The composition of wastes from printing and converting varies but in general, source reduction of these wastes will benefit printers and converters that print by reducing material needs, disposal costs and energy consumption, etc. The control of waste in the pressroom and in other departments not only makes the workplace and surrounding environment safer and more pleasant, it also lowers the liabilities associated with waste disposal and provides for improved productivity and enhances commercial viability.
The three main classifications of waste in package and label printing include:
1) Solid wastes.
This type of waste is amongst the most common and impacts on day-to-day processing. Solid waste consists of the following: spoilage, damaged plates, make-ready/machine/ink adjustment, product trialing, etc.
2) Waste water.
Wastewater from printing operations may contain lubricating oils, waste ink, as well as trace metals, etc.
3) Air emissions.
This covers VOC emissions, the release of phthalates, amines and heavy metals into the environment from activities involving the use of alcohols and wetting agents and from solvents and inks used in printing.
One of the largest generators of solid waste in the pressroom centers around on-press ink adjustment and on product trialing and make-ready. Ink adjustment on press in order to meet desired colour objectives takes time, slows product output and can result in a high level of printed waste, which is generated at high speed.
No one can afford product giveaway – but that is in effect what is happening, every time out-of spec waste is collected from a container or fed into a granulator or air trim conveyor. For those engaged in the production or use of flexographic inks the FlexiProof family of pre-press colour communication devices has been welcomed as it highlights colour matching and other issues such as ink/substrate compatibility and printability, i.e., gloss, scuff resistance, durability, etc. As the device, which is an integrated unit incorporating flexo press critical components and UV curing (FlexiProof UV & FlexiProof LED UV), product trialing, prototyping, colour regulation can be undertaken without having to resort to using a flexo production machine until process variables and inconsistencies have been resolved. This saves waste, for it is on the production machine where high levels of waste occurs, it also speeds product development and assists users in meeting customer and accreditation standards while reducing the risk of penalty clauses being invoked.
It is easy to define an environmentally friendly product or process as one that doesn’t impact on the environment. The problem is – just about everything we do, whether as producers or consumers, impacts on the environment, whether it’s the packaging we produce and then throwaway, the products we use to clean our homes or the newspaper we read at the breakfast table. So using less environmentally harmful chemicals, using distillation and recovery systems and seeking alternatives to solvents is a small but significant step.
The print industry was once a high volume user of harmful chemicals; cleaning blankets and presses with cleaning agents containing high levels of VOC emitting content. Similarly many coating and varnish materials contained gender bender and carcinogenic phthalates, heavy metals, VOC’s and HAP’s. Much has now changed and to a degree the printing and converting industries have cleaned up their act, switching to less harmful alternatives such as water based coatings.
The methods for reducing or eliminating VOCs, HAPs and other potentially problematic and outright harmful chemicals include direct substitution, indirect substitution, partial substitution and product/process substitution. Direct substitution is for example when a chemically identical plant-derived bio-chemical is substituted for petroleum formulated one. The chemical Phenol for instance used in the print industry can be produced both from plants and from petroleum. When produced from plants bio-phenol generates 80% less pollution than a petroleum-synthesised product.
Indirect substitution is where a functionally similar product, but chemically different plant-derived chemical replaces a petro-chemical one. Partial substitution as its name suggests is where some volatiles are still produced, but these are generated in much lesser amounts. Often plant-derived chemicals are used in combination. Product/process substitution involves the replacement of an oil based derived end product or other chemical structure/formulation with a more acceptable product. Water-based or aqueous inks/coating and adhesives fall within the category of product/process substitution. Printers and their customers don’t just want inks that are green they also want coatings, varnishes and other chemistries used to enhance the appearance and performance of a package or other item –to also have minimal environmental impact.
Coating formulators have explored different technologies in order to reduce solvent usage. Water based coatings for example differ from solvents in that water is used as the carrier; consequently no volatiles are emitted when the surface of a coated web is dried. Another option is UV cured coatings.
Three main components make up a UV curable coating these are liquid oligomers, liquid monomers and photo initiators. Applying a coating and then fast curing it under a UV light source provides practical and environmental benefits. Practical in that a machine’s overall footprint is reduced as the need for lengthy ovens is eliminated.
In operation the photo initiators in the coating absorbs the energy from the UV light (energy) and form free radicals, initiating the curing process as the monomers and oligomers become attached, typically creating a solid cross linked stable network to produce the desired coating property on paper, film or some other substrate in a matter of seconds.
While everyone wants an ink or coating that does no harm, no one wants to sacrifice quality and performance. Formulators and others engaged in product development need systems and equipment that will enable them to develop new products, to trial them under real world conditions, to monitor performance and to resolve technology issues, environmental concerns, etc.
As previously mentioned the FlexiProof UV or the FlexiProof LED UV for heat sensitive substrates may suit the needs of many; other options available from the RK Print Coat Instruments portfolio of products include the Rotary Koater pilot coating/print and laminating system or the VCM, a bespoke machine, one that meets specific customer requirements.
Built to order the VCM may be the solution when the machine that the customer requires is not available except as a purpose build, and when for reasons of commercial confidentiality the customer requires that all details are kept under wraps. Customers have a wide range of print and coating head technology options and machines are built to meet clean room and flameproof conditions, etc. Drying possibilities include hot air, infrared and UV curing.
By Tom Kerchiss, RK Print Coat Instruments