Advertorial: Modern cleaning of production equipment

In recent years, chemical regulations in various parts of the world (Reach in Europe, TSCA in the USA) have resulted in an increasing number of solvents and cleaning products being re-evaluated and reclassified for their toxicological effects. Well-known and highly effective substances such as NMP (N-methylpyrrolidone), NEP (N-ethylpyrrolidone) and DMF (dimethylformamide) have been subjected to stricter classifications with new labelling requirements and their use has been restricted in some cases. In the US, in particular, the EPA has for some time been focusing on eliminating the use of NMP. New regulations also affect chlorinated solvents such as dichloromethane (methylene chloride), which are subject to much stricter controls. Companies will generally be required to remove products that pose a risk to workers from their operations and replace them with more environmentally friendly and safer alternatives. Flammable solvents such as acetone also often need to be replaced for explosion protection reasons.

However, in the processing of polyurethanes or resin systems, established solvents such as NMP, NEP, DMF and methylene chloride are still occasionally used in a variety of applications. Key areas include the cleaning of moulds used in the production of PU components, the rinsing of dosing lines or mixing and dosing heads in two-component systems, and the cleaning of potting systems. Solvents are also used in the production of plastic solutions/dispersions and adhesives, and in the removal of these substances. Increasing technical requirements, stricter environmental regulations, legislation and directives demand customised solutions. Typically, the necessary cleaning is performed manually with brushes and similar tools on open and often heated moulds or in open production vessels and tanks. Employees are directly and immediately exposed to these substances through inhalation, odour and possible skin contact. From an occupational hygiene perspective, the cleaning of closed systems - such as rinsing, mixing and dosing heads and dosing lines - may be somewhat less critical, but the same restrictions apply as for "open" applications. Due to the increasingly stringent classification and labelling of established solvents under Reach, more and more users and processors are looking for functional alternatives. In addition to the technical function, the focus is usually on minimal toxicity, best possible environmental properties and positive factors with regard to occupational safety. In most cases, Färber & Schmid's latest generation of cleaners and solvers meet the properties described above.

In an era of cost-cutting and result-oriented operations, commercial aspects are clearly a priority for modern, efficiently run companies. It is therefore even more positive that the newly developed products can match, and in some cases exceed, the price/performance ratio of established problematic solvents.

A production facility that manufactures PU foam for numerous applications in the automotive sector, as well as PU elastomers via hot-casting processes, previously used NMP to clean all moulds, hose lines, and prepolymer tanks. When cleaning moulds, the main objective is usually to remove release agent residues which, in combination with cured isocyanates and polyols under pressure and heat during part production, often develop into stubborn deposits. When flushing hose lines and prepolymer tanks, it is crucial that the flushing agent offers a high dissolving power without triggering the curing of isocyanate-functional materials. The company had long been in search of alternatives that are not classified as toxic to reproduction yet fulfill the same technical requirements as NMP. After outlining its specific needs, the customer received recommendations for two suitable products: RESIN-Clean EXP-10/70 and RESIN-Clean EXP-10/100.

RESIN-Clean EXP-10/100 is an aprotic cleaner that does not contain any free OH groups, making it ideally suited for removing reactive premixes. After an initial laboratory test, production trials were soon carried out under real conditions. Having successfully passed the testing phase and been approved, the two cleaners are now used to thoroughly clean all machines and tools at comparable costs—without endangering employees.

A manufacturer of components for mechanical engineering, special vehicle construction, and conveyor technology, using its own PU elastomer formulations and Vulkollan, had been searching for a suitable replacement product for quite some time to remove stubborn release agent residues. In hot-casting PU elastomers, high temperatures result in extremely difficult-to-remove release agent residues on mold surfaces. In the past, the company used a NEP-based cleaner. Due to NEP’s reclassification under Reach, the previous supplier developed a new NEP-free cleaner and offered it as a replacement. However, since the moulds are always cleaned at room temperature after production, the new cleaner did not match the performance of the old NEP-based product. This dissatisfaction caused the production team to insist on the old product. Because of this situation, the customer was quickly willing to test a few cleaners on-site together with an application specialist from F&S.

After a few quick tests, extended trials were conducted, and the product proved to be the ideal solution. They now use RESIN-Clean EXP-3/M-V2, which has exceptionally high dissolving power even at room temperature. The customer has purchased a suitable container for immersing the mould parts and leaves them in the cleaner overnight. If, for any reason, a quick turnaround is needed, the cleaner can also be applied effectively by hand using a brush.

A company that manufactures all types of seals and PU components made from Vulkollan and Baytec had, until recently, been flushing its mixing heads with the problematic solvent DMF. Due to toxicological concerns, several alternatives were tested, and they ultimately chose RESIN-Clean HPT-PU 05. As this flushing agent has proven effective over the long term and requires no hazard labelling, a new facility in a newly constructed building at another location is now also being equipped with this new flushing agent.

Because of the lack of functional alternatives to DMF, this solvent is still used today, particularly in cleaning rollers in the lamination industry. Given that DMF is classified as both acutely toxic and toxic to reproduction, it presents significant challenges for users in terms of employee and environmental safety. Working alongside a user and a renowned supplier in the textile industry, Färber & Schmid developed a powerful solution for cleaning lamination rollers. Since the adhesives used in lamination processes are often exposed to extremely high temperatures, very stubborn, baked-on contaminants can accumulate on the rollers. The customer’s requirement was to remove these contaminants effectively at room temperature with a user-friendly product. The specially developed cleaner, SOLVETAN, fully meets these requirements and convinced the customer following extensive testing. Since then, SOLVETAN has been used to clean flame-lamination rollers and to remove liquid PU adhesives during day-to-day production.

