Airgas Inc., which has been fighting a hostile takeover attempt by Air Products & Chemicals Inc. for more than a year, on Monday released a contentious exchange of letters between three new directors and company chairman, John van Roden Jr.

The three directors, who won seats on the Airgas board in September after being nominated by Air Products, said in a letter dated Dec. 7 that they did not agree with the Airgas board position - presented publicly as unanimous - that the company was worth a minimum of $78 per share.

Airgas is based in Radnor; Air Products is in Allentown.

The three directors, John Clancy, Robert Lumpkins, and Ted Miller, also complained that the Airgas board had dragged its feet in allowing them to hire their own legal counsel and financial advisers to take a fresh look at the value of Airgas, which distributes industrial gases and welding supplies.

"We expect that Air Products will raise its offer and, accordingly, believe we need to put ourselves in the position to evaluate any improved offer on an independent, fully informed basis," they wrote to van Roden.

Van Roden responded sharply the next day, saying he was "puzzled that you can so confidently predict that Air Products will raise its offer."

He then issued a warning: "It would be a serious breach of your duty of loyalty if any of you, directly or indirectly, have been in contact with Air Products or any of its advisers or have taken any other action that would in any manner facilitate Air Products' efforts to acquire Airgas at the lowest possible price or otherwise undermine Airgas' negotiating position."

The following day, Air Products boosted its offer to $70 per share from $65.50. The latest bid values Airgas at $5.86 billion, excluding debt. The first public offer by Air Products in February was $60 per share, or about $5 billion.

At a meeting Friday, the Airgas board agreed to hire a third financial adviser to represent the entire board and to reimburse the new directors for certain legal expenses.

Contact staff writer Harold Brubaker at 215-854-4651 or hbrubaker@phillynews.com.