The use of AERODISP fumed silica dispersions to enhance waterborne coatings. Technical Information 1371

Transcription

1 The use of AERODISP fumed silica dispersions to enhance waterborne coatings Technical Information 1371

2 Table of Contents Introduction AERODISP finely dispersed aggregates AERODISP physical and chemical attributes PRIMARY ATTRIBUTES Anti-settling PRIMARY ATTRIBUTES Improved film formation Secondary attributes Fundamentals for use of AERODISP Page

3 1 Introduction 2 AERODISP finely dispersed aggregates Fumed silica, in various grades and modifications, has been used for decades in the field of coatings as thixotropes, antisettling and anti-sag agents. However, water, because of its low viscosity and high dielectric constant, has proved to be a poor grinding medium for fumed silica, making it difficult to achieve the degree of de-aggregation and dispersion of particles needed to achieve optimum benefits in waterborne coatings. Without proper dispersion, efficacy is compromised and surface appearance properties suffer. Both of these concerns can be overcome by employing pre-made dispersions in water of fumed silica. Evonik Industries offers a wide variety of fumed silica, alumina and titania dispersions in their AERODISP line of products. Lab evaluations have demonstrated that multiple performance attributes can be enhanced by the use of AERODISP fumed silica dispersions such as, improvement of pigment, filler and matting agent suspension, reduced tack, improved dirt pick-up resistance, enhanced film strength, and even improved coalescence of some resins, without compromising gloss and other appearance attributes. The optimum level of de-aggregation is achieved in the production of AERODISP, to provide an aggregate size that will not significantly influence viscosity or negatively impact optical properties. Using standard dispersion methods, it would be extremely difficult to achieve this level of de-aggregation using standard powdered fumed silica in waterborne coatings. Figure 1 Particle size distribution AERODISP vs AEROSIL 200 dispersed in water via sonication *Sonication power 40 Watts, 39 KHz AERODISP W 7520 AEROSIL 200: 0 sec sonication* AEROSIL 200: 60 sec sonication* AEROSIL 200: 30 sec sonication* AEROSIL 200: 90 sec sonication* Figure 1 shows the particle size analysis of the AERODISP W 7520 (20 % solids dispersion of AEROSIL 200) vs. AEROSIL 200 dispersed via sonication in water at varying time intervals. As Figure 1 shows, even after 90 seconds of sonication the level of de-aggregation that is achieved in the AERODISP W 7520 is not possible with standard AEROSIL 200 in powder form. In most cases, when attempting to disperse powdered fumed silica, a bi-modal distribution is produced with a peak of fine aggregates, and a second peak of much larger particles (comprising aggregates and agglomerates). These larger particles negatively affect gloss, haze, and film clarity as can be seen in Figure 2. 3

4 3 AERODISP Physical and chemical attributes Figure 2 shows AEROSIL 200 added to the acrylic resin Rhoplex AC 337 N and mixed with a high speed disperser at 4000 rpm for 15 min, vs. the AERODISP W 7520 at equal silica loading, mixed in via hand stirring with lab spatula. Figure 2 AERODISP vs AEROSIL Optical properties Resin + 1 % AEROSIL 200 Resin + 5 % AERODISP W 7520 Due to its negative charge and acidic nature, standard hydrophilic, fumed silica is somewhat limited in its use in waterborne coatings. AERODISP fumed silica dispersions are available in both acidic and alkaline forms as well as with cationic modification, providing the formulator a much greater range of versatility. There are also several stabilizers available to modify the ph based on the needs of the formulator, such as, ammonia, KOH, and NaOH. Various grades of AERODISP are available with fumed silica ranging in surface area from 90 to 300 m 2 /g and with solid contents from % silica. Also offered under the AERODISP name are dispersions of titania, alumina, and mixed oxides. The full list of AERODISP products can be found on page 7 in Figure 12. AERODISP dispersions do not contain solvent or surfactant. Therefore, these dispersions have no impact on VOC s and very little likelihood of causing incompatibility when added to a formula, as long as the ph of the AERODISP grade matches the ph range of the coating. Gloss = 61 at 60 Gloss = 79 at 60 AC-337 N Acrylic Resin - Rohm & Haas (4 mils wet) The decrease in gloss and film clarity in the clear system with the standard powered version of fumed silica is due to the inability to break down the large silica agglomerates that are still visible by the naked eye. However, use of the AERODISP provides the formulator the ability to incorporate the silica easily and already have a very small silica aggregate size with a D 50 of approximately 100 nanometers, well below the visible range. 4

