Preparation and surfactant properties of diglycerol esters of fatty acids

Abstract

Fatty acid mono‐ and diesters of diglycerol constitute the major portion of commercial polyglycerol esters; hence, their composition influences the performance of the latter as emulsifiers. The correlation of structure of the fatty acids in the mono‐ and diesters with surfactant properties is of interest. Linear diglycerol was isolated from polymerized glycerol by acetonation, fractional distillation and regeneration. Diglycerol mono‐ and diesters of undecenoic, lauric, stearic, oleic and ricinoleic acids were prepared by reacting diglycerol and fatty acids in a refluxing mixture of acetonitrile‐tetrahydrofuran (75:25) in the presence of p‐toluenesulfonic acid and molecular sieves. Mono‐ and diesters were separated by silica gel column chromatography, and their purities were ascertained by thin layer chromatography and determination of saponification value. The structures were confirmed by periodic acid oxidation, chemical‐ionization mass spectrometry and 13 C‐NMR spectroscopy. Surfactant properties of the esters were determined. Monoesters showed higher ability in surface tension reduction, emulsification and foaming than the diesters. Short‐chain fatty acid esters showed better surfactant properties than the long‐chain fatty acid esters. The presence of a central double bond in the lipophilic part of the monoesters reduced emulsion stability. The presence of a hydroxy group in acyl chain retarded foaming and surface tension reducing power.

Surfactant properties of purified polyglycerol monolaurates

“…Analysis results are shown in Table 1. The resulting 1 H NMR and the mass spectra of 2GML were the same as those reported earlier (7,8).…”

“…A cylinder with an internal diameter of 50 mm was used for foam property measurements; measurements were repeated three to four times. The respective mean values were evaluated, and the ratio of foam height at 5 min to the initial foam height was defined as foam stability (7,8,12).…”

Influência da temperatura e da natureza do catalisador na polimerização do glicerol

“…Atualmente, o glicerol derivado da indústria petroquímica (que apresenta alta pureza) é empregado na produção de cosméticos [10,11] , fármacos [12] , bronzeadores [13] , aditivos alimentares [10,11] e estabilizante para PVC [14] , aplicações que não são facilmente acessíveis para o glicerol derivado do biodiesel (que apresenta grau de pureza variável) [15] .…”

“…E nas regiões próximas às usinas de biodiesel, em 2009, o preço não ultrapassou R$ 700 t -1 [8] . Diante dessa situação, torna-se estratégico o desenvolvimento de novos processos para a conversão de glicerol em produtos de maior valor agregado [9] , pois a produção e mercado de glicerol, derivado da indústria petroquímica, já são estáveis.Atualmente, o glicerol derivado da indústria petroquímica (que apresenta alta pureza) é empregado na produção de cosméticos [10,11] , fármacos [12] , bronzeadores [13] , aditivos alimentares [10,11] e estabilizante para PVC [14] , aplicações que não são facilmente acessíveis para o glicerol derivado do biodiesel (que apresenta grau de pureza variável) [15] .Uma alternativa de transformação química, entre diversas descritas na literatura [15][16][17][18][19][20][21][22][23][24][25] , para consumir parte desse glicerol derivado do biodiesel é a reação de polimerização (Figura 2), pois os polímeros produzidos podem ter diferentes aplicações, tais como substitutos de polióis, e.g. álcool polivinílico [26] , aditivos para tintas [10] , lubrificantes [27] , aditivos para cimentos [4,28] e matéria-prima para produção de poliuretanas e resinas [12] de aplicações pouco nobres.…”

Polyglycerol Esters

“…At higher concentration and at temperatures over the Kraftt point, the emulsifier in water will exhibit mesomorphism forming different lyotropic phases, i.e. For a series of diglycerolesters of increasing acyl chain length, the surface tensions between water/air have been recorded by Kumar et al [26] and it is observed that the increasing chain length increases the surface tension. The polyglycerol ester will self-aggregate with the hydrophilic polyglycerol moiety oriented towards the surrounding water, and the fatty hydrocarbon chain packed in a more or less ordered form, away from the water.…”