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ECO-EFFICIENCY ANALYSIS DEMONSTRATES THE BENEFITS OF ULTRAVIOLET CURED ADHESIVES [2006]

Christopher A. Bradlee, EHS Team Member, BASF Corporation, Wyandotte,
Charlene A. Wall, EHS Team Member, BASF Corporation, Wyandotte
Timothy P. Sanborn, Product Marketing Manger, BASF Corporation, Charlotte
Ronald J. Horwitz, Technical Services Representative, BASF Corporation, Charlotte

An eco-efficiency study was conducted to compare the environmental impacts and total costs of UV-cured pressure sensitive adhesives (PSAs) versus thermally dried solventborne and waterborne PSAs. PSAs are designed to bond without the use of heat or moisture. They have a wide variety of consumer and commercial applications (e.g., masking tapes, office tape, labels) and continue to gain market share from mechanical fasteners. PSAs also have specialized industrial applications such as clear protective barriers on appliances and automobile components, reflective material on signs, and bonding a variety of similar and dissimilar surfaces, either permanently or temporarily. The adhesives are formulated to meet a specific cost/performance balance through the choice of an elastomer or polymer and other ingredients such as tackifying resins, additives, fillers, colorants, and oils. The general categories of elastomers and polymers used in PSAs include natural and synthetic rubbers, acrylics, and silicones. In some cases, more than one resin is used to provide additional properties not available with single resin formulations. Carriers and other additives such as rheology modifiers, defoamers, stabilizers, etc. are used to influence processing and coating behavior.

Eco-efficiency is one tool that can be used to strategically develop and pursue the best technologies for adhesive coaters. UV-cured PSAs may offer enhanced performance, higher productivity and an improved environmental footprint versus well-established water- and solvent-borne adhesives. The solvents used as carriers in the latter class of materials yield a liquid that is easily transported and applied to the substrate material (the web). The solvents are removed through evaporation and the adhesive remains on the web when the coating is dry. The pressure sensitive tapes and labels sectors use significant quantities of solvents such as toluene, heptane, MEK, xylene and mineral spirits, which are flammable liquids that have increased significantly in price in recent years. In addition to the fire and explosion hazards, the U.S. EPA considers them volatile organic compounds (VOCs) that can contribute to ambient air quality problems and are, therefore, regulated under the Clean Air Act. Toluene, MEK and xylene are classified as hazardous air pollutants (HAPS) that can cause adverse health effects. The use of solventborne adhesives can generate significant VOC and HAP emissions. VOCs and HAPS are emitted when solventborne coatings are stirred, when they are applied to the web, and when they dry. Therefore, the pressure sensitive tapes and labels sector is currently regulated by the states and the U.S. EPA. However, the U.S. EPA is developing additional regulations under the Clean Air Act Amendments that will significantly affect the use of HAPS and VOCs by the pressure sensitive tapes and labels sector.

The study focuses solely on one type of polymer, specifically acrylics, rather than comparing different types of chemistries. Remaining within the same polymer family discourages potentially uneven performance comparisons and allows the desired focus on the processing differences as a result of the carriers. Furthermore, the study compares UV-curable, solvent- and water-borne acrylic PSAs slanted toward the specialty performance realm rather than commodities such as packaging tape and general-purpose permanent label PSAs.