When evaluating the economics of implementing an alternative adhesive technology, a full range of applicable factors must be taken into account. Conventional tools used to analyze and compare costs and benefits of alternatives leave out a number of important cost factors, such as environmental compliance and future liability. Costs that must be considered for a complete analysis include raw adhesive purchase and transportation; capital equipment; energy consumption; production rates; operator efficiency; and regulatory compliance.
Raw Adhesive Purchasing Costs/Transportation Costs
The purchase price of radiant-cured adhesives tends to be more expensive than solvent-based adhesives. Comparing initial purchase prices, however, does not provide a complete cost picture. Radiant-cured adhesives are 100% solids and the entire volume is used as an adhesive, while typical adhesives lose 50-70% of their volume during application. (Ref. 6) Consequently, on a per-pound basis less radiant-cured adhesive is needed to obtain the same coating thickness as a solvent-based adhesive.
In comparing the costs of the two radiant cure technologies, ultraviolet (UV) light cured raw materials are generally 20% more expensive than electron beam (EB)-cured raw materials due to the photoinitiator additive that the UV system requires. (Ref. 2)
Once the adhesives are purchased, there is a cost in actually getting them to the user. Although radiant-cured adhesives are not in extensive use in the U.S. and specific information for transport is unavailable, it is reasonable to assume that freight costs would be less than for solvent-based adhesives, due to the reduced volume of adhesive needed for the same coating area.
Capital Equipment Costs
The National Risk Management Research Laboratory (NRMRL) published an analysis comparing capital costs of solvent-based and EB adhesive systems. This analysis showed, in 1994 dollars, that capital costs for EB adhesive systems are 27% less than conventional solvent-based adhesive systems, even when costs of air emissions controls for the latter are excluded. (Ref. 6) Between the two radiant-cured technologies, UV light-cured adhesive systems are less costly than EB-cured systems. (Refs. 2, 4) The additional requirement of emission control systems makes solvent-based adhesive systems much more expensive, as does the need for explosion-proof equipment in solvent-based adhesives processes.
The NRMRL analysis also determined that the costs for retrofitting an existing solvent-based adhesive system to an EB system, was approximately $750,000 (1994 dollars), the cost of an EB-curing mechanism. No other additional coating equipment is needed; the solvent-based adhesive system can be used. (Ref. 6)
Manufacturers considering a switch to radiant-cured adhesives must take into account not only the costs of capital, but also operational costs. These operational costs include production costs, energy costs, and regulatory costs, and although they are discussed separately below, these costs often overlap with one another.
The radiant-cured adhesive technologies have fast cure times, measured in seconds (at most), compared to minutes or hours for solvent-based systems. (6) This is an especially important factor when producing high volumes of products at high speed. UV and EB systems have additional production advantages in terms of floor space and labor requirements. Although the production runs of the radiant-cured systems are faster, it is necessary to remember that there will be an initial one-time production cost resulting from the downtime for new maintenance procedures and training, and unfamiliarity with new equipment. Table 4 compares average production speed, floor space consumption, and operator requirements for radiant-cured and solvent-based systems.
Table 4(Ref. 6)
Approximate Productivity/Efficiency/Floor Space Comparisons of
Solvent-based Systems and Radiant-Cured Adhesives
Solvent-Based UV Cured EB Cured Speed (ft/min) 750 1,000 1,600 Length of production line (ft) 150 40 40 Operators 3 to 4 1 to 2 1 to 2
Although there is little specific data, the literature implies that radiant-cured adhesive systems have an energy cost advantage over solvent-based adhesive systems. (Ref. 6) This is most likely the result of avoiding the costs of large drying and curing ovens and solvent recovery equipment for solvent-based systems.
By eliminating emissions of HAPs and other VOCs, the radiant-cured adhesive technologies offer cumulative savings in avoided emission control equipment costs, permitting fees, and hazardous waste disposal charges. There are also reductions in monitoring costs, since the radiant-cured systems do not require stringent monitoring of employee exposure to solvents, or the explosive limits of those solvents. Avoided regulatory costs are a significant factor to consider when comparing alternative adhesive systems.
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