Development Of UV Curable Ink Used On Plastic Bottle Cap

UV curable ink is a completely new type of ink to meet the low carbon environmentalpolicy, with the advantages of fast-drying, small environmental pollution as well as high printqualities, and thus it was subjected to the attention of domestic and international printing inkindustries. PE cap is one of the most common printing substrates in the food packagingindustry, because of its unique surface structure, good adhesion on its surface is alwaysdifficult to obtain for common ink. Meanwhile, with the further strengthening of the nationalenvironmental policy, the current PE caps printing must be soaked in peracetic acid(Concentration for1800ppm) at90°C for4hours sterilization processing. However, seriousdeinking phenomenon will occur after the sterilization process for the current UV inks on themarket, which severely restricted the application of UV ink printing on the PE caps. Thus,solving the problem about low resistance to peracetic acid for PE caps printing ink is adifficulty and a key point to broaden the range of UV ink applications.Raw materials for UV-curable inks were screened and optimized after a number ofcompounded and comparative experiments in this study, the influence of differentprepolymers, monomers and photoinitiators on the UV ink properties were studied.The formulation of UV ink used on PE caps was designed. UV ink with peracetic acidresistance was developed by physical grinding method. The optimum formulation of the UVcuring ink was as follow: PUA (bifunctional urethane acrylate) and PEA (tetrafunctionalpolyester acrylate) were prepolymers, each accounted for22.5%(mass fraction), TMPTA(trimethylolpropane triacrylate) and NPGDA (neopentyl glycol acrylates) were reactivemonomers, each accounted for13.5%(mass fraction), ITX and907were compounded asphotoinitiator at the content of each3%(mass fraction), carbon soot is18%, defoamer is4%.Long-chain epoxy acrylate prepolymer was synthetized. The structure of the product wascharacterized by infrared spectroscopy. The prepolymer was added to the ink formulation, theink performance was tested, and the desired results were obtained. The influence oftemperature, reaction time and catalyst type and amount on the synthesis of the prepolymerswere studied, the optimal synthesis conditions were as follows: the reaction temperature wascontrolled at70°C-75°C in the first step, the reaction time was3.0h, using ethyl acetate as thesolvent, adding0.8%-1.0%(wt) N, N-dimethyl benzyl amine as the catalyst; the reactiontemperature was controlled at80°C-95°C in the second step, the reaction time was3.0h, using0.1%(mass fraction)2-uncle butyl hydroquinone as polymerization inhibitor, adding1.0%(mass fraction) of tetraethyl ammonium bromide as a catalyst; the reaction temperature was controlled to about100°C in the third step, the reaction time was2.5h, adding0.1%(massfraction)2-uncle butyl hydroquinone as polymerization inhibitor, using1.1%(mass fraction)tetraethyl ammonium bromide as the catalyst.