EP0812902A2

EP0812902A2 - High performance hydraulic lubricants

Info

Publication number: EP0812902A2
Application number: EP97304112A
Authority: EP
Inventors: Ian Macpherson
Original assignee: Ethyl Corp
Current assignee: Ethyl Corp
Priority date: 1996-06-12
Filing date: 1997-06-12
Publication date: 1997-12-17
Also published as: EP0812902A3

Abstract

A high performance hydraulic lubricant comprising:

a) a base oil in an amount of from 90 to 99.5 wt%;
b) an antiwear lubricating additive in an amount of from 0.1 to 1.5 wt%;
c) a rust and oxidation lubricating additive in an amount of from 0.1 to 1.5 wt%; and
d) optionally, an antifoaming agent.

Description

This invention relates to lubricants, and more particularly, to a high performance hydraulic lubricant useful in a hydraulic powered system or unit.
In providing suitable lubricants for different systems, additives and agents are provided which impart enhancing properties to the base oil making up, for the most part, the desired lubricant. A base oil, used alone, provides a lubricant that is deficient in performance and does not overcome the problems occurring in the normal operation, e.g., of an automotive engine.
Hydraulic lubricants find a wide variety of service in mobile and industrial applications using various types of pumps including those of vane, gear and piston design. Severe industrial applications include plastic moulding machines. Severe mobile applications are found in garbage trucks and in off-highway equipment.
Thus, there is a need for a high performance lubricant which overcomes or at least significantly reduces the problems in a hydraulic powered system. This need is fulfilled by the present invention whereby a high performance hydraulic lubricant is provided with a good oxidation life.

SUMMARY OF THE INVENTION

A high performance hydraulic lubricant having a useful performance life ranging from about 1000 to about 10,000 operational hours, said lubricant comprising:

a) a base oil in an amount ranging from about 90.0 to about 99.5 wt% and having a kinematic viscosity at 40°C ranging from about 15.0 to about 150 cSt;
b) an antiwear lubricating additive in an amount ranging from about 0.1 to about 1.5 wt%;
c) a rust and oxidation lubricating additive in an amount ranging from about 0.1 to about 1.5 wt%; and
d) optionally, an antifoaming agent.

DETAILS OF THE PREFERRED EMBODIMENTS OF THE INVENTION

The present invention provides high performance hydraulic lubricants useful in powered hydraulic systems or units that may be used in mobile and industrial equipment including garbage trucks, cranes, plastic moulding machines, and various types of pumps.

Hydraulic Lubricant

According to the present invention, the performance of a hydraulic lubricant is generally enhanced by the addition to a suitable base oil of [1] an antiwear lubricating additive, [2] a rust and oxidation lubricating additive, and [3] (optionally) an antifoaming agent.
The resulting hydraulic lubricant has a high performance due to these components. The finished hydraulic lubricant may also include, if desired, Viscosity index improvers which are added to improve viscosity characteristics at various temperatures and pour-point depressants provided that the finished hydraulic lubricant has the following properties:

. A kinematic viscosity at 40°C ranging from about 15 cSt to about 150 cSt.
. A flash point ranging from about 65°C to about 700°C, preferably from about 95°C to about 450°C.
. A Viscosity index ranging from about 85 to about 230, preferably from about 90 to about 160.
. A pour point ranging from about -10°C to about -70°C.

The finished lubricant generally contains less than about 1500 ppm of metal and preferably less than about 1000 ppm of metal. And, the finished lubricant may contain less than 5 ppm of free phenol, preferably less than 1 ppm and most preferably is void of any detectable free phenol.

