TPC Group Inc., which makes fuel, rubber and other products from petrochemicals, said Monday that it reached a deal to sell itself to a pair of investment firms in a deal worth about $627 million.

Under the terms of the agreement with First Reserve Corp. and SK Capital Partners, TPC's shareholders would receive $40 per share in cash. TPC has nearly 15.7 million outstanding shares.

The price represents a 1 percent premium over TPC's Friday closing stock price of $39.59.

The company valued the acquisition at about $850 million when including debt.

The deal, which has been approved the company's board, is expected to close in the fourth quarter. TPC said that stockholders representing about 22 percent of its outstanding shares have agreed to vote in favor of the sale.

The company said it plans to hold a special shareholder meeting to vote on the proposed deal.

TPC shares rose 58 cents, or 1.5 percent, to $40.17 in midday trading. If the deal is completed, TPC will become a privately held company.