AERODISP WR 8520 for water-based coatings. Technical Information 1390

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1 AERODISP WR 8520 for water-based coatings Technical Information 1390

2 1 Introduction Ecological considerations are playing an increasingly important role in the paint industry. Growing environmental awareness and the legal regulations that arise from this awareness are the cause of the current strongly growing trend toward water-based coatings. The development of environmentally friendly coating materials has been one of the major tasks of the paint industry for many years. Evonik Industries, as a supplier of raw materials for the paint industry, is making a major contribution to this development through its many products. The paint industry has been using AEROSIL fumed silica as an additive with great success for decades. Both hydrophilic and hydrophobic AEROSIL fumed silica can be used in water-based paints as well, depending on the paint system. The positive effects that this use can achieve are explained in detail in Technical Information TI 1125 AEROSIL for Water-Based Coatings. This new Technical Information 1390 describes AERODISP WR 8520, a new aqueous dispersion based on hydrophobic AEROSIL fumed silica technology. AERODISP WR 8520 makes it possible to easily and effectively improve the following performance attributes in aqueous pigmented coatings and water-based clear coats: Thickening and thixotropy Anti-settling Pigment stabilization Improvement of the mechanical properties Applications: Automotive coatings Plastic coatings Wood coatings Industrial coatings 2 Development of AERODISP WR 8520 In pigmented, water-based coatings, suspension of heavy fillers and pigment is often a problem. Poor storage and transport stability can present many problems for formulators and suppliers alike. Furthermore, the coating should show a homogenous appearance, after it has been applied. Sagging is of course undesirable. For this application, Evonik Industries has developed AERODISP WR 8520, a new, structured silica dispersion that can be used in many applications, such as in automotive coatings, plastic coatings, wood coatings or industrial coatings. Figure 1 Why is AERODISP WR 8520 a structured product? In contrast to solvent-containing coatings, a water-based system with all of its additives offers outstanding dispersion conditions for AEROSIL fumed silica. Aggregates become over-dispersed; where they become so small, that they no longer come into contact with one another and can no longer build up an interactive network (see Fig. 1, left). The aggregates are so homogenously distributed that the resulting thickening effect is drastically reduced. Such a system, no longer stabilizes large, heavy pigments and fillers. Such a system also demonstrates poor sag properties when applied to vertical surfaces. 2

3 If the silica is present in structured and hydrophobic form and stabilized with special additives, the aggregates remain more stable and intact in an aqueous environment. In addition, the surface chemistry must be such that an optimum reciprocal exchange of forces is possible. In Fig. 1, this is symbolized by the arrows. This balanced interaction is the basis for an efficient network and is established only if both parameters, structure and surface chemistry are present at the same time. Intensive studies have shown that the surface chemistry of the hydrophobic AEROSIL fumed silica has to be properly selected and optimized in order to allow this intensive exchange of interactive forces in water-based coatings. Structure of aggregates are carefully preserved by dispersing the hydrophobic AEROSIL fumed silica so that it forms a 20 % solution in water in the presence of suitable additives with customized shearing forces. The optimized shear forces give the aggregates sufficient stability so that they withstand the storage and transport, as well as, formulating conditions to avoid settling and flocculation once added to coating formulations. Table 1 shows further characteristic application-specific properties of AERODISP WR Table 1 Characteristic application-specific properties of AERODISP WR 8520 Environmentally-friendly water-based dispersion using hydrophobic AEROSIL fumed silica (20 %) Customized structuring Dispersion exhibits high stability Good compatibility with many coating systems Efficient thickening and thixotropic agent Efficient anti-settling agent Minimal effect on the optical properties of water-based clear coats 3 Processing Recommendations For binder-containing water-based coatings, the recommended additive amount is a dispersion addition rate of 5 10 % (corresponding to 1 2 % AEROSIL fumed silica by weight solids), calculated on the basis of the entire coating formulation. The dispersion should be added to the coating under agitation at low to average shearing forces (e. g., dissolver), typically at the end of the batch. High shearing forces, like those generated in a media or bead mill, should be avoided; as these high shear forces would irreversibly destroy the customized structure of the aggregates! Binder molecules can actively participate in the network build-up by means of interacting forces. In water-based, binder-free or low-binder solutions like glazes, it may consequently be necessary to increase the AEROSIL fumed silica concentration to approx. 5 % (solids) since the binder will not play a significant role in network support. 4 Applications In water-based coatings, AERODISP WR 8520 is often characterized by its efficient rheological effectiveness (high thickening and thixotropic influence). We can demonstrate this on the basis of a random practical example. Fig. 2 plots the viscosity of a water-based filler used in the automotive industry versus the shearing rate. At low shear, the viscosity without AEROSIL fumed silica is quite weak, i. e., heavy pigments would easily precipitate in such a coating. Figure 2 Rheological effectiveness of AERODISP WR 8520 in a water-based filler for automotive coatings; 1 % silica AERODISP WR 8520 is compatible with many coating systems tested so far; as a rule, flocculations or other incompatibilities do not appear. η [mpas] , Shear rate γ [1/s] without AEROSIL fumed silica hydrophobic AEROSIL fumed silica powder: added using bead mill AERODISP WR 8520: added under agitation 3

