CH625829A5 - Stabilised fluid composition usable for metal machining - Google Patents

Description

The present invention aims to apply this discovery to fluids usable for metalworking. The composition according to the invention is defined in claim 1. The complexes of a metal ion and a polyfunctional organic ligand which have been described in the aforementioned patent application are preferably used as stabilizers. The stabilizing metal complexes are characterized by a very unexpected property of dissociation, caused by protons in an aqueous medium, which causes the controlled release of the metal ion in the oil and water dispersions to give the dispersions of the stability when working with metals. This dissociation property is represented by a sigmoidal curve (in "S") on a Cartesian coordinate graph of the negative logarithm (changed sign) of the concentration of the metal ion as a function of the negative logarithm (or changed sign ) of the hydrogen ion, i.e. a pM-pH diagram. Quite unexpectedly, it has been discovered that coolants for metalworking can be stabilized by preventing such fluids from attack and deterioration due to various causes. Thus, it has been stabilized against deterioration of the irrigation fluids for metalworking, by means of an additive which is a stabilizer for general purposes comprising a metal complex. For example, as described in the aforementioned patent application, certain metal complexes are effective as antimicrobial agents in spray emulsions for metal working. It has also been found that these metal complexes impart other stabilizing characteristics to metalworking fluids and allow for improvements and advantages which were hitherto unattainable in sprinkler fluids. metalwork. This stability is not only obtained with regard to the action of bacteria, but the fluids are also stabilized against degradation by physical, chemical and physicochemical causes associated with the conditions involved in metalworking, such as heat, pressure. , the composition of the particles of the metal workpiece surrounding these fluids, polyvalent ions, etc. The stability of coolants for metalworking has been found to be remarkable according to the present invention. For example, in the field of industrial cooling compositions, the service life of the fluids has been extended by a period which was for example from a few weeks to a period close to a year or even a longer period, and the results current reports indicate that the service life can even be extended indefinitely. The stabilizing metal complexes are themselves very stable at relatively high alkaline pHs of the order of about 9 or 10 to about 12. However, in an alkaline pH range greater than 7 to about 9, in which one asks to metalworking coolants to play their role, stabilizing complexes very advantageously provide stabilizing effects to these metalworking fluids. It has also been discovered in this regard that very minor amounts of the stabilizing metal complex can be added to the metalworking compositions, i.e. amounts which may be less than the amounts exhibiting biocidal activity and that, however, such metalworking coolants can be stabilized against degradation due to all the factors prevailing in the metalworking environment.

Thus, the present invention aims to impart stability to oil and water dispersions which may otherwise degrade because they are subject to deterioration due to a number of causes. For example, biostability can be imparted to metalworking fluids by introducing metal complexes, even in amounts less than the biocidal amounts. Furthermore, general stability of the emulsions can be obtained by introducing certain amounts of the metal complex to stabilize the emulsions against degradation due to foreign sources such as metal particles, polyvalent metal ions, etc. In addition, metalworking fluids can be given extreme pressure resistance and heat resistance properties using the stabilizers according to the present invention. In another of their aspects, the compositions of the present invention decrease the chemical interaction of other fragments with the emulsified particles, which would otherwise tend to decrease the stability of the emulsions. These and other advantages are obtained from the effectiveness of a stabilization action according to the principles of the present invention,

as will be understood on examining this description.

The theories or underlying reasons for the rather unexpected activities of the metal complex type stabilizers according to the present invention have been explored. Although the Applicant does not wish to limit itself to a theoretical reasoning, it thinks that this can be useful to allow a better understanding of the characteristics and the unexpected results which are obtained according to the present invention. It is currently believed, in the case of oil and water dispersions (whether it is an oil-in-water type dispersion or a water-in-oil type dispersion) that such dispersions can be biodegradable, chemically degradable due to a chemical species present in the fluid medium, and physically degradable as a result of the action of conditions such as mechanical forces, or by combinations of two or more of these factors. As is well known, such oil and water dispersions contain emulsifiers and these emulsifiers are typically of the "anionic" and / or "nonionic" type. Due to their hydrophilic and hydrophobic characteristics, emulsifiers allow the suspension of oil particles within a continuous phase of the s

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fluid. Electronegative species, such as, for example, the carboxyl and sulfonate groups of the emulsifier, impart surface electronegative charges to the oil droplet. The combined electronegativity of such an emulsified particle is generally referred to as the Zeta potential. In essence, the Zeta potential is related to the strength and distance at which the emulsified particles can repel each other and thereby prevent flocculation. Of course, this is a more than simplified representation of oil and water dispersions. However, one would expect that the introduction of a highly charged divalent metal cation or a similar species of the stabilizing metal complexes would interfere with the stability of the emulsion and possibly cause flocculation due to neutralization of the highly electronegative droplets of the emulsion. Thus, in a broader aspect, the present invention provides a method for stabilizing oil and water dispersions, as well as stabilized compositions, by adding to them a multivalent metal ion which forms a coordination bond with the agent electronegative emulsification. The stabilizing effects of such a coordination product are obtained because there is still electronegativity to prevent demulsification and, in addition, the other sensitive sites of the emulsifying agent are then blocked with respect to of an enzymatic degradation, which makes it possible to convey the metal ion, as limiting lubricant, towards the interface tool-workpiece. This action is attributed to the highly electronegative nature of the emulsified droplet initiating the dissociation of the metal complex or contributing to this dissociation and allowing the coordination of the metal cation with the electronegative entities of the emulsified droplets, for example the carboxyl, sulfonate or hydroxyl fragments. alcoholic emulsifying agents. This blockage of these functional or biosensitive groups prevents an enzymatic degradation of these structures, which is common for microbial metabolism and associated with it. However, it is quite unexpected that the introduction of metal complexes or the introduction of such metal ions does not cause demulsification of the electronegative charged droplets of the emulsion. The reason is that the quantity of positively charged ions associated with the electronegative surface of the oil droplet, if it is sufficient to confer biostability, is not sufficient to decrease the electronegativity of the particle to reach a demulsification point. Consequently, the Applicant believes that the mechanism for the formation of coordination structures with emulsifying agents is a new method for stabilizing emulsions.

It has also been found that the introduction of stabilizers of the complex metal type of the present invention contributes to heat and pressure resistance properties of the emulsion in metal working operations. Such properties of resistance to extreme conditions of heat and pressure are imparted by the structures of the metal ion coordination products and emulsifiers in the stabilized compositions of the present invention for metalworking. These properties are presented by the metal cation or by the metal complex transported to, then associated with, the electronegative species of the emulsified droplets, as mentioned above. The emulsified droplets are continuously brought into intimate contact with the tool-workpiece interface found in metalworking operations. For example, under the heat and pressure conditions of the metalworking process, the copper associated with the emulsified droplets at the interface enters an oxidation and reduction process used to lubricate the metal surfaces, but without degradation of the emulsion which would make it reach a state of possible non-use. In addition, in practice, and probably due to the formation of highly reactive cations at the tool-workpiece interface in any machining operation involving metal substrates, the coolant for metalworking becomes charged with metal ions which, by displacement, tend to displace the cations contained in the metal complex and to still allow the migration of these cations and their association with electronegative structures of the emulsified particle, in fact coating this particle by the cation.

