Metalworking process

Abstract

The invention relates to metalworking process wherein a metalworking tool processes a workpiece at a processing area of a metalworking machine; a fully synthetic metalworking fluid is supplied to at least one of the metalworking machine, the metalworking tool and the workpiece; the fully synthetic metalworking fluid takes up tramp oil, thus forming a used, tramp oil containing fully synthetic metalworking fluid; the used, tramp oil containing fully synthetic metalworking fluid is collected in a container; one or more quaternary ammonium salts of formula [N+(R1)(R2)(R3)(R4)]n Xn-, wherein residues R1, R2, R3 and R4 are selected from araliphatic and aliphatic hydrocarbon residues, with the proviso that two of residues R1, R2, R3 and R4 are hydrocarbon groups with 1 to 4 carbon atoms and the other two of these residues are hydrocarbon residues with 6 to 20 carbon atoms, Xn- being an n-valent anion, and n being 1, 2 or 3, are added to the used metalworking fluid, thus breaking the emulsion of emulsified tramp oil forming free tramp oil; the free tramp oil accumulates at an air-metalworking fluid interface and is removed thereof. Moreover, the invention relates to a method of removing emulsified tramp oil from its emulsion in a fully synthetic metalworking fluid; and the use of the specific quaternary ammonium salts in such removal step to remove emulsified tramp oil from the fully synthetic metalworking fluid. Furthermore, the invention relates to a fully synthetic metalworking fluid containing said quaternary ammonium salt.

Description

[0001] METALWORKING PROCESS

[0002] The invention relates to a metalworking process making use of a fully synthetic metalworking fluid, the process comprising a step of at least partially removing tramp oil contamination from the fully synthetic metalworking fluid. Moreover, the invention relates to a method of removing emulsified tramp oil from its emulsion in a fully synthetic metalworking fluid at least partially and the use of the specific quaternary ammonium salts in such removal step to remove emulsified tramp oil from the fully synthetic metalworking fluid. Furthermore, the invention relates to a fully synthetic metalworking fluid containing the afore-mentioned quaternary ammonium salt.

[0003] BACKGROUND OF THE INVENTION

[0004] Metalworking fluids are primarily used to reduce heat when cutting and / or forming metals, to lubricate the metalworking tools, workpieces, and machines, to remove contaminants, and to prevent corrosion.

[0005] The reduction of heat, i.e., the cooling of the workpiece is typically accomplished by reducing the frictional heat between the processing tool and the workpiece, and deducting the heat. The heat regulation serves to maintain the dimensional accuracy. The lubrication reduces the tool wear and tear, and thus prolongs the tool life, reduces power consumption of the machines, and improves the surface quality of the processed workpiece.

[0006] Metalworking fluids are widely used by companies involved in the manufacture of automotive parts, aerospace equipment, heavy equipment, and the like.

[0007] According to the European Agency for Safety and Health at Work, metalworking fluids can be grouped into a first group of oil-containing metalworking fluids comprising non-water-miscible metalworking fluids and water-miscible metalworking fluids, and a second group of oil-free metalworking fluids.

[0008] As to the non-water-miscible metalworking fluids the European Agency for Safety and Health at Work states that they mainly consist of a base oil (usually over 95%), which can be a mineral oil, ester oil (e.g. unrefined or chemically modified rapeseed oil) or synthetic oil (e.g. poly-alpha-olefin). Further, antioxidants, lubricity enhancers and antimist additives are typical ingredients of non-water-miscible metalworking fluids. However, the risk-determining component is usually the base oil, particularly, if it is aerosolized and becomes airborne due to high working load (high feed pressures, high speed of workpiece rotation and elevated temperatures during machining). Since non- water-miscible metalworking fluids are not susceptible to microbial contamination, they usually have a long service life (up to several years). The incursion of water or aqueous media must be prevented when using non-water- miscible metalworking fluids. As to the water-miscible metalworking fluids, the European Agency for Safety and Health at Work states that they are mixed with water before use, in concentrations of typically 2 to 25 %, depending on the product and type of machining. This type of metalworking fluid is also based on oil (comparable to the oil described in the preceding paragraph on non-water-miscible oils), and shares of 20 to 80 % are possible. To combine this oil with water to yield an oil-in-water emulsion, an emulsifier is necessary.

