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INSIGHT Cleveland, OH, USA Technology Forum Recent enhancements in waterborne resin system polymers as well as the way they are formulated have produced paints with a set of barrier properties that are superior to their standard solventborne analogs. New generation waterborne epoxy and curing agent dispersions, and the paints formulated from them, have been introduced with changes from older generation waterbornes. These changes include (1) totally nonionically dispersed paints in place of the older ionically dispersed types, (2) quicker coalescing, mutually soluble epoxy/amine vehicle resins rather than the former slow coalescing, highly branched epoxy/amine systems, and (3) utilization of stable, water compatible additives and fillers that complement the nonionic epoxy/amine resin vehicles. In this paper, the success of these implemented technology changes is demonstrated by comparing the performance properties of the new generation with an industry standard epoxy/polyamide solventborne paint. This paper presents novel two-component waterborne epoxy resin and amine curing agent technology for ambient cure metal coatings. INTRODUCTION This paper presents a rational view of how solventborne, two- component (2K) epoxy resin design and respective paint formulating has changed to produce higher performing waterborne protective coatings for metal. This paper demonstrates how implementing change in epoxy chemistry and coatings has produced more viable waterborne paints with better metal protection at lower levels of volatile organic compounds (VOC). The chemistry of 2K epoxy coatings has afforded good value for metal protection since the 1950s. In the U.S. alone, over 100 million pounds of 2K epoxy paints are produced from epoxy/ polyamide chemistry per year.1 For 30 years, epoxy paint producers have tweaked, remodeled, patched, and reformulated the epoxy/polyamide paint chemistry to adapt it to changing performance and environmental compliance expectations. Most of the patches and fixes have either compromised paint metal protection, fallen short on compliance, or limited the versatility of the resin system. The environmental, health, and safety costs of storing and handling high VOC, low flash, non-HAPS 2K epoxy paints narrow profit margins beyond survival. To use home building as an analogy, it is time to dismantle the old epoxy/ polyamide chemistry. We may then salvage the useful old technology pieces and put them together with mostly new materials to make new paints that meet current performance and environmental expectations. The first two parts of this paper highlight the old epoxy paint chemistry that needs change. First is a review of the 2K solventborne epoxy/polyamide resin chemistry. Next is a critique of two popular solventborne epoxy paint recipes. In these first two parts, the foundation concepts of resin design and paint formulating that are worth salvaging are identified. The third part of this paper introduces the new resin chemistry framework. In the fourth part, a new resin framework is "trimmed-out" with new formulating enhancements. Finally, in the Summary and Conclusion, the performance of a new generation of paints compared to traditional epoxy paints is presented along with the implemented changes and their respective paint performance improvements. The goal of this paper is to promote the implementation of changes in the Industrial Maintenance (IM) 2K epoxy coatings market sector by eliminating the frustrations associated with traditional epoxy paint formulations. This paper also offers improved options for Original Equipment Manufacturer (OEM) paint makers, although the formulations herein are ambient cure. For example, by the time this paper was presented, more than one OEM customer has already implemented some of the highlighted changes to extend the recoat window of standard epoxies from two weeks to over two years. EVALUATION OF TRADITIONAL 2K EPOXY/POLYAMIDO AMINE RESIN CHEMISTRY In this section, the traditional 2K bisphenol A epoxy- tall oil dimer acid polyamide resin system is critically evaluated. The bisphenol A epoxy in Figure 1 with the polyamido amine pictured in Figure 2 show the foundation chemistry of 2K solventborne epoxy paints. At a quick glance at these two resin structures it is apparent that the amine curing agent has many more -NH amine reactive sites per molecule than the bis A diglycidyl ether has oxirane sites. The diepoxy is -1,000 molecular weight with -500 equivalent weight when