5 4 PRIMARY ATTRIBUTES Anti-settling Evaluations of AERODISP as an anti-settling agent were conducted in three types of formulations; a semi-elastomeric masonry coating, an acrylic clear satin wood varnish, and a PUD clear satin wood varnish. AERODISP aqueous fumed silica dispersions produce efficient results in eliminating hard settling of pigments and matting agents without significantly affecting the viscosity of the waterborne coating. The finely dispersed silica aggregates help pigment, filler, and matting agent particles stay dispersed, and keeps them from re-agglomerating and hard packing. Control 5 % AERODISP W 7520 Figures 3, 4, and 5 show the results of using AERODISP W 7520 as an anti-settling agent in the semielastomeric architectural coating, an acrylic clear satin wood varnish, and a PUD clear satin wood varnish. Figure 4 AERODISP W 7520 as an Anti-settling Agent in Acrylic Satin Wood Varnish 10 % AERODISP W 7520 Control Control 5 % AERODISP W 7520 Figure 3 Elimination of syneresis using AERODISP W 7520 in semielastomeric masonry coating Figure 5 AERODISP W 7520 as an Anti-settling Agent PUD Clear Satin Wood Varnish In the semi-elastomeric masonry coating, the anti-settling effect of the AERODISP was observed in the reduction of syneresis common to highly pigmented systems. By suspending the pigment particles, the AERODISP prevents pigment re-agglomeration and the typical liquid layer that is forced to the top in the control. In all three formulas the AERODISP was able to eliminate settling without any significant change in viscosity. This is also an advantage when comparing AERODISP to competitive anti-settling agents, most of which work by increasing the viscosity of the formulation. Antisett-ling agents which increase viscosity often negatively impact flow and leveling as can be seen in Figure 6. The photo demonstrates the superior flow and leveling of a formula with AERODISP brushed out on black glass panels verses formulas with BYK 420 and Disparlon AQ

6 BYK % AERODISP W 7520 Disparlon AQ % BYK % Disparlon AQ % AERODISP W 7520 Figure 6 Leveling Comparison AERODISP W 7520 vs. BYK 420 and Disparlon AQ 610 Figure 8 3 Week Anti-settling Comparison, AERODISP W 7520 vs. BYK 420 and Disparlon AQ 610 at 120 F When evaluating the anti-settling performance of AERODISP W 7520 vs. the BYK 420 and Disparlon AQ 610, 1 % AERODISP W7520 showed similar ability to prevent settling at room temperature. This can be seen in Figure 7. At this low addition level, the cost impact to coatings formulas is very minimal. Along with the improved anti-settling performance and better flow and leveling achieved with the AERODISP verses alternative anti-settling technologies, improved matting efficiency was also observed as can be seen in Table 1. Figure 2 showed the AERODISP in resin alone does not influence gloss by itself. However, there is a dramatic increase in matting efficiency (reduction in gloss) due to its ability to keep the matting agent suspended as the film dries. Table 1 60 Gloss in Acrylic Clear Satin Wood Varnish, Comparison of Control with No Anti-settling Agent to Formulas With BYK 420, Disparlon AQ 610, and AERODISP W Gloss 0.4 % BYK % Disparlon AQ % AERODISP W 7520 Control % BYK % Disparlon AQ % AERODISP W Figure 7 4 Week Anti-settling Comparison, AERODISP W 7520 vs. BYK 420 and Disparlon AQ 610 at Room Temperature When the same comparison was done at elevated temperature the AERODISP significantly outperformed the BYK and Disparlon products as can be seen in Figure 8. In addition to suspension and improved gloss reduction of matted coatings, AERODISP does not significantly impact Konig hardness of lower gloss systems, as do other typical competitive anti-settling technologies. One of the negative aspects of many anti-settling technologies for water based coatings is their inherent negative effects to film hardness. Hard, inorganic particles such as silica are known to improve scratch resistance and contribute to increase hardness of resins matrices. Figure 9 shows this reduced influence to hardness of a matted resin coating contributed by AERODISP. 6

