EP4363538A1

EP4363538A1 - Aqueous lubricant composition for metalworking

Info

Publication number: EP4363538A1
Application number: EP22741249.1A
Authority: EP
Inventors: Véronique VERROUL; Richard Frelechoux
Original assignee: TotalEnergies Onetech SAS
Current assignee: TotalEnergies Onetech SAS
Priority date: 2021-07-01
Filing date: 2022-06-30
Publication date: 2024-05-08
Also published as: FR3124801A1; CN117916347A; WO2023275308A1

Abstract

The invention relates to an aqueous lubricant composition comprising at least: - water; - from 0.1% to 15% by mass of at least one water-soluble polyalkylene glycol; and - from 0.1% to 15% by mass of at least one alkoxylated castor oil, preferably ethoxylated castor oil. The invention further relates to the use of such an aqueous lubricant composition as a lubricant in a metalworking process, in particular for reducing, or even preventing, the formation of gummy residues.

Description

Title: Aqueous lubricating composition for metalworking Technical field

The present invention relates to the field of lubricating compositions, and more particularly to lubricating compositions used in metalworking processes, such as operations for machining metal parts. In particular, the present invention relates to aqueous-based lubricating compositions.

Prior technique

Lubricating compositions, also called “lubricants”, are commonly used in mechanical systems, to reduce friction between parts and thus protect them against wear. In addition to wear phenomena, friction can oppose the relative movement of the parts in contact and induce energy losses that are detrimental to the optimal functioning of the mechanical system.

Lubricants are used for multiple applications, from the lubrication of combustion vehicle engines to the lubrication of equipment used for machining operations, what is commonly called the work of metals, in particular for metal deformation operations.

Metalworking more generally corresponds to the implementation of mechanical or metallurgical processes, both diversified or more specialized, which can be defined as shaping, cutting or jointing processes. This can also concern any mechanical transformation of metal, such as machining (turning, milling, drilling, sawing, threading, among others), forming, cutting, stamping or rolling.

Operations relating to metalworking particularly require the use of lubricating compositions, with the aim of reducing the friction forces between the metal parts in contact and preventing their premature wear, while advantageously guaranteeing cooling of the latter. .

These lubricating compositions, dedicated to lubrication in metal machining processes, are also commonly designated under the names "compositions or metalworking fluids”, “lubricants or machining fluids” or “lubricants or cutting fluids”.

Conventionally, the lubricant formulations used for such machining operations are lubricants composed mainly of one or more base oils, with which are generally associated additives dedicated to stimulating the lubricating performance of base oils, such as friction modifier additives. In general, these lubricant formulations are classified according to the type of oil they contain. Thereby :

- Mineral, non-renewable fluids are those comprising mineral oils, such as paraffinic, aromatic or naphthenic oils, in their base formulation;

- Renewable fluids, of vegetable or animal origin, are those comprising vegetable or animal oils or fats in their base formulation;

- Mineral fluids of synthetic origin are those comprising mineral oils or chemically modified petrochemical derivatives, in their base formulation such as, for example, polyalphaolefins, polyalkylene glycols and hydrogenated mineral oils;

- Renewable fluids of synthetic origin are those comprising chemically modified vegetable or animal oils, in their basic formulation such as, for example, vegetable oil esters, sulphited, oxidized, esterified vegetable oils or sulphated animal oils .

Some formulations, called mixed, include a mixture of the oils listed above in their base formulation. The best known are called semi-synthetic oils and correspond to a mixture of synthetic and mineral oils.

However, the use of oils or greases in lubricating compositions for metalworking has several disadvantages. In particular, oil-based lubricants generally have low resistance to microbial attack, poor cooling properties or even a negative impact on the working environment, health or safety.

Lubricants in emulsion form, comprising an aqueous phase added to an oily phase, have thus been developed. However, these lubricants exhibit poor stability partly due to water hardness and/or salinity. In order to solve the problems related to the implementation of lubricant formulations based on oils in metalworking applications, water-based compositions have shown some interest. These formulations generally include water, supplemented with various additives in order to guarantee the tribological properties required for lubricants, in particular in terms of reducing friction and protecting parts against wear.

As examples, mention may thus be made of documents WO 2009/106359 and WO 2012/163550 which describe aqueous lubricating compositions comprising in particular water and carboxymethylcellulose salts.

Mention may also be made of document EP 3 042 946 which proposes a metalworking fluid, free of oil and emulsifier, comprising between 0.1 and 2% by weight of a cellulosic-type polymer.

Finally, document GB 1 272 100 proposes an aqueous lubricant for metalworking comprising (1) a linear polypropylene glycol or an ethylene oxide/propylene oxide copolymer with a molecular weight of between 2000 and 9000 Da, and (2 ) a polyvinyl pyrrolidone, a cellulose ether or a triethanolamine phosphate.

Unfortunately, the implementation of aqueous lubricants for application in metalworking has a major disadvantage related to the formation of what are called “gummy residues”.

These gummy residues appear after the machining operations. Once the machining equipment has stopped, the lubricant, subjected to ambient dehydration, is likely to lead to the formation of salts which, combined with the polymers present in the lubricant, can form relatively viscous and insoluble residues. in the aqueous phase, referred to as “gummy residues”.

Gummy residues adhere to the walls of the tool and are likely to cause the machining tool to jam, generally requiring undesirable maintenance operations on the machine.