n=1. The most common polyamido amine curative for low cost and relatively low viscosity has an equivalent weight of 156. This "1" type epoxy chemistry is popular for low cost, low solution viscosity, and fast lacquer dry in 2K industrial paints. The polyamido amine curing agent is very hydrophobic, or oily, due to the tall oil dimer content. It affords water resistance, good metal substrate wetting, and excellent pigment and filler wetting. The crosslinked type "1" epoxy/polyamide provides flexibility and toughness with decent impact resistance. These attributes are the foundation of the traditional epoxy resin chemistry. Critical evaluation of this resin chemistry at the molecular level allows one to quickly identify problems that limit the formulated paint performance. The foremost of these is a solubility problem. The somewhat polar, hydroxyl-bearing epoxy polyether is not soluble in concentrated solutions of the predominantly oily polyamide. Although this solubility issue is partially overcome by the selection of optimum coupling solvents, the problem is inherent in the bis A epoxy / tall oil-based polyamide resin system. This will be more obvious when we look at the solventborne paint formulations in the next section. When the polyamido amine is appropriately mixed with the epoxy component, the resin mix resembles, on a molecular level, a peanut butter sandwich (Figure 3). The planar, rigid bis A epoxy aromatic ring backbones form the bread slices. The low T^sub g^, amorphous aliphatic curing agent, like smooth peanut butter, penetrates into the layers of epoxy and, upon crosslinking, the curing agent holds the epoxy layers together. If we look at these resins the way we would look at the frame of a house, we would definitely like to keep the hardness of the bis A epoxy and the flexible, hydrophobic, pigment wetting character of the tall oil polyamido amine. The toughness and chemical resistance of these paints are attributed to the highly crosslinked, "tightly- woven-cloth" nature of the densely packed aromatic rings of bis A laced together with the more flexible polyamide. For this resin system, maximizing the performance of this resin system means maximizing the crosslinking between the epoxy and amine sites. Look closer at the contrasting equivalent weight and the contrasting rigid versus flexible backbones of these polymers in Figure 3. With a little imagination it is easy to understand that too much bis A epoxy can lead to a brittle, friable paint film, whereas too much curing agent can lead to sticky, moisturesensitive slow drying paints. The lower cost polyamido amine curing agents are too frequently used in stoichiometric excess. This common practice of using excess equivalents of curing agent is a major problem with these standard 2K epoxy systems. This practice goes against what is needed for maximum corrosion protection. For optimum salt spray and acid corrosion resistance, an excess of at least 5 to 10% epoxy over the equivalents of amine is required.2 The use of excess uncrosslinked amine causes water absorbing -NH^sub 2^ groups to remain in the paint film. Primary amines form carbonic acid and carbamic acid salts from the moisture and carbon dioxide in air (Figure 3).3 These amine salts cause surface defects called "sweat out" that lead to poor gloss in enamels and poor intercoat adhesion when these films are topcoated. These hydrated carbonic and carbamic amine salts provide a path at the metalpaint interface for moisture to cause corrosion undercutting. To insure resin compatibility and to minimize the primary amine carbonic or carbamic salt formation, solventborne epoxy/polyamide paints are usually allowed to react in the pot (induct) for at least a half-hour before they are applied. This is often referred to as the induction time. At the molecular level, it is the time it takes for the majority of the hygroscopic primary amines to react with the epoxy groups in the paint bucket, instead of reacting with the moisture and carbon dioxide in the thin applied paint film. This induction requirement often prohibits the use of plural component spray equipment when applying these 2K solventborne paints. We have just identified the two major weaknesses in the solventborne resin system framework. They are: (1) lack of initial mutual compatibility of the epoxy resin with the amine resin and (2) excess primary amine from the curing agent, which forms water sensitive defects in the paint. On the salvage list, we would like to keep the quick hardness development of the