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ХИМИЧЕСКИЕ НАУКИ
Mamedyarov M.A.
Doctor of Chemical Sciences, academician Institute of Petrochemical Processes named Y.H.Mammadaliyev NAS of Azerbaijan
Gurbanov G.N.
Doctor of Chemical Sciences Institute of Petrochemical Processes named Y.H.Mammadaliyev NAS of Azerbaijan
Aliyeva F.Kh.
Doctor of Chemical Sciences Institute of Petrochemical Processes named Y.H.Mammadaliyev NAS of Azerbaijan
Мамедьяров Магеррам Али оглы доктор химических наук, академик
Институт Нефтехимических процессов им Ю.Г.Мамедалиева НАН Азербайджана
Гурбанов Гусейн Намаз оглы доктор химических наук
Институт Нефтехимических процессов им Ю.Г.Мамедалиева НАН Азербайджана
Алиева Фатмаханым Хейбар кызы доктор химических наук
Институт Нефтехимических процессов им Ю.Г.Мамедалиева НАН Азербайджана
ESTHERS OF CYCLIC POLYOLS - THE BASIS OF SYNTHETIC LUBRICANT OILS СЛОЖНЫЕ ЭФИРЫ ЦИКЛИЧЕСКИХ ПОЛИОЛОВ - ОСНОВА СИНТЕТИЧЕСКИХ
СМАЗОЧНЫХ МАСЕЛ
Summary: In the review the results of researches on synthesis of new types of radio synthetic lubricants are represented on the basis of cyclic polyols. Identified by their physical and chemical and operational characteristics. Structural correlation of the obtained compounds has been conducted. A number of regularities between chemical structure and viscosity-temperature, thermal-oxidative, lubricating properties have been revealed. Defining the scope of the synthesized compounds.
Key words: cyclic polyols, synthetic lubricant oils, structural correlation, viscosity-temperature revealed.
Аннотация: Представлены результаты исследований по синтезу новых типов эфирных синтетических смазочных материалов на основе циклических полиолов. Определены их физико-химические и эксплуатационные характеристики. Проведена структурная корреляция полученных соединений. Выявлен ряд закономерностей между химической структурой и вязкостно-температурными, термоокислительными и смазывающими свойствами. Определены области применения синтезированных соединений.
Ключевые слова: циклические полиолы, синтетические смазочные масла, структурная корреляция, вязкостно-температурные свойства.
Intensive development of techniques, creation of new types of powerful engines, complex machines, mechanisms and devices is accompanied by strengthening of requirements to lubricants. Traditional petroleum oils frequently appear to be unsuitable and instead of them synthetic lubricant oils, including ester type with considerably better operational properties [1-2] are widely applied.
One of determining factors of radio lubricant oils - thermal and thermal oxidative stabilization - is appreciably defined by spatial structure of acid or alcohol rests. In particular, ethers with quaternary atom of carbon molecule being in P-position in relation to car-bonyl or hydroxyl group of alcohol, appeared thermally more stable, than usual ethers. The explanation has been given for this, so-called, p-hydrogen effect [3-4].
Therefore, at present from a large number of the investigated synthetic compounds of ester type the multinuclear alcohol esters without hydrogen atoms in P-position in relation to hydroxyl groups being the most suitable lubricants for aviation techniques are also widely used as a basis and components of synthetic lubricants, along with esters of two-basic car-
boxylic acids. Basically so- called neo polyol - penta erythrite, trimethylolpropane and neopenthylglycol, esters of which have good viscosity properties, high enough stabilization, good low-temperature, lubricant properties are attributed to them [5-8]. Though, they rather easily are oxidized at temperature above 1000C, but combined with selected antioxidizing additives they can be used at 175-2000C. However, toughening of operation modes of modern techniques, in particular, in wide temperatures ranges (from-60 up to +3000C and higher), at high and ultrahigh loads, at very big rate of rubbed details, shows to lubricants increased requirements [9-11]. The task of creation of the lubricants meeting these requirements, appeared rather complex. Therefore, researches in the field of synthesis of new esters with neoalkyl fragments and creation of compositions on their basis are rather actual big ,scientific and practical value.