Base Oil

The base oil mixture used according to the present invention are selected so that the finished hydraulic lubricant has the properties listed herein. Accordingly, the base oils may be any suitable oil including petroleum base oils, mineral oils, synthetic ester oils, or blends of such suitable oils.
Suitable mineral oils include those of appropriate viscosity refined from crude oil of any source including Gulf Coast, Midcontinent, Pennsylvania, California, Alaska, Middle East, North Sea, and the like. Standard refinery operations may be used in processing the mineral oil. Among the general types of petroleum oils useful in the compositions of this invention are solvent neutrals, bright stocks, cylinder stocks, residual oils, hydrocracked base stocks, paraffin oils including pale oils, and solvent extracted naphthenic oils. Such oils and blends of them are produced by a number of conventional techniques which are widely known by those skilled in the art. Small amounts (e.g., 20% by volume or less) of non-ester synthetic oils of suitable viscosity and stability (e.g., suitable hydrogenated α-olefin oligomer oils) or natural oils of suitable viscosity and stability (e.g., suitable animal or vegetable oils) can be included in the base oil compositions provided that the base oil retains the properties required for use as a base oil according to the requirements of this invention.
Synthetic ester oils which can be used include esters of dicarboxylic acids (e.g., phthalic acid, succinic acid, maleic acid, azelaic acid, suberic acid, sebacic acid, fumaric acid, adipic acid, linoleic acid dimer) with a variety of alcohols (e.g., butyl alcohol, hexyl alcohol, dodecyl alcohol, 2-ethylhexyl alcohol, ethylene glycol). Specific examples of these esters include dibutyl adipate, di(2 ethylhexyl) adipate, didodecyl adipate, di(tridecyl) adipate, di(2-ethylhexyl) sebacate, dilauryl sebacate, di-n-hexyl fumarate, dioctyl sebacate, diisooctyl azelate, diisodecyl azelate, dioctyl phthalate, didecyl phthalate, di(eicosyl) sebacate, the 2-ethylhexyl diester of linoleic acid dimer, and the complex ester formed by reacting one mole of sebacic acid with two moles of tetraethylene glycol and two moles of 2-ethylhexanoic acid. Other synthetic esters which may be used include those made from C₃-C₁₈ monocarboxylic acids and polyols and polyol ethers such as neopentyl glycol, trimethylolpropane, pentaerythritol and dipentaerythritol. Trimethylol propane tripelargonate, pentaerythritol tetracaproate, the ester formed from trimethylolpropane, caprylic acid and sebacic acid, and the polyesters derived from a C₄-C₁₄ dicarboxylic acid and one or more aliphatic dihydric C₃-C₁₂ alcohols such as derived from azelaic acid or sebacic acid and 2,2,4-trimethyl-1,6-hexanediol serve as examples.
Blends of one or more mineral oils with one or more synthetic ester oils can be used. Preferably, the base oil is predominantly hydrocarbonaceous in character. As noted above, base oils made up entirely of mineral oils are most preferred.
The base oil is present in the finished hydraulic lubricant in an amount ranging from about 90.0 to about 99.5 wt%. And, the base oil has a kinematic viscosity at 40°C ranging from about 15 to about 150 cSt. Also, the base oil has a flash point ranging from about 95° to about 700°C, preferably from about 100° to about 300°C.
The base oils useful in the present invention may, for example, and not by limitation, include those identified below by commercial name/code, number, and (manufacturer; location):
Exxon 150N (Exxon Co. U.S.A.; Houston, TX)
Chevron RLOP 140N (Chevron U.S.A. Inc.; Richmond, CA)
When a good quality base oil is used, i.e., a base oil that has undergone substantial hydrotreatment during the refining process, the rust and oxidation (R&O) lubricating additive may not be necessary to provide a high performance hydraulic lubricant.
However, when a poor quality base oil is used, i.e., a base which contains high levels of sulfur and unsaturated components, the R&O lubricating additive and the antiwear (A/W) lubricating additive are generally both necessary to be added to the base oil to provide a high performance hydraulic lubricant which can be effectively used in a hydraulic powered system.
The antifoaming agent may be optionally added to enhance the properties of the finished high performance hydraulic lubricant.
Hydraulic lubricants find a wide variety of service in mobile and industrial applications using various types of pumps inlcuding those of vane, gear and piston design. Severe industrial applications include plastic moulding machines. Severe mobile applications are found in garbage trucks and in off-highway equipment.
According to the present invention, it should be noted that neither the A/W lubricating additive nor the R&O lubricating additive contains a strongly acidic rust inhibitor, and that the A/W lubricating additive and the R&O lubricating additive are mutually compatible.
These A/W lubricating and R&O lubricating additives should be essentially devoid of acidic-type rust inhibitors. Acidic-type rust inhibitors are those which, when analyzed by the ASTM D 664 procedure, yield a Total Acidity Number (TAN) of greater than about 100 mgKOH/g equivalents. Strongly acidic rust inhibitors may cause compatibility problems during application owing to the precipitation of salts which they tend to form. These salts may include zinc or calcium which may be present in the finished oil as additive components, or may be introduced to the oil in the form of impurities and contaminants.
As indicated herein, the A/W lubricating and R&O lubricating additives are mutually compatible. That is, finished oils which contain minor portions of A/W and R&O lubricating additives do not give rise to cloudiness, haze, precipitation, or gel formation as a result of interaction or chemical reaction between the two additives. Even in the presence of minor quantities of contaminant water, the finished lubricant should remain essentailly clear and bright. Obviously, larger quantities of water (above about 1000 ppm) will give some haze or clarity reduction as water and oil are not miscible.

