Test Line for Paint

Evonik is significantly shortening the search for suitable formulations with a new, high-efficiency, fully automated system for testing paint formulations (highthroughput equipment – HTE). In doing so, Evonik is not only accelerating its own innovation speed but also that of its customers. Approximately 40 million tons of paint are used worldwide each year: paints protect surfaces against corrosion, impart special properties such as electrical or thermal conductivity, and increase the durability of consumer goods. Special demands for paints and coatings are constantly increasing. Customers face new challenges due to continuously growing complex requirements and updated, increasing regulations. A paint formulation is where craft, science, and art intersect. In addition to the main component, the binder, they contain organic solvents or water, pigments and fillers, catalysts and auxiliary solvents and additives. Moreover, different chemical equivalents can be used for each component. For this reason, the combination possibilities of substances with different contents are very numerous: when developing a paint formulation, if only 10 hardeners, 10 binders, 10 pigments and 10 additive materials need to be examined, 10⁴ or 10,000 combinations emerge. This calculation does not yet take into account variations in quantity ratios. In practice, it is not possible to account for all of these possibilities and test all combinations and quantity ratios in terms of their properties. On the other hand, systematically researching the most suitable paint formulation requires, with the necessary financial and personnel costs, at least extensive familiarity. Only in this way is nothing left to chance. To overcome this challenge, Evonik paint specialists have built a highly efficient system specifically for developing and creating paint formulas.

Testing the Perfect Formulation Faster

With this system, Evonik has greatly increased the chances of reliably finding an additive or special binder that perfectly suits the other components in the paint and the paint's intended use. Finding the right formulation is never an easy task: For example, additives occupy only a very small percentage in the formulation, yet significantly affect a paint's properties. During coating application, they eliminate foam, prevent paint pigments from clumping, and give the paint thixotropic character—meaning it is easy to apply but does not sag or drip during vertical drying. Some additives increase the paint's scratch resistance. There are numerous additives that could perfect a paint formula. Additives, depending on their chemical structure, can interact with other additives. This makes research into the optimal additive more difficult. This demonstrates how important Evonik's system is: the system allows systematically testing more formulations in the same time than ever before. For customers, this means that paint formulations can be optimized more quickly and developed faster. This saves time, which is crucial for bringing new products to market. The system is two meters high and covers approximately 120m² in a climate-controlled space. It automatically doses raw materials and formulates them into paint in the first step at the "formulation island." In the second step, surfaces, also called panels, are coated with pre-formulated paints, dried, and then transferred to the testing station. Here, the properties of the formulations are characterized as soon as the relevant paint film is cured. All steps are carried out fully automatically according to precisely defined, always reproducible programs, which is the system's most important advantage.

Complex Work Steps Fully Automated

Formulation, coating, characterization: it sounds easy, but these steps require many complex operations from the machine. The system consists of 52 elements incorporating 30 functions. Each function represents solving a specific task, for example applying a paint formulation to a panel. The 52 elements are connected via a rail system on which containers and panels travel back and forth through all parts of the system. This includes 13 robots that perform various activities such as equipping the shuttle with parts or placing panels in the oven. On average, 120 samples can be formulated in the system within 24 hours. While application is being performed on a panel and it is being characterized, experiments can be started for a new project. This is why it is also defined as a High Throughput System or High Throughput Equipment (HTE). Dosing and mixing raw materials is an important challenge for the system. One example is the viscosity of the liquid raw materials to be used, which can vary greatly. The range extends from extremely fluid liquids to liquids with very low fluidity that must first be heated in order to be dosed and filled. Some liquids can also dissolve and corrode container and tool materials. Powdered pigments and fillers also present challenges: bulk density and dispersion properties vary. This can make correct weighing and dosing difficult depending on the powder. While a well-trained technician can quickly adjust the relevant raw materials himself, this is a difficult task for a fully automated system. The HTE system overcomes this, particularly thanks to its well-designed software. This allows all parameters required for dosing to be adjusted. For liquids, these adjustments are pressure, temperature, and valve opening times; for powders, in coarse dosing it is the speed of the dosing screw, the fine dosing range, and the fine dosing oscillation amplitude. In the advanced RaceLab software developed by Evonik, all input and output data required for operating the system are compiled in a database. Thanks to its improved technology, the HTE system is fully reliable and always reproducible. It records and stores potential deviations from nominal values. Thus, when there are notable results, it can be easily determined whether there are irregularities in the work flow. The system's advantages also become apparent during the production and testing of pigment pastes. Normally, pigments need to be ground by mills, which takes considerable time. In the HTE system, a special mixer is used for this. In this mixer, the double rotation of the mixing container provides much faster breaking down and dispersion. Additionally, special air cooling prevents excessive heat generation that could damage the paint raw materials. Afterwards, in the laboratory, the separation of the mill beads from sometimes highly viscous mixtures, which previously could only be done with considerable labor, is now handled by a centrifuge in the HTE system. A specially developed filter adapter keeps the mill beads behind on one side while the paint advances on the other. All necessary movements are performed by a robot.