A provider of wear-protection coatings based on sprayed PU for dump trucks and other technical components in conveyor technology for gravel, sand, and other media had been using methylene chloride to dissolve isocyanate in a repair kit shipped to customers who need to fix damaged areas in coatings. As the business expanded globally, the classification/labelling of methylene chloride as toxic to reproduction stood in the way of worldwide airfreight shipping. After a thorough discussion of the customer’s key requirements with an on-site application engineer, the recommendation was RESIN-Clean HPT-D1. This specialty product is label-free and belongs to a new generation of eco-friendly solvents from the “High Performance Technology” series. Following successful quick tests and extensive long-term tests—including adhesion studies—RESIN-Clean HPT-D1 received final approval and has since contributed to the global success of the repair kit in a sustainable manner.

A processor of polymer concrete based on polyester resin had previously used methylene chloride to flush its screw mixers because of its excellent and very rapid cleaning performance, as well as its fast evaporation and quick surface drying. Since methylene chloride is non-flammable, it could be used in non-explosion-proof equipment. Considering the new regulations on methylene chloride, the company was obliged to find a functional alternative that addressed explosion protection and still fulfilled their cleaning requirements completely. Through close coordination and collaboration with the machine manufacturer, RESIN-Clean EXP-3/M-V2 was selected as a highly efficient specialty cleaner that fully meets the customer’s needs. The equipment manufacturer also upgraded the existing screw mixing system with a circulation-tank setup, enabling the user to further enhance cleaning performance and significantly reduce costs. Compared to methylene chloride, only a fraction of chemicals is now needed for regular system cleaning. Ultimately, both the environment and employees’ benefit, and costs are reduced overall.

A manufacturer of thermoset semifinished products planned a new large potting system for polyester- and epoxy-based resins. The goal was to avoid the additional complexity of explosion protection (EX) measures for the system and thus needed to replace acetone. Large annual volumes of acetone also contribute to high diffuse emissions, creating yet another reason to act. The cleaning requirements were very high, as acetone is widely known as an excellent solvent and is still broadly used in the resin processing industry. Since cost efficiency also played a significant role here, and because they intended to reprocess the new cleaning agent by distillation, the new flushing medium had to be distillable and free from interactions between the cleaner and resins during cleaning and subsequent storage and distillation. With RESIN-Clean HPT-PU 05, the ideal product was found—one that more than meets all the requirements. The plant is now operated in a non-EX zone to the operator’s complete satisfaction. RESIN-Clean HPT-PU 05 is continuously reprocessed via a dedicated vacuum distillation system. Consumption and associated emissions have been drastically reduced, which has in turn significantly lowered costs for raw materials and logistics.

A producer in the construction chemicals industry had either not cleaned its isocyanate tanks or only done so sporadically by manual means in the past due to a lack of alternatives. Over the years, insufficient cleaning had led to a significant build-up of material. During discussions about a container cleaning system for mobile production containers, the issue of stationary isocyanate tanks emerged. Since many PU processors have encountered cleaning problems with isocyanate contamination in the past, a highly effective product had already become established for this task. RESIN-Clean HPT-73/DB has convinced many sceptics that it is indeed possible to chemically remove cured isocyanate contaminants using specially adapted cleaning chemistry. The production tank was filled with an IBC (1,000 kg) of RESIN-Clean HPT-73/DB and kept in motion overnight. Subsequently, the isocyanate contaminants detached extensively from the tank surface. The cleaning performance of RESIN-Clean HPT-73/DB can be enhanced by heating, thus shortening the contact time required. The company now cleans the tank at regular intervals so that no further build-up can occur. The cleaner can be reused multiple times for this purpose, keeping maintenance cleaning costs very low. The images show the tank before and after the first cleaning.

The products mentioned in these practical examples and those shown in the table represent only a selection of the many options available for dissolving and cleaning PU and other plastic systems. If required, individual and customer-specific products for targeted applications can be developed and manufactured in close coordination with the client at any time. The competitive advantage of custom-developed products lies in the ability to freely define certain chemical-physical parameters. The highest requirements for toxicology, ecology, application technology, and economics can thus be met on an individual basis. In many cases, the high performance of these products leads to direct cost savings in the overall process. Our cleaners can be used both at room temperature and elevated temperatures. For very large components with vertical mould walls that cannot be immersed, viscous cleaners and solvents are available that adhere to the parts and thus work effectively. Beyond replacing the solvents mentioned, environmentally friendly alternatives for acetone and MEK are also available.

At present, the cleaning of systems and tools used for processing various plastic systems still rely extensively on solvents with highly critical classifications, often because there seem to be insufficient alternatives or due to fear of major drawbacks when switching. With the products described by Färber & Schmid, you have proven cleaning and solvent solutions at your disposal for practically every challenge. These products offer the highest degree of protection and compatibility for employees and the environment.

Holger Schlüter studied Mechanical Engineering with a focus on Plastics/Process Engineering at the University of Paderborn. After graduating, he held various positions at, among others, the BMW Group in Munich, Infineon Technologies AG, and Ter Hell Plastics GmbH. Since January 2015, Holger Schlüter has been working as a Sales Engineer at Färber & Schmid GmbH, and since January 2019, he has served as its Head of Department.

Dipl.-Ing. Holger Schlüter
Head Division Speciality Cleaners - Green Solvents
hschlueter@faerber-schmid.de

Färber & Schmid GmbH
Asangstrasse 132
D-70329 Stuttgart
www.faerber-schmid.de