Airgas says its board of directors has unanimously rejected a sweetened $5.5 billion buyout offer from rival Air Products.

Airgas Inc. says the offer of $65.50 per share still grossly undervalues the company and is only a $2 hike from Air Products' previous offer. Airgas also says its shareholders should reject some director candidates and bylaw amendment proposals from Air Products at the Airgas annual meeting next week.

Air Products and Airgas have haggled over a possible deal for months.

Air Products and Chemicals says the Airgas board's behavior aims to avoid a sale at any price. It says the company needs truly independent directors committed to maximizing Airgas shareholder value.