DE2339065A1 - SYNTHETIC ESTER LUBRICANT - Google Patents

Description

The use of aliphatic diester and complex esters as synthetic lubricating oils has because of the excellent viscosity properties of these compositions over a wide range of temperatures found widespread use. In certain applications where severe working conditions are concerned, is However, the load-bearing capacity of these synthetic lubricants is insufficient ^ to provide adequate lubrication without the use of additional chemical agents for

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Reduction of friction and the amount of wear to be considered * These additives, known as high pressure agents, generally consist of sulfur, chlorine, phosphorus or lead compounds that react on the surfaces of the metal to create lubricating films that are capable are able to withstand very high working temperatures. While these additives are effective in increasing the load-bearing capacity of the lubricant system, they also create corrosion, dirt, and tear problems, particularly in systems that employ copper, magnesium, aluminum, silver, and other metals. In some cases the corrosion is so serious that it is desirable to reduce the unit load, to improve the surface finish to increase the ül- ♦ viscosity to sit outside under pressure to apply and to take similar measures, rather than a high-pressure additive the lubricant to incorporate.

It would be desirable and very beneficial if the load bearing capacity of synthetic ester lubricants was η Without the addition of sulfur, chlorine, phosphorus and lead-containing compounds increases and so the corrosion and

other problems usually to be considered with these extreme pressure media are minimized or could be turned off completely. It would be particularly useful if extreme pressure additives would be available that could easily be made and those with synthetic ester lubricating oils would work well would be compatible.

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Non-corrosive and low-sludge-forming extreme pressure additives have now been found which can be used for synthetic ester-accepting agents and which improve the load-bearing capacity of the oils. The useful additives according to the invention are hydroxy ester compounds which contain at least one free carboxyl group and a radical which starant from the reaction of a carboxyl group with a glycidyl ester. The glycidyl esters are derived from aliphatic acids with 5 to 22 carbon atoms. Glycidyl esters derived from neo-acids are particularly useful. Preferred hydroxy ester compositions are half esters obtained from the reaction of about 0.45 to 0.55 equivalents of a glycidyl ester derived from a neo acid with a dinic acid which preferably contains 75% by weight or more dibasic C _{3 β} acid . The useful extreme pressure additives are added to synthetic ester formulations including diesters, polyesters and complex esters in amounts ranging from 0.05% to about 5% by weight of the total lubricant.

Contain the hydroxy ester compounds according to the invention at least one free carboxyl group in the molecule and at least one group of the structural formula

O OH O ti »» R-CO- Qi ₀ CHCH ₀ - OC-

in the molecule in which R is branched or straight chain Alky! Group with 4 to 21 carbon atoms. The rest of 1

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is made by reacting a carboxyl group with a Glycidyl ester of an aliphatic acid with 5 to 22 carbon atoms obtained.

Glycidyl esters, which are used to obtain the radical I, are typically formed by the reaction of epichlorohydrin and the alkali salt of the aliphatic Cj- ₂₂ acid and have the general formula

0 0

RC - 0 - CH ₇ - CH - CH, 2 ι

in which R has the same meaning as given above for I. Preferred glycidyl esters are branched chain Acids are derived and have the general formula

R ₁ O -O.

- C - CO - CtL CH - CH ₀ I 2 2

in which R _{1, R 2} and R _{3 are} alkyl groups with 1 to 4 carbon atoms, the total number of carbon atoms in the three groups being about 4 to 10 carbon atoms in total. While the glycidyl esters derived from the neo acids are preferred for the present invention are, glycyl esters of pelargonic acid, heptanoic acid, valeric acid, isostearic acid, oleic acid or the like can also expediently be used.

