|Cartridge Technology for Spray-Applied Coatings -
Low Cost, Reliable, Portable, and GREEN
Abstract: With increasing frequency cartridge-based technology is becoming the preferred method for touch-up and repair applications using high-solids coatings. Cartridge technology directly addresses many of the issues associated with batch mixing including pot life constraints, waste generation and off-ratio material proportioning/mixing. Recent data indicate there are substantial cost-savings and environmental benefits associated with cartridge use in comparison to conventional methods of touch-up and repair.
Introduction: In recent years, several factors have converged to challenge current methods for touch-up, repair and maintenance work. The coatings industry, in response to consumer demand for rapid cure technology and reductions in volatile organic compound (VOCs), has focused on high-solids, reduced-solvent coatings. Additionally, economic conditions and budget constraints have forced many facilities, particularly those in the marine industry, to extend repair cycles for many assets. When these assets are returned for maintenance, expenditures are kept to a minimum and a premium is placed on cost-saving measures.
This new demand for low-VOC, high-solids coatings, coupled with extended repair cycles and budgetary constraints, has fomented a new set of challenges for the coatings industry. Specifically, how does a painter batch mix small amounts of material with a reduced pot life while maintaining cost-saving efficiencies? This problem has vexed coatings and equipment manufacturers until the introduction of single-use, disposable plastic cartridges.
Background: Cartridges have been used for packaging epoxy adhesives and polyurethanes for almost thirty years. Adhesive manufacturers were quick to realize the myriad benefits associated with cartridge packaging for two component reactive materials: on-ratio
proportioning/mixing, the ability to dispense a small amount of material and recap for later use, reduced material waste and consumer friendly “convenience” size packaging. Since its inception, the use of cartridge technology has grown significantly and is now used extensively for adhesive applications across a broad range of markets and applications.
Not until 2002, however, did the use of cartridge technology become fully realized when the ability to spray apply reactive coatings via a cartridge system was developed and patented (Hunter, J. H. U.S. Patent 6,488,991, 2002.), (Hunter, J. H. U.S. Patent 6,572,031, 2003.). For the mixing and atomization component, this system used a unique disposable spray-tip static mixer (Hunter, J. H. U.S. Patent 6,616,068, 2003).
Spray-Tip Static Mixer
Now, the full range of benefits associated with cartridge packaging and application could be applied to sprayable coatings. Materials with short pot lives including epoxies, polyureas, polyurethanes, polyaspartics and urethane foams could now be used in smaller batches, obviating the need for expensive maintenance intensive plural component spray equipment.
As market acceptance of cartridge technology broadened, the United States Military underscored its endorsement by assigning greater than forty (40) National Stock Numbers (NSN) to pre-filled cartridges for commonly used Mil-Spec paints and coatings.
Cartridge Equipment Basics:
Cartridge-based technology consists of three basic components:
Dual-Barrel Cartridges: Designed to accommodate various two-component materials and mix ratios while providing maximum solvent and moisture resistance. Enclosed materials are correctly proportioned and kept separate until dispensed, an innovation known as “mix-on-demand” technology. Partially dispensed cartridges can be re-capped and used at a later date.
Static Mixers: Straw-like tubes that contain a helical mixing element. Materials that enter the static mixer are separated and recombined exponentially, creating a superior mix and completely eliminating the need for manual mixing of products. Static mixers allow the user to extrude or spray the materials directly from the cartridge.
Cartridge Dispensing Equipment: There are several methods to apply coatings using cartridge-based technology:
Manual Dispensing Gun: Similar to a dual-barrel caulk gun, the manual dispensing gun offers portable dispensing and does not require an air source for operation.
Wall Mount Unit: The wall mounted dispensing unit was designed to replace the paint kitchens/lockers onboard ships. The wall mount eliminates batch mixing for touch-up and small repair in a production environment.
Air-Operated Spray Gun: The air-operated cartridge spray gun, when used in conjunction with a spray-tipped static mixer, allows the applicator to dispense or spray material directly from the cartridge.
Quad Spray System: The Quad offers the largest volumetric capacity of any cartridge-based application system, making it ideally suited for larger application areas. Benefits also include a lightweight hand gun and the ability to extend material lines up to 50 feet.