The purpose of given article is synthesis of structural analogues of pentaerythrite ethers for increase in assortment of high-quality bases of synthetic oils and research of their viscosity - temperature and some
operational properties depending on their chemical structure.
With the purpose of obtaining of high-quality lubricants meeting the requirements of modern and perspective techniques, since 80th years under the guidance of academician Mamedyarov M.A. basic researches on synthesis of new ester bases and components of lubricant oils have been carried out on the basis of cyclic neopolyols, in particular, 2.2.5.5-tetramethylolcyclopentanol (TMCP) and 2.2.6.6-tetramethylolcyclohexanol (TMCH).
Proceeding from the analysis of literary data and theoretical assumptions of interrelation between chemical structure and operational properties, it is not casu-
X
rocoh2c rocoh2c
where X= -OH or -OCOR
CH2OCOR
ch2ocor
al that cyclic neopolyols have been selected as the objects. As substantiation for selection of the given objects was the natural fact that ethers of cyclic neo-polyols should possess higher thermal and thermal-oxidative characteristics, high flash temperature and viscosity index, best lubricating properties as compared with aliphatic neopolyols since they have two carbon atoms in molecule, have no p-hydrogen, and stable cycle (temperature of disintegration of a cycle 550-600°C) and more than two polar ester groups.
With the purpose of obtaining of analogues of pentaeritrite synthetic oils esters TMCH [12] and TMCP [13] have been synthesized and investigated.
X
ROCOH2C
rocoh2c
ch2ocor ch2ocor
For the reason TMCH and TMCP contain in four gem- methylol groups and spatially - complicated hy-droxyl group as well as stable cyclohexane and cyclo-pentane ring in molecule, it should be expected that their ethers should possess complex of properties essential for lubricants.
Initial cyclic neo alcohols- TMCH and TMCP have been synthesized by using known technique. Condensation of cyclic ketones - cyclopentanone and cyclohexanone with formaldehyde is carried out in the presence of alkalis, in particular calcium oxide. However, the process is not always reproduced using this technique and the yield of alcohols does not exceed 50-55 %. As a result of the researches conducted by us an influence of various factors (catalyst quantity, their Table 1 Viscosity-temperature properties of TMCH esters
X
rocoh2c rocoh2c
kinds, the order of their addition, influence of pH mediums, temperatures and mole ratio of ketones: formaldehyde: catalyst, etc.) on the yield of cyclic alcohols has been investigated in details and optimum conditions, which allow to conduct process of condensation selectively with the yield to 80 % [12] have been developed.
TMCP and TMCH esters represent a colorless oily liquid with high boiling point (for ethers TMCP -180-280°C/l mm m, and for ethers TMCH - 200-350°C/lmm m).
Viscosity-temperature properties of TMCH ethers with aliphatic monocarboxylic acids C3-C8 are given in tab. 1, and TMCP esters - in tab. 2.
ch2ocor ch2ocor
R X Viscosity, mm2/s Temperature, °C Viscosity index
100°C 50°C 0°C -30°C Temp. of hard Flash point
C3H7 OH 6.76 29.41 646 29864 -40 256 105
C3H7 OCOC3H7 10.12 43.36 812 - -40 265 117
C4H9 OH 7.17 30.76 610 26735 -42 236 113
C4H9 OCOC4H9 10.08 44.86 717 - -40 256 120
C5H11 OH 6.89 28.61 563 27351 -50 242 115
C5H11 OCOC5H11 10.19 45.16 866 - -46 276 123
C6H13 OH 7.18 29.81 587 28502 -48 258 120
C6H13 OCOC6H13 10.21 45.28 872 - -40 282 123
C7H15 OH 7.67 34.05 675 23389 -48 265 111
C7H15 OCOC7H15 10.32 45.73 877 - -46 289 112
C8H17 OH 8.11 36.83 759 23589 -48 273 110
C8H17 OCOC8H17 10.44 46.26 877 - -36 300 122
SFAC5-C6 OCOSFAC5-C6 7.04 29.50 - 27350 -42 240 117
PET and 4.50 14.90 - 9260* -60 246 125
SFA C5-C9
* at-40°C
Ul
Comparison of properties of TMCP esters with properties of corresponding TMCH esters shows that the first ones are characterized by lower solidification temperature and higher flash temperature. In all ethers of cyclic neopolyols with increase in length of acid radical viscosity increases at positive temperatures. In the negative range of temperatures there appreciable distinction viscosity values is not observed. Viscosity at 100 and 50°C from acids of isometric structure is much higher than the ethers, than those of obtained Table 2 Viscosity-temperature properties of TMCP esters
from acids of normal structure. Tetraethers, as a rule, possess lower viscosity values, than corresponding pentaether. Thermal-oxidative stabilization (TOC) of cyclic neopolyols esters (tab. 3, 4) has been investigated.