Rust and Oxidation Lubricating Additive

The concentration of the R&O lubricating additive present in the finished hydraulic lubricant depends upon the base oils employed. For example, when base oils which have undergone a hydrotreating or hydrofinishing process are used in the present invention, or when the base oils used are sythetic, the level of the R&O lubricating additive may be low, ranging from about 0.001 to about 0.2 wt%. However, when the base oils are solvent refined or contain a significant portion of solvent refined oil, the level of the R&O lubricating additive may be relatively high, ranging from about 0.2 to about 1.2 wt%.
The R&O lubricating additive comprises a rust inhibitor and an antioxidant, and accordingly, is intended to impart the properties of (a) rust inhibition and (b) antioxidancy to the finished hydraulic lubricant. The R&O lubricating additive is composed of components to enhance the hydraulic lubricant with such properties. The components that may be used in the R&O lubricating additive include:

Rust inhibitors
Antioxidants
Demulsifiers
Ashless antiwear additives
Antifoamants
Corrosion inhibitors
Sulfur scavangers

These components are well known by those skilled in the art and are, for example, described in U.S. Patent No. 5,358,652.
The R&O lubricating additive in being added to the base oil must be compatible with the A/W lubricating additive so that the hydraulic lubricant is useful. The R&O lubricating additives that may be used in the present invention, for example, and not by limitation, include the HiTEC® lubricating additives listed below and manufactured and sold by Ethyl Corporation of Richmond, Virginia:

HiTEC® 565
HiTEC® 575
HiTEC® 2568
HiTEC® 2571
HiTEC® 2572

Each of the R&O lubricating additives listed above has the following properties:

. A nitrogen level of between about 1.8 and 2.75 _wt%.
. A kinematic viscosity at 100°C of about 1.5 to about 4.5 cSt.
. A specific gravity of about 0.9 to about 1.1 gcm^-3.
. A flash point of about 95°C to about 250°C.
. A TAN of about 30 to about 90 mgKOH/g equivalents.

In addition, each R&O lubricating additive contains a rust inhibitor which has a TAN when measured in the ASTM D 664 test method of about 60 mgKOH/g equivalents. This rust inhibitor is known as HiTEC® 536 (manufactured and sold by Ethyl Corporation of Richmond, VA) and is compatible with zinc and calcium containing fluids. The HiTEC® 536 rust inhibitor may be used as the primary rust inhibitor in many additive concentrations and finished lubricants which contain zinc and calcium containing components.
With an acidic-type rust inhibitor in the R&O additive package having a TAN greater than 100 mgKOH/g equivalents of finished oil, problems may occur when such rust inhibitor is mixed with a zinc-containing antiwear lubricant, especially in the presence of contaminant water. Thus, to avoid any problems, the rust inhibitor should have a TAN of less than about 100 mgKOH/g equivalents. That is a TAN ranging from about zero to about 95, preferably from about 4 to about 60 mgKOH/g equivalents.
Although an R&O lubricating additive may not be necessary when a good quality base oil is used, the R&O lubricating additive enhances the properties of the finished hydraulic lubricant.
Accordingly, the R&O lubricating additive may contain several components which are intended to enhance the properties of the finished hydraulic lubricant in the following ways:

1) Oxidation and Thermal Stability: This parameter is measured primarily by the ASTM D 943 Test which gives an indication of the life that the lubricant would perform before significant oxidation would be expected. A very satisfactory oxidation, i.e., useful performance life, exceeds 2500 operational hours. The satisfactory range for a useful performance life may range from about 2,000 to about 10,000 operational hours.
2) Rust: The rust inhibiting properties of the lubricants are usually evaluated by the ASTM D 665B Test.
3) Water Separation: Demulsibility is a measure of the ability of a lubricant to separate from water in the event that contamination should occur. This ability of the lubricant is generally tested by the ASTM D 1401 Test.
4) Antifoam: With a foam inhibitor, i.e., antifoaming agent, in the R&O lubricating additive, the lubricant will resist the build up of foam during excessive aeration of the oil.
5) Air release and filterability: The components of the R&O additive package will prevent any excessive air extrainment or any filtration problem of the lubricant.

The R&O lubricating additive and the A/W lubricating additive are each present in the finished hydraulic lubricant in an amount ranging from about 0.1 to about 1.5 wt%.
In addition, the R&O lubricating additive is essentially devoid of metal, but at most would contribute 100 ppm of Zinc and 500 ppm of calcium, barium, magnesium, or sodium. The finished hydraulic lubricant contains less than 1500 ppm of metal or preferably less than 1000 ppm of metal. The finished hydraulic lubricant contains less than 5 ppm of free phenol and preferably less than 1 ppm of free phenol and is most preferably void of any detectable free phenol.