aromatic bis A epoxy and the good wetting and flexibility of the curing agent. With these resin chemistry pictures in mind, we can move on to dismantle the paint formulations in order to salvage components and practices from which to put together paints with optimum metal p\rotection. We will find in the next section that current "formulation fixes" do not completely overcome these two identified problems with the solventborne epoxy / polyamides. DISMANTLING TRADITIONAL 2K EPOXY/POLYAMIDO AMINE PAINT FORMULATIONS Solventborne White Primer Formulation 1 is a somewhat dated, but still popular, 2K solventborne epoxy white primer in which excess amine is used to achieve a simple mix ratio. Arrows in the left column point out formulating tools that are at issue for shoring up paint performance. The first arrow marks the zinc molybdate plus zinc oxide anticorrosive. This anticorrosive is a scavenger for aqueous corrosives that would attack the iron substrate.4 The second arrow marks barium sulfate which serves as a physical, water insoluble, protective barrier when it settles in dense platelets to the bottom of the paint film. The high density barium sulfate works well as a barrier in the cured film, but it is very difficult to keep suspended in the paint can on the shelf. The zinc molybdate and the barium sulfate are tools to shore up moisture barrier properties. The third arrow marks the clay thixotrope which delays the barium sulfate from settling. The day also helps control sag. Usually, the clay has to be preswelled with an alcohol before use. This is a chore that requires an extra paint-making step. The fourth arrow points out the unbalanced epoxy:amine equivalents ratio. This primer is formulated too high in amine equivalents per epoxy. This ratio is high enough in amine to critically compromise the paint's acid resistance. This is caused by the leftover, partially water soluble, curing agent when the paint is exposed to aqueous acid. When the amine curing agent is salted with aqueous acid it will absorb water and swell the paint. The swollen paint then becomes permeable to salts and corrosives that pass through the resin matrix to attack the substrate. The fifth arrow points out the root cause as to why epoxy:amine ratio is out of balance; the forced 1:1 component mix volume ratio. The sixth arrow shows solvents that are used to control solubility and reactivity of the epoxy and amine. Protic solvents, like ethylene glycol ethers and alcohols, are used for viscosity control and to accelerate the epoxy-amine reaction; i.e., shorten the time for the paint to dry and harden by speeding up the crosslinking. The solvents ethyl benzene, xylene, and cyclohexanone slow down the epoxy-amine reaction. The relative influence of common paint solvents on the cure speed of aromatic epoxies with ethylene amine curing agents is shown in Table 1. It is interesting to note that water is the most catalytic solvent whereas benzene, acetone, and methyl ethyl ketone retard the cure reaction. The number of organic low flash point HAP solvents in this paint pose unbearable inventory as well as environmental, health, and safety risks. Certainly, these solvent choices with their total VOCs, 4.51 lb / gal, are no longer tolerated in our industry. The next arrow, in the paint properties section, points out the high weight per gallon of the "A" component. High weight per gallon limits shelf settling stability. By now it is obvious that most of these arrows point to extra effort and cost to shore up paint performance. Some of these formulation fixes led to other patches. For example, the high density barium sulfate requires a thixotrope for shelf stability. The thixotrope in turn adds at least two extra manufacturing steps to achieve the 1:1 objective. In addition to the clay alcohol- swelling step, there is an additional step to disperse the talc in the "B" component. Without the excess soft polyamido amine, talc loading demand for sandability could have been fitted into the "A" part. Formulation 2 Despite all the faults with this solventborne primer, it has pleased many customers for 50 years with decent, yet compromised, performance as a metal primer. In the next section, a solventborne direct-to-metal (DTM) enamel evaluation illustrates these same common practice formulating deficiencies in standard 2K solventborne epoxy paints. Solventborne Gray Enamel Formulation 2 is a general purpose DTM industrial maintenance enamel. To validate that the shortcomings seen in the primer are common practice, we will