According to the current state of the art, AEROSIL fumed silica can be used to effectively raise the viscosity in solvent-containing systems at low shear rate and provide shear thinning qualities to

In many water-based coatings, such rheological response typically does not occur by adding approx. 1 % AEROSIL fumed silica in powder form and dispersing using a bead mill. (see Fig.

Figure 4 shows the performance of AERODISP WR 8520 vs control without. In comparison to the control, suspension is improved of the pigments in the waterbased coating containing AERODISP WR 8520.

After many investigations testing various powdered grades of AEROSIL fumed silica combined with additives and shear combinations, AERODISP WR 8520 is developed to give the classic rheological

With an addition rate of 5 % relative to dispersion (1% relative to AEROSIL fumed silica), the well known and expected advantages by formulators trained in the art become evident.

with low shear agitation (e.g. stirrer or dissolver) and is easy to mix into the letdown phase to get the desired viscosity build-up.

20µm 35 µm 35 µm 38 µm Anti-sagging Anti-sagging Reference AERODISP WR 8520 Figure 3 Rheological effectiveness of AERODISP WR 8520 in a water-based filler in the application step (0 120 seconds: high

000 500 0 0 100 200 300 400 time t [s] Hydrophobic AEROSIL fumed silica as powder Hydrophobic AEROSIL fumed silica as powder + additives AERODISP WR 8520 Control During the actual application

4 According to the current state of the art, AEROSIL fumed silica can be used to effectively raise the viscosity in solvent-containing systems at low shear rate and provide shear thinning qualities to mostly Newtonian systems. The quick rheological rebounding behavior, in such systems applied on vertical surfaces, once the shear is removed, is the basis of the well known anti-sag behavior. In many water-based coatings, such rheological response typically does not occur by adding approx. 1 % AEROSIL fumed silica in powder form and dispersing using a bead mill. (see Fig. 2) Only the coating containing AERODISP WR 8520 shows stability on vertical surface and sagging is prevented. (right part of Fig. 3). Figure 4 shows the performance of AERODISP WR 8520 vs control without. In comparison to the control, suspension is improved of the pigments in the waterbased coating containing AERODISP WR The dry film thickness is also even and homogeneous which is a critical parameter to maintain on vertical surfaces. After many investigations testing various powdered grades of AEROSIL fumed silica combined with additives and shear combinations, AERODISP WR 8520 is developed to give the classic rheological benefits to waterbased coatings, as AEROSIL fumed silica is known for in solvent-containing systems. With an addition rate of 5 % relative to dispersion (1% relative to AEROSIL fumed silica), the well known and expected advantages by formulators trained in the art become evident. AERODISP WR 8520 is water based dispersion based on hydrophobic fumed silica. It should be added to the final coating, with low shear agitation (e.g. stirrer or dissolver) and is easy to mix into the letdown phase to get the desired viscosity build-up. Media, bead, or high intensity mills are not recommended to incorporate it. 20µm 35 µm 35 µm 38 µm Anti-sagging Anti-sagging Reference AERODISP WR 8520 Figure 3 Rheological effectiveness of AERODISP WR 8520 in a water-based filler in the application step (0 120 seconds: high shear rate (500 s 1, simulation of the spraying process); seconds: low shear rate (0.5 s 1, simulation of the situation shortly after application) η [mpas] time t [s] Hydrophobic AEROSIL fumed silica as powder Hydrophobic AEROSIL fumed silica as powder + additives AERODISP WR 8520 Control During the actual application process, it is desirable that the viscosity of the coating should be low. This keeps the required application energy needed low and the coating should flow evenly and with ease. At high shear rate, the coating containing the AEROSIL fumed silica additive should behave as the control without AEROSIL fumed silica. Once the coating reaches the substrate, and the applied shear force is removed, extra low shear force takes over. Without proper viscosity recovery behavior, on vertical surfaces, the coating runs due to this low gravitation shear forces. Anti-settling Figure 4 Improvement of the anti-settling behavior and thixotropic behavior in a pigmented water-based coating with AERODISP WR 8520 Wide compatibility of AEROSIL fumed silica technology is a critical factor to success in solvent based coatings. Similar to the excellent performance in solvent based coatings, AERODISP WR 8520 shows wide applicability and compatibility in various water-based coatings technologies. Performance in three different water based clear coat systems and in one filler (baking system) is demonstrated in Tables

