Multipurpose lubricant based on phosphorous and sulphur compounds

Abstract

The multifunctional lubricant according to the invention comprises at least one phosphoric ester (A) of general formula: 1

Description

DESCRIPTION

[0001] The present invention relates to the field of lubricants and more particularly that of additives which can be used in industrial lubricant formulations for gearboxes, gearings, bearings, compressors, turbines, hydraulic fluids, and the like, or in lubricant formulations for the working or shaping of metals.

[0002] Lubricant additives are generally classified into three main families. The boundary additives or lubricity agents, which are generally compounds comprising a fatty chain and a polar group (for example fatty acids), make possible lubrication under conditions of low load; they form a monomolecular covering on the surface to be lubricated and thus reduce friction and wear. When the frictional conditions become more severe, the rise in the temperature results in a desorption of these so-called boundary or lubricity additives, and antiwear (AW) or extreme pressure (EP) additives are then necessary to lubricate the contact. AW and EP additives are generally compounds comprising phosphorus, chlorine or sulphur. Under high loads, AW additives make it possible to greatly reduce the wear of the components in contact; EP additives can generate a degree of wear but they prevent the phenomena of welding and of adhesion. An efficient lubricating formulation must comprise additives which make it possible to lubricate under the three systems: boundary, AW and EP; this is then termed a multifunctional lubricant.

[0003] Up until the 1990s, chlorinated paraffins were widely used because of their AW and EP spectrum but their use is tending to be greatly reduced for reasons of toxicity.

[0004] Sulphur compounds, such as, for example, polysulphides, sulphurized olefins or sulphurized fatty substances, have been used for a long time for their EP capability; they make it possible to lubricate under conditions of high load and/or of high temperatures. The use of sulphur compounds alone introduces good EP properties but the wear generated is too great. In addition, numerous sulphur derivatives are not suitable for the lubrication of yellow metals (copper, copper alloys, and the like) because of their corrosive effect.

[0005] The AW action of phosphorus derivatives is well known. They are generally phosphites or phosphoric esters (either triesters obtained by reaction of an alcohol with PCl3 or mixtures of mono- and diesters obtained by reaction of an alcohol with P2O5). The use of phosphorus compounds alone results in a strong reduction in wear but it does not make it possible to achieve systems where the frictional conditions are very severe.

[0006] The combined use of sulphur and phosphorus compounds has already been recommended in Patents U.S. Pat. No. 3,933,658, DE 2,752,218 and JP 54-154405; it makes it possible to obtain a lubricant with AW and EP properties. However, these compositions are generally not lubricious, so much so that the addition of fatty substances is necessary in order to avoid stick-slip phenomena and to reduce friction under conditions of low loads and/or temperatures. In addition, compositions based on phosphorus and sulphur compounds often cause problems of corrosion on yellow metals because of the presence of the sulphur compound.

[0007] It is now been found that the combination of a phosphoric acid ester on an ethoxylated or nonethoxylated linear fatty alcohol base and of a di-tert-alkyl polysulphide makes it possible to obtain excellent multifunctional lubricants (boundary, AW and EP) which, in the case of polysulphides lacking free sulphur (ASTM Standard D-1662), prevent the corrosion of yellow metals.

[0008] A subject-matter of the present invention is therefore a multifunctional lubricant comprising at least one phosphorus compound (A) and at least one sulphur compound (B), characterized in that the compound A is a phosphoric ester of general formula: 2

[0009] in which k is equal to 2 or 3, m is a number ranging from 0 to 8, x is equal to 1 or 2 and R represents a linear alkyl or alkenyl radical having from 10 to 20 carbon atoms, or a salt of such an ester and the compound B is a polysulphide of general formula:

R′—Sy—R′

[0010] in which y is a number ranging from 2 to 8 and R′ represents a tert-alkyl radical having from 4 to 18 carbon atoms, the A/B ratio by mass being between 0.01/1 and 1/1, preferably between 0.05/1 and 0.4/1.

[0011] Another subject-matter of the invention is an additive for multifunctional lubricants composed of the mixture of at least one phosphoric ester (A) as defined above or a salt of such an ester and of at least one polysulphide (B) as defined above in an A/B ratio by mass of between 0.01/1 and 1/1, preferably between 0.05/1 and 0.4/1.

