Answer: Interestingly enough, castor beans (despite the name) are a large, somewhat unruly plant rather than a vine; the scarlet runner bean would not be any more of a screen than the morning glories were unless you run your supports closer together. This will be true for most twining vines: in order to make a dense screen they need a lattice type of support (could be wood or wire) rather than a single string. The largest-leafed vining plant I can think of that does particularly well in containers is the moonflower vine, a morning-glory relative. If this is an annual project, you might instead consider some tall, narrow evergreens such as the "Skyrocket" Juniper which grows quickly and would quite possibly survive from year to year in a large container.
In general, the key to successful containers is to use the largest containers you can, refresh the soil each year, water regularly so that the soil never dries out completely and fertilize regularly with a water soulble fertilizer according to the label instructions. Some gardeners will also topdress the containers with compost or water occasioanlly with compost tea as well.
Q&A Library Searching Tips