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Overcoming the variables

Converters are looking for precision and higher output when it comes to coating and laminating machinery, MJ Deschamps reports.

As one of the final stages in the converting process, it is important that the coating and laminating of raw materials goes off without a hitch to produce the best possible end product for paper, plastics and textile packagers.

Tom Kerchiss is the managing director at the UK’s RK PrintCoat Instruments, which specialises in the design and manufacture of equipment producing repeatable samples of most surface coatings. These can be used for many quality control and research and development purposes, such as presentation samples, computer colour matching, and tests for gloss, strength and weathering, for example.

Mr Kerchiss says that converters need to know how to overcome the various processing variables that may occur during coating and laminating. In coating, he says, accurate tension is needed to ensure that an even coat weight is deposited on a repeatable and continuous basis – inadequate tension control in laminating can produce a range of problems, from lay-flat difficulties to de-lamination, to image elongation with printed films.

“Given the commercial considerations, the need to optimise uptime and achieve consistent quality output – greater emphasis than ever is being given to tension control with closed loop.”

Besides the thickness of a coated film, the cosmetic quality of it is also important, stresses Tom Kerchiss. Some common defects that can occur in coating and laminating include pinholes – where localised regions remain uncoated, usually due to non-uniformity – or bubbles in the coating liquid. Other defects that can arise include streaks and drips, which can be caused through irregularities on the coating film, and ribbing – a striated pattern on the coated film.

RK PrintCoat systems such as the Rotary Koater and the VCM, are two examples of machines that offer the precision needed to ensure efficient coating and laminating during converting.

The Rotary Koater is promoted as a versatile multi-tasking printing, coating and laminating machine. It can be used to test different formulations, substrates, processes, and more, and is effective as a machine for the small-scale production of specialised materials, such as holograms, security tapes, labels, and medical products.

The VCM, on the other hand, is said to be ideal for those manufacturers and converters who require a precision system for specific tasks, and has the option to select from several different coating methods, as well as drying and curing possibilities.

Faustel, a US-based manufacturer of web processing equipment for the paper, film and foil converting industry exports to Europe, having recently sold machinery to customers in Finland. The company has developed a pre-engineered pilot coater/laminator said to be ideally suited for R&D and narrow web production coating and laminating. The LabMaster Plug & Play is designed to make it possible for more companies to have their own laboratory or small-scale pilot coater, according to vice president of sales Richard Greer. Another recent converting solution from Faustel is its Vari-Coat Gravure pressurised gravure coating system, which allows precise coatweight over a range of coating thicknesses without the need to change the gravure cylinder. The machine eliminates air from entering the applicator chamber, allowing a more consistent coating film at higher speeds.

Also from the USA comes a new high speed, ‘eco-friendly’ web drying system for coatings from the Radio Frequency Co, which also sells its equipment into international markets. The Macrowave RF Drying System selectively heats only the patterned coatings (wetted sections) on the web and leaves the bound moisture in the substrate intact, thus preventing over-drying, distortion and shrinking. Capable of operating at speeds up to 1,500ft/min, the system needs only one-third to one-fifth of the floor space required for hot air and infra-red dryers, permits lower web temperatures, and provides up to 80% energy savings, according to the manufacturer.

On another eco-friendly note, US-based Novaflex has just introduced a new solventless laminating system – the Laminastar – that allows for fast clean-up and changeover, and makes it easier to re-run the same lamination with the same parameters.

Meanwhile, another innovator is the Bobst Group, whose latest laminator from its Asitrade line – the Foliostar 165 Matic – has recently doubled the offset lamination capacity for German paper-based packaging company Smurfit Kappa Lübbecke.

“Taking into account machine stops and setting-up times, our hourly output in the area of sheet lamination used to be around 2,000m². Currently, we achieve 3,000-3,500m² daily”, says Olaf Kuhlmann, manager of the Smurfit Kappa corrugated board plant in Germany.

In addition to increased output, the innovative technology is said to guarantee high production stability and reliability: after carrier sheets leave the gluing unit, they are transported to the laminating unit while the printed sheets are transported from the top, via a ramp, to the laminating point. The merging process is timed with such precision that the sheets lie ‘perfectly’ on top of each other despite the high speed. Whereas in the past, laminating tolerance used to be between one and three millimetres, today, Smurfit Kappa Lübbecke achieves a maximum tolerance of plus or minus 0.5mm thanks to the Foliostar 165 Matic.

Another company producing high speed coating and laminating machines is UK-based Drytac Europe, which recently unveiled its VersaCoater XL UV liquid coating machine, a wide format UV curable roller coater. Running at a process speed up to 33m/min, a 100m roll of printed vinyl can be coated, cured and wound back onto a core in four minutes using the roll-to-roll feature. With white liquid coatings for both flexible and rigid surfaces, this feature can replace the costly need for printing in white, and give flexibility in opacity depending on how many passes through the coater the print makes.

Other new features on the VersaCoater XL include a curing system with a split power feature for reduced power consumption, and a pneumatically controlled dual-blade scraper, which is deisgned to avoid wet prints on the back side.

In terms of coating solutions specifically for textiles, Bag Solutions Worldwide is an Austrian-based manufacturer of machinery for the production of flexible packaging made of woven polypropylene (PP). Its ecoTex 1600 coating and laminating machine for tubular and flat woven materials is said to allow economical production at high output, due to its modular design. Coating PP woven fabrics is no easy task, and the extrusion technology used in this high speed coating line was developed for maximum coating adhesion using the lowest possible amount of resin.

UK-based coating machine supplier Web Processing (M/C) recently collaborated with Thom Engineering (also British), taking established hot blade coating technology and adapting it to create a specially designed heated blade and tip technology called Ekokote. The new blade has a series of zoned heating elements, each with its own temperature control, allowing the temperature to be maintained to within 1°C.

In another development, mastics and sensitive ink compounds can also now benefit from increased protection and temperature resistance thanks to innovative new laminate foils developed by the Netherlands-based subsidiary of the Clondalkin Group, LPF Flexible Packaging,

“Mastics can be shipped to destinations all over the world and are often stocked for long periods of time under difficult circumstances, such as high temperatures and humidity,” says Barry Marron, managing director of the Clondalkin Group business unit for laminated and coated products. “So it was imperative to develop a flexible packaging solution that would protect against these elements.”

The laminate foils provide a protective barrier for atmospherically sensitive mastics and ink compounds, and high temperature resistance to prevent the degeneration of packaged products during transportation, handling and storage, he explains.

UK company bpi.films has recently published a guide to selecting polyethylene (PE) lamination films. It offers helpful advice for users of these films, which are said to be rapidly gaining in popularity due to their exceptional sealing characteristics, imbpi.films Asitrade’s Foliostar is a sheet-to-sheet laminating line that can be adapted to users’ requirements whether they require a manual take-off version or a high volume automatic machine complete with pre-feeding, logistics, and automatic stack discharge. Foliostar Faustel recently added a pilot-scale model of its Vari-Coat Gravure pressurised gravure coating system range. The new technology is said to allow precise coatweight over a range of coating thickness without the need to change the gravure cylinder.

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RK Print Coat
Radio Frequency Co
Bag Solutions Worldwide
Web Processing
LPF Flexible Packaging