For all investigated TMCH and TMCP ethers absence of deposits, in isooctanes both benzene and absence of corrosion on plates from aluminum AK-4, insignificant corrosion on plates LUX-15 is observed.
x
rocoh2c rocoh2c
,ch2ocor "ch2ocor
R X Viscosity, mm2/s Temperature, °C Viscosity index
100°C -50°C 0°C -30°C Temp. of hard Flash point
C3H7 OH 7.23 32.8 590 75512 -54 270 101
C3H7 OCOC3H7 8.02 41.4 848 76486 -54 272 81
C4H9 OH 7.63 35.40 573 77689 -54 283 102
C4H9 OCOC4H9 8.28 42.56 886 79071 -52 296 88
iso-C4H9 OH 8.31 40.4 326 28764 -56 279 99
iso-C4H9 OCOC4H9 9.65 53.3 481 29005 -56 286 95
C5H11 OH 6.98 22.4 310 24627 -54 284 181
C5H11 OCOC5H11 7.80 33.2 442 29641 -54 286 122
C6H13 OH 7.25 28.90 413 26200 -52 290 125
C6H13 OCOC6H13 8.31 33.26 461 28700 -50 295 130
C7H15 OH 7.72 29.80 428 27690 -50 293 133
C7H15 OCOC7H15 8.91 34.70 472 30042 -48 308 135
C8H17 OH 7.88 38.21 436 28021 -50 295 126
C8H17 OCOC8H17 9.12 39.04 491 33068 -46 312 124
SFA C5-C9 OCOSFA C5-C6 7.56 31.07 360 27400 -62 264 121
The increments of viscosity of ethers revealed small degree after oxidation, low acid number and small volatility, prove high thermal thermal-oxidative stabilization of the obtained cyclic complex ethers once again. At comparison of TOC ethers with ethers having acid radicals in the structure, insignificant deterioration of these properties in comparison with ethers having acid radicals of normal structure is observed. It speaks that at oxidation of ethers at high temperature, the molecules with isostructure, are ex-
posed to oxidation, further, to decomposition with formation of easy products more easily.
As it is obvious from tab. 3, 4, the length of acid radicals of ethers does not exert essential influence on their thermal-oxidative stabilization. Pentaethers of cyclic neopolyols exceed pentaerithrite ethers on all parameters (tab. 3). As for TOC of TMCH and TMCP tetraethers, they concede pentaethers and are at a level of the pentaerithrite ether and and synthetic fatty acid (SFA C5 - C9) [13, 14].
u
Table 3.
Results of tests thermal-oxidative stabilization of some TMCH esters in accordance with GOST 23797-79
X
ROCOH2C ^J^.CH2OCOR
rocoh2c ^ch2ocor
R X Viscosity at 100°C after oxidation, mm2/s Increment of viscosity, % Acid number, mgKOH/g Corrosion, mg/sm2 Volatility, mas. %
C3H7 OH 7.66 13.31 1.80 no 0.28 0.5
C3H7 OCOC3H7 11.90 17.58 0.86 no no 0.1
C4H9 OH 8.46 18.0 2.10 no 0.15 0.9
C4H9 OCOC4H9 11.86 17.66 1.30 no no 0.4
C5H11 OH 8.20 19.0 0.10 no 0.12 0.9
C5H11 OCOC5H11 11.20 9.90 0.60 no no 0.6
C6H13 OH 8.73 13.3 0.91 no 0.21 0.5
C6H13 OCOC6H13 11.48 12.4 0.56 no no 0.3
C7H15 OH 8.81 14.8 0.86 no 0.19 0.7
C7H15 OCOC7H15 11.63 11.4 0.63 no no 0.2
SFA C5-C6 OCOSFAC5-C6 8.21 16.61 0.9 no no 0.9
PET and SFA 6.07 34.90 1.89 0.110 1.790 1.20
C5-C9
Table 4.
