Take Back Control: Designing, Formulating and Possibly Producing Your Own Zero VOC Tinting System

Transcription

1 Take Back Control: Designing, Formulating and Possibly Producing Your Own Zero VOC Tinting System By: Hersjel Wehrens Market Development Manager Elementis Specialties Inc. 1 Introduction Universal colorants have been around for about 50 years, and unlike most paints, have never been seriously reformulated. Their technology is outdated, and causes many paint defects that paint manufacturers have learned to formulate around. The move to zero VOC formulations provides an opportunity to reimagine tinting systems. By breaking a tinting system apart into its most basic components it becomes possible to build a truly customized tinting system. This paper is about how, using state of the art wetting agents, dispersing agents, and humectants (to prevent tip drying) customers are able to make their own tinting systems. We will show what features a tinting system should have to keep pace with changes in the market. There is a move toward more light fast pigments, better hiding pigments and organic colorants at higher concentrations. The concurrent trends of 0 VOC formulations and diminishing trade sales alkyds means that the legacy one size fits all colorants strategy, is corrupt. Customers are looking for solutions that are tailored to their needs. 2 Tinting System History Tinting systems for architectural colorants were invented in the United States in the1950 s to meet an increasing demand for colors while reducing the amount of SKU s a store needed to keep. They contained 12 colorants with which 95% of all colors could be formulated, they have been the blue print for the industry ever since. Over the years, some colorants got switched, some pigments taken out, some added, but the basic setup is still the same. In Europe larger changes were put in place, the system was often enlarged to 16 canisters or even more; inorganic colorants were added; and higher strength organic colorants. The North American market stayed pretty much unchanged until fairly recently. With new legislation due to take effect in California in 2014 concerning VOC s in tinting system colorants companies are reimagining their tinting system. Latin America came to the tinting system game relatively late with the first systems being put into place in the late 80 s. Traditional ready mix factory tinted colors are still readily available in most markets. Tinting systems are typically only used for the higher end range of paints and have thus not met their full potential. From a tinting system point of view Latin America is a bit of an amalgam; most companies have chosen for the North American type of systems with 12 colorants, while some have gone with 12 or 16 canister European systems.

2 3 Current Trends in Tinting Systems With the change in VOC legislation in the US new life seems to have been breathed in an old industry once stagnant in technology and innovation. The changes can be broadly divided into two categories: pigmentation: anything to do with the pigment types, pigment concentration and amount of canisters used in a tinting system; and technology, anything to do with the surfactant package, glycols, humectant package, and the VOC level of the colorants of a tinting system. Pigmentation Pigmentation has always been an issue in tinting system, no matter how many canisters you have in your system you will always have to make a compromise. In the traditional 12 canister systems, there was not a lot of redundancy. There have been a number of changes in the market. Hiding power For many years the limiting factor in the concentration of colorants in a tinting system has been the accuracy of the tinting machine. Most paint companies and colorant manufacturers still formulate their colors using 1/96 th of a fluid ounce. Tinting machines, although most of the civilized world uses the metric system with SI units, tinting machines (even automatic ones) still use good ol gallons to measure the amount of colorant that is being dispensed by a tinting machine. A gallon can be divided into 128 fluid ounces and a fluid ounce in itself is divided into 1/48 th of a fluid ounce for a tinting system. The first tinting machines had an accuracy of 1/48 th of a fluid ounce, after that came the 1/96 th which was the standard for years. Most paint companies and colorant manufacturers still formulate their colors with this accuracy. Automatic machines went to 1/192 nd then 1/384 th and now can go to 1/728 th or even more accurate. Manual machines followed the trend and go to 1/384 th as well nowadays. The accuracy of a tinting machine is important since it allows for higher concentrated colorants. The original universal colorants were limited in their pigment concentration by the accuracy of the tinting machine: the smallest increment of the machine needed to give a light enough color to be able to effectively match most pastel colors in quart/liter containers of paint. Nowadays, with tinting machines 2 4 times more accurate as before the concentration of the colorants can be 2 4 times higher as well where feasible. Higher concentrated colorants have better hiding power and are more cost effective. Light fastness The traditional colorant systems have limited light fastness in the red and yellow color range. The red is a Naphthol red and the yellow is an azo yellow. Companies have worked around this problem by recommending a limited color palette to be used outside. This might work fine in countries like the USA or many countries in Europe where colors are relatively muted, but in many Latin American countries people like vibrant colors on the outside of their houses. A solution is to have more than one bright yellow or red in your system, one for economy, and one for performance.

