Rockwood Holdings said its shareholder Kohlberg Kravis Roberts & Co will sell almost half of the stake it owns in the specialty chemicals maker, sending its shares down 2% in extended trading.

Kohlberg Kravis - an asset management company - owns about 21% stake, or 15.9 million shares in Rockwood Holdings. Goldman Sachs & Co is serving as sole book running manager of the offering, the company said.

Rockwood Holdings, which makes inorganic chemicals and solutions and engineered materials, posted its seventh straight market-topping quarterly results last week.