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Solventless Cold-Box Technology Reduces Emissions and Offers Added Value in the Foundry Process
Less Solvents, Greater Added Value
A standard cold box system can be described as a three-part system: Cold box part 1 comprises around 55 % phenolic resin and 45 % solvents; part 2 mainly comprises polyisocyanate derivatives and 15 % to 30 % solvents; part 3 comprises the tertiary amine catalyst, which initiates the reaction.
The new solventless cold box technology, however, does away completely with solvents in part 2 of the cold box formulation. The solventless part-2 formulation, which has been registered for patenting, contains a special polyisocyanate component. In addition, selected additives have been developed that interact with the adapted part 1.
This means that in comparison with a standard system with 100 parts of part 1 and 100 parts of part 2 in sand, the SL system enables the use of the same 100 parts of part 1 but reduces the content in part 2 to just 80 parts. The binder mixture therefore contains the same weight of active material (phenolic resin and polyisocyanate) and additives but with the weight of solvent reduced by around one-third (Figure 1).
This enormous reduction in the weight of solvent in the SL system offers numerous benefits. Above all, having fewer solvents helps to reduce emissions throughout the entire process. In contrast to any of the systems developed so far, solventless technology also helps to reduce unwanted emissions of, for example, BTX.
The introduction of this new technology in various aluminum foundries has also shown that it exhibits outstanding shake-out performance. It is now altogether possible that with less organic material and the same amount of oxygen during casting, more energy can be expended in the bond to break up the binder bridges. This additional benefit, along with excellent dimensional accuracy, was confirmed in a series of foundry trials – a clear sign that the thermal stability of the solventless technology has been perfectly optimized to combine both properties.
Further tests have also shown that less amine is needed. Amine is used in the cold-box process as a catalyst to initiate the reaction between the OH and NCO groups. Theoretically, very little amine is needed for triggering a complete polymerization. In practice, however, amine requirements can fluctuate considerably depending on the differences in the formulation of the binder. This is because amines exhibit different levels of solubility in the different solvents. The weaker the affinity of the amine with the solvent, the greater the efficiency, which explains why reducing the solvent in a binder system also means less amine is needed. Ultimately, the moisture resistance of the cores has been optimized without affecting the bench life of the sand (Figure 2).
With all the benefits it offers, solventless cold box technology is the perfect solution for meeting the current and future requirements of foundries and especially in regard to the ever-increasing demand for new casting mold designs and the ever more stringent customer demands.
Thanks to its ecofriendly and high-performance ECOCURE SL technology, ASK Chemicals is making yet another decisive contribution to meeting the future environmental and economic requirements of the foundry industry.
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