Akzo Nobel NV, Europe’s largest coatings company, rejected an unsolicited 20.9 billion-euro takeover bid from PPG Industries Inc. and said it may separate its specialty chemicals business to boost the stock price. PPG’s bid, worth 83 euros a share at the end of February, substantially undervalued the company, Amsterdam-based Akzo said in a statement Thursday, confirming a Bloomberg News report that the U.S. company was exploring a deal.