Thus, there remains a need to have an aqueous lubricating composition, for metalworking, generating little or no gummy residue, while maintaining, or even improving, the tribological properties of the lubricant, in particular in terms of anti-corrosion properties. wear and extreme pressure.

The present invention aims precisely to meet this need. Disclosure of Invention

The present invention thus proposes a new aqueous lubricating composition having tribological properties, in particular extreme pressure and anti-wear, suitable for its implementation for metalworking, and leading to a low formation, or even the absence, gummy residues after its use in the machining equipment.

More particularly, an aqueous lubricating composition is described, in particular for metalworking, comprising at least:

- water, preferably reverse osmosis water;

- from 0.001 to 80% by mass of at least one polyalkylene glycol; and

- from 0.001 to 50% by mass of at least one alkoxylated castor oil, preferably ethoxylated, the percentages being expressed relative to the total mass of the composition.

Thus, the present invention relates, according to a first of its aspects, to an aqueous lubricating composition, in particular for metalworking, comprising at least:

- water, preferably reverse osmosis water;

- from 0.1% to 15% by weight of at least one water-soluble polyalkylene glycol; and

- from 0.1% to 15% by mass of at least one alkoxylated castor oil, preferably ethoxylated, the percentages being expressed relative to the total mass of the composition.

In particular, water-soluble polyalkylene glycol and/or alkoxylated, preferably ethoxylated, castor oil are not used as emulsifiers.

By “aqueous composition” within the meaning of the present invention, is meant a composition comprising water as base fluid, in other words as majority solvent. In particular, the water, preferably by reverse osmosis, preferably represents at least 50% by mass of the total mass of the lubricating composition.

In the remainder of the text, the term “aqueous lubricating composition” or “aqueous lubricant” will denote a water-based lubricating composition according to the invention.

By "osmosed water" within the meaning of the present invention, is meant water which has undergone purification, in particular by a reverse osmosis process, in order to reduce the content of organic and/or mineral compounds, for example to a lower content to 5.0% by weight, preferably less than 1.0% by weight. In the rest of the text, the expressions “demineralised water” or even “ultrapure water” will be considered as equivalent or synonyms of the term "osmosis water". In particular, osmosed water can be “deionized water”, in other words water having undergone purification in order to reduce the content of ions, such as the Ca ²⁺ and HCO ₃ ions generally present in water. Preferably deionized water does not include ions.

Against all expectations, the inventors have discovered that the combined implementation of at least one polyalkylene glycol and at least one alkoxylated castor oil, in particular ethoxylated, provides access to an aqueous fluid having excellent tribological properties , adapted to its implementation as a lubricant for metalworking, while leading to a very low formation of gummy residues after use.

Thus, as illustrated in the examples which follow, it is possible, by supplementing an aqueous formulation, by the combination of at least one polyalkylene glycol and at least one alkoxylated castor oil, in particular ethoxylated, to access a lubricating fluid resulting in significantly reduced gummy residue formation.

The combination of at least one polyalkylene glycol and an alkoxylated castor oil, in particular ethoxylated, at the level of an aqueous lubricating composition more particularly has a synergistic effect on the reduction of the formation of gummy residues after use, while not impacting, or even improving, the anti-wear and extreme-pressure properties of the aqueous lubricant.

The propensity of a lubricant formulation to form gummy residues can be evaluated as described in the examples which follow.

There is thus described the use of the combination of at least one polyalkylene glycol and at least one alkoxylated castor oil, in particular ethoxylated, in an aqueous lubricating composition, to reduce its propensity to form gummy residues after its application. used as a lubricant for metalworking.

The invention thus relates to the use of the combination of at least one water-soluble polyalkylene glycol and at least one alkoxylated castor oil, in particular ethoxylated, in an aqueous lubricating composition, to reduce its propensity to form gummy residues after its use as a lubricant for metalworking.

Furthermore, the combination of at least one polyalkylene glycol and at least one alkoxylated castor oil does not impact the tribological properties of the lubricant formulation, in in particular the friction reduction performance under extreme pressure conditions.

The aqueous lubricating composition according to the invention thus has good anti-wear and extreme-pressure properties, and even, surprisingly, improved anti-wear and/or extreme-pressure properties compared to a composition not comprising alkoxylated castor or polyalkylene glycol according to the invention.

The anti-wear and extreme-pressure properties can be evaluated by an extreme-pressure 4-ball test, in particular according to the ASTM D2783 standard, as detailed in the examples below. As demonstrated in the examples, an aqueous lubricating composition according to the invention makes it possible to achieve high weld load values, without a significant increase in the wear diameter, which testifies to its excellent tribological properties.

Thus, the aqueous compositions according to the invention prove to be particularly advantageous for use as lubricants for metalworking. They can thus be used as metalworking fluids, for various applications, replacing the lubricants conventionally used, in particular hydrocarbon lubricants.

The invention thus relates, according to another of its aspects, to the use of an aqueous lubricating composition according to the invention, as a lubricant in a metalworking process.

An aqueous composition according to the invention can be more particularly used as a lubricant in any metal machining operation, for example in processes for shaping, cutting, jointing or any other transformation of the metal such as metal forming. , stamping, rolling, etc.

It can be intended to be implemented for the work of various metals, such as aluminum, steel, galvanized steel or even yellow metals.

The invention also relates to a process for working metals using, as lubricant, an aqueous lubricating composition according to the invention. Said method comprises in particular a step of applying an aqueous lubricating composition according to the invention on the surface of at least a part of the machining tool (or apparatus) and/or of a metal workpiece.

