Bobst offers a pre-processing solution that guarantees perfect adhesion of adhesive to the glue flap for synthetic packaging and for laminated and varnished paperboards such as metallised boxes, writes Benjamin Daniel.
The trend in the packaging industry is toward continuously rising design and quality requirements. Manufacturers count more and more on the appeal of finishes like high-gloss printing, soft-touch coatings, or hologram printing to attract consumers. And display and window packaging often involve special combinations of materials.
These materials must be joined to each other cost effectively, at high speeds, and most of all reliably. This requires an especially robust, high-performance pretreatment process: Openair® Plasma.
When integrated inline, plasma activation creates ideal surface properties for subsequent process steps, such as gluing, printing or laminating.
Particular advantages of Openair® Plasma technology in manufacturing carton packaging:
- Makes high processing speeds possible,
- No open flames mean greater process safety,
- Robust, durable technology,
- Simple process monitoring,
- Cost effective.
This innovation, developed by the German firm Plasmatreat, is compatible with all your Bobst folder-gluers. Widespread in the car industry, plasma treatment has proven to be highly reliable and has become an indispensable element in new processes for joining synthetic materials. The advantages related to its use in the packaging industry are numerous.
Reduction in running costs
Plasma treatment reduces running costs by making it possible to use standard water-based adhesives to glue packaging which has been laminated, metallised or printed UV on the carton face.
Without plasma treatment, this type of packaging requires special and expensive hot melt adhesives or requires laquer cut-out in the glue flap. Another process frequently used on such packaging is mechanical milling, which is difficult and generates dust and inconvenience.
Advantages
With remarkable effectiveness, plasma treatment restores the surface tension necessary for perfect and long-lasting gluing. In addition to this increase in surface tension, plasma has the advantage of cleaning any organic residues and dust which may be on the glue flaps, while not leaving any trace on the treated surface.
This process is very beneficial and can be carried out at high linear speed – up to 650m/min – so is compatible with all Bobst folder-gluers. Easy to install and easy to use, plasma treatment does not require any additional resources other than electricity and compressed air.
The problem of surface tension
Whatever adhesive is used, the gluing of synthetic materials requires sufficient surface tension. This is calculated in milli-Newtons per metre (mN/m) and represents a challenge when it comes to the gluing of packaging. On materials with an ‘absorptivity’ – or surface tension – of less than 38 mN/m, the adhesive spreads out in droplets over the glue flap. This considerably decreases the number of points of contacts and equally reduces adhesion.
During the production of synthetic materials, the surface tension is sufficient for the printing and gluing of cartons. The problem is that the surface tension tends to decrease quickly with increased temperature and length of storage and so passes below the acceptable limit. Plasma treatment increases the surface tension more than 72 mN/m and ensures perfect adhesion of the adhesive to the glue flap.
Physical and chemical preparation
The treatment is best carried out on the folder-gluer, immediately before the gluing station, and only on the glue flap. For a simple box or automatic crashlock, a high voltage created plasma jet, of high intensity using normal compressed air, is produced as the glue flap passes and this modifies its molecular structure. Conscious of the environment, this process does not release any ozone.
Quality, one of our principal concerns
Bobst continually seeks out new ideas to help its customers achieve the highest quality of product and since November 2007, Bobst is the representative for plasma treatment in folder-gluers. Contact us to find out more about the advantages that this technology offers.
Bobst: A question of surface tension
Bobst is the leading supplier of equipment and services in the folding-carton, corrugated board and flexible materials converting industries.
In line with its policy of always offering high performance solutions to its customers, Bobst has signed an exclusive deal with Plasmatreat to represent their Openair® plasma systems in the area of packaging folding and gluing.
Surface tension is the key to the bonding of synthetic laminated, varnish coated and fully plastic boxes.
With low surface tension, the resultant bond is poor because adhesion occurs only at the points where glue droplets form. However, following atmospheric plasma treatment and the consequent rise in surface tension above 72mN/m, the adhesive will adhere to the entire surface and will form a homogeneous high strength bond. It is to ensure this homogeneous bond that plasma treatment is carried out inline, immediately before gluing.
Thanks to this exclusive agreement with Plasmatreat, Bobst has made it possible for its customers to benefit from the clear economic advantages of reducing their glue investment when processing laminated boxes, and of reducing print costs, by removing the need to create varnish cut-outs on varnished boxes – all the while maintaining high production speeds.
Customer testimonial
Al Shurook Group, Amman Jordan
Maamoun Kotob, managing director, Al Shurook Group
“We installed the Plasma Treat technology through Bobst in early 2011. Before going for the Plasma Treat technology, we were facing gluing problems on laminated board with PE and UV varnished boards as the gluing application was not meeting our quality standards. However, with the new Plasma Treat technology, it now helps us to overcome all gluing problems and all our custmers are very happy with the quality. As for Bobst, we are happy dealing with them. Although their pricing is higher than competitors, we have the best services and aftersales support beside their excellent technical experience. So we skip the price issue as it is worth it at the end of the day.”