A South Korean investment group has agreed to purchase the U.S. silicones maker Momentive Performance Materials in a deal valued at $3.1 billion, including debt and other liabilities. The buyers include the chemical and silicones producer KCC Corp., the quartz and ceramics supplier Wonik QnC, and the private equity firm SJL Partners. According to the credit rating agency Moody’s, KCC and Wonik, will own 45% and 5% of Momentive, respectively. SJL will hold the balance. Momentive had before-tax earnings of $293 million on $2.3 billion in sales last year. About half of its sales came from silicones. Another 40% were from its additives business, which supplies urethane additives, silicone fluids, and silanes. The company also has a small quartz business. Momentive was General Electric’s silicones business until the private equity firm Apollo Global Management bought it in 2006 for $3.2 billion. Over the years Momentive spent time in bankruptcy and made two attempts at initial public offerings of stock.