From Chemistry to Radiation-Curing Solutions
In a company covering a wide range of R&D activities, synergies are usually sought and identified in a formalized way. Technology developments responding to new market needs, however, require, as a rule, joint efforts by industrial partners specialized in complementary technology branches. The procedure here is less conceivable and predictable than with internal innovation processes.
The development of UV-curing technologies has been largely driven by joint efforts of all its stakeholders, including raw material manufacturers, formulators, equipment manufacturers and end users, as well as university researchers and consultants. Focus Groups established within the RadTech organization are good examples of partnerships facilitating such endeavors. This has been demonstrated by successful work in the UV powder and automotive area.
With this paper we would like to address the idea of value chain technology development and marketing by means of a few ongoing collaborations in the UV-curing area. In these projects we participate as raw material suppliers with the most comprehensive range of additives in the paint industry (Figure 1), creating effects throughout the whole value chain (Figure 2) and with expertise on their combined use.
RadTech NA Automotive Focus Group and Team UVThe RadTech NA Automotive Focus Group (AFG) has brought together leading paint companies, equipment suppliers, raw material suppliers and consultants with the objective to increase penetration of UV-curing technology in automotive OEM. Previous studies1-4 carried out by key players from these industries, partly as a joint effort, have impressively demonstrated the potential of UV-cured topcoats in providing a significant improvement in scratch and solvent resistance while reaching or exceeding the durability of the most advanced commercial thermoset systems.
In September 2000, decision makers from all major automakers and all major part suppliers attended the first AFG symposium, which presented the state of the art in UV-curing technology. Industry experts on safety, formulation, application, processing and durability presented the latest information. The proceedings were provided to attendees on CD. This symposium has been followed up by similar symposia at RadTech Europe in 2001, and RadTech Indianapolis in 2002. Another major event in the Detroit area occurred in late September 2003.
The Team UV Racecar project began in 2001, which involved a group of 17 AFG member companies with the intention to demonstrate the superior decorative and performance characteristics of UV inks, coatings and adhesives on a racecar. The Team UV car has been displayed at many coating shows and events. Plans for a new Team UV car are currently under discussion.
Current Automotive Focus Group projects include:
- Providing information and speakers for auto industry events to promote UV cure;
- Developing an effective section of the RadTech website where information is available in practical, understandable form;
- Designing industry events where those involved in OEM, refinish and component markets can find state-of-the-art information and interact with industry experts in chemistry and equipment;
- Providing the latest information on UV cure in the annual automotive edition of RadTech Report magazine, distributed to well over 1000 key industry contacts;
- Developing cost models that members can use to support the use of UV to customers.
Members of the AFG agree that it is worth their time and effort to achieve the goal of advancing the cause of UV curing in the automotive industry. UV curing may be the single technology that achieves the advances needed for future automotive coatings, despite unsolved problems like curing of shaded areas. This will not happen quickly, but, with cooperation and commitment, the problems can be solved and the technology adopted.
A recent example of the success of this approach is the Ford concept Model U. The Model U is a concept car demonstrating innovative Green technologies, such as the use of hydrogen as a fuel and renewable resources as raw materials for plastic parts. Interestingly, the Model U has a high-performance, low-VOC developmental UV-cure clearcoat supplied by Akzo Nobel.
In this particular case, the co-operative effort was focused on marketing throughout the value chain. In general, individual companies carried out technology and product developments. It is likely that in the future, the most successful projects will be the result of both co-development of key technologies and co-marketing of the benefits throughout the value chain.
UV-Curable Composites and Gel CoatsComposites in the present context are materials in which the radical co-polymerization product of an unsaturated polyester resin and styrene acts as a matrix for glass fiber structural elements, providing the mechanical strength and stability against deformation even at elevated temperatures. Parts of such materials are manufactured by automatic processes such as press molding or injection molding, or are handcrafted by contact molding. Conventional manufacturing involves thermal cure in an oven using peroxides as radical initiators, often in combination with cobalt salts and amines as accelerators for curing at lower temperatures.
One important drawback, especially in the thermal cure of open molds, is styrene emission into the environment. It has been shown in the 90's that this safety hazard can be largely eliminated by conversion from thermal to UV cure. UV curing is a "cold" polymerization process and comparatively much faster than thermal curing. It produces almost immediately a barrier surface layer preventing styrene evaporation. Additional benefits recognized from using UV-curable composite formulations include:
- one-pot system with long shelf life;
- full control of the curing process;
- shorter cycle times;
- re-use of excess formulations.
