Airgas on Thursday repeated its view that a $5.1 billion hostile bid by Air ProductsAir "grossly undervalues" the company, after larger rival Air Products earlier extended its tender offer for Airgas.

Air Products said its $60-per-share offer to Airgas will now expire at midnight on June 4. As of Thursday, about 12,291 shares of Airgas stock had been tendered, according to the statement from Air Products.

The Air Products' offer, made in February, was originally due to expire on April 9.