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    Home > Coatings News > Paints and Coatings Market > High-performance varnish and color paint with a water-based UVA/HALS mixture

    High-performance varnish and color paint with a water-based UVA/HALS mixture

    • Last Update: 2020-12-30
    • Source: Internet
    • Author: User
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    With changes in regulations and the need to reduce VOC content, water-based coatings are emerging for many indoor woodworkings, such as furniture and tile flooring, as well as outdoor wood, such as carpentry, outdoor decorative carpentry or outdoor paving. To emphasize natural beauty and wood color, most coatings are transparent. However, in order to protect the wood, the coating itself must be resistant to harsh environmental factors such as UV radiation, rain and temperature change1. Light stabilizers such as UVAs and blocked amine photostates (HALS) play an important role in the inherent protection of these coatings. Their respective roles have been described before 2-4. For outdoor use, the combination of UVA and HALS has obvious advantages. UV absorbents can be used to internally coat and protect wood due to increased absorption of ultraviolet light as the thickness of the coating increases (Bill Lamber's Law). HALS is effective throughout the film thickness range and functions as a free-form capture agent, suppressing photooxidation degradation reactions that occur inside the substitli and helping to maintain elasticity, gloss and water resistance. HALS is effective on coating surfaces, providing higher resistance to powdering (in paint), better photoresist, reduced adhesion to substrates, and less coating cracking.
    as long as it is solvent-based coatings, it is not a problem to add hydrophobic light stabilizers to the formulation, as they are very compatible with each other. However, the challenge is to introduce more and more water-based coatings into the market, and the long-term stability of coatings is also more demanding. The addition of hydrophobic light stabilizers to water-based coatings can only be achieved by using solvent-assisted and high-energy dispersion methods. Adding solvent aid can cause possible environmental problems and reduce overall coating performance due to plasticizer and seepage.
    New Capsule Additive Technology
    In order to overcome the problem of adding hydrophobic light stabilizers to water-based formulations, a new capsule additive technology (NEAT)5 has been developed. With this technique, traditional hydrophobic light stabilizers are made to be water-compatible and can be easily added to coating formulations without the use of solvents or surfactants6. The NEAT method is based on a microcapsules technique in which two steps are required to prepare these products. First, stable emulsions are produced by light stabilizers and monobodies through high shear emulsification techniques; In the second step, the polymerization of these emulsion droplets leads to the formation of a stable, low-viscosity water-based dispersion 6-7. The polymerization conditions are selected to ensure that the hydrophobic compound is evenly distributed in the polymer particles. Even at higher concentrations, this NEAT method ensures extensive compatibility with water-based dispersants.
    the first NEAT UVA/HALS
    in the past few years, SINGLE products for single components (UVA and HALS) have been introduced (Table 1). NEAT-type benzene triamcinolone UVA (NEAT-BTZ), NEAT-type triamcinolone UVA (NEAT-TZT-1 (blue shift), NEAT-TZT-2 (red shift) and NEAT-TZT-3 (advanced) and HALS (NEAT-HALS) are used in different systems. Due to their limited activity content (20%-30% at the time of product delivery), neat-UVA and NEAT-HALS use at the same time may produce excessive moisture, forcing customers to adjust coating formulations. In order to overcome this problem, a new hybrid based on NEAT technology has been developed. This new product (NEAT-mixture) is based on a combination of high-performance triginoid UVA and non-reactive HALS. The active content of this blend has been optimized to 40% to ensure the lowest possible impact when re-formulated.
    new blend has a low viscosity and can be added to a watery formula with a simple stir. It does not contain any solvents, which allows the Xi/R43 to be formulated into a paint formulation without marking. The addition of this new product will not affect the long-term storage stability of the formula.
    the transparency and color of the dry film
    One of the most interesting features of neat-mixtures is that they have a very low effect on the transparency and shadow of dry films. Table 2 shows the fog shadow values, e-E(on black/white paper jam) and the yellowing index YI values obtained using acrylic dispersant high gloss paint with and without the addition of light stabilizers.
    by adding hydrophobic benzene triamcinolone (HBIC-BTZ), the fog shadow values, the values of E and YI are very close to the reference values of the paint film that do not add stabilizers.
