The folding shower curtain doesn't need to be washed. It's a SHUB. One of the extras you got with a Sunline. New they are about $250!
From the web site;
screen provides maximum access into and out of the bathing area, and can be fitted to most existing showers and baths. Installation is fast and easy, and the durable material is mildew and mold free
and backed by a 5-year guarantee! Say good-bye to your high-maintenance shower curtain and enjoy the convenience of the SHUB® disappearing shower screen!