AEROSIL R 9200 to Improve the Scratch Resistance of Paint and Coating Systems. Technical Information 1284

Transcription

1 to Improve the Scratch Resistance of Paint and Coating Systems Technical Information 1284

2 1 Introduction 2 Features of structuremodified products In the paints and coatings industry, highly-dispersed fumed silica is primarily used to control the rheology of liquid paint systems. In addition to generating structural viscosity and behaving as an anti-settling agent for pigments, it has been repeatedly shown that highly-dispersed silica can positively influence the mechanical properties of paints and coating films. Scratch resistance often plays an important role in modern paint and coating systems. Technical experts at Evonik Industries have developed a new generation of structuremodified fumed silica that significantly improve the scratch resistance of UV-curing, high-solid as well as conventional solvent based two pack systems. The special production method used to produce structuremodified grades result in properties that are distinctly different from those of conventional products. When compared to a material that is not structuremodified, the compacted bulk density of is twice to three times higher. This promotes quick incorporation into the binder system, while simultaneously reducing the formation of dust. Figure 1 shows the difference in bulk densities between non-structure-modified and. By combining a chemical and mechanical treatment, these structure-modified products barely affect the rheology of paint and coating systems. Quantities of up to 10 percent by weight can be incorporated significantly increasing viscosity. substantially increases the mechanical stability of coatings against scratching. has been successfully introduced to the market for UV-curing, high solid and conventional solvent based two pack systems. Following the development of R 7200 and R 8200, represents a further contribution to an innovative new product portfolio of structure-modified hydrophobic silica. non-structure modified To make it easier for our customers to handle this innovative fumed silica Evonik developed a user-friendly dispersion: AERODISP 1030, a 30 wt.% dispersion of in 1-methoxy-2-propylacetate (MPA). Figure 1 Comparison of the bulk densities of a conventional material with. Both measuring cylinders hold the same weight of 2

3 3 Dispersing structure-modified products The reduced effect of structure-modified products on the rheology of paint and coating systems plays a particularly important role in increasing scratch resistance. Figure 2 and 3 demonstrate the reduced influence on the rheology of in different binder systems, compared to non-structure-modified grades. Only the special mechanical treatment of structure-modified allows the addition of the amount necessary (up to 10 % by weight) to increase scratch resistance of coatings films significant increase of the viscosity. Vis c osi ty [mpa s ] Figure 2 20, , , , Figure 3 The effect of on the rheology in a UVcuring varnish based on polyester acrylate, compared to nonstructure-modified. The data were generated with a Physica rotary viscosimeter. 0 0, Shear rate [s ] 5% hydrophobic, nonstructure-modified 10 % Effect of on rheology in a solvent based two pack varnish, compared to non-structure-modified. The data were generated with a Brookfield viscometer; on total formulation. Silica produced by flame hydrolysis from SiCl 4 does not consist of primary particles but of agglomerated aggregates. Using suitable dispersing techniques, the agglomerates can be broken down to the aggregate level. This minimizes the influence on the optical properties of the coating film, even at high concentrations. Based on previous experience, we recommend using a two step process to disperse structure-modified products. Working with, the silica is first wetted by using a dissolver. It should then be fed slowly into the formulation with the dissolver at a low speed for optimum wetting and to prevent the formation of dust. After this step is complete, dispersing is carried out in a second step with a bead mill. The results mentioned in this Technical Information were achieved with a Getzmann SL 5 laboratory bead mill, using glass beads as grinding elements. Optical properties can be optimized by using a ceramicclad bead mill chamber in combination with finer beads. After dispersing in clear coat formulations, the grindometer value should not exceed 10 µm. Another way to optimize the dispersing results is the master batch method, especially for high-solid and conventional systems. Depending on the viscosity and wetting properties of the binder, should be used at concentrations of 10 to 2 calculated in reference to the binder solids. To make it easier for our customers to handle this innovative fumed silica we recommend to test the user-friendly dispersion: AERODISP 1030, a 30 wt. % dispersion of in 1-methoxy-2-propylacetate (MPA) which was dispersed in a bead mill with 0.5 mm ZrO 2 beads. Viscosity [mpa s ] hydrophobic, non-structure modified 6 rpm 60 rpm 3

4 4 Methods used to generate and measure scratching The scratch resistance of surfaces is tested by many different methods in the coatings industry. A basic distinction is made between dry scratching and scratching using an abrasive slurry. The results presented in this Technical Information were obtained using a Crockmeter (dry method) and an Elcometer 1720 (wet method). In addition, a car wash simulator from Amtec Kistler is available at Evonik to produce scratches in accordance with ISO This type of equipment reproduces the scratching generated by a car wash as accurately as possible. A water based quartz slurry was used as abrasive medium in the wet method. Figure 5 Amtec laboratory washing system, made by Amtec Kistler GmbH, Prittriching Gloss and haze of the surfaces were measured before and after scratching. Based on these results, the percentage of residual gloss can be calculated. Figure 4 Elcometer 1720, made by Elcometer Instruments GmbH, Aalen Figure 6 Crockmeter, made by Karl Schröder KG, Weinheim 4

