EP0931126A1

EP0931126A1 - Use of surfactants with low molecular weight as agents for improving the filterability in lubricants

Info

Publication number: EP0931126A1
Application number: EP98917285A
Authority: EP
Inventors: Olivier Clement; Christophe Le Sausse; Dominique Batelier; Jacques Cazin
Original assignee: Chevron Chemical SA
Current assignee: Chevron Oronite SAS
Priority date: 1997-04-11
Filing date: 1998-04-01
Publication date: 1999-07-28
Also published as: WO1998046708A1; JP2002501558A; FR2762005B1; CA2257877A1; FR2762005A1; US20020049144A1

Abstract

The invention concerns a lubricating fluid comprising: 1) a predominant amount of an oil with appropriate lubricating viscosity; and 2) an effective amount of an agent improving the filterability or one of their mixtures, corresponding to the following formula: R-Z, in which Z represents a polar group selected from the group consisting of a) phosphoric esters; b) amides; c) ethers; d) amino-alcohol's; e) ethoxylated amines or f) their mixtures, and R represents a lipophilic chain with 14 to 24 carbon atoms. The invention also concerns the use of the filterability-enhancing agent described above for improving the filterability of hydraulic oils, and a method for preparing hydraulic fluids with improved filterability.

Description

Use of low molecular weight surfactants as agents improving filterability in hydraulic lubricants

Field of the invention

The present invention relates to lubricating fluids having improved filterability characteristics, and effective additives to improve the filterability characteristics of lubricating fluids such as hydraulic oils. The present invention relates more particularly to lubricating fluids and additives comprising an effective amount of a filterability improving agent which comprises at least one polar group and at least one lipophilic chain having 14 to 24 carbon atoms.

Technological background Most of the lubricating oils currently used, such as hydraulic fluids and similar fluids, contain additives which are designed to give optimum performance with regard to the inhibition of wear, protection against rust. , demulsification, thermal stability, hydrolysis stability and oxidation stability, air release capacity and inhibition of foaming. In addition, hydraulic oils must have extremely good filterability properties which are measured and evaluated using a number of detailed filterability tests such as AFNOR NFE 48690, 48691 and 48693, CETOP RP 124H, DENISON and PALL . Unfortunately, the field of formulation required to meet the main performance criteria is often antagonistic to good filterability because, in general, the use of additives is detrimental to filterability. For example, the use of viscosity index improving agents (VIA) and pour point lowering agents (APE) has made it more difficult to formulation of oils with a high viscosity index and / or better properties at low temperatures.

The filterability of hydraulic oils is currently an essential technical point since it constitutes an important imperative for current formulations and future formulations. Most hydraulic systems do use decontamination filters. Contaminants can consist of metal particles, dust, lacquers, polymers resulting from oxidation and thermal stability phenomena. In fact, the limitation of pollution by hydraulic oils has become decisive for obtaining good performance in service, also including improved wear inhibition by reduction of abrasive particles. As a result, the trend is to further reduce the porosity of the filters (in-line) to around 3 micrometers in some cases. Consequently, dry and wet filterability tests have been developed to assess, and to offer means of improving, the filterability performance of hydraulic oils. However, due to the very fine porosity of the filters used in these bench tests and also due to the presence of water in some of these operating modes, the performance of hydraulic oils is sometimes below acceptable criteria.

The presence of water having a negative impact on the filterability performance of hydraulic oils, most bench filterability tests currently used include a storage period for the oil artificially contaminated with water. The presence of water poses a problem because the water undergoes adsorption by calcium carbonates and calcium hydroxides which are part of the detergent calcium salts which are commonly present in hydraulic additives. In addition, water interacts with ZDDP by releasing ZnO. These interactions lead to fine deposits which tend to clog the filters.

Various technologies have been used in the past to try to solve these problems. The most common means known to date consist in using metal carboxylates as described in document GB 2 293 389, in reducing the concentrations of ZDDP by approximately 8 mM / kg of oil to a value equal to or less than about 4 mM / kg of oil, or to formulate the additives with particular agents improving the viscosity index which are less harmful for the filterability.

