CS257027B1 - Method of qualitative analysis and determination of relative and absolute proportion of alkyiester components of methacrylate additive for lubricating oils - Google Patents

Abstract

Method of qualitative analysis and determination of the relative and absolute representation of alkyl ester components of a methacrylate additive for lubricating oils by cleavage of the additive sample with hydroiodic acid, subsequent reaction with Ag salt of 3,5-dinitrobenzoic acid, identification of the resulting alkyl dinitrobenzoates and quantitative evaluation of the chromatogram, whereby the identification of alkyl dinitrobenzoates is carried out by thin-layer chromatography on silica gel impregnated with 5% vaseline oil in heptane with a mobile phase of dimethylformamide-methanol-water in a ratio of 2 to 8:1:1, using the Yanovsky detection reaction.

Description

The invention relates to a method of qualitative analysis and determination of the relative and absolute representation of alkyl ester components of a methacrylate additive for lubricating oils.

Methacrylate additives are commonly used as viscosity additives for lubricating oils in order to increase their viscosity indices. They are complicated mixtures of substances containing polymerized alkyl esters of methacrylic acid, where the alkyl chain contains approximately 4 to 18 carbon atoms, with a relative molecular weight of 5,000 to 20,000, or copolymerized alkyl esters of methacrylic acid with other, for example nitrogenous substances and other additives affecting the application properties of methacrylate additives for lubricating oils, such as alkylaryl phosphates,

Ba- and Ca- sulfonates, carbonates and phenolates, Ba-phosphonates, polyamides, Zn-dialkyldithiophosphates, etc. All of the above additive components are dispersed in 30 to 50% mineral oil.

The analysis of the composition of additives and determination of the constitution of individual components has not yet been carried out due to the immense complexity and variability of the mixtures, which would assume the mutual separation of the individual components as the first stage. This is completely unsolvable due to the possibility of polymerization and also the close physicochemical properties. Also, the gel-like and sticky nature of the analyzed mixture makes it difficult to use known analytical principles.

The issue of determining the composition therefore had to be divided into several stages:

- isolation of macromolecules! components

- determination of the basic type of additive

- proof, identification and determination of the alcoholic component of methacrylate ester

- Isolation of macromolecular substances can be commonly performed by dialysis using a membrane with hexane or petroleum ether or by chromatographic separation of individual components. Dialysis was chosen as the optimal method for the determination according to the invention.

- The basic types of additives can be determined by the common technique of IR spectroscopy (Vergos T.,

Štěpina V., Oil and Coal 21, 32 to 39 (1979) - For the analysis of polymerized components of the additive, the pyrolytic method was chosen in combination with GLC (Gas-Liquid-Chromatography) - Fišer J. (private communication) for methyl and butyl acrylates the method (HPLC) High Performance Liquid Chromatography after cleavage with hydroiodic acid (Dumont E. Fress, Z. Anal. Chem. 295, 21 to 23 (1979). For the identification of alkyl iodides, it was possible to use the paper chromatography method after their conversion to 3,5-dinitrobenzoates. (Gasparič J., Borecký J. Chromatogr. 5., 466-99 (1961), which was not used for macromolecular substances. By optimally choosing the above methods and the conditions of the procedures used, it was possible to perform a reproducible analysis of the methacrylate components of the additive according to the invention, which had never been performed in this way before. To accelerate and to improve the quality of the separation of components, the method of thin-layer chromatography on silica gel impregnated with a non-polar phase was newly used.

The method of qualitative analysis and determination of the relative and absolute representation of alkyl ester components of a methacrylate additive for lubricating oils by cleavage of the additive sample with hydroiodic acid, subsequent reaction with Ag salt of 3,5-dinitrobenzoic acid, identification of the resulting alkyl dinitrobenzoates and quantitative evaluation of the chromatogram consists, according to the invention, in that the identification of alkyl dinitrobenzoates is carried out by thin-layer chromatography on silica gel impregnated with 5% vaseline oil in heptane with a mobile phase of dimethylformamide-methanol-water in a ratio of 2 to 8:1:1 using the Yanovsky detection reaction.