7 5 PRIMARY ATTRIBUTES Improved Film Formation Konig Hardness [AC 337 N Clear Satin] Figure 9 Konig Hardness in Acrylic Clear Satin Wood Varnish, Comparison of No Anti-settling Agent vs. Formulas With BYK 420, Disparlon AQ 610 and AERODISP W Control W 7520 Byk 420 Disparlon AQ 610 Another attribute observed when evaluating AERODISP technology in clear latex resins is improved film formation. Through research done by the Univeristy of Minnesota, clear understanding was gained as to the mechanism of how AERODISP improves film formation. In the majority of acrylic resins tested, AERODISP improved film formation by reducing the coating s tendency to crack and lowering minimum film forming temperature. In Figure 10 the improvement in film formation is seen with 5 % AERODISP W 7520 added to the Rhoplex AC 337 N acrylic resin, compared to the resin alone. The cracking in the control film is due to natural stresses which occur in the film during the drying process. 24 hrs 72 hrs 1 week As AERODISP does not contain solvent or any wetting additives, it does not contribute to VOC s. Also due to not containing wetting additives which are often needed to stabilize such types of particle dispersions, problems of incompatibility are far reduced. High compatibility to a wide variety of coatings systems is supported by AERODISP s uncomplicated formula of water, fumed silica and ph stabilizer. Resin only Gloss = 50 at 60 Gloss = 79 at 60 The major parameter formulators need to be sensitive to is matching the ph of the AERODISP grade to the final ph of the coating. Flocculation will occur in cases where basic AERODISP grades are pared with acidic coatings (and vice-a-versa). 40 x magnification 40 x magnification Figure 10 Improved Film Formation in Rhoplex AC 337 N Acrylic Resin with 5 % AERODISP W 7520 AERODISP helps prevent this cracking due to the reinforcing characteristics of fumed silica. Reinforcement is an attribute fumed silica has become known for in other highly filled sytems, due to is small size and high surface area. Therefore AERODISP has the potential to increase the fracture resistance of the coating. This seems to be the case in softer resins, which don t have a difficulty coalescing, but do not form a clear film at room temperature due to their tendency to crack, without the addition of co-solvent or plasticizer. A plasticizer or co-solvent can be used to overcome this cracking, also lowering minimum film forming temperature. However, co-solvents contribute to VOC and plasticizers tend to make films softer and less durable. The AERODISP is able to overcome this cracking tendency without contribution to VOC, while maintaining or increasing the hardness and durability of a film. 7

8 5 C 5 C 5 C 5 C 14 C 14 C 7 C 7 C 17 C 17 C 15 C 15 C Figure 11 Reduction of cracking in Rhoplex AC 337 N Acrylic with 7 % AERODISP W 7520 on the right vs. resin alone on the left, at various temperatures Figure 12 Reduction of cracking in Rhoplex EL 2000 Acrylic with 7 % AERODISP W 7520 on the right vs. resin alone on the left, at various temperatures The study done by the University of Minnesota shows that, AERODISP is active early in the drying process, immediately reducing the films natural tendency to crack. Results from this study can be seen in Figures Figures 11 and 12 show two different resins with AERODISP, versus the resins alone, under microscopy at various temperatures, on an MFFT (minimum film formation temperature) bar. In both the AC 337 N and EL 2000 resin, the films with the AERODISP show less cracking at each of the temperatures than the resin alone. Even at temperatures as low as 5 C the AERODISP containing samples show less frequent cracking and greater crack spacing. Figure 13 shows the effect of the AERODISP on the MFFT. In both cases the resins are able to form a complete crack free film at lower temperatures with AERODISP then the resin alone, avoiding the need for any co-solvent or plasticizer. 8

