The best and worst feature of paper is its ability to absorb and retain water. The paper making process is a water-intensive operation that allows us to make paper efficiently and also allows us to recycle paper and corrugated materials. There are many products we count on every day for their water absorbing properties; in particular for personal hygiene. However, for those of us involved in the packaging and the supply chain, water and water vapor causes trouble by weakening corrugated and other paper products.
Corrugated is the most common material used for making shipping boxes and transport packaging and moisture can weaken the strength of the box very quickly and dramatically. Cranking up the relative humidity to 80% reduces stacking strength by one-third. If the corrugated gets wet, stacking strength is virtually ZERO. Liquid water can also cause sufficient cosmetic damage to cause the box to be unsaleable whether the product inside damaged or not. This is why it is so important to keep your corrugated boxes dry in your supply chain.
There are coatings for corrugated materials, some better than others. I have had countless cups of coffee in paper cups, but the reason the cup holds together is because the inside, and sometimes the outside is lined with polyethylene. The polyethylene coating keeps my coffee cup from becoming a soggy mess in my hand, but makes the cup very UN-friendly to the paper recycling process.
There have been many efforts in the past to come up with a new way to make the paper water resistant and still work in the repulping operations that converts post-consumer fiber material back into paper. The most common coatings used today use water-based chemistry to coat an entire side (flood coat) of material (paper or corrugated) using a wet roller and controlling application thickness very closely to assure the product dries fully in the converting process.
Last year a new kid on the block began touting a new process and some new chemistry to bring water resistance to the paper and corrugated industries. PackagingDigest indicates that BT3 Technologies are wet coating the web, then controlling the vapor pressure of the fatty acids onto the paper substrate with heat to drive off the excess. The fatty acids are reportedly from plant based chemistry. Traditional vapor deposition works by laying down molecular layer(s) onto an entire surface. Similarly, BT3 is coating the entire surface; however, the target of the coating is the hydroxyl group on the paper to which their fatty acid can bond. They refer to this combination of wetting, heating and chemical bonding as ‘chromatografting’. This year, Packaging Digest reports that BASF signed an agreement with BT3.
There has been a lot of buzz in the media lately about coatings that are super water repellent (my new Samsung phone is claiming to be water resistant, but I’m not going to be the one to test it on purpose). Most of these new water repelling coatings are also based on some type of very thin layer (typically a single molecule thick) of super-hydrophobic material.
BT3 Technologies will need to scale up their process window (currently at a web of 9.5”), however, their process speed is well within corrugated process windows at ~1300 ft/min. Additionally, BT3 is creating additional grease and gas barriers by combining their chromatografting with previously treated paper with polyvinyl alcohol (PVOH). With the addition of BASF chemical engineering muscle, it’s possible this may become a viable and valuable new coating.
Leave a comment where yous see the greatest potential for this technology in Packaging!
Leave a comment where yous see the greatest potential for this technology in Packaging!
The military was one of the few customers called out waxed corrugate. Certainly, for cosmetic reasons some use liquid lamination on higher end goods in corrugate (just got one this week), and coasted corrugate is used for bulk food transport, especially produce and meats. But it would seem to be, by sheer volume, frozen food cartons would be the best target. Most are SBS, some not, but still PE coated. Walking down the food aisles that's the most obvious high volume use. That and fast food (should it be allowed for 'hot fill') would top my list for most interested customer, if the price is right, not corrugate.
ReplyDeleteEric,
ReplyDeleteWax-alternative coatings have been around for a while now. Some work better than others and application thickness and temperatures vary by chemistry. There are a variety of issues in conversion and getting speeds of 1300/ft/min. might happen. I would caution you that our experience has been you need more than just a coated liner to play with high moisture environments. Our anti-wicking medium coupled with special adhesives and a coated liner has held water in one of our corrugated coolers for over 30 days. Water tends to evaporate before penetrating our liner.
Iced fish/meat/poultry are standard markets.