The analysis can also be carried out by first dialysis a technical sample of the additive using petroleum ether. The examples given below illustrate the implementation of the analysis procedure according to the invention.

Example 1

0.6 g of a mixture of monomeric esters of methacrylic acid with the composition of 0.1 g of n-butyl ester of methacrylic acid (boiling point 163 °C/760 mm),'· 0.1 g of n-hexyl ester of methacrylic acid, (boiling point 85 to 109 °C/35 mm), 0.1 g of n-octyl ester of methacrylic acid (boiling point 160 to 165 °C/15 mm), 0.1 g of n-dodecyl ester of methacrylic acid, (boiling point 145 to 165 °C/5 mm),

0.1 g of methacrylic acid hexadecyl ester (boiling point 170 to 212 °C/5 mm), 0.1 g of methacrylic acid n-octadecyl ester (solidification point 28 to 29 °C) are digested in a sealed glass ampoule with 1 ml of freshly distilled hydroiodic acid at 180 °C for 1 hour. After cooling to room temperature, the contents of the ampoule are diluted with 10 ml of water and the mixture of alkyl iodides formed is separated by extraction with 5 ml of benzene. The benzene extract is purified by shaking with 10 ml of water, then 10 ml of 5% sodium bicarbonate solution and finally 5 ml of water. After drying with anhydrous magnesium sulfate, the benzene portion is transferred to an ampoule and after adding 0.2 g of silver 3,5-dinitrobenzoate, the closed ampoule is heated to 100 °C for 1 hour. The unreacted silver salt of the acid

3.5-dinitrobenzoic acid is filtered off and the filtrate is made up to a volume of 10 ml with acetone. Resultant

3,5-dinitrobenzoates n-butyl, n-hexyl, n-octyl, n-dodecyl, n-hexadecyl and n-octadecyl are used to identify and determine the content of alcoholic components of the starting methacrylate esters.

On a Silufol plate measuring 20x20 cm, which was impregnated by stretching with a 5% heptane solution of vaseline oil before use, 2 µl of the solutions of the analyzed samples and 2 µl of acetone solutions of standard alkyl 3,5-dinitrobenzoates are applied to a start 2 cm from the edge of the plate. It is developed in ascending order with mixtures of dimethylformamide-methanol-water solvents (2 to 8:1:1). The content of dimethylformamide varies according to the length of the alkyl chain of the corresponding

3.5-dinitrobenzoates so that 3,5-dinitrobenzoates with an ester group are optimally separated by the system: dimethylformamide-methanol-water (2:1:1)

Cg to C^ ₂ by the system ·' dimethylformamide-methanol-water (4:1:1) and C^2 C].g by the system

Sg : dimethylformamide-methanol-water (8:1:1).

After the chromatogram has developed (after about 2 hours) and the components of the solvent mixture have flowed out, the detection of alkyl 3,5-dinitrobenzoates is carried out using the Yanovsky color reaction. The reagent is prepared by dissolving 1 g of sodium in 50 ml of ethanol and, just before spraying, it is mixed with acetone in a ratio of 1:4. Intense blue-colored spots of alkaline 3,5-dinitrobenzoates appear on the chromatogram. The following R _f values can be used to identify them:

system

3,5-dinitrobenzoate ^With 1 ^With 2 ^With 3 n-butyl 0.57 0.83 n-hexyl 0.37 0.72 0.87 n-octyl 0.20 0.57 0.81 n-dodecyl 0.06 0.26 0.69 n-hexadecyl - 0.09 0.44 n-octadecyl - - 0.24

