CA1070665A

CA1070665A - High viscosity neutral complex polyester lubricants

Info

Publication number: CA1070665A
Application number: CA265,571A
Authority: CA
Inventors: Karlheinz Koch; Willi Breitzke
Original assignee: Henkel AG and Co KGaA
Current assignee: Henkel AG and Co KGaA
Priority date: 1975-11-14
Filing date: 1976-11-12
Publication date: 1980-01-29
Also published as: DE2551173C2; IT1068006B; NL7611801A; JPS6366294A; JPS6221775B2; JPS5261674A; GB1541143A; DE2551173A1; JPS6340839B2

Abstract

ABSTRACT OF THE DISCLOSURE

A high viscosity neutral complex polyester lubricant reaction product produced by esterifying a mixture of (a) branched alkanepolyols having 2 to 4 primary hydroxyls and 4 to 10 carbon atoms, (b) polyacids selected from the group consisting of dimeric fatty acids and trimeric fatty acids derived by polymeri-zation of unsaturated fatty acids having 16 to 18 carbon atoms, (c) alkanoic acids having 6 to 16 carbon atoms, the acid number of said polyester being 0.3 or below and the hydroxyl number of said polyester being below 0.5, the pro-portion of hydroxyl groups esterified by said alkanoic acids being from 50% to 90%. The said complex polyester lubricant having a low pour point, a high viscosity and a high viscosity index.

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Description

-" ~o70665 Synthetic esters, the so-called ester oils, have beeA increasingly used in recent years as high-grade lubricat-ing oils. Thus, diesters of dicarboxylic acids with monovalent alcohols, such as dioctyl sebacate or dinonyl adipate, or esters of polyols with monocarboxylic acids, such as trimethylol propane tripelargonate, have been proposed as lubricants for ,~ :
aircraft turbines. In recent times, so-called complex esters have also been developed for lubricating problems of this type.
In addition to polyhydric alcohols, such as trimethylolpropane or neopentylglycol, these complex esters contain, as esterifi-cation components, monocarboxylic acids having 6 to 10 carbon atoms, and dicarboxylic acids, such as sebacic acid or azelaic acid. The suitability of the synthetic esters as lubricants results from the fact that they have a more favorable viscosity/
temperature behavior than conventional lubricants based on mineral oils, and that upon adjusting to com arable viscosities, the pour points are distinctly lower. However, for many ranges of application, for example, for the new multigrade transmission oil class 80 W-90 (see U.S. Military Specifica-tion Mil-L-2105 C), which requires highly viscous transmission oils having viscoxity values of at least 14 cSt at 210F and a maximum of 150,000 cP at -15F, the known synthetic esters are unsuitable owing to their limited viscosity properties. -On the oth~r hand, however, lubricating oils based on mineral oils, and which have adequate viscosity properties can only be manufactured by adding polymers, such as a styrene/
butadiene copolymer (German Auslegeschrift No. 1,811,516).
When adding copolymers to increase the viscosity of transmis-sion oils, one disadvantage is the shearing sensitivity of the polymers. As a result of shearing, i.e., by irreversible ~ .

fracture of the polymers, considerable reductions in the viscosity of the corresponding oils occur.
An ob~ect of the present inven-tion is the develop-ment of a synthet.ic ester oil which, in addition to having a low pour point, has a high viscosity and a satisfactory viscosity/temperature behavior (high viscosity index).
Another object of the present inven,ion is the development of a high viscosity neutral complex polyester lubricant produced by esterifying a mixture of (a) a branched alkanepolyol having 2 to 4 prir.. ary hydroxyls and 4 to 10 carbon atoms, (b) polyacids selected from the group consisting of dimeric fatty acids and trimeric fatty acids produced by the dimerization of unsaturated fatty acids having 16 to 18 carbon atoms, and (c) alkanoic acids having 6 to 16 carbon atoms, in such proportions that the acid numb~r of said polyester is ,;
0.3 or below, the hydroxyl number of said polyester is 0.5 or below, and the proportion of said hydroxyl groups being ester-ified by said alkanoic acid is from 50~ to 90~.
These and other objects of the invention will become more apparent as the description thereof proceeds.
The present invention relates to novel, highly viscous neutral complex esters of polyols wlth polymeric fatty acids and aliphatic monocarboxylic acids, and their use in ; ~ lubricating oils.
More particularly, we have now discovered that the requirements of a high viscosity lubricant with a low pour point have been met, to an extent not hitherto attained, by novel, neutral complex esters derived from:

