Air Products & Chemicals Inc ended its year-long battle for Airgas Inc after a Delaware judge upheld Airgas's use of a "poison pill" defense against a $5.9 billion hostile bid by Air Products. The judge's ruling blocked Air Products from buying its rival for $70 a share. Air Products spent a year pursuing the deal, which would have transformed it into the dominant North America supplier of industrial gases, used in hospitals, factories and by welders.

"While acquiring Airgas at an appropriate price would have been a value-creating opportunity, Air Products has many other compelling growth opportunities around the world that we are continuing to pursue," said John McGlade, chairman of Air Products. A poison pill is meant to give a board of directors time to find alternatives and explain to shareholders why a hostile bid is inadequate. The measure has been criticized as a way for management to entrench itself at the expense of shareholders, who are prevented from accepting the offer.

Shares of Airgas fell more than 4 percent to about $61 after the ruling, which was published after the New York Stock Exchange closed. The cases are Air Products and Chemicals Inc v Airgas Inc et al, Delaware Chancery Court, No. 5249 and In re Airgas Inc Shareholder Litigation, No 5256.