critique the formulation of this enamel recipe. In this paint, the 3:1 combining ratio is a highlighted feature. Maintenance departments and do-it- yourself consumers prefer a 3:1 or 4:1 mix ratio. These ratios allow convenient small packaging from one-quart to five-gallon piggybacks of the two components. Formulation 2 demonstrates the type of pigments, fillers, solvents, solvent levels, and flow modifiers used to obtain coalescence and high gloss with a DTM enamel. Painters often select epoxy enamels over other 2K paints because they have a long enough pot life between mixing and gelling to do a work shift of painting. This long pot life eliminates the need for plural component spray equipment. After the 2K enamel is mixed and allowed to induct, it provides at least a full 8-10 hr of painting with good applied film properties. As in the primer, corrosion protection is compromised to obtain these pot life and mix ratio priorities. The first arrow in this enamel recipe marks the calcium carbonate that is used to lower paint cost. Again, as in the primer, barium sulfate is used to enhance barrier properties. As mentioned earlier, the dense barium sulfate requires clay to provide thixotropy to delay the dispersed pigments and fillers from settling. The sixth arrow marks a butylated urea resin that is used to enhance resin compatibility, flow, leveling, and gloss. Unless this paint is baked, the urea resin, Beetle(R) 216-8, does not crosslink or enhance corrosion protection. Methyl isobutyl ketone (MIBK) is used in the curing agent component to make it compatible with the epoxy. MIBK slows down the reaction between the epoxy and amine. This extra solvent extends the paint pot life but leads to a high VOC: 3.7 lb / gal. This high organic solvent level helps the compatibility of the resin and curing agent but still does not completely fix the lack of resin mutual solubility. Due to the high VOC, this enamel requires 14 days for solvent evaporation and crosslinking before it is resistant to aqueous chemicals. This two-week cure requirement is necessary for the high level of slow solvents to migrate from the film, even though the curing agent contains a very high level of fast crosslinking primary amines. Within a few weeks of full cure this enamel will begin to drop in gloss due to the migration of the carbonic salted amines to the paint surface. For this reason, the recoat window of this paint may be limited to less than six weeks. This short recoat window is intolerable for small auto or equipment parts that require recoating to color match brand specified colors after being inventoried in the supply train for up to two years. Enough amine carbonate salt accumulates on the surface of the coating after a couple months to cause intercoat adhesion problems between this epoxy enamel and a color match second coat. These recipe "convenience" fixes must be significantly changed for the enamels if corrosion protection is the first priority. In this enamel, as in the primer, barrier properties are shored up with additives to compensate for the amine/epoxy imbalance. The enamel has -50% excess ofNH per oxirane. This excess amine shortens the paint pot life and weakens barrier properties. The compatibility of the epoxy with the oily polyamide is, here again, improved but not fixed by selected coupling solvents. The extra ketone extends the useful paint gloss pot life but it also slows the protective property development of the applied paint. For DTM corrosion protection as well as for VOC compliance, not only must the resin and curing agent be modified but paint formulation modifications are also required. NEW GENERATION 2K WATERBORNE EPOXY: IMPLEMENTING RESIN CHANGES Understanding the changes needed in the solventborne epoxy paints, including which resin and paint attributes can be salvaged, makes it easier to confidently design a new paint system for corrosion protection. This new generation resin system is built on the standard bisphenol A cost / performance foundation without having to use excess equivalents of amine curing agent to obtain convenient component mix ratios. The new resin system is designed to take advantage of water as a cheap, catalytic solvent that allows higher molecular weight epoxy polymers to be delivered at low viscosities. Delivering these resins as aqueous dispersions also offers an additional dimension to extend the paint pot life. As a bonus benefit, when water is used as the solvent, paints can be more readily formulated at reasonable viscosities that meet the VOC and