Glycols and Other Polyhydric Alcohols

Among the glycols used for the synthesis of UPs, 2-methyl-1,3-propanediol (MPD) is preferred both due to its high reactivity in polyesterification and the improved properties of cured UPRs using MPD. The increased polyesterification rate of MPD with maleic anhydride, phthahc anhydride and isophthaUc acid was ascertained [18]. Kinetic studies were carried out. 

UPRs with enhanced chemical, thermal and mechanical resistance were synthesized from neopentyl glycol and isophthalic acid [19]. Phosphorus-containing catalysts, especially a composition of orffio-phosphoric acid with molybdenum trioxide, were foimd to be the most effective in decreasing polyesterification time and giving light-colored products. Next, the properties 

The resin based on neopentyl glycol was characterized by higher impact and flexural strength as well as higher chemical and thermal resistance. 

Soluble unsaturated polyesters were synthesized from maleic anhydride and glycidol in dimethoxyethane. At 80 °C, an acid anhydride ring opening occurred and monomaleate ester was formed. In the second step, at 120 °C, the epoxy ring was opened by the COOH group (Fig. 5), formed in the first step [20]. 

Properties Isophthalic-neopentyl resin orfho-Phthalic resin (Polimal 109) 

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F5TeO(CH2)2OTeF5, cis-[0(CH2)20]TeF4, and related compounds are formed in reactions of TeF with ethylene glycol and other polyhydric alcohols (69). The alkoxotellurium(VI) fluorides isolated so far are distillable liquids with considerable stability against hydrolysis. Some of these compounds have been prepared more easily by reacting diazoalkanes with pentafluoroorthotelluric acid (174), as in Eq. (11) ... 

Access to 1,2-Propylene Glycol and Other Polyhydric Alcohols... 

An exhaustive study of the stability of aspirin in polyethylene glycols (substituted, unsubstituted and esterified), as well as other polyhydric alcohols, was undertaken by Whithworth and collaborators 79-183... 

Figure 13.18 shows the effect of sorbitol. Agradual decrease in the CP with an increase in sorbitol concentration was observed. Some other polyhydric alcohols (including saccharides, viz. mannitol, glucose, sucrose, fructose, etc.) induced a similar decrease. A decrease in CP with saccharides has been observed for polyethylene glycol (PEG) and for sorbitol on polysorbate, a nonionic surfactant (Zatz and Lue, 1987 Attwood et al., 1989). Sjoberg et al. (1989) showed that all saccharides decrease the CP of PEG, which is well described by mean Leld theory. Also, an explanation was given for the difference between the saccharides in their ability to decrease the CP in aqueous PEG solutions. 

Fig. 3 Conversion of sucrose to 1,2-propyleneglycol, ethylene glycol and other di- and polyhydric alcohols [19, 20]...

The salt content is limited due to its effect upon acceptability so the polyhydric alcohols and sugars are normally utilized at higher levels (Davies et al., 1976) in order to lower the a ,. Propylene glycol is the polyhydric alcohol of choice, although others, such as glycerol, have also been utilized (Burrows and Barker, 1976). 

These derivatives are generally liquids and hence are of little value for characterisation the polyhydric alcohols, on the other hand, afford solid benzoates. Thus the benzoates of ethylene glycol, trimethylene glycol and glycerol melt at 73°, 58°, and 76° respectively (see Section 111,136). 

Alkyd resins are produced by reaction of a polybasic acid, such as phthaUc or maleic anhydride, with a polyhydric alcohol, such as glycerol, pentaerythritol, or glycol, in the presence of an oil or fatty acid. The resulting polymeric material can be further modified with other polymers and chemicals such as acryhcs, siUcones, and natural oils. On account of the broad selection of various polybasic acids, polyhydric alcohols, oils and fatty acids, and other modifying ingredients, many different types of alkyd resins can be produced that have a wide range of coating properties (see Alkyd resins). 

Fuels cells are of interest both from energetic and environmental considerations. When methanol is fed directly to an anode, as in Direct Methanol Fuel Cells , electric power is generated, making the devices suitable for small and lightweight uses [53], Alternative fuels such as polyhydric alcohols like ethylene glycol and glycerol are much less volatile and toxic, on the one hand, and electrochemically oxidizable on the other [54]. Therefore, the electrochemical oxidation of various polyhydric alcohols has been investigated in acidic as well as in alkaline conditions. 

Separations of polyhydric alcohols by gas-liquid chromatography are of interest in fields other than carbohydrate chemistry, and it is convenient to make brief mention of some of these applications. Several references to the separation of polyhydric compounds without the formation of derivatives are given in the paper by Verachtert,473 and similar methods related to the separation of acyclic and alicyclic diols,617 to the separation of a series of a,(u-diols,818 to the analysis of ethylene glycol, methanol, and diethylene glycol,819 and to the an-... 

In addition to the above waxes there is a group of synthetic wax-like emnlsifiahle materials extensively employed in the industries. They are the polyhydric alcohol fatty acid esters, such as ethylene glycol monostearate, glyceryl monostearate, glycerol distearate, and a number of others. 

A series of polyhydric alcohols, ranging from ethylene glycol to hexitols was examined, at 20° and in the presence of a large excess of lead tetraacetate, by Hockett and coworkers.44 The compounds yielded a family of oxidation-rate curves in which the position of a curve was a function of the number of free carbinol groups in an unbroken series, but there was no simple stoichiometric relation between the number of alcohol groups and the amount of oxidant consumed. At least part of this complexity appeared to be caused by simultaneous oxidation of the formic acid produced in the reaction. The formic acid was converted smoothly to carbon dioxide in about quantitative yield when water was added to the acetic acid solution and the reaction temperature was raised45 - 48 to 35-45°. However, other... 

In this section, consideration will be given to the actual processes of acetal- or ketal-formation and not to the more indirect methods by which acetals and ketals of the polyhydric alcohols may be synthesized from compounds (e.g. derivatives of the monosaccharides) containing preformed alkylidene or arylidene groupings. The condensation of a carbonyl compound with a glycol is facilitated by acidic catalysts, and, since the reaction is reversible, by dehydration. The catalysts most frequently employed are concentrated sulfuric, hydrochloric and hydro-bromic acids, gaseous hydrogen chloride, zinc chloride and cupric sulfate others are phosphorus pentoxide, sulfosalicylic acid, and anhydrous sodium sulfate. The formation of benzylidene compounds is promoted less efficiently by phosphorus pentoxide than by either concentrated sulfuric acid or concentrated hydrochloric acid 1" the reaction is assisted by chloro- and nitro-substituents on the aromatic nucleus, but hindered by methyl- and methoxy-groups.18... 

Sorbitol Solution occurs as a clear, colorless, syrupy liquid. It is a water solution of sorbitol (C6H1406) containing a small amount of mannitol and other isomeric polyhydric alcohols. It is miscible with water, with ethanol, with glycerin, and with propylene glycol. It sometimes separates into crystalline masses. 

Alkyd resins have been the workhorse for the coatings industry over the last half century. The term alkyd was coined to define the reaction product of polyhydric alcohols and polybasic acids, in other words, polyesters. However, its definition has been narrowed to include only those polyesters containing monobasic acids, usually long-chain fatty acids. Thus thermoplastic polyesters typified by polyethylene terephthalate (PET) used in synthetic fibers, films, and plastics and unsaturated polyesters typified by the condensation product of glycols and unsaturated dibasic acids (which are widely used in conjunction with vinylic monomers in making sheet molding compounds or other thermosetting molded plastics) are not considered as part of the alkyd family and are beyond the scope of the present discussion. 

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