SMART PU HARDENERS: EFFICIENCY, SUSTAINABILITY AND MORE

Transcription

1 SMART PU HARDENERS: EFFICIENCY, SUSTAINABILITY AND MORE D.I. Rolf Roschu, Dr. G. Behnken, A. Hecking, Dr. Ch. Irle, Dr. Jan Weikard Covestro Deutschland AG, Leverkusen, Germany 1. INTRODUCTION Does a low viscous polyisocyanate contribute to elasticity? Can an aliphatic hardener make a PU coating dry faster? Will a cross linker influence adhesion? Is it possible to have faster drying and perfect adhesion of PU coatings triggered by the same smart molecule? And what about sustainability? PU cross linkers are known as versatile and efficient tools to crosslink coatings formulations, resulting in high performance coatings in many industries and end uses. However, the perceived role of the hardener itself often is limited to be an as-good-as-possible match to the polyol component which on the other hand has the most significant impact on performance and processing. A series of innovative smart hardeners is highlighted in this paper; all of which will fundamentally question that perception, as they strongly trigger performance and thus add value to PU coatings. Two further examples, coming straight from our development labs, will be highlighted. A new thermolatent hardener, that offers significantly improved curing speed for 2K PU high gloss clear coatings, as well as a new bio-based hardener for the development of more sustainable polyurethanes. Especially this hardener can be potentially used for coatings, adhesives and any application where standard, mineral-oil-based hardeners are used. 2. POLYURETHANE COATINGS For many years, polyurethane coatings have been established as the industry standard for high performance, efficient and robust coatings processes [1]. Originated by Kuno Wagner [2] in the 1960s, the evolution of polyisocyanate technology has been the technology driver to create a broad range of raw materials - poylols and crosslinkers - designed to fulfill the needs of diverse industries all over the world: Automotive industry and refinish, infrastructure as well as industrial coatings. In parallel to PU s increasing market penetration, the demand for solutions with reduced environmental impact has constantly increased. Raw material and coatings industries have been developing PU solutions with significantly reduced solvent emissions. For two decades, innovative solutions have been penetrating into global markets: Waterborne and high solids PU formulations fulfil the industries performance requirements, and in addition contribute to a significant reduction of emissions. Formulating polyurethane coatings in most cases starts by choosing the right polyol. The huge diversity of available alternatives is certainly an important argument supporting the un-

2 matched competitiveness of PU technology. The role of the hardener in many cases is defined by crosslinking the polyol. The hardener, first of all, is required to be compatible with the polyol component, and to chemically react with the polyol in an efficient way. With respect to low emission systems, also viscosity of the hardener is an important parameter influencing solvent content of high-solids systems and miscibility of waterborne formulations. 3. SMART PU HARDENERS IN TERMS OF VISCOSITY AND FUNCTIONALITY The general perception of the function of PU cross linkers is quite limited and focusing on a sufficient interaction with the polyol which is the main driver for final performance and processing speed. As a result, in most end use markets, coatings formulators are used to choose from a limited range of standard polyisocyanates. The line starts typically with a biuret hardener at a viscosity of mpas and goes down to low viscous isocyanurate or iminooxadiazinedione [3] hardeners at 730 mpas. Accordingly, those hardeners have functionalities between 3 and 4. In line with common perception, the hardener s impact is limited to steer application viscosity (influenced by hardener viscosity in the range mentioned above) as well as crosslinking efficiency and speed (influenced by the respective functionality). Since the 1960s there has been a significant widening in understanding of design of PU hardeners. Ground breaking technological achievements paved the road towards particularly low viscous hardeners. Yet, the growing variety of chemical modifications of isocyanates also opens the door towards novel hardeners, enabling coating formulators to improve formulations, add functions, and to add further value to their products. The broad variety of isocyanate derivatives is our toolbox. The key to innovative PU cross linkers is to choose the right synergy of structures to design smart hardeners. Based on this approach we want to describe a twofold extension of the commonly perceived range of polyisocyanates (Fig.1). First: We expand the range of viscosity/ functionality into both directions: higher functionality than 4 ( faster curing) and viscosities lower than 730 mpas ( reduced emissions). Second: In addition to this linear range, we will step into a second dimension and discuss the benefits of adding functionalities to the hardeners, resulting in a major impact on coatings performance. Fig.1: Two-dimensional canvas of smart PU hardeners built around 1-dimensional line of standard hardeners.