The lubricating fluid according to the invention advantageously makes it possible to reduce the friction between the tool or the machining apparatus and the machined metal part.

The present invention also relates to the use of an aqueous lubricating composition according to the invention for reducing, or even preventing (avoiding), the formation of gummy residues after a metal machining operation involving said composition as a lubricating fluid.

It relates more particularly to the use of an aqueous lubricating composition according to the invention for reducing friction during a metal machining operation, in particular friction between the machining tool and the metal part, as well only to reduce, or even prevent, the appearance of gummy residues after a metal machining operation involving said composition as a lubricating fluid.

The invention also relates, according to another of its aspects, to a method for lubricating the tool (or apparatus) implemented for a metal machining operation and/or a metal workpiece, comprising at at least one step of bringing part of the surface of said tool and/or of said part into contact with at least one aqueous lubricating composition according to the invention.

Finally, advantageously, a lubricating composition according to the invention, formed mainly from water, has little toxicological impact, in particular for the people using this lubricant. Advantageously, even though water is the predominant solvent of an aqueous lubricant according to the invention, the treated surface is correctly lubricated.

In addition, the presence of a significant proportion of water facilitates the cleaning of metal surfaces and the removal of the lubricant after machining, in particular by simply passing or rinsing with water.

Other characteristics, variants and advantages of an aqueous lubricating composition according to the invention will emerge better on reading the description and the examples which follow, given by way of non-limiting illustration of the invention. The expressions "between ... and ...", "ranging from ... to ...", "formed from ... to ...", and "varying from ... to ..." , must be understood as terminals included, unless otherwise stated.

In the description and the examples, unless otherwise indicated, the percentages are percentages by weight. The percentages are therefore expressed by mass relative to the total mass of the composition. Temperature is in degrees Celsius unless otherwise specified, and pressure is atmospheric pressure unless otherwise specified.

Detailed Description AQUEOUS COMPOSITION

As mentioned above, an aqueous lubricating composition according to the invention, also called aqueous lubricant, is a formulation comprising water as the majority solvent.

Within the meaning of the invention, by “major solvent”, it is meant that the water is present in a greater quantity than any other solvent possibly present in the composition. Preferably, an aqueous lubricating composition according to the invention comprises at least 50% by weight of water, in particular osmosis water, preferably between 50% and 90% by weight, more preferably between 60% and 75% by weight, relative to the total mass of the composition.

Through its role as a solvent, water makes it possible to solubilize the polyalkylene glycol(s) and the alkoxylated, preferably ethoxylated, castor oil used according to the invention, as well as any additive optionally present in the composition, in particular chosen among those detailed in the following text.

Advantageously, in addition to its role as a solvent, water provides access to a lubricating composition having good cooling properties, useful in the field of metal machining.

According to a particular embodiment, the water used in an aqueous lubricating composition according to the invention is deionized water or osmosed water. Advantageously, deionized water does not include ions, such as the Ca ²⁺ and HCO 3 ions generally present in water, which are responsible for the conduction of electricity in the water. The use of deionized water is therefore particularly advantageous in the context of the use of the aqueous lubricant according to the invention for applications requiring a fluid that conducts little or no electricity.

An aqueous lubricating composition according to the invention differs from hydrocarbon lubricants, which comprise a major proportion of one or more base oils which are not soluble in water.

By “water-insoluble oil”, is meant in particular an oil which does not substantially dissolve in water at room temperature (at about 25° C.). In particular, an oil that is not soluble in water has a solubility in water of less than 0.2 g/L, at room temperature.

These include in particular lubricating base oils belonging to groups I to V according to the classes defined in the API classification (or their equivalents according to the ATIEL classification) and their mixtures.

Preferably, an aqueous lubricating composition according to the present invention comprises less than 20% by mass of base oil(s) which are not soluble in water, preferably less than 10% by mass, in particular less than 5% by mass , relative to the total mass of the composition.

Advantageously, an aqueous lubricating composition according to the invention is completely free of oil which is not soluble in water.

POLYALKYLENE GLYCOL

As indicated previously, an aqueous lubricating composition according to the invention comprises from 0.1 to 15% by weight of at least one polyalkylene glycol.

It is understood that a lubricating composition according to the invention may comprise a single polyalkylene glycol, or a mixture of at least two distinct polyalkylene glycols, in particular as described below.

Polyalkylene glycols (denoted “PAG”) are homo- or co-polymers made up of alkylene oxide units.

In particular, polyalkylene glycols are not used in a composition according to the invention as emulsifiers.

According to the invention, the polyalkylene glycols are soluble in water. By "water-soluble" is meant a polyalkylene glycol having a solubility in water of at least 10 g/L, preferably of at least 500 g/L, in water at room temperature (about 25°C).

The polyalkylene glycols can be more particularly formed from C1-C4 alkylene oxide units, preferably C1-C3, more particularly C2-C3. Advantageously, a polyalkylene glycol used in an aqueous lubricating composition according to the invention comprises at least 50% by mass of propylene oxide and/or ethylene oxide units.

It may be a copolymer, in particular a random one, comprising ethylene oxide, propylene oxide and/or butylene oxide units. Preferably, it may be a copolymer, in particular a random one, of ethylene oxide/propylene oxide.

Preferably, a polyalkylene glycol used in an aqueous lubricating composition according to the invention has a mass-average molar mass (Mn) of between 100 and 25,000 g. mol ¹ , preferably between 5,000 and 21,000 g. mol ¹ .

