Studies On The Sucrose Stearate-Based Surfactants

Sucrose shows poor affinity to fatty acid ester, traditional solvent-free process has to becarried out by means of high temperature (170～190℃) and large amounts of soap (25～40%)to prevent the phase separation between sucrose and MS, and the aggregation of sucrose. Inmy research work, a novel preparation processs for sucrose stearate (SSE) consisting ofsolvent-free colloid process and alcoholic separation was developed. A suspension of finelydivided sucrose particles in a continuous MS medium was formed by a special pretreatment,in which the particles were approximately 50～1000 nm in size, and transesterification reactionoccurred successfully in enlarged phase interface between sucrose and MS. The influences ofreaction conditions on the conversion of MS, the yield of SSE and monoester content wereinvestigated in detail. The results showed that the optimized conditions were that potassiumcarbonate catalyst was 2.0% (mass ratio), potassium stearate was 15% (mass ratio), reactiontemperature was 130℃, reaction time was 2.5 h, and molar ratio of sucrose to MS was 1.25(molar ratio). Under the optimum conditions the conversion of MS was 100%, and afterpurification by the improved metallic salt method, the proportion of monoesters in thepurified products was up to 61.2%, and the yield of SSE was 63.2%. A novel alcoholicseparation approach was developed to separate sucrose monoester and sucrose polyester. Itwas found that SSE can be quantitatively separated into two fractions, one withhigh-monoester content, and the other with low-monoester content. The amount of the solventand separation temperature had great effect on the monoester content of SSE, and monoestercontent increased with the decrease of amount of the solvent and separation temperature. Thehighest monoester content was up to 91.6%. The qualities of SSE prepared by solvent-freecolloid process were better than that of commercial sucrose stearate DK F-160 and DK F-50of Daiichi Kogyo Seiyaku. Compared with traditional solvent-free process, solvent-freecolloid process with high MS conversion, high quality, high yield, high monoester content,low reaction temperature (130℃) and small amount of potassium stearate (15%), was apromising processs for industrial production of sucrose esters.In my research work, IR, ¹H NMR, ESI-MS and MALDI-TOFMS were applied for thequalitative analysis of SSE. The qualitative analysis of the SSE, soap, fatty acid, sucrose andMS in crude and purified products were obtained by using TLC, the quantitative analysis ofMS were obtained by using TLC scanner. HPLC-ELSD was also used for the quantitativeanalysis of SSE. When C₈ column and the eluent consisted of a mixture of methanol and tetrahydrofuran were used, the separation of sucrose, sucrose monoesters, fatty acid, MS,diesters and polyesters was completely achieved. In addition, the analysis time was shortenedfrom 170min to 110min. Commercial and synthesized SSE containing mono-, di-, tri- orhigher esters were qualitatively analyzed using electrospray ionization-mass spectrometry(ESI-MS).Relationships of the composition and structure of SSE with surface properties,interfacial properties, foamability and foam stability, stability in hard water and emulsifyingpower were investigated. The synergism of SSE with other surfactants was also studied.Three novel sucrose stearate surfactants: hydrophobic modified sucrosetolyloctadecanoate (STODE), sucrose stearate- maleate (MSS) containing anion groups andsucrose stearate-lycine (SSL) containing quaternary ammonium cationic groups weredesigned and prepared. Some physiochemical properties of SSE, STODE, MSS and SSL wereinvestigated. Compared with SSE, STODE had excellent interfacial properties, when in thesame concentration (C=1.0 g/L),γ_IT of SSE was 12.0 mN m^-1,γ_IT of STODE was 0.07 mNm^-1; MSS exhibited remarkably higher solubility and emulsifying properties than SSE,especially in the presence of NaCl, and excellent stability in hard water (5 level); SSLexhibited excellent stability in hard water (5 level).