The detected chromatogram is evaluated either visually^ or using a spectral evaluator ERI-10/C.Zeiss, Jena/ in reflected light using a filter with a value of λ. = 600 nm. The graphic record of the absorbance of the spot is expressed by a peak, the area of which was quantified by the weighing method. The relative percentage of the individual components of the methacrylate ester mixtures was determined from the ratio of the recorded peak areas and was expressed for the individual components in percentage and by weight:

methacrylic acid ester representation (rel. %) contents (g> n-butyl- 16.72 0.100 35 n-hexyl- 16.68 0.100 1 n-octyl- 16.49 0.098 95 n-dodecyl- 16.62 0.097 5

n-hexadecyl- 16.73 0.100 4 n-octadecyl- 16.76 0.100 7

The calculation of the absolute amount of individual esters in the mixture was performed using a calibration graph constructed from the measured values of the relevant standards and it was found that the initial sample contained individual methacrylic acid esters in the following amounts:

methacrylic acid ester value subtracted content in original

from the calibrator, graph mixtures (g) <^g) n-butyl- 20.1 0.100 5 n-hexyl- 20.0 0.100 0 n-octyl- 19.8 0.099 n-dodecyl- 19.9 0.099 5 n-hexadecyl- 20.1 0.100 5 n-octadecyl- 20.1 0.100 5

Example 2

0.6 g of a polymerized mixture of methacrylic acid esters (from Example 1), containing n-butylη-hexyl-, n-octyl-, η-dodecyl-, n-hexadecyl- and n-octadecyl methacrylic acid esters, was digested with 1 ml of hydroiodic acid at 180 °C for 1 hour. The reaction mixture of the released alkyl iodides was processed for their identification and determination after conversion to 3,5-dinitrobenzoates.

» in example 1). The analysis was detected next- composition sample methacrylic acid ester representation m. %) contents (g) n-butyl- 16.70 0.100 2 n-hexyl- 16.58 0.099 5 n-octyl- 16.45 0.098 7 n-dodecyl- 16.68 0.100 1 n-hexadecyl- 16.81 0.100 9 n-octadecyl- 16.78 0.100 7

Example 3 g of a technical sample of the additive was purified from monomeric and oligomeric components by dialysis with 2,000 ml of petroleum ether. A dialysis apparatus with a rubber membrane was used for purification, and dialysis was performed at the boiling point of the solvent continuously for 10 days.

0.6 g of the portion that passed through the membrane and contained a mixture of polymerized methacrylic acid esters was subjected to cleavage with hydroiodic acid at 180 for 1 hour after drying, as shown in Examples 1 and 2. The reaction mixture of the resulting alkyl iodides was analogously processed to 3,5-dinitrobenzoates, whose further analysis revealed the following composition of the ester components of the additive, expressed by the following results:

methacrylic acid ester representation (rel. %) content (g) n-butyl- 1.2 0.072 n-hexyl- 1.8 0.108 n-octyl- 15.1 0.906 n-dodecyl- 0.8 0.048 n-hexadecyl- 42.1 2,527 n-octadecyl- 39.0 2,340

Example 4 g of a technical sample of the additive, containing a mixture of polymerized or copolymerized methacrylate esters together with mineral oil and other substances, was cleaved in an ampoule of 1 ml of hydroiodic acid at 180 °C for 1 hour and the resulting alkyl iodides were converted to 3,5-dinitrobenzoates (examples 1 to 3) - After chromatographic analysis and densitometric evaluation, the results of the relative representation of individual ester components in the additive and their absolute values were obtained:

methacrylic acid ester representation (rel. %) contents -butyl- 0.51 0.032 n-hexyl- 0.83 0.048 n-octyl- 6.82 0.407 n-dodecyl- 0.20 0.021 n-hexadecyl- 18.99 1,137 n-octadecyl- 17.55 1,053

SUBJECT OF THE INVENTION

Claims (1)

SUBJECT OF THE INVENTION Method of qualitative analysis and determination of relative and absolute proportion of alkyl ester components of methacrylate additive for lubricating oils by digestion of additive sample with hydroiodic acid, subsequent reaction with Ag salt of 3,5-dinitrobenzoic acid, identification of formed alkyl dinitrobenzoates and is performed by thin layer chromatography on silica gel impregnated with 5% petrolatum oil in heptane with dimethylformamide-methanol-water mobile phase in a ratio of 2 to 8: 1: 1 using the Yanovsky detection reaction.