International Paper, a global supplier of packaging materials and uncoated paper, said Monday that it is buying the containerboard unit of Weyerhaeuser Co. for $6 billion in cash.

Memphis-based International Paper said it will pay for the purchase through increased debt. The planned purchase would make International Paper the largest containerboard producer in North America, with a 29 percent market share.

The sale includes nine container board mills; 72 packaging locations; 10 specialty-packaging plants; four kraft bag and sack locations, and 19 recycling plants. About 14,300 employees work at the containerboard packaging and recycling business.

Weyerhaeuser has a recycling facility in Salt Lake City with about 20 employees. International Paper spokeswoman Amy Sawyer said it is "too soon to tell" if there will be layoffs in Salt Lake because of the acquisition.

The sale is expected to close in the third quarter of 2008, subject to regulatory reviews and completion of financing, International Paper said.