Summary of the invention

The inventors have discovered that it is possible to improve the filterability properties of lubricating oils by using filterability improving agents comprising at least one polar group and at least one lipophilic chain having a particular length. More advantageously, when using the compounds described below, the filterability performance is improved but this improvement obtained is generally not detrimental for the main performance criteria and can even have positive effects in certain cases. The present invention relates generally to a lubricating fluid, in particular a hydraulic oil, comprising:

1) a dominant quantity of an oil of viscosity suitable for lubrication; and

2) from 0.03% to 0.06% of a filterability improving agent, corresponding to the following formula:

R-Z

in which Z represents a polar group containing one or more substituents chosen from: a) phosphoric esters; b) amides; c) ethers; d) amino alcohols; e) ethoxylated amines; f) mixtures thereof.

The number of these polar group substituents can vary from 1 to 30 but usually a number of 3 to 5 polar substituents is preferred. As regards the lipophilic chain R forming the other portion of the filterability improving agent used in the present invention, this chain usually consists of a saturated or unsaturated hydrocarbyl chain having 14 to 24 and preferably 17 to 19 carbon atoms . The hydrocarbyl chain can be straight or branched, although straight chains are usually preferred. Although this lipophilic chain is preferably unsubstituted, it is possible to incorporate substituents or to insert heteroatoms or various groups in the chain provided that these insertions or substituents have no significant effect on the total polarity of the molecule.

The present invention also relates to the use of the agents for improving the filterability described in the present specification for improving the filterability of oils, in particular hydraulic oils.

The present invention also relates to a process for the production of a hydraulic fluid with improved filterability, which comprises mixing the following constituents: a) a dominant quantity of an oil of viscosity suitable for lubrication; and b) from 0.03% to 0.06% of a filterability improving agent, corresponding to the following formula

RZ wherein Z represents a polar group containing one or more substituents selected from the group consisting of a) phosphoric esters; b) amides; c) ethers; d) amino alcohols; e) ethoxylated amines; f) mixtures thereof, and R represents a lipophilic chain having 14 to 24 carbon atoms.

Detailed description of the invention

In order to better demonstrate the structural relationship between the polar group and the lipophilic chain of the filterability enhancing agents of the present invention, examples of preferred categories of compounds are presented below.

A large group of filterability enhancing agents includes those in which the polar group Z contains one or more constituents selected from: a) phosphoric esters; b) fatty amides; c) polyethers; d) ethoxylated amines; e) their mixtures. Each member of this group can itself form, with the appropriate hydrocarbyl chain, independent subgroups of agents improving filterability falling within the scope of the present invention.

A subgroup of specific phosphoric esters includes phosphoric esters corresponding to the following formula: O - X

/

O = P - O - X

\ O - X

wherein X represents H or R and at least one of the symbols X represents R, and R represents a saturated or unsaturated hydrocarbyl chain which may comprise ether groups. The hydrocarbyl chain has 14 to 24 carbon atoms, advantageously 14 to 24 carbon atoms and preferably 17 to 19 carbon atoms. Highly advantageously, R represents a group [CH ₃ - CH ₂ ) n - CH ₂ -f O - CH ₂ - CH ₂ ) - ₃ ]. An example of such phosphoric esters consists of RHODAFAC PA35 commercially available, supplied by Rhône Poulenc. A subgroup of polyethers comprises compounds corresponding to the formula:

R-0- (CH ₂ -CH ₂ 0) _x H

in which X represents an integer from 3 to 12, preferably equal to 9, and R represents a hydrocarbyl chain having 14 to 24 carbon atoms and in which, more advantageously, R represents a group C ₅ H ₃₁ , the polar group Z being represented by -0- (CH ₂ -CH ₂ 0) _x H.

