A Delaware judge has ordered Apollo Management and Hexion, a speciality chemicals company owned by Apollo, to use its best efforts to close an agreed $6.5bn takeover of Huntsman despite a slump in the chemicals and credit markets.

Hexion and Apollo had argued they should be able to walk away from the deal because the combined company would be insolvent. They also had claimed that Huntsman was also not entitled to a $325m break-up fee.