    -dispersed water-based UVA/HALS mixture (GRIND-mixture) showed a significant increase in e-E, indicating a high fog shadow. The fog shadow value is affected by the particle size and its distribution. Therefore, water-based UVA/HALS mixtures are only available for high gloss and high transparency coatings.
    increase in the concentration of NEAT-mixtures compared to the reference sample, and the increase in fog shadow values and e-E is very limited. This new product is suitable for high glossy paint and half-light systems. A small increase in the yellowness index YI was observed, so the NEOT mixture may not be suitable for very white substrates. For wood substrates, the higher YI value is negligible.
    light resistance
    In order to ensure the coating's long-term protective effect on the substrate below, UV absorbers are essential for excellent light resistance (i.e. luxus resistance), excellent intrinsic light stability (i.e., photolytic and photooxidant resistance), and good resistance to migration and loss.
    test was conducted in the Asia-Pacific Ras xenon tester XENOTEST 1200-LM, in accordance with the cycle-method A (2004) of DIN EN ISO 11341 Method 1. Test conditions: internal and external filters, 102 minutes of light, black standard temperature BST: (65±3), PRT: (38±3), relative humidity (50± 10), followed by 18 minutes of light and front spray, BST: (38±3), PRT: (38±3), relative humidity (95±10). The output power of the xenon lamp is 60W/cm2 between 300 and 400nm.
    water-based coating with light stabilizers on the glass plate with a dry film thickness of 30 microns. The amount of UV absorbent residue at different exposure points is monitored by recording changes in the absorption spectrum at the maximum radon. The results are shown in Figure 1.
    addition of HBIC-BTZ to obtain a minimum UV absorber retention value, after 3000h DIN EN ISO 11341 exposure, the coating contains only 45% of the original concentration. Since the GRIND-mixture consists of benzene triamcinolone UVA, it is expected to be of the same order of magnitude (50% compared to 45%) as HBIC-BTC.
    addED-mixture to get the best results, for all three concentrations, exposure of 3000h resulting in UVA retention values between 80% and 90%. The light stability of the UVA in the new blend is much better than that of the previous sample. With excellent light stability coupled with excellent loss resistance, the product to be selected for long-term protection is the NEOT-mixture.
    color stability and photoresist
    water-based paint applied to pine boards. The back and edges of the wood substrate are coated with the same finish without stabilizers. First coated primer, wet film thickness WFT is 80g/m2, then coated with two high-gloss transparent finishes (acrylic dispersions), wet film thickness of 300g/m2 (2×150g/m2). Place the model in the UVTest ™ UV condensation aging test box and test in accordance with DIN EN 927-6 specifications. Test conditions: 24 hours dark/condensation (blackboard temperature BPT: (45±3) degrees C), followed by 48 cycles, each consisting of 2.5 hours of light (blackboard temperature BPT: (60±3) degrees C) and 0.5 hours dark/spray (blackboard temperature BPT: (22±3) degrees C). Irradiance of fluorescent UV lamps: 0.89W/cm2 at 340 nm. Monitor the chroma chromaitude of E and 60 degrees gloss during Q-UV exposure (Figures 2 and 3).
    Coatings (control samples) that do not have a stabilizer added show significant color change after 240 hours of exposure, and the initial cracking begins after 960 hours, even though the gloss remains at the same level. After 1500 hours of exposure, the entire model is completely invalidated.
    traditional hydrophobic benzene triamcinolone UVA (HBIC-BTZ) to maintain a moderate color change (22 unit values) at the initial 1000h. This explains why this UVA is widely used for medium-required protection. Exposure for more than 1000 hours, wood color change increased dramatically, due to the absence of HALS in the coating to protect the substation, 4000 hours of exposure began to appear after the initial cracking. As you've seen before, there is no obvious effect on gloss. The properties of HALS, especially its alkalinity (expressed in pKb), seriously affect the role of HALS in water-based coatings. For HBIC-mixtures (highly alkaline HALS and HBIC-UVA mixtures (i.e. low pKb), it is easy to observe that HALS does not protect the paint film as expected: cracking after 4000h and a lower gloss after 240 hours (53 to 78) compared to the control sample. This behavior can be explained by the fact that HALS reacts with an acidic surfactant in a water-based acrylic dispersion to produce small crystals or shadows, thereby reducing the gloss of the coating.