non-HATS customer expectations. Now Generation Epoxy Resin Dispersion Figure 4 is a model of the new generation "1" type epoxy resin. It has three distinctive polymer segments: (1) the standard bis A aromatic segment that forms planar, close-packed hard films; (2) the aliphatic, hydrocarbon R groups that wet pigments and wet nonpolar substrates; and (3) the appropriately-sized polyethylene oxide (PEO) hydrophile. This all-important PEO segment is the middle of the polymer. It delivers water dispersibility, film flexibility, additive/ filler compatibility, and paint stability. This PEO segment also controls sag resistance of the paint. The orientation of the three resin segments in the paint are as important as the layout of the plumbing and electrical work in a new house. Simply stated, the PEO is similar to the plumbing; it controls the movement of water in the paint film. The hydrophobic segments insulate the paint film from the flow of ions much the way insulation on electrical wire functions. The number of epoxy end groups determines the crosslink densi\ty. Figure 5 models the resin's tendency to self-assemble into particles in water. The epoxy groups on the hydrophobic segments concentrate toward the micelle hydrophobic center, whereas the more water soluble portions of the polymer migrate toward the water phase. As the PEO segments are pulled into the water phase the epoxy reactive sites attached to the hydrophobic polymer segments assemble to form the resin particles.9 The resulting micelle formation is facilitated by cosolvents, reactive diluents, and the highly specialized design of the PEO segments. The PEO segments are optimally located in the epoxy resin backbone in such a manner that they are rendered encapsulated by the hydrophobic polymer segments in the cured film.10,11 Formulation 3 New Generation Curing Agent Resin Looking at the curing agent model in Figure 6, it is now easier to see similarity between the new generation type "1" epoxy and the matched curing agent. The mutual solubility of resin and curing agent polymers is illustrated in Figure 7. This mutual solubility is built into the matched epoxy resin and curing agent. This "like dissolves like" compatibility eliminates the induction time. It greatly minimizes the need for cosolvents and it promotes the fast particle coalescence required for high gloss early in the pot life. The polyaromatic segments of the curing agent are designed for solubility in the bis A segments of the epoxy resin. The PEO segments and the aliphatic segments of the curing agent are also designed to enhance compatibility and coalescence with the new generation epoxy resin. By design, both epoxy and curing agent are multifunctional polymers with hard aromatic sections. Both have flexible sections and built in nonionic dispersants, but neither resin is ionic or water-soluble. In order to insure quicker curing agent homogeneity in the mixed epoxy-amine paint, the equivalent weight of the curing agent is made higher than the polyamido amine standard curing agent discussed in the first section. This also allows the relative volume of curing agent in the paint to be increased over that which is in the standard solventborne epoxy system. This larger volume of curing agent accommodates 1:1 and 3:1 simple paint combining volumes without having to use excess curing agent. The equivalent weight of the new generation epoxy is 525 and the companion curing agent is 225. As shown in Figure 6, the curing agent is designed with predominately secondary amine functionality with very little primary amine. This minimizes the detrimental carbonic and carbamic salts that form with primary amines. The curing agent resin is made at a lower Tg than the epoxy resin in order to facilitate film formation at lower temperatures without having to use volatile organic cosolvents. This lower minimum film forming temperature (MFFT) of the dispersed resins allows paints to be formulated at very low VOCs. The molecular weights of the epoxy and curing agent are higher than the old standard products to facilitate faster lacquer dry. By providing the resins in a dispersed form, the higher viscosity penalty for the higher molecular weight is avoided. Likewise, there is no viscosity penalty for having additional branching in the resin backbones. Both the branching and the higher molecular weight of the epoxy resin and curing agent speed up the cure rate of the new generation paints to insure quicker backto-service times for the painted substrate. NEW GENERATION EPOXY PAINT: