AQUEOUS FLUIDS

Abstract: The use of a water-soluble hydroxyl di- or tri- carboxylic acid, generally in combination with an alkanolamine in an oil water fluid especially metal working or hydraulic fluids results in a fluid having excellent hard water compatibility, low foaming tendency in soft water and a good biostability; other additives such as emulsifiers, copper passivators and the like are generally present.

Description: The present invention relates to water and oil fluids; especially water and oil cutting fluids and hydraulic fluids, emulsifiable oils suitable for incorporation into water for production of such fluids, additives and additive concentrates for incorporation into such fluids and emlusifiable oils. Emulsified oils are now used in a large number of machining operations due to an industry demand for higher production rates, lower costs, improved environmental conditions and better operator acceptance. Emulsions are generally used where cooling is more important than lubrication. In operations such as broaching, deep drilling, or where surface finish is particularly critical, neat oils may still be used, but the development of extreme pressure additives in emulsions has increased their applicability and use. The emulsions are generally prepared from emulsifiable oils supplied to the final user for incorporation into the water. The emulsifiable oils frequently contain additives which can be supplied as an additive package, formulation or concentrate to the producer of the emulsifiable cutting oil. The invention relates to particular additives, concentrates, emulsifiable oils and water/oil fluids containing the additives. Amongst the various types of fluids, there is a marked trend towards those having an optimised combination of lubricating, cooling and long-life properties. Such fluids are obtained by micro-emulsification of a base oil formulated with anti-corrosion and biostability agents. The micro-emulsion type of cutting fluid has good stability due to the very small size of their hydrocarbon droplets which do not tend to coalesce during storage. This feature is a key advantage over conventional fluids forming white emulsion whose hydrocarbon droplet size is much larger, where formulation with water-soluble biostability agents is difficult. Aqueous metal working fluids have been known for many years and different additives have been developed to provide oils useful for different types of metal working and for use with different types of water. For example, it is kown that salts of long-chain alkylsulphonamidocarboxylic acids have an emulsifying and corrosion-inhibiting effect when used in metal processing. Compounds of this type, which are described in German Patent No. 900041, are generally obtained in admixture with the starting hydrocarbon because of their preparation method, and they are mainly applied in the form of oils. For reasons of the sensitivity of such emulsions to foreign salts, elevated temperature and germ infection, oil-free metal processing agents have been developed such as those described in United Kingdom Patent No. 1298672 and German Offenlegungsschrift No. 1771548. However, these water-soluble metal processing agents, although being free from the drawbacks of the emulsions, display an insufficient activity especially in hard water; precipitation of calcium salts provokes formation of sticky deposits on the machines and results in depletion of active substances in the solution. For improving the corrosion-proofing effect, sodium nitrite has often been added to the fluids. However, because of the toxicity problems and the risk of formation of the carcenogenic nitrosamines from nitrite and the amines contained in many corrosion inhibitors, such additives are not widely used. It is also known from, for example, United States Patents 2999564, 3764593, 3769214 and 4400284, that mixtures of boric acid and alkanolamines, to which fatty acids having from 18 to 22 carbon atoms are optionally added; yield water-soluble metal working fluids; boric acid providing resistance to bacteria formation. However, apart from an insufficient corrosion-inhibiting effect, these fluids have the disadvantage of foaming during use. It has also been proposed in United States Patent 3371047 that salts of the alkanolamines and hydroxy carboxylic acids, such as citric acid, tartaric acid maybe used optionally together with boron containing compounds in an oil free metal coating formulation using an excess of acid relative to the alkanolamine United Kingdom Patent 1345593 discloses the use of similar salts in oil free systems for metal coating. United States Patent 4129509 suggests that the use of metal tartrates and citrates is a convenient way of