CRAIN'S CLEVELAND BUSINESS - RPM International (NYSE: RPM), the Medina-based specialty coatings company, announced it has acquired Key Resin Company, a Batavia, Ohio-based manufacturer of polymer flooring and coating systems.Key Resin boasts annual net sales of about $25 million, according to a news release. Terms of the transaction, which is expected to be accretive to earnings within a year, were not disclosed.Once complete, Key Resin, which primarily services the North American market, will operate as one of RPM's