Swiss specialty chemicals producer Clariant has hired US investment bank Goldman Sachs as an additional advisor to fend off a campaign by activist investor White Tale to stop the proposed $20 billion merger with US-based Huntsman.

“Goldman has been taken on board because of their knowledge and ties to US investors and ability to predict and pre-empt White Tales’ next moves,” a person close to the matter told Reuters news agency.

White Tale, an acquisition vehicle for US hedge funds Corvex and 40 North, owns 10% of Clariant and has criticized the merger for lacking strategic rationale and undermining the Swiss group’s strategy of becoming a pure-play specialty chemicals company.

The investor believes that a direct sale of Clariant, or some of its parts, would yield a higher return than combining with Huntsman.  Without having made any specific demands, White Tale is said to have but it has approached fellow shareholders to explore alternative options. These could include the group divesting its Plastics & Coatings division, its largest business unit said to account for 40% of sales. With the proceeds, Clariant could then pay a special dividend, which could in turn lure investors to accept an alternative to the merger.

At Clariant’s press conference to present half-year results last week, CEO, Hariolf Kottmann conceded that the Swiss player might shed the plastics assets, including masterbatches, pigments and additives, which were spun off into a separate company at the beginning of 2016. Since the spin-off was announced, analysts have urged the Swiss group to divest the business.

“We've always said that we could part from these items when the time is right," Kottmann commented. In an update on the merger plans, the CEO suggested that in merging with Huntsman Clariant could divest up to 25% of its portfolio.