“No-bake” foundry mix with extended work time

摘要

A “no-bake” process allows the forming of larger metal castings, by providing longer work times, in the range of about 45 to about 60 minutes. This is achieved using a liquid curing catalyst that is a pyridine, substituted at the second or third position with a moiety having a molecular weight in the range of about 30 to about 100 mwu. Examples of the liquid curing catalyst include 2-ethanolpyridine, 3-chloropyridine and 2-methoxypyridine. When combined with a two-part polyurethane binder precursor and a foundry aggregate, the liquid curing catalyst provides not only the longer work time, but also a strip time that is less than about 167% of the work time, as measured from the point of activating the polyurethane precursors by mixing them in the presence of the curing catalyst.

主权项

1. A binder composition for a foundry mix, comprising:
a polyurethane binder precursor, provided in two parts, the first part comprising a polyol component and the second part comprising a polyisocyanate component; and a liquid curing catalyst that is 2-ethanolpyridine, the liquid curing catalyst being present in the range of about 5 to 7 weight percent based on the weight of the first part of the polyurethane binder component, selected to provide a work time in the range of about 45 minutes to about 60 minutes after being mixed with the polyurethane binder precursors and an appropriate foundry aggregate and a strip time that is less than 167% of the work time, as measured from the same starting point.