MD80 CREW HAD ENCOUNTER WITH WAKE TURB DEPARTING RWY 22L AT ORD.

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WAKE TURB ENCOUNTER. WE WERE CLRED FOR TKOF WITH A TURN TO 140 DEG HDG WHILE PRECEDING B737 DEP WAS STILL ON RWY. THE B737 LIFTED OFF BEFORE WE RELEASED THE BRAKES. THE L TURN TO 140 DEGS AT 400 FT TOOK US THROUGH THE WAKE TURB OF THE B737 RESULTING IN A VERY RAPID ROLL OF 20-25 DEGS TO THE L. THIS WAS COUNTERACTED WITH NO FURTHER PROBS BUT IT WAS VERY DISCONCERTING CONSIDERING THE RELATIVELY LOW ALT OF APPROX 600 FT AGL. I REGRET NOT INFORMING THE TWR OF THIS ENCOUNTER. ALTHOUGH I DID INFORM THE DFW TWR OF A WAKE ENCOUNTER UNDER ALMOST EXACTLY THE SAME CIRCUMSTANCES ON A PREVIOUS OCCASION. AFTER 2 OF THESE ENCOUNTERS AT LOW ALT; I DON'T CONSIDER IT SAFE TO TAKE OFF IMMEDIATELY AFTER A PRECEDING JET; EVEN ONE OF SIMILAR TYPE TO CAUSE A LARGE UNCOMMANDED ROLL WHEN IN CLOSE PROX. I THINK THAT THIS ISSUE SHOULD BE RAISED WITH THE CTLRS AS A SAFETY MATTER. IN THE FUTURE; I WILL NOT ACCEPT ANY CLRNC TO TAKE OFF WHILE THE PRECEDING PLANE IS STILL ROLLING. IT MAY BE A LEGAL CLRNC BUT IT'S NOT SMART.