Preparing Cartridges for Use: Preparing pre-filled cartridges for use requires a few simple steps.
Gently agitate the cartridge for two minutes to ensure there are no settled materials.
Remove retaining nut and end-cap.
Place mixer onto cartridge nozzle and tighten retaining nut.
Insert cartridge into dispensing gun.
Phase / Purge the cartridge of any air and initial material that may be off ratio.
Cartridge is now ready to be dispensed.
The Benefits of Cartridges: Cartridges directly address many of the current challenges endemic to touch-up, repair and maintenance applications, especially those using high-solids coatings.
Mix-on-Demand Technology: Cartridges allow the desired amount of material to be dispensed or sprayed; the cartridge can then be re-capped for later use, eliminating the need to use an entire kit of material or dispose of unused mixed material.
Elimination of Pot-Life Constraints: The mix-on-demand technology employed by cartridge technology eliminates pot-life constraints as materials are mixed as needed in the amount needed. The need to mix the entire batch of material is eliminated, a critical problem for rapid cure systems. Additionally, some paint companies employing cartridge technology have eliminated induction time requirements for certain materials based on the superior mix achieved.
Consistent On-Ratio Proportioning and Mixing: Cartridges allow for material to be proportioned correctly according to volumetric mix ratio and obviate the need for applicators to “eye-ball” materials when batch mixing. Additionally, the static mixing tip employed by the cartridges provides a superior mix when compared to hand mixing methods, thus ensuring an accurate, repeatable mix for each application. Rework on previously painted substrates is minimized significantly.
Ease of Use and Portability: Workers using the cartridge dispense or spray system can be trained within minutes. The entire cartridge system, including dispensing gun, weighs less than 10 lbs and can easily be transferred among locations.
Low-Cost Compared to Conventional (Spray) Systems: The cartridge application system costs a fraction of the price of a conventional spray system (depending on the system used, usually less than $500.00).
Reduction in Set-up and Clean-up Time: The cartridge system takes only a few minutes to set-up and requires no clean-up (i.e. no flushing of material lines, cleaning mixers, etc.), greatly enhancing worker productivity and throughput.
Elimination of Material and Hazardous Waste: Cartridges, when fully evacuated of material, contain just a few milliliters of waste. Almost 100% of the material contained within the cartridge can be used for application, greatly reducing material waste and associated hazardous waste disposal charges. Less waste results in substantial cost-savings to the end user. In many cases discharged cartridges can be disposed of in standard waste streams. Always verify with local disposal regulations first.
Minimizes Worker Exposure to VOCs: Cartridge-based technology is essentially a “closed system.” With pre-filled cartridges, applicators do not have to batch mix materials, thus eliminating worker exposure to open containers and minimizing contact with VOCs.
Verification of Cost Savings/Total Cost Reduction - Case Studies:
Cartridge-based technology significantly reduces total operational costs. This reduction in operational costs has been substantiated by the growing use of cartridge technology in both the public and private sector. Actual time and cost-savings have been documented via two case studies detailed below:
Case Study #1: Camp Carroll, Waegwan, South Korea (August 2007):
In conjunction with the U.S. Army TACOM Life Cycle Management Command, HUMVEE vehicles were painted using cartridges filled with MIL-DTL-64159 (CARC) Paint. Results were compared to conventional methods of painting using MIL-DTL-64159. A brief summary of the results are as follows.
Time to mix 1.5 gallons of material (post-adding de-ionized water):
Conventional Method (batch mixing using Jiffy mixer) = 25:30 minutes
Cartridge Method (using pneumatic wall dispenser) = 12:43 minutes
○ Conventional Spray (using cup gun) = 18:14 minutes
○ Cartridge Method (using hand-held spray gun) = 10 seconds
● Time Required to Paint Entire HUMVEE
○ Conventional Method (batch mix and cup gun) = 82:02 minutes
○ Cartridge Method (using hand-held spray gun) = 78:02 minutes
Hand Mixing Materials Wall Mount Mixing and
As the above referenced time studies show, significant time is saved using cartridge-based mixing and application methods. The time savings associated with cartridges are more pronounced with smaller/touch-up applications, especially those involving hand mixing of materials for brush and roll applications. As the size of the application increases, the time associated with conventional and cartridge application methods tend to converge.
