Polyester melt polymerization processes

Poly(ethylene terephthalate) (PET) which is manufactured by a stagewise melt polymerization process consisting of transesterification, prepolymerization and finishing polymerization steps, is one of the fastest growing thermoplastic polyesters used extensively for fibers, films, bottles, injection molded parts and other products [1], Considerable scientific effort has been made to elucidate its properties. Important aspects can be studied using solid-state NMR spectroscopy to determine morphology, orientation and mobility in the bulk material. 

LCPs can be manufactured by applying the conventional polycondensation process for polyesters. Although Grammont s process was based on the solution method using acid chloride developed by Owens-Coming [12, 13], processes of other producers are based on the following melt polymerization process [14—17]. 

Synthetic Fiber and Plastics Industries. In the synthetic fibers and plastics industries, the substrate itself serves as the solvent, and the whitener is not appHed from solutions as in textiles. Table 6 Hsts the types of FWAs used in the synthetic fibers and plastic industries. In the case of synthetic fibers, such as polyamide and polyester produced by the melt-spinning process, FWAs can be added at the start or during the course of polymerization or polycondensation. However, FWAs can also be powdered onto the polymer chips prior to spinning. The above types of appHcation place severe thermal and chemical demands on FWAs. They must not interfere with the polymerization reaction and must remain stable under spinning conditions. 

Why is it so important to remove water from polyesters during the polymerization processing as well as during melt processing ... 

The Eastman Chemical Company is the sole producer of CHDM in the USA. CHDM is typically produced as a mixture of cis- and trans-isomers, with an equilibrium ratio of approximately 30/70 cis/trans. Additional patents disclose technology for affecting the CHDM isomer ratio [19] and for isomerization of d.v-CHDM to tran.v-CHDM [14], Most commercial CHDM polyesters are prepared from the approximately 30/70 cis/trans ratio, with this isomer ratio being maintained throughout the polymerization process. The effect of the cis- and trans-CHDM isomer ratio on the melting point of terephthalate-based polyester has been previously studied and reported [9, 20], This relationship is shown in Figure 7.1. 

Various a-methylenemacrolides were enzymatically polymerized to polyesters having polymerizable methacrylic methylene groups in the main chain (Fig. 3, left). The free-radical polymerization of these materials produced crosslinked polymer gels [10, 12]. A different chemoenzymatic approach to crosslinked polymers was recently introduced by van der Meulen et al. for novel biomedical materials [11]. Unsaturated macrolactones like globalide and ambrettolide were polymerized by enzymatic ROP. The clear advantage of the enzymatic process is that polymerizations of macrolactones occur very fast as compared to the chemically catalyzed reactions [13]. Thermal crosslinking of the unsaturated polymers in the melt yielded insoluble and fully amorphous materials (Fig. 3, right). 

A number of thermotropic polyester-carbonates were prepared through melt-polymerization of substituted hydroquinones and diphenyl tere-phthalate and diphenyl carbonate to have high molecular weight, with reduced viscosity in the range of 2-3. The molecular weights of the polymers can be advanced further by solid state heat-treatment, with the rate of postpolymerization depending on temperature and Concentration of catalyst. Samples of some compositions can be spun into high performance fibers and processed into self-reinforced plastics. The properties of thermotropic polyester-carbonates and polyesters were compared as fibers and plastics. 

Because high molecular weight thermotropic polyester-carbonate products can be obtained by this process, the difficulty in obtaining high molecular weight materials directly from melt-polymerization is circumvented. 

It has been found that carbonyl bislactam is much more reactive than the other bislactam compounds mentioned above. Carbonyl bislactam can be obtained through the reaction of the lactam with phosgene. Preferably, the carbonyl bislactam is added to the melted polyamide or polyester product stream in the polymerization process as it leaves the polymerization reactor. 

A fifth factor is certainly ease of preparation and in this characteristic the melt prepared thermotropic polymers are particularly favored. All of the polymers described thus far may be made in a conventional melt acidolysis process starting with the acetoxy derivatives of the hydroxyl containing monomers used. A typical polymerization scheme is shown in Figure 8, the preparation of the two component polyester derived from the acetylated hydroxybenzoic and hydroxynaphthoic acids. The polymerization may be carried out with or without added catalysts. The poly(ester-amides) commented on here, and the more recently reported aromatic, thermotropic poly(ester-carbonates) and poly(ester-imides), may all be synthesized in a similar manner. 

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