Corvex Master Fund Ltd, controlled by investor Keith Meister, has teamed up with the investment arm of roofing making Standard Industries, 40 North Latitude Master Fund Ltd., to buy a 7.2% stake in Clariant.
The shareholders said the terms of Huntsman's bid grossly undervalues Clariant.
“There are excellent opportunities to unlock value from the many high-quality businesses that currently comprise Clariant," a spokesman for White Tale, a company Corvex and Standard Industries created to buy the Clariant stake, said.
"Unfortunately, we do not believe that the proposed merger with the Huntsman Corporation is one of those options."
In response, a Clariant spokesman said: "We have noticed the increased investment of Corvex / 40 North in Clariant and their demands. We are taking all of our shareholders' interests seriously and maintain our long-practiced open and engaging attitude with them. In that spirit we are in contact with Corvex / 40 North."
Clariant and Huntsman announced their plans to create a US$14bn chemicals giant in May. Under the terms of the deal, Clariant shareholders would own 52% of the combined group with Hunstman owning the rest.
The merged company would offer a range of chemicals such as automotive fluids, polyurethanes, pigments, additives and resins that are used in sectors including aerospace, household-cleaning and agriculture.