The Basics of Flexo Ink Chemistries from qocsuing's blog

The Basics of Flexo Ink Chemistries

Ink—that magical, mystical fluid—delights designers, annoys accountants, inspires inkies and P-O’s press operators! We use it in flexo presses every day, all day, across the country and around the world, yet so many people don’t understand how ink really works, what it can and can’t do, and how to use it best to maximize productivity in the pressroom.Get more news about flexo ink factory,you can vist our website!

Last year, FTA asked me to do an FTA Member Webinar on the basics of flexographic inks. We had good attendance, a lot of questions and a lot of follow-up communications. In this article, I’ll try to recap the information that was conveyed in the webinar, along with a little bit of further detail about some of the topics that were of most interest to folks. I’ll cover the basics of all three common flexographic ink chemistries—water based, solvent based and energy curable. We’ll explore the basic ingredients used in each chemistry, how they work in each type of ink and how they perform their functions on press. You’ll learn how ink manufacturers make these inks in both large bulk form and in small batches. Also covered will be typical quality control (QC) checks used, and the tools and equipment required to perform those checks, both in the QC lab and in your pressroom. Finally, we’ll cover some on-press variables that can affect ink performance and some basic suggestions for troubleshooting common ink problems.
As previously mentioned, flexographic inks are divided into three main categories. Water-based inks are used on wide web flexo presses for applications like paper packaging, overwraps, bags, etc., and in narrow web flexo for products like pressure-sensitive labels, tags, envelopes and the like. Solvent-based inks are used primarily in wide web applications like film packaging, overwraps, bags, pouches, etc.; they see very little use in narrow web, but are occasionally the ink of choice for adhesives, coatings, etc. And lastly, the category of energy-curable inks covers three main energy curing methods—ultraviolet (UV), light-emitting diode (LED) and electron beam (EB). Both UV and LED are in widespread use in the narrow web portion of the flexo industry, with EB used to a much lower degree in both wide and narrow web.

Colorant: Pigments or dyes, used to impart the color or shade to the finished ink
Resin (vehicle): The backbone of the ink system, used to carry the colorant and bond it to the substrate, typically made of a variety of different waxes/lacquers, chosen for their intended use and end requirements
Solvent: A chemical used to solubilize the resin and change it to a liquid state, chosen specifically to work with the resin that’s used; the solvent is also used as the diluent, to reduce the viscosity
Surfactant: Often a defoamer or wetting agent is used to affect the surface energy of the ink
Additives: Anything else the formulator needs to include to make the ink work for its intended use—products like waxes, silicones, etc.
In summary, the basic ingredients of each ink chemistry vary mainly in the type of resin system used, and the method of drying or curing used. Each chemistry has its strengths and weaknesses, because each is utilized for different print applications, based on the suitability for the end product. Some colorants work better in one chemistry versus another, due to their relative ability to “wet out” those pigments.

Both water-based and solvent-based inks dry by evaporation, absorption or a combination of both. Energy-curable systems dry by being “cured” after exposure to energy; in the case of UV and LED inks, that energy is light, where for EB inks the energy is a stream of electrons.