Long live the paperboard carton

While paperboard and corrugated cartons face competition from flexible packaging they are often used to reinforce protection properties of film, says RK Print Coat Instruments

Many packaging technologists would agree that when it comes to new product introductions, folding paperboard carton and its first cousin the corrugated container has experienced tough competition from other packaging mediums especially flexible films. Plastic films have provided cost-related benefits; material costs can be reduced through weight reduction; in the retail environment filmic and flexibles in general offer good stackability.

While its true that ‘semi rigid and rigid’ materials have taken a hit from flexible materials in some areas, paper board cartons and corrugated have a lot to offer. Apart from the bill-boarding opportunities, these materials can reinforce the protection and containment properties of alternative packaging mediums such as flexibles.

“Take moist pet food pouches for example,” says Tom Kerchiss, managing director of sample preparation system and coating technology specialist RK Print Coat Instruments. “These flexible pouches rarely stand alone on the retail shelf. Generally they are stacked, transported and then displayed on the retail shelf in cartons. The reason for this is that not only does a relatively lightweight carton prevent product damage, the surface of the carton also provides enormous marketing opportunities for brand owner and retailer alike. Graphics and colour on cartons can be bold and vibrant while the carton structure itself allows for a variety of value added effects to be added such as embossing.”

Vibrant colour and graphics

Today’s technological advances in flexography have opened up what some used to regard as a limiting printing method. Faced with coarse screens, designers did not have much room to manoeuvre but now more than ever, flexo can create folding carton packages with vibrant colour and sharp  graphics.

Improved plate technology has slowed for smaller dots, smoother vignettes and sharper definition. Flexo also provides the ‘potential’ to contain costs. Manufacturing a product efficiently is essential in today’s competitive and often difficult market. Innovations such as inline flexo presses provide process efficiencies and quality that rivals offset. The web fed inline press design reduces most carton production to a single pass proposition, providing workflow efficiencies.

Strengths of corrugated board

Corrugated board combines both strength and rigidity with the flexibility and ability to absorb shocks, offering material saving. There is hardly any other packaging material that gives such rigidity using so little material. These interesting properties are obtained by gluing together various layers; an undulating middle layer (flutes) with plain layers on each side – the result of which is a light and rigid framework.

Tom Kerchiss says that in many instances today’s consumers are not always aware they are encountering corrugated board. The reason is that its characteristics have changed considerably in order to meet the self-service requirements of retailers and warehouses. Spurred on by the simple realisation that attractive packaging sells, today’s expensive and sophisticated capital goods are sold off the shelf in brightly coloured graphically complex containers.

Much corrugated board is printed flexo, either directly onto the finished board, preprinting on the outer layer or liner, or by laminating. Defects that can occur during the corrugating process may impact on flexo print quality and on production rates. These are associated with flute integrity, calliper, wash-boarding and warped board.

Ink formulation, photopolymer plate selection, and anilox and inking systems, all of which make major contribution to the final print quality, must be chosen or formulated with care if print quality and workflow consistency is to be achieved.

Other factors that impact on print quality include achieving the optimum printing pressure; the pressure that will affect good ink transfer to the linerboard and viscosity profile during the print run, colour matching and ink drying speed.

Applying high quality print directly to corrugated is difficult because of the construction of board. The flutes cause an uneven pressure which in turn gives an unequal pressure which gives an uneven quality of print. In addition, manufacturers would rather not squeeze the material between printing rollers and risk deformation of the fluting and subsequent reduction of strength. So methods have been developed to pre-print the outermost layer prior to gluing to the fluting in the board machine. The technique of pre-printed liner has revolutionised decorative possibilities. A downside is that  manufacturing corrugated board with pre-printed liner is expensive; to make it economical it is favoured for long runs where possible. Another option is to laminate a pre-printed liner. This gives the best results since the printing can be undertaken on the highest grade of paper. Again an expensive option but recommended when exclusive high quality, high value consumer and/or industrial goods are being sold.

Brand presentation

Everyone from the manufacturer of corrugated board to the printer and customer look to brand presentation. Poor printability and thus poor presentation affects sales, consequently there is a high level of shared goal setting between manufacturer, printer, ink and other consumable formulator and the customer.

To achieve and maintain quality benchmarking devices such as the FlexiProof are gaining widespread acceptance. New configurations and improved components and consumables have undoubtedly improved profitability with faster set up, quicker changeovers and reduced downtime. Even so there is still room for production efficiencies and hence improved profitability. Tom Kerchiss says that the advancement in technologies now make it possible to accurately achieve and control numerical colour specifications for printed colour standards. The problem is that controlling colour takes time and remains challenging. Colour matching offpress reduces on-press waste and press downtime which translates into more uptime and therefore improved throughput and hopefully profitability.

The FlexiProof colour communication concept developed by RK Print Coat Instruments which is suitable for folding carton, corrugated and other materials (including flexibles) addresses these issues. The FlexiProof 100 and FlexiProof UV compact benchtop colour communication devices incorporate application critical flexo components, enabling users and producers of flexo inks to control colour off-press. They provide customers with an on-the –spot presentation sample, determining printability/substrate compatibility. Undertaking pilot runs on a FlexiProof frees up the production press for income generating output.

RK Print Coat Instruments

T: +44 (0)1763 852187