A preferred subgroup of ethoxylated amines includes ethoxylated amines comprising at least two ethoxy groups. A more preferred group includes ethoxylated amines corresponding to the following formula CH ₂ CH ₂ OH

/

CH ₂ CH ₂ CH ₂ N / \ RN CH ₂ CH ₂ OH

\

CH ₂ CH ₂ OH

in which R represents a hydrocarbyl chain having 14 to 24 carbon atoms, and in particular an aliphatic chain C ₁₈ H ₃₅ .

A preferred subgroup of unsubstituted fatty amides comprises compounds of the following formula:

H ₂ N-CO-R

in which R represents a hydrocarbyl chain having 14 to 24 carbon atoms and preferably 17 to 19 carbon atoms.

The concentration of the filterability improving agents described above must be adjusted so that the desired effect (improvement in the filterability characteristics of the oil) is obtained without being detrimental to the other performances resulting from the action of other additives which may be present in the oil composition. More particularly, it is considered that excessive concentrations of the compounds used in the context of the present invention may have harmful effects, in particular on the oxidation stability, the thermal stability and the hydrolysis stability of the oil. finished. For example, it turns out that high concentrations have negative effects on tests such as ASTM-D4310, ASTM-D943 and ASTM-D2619.

The exact mechanism of action of the compounds used in the context of the present invention on the improvement of filterability is not fully understood. Without wishing to be bound by any particular theory, the inventors consider that there is no properly significant interaction said between the agents improving filterability and the other compounds present in the lubricating oil.

However, it turns out that, in the competitive interactions taking place between solid particles, polymers (IV improving agents, APE) and the water present in the oil, the polar substituents of the agents improving the filterability have an effect. preferential dispersant on solid particles, which makes it possible to avoid the formation of aggregates of certain dimensions and, consequently, clogging of the filters. It also appears that the polar substituents of the filterability enhancing agents of the present invention exhibit some type of inhibition of the adverse effects of viscosity index improving agents and pour point lowering agents also through preferential interactions with solid particles.

It also appears that there is an important relationship between the polar substituents and the lipophilic chain. It is possible to determine the choice of polar substituents and lipophilic substituents for the preparation of a particular filterability improving agent, in accordance with the present invention, by referring to the calculation of their polar / lipophilic ratio. A suitable method for calculating this ratio has been described in a publication by "Atlas Chemical France" entitled "The HLB system of ATLAS". In this document which is cited by way of reference in the present application, the polar / lipophilic ratio is identified by the hydrophilic / lipophilic equilibrium ratio (H.L.B.).

It is possible to use a mixture of filterability improving agents, although a cumulative effect of the filterability properties is not necessarily observed. However, the inventors consider that complementary and even synergistic effects can occur when a plurality of different filterability improving agents is used in the same formulation. However, it should be borne in mind that the total concentration of the mixture of filterability improving agents should not significantly exceed the concentrations described above in order to avoid undesirable side effects which could hamper the overall properties of the lubricating fluid formulation.

Filterability improvers of the present invention are particularly useful for improving the filterability characteristics of lubricating oils and, preferably, hydraulic oils. They are effective regardless of the presence or absence of an agent improving the viscosity index in the oil. The improvement in filterability can be obtained for considerably different viscosity intervals. For example, in hydraulic oils and industrial oils, an improvement in filterability can be obtained for qualities ranging from ISO VG 15 to 150, preferably for qualities ranging from ISO VG 32 to 68.

As an example, the AFNOR NFE 48691 filterability test comprises the following stages: - formulation of the oil incorporation of 0.2% by weight of water and mixture to form a storage emulsion at 70 ° C. for 72 hours , then storage at room temperature (24 hours) - filtration of 300 ml of the oil on a 0.8 mm Millipore filter at a pressure depending on the filtration speed measurement of the time required to filter 50, 100, 200 and 300 ml oil and calculation of the corresponding IFE values.

