Page 2 of catalogue Pad printing inks of Teca-Print AG

INK USE INFORMATION
THE PAD PRINTING PROCESS The basic principle of the pad printing process is that the ink becomes tacky due to evaporation, first in the cliché before ink pick-up and then on the pad. This effect is used to transfer the ink from the cliché to the pad and then from the pad to the workpiece. 1. Pre-treatment of polyolefines To obtain an optimum ink adhesion on polyolefine, polyethylen (PE) and polypropylen (PP), materials must be pre-treated. The surface tension must be at least 38 Dyn = 0.038 N / m. The surface tension can be tested using the test pen (see accessories list on our website), which is filled with ink adjusted to exactly this value. If the surface tension is below 0.038 N / m, more intense pre-treatment is needed. The possibilities for pre-treatment are flaming, corona or primer / adhesion promoter MT. 2. Post-treatment of polyoxides Another group of materials that require extra measures for good ink adhesion are polyoxides, e.g. acetyl resin, delrin, Hostaform C etc. After the print the materials must be subjected to a thermal shock to achieve a chemical reaction of the ink with the material surface. The thermal shock should be approx. 350 °C and can be generated with a flaming or thermodiffusion (hot-air) unit. 3. Curing time 2-component inks usually require 2 – 6 days for chemical curing. After this time, an optimum adhesion, chemical resistance and abrasion resistance are achieved. However, with that in mind, further work with the printed parts (e.g. packaging or part assembly) is possible once the part is dry to the touch, as long as the image is not altered by a sharp or rough surface. See “ink and hardener properties” chart. 4. Chemical resistance 1-component inks never achieve the same chemical resistance as 2-component inks. 1-component inks are mainly used on materials which are easily etched by the mixed ink. In this case the substrate has no better chemical properties resistance than the printed 1-component ink itself. 5. Abrasion resistance When high abrasion resistance is required, 2-component inks should be used. 6. The viscosity process All inks must be adjusted to the correct viscosity. With 2-component inks, it is critical that ink and hardener are thoroughly mixed prior to adding thinner. If this is not observed, lumps of concentrated hardener remain resulting in partial curing of the ink, which has an adverse effect on the subsequent ink transfer and adhesion. The desired working viscosity is achieved through the addition of thinner in small amounts while constantly stirring. If thinner is added all at once or in large quantities, the ink Pigments are washed out of the resin. This is called ink pigment shock and the ink will be flaky and unusable. During printing, thinner evaporates and the ink thickens. Therefore, thinner must be replaced in regular intervals; once again in small quantities. As for the open ink well system, the thinner is mixed with the ink using a spatula after the doctor blade has been removed. Ink viscosity adjustment depends on the ink colour tone. Certain pigments cause thixotropic reactions. Both thixotropic and high-density inks can not be tested with the Viscospatula. If you reach good printing results with a particular ink, put some of it into a mixing cup, stir it well, and test the viscosity. Keep note of your test results for when you next use the same ink again. 7. Use of retarders Usually, ink viscosity should be only adjusted using thinner. If there are exceptional environmental influences, such as high room temperatures, drafts, prolonged cycle times among other things, retarder can be added in controlled quantities. We recommend to produce a quantity of your own custom retarder out of thinner and retarder, for example mixed 4:1, and use it to adjust ink viscosity. 8. Flow agent Flow agent is used to reduce the ink’s surface tension. Flow agent contains silicone and therefore only small quantities should be added, approx. 1 drop / 10 g ink. Remember that flow agent reduces ink adhesion! 9. Pot life 2-component ink systems cause a chemical reaction. Pot life is reduced by high room temperatures and a high relative air humidity (RAH).

MIXING SYSTEMS, RECIPES AND INK RANGE
Mixing Systems For all ink ranges, mixing systems are available. Recipes We have recipes for over 1000 colour shades available free of charge. All colour recipes are based on printing made on white backgrounds. Data can be ordered for HKS, RAL and PMS. Please ask for our recipe catalogue (or download the pdf from www.teca-print.com). For printing onto dark substrates, transparent objects and mirror areas, special shade recipes need to be formulated. For this we require the exact colour reference of the desired ink tone (PMS, HKS, RAL or a sample) and the colour shade of the substrate (preferably a sample). Ink range (HD = extra opaque inks) All ink types are available only in NT pigmentations and conform to EN 71, part 3, safety of toys, migration of certain elements.