WO2001066677A1 - Multipurpose lubricant based on phosphorous and sulphur compounds - Google Patents

Abstract

The invention concerns a multipurpose lubricant comprising at least a phosphoric ester (A) of general formula (I) wherein: k = 2 or 3; m is a number from 0 to 8; x = 1 or 2 and R represents a linear alkyl or alkenyl radical with 10 to 20 carbon atoms or a salt of such an ester, and at least a polysulphide (B) of general formula: R'-Sy-R' wherein y is a number ranging from 2 to 8 and R' represents a tertio-alkyl radical with 4 to 18 carbon atoms, the volume ratio ranging between 0.01/1 to 1/1.

Description

MULTIFUNCTIONAL LUBRICANT BASED ON PHOSPHORUS COMPOUNDS AND SULFUR COMPOUNDS

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

Lubricant additives are generally classified into three main families. Limiting additives or lubricants, which are generally compounds comprising a fatty chain and a polar group (for example, fatty acids), allow lubrication under conditions of low loads; they form a monomolecular mat on the surface to be lubricated and thus reduce friction and wear. When the friction conditions become more severe. the rise in temperature leads to a desorption of these so-called limit or unctuous additives and anti-wear (AU) or extreme pressure (EP) additives are then necessary to lubricate the contact. AU and EP additives are generally compounds containing phosphorus, chlorine or sulfur. Under heavy loads, AU additives make it possible to greatly reduce the wear of the parts in contact; EP additives can cause some wear, but they prevent welding and adhesion phenomena. An effective lubricant formulation must include additives which make it possible to lubricate in the three regimes: limit, AU and EP; this is called a multifunctional lubricant.

Until the 1990s, chlorinated paraffins were widely used because of their AU and EP spectrum, but their use tends to be very reduced for reasons of toxicity.

Sulfur compounds such as, for example, polysulfides, sulfurized olefins or sulfurized fatty substances, have been used for a long time for their EP capacity; they make it possible to lubricate under conditions of high load and / or high temperatures. The use of sulfur compounds alone provides good EP properties, but the wear generated is too great. In addition, many sulfur derivatives are not suitable for the lubrication of yellow metals (copper, copper alloys, etc.) because of their corrosive action.

The AU action of phosphorus derivatives is well known. They are generally phosphites or phosphoric esters (either triesters obtained by reaction of an alcohol on PCI ₃ , or mixtures of mono and diesters obtained by reaction of an alcohol on P ₂ O ₅ ). The use alone of phosphorous compounds leads to a strong reduction of wear, but it does not allow to reach regimes where the friction conditions are very severe.

The combined use of sulfur and phosphorous compounds has already been advocated in US patents 3,933,658, DE 2,752,218 and JP 54-154405; it provides a lubricant with AU and EP properties. However, these compositions are generally not smooth so that the addition of fatty substances is necessary to avoid grazing phenomena (stick-slip) and to reduce friction under conditions of low loads and / or temperatures. In addition, compositions based on phosphorus and sulfur compounds often cause corrosion problems on yellow metals due to the presence of the sulfur compound.

It has now been found that the combination of a phosphoric acid ester based on linear fatty alcohol, ethoxylated or not, and a di-tertioalkyl polysulfide makes it possible to obtain excellent multifunctional lubricants (limit , AU and EP) which, in the case of polysulphides without free sulfur (standard ASTM D-1662), prevent corrosion of yellow metals.

A subject of the present invention is therefore a multifunctional lubricant comprising at least one phosphorus compound (A) and at least one sulfur compound (B), characterized in that compound A is a phosphoric ester of general formula:

(HO) 3. _x ~ P- (θC _k H _2k ) _rn -OR] χ

O

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 a as an ester, compound B is a polysulfide of general formula:

R'-S _y -R '

in which y is a number ranging from 2 to 8 and R ¹ represents a tertioalkyl radical having from 4 to 18 carbon atoms, the mass ratio A / B being between 0.01 / 1 and 1/1, preferably between 0.05 / 1 and 0.4 / 1.

The invention also relates to an additive for multifunctional lubricants consisting of the mixture of at least one phosphoric ester (A) as defined above or a salt of such an ester and at least one polysulfide (B) as defined above, in an A / B mass ratio of between 0.01 / 1 and 1/1, preferably between 0.05 / 1 and 0.4 / 1. Among the phosphoric esters (A), those in which k is equal to 2, m is between 2 and 6 and R is a radical containing from 12 to 18 carbon atoms, more particularly the lauryl, stearyl, oleyl or linoleyl. The phosphoric esters (A) which are most often mixtures of mono- and di-esters in proportions ranging from 10/90 to 90/10, can be used in the acid form or in the form of alkali, ammonium or alkanolamines.

Among the polysulfides (B), those in which the number is between 3 and 5 and the radical R ′ contains from 4 to 12 carbon atoms are preferred. More particularly preferred are di-tertiobutyl trisulfide, di-tertononyl pentasulfide, di-tertiododecyl trisulfide and di-tertiododecyl pentasulfide.

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 can be facilitated by heating.

The multifunctional lubricants according to the invention can be obtained by incorporating 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, synthetic or of animal or vegetable origin and contain additives conventionally used in lubricants such as, for example, lubricants, corrosion inhibitors, emulsifiers, alkaline agents, etc.