[0012] Preference is given, among the phosphoric esters (A), to those in which k is equal to 2, m is between 2 and 6 and R is a radical comprising from 12 to 18 carbon atoms, more particularly the lauryl, stearyl, oleyl or linoleyl radical. The phosphoric esters (A), which are generally mixtures of mono- and diesters in proportions ranging from 10/90 to 90/10, can be used in the acidic form or in the form of alkali metal, ammonium or alkanolamine salts.

[0013] Preference is given, among the polysulphides (B), to those in which the number y is between 3 and 5 and the R′ radical comprises from 4 to 12 carbon atoms. Di-tert-butyl trisulphide, di-tert-nonyl pentasulphide, di-tert-dodecyl trisulphide and di-tert-dodecyl pentasulphide are more particularly preferred.

[0014] The additive according to the invention can be prepared by simple mixing of the compounds (A) and (B), which are generally liquid at room temperature. In some cases, the operation may be facilitated by heating.

[0015] The multifunctional lubricants according to the invention can be obtained by incorporation of the additive according to the invention in whole oils or in soluble oils (emulsions and microemulsions) in a proportion of 1 to 100 parts of additive (preferably 2 to 50 and more particularly 5 to 20) per 100 parts of oil. The oils can be mineral or synthetic or of animal or vegetable origin and can comprise additives conventionally used in lubricants, such as, for example, lubricity agents, corrosion inhibitors, emulsifiers, alkaline agents and the like.

EXAMPLES

[0016] In the following examples, which illustrate the invention without limiting it, the parts and percentages shown are expressed by weight. The names and the chemical natures of the compounds used in these examples are specified in the following Table 1. 1 TABLE 1 Type of product Name Chemical nature Mineral oil 100NSO3 Paraffin oil, 100 Neutral Phosphorus Beycostat A684 Phosphoric ester of oleyl compounds alcohol comprising 4.5 EO* Beycostat A244 Phosphoric ester of lauryl alcohol comprising 4 EO Beycostat AB04 Phosphoric ester of nonyl- phenol comprising 4 EO Beycostat A136 Phosphoric ester of isotri- decyl alcohol comprising 6 EO Beycostat A130 Phosphoric ester of iso-tridecyl alcohol Beycostat A081 Phosphoric ester of ethylhexanol Sulphur TPS 20 Di-tert-dodecyl trisulphide compounds TPS 32 Di-tert-dodecyl pentasulphide TPS 37 Di-tert-nonyl pentasulphide TPS 44 Di-tert-butyl trisulphide *EO = ethylene oxide

[0017] The phosphoric esters which are sold by the Applicant Company are predominantly composed of monoesters. The polysulphides TPS 20, TPS 32, TPS 37 and TPS 44 are sold by the Company ATOFINA.

[0018] The performances of the lubricants were evaluated according to the following experimental procedures:

[0019] 1. 4-ball extreme pressure test (ASTM D-2783):

[0020] Evaluation of the antiwear capability by the highest possible value of the load before seizing up (typically >100 kg) and of the extreme pressure capability by the highest possible value of the welding load (typically >315 kg).

[0021] Conditions: 1500 rev/min, increasing loads for 10 seconds.

[0022] 2. 4-ball wear test (ASTM D-4172):

[0023] Evaluation of the antiwear capability by the lowest possible value of the wear scar (typically <0.60 mm).

[0024] Conditions: 1500 rev/min, 40 kg, 3600 seconds, 75° C.

[0025] 3. Ball-disc test:

[0026] Evaluation of the lubricity or boundary capability of a lubricant by the value of the coefficient of friction &mgr;, which must be as low as possible, typically <0.05.

[0027] The ball-disc test consists in rotating a disc at a constant speed under a ball to which is applied a constant load. The disc and the ball are immersed in the lubricant. A force sensor measures the coefficient of friction of the ball-disc lubricated contact.

[0028] Conditions: 1 rev/min, 1 kg, 30 min, 100C6 steel ball on an aluminium 3104 disc.

[0029] 4. Corrosion-resistant properties with regard to a copper strip (ASTM D-130):

[0030] As sulphur additives have a tendency to corrode yellow metals because of the presence of free sulphur, this test evaluates the corrosiveness of the formulations with regard to a copper strip.

[0031] The test consists in immersing a polished copper plate in a test tube comprising 30 ml of formulation for 24 h at 60° C. At the end of the test period, the plate is suitably washed and compared with reference corroded strips (the classification ranging from 1a for the least corroded to 4c for the most corroded).

[0032] 27 additive compositions prepared from the products in Table 1 are summarized in the following Table 2.

