Patent ID: 6140386
Filing Date: 2000-10-31
Classification: C09D

Abstract:
An aqueous unpigmented coating and printing ink composition substantially devoid of volatile organic solvents, having a viscosity of about 10 to 50 poises and useful for gravure and flexographic printing on hydrophobic smooth, non-porous plastic and metal substrates prepared by a process comprising:dispersing a low molecular weight hydrophobic ultra-violet curable vinyl functional oligomer in an aqueous medium in the presence of an oil-in-water emulsifier-coemulsifier combination in which the molar ratio of emulsifier to coemulsifier is about 4:1 to 1:4, and subjecting the resulting crude aqueous oligomer emulsion to the action of comminuting forces sufficient to reduce the average particle size of the oligomer below about 1 micron and below the critical particle diameter which in practice will never settle, and wherein said emulsifier comprises a nonionic, anionic, cationic, amphoteric or zwitterionic surfactant or any mixture thereof, said coemulsifier comprises a water insoluble hydrocarbon, hydrocarbyl alcohol, ester, ether, amine or halide containing an aliphatic hydrocarbyl moiety of at least 8 carbon atoms, or any mixture thereof, and said oligomer emulsion contains an effective amount of a photoinitiator; andadding about 1 to 10% by weight of the composition of a water soluble or water reducible polymeric thickener in an amount effective to provide the composition with a viscosity of about 10 to 50 poises and rheology properties to sustain a rapid decrease in viscosity with increasing rate of shear to a plateau value of about 2 to 5 poises at high shear rates of about 10.sup.3 to 10.sup.4 reciprocal seconds followed by a corresponding increase in viscosity upon cessation of the shear, such composition being capable of yielding clear cured films as low as about 2 microns in thickness.