9 Figure 13 Reduction of MFFT in Rhoplex AC 337 N and EL 2000 acrylic resins from Rohm and Haas with the addition of AERODISP W 7520 Figure 15 Measurement of crack spacing in films with Rhoplex EL 2000 acrylic resin from Rohm and Haas with and without the addition of AERODISP W 7520 at various drying temperatures Minimum drying temperature where a crack-freecoating can be created [ C] Minimum drying temperature Pure AC AC + 7 % AERODISP Pure El El + 5 % AERODISP Crack spacing [mm] Temperature [ C] Further indication of AERODISP reducing cracking tendency in acrylic resins is, by the increased amount of crack spacing at various temperatures with the presence of the AERODISP. This can be seen in Figures 14 and 15, where crack spacing seen at various temperatures in the AC 337 N and EL 2000 resins alone, is compared to the crack spacing in the resins with AERODISP. At all of the temperatures there is more space between cracks in the resins with the AERODISP indicating less crack frequency. Figure 14 Measurement of crack spacing in films with Rhoplex AC 337 N acrylic resin from Rohm and Haas with and without the addition of AERODISP W 7520 at various drying temperatures El El + 5 % SiO 2 Although not all testing was conclusive, observations would suggest that AERODISP shows the most improvement in film formation in acrylic resins that contain soft latex particles, with an MMFT of less than 15 C. These resins would have no problem coalescing at room temperature. Therefore, problems in film formation with these resins would likely be due to crack formation, which the AERODISP would help to overcome. Film formation problems in resins containing harder particles, or those with an MMFT of greater than 22 C, would likely be due to lack of coalescence. Because the AERODISP does not play a role in helping a film coalesce, it would likely not provide any improvement in film formation alone in these instances Crack spacing [mm] Temperature [ C] AC AC, 7 % SiO 2 9

10 6 Secondary Attributes In all of the formulations tested, along with the clear benefits of anti-settling and improved film formation, the AERODISP also enhanced other secondary attributes. In the semi-elastomeric masonry coating, not only was settling prevented, but an improvement in sag resistance, as well as reduction of film tack and dirt pickup was observed. In Figure 16 the improvement in sag resistance is demonstrated, with sag occurring at 35 mils in the system without AERODISP, while the AERODISP containing system remains vertical stable even at 45 mils. This improved vertical stability is accomplished without a notable increase in viscosity. Highly filled systems are often observed to crack on drying as particles shift and cause stress within the film. The ability of the AERODISP to control particle mobility and support improved particle packing directly influences this interface. Figure 18 illustrates the reduced cracking tendency when AERODISP is applied. EIFS coating are highly sand filled. As the sand particles shift in the drying process, cracks form, as can be seen in the control. With 5 % AERODISP W 7520, contributing smaller silica aggregates combined with the absorption nature of the fumed silica itself, help stabilize the motion of the larger sand particles and reduce the stress they cause within the drying film. Mils Figure 16 Improvement in Sag Resistance with 5 % AERODISP W 7520 in a Semi-elastomeric Masonry Coating on the left vs. the coating with no AERODISP on the right Figure 18 Reduction of Cracking in EIFS coating with 5 % AERODISP W 7520 Fumed silica, while not porous, has notable oil absorption and when incorporated into highly filled systems help to reduce the film tack. Due to its ability to absorb and function to fill in small spaces between larger filler and pigment particles, it also helps to make the final coating film less porous, increasing the dirt pickup resistance observed in Figure 17. Figure 17 Reduction of Film Tack and Dirt Pickup With 5 % AERODISP W 7520 in a Semi-elastomeric Masonry Coating on the left vs. the coating with no AERODISP on the right 10

