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Unformatted text preview: FIELD PROBLEMS WITH NEW HIGH SOLIDS PRODUCTS
Kirby Buesing, Technical Service Manager - The Valspar Corporation Source: SSPC, The Society of Protective Coatings Abstract: The trend in the painting industry is moving toward very high solids products to meet VOC regulations. The way we handle, store and apply these products is as much a change as the products themselves. There are a whole new set of rules and problems that this paper presents to help us all deal with the new technology and make it work. For many years, one way to determine whether too much paint had been applied to a vertical surface was by looking for runs and sags. Paint products had enough solvent in them from the factory to give the proper flow characteristics needed for application. On top of this, the old time painter also added a glug or two of thinner to make the product work even better. VOC regulations have caused the industry to make a big change. Many of yesterday's tricks are no longer allowed. The workhorse products of the industry have become epoxies, urethanes and acrylics. The reason is that the epoxies and urethanes have been somewhat easier to formulate as either high solids or water reducible systems. The acrylics or modified acrylic products are either water reducible or low enough in solids that they usually do not cause application or handling problems. High solids epoxies have been around for some thirty plus years. Some of the epoxies from that era were one hundred percent. These products were usually very difficult to apply. They required special plural component equipment because of their short pot life. Most maintenance contractors would not have this expensive equipment in their possession. This limited the use of these products to fixed application sites such as fabrication and manufacturing plants. Some paint manufacturing companies supplied the equipment to the contractor to apply their products. These were usually specialized applications such as riveted tank seam sealing. The new generation high solids epoxies of today still cause field application problems. It is very common to have an intermediate coat be an epoxy with volume solids of seventy, eighty or even ninety percent. The epoxy resin technology has progressed to give us products with higher solids and lower viscosity. This has helped with the application properties, but with the higher resin solids it also requires more pigmentation, which raises the viscosity. The raw material suppliers, coatings manufacturers, application equipment manufacturers, owners and paint contractors have all had to change to meet these requirements. In addition to the raw material suppliers and coatings manufacturers, the application equipment manufacturers have also met the challenge of high solids products. There are two very significant changes made in equipment that have allowed us to properly apply the higher solids products. One change is that the newer airless spray pumps have higher-pressure ratios. The old standard thirty to one pump had difficulty supplying 2500 pounds of pressure at the tip. This was sufficient pressure to break up the old lower solids products. Even some of the 70% volume solids products require 2800 hundred pounds of tip pressure to properly atomize the material with a production size tip. The new airless pumps on the market easily supply up to 5,000 pounds of pressure at the tip. This allows the equipment to handle the products using a variety of lengths of fluid hose, a variety of tip sizes and additional guns on each pump. In addition, equipment people have made great strides in designing equipment to handle the higher-solids products. The newer High Volume Low Pressure spray guns can handle most of the products. And, because of the low atomization pressures used, there is much less orange peel. It may be necessary to starve the gun of fluid and make more passes to obtain the higher film builds of the higher solids materials, but with experience the thickness required can be achieved. The other significant change with application equipment is the introduction of power roller systems that actually work. The pumps, hoses and valves are the same as those used for spray application but the roller, handle and cover are much improved. The high pressures needed to pump the high solids products no longer blow the seals on the newer handles. The power rollers allow the applicator to achieve the 5 to 7 dry mils usually recommended for these products. It has been documented in at least one instance, that a paint crew can role a large tank faster than they can spray it. It is no longer necessary to specify two thin coats of high build epoxy to achieve the desired thickness when roller applying. Paint contractors in the maintenance business have had to learn and train their crews to roller apply even the high builds in one pass to remain competitive. The coatings formulators have made changes to meet the requirements. With the introduction of the equipment to handle the higher solids, the requirement for longer pot life has surfaced. The pot life of some typical 100% solids products today is 45 minutes at 75°F. This is not a long time, but with the proper training a paint crew can spray apply the material with the standard single component pumps. The old products typically had a pot life of no more than 20 minutes. The older products have been hot potted, but there were more problem applications than there were good applications. With a pot life of 45 minutes, you must be very efficient in the mixing