The number average molecular weight can be measured by gel permeation chromatography (GPC).

Preferably, a polyalkylene glycol used in an aqueous lubricating composition according to the invention has a kinematic viscosity measured at 100° C. (KV100), according to the ASTM D445 standard, of between 100 and 5000 mm ² /s, in particular between 150 and 3000 mm ² /s, for example between 1500 and 3000 mm ² /s or between 100 and 250 mm ² /s.

Preferably, a polyalkylene glycol used in an aqueous lubricating composition according to the invention has a kinematic viscosity measured at 40° C. (KV40), according to the ASTM D445 standard, of between 500 and 30,000 mm ² /s, more particularly between 1,000 and 25,000 mm ² /s, for example between 10,000 and 25,000 mm ² /s or between 500 and 2,500 mm ² /.

The flash point of a polyalkylene glycol used in an aqueous lubricating composition according to the invention is preferably greater than or equal to 160° C., in particular greater than or equal to 220° C., for example between 220° C. and 300° C. °C. Flash point can be measured by ISO 2592 or ASTM D92.

Preferably, a polyalkylene glycol used in an aqueous lubricating composition according to the invention has a viscosity index measured according to the ASTM D2270 standard, of between 100 and 800, preferably between 250 and 550. Such polyalkylene glycols may be commercially available or synthesized according to methods known to those skilled in the art. They can be obtained for example by polymerization or copolymerization of alkylene oxides having between 2 and 4 carbon atoms. An example of synthesis is for example detailed in document US 2012/0108482, by reaction between one or more alcohols having between 2 and 12 carbon atoms, in particular polyols, such as diols, with alkylene oxides, in particular ethylene oxide, propylene oxide and/or butylene oxide. The alcohol can preferably be a diol, in particular 1,2-propanediol.

The said polyalkylene glycol compound(s) are used in an aqueous lubricating composition according to the invention in a content of between 0.1% and 15% by weight, more preferably between 1% and 10% by weight, in particular between 2% and 5 % by mass, relative to the total mass of the composition.

ALCOXYLATED CASTOR OIL

As indicated previously, an aqueous lubricating composition according to the invention comprises from 0.1 to 15% by mass of at least one alkoxylated castor oil, in particular ethoxylated.

In particular, alkoxylated castor oil, in particular ethoxylated, is not used in a composition according to the invention as an emulsifier.

It is understood that a lubricating composition according to the invention may comprise a single alkoxylated castor oil, in particular ethoxylated, or a mixture of at least two distinct particular alkoxylated castor oils, in particular as described below.

Castor oil is composed of fatty acid triglycerides, mainly Ci ₆ to Ci ₈ fatty acid. More particularly, ricinolein, triglyceride of ricinoleic acid (Cis fatty acid) is the major constituent of castor oil.

An alkoxylated castor oil is formed from alkoxylated triglycerides.

Preferably, a lubricating composition according to the invention comprises an alkoxylated (Ci-C4) castor oil, preferably ethoxylated.

It can be obtained by alkoxylation of castor oil with an alkylene oxide, in particular C 1 to C ₄ , or even by transesterification with a polyalkylene glycol, in particular a poly(Ci-C4) alkylene glycol. Preferably, a lubricating composition according to the invention uses an ethoxylated castor oil. It can be obtained by ethoxylation of castor oil with ethylene oxide, or even by transesterification of castor oil with a polyethylene glycol.

According to a particular embodiment, a lubricating composition according to the invention uses an ethoxylated castor oil, obtained by reaction of castor oil with ethylene oxide, in a molar ratio castor oil: oxide of ethylene between 1:1 and 1:100.

An ethoxylated castor oil used in a lubricating composition according to the invention may in particular comprise at least 20 oxyethylene groups, preferably from 35 to 45 oxyethylene groups.

Preferably, it is an ethoxylated castor oil obtained by reaction of castor oil with ethylene oxide, in a castor oil: ethylene oxide molar ratio of approximately

I: 35, denoted “PEG-35-castor oil”.

As mentioned above, the alkoxylated, preferably ethoxylated, castor oil, in particular as described above, is used at a rate of 0.1% to 15% by mass, relative to the total mass of the composition, in particular of 1% to 10% by mass, and more particularly from 2% to 5% by mass, relative to the total mass of the composition.

ADDITIVES

An aqueous lubricating composition according to the invention may also comprise various additives.

It is understood that the said additive(s) are compatible with their use in an aqueous medium. Advantageously, the additives are implemented in a form that is soluble or emulsifiable in water, for example in the form of salts or ionic liquids.

The said additive(s) are of course chosen with regard to the intended application for the aqueous lubricant.

Of course, those skilled in the art will take care to choose the possible additives and/or their quantity in such a way that the advantageous properties of the aqueous lubricating composition according to the invention, in particular the advantageous effect of reducing gum residues, after the implementation of the lubricating composition for metalworking and the tribological properties, in particular extreme pressure properties and protection of the parts against wear, are not altered by the envisaged addition.

Such additives can be more particularly chosen from anti-foaming agents, biocides, pH regulators, corrosion inhibitors, anti-wear and/or extreme pressure additives, sequestering agents, metal passivating agents, colorants, dispersants, emulsifying agents, wetting agents, and mixtures thereof. Advantageously, an aqueous lubricating composition according to the invention may comprise one or more additives chosen from anti-foaming agents, biocides, pH regulators, corrosion inhibitors, sequestering agents, metal passivating agents, emulsifying agents and their mixtures.

