* Deal worth $110 mln, offer priced at just 0.8 pct premium
* Recent purchase took Solvay's holding above 50 pct
* Vinythai, Solvay shares up
(Adds comments by analyst, Solvay; shares)
By Khettiya Jittapong and Aaron Gray-Block
BANGKOK/AMSTERDAM, Dec 11 (Reuters) - Belgium's Solvay SA is to make a compulsory offer worth 3.64 billion baht ($110 million) for the shares it does not already own in Thai PVC maker Vinythai, as it seeks emerging market growth.
Its Dutch subsidiary, Solvay Chemicals and Plastics Holding B.V., would buy Vinythai shares at 6.15 baht ($0.186) each, just above the last price traded before the announcement of 6.10 baht, Thailand's second largest PVC maker said in a statement.
Vinythai shares, untraded on Friday before the offer was announced, were up 2.5 percent at 6.25 baht at 1026 GMT, while Solvay shares were up 0.7 percent in Brussels, lagging a 1.9 percent rise in the DJ Stoxx European Chemicals index.
Vinythai is valued at around $218 million on the Thai bourse, while Solvay has a market capitalisation of about 6.2 billion euros ($9.1 billion).
Solvay recently bought "a limited number" of Vinythai shares on the open market, bringing its total stake to slightly more than 50 percent, spokesman Erik de Leye said. That meant Solvay had to make a buyout offer to minority shareholders.
Solvay is one of the world's leading producers of polyvinyl chloride (PVC), heavily used in construction, and reiterated its interest in expanding its presence in the region.
"We want to grow in Southeast Asia and emerging markets. It is becoming a big market and it is part of our strategy to grow our presence and market share in that part of the world," De Leye said.
The offer period was expected to run from Dec. 16 to Jan. 21, 2010, and Thailand's third largest lender, Siam Commercial Bank, will arrange the offer.
'TECHNICALITY'
But RBS analyst Mutlu Gundogan suggested the offer was more of a technicality, pointing to what he said was the low value of the bid and Solvay's statement it had no intention to increase the offer price or to extend the offer period.
"I think it is pretty clear that you have to do this but you are happy with the current shareholder structure," Gundogan said, adding the chances of success of the offer were limited.
Solvay spokesman De Leye stressed, however, the offer price of 6.15 Thai baht was "fair value".
KBC Securities analyst Wim Hoste said Solvay's offer to buy out minority shareholders was a "logical step".
PTT Chemical, Thailand's biggest olefins maker, owns 24.98 percent of Vinythai and supplies ethylene to the plant, while Solvay said Chareon Pokphand Group, Thailand's top agribusiness conglomerate, has 11.87 percent.
RBS' Gundogan added that PTT Chemical Public Company is an essential partner to Vinythai and Solvay has indicated in the past that it believes having a local partner is necessary.
Vinythai, which has capacity to produce 280,000 tonnes of polyvinyl chloride (PVC) a year, competes with market leader Thai Plastic and Chemicals PCL, controlled by top industrial conglomerate Siam Cement.
Solvay transferred its 49.99 percent stake in Vinythai to Solvay Chemicals in August as part of a reorganisation of its global business. ($1=.6799 euro) ($1=33.12 Baht) (Editing by Alan Raybould and Simon Jessop)