There is no specific number. However, if you have only worked with one or two teams, you likely do not have enough coaching hours outside of the ScrumMaster role. The first person to qualify for CTC had 30 teams across three organizations on his experience list. Please provide details if you were working with other non-Scrum teams or groups in your coaching, such as a product group or IT operations.
How Many Teams Must I Have Worked with to Qualify as a Certified Team Coach?