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Since the compositions according to the invention necessarily have a group of formula (I) and also a free one Contain carboxyl group, the acids used to prepare the hydroxyester compounds must necessarily be dibasic, i.e. contain at least two carboxyl groups. While two carboxyl groups are essential, in order to obtain the compound according to the invention, the acids can contain three, four or more carboxyl groups. In practice, however, with increasing numbers of carboxyl groups, which are present in the starting acid increases the complexity of the products and the extreme pressure properties the additives aren't that great. When dibasic acids are used, half-esters result. Independent of the number of carboxyl groups, the acid should have a molecular weight which is greater than about 480 and therefore must necessarily have at least 30 carbon atoms contain. Acids which meet the aforementioned requirements become useful through the polymerization from unsaturated monomeric fatty acids containing about 18 to 22 carbon atoms. These monomers Acids contain one or more sites of unsaturation and include such acids as oleic acid, linoleic acid, Eleostearic acid, ricinoleic acid, linolenic acid, or the like. Process for the formation of polymeric acids high molecular weight are disclosed, for example, in U.S. Patents 2,482,761; 2,793,219 and 2,793,220. By Varying the reaction conditions used in the polymerization can change the ratio of dimeric, trimeric and higher acids can be varied.

Dimer acids obtained ₃ if two molecules of monomeric acid combined v / ground are particularly suitable for the invention. These acids are commercially available and are called "Empol" dimers and trimers

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Acids sold (Manufacturer: Emery Industries, Inc.). The average number of carbon atoms in these products varies from about 36 to 54 carbon atoms. Preferred acids for the formation of the hydroxy ester additives according to the invention contain at least 75% by weight of dibasic C-jg acid, while the remainder of the acid composition comprises trimeric acid, ie tribasic C ₅ - acids and small amounts of tetraric or higher acids. Particularly useful acid additives contain 85% or more dibasic C 1-4 acids.

The hydroxy ester compounds used as extreme pressure agents useful according to the invention are made by the reaction of the glycidyl ester described above and more polybasic Acids obtained. This reaction is preferably carried out in the absence of a catalyst, but it can if desired, a catalyst can be used to accelerate the reaction rate. The reaction rates are generally sufficient that catalysts are not necessary without the use of Catalysts will also provide a purer reaction product and will also result in costly washing operations to remove the catalyst residues avoided. The reaction can be carried out over a wide temperature range however, since it is desirable from an economic point of view. to have a high reaction speed, Temperatures between about 15o and 25o ° C and preferably from 180 to 22o C are used. The response time is on the temperature and the particular reactants employed addicted. Usually, at a temperature of about 200 ° C, the reaction takes about 1 to 2 hours. The ratio of reactants will depend on the particular composition and number desired of carboxyl groups on the acid to be reacted with the glycidyl ester varies. The preferred dibasic

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C 1 -C acids can be, for example, about 0.3 to 0.7 equivalent Glycidyl ester per equivalent of dibasic acid is used get, while particularly useful compositions with about 0.45 to 0.55 equivalents of glycidyl ester can be obtained per equivalent of dibasic acid. The application of the latter range of respondents provides enough glycidyl functions for the reaction with approximately half of the carboxyl groups, see above that half esters are obtained. If acids that are more than contain two carboxyl functions are used, the equivalence ratio is varied accordingly, but in none If so, the glycidyl ester exceeds an amount calculated to have less than one free carboxyl group is delivered in the molecule. The compositions obtained can consist of a mixture of products, of some of which contain more or less than the desired degree of substitution, as long as the average composition meets the requirements defined above, i.e. at least one free carboxyl group and at least has a Type I group.

The amount of the hydroxy ester compound used can can be varied widely, but preferably these are extreme pressure additives in the synthetic lubricant in amounts of about 0.01% to about 5% by weight of the total schnapps available. Preferably the additives according to the invention are used in an amount in the range from about 0.1 to 1.5 percent by weight of the lubricant composition. With these quantities, the hydroxyls are sternly * High-pressure agents that are effective in bonds and improve the load-bearing capacity of the lubricant and also reduce metal corrosion and sludge formation in both petroleum abrasives as well as in synthetic ester lubricants

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lower edge. The additives according to the invention can be mixed with other materials commonly used in lubricant compositions be introduced, such as oxidation inhibitors, detergents, dyes, anti-foaming agents, Viscosity improvers, additional corrosion inhibitors, extreme pressure agents or the like are used reach. Compounds of the type mentioned above include p-aminodiphenylamine, phenyl - χ-naphthylamine, phenothiazine, Polymethyl acrylates, silicon-containing polymers, Polyisobutylenes, petroleum sulfonates, sorbitan monooleate, the Barium salt of isononyl phenol sulfide or the like. Usually these additional ingredients constitute about 0.1 to 10% by weight of the total lubricant composition represent.