In the AFNOR NFE 48691 tests, the filterability indices calculated for the test oils containing filterability improving agents were significantly improved compared to reference formulations which do not include the filterability improving agents and, in fact, are close to the "ideal" filterability index which is equal to 1. In addition, the incorporation of low concentrations of the agents improving filterability used in the The present invention in additives generally does not appear to be harmful for other properties such as wear inhibition, oxidation stability or thermal stability or else the hydrolysis performance of hydraulic oils. This was measured using tests such as the FZG seizure test, the Denison and Vickers Vane tests and the piston pump tests and the Cincinnati Milacron thermal stability tests as well as the ASTM D943 and ATMD 4310 oxidation tests. and the ASTM D2619 hydrolysis stability test. As mentioned above, it has also been noted that some of the agents improving filterability can have an advantageous effect on thermal stability and oxidation performance.

Those skilled in the art wishing to use the teachings of the present invention to prepare suitable lubricating fluids can effect this preparation using base oils and additives currently available. Information regarding these other constituents is briefly presented below.

Basic lubricant

The basic lubricant can be chosen from hydraulic / transmission fluids, hydraulic fluids for brakes, fluids for power steering and fluids for tractors, the precise composition of which may vary slightly.

The lubricating oils of the present invention comprise a dominant amount of an oil of lubricating viscosity. This oil can be any hydrocarbon-based lubricating oil or a synthetic base oil. It can be derived from synthetic or natural sources and it can be a paraffinic, naphthenic or asphalt base oil or consist of a mixture thereof.

In one embodiment, the oil of lubricating viscosity is prepared from a crude mineral oil by methods physical separation, such as distillation, deasphalting and dewaxing, or it can be prepared by chemical conversion, such as catalytic or non-catalytic hydrotreatment of mineral oil fractions, or by a combination of chemical separation processes and a chemical conversion; or it may consist of a basic synthetic hydrocarbon oil. Preferably, the oil of viscosity suitable for lubrication has a kinematic viscosity of 5 to 220 cSt at 40 ° C.

Other Additives Other additives which are well known in the art may be present in the increased filterability hydraulic fluid of the present invention. These additives may include, for example, antioxidants, viscosity index improvers, detergents, rust inhibitors, demulsifiers, foam inhibitors, corrosion inhibitors, pour point lowering agents and d other antiwear agents. Examples of these additives are shown below:

Antioxidants: include sterically hindered alkylphenols such as 2,6-di-tertio-butylphenol, 2,6-di-tertio-butyl-p-cresol and 2,6-di-tertio-butyl-4- ( 2-octyl-3-propanoic) -phenol; N.N-di (alkylphenyl) amines; and alkylated phenylene diamines.

Viscosity index improvers: include polymeric alkylmethacrylates and olefinic copolymers, such as an ethylene-propylene copolymer or a styrene-butadiene copolymer.

Detergents: include calcium alkylsalicylates, calcium alkylphenates and calcium alkarylsulfonates.

Anti-rust additives: include alkenyl succinic agents (short chains), their partial esters and their nitrogen derivatives; and synthetic alkarylsulfonates, such as metallic dinonyinaphthalenesulfonates. Demulsifiers: include alkoxylated phenols and phenol-formaldehyde resins as well as synthetic alkylarylsulfonates, such as metallic dinonyinaphthalenesulfonates.

Foaming inhibitors: include polymers of alkyl methacrylate and polymers of dimethylsilicone.

Corrosion inhibitors: include 2,5-dimercapto-1, 3,4-thiadiazoles and their derivatives, mercaptobenzothiazoles, alkyltriazoles and benzotriazoles.

Pour Point Lowering Agents (APEs): include polymethacrylates.

Antiwear agents: zinc alkyldithiophosphates (preferred), aryl phosphates and phosphites, sulphide esters and phosphosulphide compounds, metallic or ashless dithiocarbamates.

The hydraulic fluidity with increased filterability of the present invention can be produced by mixing the oil of clean viscosity with the lubrication and the agent improving the filterability together with the other additives described above which may be present in the oil of clean viscosity lubrication. The constituents of this mixture can interact during the mixing operation by modifying the filterability improving agent and / or the other additives. The various preferential conditions indicated above apply both to lubricating fluids and to the process for the production of a hydraulic fluid as well as to the uses according to the present invention.

The present invention is further illustrated by the following examples which are offered by way of illustration of the present invention. They are not intended to limit it.

