* Construction chemical industry has seen consolidation
* BASF says unit not large enough to compete successfully
* Shares at 2-year low (Adds details on possible value, rivals, overall market, products)
By Ludwig Burger and Arno Schuetze
FRANKFURT, Oct 26 (Reuters) - Chemicals group BASF said it planned to sell its Construction Chemicals unit or find a merger partner for it, as new Chief Executive Martin Brudermueller looks for ways to boost the group's share price.
Construction Chemicals is the world's largest maker of chemical additives for concrete. Its products were used to build the world's longest railway tunnel in Switzerland as well as London's new underground train line, the Elizabeth line, but BASF said the unit was not large enough to compete successfully on its own over the longer term.
"Neither are we satisfied with the (group) business development nor with our share price development," Brudermueller told journalists in a conference call after the chemicals giant released third-quarter results.
BASF shares were down 1.9 percent at 65.42 euros at 0941 GMT, their lowest in more than two years.
When he took over in May, Brudermueller threw his weight behind the company's strategy of keeping divergent businesses folded into one company.
The CEO, who is scheduled to outline his strategic vision in more detail on Nov. 20, said portfolio reviews would continue, adding that the decision on construction chemicals did not mark a policy change.
"The unit has a very low degree of integration into the rest of the BASF network and it does not fully meet our expectations regarding profitability," said finance chief Hans-Ulrich Engel.
Construction Chemicals had sales of 2.4 billion euros ($2.7 billion) in 2017 with about 7,000 staff and Baader Helvea analyst Markus Mayer said it could be valued at 2.4 billion-3 billion euros.
Sika, GCP or LafargeHolcim could be prospective partners, Baader's Mayer said. He added that the BASF unit's earnings had not grown much since it was acquired from Degussa in 2006 for 2.7 billion including debt.
BASF would not provide earnings figures or a price tag, but BASF said it plans to sign a deal for the unit some time next year.
Beyond additives for concrete, the business offers a range of substances for builders, including concrete repair fillers, grouts and sealants under a business dubbed Construction Systems, where BASF is the No. 4 player globally.
A deal "should help establish a very strong player, in particular in Construction Systems, given the ongoing round of consolidation in construction chemicals," said CFO Engel.
The construction chemicals sector is seeing a wave of consolidation. While St. Gobain failed with its takeover of Swiss-based Sika, private equity firm Cinven acquired France's Chryso.
Currently, buyout group CVC has engaged investment bank Lazard to find a buyer for French chemical company Parex, which could be valued at around 2 billion euros, people close to the matter have said.
The former Lafarge unit, which reported 2016 earnings before interest, tax, depreciation and amortization of 158 million euros, has attracted interest from Chinese and Western construction materials groups, the people said.
BASF, which is the world's largest maker of chemicals and plastics for the car industry, earlier said quarterly operating profit fell 14 percent as stricter emission rules and trade barriers dented its business with automakers. ($1 = 0.8787 euros) (Reporting by Ludwig Burger; Editing by Maria Sheahan and Susan Fenton)