Why would each patch produce a new leak before resintalling tube?
You may have a sort of systematic effect, such as debris (puncture causing material) near the patch site, or missing rim tape or something depending on where the patch is. It may not be easy to find the causing material unless the tire is flexed under load though, which is why you might just not see it.

Either that, or you're consistently not applying the patch right (which you just need to follow the directions in the patch kit).