RADNOR, Pa. — Airgas Inc.'s board has unanimously rejected rival Air Products & Chemicals Inc.'s $5.88 billion acquisition offer.

Shares of Airgas fell $2.13, or 3.4 percent, to $61.09 in midday trading on Wednesday, while Air Products' stock added 11 cents to $90.64, earlier hitting a new 52-week high of $91.

Air Products raised its bid by 7 percent to $70 per share earlier this month, calling it the "best and final" offer in its 14-month pursuit of a deal.

Airgas' board said Wednesday the revised bid was "clearly inadequate," explaining that it believes the Radnor, Pa.-based company is worth at least $78 per share. Air Products' offer is set to expire on Jan. 14.

Airgas is recommending stockholders not tender shares into the revised bid.

Airgas sells industrial and medical gases and provides gas equipment, welding products, tools and safety gear. Air Products, based in Allentown, Pa., sells gases for industrial, medical and other uses.