introducing metal ions into a cutting oil. In this patent the quantity of acid introduced is extremely small. Ullmans Encyklopadie der technischen Chemie volume 20 pages 558, 559, 635, 643 4th Edition, Verloz Chemie 1981 describes the use of citric acid and ascorbic acid as antioxidant additives in lubricating oils. It has also been proposed that piperazine derivatives formed in a condensation reaction at elevated temperature from amino-alcohols, boric acid and carboxylic acids, be used as corrosion inhibitor, cooling, lubricating and cutting agent (German Patent No. 1620447). However, their corrosion-inhibiting action is not superior to that of the hitherto known products. Various emulsifiers have been proposed for the production of water in oil and oil in water emulsions. Typical emulsifiers are the sulphonates, such as the natural and synthetic petroleum sulphonates and the synthetic alkylaryl sulphonates, such as the C₁₂-C₂₄ alkyl benzene and toluene sulphonates and mixtures therefore as described in United Kingdom patent specification 1476891. Whilst many cutting oils containing the additives of the type described above and fluids obtained therefrom have been satisfactory and have been accepted commercially, there is still need for additives which may be used in hard or soft water leading to good compatibility between oil and hard water, a low foaming tendency when soft water is used, good bio-stability and a sufficiently low pH. In addition from an environmental standpoint there is a need to reduce or eliminate the boron content of aqueous cutting fluids. Hydraulic fluids are used in many mechanical operations and are generally oil in water emulsions. Whilst foaming is less critical than in metal working it is important in many uses that these fluids have good bio-stability and, especially in applications such as hydraulic supports for rooves in mines that a stable emulsion can be formed with the water that is naturally available on site which can be very hard containing large amounts of calcium. We have now found according to the present invention that oil/water fluids having a good combination of anti-bacterial properties compatibility of oil and hard water and a reduced foaming tendency when used in soft water and at times a reduced boron content may be obtained by the use as additive of a water-soluble hydroxy di- or tri- carboxylic acid particularly in combination with an alkanolamine which is in excess. The invention also provides additive concentrates for incorporation into emulsifiable oils containing a mixture of an alkanolamine and a water soluble hydroxy di- or tri-carboxylic acid optionally together with other additives. The invention further provides emulsifiable oils containing a mixture of an alkanolamine and a water soluble hydroxyl di- or tri- carboxylic acid optionally together with other additives. In a further aspect the invention provides water and oil fluids containing the combination of an alkanolamine and a water-soluble hydroxy di- or tri- carboxyllc acid optionally together with other additives. Where the fluids of the present invention are aqueous metal working fluids they may be water in oil emulsions or oil in water emulsions, largely depending upon whether lubrication or cooling is the more important. We are, however, particularly concerned with the currently more popular high water content micro emulsion cutting fluids. The additives may be supplied to a producer of emulsifiable oils or to the producer of the aqueous fluids. In either instance they may be supplied as a solution or an emulsion of the various additives for incorporation into oil or the bulk of the water. The solution may be in oil or water and if in oil it will generally contain some water. The emulsifiable oil supplied to the final user generally contains an emulsifier to enable the production of oil in water or water in oil emulsions and any suitable emulsifier may be used, the choice depending upon the nature of the oil and the type of emulsion required. Alternatively the final user may introduce the emulsifier into the fluid separately. Salts of the synthetic alkyl benzene sulphonic acids, particularly the mixtures which form the subject of United Kingdom Patent No. 1476891 are our preferred emulsifier, other suitable emulsifiers are the sulphamido carboxylates such as those described in French Patent 2403396 and the sulphonates described in European Patent Application 0015491. The preferred emulsifiers are salts of alkylaryl sulfonic acids and an organic or mineral base, wherein the molecular weights of the acids from which the salts are derived are distributed in accordance with the function C = f (M), where C denotes concentration and M denotes molecular weight