Mono-material corrugated board: Move forward with recyclable coatings

As brand ambassadors and carriers of information, corrugated board packaging by the Panther Group, finished using flexo preprint or direct printing, offset or digital printing processes, is an established service provider for almost all industrial sectors. The high-quality, multicolored design of packaging is on a level with the protective properties that contribute to the integrity and quality preservation of the filling goods. With varnishes and coatings, produced in a single operation on Panther Print's flexo preprint system, there is a wide range available to significantly expand the performance criteria of corrugated board.

The food industry, for example, can benefit from Panther Print's coating technology for numerous products: inner coatings for vegetable trays or for packaging frozen fish are equipped with water-resistant barriers.

Corrugated board packaging with fat-resistant barriers on the inner lining offers semi-finished products or raw chocolate, i.e. products with a high fat content, optimum product protection. Their effectiveness is also determined in suitable tests, for example DIN 53116.

There are further requirements for baked goods: cakes or pizzas packed in corrugated board with heat-resistant coatings on the inner surface offer safe handling. Specific barrier coatings can also be implemented for deep-freeze applications, which allow the products to be frozen, thawed and baked in the packaging.

An equally wide range of interesting possible applications can be found in the non-food sector. For example, corrugated board packaging with antistatic coatings or paint finishes for electronic items are beneficial. Non-stick coatings on corrugated board improve the properties of adhesive packaging. Coatings for dust binding were developed for the glass industry.

Avoidance of waste and product protection go hand in hand
The examples given so far show the compatibility of the greatest possible protection of packaged goods with packaging designed for recycling, which contributes to avoiding waste and substitutes more problematic solutions.

The varnishes and printing inks used in the Panther Group are water-based acrylic resin varnish, paints and coatings that are practically solvent-free. According to the definition of the printing ink industry, these products are also considered to be free of heavy metals. When disposed of properly, there are no less toxic (harmful to health) and certainly no toxic substances within the meaning of the Ordinance on Hazardous Substances. Corrugated board packaging coated with these coatings is fully recyclable and can be returned to the paper raw material cycle at any time, while the recyclability of other surface finishes, such as cellophane wrapping and UV coating, is not fully guaranteed.

The high demand for the increased use of recycled paper can also be met in flexo pre-printing. However, it should be noted, that the papers produced by these secondary fibers can pose more challenges in the production process than paper grades produced by primary fibers. This fact is due to the shortening of the paper fibers in the recycling process. This inevitably affects the strength and printability of the paper. There is also an increased occurrence of paper dust, which can have a negative effect on the printed image. Therefore, prints on uncoated recycled qualities should only be made up to a 34s grid.

Water-based printing inks have proven to be very suitable for flexo printing. The flexo preprint process in particular has taken advantage of this. The practical advantages lie primarily in the use of water as a solvent, which allows easy disposal. Since Panther Print only uses water-based inks, the products can be easily recycled with waste paper. Toxic heavy metals are not used with these paints.

Varnishes and coatings: protection and enhancement of packaging
Corrugated board packaging can be provided with a wide variety of coatings. These include high-gloss finishes, protective finishes, anti-slip finishes and various coatings. All varnishes and coatings refine the packaging.

First, the varnishes and coatings protect the packaging against color abrasion, annoying scratches, moisture or grease penetration. At the Panther Group, these coatings are applied in preprint coating units supported by transfer rollers and squeegee systems in one operation during the printing process.

Depending on the intended areas of application, the types of varnish and coating differ:
High-gloss coatings are mainly used to visually enhance the print and packaging. Because glossy packaging has a valuable and high-quality impression for the end consumer.

A direct definition of the gloss is only possible to a limited extent, since this is a sensory impression of the viewer and his viewing angle. Different gloss effects can be achieved depending on the paper qualities used (coated/uncoated) and the amount of varnish applied.

Protective coatings primarily serve to protect the printing and not so much to enhance the packaging's appearance. A glossy effect is not necessarily given here. This coating is characterized in particular by its extremely high temperature resistance as well as scratch and abrasion resistance.

These will continue to be promoted in the future through technical development and the competencies of the team at Panther Print in Wustermark (Berlin-Brandenburg/Germany) for the benefit of the numerous areas of application. In partnership with other members of the flexo preprint process chain, such as ink and pigment manufacturers, machine builders, those involved in prepress, etc., solutions are developed in order to be able to react to changing market situations.