DEVELOPMENTS IN COLOR SPACE ANALYSIS FOR INCREASED COLOR SPACE COVERAGE IN FAÇADE, INDUSTRIAL AND ARCHITECTURAL COATINGS.

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1 DEVELOPMENTS IN COLOR SPACE ANALYSIS FOR INCREASED COLOR SPACE COVERAGE IN FAÇADE, INDUSTRIAL AND ARCHITECTURAL COATINGS. Dr. Brij Mohal Chromaflo Technologies Corporation INTRODUCTION With the advent of the 21st century, many challenges and opportunities have arisen. Increased global competition has brought down the prices of specialty pigments that were once were too high for practical use in architectural coatings. Increased legislation for limiting VOCs and the growing consumer awareness of green products has moved the industry toward low or no VOC products in both architectural as well as industrial coatings. Consumers, when choosing products, are wanting it all - performance, quality and color choice. Consumers want to convey their individuality and color choice is one of the most expressive ways to accomplish that. Although color palettes in general, have grown smaller, since too large of a selection makes it difficult to select, it is important to have a wide range of color types to choose. With the increased competition, product differentiation has become more important. Additionally, with current dispenser technology, that has increased accuracy and more canisters commonly available, the colorant options now available allow for customization of colorant modules. The colorants offer expansion of color space in multiple ways: the use of specialty pigments expands the color palette for façade systems while maintaining durability. High Performance colorants also either maintain or expand color space, while at the same time increasing the fade resistance. High strength colorants allow for palette expansion by optimizing the bases. Probably, one of the strongest statements made in the market are the high opacity colorants. PIGMENT SELECTION The selection of pigments is critical in all three applications be it façade, industrial or architectural application. However, the requirements in the façade area are different and specific. In case of façade applications, the primary requirements are exterior durability combined with stability to alkali. In facade application there is significant residual alkali due to the substrate. The traditional colorant line up is shown in Table 1. Table 1: Traditional Colorant Line-up 1 ORGANIC INORGANIC AXX Organic Yellow (PY74) C Yellow Oxide (PY 42) D Green (PG 7) F Red Oxide (PR 101) E Blue (PB 15:1) I Brown Oxide (Pigment blend) V Magenta (PR 122) L Raw Umber (PBr 7) R Organic Red (PR 188/254) KX White (PW 6) T - Medium Yellow (Blends) B Black (PB 7) 1

2 FAÇADE APPLICATION The pigments most suitable for façade application are the inorganic pigments primarily the oxides. For façade applications, the inorganic pigments used in the colorants offer the durability needed. The traditional oxides that have been used are the very cost effective ones, Yellow Oxide, Red Iron Oxide, Raw Umber and Brown Oxide, which provide a palette range as shown in Figure 1. The a*b* plots shown here, show the color gamut available in each base type at the maximum colorant loading for each colorant. For this comparison the pastel base loading is two ounces per gallon of a traditional architectural paint. Figure 1: Comparisons of oxides with the organic colorants in CIE LAB a*b* color space for a pastel base As can be seen in the figure, the traditional oxide based inorganic pigments provide a very limited color space as compared to the organic colorants shown in the CIE LAB a*b* color gamut plots. The oxides are economical, provide excellent hiding and are very durable. The EIFS/Stucco market uses the oxides for their color palette. However, the organic pigment containing colorants are what define the color gamut available. The uses of the organic colorants though providing larger color space do not provide the durability or the stability to the alkaline environment. Thus what is required are a new set of pigments that provide the durability and expanded color space. The use of specialty pigments expands the color palette for façade systems while maintaining durability. For façade applications, high performance colorants further expand color space, while at the same time increasing the fade resistance. With the addition of Bismuth Vanadate, Chrome Oxide Green and Cobalt Blue colorants, the color gamut plots in Figure 2 show the substantial color space enhancement while maintaining durability and opacity. Figure 2: Color space analysis for façade applications using façade and façade plus colorants. 2

