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Improve Adhesion of Cationic UV Coatings Containing Cyclic Diols to Metal and Plastic Substrates

IP.com Disclosure Number: IPCOM000022248D
Publication Date: 2004-Mar-02
Document File: 7 page(s) / 120K

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Abstract

A benefit of using cationic UV coatings is good adhesion to a variety of substrates. Although cationic UV coatings generally have good adhesion there is a need to improve their adhesion to some difficult substrates. We found that adhesion of cationic UV coatings containing cycloaliphatic epoxy resins to metals and plastics was greatly improved by including tricyclodecanedimethanol (TCDM) (CASRN 26896-48-0 and 26160-83-8) or cyclohexanedimethanol (CHDM) (CASRN 3971-28-6 and 105-08-5) in the coating. Cationic UV cure coatings containing TCDM or CHDM had improved adhesion compared to coatings containing a variety of other polyols to a variety of metal and plastic substrates. The improved adhesion was demonstrated using two cycloaliphatic epoxides (CYRACURE UVR-6110 and ERLX-4360). Although both TCDM and CHDM showed improved adhesion, the coatings containing TCDM had better adhesion using difficult substrates like tin-free steel (TFS). It was also demonstrated that cationic UV cure coatings containing ERLX-4360 had improved adhesion compared to ones containing UVR-6110. This was true for coatings containing several polyols and no polyol and using several metal and plastic substrates.

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Improve Adhesion of Cationic UV Coatings Containing Cyclic Diols to Metal and Plastic Substrates

Abstract

A benefit of using cationic UV coatings is good adhesion to a variety of substrates. Although cationic UV coatings generally have good adhesion there is a need to improve their adhesion to some difficult substrates. We found that adhesion of cationic UV coatings containing cycloaliphatic epoxy resins to metals and plastics was greatly improved by including tricyclodecanedimethanol (TCDM) (CASRN 26896-48-0 and 26160-83-8) or cyclohexanedimethanol (CHDM) (CASRN 3971-28-6 and 105-08-5) in the coating. Cationic UV cure coatings containing TCDM or CHDM had improved adhesion compared to coatings containing a variety of other polyols to a variety of metal and plastic substrates. The improved adhesion was demonstrated using two cycloaliphatic epoxides (CYRACURE UVR-6110 and ERLX-4360). Although both TCDM and CHDM showed improved adhesion, the coatings containing TCDM had better adhesion using difficult substrates like tin-free steel (TFS). It was also demonstrated that cationic UV cure coatings containing ERLX-4360 had improved adhesion compared to ones containing UVR-6110. This was true for coatings containing several polyols and no polyol and using several metal and plastic substrates.

Introduction

Cationic UV cure coatings, inks, and adhesives containing cycloaliphatic epoxides are used commercially to coat, decorate, and laminate a variety of metal, plastic, film, and foil objects. Some benefits of using cationic UV compositions included adhesion and flexibility. The adhesion benefit of cationic UV coatings is often attributed to minimal volume shrinkage during cure. Cationic UV coatings typically shrink less than about 5% by volume during cure. Although cationic UV coatings and inks generally adhere well to a variety of substrates (so-called "universal" adhesion), there is a need to improve their adhesion to some difficult substrates.

The adhesion of cationic coatings to some difficult substrates can frequently be improved by thermal treating the coated object after UV cure. Tin-free steel (TFS) is a tin mill product used to make food can ends. Cationic UV coatings are used to coat and protect the outside surfaces of some TFS food can ends. As an example, UV coatings generally have poor adhesion to TFS after UV cure and the adhesion of the cationic UV coatings to TFS can be greatly improved by thermal treating the coated TFS after UV curing.

A monolayer of an organic lubricant is applied to TFS surfaces during the manufacture of TFS coils used to make can ends. The purpose of the lubricant is to promote improved handling of the TFS and to prevent scratching its surface. The lubricant applied to TFS made in the U.S. is typically BSO, which is a mixture containing butyl stearate and butyl palmitate. Experts in the field believe the presence of the lubricant on the TFS interferes with UV coating adhesion.

Coils of TFS are cut into sheets and st...