a thermoplastic resin processing machine has removably affixed onto its loading hopper a ratio loader which has a source of vacuum and two conduits leading to two different reservoirs of thermoplastic resin pellets . the ratio loader has a container having a movable internal separation wall in a vertical plane which is moved horizontally , for example , by rotation of a screwthreaded shaft having a handle at one of its ends . the ratio loader container has a bottom orifice to the thermoplastic processing machine , which orifice is coverable by a flap which is normally closed by a spring and is held closed by the vacuum .