Urethane Nobake binders have been a popular binder choice for sand nobake foundries for decades. Foundries will choose this type of binder system to maintain a high production environment, flexibility in production rates, high mold-strengths fast, reclaimable spent sand, easy to use, and reasonably good casting quality.
Unfortunately, the vast majority of urethane nobake binders available today, as they did in the 1970s and 1980s, still come with irritating petroleum odors that can fill a work environment along with inducing nearby neighbors to launch complaints, while also bringing flammable labeling on containers creating insurance and shipping issues. Other drawback backs to the standard aromatic petroleum solvent urethane nobake binders include the potential of petroleum related casting surface staining, slow strength development with short work times creating a cautious delay in stripping molds, and low hot-strengths creating rough casting surfaces with the potential of veining.
Since 2015 United Erie has been trialing and developing an environmentally friendly urethane nobake binder system, Uniset BIOZERO. Initially started as a project to develop a more economical binder system, it morphed into a significant environmental binder system with several performance advantages. This binder system represents the first environmental and economical urethane binder system available. Initially, the resin system needed to have its formula adjusted to provide for resin and performance stability. This formula adjusting took a good deal of lab work and field trials to get right. But from the very first field trial the potential for this new system was obvious and apparent. Based on the lack of odor and noticeable high performance it received the workers and managers attention.
With dozens of trials having been completed and numerous foundries already having switched over to Uniset BIOZERO, this unique 3-part system has been found to maintain numerous advantages in comparison to standard urethane systems. There does exist low odor solventless urethane nobake binders on the market, however, Uniset BIOZERO is unique in that it contains a biosolvent that has no odor at room temperature while providing this binder system the ability to sufficiently coat the sand. The difficulty with a solventless urethane nobake binder system is a lack of coatability created by high resin viscosity. The biosolvent in this resin system, correctly formulated provides very low resin viscosity leading to good coatability, rapid reactivity accompanied with rapid tensile strength development.
A sand-resin mix with this new binder system can be made to have a short work-time of well under 1 minute permitting rapid stripping or stretched to near 3 hours permitting the making of a very large mold.
During these foundry trials the initial impact of this new binder system is the near complete lack of odor at the mixing stations. There is a sense of relief with the disappearance of the normally present mal-odors associated with standard urethane nobake binder systems.
Once the molds are prepared and the work time reached, the strip time can closely follow as strengths rapidly climb to full strength and are rapidly pour-ready. Molds are typically stripped fast with no scrap and sharp edge-hardness. This new binder system also displays flexibility in the ability to become a 2-part binder system with extended work time of 1-3 hours, but with relatively fast strip times and fast strength development. Again, no odor is present during this stage and in this area of production.
The graph comparison below is a typical strength comparison between the newly developed biosolvent containing urethane system and a standard petroleum solvent system. The comparison of the two systems was done on new round grain silica sand with 1.0% binder having the same work time, and measuring the strength growth there-after. The significant strength increase observed for the biosolvent urethane system is much more rapid and explains all the positive comments provided during the many field trials, which has come to be known as the “Wow-Zone”. Molds made with this new system are ready to be poured in an unusually short period of time.
As the molds are prepared for casting, it has been found at several locations that there is no need for a coating like standard petroleum urethane nobake binders typically require. Despite all the lab work that went into the formulating of Uniset BIOZERO, casting improvement was not predicted but was realized during the trials. 7 out of 10 trials resulted in significant casting surface finish improvement, especially in aluminum castings. Foundry personnel would notice a smoother, shinier casting surface. One foundry, upon the change-over, no longer required polishing of castings. This has lead to the conclusion this binder system has improved hot-strengths better able to withstand the molten metal surface. This continues to be observed during ongoing trials. Typical foundry casting cleaners remark that there is a 50% reduction in the cleaning time associated with Uniset BIOZERO castings.
The low non-toxic odor that occurs during pouring allow for molds to be shaken-out earlier with less discomfort and anxiety. Despite maintaining higher than normal hot-strengths this binder system also displays good shake-out characteristics.
This new, unique, advantageous urethane binder system has pleasantly surprised numerous foundry locations that were using standard petroleum urethane binders. There have been many noted positive comments from workers, managers, owners, and in one special case-the cessation of neighborly mal-odor 911 complaints.
There is also built in humidity resistance with this binder system that most standard urethane nobake binder systems would not have, allowing for improved mold/core shelf-life in warm humid summer conditions.
Trial and Binder Change-Over Observations and Comments:
• No Flammability Labeling provides less complications with insurance and shipping
• No smell with the binder results with not only more breathable air in the mixing stations, but no odors on worker clothing, clothes last longer and there is less of a need to purchase new clothing, workers and their families are generally relieved with the removal of odor
• Fast strength development reduces wait time for stripping
• Fast-High strengths allows for binder level reduction
• No petroleum in the binder system eliminates the dark oil related stains commonly observed on castings
• With Magnesium castings, typical dark spots created by metal-mold reactions are reduced or eliminated
• Improved casting quality noted for Aluminum, Bronze, Magnesium, and Brass
• In mechanical reclaiming, gradual replacement of petroleum based binder on reclaim sand with biosolvent binder results in gradual disappearance of petroleum stains, along with higher quality castings
• Higher hot-strengths improve casting finish, and in some cases eliminates the need for coatings
• Reclaimable sand, mechanical and thermal
• Pouring and shake-out odors/vapor are mild and non-toxic, metal pouring people generally relieved with the less toxic odors
• Maintains great shake-out characteristics