The chemical nature of the metal complex stabilizer is such that this complex is very soluble in aqueous media, but, due to its remarkable dissociation property under the influence of protons at the pH of metal working conditions, this complex dissociates easily so that the metal cation is transported from the aqueous phase to the oily phase of the emulsion. This surprising phenomenon has been shown by the extraction of the two phases of the oil and water emulsion treated with the metal complex at concentrations which are even much lower than those considered to be of biocidal nature. More particularly, emulsions have been studied treated with a quantity of disodium monocupric citrate (disodium citrate-copper) providing approximately 50 to approximately 100 mg of Cu ++ per liter of emulsion, which constitutes for example the Vio or the h of the biocidal dose in a particular environment. Examination of the mixture of the metal complex agent and the emulsions, by extraction of two phases using chloroform or other chlorinated hydrocarbons, reveals that copper is present in the organic phase. If the exact mechanism of this reaction has not been elucidated in a specific way, it has nevertheless been empirically observed the biostability, the chemical stability and the physico-chemical stabilities conferred as a result of the treatment of the emulsions with metal complexes of the present invention. In addition, the biostability conferred by the addition of quantities of metal complexes lower than the biocidal or biostatic quantities is considered to be remarkable and must be associated with the reaction of fragments of the organic phase making them not susceptible to bacterial attack, in contrast to a direct reaction of cations with microbial entities associated with the aqueous phase.

It has been noted before that polyvalent metal cations can be generated during machining, such as cations of iron, aluminum, etc. Furthermore, other polyvalent metal cations, such as calcium and magnesium, may be present in the aqueous medium used in coolants for metalworking. These ions can be designated, in another way, as being “generated ions”, that is to say those produced by the machining operations, or being “native ions”, that is to say say those inherently present in the aqueous medium of metalworking fluid compositions. These versatile cations normally interfere with metalworking processes and they also contribute to the instability of emulsified particles. However, it has been empirically determined that the stabilizers of the present invention make emulsions stable by protecting them from discomfort due to such polyvalent metal ions, i.e. those generated during metalworking operations or those inherently present in metalworking fluids. Thus, the stabilizing action constituents of the compositions of the present invention for metalworking tend, after their dissociation, not only to impart stability to the emulsified particles due to their association with these particles (and this results in inherent advantages ), but also to complex polyvalent metal ions whose presence is inappropriate in the medium.

The metal complexes which are used as stabilizers in the compositions and methods of the present invention liberate large amounts of the metal ion from these struc5

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coordination tures at a pH of about 4 to about 9 and, even better, at a pH of about 7 to about 9 or 10, i.e. those normally encountered in compositions for metalwork. On demand, and due to their remarkable dissociation properties shown by the sigmoidal shape of the representative curve on a pM-PH diagram, these agents offer a controlled release of metal ions at a pH compatible with the working conditions of metals. In addition, as indicated above, due to the nature of the organic ligand of metal complexes, the activity of other polyvalent metal cations or other foreign fragments present in metalworking fluids and which could , otherwise, imparting instability or impairing the stability of metal working emulsions is inhibited. Therefore, the metal complexes which are stabilizers of the present invention must be differentiated from other metal complexes in which the metal cations have been complexed with organic ligands represented by ethylenedediaminetetraacetic acid (EDTA), the acid diethylenetriaminepentacetique (DTPA), other amino acids, etc., which have relatively high chemical stability or inertness and which do not make the metal ion available in amounts which can be coordinated to a degree important, with electronegative emulsifiers and therefore these other complexes cannot impart stability to the emulsion. Likewise, such known complexes do not offer a controlled dissociation or release property of the metal ion, a property represented by a sigmoidal curve on a pM-pH diagram. On the contrary, due to their stability and chemical inertness, such known metal complexes tend to dissociate to a lesser degree and in a rather linear fashion. Furthermore, the present invention provides complexes which, due to their ionic nature, are capable of dissolving in large concentrations in an aqueous medium and which, however, remain in stable form. This property of solubility, in particular in alkaline media as in the present case, makes it possible to produce concentrates capable of producing on demand, in an emulsion, the metal ion making it possible to confer stability on the emulsion in the conditions of use of this emulsion for metalworking. Such a solubility property is to be distinguished from the case of the rather insoluble metal compounds of the prior art which use or comprise metal cation constituents and anionic constituents and which are virtually insoluble in such media, or metal complexes which, although they are soluble, fix the metal ion in such a complex state that it is only weakly dissociated and, therefore, hardly available for a release of this metal ion and its coordination with the particle emulsified.

As used in the present description and as it is known in practice, the expression “metalworking fluid composition” applies to fluids whose role is to lubricate, cool, clean and inhibit the decomposition of metal surfaces during the work of these metals. These fluids are well known to those who practice the art of metalworking. There are two fundamental areas in metalworking, namely mechanical operations designating shaping by cutting tool, cutting, drilling, milling, turning, lathe work, boring, grinding, etc., as well as shaping, bending or folding, rolling, stretching, etc .; and non-mechanical operations designating washing, quenching after heat treatment, etc. It is generally accepted that, for mechanical operations, the compositions for working with metals perform the roles of lubrication, cooling, cleaning and inhibiting rust, while in non-mechanical operations these compositions play mainly roles cleaning, rust inhibition and cooling.

The oil and water dispersions constituting the metalworking compositions containing the stabilizer according to the principles of the present invention can, as mentioned above, be of the oil-in-water type or of the water-in-type oil. These dispersions have above all been designated in practice as being oil emulsions or soluble oil compositions. Such compositions are essentially characterized in that they comprise two phases, namely a liquid in liquid, and that there is a dispersed phase and a continuous phase. Perhaps conventionally when the particle size of the dispersed phase is of an order of magnitude greater than about 0.1 microns, they are called "emulsions". When the particle size is in the colloidal range of about 1 millimicron to about 0.1 micron, the dispersion can be colloidal in nature. Therefore, whether one wishes to characterize them as a coarse emulsion or as a colloidal suspension, the fluid compositions essentially consist of an organic phase and an aqueous phase, that is to say a two-phase system consisting of a liquid in another liquid in which the first liquid is immiscible. In addition, the term "oil" is used here to identify a large class of substances of mineral, vegetable, animal, essential or edible origin. However, oils used for metalworking usually come from the class of mineral oils, derived directly from petroleum or from a petroleum-derived product, and, in particular, these oils belong to the class of lubricating oils. These dispersions include emulsifiers typically belonging to the anionic or nonionic type. In the case of anionic agents, the anionic portion has the polar nature required to exert the desired surface activity effects (or the desired surface active effects) and this portion confers electronegativity on the droplets or particles of the oil in suspension. . In the case of nonionic agents, electronegativity is imparted to the oil particle due to the inherent high density of electronegativity. Most often, the emulsifying agents which are used in emulsions for working with metals are anionic and / or nonionic surfactants. The molecule of anionic surfactants contains a portion containing negatively charged ions and an olephile or dispersible portion in oil. The surfactant can be (1) from the group of saponified fatty acids or soaps, or (2) saponified petroleum oil, such as sodium salts of sulfonates or organic sulfates or (3) saponified esters, alcohols or saponified glycols, the latter being well known under the name of anionic synthetic surfactants. Examples of such anionic detergents include alkylaryl sulfonates of amines and their salts, such as dodecyl benzene sulfonates or diethanolamine salts of dodecyl benzene sulfonic acid; sulfates of linear primary alcohols or fatty alcohols (C6-C24) which are products of the oxo process (such as sodium lauryl sulfate). A light saponified petroleum oil, such as a sulfonated petroleum distillation residue (such as so-called mahogany oil) is common. In general, the majority of surfactants or emulsifiers of the "anionic" type are alkali or amine salts of organic acids. Frequently, sulfonic acids are used whose structure of the organic portion is not well known, as in the case of the familiar "petroleum-sulfonates". Most of these sulfonates contain many chemical species. The general class name given to most of these sulfonates is "alkylaryl sulfonate". It simply means that a paraffinic hydrocarbon is linked to a nucleus of an aromatic or benzene hydrocarbon (usually benzene or naphthalene) and that the aromatic portion has been sulfonated. Examples of sulfonated fatty acids (C6-C24) consist of sodium or potassium salts5

