Metallized paper: How is it produced and how it can be use?

A metallized paper is a product that is coated with a layer of aluminium with a matte or gloss finish which offers decorative and protective properties to the product.

For more information, please visit Vacumm Metallized Paper.

Two different systems can be used to create metallized paper:

Lamination

This process involves a gluing process on the paper, normally a non-coated one, to a sheet of aluminiun with a thickness between 9 and 12 micron. This system is used increasingly less owing to the high consumption of aluminium.

Vacuum metallization

This system, which we are going to look at in depth, is the most used and it consists of  heating aluminium or another material in a vacuum chamber, vaporizing or sublimating it, and depositing a thin layer on the surface of the a coated substrate. In this case, the main advantage is that 300 times less aluminium is used than in the previous case.

In both cases this type of substrate offers a solution to achieve the distinctive, metallic finish on packaging with only a fraction of the aluminium content of traditional foils. Let's see some more details about the vacuum production process.

What is a vacuum production method and what does it consist? 

As mentioned before the best way to produced a metallized paper it's through a vacuum metallization.
The process of producing the metallized paper by the direct high vacuum method consists of three independent processes, which are the following:

Varnishing

A thin layer of varnish is applied to the coated substrate in order to prepare the surface for subsequent metallization. The paper is pre-coated with lacquers that are applied to smooth out the surface of the paper to act as a barrier between the paper and the metallized layer and to improve the adhesion of the vaporized metal. The varnish is applied in the varnisher through a process similar to gravure printing. Once the varnish has been applied, the paper passes through the hot air drying unitin order to remove the solvents of the varnish and therefore dry the paper until it has a moisture level of between 2 and 3%. Next, and within the same varnisher, the paper passes through a set of refrigerated rollers which prevent the paper from sticking in the winder.

Metallization

This phase is probably the most critical point during the production process. Once the reeks of paper have undergone the varnishing process they are sent to the metallization area, where they are introduced one by one in order for the layer of aluminium to be applied to the paper. The pre-coated paper is then metallized directly. The varnished paper is placed in a "metallization chamber" where the layer of aluminium is applied through a vaporizing or sublimating process. 

Lacquering

All metallized papers are then top coated and re-moisturized as a final process. Once the reel is placed in the lacquering machine, the metallized paper passes through corona treating that facilitates the anchorage of the lacquer on the aluminium. This corona treating acts by increasing the surface tension of the metallized surface. Once the corona process has taken place the lacquer is applied using a system of gravure, as in the varnisher, and is subsequently dried using hot air tunnels.

When the product is coloured, it is the lacquer itself that is coloured with the final colour of the product. The classic colour is gold, but from a technical point of view other colorants could be used if this were necessary. Once dry, the metallized paper passes through cooling rollers, and the water and the dorsal treatment are subsequently applied. This is to ensure that the paper has the final moisture necessary for the finished product and to maintain flatness when it is transformed into sheets or labels.

The coating protects the aluminium from damage and serves as a print receptive primer for multiple printing applications. A thin layer of lacquer is applied to give the final characteristics of the paper such as printing features, colour such as for gold susbtrates or matte / gloss finishings. 

The product obtained is recyclable in a similar way to other special papers. 
The metallized surface of the product is plastic in nature, or in other words, it is waterproof and non-absorbent. It offers a series of barrier properties to the coated paper, forming a barrier against light, water vapour, oxygen and odours.

Barrier properties

Our papers offer different barrier properties, and increasingly these present stand-alone benefits for end-users and their supply chain, regardless of other advantages like shelf appeal. Our papers naturally offer good barriers for light, but with special coatings, we offer additional, more specialized barriers too, such as barriers for grease or water moisture. 

The result is that for specific applications (in a variety of industries, but particularly for food both for direct and indirect contact with consumable goods) using our metallized papers offer sustainable, functional and visual benefits.  

Barrier properties enhance the technical features of our products and mean that brands can combine shelf appeal and premiumization with functional packaging that can support freshness, aroma and taste retention, guarding against moisture and so on.  

When it comes to food packaging, there tends not to be a ‘one-size-fits-all’ solution. In essence, different types of foods have different packaging requirements. That said, with excellent barrier properties, the fact that our papers are easy to recycle and offer visual appeal makes metallized papers particularly sought-after as sustainable materials.  

Feasibility and testing

Customers or parties in the supply chain approach us when they have a potential application for which they’d like to consider metallized paper. They may want to use metallized paper for aesthetic reasons, functionality or a mixture of both, but often the change is motivated by a desire to see if our papers are suitable substitutes for multi-layer materials. 

Whatever the rationale, our Research and Development team propose a design for the suggested application and then make prototype lab-made samples which are evaluated under TAPPI, ISO or ASTM methods to see if our papers are compatible for the application and/or as a replacement for the with exiting multi-material option.