procedures. There is no longer the easy box method or break a branch from the nearest tree and stir the paint. A power mixer is an absolute must. The power mixer has to have sufficient power to mix a paste consistency, as most of these products tend to gel up in storage. It is beneficial to have longer handles installed on the mixer. It may even become necessary to have some sort of device to clamp the pail or container so it will not spin with the powerful mixing motor. Complete mixing of each component separately is a must if both of them are in a gel state. This usually breaks down the gel and makes mixing the two components faster and more efficient. Do the mixing in the area of the paint pump so time is not lost in transporting the mixed material. Do not over mix as this creates heat that will shorten the pot life. It may be necessary to make some changes to the paint pump when working with this high viscosity paint. Paint pumps are usually set up with a pick up hose of up to one inch inside diameter. This inside diameter tends to get smaller as the pump is used and cured paint builds up on the walls. This will cause the pump to starve or overwork in picking up the product. This hose can be removed and a short length of pipe added to the bottom of the foot to reach the bottom of the pail or the pail can be raised to the bottom of the pump. The pump filter should be changed to a thirty mesh. A sixty or one hundred mesh filter may lower the pressure too much. With the use of a self-cleaning spray tip and good house keeping around the mixing area, there should not be too much trouble with tip stoppage. Use a front fed type of spray gun. The type with springs or filters in the handles may cause too much restriction or pressure loss. The old rule to remove fingers from the spray pattern was to lower tip size or increase the pump pressure. With these high solids products, that may no longer be the way to remove the fingers. It may be necessary to use a larger tip allowing the material to atomize properly. Transportation and storage of the newer products is more involved than the storage we were used to. When paint was delivered to the job site it was usually stored in the open, near the unit to be painted. If that happened to be out in the sun or out in the cold weather, it did not matter. The temperature of the product is going to affect the properties of the product. The increased temperature of storing the material in the sunlight will most certainly shorten the pot life of the mixed material. Cold temperature can cause the material to increase in viscosity to the point that it cannot be mixed properly. If either of these conditions is encountered in transporting the material from the factory to the job site, the material should be stored to allow it to reach the 75°F range before application is attempted. The material should be kept in the climate-controlled storage until just before its use. The owners of the units have had to become more involved in the coatings procedure. Most often, the proper storage of the material can only be supplied by the owners. This has increased involvement in the project by the owners, but it has also been a benefit to them. The one hundred percent volume solids has allowed single coat tank linings, faster cure times for faster return to service, and less overall waste for the owner to deal with. There is still a requirement for plural component equipment in the coatings industry. Many of the one hundred percent solids urethanes on the market have a very short pot life. Some of them have a pot life of 7 to 10 seconds. The applicator cannot release the trigger on the gun until it has been flushed with solvent. These products usually have very specialized services such as in storage of aggressive commodities, secondary containment for aggressive products and external maintenance for buried piping. The plural component pumps can be made to be portable. They are usually truck or trailer mounted along with a power generator as some of the products have to be heated to be pumped. This equipment is usually owned and operated by a contractor that specializes in this type of work. This equipment requires more and better maintenance to function properly. Another area that plural component equipment is used is in the fabrication industry. Where the same products are used every day, plural component equipment can reduce labor costs along with the cost of lost material. The material is mixed as it is needed. In conclusion, the present day coating products are successful because of cooperation from all parties concerned. Without this cooperation, we would not be able to meet the regulations that are so needed for our environment The raw material suppliers met the need for the low viscosity, high solids raw materials and the paint suppliers were able to formulate products from these raw materials that met the chemical resistance and regulation requirements. The application equipment manufacturers were able to supply the equipment to handle the higher solids products. The contractors and owners had to work together to test apply the products and find ways to deal with the increased participation required by all. The industry has learned some very valuable information in the past few years that will help all of us deal with the field problems we will encounter with the even newer generation of coatings. ...
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This note was uploaded on 03/17/2010 for the course ME ME78212 taught by Professor Prof.sulis during the Spring '10 term at Institut Teknologi Bandung.
- Spring '10