[0009] Fully synthetic metalworking fluids differ from the afore-mentioned non-water-miscible metalworking fluids and water-miscible metalworking fluids in that they are free of oils. Other than the oil-containing water-miscible metalworking fluids they do not need emulsifiers. Instead of oils, water-soluble synthetic lubricants are used. Mixing fully synthetic metalworking fluids in water, yields a transparent to an at most lightly opalescent aqueous metalworking fluid.

[0010] When making use of metalworking fluids in a metalworking process, they may be stored in a sump or tank located under the machining equipment. In use, the metalworking fluid will flow down and be collected in the sump for recirculation through the machining equipment. The sump will also collect other oily fluids such as way oil, air set oil and other types of petroleum-based fluids known as "tramp oil.” The tramp oil contaminates the metalworking fluid. Since metalworking fluids are typically circulated in the metalworking process, they are supplied from a container (sump or tank) to the processing area repeatedly and at least partially returned to the container after each use. If the metalworking fluid is circulated in such way, the tramp oil, which contaminates the metalworking fluid accumulates in the metalworking fluid. The contaminated metalworking fluid reduces the life of the metalworking fluid and machining equipment and has detrimental effects on the quality of the process and the processed workpieces.

[0011] There have been attempts to remove such tramp oil from the contaminated metalworking fluid by use of a disk skimmer that uses a slender plastic wheel that dips down into the sump. As the wheel rotates back up out of the sump, a wiper mechanism removes the tramp oil that happens to adhere to the plastic wheel. A shortcoming of the device is that only a limited volume of metalworking fluid is processed as determined by the surface area of the wheel. This is a shortcoming of a similar skimming type system that uses a belt or tube that dips down into the metalworking fluid instead of a wheel.

[0012] Another example of the prior art is a tramp oil separator device. The contaminated metalworking fluid is extracted from the machining equipment sump and pumped into a vessel that allows the tramp oil to float to the top of the vessel where it is siphoned off. However, the remaining metalworking fluid is not sufficiently removed of tramp oil through the separation process and this method is a relatively slow processing method. Thus, a fundamental problem with the fully synthetic metalworking fluids is that the longer they are used the more they become "contaminated" with impurities, particularly tramp oil, such as oily fluids from leaky systems or corrosion protection oils from upstream processing. These are only tolerated up to a certain percentage, and beyond this machining problems can arise.

[0013] Such used and contaminated metalworking fluids are generally at least cleaned by filtration, particularly to extend their period of use and to enhance the surface quality of the processed workpiece. For machine tools with metalworking fluid supply through a spindle and tool, a filter device is often prescribed by the manufacturer. Special coolant filters, sedimentation tanks or magnetic separators as well as centrifuges and / or oil separators (i.e., oil skimmers) are used for this purpose.

[0014] US 2010 / 0089833 A1 describes a method of removing such contaminations from water-soluble metalworking fluids by filtration, particularly by use of a particle filter, wherein the particle filter removes metal filings and debris from a water-soluble metalworking fluid; and a tramp oil filter, wherein the tramp oil filter removes tramp oil contaminating the metalworking fluid. The tramp oil filter proposed in US 2010 / 0089833 A1 includes hydrophobic material to absorb tramp oil, more preferably a cellulose-based hydrophobic material to absorb tramp oil. Thus, US 2010 / 0089833 A1 only relies on absorption of the tramp oil by the filter material. While this method does not only allow to remove tramp oil from the surface of the fully synthetic metalworking fluid by skimming, but also from the bulk phase of the metalworking fluid, wherein microdroplets of the tramp oil may be dispersed, the method still requires the use of filter pods containing the filter material. Such filter pods need to be removed from the tramp oil filter regularly, when the absorption capacity is reached and are to be disposed, i.e., they are not reusable.

[0015] Thus, there is an ongoing desire to provide a method for removing tramp oil from the surface of fully synthetic metal working fluids, as well as from their bulk phases, without the need of installed filtrations pods and filtration materials, thereby preventing the production of waste.

[0016] Furthermore, while water-miscible and particularly water-soluble metalworking fluids, such as fully synthetic metalworking fluids are often desired from an environmental view, they encourage microbial contaminations and the use of biocides to prevent or inhibit the growth of microorganisms becomes necessary.

[0017] The present invention relates to the use of fully synthetic metalworking fluids. While semi-synthetic metalworking fluids make use of so-called splitting agents for oil control, this is typically not the case for the fully synthetic metalworking fluids, although it is not completely excluded. However, if splitting agents are used in prior art fully synthetic metalworking fluids, they are used in amounts which are low to avoid excessive foam formation, and such amounts are also too low to sufficiently remove tramp oil.

