Melamine Revisited

Barrier-coated flexible packaging, both metallized and clear, is a much-favored choice among brand owners and retailers across the globe today. It offers consumer convenience in terms of reduced weight, compared to most rigid packaging, and ease of handling, particularly for liquids and foods.

Traditionally, vacuum metallizing has been the preferred technology, but now that market position is challenged by a new clear vacuum-coating technology based on the vapor deposition of melamine. Melamine is inexpensive, widely available, environmentally friendly, fully recyclable, biodegradable, and FDA-approved for direct food contact.

New Sustainable Technology

This globally patented innovation, branded Symphase Technology, comes from Stamicarbon DSM, a diversified multinational company based in the Netherlands. DSM is active worldwide in developing products and services for many key markets today, particularly nutritional and pharmaceutical ingredients and performance materials. It is reported to be the world's largest producer of melamine for all its many uses, including the familiar wood- and paper-based products such as decorative and floor laminates.

Symphase melamine-based technology has strong possibilities in the packaging market: Not only is it totally environmentally benign, but it also is unhampered by the cost pressures that attend metallizing today.

Two Pathways to Gas Barrier Coatings

This new physical vapor deposition process uses a combination of nano-technology and supramolecular chemistry to create two types of functional gas barrier coatings to maintain product freshness: Freshure-Single Coat, a stand-alone, single-layer, transparent, high-gas-barrier coating; and Freshure-Top Coat, an additional in-line top coat to protect oxide- or metallized vacuum-coated film layers and improve barrier performance. Both bring benefits for converters and brand owners in terms of reduced cost of ownership without any compromise on quality.

Melamine Coating Process

Melamine coating is a “soft” deposition process that requires no expensive cooling or high vacuum systems. Under moderate vacuum conditions and above its low sublimation temperature of 200 deg C, melamine can cover large surface areas in a fraction of a second, creating a nano-layer of transparent crystalline coating with very high gas barrier properties.

This can be achieved via a roll-to-roll coating process at speeds higher than 10 m/sec, on film substrates such as biaxially oriented polypropylene (BOPP), polyethylene terephthalate, oriented polyamide, and polylactic acid. Pump downtimes and cooling periods are lower than those experienced in traditional vacuum coating, so higher cycle times are achievable.

The low coating temperature also makes it possible to coat temperature-sensitive polymers such as polyethylene, and unlike aluminum (Al) metallization, there is no requirement for special-grade, temperature-resistant BOPP films.

High-speed coating is possible with both of the new coatings and is commercially proven. Melamine evaporators can be retrofitted successfully to existing vacuum metallizers, and a brand new vacuum coater will shortly come on-line with a 1.6-m-wide melamine evaporator. Therefore, capital investment in this new process can be relatively low.

Clear Packaging Potential

Clear film packaging that provides a “window” on the package to show the product is a good example of the possibilities of the single-layer coating. It gives a cost-effective, transparent, high-gas-barrier coating on a variety of plastic packaging films and can be converted under standard lamination conditions.

The coating is microwavable and less brittle than metal oxide coatings, has self-healing properties, and retains its oxygen barrier properties in very high temperatures and humidities. Its oxygen barrier values compare with, and sometimes exceed, those achieved with other vacuum-processed coatings (Al, aluminum oxide, silicon oxide) and alternative barrier technologies (polyvinylidene chloride, ethylene vinyl alcohol, etc.).

Active Protection

The top coat is designed to provide “active” protection of an oxide-coated/metallized layer and give improved all-round barrier performance in the vacuum chamber, during conversion, and in food and liquid packaging end use. Dependent, of course, on the chosen substrate, x2 barrier enhancement is achievable.

It retains its surface tension for 6 — 12 months compared to about 60 days with standard metallized films, so no in-line corona treatment is required prior to conversion, and lamination speed can be increased by at least 30%.

Instant Printability

An additional and valuable benefit of the new melamine coatings is their instant printability. Print can add an extra dimension to packaging, reinforcing branding messages and providing in-pack promotional opportunities. This is an area where traditional barrier coatings on flexible packaging are challenged.

Conventional metallized films often require off-line print primers. These may not be “water clear,” thus reducing metallic gloss levels, and can damage the oxide/metallized layer. Application of such print primers also adds a further step to the packaging production process.

DSM is actively engaged in licensing the new coatings for flexible packaging applications and reports strong interest from converters and brand owners across the Americas, Europe, and Asia. The core technology also is viewed as having future applications in key markets such as electronics, medical devices, and disposables, where the characteristics of melamine meet both converting and end-use aspirations.

It is interesting to see an old-established substance like melamine make a technology leap into leading-edge conversion of “high tech” packaging.

Ann Hirst-Smith is a UK-based freelance journalist specializing in the labeling and packaging businesses. She can be reached at ahirst-smith@btconnect.com.

Licensing Available

Readers interested in licensing possibilities may contact Dr. Shahab Jahromi, business manager, DSM Licensing Center at +31 46 476 1164; e-mail shahab.jahromi@dsm.com.


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