Sucrose-glycerol polyols

The mixtures rich in sucrose are practically impossible to stir. The mixtures of sucrose/glycerol (1-3/1) are easy to stir at 110-120 °C. Unfortunately, for higher ratios of sucrose/second polyol this variant of technology is impossible to apply. 

This method of direct propoxylation of mixtures between sucrose and a second polyol is often used in practice, the most important polyols being based on sucrose - glycerol, sucrose - triethanolamine and sucrose - diethyleneglycol. 

Table 13.5 The characteristics of some sucrose - glycerol based rigid polyether polyols for rigid PU foams (structures I, II and III) ...

Polyether polyol based on sucrose-glycerol mixture... 

Surface-Active Agents. Polyol (eg, glycerol, sorbitol, sucrose, and propylene glycol) or poly(ethylene oxide) esters of long-chain fatty acids are nonionic surfactants (qv) used in foods, pharmaceuticals, cosmetics, textiles, cleaning compounds, and many other appHcations (103,104). Those that are most widely used are included in Table 3. 

FIGURE 1 Molecular formulas of some sweet molecules, representative of the major natural classes carbohydrates (sucrose), polyols (glycerol, sorbitol), amino acids (glycine, tryptophan), peptides (aspartame, monatin). 

The most important low molecular weight polyols used as starters for polyether polyols destined for rigid PU foams synthesis are glycerol, trimethylolpropane (TMP), triethanolamine, pentaerythritol, dipentaerythritol, a-methyl glucoside, xylitol, sorbitol and sucrose [1-27]. The main properties of these starter polyols, which are of interest for polyurethane chemistry, are presented in Table 13.1. 

The representative examples are the synthesis of sucrose-based polyether polyols with a low melting point. Sucrose is well solvated by low molecular weight polyols such as glycerol, diethylene glycol, dipropylene glycol, triethanolamine and sorbitol. At the... 

One can easily imagine that if the glycerol is replaced by triethanolamine [9, 10] or by DEG [51], the resulting polyols are of course a mixture of propoxylated sucrose with propoxylated triethanolamine or propoxylated DEG (13.29). 

The polyols that can be used for transesterification with castor oil are glycerol, trimethylolpropane, pentaerythritol, sorbitol, and sucrose. The catalysts of the reaction between castor oil and various polyols are alkali alcoholates, such as sodium methoxide or potassium methoxide. Thus, by the reaction of one mol of castor oil with two mols of glycerol, a mixture of mono, di and triglycerides of ricinoleic acid, having a much higher hydroxyl number than the initial castor oil, of around 420-430 mg KOH/g (reaction 17.5) is obtained. 

Thus, the polyol nature has a marked effect on the fire resistance, which is in fact the order of thermostability. The most thermostable polyols lead to polyurethanes with improved fire resistance. Thus, polyesters are superior to polyethers in so far as the fire resistance of the resulting polyurethanes is concerned. Cycloaliphatic polyols (for example polyols based on carbohydrates, such as sucrose or alkyl glucosides) produce polyurethanes with superior fire resistance as compared to the simple aliphatic polyols (for example polyether based on glycerol or on pentaerythritol). 

Polyether polyols are prepared commercially by the base-catalyzed addition of alkylene oxides such as propylene, ethylene, and butylene oxide to di- or polyfunctional alcohols. Since, for most applications, it is desirable to have hydrophobic urethane compositions, propylene oxide is usually used alone or in combination with small amounts (generally less than 10%) of ethylene oxide. The alcohols used in the manufacture of polyethers include glycols (e.g., propylene glycol) for diols, glycerol, trimethylolpropane, and 1,2,6-hexanetri o 1 for triols, pentaerythritol and a-methyl glucoside for tetrols, sorbitol for hexitols, and sucrose for octols. The base-catalyzed addition of... 

Polyols Sucrose, sorbitan, glycerol, ethylene glycol, etc... 

Sucrose utilization research has been directed mainly toweird use in place of glycerol and other polyols in alkyds for solvent systems. This was in keep-... 

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