3 The result of using smart hardeners can be measured by physical testing: higher elongation at break and tensile strength, improved tear strength. Or, ultimately, in significantly better performance and added value of functional coatings, such as fast curing systems, low VOC emissions, self-healing clear coats, high end elastomeric coatings LOW VISCOUS PU HARDENERS I: REDUCE EMISSIONS The global trend towards reduced emissions has created a strong demand for waterborne or very high solids coatings. In most cases, stringent emission regulations can only be met by carefully selecting tailor-made components on both polyol- and hardener end. Hardener selection has to take into account that lower viscosity ( ease of mixing) often goes hand in hand with low functionality (reduced chemical resistance). A major breakthrough was marked by lowest viscous trimers, at a viscosity of 730 mpas1, while maintaining functionality above 3. As a consequence of the relatively high functionality, resulting performance and process productivity meet the market s requirements. Recent developments in our labs put an even further reduced viscosity of 500 mpas into practise, without sacrificing performance: building on asymmetric trimer structures, for the first time an average functionality of 3 can be matched even at a viscosity of 500 mpas in our new hardener 40LVI. Accordingly, a water based coating can be formulated, using reduced amount of solvent to dilute the hardener. Our evaluation of drying performance and chemical resistance confirm, that little to no difference is observed when switching from standard asymmetric trimer to our newly developed hardener 40LVI at lowest viscosity, as can be seen in the picture 2. The same conclusion applies for high and very high solids coatings: same performance and efficiency, reduced emissions. Fig. 2: Lowest viscosity hardener 40LVI enables easy-to-mix water borne formulations

4 3.2. LOW VISCOUS PU HARDENERS II: IMPROVE ELASTICITY AND MECHANICAL RESISTANCE Elastomeric coatings are gaining importance in many end uses. The typical profile of elastomeric coatings can be perfectly addressed by PU technology: Elasticity, mechanical strength, high solids content formulations. The hardener itself can significantly contribute to maximizing performance of such systems, so we want to highlight two innovative approaches. Our new hardener 63EEI is a smart cross linker in fast curing systems, targeting construction and on-site applications. From a molecular view, 63EEI combines long chain, elastic moieties with a linear structure. Its high molecular weight makes it the preferred partner of low molecular weight coreactants: 63EEI was particularly developed to outperform in elastomeric coatings, combined with aspartic esters. Resulting coatings exhibit highest elongation at break and abrasion resistance combined with lowest content of solvent, high film built and unmatched, fast curing speed. A different hardener concept leads to 60ELVI. It is a perfect match to the profile of Elastomeric spray coatings. 60ELVI combines a low molecular weight and highly elastic structure. Its particularly high compatibility makes 60ELVI the preferred partner for elastic polyols. This includes polyols of high molecular weight and high hydrophobicity. Photo 1 highlights a very demanding application for elastomeric coatings: the surface of the platform of pick-up trucks has to be highly stable, both against mechanical damage as well as against weathering. The development of formulations suited to fulfill all these requirements revealed: The best performance is achieved by not only choosing an elastic and weather stable polyol. It turned out to be crucial to also go for an optimized hardener. Photo 1: Elastomeric coating in pick-uptruck Our cross linker 60ELVI contributes to the core needs of elastomeric coatings: A highly elastic molecular structure is combined with sufficient crosslink density. As a result, durability of formulations turned out to be quite unique. Combining 60ELVI with an elastic polyester-polyol as coreactant, results in a highly durable protection. In other words: high elongation at break, combined with high tensile- as well as shear strength at lowest VOC content in the respective formulations. Performance of this very elastic hardener, compared to established trimer- and uretdione crosslinkers, is outlined in picture 3.

