EP1156100A1 - Waterborn multifunctional lubricant based on dithiodiglycolic acid - Google Patents

Abstract

Multifunctional aqueous lubricant, comprising at least one water-soluble salt of dithio-diglycolic acid and at least one water soluble compound selected from phosphoric ester (I) and salt of alkyl-thioacid (II), at wt. ratio of dithio-diglycolic acid to compound (I) and (II) as 1/1-20/1, is new. The lubricant comprises at least one water-soluble salt of dithio-diglycolic acid and at least one water-soluble compound selected from: (a) phosphoric esters of formula (HO)3-x -P(O)- ((OCkH2k)m -OR)x (I) and their salts; and (b) water-soluble salts of alkylthio-acids of formula R'-S-(CH2)n - COOH (II). R = 6-20C alkyl, alkenyl or alkylaryl; k = 2 or 3; m = 0-20; x = 1 or 2; n = 1-10; R' = 6-20C alkyl, alkenyl or aryl radical. An Independent claim is also included for an additive to multifunctional aqueous lubricant, comprising aqueous solution of at least one water-soluble salt of dithio-diglycolic acid and at least one water soluble compound selected from phosphoric esters (I) and their salts, and salts of alkyl-thioacid (II), as claimed.

Description

The invention relates to the field of lubricants and more particularly for object that of the aqueous lubricants useful for the work or the shaping of metals.

Metal working or shaping operations require the use of a lubricant in order to reduce the forces between the workpiece and the tool, remove chips and debris, cool and check the surface finish of the part or of the worked sheet. Traditionally, oil-based lubricants have been used. These are whole oils or emulsions to which oiling agents, anti-wear (AU) and / or extreme pressure (EP) additives have been optionally assistants. The lubricants form a monomolecular mat on the surface to be lubricate and thus reduce wear and friction. When the conditions of friction become more severe, the rise in temperature causes a desorption of these lubricants, and AU or EP additives (generally compounds containing phosphorus, chlorine or sulfur) are then necessary to lubricate the contact. Under heavy loads, AU additives reduce heavy wear of the parts in contact; EP additives can cause some wear but prevent welding and adhesion phenomena. The whole oils have excellent lubricating properties but, when rates are high, the evacuation of heat requires the use of emulsions. However, the use of emulsions also tends to be reduced because, over time, they degrade and cause bad odors.

This is why more and more aqueous fluids are being developed which are either synthetic fluids (aqueous solutions based on soluble additives in water), or semi-synthetic fluids (oil-in-water microemulsions containing a large quantity of emulsifiers). However, if the aqueous fluids evacuate heat very well and have improved resistance to bacterial growth, their use is often limited to metal working operations where friction and wear conditions are not too severe. Indeed, the additives AU and EP having been developed for oils, very few of them are soluble in water and suitable for aqueous fluids.

There is a plethora of oil soluble AU or EP additives, but the number water soluble AU or EP additives is much more restricted. It is possible nevertheless to distinguish two main classes of water-soluble additives: phosphorus compounds and sulfur compounds.

Among the phosphorus compounds, the most used are the phosphoric acid esters obtained by reaction of a fatty alcohol, ethoxylated or not, on P ₂ O ₅ . They are soluble in water by neutralization in the form of alkaline salt, ammonium or alkanolamine or else thanks to their ethoxylated part. Widely used in aqueous metal working or shaping fluids due to their AU, emulsifying and corrosion-inhibiting properties, these esters are however not suitable for operations where the friction and wear conditions are very severe.

Among the sulfur compounds, mention may be made of alkylthio-acids which are monosulfides consisting of an alkyl chain generally comprising between 6 and 18 carbon atoms and a carboxylic acid group. Soluble in water by neutralization in the form of alkali, ammonium or alkanolamine salts, they are used in aqueous working or metal forming lubricants for their AU and corrosion inhibiting properties. However, their EP capacity is insufficient for very severe operations.

In Lubr. Eng. 1977, 33 (6), 291-298, R. W. Mold et al. reported EP properties of some water-soluble sulfur additives such as sodium thiosalicylic acid, 2-mercaptopropionic, 2,2'-dithiodibenzoic acid, 2,2'-dithiodipropionic and dithiodiglycolic. The use of 3,3'-dithiodipropionic acid salts or dithiodiglycol as EP additives for aqueous lubricants has been the subject of patents EP 288 375, JP 63-265997 and EP 183 050, 3,3'-dithiodipropionic acid can be combined with alkylthio-acids for lubricants aqueous stamping (JP 10-110181). Very recently, synergies on the EP capacity between this type of acids and orthophosphoric acid have been observed (JP 08-302380).