    the performance of benzene triamcinolone UVA present in the GRIND-mixture was compared with that of HBIC-BTZ. Because HALS is present in this mixture, it can be seen that it does not react with acidic surfactants in the dispersion, so it can effectively protect the base material. No cracks were found after 4,000 hours of exposure. The main disadvantage of the GRIND-mixture is its fog shadow, which is represented by a poor gloss value (20 units lower than the control sample). As mentioned earlier, this product is not suitable for transparent highlight finishes.
    adds a new NEOT-mixture, the color change of the wood is delayed and slowed down. UVA present in the new mixture provides optimal protection for wood and coatings. In addition, HALS contained in the mix is not affected by the presence of acidic parts, which can protect the network structure of the substitlyte and prevent further photooxidation reactions. Even after 4000 hours of exposure, the coating remains intact and the gloss basically remains at the level at which exposure begins.
    the NEOT UVA/HALS mixture in the water-based outdoor paint formula
    the above findings are based on the varnish formula 8 for carpentry boards. THET mixture was further evaluated in the outdoor white paint formulation for the addition of Acronal LR9014. Three white paint formulations were prepared, one with no added light stabilizer, one with an HBIC mixture that added 3.0% of the active components of the resin solid (mass ratio) and the other with a NEAT mixture with an active component that accounted for 2.0% of the resin solids (mass ratio). Apply these formulations to pine products, wet film thickness WFT-4 mils, and dry it for 7 days. According to cycle 1 of asTM G155, an accelerated aging test was conducted in the Asia-Pacific Las Ci5000 Xenon Lamp Aging Test Machine (daylight filter, 340 nm irradiance: 0.35 watts/m2, 102 minutes of light at 63 degrees C blackboard temperature; followed by 18 minutes of light and water spray, air temperature is not controlled). The percentage change in the gloss value of 60 degrees was measured periodically during the accelerated aging test. Judging by the change in the gloss value of 60 degrees in Figure 4, the NEAT mixture is significantly superior to the formula without the addition of light stabilizers and the formulation of the added HBIC mixture. In addition, neat mixtures are superior to the formulation of lower concentration HBIC mixtures, i.e. the active components that account for 2.0% (mass ratio) of resin solids and the active components that account for 3.0% (mass ratio) of resin solids are added.
    Summary
    a new water dispersion mix consisting of high-performance UV absorbers and non-reactive blocked amine light stabilizers is designed to meet the long-term weather resistance requirements of the outdoor decoration, paving and carpentry board markets.
    this easy-to-disperse, solvent-free, sun protection solution provides superior light resistance and excellent coating protection, extending coating life. With the right concentration and the right substation, it is easy to achieve the expected light color change of wood, good light preservation and cracking resistance. Using NEOT technology, water-based coating formulations without labeling are available. NEAT-mixtures do not affect optical properties, such as the transparency and gloss of varnish.
    it can be added to the recipe by simply stirring. In addition, it does not adversely affect the storage stability of coating formulations.
    reference
    Valet, A. Light Stabilizers for Paints, ISBN 3-87870-443-7, C.R. Vincentz Verlag, Hannover, Germany, 45-128 (1997).
    Decker, C.; Biry, S.; Zahouily, K. Photostabilisation of Organic Coatings, Polym. Degrad. Stab., 49, 111-119 (1995).
    Schaller, C.; Rogez, D.; Braig, A. J. Coat. Technol. Res., (2012) 9 (4) 433-411.
    Schaller, C.; Rogez, D. J. Coat. Technol. Res. (2007), 4 (4) 401-409.
    Peter, W.; Schaller, C.; Schellenberg, C. ISCHP Conference, Quebec City, Canada, September 24-25 (2007).
    Peter, W.; Schaller, C.; Schellenber。
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