5 Fig.3: Mechanical strength and elongation at break of elastomeric PU spray coatings based on smart hardener 60ELVI, compared to low viscous standard Desmodur N hardeners (3900: asymmetric trimer, 3400: uretdione). Viscosity NCO content Elasticity Compatibility Recommended polyol mpas wt.-% 63EEI ,0 Aspartic esters 60ELVI ,5 Elastic polyesters Table 1: Elastic, low viscous PU hardeners at a glance 3.3. FAST CURING PU HARDENERS I: INCREASE PRODUCTIVITY Automotive refinish coatings are one of the lighthouse applications of PU systems. Drying speed, performance and easy handling are key for success of PU technology at car-body shops influenced by optimizing the hardener component. The exchange of the hardener from standard isocyanurate to a higher functional cross linker (90HFI) leads to a significant improvement of drying speed. 90HFI exhibits an average functionality around 4,5 this leads to fast molecular weight build up and thus fast hardness development. Acceleration depends on the A-component used. Generally, a time saving of 10% to 25% can be expected in medium/ high solids formulations. Key application parameters, such as pot life and appearance, are widely untouched. Also to be noticed is a remarkable improvement of chemical resistance, in particular during the first days after application worldwide. In order to adopt formulations to different curing speeds, the most typical measure is to work on the polyol or solvent composition. In addition, speed of drying can also be widely FAST CURING PU HARDENERS II: ADDED VALUE THROUGH HIGH FUNCTIONAL, ELASTIC HARDENER What if we increase functionality further up? Without sacrificing viscosity and elasticity? Our cross linker 10EHFI is building on its highly branched molecular structure exhibiting an average functionality around 6. 10EHFI exhibits a viscosity of 500 mpas, at a solids content of

6 80%. Through its highly branched structure, formulations based on this hardener achieve fastest curing and quite high hardness. In addition, the same molecule design of cross linker 10EHFI boosts elasticity of respective formulations. In other words, the combination of hardness and elasticity, which is one key feature of PU systems, is particularly pronounced. Consequently, 10EHFI has similar benefits as mentioned for 90HFI: Combined with suited polyols and formulated e. g. for car refinish application, it will lead to extremely fast drying (see picture 4) and high chemical resistance. In addition, the elastic molecular structure of 10EHFI adds important features to the coatings performance: Pronounced self-healing of hard clear coats and significantly improved adhesion, for example on plastic substrates or basecoats. The performance of 10EHFI, as described, is a particularly good fit to the requirements of the plastic coatings industry: Hardness development is significantly faster, while end hardness is on the same level. This means: Best coatings results in significantly reduced cycle times, without sacrificing low temperature elasticity. Also, coated parts can be handled safely after a relatively short drying period. 10EHFI therefore is perfectly suited to be developed further by adopting Covestro s latent hardener technology PRODUCTS 40LVI is a hardener offering lowest viscosity, particularly designed for waterborne and high solids industrial coatings. Although viscosity is at only 500 mpas, the hardener exhibits an average functionality of 3, which ensures higher chemical resistance, as compared to established low viscous types in the market. 63EEI is a low viscous, highly elastic hardener with particularly high molecular weight. It outperforms in elastomeric flooring- and waterproofing formulations. Particularly suited partners for 63EEI are fast reacting aspartate coreactants. 60ELVI offers an elastic structure in a small molecule: it maximizes mechanical performance and compatibility in spray applied formulations with elastic polyols. 90HFI is a fast drying, high functional hardener: average functionality is 4,5. In most cases it can be used as a drop-in for standard isocyanurate hardeners, leading to a significant boost in drying speed and chemical resistance. 10EHFI gets even further, turning an average functionality of 6 into reality. Added value to high performance formulations comes from its highly elastic molecular structure and narrow molecular weight distribution: further speed up of curing, high chemical resistance, selfhealing surfaces, perfect adhesion on a wide variety of substrates as well as a relatively low viscosity.