An aqueous lubricating composition according to the invention may more particularly comprise from 1 to 50% by mass of additives, in particular from 5 to 40% by mass of additives, relative to the total mass of the composition.

Corrosion inhibitor

An aqueous lubricating composition according to the invention may comprise at least one corrosion inhibiting agent. Corrosion inhibitors advantageously reduce or even prevent corrosion of metal parts. The nature of said corrosion inhibitor(s) can be chosen with regard to the metal to be protected against corrosion, such as aluminum, steel, galvanized steel, yellow metals, for example copper or brass. Among the inorganic corrosion inhibitors mention may be made of nitrites, sulphites, silicates, borates, sodium, potassium, calcium or magnesium phosphates, alkali metal phosphates, hydroxides, molybdates, sulphates of zinc, magnesium or nickel.

Among the organic corrosion inhibitors, mention may be made of aliphatic monocarboxylic acids, in particular having from 4 to 15 carbon atoms, for example octanoic acid, aliphatic dicarboxylic acids having from 4 to 15 carbon atoms, for example dioic decane (sebacic acid), undecane dioic acid, dodecane dioic acid, isononanoic acid or mixtures thereof, polycarboxylic acids optionally neutralized by triethanolamine, such as l,3,5-triazine-2 acid ,4,6-tri-(6-aminocaproic), alkanoylamidocarboxylic acids, in particular isononanoylamidocaproic acid, 6-[[(4-methylphenyl)sulfonyl]amino]hexanoic acid, and their mixtures. Borated amides, products of the reaction of amines or amino-alcohols with boric acid, can also be used.

An aqueous lubricating composition according to the invention may in particular comprise from 0.01% to 15% by mass of corrosion inhibitor(s), preferably from 1.0% to 13% by mass, relative to the total mass of the composition. .

Anti-wear/extreme pressure additive

An aqueous lubricating composition according to the invention may comprise at least one anti-wear and/or extreme pressure additive. Their function is to reduce wear and the coefficient of friction, or to prevent metal-metal contact by forming a protective film adsorbed on these surfaces.

An aqueous lubricating composition according to the invention may comprise between 0.001% and 50% by mass of anti-wear and/or extreme-pressure additive(s), in particular sulfur fatty acid(s), as defined above, preferably between 0.2% and 5% by weight, relative to the total weight of the composition.

Advantageously, a composition according to the invention, combining at least one polyalkylene glycol and at least one alkoxylated castor oil, in particular ethoxylated, has good anti-wear and extreme pressure properties, even in the absence of additives. anti-wear and/or extreme-pressure annexes.

Thus, according to a particular embodiment, a lubricating composition according to the invention comprises less than 1% by mass of anti-wear and/or extreme pressure additives, in particular less than 0.5% by mass, in particular less than 0, 1% by weight of anti-wear and/or extreme-pressure additives, or even is free of anti-wear and/or extreme-pressure additive.

Defoamer

An aqueous lubricating composition according to the invention may comprise at least one antifoam additive. Defoamers prevent foaming of the lubricating fluid.

It may, for example, be an anti-foaming agent based on polysiloxanes or acrylate polymers. Preferably, the anti-foaming agent is chosen from three-dimensional siloxanes. Also, the anti-foaming agents can be polar polymers such as polymethylsiloxanes or polyacrylates.

In particular, an aqueous lubricating composition according to the invention may comprise from 0.001% to 3.0% by mass of antifoam additive(s), preferably from 0.005% to 1.5% by mass, relative to the total mass of the lubricating composition.

pH regulator

An aqueous lubricating composition according to the invention may comprise at least one pH regulating additive, in particular an alkaline buffer. The pH regulator makes it possible to maintain the desired pH of the lubricating composition, in particular in order to preserve an alkaline pH, advantageously between 8 and 11, so as in particular to prevent corrosion of the metal surfaces.

The pH regulator can be chosen from the family of amines, in particular alkanolamines and amino alcohols.

It may in particular be a pH-regulating additive chosen from ethanolamines, such as monoethanolamine (MEA), diethanolamine (DEA); triethanolamine (TEA), diglycolamine (DGA) isopropanolamines, such as mono-isopropanolamine (MIPA), diisopropanolamine (DIPA) and triisopropanolamine (TIPA), ethylene amines, such as ethylene diamine (EDA), diethylene triamine (DETA), triethylene tetramine (TETA) and tetraethylene pentamine (TEPA), alkanolamines, such as methyldiethanol amine (MDEA), cyclamines, such as cyclohexylamine, 2-amino-2-ethyl- 1,3-propanediol, 2-amino-2-methyl-1-propanol and mixtures thereof.

An aqueous lubricating composition according to the invention may in particular comprise from 1% to 25% by mass of pH regulator additive(s), preferably from 5% to 20% by mass, relative to the total mass of the composition. .

Metal passivators

An aqueous lubricating composition according to the invention may comprise at least one metal-passivating agent. Metal passivators protect metal parts by promoting the formation of metal oxide on their surface.

