* Corvex's Meister, NYC's 40 North oppose merger
* Clariant says in contact with Corvex (Adds investor comment on merger, analyst comment, updates shares)
ZURICH, July 4 (Reuters) - Activist investor Keith Meister's Corvex hedge fund and New York's 40 North said on Tuesday they had taken a 7.2 percent stake in Clariant to fight the Swiss chemical maker's planned merger with Huntsman Corp .
"There are excellent opportunities to unlock value from the many high quality businesses that currently comprise Clariant," a spokesman for White Tale, the vehicle they created to buy the stake, said.
"Unfortunately, we do not believe that the proposed merger with the Huntsman Corporation is one of those options."
Meister, a Carl Icahn protege, with Corvex manages assets worth $6 billion and took a 5.5 percent stake in communications company Century Inc earlier this year.
40 North, run by New York real estate investor David Winter and former Bear, Stearns & Company financial analyst David Millstone, held a stake in Clariant before linking with Corvex in their bid to overturn the Huntsman deal. Winter and Millstone are also co-CEOs of roofing maker Standard Industries.
Clariant, which on Tuesday noted the increased investment by Corvex without addressing Corvex's opposition to the merger, said it has been in contact with the hedge fund since last year when it initially took a stake.
"As with all our shareholders we maintain an open dialog with them," a Clariant spokesman said.
Huntsman did not return a phone call seeking immediate comment.
Both shares rose after the news, with Clariant up 2.65 percent and Huntsman up 1.63 percent as of 0847 GMT.
Clariant and Huntsman in May announced a merger valued at around $20 billion including debt in which Clariant shareholders would hold 52 percent of the combination.
At the time, they talked up the friendship between chief executives Hariolf Kottmann and Peter Huntsman as well as prospects for faster growth for the combined company as rationale for "a merger of equals."
The deal, creating a company with about $13 billion in annual sales, had the support of German families that own almost 14 percent of the Swiss group.
Some analysts said the transaction makes sense, in particular after Huntsman spins off its Venator pigments business in an IPO.
"Huntsmans portfolio, after the pending Venator spin-off, offers a highly complementary growth portfolio, in our view - complementary in a way that it puts both companies on a sounder, broader footing," Kepler Cheuvreux's Christian Faitz said.
Still, some investors said the merger always looked like a defensive move designed to protect Clariant or Huntsman from being swallowed up by a larger group.
"We sold our position following the Huntsman announcement," said a former top-10 investor in Clariant. "The logic for value accretion for Clariant shareholders was questionable, so I do understand where Corvex is coming from.
Baader Helvea analyst Markus Mayer said a counteroffer was now more likely, citing Germany's Evonik and Lanxess as having courted Clariant in the past and as companies including BASF that could still be interested in the Swiss company.
Corvex and 40 North contend the transaction lacks strategic rationale and undercuts Clariant's strategy of becoming a pure-play specialty chemicals company.
"Clariant will be exchanging almost half its shares for what is primarily a commodity and intermediates business which will further dilute its multiple and create a larger conglomerate discount," the White Tale spokesman said.
"Shareholders ought to reject this value destructive merger," they said. White Tale said it hoped Clariant could address its "many concerns" about the proposed merger but did not present any alternative plan.
No date has yet been set for shareholders to vote on the merger, Clariant said. (Reporting by John Miller in Zurich and Maiya Keidan, and Simon Jessop in London; editing by John Revill and Jason Neely)