7 4. SMART PU HARDENERS IN TERMS OF EFFICIENCY (THERMOLATENT HARDENERS) Polyurethanes are one of the very few polymer systems relevant for coatings technology that allow for a wide application range with respect to temperature, substrate, and environment. However, in numerous applications the crosslinking reaction is not fast enough by itself and has to be catalyzed and/or heat has to be applied. This necessity can be turned into fortune as especially two component polyurethane systems can benefit from a decoupling of the desired fast crosslinking reaction at the substrate and an as-slow-as-possible reaction during mixing and handling of the components and before application to the substrate. This has been addressed with the thermolatent hardener (TLH) concept introduced by us at the Nuremberg Coatings Congress in 2013 [4] and 2015 [5]. In continuation of the a.m. work, we report here on some further typical applications of the thermolatent hardener in various fields of 2K polyurethane coatings technology THERMOLATENT HARDENER APPLICATIONS IN PLASTICS COATINGS A very prominent example of 2K polyurethane coatings technology is the plastics coatings process. Here one faces limitations in maximum curing temperature as most plastic substrates do not allow for excessive heating for extended periods of time. Catalysis is a must. Standard formulations containing DBTL as the catalyst suffer from a short potlife which can only partly be overcome by careful adjustment of catalyst concentration. Due to this and increasing concern on organo-tin compounds, derivatives of different metals (e.g. Bi, Zr, Ti, Zn) are used in standard coatings line material today - often at the expense of activity and/or versatility. The TLH technology is able to close this gap as is outlined in Fig. 4. Fig.4 Advantages of TLH-technology in plastics coatings

8 Potlife at room temperature (23 C) is acceptably long for convenient handling of the ready-touse formulation (fig. 1, left) while curing speed at reaction temperature (80 C) matches that of the DBTL-catalyzed system (fig. 1, right) and makes it perfectly suitable for plastic substrates. Additionally, the immediate onset of the DBTL-catalyzed reaction is detrimental to the appearance of the final film. This actually goes beyond plastics coatings and addresses a more general topic highly relevant for many high-gloss applications THERMOLATENT HARDENER APPLICATIONS IN METAL COATINGS Inspired by the positive findings in plastics coatings outlined above, the question arose whether the effect may also be beneficial to coatings at metal substrates were temperature limitations do not play as much of a role taking ecological and economical considerations aside which always favor the lower temperature due to energy savings in the baking process. Here, a positive influence on optical properties, especially gloss usually described by appearance parameters like DOI or orange peel as determined by wave-scan measurements, is of importance. OEM processes on metal furnishing 2K polyurethane technology usually operate at 140 C usually without catalysis of the NCO-OH-reaction and yield optimal results regarding appearance. But this temperature is far beyond any imaginable protocol that would involve exterior parts not being made of metal or other very thermoresistant matter being coated at the same time, e.g. bumpers, mirror-frames, and the like usually made of thermoplastics. In order to investigate this, a comparison of catalyzed and non-catalyzed formulations at 90 C and 140 C (reference, no catalyst) has been made based on a simplified automotive OEM clear coat formulation (acrylic polyol, polyisocyanate). The reaction progress was monitored by NCO-consumption and recorded over time. The results (Fig. 5) clearly demonstrate that TLH technology - optionally with slight adjustment of TLH recipe (TLH 1 vs. TLH 2) - offers possibilities for future developments aiming at lower line temperature and/or multiple material constructions being coated simultaneously. Fig.5: Comparison of NCO-consumption in non-catalyzed and catalyzed metal coatings

