High molecular mass copolyesters

Low molecular mass linear and branched polyester resins are produced in a one-stage process at 125-240 C. The volatile condensation products are removed in vacuo (melt condensation process) or by passing a stream of inert gas through the resin melt (gas stream condensation process). Polycondensation in solution with azeotropic removal of water by solvent distillation (azeotropic process) is of lesser importance. High molecular mass copolyesters are produced in two stages as is used for poly(ethylene terephthalate). A precondensate is first obtained by transesterification of dimethyl terephthalate with an excess of diols. In the second stage, the molecular mass of the precondensate is adjusted to the desired value by polycondensation in special reactors with the maximum possible elimination of water and excess diols in vacuo at ca. 250 C. 

Special Uses. High molecular mass copolyester resins are used in the manufacture of flexible packaging. Terephthalate resins are particularly suitable as adhesion promotors for printing inks, lacquers, and adhesives on poly(ethylene terephthalate) films. Some polyester printing inks adhere directly to these sheets. Lacquers that can be heat sealed at relatively low temperature can be produced from high molecular mass, soft copolyester resins. Special linear copolyester resins are used for magnetic tape coatings [2.97]. 

Materials. Completely aromatic random copolyester CPE-1 was synthesized by melt polycondensation, where TPA, PHQ, and HBA (45, 45, and 10 mol %, respectively) were used as initial components. To increase the molecular mass, the final stage of polycondensation was carried out in the solid state in vacuum at 260°C. Varying the duration of this final stage, one obtaines samples with different molecular weight. The molecular weight was estimated from the measurement of relative viscosity of copolyester solutions (0.5 g/dl) in a trifluoroacetic acid-chloroform (60 40%) mixed solvent. For the CPE-1 samples studied, the specific viscosity was 2.7, 3.4, 4.4, 4.7, and 6.4. We studied highly oriented CPE-1 fibers. The fibers were... 

Cl in conjunction with a direct exposure probe is known as desorption chemical ionization (DCI). [30,89,90] In DCI, the analyte is applied from solution or suspension to the outside of a thin resistively heated wire loop or coil. Then, the analyte is directly exposed to the reagent gas plasma while being rapidly heated at rates of several hundred °C s and to temperatures up to about 1500 °C (Chap. 5.3.2 and Fig. 5.16). The actual shape of the wire, the method how exactly the sample is applied to it, and the heating rate are of importance for the analytical result. [91,92] The rapid heating of the sample plays an important role in promoting molecular species rather than pyrolysis products. [93] A laser can be used to effect extremely fast evaporation from the probe prior to CL [94] In case of nonavailability of a dedicated DCI probe, a field emitter on a field desorption probe (Chap. 8) might serve as a replacement. [30,95] Different from desorption electron ionization (DEI), DCI plays an important role. [92] DCI can be employed to detect arsenic compounds present in the marine and terrestrial environment [96], to determine the sequence distribution of P-hydroxyalkanoate units in bacterial copolyesters [97], to identify additives in polymer extracts [98] and more. [99] Provided appropriate experimental setup, high resolution and accurate mass measurements can also be achieved in DCI mode. [100]... 

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