The refined glycerol 500kg and NaOH (5kg) aqueous solution were stirred and mixed evenly. The water was removed by heating and steaming. Under the protection of inert gas, the condensation reaction was carried out by heating and stirring at 260 C, and the generated water was removed at any time. The degree of polymerization of glycerol was determined by measuring the refractive index of the reactant. Under the protection of 266.6a pressure and inert gas, unreacted glycerol was evaporated at 220-225 C, then cooled.
A mixture of 450kg stearic acid and 485 kg glycerol polymer was stirred and esterified at 200~230℃. The reaction depth was controlled by measuring the acid value of the reaction water or by measuring the acid value of the reactant. After the reaction, it is cooled under the protection of inert gas, and the unreacted polyglycerol is separated from the reaction product at rest. In order to be suitable for different uses, the reactants can be decolorized, deodorized and decatalyzed.
The transesterification reaction between polyglycerol and oil under alkaline condition is the same as that between glycerol and oil. The product obtained by transesterification reaction is more complex than that of polyglycerol and fatty acid. Besides mono-fatty acid glycerol ester, bis-fatty acid glycerol ester and tri-fatty acid glycerol ester, it also contains free glycerol and polyglycerol. Free glycerol and polyglycerol are removed by static stratification. Practice has proved that catalyst, reaction temperature, reaction time, stirring form and stirring effect, cooling mode have great influence on product quality. The quality standards of polyglyceride fatty acid esters and triglyceride monostearates are shown in tables 7.4 and 7.5.
Quality Standard for Polyglyceride Fatty Acids
|Total fatty acid ester content /%||＞90||——|
|Free fatty acids (oleic acid) %||＜6||——|
|Total glycerol %||18-60||——|
|Free glycerol %||＜7||——|
|Burning residue or sulfated ash （800±25）℃ / %||＜0.5|
|Heavy metals (Pb) ppm||——||＜10|
|Arsenic (in As) ppm||＜3||＜3|
|lead / ppm||＜10||——|
|Copper + Zinc（Zn＜25）/ppm||＜50||——|
Remark: The content of pentaglycerol and higher polyglycerol in polyglycerol should not exceed 10%.
|Chart 7.5 Quality standard for triglyceride Monostearate GB13510-92|
|acid value（mgKOH/g)||≤5||Arsenic (in As) /%||＜0.0003|
|Saponification value（mgKOH/g)||120-135||Heavy metals (Pb) %||＜0.001|
|iodine value（gI/100g)||≤3.0||melting point /℃||53-58|
|sulfate ash /%||≤1.0|