11 7 Fundamentals for Use of AERODISP Summary AERODISP, due to its low viscosity and lack of solvent and surfactants, can be very easily added to a formula, with little risk of incompatibility, or potential to cause other adverse performance characteristics. However, when formulating with AERODISP there are several factors which influence performance. Due to the high surface area and oil absorption of fumed silica, AERODISP fumed silica dispersions affect pigment volume concentration. Therefore, in highly filled systems the critical pigment volume concentration should be calculated to make sure it is not exceeded with the addition of the AERODISP. Maintaining consistent ph is also critical to success. The formulation ph will dictate which ph of AERODISP should be used. As there are both acidic and alkaline versions available, it is important to make sure the appropriate version is selected based on the ph of the formula. The AERODISP dispersions are generally lower in solids, and the additional water contribution needs to be considered. Due to the extra water being brought into formulations with AERODISP usage, there needs to be some level of free water in the formula which can be substituted with the addition of AERODISP. Lab evaluations have demonstrated that with certain urethane type rheology modifiers, some synergy occurs whereby more significant increase in viscosity is observed. This can easily be adjusted for by using slightly less of the rheology modifier. AERODISP can typically be added anywhere in the formulation process or even into the grind stage. However, it is recommended to add the AERODISP at the end of the formula or in the letdown stage, before any rheology modifier is added. By using this suggested sequence of addition, if there is synergy between the AERODISP and the rheology modifier in the formula, the viscosity can be post adjusted by holding out some of the rheology modifier. AERODISP is a new form of a well known, long standing additive that can improve a variety of performance attributes in waterborne coatings. Its easy to use, liquid form overcomes the challenges of using traditional powder versions of fumed silica. As an anti-settling agent AERODISP proves to be efficient and, demonstrates advantages of good flow and leveling, better heat age stability, better matting efficiency in matted systems, and better Konig hardness, then other technologies. Due to its solvent and surfactant free nature, it is easy to use and very versatile in a wide range of waterborne systems. AERODISP also provides the potential to lower VOC s by improving film formation and the possibility to reduce cosolvent with a number of acrylic resins. Along with these main benefits, further performance enhancements gained by using AERODISP in waterborne coatings are the other secondary attributes that can be expected. These include: Improved sag resistance Reduced cracking in highly filled systems Improved film hardness Reduced dirt pick-up Reduced film tack Fumed silica enjoys a long standing tradition to improve a wide variety of coatings performance properties in many types of coating technologies. Now AERODISP fumed silica dispersions are an innovative form for water based coatings also bringing high performance in an easy-to-use form. 11

12 Figure 19 Full Line of AERODISP Products and Properties Particle (s) Particle(s) Solids ph-value Viscosity Density Avg Particle Size Stablity Stabilization/Comments [wt-%] [mpa s] [g/cm 3 ] [µm] [months] SiO 2 -Dispersion, alkaline AERODISP W 7622 SILICA < Ammonium Hydroxide AERODISP W 7520 SILICA < Ammonium Hydroxide AERODISP W 7520 N SILICA < NaOH AERODISP W 1226 SILICA < formerly K330 SiO 2 -Dispersion, acidic AERODISP W 7512 S SILICA < NH 4Cl AERODISP W 1714 MOX < Phosphate/formerly K 315 AERODISP W 7215 S SILICA < NH 4Cl AERODISP W 1824 MOX < Phosphate/formerly K 328 AERODISP W 1836 MOX < Phosphate/formerly K342 SiO 2 -Dispersion, cationic AERODISP WK 341 AERODISP WK 7330 Al 2 O 3 -Dispersion SPECIAL SILICA SPECIAL SILICA < 1, cationic polymer/ formerly VP < 1, cationic polymer AERODISP W 630 ALUMINA < 3, Acetic Acid AERODISP W440 ALUMINA < 1, Acetic Acid Special Grades AERODISP G 1220 SILICA 20 < Ethylene Glycol Dispersion of Silica AERODISP W 740 X TITANIA < < TiO 2 Dispersion High Energy Milling Domestic Supply Imported 12