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sium of myristic, palmitic, stearic, oleic or linoleic acids, or mixtures thereof. Likewise, in this class of anionic surfactants, there are the alkaline and alkaline earth salts of neutral phosphoric acid esters of oxyalkylated (oxyethylated) higher alkyl phenols or of oxyalkylated aliphatic monoalcohols. Examples are the sodium and potassium salts of phosphoric esters of adducts of ethylene oxide on isodecyl alcohol. Thus, anionic surfactants or emulsifying agents which are designated here include soaps or synthetic surfactants from the class of alkaline salts, alkaline earth salts and amine salts of sulfonates, phosphates or sulfates organic.

Nonionic surfactants which are suitable for use commonly have hydrophilic portions or side chains usually belonging to the polyoxyalkylene type. The part of the molecule soluble or dispersible in oils comes from fatty acids, alcohols, amides or amines. Thanks to an appropriate choice of starting materials and to the adjustment of the length of the polyoxyalkylene chain, it is possible to vary, as is well known, the surface active parts of nonionic surfactants. Suitable examples of nonionic surfactants include alkylphenoxy polyoxyethylene glycols, for example an adduct of ethylene oxide on octyl phenol, nonyl phenol or tridecyl phenol, etc. These nonionic surfactants are usually prepared by the reaction of the alkylphenol with ethylene oxide. Other specific examples of non-ionic detergents include glycerol monooleate, oleylmonoisopropanolamide, sorbitol dioleate, alkylolamides which are prepared by reacting alkanolamines such as monoisopropanolamine, diethanolamine or monobutanolamine, with fatty acids such as oleic, pelargonic, lauric and elaidic acid.

As is well known in practice, metalworking compositions are typically formulated by combining a lubricating oil, such as a solvent-refined paraffinic or naphthenic oil, an anionic emulsifier as mentioned above, and special additives including anti-rust agents, etc. Commonly, in industry, such compositions containing the additives are called "waterless oil" and then the composition of the waterless oil is mixed with enough water to obtain an emulsion. The volume of water will vary depending on the various factors and whether the emulsion is an oil in water or water in oil type emulsion. For example, the proportion of the oily phase can vary between wide limits ranging from approximately 1 to approximately 95% by weight or even more, the remainder consisting of the aqueous phase and other quantities of the emulsifying agents and additives. Usually, the proportion of an emulsifying agent can be between about 5 and about 50% by weight. To obtain lubricating compositions and cutting oil compositions, the oil composition without water is mixed with a volume of water sufficient to obtain an emulsion containing by volume about 90 to about 99%.

of water and containing 10% to 1% by volume of oil. The ingredients of waterless oil are usually about 30 to about 90% of a lubricating oil, about 10 to about 25% of an emulsifier, the rest may be made up of additives of the type mentioned above. above.

In the lubricating oil composition, the stabilizing metal ion is present in an amount which can effectively ensure the stability of metalworking. This effective amount can vary depending on a number of factors, including the particular metal being worked on, the pH, the impurities and the amounts of the oily phase and the aqueous phase, the emulsifier, the metal cations. that we are working on, the particular metal complex, etc. Typically, for example, in an emulsion formed from the composition of the waterless oil as mentioned above, the stabilizing metal ion is usually contained in an amount of from about 10 to about 500 mg of the metal ion per liter of the oily phase. When a metal complex provides the metal ion, the complex is added to the aqueous phase. After such an addition, the metal ion migrates, as explained above, to form coordination bonds with the emulsifying agent by establishing a balance between the oily phase and the aqueous phase. When during metalworking the metal ion depletes in either phase, additional complex can be added to keep the stabilizing amount effective. More particularly, in a composition of cutting oil or lubricating oil for working iron, formed of approximately 97% by volume of water and 3% by volume of oil as mentioned above, with approximately 10 at 15% of an emulsifier, and when using disodium mono-citrate citrate as a stabilizing agent, an amount of 500 mg of copper per liter of the aqueous phase will make it possible to obtain a toxic action against bacteria. However, as mentioned above, the stability of the metalworking fluid can be imparted to the emulsion with as little as 10 to 100 mg of the copper cation per liter, which is much lower than the levels exerting a toxic action. However, quantities of the metal complexing agent or of the ion leaving these intervals can be used.

The metal working stabilizers of the present invention can be supplied to the emulsion in a number of ways. For example, the stabilizing metal complex can be added to the aqueous phase of the emulsion before preparation, and then the waterless oil composition containing the oil, the emulsifier and the additives can be added to thereby form the emulsion, maybe with a little agitation. Furthermore, the emulsion can firstly be formed and then the stabilizing metal complex is added to the emulsion thus formed. The emulsion is formed so as not to decompose the complexing agent of the metal. In particular, in the case of complexes of the zinc, nickel and copper citrate type, these complexes are relatively stable under alkaline conditions up to a pH of approximately 12, but they still confer the desired stabilizing effect on an alkaline pH ranging up to a maximum of about 9 to 10 to metal working emulsions. Thus, the pH of the fluid compositions on the alkaline side is adjusted, between approximately 7 and approximately 10, so that the metal complex is not broken down first, and a pH lying in the middle of 1 is thus obtained. 'interval and that is about 8.5.