9 4.3. APPEARANCE AND THERMOLATENT HARDENER TECHNOLOGY The human eye is a sensitive probe for uneven surfaces. It differentiates between coated surfaces made by a 2K PU coating containing no catalyst at all versus those containing standard catalysts that already accelerate the NCO-OH-reaction after mixing of the two components. Assuming that the non-catalyzed coating system is the benchmark for appearance - though at the expense of considerably extended drying time (at lower bake temperature) or higher energy consumption (at standard OEM line temperature) - the question lies at hand, whether the TLH technology could be beneficial, too. Fig.6: Comparison of crosslinking and appearance in non-catalyzed and catalyzed systems at 100 C and 140 C Figure 6 exhibits a comparison of 3 different systems uncatalyzed; DBTL-catalyzed; and TLH all cured for 30 min at 100 C again in comparison to the standard-oem-line situation: 140 C, 30 min, no catalyst. Most surprisingly, the TLH system cured at 100 C not only exceeds the degree of crosslinking of the DBTL-catalyzed hardener but even has advantages compared to the uncatalyzed system cured at 140 C, both directly after stoving and after aging as well! The topic appearance - illustrated by a rather generic orange peel versus high gloss panel in figure 6 can be further on detected by so-called appearance-checkers in fully automated processes like waviness- or wavescan measurements. The structure spectra obtained this way are demonstrated in figures 7 and 8. The coatings investigated here were applied via electrostatic equipment with a RobPainter (of Lac Tec ) both horizontally and vertically with uniform film thicknesses on panels coated with a standard electro deposition coating, followed by an anthracite OEM waterborne primer

10 surfacer, an uni-black OEM waterborne base coat and the three different hardeners as described above being part each of a tested 2K OEM solvent-borne clear coat. The waviness results in figure 7 and the structure spectrum of wavescan measurements in figure 8, both for vertical application, demonstrate that the addition of conventional catalyst DBTL has a negative influence on the appearance, that gets worse with increasing catalyst concentration. The TLH, in contrast, has only a marginal impact on appearance parameters. As the additive package in the paint has remained completely unaltered compared to the uncatalyzed formulation, an optimization for the TLH based coatings formulation should lead to further improvements. Fig.7: Waviness measurement of a vertically ESTA applied OEM 2K PU clear coat Fig.8: Structure spectrum of a wavescan measurement for a vertically ESTA applied OEM 2K PU clearcoat

11 At least a performance overview of the 3 systems, uncatalyzed, DBTL-catalyzed and TLH is shown in table 2. Properties standard hardener (no catalyst) standard hardener + DBTL TLH Appearance after Robotic Bell Application Pot Life Early Chemical & Mechanical Resistance Low Temp Curing / Energy Savings Table 2: Performance overview: uncatalyzed-, DBTL-catalyzed- and TLH-system 5. SMART PU HARDENERS IN TERMS OF SUSTAINABILITY, HIGH PERFORMANCE ENABLED BY NATURE The ecological compatibility of products is becoming a critical factor for businesses that want to defend their position and grow in the market, because consumers are increasingly deciding in favor of sustainable goods and making sure they incorporate renewable materials. In striving to fulfill these consumer demands, brand owners are in search of bio-based, sustainable materials. This applies to the automotive industry, but also to Ikea furniture stores and the Coca Cola company, which designates bottles as plant bottles if they are made partially from plants [6] GREEN PRODUCT TREND HITS THE COATINGS INDUSTRY The coatings and adhesives industry has recognized this trend towards eco-friendly products. The right starting materials can make a key contribution to fulfilling sustainability demands in the coatings and adhesives industry. Covestro is currently launching a new highperformance hardener made from renewable raw materials. It is the perfect addition to the bio-based polyols already used in polyurethane coatings and adhesives. Now these coatings can be formulated almost entirely from bio-based components PRODUCTION WITH REDUCED CO 2 FOOTPRINT The hardener is a trimer of pentamethylene diisocyanate (PDI) as shown in Fig 9. PDI is manufactured from pentamethylene diamine (PDA) using innovate ive gas-phase technology, which consumes significantly less energy and solvent than conventional processes.