Thermal-oxidative stabilization of some TMCP esters
R X Viscosity at )0°C after oxidation, mm2/s - s ' > 0 S ii bm /H 0 ^ Loss of mass under corrosion, mg/sm2 in s, I % t+H '.{3 O
a 0 w 0 r g T3 sg AK-4 mx-15 tyi O s ° z hJ 0 0
C4H9 OH 8.89 16.71 1.93 0.18 0.15 0.05
C4H9 OCOC4H9 9.17 10.73 0.96 0.11 no 0.02
Iso-C4H9 OH 9.87 18.78 2.111 0.14 0.11 0.03
Iso-C4H9 OCOC4H9 10.82 12.12 2.0 0.08 no no
C5H11 OH 8.08 15.07 2.08 0.09 no 0.07
C5H11 OCOC5H11 8.64 10.17 1.0 0.11 no 0.01
C6H13 OH 8.43 16.5 1.8 0.16 0.13 0.3
C6H13 OCOC6H13 9.56 15.2 1.2 0.10 no no
SFAC5-C6 OCOSFA C5-C6 8.30 9.60 1.50 no no 0.5
TOC of the cyclic polyols ethers is affected by nature and alcohol cyclic fragment ethers containing five-term ring, exceed ethers with cyclohexane ring on thermal-oxidative stabilization.
It is known that presence of hydroxyl groups in polyethers that, in particular, in ethers of pen-taerithrite, negatively influences their thermal-oxidative stabilization [15]. Free hydroxyl group of TMCH and TMCP tetraethers is located directly in a nucleus and is shielded by next ester groups. In addition, at studying influence of hydroxyl number on stabilization of cyclic neo polyols ethers it appeared
that all synthesized tetraethers on TOC concede pen-taethers (tab. 3-4).
On compensatory - manometrical installation at 1000C TOC of tetra- and pentacaproates of TMCH, TMCH tetraisovaleriate and incomplete pentaeritrite ethers SOA of fr. C5 - C6, hydroxyl numbers have been investigated. Thermal-oxidative stabilization of samples has been estimated using two kinetic parameters: the maximal oxidation rate and time of its attainment:
LIB
Vmax, mol (Î/S) тvmax, h.
Tetra caproate TMCH 12.10 1.13
Pentacaproate TMCH 13.63 1.33
Tetraisovaleriate TMCH 14.67 0.20
Pentaerithrite ether
Laboratory:
Commodity:
brand 1/3 13.49 1.24
brand 3/3 12.55 1.19
As it is obvious from obtained data all ethers at 160°C have approximately the same maximal oxidation rate as pentaerithrite commodity ether. TMCH tetracaproate concedes pentacaproate on time of attainment of maximal oxidation rate and is at a level of pentaerithrite commodity ether of 3/3 brand.
Incomplete pentaerithrite ethers with various hy-droxyl numbers sharply concede to commodity samples. Thus, it has been established that presence of free hydroxyl groups at TMCH tetraether and incomplete pentaerithrite ethers is inadequate which indicates the shielded position of hydroxyl groups at TMCH tetrae-ther. The ethers with acid radicals of isometric structure, on time of achievement of the maximal oxidation rate concede to ethers with acid radicals of normal
CH2OH -CH2OH
(CH2),
where R= C5 - C9 ; n=0, 1
/
.1
V
-OH
Ol
X-R
-CH2OH
ch,OH
Cl
structure by six times. This fact once again proves ease of oxidability of acid radicals of isometric structure as compared with normal structures. So, it has been established that the nature of acid radical renders rather appreciable influence on thermal-oxidative stabilization of cyclic neopolyols ethers [16].
