Theoretically, coatings applied by the UNICARB system are no different than conventionally applied coatings. In a cured coating film, the delivery solvent rarely plays a role. Its only purpose is to lower the viscosity so that the material can be sprayed. After application, the delivery solvent evaporates and leaves the film. Supercritical CO2 is used by the UNICARB system to replace the organic delivery solvents. Other solvents and materials such as the resin system, pigment package, and other additives remain unchanged. The CO2 supplies an atomization mechanism and is vaporized from the coating during the atomization process.

For material to be used in the UNICARB system, the coating supplier must know of the intent to use supercritical CO2 as the solvent. Testing is required to ensure the CO2 will properly dissolve in the organic coating material, provide adequate solvent properties, and is compatible with the other materials. Other major components of the coating system remain unchanged.

The UNICARB equipment is more complex than conventional spray systems although its operation is as simple. Operators and facility maintenance personnel would require three days of training with the equipment. Operators would need to be trained on the aspects of airless sprayers, specifically the effect of nozzle selection on spray pattern and application rate. Typical spray practices will need to be followed. The operator would be able to select the correct nozzle (spray pattern) for different parts, and personnel spraying preferences.

Once the ratio of paint to CO2 is set for a given coating, it will not require changing. However, regular maintenance is necessary to ensure correct calibration of critical measurement components. If these components are neglected, an improper mixture of coating and CO2 could occur, resulting in application problems. One 50-lb CO2 cylinder should supply the needs of 19 trailers.

• Elimination or significant reduction of VOCs used as solvents in paints, which are associated with the formation of smog typically regulated by federal and state agencies as well as local air pollution control districts.
  
• Elimination of hazardous air pollutants (HAPs) used as solvents in paints, which are regulated by federal, state, and local regulations including the National Emissions Standards for Hazardous Air Pollutants (NESHAPs) (40 CFR 63).
  
• Elimination of all SARA Title III reporting substances from coating processes (40 CFR 300, 355, 370, and 372; and EO 13148).
  
• Reduced generation of coating waste and cleaning solvents that may need to be handled and disposed as hazardous waste under 40 CFR 260 and related sections.
  
• Reduced occupational exposures that are regulated under 29 CFR 1910.

Compliance benefits include: 1) elimination of recordkeeping and reporting requirements under the Title V Operating Permits Program, NESHAP Program and SARA programs, 2) reduced administrative burden associated with hazardous waste (i.e., tracking, plans, reports, and training), and 3) reduced administrative burden associated with OSHA (i.e., training and recordkeeping).

The Compliance Benefits listed here are only meant to be used as general guidelines and are not meant to be strictly interpreted. Actual Compliance Benefits will vary depending on the factors involved, e.g., the amount of workload involved.

Proper design, operation, and maintenance of the equipment is required for its safe use. The spray booth must be well ventilated. Additional health concerns depend on the coating being applied. Solvent-based coatings can irritate the lungs and mucous membranes. Prolonged exposure can affect the respiration system and/or the central nervous system. Proper personnel protective equipment should be worn, if required.

Consult your local industrial health specialist, your local health and safety personnel, and the appropriate MSDS prior to implementing any of these technologies.

• Reduced environmental impact associated with hazardous solvents and solid/hazardous waste generated for disposal.
• Improved health and safety working conditions and decreased health-related costs (liability risks, protective equipment costs, and monitoring costs) compared to the use of VOC-containing coatings.
• Reduced manufacturing costs as a result of less raw material usage due to the higher transfer efficiency.
• Produces larger spray patterns, provided that the fluid delivery rate is uniform, which can provide faster, more efficient coating of a given surface area.

• Coating materials need to be reformulated by the manufacturer to remove the solvents no longer needed.
• Equipment training is needed.
  
• Cleaning of the equipment is more time consuming than other processes.

• Average cost savings per trailer was in excess of 50 percent.
  
• The simple return on investment to recover the cost of equipment is 0.8 years.
• RIA would emit 7.4 lbs. of VOC less per trailer than baseline operation.
• Because RIA would require almost two gallons of paint less per trailer, the installation would require storage, procurement, and spraying of 1235 gallons less of paint per year.
• Due to decrease in spraying times, RIA could save 156 labor hours per year.

Assumptions:

• Based on data from an industrial painting line at Rock Island Arsenal (RIA), IL
• Topcoat is a single component, moisture-cure urethane coating (MIL-C-53039)
• Electrostatic spray gun (Graco manual spray gun) with a nozzle featuring a 6" spray pattern
• Mixture ratio: 3.3 ml of paint to 1 g of CO2
• Temperature 60 °C
• Pressure 1500 psig
• On average, 3-5 wet mils were achieved to meet baseline operations.
• 4 trailers were used, with temperatures ranging from 83-88 °F and relative humidity ranging from 46-67.
• The operational cost per trailer is $58. This figure is based on the following conclusions:
  • Due to a decrease in spraying times, RIA could save 156 labor hours per year at a production rate of 12 trailers per week.
    
  • The UNICARB system used an average of 0.77 gallons of coating per trailer vs. 2.5-3 gallons baseline.
    
  • Spraying times for the UNICARB system was 39 minutes per trailer vs. 45-60 minutes baseline.

  Note: Utility costs were not included, and could be considered insignificant.
  

  
  

Table 1. Material Costs

Item	Cost ($)	Usage/trailer
2.8 lb/gal VOC coating	75-100/gal	0.77 gal
3.5 lb/gal VOC coating	60/gal	~2.75 gal
50 lbs CO2 cylinder CO2 cylinder rental 30/yr	6.5 1.92 lbs	N/A

Economic Analysis Summary:

• Capital Cost: Equipment costs range from $40,000 to 90,000. This range takes into account other factors that affect costs, including coating recirculation, application rate, number of spray guns used simultaneously per system, spray gun (electrostatic/manual), and operator interface/operations data requirements. Recent technological advancements in equipment design have firmed the cost for the equipment to spray this coating at $50,000.
  
  
• Payback Period for Investment in Equipment/Process: 0.8 years, using an equipment cost of $40,000 and a production rate of 12 trailers per week (624 per year)

None identified.

Appropriate authority for making process changes should always be sought and obtained prior to procuring or implementing any of the technologies identified herein.

Concurrent Technologies Corporation. UNICARB CO2 Painting Demonstration for Rock Island Arsenal (RIA). Demonstration Data Analysis/Report. October 16, 1998.