In a presently preferred form, the agent of the present invention comprises a monometallic complex of a multivalent metal and a polyfunctional organic ligand, in a 1: 1 ratio between the metal and the ligand, the complex having a property of dissociation represented by a sigmoidal curve (in S) on a pM diagram or graph as a function of pH. A specific example of the metal complex is monocopper- (II) -citrate dialcalin represented by monocopper- (II) -disodium citrate, dipotassium or dilithium. These dialkaline- (II) -citrates have a dissociation property represented by an S-shaped (sigmoidal) curve, the two fragments of the curve meeting at a point lying in a pH range between approximately 7 and approximately 9. It has been established that these monocopper complexes (II) are very stable in basic media, of the order of about 9 to about 12, that is to say that they have a stability constant. effective, Ketf, of the order of about 1012 to about 1013. However, at a pH of about 7-8, Ketf of these single-copper- (II) -citrate complexes is of the order of about 105 at around 108. This is why at a pH of around 7

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8 or close to these values, the effective stability constant of the single-copper- (II) -citrate complex is considerably lower (less than a thousand to several hundred thousand times), and a large concentration of free Cu ++ is available for toxic or stabilizing activity. For example, approximately 10% of the copper present in the complex is in the ionized state at a pH equal to 7 or close to this value, while approximately 0.1% of the copper is ionized at a pH equal to

9 or close to this value. This would not be true for an EDTA complex or a polyamine of a multivalent metal such as copper, since its stability constant (1014 to 1016) will only vary very slightly in the normal pH range from 7 to 9. Such complexes formed with EDTA do have a pH effect on the stability constant, but this is represented by a smooth smooth curve reaching a limiting effect by dissociation caused by protons at pH values from about 7 to about 9, giving only about 0.0001% of an ionized species at a pH of 7 or close to this value up to a value as low as 0.00001% of the ionized species at a pH equal to 9 or close to this value. It should be understood that complexes with stabilizing or antimicrobial action will function in a pH range of between about 3 and about 12. Above about pH 12, the complexes will tend to be destroyed by alkaline media, by precipitating these media in the form of hydrated metal oxides. Below a pH value of around 6, i.e. around 3 to around 6, the instability of the metal complex results in a high concentration of free Cu ++ in solution, which will create biostability and will exercise other stabilizing roles as mentioned above. In the average range from about 7 to about 9, the set release is very effective. Thus, these complexes provide controlled release of the metal ion (between about 10% and about 0.1% of a complexed metal) in the pH range between about 7 and 9; this metal ion is then available for roles of coordination, antimicrobial action and stabilization.

According to this description and the currently preferred embodiment, it will appear that other complexes of polyfunctional organic metals and ligands respond to the model of the present invention when they show the dissociation property characterized by a sigmoidal or S-shaped curve. in a normal pM-pH diagram. For example, based on the monometallic complex of a polyfunctional organic ligand of the present invention, it is possible to use other metal ions of monovalent or multivalent nature, in particular divalent and polyvalent cations and in particular zinc, nickel , chromium, bismuth, mercury, silver, cobalt, and other metallic cations or similar heavy metals. Heavy metal complexes are considered more toxic than those of light metals. Other polyfunctional organic ligands can be replaced with the citric acid cited as a specific example by the preferred embodiment of the present invention. Among other polyfunctional ligands, there is the broader class of alpha- or beta-hydroxypolycarbo-xylic acids in which citric acid is included. Likewise, it is possible to introduce into the molecular model metal complexes of the present invention, in place of citric acid, of other acids comprising as substituents functional groups such as alpha-, or beta-amino groups, sulfhydro, phos-phinol, etc., and similar results can be obtained. In general, from the point of view of the formula of a metal complex, the monometallic complex of copper and citric acid corresponds to a complex formula represented by one or the other of the structural or structural formulas ( A) and (B) below:

O.

Q

\

—O

/

10

1S

20

25

(B)

c-cm-c-o-cu

O CH2-C-O

o o .0

20

H20

■ H20

o_

Form (A) is believed to be the preferred form when applying free energy considerations. A single proton introduced into the structure of the complex represented by the form (A) or (B) prevents the formation of given coor-3o nuclei which are stable with five or six members. With the introduction of a proton, only seven-membered nuclei can be formed by the coordination of electron-donating acetate groups, and such structures of seven-membered (heptagonal) nuclei are unstable. Consequently, the molecule of the complex dissociates and presents the metal ion which can exert its toxic or stabilizing effects. In comparison, metal complexes and EDTA or other polyamines require four or more protons, and therefore greater acidity, to dissociate the complex. This explains the weak effect of pH 40 on such complexes in a pM-pH diagram.

The forms (A) and (B) of structure can be more generally represented by the following models:

45 MODEL A

(R) -

so

-Z:

-X:

M Y

ss MODEL B

-z,

(R) -

60

-X: M

(R)

In the above models, the segments formed by a solid line 65 represent a chemical bond between elements of the structure of the structure of the molecule; X, Y and Z represent donors of electron pairs; (R) represents any element or molecule or group, M represents

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a metal; the affinity of X for protons is greater than that of Z, Y or R. It will therefore be understood that it can be replaced by other pairs of Lewis base protons and by other metal ions, oxygen , divalent copper or, in this case, the carbon atoms of these structural models to obtain a molecular model which will dissociate in a similar way when we introduce a proton or a species whose behavior is similar to the behavior represented by the sigmoidal curve or S-shaped on a pM-pH diagram. Molecular models therefore constitute another form of expression of the stabilizing agents of the present invention.

The invention and its various embodiments and advantages will be better understood when reference is made to the following examples, to the detailed descriptions which follow and to the figure illustrating the preparation of the complexes and their activity.

COMPLEX PREPARATIONS

A. Single-copper- (II) -dithithium citrate

10 millimoles of lithium citrate are dissolved in 10 ml of water. To this solution, 10 millimoles of cupric chloride (CuCh -2H20) are gradually added each year with stirring. A dark blue solution is formed. It is neutralized to a pH of about 7 with 10 millimoles of lithium hydroxide (LiOH ■ H2O). When evaporated to dryness, this solution gives a dark blue semi-crystalline solid. This solid is ground to obtain a fine powder and the lithium chloride is extracted with 50 ml of anhydrous methanol, five times, at 35 ° C. The blue solid, which remains as a residue, is kept under vacuum to remove the methanol and dry it. Attempts have been made to crystallize the salt in water / organic solvent systems but, which seems to be due to the extremely hygroscopic nature of the salt and to the large negative charge of the ionized molecule, the solid obtained was microcrystalline to amorphous. The following formula is proposed for the 1: 1 complex of copper and citrate, based on the elucidation of the structure and the analyzes described below:

LÌ2Q1C6H4O7 • XH2O

Depending on the degree of hydration, the molecular weights corresponding to the formula below (M.M.) and the corresponding percentages of copper content are proposed:

LÌ2CUC6H407-XH20

M.M.: 265.51 for X = 0; % of Cu = 23.93

M.M .: 283.53 for X = 1; % of Cu = 22.41

M.M .: 301.54 for X = 2; % of Cu = 21.07

M.M .: 319.56 for X = 3; % of Cu = 19.88

The copper content observed for variously dried samples of the solid complex is between 20% and 23%. The compound (1: 1 solid complex) is extremely soluble in water. A solution as concentrated as a two molar solution can be produced quite easily.

Up to a pH of 11.5, there is no effect on the solubility of the compound in water. Above this pH, the complex decomposes, giving a greenish-brown precipitate, which is probably constituted by hydrated oxides of copper. The solid 1: 1 complex can be used as a stabilizing agent with or without the removal of the lithium chloride formed during its preparation.

