The former private equity unit of French insurer AXA said it has raised $9 billion to buy stakes in existing buyout funds, the largest such pool ever assembled, highlighting the growing demand for second-hand private equity investments.

The amount eclipses the $7.1 billion that Ardian, then a unit of AXA, raised for so-called secondaries in 2012. Ardian, formerly known as AXA Private Equity, in September spun out of the Paris-based insurer, which still owns a minority stake in the business.