Antiwear Lubricating Additive

The A/W lubricating additives are similar to the R&O lubricating additives in that they are intended to impart the same properties of the R&O lubricating additives, namely, (a) rust-inhibition and (b) antioxidancy. In addition, however, these additives impart an extreme pressure performance, i.e., resistance to high pressures.
The A/W lubricating additives provide a boundary or surface lubricant to metal by forming a resistant coating (e.g., sulfide) on the metal surfaces. That is why the A/W additives are usually a phosphorous/sulfur type. For example, the A/W additive may be a Zinc dialkyldithiophosphate (ZDDP). Other antiwear additives that may be used, include phosphites, phosphares, and alkylamine salts.
The A/W lubricating additives that are compatible with the R&O lubricating additives are HiTEC® products manufactured and sold by Ethyl Corporation of Richmond, Virginia and other commercial A/W lubricating additives. The A/W lubricating additives that may be used, for example, and not by limitation, include those identified below by commercial name/code, number, and (manufacturer/ location):

HiTEC®-2915 (Ethyl Corporation; Richmond, VA)
HiTEC®-2940 (Ethyl Corporation)
HiTEC®-2916 (Ethyl Corporation)
Lubrizol 5178 (Lubrizol Co.; Wickliffe, OH)
ELCO 130A (Elco Corp.; Cleveland, OH)

The A/W lubricating additives have a zinc level (wt%), phosphorous level (wt%), Specific Gravity (Sp. Gr.) as set forth below:

Zinc, wt% Phosphorus, wt% Sp. Gr.

HiTEC®-2915 4 3.4 1.0

HiTEC®-2940 3.4 2.8 1.0

HiTEC®-2916 4 3.3 1.0

Lubrizol 5178 5.5 4.5 1.0

ELCO 130A 6.6 5.5 1.0
The A/W lubricating additive may be used in other appplications in the appropriate base oil as a hydraulic additive. The A/W lubricating additve enhances the hydraulic lubricant performance without the use of the R&O lubricating additive. However, the performance of such a lubricant would be improved by addition of the R&O lubricating additive. In addition, the R&O lubricating additive which in appropriate base oils provides some circulating, turbine, and heat-transfer performance without the use of the A/W lubricating additive. However, the performance of such a lubricant would be expected to improve by addition of certain A/W lubricating additives.

Antifoaming Agent

The antifoaming agent may be optionally added to prevent or at least reduce the foaming on the surface of the finished hydraulic lubricant. Such foaming could impede or prevent the performance of the desired hydraulic lubricant. The antifoaming agent may be an acrylic copolymer composite. Also, the antifoaming agent may either contain silicon or be silicon free. However, the silicon free antifoaming agents are preferred. The antifoaming agents useful in the present invention may, for example, and not by limitation, include those identified below by commercial name/code, number, and (manufacturer; location):

Monsanto PC 1244 (Monsanto Corp.; St. Louis, MO)
Monsanto PC 1344 (Monsanto Corp.)
Monsanto PC 1644 (Monsanto Corp.)
Dow Corning Fluid (Dow Corning Co., Midland, Michigan)

The practice and advantages of this invention are illustrated by the following examples in which all percentages are by weight unless otherwise specified.

Example I

A hydraulic lubricant, i.e., an ISO 32 hydraulic antiwear oil is prepared by mixing the following (wt%):

EXXON 150N Base Oil 98.88

Monsanto PC 1244--Antifoaming Agent 0.02

HiTEC® 2916--A/W Lubricating Additive 0.85

HiTEC® 565--R&O Lubricating Additive 0.25
The resulting hydraulic lubricant is a high performance ISO 32 hydraulic fluid suitable for use in mobile and industrial applications, and has a useful performance life of greater than about 1000 operational hours.

Example II

A hydraulic lubricant, i.e., an ISO 32 hydraulic antiwear oil is prepared by mixing the following (wt%):

EXXON 150N Base Oil 98.78

Monsanto PC 1244--Antifoaming Agent 0.02

HiTEC® 2916--A/W Lubricating Additive 0.80

HiTEC® 2568--R&O Lubricating Additive 0.40
The resulting hydraulic lubricant is a high performance ISO 32 hydraulic fluid suitable for use in mobile and industrial applications, and has a useful performance life of greater than about 2000 operational hours.

