DUESSELDORF, Germany, Sept 12 (Reuters) - The chief executive of German chemical distribution group Brenntag , which has come under pressure from activist investors to break up its businesses, said he welcomed billionaire Klaus-Michael Kuehne's purchase of an enlarged stake in the company.

"We are happy about any investor who can identify with the strategy that the company has developed and who supports it too," CEO Christian Kohlpaintner told journalists at a media event in Duesseldorf late on Monday, when asked to comment on Kuehne.

Kuehne, who controls Swiss logistics firm Kuehne & Nagel and owns the biggest share in German airline Lufthansa , earlier this month raised his stake in Brenntag to 10% from 5.18%.

The Brenntag CEO on Monday reaffirmed that any structural change should not be rushed. The specialty chemicals division needs to improve to catch up with competitors but can do so under Brenntag's current setup, Kohlpaintner added.

Brenntag is facing calls from Engine Capital and PrimeStone to spin off its specialties business, joining other German companies Bayer and Thyssenkrupp in facing similar demands from activist investors.

Brenntag's management in June prevailed against those investors by winning support for its nominations for its supervisory board at its annual shareholder meeting, rejecting PrimeStone Capital's counter-motions.

Kuehne was among the supporters of the company's nominations. (Reporting by Matthias Inverardi in Duesseldorf; Writing by Ludwig Burger; Editing by Rachel More)