NO833366L - LUBRICATING OIL FOR MOVING PARTS IN VEHICLES - Google Patents

Description

Synthetic lubricating oils are increasingly used because of their uniformity and stability. In particular, synthetic lubricating oils containing polyol esters exhibit many desirable properties.

A lubricating oil for moving parts in modern vehicles must satisfy a number of precise criteria. Newer moving parts may be encased in sound-absorbing materials which have the side effect of acting as heat insulators and increasing the lubricating oil temperature.

The packing swelling characteristics of a lubricating oil mixture are of great importance if leakage of machine fluids is to be kept at an acceptable level. Polyol esters used as lubricating oils often exhibit a propensity for unacceptably high packing swelling. Poly-α-olefins used as lubricating oils often exhibit negative packing swelling and are not as heat stable as polyolesters.

US Patent No. 4,144,183 describes improving the viscosity-temperature behavior of ester oils using mixtures of linear and branched carboxylic acids in a polyol esterification. US Patent No. 4,234,497 describes the improvement of the packing compatibility characteristics of polyol ester lubricating oils by esterification of a polyol with a mixture of iso-palmitic acid and one C₁-C₂ carboxylic acid.

Synthetic lubricating oils are often given desirable viscosity characteristics by including a viscosity index improver. The viscosity index improver is usually a polymer that degrades over time. This gradual degradation limits the shelf life of a formulated lubricating oil. It is desirable to produce synthetic lubricating oil blends for moving parts which have good stability, acceptable viscosity range and good gasket swelling characteristics without any inclusion of a degradable viscosity index improver or a gasket swelling agent.

This invention relates to lubricating oil mixtures and methods of using them when lubricating machines.

A synthetic lubricating oil compound for moving parts is formulated from: (A) a polyol ester prepared by the esterification of trimethylolpropane with a monocarboxylic acid of 8 to 12 carbon atoms,

(B) a polyol ester prepared by esterification of trimethylolpropane

with a branched chain monocarboxylic acid of 18 to 24 carbon atoms, and (C) a liquid poly-α-olefin.

The synthetic lubricating oil according to this invention is intended for moving parts in internal combustion engines in general and extra powerful use. It can especially be used for extra powerful moving parts in commercial vehicles on roads, such as buses and trucks.

The defining characteristics of an acceptable moving parts lubricating oil for the purposes of this invention are those set forth in the "Detroit Diesel Allison 10W Type C-3 Hydraulic Transmission Fluid Standard". The synthetic lubricating oils of this invention are qualified by the lubricating oil rating of "Detroit Diesel Allison 10W Type C-3", and meet the test specifications set forth in Table I below.

The synthetic lubricating oil for moving parts according to this invention has as its essential ingredients:

(A) a polyol ester of the formula:

where R , R^ and R^ are the same or different and are -OCH2(CH2)xCH3 radicals where x is an integer from 6 to 10,

(B) a polyol ester of the formula:

where R^, R1- and Rg are the same or different and are iso-Cn~

hydrocarbon radicals, where n is an integer from 18 to 24, and

(C) a poly-α-olefin having a centistoke viscosity of from about 3 to approx. 6, where the weight ratio between ingredient (A) and

ingredient (B) is from approx. 2:1 to approx. 1:2, the weight ratio between the sum of ingredients (A) plus (B) and ingredient (C) is from approx. 2.4:1 to approx. 1.5:1, and the sum of ingredient (A) plus ingredient (B) plus ingredient (C) amounts to at least approx. 90% by weight. of said mixture.

The weight ratio between ingredient (A) and ingredient (B) is preferably from 1.6:1 to 1.2:1, and the weight ratio between the sum of ingredients (A) plus (B) and ingredient (C) is preferably from 2, 1:1 to 1.6:1.