5 Table 2 Overview of the various water-based test formulations Test formulation Binder Producer Result* 2-component clear coat Bayhydrol A 145 Bayhydur Table 4 Test system: clear coat 2 AERODISP WR 8520 Macrynal VSM 6299w without AEROSIL 2-component clear coat Macrynal VSM 6299w Bayhydur 304 Cytec ++ Additol VXW Additol VXW component clear coat Macrynal SM 6810w Bayhydur 304 Cytec ++ Deionized water : butyl glycol (1:1,5) 2,5 2,5 DMEA 10 % in water ph = Filler (baking system) Bayhydrol E 270 Baytherm 3146 / VP LS 2153 Cymel 327 Cytec ++ AERODISP WR Deionized water 8 Stir for 10 min at 2000 rpm Hardener * Results for compatibility, rheological effect and anti-settling effect (in the filler) Butyl glycol acetate 3 3 Bayhydur Table 3 Test system: clear coat 1 AERODISP WR 8520 without AEROSIL Table 5 Test system: clear coat 3 Bayhydrol A Surfynol 104 BC 1 1 Additives ** 1 1 Deionized water 1 1 DMEA 10 % in water ph = AERODISP WR Deionized water 8 Hardener Stir for 10 min at 2000 rpm Proglyde DMM 3 3 Bayhydur ** Additives Butyl glycol 90 BorchiGol LA Baysilone AERODISP WR 8520 Macrynal SM 6810w Additol VXW Additol VXW Water : butyl glycol (1:1.5) DMEA 10 % in water ph = AERODISP WR Deionized water 8 Hardener without AEROSIL Stir for 10 min at 2000 rpm Butyl glycol acetate 3 3 Bayhydur

6 Binder mixture Mill base (pigments) Bayhydrol E Bayhytherm Bayhytherm VP LS Cymel Byk DMEA 10 % in water 1 1 Deionized water 4 4 Sum Bayhydrol E Deionized water 7 7 DMEA 10 % in water Surfynol 104 E BYK Tronox R-FD-I Bayferrox 303 T Blanc fix Micro Talkum IT extra Sum Filler Binder mixture Mill base (pigments) AERODISP WR Deionized water DMEA 10 % in water ph 8.6 Table 6 Test system: water-based coating The rheological effectiveness of AERODISP WR 8520 is compared to that of several polyurethane thickeners in Figures 5 6. Using an appropriate polyurethane thickener, it is possible to obtain a viscosity level that is comparable to that of the AERODISP WR 8520 containing coating, for the same active additive level (5 % dispersion corresponds to 1% silica powder). Though the viscosity of the polyurethane additive containing coatings is comparable at low shear rate, the desired shear thinning behavior under increasing shear rate is much lower. This typically results in poor application efficiency, as high shear rate is used to apply many types of coatings. η [mpas] Figure 5 Comparative studies in a water-based pigmented coating system Shear rate γ [1/s] 1% PUR 1 1% PUR 2 1% PUR 3 5% AERODISP WR 8520 control 1 % AEROSIL fumed silica or competing products, based on entire formulation: Bayhydrol E 270 Baytherm 3146 Baytherm VP LS