Gel coats are pigmented coatings applied on the exterior side of the composite part as a protective layer or as a decorative layer providing smoothness, gloss and color. UV-curable gel coats have been developed with the advent of UV composites. The UV curing of opaque-colored gel coats is no less challenging. Best results are achieved with BAPO photoinitiators in combination with a-hydroxy ketones. In contact molding, gel coat is applied by spraying on the surface of the open mold that has been previously treated with a release agent. After partial UV cure, the gel coat is covered with a first layer of composite material and then fully cured after repeated UV exposure. Additional composite layers are applied until the desired thickness is achieved (Figure 3).
We have recently entered into a collaboration with a composite manufacturer and its formulator with the objective to increase the market penetration of the UV technology by jointly optimizing the UV composite and gel coat manufacturing process and offering it to potential end users. The project partners holding strategic positions within the value chain (Figure 4) are thoroughly convinced of the superiority of the UV approach with respect to economy, ecology and safety.
This joint project holds challenges both on the technical and on the marketing sides. Among them is the clear perception that end users want a superior solution rather than just chemicals or dedicated equipment. An even more challenging perception is that each end user needs a special solution. Hence, success calls for careful selection and adaptation of all constituent parts of such a technology package and their proper alignment towards a robust, cost-effective and highly competitive process by specialists in the respective fields as well as for continued joint support of the end users.
The capital investment linked to the introduction of a new manufacturing process must be justified by the prospective return. Model calculations are mostly based on quantitative parameters. In this particular case an additional challenge is, therefore, to sell ecological and safety benefits. Tightening legal regulations, on the other hand, are imposing their inevitable pressures.
UV-Curable, Cationic, White Base Coatings for Two-Piece Aluminum CansWhite coatings are often applied on beer, beverage and aerosol cans as an opaque base for high-quality, multicolor halftone graphics and product information. Waterborne thermosetting coatings have superseded solventborne systems in the majority of beer and beverage can manufacturing plants. This led to a significant reduction, but not to an elimination, of VOCs and hazardous air pollutant (HAP) emissions, because waterborne coatings may contain 13 to 27% solvent, which is used to control viscosity, disperse pigments and aid in wetting. Tightening environmental regulations urge development and introduction of virtually emissionless coating processes.
100%-solid UV-curable coatings attracted the can industry's attention more than two decades ago. Acrylate-based UV overprint varnishes were first introduced by Coors Brewing Co. The inherent deficiencies of acrylate systems with regard to adhesion, flexibility and pasteurization resistance were remedied later by the introduction of cationic epoxy-based UV clearcoats. However, UV curing of white cationic base coatings remained a challenge, not least because the most efficient cationic photoinitiator salts contain the heavy metal antimony, which was rejected by most formulators. The speed requirements also suggested the use of expensive cycloaliphatic epoxies as principal formulation components.
We took up these challenges as an additives manufacturer by developing model formulations based on cheap glycidylether resins and heavy-metal-free salts as photoinitiators7,8. Unexpectedly, specific iodonium hexafluorophosphate salts showed higher reactivity than iodonium hexafluoroantimonate photoinitiators in glycidylether formulations and enabled cure of opaque white can coatings meeting or exceeding end-use requirements. At this point collaborations with leading metal container coating formulators were initiated to ensure market proximity and a faster promotion of this technology along the value chain. Later, resin and monomer manufacturers became involved in this project. The joint efforts attracted considerable market attention and opened up new potential applications such as flexographic printing inks.
ConclusionsThe radiation-curing market teaches us that inclusion and alignment of potential stakeholders down the value chain is as important as early and strong promotion of new ideas. Radiation curing requires fundamental changes in material and process technologies, leading to improved material properties but also to numerous challenges during implementation. Such challenges can be best met by close co-operation between technology leaders in complementary fields. Their combined market knowledge, together with the support of end users, are key factors for sustained success.
For more information on radiation curing solutions, write to Ciba Specialty Chemicals, Coatings Business Line, 540 White Plains Road, Tarrytown, NY 10591; call 800/200.4759; or visit www.cibasc.com.
References1. Misev, L. 8th Fusion UV Seminar, Tokyo and Osaka, 2000
2. Valet, A. Prog. In Org. Coat. 35 (1999), 223
3. Meisenburg, U. and Allard, M. RadTech North America 2000, Baltimore
4. Rekowski, V. and Frigge, E. RadTech North America 2000, Baltimore
5. Sitzmann, E.V. et al. Conf. Proc., RadTech Europe 2001, Basel
6. Jung, T. et al. Conf. Proc., RadTech Europe 1999, Berlin
7. Misev, L. U.S. Patent 6,235,807 B1
8. Misev, L. et al. WO 99/56177