BACKGROUND OF THE INVENTION Environmentally friendly technologies are poised for rapid growth as governmental regulations control the use of volatile organic compounds (VOC).

Radiation curable coatings technology, an emerging force for various coatings and adhesives applications, often involves the use of VOCs. The radiation sources used for these applications include UV, electron beam, microwave, and infrared.

Traditional coatings are based on either organic solvent-bome or water- borne systems in which the polymer to be coated is dispersed or dissolved in a medium that provides the necessary flow rheology for coatings formulations. After the coating is applied to the substrate, the medium is no longer needed. In practice, a heating chamber is used to evaporate water or organic solvent from the substrate.

In the case of organic solvent-bome systems, a recovery or an incineration unit is needed to address the environmental issues.

In the radiation curable process, monomer (of the resultant polymer which will serve as the coating) itself acts as the process medium. A typical radiation curable formulation mainly comprises oligomer resin and monomer. Examples of oligomer resins used are epoxy, epoxy-acrylate, and urethane-acrylate. Alkyl acrylate, di-or tri-functional acrylate monomers are also used as reactive diluents to provide the required viscosity and the network structure required for a finished

product. The radiation curable formulation generally contains an initiator, which is capable of being activated by the radiation source, generating free radicals. The formulation when cured will be converted into polymeric composition with no residual solvent or water to vaporize. Thus, radiation curing is energy efficient, cost-effective, provides faster cure, and thus affords higher productivity. Coatings can be formulated to 100% solids where minimum waste is generated, and heat sensitive substrates can be easily coated.

While radiation curing technology offers many advantages over traditional water-borne or solvent-borne coatings, one limitation is that the VOC tends to be the main environmental issue because of the monomer volatility. A second concern is that currently used monomers have unacceptable odor for many purposes.

Thus there is a need for monomers capable of being polymerized by radiation and yet to have low VOC and low odor.

SUMMARY OF THE INVENTION The present inventors have discovered that the use of vinyl neoester monomers in radiation curable coatings technology provides a low VOC medium with low odor. Typical vinyl neoester monomers have high boiling points, low viscosities, and low odor. This family of monomers, when mixed with a suitable initiator, can be cured by either ultraviolet (W) or electron beam radiation. These monomers can be used as a comonomer or as a reactive diluent in commonly used radiation curable formulations.

The vinyl neoester monomers according to the present inventon have the following general structure:

wherein Ri, R2, and R ? are independently selected from hydrocarbyl groups, which may be branched or straight chain, each having preferably from 1 to 10 carbon atoms. More preferably R, + R2 + Ru range from 3 to 23 carbon atoms, still more preferably from 5 to 23 carbon atoms, and even more preferably from 8 to 14 carbon atoms. A typical commercial product normally contains the blend of various isomers. For example, vinyl neodecanoate (EXXARR Neo-10) consists of isomers with average R, + R2 + R3 equal to eight carbon atoms. For vinyl neododecanoate (EXXARO Neo-12), the blend of isomers have an average R, + R2 + R3 equal to ten carbon atoms.

The use of vinyl neoesters provides for radiation curable formulation having very low VOCs and low odor. These and other objects, features, and advantages of the present invention will become apparent as reference is made to the following detailed description of the preferred embodiments, specific examples, and the attached claims.

DETAILED DESCRIPTION OF THE INVENTION Preferable vinyl neoesters include vinyl neodecanoate (available from ExxonMobil Chemical Company as EXXARX Neo-10) and vinyl neododecanoate available from ExxonMobil Chemical Company as EXXARS) Neo-12), have low viscosities, high boiling points in the range of 193-247 C, and very low odor. These types of monomers are therefore ideal for radiation curable applications that can replace alkyl acrylates. Since these monomers also have low viscosity, they can also function as reactive diluents for the high molecular weight oligomer resins.

In order to demonstrate that vinyl neoester monomers function as reactive diluents and can be cured by radiation, formulations shown in Table I were prepared. All of these formulations formed clear solutions and the Brookfield viscosities decreased with increasing amounts of EXXARX Neo-12. These formulations were coated over steel panels at a controlled wet film thickness of 3 mils. Panels were passed five times under a laboratory Fusions ut cure unit consisting of a medium pressure mercury lamp of 600 watt/square inch intensity, and at a belt speed at 50 RPM. All the coated films cured completely to form tack free coatings. Formulations up to 20% of Neo-12 gave very clear films.

In Table 1 below CyracureX UVR 6100 is a cycloaliphatic epoxide resin available from Union Carbide. UVI 6990 and UVI 6974 are mixed triarylsulfonium hexafluoro phosphate and antimonate salts respectively ; these photoinitiators are available from Union Carbide. FC430 is a coating additive for effective wetting and leveling, available from 3M. Brookfield Viscosities were determined at 25 C using Spindle # 18 at 0.6 RPM using Model DV-II.