EXAMPLES

COMPARATIVE EXAMPLE: A formulation of basic additives containing functional amounts of zinc dithiophosphate, of a dithiocarbamate without ash, calcium-containing detergent, phenolic antioxidant, anti-rust additives, demulsifiers, foam inhibitor based on silicone polymer, were mixed so that the formulation of basic additives (XOIE 303J) represents 0.80% by weight of the finished oil formulation. The finished oil formulation had a kinematic viscosity at 40 ° C equal to about 46 cSt.

COMPARATIVE EXAMPLE A: The base additive formulation was mixed in a refined base oil with a solvent "A", with the addition of an APE additive (of PMA type) at a dose of 0.2% by weight.

EXAMPLE 1 An amount of 0.05% by weight of a commercial phosphoric ester "P1" (Rhodafac PA35 from Rhône Poulenc) was added to the finished oil of Comparative Example A.

EXAMPLE 2 An amount of 0.05% by weight of a commercial phosphoric ester "P2" (CRODAFOS N3A from Croda) was added to the finished oil of Comparative Example A.

EXAMPLE 3 An amount of 0.05% by weight of a commercial phosphoric ester "P3" (CRODAFOS N5A from Croda) was added to the finished oil of Comparative Example A.

EXAMPLE 4 An amount of 0.03% by weight of a commercial fatty amide "OL" (CRODAMIDE O from Croda or Armeed O from Akzo) was added to the finished oil of Comparative Example A. COMPARATIVE EXAMPLE B: The formulation of base additives was mixed in a refined base oil with a solvent "B", with the addition of an APE additive (of PMA type) at a dose of 0.2% by weight.

EXAMPLE 5 An amount of 0.05% by weight of a commercial phosphoric ester "P1" (Rhodafac P PA35 from Rhône Poulenc was added to the finished oil of Comparative Example B.

EXAMPLE 6 An amount of 0.05% by weight of a commercial phosphoric ester "P2" (CRODAFOS N3A from Croda) was added to the finished oil of Comparative Example B.

EXAMPLE 7 An amount of 0.05% by weight of a commercial phosphoric ester "P3" (CRODAFOS N5A from Croda) was added to the finished oil of Comparative Example B.

EXAMPLE 8 An amount of 0.03% by weight of a commercial fatty amide "OL" (CRODAMIDE O from Croda or Armeed O from Akzo) was added to the finished oil of Comparative Example B.

COMPARATIVE EXAMPLE C: The formulation of base additives was mixed in a refined base oil with a solvent "C", with the addition of an APE additive (of PMA type) at a dose of 0.2% by weight and addition of an AIV additive (PMA type) at a dose of 4.65% by weight.

EXAMPLE 9 An amount of 0.05% by weight of a commercial phosphoric ester "P1" (Rhodafac PA 35 from Rhône Poulenc) was added to the finished oil of Comparative Example C. EXAMPLE 10 An amount of 0.05% by weight of a commercial phosphoric ester "P2" (CRODAFOS N3A from Croda) was added to the finished oil of Comparative Example C.

EXAMPLE 11 An amount of 0.05% by weight of a commercial phosphoric ester "P3" (CRODAFOS N5A from Croda) was added to the finished oil of Comparative Example C.

EXAMPLE 12 An amount of 0.03% by weight of a commercial fatty amide "OL" (CRODAMIDE O from Croda or Armeed O from Akzo) was added to the finished oil of Comparative Example C.

COMPARATIVE EXAMPLE D: The formulation of base additives was mixed with a "specialty of base formulation" containing a certain quantity of AIV additive (of PMA type).

EXAMPLE 13 An amount of 0.05% by weight of a commercial phosphoric ester "P1" (Rhodafac PA 35 from Rhône Poulenc) was added to the finished oil of Comparative Example D.

EXAMPLE 14 An amount of 0.05% by weight of a commercial phosphoric ester "P2" (CRODAFOS N3A from Croda) was added to the finished oil of Comparative Example D.

