a Basis for Light-Curable Coatings... 

Table XII. Changes in Weight of Light Curable Epoxide Coatings During Various Stages of Processing PERCENT CHANGE IN WEIGHT ...

Onium salts have many of the characteristics required of photosensitive initiators for light-curable coatings. Aryl-diazonium, aryliodonium and arylsulfonium salts all initiate rapid cure. Storage life of photosensitized formulations ranges from a few hours to more than six months, depending upon structure of the photoinitiator, composition of the coating and storage conditions. 

The combination of arylonium salts with selected epoxy resins provides the essentials for a viable system of light-curable coatings and should invite further investigation. 

Watt, W. R., "Light Curable Coatings from Photosensitized Epoxides", 14th Annual Coatings Symposium, North Dakota State University. (1974)... 

Wire coatings are often based on polyolefins or on poly(vinyl chloride). Many other electron-beam curable materials for surface coatings, however, are veiy similar in composition to the ultraviolet-light curable ones. No photoinitiators, however, are needed. 

Discuss typical ultraviolet-light curable coating compositions by free-radical and by cationic mechanisms. 

There is some interest in water dispersible light curable coatings and binders. Thus, Heischkel et al, reported preparation of a water based radiation curable polyurethane acrylate coating. Some of the water soluble or dispersible monomers are diethylaminoethyl acrylate, butanediol monoacrylate, vinyl caparolactam, and propylene glycol monoacrylate. 

The basic components of light curable coating formulations are presented in Table 3.2. 

Many aspects of the polymerization reactions of light curable coatings, however, are more complex. A number of attempts were made to describe the kinetic pictures of photocuring. Some of these are presented below. 

Some Examples of Light Curable Coating Compositions... 

Yasuda and Tano describe a Japanese patent for light curable compositions that are useful as coating materials. These consist of (A) 15-70% of a polyol, polyglycidyl ether,... 

Wang and Cheng reported preparation of ultraviolet light-curable resin for coating optical fibers. It consists of polydimethylsiloxane epoxy acrylate and polyethylene glycol urethane acrylate. To this were added in different proportions trimethylolpropane triacrylate to modify the properties of blends. After addition of a photoinitiator the choice formulation photo cured in 5 seconds. 

Tetrahydrofurfuryl alcohol (THFA) is used to prepare tetrahydrofurfuryl acrylate and methacrylate in transesterification reactions with lower acrylate esters. These reactive monomers are used in the formulation of ultraviolet light-curable adhesives, coating, paints, and printing inks. THFA is an effective coalescing solvent for latex paints and is used in epoxy resin formulations. The oleic acid ester of THFA is used as a plasticizer for vinyl resin products. The high solvency of tetrahydrofurfuryl alcohol for dyes permits higher dye... 

Dowling, J.P., Ultra-violet light curable adhesives, in Chemistry and Technology of UV and EB formulation for Coatings, Inks and Paints, Vol. I, P.K.T. Oldring (Ed.) (pp. 1-33), SITA Technology, London, 1997. 

Block copolymer latexes Electrodeposition resins Light-curable compositions Synthetic drying oils Corrosion-resistant electrodeposition coatings... 

DPC is an adaptation of DSC which involves the use of an ultraviolet or visible light source to study the behaviour or photoreactive systems and has specific application to light curable coatings, films, inks, adhesives and dental materials. In particular, it can be used to study the effect of different initiator systems on the cure behaviour of these products, and to investigate the influence that parameters such as the other additives in the products and the cure conditions have on the cure rate etc. The technique is therefore particularly useful for studying the curing behaviour of coatings and inks. 

The majority of the commercial radiation-curable coating systems (high energy electron and light-cured coating systems) are clear or contain siflca... 

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