The sum of ingredient (A) plus ingredient (B) plus ingredient (C) preferably amounts to from approx. 90 to approx. 93% by weight of the mixture. The synthetic lubricating oil for moving parts essentially consists of three essential parts (ie A, B, C) and conventional optional lubricating oil ingredients. The possible ingredients in the lubricating oil mixture preferably amount to less

than 8% by weight of the total mixture.

It has been found that a suitable ratio for (A) : (B) and a suitable ratio for (A+B) : (C) can be approximated by a linear additive model where each ingredient contributes to the total viscosity in direct proportion to its individual viscosity multiplied by its weight ratio in the mixture (within the ratio ranges taught in this specification). The viscosity characteristics of the final formulated lubricating oil mixture can be optimized by mixing aliquots of all ingredients (with any additives) and then making a slight adjustment of. the viscosity by suitable addition of any of the ingredients (A), (B) or (C).

The polyol ester ingredients (A) and (B) described in the preceding section can be prepared by conventional esterification methods. Suitable conventional esterification techniques are described in US Patent No. 3,778,454, column 4, lines 9 to 75, and column 5, lines 1 to 12, and this disclosure is incorporated herein by reference.

Ingredient (A) in the mixture according to the invention is conventionally prepared by full esterification of trimethylolpropane (TMP) with a monocarboxylic acid with a linear chain or a mixture of monocarboxylic acids with linear chains having from 8 to 12 carbon atoms. Suitable acids for esterification of TMP to produce ingredient (A) are n-octanoic acid, n-nonanoic acid and decanoic acid. Mixtures of linear-chain C 8 -C 2 carboxylic acids can be used if desired. Nonanoic acid is particularly preferred in the esterification of TMP to give an ester oil suitable for ingredient (A).

Ingredient (B) in the mixture according to the invention is conveniently prepared by full esterification of trimethylolpropane with a branched-chain carboxylic acid containing from 18 to 24 carbon atoms. Examples of suitable monocarboxylic acids for esterification of TMP to give ingredient (B) are isostearic acid, iso-octadecanoic acids, and symmetrically branched chain acids of 18 or more carbon atoms, as described in US Patent No. 4,144,183, column 4, lines 55-68, and column 5, lines 1-39. Mixtures of iso C-^g_2^-monocarboxylic acids can be used. Trimethylolpropane tri-isostearate is a particularly preferred ester oil for use as ingredient (B).

Ingredient (C) in the mixture according to the invention is a poly-α-olefin which has a viscosity of from approx. 3 to approx. 6 cSt (viscosity measured at 98.9°C). Poly-α-olefins of suitable viscosity can be prepared by a variety of cracking or oligomerization processes, as described in the Encyclopedia of Chemical Technology, 3rd ed. Vol. 16, pp. 487-492, ISBN 0-471-02069-9, the disclosure of which is hereby incorporated by reference. Olefin oligomers which are within the fractional range Cg to C2q (as described on p. 492 of the above-mentioned Encyclopedia of Chemical Technology) are preferred for use as ingredient (C). A poly-a-decene that has a viscosity of approx. 4 cSt, is particularly preferred when carrying out this invention.

The remainder of the lubricating oil mixture (less than 10% by weight) may optionally include, conventional lubricating oil additives such as a corrosion inhibitor, an antioxidant, an anti-wear agent,

a metal deactivator, an antifoam agent and a colorant. It is a preferred aspect of this invention that the lubricating oil composition does not contain any polymer viscosity index improver or any gasket swelling agent. Viscosity improvers are unnecessary to achieve the desired physical properties of the lubricating oil mixture, and they provide a site for degradation.

The synthetic lubricating oil composition for moving parts according to this invention is obtained by uniformly mixing the essential ingredients (A), (B) and (C) together with any selected optional ingredients. Dissolution of certain possible ingredients is remedied by the use of elevated temperatures. The final formulated mixture may be filtered or otherwise treated to remove particulate contaminants.

