Smart-Formulation-Journal-2012

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4 AEROSIL® Fumed Silica for Coating Defoamer • Hydrophobic AEROSIL® fumed silica is an effective booster silica in defoamer formulations for waterborn coatings. • Increasing concentrations of hydrophobic AEROSIL® fumed silica products (1 to 2 % by weight) result in better deaerator / defoamer performance. • AEROSIL® grades exhibit a better antisettling stability in deaerator / defoamer formulations when more dispersing energy is applied in their manufacture. • All hydrophobic AEROSIL® grades are compatible with the tested polyurethane binder system. • Performance and compatibility of hydrophobic AEROSIL® grades with the examined acrylate / methacrylate and polyvinyl acetate binder systems improve with increasing hydrophobicity. Silica in Coating Defoamer Surfactants are used in modern industrial coating formulations in order to facilitate dispersion and wetting of pigments and enhance incorporation of water-insoluble binders into water-borne paints. An undesired side effect of surfactants, however, is the stabilization of air bubbles, incorporated during the manufacture or application of coatings. Therefore, defoamers are often added in the preparation of coating formulations. For providing deaeration as well as defoaming effects, defoamers must exert interfacial activity. A challenge remains: the defoamer applied needs to be partly incompatible with the coating formulation for the desired deaeration / antifoam effect, but must also be compatible enough with the respective binder system. Otherwise “fish eyes” and other failures may occur. The refore, several hydrophobic AEROSIL® fumed silica grades were compared as part of a standard defoamer formulation. The designation “R” in the AEROSIL® R grades indicates surface treated (hydrophobized) fumed silica. In all experiments a mixture of polyethersiloxanes (38 % by weight) and white oil Ondina® 913 (60 – 61 % by weight) was used as a base defoamer formulation. Different hydrophobized AEROSIL® fumed silica types were incorporated as defoamer / deaerator booster. We addressed the question, which physico-chemical parameter of the silica (e. g. surface area, silanol group density, C-content, hydrophobicity) influences the settling behav- Table Process Parameters Used to Prepare the Defoamer Formulation with Different Hydrophobic AEROSIL® Grades Dispersing Energy Low (Lab stirrer at 1000 rpm) Medium (Dissolver-blade at 2000 rpm) High (Ultra-Turrax® at 10.000 rpm) AEROSIL® concentration 1 % by weight 1.5 % by weight 2 % by weight Hydrophobic AEROSIL® fumed silica investigated AEROSIL® R 972 AEROSIL® R 104 AEROSIL® R 974 AEROSIL® R 106 AEROSIL® R 805 AEROSIL® R 812 AEROSIL® R 812 S AEROSIL® R 202 ior, the performance and finally the compatibility the most. It is well known that the incorporation of fumed silica into a defoamer formulation may be critical with regard to silica concentration and the dispersing energy. In order to limit the number of defoamer formulations and the respective application tests a program was set up according to a design of experiments (DoE). Microscopic and rheological evaluations accompanied the settling behavior of the respective AEROSIL® fumed silica product in the defoamer formulation. In a second step, the defoamer formulations were applied to three different binder systems. Air content was evaluated gravimetrically and finally the flow out test on a polyethylene covered slope was examined for compatibility, e. g. fish-eyes, spots or other failures. Sedimentation Stability of Hydrophobic AEROSIL® Fumed Silica in Defoamer Formulations Initially the focus was on the sedimentation stability of hydrophobic AEROSIL® fumed silica in the defoamer formulation. Eight different hydrophobic AEROSIL® grades were dispersed into the defoamer formulation at three levels of dispersing energy and in three different concentrations (see table). The combined results of the visual, microscopic and rheological evaluations were as expected. They showed that the highest sedimentation stability of the defoamer was achieved when using a) the highest dispersing energy (10 000 rpm, Ultra-Turrax®) and b) the highest AEROSIL® concentration (2 % by weight). The sedimentation stability correlated well with the hydrophobic nature of the respective fumed booster silica. AEROSIL® R 972, AEROSIL® R 104 and AEROSIL® R 974 tend to sediment easier (relative score about 70) in the SILIKOPUR® 8080 – an Innovative Combination of Polyurethane and Silicone! SILIKOPUR® 8080 is a one-pack, silicone-modified polyurethane manufactured using a targeted combination of silicone and polyurethane components. While polyester polyol is used in the manufacture of conventional PU dispersions, hydroxyfunctional organosiloxane is used in the synthesis of SILIKOPUR® 8080. This gives the product the unique properties of silicone-containing compounds. Coatings based on SILIKOPUR® 8080 are used substantially on leather, textiles, wood and plastics. They distinguish themselves principally by a high elasticity which is retained even at low temperatures. The coatings also exhibit hydrophobic characteristics and a non-stick effect. Used in combination with acrylic binders, the product can improve abrasion resistance. SILIKOPUR® 8080 can be diluted with water and is air-drying. Contact Dr. Sascha Herrwerth sascha.herrwerth@evonik.com Smart Formulating Journal | Issue 9 | April 2012
