Sorry for those looking for XXX material, it is not the kind of material you would be expecting. But rule is rule, as long as it is explicitly stated in the bible.
There are other rules which have not been quoted in that post.
If a man strikes his male or female slave with a rod and he dies at his hand, he shall be punished. If, however, he survives a day or two, no vengeance shall be taken; for he is his property. Exodus 21, 21-22
That means you can beat up your sex slave so badly that s/he dies after 1 day or two, BUT NOT IMMEDIATELY. I suppose water-boarding would be allowed too.
If a man strikes the eye of his male or female slave, and destroys it, he shall let him go free on account of his eye. And if he knocks out a tooth of his male or female slave, he shall let him go free on account of his tooth. Exodus 21, 26-27
Whatever you do, you must keep the eye and tooth of the slave in place in order to continue owning the slave. That may be a bit difficult, right?