Getting the perfect bond for your print-package - The Noel D'Cunha Sunday Column

Producing a print or a packaging job is not easy, because it takes a minor glitch to ruin a perfect product. There are many factors that come into play when printing and or producing a packaging product.

15 Jul 2017 | By Noel D'Cunha

Let’s take the case of adhesive. It is the single most important ingredient that ultimately bonds the print-packaging job. There are many factors that affect the surface tension of the substrate and can influence the adhesive’s ability to bond.

Then, there’s the aspect of cost and sustainability.

On 27 JulyPrintWeek India will host a Webinar on “Building a sustainable and green print environment” powered by Pidilite Industries, the sponsor of PrintWeek India Packaging Converter of the Year 2017. Among the speakers are – Animesh Kejriwal of Parksons Graphics, Vipul Arora of ITC PPD, and Selvakumar Kadakarai, Lovely Offset, who will discuss approaches adopted in energy efficient measure and how they evaluate energy intensity.

Pidilite Industries, business manager Sanjiv Kalra will present Pidilite’s views on how its adhesives help in becoming green and sustainable.

But before that here are a few tips you can follow to get the right bonding for your print-packaging products.

When glueing, how should one go about the process?

Glue selection depends on factors like nature of the substrate, properties of glueing area, type of machine being used, type of applicators, speed of glueing operation, performance requirements. “Expected shelf-life and nature of products to be filled or packaging; and transit or storage conditions also matter,” says Kalra of Pidilite Industries.

Harsh Gupta, the regional GM – India, Middle East & Egypt for HB Fuller, says, “Another important aspect in the case of book-binding is the final destination of the books, which may be local or may involve exporting to regions with a different climate.” He emphasis, “The rule of thumb for selecting the optimal adhesive is summarised as ‘ESPCEQ’. This stands for equipment, substrate, plant condition, cost, end-use and quality.”

Converters or even commercial printers using adhesives and sealants in their product assembly process have difficult decisions to make other than selecting the right material to use in their bonding, sealing, gasketing or potting process. “Along with selecting the right dispensing equipment, they must also find the best method for applying the material,” says, Deepak Bhatnagar, steering unit manager (South Asia) for packaging & graphic arts at Henkel.

Bhatnagar goes a step ahead and says that the suppliers of adhesives should be involved as early as possible, ideally at the design stage itself. “It will also for the right adhesive to be recommended or developed. It will also help support the designing of new applications.” It is interesting to note that a minor change in the selection of adhesives at the early product design stage can provide much greater bond strength and improved quality.

Types of glue and trend

The three main types of adhesives are water-based, solvent-based and hot-melt adhesives. Each of these technologies has its pros and cons. For example, water-based adhesives are very cost effective solutions; however, they require porous substrates and have a longer drying time as compared to other adhesive types to allow the water to evaporate. On the other hand, hotmelt adhesives dry much faster and are versatile but by nature they tend to soften at elevated temperatures. Lastly, solvent-based adhesives offer fast drying and broad performance profile.

“With technological developments taking place water-based and hotmelt glues are capable of meeting high-speed requirements,” says Kalra of Pidilite. “In addition, they are designed for better machinability.”

But solvents are increasingly raising health concerns. As adhesive manufacturers strive to reduce volatile organic compound (VOC) emissions and improve air quality, particularly in the packaging segment, solvents are gradually being edged out by water-based and hot-melt solutions.

The future of the bonding and packaging industry, in terms of adhesive usage, lies between water-based, hot melt and reactive hot melt technologies, says Gupta of HB Fuller. “In flexible packaging, solvent-based technology still plays a strong role, however, there is a clear market trend towards solvent-less technology.”

He adds, “The future for water-based adhesives, despite the current optimism, is very interesting. The customer market is approaching these products with some caution as their performance capabilities are being proven.”

Glue pattern

It is important to believe that the perfect glue pattern varies from package to package, and more specifically, customer to customer. Like adhesive selection, the choice of glue pattern has a vital influence on functional parameters and cost optimisation. “These parameters are machine speed (linear speed); end use (load pattern on pack); strength of glue joint required, especially given the gsm variation; and the type of coating used,” says Gupta.

But does one-size-fits-all? Considering the diversity in machine types and speeds, environmental conditions and substrate combinations, unfortunately, one size does not fit all, says, Bhagnagar of Henkel. “It is important to engage with an adhesives supplier and get a recommendation on the type of adhesive that should be used, which will offer the best performance for the specific settings.”

Potential area of saving

Though adhesives are not as major an expense as paper or paperboards, the cost is still significant. It’s a potential area for savings when done efficiently. With the right product, line speeds can be increased, adhesive consumption reduced and the expense of cleaning, maintenance and early replacement of ‘gummed-up’ parts can be avoided.

While some adhesive manufacturers have special adhesive like HB Fuller’s Adventra 9280 hotmelt packaging adhesive, developed specifically as a one-stop solution to a number of challenges posed by difficult-to-bond substrates, there are others like Henkel who use proprietary online glue measurement system like Procontrol to set up optimum operational conditions such as temperature and pressure.

Whatever your applications and the challenges you are facing, it is always a good idea to talk to an adhesive specialist.

That said, there’s a trend for cost saving in the market. Depending on how costs saving projects are handled they can be a real threat to quality and safety whether of the operators or the consumers.

For example: using cheaper adhesives can mean increased downtime and maintenance issues (nozzles clogging, charring). Alternatively, decreasing the adhesive consumption without testing and support can also be a risk. The solution is to use an adhesive that is more expensive but that is designed to be used in small quantities.

Equipment maintenance: Handling nozzle clogging issues

Nozzle clogging leads to machine down time. The main reason for nozzle clogging is char or foreign particles. Here below are some tips to avoid clogging of nozzles:

Maintain proper and consistent cleaning cycles

Low-quality hot melt glues can lead to charring. By using the best quality adhesives, one can prevent clogging issues

Make sure that no foreign particle enters the hot melt tank

Also ensure that the filters are in good condition

Do not keep heating the adhesive, if it is no longer in use

Maintain 75% adhesive level in the tank

Before changing the adhesive, ensure that the tank and application equipment are properly flushed

Using special cleaner designed for hotmelt cleaning. Normally waxes are used for cleaning

Speciality cleaners are more effective as compared to waxes

Bring down temperatures when machine is in idle condition

Clean the melting tanks and application systems regularly

Use appropriate solutions for cold cleaning of surface soiling on application equipment, conveyor belts or other machine parts