Acrylic epoxy binder speeds core production, improves mixed sand benchlife. (New Product).

As sand foundries look to increase productivity and decrease cost, one of the areas that has the biggest impact is the selection and leveraging of the casting process. Some problems that plague sand users include downtime associated with mixer and machine cleanup, excessive scrapped cores, escaped gases and the ability to produce high quality cores and molds consistently. The process that is the most efficient with the lowest total cost to produce castings is fundamental to success.

The free radical cure (FRC) process is based on acrylic-epoxy binder technology and involves the use of two liquid binders and sulfur dioxide gas for curing. Ashland Specialty Chemical Co., Dublin, Ohio, has developed two FRC binders that improve the casting process for iron steel and aluminum applications.

The Thermoshield binder for iron and steel applications produces a sand/binder mixture that exhibits the hot strength and erosion resistance of phenolic binders, in addition to having zero or low nitrogen, no water and good veining resistance. The chemistry of this binder consists of carbon, oxygen and hydrogen--it doesn't contain nitrogen, so it doesn't require iron oxide and other nitrogen scavengers. The hot strength and erosion resistance of the sand/binder mixture reduce the need for coatings in thin-walled iron and steel castings.

The SBX binder for aluminum foundries provides sand removal efficiency and/or shakeout properties as good as furan while maintaining acrylic-epoxy coremaking productivity and casting dimensional attributes. The use of low binder levels and the lack of solvent in this sand mixture offers lower gas volume. The binder also may be formulated to enhance sand removal and reduce the need for excessive shakeout processes. Sand mixed with this binder also can be reclaimed by mechanical or thermal methods.

Both the binders for iron and steel and for aluminum applications benefit from the advantages of the FRC process. The binders and sand are mixed and blown into a vented pattern and then gassed with sulfur dioxide/nitrogen ([SO.sub.2]/[N.sub.2]) for curing. The superheated [SO.sub.2]/[N.sub.2] gas reduces the amount of residual [SO.sub.2] left in the core or mold by up to 70%. This reduces purge times by up to 50%, thereby increasing core machine productivity by 10%.

The [SO.sub.2] then is sent to a packed tower-type scrubber and is scrubbed with water and sodium hydroxide (NaOH) at 5%. The by-product is a sodium-sulfate and water solution that is accepted by most municipal sewer systems.

Once the acrylic-epoxy binders are mixed with sand, no reaction occurs until the sand mix is gassed with [SO.sub.2]. Mixed sand will not harden in the mixer, hopper or blow magazine, and no clean-up is needed in these areas. This results in sand that does not change in flowability and a reduction or elimination of the variability in core and mold density. The benefit is a significant reduction in core scrap and consistent high-density cores and molds.

Circle No. 001 on last page.