Werner Baumann, seen as heir apparent to Bayer Chief Executive Marijn Dekkers, says he will fight for the independence of Germany's largest drugmaker after the spin-off of its plastics unit.

"We will always try anew every day to defend our independence through our performance and the decisions that we make," said the 52-year-old, who will head Bayer's main healthcare arm from April.

In an interview with Reuters, Baumann said Bayer did not need a merger to make it more successful, even if there were few synergies between the healthcare, veterinary drugs and crop protection businesses.

He said the group was getting "good initial results" from early-stage research across its life science units, which costs a double-digit million euro amount per year, but added that this was not the reason for keeping the businesses under one roof.

"We never said we wanted to become a life science company," he said. "Our portfolio is rather the result of a) what we are good at and b) what we regard as attractive markets in terms of long-term growth, profitability and barriers to market entry."

Baumann said what will remain of the conglomerate after the planned split-off of its plastics unit is a result of what he and his fellow executives are best at managing and not held together by synergies -- the potential for which is often cited as a driver behind mergers and acquisitions.

"Synergies per se are no raison d'etre for organizational structures and businesses," he said.

Bayer, which invented Aspirin and polyurethane foams, unveiled plans in September to list its plastics business on the stock market to focus on its more profitable life-science businesses around human, animal and plant health.

CEO Dekkers has stressed the research synergies to be gained between the various life sciences.

He will step down at the end of 2016 and has said it will be up to the supervisory board to pick a successor, but Baumann is widely seen as the front-runner.

Baumann, a former group finance chief who is also responsible for group strategy, has spent his entire career at Bayer, having played key roles in folding Roche's consumer health unit and rival drugmaker Schering into Bayer.

Baumann dismissed the premium put on pure-play stocks by most equity fund managers, who find it harder to build an industry mix from conglomerates in their portfolios.

"That's the difference between companies and shareholders... We have about 120,000 staff, soon about 100,000, with some families having worked for the company in the sixth or seventh generation."

"Our responsibility in society goes far, far beyond our shareholders," said the father of four.

Major healthcare players are in the midst of a series of asset sales and swaps to better focus on the types of medicines that will bring them the most growth, exemplified by a complex $20 billion transaction between GlaxoSmithKline and Novartis.

Pfizer has in recent years severed its animal health business, now known as Zoetis, and is seen as possibly splitting off its patent-free established products arm.

Bayer's relative conservatism is in contrast to such radical ideas, but despite this the stock has been a boon to investors.

It has yielded a total return of about 90 percent over the last two years, compared with the 56 percent performance of the STOXX Europe 600 Health Care index, driven by the launch of new drugs, the purchase of Merck & Co's consumer health business and its plans to split off plastics.