The metal passivating agents may for example be chosen from triazole derivatives, such as tetrahydrobenzotriazole (THBTZ), tolyltryazole (TTZ), benzotriazole (BTZ), amines substituted with a triazole group, such as N,N-bis(2-ethylhexyl)-l,2,4-triazol-l-yl methanamine, N'-bis(2 ethylhexyl)- 4-Methyl-lH- benzotriazol-l-methyl-amine, N,N-bis(heptyl)-ar-methyl-lH-benzotriazol-l-methanamine, N,N-bis(nonyl)-ar-methyl-lH -benzotriazole-l-methanamine, N,N-bis(decyl)-ar-methyl-1H-benzotriazole-1-methanamine, N,N-bis(undecyl)-ar-methyl-1H-benzotriazole-1-methanamine, N,N-bis(dodecyl)-ar-methyl-1H-benzotriazole-l-methanamine, N,N-bis(2-ethylhexyl)-ar-methyl-1H-benzotriazole-l-methanamine,

1.2.4-triazoles, benzimidazoles, 2-alkyldithiobenzimidazoles, 2-alkyldithiobenzothiazoles, 2-(N,N-dialkyldithiocarbamoyl)benzothiazoles, 2,5-bis(alkyldithio)-1,3,4-thiadiazoles, such as 2,5-bis(tert-octyldithio)-l,3,4-thiadiazole,

2.5-bis(tert-nonyldithio)-l,3,4-thiadiazole, 2,5-bis(tert-decyldithio)-l,3,4-thiadiazole,

2.5-bis(tert-undecyldithio)-l,3,4-thiadiazole, 2,5-bis(tert-dodecyldithio)-l,3,4-thiadiazole, 2,5-bis(tert-tridecyldithio)-l ,3,4-thiadiazole, 2,5-bis(tert-tetradecyldithio)-

1.3.4-thiadiazole, 2,5-bis(tert-pentadecyldithio)-l,3,4-thiadiazole, 2,5-bis(tert-hexadecyldithio)-l,3,4-thiadiazole, 2,5 -bis(tert-heptadecyldithio)-l,3,4-thiadiazole, the

2.5-bis(tert-octadecyldithio)-l,3,4-thiadiazole, 2,5-bis(tert-nonadecyldithio)-l,3,4-thiadiazole, 2,5-bis(tert-eicosyldithio)-l ,3,4-thiadiazole, 2,5-bis(N,N-dialkyldithiocarbamoyl)-1,3,4-thiadiazoles, 2-alkyldithio-5-mercaptothiadiazoles, and mixtures thereof.

Preferably, the metal-passivating agents are chosen from tetrahydrobenzotriazole (THBTZ), tolyltriazole (TTZ), benzotriazole (BTZ), and their salts, taken alone or in mixtures.

An aqueous lubricating composition according to the invention may in particular comprise from 0.01% to 2.0% by mass of metal-passivating agent(s), preferably from 0.1% to 1.0% by mass, more preferably from 0 2% to 0.8% by mass, relative to the total mass of the composition.

Dyes

An aqueous lubricating composition according to the invention may comprise one or more colorants. Dyes can be natural or synthetic, usually organic. The dyes that can be used in an aqueous lubricating composition can be more particularly chosen from natural water-soluble dyes or synthetic, e.g. the dyes FDC Red 4, DC Red 6, DC Red 22, DC Red 28, DC Red 30, DC Red 33, DC Orange 4, DC Yellow 5, DC Yellow 6, DC Yellow 8, FDC Green 3, DC Green 5, FDC Blue 1, betanin (beetroot), carmine, a chlorophyllin, methylene blue, anthocyanins (enocianine, black carrot and hibiscus), caramel and riboflavin.

An aqueous lubricating composition according to the invention may comprise between 0.01% and 2.0% by weight of dye(s), preferably between 0.01% and 1.5% by weight, more preferably between 0.02% and 1 0.0% by mass, relative to the total mass of the composition.

Emulsifying agents

An aqueous lubricating composition according to the invention may comprise one or more emulsifying agents, also called emulsifiers. Their function is to generate stable emulsions in water.

The emulsifying agents can be more particularly nonionic, such as for example ethoxylated fatty alcohols, ethoxylated fatty acids, compounds resulting from the reaction between propylene oxide, ethylenediamine and optionally ethylene oxide, amides ethoxylated fats; anionic, for example soaps of KOH, NaOH; sulphonates; cationics, such as quaternary ammonium compounds; or alternatively water-soluble or emulsifiable carboxylic acid esters.

In particular, an aqueous lubricating composition according to the invention may comprise from 0.01% to 10% by mass of emulsifying agent(s), preferably from 0.1% to 5.0% by mass, relative to the total mass of the lubricating composition.

Sequestering agents

An aqueous lubricating composition according to the invention may comprise at least one sequestering agent. Sequestering agents, also called chelating agents, make it possible to limit the incrustation of metal ions in the composition.

As examples of sequestering agents, mention may be made of those derived from phosphonic acids and phosphonates, such as diethylenetriaminepentamethyl phosphonic acid (DTPMPA), amino tri(methylene phosphonic) acid (ATMP), hydroxyethanediphosphonate (HEDP), 1-hydroxyethylidene 1,1-diphosphonate, 2- hydroxyethylamine di(methylene phosphonic) (HEAMBP), diethylene triamino penta(methylene phosphonic) acid (DTMP), multifunctional organic acids and hydroxy acids, such as ethylene diamine tetraacetic acid (EDTA), pteroyl-L-glutamic acid (PGLU), organic polyacids, such as maleic acid and polyaspartic acid, polysaccharides and carbohydrates, such as inulin, carboxymethylinulin and carboxymethylchitosan.