3 Technology Technology hasn t changed in tinting systems for decades with the major suppliers relying on a combination of 5 6 different anionic and nonionic dispersants to disperse the pigments and, very important, make the colorant compatible with solventborne alkyd paints. Compatibility in alkyds The vast majority of architectural tinting systems are water based colorants that are made compatible with solventborne paints by adding copious amounts of extra surfactants to emulsify the water in the solvent phase. These large amounts of extra surfactants can wreak all kinds of havoc on paint properties. They cause the dreaded viscosity drop when adding universal colorants to paints thickened with associative thickeners. They can influence early water resistance, they can influence blocking resistance, scrub resistance (both positively and negatively), gloss, you name it. VOC, APE In Europe VOC has been a major issue in the paint industry since the mid 1990 s starting in Scandinavia, and working its way down to Southern Europe. In the United States the strange phenomenon occurred where the VOC of colorants that were added in a paint store to the paint (e.a. with a tinting system) didn t count toward total VOC this will change in 2014, well at least for part of California. Alkyl Phenol Ethoxylates are chemical compounds that are bad for aquatic life when they end up in the surface water; they have been banned in Europe for years. Any new development should be APE free to start off with. Viscosity drop Associative HEUR Thickeners have been a main stay in the rheological additives market. Up until now they have had one major drawback: the more efficient they are, the more subject they become to something that is known in the industry as viscosity drop. Viscosity drop occurs at its worst when a waterbased acrylic paint that is formulated with a HEUR associative thickener is tinted with so called Point of Sales (POS) colorants (figure 1). The viscosity might drop as much as 55 KU. Especially deeper colors that require more colorant addition are affected. Paint manufacturers have learned to formulate around this problem by using combinations of thickeners to reduce the viscosity drop, but the core issue has never been addressed; the colorants are causing the drop. The effect of the drop in viscosity can be quite severe resulting in thin coatings and increased sag. The loss in rheology can cause instability of the paint film resulting in color acceptance issues like floating showing as a darkening of the color with a lighter rub up. In addition, there can be a significant colorantto colorant variation in the amount of viscosity drop observed which makes it difficult to predict the final viscosity for a paint that is tinted to a specific color. The major components that are responsible for the observed viscosity drop are the surfactants used in the colorants. However, not all surfactants produce a viscosity drop, nor is the observed viscosity change a simple function of the surfactant concentration. In fact, formulators use this effect when formulating a base paint where the intentional addition of surfactants alters the rheology of base paint. One surfactant can produce a net build in the viscosity while another surfactant can produce a net reduction in viscosity but only after it goes through a viscosity maximum. Typically, there is a positive correlation of the viscosity drop to the HLB scale (Hydrophile Lipophile Balance) of the surfactant with high HLB

4 surfactants leading to higher viscosity drops. New tinting systems should be developed to have limited viscosity drop. 4 Tinting System Design It seems that a one size fits all colorant system is not going to do the trick. Many paint manufacturers are looking for customized options. So we wanted to design a colorant line that can be as flexible as possible, so it can meet all the different needs and can be customized easily. We started by developing a colorant on a dispersant package that causes the least amount of viscosity drop, keeping this colorant as simple as possible: maximum pigment concentration, ultra low VOC, APE free, and just compatible with waterbased coatings (not universal). Using this high concentrated simple colorant as a starting point all additional colorant properties can be achieved in the let down to the regular POS strength of the colorant. The let down determines if the colorant is going to be universal (by adding 6 7% dispersant extra) or not, if the colorant is going to be low VOC, ethylene glycol based, or propylene glycol based. All these additives need to be carefully screened to ensure that they do not have an effect on the viscosity of the associative thickened paint. The first colorant we developed was a high concentrated, APE free, low VOC, aqueous only, black colorant. Black because it is one of the colorants that show the biggest viscosity drop, black because it is very difficult to stabilize properly. Once we developed it we tested if we could let it down to the (much lower) POS strength using an extender slurry based on the same dispersants as the black was based on. Once we formulated a well working extender slurry (look at it as a transparent colorant), we determined which surfactants could be added to this mixture to make it compatible with solventborne alkyds, without influencing the viscosity of an associative thickened waterborne paint. After this we developed the other high concentrated versions of the 11 colorants typically found in an architectural POS colorant system. To ensure consistent and predictable results across the different colors we used the same dispersant package for all colorants although the amounts and ratios of the different dispersants in this package may vary from color to color. All other lines will be let downs from these high concentrated colorants so they will all be based on these same dispersants. This has the advantage that change overs from one line to the next (e.g. from ethylene glycol universal to low VOC aqueous) will be relatively easy and straight forward. Considering the amount of possible combinations we decided to commercialize four different colorant lines. We decided to let the high concentrated colorant line down with a APE free, zero VOC kaolin clay slurry to make a non universal, zero VOC and APE free POS colorant line with the same pigments and strengths as what is currently available in the market. The second colorant line was made from the high concentrated colorants by letting them down with an ethylene glycol based kaolin clay slurry, together with 6 7% of extra surfactant resulting in an APE free, universal colorant line mimicking what is currently available in the market. The third line we commercialized is the same as the UT line where the glycol has been replaced with a high boiling point humectant combination to make a zero VOC universal line. A blend of proprietary humectants is added to give the color a better open time, so it doesn t block the nozzles of the tinting machine resulting in misstints. We also decided to commercialize the high concentrated colorant as VOC free alternatives for inplant tinting