3 As seen in Figure 2 CIE LAB a*b* plot, the additional façade colorant offering, broaden the color space substantially. The Façade grouping adds four additional inorganic colorants, and the Façade Plus grouping adds the same four colorants with an additional three colorants. Figure 3: Color Space analysis for façade application in a pastel and neutral base As seen in Figure 3 CIE LAB a*b* plot, the additional inorganic colorant offering, broaden the color space substantially. As discussed previously, the traditional oxides provide a limited color gamut, while adding in the Bismuth Vanadate, Chrome Oxide Green and Cobalt Blue colorants, the available color space is greatly expanded, while maintaining durability and excellent opacity. The addition of more inorganic colorants listed, enlarge the gamut even more. The effect is even more produced in the neutral base. It is fortuitous that the effect is more prevalent in the neutral base where coincidentally the majority of the façade application occurs. IR REFLECTIVE PIGMENTS The advances in pigment technology has expanded the coating s formulator tool kit so they may match more vibrant colors, demanded in the market, yet possess greater 3

4 infrared reflectivity (IRR) for the requests of a greener society. In the past, the solution for heat reduction was the use of white paint. TiO2 (the principal component of white paint) inherently has high IR reflection but the palette is limited to very light pastels, without carbon black. The chemistry of an infrared reflective coating systems, pigmented with IRR colorants, affords lower heat build; the results include: reduced thermal warpage, reduced thermal cycling degradation, lower energy costs related to cooling, and improved comfort and functionality of dark color exterior objects such as park benches, hand railings, and even polymer concrete. Some of the pigments used in the façade module are also coincidentally IR reflective. Total solar reflectance is the measure of the amount of sunlight reflected from an object. The greater the reflectance the cooler the object. The total solar reflectance is measured using a Solar Spectral Reflectometer 2. Infrared reflective pigmentation technology allows the user to achieve a specific color space in the visible light range while reflecting incident light in the near infrared range of the electromagnetic spectrum. The reflection of light in the near infrared reduces the temperature of the coated object by lowering overall energy absorption from terrestrial solar irradiance (less absorbed energy equals less energy converted to heat). To demonstrate the IRR performance advantage, a traditional gray coating was compared to an infrared reflective gray coating. Both gray coatings have a very similar L* values, E= the two greys are achromatically equivalent (Figure 4). Figure 4: A visible light photograph of the IRR Gray (Left) and the Traditional Gray (Right) 4

5 Figure 5: A photograph of the IRR Gray (Left) and the Traditional Gray (Right) using an infrared high pass filter (850 nm >) Figure 5 shows the same gray colors using infra-red light. When measured by a solar spectral reflectometer, the total solar reflectance of the traditional gray coating is 17.5%, and the total solar reflectance of the infrared reflective gray coating is 47.1%. While the visible color difference is negligible, the total solar reflectance indicates a raw 29.6 % difference, almost a 20 O F reduction in ASTM 3 Heat build. Studies in green color space has similar results where a traditional green pigment match can be simulated with IRR pigments with a 29.2%TSR variance yielding almost a 17 O F reduction in ASTM Heat build. It is critical to understand that formulation component impact the IRR results. Even the smallest concentration of carbon black renders the coating, non-irr. INDUSTRIAL APPLICATIONS The inorganic colorants are the foundation of the industrial colorant system, and the organic colorants define the potential color palette available. Increased colorant strength allows for base optimization and increased opacity in clear base. The desire for color choice has also grown for industrial applications. In addition, the color space that was obtained by traditional colorants/pigments is now available through higher performing colorants/pigments. The traditional industrial colorant line-up was chosen for their overall performance properties that are suitable for a wide variety of industrial applications. The additional colorants in the line-up have brought significant improvements in opacity, fade resistance or color range. Table 2 shows the traditional and additional line up of colorants for industrial applications. 5

6 Table 2: Traditional and additional line up of colorants for industrial applications TRADITIONAL White ADDITIONAL Reds (PR 170) DPP Red (PR 254) Orange (PO 34/36) DPP Orange (PO 73) Red Oxide Burnt Umber Yellow Oxide Medium Yellow (PY 83/151) PY 83 Organic Yellow (PY 175) Bismuth Vanadate (PY 184) Phthalo Green Phthalo Blue Quinacridone Violet (PV19) Carbazole Violet (PY 23) Black Figure 6 shows the CIE LAB a*b* plot shows equal volume comparison (4 ounces of colorant in a typical white base), between a selection of colorants with high performance/high strength colorants versus the conventional industrial colorant line-up. Figure 6: Color Space analysis for industrial application in a pastel base In industrial application the technologies of the colorants are different for the solventborne and the water-borne; however, the pigment line-up is usually the same for tinting applications. Figure 7 shows the panels of colorants at full loading (16 ounces/gal) in a clear base, the improvement in opacity is a welcomed solution to requiring numerous coats to obtain opacity. Figure 7: Opacity panels for yellows and red in industrial applications 6