An aqueous lubricating composition according to the invention may comprise from 0.001% to 2.0% by mass of sequestering agent(s), preferably from 0.01% to 1.0% by mass, relative to the total mass of composition.

Biocides

An aqueous lubricating composition according to the invention may comprise at least one biocidal agent with fungicidal and/or bactericidal action. Biocides can be used to improve the biological stability of the composition by limiting the proliferation of bacteria, fungi and yeasts in the lubricating fluid.

Such biocides can be chosen from parabens, aldehydes, reactive acetylacetone compounds, isothiazolinones, phenolic compounds, acid salts, halogenated compounds, quaternary ammoniums, certain alcohols and mixtures thereof.

Preferably, the biocides can be chosen from optionally substituted benzisothiazolinones (BIT), such as N-butyl-1,2-benzisothiazolin-3-one, methylisothiazolinones (MIT), mixtures of methylisothiazolinone and chloromethylisothiazolinone (MIT/ CMIT), orthophenyl-phenol (OPP) or its sodium salt, 3-iodo-2-propynylbutylcarbamate (IPBC), chloro-cresol and N,N-methylene-bis-morpholine (MBM); sorbic acid; preferably from orthophenyl-phenol (OPP) or its sodium salt, 3-iodo-2-propynylbutylcarbamate, chloro-cresol, benzisothiazolinones and N,N-methylene-isomorpholine.

An aqueous lubricating composition according to the invention may in particular comprise between 0.01% and 10% by mass of biocide(s), preferably between 0.1% and 5.0% by mass, relative to the total mass of the composition.

According to a particular embodiment, an aqueous lubricating composition according to the invention comprises: - at least 50% by weight of water, preferably reverse osmosis water;

- from 0.1% to 15% by weight of at least one water-soluble polyalkylene glycol, in particular as defined previously;

- from 0.1% to 15% by mass of at least one alkoxylated castor oil, preferably ethoxylated; and

- optionally from 1% to 50% by mass, in particular from 5 to 40% by mass, of one or more additives chosen from anti-foaming agents, biocides, pH regulators, corrosion inhibitors, sequestering agents, metal passivating agents, emulsifying agents, and mixtures thereof, the contents being expressed relative to the total mass of the lubricating composition.

In particular, an aqueous lubricating composition according to the invention may consist of:

- 0.1% to 15% by weight of at least one water-soluble polyalkylene glycol, in particular as defined above;

- 0.1% to 15% by mass of at least one alkoxylated castor oil, preferably ethoxylated; and

- optionally from 1% to 50% by mass, in particular from 5 to 40% by mass, of one or more additives chosen from anti-foaming agents, biocides, pH regulators, corrosion inhibitors, sequestering agents, metal passivating agents, emulsifying agents, and mixtures thereof, the contents being expressed relative to the total mass of the lubricating composition, and the remainder consisting of water, preferably osmosed water.

According to the invention, the particular, advantageous or preferred characteristics of the composition according to the invention, make it possible to define uses according to the invention which are also particular, advantageous or preferred.

The invention will now be described by means of the following examples given of course by way of non-limiting illustration of the invention.

Example

Evaluation of tribological properties The extreme-pressure and anti-wear properties of the lubricating compositions are evaluated by the 4-ball test according to the ASTM D2783 standard adapted with the following parameters:

- speed close to 1500 rpm,

- ambient temperature, i.e. around 20°C,

- 1 minute charging time.

The extreme pressure measurement is carried out by rotating a stainless steel ball on three stainless steel balls, also kept immobile, the 4 balls being entirely covered with a film of lubricant. A load is applied to the balls and gradually increased (every minute according to the parameters above) until the balls weld together. The balls are changed before each increase in load.

The extreme pressure power corresponds to the value of the load from which the 4 balls are welded, preventing the rotation of the upper ball on the 3 others. The greater the load, the greater the extreme pressure power.

This method also makes it possible to evaluate the anti-wear properties of a lubricating composition. During the gradual increase in load, it is possible to determine, at each level, the diameter of wear on the 3 balls. The smaller the wear diameter, the more effective the lubricant is in preventing wear (or seizing) of parts.

The wear diameter values provided in the following examples are those obtained for the load value preceding the welding of the balls.

It is common practice to dilute the compositions before carrying out the load tests, and the dilution rate is therefore specified in the results below.

Measurement of gummy residue formation

The test for evaluating the formation of gummy residues is taken from standard ISO/TS 12-927 part B.6, for which the time and temperature parameters have been adapted. This standard makes it possible to simulate the residual gummy stickiness of a product. Thus, this test makes it possible to assess whether a product remaining on the machine when stopped after machining, for example left in the open air, will tend to cause a blockage phenomenon on restarting, due to the presence of sticky dried residues on the tooling.

The formation of gummy residues is quantified by measuring the mass of water-insoluble residues after use of the composition. To do this, the composition to be tested is placed in a ventilated oven at a temperature of 90° C. for 20 hours. The mass of composition is measured before and after passing through the oven. The composition is then dissolved in osmosed water for 15 minutes at ambient temperature and with mechanical stirring at a speed of 600 revolutions/minute. The insoluble residues correspond to the gummy residues formed. These are filtered and weighed to determine the quantity in milligrams. The greater the quantity of residues, the more this means that the lubricating composition will have a tendency to form undesirable gummy residues, after its use as a lubricant in machining machines.

Example 1: Preparation of the lubricating compositions II, C1 and C2

An aqueous lubricating composition according to the invention (II), and two comparative aqueous lubricating compositions, C1 not comprising polyalkylene glycol and C2 not comprising alkoxylated castor oil, were formulated according to the protocol below, in the mass percentages indicated in the following table 1.