of individual acids, which function has two distinct molecular weight maximum M₁ and M₂, with M₁ > M₂. These sulfonic acid salts may be either inorganic or organic. The preferred inorganic salts are sodium salts. However, ammonium salts, or those of the other alkali metals, or of the alkalkine earth metals are possible. The organic bases which may be employed are nitrogen bases, for example, a primary, secondary or tertiary amine, a polyamine, an alkanolamine etc. The preferred organic bases are monoethanolamine, diethanolamine, triethanolamine. We prefer that the value of M₁ should be at least 270. The value of M₁ may be 270 to 360, but is preferably 270 to 400 and is more preferably from 360 to 400. In general, the value of M₂ should be from 350 to 600 and is preferably from 450 to 550. It is also preferred that the difference M₂-M₁ shall be at least 40, desirably in the range 40 to 350. Especially advantageous emulsifier compositions are obtained when the difference M₂-M₁ lies in the range 80 to 350, particularly 80 to 220. The overall mean molecular weight of the alkylaryl sulfonic acids contained in the alkylaryl sulfonate compositions is chosen as a function of the nature of the base with which they are combined and of the particular use for which the emulsifier is intended. The most favourable overall mean molecular weight depends in particular on the more or less polar character of the organic phase it is desired to disperse in water. In most cases the overall mean is between 300 and 550, preferably 300 to 500, more preferably 375 to 500. It is preferred that the alkyl groups of the alkylaryl sulfonates are branched-chain alkyl groups since improved emulsion stability is often found in such cases. Accordingly, it is preferred that at least a proportion of an emulsifier composition is made up of branched-chain alkyl type compounds. Preferably a major proportion, and most preferably all, the composition is of such compounds. Highly preferred are alkylaryl sulfonates derived from benzene and orthoxylene, especially when the alkyl groups are branched-chain, for example, when propylene, butene or isobutylene oligomers are used for alkylation. We prefer that the emulsifiable cutting oil for incorporation into bulk water contains from 3 to 35 wt %, preferably 3 to 25 wt %, more preferably 7 to 20 wt % of the emulsifier. Where the fluids of the present invention are to be used for metal working they may be boron free although small amounts of boron may be required for the necessary anti-bacterial properties. Boron may be provided by incorporating boric acid or any other boron compound that forms boric acid upon being dissolved in water, such as metaboric acid or boric oxide. It is believed that the boric acid forms an addition product or salt with the amine which is a syrupy liquid and does not precipitate out of the cutting fluid. The emulsifiable oil may contain up to 30 wt % boric acid although we prefer that it contains from 2 to 6 wt % of boric acid to give no more than 1.0, preferably no more than 0.4 wt % boron in the final aqueous metal working fluid. Examples of hydroxy di- or tri-carboxylic acids which may be used are tartaric and citric acids. It is important that the acid used be soluble in water. We prefer that the additive concentrate contain from 3.0 to 50.0 wt % of the acid and the emulsifiable oil contain from 1.0 to 10 wt % more preferably 1.0 to 7 wt % of the acid. The alkanolamines used in the present invention, are those which contain from one to three aliphatic radicals, each containing from one to four carbon atoms, and have at least one hydroxy group attached to a carbon atom, and include primary, secondary and tertiary alkylol amines such as mono- di-or triethanolamine. These amines are generally water-soluble and have no offensive odour. The preferred amine for use in preparing the cutting fluid of the invention is diethanolamine, which ordinarily contains minor amounts of mono-or triethanolamine, and has no odour. We prefer that both the emulsifiable oil and the aqueous fluid contain an excess of alkanolamine relative to total acid content, i.e. the hydroxyl di- or tri-carboxylic acid together with any boric acid that may be present. We prefer to use a 10 to 20 % excess and a typical emulsifiable oil contains 10 to 35 wt % of alkanolamine. A coupling agent such as a non-ionic wetting agent is generally used in aqueous metal working fluids embodying the invention. To improve the compatibility of the components, any desired non-ionic wetting agent may be used, such as a condensation product of ethylene oxide; a condensation product of a fatty acid or derivative, such as a derivative of a fatty acid, fatty alcohol, fatty amide or fatty