7 Customization of a colorant module, to include DPP red and Bismuth Vanadate, would be very advantageous to address bright reds and yellows that typically have poor hiding. Wider color selection can offer a competitive advantage. Since waterborne and low VOC solvent-borne colorants are increasing in use, they provide a solution for tighter VOC legislation and consumer preference. Legacy formulas are an important consideration, and working with your colorant supplier can assist in the right approach in establishing a new colorant module. ARCHITECTURAL APPLICATIONS For architectural coatings applications, the inorganic colorants in the traditional line-up are still the building blocks of the colorant system. Where the change has taken place, is in the offering of the organic colorants, which has offerings of improved the fade resistance, opacity and high strength options. With additional choices, customization in the colorant modules can now be done to best suit the application and offer differentiation in the palette offering. As an additional benefit, the color space available can be expanded of the traditional 12-colorant line-up with these added benefits included as shown in Figure 8. Figure 8: Color Space analysis for traditional and High Performance architectural colorants in a pastel and tint base 7

8 The availability of better red and yellow pigments at reasonable cost has allowed for improvements in both the durability and brightness of the colorants available for the architectural market. The fade resistant improvements now available for colorants in the yellow region strengthen what has been considered the weak link for exterior applications. Figure 8 shows the CIE LAB a*b* plots for equal volume comparisons between the traditional 12 colorant line-up for Architectural coatings and a selection of high performance and high strength colorants. The colorant loadings for one gallon of base are: Pastel Base loading is 2 ounces and the Tint Base is 4 ounces. The fade resistance data for the traditional AXX colorant and the AGF colorants are shown in Figure 9 and for the traditional R colorants and the REE are shown in Figure 10. Figure 9: Fade data 4 for the AXX and AGF yellow colorants at a two ounce loading in a pastel base using a Xenon-Arc instrument Figure 10: Fade data for the R and REE red colorants at a two ounce loading in a pastel base using a Xenon-Arc instrument 8

9 In addition to the increased fade resistance of the new REE red colorant there is an increase in opacity due to both the pigment type as well as the higher pigment loading shown in Figure 11. Figure 11: Opacity comparisons of the R and REE colorants at equal volume loading in a neutral base The architectural segment calls for the broadest representation of colors possible. This is truly best represented in 3-D CIE L*a*b* color space (Figure 12). Figure 12: 3-D CIE L*a*b* color space plotting of traditional and new colorants A color system that uses the traditional 12 colorants is represented by the green spheres. A color collection emphasizing the clean, bright and deep colors of the high performance and high strength colorants now available are represented by the blue spheres. The blue spheres on this CIE L*a*b* plot, show how the color gamut is pushed out in all directions with the inclusion of high performance and high-strength colorants. 9

10 As seen in the CIE L*a*b* plot and previous a*b* plots presented, the DPP Orange and Red brighten the yellow-red region, and the Carbazole Violet expands the magenta-blue region. Often violets have been referred to as not that important for color palettes, however, that may have been due to the limited availability of good, deep true violets not being available. With newer dispensing technology now available with higher accuracy of dispense, i.e. 384ths/ounce there are many opportunities to customize the colorant module used. The selection can be tailored to the needs of the specific application. For instance, taking into cost considerations, formulas can be set up as interior and exterior. If one/two coat hide is the need, additional colorants such DPP red and Bismuth Vanadate could be added. A typical example showing how new colorants can be incorporated in a traditional 12 colorant system that increases durability, does not change the number of canister and preserves most legacy formulation is shown in figure 13. Figure 13: A more durable system that increase durability and retains the traditional twelve canister arrangement CONCLUSIONS As has been discussed, the coatings industry is now taking advantage of the newer higher performance pigments available in the market place. With the ease that information and trends are shared globally, this has resulted in higher demand for wider color selection, which includes brighter and cleaner colors. Custom color selections are becoming more popular for focusing on customer needs and for product differentiation, cost and performance considerations. Consumers desire a wider color selection with improved durability, performance and opacity. New offerings address environmental concerns. High performance and high strength colorants provide a wider color gamut that include cleaner, brighter and deeper color selections. 10

11 REFERENCES (1) Technical Line Sheets from Chromaflo s web-site (2) Solar Spectral Reflectometer available from Devices and Services. (3) ASTM G (4) Brij Mohal Abrafati 2003, DURABILITY OF PIGMENTS IN COATINGS APPLICATIONS 11