[0033] Only the compositions 6 to 15 and 17 are in accordance with the present invention. The others do not comprise phosphorus compound (compositions 1 to 4) or do not comprise sulphur compound (compositions 5, 16, 18, 20, 22 and 24) or comprise a phosphorus compound derived from a nonlinear alcohol (compositions 19, 21, 23, and 25 to 27). 2 TABLE 2 Sulphur compound Phosphorus compound Composition Amount Amount number Name (parts) Name (parts) 1 TPS 20 100 none 0 2 TPS 32 100 none 0 3 TPS 37 100 none 0 4 TPS 44 100 none 0 5 none 0 Beycostat A684 100 6 TPS 20 100 Beycostat A684 5 7 TPS 20 100 Beycostat A684 10 8 TPS 20 100 Beycostat A684 20 9 TPS 20 100 Beycostat A684 40 10 TPS 32 100 Beycostat A684 5 11 TPS 32 100 Beycostat A684 10 12 TPS 32 100 Beycostat A684 20 13 TPS 32 100 Beycostat A684 40 14 TPS 37 100 Beycostat A684 5 15 TPS 44 100 Beycostat A684 5 16 none 0 Beycostat A244 100 17 TPS 20 100 Beycostat A244 5 18 none 0 Beycostat AB04 100 19 TPS 20 100 Beycostat AB04 5 20 none 0 Beycostat A136 100 21 TPS 20 100 Beycostat A136 5 22 none 0 Beycostat A130 100 23 TPS 20 100 Beycostat A130 5 24 none 0 Beycostat A081 100 25 TPS 20 100 Beycostat A081 5 26 TPS 20 100 Beycostat AB04 40 27 TPS 32 100 Beycostat AB04 40

Examples 1 to 30

[0034] The compositions in Table 2 were diluted in a 100 Neutral whole paraffin oil and the performances of the formulations thus obtained are collated in the following Table 3, where the percentage of dilution indicates the proportion of additive composition in the formulation. 3 TABLE 3 4-ball wear 4-ball EP Ball- Wear Seizing Welding Corrosion Example Compo- Dilution disc diameter load load Copper number sition (%) &mgr; (mm) (kg) (kg) strip 1 —  0% 0.13  1.70 50 26 1b 2 1 10% 0.082 0.78 100 400 3b 3 2 10% 0.075 1.10 100 500 4c 4 3 10% 0.087 1.18 100 500 4c 5 4 10% 0.077 1.11 126 500 3a 6 5 0.5%  0.036 0.43 100 160 1b 7 6 10% 0.047 0.47 160 400 1b 8 10 10% 0.046 0.51 126 620 4c 9 14 10% 0.044 0.45 200 620 4c 10 15 10% 0.043 0.54 200 620 1b 11 7 10% 0.044 — 160 400 — 12 7  5% 0.044 — 100 250 — 13 8 10% 0.043 — 126 400 1b 14 8  5% 0.041 — 126 250 — 15 9  5% 0.041 — 126 250 — 16 11 10% 0.039 200 500 — 17 11  5% 0.041 126 400 — 18 12 10% 0.038 200 500 4c 19 12  5% 0.040 126 250 — 20 13  5% 0.038 126 400 — 21 16  2% — 100 250 — 22 17 10% 0.045 160 400 — 23 18  2% — 126 200 — 24 19 10% 0.070 160 400 — 25 20  2% — 126 200 — 26 21 10% 0.062 160 400 — 27 22  2% — 100 200 — 28 23 10% 0.074 126 315 — 29 24  2% — 100 250 — 30 25 10% 0.103 126 250 —

[0035] On examination of the results in Table 3, it is found that the choice of the phosphoric ester is determining, since the lubricants of Examples 24, 26, 28 and 30, comprising an ester not in accordance with the invention, exhibit a high coefficient of friction (>0.05) and thus a lack of lubricity. In addition, it is observed (Examples 7, 10 and 13) that there is inhibition of the corrosion with regard to yellow metals when the polysulphide does not comprise free sulphur.

Examples 31 to 39

[0036] Nine lubricants, the performances of which are collated in the following Table 4, were prepared by dispersion in water of the additive compositions 5, 7, 9, 12, 13, 16, 18, 26 and 27 in Table 2.

