Alkoxylation Viscosity

Three different mechanisms of perester homolytic decay are known [3,4] splitting of the weakest O—O bond with the formation of alkoxyl and acyloxyl radicals, concerted fragmentation with simultaneous splitting of O—O and C—C(O) bonds [3,4], and some ortho-substituted benzoyl peresters are decomposed by the mechanism of decomposition with anchimeric assistance [3,4]. The rate constants of perester decomposition and values of e = k l2kd are collected in the Handbook of Radical Initiators [4]. The yield of cage reaction products increases with increasing viscosity of the solvent. 

The effect on the viscosity decrease by the introduction of EO units in the polyetheric chains is more significant in the case of aromatic diamine alkoxylation, such as the alkoxylation of o-TDA [4]. 

The third method to decrease the viscosity of aminic polyols is the alkoxylation of a mixture between a polyamine (which leads to very viscous polyols) with a monoamine, such as monoethanolamine, diethanolamine, diisopropanolamine or monoisopropanolamine, (which lead to fluid polyols). The quantity of monoamine is calculated so as not to affect markedly the functionality of the final aminic polyol. 

The anhydrised Mannich base is heated under nitrogen at 80-125 °C (preferably at 80-90 °C to avoid viscosity increase) and PO (or a mixture of PO-EO or EO) is added stepwise within 4-6 hours. The reaction does not need a catalyst. The alkoxylation reaction is catalysed just by the tertiary amino nitrogen formed as a consequence of the Mannich reaction. 

Addition of EO, together with PO (15-20% EO in the mixture with PO [16-18]), leads to Mannich polyols with lower viscosities than the polyols based exclusively on PO. By using a mixture of diethanolamine and diisopropanolamine (1 1 molar), Mannich polyols with lower viscosities than the Mannich polyols based exclusively on diethanolamine are obtained [11]. As mentioned previously, lower alkoxylation temperatures of 80-90 °C (maximum 95 °C), are preferred because polyols with lower final viscosities are obtained and the alkoxylation rate is higher at lower temperatures than at higher ones (see chapter 13). 

The last traces of alkylene oxides are removed by vacuum distillation at 100-110 °C. After the phenolic group alkoxylation, that is the first group which is alkoxylated, the resulting structure becomes much more stable and it is possible to develop degassing at higher temperature, without the risk of viscosity increase. The resulting Mannich polyols are used in polyurethane foam fabrication without any other supplementary purification. The reactions involved in the alkoxylation of Mannich bases to Mannich polyols are presented in reaction 15.10 [9]. 

The alkoxylation of the Mannich base with PO (or PO-EO mixtures), takes place by the stepwise addition of the oxiranic monomers, at 80-95 °C, in an inert nitrogen atmosphere [5, 9]. Figure 15.4 shows that the Mannich polyols obtained by the oxazolidine technology have lower viscosities than the corresponding Mannich polyols obtained by classical Mannich reactions. This effect is explained by the low viscosity of the intermediate Mannich bases used as starters. 

The alkoxylation of lignin is possible in a solvent (dimethylformamide, N-methylpyrrolidone or in liquid PO [20]). A process using a lignin-glycerol mixture (3 1) in a polyether polyol based on lignin was developed [20]. The catalysts of this reaction are KOH, but a tertiary amine, such as dimethylaminoethanol is preferred. By alkoxylation with a PO-EO mixture (e.g., 18-25% ethylene oxide EO) a totally liquid dark-brown lignin-based polyether polyol with a viscosity in the range 4,700-8,000 mPa-s at 25 °C, with an hydroxyl number... 

The recovered polyols shown in Table 20.2 have a lower acidity due to the alkoxylation of acidic groups, lower hydroxyl numbers and higher viscosities (due to the alkoxylation of diphenylmethane diamine, which leads to high viscosity polyols) compared to the polyols resulting directly from glycolysis (Table 20.1). 

Density has been found to decrease in the order of brominated polyurethanes (1.26 g cm ) > chlorinated polyurethanes (1.15 g cm ) > alkoxyl-ated polyurethanes (1.11 g cm ) > polyurethanes (1.09 g cm ). The value increases with an increase of the NCO/OH ratio which may be due to an increase in rigidity in the structure and to an increase in virtual cross-linking by H-bonding and other molecular interactions.However, the viscosity is dependent on the nature of the polyurethanes which is related to the physical and chemical structures, molecular weight and distribution of the polymers. For example, resinous polyurethanes prepared for the surface... 

After its colhsion with an HA macromolecule (compare reaction 5), the generated peroxyl type macroradical yields a high molar mass hydroperoxide which subsequently, mostly induced by the present Cu(l) ions AOOH + Cu(l) —> AO + HO" + Cu(ll), yields an alkoxyl type macroradical (AO ). This is a presmned intermediate of the main chain sphtting, resulting in biopolymer fragments whose solution is characterized by a reduced dynamic viscosity (compare Scheme 1 [14]). 

Typical examples are fatty acid polyglycol esters and their homologs, alkoxylated long chain alcohols, alkoxylated triglycerides, and the salts of phosphated alcohols or alkoxylated alcohols [103]. Spin finishes for low dtex PP sample fibers tend to exhibit low emulsion viscosities, medium static and dynamic surface tensions, while overall low surface tensions are more desirable for coarse fibers [105-107]. 

Besides the examples listed above, a wide range of other compounds with diverse properties can be envisaged using different tail groups other than natural fatty acids and monoglycerides. As an example, alkoxylated alcohols have been esterified with carboxylic acids such as citric acid with potential applications for high-viscosity surfactants in cosmetics [14]. In addition to esters, amides of carboxylic acids linked with lipophilic groups are also known from the patent literature [15]. 

H. is produced by - alkoxylation of alkali-cellulose suspended in solvents, such as acetone, isopropanol or tcrt.butanol 0.8-1.5 moles of alkali per AGU are necessary. To decrease viscosity, the alkali-cellulose is degraded by aging (- cellulose) before reaction or by adding hydrogen peroxide to the alkaline reaction mixture. For better efficiency, the addition of ethylene oxide is carried out in two stages. After the first reaction step, only catalytic amounts of alkali are necessary. Reaction takes place in 1-4 h at 30-80 °C and is stopped by neutralization with hydrochloric or acetic acid. Salts are removed by washing with alcohol/water mixtures. If retarded dissolution in water is desired, the wet product is treated with glyoxal. 

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