B. Single copper (II) disodium citrate

(1) Equimolar solutions of copper chloride and sodium citrate are added to water as in (A) above to obtain a dark blue solution having a pH of about 5. It is placed in a vial. decant an aliquot part (50 ml) of this solution. Add an equal volume of anhydrous acetone and shake the vial to mix. After rest, a two-phase system is obtained. A blue liquid phase rests at the bottom of the bulb in a reduced volume of approximately 25 ml, while the upper layer (approximately 75 ml) is slightly cloudy and colorless while it had the clarity of the crystal before the mixing process. by shaking. The blue liquid (oily and viscous) which is collected in a second separating funnel is removed from the bulb by the tap. The cloudy supernatant is placed in a beaker and evaporated to dryness on a boiling water bath. To the second separating funnel, about 25 ml of anhydrous acetone are added, which causes an almost instant formation of a plastic-like mass at the bottom of the funnel, as opposed to the oily liquid that was present there. . The supernatant liquid of the plastic mass is placed in a second beaker and it is called supernatant liquid 2. The addition of distilled water to the mass analogous to plastic material results in the immediate redissolution of the material. The total volume of the redissolved substance is adjusted to 25 ml, which again leads to the formation of an oily and viscous liquid. After the supernatant liquor 1 has evaporated to dryness, microscopic examination of the dry residue reveals the presence of large, well-defined amounts of sodium chloride crystals. Evaporation of the supernatant liquid 2 gives a very finely divided pulverulent residue which contains a small number of distinct crystals of sodium chloride. Analysis to detect the copper content of the blue oil solution which has been subjected to a double extraction reveals that the solution contains approximately 125 mg of copper per milliliter, which represents a concentrate of the metal complex which originally contained approximately 65 mg / ml. The large decrease in the amount of sodium chloride in the supernatant 2 indicates that most of the salt, a constituent of the impurity by-product, has been removed. A portion of the concentrate was allowed to evaporate and the existence of a clearly crystalline material was noted.

(2) The procedures of the preceding paragraph were repeated (1), except that the pH of the blue solution initially formed was adjusted to a value of approximately 5 to approximately 7 with a KOH solution to neutralize the HCl form. After carrying out the extraction and evaporation operations, a concentrate of the metal complex was obtained which, after evaporation, gave clearly crystalline material.

(3) Equimolar aliquots of copper sulphate and sodium citrate were combined as in paragraph (1) and then the pH was adjusted with NaOH to approximately 7. Extraction and evaporation operations of the resulting blue solution, as described above, gave an amorphous powder having no visible crystalline structure.

The following formula is proposed for the single copper- (II) -disodium citrate prepared in paragraphs (1) to (3) above, based on the elucidation of the structure and on the analyzes described below:

Na2CuCsH207-XH20

C. Disodium monozinc-citrate

Using the following ingredients, a zinc complex was prepared which is a stabilizer analogous to the copper complex of (B) above:

50 ml cold water

29.4 g of trisodium citrate dihydrate

13.6 g zinc chloride (ZnCk)

Concentrated HCl

NaOH lozenges

s

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The ZnCk was ground into fine particles with a mortar (and pestle) and then dissolved in water. The pH was adjusted to between 0.5 and 1.0 with HCl. Sodium citrate was added slowly, adding HCl to keep the pH below 1.0. When all of the material had dissolved, the solution was slowly neutralized with NaOH pellets. The remaining material and solution were decanted at pH 7.2, the pH was adjusted to a value of 8.5-9.0 and then extracted with a double volume of a 50:50 solution. ethanol-acetone. The material was collected on a Büchner funnel using Whatman No. 42 filter paper. Alternatively, the solution can be dried in vacuo at 70 ° C.

D. Disodium mono-citrate

A stabilizing nickel complex is prepared using the following ingredients:

40 ml cold water

38.4 g anhydrous citric acid

47.5 g of nickel chloride (NiCh), finely ground,

and NaOH flakes

Citric acid is dissolved in water. The nickel salt is added slowly, constantly following the pH. When all of the material is in solution, NaOH flakes are added slowly (to minimize heat generation) to adjust the pH to a value between 4.0 and 5.0. Approximately 100 ml are obtained containing approximately 117 mg of Ni ++ per milliliter.

E. Disodium citrate-citrate

A stabilizing mercury complex is prepared using the following ingredients:

40 ml water 2.2 g mercuric oxide (HgO)

1.9 g anhydrous citric acid and NaOH tablets

The citric acid is dissolved in water and the solution is heated to a temperature not higher than 50 ° C. HgO is added slowly, with vigorous stirring, and allowed to react until the solution is clear. The pH is adjusted with NaOH pellets to 8.5-9.0, making sure that the temperature does not exceed 50 ° C. The material can be crystallized by either of the methods described in the case of the zinc complex in (C) above.

DETERMINATION OF THE DISSOCIATION OF THE METAL COMPLEX It was determined over a range of pH between 3 and 12 units, using a specific electrode for the copper ion- (II) [(Orion Copper II) Specific Electrode]), the property dissociation of the 1: 1 complex of copper and citrate prepared by the above techniques. The pH of 50 ml samples of the 1: 1 solution of citrate and copper (0.0068 molar) was adjusted to values of 3, 4, 5, 6, 7, 8, 9, 10.11 and 12, by subsequently determining, using the specific electrode for the copper ion, the concentration of the free copper ion. The following values were obtained for the concentration of free copper ion at the indicated pH, and the negative logarithms of the concentration of copper ion were determined.

PH table

Cu ++

pM

3

3.2X10-3

2,495

4

9.0 X10 "4

3.096

5

2.5 X10-4

3.602

6

5.3 X 10-s

4.276

7

1.0 X10-5

5,000

8

8.0 X10-8

7.097

9

8.8 X10-12

11,055

10

9.6 X10 "13

12,018

11

3.3 XlO-13

12,482

12

1.34 X10-13

12,873

From these data, a pM-pH curve was constructed to indicate the relationship between the concentration of the free Cu + + ion and the pH, as illustrated in the attached single figure. This figure is a graph in Cartesian coordinates (solid black line) of the negative logarithm (i.e. change sign) of the concentration of the metal ion (pM) as a function of the negative logarithm (i.e. i.e. changed sign) of the hydrogen ion concentration (pH) at the points indicated in the table above. This graph is an S-shaped (sigmoidal) curve representing the dissociation property (caused by protons) of the metal complex. In the pH range between about 9 and 12, the complex is very stable and the concentration of free Cu ++ is low. At a pH of around 7, the complex is relatively unstable and the dissociation into free Cu ++ is high, which allows the role of stabilizer. In the range of about 7 to about 9, Cu ++ is available for controlled release: about 10% to about 0.1% dissociation of Cu ++ from the complex occurs. This unexpected behavior of pH dissociation makes the complexes extremely effective as antimicrobial or stabilizing agents for metalworking compositions.

In comparison, a curve concerning the copper complex of EDTA is represented in the appended figure by the broken line, according to the indications of A. Ringbom, “Complexation in Analytical Chemistry”, J. Wiley & Sons, NY, 1963, page 360 As illustrated, the effect of pH on the copper complex of EDTA is represented by a smooth and regular curve reaching a limiting effect by dissociation caused by a proton at about pH 7-9, which does not give, for example, only about 0.001% to 0.00001% of the ionized product.