:; ` 1070665 (a) polyvalene, branched, aliphatic alcohols having 2 to 4 primary hydroxy groups and 4 to 10 carbon atoms, (b) dimeric and/or trimeric fatty acids produced by polymerization of unsaturated fatty acids having 16 to 18 carbon atoms, and (c) saturated 4traight chain or branched chain, aliphatic mono-carboxylic acids having 6 to 16 carbon atoms, the proportion of the hydroxy groups esterified by monocarboxylic acits being 50% to 90%.
Our invention is, therefore, a high viscosity neutral complex polyester lubricant produced by esterifying a mixture of ~ (a) a branched alkanepolyol having 2 to 4 primary hydroxyls and .: 4 to lO carbon atoms, (b) polyacids produced by the dimerization and trimerization of unsaturated fatty acids having 16 to 18 carbon .
atoms, wherein said polyacids are a mixture containing at least 75% of dimeric fatty acids, and (c) alkanoic acids having 6 to 16 carbon atom~ selected from the group consisting of (1) mixtures of saturated fatty acids having 6 to 12 carbon atoms, and (2) alkanoic acids having 12 to 16 carbon atoms and having a branched chain in the a-position to the carboxyl group, in such proportions that the acid number of said polyester is 0.3 or below, the hydroxyl number of said polyester is 0.5 or below, and the proportion of said hydroxyl groups being esterified by said alkanoic acid i8 from 50% to 90%.
The alcoholic component forming the basis of the highly viscous, neutral complex esters in accordance with the present invention can be any branched, aliphatlc polyol having 2 to 4 primary hydroxy groups and 4 to 10 carbon atoms, more particularly a branched alkanepolyol having 2 to 4 primary hydroxyls and 4 to 10 carbon atoms, such as neopentyl glycol, trimethyl-olethane, trimethylolpropane or pentaerythritol. The trihydric :
alcohol trimethlolpropane is particularly important.

The polycarboxylic acid component is a mixture of 3- :
~, :
, ' : . .: ' ' '' , --` 1070665 polyacids selected from the group consisting of dimeric fatty acids and trimerlc fatty acids produced by the dimerlzation of unsaturated fatty acids having 16 to 18 carbon atoms. The mixtures of dimeric and trimeric fatty acids produced by dimerization of olefinically-unsaturated fatty acids having 16 to 18 carbon atoms are preferred as the polymeric fatty acids, and those wherein the mixtures have a content of 75% by weight, and in excess thereof, -of dimeric fatty acids are preferred. Such mixtures of polymeric fatty acids are obtained, for example, by thermal polymerization of olefinically-unsaturated fatty acids, such as oleic acid, ~ linoleic acid or linolenic acid or fatty acid mixtures having a ; content of olefinically-unsaturated fatty acids, such as the fatty acids obtained from soybean oil or tall oil, at temperatures of approximately 200C to 300C in the presence of small quantities of water and a mineral catalyst such as montmorillonite.

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The monocarboxylic acid component of the neutral complex esters in accordance with the present invention may comprise a wide variety of saturated, straight chain or branched chain, aliphatic monocarboxylic acids or alkanoic acids having 6 to 16 carbon atoms. By way of example, fatty acids, such as capronic acid, caprylic acid, capric acid, lauric - acid, myristic acid or palmitic acid and mixtures thereof, are suitable. Preference is given to mixtures of saturated fatty acids having 6 to 12 carbon atoms, which, for example, are produced as pre-run fatty acids during the distillation of coconut fatty acids.
Branched chain monocarboxylic acids which have proved to be particularly advantaveous are the alkanoic acids, havi~g 12 to 16 carbon atoms, branched in the ~-position to the carboxyl group. Carboxylic acids of this type can be produced by, for example, Guerbetizi~g of medium chain length, -unbranched, saturated alcohols and subsequent oxidation of the alcohols which are obtained. These acids are branched in the second position and have a corresponding total number of carbon atoms. An isopalmitic acid manufactured in this manner by oxidation of 2-hexyldecanol was preferred as the monocar-boxylic acid component in the complex esters in accordance with the present invention.
The complex esters, in accordance with the present invention, of branched alkanepolyols having 2 to 4 primary hydroxy groups, polymeric, substantially dimeric, fatty acids and saturated, straight chain or branched chain alkanoic acids can be produced in accordance with known esterification pro-cesses by heating the reactants (to 200C in a nitrogen atmosphere) in the presence of an esterification catalyst such '.