Case Study #2: Northrup Grumman Newport News Shipyard (December 2005):
Paint cartridges filled with MIL-DTL-24441 Formula 150 Green (two component anti-corrosive epoxy primer system) were used and compared to conventional batch mixing/brush and roll application methods. Using a loaded labor rate of $50.00 per hour with 100 painters working 8 hours/day and $50.00 per two gallon kit of paint, the following was observed:
Reduction of two man hours per painter in waiting in queue for draw of paint (100 painters x 2 hours x $50.00/hr = $10,000 per day saved).
15-25% reduction (approximately one hour) in application man hours (100 painters x 1 hour x $50.00/hr = $5,000 per day saved).
Material waste reduced by 25% ($25.00 gallon x .25% = $6.25 x 100 painters = $625.00 saved per day).
Disposal costs reduced by 50 gallons for all painters combined ($275.00 to dispose of 55-gallon drum).
Total Cost Savings per Day = $15,900 per day or $4.2 million per year.
Both case studies clearly indicate the tremendous time and labor savings (i.e. total cost reduction) associated with cartridge use compared to traditional methods used for touch-up/repair applications. Cartridges completely eliminate or minimize many costly steps associated with touch-up/repair, including hand/batch mixing, set-up, clean-up and disposal of unused hazardous materials.
Additional Cost Savings through Environmental Benefits:
In July 2003, in association with the American Shipbuilding Association (ASA), the United States Environmental Protection Agency published an implementation guide for the shipbuilding and ship repair industry. Among other procedures, the EPA documented dry-dock painting processes, detailing the steps and assembling into a publication named the “The Environmental Management Systems Implementation Guide (EMS Guide).” The EMS Guide is meant to “assist shipbuilding and ship repair facilities in weaving environmental decision-making into the fabric of the way they do business . . . not only to achieve better compliance assurance, but also to improve environmental performance in areas such as resource conservation, energy efficiency, water-use efficiency, land use, and mitigation of impacts associated with noise, odor, and dust.”
These procedures, when conducted using cartridge-based technology, show significant labor and cost savings through process efficiencies, step elimination, minimization of bulk materials required and reduction in hazardous waste generation. Rare is the instance in which total costs are reduced and environmental benefits are realized.
As the flowcharts below indicate, most of the steps associated with clean-up and (hazardous) waste disposal are eliminated, primarily as a result of almost complete material evacuation from the cartridges (i.e. reduced waste disposal costs) and the removal of solvent-based cleaners and contaminated disposables.
CONCLUSION: Cartridge-based technology significantly reduces the total costs associated with touch-up and repair applications compared to conventional methods. It provides a proven, cost-effective method for addressing many of the issues associated with batch mixing including pot-life constraints (of high-solids materials), off-ratio material proportioning/mixing and waste generation.
Cartridge technology continues to gain widespread industry acceptance and is ideal for applying a wide range of coatings, from epoxy paints to polyureas, industrial foams and a host of other two-component reactive materials.
These costs savings result in significantly higher profit margins and greater worker productivity. Along with the economic benefits is the waste minimization aspect of cartridge use, further enhancing cost-saving measures through environmental compliance and conservation.
These benefits bode well for the continued growth of cartridge spray technology in the marketplace.
Hunter, Jack H., US Patent 6,488,991 B1, Dec. 3, 2002.
Hunter, Jack H., US Patent 6,572,031 B2, June 3, 2003.
Hunter, Jack H., US Patent 6,616,068 B2, Sept. 9, 2002.
Peter H. Kuzyk
Peter H. Kuzyk is Vice President – Sales & Business Development for Plas-Pak Industries, Inc. in Norwich, CT. USA. Previous to this he was Managing Director Enthone-OMI (Australia); a division of Cookson Electronics.
Jack H. Hunter
Jack H. Hunter is Sales & Development Manager – HSS Spray Systems for Plas-Pak Industries, Inc. in Norwich CT. Previous to this he was Spray Applications Specialist for Bayer Corporation.
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