The existence in dilute solutions of complexes exhibiting the ratio of a metal to a citrate has been suggested in the publication by M. Bobtelsky and J. Jordan, J. Amer. Chem. Soc., Volume 67 (1945), page 1824. However, no one has cited the remarkable antimicrobial or stabilization activities of an emulsion characterizing these derivatives nor their capacities to form coordination structures with emulsified droplets. In addition, the Applicant has also discovered other remarkable properties of these complexes in metalworking fluids, as described here in detail.

In addition, the Applicant has prepared solid metal complexes of the mono-copper- (II) dialkaline citrate type, and such solid forms are surprisingly unexpected. The Applicant has also been able to produce high concentrations in solution of these metal complexes. The nature of these complexes has been clearly established by the use of analytical criteria, namely: (1) the method of the ratio between the moles, which was introduced by Yoe and Jones (JH Yoe and AL Jones: Ind. Eng. Chem. Anal. Edition, 16; 111,1944); (2) the method of continuous variation attributed to Job and modified by Vosburgh and Cooper (W.C. Vosburg et s

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G.R. Cooper: J. Am. Chem. Soc., 63; 437.1941); (3) the dependence of the formation of the complex on the pH; and (4) determining the apparent stability constant of the complex. Spectrophotometry studies, including visible spectrum and ultraviolet spectroscopy, pH determinations, as well as infrared spectroscopy measurements served as additional means of confirming the discoveries made by the Applicant on training and the molecular composition of the 1: 1 complex of copper- (II) and citrate.

(1) Cu + 2 + -OOC

\ (CH2COO-) 2 v ^ HO

The 1: 1 copper complexes used here as antimicrobial or stabilizing agents are very highly soluble, which indicates the ionic nature of these complexes. This is further confirmed by the observation of the migration towards the anode (positive electrode) of the colored band of solution of the complex in electrophoresis experiments. The visible and ultraviolet spectra show the formation of a 1: 1 compound. The overall reaction for the formation of the structure form complex (B) seems to be:

SV / ^ C (CH2COO-) 2

+ H +

(2) H + + OH "HzO

(based)

(Cu-Citrate-2) (H +) (Cu + 2) (Citrate-3)

(Cu-Citrate-2) Keff ~~ (Cu + 2) (Citrate "3)

Thus, instead of complexing the -COO- groups only, the alcoholic hydroxyl group - OH ionizes and is involved in coordination. This forms a stable five-membered nucleus and probably a six-membered nucleus. Thus, the reaction is shifted to the right (stabilized) by OH "(base) when the H + product is removed as the reaction continues. This results in the very high value of the effective stability constant, Keff. such reaction, the constant Keff depends on the pH but it is linked to the absolute stability constant, Kabs, by the relations:

(Cu-Citrate =)

Keff = "

(Cu ++) (Citrate-3)

_ (Cu-Citrate =) (H +)

(Cu ++) (Citrate-3)

Ka * = Keff (H +)

Applicants have found that Kabs has, for the 1: 1 complex, a constant value of about 1013 (strong complex) in the pH range of about 9 to 12. The apparent value of Kabs drops sharply at pH 7 to 9 and, at pH values below about 7, there is a further decrease indicating that the complex exists in finite concentrations even at a pH of 3 to 7.

It is believed that another important feature of the complexes of the present invention can function by allowing them to play the role of very effective bactericides. We can take for example the case where bacteria develop in a medium having a pH of about 9 to about 11 for example and where a complex of monocopper (II) -citrate dialkaline is introduced. As indicated above, an environment with an alkaline pH makes the copper (II) -citrate complex very stable. It is assumed that due to its immediate attachment to the surface of a cell, one should not expect that the free cuprous ion will cross the membrane of a cell at all or, at best, will not not cross as easily as the complex form. Furthermore, the complex easily crosses the membrane of a cell, perhaps because (1) its organic nature would allow it to serve as a metabolic substrate on which the growth or proliferation of bacteria would depend, or (2) the low charge density. dianonic of the complex would increase its permeability for crossing the wall of the microbial cell. After crossing the cell membrane, it is expected that the complex will be subjected to an environment with a pH of about 7. So, after this crossing or this transport, the particular complex is very unstable and labile; the copper ion is therefore abundantly and rapidly released for the denaturation of cellular proteins or to otherwise interfere with the biochemical reactions of intracellular metabolism so as to cause cell death. On the contrary, when other known complexes can undergo this transport or this passage under such circumstances, these known complexes are quite stable and kinetically inert, and they will not be effective, because copper is too closely linked, even with intracellular pH of around 7, so that it is excessively toxic.

The metal complexes of the present invention have very remarkable antimicrobial properties in comparison with the compounds of the prior art. For example, the formation of heavy metal salts of carboxylic acids is quite common. However, with the exception of low molecular weight acid salts, they are usually insoluble in water. This is shown by the dicuivric citrate (II) cited in the literature (Cm citrate) 2 ■ 5H2O. This compound is formed by heating a strongly basic solution of sodium citrate with Cu + +. Dicuivic citrate (having a ratio of 2. copper atoms to a citrate ion) precipitates from the solution. This dicuivric citrate has the following properties: (1) insolubility in water (with an overall net charge of the com-55 posed which is zero: 2Cu ++ and the citrate ion "4); the reaction is:

2Cu ++ + Citrate = <Cu2citrate 1 + H +

6 "and it is pushed towards its completion by the reaction of H + of the product with OH" in basic medium; (2) a light green color in solid form; and (3) the elementary analysis confirms the ratio of 2Cu for a The insolubility of dicuivric citrate has also limited the effectiveness of this compound as a bactericide and, while it has been proposed so far in pharmaceutical applications, its use has been limited.

As explained above, the compositions of metalworking fluids can be formulated from nom25

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many different types of specific ingredients. See, for example, the aforementioned patents and "American Society of Tool Engineers - Tool Engineer's Handbook", first edition, 1953, pages 357 et seq., To which reference may be made.

The following specific (and non-limiting) examples serve to illustrate metalworking fluids and to show the implementation of the principles of the present invention.

Example 1

A cutting fluid composition is prepared by mixing (on a volumetric basis) the following ingredients:

1% sodium xylene sulfonate

9% of a naphthalene sulfonate

90% of a mineral oil

This mixture is used to prepare, by mixing with water, an emulsion at 3% by volume and the pH is adjusted to about 8.5-8.9 by the addition of HCl. The disodium monocultivate citrate (mono-copper-disodium citrate), as prepared above, is added to the emulsion to obtain in the aqueous phase 100 mg of Cu ++ per liter. When such a fluid is used in metal shaping operations by removal, it has been found that all of the advantages discussed herein can be obtained.

Example 2

A grinding or grinding fluid composition is prepared, using the same stages as in Example 1 with similar results, except that 50% naphthalene sulfonate is used as the ingredients of the emulsion. % of a mineral oil and 35% of tall oil.

To show the coordination of the metal ions with the emulsified droplets for obtaining stabilization activities according to the present invention, the following experiments were carried out.

Experiment 1

Relation between the concentration of copper in the oil phase and the water phase, on the one hand, and the percentage of oil in the emulsion and the initial concentration of the metal complex, on the other hand.