5 used standard defoamer formulation, whereas the more hydrophobic fumed silica products AEROSIL® R 812 S and AEROSIL® R 202 exhibited a better antisettling behavior (relative score about 80, see figure 1). Figure 1 Sedimentation Stability of Different Hydrophobic AEROSIL® Fumed Silica Grades Increasing Hydrophobicity AEROSIL® R 972 AEROSIL® R 104 AEROSIL® R 974 AEROSIL® R 106 AEROSIL® R 805 AEROSIL® R 812 AEROSIL® R 812S AEROSIL® R 202 60 70 80 90 Relative Score Figure 2 Performance and Compatibility of Hydrophobic AEROSIL® Grades in Different Binder Systems Increasing Hydrophobicity AEROSIL® R 972 AEROSIL® R 104 AEROSIL® R 974 AEROSIL® R 106 AEROSIL® R 805 AEROSIL® R 812 AEROSIL® R 812S AEROSIL® R 202 Performance and Compatibility of Hydrophobic AEROSIL® Grades The defoamer formulations above were added at three different defoamer concentrations (0.1 %, 0.175 %, and 0.25 % by weight) to the respective binder system and the 0,8 0,9 1 Relative Score mixture was stirred for one minute at 3000 rpm (laboratory stirrer) in order to allow air introduction, followed by immediate gravimetrical estimation of the air content and subsequent flow-out test for compatibility evaluation and scoring. The defoamer / deaerator performance and compatibility of the respective defoamer formulation in three different dispersion systems systems a) Acrylate / methacrylate (Mowilith® 7717, Celanese) b) Polyurethane (APU® 1035, Alberdingk-Boley) c) Polyvinylacetate (Airflex® CEF 10, now Wacker) was then evaluated and scored. The performance / compatibility in the polyurethane-dispersion was found to be very good with all of the tested defoamer formulations and hydrophobic fumed silica AEROSIL® grades (APU® 1035, purple columns, all score close to 1, see figure 2). In case of the acrylate / methacrylate binder (Mowilith® 7717, grey columns, score 0.85-0.93) as well as with the polyvinylacetate – binder system (Airflex® CEF 10, light purple columns, score 0.89-1.0) the hydrophobic AEROSIL® grades exhibited a broader range in their performance and compatibility with the binder system. It could be seen that the less hydrophobic AEROSIL® products AEROSIL® R 972, AEROSIL® R 104 and AEROSIL® R 974 are less compatible with these binder systems than the more hydrophobic grades, AEROSIL® R 812 S, AEROSIL® R 8200 and AEROSIL® R 202. Although the results clearly indicate that in the given formulation higher hydrophobic AEROSIL® contents provide better results, it should be mentioned that it is difficult to predict the behavior of fumed booster silica in other coating defoamer formulations with regard to settling and compatibility. Hence it is known that in other defoamer base formulations, also less hydrophobic AEROSIL® R 972 and AEROSIL® R 974 are used successfully in coating defoamer formulations. Contact Dr. H.-W. Wollenweber horst-werner.wollenweber@evonik.com Mowilith 7717 APU 1035 AirFlexCEF 10 UV Coatings: as Matte as it Gets When one thinks of eco-friendly coatings, UV-curable coatings immediately spring to mind. Traditional uses are for wood and furniture lacquers and printing inks. As we know, application on plastics and metal substrates is also significant for coatings such as these. The gloss of such UV coatings should, of course, be able to be varied over a large range from high to low gloss including dull matte finishes. Strong matting is often required, but dull matte finishes are particularly difficult to achieve with UV coatings. Increasing the matting agent content usually leads to undesirable higher viscosities, yield point anomalies and thixotropic effects and, consequently, problems during the application process (e. g. with roll units). The quality of the coatings surface also leaves much to be desired because of flow problems or air inclusions. The solution: optimal wetting of the surface of matting agents TEGO® Dispers 688, a new polymeric wetting and dispersing additive from Evonik, has been developed specifically for optimal wetting and stabilization of matting agent surfaces. TEGO® Dispers 688 enables the formulator to significantly lower the viscosity of the matte formulation. The yield point of such formulations is also lowered and thixotropic effects reduced. This results in good matting and problem-free application. Lowering the yield point positively affects the flow and degassing of the coating film. TEGO® Dispers 688 is highly effective on the most diverse matting agents in UV formulations based on all the common types of oligomers. TEGO® Dispers 688 offers the positive effects mentioned above. It also suppresses the undesirable reglossing (gloss-up) of the coating which occurs with many other wetting and dispersing additives. Contact Heike Semmler heike.semmler@evonik.com Smart Formulating Journal | Issue 9 | April 2012
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Page 3: 3 Corrosion Protection Systems Envi
Page 7 and 8: 7 TEGO® AddBond - the Multitasking
Page 9 and 10: 9 Product Overview NANOPOX I Produc

Smart-Formulation-Journal-2012

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