IMPLEMENTING PAINT FORMULATION CHANGES New performance enhancing paint additives were selected as a means of implementing needed changes to the standard 2K epoxy paints. However, the first arrow in Formulation 3 is not a new additive. It is the old polyamide salvaged to pacify the pigments' oil absorbency. In combination with Rhodameen OA910, it is superior for wetting and dispersing pigment, especially carbon black. The Optiflo TX1492 is a nonionic water soluble hydrophobic modified synthetic thixotrope that serves to stabilize the dispersed pigments. This particular thixotrope enhances the shelf stability of the pigmented curing agent component without compromising the gloss or water sensitivity of the cured paint. This thixotrope works well for pigmenting either the amine dispersion or the epoxy dispersion. Dipropylene glycol mono methyl ether (DPM) serves not only as a good resin and water coupling solvent, but also as an antifreeze for the waterborne pigmented curing agent component. DPM is the preferred gloss promoting coalescent for this 2K system. The DPM level used in this formulation does not hurt the paint dry time. The BYK 22, BYK 24, BYK 28, and BYK 307 silicones in the pigment grind promote both foam release in the wet paint and surface abrasion resistance in the cured paint. Of these silicone-based additives, BYK 22 is the most effective for defoaming, whereas BYK 307 is the most effective for mar resistance. The Raybo 60 is a flash rust inhibitor. The use of sodium and potassium nitritebased flash rust inhibitors should be minimized to insure the water immersion resistance of the paint. In this new generation gray enamel, the 1:1 volume ratio is highlighted along with the stoichiometry of 1:1 epoxy per amine hydrogen. The Cardura E-10 is a hydrophobic, branched alkyl glycidyl ester (Figure 7). It reacts moderately fast with amines. It is used to promote gloss and leveling in this enamel formulation. It reacts slower with secondary amines than an aromatic bis A epoxy. By the nature of its reactivity and solubility it concentrates at the air- film interface to consume amines that could cause sweat out or early loss of cured paint gloss. Aromatic epoxides such as the cresyl glycidyl ether (Figure 8) react faster with less compromise of paint film hardness. The preference for monoepoxide as a reactive modifier in this new generation paint system is driven by the need for gloss and water immersion resistance. Cardura E-10 offers better film hardness, gloss, and water immersion resistance than long chain alkyl glycidyl ethers. As shown in Table 2, the long chain alkoxy monoglycidyl ethers tend to plasticize films, thus increasing the moisture absorption of the cured paint. The Cardura E-10 serves an additional purpose in this formulation. It is an excellent carrier for dispersing epoxy silanes (Figure 9) into the aqueous epoxy dispersion. The silanes are good pigment wetters. The Silquest A 2287, as an alkoxy glycidyl ether, is relatively stable in water. However, the methyl diethoxy silane end of the molecule will hydrolyze at a high pH.12 The Cardura E-10 provides a hydrophobic carrier to protect the silane from hydrolysis until the aqueous epoxy component is mixed with the amine dispersion.13 In an applied coating, the silanes migrate to the coating-metal interface as well as to the paint-air surface.14 The alkoxy silanes are excellent adhesion promoters at the metal-paint interface. The epoxy end of the silane molecule promotes adhesion to metal by tying up the carbonic salt-forming primary amines. It also reacts with hydroxyls on the metal surface via the alkoxy silane. Coupling of the metal surface hydroxyls via the alkoxy silane condensation with epoxy hydroxyls is a third mode of promoting adhesion to the metal substrate.15 Because the pH of the amine curing agent dispersion is significantly higher than the epoxy dispersion, amino silanes in the curing agent component have shorter shelf lives than epoxy silanes in the epoxy side. Thus, the condensation of silanes in the epoxy side is activated when the curing agent dispersion is added.16 The coalescence and cure speed of the paint resin matrix is greatly improved by the selection of the appropriate reactive diluents. With the appropriate combination of epoxy and silane diluents the ambient cure cycle for water immersion resistance is shortened from 14 to 10 days for the new generation paints. The cosolvents, diacetone alcohol and propylene glycol mono normal butyl ether (PnB), are selected for the epoxy dispersion