Methods

Emulsions are prepared so that they contain 2.5%, 5.0% and 10.0% oil in water. 10 ml of each emulsion are pipetted into the 16 X 100 mm test tube. 1 ml samples are removed from each emulsion. To each of these tubes is added disodium monocuivic citrate (disodium citrate-copper; which is hereinafter called the metal complex) so as to reach final Cu ++ concentrations of 50 ppm, 100 ppm, and 150 ppm. 1 ml samples are taken immediately after mixing the metal complex and emulsions. Samples are taken again after 1 hour, during which mixing has sometimes been carried out.

The oil samples are extracted by adding an equal volume of dichloroethane and a drop of saturated KCl, mixing and rotating for 5 minutes at maximum speed on a centrifuge. 0.5 ml of the organic layer (lower) and 0.1 ml of the aqueous layer are removed from different test tubes, and 4.9 ml of water is added to the aqueous sample. 0.2 ml of copper reagent # 1 is added to each tube, while mixing, then 0.2 ml of reagent # 2 is added. All the tubes are mixed well and 5.0 are added. ml of water to the tubes containing the organic extract. The tubes containing the organic phase are again agitated and the organic material is left to settle towards the bottom. The optical density of the tubes is read at 700 nm relative to appropriate blank tests (organic or aqueous extract of emulsions to which no metal complex has been added).

Results and conclusions The experimental results are presented in Table I below. The percentage of copper was determined in each phase by correcting the absorption A700 to take account of the volume differences between the organic extract and the aqueous extract and adding the values of A700 for each phase. It has been assumed that the total percentage of A700 for each phase is directly related to the percentage of total copper present in each phase:

Table I

Percentage of total copper in each phase as a function of time (T), percentage of oil and copper concentration.

50 ppm metal complex in Cu ++ Total percentage of Cu ++

% oil

Organic phase To T60

To aqueous phase

Tfio

2.5

0.9

0.0

99.1

100.0

5.0

13.0

22.7

87.0

77.3

10.0

19.2

25.9

80.8

74.1

100 ppm metal complex in Cu ++ Percentage of total Cu ++

% oil

Organic phase To T6O

To aqueous phase

T „o

2.5

0.8

3.6

99.2

96.4

5.0

10.6

12.2

89.4

87.8

10.0

12.7

13.6

87.3

86.4

150 ppm of metal complex in Cu ++ Total percentage of Cu ++

% oil

Organic phase Tq T6O

To aqueous phase

T., o

2.5

1.0

1.0

99.0

99.0

5.0

8.4

11.7

91.6

88.3

10.0

11.9

12.6

88.1

87.4

The results obtained clearly show that for any concentration of the metal complex, the total percentage of copper present in the organic phase increases slowly over time. This effect was most marked in samples containing 5.0% oil in the emulsion. The absorption of Cu ++ in the oil layer seems to be, in enzymological terminology, of the first order compared to the concentration of the oil and of the metal complex, the concentration of copper in the oil stabilizing at the saturation point. oil. As studied below, we expect to obtain for the transfer speed of Cu + + in the oily phase a curve of the Michaelis-Menten type.

At a given time and at a given concentration of the metal complex, the percentage of total copper in the organic phase is directly linked to the percentage of oil in the emulsion. The correlation was especially evident in the case of samples containing 50 ppm of the metal complex. The amount of copper in the organic phase depends on the s

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concentration of oil in the sample, which indicates that copper binds or binds directly by coordination to the surface of the oil particles.

When the concentration of the metal complex was increased, an equivalent increase in the percentage of Cu ++ in the organic phase was not seen. This phenomenon suggests several different transfer mechanisms of Cu ++ for its passage through the oil. The size of the emulsion oil particles is certainly not uniform. Therefore, the contact area of all of the oil particles present in a 10.0% oil emulsion is not four times where X +++ is any simple or complex cation for - 20 both three positive charges; ki is determined by the dissociation constant of the metal complex at pH 9, and k3 by the rate of absorption of copper in the oily phase and the affinity of the citrate gragment and of the divalent and trivalent cations for each other. Obviously, ki> k2 and k3> k4, 2s since with a greatly increased time period and shear, virtually all of the copper was found in the organic phase. The notions of a relation of equilibrium and dependence of absorption with respect to time have a good correlation with curves of the Michaelis-Menten type.

Experiment 2

Relationship between the concentration of copper in the oily phase and in the aqueous phase, on the one hand, and the 3s shear of the oil particles, on the other hand.

Methods

A 50% oil concentrate is sheared by passing it three times through a 56 X 106 Pa homogenizer. The oil particles are found to be less than 0.1 micron in diameter. It is found that the same concentrate, if not homogenized, has a large particle size range (0.8 to 3 microns), the average diameter being about 1.5 microns. "

The two concentrates are mixed with tap water to obtain emulsions with 10% oil in water,

since previous experience has shown that an emulsion containing this percentage of oil gives the greatest speed of passage of Cu + + by adsorption in the oily phase. n / a A sample (2 ml) of each emulsion is taken and centrifuged to remove any coarse particulate matter present. Metal complex is added to each emulsion to obtain 100 ppm of Cu ++ and samples of 2 ml are taken which are immediately centrifuged. Aliquots of supernatant liquid (1 ml) are extracted and assayed as described in experiment 1. The emulsions are gently shaken for 1 hour then samples (2 ml) are taken which treated as described above after 10 minutes, 30 minutes and 60 minutes. "O

Results obtained Table II below shows the experimental results 65 obtained. The percentage of copper in each phase was determined as described in experiment 1.

as large as that obtained in the case of a 2.5% oil emulsion. The variation in particle size affects the amount of copper that can be transferred to the organic layer. A balance may exist between the copper present in the oily phase and that present in the aqueous phase. The “equilibrium constants” for the two-way transfer can be determined by the concentrations of the metal complex in the aqueous phase, ie the concentration of the reacted body, and the concentrations of organic salts. of copper and citrate. The transfer of the metal complex can be described as follows:

Cu ++ • oil = + X +++ • Citrate =

11 11

Cu ++ + oil = X +++ + Citrate s Table 11

Total percentage of copper in each phase as a function of time and homogenization.

Total percentage of Cu ++ (100 ppm of metal complex added)

Time

Organic phase

Aqueous phase

(min)

Homogenized

Not homogeneous.

Homogenized

Not homogeneous.

0

13.5

11.3

86.5

88.7

10

18.3

20.3

81.7

79.7

30

25.3

14.9

74.7

85.1

60

27.0

18.1

73.0

81.9

A comparison of these results with those from Experiment 1 shows that a considerably greater amount of copper has passed by adsorption in the organic phase of the homogenized material and a little more in the organic phase of the non-homogenized material. If the concentration of the metal complex added to these samples, particularly to the homogenized material, had been increased, one would expect to find a higher proportion of copper in the organic layer. In a cooling fluid which is circulated for metalworking and which has large concentrations of divalent cations, such as Mg ++ and Ca ++ present to compete for a reaction with the citrate moiety, the speed of the reaction d copper adsorption (ki and k3) should be greater.

The results of this experiment clearly show the validity of a Michaelis-Menten analysis of the adsorption rate of copper. The greatest speed of adsorption of copper in the organic phase of the homogenized sample occurs during the first ten minutes following the addition of the metal complex to the coolant.

