Beyond claggy glue!

There was a momentous commencement to the October meeting of Australian Institute of Packaging (AIP). Peter Funnell, the Victorian chair of Surface Coatings Association Australia (SCAA), made a presentation to Robert Beth of Ability Building Chemicals, who has just clicked over 50 years as a member of SCAA.

When Robert, and a number of other AIP members, commenced work, labels were still being attached to parcels using a glue pot and a brush. Even the humble stamp was affixed the same way at the post office counter.

As the meeting’s larger-than-usual audience was to find out during the three presentations that followed, the now ubiquitous self-adhesive label needs more than claggy glue to become affixed.

PSA labels explained

Lance Barlow, BASF industry manager, spoke on PSA label innovations and technologies. PSA stands for pressure-sensitive adhesive, which is much more that it sounds. Simplified, Lance said that a PSA label is adhesive sandwiched between a siliconised release agent and a face stock.

They are permanently tacky at room temperature, adhere to a surface with only light pressure and do not need water or heat to activate the adhesive and create a bond. The uses of PSAs can be found in labels (eg, health and beauty products), graphics (eg, point-of-purchase displays), tapes (eg, painters masking) and in protective films (eg, household appliances).

Lance gave an overview of the application methods and many of the ways that labels or tapes are used in everyday activities. He went on to explain the trends and demands for water-based PSA labels over the years. The coating weights have reduced from 20 to 17 gsm and the tackiness has been lowered to minimise bleed. The adhesion to plastics has improved, as has the clarity and the resistance to water whitening for clear labels on clear bottles. Examples of the latter two are to be seen in shampoo and wine bottles.

Lance then discussed the technical aspects of manufacture and spoke about the various monomers used. The key attributes of emulsion polymers include the environmental advantages, because they are water-based. One aspect that really needs consideration in the marketplace is how a label ages. Labels are subject to heat, ultraviolet and mechanical intrusion, so they have to be durable and cope with the weather aspects of daily life. Lance’s mantra was: the secret is to have improved peel and tack at point of application without impacting cohesion too much.

The finale to his presentation was about coater-ready polymers that are compatible with gravure, slot die or curtain coating. The product needs correct surfactant and wetting properties, as well as the correct tackiness. The secret here is to have improved peel and tack at the expense of shear.

In terms of speed, Australia lags behind Germany, where there exists a coating machine that can attain a speed of 1000 m/min and a hot melt coater that runs at 500 m/min.

Novel applications

Dr Carol Lawrence, FAIP Sustainability & Technical Service Specialist UPM Raflatac Oceania, then gave an insight into pressure-sensitive adhesives for novel self-adhesive labels.

The principles of manufacture of PSA labels are similar to that already described, but Carol was able to expand on what her company calls the label stock value chain. In 2014, global product decoration analysis shows that 39% of sales came from self-adhesives, 37% from preglued and 17% from sleeves, with the other 7% from in-mould and others.

Sleeve labels, mainly used in the beverage industry, are a major post-consumer problem when used on glass containers. The sleeves become contaminants when glass bottles are crushed to make cullet for new batching. 

There are over 12 defined areas where PSA labels are used. It would appear that the applications are as diverse as the materials onto which labels are affixed. PSA labels are affixed to all manner of common items, ranging from motor tyres and lubricants to delicate personal cosmetics.

What about the ink?

It is all well and good to know how labels are printed, but it all would be very bland without ink. Richard Lau, business manager of DIC Australia, gave a colourful presentation about inks and inking.

Printing inks equate to 30% of a company’s production. Richard’s agenda was to explain how colour management is evolving and how critical the regulations around food packaging have become.

About the time that claggy glues were being phased out at post offices, there were still some steel nib pens being dipped into inkwells on the counters. Now it is the digital age of colour management — and how different the printing trade has become!

Richard explained that printed samples, wet ink and Pantone books are no longer the final authority of approved colour for major brand owners as digital proofing methods improve.

Colour communication is increasing with embedded artwork files. Data stores in them are being passed on to presses electronically. Everyone in the workflow has value, with higher quality results and faster design, proof and print cycles. It is also more environmentally accepted and the costs are reduced, as is waste.

The digital age was well and truly demonstrated, as Richard also had splendid graphic to demonstrate what he referred to as The Sun-Colour Box. It felt more like Star Wars than a packaging seminar. It really is not that daunting, for the whole distribution system of preparation, editing and sign-off is all done using internet technology. Suppliers access common colour data firsthand from Pantone LIVE, utilising enabled production software and the cloud.

Once the standards are in the cloud, then the entire packaging supply chain can connect with an annual subscription. They do this via the production software, which they utilise every day. DIC offers an open ecosystem, which allows multiple partners to get involved and connect their software to the cloud.

The brand owner can control who has access to their special colours via a brand portal. Designers connect via an Adobe Illustrator plug-in, which allows them to see brand-approved colours and enables them to view a design under different conditions.

A case study about Heinz baked beans labelling was demonstrated. Before the company changed over to the digital processing of data, every example tested showed inconsistent colour against the brand owner’s original specification.

The second case study discussed by Richard was about the Chesapeake Company.

Richard then addressed the important issue of migration of inks, which is a major global concern. Ink manufacturers seem to have been a victim of the ‘law of unintended consequences’. For instance, the recycling of fibreboard has not only contributed to migration of inks but also chemicals from contaminants, such as tapes included in the recycled pulp.

Critical to the necessity to stop migration are the health concerns around food.

Currently there is no EU or Australian legislation specifically defining the acceptable level of migration of ink constituents into foodstuffs. But Richard suggests that the Swiss Food Packaging Ordinance is a positive list of raw materials for use in food packaging printing.

Here are possible solutions:

• Reduced levels = reduced risk.
• Avoid low-molecular-weight monomers and/or oligomers.
• Use materials with a high number of reactive groups to ensure they are chemically locked into the cross-linked ink film.
• Select non-reactive materials so that they are large and can get physically trapped in the cross-linked film.
• Use food-grade additives if possible.

Richard’s final summation was that low-migration printing is not just about ink!

Image credit: ©iStockphoto.com/johnnyscriv