* To shut some plants temporarily in H1 2009
* Shares fall as much as 10.5 percent
FRANKFURT, Dec 17 (Reuters) - German drugs and chemicals group Merck will shutter several plants for weeks in the first half of next year to address a collapse in demand, the company said on Wednesday, sending its shares reeling.
"Strongly reduced demand in businesses segments such as the automobile industry and consumer electronics caused by the current economic slowdown has resulted in a substantial decrease in demand for products from (the) liquid crystals division as well as from the business unit Effect Pigments," it said.
"Therefore Merck will shut down several manufacturing facilities as well as business operations on a temporary basis as needed for several weeks in the first half of 2009."
It said around 800 people work at these sites in Germany, Asia and the United States.
Output at its main German plants in Darmstadt and Gernsheim will be regulated by adjusting working hours and vacation time, it said, adding it could transfer some staff to other operations such as pharmaceuticals production.
The company's shares fell as much as 10.5 percent on the news and were off 9.2 percent at 56 euros by 1010 GMT, the biggest decliners among German blue chips.
"Merck shares have held up pretty well (in the past). One thought that because of their drugs unit, they would remain relatively stable. Apparently the liquid crystal division has managed to have a negative effect on results," one trader said.
"Merck used to be a stable refuge in volatile phases," a second trader added. (Reporting by Michael Shields and Tyler Sitte; Editing by Rupert Winchester) (michael.shields@thomsonreuters.com, Reuters Messaging: michael.shields.reuters.com@reuters.net; +49 69 7565 1266))