PFFC - October 2008 - (Page 51)

UV/EB INKS the ink develops physical properties (a.k.a. scratch resistance) more The white ink layer was removed (Figure 3) to isolate the UV/EB quickly. The slowest curing materials are lower Tg materials. ink components for two reasons. First, the white ink adds another Fast cure speed is nice but means nothing unless substrate layer where failure can occur and makes it harder to control what is adhesion is very good. Adhesion was tested two different ways: happening between the two layers of ink. Second, making a white First using 610-tape adhesion, and second with ice crinkle ink does not allow for the same amount of variance in oligomer type. adhesion involving prints being submerged in ice water for 15 The chosen substrate and laminate was 2-mil Melinex 813, min, removed, and checked for adhesion by scratching the ink. from DuPont Teijin Films, a PET with a water-based coating The goal of this initial project was to understand the interacto improve adhesion. It is commonly used in laminate structions between UV flexo ink oligomers and UV laminating adhetures for food packaging. The UV laminating adhesive is com- sive used to assemble the structure. Current UV laminating admercially available and designed for PET-to-PET laminations. hesives, like all UV/EB systems, contain some acrylate monomer All inks used were cyan UV flexo inks. All of the ink prints were in the liquid system. In a UV laminating adhesive, the monomers made using a HarperScientific Phantom hand proofer equipped tend to be low Tg, low molecular weight, and adhesion-promoting with a 600 line/in. (2.41 bcm) anilox roll. The standard UV flexo monomers, giving the adhesive its desired cured properties. In sysformulation in Table I was used. tems for plastics, the monomers promote adhesion by “biting” into UV flexo inks were printed onto the PET, then cured at 100 the substrate. Upon cure, an interpenetrating network (IPN) ties fpm using a Fusion 600 W/in. H Table I. Cyan UV Flexo Formulation lamp at 70% power. This gave an integrated energy of 76 mJ/cm2 on an Used for the Evaluations International Light IL390 radiometer. Component % Purpose or Structure To test for cure speed of the inks, Oligomer or monomer 35.0 Component to be evaluated the belt speed of the curing unit was adjusted to decrease the energy delivCiba Irgalite Blue GLVO 20.0 Cyan pigment ered to the ink. The UV laminating CD562 11.0 Acrylate ester adhesive was drawn down and nipped SR492 10.5 Propoxylated Trimethylolpropane Triacrylate on top of the printed and cured UV Polyester Acrylate 10.0 Pigment wetting flexo ink. The adhesive cured at 50 fpm using a Fusion 600 W/in. D Ciba Irgacure 369 3.5 2-Benzyl-2-(dimethylamino)-1-[4-(4-morpholinyl)phenyl]-1-butanone lamp at 100% power for an inteLamberti Esacure KS300 3.0 Alpha-hydroxycyclohexyl-phenyl ketone grated energy of 625 mJ/cm2 on an Lamberti Esacure TZT 1.0 Blend of Methylbenzophenone and Trimethylbenzophenone International Light IL390 radiometer. Fifteen different monomers and Lamberti Esacure ITX 0.5 Isopropylthioxanthone oligomers were evaluated for various Lubrizol Solsperse 39000 5.0 Hyperdispersant properties relating to the laminaByk-UV3510 0.5 Silicone wetting aid tion. They were chosen based on chemistry type and different physiTable II. List of Different Monomers and cal properties (Table II). The inks were evaluated for liqOligomers that Were Tested uid ink properties. All of the inks Component showed no particles on a Hegman Designation in Acrylate grind gauge. Once milled, each Original Paper Chemistry Unique Attribute Functionality ink’s rheology was measured using SR833S Monomer 1 Diacrylate Monomer High Tg, hard 2 a Brookfield DV-III rheometer equipped with a CP42 spindle. SR492 Monomer 2 Triacrylate Monomer Cross-link density 3 As expected, ink viscosity varCN131B Oligomer 1 Epoxy Acrylate Flexible 1 ies greatly as different monomers CN120Z Oligomer 2 Epoxy Acrylate High Tg, hard 2 and oligomers are added. The inks based on CN120Z, CNUVE151, CNUVE151 Oligomer 3 Epoxy Acrylate High Tg, hard 2 CN9893, CN710, and CN820 were CN991 Oligomer 4 Urethane Acrylate Flexible 2 very viscous and difficult to achieve CN994 Oligomer 5 Urethane Acrylate Hard 2 consistent prints. Still, some of the Oligomer 6 Urethane Acrylate Very flexible 2 very viscous oligomers studied could CN9893 not be used at high percentages in a CN2262 Oligomer 7 Polyester Acrylate Abrasion resistant 4 commercial UV flexo ink. PRO6196 Oligomer 8 Polyester Acrylate Tough 4 Cure speed among the UV flexo inks CN293 Oligomer 9 Polyester Acrylate Hard 6 depends on three factors: the homopolymer Tg (glass transition temperaCN386US Oligomer 10 Acrylated Amine Surface cure 2 ture), the acrylate functionality, and the CN549 Oligomer 11 Modified Polyether Acrylate Surface cure 4 abstractable hydrogens of the different CN710 Oligomer 12 Polyester Acrylate Adhesion, flexibility 1 monomers or oligomers. The faster the CN820 Oligomer 13 Acrylic Oligomer Adhesion, hard 2 cure speed, the higher the Tg. Hence, WWW.PFFC-ONLINE.COM OCTOBER 2008 | 51 Experimental http://www.pffc-online.com

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PFFC - October 2008 Contents First Glance Calendar of Events From the Editor Web Lines Process Management News Clips Narrow Web & Label Reporter Narrow Web & Label What's New Products Shrink Sleeves Carton & Box Reporter Carton & Box What's New Products Cover Story - Custom Coating Core Shafts Show Preview Flexo Printing Film Converting Static Control UV/EB Inks What's New Products Trade Show in Print Services Directory Classified Marketplace Equipment Buyers & Sellers Advertisers Index Experience Speaks

PFFC - October 2008

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