13 Formulations: Acrylic Clear Satin Control AC 337N Water Tego Foamex ACEMATT TS Proplyene Glycol Texanol Acrylic Clear Satin BYK 420 AC 337 N Tego Foamex BYK ACEMATT TS Water Proplyene Glycol Texanol Acrylic Clear Satin 1 % AERODISP W 7520 Rhoplex AC 337 N Tego Foamex AERODISP W ACEMATT TS Water Proplyene Glycol Texanol Acrylic Clear Satin Disparlon AQ 610 AC 337 N Tego Foamex Disparlon AQ ACEMATT TS AC 337 N Water Proplyene Glycol Acrylic Clear Satin 5 % AERODISP W 7520 AC 337 N Tego Foamex AERODISP W ACEMATT TS Water Proplyene Glycol Texanol PUD Clear Satin 5 % AERODISP W 7520 Urotuf F TS BYK Mang Hydrocure III Water Dri RX HF DPM Surf 104DPM Tego Foamex Proxel

14 PUD Clear Satin 5 % AERODISP W 7520 F OK BYK Mang Hydrocure III Water Dri RX HF DPM Surf 104 DPM Tego Foamex AERODISP W Proxel EIFS 5 % AERODISP W 7520 El Ethylene Glycol Nopco NXZ TI PURE R Temisca #15 Sand Unimin sand Minex Attagel Rozone Texanol Acrysol ASE AERODISP W WATER Ammonia (28 %) EIFS Control El Ethylene Glycol Nopco NXZ TI PURE R Temisca #15 Sand Unimin sand Minex Attagel Rozone Texanol Acrysol ASE WATER Ammonia (28 %) Semi-elastomer Masonry Coating Carboset AE Water Drew Plus L AERODISP W Ethylene Glycol Natrosol 250 MBR Tamol Triton CF Drew Plus L Troysan Kronos Optiwhite Imsil A Atomite Texanol Drew Plus L POLYPHASE AFI AMMONIA Acrysol RM

15 Semi-elastomer Masonry Coating Carboset AE Water Drew Plus L AERODISP W Ethylene Glycol Natrosol 250 MBR Tamol Triton CF Drew Plus L Troysan Kronos Optiwhite Imsil A Atomite Texanol Drew Plus L POLYPHASE AFI AMMONIA Acrysol RM Semi-elastomer Masonry Coating 5 % AERODISP W 7520 Material Carboset AE Water Drew Plus L AERODISP W Ethylene Glycol Natrosol 250 MBR Tamol Triton CF Drew Plus L Troysan Kronos Optiwhite Imsil A Atomite Texanol Drew Plus L Polyphase AFI AMMONIA ACRYSOL RM AERODISP W Semi-elastomer Masonry Coating 10 % AERODISP W 7520 Carboset AE Water Drew Plus L AERODISP W Ethylene Glycol Natrosol 250 MBR Tamol Triton CF Drew Plus L Troysan Kronos Optiwhite Imsil A Atomite Texanol Drew Plus L Polyphase AFI AMMONIA ACRYSOL RM AERODISP W

16 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, without prior or subsequent notice. AEROSIL, AERODISP, AEROXIDE and SIPERNAT are registered trademarks of Evonik Industries AG or its subsidiaries. BYK is a registered trademark of BYK-Chemie Disparlon is a registered trademark of King Industries. 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