It has now been found that the combination of a water-soluble salt of the acid dithiodiglycolic with a water-soluble phosphoric ester or a water-soluble salt of an alkylthio-acid makes it possible to obtain multifunctional aqueous lubricants (smooth, AU and EP).

a) les esters phosphoriques de formule générale (I):

dans laquelle R représente un radical alkyle, alcényle ou alkylaryle dont le nombre d'atomes de carbone peut aller de 6 à 20, x est égal à 1 ou 2, k est égal à 2 ou 3 et m est un nombre allant de 0 à 20, et leurs sels, et

b) les sels hydrosolubles des alkylthio-acides de formule générale :

dans laquelle n peut aller de 1 à 10, et R' désigne un radical alkyle, alcényle ou aryle comprenant de 6 à 20 atomes de carbone.

The present invention therefore relates to a multifunctional aqueous lubricant characterized in that it comprises at least one water-soluble salt of dithiodiglycolic acid and at least one water-soluble compound chosen from the group consisting of:

a) the phosphoric esters of general formula (I):

in which R represents an alkyl, alkenyl or alkylaryl radical the number of carbon atoms of which can range from 6 to 20, x is equal to 1 or 2, k is equal to 2 or 3 and m is a number ranging from 0 to 20, and their salts, and

b) the water-soluble salts of the alkylthio-acids of general formula:

in which n can range from 1 to 10, and R ′ denotes an alkyl, alkenyl or aryl radical comprising from 6 to 20 carbon atoms.

The subject of the invention is also an additive for a multifunctional aqueous lubricant. consisting of an aqueous solution of at least one water-soluble salt of dithiodiglycolic acid and at least one water-soluble compound chosen from the group consisting of the phosphoric acid esters (I) and their salts and by the salts water-soluble alkylthio-acids (II).

As water-soluble salts of dithiodiglycolic acid S ₂ (CH ₂ COOH) _2, there may be mentioned more particularly the alkali metal, ammonium or alkanolamine salts such as, for example, monoethanolamine, diethanolamine and triethanolamine.

Among the phosphoric esters (I), those in which k is equal are preferred. at 2, m is a number ranging from 0 to 10 (in particular 4 to 5) and R is a radical containing 10 to 18 carbon atoms. Phosphoric esters (I) are the most often mixtures of mono- and di-esters in proportions ranging from 10/90 to 90/10. When they are not by themselves water-soluble, these esters can be used in the form of alkali metal, ammonium or alkanolamine salts.

Among the alkylthio-acids (II), those in which n is equal to 1 are preferred. or 2 and the radical R 'contains from 8 to 18 carbon atoms. As water-soluble salts of these acids, the alkali metal, ammonium salts are preferably used or an alkanolamine such as monoethanolamine, diethanolamine and triethanolamine.

In the multifunctional aqueous lubricant according to the invention as well as in the additive that can be used for its preparation, the mass ratio: dithiodiglycolic acid / compound (s) I and / or II can range from 1/1 to 20/1, but is preferably understood between 2/1 and 10/1.

In the multifunctional aqueous lubricant according to the invention, the concentration total mass in dithiodiglycolic acid and in compound (s) I and / or II can range from 0.01 to 20% and is preferably between 0.1 and 10%.

The additive according to the invention can be stored in the form of a dilutable concentrate later in synthetic fluids (true solutions) or semi-synthetic fluids (microemulsions). This concentrate may contain additives conventionally used in synthetic or semi-synthetic fluids such as inhibitors corrosion, emulsifiers, lubricant additives, alkaline agents, anti-foaming agents, ... In these concentrates, the total mass content of acid dithiodiglycolic and in compound (s) I and / or II can range from 1 to 50% and is preferably between 15 and 35%.

EXAMPLES

In the following examples which illustrate the invention without limiting it, the percentages indicated are expressed by weight.

Table I below specifies the chemical nature of the compounds used in these examples. Designation Chemical nature ADTDG Dithiodiglycolic acid ALTP Laurylthiopropionic acid AL Lauric acid Beycostat A684 Phosphoric ester of oleic alcohol at 4.5 EO Beycostat A244 Phosphoric ester of lauric alcohol with 4 EO Beycostat AB04 Phosphoric ester of nonylphenol with 4 EO

Phosphoric esters, sold by CECA S.A., are mixtures of mono- and diesters, predominantly monoester.

The formulations tested, all clear, were produced by diluting the compounds in water and in the case of acids, stoichiometric neutralization at monoethanolamine (MEA), soda or potash. Phosphoric esters have been diluted in water as is.

The performances of the various formulations were evaluated 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 load before seizing the as high as possible (typically ≥ 63 kg) and extreme pressure power by the highest possible welding load value (typically ≥ 250 kg).

Conditions: 1500 rpm, increasing loads for 10 seconds.

2. 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 ≤ 0.10.

The ball-disc test consists of spinning 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 min, 100C6 steel ball on aluminum disc 3104.

3. Falex wear test (ASTM D2670-88)

A steel shaft immersed in the lubricant rotates at constant speed between two V-shaped jaws on which a constant load is applied. AT at the end of the test, the weight loss of the two ves and of the axis is measured and must be less than 20 mg so that the formulation has anti-wear properties.

Conditions: 290 rpm, 480 kg, 15 min, axis and ves in 100C6 steel.