12 Covestro s suppliers use biotechnology specifically fermentation to manufacture PDA from biomass. PDI therefore is synthesized in just two steps, as opposed to the four required for the petrochemical synthesis of the corresponding substance hexamethylene diisocyanate, a conventional diisocyanate raw material. According to an internal evaluation, the CO 2 footprint of bio-based PDI production is significantly reduced compared to petrochemical HDI production. The energy efficiency of PDI production is significantly better. Fig.9: Structural formulas of Pentamethylene diisocyanate (PDI) and PDI trimer. The carbon atoms from biomass are shown in green. PDA is sourced from the starch in field corn, which is converted enzymatically by specially developed microorganisms in a highly efficient process. Field corn is not suitable for human consumption, meaning that PDA manufacturing does not compete directly with food production. Substances made from field corn can already be found in bio-fuels and numerous other products, such as paper, cosmetics, cleaners and textiles. Based on an estimation, only 80 square kilometers of cropland an area slightly larger than the city of Leverkusen are required to produce 20,000 tons of the new hardener, enough to apply three coats of paint to 30 million motor vehicles. To make production even more sustainable, PDA suppliers are working intensively on ways to use bio-waste or cellulose instead of field corn. Field corn supplies the carbon for all five of the non-functionalized carbon atoms in PDI. In other words, of the seven total carbon atoms in the monomer, five or 71 percent are plantbased, as confirmed by C-14 radiocarbon testing in accordance with the ASTM D8666 standard [7] PERFORMANCE LEVEL COMPARED TO PETROCHEMICAL HARDENERS The new hardener was developed for the same applications as the successful HDI-based hardener Desmodur N 3300 from Covestro, a well-established product for automotive OEM coatings, automotive refinishing, industrial and anti-corrosion as well as wood coatings. The viscosity of the solvent-free, bio-based hardener is approx. 9,000 mpa s, meaning it is higher than that of the conventional hardener (3,000 mpa s). However, in practice this is not significant. The viscosities of the conventional hardener and the new bio-based alternative equalize in formulations using common solvents and having a solids content of less than 75 percent. The reason behind this behavior: In the solvent-free state, because of their higher polarity, the stacked PDI trimers attract one another more strongly than the HDI trimers. However, just a small amount of solvent is sufficient to break down the stacking. As soon as this happens, the inter-molecular forces of PDI and HDI trimers differ insignificantly.

13 Fig. 10 gives an overview of the bio-based hardener s properties. Coatings formulated with this component show the same performance as formulated with a conventional hardener in terms of weathering, scratch and chemical resistance, hardness or processing (pot life). They even dry slightly faster. The bio-based hardener offers major advantages when it comes to compatibility, particularly with highly functionalized polyols. This fact can be illustrated using examples of coatings formulated with highly branched polyesters: The gloss of the petrochemical coating is measurably and visibly lower than that of the bio-based coating. Reason for that is the lack of compatibility between the hardener and the polyester. For coating manufacturers, the better compatibility of the new hardener offers greater freedom in formulation work. Fig.10: Properties of coatings based on the new PDI hardener (green curve), compared with those containing the conventional HDI hardener (blue curve) APPLICATION EXAMPLES Automotive OEM coatings: Until now, car makers have used renewable raw materials primarily in the automotive interior. But now these new raw materials can take over a vehicle s outer skin as well, which carries very high emotional value. Tests have confirmed that coatings with this new hardener meet the high demands of automotive manufactures just as well as those made from established hardeners. Weathering, chemical resistance, scratch resistance: No significant difference can be detected. Automotive refinishing coatings are applied at lower temperatures (40-70 C) than automotive OEM coatings, and therefore are formulated differently. In this segment as well, coatings made with the bio-based hardener are on par with the properties of conventional PU coatings, for example in terms of dry and wet scratch resistance, weathering resistance and processing. Coatings incorporating the bio-based hardener even reach drying stage T4 (DIN 53150) faster than the conventional ones.

