(Reuters) - German industrial gases group Linde LING.DE urged investors to tender their shares in an exchange offer for its planned $80 billion merger with U.S. peer Praxair PX.N as a deadline approaches to reach 75 percent acceptance.

FILE PHOTO: Linde Group headquarters is pictured in Munich, Germany August 15, 2016. REUTERS/Michaela Rehle/Files

As of Oct. 4, seven weeks after the offer was launched, it had been accepted for 27.7 percent of outstanding Linde shares. The acceptance period ends at midnight on Oct. 24.

“We have been encouraged by the number of shareholders that have already accepted the offer. Now that we are entering the final phase of the offer period, I would like to address you personally,” Chief Executive Aldo Belloni wrote in a letter to shareholders on Thursday.

The planned all-share merger of equals will create a global leader to overtake France's Air Liquide AIRP.PA with a combined market value of $80 billion, revenue of $28.7 billion and 88,000 staff.

Institutional investors who have accepted include Norway’s $1 trillion wealth fund Norges, Schroder Investment Management and Union Investment.

Deutsche Boerse DB1Gn.DE, at a comparable point about two-thirds of the way through its exchange offer for a planned merger with the London Stock Exchange LSE.L, had about 1 percent acceptance.

That deal, which was undermined by Britain’s vote to leave the European Union, eventually failed after European regulators blocked it over monopoly concerns.

Praxair shareholders have already voted in favor of the Linde deal at an extraordinary meeting on Sept. 27.

Linde estimates that individual retail investors own about 22 percent of its shares, while 10-13 percent may be held by index-tracker funds, some of which have rules which forbid them from tendering until acceptance reaches a certain level.

Chairman Wolfgang Reitzle told Reuters in June that tracking down retail investors would be tough.