The synthetic lubricating oil mixture according to this invention can be used in a method for lubricating machines. Lubrication of machines is achieved by bringing the moving parts of a machine into contact with the lubricating oil mixture. The lubricating oil can be brought into contact with the machine parts in such conventional ways as by spraying, dipping or filling. This lubrication method is used in particular when treating metal parts in the moving parts of a vehicle.

The following example illustrates the practice of the invention.

EXAMPLE

METHOD: Approximately 75.7 liters (about 68,000 grams) of lubricating oil for moving parts was prepared as follows: In a clean, dry vessel, the above amounts of phenyl-a-naphthylamine and benzotriazole were added to the trimethylolpropane tripelargonate. These materials were stirred while heating at 71.1 - 76.7°C for one hour to dissolve the solids and form a premix.

Then, the indicated amounts of the remaining lubricating oil mixture components were added to a 75.7 liter vessel, together with the premix. The entire combined formulation was stirred under heating for 1 1/2 hours at 60-65.6°C to achieve uniform mixing. The cooled mixture was then filtered through Viscon filter paper and the filtrate was stored.

The mixed lubricating oil mixture for moving parts in this example had the following physical properties:

Although the present invention has been described with reference to particular embodiments, it should be understood that such embodiments are not intended to limit the scope of the protection according to the claims.

Claims (10)

1. 10W lubricating oil mixture for moving parts comprising a mixture of ingredients (A), (B) and (C), characterized in that ingredient (A) is a polyol ester of the formula: wherein R^ , R2 and R^ , which are the same or different, are -OCH2 (CH2 )x CH3 radicals where x is an integer from 6 to 10, ingredient (B) is a polyol ester of the formula: wherein R 1 , R 5 and R 8 , which are the same or different, are iso-Cn hydrocarbon radicals where n is an integer from 18 to 24, and ingredient (C) is a poly-α-olefin having a viscosity of from about 3 to approx. 6 centistokes, in which the weight ratio between ingredient (A) and ingredient (B) is from approx. 2:1 to approx. 1:2, the weight ratio between the sum of the ingredients (A) plus (B) and the ingredient (C) is from approx. 2.4:1 to approx. 1.5:1 and the sum of ingredient (A) plus ingredient (B) plus ingredient (C) amounts to at least approx. 90% by weight of said mixture. 2. Lubricating oil mixture for moving parts according to claim 1, characterized in that ingredient (A) is trimethylolpropane triheptanoate. 3. Lubricating oil mixture for moving parts according to claim 1, characterized in that ingredient (B) is trimethylolpropane triisostearate. 4. Lubricating oil mixture according to claim 1, characterized in that ingredient (C) is e-t poly-a-olefin obtained as a Cg-C2Q fraction. 5. Lubricating oil mixture for moving parts according to claim 1, 2 or 3, characterized in that ingredient (C) is poly-a-decene having a viscosity of 3.5 to 4.2 centistokes. 6. Lubricating oil mixture for moving parts according to claim 1, 2, 3 or 4, characterized in that the weight ratio between ingredient (A) and ingredient (B) is from 1.6:1 to 1.2:1 and the weight ratio between the sum of ingredients (A) plus (B) and ingredient (C) are from 2.1:1 to 1.6:1. 7. Lubricating oil mixture for moving parts according to claim 6, characterized in that ingredient (A) is trimethylolpropane triheptanoate, ingredient (B) is trimethylolpropane triisostearate and ingredient (C) is poly-a-decene. 8. Lubricating oil mixture for moving parts according to claim 1, characterized in that said mixture contains up to 10% by weight of any ingredients selected from the group consisting of one corrosion inhibitor, an antioxidant, an antiwear agent, a metal deactivator, an antifoam agent and a dye. 9. Lubricating oil mixture for moving parts according to claim 8, characterized in that the possible ingredients make up less than 8% by weight of said lubricating oil mixture. 10. Use of the lubricating oil mixture according to any one of claims 1, 6 or 8 for the lubrication of moving parts in machines, e.g. moving parts in a vehicle.