Between 10 and 60 minutes, there is a slower rate of copper adsorption. More copper was adsorbed by the homogenized oil particles than by the non-homogenized oil particles. We see a much higher initial copper adsorption speed in the case of the homogenized oil sample, which is due to the huge specific contact surface of the oil particles. These effects verify the fact that the adsorption of copper in oil is also a surface phenomenon, that is to say that copper attaches to the surface of oil particles rather than incorporating them. particles.

It goes without saying that the invention has been described only by way of illustration, but not limitation, and that it is capable of receiving various variants coming within its scope and its spirit.

ki ~ k3

* ■ Cu ++ + Citrate k4 complex

Na metal

B

1 sheet of drawings

Claims (24)

625,829 2 1. Stabilized fluid composition usable for metalworking, characterized in that it comprises a dispersion of oil and water, an emulsifying agent chosen from anionic agents, nonionic agents and their mixtures, which confer electronegativity to the oily phase of the dispersion, and, as a stabilizer present in an amount effective for stabilization, a multivalent metal ion bonded to the electronegative oily phase in order to impart stability to the emulsion. 2. Composition according to claim 1, characterized in that the effective amount of the metal ion is between 10 and 500 mg of this ion per liter of the oily phase. 3. Composition according to claim 1 or 2, characterized in that the stabilizing ion is present in the form of a complex with a polyfunctional organic ligand, this complex having in aqueous medium a dissociation property, caused by protons, represented by a sigmoidal or S-shaped curve on a Cartesian coordinate diagram showing the negative logarithm of the concentration of the metal ion as a function of the negative logarithm of the concentration of the hydrogen ion, this dissociation property causing the controlled release metal ion to impart stability to the dispersion. 4. Composition according to claim 3, characterized in that it has an alkaline pH ranging up to a maximum of 12. 5. Composition according to claim 3, characterized in that it has an alkaline pH between 7 and 9. 6. Composition according to claim 3, characterized in that the regulated release of the metal ion is such that there is release of 10% to 0.1% of this metal ion of the complex in a pH range ranging from 7 to 9. 7. Composition according to claim 3, characterized in that the metal complex is a complex, in a ratio of 1: 1, of a divalent metal ion and a polyfunctional organic ligand. 8. Composition according to claim 7, characterized in that the metal is copper, nickel or mercury, and the ligand is citric acid. 9. Composition according to claim 7, characterized in that the organic ligand is an alpha-hydroxylated polycarboxylic acid. 10. Composition according to claim 3, characterized in that the metal complex is a monocopper (II) -citrate dial-calin. 11. Composition according to claim 3, characterized in that the metal complex is contained in an amount providing from 10 mg to 500 mg of the metal ion per liter of the aqueous phase. 12. A method for preparing a stabilized fluid composition according to claim 1, characterized in that a dispersion of oil and water is prepared with said emulsifying agent, and the aqueous phase of this composition is supplied a quantity, with stabilizing action, of the multivalent metal ion to be fixed in the electronegative oily phase. 13. The method of claim 12 for preparing the composition according to claim 3, characterized in that the metal ion is introduced into the aqueous phase in the form of said complex. 14. Method according to claim 13, characterized in that the dispersion is first prepared and the metal complex is introduced into the aqueous phase of the dispersion. 15. The method of claim 13, characterized in that the metal complex is introduced into the aqueous phase of the composition before the preparation of the dispersion. 16. Method according to claim 13, characterized in that the dispersion has an alkaline pH of less than 12. 17. The method of claim 13, characterized in that the dispersion has an alkaline pH between 7 and 9. 18. The method of claim 17, characterized in that after dissociation, the ligand of the complex acts as a buffer maintaining the pH in the above range. 19. The method of claim 13, characterized in that this complex is a dialcal monometal chelate of an alpha-hydroxylated polycarboxylic acid. 20. The method of claim 19, characterized in that the chelate is monocopper (II) -ditaline dialkaline. 21. The method of claim 20, characterized in that the chelate is provided in an aqueous mixture. 22. The method of claim 20, characterized in that introduced into the aqueous phase from 10 to 100 mg of the ion of the copper metal per liter. 23. Use of the composition according to claim 1 for working metals. 24. Use according to claim 23 of the composition according to claim 10, characterized in that one maintains in the aqueous phase from 10 to 100 mg of the copper ion per liter during the working of metals. Fluid compositions for metalworking are well known in practice, used to lubricate and cool various metal surfaces during metalworking operations such as cutting, shaping by a cutting tool, lathe work, drilling , grinding, quenching, etc. In the past, metalworking compositions have not exhibited extended service life. For example, oil and water emulsions or dispersions usually deteriorate in service or even undergo physical decomposition in a limited period of time as short as a few weeks. The deterioration of emulsions has been attributed to a number of causes present in metal working operations which include the introduction of foreign matter such as grains or dirt, metal particles, polyvalent metal ions, bacteria, metal working conditions including pressure and temperature, etc., among other factors. Therefore, the prolonged lack of stability of metalworking compositions has imposed serious direct and indirect disadvantages regarding their use in metalworking operations. For example, the short life of metalworking coolants increases the labor and material costs associated with handling and using fluids in metalworking equipment . In addition, the deterioration of these fluids increases the wear of the metalworking machines themselves and decreases the life of the tools due to a loss of the good behavior of the coolants for metalworking. Other ancillary effects of the deterioration of metalworking coolants include an increase in the number of (partially) machined parts to be scrapped, a decrease in production and an increase in associated costs. during the machine downtime, the costs of disposing of the released fluids, workers' health concerns associated with the use of these fluids, and environmental pollution. Therefore, metalworking coolant compositions which have an extended service life and which are stabilized with respect to deterioration due to the conditions of such metalworking 5 1 " 15 20 25 30 35 40 45 50 55 60 65 3 625,829 metals, among other interesting properties, are very important not only for the industry in which such compositions are used, but also for the environment in which we live. The prior art has attempted various approaches to improve coolant compositions for metalworking and to try to overcome or minimize the direct and indirect disadvantages involved in the use of these coolants for metalworking. Representative examples of prior art patents in this area are U.S. Patents 2,688,146, No. 3,240,701, No. 3,244,630 and No. 3,365,397. Such patents, and the efforts of others, have been directed essentially to overcoming the factors contributing to the deterioration and rupture of emulsions. Suffice it to say that the results of these efforts have been far from satisfactory and that there is a need for improved compositions for metalworking, ensuring new results and overcoming the current problems and drawbacks. As described in the US patent application filed on July 21, 1975 under No. 597,756 by Sudhir K. Shringa-purcy and Gérald L. Maurer, the antimicrobial activity of certain metal complexes, for example mono-copper ( II) - dialkaline citrates, has been established by their toxic action and inhibition of growth exerted against a certain number of microbes in an oil emulsion medium serving as a cooling agent in various machining operations . The efficiency of metal complexes has thus been established in industrial coolants in which a number of microbes have been found to proliferate. As also described in the aforementioned patent application, it has been found important that at alkaline pHs of metal working conditions, metal complexes are remarkably effective.