The present invention relates to industrial high relative viscosity (RV) filaments, such as, for use in papermaking machine felts and other staple fiber applications. The invention is further directed to apparatus and processes for solid phase polymerization (SPP) of polyamide flake suitable for use, such as, in remelting and then spinning the industrial high RV filaments. The invention is also directed to processes for melt phase polymerization (MPP) of molten polymer for making the filaments.