to not only enhance the coalescence of the applied paint but also to extend the shelf stability of the epoxy groups in the presence of water. This combination of ketone with a less water soluble, more hydrophobic solvent like PnB pushes water out of the epoxy particle. This is due to more hydrophobic solvents partitioning favorably to the resin phase of the dispersion.17 Less water and less protic solvent in the epoxy resin particle lowers the epoxy reactivity and thus improves the shelf life of the epoxy groups. Likewise, secondary hydroxyl cosolvents, compared to primary hydroxyl cosolvents, extend the shelf life of the epoxy groups in the paint. This organic cosolvent effect on the epoxy dispersion stability is shown in Figure 10. The epoxy dispersion stability in Figure 10 is reported with cosolvent modifications of 10 pph. Solvent blends are at a 50/50 ratio where added. Usually, the solvents that are good for epoxy group stability are also good for the paint component viscosity stability. Figure 11, at 4 pph modification, shows stability comparisons of the new generation epoxy dispersions modified with 50/50 blends of cosolvents which are post added. Methyl normal amyl ketone (MnAK) is excellent for epoxy and viscosity stability. However, since it obviously partitions to the dispersion resin phase it imparts a high initial viscosity to the paint. Therefore, its use is limited to low- solids, thin-film paints. The solvent, dipropylene glycol normal butyl ether (DPnB) is excellent for coalescing the dispersed new generation resins. It may be used to enhance gloss. However, it also significantly retards the film property development in the applied paint because it is very slow to evaporate. The overall preferred cosolvents for viscosity, paint stability, paint film hardness deve\lopment, and acceptable paint flash points are PnB and diacetone alcohol. SUMMARY AND CONCLUSION Comparison of New Generation to Solventborne 2K Epoxy The implemented changes combined in the new generation 2K epoxy resins and paints are summarized as follows: (1) the amine and the epoxy resins were changed to maximize their mutual solubility and coalescence before they crosslink; (2) the carbonic and carbamic acid salts in the cured paint were minimized by formulating paints at near 1:1 stoichiometric ratios from predominantly secondary amine functional curing agents; and (3) the new generation paints were formulated using reactive diluents, cosolvents, and a nonionic thixotrope for optimum paint stability, coalescence, and cure. The anticipated paint performance enhancements and trade-offs are shown in Tables 3-6. Table 3 shows that the new generation primer dries harder, quicker, and develops salt spray resistance earlier than the standard solventborne primer. The slower development of ketone resistance of the 2K waterborne primer is due to the predominant secondary amine content in the curing agent which crosslinks much slower than primary amines. However, as shown in Table 5, the ketone resistance of the new generation enamel after 14 days is comparable to the standard solventborne enamel. The superior salt fog resistance of the new generation primer at sevendays cure is shown in Table 4. The water immersion resistance of the new generation enamel at 14-day cure is comparable to the solventborne standard but the salt fog resistance of the new generation is noticeably better (Table 5). As shown in Table 6, the new generation white primer has significantly better acetic and hydrochloric acid resistance with good aqueous base resistance compared to the solventborne standard epoxy primer. Implemented Changes Add Value in Vehicle Resins and Paints The changes implemented in the new generation system are tabulated beside their respective improvements in the performance of the metal coating in Table 7. This table shows how these resin and formulation changes are translated into added value in the new generation paints. The most significant value enhancements of these waterborne new generation paints add up to shorter cycles for the paint. In the real world, a shorter cure cycle means that a primer can be sanded and coated in four hours instead of 24 hours. A shorter cure cycle also means a freshly painted metal loading dock ramp will be out of service for only two or three days instead of one week. The shorter cure cycle for OEM finishes means that a part or component can be packaged and shipped directly off the end of the coating line instead of having to be racked for 24 hours for paint drying before