so treated may be any continuous yarn including for example fibrous threads roves whether crimped or stuffed and including artificial and synthetic materials where heat treatment of the yarn is included the lack of yarn tension provided by the present invention is particularly advantageous in regard to the structural integrity of the yarn further the lack of tensioned elongation during the treating process produces a treated yarn of minimal residual shrinking since the yarn is free to shrink during the treatment this is particularly important in treating compound synthetic yarns which have been crimped a latent crimping bilaminar compound yarn of diethylene glycol polyterephthalate and butylene glycol polyterephthalate reticulated with 0 3 mol of trimethylol propane as disclosed in french patent application 72 16921 filed may 4 1972 now french pat no 2 182 766 was heat slackened or relaxed in conjunction with its extrusion drawing to 180 dtex 32 strands the yarn treating unit was in accordance with that disclosed in fig1 and of the following specifications ______________________________________length of unit 200mmgroove diameter 137mmgroove depth 15mmgroove turns 20 spiralsapertures 4 per turn______________________________________ the drawn yarn was fed to the yarn treating unit by a pneumatic traction nozzle at 2300 meters minute saturated steam at 102 u00b0 c and 300g cm 2 was supplied to the.