The formulation protocol is as follows:

The alkoxylated castor oil is dissolved in reverse osmosis water. The solution is stirred for 30 minutes at ambient temperature (around 20° C.). At this stage, the solution may not be clear.

Then, the other components are added as follows: introduction of the pH-regulating additive(s), then of the corrosion-inhibiting additive(s) by heating the mixture to a temperature of 40 to 50°C. The solution is stirred using a magnetic bar for a period ranging from 1 hour to 1 hour 30 minutes. The following compounds are then added, sequentially every 5 minutes, in the following order and always with stirring: passivator( s), sequestering agent(s), PAG, then optionally wetting agent(s), antifoam agent(s) and biocide(s).

Finally, a final agitation is carried out for a period of 1 hour. [Table 1]

¹¹¹ The additive(s) are chosen from anti-corrosion agents, passivators, sequestering agents, pH regulators, antifoams and biocides. Example 2: Characterization of the compositions according to the invention and comparisons

Tribological properties were measured for each composition, as detailed in the protocol above.

The results are compiled in Table 2 below.

[Table 2]

Composition II according to the invention has a welding load equivalent to that obtained for comparative composition C2 and better than that obtained for comparative composition C1, and a wear diameter of the same order of magnitude.

Thus, a lubricating composition in accordance with the invention, incorporating at least one polyalkylene glycol and alkoxylated castor oil, has excellent extreme pressure and anti-wear properties, equivalent or even better than those obtained with a composition not comprising no such combination of ingredients. Furthermore, the gummy residues were quantified for each composition, and the results are provided in Table 3 below.

[Table 3] Composition II according to the invention has a mass of insoluble compounds, corresponding to the gummy residues, significantly lower than those obtained for the comparative compositions C1 and C2.

Thus, a lubricating composition in accordance with the invention, combining at least one polyalkylene glycol and alkoxylated castor oil, in particular ethoxylated, advantageously makes it possible to lead to significantly reduced amounts of gummy residues, after its use at the level of the machining equipment.

Example 3: Preparation of the lubricating composition 12

An aqueous lubricating composition according to the invention (12) was formulated according to the protocol below, in the mass percentages indicated in the following table 4.

The formulation protocol is identical to that detailed in example 1.

[Table 4]

¹¹¹ The additive(s) are chosen from anti-corrosion agents, passivators, sequestering agents, pH regulators, antifoams and biocides. Example 4: Characterization of the composition according to the invention

The tribological properties were measured for composition 12 according to the invention, as detailed in the protocol described above.

The results are compiled in Table 5 below. [Table 5]

Composition 12 according to the invention has a high welding load. It also has a small wear diameter.

Thus, a lubricating composition in accordance with the invention, incorporating at least one polyalkylene glycol and alkoxylated castor oil, has excellent extreme pressure and anti-wear properties.

Furthermore, the gummy residues were quantified for composition 12 according to the invention, and the results are provided in table 6 below. [Table 6]

Composition 12 according to the invention has zero mass of insoluble compounds, corresponding to the gummy residues.

Claims

1. Aqueous lubricating composition, in particular for metalworking, comprising at least:

- water, preferably reverse osmosis water;

2. Aqueous lubricating composition according to claim 1, comprising at least 50% by weight of water, in particular osmosed water, preferably between 50% and 90% by weight, more preferably between 60% and 75% by weight, relative to the total mass of said composition.

3. Aqueous lubricating composition according to claim 1 or 2, in which the said polyalkylene glycol(s) are chosen from copolymers, in particular random ones, comprising ethylene oxide, propylene oxide and/or butylene oxide units.

4. Aqueous lubricating composition according to any one of the preceding claims, comprising from 1% to 10% by mass of polyalkylene glycol(s), more preferably from 2% to 5% by mass, relative to the total mass of the composition.

5. Aqueous lubricating composition according to any one of the preceding claims, in which the alkoxylated castor oil is an ethoxylated castor oil, obtained by reaction of castor oil with ethylene oxide, in a molar ratio castor oil: ethylene oxide between 1:1 and 1:100, and in particular 1:35.

6. Aqueous lubricating composition according to any one of the preceding claims, comprising from 1% to 10% by weight of alkoxylated castor oil(s), and more particularly from 2% to 5% by weight, relative to the total mass the composition.

7. Aqueous lubricating composition according to any one of the preceding claims, comprising one or more additives chosen from anti-foam agents, biocides, pH regulators, corrosion inhibitors, anti-wear and/or extreme- pressure, sequestering agents, metal passivating agents, colorants, dispersants, emulsifying agents, and mixtures thereof, in particular chosen from antifoaming agents, biocides, pH regulators, corrosion inhibitors, sequestering agents, metal passivating agents, emulsifying agents and mixtures thereof.

8. Use of an aqueous lubricating composition as defined according to any one of the preceding claims as a lubricant in a metalworking process.

9. Use of an aqueous lubricating composition as defined according to any one of claims 1 to 7, to reduce, or even prevent, the formation of gummy residues after a metal machining operation involving said composition as a fluid lubricant.

10. Use of the combination of at least one water-soluble polyalkylene glycol and at least one alkoxylated castor oil, in particular ethoxylated, in an aqueous lubricating composition, to reduce its propensity to form gummy residues after its used as a lubricant for metalworking.