7 The step function curve shown in Figure 6 confirms this behavior. Even when the polyurethane concentration is reduced to 0.5 % to attain a comparable viscosity level to that of the sample containing AEROSIL fumed silica, at low shear rate ( seconds; simulation after application), at high shear (0 120 seconds; spray) the viscosity of the coatings containing polyurethane thickeners will be too high which can create problems during application. 5 Physico-Chemical Data of AERODISP WR 8520 Physico-chemical Data Properties Unit Typical Value Solids content based on the ignition residue of the dispersion wt.% 20 ± 1 Coatings can be adjusted with water. In some cases, this requires large amounts of water (up to aapox. 15 %). Even in these cases, the thixotropic behavior is still significantly improved in the coating containing AERODISP WR In review of adjusted coatings with the polyurethane additives, little improvement is detected. This situation is reflected in Figure 6. Stabilizing agent ph DIN EN ISO 787 / 9 Viscosity DIN EN ISO 3219, 100 s 1, 23 C Mean aggregate size d-50 value Density 20 C DMEA mpa s 100 μm 0.12 g / cm η [mpas] Figure 6 Comparative studies in a water-based pigmented coating system time t [s] 0,5% PUR 1 0,5% PUR 2 0,5% PUR 3 5 % AERODISP WR 8520 control Addition of water for 25 s. DIN 4 mm Start of running Control 2 % 25 μm 5 % AERODISP WR % 40μm 0.5 % PUR 1 13 % 25 μm 0.5 % PUR 2 14 % 25 μm 0.5 % PUR 3 16 % 25 μm 1 % AEROSIL fumed silica or 0.5 % competing products, based on entire formulation: Bayhydrol E 270 Baytherm 3146 Baytherm VP LS 2153 The data represents typical values (no product specification) Safety and Handling An MSDS is supplied with every first delivery. Of course, you can also request an MSDS or any other information regarding product safety at any time, or download it as a registered user at Packaging and Storage Depending on the region, AERODISP WR 8520 is available in 60 kg containers, 220 kg drums, 1000 kg intermediate bulk containers (IBC s). All dispersions must be protected from extreme heat and frost. The product should be used within twelve months from the date of production. Registration AERODISP WR 8520 CAS-Nr.* EINECS (Europe) TSCA (USA) DSL (Canada) AICS (Australia) PICCS (Philippines) ECL (Korea) ENCS (Japan) IECS (China) * Data refer to the inorganic substance used All components of this dispersion are listed in the inventories above 7

8 This information and any recommendations, technical or otherwise, are presented in good faith and believed to be correct as of the date prepared. Recipients of this information and recommendations must make their own determination as to its suitability for their purposes. In no event shall Evonik assume liability for damages or losses of any kind or nature that result from the use of or reliance upon this information and recommendations. EVONIK EXPRESSLY DISCLAIMS ANY REP- RESENTATIONS AND WARRANTIES OF ANY KIND, WHETHER EXPRESS OR IMPLIED, AS TO THE ACCURACY, COMPLETENESS, NON- INFRINGEMENT, MERCHANTABILITY AND/OR FITNESS FOR A PARTICULAR PURPOSE (EVEN IF EVONIK IS AWARE OF SUCH PURPOSE) WITH RESPECT TO ANY INFORMATION AND REC- OMMENDATIONS PROVIDED. Reference to any trade names used by other companies is neither a recommendation nor an endorsement of the corresponding product, and does not imply that similar products could not be used. Evonik reserves the right to make any changes to the information and/ or recommendations at any time, without prior or subsequent notice. AERODISP is a registered trademark of Evonik Industries AG or its subsidiary companies. Europe / Middle-East / Africa / Latin America Evonik Resource Efficiency GmbH Business Line Silica Rodenbacher Chaussee Hanau-Wolfgang Germany PHONE FAX ask-si@evonik.com North America Asia / Pacific Evonik Corporation 299 Jefferson Road Parsippany, NJ USA PHONE FAX ask-si-nafta@evonik.com Evonik (SEA) Pte. Ltd. Business Line Silica 3 International Business Park #07 18 Nordic European Centre Singapore PHONE FAX ask-si-asia@evonik.com L+L , vnd TI 1390, us.indd 21. Jul 2015; 14:31 Uhr

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