EXAMPLES

In the following examples which illustrate the invention without limiting it, the parts and percentages indicated are expressed by weight. Table 1 below specifies the name and the chemical nature of the compounds used in these examples.

TABLE 1

* OE = ethylene oxide

The phosphoric esters which are marketed by the applicant consist mainly of mono-esters The polysulphides TPS 20, TPS 32, TPS 37 and TPS 44 are marketed by the company ATOFINA

Lubricant performance was assessed according to the following experimental procedures

1. Test 4 extreme pressure balls (ASTM D-2783):

Evaluation of the anti-wear power by the value of the highest possible load before seizing (typically 100 kg) and of the extreme pressure power by the value of the highest possible welding load (typically ≥ 315 kg) Conditions 1500 rpm, increasing charges for 10 seconds

2. Test 4 wear balls (ASTM D-4172):

Evaluation of the anti-wear power by the value of the smallest possible wear imprint (typically ≤ 0.60mm)

Conditions 1500 rpm, 40 kg 3600 seconds, 75 ° C 3. Disc ball test:

Evaluation of the creamy or limit power of a lubricant by the value of the coefficient of friction μ which must be as low as possible, typically ≤ 0 05

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

Conditions: 1 rpm, 1 kg, 30 mm, 100C6 steel ball on aluminum disc

4. Anti-corrosion properties on copper strip (ASTM D-130):

Since sulfur additives tend to corrode yellow metals due to the presence of free sulfur, this test evaluates the corrosive power of formulations on a copper strip.

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

Table 2 below summarizes 27 additive compositions prepared from the products in Table 1.

Only compositions 6 to 15 and 17 are in accordance with the present invention The others do not contain a phosphorus compound (compositions 1 to 4) or no sulfur compound (compositions 5, 16, 18, 20, 22 and 24) or contain a phosphorus compound derived from a non-linear alcohol (compositions 19, 21, 23 and 25 to 27).

TABLE 2

EXEMPLES 1 A 30

EXAMPLES 1 TO 30

The compositions of Table 2 were diluted in a 100 neutral Neutral paraffin oil and the performance of the formulations thus obtained are collated in Table 3 below where the percentage of dilution indicates the proportion of additive composition in the formulation.

TABLE 3

TABLEAU 3 (suite.

TABLE 3 (continued.

On examining the results in Table 3, it can be seen that the choice of phosphoric ester is decisive since the lubricants of Examples 24, 26, 28 and 30 containing an ester not in accordance with the invention have a high coefficient of friction (> 0.05) and therefore a lack of oiliness. The inhibition of corrosion on yellow metals is also observed (examples 7, 10 and 13) when the polysulfide does not contain free sulfur.

EXAMPLES 31 TO 39

By dispersion in water of the additive compositions 5, 7, 9, 12, 13, 16. 18, 26 and 27 of Table 2. 9 lubricants were prepared, the performances of which are collated in Table 4 below.

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. TABLE 4

EXAMPLES 40 to 44

With 5% paraffinic oil 100 Neutral, 9.5% polyethoxylated lauπque alcohol (4 EO), 0.5% sodium dodecylbenzenesulfonate and 85% water, a non-additive microemulsion was prepared (example 40)

To samples of this microemulsion, the additive composition 1, 2, 5 or 7 from Table 2 was then added and heated to 50 ° C. for homogenization.

The performances of the lubricants thus obtained, translucent at room temperature, are collated in Table 5 below

TABLE 5

Claims

1. Multifunctional lubricant comprising at least one phosphorus compound (A) and at least one sulfur compound (B), characterized in that compound A is a phosphoric ester of general formula (HO) 3_ _x -P— f (OC _k H _{2k) m} -OR] χ O 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 a such ester, compound B is a polysulfide of general formula R'-Sy-R ' in which y is a number ranging from 2 to 8 and R 'represents a tertioalkyl radical having from 4 to 18 carbon atoms, the mass ratio A / B 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, wherein the number y is between 3 and 5 and R 'is a tertioalkyl radical having from 4 to 12 carbon atoms 4. Lubricant according to one of claims 1 to 3, in which the mass ratio A / B 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 di-esters, the number k being equal to 2, the number m being between 4 and 5 and R being the lauryl, stearyle, oleyl or noleyl radical 6. Lubricant according to one of claims 1 to 5, in which the compound B is di-tertiobutyl trisulfide, di-tertiononyl pentasulfide, di-tertiododecyl trisulfide or di-tertiododecyl pentasulfide 7. Additive for multifunctional lubricant, characterized in that it contains at least one phosphoric ester (A) of general formula (HO) 3-χ -Pf (OC _k H _2k ) _m -ORj _x O 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 a such ester, and at least one polysulfide (B) of general formula R'-S _y -R ' in which y is a number ranging from 2 to 8 and R 'represents a tertioalkyl radical having from 4 to 18 carbon atoms, the mass ratio A / B 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 tertioalkyl radical having from 4 to 12 carbon atoms 10. Additive according to one of claims 7 to 9, in which the mass ratio A / B 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 di-esters, the number k being equal to 2, the number m being between 4 and 5 and R being the lauryl, stearyle, oleyl or noleyl radical 12. Additive according to one of claims 7 to 11, in which the compound B is di-tertiobutyl trisulfide, di-tertiononyl pentasulfide, di-tertiododecyl trisulfide or di-tertiododecyl pentasulfide