Lubricants for which the hydroxyester compounds In accordance with the invention useful additives are the synthetic ester lubricating oils, which diesters, polyesters and include complex esters. Diester lubricant oils are typical dicarboxylic acids that are completely monohydric Alcohols are esterified and the general formula

R ¹ OOC - (CIL) -COOR ¹ n.

in which η is an integer from 6 to 15 and R ^{1 is} a branched or straight-chain hydrocarbon radical with about 1 to 16 carbon atoms. Preferred diesters of the type mentioned above are derived from adipic acid, azelaic acid and sebacic acid with a branched chain C _g or C _q alcohol. Useful synthetic diester lubricants include di-2-ethylhexyl sebacate, di-2-ethylhexyl isose sebacate, di-n-nonyl adipate, di-n-heptyl isose sebacate, or the like. Diesters derived from the

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Oxo alcohols are produced which are mixtures of branched-chain, aliphatic primary alcohols _} which have been obtained by reacting olefin oligomers with carbon monoxide and hydrogen in the presence of a suitable catalyst with subsequent hydrogenation. Examples of such diesters are: di-Cg-oxoadipate, di-C, oxoadipate, di-Cg-oxoazelate, di-C_-oxoadipate, di-C, _3- oxo-pimelate, or the like. Diesters derived from the reaction of glycols fully esterified with monocarboxylic acids are also useful synthetic base lubricants for use with the extreme pressure additives of the invention.

Polyesters obtained from the reaction of polyhydric alcohols with monocarboxylic acids can also Applied as a synthetic oil · These include products made with trimethylolpropane and pentaerythritol Acids such as caproic acid, caprylic acid and pelargonic acid are derived and result in triesters and tetraesters, respectively. the polymeric forms of pentaerythritol can also be used to obtain synthetic polyester screw oils, Complex esters that are used as synthetic base oils are those that are produced, for example, by the esterification of a dicarboxylic acid with a glycol and a monofunctional alcohol or a monocarboxylic acid. In general, a wide variety of synthetic ester-based oils can be used get used and has improved load-bearing properties when a small amount of the high pressure agent according to is incorporated into the invention. The synthetic ester oils and processes for their preparation are known and in numerous ways Publications described «

The invention is illustrated below by way of examples explained in more detail. In these examples, all parts and percentages are by weight unless otherwise specified is specified. 409807/0892

example 1

An acid terminated hydroxy ester compound essentially of the formula

0 OH 0 ₁ JL ₁ -CO-CiLCi 1OL-OC-C ₄ H, _C001 ί

was obtained by reacting 1 mole (586 g) of a dibasic C ₃₆ acid with a molecular weight of approximately 565 (Empol lolo dimer acid) with one mole (245 g) of a glycidyl ester of a neo acid with an average molecular weight of about 245 (Cardura E. ) manufactured. The reaction was carried out at 22o C for half an hour under a nitrogen blanket »The final product had an acid number of 39, a hydroxyl number of 68, a flash point of 271 ° C (52o ° F) and a burn point of 332 ° C (63o ° F) .

