Chemicals maker DuPont has shortlisted four potential buyers for its car paint business after evaluating revised offers received on April 30, according to people familiar with the matter.

The consortium of Blackstone Group and Bain Capital, the KKR & Co LP -Onex Corp pair, Carlyle Group, and Apollo Global Management have advanced to the next round as DuPont seeks to negotiate with a smaller number of potential buyers, the sources said.

Sources have said the unit could be worth as much as $4 billion.

The business attracted initial bids from other private equity groups -- a consortium of TPG Capital Management and Advent International; and Clayton Dubilier & Rice teamed up with CVC Capital Partners, Reuters has reported.

Those groups are now out of the process, the sources said.

The four shortlisted parties have been given access to more detailed financial information to allow for in-depth due diligence, they said. DuPont spokesman Gregg Schmidt declined to comment as did representatives from Carlyle, KKR, Bain, TPG, Advent, CD&R and CVC.

Several of the buyout firms have concerns about DuPont's earnings assumptions for the business as well as an industry trend, the sources said. The buyout firms are also worried about the industry trend of volumes of paint sales to auto body shops being on a steady decline in the developed world, the sources added.

The performance coatings business primarily sells to Maaco and other auto paint refinishers. Ford Motor and General Motors are also key customers, though selling to so-called original equipment manufacturers are not as lucrative.