Imasco agreed to sell Genstar Gypsum Products.

The Montreal-based tobacco and retailing company said it had agreed to sell the unit for $241 million in cash to Domtar Inc., a diversified company also based in Montreal. Genstar Gypsum, based in Irving, Tex., is a subsidiary of Genstar Corp., which was bought by Imasco earlier this year for $1.9 billion. Imasco, which also owns Hardee’s Food Systems, Imperial Tobacco and Peoples Drug Stores, has been selling Genstar’s assets except for Canada Trustco Mortgage Corp., a financial services business.