5 5 UV-curing varnish 6 2 pack varnish 5.1 Guide formulation 6.1 Guide formulation Mill Base weight % Laromer PE 44 F BASF AG 68.0 Tripropylene glycol diacrylate (TPGDA) BASF AG 32.0 Evonik Industries AG 10.0 Hardener Darocur 1173 Ciba Speciality Chemicals 4.4 Total Mill Base weight % Macrynal SM % Cytec Surface Specialties 40.0 Butyl acetate 15.0 Xylene 5.0 Evonik Industries AG 5.0 Let Down Macrynal SM 510, 60 % Cytec Surface Specialties 10.0 Xylene 4.0 Ethoxypropylacetate Scratch resistance Butylglycolacetate pack high-solid varnish Vestanat HB 2640 MX Evonik Industries AG 21.0 Total Reflectometer Value Figure Improved scratch resistance with in a UV-curing varnish based on polyester acrylate. The scratching was done with the Elcometer 1720; 40 double strokes with boar bristle brushes, quartz slurry Scratch resistance By using in the formulation, the scratch resistance of this solvent-containing two pack varnish is significantly improved. The quartz concentration in the abrasive slurry has a strong influence on the degree of scratching. The 0.1 quartz slurry as per ISO has less of an impact on the results than anticipated % 1 Figure 8 Improved scratch resistance with in a two pack varnish. Scratching was generated with an Elcometer 1720; 40 double strokes with boar bristle brushes; 0.1 quartz slurry in comparison to a quartz slurry. 20 Glos 20 Glos after Scatching Figure 7 demonstrates the improved scratch resistance. Gloss retention is significantly greater with in the formulation. In this UV-curing varnish, increasing the amount of could further improve the scratch resistance. The gloss of the coating prior to scratching is hardly influenced by increasing the amount of. 20 -Reflectometer Value Quartz slurry Quartz slurry Gloss before Scratching Gloss after Scratching 5

6 7 2K High-solid clear coating 7.1 Guide formulation Mill Base weight % Macrynal SM 565, 70 % Cytec Surface Specialties 61.0 Butyl acetate 7.3 In addition to gloss, haze is also negatively influenced by scratching. Figure 10 shows an increase in haze after scratching as a function of the quartz concentration in the abrasive medium. By adding, gloss can be improved and haze formation can be reduced. Methoxypropylacetate 1.7 Solvesso 100 Exxon Chemical GmbH 2.0 Xylene 2.7 Evonik Industries AG 5.0 Figure 10 Influence of on haze formation in a two pack high solid varnish. Scratching was generated with the Elcometer 1720; 40 double strokes using boar bristle brushes; comparison of 0.1 quartz slurry and quartz slurry. Let Down Vestanat HT 20 L Evonik Industries AG 22.3 Butyl acetate 2.0 Solvesso 100 Exxon Chemical GmbH 1.0 Total Scratch resistance Figure 9 compares the results of dry scratching of a two pack high-solid varnish using a Crockmeter and wet scratching using an Elcometer Although the Crockmeter method proves to be more abrasive, both methods confirm an improved scratch resistance when is in the formulation. Haze Haze before Scratching 0.1 Quartz slurry ige Quartz slurry Haze after Scratching Figure 9 Improved scratch resistance with in a two pack high-solid varnish. The scratching was generated with a Crockmeter, using abrasive paper and the Elcometer 1720, 40 double strokes with boar bristle brushes; 0.1 quartz slurry. 20 -Reflectometer Value Crockmeter (Dry Scratching) Elcometer 1720 (Wet Scratching) 40 Gloss before Scratching Gloss before Scratching Gloss after Scratching Gloss after Scratching 6

7 8 Summary In order to demonstrate the effectiveness of AERODISP 1030 we added 16 % of this dispersion (appr. ) to a two-component clear coat in relation to the total formulation (10 % based on binder) at Figure 11. The Figure 12 consist of the lacquer. To assess scratch resistance we used an Elcometer 1720 with a slurry of quartz and water (see Figure 4). The evidence shows that the use of AERODISP 1030 clearly improves scratch resistance. Residual gloss after scratching is significantly greater in Figure 11. Furthermore, the test also demonstrated that the lacquer still shows excellent optical properties even admixture of the dispersion. The structure-modified hydrophobic fumed silica is distinguished by the following properties when used in paints and varnishes: increases the scratch resistance of UV-curing, two pack and conventional high solid systems. Low rheological activity allows the added amount to be increased up to ten percent by weight, generating any noticeable structural viscosity. Low compacted bulk density makes easy to incorporate with a dissolver. Dispersing should be carried out with a bead mill or other adequate equipment. AERODISP 1030, a 30 wt. % dispersion of in 1-methoxy-2-propylacetate (MPA) was developed to make it easier for our customers to handle this innovative fumed silica. Figure 11 High Solids 2C-Clear Coat with appr. AERODSIP 1030 Figure 12 High Solids 2C-Clear Coat AERODSIP

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 REPRESENTATIONS 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 RECOMMENDATIONS 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, prior or subsequent notice. is a registered trademark of Evonik Industries AG or its subsidiaries. Europe / Middle-East / Africa / Latin America Evonik Resource Efficiency GmbH Business Line Silica Rodenbacher Chaussee Hanau Germany phone fax ask-si@evonik.com North America Asia Pacific Evonik Corporation Business Line Silica 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 TI JUL15