July 6 (Reuters) - Billionaire Tom Gores' private equity firm Platinum Equity said on Tuesday it would buy specialty chemicals maker Solenis in a deal valued at $5.25 billion, including debt, and merge it with Sigura Water, a company it bought in 2019.

Platinum Equity will acquire Solenis from Clayton, Dubilier & Rice and BASF. The German chemicals giant BASF holds a 49% stake in Wilmington, Delaware-headquartered Solenis.

The merger of Solenis with Sigura allows the latter to scale up its water-treatment products and supply chemicals to food packaging and paper industries at a time of rising investor demand, Platinum Equity said in a statement.

Founded in 1907, Solenis supplies specialty chemicals and services for process, functional and water treatment applications to consumer and industrial markets. It has 41 manufacturing facilities.

The combined company is expected to generate about $3.5 billion in revenue, Platinum Equity said.

Solenis chief executive John Panichella will lead the combined company. The merger is expected to be completed before the end of 2021.

BASF and Solenis agreed in 2018 to combine their paper and water chemicals businesses, which had come under competitive pressure. The combined business competes with privately-held SNF of France, Kemira and Ecolab's Nalco unit. (Reporting by Abhijith G in Bengaluru; Editing by Krishna Chandra Eluri)