I would think twice about this, not sure how well it would launder or hold up in a quilt :D:D:D

i've used rayon that was left over from dressmaking days. i washed it on hot, dried it on hot and what died, died. what survived i used. i starched before cutting and machine quilted the heck out of it to stabilize it. it's the quilt in my avatar. it's mixed with cotton, poly and poly blends. it's been used and washed and it's holding up well. i also can't stand to throw anything out.

That's what I would do with rayon. I don't normally prewash, but I'd prewash and dry it twice to make sure it could stand up to use in a quilt.