Naphthalene based LCPs

In addition to the 2,6-naphthalene based LCPs, an interesting aromatic LC polyester with 2,6-substituted DBD moieties has been disclosed in several patents [15, 16]. 

The global market for LCPs is about 4,540 tonnes, with about 50% in the Asia-Pacific market, 40% in the U.S., and 10% in Europe [News-MP, 1995]. Despite their cost, LCPs are enjoying 25% annual growth worldwide and are forecast to maintain that level through the decade. Growth is 20% in the U.S. and Europe, 30% in Asia. Most LCPs are made from naphthalene-based and biphenyl-based monomers, as shown in Scheme 1. 

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

Specifically, Celanese has defined families of thermotropic polyesters derived from 2,6-naphthalene dicarboxylic acid (NOA), 2,6-dihydroxynaph-thalene (DHN) or 6-hydroxy-2-naphthoic acid (HNA). Indeed, the Vectra LCP engineering resins of Celanese Corporation are based on these monomers. 

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]). 

In late 1985 Hoechst Celanese commercialized a family of LCPs under the trademark Vectra. Based on hydroxybenzoic acid and naphthalene derivatives, like Xydar , Vectra LCP exhibits a nematic structure. Although Xydar and Vectra are classified genetically as wholly aromatic polyesters with similar basic structures, it is important to note that many of the characteristics of the LCP polymer systems vary significantly with their chemical compositions. Other companies that are commercially active include Sumitomo Chemical, Mitsubishi Chemical, Ueto and Unitika. 

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