amine, with ethylene oxide; and a reaction product obtained by the condensation of an oxyalkylaryl compound, such as a derivative of an alkylphenol or alkylnaphthol, with ethylene oxide. It is preferable that the non-ionic wetting agent employed be water-soluble. Typical non-ionic wetting agents include the polyethoxyesters of fatty acids, the monooleate of a polyethylene glycol, the monolaurate of a polyethylene glycol, the polyethoxyethers of fatty alcohols, the condensation product of an alkylphenol such as dodecyl phenol with 12 moles of ethylene oxide, and the sulfonated product of the condensation of an alkylphenol or an alkylnaphthol with ethylene oxide. A particularly useful non-ionic wetting agent is an alkyl phenoxy polyethoxy ethanol such as octyl or nonyl phenoxy polyethoxy ethanol. We also find, particularly when emulsifiers other than sulphonic acids and sulphonates are used that carboxylic acids such as neo acids and fatty acids may be included to enhance emulsion production. The amount required depends on the other components present but typically 2 to 10% based on the hydroxy di- or tri- carboxylic acid or 10% to 30% if boric acid is also present. A typical emulsifiable oil according to the invention contains: 7 to 25 wt % emulsifier 0 to 15 wt % boric acid 1 to 10 wt % hydroxy di- or tri- carboxylic acid Up to 35 wt % alkanaolamine and an excess relative to the total acid content 0 to 60 wt % water with the balance oil. Which is then included at from 1 to 10 wt %, preferably 1 to 5 wt %, more preferably 2 to 5 wt % in water to give the final aqueous fluid containing (i) from 0.07 to 2.5 wt % of an emulsifier (ii) from 0 to 1.5 wt % boric acid (iii) 0.01 to 1.0 wt % of a hydroxy di- or tri-carboxylic acid (iv) up to 3.5 wt % of an alkanolamine sufficient to provide an excess relative to the total acid content (v) up to 15 wt % oil An aqueous metal working fluid embodying the invention may be used in all metal working operations but gives excellent results in applications in which the pressure per unit of area is relatively low, such as surface grinding operations especially where a number of pieces are being ground simultaneously. For heavy-duty applications, in which the pressure per unit of area is relatively high, an aqueous fluid embodying the invention preferably contains, in addition to the reaction product, antiwear additives such as phosphate esters, sulphurised hydrocarbons and copper passivator such as benzotriazole, tolyltriazole and its derivatives, thiadiazole and dimercapto thiadiazole. Other ingredients which may be incorporated in the aqueous fluids include silicone anti-foaming agents and biocides. The hydroxy di- or tri- carboxylic acid used in this invention, together with the alkanolamine, has been found to generally result in improved hard water compatibility, to give a low foaming tendency in fluids based on soft water and good biostability. However, use of the composition in soft water can result in some undesirable foaming during use and the present invention also includes the inclusion of calcium and/or magnesium salts to reduce foaming of soft water systems. The calcium and/or magnesium can be provided by the inclusion of halides, sulphates, sulphonates or carboxylates which may be present in the additive concentrate, the emulsifiable oil or added separately to the aqueous fluid. Conveniently, from 0.01 to 0.5 wt % of calcium or magnesium is incorporated in the fluid for use in water of hardness lower than 20 o French degree TH (corresponding to 200 ppm of calcium carbonate). The improved hard water compatibility is especially useful in the production of hydraulic fluids such as those used in mining operations as for example in the support of rooves where the local water is extremely hard, for example above 500 ppm of calcium carbonate. Although the presence of water in the emulsifiable oil is not essential the inclusion of water gives a control of its viscosity which is preferred to be below 500 centistokes at 20 o C for easier handling. We prefer that the formulation contain from 0 to 60 wt % water. The emulsifiable oil generally contains 5 to 35, more preferably 5 to 14 wt % oil although larger amounts could be used which may be all the oil required in the final fluid or further oil may be added. Any type of oil may be used, mineral or synthetic and the mineral oils may be paraffinic or naphthenic although it may be necessary to alter the additives particularly any emulsifier according to the type of oil. In the preparation of an emulsifiable oil embodying the invention, the ingredients are mixed at ordinary temperatures to produce a water-miscible fluid. We prefer to first mix the water and the alkanolamine then add the