Example 2

The half-ester prepared according to Example 1 was tested in a synthetic ester-based lubricant. The basic lubricant used was a mixture vpn about 93 parts of a Koraplexesters that derived from monopentaerythritol with a mixture of acids from about 5o% isovaleric acid, 25% pelargonic acid and 25% of a mixture of Cg to C _g -einbasisehen acids was esterified (Erofac 121o low molecular weight acid) and about 7 parts of a polyester made from the reaction product of 1 col

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Azelaic acid, 2 moles of monopentaerythritol, and 4 moles of one Mixture of monobasic Cg to C "acids (Emfaa I21o). The extreme pressure agents of Example 1 were used in the base lubricant incorporated in an amount of 0.5% and 1.0%, and the load-bearing capacity of the lubricating oils was increased to a Ryder gear machine according to (Federal Test Method Standard No. 791a, Method 65o8). The results are given in the table below. The values show it is apparent that by incorporating a small amount of the hydroxy ester compounds into synthetic ester lubricants significantly increases the load-bearing capacity of the lubricant will. It has also been observed that the lubricating oils thus composed have excellent oxidation stability, are resistant to sludge build-up and have an extremely low corrosion effect on copper, magnesium, iron, Have aluminum and lead. Similar results are obtained with other synthetic ester lubricants containing the hydroxy ester additive included ,, received.

It appears that it is completely unexpected that the hydroxy ester compounds will act as useful extreme pressure additives for synthetic ester lubricants _; if structurally similar additives are used, but which do not show any significant improvement in the extreme pressure properties. For example, a dibasic C ₃₆ acid was completely esterified with a mixture (5o: 5o) of methyl alcohol and 2-ethylhexyl alcohol and a half ester of the dibasic C _3g acid, prepared with methyl alcohol, and tested in synthetic ester base oils. No significant improvement in load carrying capacity was observed in any case, rather a substantial decrease in lubricity was observed with the full ester when the lubricant was subjected to the Ryder Gear Test.

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Tabel

Test Oil Rating Pounds Per Inch Reference Relative Rating Side A Side B "(Medium) (Medium)

. (psi)

Basic lubrication

medium 2540 2289 24-15 2920 82.7%

ο '

^ Basic

° medium with 0.5% N

• ^ Hydroxy ester additive 264-8 3102 2875 29A0 97.8% ^

S

^ Grundsciimier- '' V

medium with 1.0%
Hydroxy ester additive 2805 2872 2839 2920 97.2%

CO CO CD O

Claims (5)

Claims 1. Non-corrosive, low-sludge-forming synthetic ester lubricant, with improved extreme pressure properties, characterized in that it is a synthetic ester consisting of diesters, polyesters and complex esters and about o, ol to 5 wt .-% based on the total lubricant composition of a hydroxy ester compound which comprises at least one free carboxyl group and at least one group having the structural formula 0 OH 0 Il I. It R - CO - CH ₇ CtUL- -OC (D contains, in which R is a branched or straight-chain alkyl radical having 4 to 21 carbon atoms. 2. Synthetic ester lubricant according to claim 1, characterized in that the hydroxy ester compound is derived from a polybasic acid which is at least Contains 3o carbon atoms and has a molecular weight greater than about 48o and a glycidyl ester of the general formula RC - 0 - CH ₂ - ΟΙ - CH comprises, in which R is a branched or straight-chain alkyl 409807/0892 remainder with 4 to 21 carbon atoms. Is 3. Synthetic Esterschmiermittel according to claim 2 / characterized in that the hydroxyester from the reaction of a zwe! Basic acid having about 36 to 54 carbon atoms and a content of 75 wt .-% vzenigstens dibasic acid derived _3g C with a glycidyl ester of neo-acid and the formula R ₁ "0 0. fl ι« / \ R ₀ - C - CO - CH ₀ CH - CH-, 2 \ 2 2 -, in which R _{1, R 2} and R _{3 are} alkyl groups with 1 to 4 carbon atoms, the total number of carbon atoms in the three groups being a total of 4 to 10 carbon atoms " 4. Synthetic lubricant according to claim 3, characterized characterized in that the dimer acid contains 85% or more dibasic C ^ g acid and with etv / a o.45 to o.55 Equivalent of glycidyl ester per equivalent of dibasic acid is implemented. 5. Synthetic ester lubricant according to claim 4, characterized in that the hydroxy ester compound consists essentially of the half-ester of the formula 0 OH 0 11 T it CO-ai-CHQVOC-C H OOOH JJ «> 4 Oc consists· AG9807 / 0892