In the following table 2 which summarizes the composition of the different formulations tested and their performance, an abbreviation such as AL / MEA means that lauric acid (AL) was neutralized by monoethanolamine (MEA).

In the case of acids, the percentage indicated corresponds to free acid and not to salt. N ° of ex. Compound I or II % Dithiodiglycolic acid salt % Falex wear Disc ball 4 EP balls Weight loss (mg) µ Seizure load (kg) Welding load (kg) 1 AL / MEA 2 No 0 44 0.065 50 126 2 ALTP / MEA 2 No 0 5 0.045 80 126 3 Beycostat A684 2 No 0 5 0.033 100 160 4 Beycostat A244 2 No 0 breaking 0.038 100 160 5 Beycostat AB04 2 No 0 6 0.064 100 160 6 No 0 ADTDG / MEA 5 - 0.4 20 400 7 No 0 ADTDG / K 5 - 0.4 20 800 8 No 0 ADTDG / Na 5 83 0.4 16 800 9 Beycostat A684 2 ADTDG / MEA 5 - 0.035 100 315 10 Beycostat A684 2 ADTDG / K 5 - 0.035 100 500 11 Beycostat A684 2 ADTDG / Na 5 3 0.036 100 400 12 Beycostat A684 0.5 ADTDG / Na 5 3 0.033 100 500 13 Beycostat A244 2 ADTDG / Na 5 5 0.043 126 620 14 Beycostat AB04 2 ADTDG / Na 5 3 0.086 100 500 15 ALTP / MEA 2 ADTDG / MEA 5 16 0.050 80 250 16 AL / MEA 2 ADTDG / MEA 5 33 0.056 50 400

Upon examination of the results of this table, it can be seen that only the formulations examples 9 to 15, in accordance with the invention, exhibit properties smooth (µ <0.1), AU (binding load ≥ 63 kg) and EP (welding load ≥ 250 kg).

The formulations of Examples 1 to 5 which do not contain ADTDG salt all have a welding load of less than 250 kg and the formulations of examples 6 to 8 which do not contain compound I or II all have a charge before seizing less than 63 kg and a coefficient of friction greater than 0.1.

The formulation of Example 16 which contains a mixture of lauric acid salts and dithiodiglycolic acid does not have antiwear properties (last load before seizing <63 kg and wear in Falex> 20 mg).

Claims (12)

Multifunctional aqueous lubricant comprising at least one water-soluble salt of dithiodiglycolic acid and at least one water-soluble compound chosen from the group consisting of:
a) the phosphoric esters of general formula (I):

in which R represents an alkyl, alkenyl or alkylaryl radical having from 6 to 20 carbon atoms, k is equal to 2 or 3, m is a number ranging from 0 to 20, x is equal to 1 or 2 and their salts, and
b) the water-soluble salts of the alkylthio-acids of general formula:

in which n is a number ranging from 1 to 10 and R ′ represents an alkyl, alkenyl or aryl radical having from 6 to 20 carbon atoms,
the dithiodiglycoiic acid / compound (s) I and / or II mass ratio being between 1/1 and 20/1. Lubricant according to claim 1, in which k is equal to 2, m is a number ranging from 0 to 10 and R is a radical having from 10 to 18 carbon atoms. Lubricant according to claim 1 or 2, in which n is equal to 1 or 2 and R 'is a radical having 8 to 18 carbon atoms. Lubricant according to one of claims 1 to 3, in which the ratio mass dithiodiglycolic acid / compound (s) I and / or II is between 2/1 and 10/1. Lubricant according to one of Claims 1 to 4, in which the compound (I) is a mixture of phosphoric mono- and di-esters, the number k being equal to 2 and the number m being between 4 and 5. Lubricant according to one of Claims 1 to 5, in which the dithiodiglycolic acid and the alkylthio-acids (II) are in the form of alkali metal salts, ammonium or an alkanolamine. Multifunctional aqueous lubricant additive, characterized in that it consists of an aqueous solution of at least one water-soluble salt of dithiodiglycolic acid and at least one water-soluble compound chosen from the group consisting of esters of phosphoric acid (I) and their salts and by the water-soluble salts of the alkylthio-acids (II) as defined in claim 1. Additive according to claim 7, in which k is equal to 2, m is a number ranging from 0 to 10 and R is a radical having from 10 to 18 carbon atoms. Additive according to claim 7 or 8, in which n is equal to 1 or 2 and R ' is a radical having 8 to 18 carbon atoms. Additive according to one of Claims 7 to 9, in which the mass ratio dithiodiglycolic acid / compound (s) I and / or II is between 2/1 and 10/1. Additive according to one of Claims 7 to 10, in which the compound (I) is a mixture of phosphoric mono- and di-esters, the number k being equal to 2 and the number m being between 4 and 5. Additive according to one of Claims 7 to 11, in which the dithiodiglycolic acid and the alkylthio-acids (II) are in the form of alkali metal salts, ammonium or an alkanolamine.