Fun with Bag-on-Valve BY KEVIN VERVILLE Global Technical Director, Summit Packaging Systems See Bag Inner/Sealant Layer PE or PP Other Layer ??? Core Aluminum Other Layer ??? Outer Layer ??? 26 Spray April 2013 See Valve PE or PP ? Wide Open Valve Secondary Product Ports See Bag-on-Valve Bag-on-Valve (BOV) packaging systems are becoming increasingly popular, however sometimes even the basics elude both technical and non-technical industry members alike. The following “primer” will help readers grasp the fundamentals of BOVs, and can be used as a guide for future reference. This information was originally presented at the National Aerosol Association (NAA) 27th Annual Conference in San Antonio, TX. A BOV system is a barrier system that separates the product from the propellant, the bag being the barrier. When selecting a bag, it is important to remember that the bag is a major cost driver of BOV packaging. All bags currently used in today’s market have an aluminum core. It doesn’t have to be aluminum, but it’s an excellent barrier. Other materials are used as additional layers to provide strength and prevent migration between product and propellant. The inner sealant layer is usually polyethylene or polypropylene. On the left is a pouch that is slightly opened at the top. On the right, the bottom of the bag is “butterflied” open. Most bags are gusseted to maximize fill volume within the container. This shows a typical valve used on a BOV package. The only difference is that the tail piece is elongated so as to provide the sealant surface for the bag. There are top ports and an entrance through the dip tube, but the top ports are not a vapor tap—they are for dispensing product. One of the challenges with BOV packaging is that many of the mechanical options to control the spray characteristics are lost, as compared to a conventional aerosol system. For instance, the propellant outside the barrier cannot be relied upon to help atomize the product or affect spray rate because it remains in the container and is not emitted. Also, the stem orifice is larger for BOV. Products are filled by pushing the product backwards through the valve. Fast filling speeds are therefore dependent on the valve being wide open. As opposed to a traditional aerosol, a BOV cannot limit the orifice size to push large amounts of liquid through to achieve desired spray characteristics. One of the challenges for BOV is that, since the valve has to be wide open, the actuator must be relied upon to do everything to achieve spray performance. It must limit the spray rate, requiring it to do 100% of the atomization and 100% of the particle size determination. Formulation work can help, but BOV is a constrained system in that most of the tricks of the trade that have been developed to produce desired spray characteristics over the last fifty years are not available for product development. This point is true for all barrier packs. This shows the extended portion of the valve, the valve body and the valve inserted into the opened pouch. The valve is dropped into the pouch and heat sealed onto the valve. Pouches are also heat-sealed.
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