by clicking the arrows at the side of the page, or by using the toolbar.
by clicking anywhere on the page.
by dragging the page around when zoomed in.
by clicking anywhere on the page when zoomed in.
web sites or send emails by clicking on hyperlinks.
Email this page to a friend
Search this issue
Index - jump to page or section
Archive - view past issues
FLEXO Magazine : September 2009
66 FLEXO SEPTEMBER 2009 www.flexography.org TECHNOLOGIES & TECHNIQUES TABLE 2. Packaging flexo (magenta) ink starting formulation (The Chemidex, Cybrary14) Ingredient Reg. Water-based Flexo Formulation (%) Half Luron Formulation (%) Full Luron Formulation (%) Pigment Dispersion 50.0 50.0 50.0 JONCRYL 77 23.0 11.5 - Luron binder - 11.5 23.0 JONCRYL 2153 10.0 10.0 10.0 JONCRYL 60 10.0 10.0 10.0 JONCRYL WAX 26 5.0 5.0 5.0 Surfactant (DF-75) 1.0 1.0 1.0 Antifoam 0.3 0.3 0.3 Water 7.0 7.0 7.0 TABLE 3. Solid contents of Regular, Half Luron and Full Luron inks. Ink Formulations Solid Contents (%) Regular water-based Flexo Ink 42.66 Half Luron water-based Ink 34.42 Full Luron water-based Ink 29.59 FLEXO PROOFING/PRINTING Ink formulations were screened on a laboratory K-proofer in flexo mode, and several of the best formulations were selected to be printed on a narrow web flexo press. A Comco Commander narrow web flexo press (Figure 2), equipped with chambered doctor blade inking system, 150lpi photo- polymer plate and medium (3M's SA 2300 MS) tape were employed. A banded ceramic anilox roll with three different screen rulings, 600lpi, 700lpi and 800lpi with 2.80, 2.5, and 2.01bcm respectively was used. A 150lpi photopolymer plate with tone steps, solids text and reverse text was used. Press speed was 100fpm. ANALYTICAL Ink viscosity was measured as efflux time on a No. 2 Zahn cup. The printability study in terms of optical density and CIE L*a*b* color coordinate measurements was executed, using an X-Rite 530 Spectrodensitometer. Specular gloss was measured using a Nova Gloss Meter with 60° geometry on solid colors, and calculated as an average of five measure- ments. Print mottle was studied by Verity IA software, and dot detail was measured by image analysis using ImageXpert. An end-use ink property, rub resistance was also investigated. The testing was done only for solids printed with 600lpi anilox on both CNB and SBS board substrates. One hundred strokes on a Sutherland rub tester were made on each sample using a 4lb weight. The optical density was measured before and after rubbing. Rub resistance was calculated as: Rub resistance= [Optical density after rub/ Optical density before rub] x 100 RESULTS AND DISCUSSION Initially, research began with the formulation of water- based inks from several bio-based materials, such as veg- etable protein products (VPP), zein protein, and potato starch. None of these materials gave feasible ink properties such as film formation, resolubility, and adhesion to the substrate, which are easily achievable by acrylic resins found in conven- tional water-based ink chemistry and are essential for flexo printing performance. In the second phase, we focused on a readily dissolved resin (Luron binder, BASF). Inks were formu- lated with Luron as a sole ink polymer and also in combina- tion with acrylic resins such as Joncryl 77, Joncryl 2153 and Joncryl 60. Inks were first proofed on a laboratory K-proofer in flexo mode, where ink is transferred from the printing plate to a plain stereo roller and then onto the substrate. Eight initial bio-based formulations were tested, and narrowed down to the three best ones, to be tested on the Comco Commander narrow web flexo press at Western Michigan University's printing pilot plant. Selected inks were not adjusted to the same viscosity when printing on the Comco Commander flexo press, and therefore it was not easy to compare them. For fair comparison, further investigation would be necessary to optimize performance of FIGURE 3 (A). Optical density of Regular, Half Luron and Full Luron magenta ink with different anilox line counts on CNB board substrate. FIGURE 3 (B). Optical density of Regular, Half Luron and Full Luron magenta ink with different anilox line counts on SBS board substrate.