Due to increasing regulatory pressure and economic demands, the past decade has seen significant developments within the protective coatings industry. For example, the 2006 introduction of the REACH (Registration, Evaluation, Authorisation and restriction of Chemicals) legislation by the European Union, aimed to regulate the use of hazardous chemicals.
The deadline for the final stage requires the registration of all substances supplied at above one tonne per year, and has resulted in an increased demand for solutions that have no substances of very high concern (SVHC), as well as a reasonable environmental, and health and safety (EHS) profile.
Along with growing pressures for reduced volatile organic compound (VOC) levels, these chemical safety regulations have made it increasingly complex and costly for manufacturers to supply coatings that are in line with the specific regulations now in place. Such cost increases are often passed on to the end users however, to compensate for the higher cost per kilogram of products, there has been a shift within the industry to focus on reducing the cost of projects from start to finish. As the price for raw materials becomes even more competitive, coatings producers are increasingly focusing on the total expenditure of projects, rather than the costs of individual components. For cooler climates, where application is often weather-dependent, this offers a range of benefits and specialized products are being developed that can help extend application windows, or reduce maintenance cycles.
Following direct feedback from its customers around these issues, Huntsman Advanced Materials, a division of Huntsman Corporation, recognized that there was a clear need for coatings that were both regulatory compliant and helped bring down the whole-life cost of a project. As a result, the company developed its new product range, Ara® Cool.
Meeting regulatory requirements in low temperatures
When developing the new range, Huntsman Advanced Materials considered the whole life cost of a typical project during the development process, enabling it to truly understand the issues faced by its customers and how the attributes of a product can impact costs over a 20 or 30-year period. It was concluded that specifically developed technologies for faster curing in colder climates could add real value for a number of different reasons:
• Improved drying times:
- Allows application periods to be extended into the cooler seasons
- Avoids breaks in the application schedules, saving man hours and reducing applicator costs
• Longer pot life:
- Less product waste
- Lower temperatures in drying ovens, saving energy and reducing utilities bills
- Reduced curing time in ovens when cured at elevated temperatures
- Increased throughput in industrial lines
Once it had been established that there were tangible benefits to developing a range of this kind, it was also clear that any new products needed to meet technical requirements for low temperature cure applications, as well as any regulations being introduced in 2018 and beyond.
Creating the range
The research carried out by Huntsman Advanced Materials not only ensured it had a thorough understanding of the key issues affecting the industry, but highlighted significant and tangible benefits to developing a range of products that offered extended pot life, increased curing speeds and low VOC levels. Although there were solutions in the market that had these characteristics individually, there wasn't one which offered all three.
The next step was to then understand which of the available chemistries was most suited to deliver the desired benefits. Huntsman Advanced Materials looked at the three available curatives: surface tolerant Reactive Polyamid-Amines (RPAAs), modified phenalkamines and adduct hardeners in organic solvents. The tests measured curing speed at 5°C, anti-corrosion performance, VOC levels, pot life and compliance with EHS and regulations.
The results showed that, although surface tolerant RPAAs are the industry benchmark for their adhesion properties, they are unable to cure at temperatures lower than 15°C. Through using traditional accelerators or Mannich-Base type co-hardeners, it is possible to improve the curing profile of RPAAs at lower temperatures, but this can cause negative side effects such as brittleness, discolouration and a decrease in anticorrosion performance.
Modified phenalkamines, a specific set of Mannich-Base type hardeners, showed a better cure performance between temperatures of 8-15°C; however, formulating with standard phenalkamines can cause challenges including potential intercoat adhesion issues, strong discolouration and high levels of residual volatiles amines. While there are modified chemistries that have been designed to reduce these negative features as much as possible, they don't always improve the cure speed and can sometimes have an adverse impact on reactivity.
Finally, while adduct hardeners in organic solvents proved to be superior in achieving quick tack-free speeds at low temperatures without chemical crosslinking with epoxy resins, VOC requirements below 350g/l were not met, as a lot of solvent was needed in formulations to achieve the right application viscosity.
On the basis of the results, all three solutions were discounted and it was concluded that significant compromises on at least one of the key parameters (anticorrosion performance, pot life, VOC content and product safety) would be required to achieve curing profiles between 0-10°C with existing solutions. As the trials showed that Mannich-Base chemistry was the best placed to achieve the preferred cure profile, Huntsman Advanced Materials decided to look into this solution further, developing several different chemical approaches, until the desired outcome was achieved.
Responding to industry demands
The extensive testing led Huntsman Advanced Materials to realize that, by creating a portfolio of products, it could target a wider variety of industry requirements. In addition to meeting the demand for fast curing speeds at low temperatures and reduced VOC levels, the Ara® Cool range also provides excellent surface appearance and adhesion properties. Figure 1 shows the different properties of the Ara® Cool products, when compared to the originally trialled chemistries. The results demonstrate that Ara® Cool is the only solution that meets all attributes.
Figure 1
Rating: 1 = excellent 2 = good 3 = ok 4 = acceptable 5 = not suitable
- Ara® Cool 3077 is a zero-VOC multipurpose low temperature curing hardener, which is formulated without benzyl alcohol and is SVHC free. It has been designed to deliver superior reactivity at temperatures as low as 5°C and can be used either as the sole curing agent or a co-accelerator for slow hardeners. Ara® Cool 3077 is the least viscous of the three products within the range, despite its zero-solvent content.
- Ara® Cool 1047 W 80 is a surface tolerant low temperature curing hardener for metallic surfaces, which offers at least the same anticorrosion performance as the best in class competitive technology. It provides excellent corrosion protection for critical substrates that require fast hardness development at 5°C or less, and offers superior surface appearance and excellent adhesion, even under humid or cold conditions. Ara® Cool 1047 W 80 contains approximately 20% solvent, and is suitable for use in solvent-containing formulations.
- Ara® Cool 1034 XW 90 is a modified Mannich-Base type ultra-high solid hardener for pre-treated steel surfaces. With a slightly higher viscosity, it boasts an extremely long pot life and has outstanding low temperature reactivity. SVHC-free, Ara® Cool 1034 XW 90 has a solvent content of roughly 10%, so is extremely low VOC.
Futureproofed solutions
With the increasing regulations across the coatings industry, there has been a growing demand for innovative solutions that provide compliant yet effective protection, even in the most extreme climates. Answering these requirements, alongside the need for reduced SVHC and VOC levels, the Ara® Cool range from Huntsman Advanced Materials enables formulators to be assured that their products comply with current regulations, as well as more stringent ones that may arise in the future. In addition, the range brings fast cure speeds and longer pot life to the market, allowing applicators to work more efficiently by saving time and – most of all – reduce overall project expenditure.