acid, any extreme pressure additives, then the emulsifier and the oil. The surfactant and any other wetting agent may also be added at room temperature, with stirring, to the aqueous solution prepared from the amine and boric acid when used. Preferably the amount of the non-ionic wetting agent is at least 5 percent by weight of the amount of the emulsifier. When an amine salt of a fatty acid is incorporated in the fluid, the amount of the non-ionic wetting agent may be as much as 30 percent by weight of the amount of the emulsifier in order to hold the salt in solution and to prevent the precipitation of a calcium/magnesium soap if the concentrate is to be diluted with hard water. The ingredients which form an aqueous fluid embodying the invention may be mixed in any desired order, but it is usually convenient to mix the major ingredients to form a liquid of relatively large bulk with which the minor ingredients may be readily mixed. The additives may be supplied to the producer of the emulsifiable oil or the producer of the aqueous fluid in the form of a concentrate which preferably contains only the minimum amount of water required to form a stable liquid generally 1 to 10 wt %. Typically the concentrates contain from 3.0 to 50 wt % of the hydroxy di- or tri- carboxylic acid, from 0 to 30 wt % of boric acid, up to 35 wt % of alkanolamine and an excess relative to the total acid content, 3.0 to 50 wt % of emulsifier optionally other additives the balance being water or oil and water. The concentrate is then incorporated either into oil to give the emulsifiable oil or direct in water to give the final fluid. Cutting fluids generally contain 1 to 10 wt % of such a concentrate, preferably 1-5 wt %. EXAMPLES EXAMPLE 1 The emulsifiable oils of Table 1 were prepared and incorporated into water at 3 wt % to give cutting fluids having the performance set out in Table 1. EXAMPLE 2 For comparison similar emulsifiable cutting oils were made using other carboxylic acids with the following results. EXAMPLE 3 Further emulsifiable cutting oils were prepared using different emulsifiers and containing various amounts of an additive package (Package A) containing Component mass % Ortho Boric acid 8.51 Diethanolamine 67.16 Ethoxylated tolytriazole 0.45 Tartaric acid 13.88 Water 10.00 The emulsifiable oils and performance in the cutting oil were as follows EXAMPLE 4 Additive Package B was prepared as follows: PACKAGE B Component mass % Citric acid 8.53 Diethanolamine 74.84 Polycarboxylic acid 2.37 Ethoxylalated tolyltriazole 0.47 Tartaric acid 3.78 Water 10.01 and tested with the emulsifiers used in Example 3 in the following formulation to give the following results EXAMPLE 5 An emulsifiable oil for use in a hydraulic fluid containing very hard water (750 ppm of calcium carbonate) was prepared as follows. 100 N oil 9.10 Citric acid 6.29 Diethanolamine 30.41 Synacto 2000 14.65 Butyl carbitol 3.99 Water 35.56 When incorporated at 5% in the test water NCB 19 the pH was 9.3 and the hard water compatibility test NCB 463/1981 Appendix A was passed and the corrosion according to test NCB 463/1981 (App. B) in 2 wt % in test water containing 2.9 mg/l NaCl solution gave no rusting The NCB 463/1981 Tests are standard tests as used by the United Kingdom National Coal Board. The oil was also tested at 5 vol % in soft water containing CaSO₄ solution (equivalent to 50 ppm CaCO₃) for its foaming tendency and found to give a foam volume after 15 min of 4 ml. EXAMPLE 6 The Synacto 2000 used in Example 5 was replaced by other emulsifiers such as the product Synacto 416 marketed by Esso Chemical to give the following emulsifiable oil Component (mass %) Synacto 416 19.0 Di-ethanol amine 38.3 Oil (Shell MVIN 40) 8.3 Water 24.4 Citric acid 10.0 The oil was tested at 2 and 5 wt % in Minteck A water (2000 ppm CaCO₃ + 2000 ppm NaCl) to give the following results at 70 o C at 45 o C H₂O separation none none Floculation none none Precipitation of solids none none Oil separation, curds or cream none none The oil was tested at 2 and 5 wt % in Minteck B water (2000 ppm CaCO₃ + 4000 ppm NaCl) to give the following results at 70 o C at 45 o C H₂O separation none none Floculation none none Precipitation of solids none none Oil separation, curds or cream none none In addition the emulsified oil had the following properties: EXAMPLE 7 A boron-free additive formulation Package C was prepared as follows: mass % Ethoxylated tolyl triazole 0.2 Polycarboxylic acid 1.0 Dodecyl succinic anhydride 1.2 Citric acid 3.6 Tartaric acid 1.6 Diethanolamine 31.9 Water 21.6 Synacto 2000 24.0 Stanco 90 14.9 The formulation was incorporated at various volumes in DIN water containing 360 ppm calcium carbonate and tested as follows: pH at 2% volume 9.3 pH at 2.5% volume 9.4 pH at 3.0% volume 9.4 Paper test DIN 51.360-2 at 2% vol 1 at 2.5% vol 0 at 3.0% vol 0 The formation was also tested for foaming in various waters using the CNOMO D 655212 test The microemulsion was tested for biostability at 3 wt % in water together with other commercially available bactericides using the test described in Example 1 to give the following results

