Low-VOC Cleaners and Cost Savings

There is significant potential for reducing VOC values in cleaning agents and optimizing costs. Meeting manufacturers' requirements and selecting the right product are crucial factors in this regard. A case study conducted for a company producing parts for the automotive sector demonstrated that costs can be optimized without compromising the quality of painted parts. One consequence of the European Solvent Directive is that VOC-containing products or materials must have a minimum VOC emission ratio. Water-based paints, high-solids coatings and electrostatic spray painting systems with a wide range of applications fall within this scope. Although this regulation has not yet come into force, it is increasing interest in the widespread use of solvents for cleaning bells, headers, mixing units and pipes. Solvents used in this application are typically diluted with deionized water at a 50% ratio. Painting systems within production processes should be cleaned frequently. During the painting process, cleaning is sometimes performed to change colors or to remove paint residues from previously painted areas, with the aim of reducing the number of defective products. If systems are not cleaned effectively, serious problems such as color variation, spotting or crater formation can occur on painted surfaces. Many painting systems and units are cleaned with the help of butyl glycol, isopropanol, amine or other solvents contained in paints. During this cleaning, solvents are diluted with deionized water at a ratio of 20-50%. As a result, the VOC value also changes by the same proportion. However, ready-to-use solutions can also be preferred. The amount of cleaning agent used can vary depending on the type of application. For example, in the automotive industry where circulation is applied with automatic dosing, temporary cleaning on painting lines requires 5-20 milliliters of cleaner, during color changes 2-25 liters, and during paint changes 2-3 m3 of cleaner may be needed. For this reason, it is a fact that for a weekly cleaning process, 20 m3 of cleaning solvent is required. However, when quantities are this high, waste management becomes increasingly important. Additionally, VOC use, environmental factors and cost will play an important role.

Important Properties of Cleaning Agents

The most important property of a cleaning agent is that it does not show incompatibility with the paint used and can clean all traces and stains remaining after painting. However, special requirements are also possible depending on the type of paint and the painting method (robot, spray, manual).

Foaming:

Foaming plays an important role in electrostatic spray painting systems with internal loading and isolation functions containing balls in valves or pipes. If excessive foam remains inside the pipes after the cleaning process, sudden ignition can occur due to high voltage. This can cause damage to plastic parts and painted surfaces. The use of cleaning agents that produce excessive foam can cause clogging inside pipes due to foam. This is also an indication of insufficient line cleaning. As a result, after color changes, color mixing may occur due to insufficient cleaning. If the system is discharged to a coagulation unit, the use of high-foam-producing cleaners should be avoided. For this purpose, an increase in the costs of defoamers and other chemicals used for this purpose can be observed.

Conductivity:

In processes with an isolated feed line, cleaners with low electrical conductivity should be used. This will provide ohmic resistance.

pH Value:

When metallic paints are used, the most important requirement to avoid hydrogen gas production is that the pH value of the cleaning agent used should not exceed 10.5. However, it is also not recommended for the pH value to be less than 7, because many paint types will undergo precipitation and sedimentation at low pH values, creating other physical problems.

Material Compatibility:

If the cleaning chemical used is not compatible with the paint, serious problems such as gelling, sedimentation and precipitation will occur in the feed lines. Additionally, this will damage equipment such as paint feed lines, pipes and in-line cleaning balls, resulting in extra costs.

Cleaning Tests:

To determine the appropriate cleaner, in addition to the criteria and requirements mentioned earlier (foaming, conductivity, pH, compatibility), some tests processed in a laboratory environment must also be performed. The most well-known of these is a method called the burette test. The burette test is a highly effective method for testing cleaning chemicals, with fast and adequate results. The bell test is a method that provides information on the selection of chemicals to be used for high-speed rotating atomizer cleaning. At this point, the mechanical properties of materials must also be taken into account. However, for almost all applications, line cleaning to be performed in production is unavoidable in terms of providing more accurate and applicable results.

Cost Savings:

As mentioned earlier, there are many opportunities to develop and cost savings with the cleaners used in painting systems. In some cases, using a completely new and different product can even provide cost savings. However, it is also possible to reduce or optimize the cost resulting from the current cleaning chemical use sequence. A direct way to reduce costs is to use a cheaper equivalent product or to reduce consumption amounts. In addition, reducing the consumption amount of the cleaning agent will mean a reduction in VOC value, which will significantly reduce VOC emissions.

We can summarize the factors providing indirect cost savings as follows:

1. Transfer of used cleaning solutions to the coagulation unit (paint sludge separation systems). 2. Reduction of waste costs. 3. Reduction in the amount of defoamer used (in the coagulation unit). 4. Use of high-performance cleaning chemicals. 5. Reduction in cleaning time. 6. Reduction in the need for cleaning chemicals used during general maintenance. 7. Reduction in defective products. 8. Reduction in cleaning chemical consumption. 9. Reduction in VOC emissions. 10. Preference for concentrated products over ready-to-use products. 11. Reduction in CO2 emissions (environmental factors). When it comes to cleaning agents in question, there is significant potential for reducing VOC emissions and lowering costs. A professional perspective in the selection of cleaning products enables your company's needs to be met. For some time, agents used in the cleaning of solvent-based varnishes have contained less volatile substances instead of solvents with high VOC ratios. Since the performance of cleaners varies depending on how well the surface is stripped of paint, there is very little room for maneuver with these types of products. However, there is considerable potential for reducing VOC emissions, and very important work is being done to develop synergistic solvent mixtures that provide the best possible combination of volatility and cleaning performance. In light of all the technical details described above, the biggest obstacle to the market introduction of low-VOC cleaners can be explained by the fact that these products are more expensive compared to some basic chemicals such as butyl acetate or xylene.

Supplier Example for the Automotive Industry:

This example demonstrates, in practice, how cost savings can be achieved. • Parts to be painted: Plastic injection-molded vehicle bumpers, • Wet cleaning with air circulation, • Three-stage coating: 2K water-based primer, 1K water-based topcoat and 1K water-based varnish, • Electrostatic pressure air application, • Production period: 3 shifts, 5 days per week production, • Cleaner: Ready-to-use product, • Monthly consumption: 80 tons of cleaner consumption and approximately 100 tons of solvent waste, • Deionized water is available for water conditioning. Let us assume that the purpose of this study is to reduce costs by selecting a new cleaning agent. Let us assume that reducing VOC emissions is not a requirement. Let us assume that it is preferred to use a concentrated cleaner diluted with deionized water at a ratio of 10%. Let us take into account that the current waste system is maintained, meaning that the cleaning solvent is disposed of as waste before reaching the coagulation unit. As a result, considering that the concentration used in the current system and other production processes do not change, we can assume that the company can achieve approximately EUR 70,000 in annual savings through this new-generation cleaner work. Additionally, new-generation cleaners will provide significant convenience in handling and transportation processes. Uwe Hilsenbek / Research and Development Director - Zeller+Gmelin GmbH & Co. KG Murat Bekmez / Key Account Manager - Zeller+Gmelin GmbH & Co. KG