.. . . . ..

as powdered tin, p-toluene sulfonic acid or others, while removing the water formed. Alternatively, esterification can be effected in two stages, the alcoholic component being reacted with dimeric fatty acids in the first step and being - further esterified with the monocarboxylic acid after partial reaction has been completed. Preferably a slight excess of the alkanoic acid is employed. For the purpose of purifying the product of esterification, the latter may be treated with ; an additive of l~to 5% by weight of activated bleaching clay.
Any free monocarboxylic acid which is still present can be removed by distillation, so that complex esters are produced whose acid numbers lie below 0.3 and whose hydroxyl numbers æe below 0.5 Owing to their excellent properties, namely, their high viscosity, their low pour point and their favorable viscosity/temperature behavior, the neutral complex esters in accordance with the present invention are eminently suitably for use as lubricants, particularly for transmission fluid and lubricants for two-stroke piston engines.
The complex esters in accordance with the present invention may constitute the sole oil base in the finished lubricant, or they may be mixed as a mixture component with other products which are already known for this purpose. When used as mixing components in lubricant and transmission oils, any optional quantity ratios may be mixed which are deter-mined exclusively by the required properties such as viscosity pour point, and viscosity/temperature behavior. Ho~ever, the content of complex esters will not usually be below 10%, and preferably not below 30%, by weight in the finished product.
Various additives such as oxidation and corrosion inhibitors, -~ 1070665 dispersing agents, high pressure additives, anti-foaming agents, metal deactivators and other additives suitable for use in lubricant formulations based on synthetic esters, can be added in conventional effective quantities.
The following examples are intended to further illustrate the present invention, but wlthout limiting the invention thereof.

EXA~LE 1 Production of the Neutral Complex ~sters 268 gm (2 mols) of trimethylolpropane, 565 gm (approx-imately 1 mol) of dimeric fatty acid (a mixture of approxlmately -95~ by weight of dimerize.d fatty acids, approximately 4% by weight of trimerized fatty acids, and approximately 1~ by weight of non-polymerized unsaturated fatty acids, the start-ing unsaturated fatty acid being a mixture of olefinically unsaturated fatty acids having 16 to 18 carbon atoms), and 632 gm (approximately 4 mols) of C6 to C12 saturated fatty acids (a mixture of approximately 5~ by weight of C6 fatty acids, approximately 45~ ~y weight of C8 fatty acids, approxi-mately 45% by weight of C10 fatty acids, and approximately 5% by weight of C12 fatty acids as obtained from the distilla-tion of coconut fatty acid), were heated to 200C in an auto-clave provided with a water separator under passage of nitro-gen, the nitrogen acting as a carrier gas to flush out the water ofreaction. A mixture of powdered tin 1.5 gm and p-toluene sulfonic acid 1.5 gm was used as an esterification catalyst.
~owards the end of the reaction, further esterification was carried out at the same temperature, but under reduced pressure (approximately 70 torr). After cooling to 120C, 1.5 gm (approximately 1~ by weight) of .' ~ .

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activated bleaching clay were added and the mixture was again :
; heated to 200C and the surplus monocarboxylic acid was dis-tilled off in vacuo. The acid number of the product A of esterification (the proportion esterified with monocarboxylic . acid was 67%) was 0.28. The product had a viscosity of 6~8 . cSt at 37.8C = (100F), and 57 cSt at 99C = (210F). The viscosity index was 164 and the pour point was -38C.
The complex esters given in the following Table I
were produced in conformity with the above method.

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~070665 .:
EXA~IPLE 8 :: USE
: Ageing tests at high temperatures were carried out with a lubricating oil manufactured on the basis of the com-plex esters in accordance with the present invention, and with a commercially available lubricating oil. In addition, the compatibility of those oils with various seal materials also was tested. A commercially available single grade oil of the class SAE 80 and a multi-grade oil, in accordance with the present invention of the specification SAE 80 W-90 were used - in the tests. The composition of the oil in accordance with the present invention was as follows:
93.5~ by weight of Product D of Example 4 (complex ester of 1 mol of trimethylolpropane, 0.3 mol of dimeric - fatty acid [75%] and 2.4 mol of C6-C12 pre-run ' fatty acid), 6.5~ by weight of a commercially available transmi~sion ,- oil,additive (ANGLAMOL 99 Or Lubrizol?.

The characteristic data of the oil in acc~dance with the present invention given in Table II show that the .' additive used did not contain any agent for lowering the pour point and any V.I. improver.

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. . . .. . .. . . . . . . . .