Example III

A hydraulic lubricant, i.e., an ISO 32 hydraulic fluid is prepared by mixing the following (wt%):

EXXON 150N Base Oil 98.58

Monsanto PC 1644--Antifoaming Agent 0.02

HiTEC® 9195--A/W Lubricating Additive 0.85

HiTEC 2568--R&O Lubricating Additive 0.55
The resulting hydraulic lubricant is a high performance ISO 32 hydraulic fluid suitable for use in mobile and industrial applications, and has a useful performance life of greater than about 2000 operational hours.

Example IV

A hydraulic lubricant, i.e., an ISO 32 hydraulic fluid is prepared by mixing the following (wt%):

EXXON 150N Base Oil 99.13

Monsanto PC 1244--Antifoaming Agent 0.02

HiTEC® 2916--A/W Lubricating Additive 0.85
The resulting hydraulic lubricant is a high performance ISO 32 hydraulic fluid suitable for use in mobile and industrial applications, and has a useful performance life of greater than about 1000 operational hours.

Example V

A hydraulic lubricant, i.e., a second ISO 32 hydraulic fluid is prepared by mixing the following (wt%):

Chevron RLOP 140N 99.12

HiTEC® 2916--A/W Lubricating Additive 0.85

Monsanto PC 1244--Antifoaming Agent 0.02

HiTEC® 2571--R&O Lubricating Additive 0.01
The resulting hydraulic lubricant is a high performance ISO 32 hydraulic fluid suitable for use in mobile and industrial applications, and has a useful performance life of greater than about 3000 operational hours.
While the preferred embodiments have been fully described and depicted for the purposes of explaining the principles of the present invention, it will be appreciated by those skilled in the art that modifications and changes may be made thereto without departing from the scope of the invention set forth in the appended claims.

Claims

A high performance hydraulic lubricant comprising:
a) a base oil in an amount of from 90 to 99.5 wt%;

b) an antiwear lubricating additive in an amount of from 0.1 to 1.5 wt%;

c) a rust and oxidation inhibiting additive comprising a rust inhibitor and an antioxidant,

in an amount of from 0.001 to 1.5 wt%; and d) optionally, an antifoaming agent.
A lubricant according to claim 1, wherein said base oil has a kinematic viscosity at 40°C of from 15 to 150 cSt.
A lubricant according to claim 1 or claim 2, wherein said base oil has a flash point of from 95°C to 700°C.
A lubricant according to any one of claims 1 to 3, wherein said antiwear lubricating additive comprises a zinc dialkyldithiophosphate.
A lubricant according to any one of claims 1 to 4, wherein the rust and oxidation inhibiting additive is present in an amount of from 0.1 to 1.5 wt%.
A lubricant according to any one of claims 1 to 5, wherein said rust and oxidation inhibiting additive has a Total Acidity Number (TAN) of 30 to 90 mgKOH/g equivalents.
A lubricant according to any one of claims 1 to 6, wherein said rust and oxidation inhibiting additive has a nitrogen content of between 1.8 and 2.75 wt%.
A lubricant according to any one of claims 1 to 7, wherein said rust and oxidation inhibiting additive has a kinematic viscosity at 100°C of 1.5 to 4.5 cst.
A lubricant according to any one of claims 1 to 8, wherein said rust and oxidation inhibiting additive has a specific gravity of 0.9 to 1.1 g/cm³.
A lubricant according to any one of claims 1 to 9, wherein said rust and oxidation inhibiting additive has a flash point of from 95°C to 250°C.
A lubricant according to any one of claims 1 to 10, wherein the antifoaming agent is present in an amount of from 0.01 to 0.05 wt%.
A lubricant according to any one of claims 1 to 11, wherein said antifoaming agent is an acrylic copolymer composite.
A lubricant according to claim 12, wherein said acrylic copolymer composite is present in an amount of from 0.01 to 0.05 wt%.
A lubricant according to any one of claims 1 to 13, wherein said antifoaming agent is silicon free.
A lubricant according to any one of claims 1 to 14, having a pour point of from -10°C to -70°C.
A lubricant according to any one of claims 1 to 15, which contains less than 1 ppm of free phenol.
A lubricant according to any one of claims 1 to 16, having a flash point of from 65°C to 700°C.
A lubricant according to any one of claims 1 to 17, having a viscosity index of between 85 and 230.
A lubricant according to any one of claims 1 to 18, which contains less than 1000 ppm of metal.
A method for improving the performance of a hydraulic powered system or unit which method comprises using as hydraulic lubricant in said system or unit a hydraulic lubricant as defined in any one of claims 1 to 19.
Use of a hydraulic lubricant as defined in any one of claims 1 to 19 in a hydraulic powered system or unit.