Synthesis And Performance Of Polyhydroxy Stearic Acids From Natural Fats And Oil

Natural oils have attracted much more attention for their renewable property, and the derivation reaction of those oils is one of the most focus in the oil chemical research. Obtained by the hydrolysis of natural oils, fatty acids are widely used in daily chemical industry especially for the soap industry for their nontoxic, harmless, biodegradable, rich and delicate foam and strong detergency. However, those traditional soaps have the defects of lower solubility and hard water tolerance in the neutral pH environment. In addition, solubility of saturated fatty acid soap is low at ambient temperature, and unsaturated fatty acid soap with good solubility is susceptible to oxidation even at room temperature. All the above deficiencies limit the application of fatty acids. Hydroxy acid which is rare in nature is much more solvable in water than the saturated or unsaturated fatty acids of the same alkyl chain length. This study focuses on the performance of polyhydroxy fatty acids with different number of hydroxyl groups by the strategy of the oxidation and subsequent hydrolysis of the corresponding unsaturated fatty acid which was obtained by hydrolysis of nature oils. The structures of these polyhydroxy fatty acid were characterized by FT-IR,1H-NMR and ESI-MS. The performance such as solubility, foam property and hard water tolerance of these polyhydroxy fatty acids was investigated in detail at ambient temperature in neutral pH circumstance. The main details and conclusions are as fallowings:High content oleic acid (OA) was prepared by urea adduction fractionation of the purchased90%(w/w) content oleic acid, when m (mixed fatty acids): m (urea): V[ethanol (95%)] was1:1.5:8, the content of oleic acid reached96%(w/w) detected by gas chromatography.98%(w/w) high content linoleic acid (LA) was obtained through the process of saponification, acidification and urea adduction with m (mixed fatty acids): m (urea): V [ethanol (95%)]=1:2.5:8. Perilla oil was successively saponified, acidified, urea adducted with m (mixed fatty acid): m (urea): V[ethanol (95%)]=1:3:9, resulting in88%(w/w) content of linolenic acid (LNA). Linolenic acid of97%(w/w) content was further obtained through silver nitrate-silica gel column chromatography separation.9,10-dihydroxy stearic acid (DHSA),9,10,12,13-Tetrahydroxyl stearic acid (THSA),9,10,12,13,15,16-hexahydroxy stearic acid (HHSA) were seperately synthesized from high content oleic acid, linoleic acid and linolenic acid by a two-step-one-pot method with low concentration of hydrogen peroxide as an oxidizing agent. Formic acid was recycled by distillation and the conversion rate of each unsaturated fatty acid reached98.2%、97.9%and98.8%. The molecular structure of the further purified products by crystallization in an organic solvent were confirmed by FT-IR, ESI-MS,1H-NMR, The yield of DHSA, THSA, and HHSA were55%,12%, and15%, respectively. Surface chemical properties and application performance of polyhydroxy stearic acid soaps were carried out. Krafft point, calcium ion stability, lime soap dispersant requirement, surface tension, critical micelle concentration and foam performance and other properties of SDHS, STHS and SHHS were investigated and compared with those of sodium soaps of oleic acid, linoleic acid, linolenic acid and stearic acid. The experimental results showed that STHS and SHHS displayed unique lime soap dispersing power and calcium ion stability in hard water, and better solubility in cold water and at neutral pH condition superior to all the other tested sodium soaps, the Krafft point of STHS and SHHS are all below0℃in the common conditions (pH10). the Krafft point of STHS is41℃in neutral conditions (pH7), while the Krafft point of SHHS is also below0℃. STHS and SHHS possess the power to easily dissolve not only in hard water and at neutral pH condition against ordinary sodium soaps of all other fatty acids, but also in cold water against sodium soaps of saturated fatty acids, and inoxidizability against sodium soaps of unsaturated fatty acids. Therefore, STHS and SHHS have the potential to act as the new soap-base surfactant formulating of neutral soaps, cold water soaps and hard water soaps.