Heat from inside - good for the environment
First, a quiz question: What everyday things were once – in the 1970s, for instance – packed in plastic bags? The right answer is …. practically nothing, with the exception of a few fruit juices. But if you go through a supermarket with alert eyes nowadays and look at the shelves, you will see that plastic pouches have taken over in many segments for packing sauces, ketchup, mayonnaise, fruit purees, yoghurts, baby food, all sorts of beverages, rice, sugar, washing lotion, soap, shampoo, detergent, motor oil, windscreen cleaner, even gypsum plaster. And these are only a few examples of the many products that are filled into pouches. The pouch is on the advance and has meanwhile gained immense significance as a packaging.
Diversity in pouches
There are numerous good reasons for the pouch to have become so popular among producers, fillers, sellers and consumers. The comparatively large surface provides plenty of space for marketing slogans, product data and photos. In contrast to bottles, cans or jars, there are hardly any rounded or curved areas which adds greatly to the visual impact. Another major advantage is the unbeatably low weight of the pouch compared to all other forms of packaging. In all phases of a pouch life, this has solely positive effects on its carbon footprint. Let’s start with the transportation from the pouch producer to the filling plant: since an empty pouch is not only lighter than a comparable bottle, but also a lot smaller, a truck can transport a much greater quantity of pouches. The space available in the truck is put to optimum use, whereas carrying empty bottles means moving a lot of air as well. It’s the same at the filling plant: as a result of the reduced space required and the low net weight of the pouch, internal transportation is much easier and the storage space needed until filling actually takes place is much less than for bottles. Because of the low weight, further transport to intermediate storage facilities and the selling companies is much more efficient than for product packed in glass or plastic bottles.
Laminate foils as pouch sheaths
But as with almost everything in life, pouch packaging – despite all its benefits - has two tiny flaws. To explain these, though, I need to give you a bit of background information. The main components of pouch packaging are the pouch and the so-called weld-spout, i.e. the spout with the relevant closure. Depending on the filling system used, the weld-spout is sealed to the pouch using heat and high pressure either before or after it has been filled with the relevant product. This is done by inserting the weld-spout into the upper opening of the pouch, then pressing the pouch foil against the weld-spout from both sides with the aid of so-called sealing jaws. In the process, the sealing jaws are heated to 140 degrees C or more, a temperature at which the plastic inside the pouch can bond with the plastic of the weld-spout. This is all done in just fractions of a second. To establish this seal, the weld-spout and the inner foil of the pouch need to be made of the same material – generally polyethylene (PE). At the same time, though, the outer layer of the pouch must be prevented from becoming soft as this could cause leaks and spoil the appearance. To avoid this, a different type of plastic with a higher melting temperature is used, for example polyethylene terephthalate, better known as PET. And now we come to the flaws mentioned above. Despite using the more heat-resistant PET, warping in the upper part of the outer layer of the pouch is not infrequent. Normally, this is nothing dramatic, but it doesn’t look nice. It is caused by the welding ribs of the weld-spout which are pressed through the heated PET by the high pressure, leaving visible traces. Due to the fact that a laminate, i.e. a foil consisting of at least two different materials, is needed for the production of the pouch foil, the pouch can only be recycled at considerable cost and effort. If the pouch consisted of just one type of plastic – a mono-material - and if this were identical with the plastic used for the weld-spout, conventional recycling would be a simple, unproblematic matter.
Mono-material pouches added value for consumer and environment
Inspired by the idea of this potential for improvements, MENSHEN started thinking about a new technology which would allow the use of a mono-material for the pouch on the one hand, whilst warranting a less harmful sealing process on the other. As already described above, formerly everything was heated by the sealing jaws from the outside through the pouch layers to the weld-spout. The inner pouch foil layer and the surface of the weld-spout melted and were then pressed together by the pressure from the sealing jaws, forming a permanent bond when they cooled down. If the outer layer of the pouch were also made of PE, it would melt during this process as well, become severely deformed and probably lead to leakages. So, the question was how to implement a pouch made solely of PE so that it was recyclable, but which wouldn’t warp, still looked presentable, and remained tight. After some consideration, in the end the solution was not so difficult. Instead of the heat being applied to the entire outer sheath of the pouch, from there to the inner layer until it reached the weld-spout, the process is now done in reverse. The weld-spout is still heated by two sealing jaws until the temperature is sufficient to melt the inner surface of the pouch, too, once the two materials are pressed together. At the same time, there is no contact between the sealing jaws and the weld-spout while the weld-spout is heating; they are separated by just hundredths of millimetres. This prevents the device from becoming clogged by residual material. A permanent bond is established as soon as the weld-spout with its melted surface is inserted into the pouch and pressed against the inner foil. The main advantage is that after contact with the cold pouch, the heat is not sufficient to reach the outer surface. As a result, the outside of the pouch remains smooth and intact. With this technology, it is possible to use a PE material for the outer layer of the pouch, so that the entire packaging unit is made of a PE mono-material. The positive consequence is that the packing unit can be easily recycled after use without any negative effects. Another sustainable solution from MENSHEN which contributes towards conserving essential resources and our environment.