5 This concept is extremely flexible and makes us very adapt to react to shifts in the architectural coatings market. It is relatively easy to customize these colorants In order to make a special line, you only need to develop a new extender slurry to let the high concentrated colorants down with. You can make a low VOC universal line, that contains calcium carbonate instead of kaolin clay, you can make a propylene glycol containing non universal colorant line, you can even double or quadruple most of the organic colorants resulting in better hiding power or lower additions of colorants. Most companies in the Americas are limited by the amount of canisters they have in their system; for most companies this is 12. The investment to retrofit current machines or replace them is often found cost prohibitive so the name of the game is to get as many of the design features and benefits out of the current 12 canister systems. Fortunately there is some redundancy built into tinting systems. In order to make most colors usually found in color marketing tools like color fandecks you only need 9 colorants: A yellow oxide and red oxide. Red and yellow oxide are very durable, inexpensive pigments that are used in a vast range of popular colors, though not strictly necessary to reach a broad spectrum of colorants their light and chemical fastness (and their cost) make them inescapable in the making of a tinting system. A white is paradoxically needed to make dark colors. White is usually only used in the neutral/clear base. It is added in color matching when a color in this base needs to be made a little lighter. A black is needed to make colors darker and less saturated. It is also used a lot in the popular earth tone, beige and ochre colors. The organic yellow and red is the more problematic area. Where before inexpensive, high opacity, lead chromate yellows and molybdate reds were used, because of their toxicity they were replaced by organic red and yellows. Organic yellows and red have the disadvantage that they don t hide very well, and are relatively expensive. This is more the case now for the yellow, since with the recent glut of DPP producers this opaque red pigment has become relatively inexpensive and widely used in tinting systems. Bismuth Vanadate, a bright inorganic yellow, with good opacity and good exterior durability is cost prohibitive for most architectural applications. A magenta, phthalo blue and phtalo green round out the nine basic colorants you need to make a tinting system work. The phthalos are organic pigments with very decent light fastness. In most tinting systems though they are very low concentrated, so they will not give good opacity to colors. This makes 9 colorants, which means that there are 3 canisters left open to play with if we assume a 12 canister system. Anything you add to this system at this point is used to improve the system. You could add a high concentrated version of the blue for lower cost of use, or better opacity in mass tones, add a DPP red for better light fastness and better hiding, or a bismuth Vanadate yellow, for better light fastness you could add a higher concentrated magenta for more opaque burgundy and violet colors. Using high concentrated colorants has two major benefits, it can give you better opacity in deep colors and in the other bases it will reduce the amount of colorant that needs to be added to reach the same colors. This will be better for the paint (less colorant addition is always better), but will also be less expensive. Let s assume 2 pigment dispersions, one at 5% pigment concentration, and one at 40% pigment concentration. Let s say the pigment costs $ 16/kg and the rest of the colorant, the dispersants, fillers, glycols, cost $ 1 per kg. In that case the low concentrated colorant costs 0.05* $ *$1= $ 1.75/kg. The high concentrated colorant costs: 0.4* $ * $1= $ 7.00/kg. The cost is four times higher, but the concentration is eight times higher, making the colorant 2 times less expensive to use. This just takes raw material cost into account. It also takes 8 times less time to produce, 8 times less

6 colorant to QC, 8 times less colorant to ship, etc. All in all it is a way to take some of the cost out of a tinting system. 5 Base Paint Matrix Theoretically you just need one base for a tinting system. A clear base; most colors will be mixed by adding a white colorant. This approach has obvious disadvantages: there is only a limited amount of colorant you can add to a paint before the colorant will affect the paint properties too much; for universal colorants this is 10% 12% by volume. Since architectural paints are usually applied at relatively thin films that amount of colorant cannot guarantee full opacity. Cost is an issue too; in order to work with just 1 base all colors will be made with the maximum amount of colorant added, the full 10% by volume. Since colorants are usually much more expensive than paint this can become pretty pricey. To reduce colorant addition more bases are added. A good number of bases to have are three to four: a pastel to make pastels, which will be up to 70 % of your total volume, a medium to make midtones, a deep to make deeptones and a clear base to make the darkest colors. Colored bases are for a large part a thing of the past. They are added to a tinting system to combat a particular problem: hiding power of yellow and red colors made in a neutral/clear base. From a technical point of view they don t work well: in order to get good hiding power they need to be formulated with high organic yellow or organic red pigmentation. This amount of pigment then makes it difficult to move the base over when matching a color. Traditional universal colorants are pretty low concentrated, so not enough pigment can be added with the colorant addition to shade the colored base in one direction or the other. Colored bases consequently can cover only a very limited color space, usually less than 1% of a typical fandeck. Commercially they don t work for the same reason, only very few colors are actually made with them, and typically they are the type of colors that are not very popular (bright yellow, orange and red) in a typical setting were architectural paints are being used. At the end you are adding a lot of SKU s 6 Producing your own colorants Elementis is in the unique position in that it sells both dispersants and tinting systems, so it sells both the building blocks and the end product. This makes us uniquely suited as a partner in your tinting system needs, we can help you with implementing a ready made tinting system, but can also help you develop your own tinting system using our expertise in actual working universal colorants using our vast array of wetting agents, dispersants and humectants.