Ch. Hwo, H. Brown, P. Casey, H. Chuah, K. Dangayach, Th. Forschner, M. Moerman and L. Oliveri, Shell Chemical Company, Westhollow Technology Center, Houston, Texas/USA Reprint from Chemical Fibers International, Vol. 50 (2000) No. 1, February 2000 IBP International Business Publishers GmbH, 60326 Frankfurt/Main, Germany, firstname.lastname@example.org Lectureheld at the Polyester ‘99 World Congress, October 25-28, '99 in Zurich, Switzerland Polytrimethylene terephthalate (PTT) is an aromatic polyester made by the polycondensation of 1,3propanediol (PDO) and terephthalic acid. PTT polymer has been melt extruded successfully, from both commercial and pilot lines, into a variety of fibers such as filament yarns, staple fibers, and nonwovens from spunbondand meltblown processes. Power stretch and recovery, and soft touch (good hand) elastic fabrics (both knitted and woven) can be made from the PTT fibers. PTT fibers or fabrics can be dyed readily at atmospheric boil. The molecular structure (formula) of Polytrimethylene terephthalate (PTT) is shown in Fig. 1.
Fig. 1 Structure of PTT
Shell Chemical previously reported on the properties of PTT[1-5] including the introduction of PTT to the fiber industry by Shell Chemical Company. PTT has been recently introduced as a commercial polymer, joining the other aromatic polyesters, polyethylene terephthalate (PET) and polybutylene terephthalate (PBT). Commercialization was made viable by a breakthrough in synthesis of the monomer 1,3-propanediol (Fig. 2) which enabled the polymer to beproduced at costs suitable for commercialization. PTT is generally made by the melt condensation polymerization of 1,3-propanediol (PDO) and terephthalic acid. The polymer produced is similar in characteristics, molecular weight and molecular weight distribution to other polyesters (Fig. 3) and is intended for fiber, film, and ETP markets, particularly those dominated by nylon, PET, or PBT.
Fig. 2Synthetic route to PDO Ethylene oxide route – one step
PTT is not new, the developing technology surrounding this polymer appears to offer the promise of opportunities in the carpet , textile , film and packaging  ETP  and other market places [9,10]. The technology development related to PTT fibers for textile end-uses or applications will be shared in this presentation. PTT is easy toextrude, but must be dry (like PET) in order to get a stable threadline. The key properties of PTT vs. other thermoplastics used in fiber production are shown in Table 1. PTT filament yarns From polymer to POY, SDY (HOY, FDY), SD/POY and UDF Drying: Drying: Like PET or PA, it is necessary to dry PTT polymers (chips) prior to extrusion and spinning. However, unlike the practice for PET, it is notnecessary to use a crystallizer for the drying of PTT polymers (chips). A stage dryer is all that is necessary. The recommended drying condition for PTT is listed as in Table 2. The key point is to dry the polymer to less than 30 ppm in moisture content.
Extrusion: In general, the extrusion temperature is 30°C less than that used for PET. The recommended melt temperature range is 245 to 265°C.Melt temperature higher than 265°C will give a significant rate of degradation of the polymer. Conventional extruders used for PET and PA 6 or PA 66 are also suitable for PTT.
Fig. 3 Commercial aromatic Polyesters
Spinning: Several melt spinning processes for Corterra PTT are possible for untexturized yarns (or filaments): POY, Spin-Drawn Yarn (SDY or FDY), POY from Spin-Draw-Machine andUndrawn Filament (UDF). PTT POY may be made from spinning with or without godets at reasonable spinning speeds (from 2500 to 5000 m/min). Fig. 4 and 5 are the relation of tenacity and elongation versus spinning speed respectively for POY of PTT using a spinning line without godets. A spinneret with 0.35 mm round hole size and L/D ratio of 2.0 was used to generate these figures. POY may also be...