[0037] Examples 31 to 33 correspond to the phosphorus compounds alone dispersed in water. Examples 34 to 37 are in accordance with the invention. Examples 38 and 39 are not in accordance with the invention. 4 TABLE 4 4-ball EP Ball- Seizing Welding Example Dilution disc load load number Composition (%) &mgr; (kg) (kg) 31 5 2% 0.033 80 160 32 16 2% 0.038 100 160 33 18 2% 0.064 100 160 34 7 10% 0.050 200 400 35 9 5% 0.043 160 315 36 12 5% 0.044 200 315 37 13 5% 0.039 160 315 38 26 5% 0.081 160 200 39 27 5% 0.072 200 250

Examples 40 to 44

[0038] A non-additivated microemulsion (Example 40) was prepared with 5% of 100 Neutral paraffin oil, 9.5% of polyethoxylated (4 EO) lauryl alcohol, 0.5% of sodium dodecylbenzenesulphonate and 85% of water.

[0039] The additive composition 1, 2, 5 or 7 in Table 2 was subsequently added to samples of this microemulsion and the mixture was heated at 50° C. for homogenization.

[0040] The performances of the lubricants thus obtained, which are translucent at room temperature, are collated in the following Table 5. 5 TABLE 5 4-ball EP Ball- Seizing Welding Example Dilution disc load load number Composition (%) &mgr; (kg) (kg) 40 none 0% 0.218 40 126 41 1 5% 0.146 63 200 42 2 5% 0.212 63 200 43 5 2% 0.045 80 160 44 7 10% 0.050 126 315

Claims

1. Multifunctional lubricant comprising at least one phosphorus compound (A) and at least one sulphur compound (B), characterized in that the compound A is a phosphoric ester of general formula:

3

in which k is equal to 2 or 3, m is a number ranging from 0 to 8, x is equal to 1 or 2 and R represents a linear alkyl or alkenyl radical having from 10 to 20 carbon atoms, or a salt of such an ester and the compound B is a polysulphide of general formula:

R′—Sy—R′

in which y is a number ranging from 2 to 8 and R′ represents a tert-alkyl radical having from 4 to 18 carbon atoms, the a/b ratio by mass being between 0.01/1 and 1/1.

2. Lubricant according to claim 1, in which k is equal to 2, m is a number ranging from 2 to 6 and R is a radical having from 12 to 18 carbon atoms.

3. Lubricant according to claim 1 or 2, in which the number y is between 3 and 5 and R′ is a tert-alkyl radical having from 4 to 12 carbon atoms.

4. Lubricant according to one of claims 1 to 3, in which the A/B ratio by mass is between 0.05/1 and 0.4/1.

5. Lubricant according to one of claims 1 to 4, in which the compound A is a mixture of phosphoric mono- and diesters, the number k being equal to 2, the number m being between 4 and 5 and R being the lauryl, stearyl, oleyl or linoleyl radical.

6. Lubricant according to one of claims 1 to 5, in which the compound B is di-tert-butyl trisulphide, di-tert-nonyl pentasulphide, di-tert-dodecyl trisulphide or di-tert-dodecyl pentasulphide.

7. Multifunctional lubricant additive, characterized in that it comprises at least one phosphoric ester (A) of general formula:

4

in which k is equal to 2 or 3, m is a number ranging from 0 to 8, x is equal to 1 or 2 and R represents a linear alkyl or alkenyl radical having from 10 to 20 carbon atoms, or a salt of such an ester and at least one polysulphide (B) of general formula:

R′—Sy—R′

in which y is a number ranging from 2 to 8 and R′ represents a tert-alkyl radical having from 4 to 18 carbon atoms, the A/B ratio by mass being between 0.01/1 and 1/1.

8. Additive according to claim 7, in which k is equal to 2, m is a number ranging from 2 to 6 and R is a radical having from 12 to 18 carbon atoms.

9. Additive according to claim 7 or 8, in which the number y is between 3 and 5 and R′ is a tert-alkyl radical having from 4 to 12 carbon atoms.

10. Additive according to one of claims 7 to 9, in which the A/B ratio by mass is between 0.05/1 and 0.4/1.

11. Additive according to one of claims 7 to 10, in which the compound A is a mixture of phosphoric mono- and diesters, the number k being equal to 2, the number m being between 4 and 5 and R being the lauryl, stearyl, oleyl or linoleyl radical.

12. Additive according to one of claims 7 to 11, in which the compound B is di-tert-butyl trisulphide, di-tert-nonyl pentasulphide, di-tert-dodecyl trisulphide or di-tert-dodecyl pentasulphide.