Polyester linear polyesters

Resin and Polymer Solvent. Dimethylacetamide is an exceUent solvent for synthetic and natural resins. It readily dissolves vinyl polymers, acrylates, ceUulose derivatives, styrene polymers, and linear polyesters. Because of its high polarity, DMAC has been found particularly useful as a solvent for polyacrylonitrile, its copolymers, and interpolymers. Copolymers containing at least 85% acrylonitrile dissolve ia DMAC to form solutions suitable for the production of films and yams (9). DMAC is reportedly an exceUent solvent for the copolymers of acrylonitrile and vinyl formate (10), vinylpyridine (11), or aUyl glycidyl ether (12). 

The largest commercial use of ethylene glycol is its reaction with dicarboxyUc acids to form linear polyesters. Poly(ethylene terephthalate)... 

Esters. Neopentyl glycol diesters are usually Hquids or low melting soflds. Polyesters of neopentyl glycol, and in particular unsaturated polyesters, are prepared by reaction with polybasic acids at atmospheric pressure. High molecular weight linear polyesters (qv) are prepared by the reaction of neopentyl glycol and the ester (usually the methyl ester) of a dibasic acid through transesterification (37—38). The reaction is usually performed at elevated temperatures, in vacuo, in the presence of a metallic catalyst. 

Manufacture. The manufacture of 1,4-cyclohexanedimethanol can be accompHshed by the catalytic reduction under pressure of dimethyl terephthalate ia a methanol solution (47,65). This glycol also may be prepared by the depolymerization and catalytic reduction of linear polyesters that have alkylene terephthalates as primary constituents. Poly(ethylene terephthalate) may be hydrogenated ia the presence of methanol under pressure and heat to give good yields of the glycol (see Polyesters) (66,67). 

Because lactic acid has both hydroxyl and carboxyl functional groups, it undergoes iatramolecular or self-esterificatioa and forms linear polyesters, lactoyUactic acid (4) and higher poly(lactic acid)s, or the cycUc dimer 3,6-dimethyl-/)-dioxane-2,5-dione [95-96-5] (dilactide) (5). Whereas the linear polyesters, lactoyUactic acid and poly(lactic acid)s, are produced under typical condensation conditions such as by removal of water ia the preseace of acidic catalysts, the formation of dilactide with high yield and selectivity requires the use of special catalysts which are primarily weakly basic. The use of tin and ziac oxides and organostaimates and -titanates has been reported (6,21,22). 

Polyester polyols are based on saturated aHphatic or aromatic carboxyHc acids and diols or mixtures of diols. The carboxyHc acid of choice is adipic acid (qv) because of its favorable cost/performance ratio. For elastomers, linear polyester polyols of ca 2000 mol wt are preferred. Branched polyester polyols, formulated from higher functional glycols, are used for foam and coatings appHcations. Phthalates and terephthalates are also used. 

Materials are also blended with VDC copolymers to improve toughness (211—214). VinyHdene chloride copolymer blended with ethylene—vinyl acetate copolymers improves toughness and lowers heat-seal temperatures (215,216). Adhesion of a VDC copolymer coating to polyester can be achieved by blending the copolymer with a linear polyester resin (217). 

It is essential to neutralize any strong acid present before distilling lactic esters otherwise, condensation by ester interchange occurs, with liberation of alcohol and production of polylactic acid, a linear polyester. Other neutralizing agents, such as alkali or alkaline-earth hydroxides or carbonates, doubtless could be used satisfactorily instead of sodium acetate. 

An alternative technique is that of condensation polymerisation. A simple example of this is seen in the manufacture of linear polyesters. Here a dibasic acid is reacted with a dihydroxy compound, e.g. a glycol (Figure 2.5). 

Carothers also produced a number of aliphatic linear polyesters but these did not fulfil his requirements for a fibre-forming polymer which were eventually met by the polyamide, nylon 66. As a consequence the polyesters were discarded by Carothers. However, in 1941 Whinfield and Dickson working at the Calico Printers Association in England announced the discovery of a fibre from poly(ethylene terephthalate). Prompted by the success of such a polymer, Farbenfabriken Bayer initiated a programme in search of other useful polymers containing aromatic rings in the main chain. Carbonic acid derivatives were reacted with many dihydroxy compounds and one of these, bis-phenol A, produced a polymer of immediate promise. 

Linear polyesters were studied by Carothers during his classieal researches into the development of the nylons but it was left to Whinfield and Dickson to discover polyfethylene terephthalate) (BP 578079), now of great importance in the manufacture of fibres (e.g. Terylene, Dacron) and films (e.g. Melinex, Mylar). The fibres were first announced in 1941. 

As shown in the introductory section to this chapter, polyesters may be produced in many ways, one of which is the method of ester exchange. This has been of importance in the manufacture of linear polyesters for a number of reasons which include the following ... 

With one exception no other high molecular weight linear polyesters have achieved any sort of commercial significance for films and fibres. The one exception is the condensation polymer of dimethyl terephthalate and 1,4-cyclo-hexylene glycol (also known as 1,4-cyclohexanedimethanol) (Figure 25.19). 

Are long-chain linear polyesters of carbonic acid and dihydric phenols, such as bisf ... 

This is a linear polyester containing phthalic anhydride to ensure hydrocarbon solubility and maleic anhydride to enable copolymerisation to take place, esterified with 2-propanediol. The ester is dissolved in styrene which initially acts as the solvent and subsequently as film former when it is copolymerised with the double bond in the ester by free radical induced polymerisation. 

Linear polyesters Polyesters may be obtained in a wide variety of forms including rubbers, fibres, films, laminating resins, surface coatings and thermoplastic moulding powders. The last named are somewhat similar to the nylons but are more rigid. Chemical applications, would appear to be limited because of their sensitivity to alkaline solutions and hot water. 

Polyarylates are highly aromatic linear polyesters with high values of (up to 194°C has been quoted) and which are self-extinguishing. 

The use of furan bifunctional monomers for the preparation of linear polyesters and polyamides has been reported by several authors in the last two decades and two... 

The nature—aliphatic or aromatic — of the bivalent —R1— and —R2— radicals in polyester chains (Scheme 2.1) exerts a profound influence on the properties of polyesters and define four main classes of linear polyesters ... 

Another important type of condensation polymer are the linear polyesters, such as poly (ethylene terephthalate) (PET) and poly (butylene terephthalate) (PBT). Copolymers of polyesters and PA have been studied in detail, and it has been shown that random copolyesteramides have a low structural order and a low melting temperature. This is even the case for structurally similar systems such as when the group between the ester unit is the same as that between the amide unit, as in caprolactam-caprolactone copolymers (Fig. 3.10).22 Esters and amide units have different cell structures and the structures are not therefore isomorphous. If block copolymers are formed of ester and amide segments, then two melting temperatures are present. 

Thermoplastic linear polyesters, 18 Thermoplastic polyesters, 20-29, 31 commercial (table), 21-22 number-average molar mass of, 45... 

The presence of a large number of chain-ends in the fully synthesized dendrimer molecules makes them highly soluble and also readily miscible, for example with other dendrimer solutions. The solubility is controlled by the nature of the end-groups, so that dendrimers with hydrophilic groups, such as hydroxyl or carboxylic acid, at the ends of the branches are soluble in polar solvents, whereas dendrimers with hydrophobic end-groups are soluble in non-polar solvents. The density of the end-groups at the surface of the dendrimer molecule means that they have proportionately more influence on the solubility than in linear polymers. Hence a dendritic polyester has been shown to be more soluble in tetrahydrofuran than an equivalent linear polyester. 

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