A method is disclosed for producing a vacuum and for separating condensable components present in vapor which accumulates during the production of a polymer by melt-phase polycondensation under vacuum. Vapor produced during the production of polymers by melt-phase polycondensation in at least one reaction step under vacuum is drawn of by at least one steam jet vacuum pump with a down stream injection condenser. The steam jet vacuum pump is driven with alkylene carbonate in vapor form and liquid alkylene carbonate is then supplied to the injection condenser as coolant.