Objective Variables Instead of Subjective Tests

To evaluate the storage stability of a pigment paste in the laboratory, a visual inspection is performed and a spatula is used to check whether sedimentation has occurred. Transferring such visual and tactile skills to a machine requires considerable effort. The HTE system developers found another solution: a measurement head determines what mechanical resistance it will encounter as it is immersed in the sample. An objective variable replaces the more subjective human evaluation. Another challenge faced by a fully automated system is applying the created paint film to the panel with the aid of an applicator. The panel should not shift during application, the paint quantity should be at the desired film thickness, and it should not smear to the sides to avoid contaminating the next panel. A specially designed robot handles these tasks. The robot applies exactly equal amounts of paint at equal film thickness to each panel and cleans the panel with different washing solutions before repeating operations. The HTE system also offers advantages in the rub-out test for evaluating pigment stabilization. This procedure is done in the laboratory by rubbing a finger over the freshly applied paint layer. If pigments are not sufficiently stabilized, the rubbing forces applied cause a visible color change on the surface. When performing this test, care must be taken to ensure that the material is not pushed to the side during rubbing or that voids are not created in the paint film. In the HTE system, this subjective method is replaced by precise control where variables can be adjusted through software as desired for each paint system. Overall, the system reduces the workload on laboratory staff by handling tedious, routine tasks. This allows staff to focus on planning experiments and evaluating data.

Versatile Use Around the Clock

RaceLab allows all work steps to be planned in detail. With up to 600 different variables, 40 different work steps can be precisely defined in an HTE system. This enables Evonik to freely combine each different work step with another and meet the very different demands of its customers. The HTE system is completely versatile and can be used around the clock. Furthermore, RaceLab records all measurement data and allows evaluation of complex research series. The generation of far more data in the HTE system in extremely short times than ever before in the laboratory is an important advantage. This creates a continuously growing data pool that can be analyzed in the future using data mining methods. Perhaps the number of required experiments could even be reduced. Because thanks to existing data, artificial intelligence or computers can find what is needed among existing data. At the very least, it can point out the areas that require detailed analysis. Customers can thus further accelerate their innovation speed with the help of Evonik and the HTE system.

Advantages of the HTE System

1. Operates fully automatically, delivers reproducible results, versatile in use, 2. Formulates paint from many different types of raw materials, 3. Characterizes liquid formulations before application, 4. Coats panels precisely and dries or cures the paint, 5. Characterizes the manufactured coatings, 6. Creates a continuously growing data pool for analyses that can be conducted in the future via data mining.   Ebru Pilavci Erisi / Senior Sales Manager, Paints and Coatings Additives Evonik Ticaret Ltd. Şti. Ellen Reuter / Innovation Management Manager, Additives Claudia Bramlage / Senior Research and Development Manager, Additives