2,6-Naphthalene dicarboxylic acid NDA

This class of monomers is also referred to as crankshaft monomers. Examples of such monomers are 6-hydroxy-2-naphtho-ic acid (HNA), 2,6-dihydroxynaphthalene (DHN), and 2,6-naphthalene dicarboxylic acid (NDA) (Fig. 9) [14]. 

Crude 2,6-naphthalene dicarboxylic acid (2,6-NDA) can be prepared by oxidizing 2,6-dialkylnaphthalenes in the liquid phase with molecular oxygen in the presence of a transition metal catalyst and an oxidation promoter. Typically, such catalysts include mixtures of cobalt and manganese promoted with bromine as an oxidation promoter. The 2,6-NDA prepared by the process, contains impurities, such as trimellitic acid (TMLA), and aldehydes. Typical amounts of impurities are shown in Table 11.1. 

N Clear Sodium Silicate. See Sodium silicate NCMC. See Carboxymethyl chitosan N-Creamer 46. See Food starch, modified NCS. See N-Chlorosuccinimide NC Size C-25. See Styrene/acrylates copolymer ND-201 Syrup. See Malt extract 2,6-NDA. See 2,6-Naphthalene dicarboxylic acid NDBC NDBC. See Nickel dibutyidithiocarbamate NDEA. See N-Nitrosodiethylamine NDGA. See Nordihydroguaiaretic acid NDI. See 1,5-Naphthalene diisocyanate NDMA. See N,N-Dimethyl-p-nitrosoaniline N-Nitrosodimethylamine... 

Thermotropic aromatic copolyester fibers are produced by melt spinning since the combination of an aromatic backbone and flexible segments results in an LCP which can be melt processed. Copolyesters, such as p-hydroxybenzoic add (PHBA) modified poly(ethylene terephthalate) (PET), 60/40 PHBA/PET (X7G) polymers, have been produced by the Tennessee Eastman Company [425-427]. Other melt processable nematic thermotropic LCPs (TLCP), based on combinations of 2,6-naphthalene dicarboxylic add (NDA), 2,6-dihydroxynaphthalene (DHN) and 6-hydroxy-2-naphthoic acid (HNA), and referred to as Vectra LCP resins, have been conunercialized (trademark by Hoechst Celanese Corporation [406]). 

Naphthalene-2,6-Dicarboxylic Acid. NDA is more compHcated to synthesize on an industrial scale. The preferred starting material is... 

Although the superior properties of PEN have been known for many years, the unavailability of the naphthalate monomer has delayed the development of commercial markets, until relatively recently (1995) when the Amoco Chemical Company offered high purity naphthalene-2,6-dimethyl dicarboxylate (NDC) in amounts of up to 60 million pounds per year. This diester is produced by a five-step synthetic route, starting from the readily available compounds, o-xylene and 1,4-butadiene [3], Prior to this, the NDC diester was obtained by extraction of 2,6-dimethylnaphthalene (DMN) from petroleum streams, where it was present in relatively low abundance. Oxidation of DMN to crude 2,6-naphthalene dixcarboxylic (NDA) is conducted by a similar process to that used for conversion of p-xylcnc to purified terephthalic acid (TA), crude NDA is esterified with methanol, and is then distilled to yield high purity NDC. Other companies (e.g. the Mitsubishi Gas Chemical Company) followed Amoco s introduction with lesser amounts of NDC. Teijin [4] has manufactured PEN for many years for its own captive uses in films. 

Du Pont s Zenite range of LCPs have been reintroduced. These materials are also LCP polyesters based on HBA copolymers with, it is believed, various amounts of 4,4,-biphenol, terephthalic acid, and naphthalene-2,6-dicarboxylic acid (NDA) as comonomers. Their compositions are thus similar to those of XYDAR with added NDA to further reduce the melting point (235,236). 

In a series of experiments, the TPA in PET has been modified with other aromatic dicarboxylic acids, such as IRA, o-phthalic acid, and certain isomers of naphthalene dicarboxylic acid, i.e., 2,6-NDA, 1,5-NDA, and 1,8-NDA [72]. The oxygen permeability and other properties of the amorphous copolymers of PET modified with amounts of 10% of another carboxylic acid unit are shown in Table 11.8. 

Inspection of Table 11.8 reveals that among the naphthalene dicarboxylic acid isomers, only 2,6-NDA is really effective in reducing the permeability. Most effective is o-phthaUc acid, however, there is a depression of the glass transition temperature. By annealing, the degree of crystallization increases up to... 

PEN film for audio- and videotape and various electronic appHcations and blow molded PEN containers for hot-fill appHcations are already being marketed in Japan. NDA is unlikely to ever become as inexpensive as terephthaUc acid but novel NDA-based polyesters will become available if a market need exists. One example could be the experimental polyester PBN (Celanese Corp.) this is the NDA analogue of PBT, poly(l,4-butylene naphthalene-2,6-dicarboxylate) [28779-82-0]. It has a high rate of crystallization, faster even than that of PBT, and its combination of physical properties is weU-suited for injection molding. 

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