Coating has it covered

1 July 2014

As the growth of flexible packaging in the narrow web industry continues, so does the demand for high quality graphics. Laminating the printed substrate not only protects the packaging from scuff and damage to the print during transit, but it can also enhance the graphics and maintain value to the consumer at point of purchase

Barrier properties are extremely important especially for packaged food which must be protected against the penetration of moisture, gas and, depending on the product, light. The stronger the barrier properties, the safer the product and the longer its shelf life. The emergence of increasingly thinner packaging materials, decreasing quantities of ink or adhesives used in packaging manufacturing, and their disposal are topics of particular interest to converting companies.

From the point of view of a converting machine manufacturer, all of the above is extremely important, as the design of the machine bears an impact on the characteristics of the final packaging material. Laminated structures are becoming more and more sophisticated and are used to package an increasingly wide range of products. The choice of the most suitable lamination process
is mainly dictated by the end use of the product, and a number of different technologies are available.

Tension control - Bobst
One of the most important considerations for the efficiency of laminating equipment is setting and controlling the tension of the
substrates. Precise and consistent web tension control from the unwinder to the rewinder is crucial for the quality of the laminated structure, as it avoids the formation of defects in the material. The tension control system on the Bobst CL 850 - CL 1000 multi-technology laminators is extremely sensitive and can be maintained at very low tolerances throughout the wide range of flexible
substrates handled by the machines, including very thin aluminium foil, extensible films and paper.

Another fundamental aspect that has a considerable impact on both the economics of the process and the quality of the final
laminated structure is the machine's ability to control and manage the variables that impact on the efficiency of the adhesive metering and coating, which differ according to the process application.

A noteworthy development for solvent-based applications is Bobst's flexo coating system, which is widely acknowledged as the
highest quality system by imparting a much superior aesthetic quality to the laminated structure through a lower solvent-based adhesive coating weight, but with comparable bond strength. The system is especially effective for applying the adhesive directly onto thin aluminium foil at high speed, ensuring the best quality end-product, as it prevents the formation of 'orange peel' or wrinkles and foil breakage.

Another key area where Bobst technology succeeds in maximising efficiency and minimising residual solvent and energy consumption with solvent-based adhesives is the drying and ventilation system of its CL 850 - CL 1000 machines through the dryer
fitted with impingement and flotation type dual technology nozzles. This enables the process to be very efficient and flexible. The
effectiveness of the system impacts on the drying heat transfer in such a way that the solvent continues to evaporate and the freed solvent is carried away from the web surface, minimising solvent retention on the web.

High quality sustainable printing: offset EB and flexo WB In printing, Comexi Group has taken a step forward in its commitment to sustainability and the highest quality through its offset and flexo technologies with water-based inks. The Comexi Offset CI8 is a clear example of the innovative and ecological will of the Spanish group. It offers a solution that effectively responds to four current market demands: high quality, time to market, respect for the environment and cost reduction.

The CI8 press is said to adjust the offset central impression technology to flexible material, reducing costs and time to market, while offering high quality and high speeds. Moreover, this solution includes electron beam curing. In contrast to UV cured inks, EB cured inks contain no photoinitiators, which prevents the risk of migration, making the process perfectly suitable for food grade packaging.

As for flexographic printing, Comexi's Flexo F2 WB offers a solution for companies that want to step up to solventless printing with
high speeds and without quality loss.

To achieve the adaptation to these kind of inks, the Flexo F2 WB has a high flow drying system exclusively dedicated to the drying of
white as a first colour background with dehumidified air. The drying capacity between colours has also been increased by 50 per cent, and by 30 per cent in the final tunnel regarding the solvent based inks machine. Apart from that, a stainless steel ink system specially designed to work with water- based inks has been incorporated.

Water-based printing
When flexible packaging is printed with solvent-based inks, the solvents have to be recovered and incinerated after printing. Flexographic printers using such solvent-based products are forced to invest in incineration equipment or substitute these inks with solventless or low solvent alternatives, as they are affected by European legislation to control solvent emission. In addition, they have come undergrowing pressure from brand-owners requesting information on carbon footprint or sustainability.

Therefore, more and more printers are converting to water-based inks. Consequently, ink producers increasingly face demand for water-based raw materials whereas converters need new technical equipment for both water-based printing and lamination.

Pigments, resins and additives from BASF are key ingredients of the ink that is printed onto such flexible packaging as bags of
potato chips. Packaging manufacturers and printers set two central quality requirements that printing inks need to meet: on the one
hand, they must give good performance properties, ie, resistance or lamination bond strength. On the other hand, the ink should show good printability and resolubility at the press.

Comexi innovations support the strategy on leading the transition to a sustainable and high quality printing
The Flexo F2 WB will be Comexi's main focus on water-based flexo printing and electron beam, claiming it is the most suitable 8-colour machine for medium and long runs without compromising speed and/or quality.

In Comexi's new Flexo F2 WB water-based flexo printing machine, the inks were intensively tested to ensure that the feasibility of water-based surface and lamination printing at high speeds with good printability has been achieved. In addition, Comexi is also moving on with new solutions such as the new Flexo F4 WB press for short runs.

BASF products drive forward the conversion to water-based flexible packaging printing Two BASF raw materials enable the industry to convert to water-based inks for flexible packaging. First, the company developed a
water-based resin portfolio enabling inks with performance properties required for medium duty flexible packaging applications: the Joncryl FLX line for surface and lamination printing. It is claimed that inks formulated with these resins can achieve similar quality characteristics to solvent-based inks.

BASF is also developing a water-based electron beam cross linking (EB) technology to enable the industry to formulate water-based
printing inks for medium to high duty flexible packaging applications - the Laromer EB concept. This will complement the Joncryl FLX line, allowing the formulation of a water-based flexible packaging ink portfolio that can be applied on water-based flexo printing presses such as the Comexi Flexo F2 WB.

Company news
A major Chinese company has placed an order for Kroenert's MCO5000 for the manufacture of technical products. It is a modular line with standard components that can be modified according to the customers' requirements, easily extendable at a later stage. The line has two five-roller coating systems for the processing of 100% silicon, and a Drytec flotation dryer, making production speeds of up to 500m/min (1,640 fpm) possible.

Michelman Michelman has introduced Nomar 73, a new coating that is applied to paper and corrugated to protect packaged goods
from abrasions that can occur while the package is in transit. Formulated with advanced polymer technology, the versatile new
coating can be applied offline or in-line on a corrugator, is hotmelt and cold-set gluable, and is repulpable. It meets FDA regulations for dry food contact, and for aqueous and fatty food contact with food type IV-A, V and VII under conditions of use E-G, and with food types VIII and IX without conditions of use restrictions.

Evonik Heat-seal binders from Evonik Industries are a major component of heat seal coatings for aluminum foils and plastics films. These binders provide a secure seal for food and pharmaceutical blister packaging. Lids for yogurt cups can be opened smoothly with a clean peel and with no residual materials: the heat-seal coating does not delaminate or produce stringing. As a result, PVC-free binders with Degalan have become established as the standard for dairy product packaging in Europe (EMEA). Degalan is also used as a universal binder for manufacturing heat-seal lacquers applied directly to aluminum foils in order to seal with polypropylene (PP), polystyrene (PS), polyethylene terephthalate (PET), or vinyl (PVC).

Coating units are of modular design, and many of them are configured on interchangeable trolleys in order to minimise machine downtime and can be used on:

Coating widths from a few millimeters to several metres

Coating weights from 0.1 g/m² to 1,000g/m²

Coating speeds from 0.1 m/min to 1,525m/min

Coating media with a wide range of viscosities and varied solvents

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