1~75)665 T A B L E I I
CHARACTERISTIC DATA OF THE
LUBRICATING OILS TESTED
.
,.
CharacteristicIn Accordance Commercially ValueWith InventionAvailable .
~in. viscosity at 37.8C 147 cSt115.4 cSt 7i Kin. viscosity at 98.9C 18 cSt 11.5 cSt ~yn. viscosity at -26.1C 25,000 cPs o 1 i d Viscosity index 146 94 Pour point -41C -l9CC
Acid number 0.4 2.8 . .
: , .
a) Aging Tests The lubricating oils to be tested were heated to ; 160C and 200C, respectively, for eight hours in a glass flask, a quantity of air being conducted through the flask dur-ing this period of time at a rate of 10 liters per hour. The changes in the viscosities and acid numbers were determined from the samples aged at 200C.

In AccordanceCommercially with InventionAvailable Change in viscosity at 99C (210F)+ 33.2 ~ 52.7 in percent Increase in acid number 1.3 3.4 The lubricant in accordance with the present inven-tion exhibited a substantially smaller degree of aging than the commercially available product.

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::~ 10706~;5 ..
The bearing capacities of the products aged at 160C were determined on a frictional wear balance according to Reichert. The wear was determined under a load of 1500 kp/mm2 during friction of steel on steel (length of slide path 100 mm).

In AccordanceCommercially With Invention Available Bearing capacity of ~ the aged sample1,250 750 ,,. 10 (kg/cm2) '.' b) Swelling Behavior of Seal Materials , `~ In accordance with the regulations laid down by DIN 53,521, various seal materials were immersed for 70 hours in the lubricating oils which were to be tested and which had been heated to 100C. The increase in weight of the seal materials was subsequently determined.

Increase in Weight After Swelling in Percent In Accordance Commercially Seal Material With Invention Available Rubber ~NBR 61679) 11.7 15.5 Silicone 10.7 13.2 The lubricating oils, in accordance with the present invention based on complex esters also gave better results in this test and, with the seal materials tested, lead to less swelling than is the case with known commercially available oils.

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1~70665 The preceding specific embodiments are illustrative of the practice of the invention. It is to be understood, however, that other expedients known to those skilled in the ~` art, or disclosed herein, may be employed without departing .. from the spirit of the invention or the scope of the appended claims.

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Claims

The embodiments of the invention in which an exclu-sive property or privilege is claimed are defined as follows:

1. A high viscosity neutral complex polyester lubricant produced by esterifying a mixture of (a) a branched alkanepolyol having 2 to 4 primary hydroxyls and 4 to 10 carbon atoms, (b) polyacids produced by the dimerization and trimerization of unsaturated fatty acids having 16 to 18 carbon atoms, wherein said polyacids are a mixture containing at least 75% of dimeric fatty acids, and (c) alkanoic acids having 6 to 16 carbon atoms selected from the group consisting of (1) mixtures of saturated fatty acids having 6 to 12 carbon atoms, and (2) alkanoic acids having 12 to 16 carbon atoms and having a branched chain in the a position to the carboxyl group, in such proportions that the acid number of said polyester is 0.3 or below, the hydroxyl number of said polyester is 0.5 or below, and the proportion of said hydroxyl groups being esterified by said alkanoic acid is from 50% to 90%.

2. The complex polyester lubricant of Claim 1 wherein said branched alkanepolyol is a member selected from the group consisting of neopentyl glycol, trimethylolethane, trimethylolpropane and pentaerythritol.

3. The complex polyester lubricant of Claim 1 wherein said branched alkanepolyol is trimethylolpropane.

4. The complex polyester lubricant of Claim 1 wherein said alkanoic acid is a mixture of saturated fatty acids having 6 to 16 carbon atoms obtained as a first cut from the distillation of a coconut fatty acid.

5. The complex polyester lubricant of Claim 1 wherein said alkanoic acid is isopalmitic acid obtained by oxidation of 2-hexyl-decanol obtained by Guerbet synthesis of octanol.

6. In the process of lubricating comprising the step of interposing a layer of a lubricant between moving solid parts, the improvement consisting of using the complex polyester lubricant of Claim 1, as said lubricant.

7. A lubricant composition comprising at least 10% by weight of the complex polyester lubricant of Claim 1.

8. The complex polyester lubricant of Claim 1 having a viscosity of 37.8°C of from 113 to 896 centiStokes, a Viscosity Index of from 146 to 170, and a pour point of from -59°C to -20°.C.