Mold Cleaners in Polyurethane Molding Cycles

Mold Cleaners in Polyurethane Molding Cycles

Polyurethane is used in the automotive, furniture and footwear sectors through molding. The molds used are generally made of aluminum alloys, steel and other metals, and in some cases from materials such as epoxy and polyester. Polyurethane is obtained by pouring component A, which contains polyol mixtures and various additives such as chain extenders, crosslinkers and catalysts, and component B, which contains isocyanate prepolymers, into molds using a dosing machine with a mixing head. Mold release agents are used to prevent polyurethane mixtures, which have a highly sticky structure in the first 10-20 seconds, from adhering to the molds. Mold release agents consist of non-polar film-forming polymers and oils and/or particles that provide lubrication, dispersed in water or hydrocarbon solvents. The oils and/or particles that provide lubrication contained in the mold release agent leave the mold together with the molded part, while the film-forming polymers remain on the mold surface. This film layer, necessary for mold release, accumulates on the mold over time during the production cycle and causes contamination. Mold contamination consists of the film created by the mold release agent and partially accumulated polyurethane particles on the mold. The polyurethane molding cycle in outline is as follows: • A new or cleaned mold is brought to the production area and attached to the polyurethane machine. • The molds are brought to the mold temperature recommended by the polyurethane manufacturer. • Mold release agent is applied to the mold generally by spraying, sometimes by brush. On clean molds, this process is repeated 3-4 times to condition the mold and ensure sufficient film formation from the mold release agent. • A determined amount is poured into the mold using the polyurethane machine and the mold closes. • After the reaction, which is generally completed within 3-6 minutes, the molds are opened and the part is removed from the mold. • The cycle continues by applying mold release agent again. • At the end of these cycles, the mold surface is sent for cleaning when the mold release agent film accumulates on the mold and affects the pattern, and the surface of the produced part begins to deteriorate. Mold cleaning can be performed by physical or chemical methods, or sometimes by both physical and chemical methods. Physical methods are carried out using sandblasting, dry ice, steel wool with abrasive surfaces, or the hard green side of dish sponges, depending on the mold structure and size. Dry ice application is among the most commonly applied physical cleaning methods. Carbon dioxide ice particles, which have sublimation properties, are sprayed onto the mold using machines specially designed for this purpose. While this process achieves results similar to sandblasting, it provides much cleaner cleaning than sandblasting, and large molds are generally cleaned this way. Mold cleaning using chemical methods: the conventional and most effective method is application of DMF to molds between 60°C and 80°C and allowing it to soak, and another effective chemical is NMP. However, these chemicals are highly toxic and are on the SVHC list. These chemicals are harmful to the fetus and hepatotoxic to the liver. In our country, these chemicals are still frequently used due to their effectiveness and lack of legal regulation. Formulas containing much safer chemicals have been developed to replace these effective but extremely toxic chemicals. Although this group of cleaning materials does not work as fast as DMF (n,n-dimethyl formamide, CAS#68-12-2) and NMP (1-methyl-2-pyrrolidone, CAS#872-50-4), they have much less toxic content and are easier to use. With good production planning, molds can be safely cleaned. Properties that should be present in a mold cleaner: • Ability to clean the mold within reasonable timeframes, • Long shelf life, • Thixotropic effect when needed (especially for vertical applications), • Absence of prohibited materials, • No corrosive effects on the mold. Armaclean 0555, newly developed by Teknik Kimya, is a next-generation mold cleaner that incorporates all these properties, contains no SVHC, and is REACH compliant. Sources / References: 1. http://echa.europa.eu 2.http://www.lyindustrial.com/kuru-buzla-temizlik/ 3. http://www.icebergkurubuz.com 4. Merck, MSDS, 1-methyl-2-pyrrolidone 5. Merck, MSDS, n,n-dimethyl formamide 6. Kilo, S., Göen, T., & Drexler, H. (2016). Cross-sectional study on N, N-dimethylformamide (DMF); effects on liver and alcohol intolerance. International archives of occupational and environmental health, 89(8), 1309-1320. 7. Jyothi, K., Kalyani, D., & Nachiappan, V. (2012). Effect of acute exposure of N, N-dimethylformamide, an industrial solvent on lipid peroxidation and antioxidants in liver and kidney of rats. 8. TDS, Armaclean 0555 İlker Akça Chemist Technical Operations Director Teknik Kimya