packaging. Packaging parts directly from the end of the coating line not only eliminates warehousing and inventory, it also means quicker returns on the paint raw material inventory costs. The ability to apply the new generation coatings without an induction time saves labor costs and material costs. The elimination of induction time also allows the use of plural component spray equipment to apply the new generation paints. In addition to the added value from shorter cure cycles, the improvements in water, acid, base, and salt spray resistances add value to the protected metal structure, part, or substrate. These performance enhancements of cure speed and corrosion resistance, along with the environmental compliance and "user friendliness" of this new generation of waterborne technology should allow coatings makers and applicators to command a higher premium for these waterborne epoxy paints. References (1) Miron, J. et al., "Coatings, VI.; A Multiple-Client Study," Skiest Inc., Whippany, NJ, October, pp. 42-57 (1998). (2) Jackson, M.A., "Guidelines to Formulation of Waterborne Epoxy Primers," J. Prot. Coat. Linings, April, pp. 54-64 (1990). (3) Lucas, P.A., Clark, P.A., Haney, R.J., and Kittek, R.K., J. Prot. Coat. Linings, August, pp. 20-27 (1998). (4) Wicks, Z.W., "Corrosion Protection by Coatings," Federation Series on Coatings Technology, Philadelphia, p. 9 (1987). (5) Bulletin SC: 1902-94 Starting Point Formulation 1025. Resolution PP website www.resins.com. (6) Gough, L.J. and Smith, LT., J. Coatings Chemists' Assn., Vol. 43, p. 409 (1960). (7) Schecter, L., Wynstra, J., and Kurkjy, R.P., "Glycidyl Ether Reactions with Amines," Ind. Eng. Chem., January, pp. 94-97 (1956). (8) Abstracted from Resolution Performance Products website www.resins.com, bul letin SO 1942-94 Starting Point Formulation 1006. (9) Palmer, B.J. and Liu, J., "Simulations of Micelle Self- Assembly in Surfactant Solutions," Langmuir, Vol. 12, pp. 746-753 (1996). (10) Becher, P., Emulsions- Theory and Practice, 2nd ed., Reinhold, New York, 1965. (11) Austgen, D.M., et. al., "Determination of the Hamaker- Lifshitz Coefficient for Bisphenol A Diglycidyl Ether; Application to Emulsion Stability," Shell Development Co. WRC RAB, January, pp. 179181 (1993). (12) Arkles, B., Steinmetz, J.R., Zazayczny, J., and Mehta, P., "Factors Contributing to the Stability of Alkoxysilanes in Aqueous Solution," J. Adh. Sci. Technol., Vol. 6, No. 1, pp. 193-206 (1992). (13) Ugelstad, J., "Swelling Capacity of Aqueous Dispersions of Oligomer and Polymer Substances and Mixtures Thereof," Macromol. Chem., Vol. 179, pp. 815-817 (1978). (14) From Crompton Organo Silicones Group website www.osiorganosilicones.com. Huang, M.W. and Waldman, B.A., "Water Stable Silquest Silanes and Their Use in Latex Sealant and Adhesive Applications," 22 pages (2000). (15) Erickeson, P.W. and Plueddemann, E.P., "Interfaces in Polymer Matrix Com posites," in Composite Materials, Vol. 6, Ch. 1., Plueddemann, E.P. (Ed.), Academic Press, New York, 1974. (16) Holubka, JW. and Dickie, R.A., "Resin Structure and the Corrosion Resistance of Organic Coatings," JOURNAL OF COATINGs TECHNOLOGY, 56, No. 714, 43-46 (1984). (17) Bodwell, J.R., Dehm, D.C., and Law, M.P., "Solvent Distribution Studies for the Coatings Formulator: Waterborne Container and General Industrial Coatings," Proc. of the Waterborne, High Solids, and Powder Coatings Symposium, February, 174-190 (1991). (18) Bulletin SO 2996-00R NEW GEN(TM) White Primer Starting Point. Formulation 1700; Resolution Performance Products website www.resins.com. (19) Weinmann, D.J., et al., "Formulating Waterborne Epoxy Coatings," 44th Annual Technical Symposium; Waterborne Coatings: Sink or Swim, Cleveland, OH, May 17-18,2001. (20) Bulletin SC: 1898-94 EPON 1001-CX-75/ Epi-Cure-X-70 Gloss White Enamel Starting Point Formulation 1020; Resolution Performance Products website www.resins.com. (21) Bulletin SC: 2997-00R NEW GEN(TM) Gloss White Enamel Starting Point Formulation 1025; Resolution Performance Products website www.resins.com. Jim D. Elmore, Derek S. Kincaid, Pratap C. Komar, and Jon E. Nielsen Resolution Performance Products LLC* Presented at the 79th Annual Meeting of the Federation of Societies for Coatings Technology, on November 4-7, 2001, in Atlanta, GA. *P.O. Box 1380, Houston, TX 77251.
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Source: Copyright Federation of Societies for Coatings Technology Aug 2002 - JCT - Journal of Coatings Technology
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