Table 1 Fonnulations Ex. 1 Ex. 2 Ex. 3 Ex. 4 Cyracure"UVR 6 100, g 100 80 60 40 EXXAReD Neo-12, g O 20 40 60 UVI 6990, g 0. 75 0. 75 0. 75 0. 75 UVI 6974, g 0. 75 0. 75 0. 75 0. 75 Benzophenone,g 0. 75 0. 75 0. 75 0. 75 FC430,g 0. 5 0. 5 0. 5 0. 5 Brookfield Viscosity, cPs 145 90 2 45. 1 14. 0

In a similar experiment, formulations using EXXARS Neo-12 monomer as reactive diluent for epoxy acrylate resin were prepared according to the composition shown in Table 2. These formulations were draw down on cold rolled steel panels at 3 mils wet film thickness and then cured under LJV light, as above, in two passes. All formulations were completely cured to yield clear and smooth coatings.

In Table 2, below, Photomer 3016 is an epoxyacrylate resin from Henkel.

IrgacureW 651 (a, a-dimethoxy, a-phenyl acetophenone) is a photoinitiator from Ciba-Geigy. Benzophenone is a photoinitiator and triethanolamine is a photoactivator, both available from numerous sources. Even though formulations Ex. 5 to Ex. 9 formed 100% solids coatings formulations with necessary viscosity profiles required for coatings applications, toluene was added to all the formulations for comparative purposes and to make other formulations reach the desired flow. Brookfield Viscosites were determined at 25° C using Spindle #31 at 1.5 RPM using Model DV-II.

Table 2 Formulations Ex. 5 Ex. 6 Ex. 7 Ex. 8 Ex. 9 Photomer 3016 100 90 80 70 60 EXXARt) Neo-12 O 10 20 30 40 Irgacure 651 4 4 4 4 4 Benzophenone 2 2 2 2 2 Triethanolamine l I I l Toluene 10 10 10 10 Brookfield Viscosity, cPs 12600 2190 1800 1450 1010

One of ordinary skill in the art in possession of the present disclosure will recognize that the particular oligomer and monomer choices will depend on the final film properties desired. The vinyl neoester monomers suitable for this application cover a wide range of molecular weights with R1 + R2 + R3 from 5 to 23 carbon atoms. Examples of oligomer resins used are epoxy acrylate, urethane acrylate, polyester acrylate, epoxy, silicone epoxy, and epoxy silane. Although the above experiments were carried out under UV radiation, other radiation sources such as electron beam, microwave, and infrared can also be used for similar curing purposes.

Radiation curable formulations can be used in a wide range of end use coating operations such as in automotive, electronic, release, overprint, pre- finished wood, wood furniture, plastic substrates, hardwood flooring, fiber optics, nail polish, metal containers, coil metal, and the like.

The present inventors have shown that vinyl neoesters may be used in radiation curable applications. Preferred embodiments include: A radiation curable formulation comprising a radiation-curable monomer or oligomer resin and a comonomer or reactive diluent having the vinyl neoester structure shown previously, preferably wherein Ri, R2, and RR are independently selected from Cl to C 10 hydrocarbyl groups and other preferred and more preferred limitations to these substituents as described above, particularly wherein Rl + Ruz + R3 ranges from 3 to 23 carbon atoms ; and most preferably such formulations wherein the comonomer or reactive diluent is selected from vinyl neodecanoate, vinyl neododecanoate, and mixtures thereof, such formulations wherein the vinyl neoester is a comonomer with one or more radiation curable monomers, most preferably alkyl acrylates; or wherein the vinyl neoester is a reactive diluent with a radiation curable oligomer resin, particularly oligomer resins selected from epoxy acrylate, urethane acrylate, polyester acrylate, epoxy, silicone epoxy, epoxy silane, and mixtures thereof.

In another embodiment, the present invention concerns articles coated with such a radiation cureable coating, e. g., an article including a substrate having a

coating on at least one surface, the coating comprising a polymer formed by curing, using a radiation source, a radiation curable monomer, particularly alkyl acrylates, and/or oligomer resin (preferably those specifically mentioned above) in the presence of a vinyl neoester as comonomer or reactive diluent. Particularly preferred is such an article where the polymer coating is formed by curing a vinyl neoester and an oligomer resin selected from epoxy acrylate, urethane acrylate, polyester acrylate, epoxy, silicon epoxy, epoxy silane, and mixtures thereof.

Still another preferred embodiment is a method of providing a coating using radiation curable formulation, the improvement comprising using a vinyl neoester as comonomer with a radiation curable monomer such as alkyl acrylates or reactive diluent with radiation curable oligomer resins, such as epoxy acrylate, urethane acrylate, polyester acrylate, epoxy, silicon epoxy, epoxy silane, and mixtures thereof.