On the basis of cyclic neopolyols - TMCH and TMCP and acids C5-C9 of neo structure a number of new esters has been synthesized. As it is known, neo acids due to the shielding of carboxylic groups by neighbor alkyl radicals are hardly esterifies with alcohols in conditions esterification of aliphatic monocar-boxylic acids of normal structure. Therefore, at obtaining of ethers neoacids chloranhydrides are used:
Ph
HCl
(CH2)
a
(CH2OCOR)2
OCOR
(CH2OCOR)2
The synthesized ethers due to high thermal-oxidative stabilization, high viscosity level, flash point and the best lubricating properties in comparison with aliphatic neopolyols allow to apply them as oils to clockworks and precision time instruments operating in extreme conditions: under water and in the temperature range from -30 to 250°C [17].
As it is known [1, 2, 8], lubricating properties of lubricant oils are directly connected to chemical struc-
ture of the molecule of ethers. First of all presence of the polar centers as well as spatial conformation molecules exert good influence on lubricating properties.
To study correlation between chemical structure and lubricating ability of some TMCH and TMCP ethers their lubricating properties by the four-ball friction tester (FBT) in accordance with GOST 9490-75 have been determined and the data are given in tab. 5.
Lubricating properties of cyclic polyols ethers
Table 5
№ Name of ether Critical load, Pk, H Wear parameter, Dee, mm
1. TMCH tetracaproate 710 0.78
2. TMCH pentacaproate 670 0.80
3. TMCH and SFA C5 - C6 ethers 690 0.75
4. Diphenoxy-2.2.6.6-tetraalkylcarbonyloxymethylenecyclohexylphosphyte 720 0.73
Phenyldinolyloxy-2.2.6.6- tetraalkylcarbonyloxymethylenecyclohexyloxane
5. TMCP tetracaproate 680 0.72
TMCP pentacaproate
6. TMCP and SFA C5 - C6 ether 700 0.75
7. Diphenoxy-2.2.5.5-tetraalkylcarbonyloxymethylenecyclopentylphosphyte 650 0.76
8. Phenyldinolyloxy-2.2.6.6- tetraalkylcarbonyloxymethylenecyclopentyloxane 680 0.70
9. TMCP tetraisovaleriate 780 0.60
Pentaerithrite and SFA C5 - C9 ether
10. 740 0.65
11. 600 0.80
12. 500 0.79
+
у
As it is obvious from the table TMCH and TMCP tetracaproate possess the best antiwear and antiweld-ing properties, than pentaether corresponding to them. It indicates the presence of the first free hydroxyl groups in the molecule able to form stronger donor-acceptor bond with the rubed surfaces, thus representing the additional polar center that improves antiwear properties of tetraethers.
TMCH and TMCP ethers with SFA frac. Cs-Ce are almost on the same level with corresponding ethers of individual monocarboxylic acids.
From the table s data it is obvious that all synthesized ethers exceed ethers pentaerithrite on critical loading, and in some cases on parameter are at their level on wearingproperties, and in case of introduction of heteroatoms even exceed pentaerithrite ethers.
High lubricating ability of cyclic polyols ethers and their derivatives in comparison with pentaerithrite ethers is explained by their chemical structure, i.e. presence of plenty of polar groups, saturated to five and, hexamerous cyclic fragments in the structure.
CONCLUSIONS
1. New esters of cyclic neopolyols with aliphatic monocarboxylic acids C3 - Cs of normal and isometric structure have been obtained.
2. Physical and chemical, viscosity -temperature, thermal and thermal-oxidative properties as well as lubricating properties of the given compounds have been determined. Structural correlation between chemical structure and operational characteristic of these ethers has been made, a number of regularities enable to purposefully conduct experiment, has been revealed more selectively. Synthesized high-quality esters have been proposed as the bases and components to perspective lubricants.
3. Some of the obtained compounds are recommended as the dispersive medium of perspective high-temperature plastic lubricants, as the compressor oils operating in a special mode, as a component to aviation oils of temperatures operating in wide range, as a basis for oil cutting emulsion (CE) for processing metal by cutting, etc.
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12
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This work was supported by the Science Development Foundation under the President of the Republic of Azerbaijan - Grant №EIF-2014-9(24)-KETPL-14/05/4
