Figure 5. Spray pattern consistency vs. can pressure January 2016 Spray 29 and Fluidic MBUs. Similar to examples shown above for spray patterns, BOV and LPG delivery systems were used. Figure 4 shows droplet size distribution from a Malvern Spraytec at 4.5" from the nozzle exit. The Fluidic MBU has the largest droplets at 105μm (DV50) compared to Swirl MBUs at 54μm and 43μm respectively. Remember, air care applications typically target droplet sizes in the 35–70μm range with the intention of enabling quick evaporation and proliferation of the product (fragrance) without wetting of adjacent surfaces. For such products, the preferred nozzle would be an optimized Swirl MBU. However, for most other applications, these smaller droplet sizes are not appropriate so companies typically explore changing delivery rates, can pressures, formulation and other nozzle parameters. None of these can effectively approach the coarser droplet sizes from Fluidic MBUs to reduce product odors/ fumes, inhalation and wind drift. Another noticeable impact on spray performance due to droplet sizes is when the product is used outdoors, where drops generated by a Swirl MBU are adversely (and easily) affected by wind drift. Based on droplet aerodynamics, sub-60μm droplets (DV50) will exhibit significant wind drift. Crosswinds as slow as 2mph can cause Swirl MBUs to deliver less than 75% of the product to the target. At 5mph (a more typical wind speed), the amount of product reaching the target drops to below 50% for Swirl MBUs. Conversely, Fluidic MBUs (at 2mph and 5mph) can deliver as much as 90% and 80% respectively of the product to the target. Spray pattern consistency When comparing nozzle designs, a less obvious spray performance characteristic is pattern consistency over the life of the can as can pressures diminish or in general, spray formation with increasing pressures. The impact of nozzle selection on this attribute is dramatic when comparing Fluidic MBUs to Swirl MBUs as a function of can pressure. Based on alcohol paper spray patterns, the diagrams in Figure 5 show spray size degradation for Swirl and Fluidic MBUs. Product sprayed was an ethanol mixture in a compressed gas delivery system. With the Swirl MBU, coverage areas shrink to about 25% of the original size when pressure is reduced from 100 to 25psi. Correspondingly, the Fluidic MBU 25psi coverage is 75% of the original size, which is a significant improvement when compared to the spray area reduction commonly experienced from Swirl MBUs. These results are quite relevant for many applications, including trigger and finger pump delivery systems. As a result, Fluidic MBUs enable use of lower can pressures in aerosols and produce consistent and uniform spray patterns for aerosols and pump packages. When considering spray shape, once again the variety of avail- Figure 3. Swirl LPG cross section able patterns is typically dictated by nozzle selection. Fluidic MBUs can produce a wide range of pattern shapes from narrow rectangular strips to square patterns. The designs can have an adjustability feature (vertical/horizontal) similar to some spray paints on the market. The pattern generated by Swirl MBUs are mostly limited to a circular shape. The big picture Over the years, there has been little innovation in insert/nozzle technology for consumer packaged goods. The most widely used technology is the Swirl MBU, and in many cases rightly so. Common knowledge supports its proliferation. Swirl MBUs are intended for fine atomization and are well-suited for air care and applications that benefit from fine drops. As described, they have inherent limitations of slow spray development, non-uniform distribution, round patterns and fine drops.1 The Fluidic MBU is a very good general purpose spray with uniform, fast developing, slightly coarse droplets and targeted pattern for almost all other applications where fine drops are not needed. For the big picture, Fluidic MBU technology open doors for advances in the consumer spray experience. Its robust spray performance also widens the design space for manufacturers when it comes to packaging and formulation. They also help reduce propellants, can pressure and VOC levels. We make design decisions daily and often make use of ideas that are “outside the box,” but rarely do we consider focusing on the nozzle design other than to adjust spray angles or delivery rates. Seldom do we have the opportunity, or the time, to venture into new territory with different nozzle technologies. However, taking into account disruptive nozzle technologies, it can help ensure optimum product performance. Match the formula and delivery system with the correct nozzle technology and the glass slipper will fit every time. Spray 1 Lefebvre, A. (1988) Atomization & Sprays. CRC Press Figure 4. Droplet size distributions using Malvern Spraytec
Spray January 2016
To see the actual publication please follow the link above