14 Corrosion protection: This improved drying displayed by coatings containing the bio-based hardener is also obtained in anti-corrosion formulations. The processing time (pot life) is only slightly shorter despite the improved drying behavior. Wood coatings: The new, bio-based hardener is suitable for 2K PU wood clearcoats in both matte and gloss formulations. With regard to chemical resistance, scratch resistance and gloss, it demonstrates the same high performance as conventional hardeners, and shows slight improvement regarding the drying time NEW TECHNOLOGY PLATFORM Covestro is not planning to commercialize the PDI monomer, but instead wants to use it as the basis for a new technology platform. Blocked, hydrophilic, silanized and waterborne PDI polyurethane dispersions have already been developed and tested during the development phase of the new hardener. The properties of these modified systems are very similar to those of the established HDI products. 6. SUMMARY AND OUTLOOK PU cross linkers have been known as versatile and efficient tools to crosslink coatings formulations, resulting in high performance coatings in many industries and end uses. The role of the hardener itself often is limited to interact as efficiently as possible with the polyol component which on the other hand is perceived to have the most significant impact on performance and processing. A series of innovative smart hardeners is highlighted to fundamentally question this perception, as these smart crosslinkers trigger performance and contribute added value to PU coatings. Thermolatent hardener technology (TLH technology) allows maintaining the highest level of appearance in 2 component polyurethane coatings applications, including 2K PU clear coats. A reduction of curing time by 30% compared to current line systems allows for capacity alignment, more robust handling, and higher yield of the entire production process. Only slight adjustments of formulations for plastics coatings are needed. In the case of metal coatings an optimization of the TLH based coatings formulation should lead to further improvements. Midterm, the TLH technology will help to enable low temperature OEM curing processes that include metal, pre-e-coated metal, composites and plastic parts being coated in the same paint line. A bio-based, high-performance hardener for polyurethane (PU) coatings and adhesives was developed. It is the first product of a new platform based on pentamethylene diisocyanate (PDI). The bio-based hardener supports coatings that are just as weather-, chemical- and scratch-resistant, and easy to apply as conventional coatings made exclusively with petrochemical inputs. The innovative hardener even offers greater freedom in formulation-work and faster drying. Coatings manufacturers and their customers can now improve their carbon

15 footprint, and automobile companies and other brand manufacturers can position themselves as pioneers in sustainable materials by achieving a higher bio-content. ACKNOWLEDGEMENTS Dr. Berta Vega Sánchez, Dr. Frank U. Richter, Michael Grahl, Robert Reyer, Karl-Heinrich Wührer and Thomas Klimmasch (Covestro Deutschland AG, Leverkusen, Germany) are acknowledged for their valuable contribution to this paper. LITERATURE 1) H.-U. Meier-Westhues, Polyurethanes: Coatings, Adhesives and Sealants, Vincentz Verlag, Stuttgart (2007). 2) K. Wagner, Verfahren zur Herstellung von Polyisocyanaten mit Biuret-Struktur, DE , ) F. Richter et. al., Isocyanate trimers and mixtures of isocyanate trimers, production and use thereof, EP , ) Thermolatent Catalysts for the Urethane Formation, F. U. Richter, M. Grahl, L. Iovkova-Berends, G. Bradtmöller, T. Zöller, K. Jurkschat, 2013 Nuremberg Coatings Conference Congress 5) Recent developments on controlled polyurethane formation by thermolatent catalysis, F. U. Richter, 2015 Nuremberg Coatings Conference Congress 6) 7)