V. V. Sinitsyn

Properties of lithium greases as a function of degree of unsaturation of technical 12-hydroxystearic acid

Conclusions1.The presence of unsaturated acids (ricinoleic, oleic) in HCO and in technical 12-HoSt decreases significantly the thickening effect on it of Li-soaps. The strength, viscosity, and drop point temperature decrease in the greases and the colloidal stability deteriorates.2.The thickening effect of Li-soaps of HCO and 12-HoSt depends on the degree of unsaturation approximately identically. At the same time, the thickening ability of Li-soaps of HCO in comparison with soaps of 12-HoSt (at equal iodine numbers) is significantly lower.3.The decrease in iodine numbers of saponifiable components leads to an increase in length of soap fibers and the appearance of characteristic twisted crystallites. Going from HCO to 12-HoSt increases the particle dispersion of the thickening agent.

Complex calcium greases from soaps of individual and mixed acids

Summary1.The thickening power of cCa soaps increases with increasing chain length of the hydrocarbon radical in the high-molecular-weight saponifiable component. The viscosity-temperature characteristics become poorer. In order to produce cCa greases that are satisfactory in rheological characteristics and in other respects, C22 (behenic) and higher carboxylic acids must be excluded from the high molecular weight saponifiables.2.The characteristics of a grease thickened with a cCa soap from a mixture of individual carboxylic acids will be intermediate with respect to the characteristics of greases prepared from soaps of the individual acids present in the mixture.

Viscosity of dispersion medium and properties of complex calcium greases

Summary1.The yield properties, colloidal and mechanical stability, and heat-hardening of complex calcium greases depend very little on the viscosity of the dispersion medium.2.As the base-oil viscosity is increased (above 120 cSt at 50 °C), the apparent viscosity of complex calcium greases at 0 °C also increased. The increase in grease viscosity is slight compared to the increase in base-oil viscosity.3.The viscosity-temperature characteristic (VTC) and viscosity-shear characteristic (VSC) of complex calcium greases depend very little on the viscosity-temperature properties of the dispersion medium.

Ratio between the low- and high -molecular-weight carboxylic acids in kCa greases based on soaps of 12-hydroxystearic acid

Conclusions1.The properties of greases thickened with the kCa soaps of technical 12-hydroxystearic and acetic acids depend on a change in the molar ratio of LM and HM acids to a lesser extent than kCa greases based on the soaps of fatty acids.2.A change in the molar ratio of LM and HM acids markedly affects only the tensile strength of a grease and had scarcely any effect on its viscous properties, colloidal and mechanical stability, and thermal and moisture hardening.3.The optimum HAc: 12-OHSt ratio is approximately 3∶1.

Surface-active agents in complex calcium greases based on soaps of 12-hydroxystearic acid

Conclusions1.The dependence of thickening effect of a cCa-soap of 12-HOSt on glycerin concentration in the grease has an extreme character, having a minimum corresponding to 0.5–0.7% glycerin.2.An increase in glycerin concentration above 2% shows up unfavorably on the thermal and moisture strengthening of cCa-greases.3.The properties of cCa-greases based on soaps of 12-HOSt are not very sensitive to a change in basicity and acidity. Only the presence of more than 1.5% free acids (calculated to HO1) worsens the mechanical stability and increases their thermal strengthening.

Free alkalies and acids in soft greases

Conclusions1.An extreme type of dependence of the thickening action of the Li soap of 12 -hydroxystearic acid on the content of excess free alkali or acid in the soap-oil system has been established. The maximum in strength, or viscosity and the minimum in ability of oil to be pressed out, etc., corresponds to a neutral reaction of the system.2.The change in morphological features of the soap fibers which form the structural framework of the systems studied agrees with the change in their rheological and other characteristics.3.The effect of free alkali is intimately connected with the presence or absence of hydroxyl groups in the soap molecules (soap micelle). Qualitatively the action of OH groups is displayed regardless of whether they enter into the make-up of the soap molecule anion, are included in the form of hydration water, or are bound in the soap micelle as excess free MeOH.

Relationship between low- and high-molecular-weight acids in complex calcium greases based on soaps of synthetic fatty acids

Summary1.The properties of cCa greases based on both narrow and especially wide SFA fractions depend less on the molar ratio of the low- and high-molecular weight acids than for cCa greases based on soaps of individual carboxylic acids. The optimum molar ratio of HAc to the narrow SFA fractions is approximately 2∶1 while for wide C10–C20 SFA fractions it is 1.5∶ 1, which is lower than for individual carboxylic acids (3∶1).2.A cCa soap of SFA fractions has a reduced thickening effect compared with the soaps of individual carboxylic acids. They surpass the greases thickened with the cCa soap of individual carboxylic acids in a number of properties (viscosity-temperature behavior, colloidal stability). Both wide and narrow SFA fractions are promising raw materials for preparing cCa greases.

Group composition of residual basic oil and properties of complex calcium lubricants

Conclusions1.The group composition of the dispersion media (paraffinic-naphthenic and aromatic fractions of type MS-20 residual oils) has only a slight effect on the principal properties of complex calcium lubricants.2.The addition of an extract of polycyclic aromatic hydrocarbons, separated out from IS-45 oil distillate during phenol purification, weakens complex calcium lubricants prepared on the basis of the residual oils.

Effect of the degree of saturation of hydroxy-fatty acids on the properties of complex calcium-lubricants

Conclusions1.It has been established that KCa-lubricants can be produced from soaps of HCO and technical 12-H(OH)St of different degrees of hydrogenation (iodine numbers ranging from 6.9 to33 g I2/100 g). The lubricants have good operation properties and their mechanical stability exceeds that of KCa-lubricants prepared from stearic acid and synthetic fatty acids.2.Reduction of the iodine number of the saponifiable compounds improves the thickening action of the KCa-soap and hardly affects the thermal strength and the mechanical stability of the lubricants examined.3.Utilization of technical 12-H(OH)St isolated from hydrogenated castor oil, instead of the hydrogenated oil itself, noticeably improves the thickening action of KCa-soap.

Optimum raw material for production of synthetic solidols

Summary1.Variations in the chain length (molecular weight) of individual fatty acids or of average molecular weight of narrow SFA fractions cause a substantial change in the rheological and other characteristics of solidols prepared from these acids. The maximum thickening effect for calcium soaps of individual acids corresponds to stearic (C18) acid or narrow SFA fraction of similar molecular weight.Higher or lower molecular weights of the acid lead to decreases in viscosity and yield value of the greases and to poorer colloidal stability (oil separation).2.The use of a mixture of individual acids or of mixtures of SFA fractions increases the thickening power of the calcium soaps. Broadening the distillation range of the acids has a favorable effect on the rheological and other properties of the solidols, but only up to a definite limit, after which the solidol quality again begins to worsen.3.In order to obtain the greatest thickening effect in the production of synthetic solidols, it is advisable to use a C13-C22 fraction of thermally treated distilled SFAs of not less than 95% purity. Control over the SFA composition must be accomplished by gas chromatography.