Claims: Claims for the following Contracting States : BE, CH, LI, DE, FR, GB, IT, LU, NL, SE Use in water and oil emulsions suitable for use as cutting fluids or hydraulic fluids of the combination of one or more hydroxy di- or tri- carboxylic acids and an alkanolamine, the relative proportion of alkanolamine being sufficient to provide a stoichiometric excess relative to the total acid content of the fluid. Use according to claim 1 wherein the acid is one or both of citric and tartaric acids. Use according to claim 1 or claim 2 wherein the alkanolamine is ethanolamine, diethanolamine or triethanolamine. Use according to any preceding claim wherein the emulsion is a micro-emulsion. A water and oil emulsion suitable for use as a cutting fluid or hydraulic fluid comprising: i. from 0.07 to 2.5 wt.% of an emulsifier ii. from 0 to 1.5 wt.% of boric acid iii. from 0.01 to 1.0 wt.% of a hydroxy di- or tri-carboxylic acid iv. up to 3.5 wt.% of an alkanolamine sufficient to provide a stoichiometric excess relative to the total acid content of the fluid. v. up to 15 wt.% of oil vi. balance (after addition of any optional ingredients) water. An emulsion according to claim 5 wherein the acid is one or both of citric and tartaric acids. An emulsion according to claim 5 or claim 6 wherein the alkanolamine is ethanolamine, diethanolamine or triethanolamine. An emulsion according to any of claims 5 to 7 wherein the emulsion is a micro-emulsion. An emulsifiable oil suitable for emulsification to a cutting fluid or hydraulic fluid comprising: i. from 7 to 25 wt.% of an emulsifier ii. from 0 to 15 wt.% of boric acid iii. from 1 to 10 wt.% of a hydroxy di- or tri- carboxylic acid iv. up to 35 wt.% of an alkanolamine sufficient to provide a stoichiometric excess relative to the total acid content of the fluid. v. from 0 to 60 wt.% water vi. balance (after addition of any optional ingredients) oil. An emulsifiable oil according to claim 9 wherein the acid is one or both of citric and tartaric acids. An emulsifiable oil according to claim 9 or claim 10 wherein the alkanolamine is ethanolamine, diethanolamine or triethanolamine. An emulsifiable oil according to any of claims 9 to 11 wherein the emulsion is a micro-emulsion. An additive concentrate suitable for addition to an oil to produce an emulsifiable oil according to claim 9 comprising: i. from 3 to 50 wt.% of an emulsifier ii. from 0 to 30 wt.% of boric acid iii. from 3 to 50 wt.% of a hydroxy di- or tri- carboxylic acid iv. up to 35 wt.% of an alkanolamine sufficient to provide a stoichiometric excess relative to the total acid content of the fluid. v. balance (after addition of any optional ingredients) water and/or oil. An additive concentrate according to claim 13 wherein the acid is one or both of citric and tartaric acids. An additive concentrate according to claim 13 or claim 14 wherein the alkanolamine is ethanolamine, diethanolamine or triethanolamine. An additive concentrate according to any of claims 13 to 15 wherein the emulsion is a micro-emulsion. Claims for the following Contracting State : AT A process for preparing a water and oil emulsion suitable for use as a cutting fluid or hydraulic fluid by incorporating therein the combination of one or more hydroxy di- or tri-carboxylic acids and an alkanolamine, the relative proportion of alkanolamine being sufficient to provide a stoichiometric excess relative to the total acid content of the fluid. A process according to claim 1 wherein there are emulsified with water; i. from 0.07 to 2.5 wt.% of an emulsifier ii. from 0 to 1.5 wt.% of boric acid iii. from 0.01 to 1.0 wt.% of a hydroxy di- or tri-carboxylic acid iv. up to 3.5 wt.% of an alkanolamine sufficient to provide a stoichiometric excess relative to the total acid content of the fluid. v. up to 15 wt% of oil A process according to claim 1 or claim 2 wherein the acid is one or both of citric and tartaric acids. A process according to any preceding claim wherein the alkanolamine is ethanolamine, diethanolamine or triethanolamine. A process according to any preceding claim wherein the ingredients are subjected to micro-emulsification.

Inventors: KECH, FERNAND JEROME, LENACK, ALAIN LOUIS PIERRE
Applicants: EXXON CHEMICAL PATENTS INC.
Application year: 1986
Main classification: C10M173
IPC codes: C10M173, C10N20, C10N30, C10N40