EXAMPLE 15 An amount of 0.05% by weight of a commercial phosphoric ester "P3" (CRODAFOS N5A from Croda) was added to the finished oil of Comparative Example D. EXAMPLE 16 An amount of 0.03% by weight of a commercial fatty amide "OL" (CRODAMIDE O from Croda or Armeed O from Akzo) was added to the finished oil of Comparative Example D.

The above examples were evaluated in the AFNOR NFE 48690 (A, B, C, D) and AFNOR NFE 48691 filterability tests. Table 1 below summarizes the test results.

TABLE 1

Filterability tests on HM and HV formulations in ISO VG 46 quality oil (IF and IFE filterability index)

Claims

1. Lubricating fluid comprising:

1) a dominant quantity of an oil of viscosity suitable for lubrication; and

2) from 0.03% to 0.06% of a filterability improving agent or of a mixture thereof, corresponding to the following formula:

R-Z wherein Z represents a polar group containing one or more substituents selected from the group consisting of a) phosphoric esters; b) amides; c) ethers; d) amino alcohols; e) ethoxylated amines; f) mixtures thereof, and R represents a lipophilic chain having 14 to 24 carbon atoms.

2. Lubricating fluid according to claim 1, wherein R comprises 17 to 19 carbon atoms.

3. A lubricating fluid according to claim 1 or 2, wherein Z is selected from the group consisting of a) phosphoric esters; b) polyethers; c) ethoxylated amines; d) mixtures thereof.

4. Lubricating fluid according to any one of claims 1 to 3, in which the agent improving the filterability is a phosphoric ester corresponding to the following formula: O - X / O = P - O - X

\ O - X

wherein X represents H or R and at least one of the symbols X represents R, and R represents a saturated or unsaturated hydrocarbyl chain which can comprise ether groups, said hydrocarbyl chain having 14 to 24 carbon atoms and preferably 17 to 19 atoms of carbon.

5. Lubricating fluid according to any one of claims 1 to 3, in which the agent improving the filterability is a compound corresponding to the formula R-0- (CH ₂ -CH ₂ 0) _x H, in which X represents a integer from 3 to 12, preferably equal to 9, and R represents a hydrocarbyl chain having 14 to 24 carbon atoms, R preferably representing a group C ₁₁ H ₂₃ or

6. Lubricating fluid according to claim 3, wherein the ethoxylated amine comprises at least two ethoxy groups.

7. Lubricating fluid according to claim 6, in which the agent improving the filterability is a compound corresponding to the following formula:

CH ₂ CH ₂ OH / CH ₂ CH ₂ CH ₂ N / \

RN CH ₂ CH ₂ OH

\ CH ₂ CH ₂ OH

wherein R represents a hydrocarbyl chain having 14 to 24 carbon atoms, and R preferably represents an aliphatic chain C ₁₈ H ₃₅ .

8. Lubricating fluid according to claim 1, in which the agent improving the filterability is an unsubstituted fatty amide corresponding to the following formula: H ₂ N-CO-R

9. Lubricating fluid according to any one of claims 1 to 8, said lubricating fluid consisting of a hydraulic oil.

10. Additive for a lubricating fluid, comprising an effective amount of a filterability improving agent according to any one of claims 1 to 8.

11. Use of an effective amount of an agent improving the filterability according to any one of claims 1 to 8 as an additive intended to improve the filterability of a lubricating fluid.

12. Use according to claim 11, wherein the lubricating fluid is a hydraulic oil.

13. Use according to claim 11 or 12, wherein the concentration of the filterability improving agent in said fluid is equal to

0.03% to 0.06% by weight.

14. Use according to any one of claims 11 to 13, said use being intended for a hydraulic system containing a piston pump having wear surfaces containing copper or a copper alloy and, optionally, a vane pump having wear surfaces containing steel.

15. A process for the production of a hydraulic fluid with improved filterability, which comprises mixing the following constituents: a) a dominant quantity of an oil of viscosity suitable for lubrication; and b) from 0.03% to 0.06% of a filterability improving agent, corresponding to the following formula