Bellevue, Wash.-based workflow automation company Nintex announced today that it will sell a majority stake to private equity giant TPG Capital, the private equity platform of global alternative asset firm TPG. Investment firm Thoma Bravo purchased a majority stake in Nintex three years ago, and will make a new equity investment while retaining a significant minority interest in the company. Founded in 2006, Nintex has more than 10,000 customers and generates more than $250 million in annual sales. It bought K2 Software last year.