[0018] It is the aim of the present invention to provide a metalworking process comprising a step of at least partially removing tramp oil from at least part of the bulk phase of a contaminated fully synthetic metalworking fluid without the need of a fixed installation of filtration pads and filter materials and to further equip the fully synthetic metalworking fluid with an antimicrobial, particularly antibacterial property by the same means as used to remove and / or decontaminate the fully synthetic metalworking fluid. Such means should not only provide long-term stability to the metalworking fluid and resistance towards microorganisms, but should also be compatible with all materials, particularly workpieces and tools. Particularly, such means should not promote corrosion or discoloration or other detrimental changes to the surfaces, with which the metalworking fluid is in contact. Likewise, foam formation should be avoided. Of course, metalworking processes, such as welding, must not be negatively affected.

[0019] Further aims are to provide a method of removing emulsified tramp oil from the bulk phase of a fully synthetic metalworking fluid, and to provide a fully synthetic metalworking fluid equipped with the intrinsic ability to remove tramp oil getting into the metalworking fluid from the bulk phase of the metalworking fluid.

[0020] SUMMARY

[0021] The aims of the invention are solved by the subject matter as claimed and described herein below in further detail.

[0022] A first subject matter of the present invention is to provide a metalworking process, wherein

[0023] (I) a metalworking tool processes a workpiece at a processing area of a metalworking machine;

[0024] (II) a fully synthetic metalworking fluid is supplied to at least one of the metalworking machine, the metalworking tool and the workpiece;

[0025] (ill) the fully synthetic metalworking fluid takes up tramp oil, thus forming a used, tramp oil containing fully synthetic metalworking fluid;

[0026] (iv) the used, tramp oil containing fully synthetic metalworking fluid is collected in a container and preferably analyzed for the presence and / or amount of free and emulsified tramp oil;

[0027] (v) one or more quaternary ammonium salts of formula

[0028] [N+(R1)(R2)(R3)(R4)]nXn', wherein residues R1, R2, R3and R4are selected from araliphatic and aliphatic hydrocarbon residues, with the proviso that two of residues R1, R2, R3and R4are hydrocarbon groups with 1 to 4 carbon atoms and the other two of these residues are hydrocarbon residues with 6 to 20 carbon atoms, Xn- being an n-valent anion, and n being 1 , 2 or 3, are added to the used, tramp oil containing fully synthetic metalworking fluid, if emulsified tramp oil is present or exceeds a pre-set amount, thus at least partially breaking the emulsion of emulsified tramp oil in the fully synthetic metalworking fluid forming free tramp oil; and

[0029] (vi) the free tramp oil resulting from breaking the emulsion of emulsified tramp oil accumulates at an air-metalworking fluid interface and is removed thereof to form an at least partially purified fully synthetic metalworking fluid.

[0030] Herein below, the metalworking process and its preferred embodiments are also denoted as "metalworking process of the invention” or "metalworking process according to the invention.”

[0031] The second subject matter of the present invention is a method of removing emulsified tramp oil from its emulsion in a fully synthetic metalworking fluid at least partially, by

[0032] (a) adding one or more quaternary ammonium salts as defined above and in preferred embodiments below to the fully synthetic metalworking fluid containing emulsified tramp oil, thus breaking the emulsion at least partially to form free tramp oil accumulating at the air-metalworking fluid interface,

[0033] (b) removing the free tramp oil resulting from breaking the emulsion of emulsified tramp oil at the airmetalworking fluid interface at least partially.

[0034] Herein below, the method of removing emulsified tramp oil from its emulsion in a fully synthetic metalworking fluid and its preferred embodiments are also denoted as "tramp oil removing method of the invention” or "tramp oil removing method according to the invention.”

[0035] A third subject matter of the invention is the use of one or more quaternary ammonium salts as defined for the metalworking process of the invention above and in preferred embodiments below, in a fully synthetic metalworking fluid to separate emulsified tramp oil from the bulk phase of the fully synthetic metalworking fluid at least partially.

[0036] Herein below, the use and its preferred embodiments are also denoted as "use of the invention” or "use according to the invention.”

[0037] Yet another subject matter of the invention is a fully synthetic metalworking fluid comprising a quaternary ammonium salt as defined above and herein below. Herein below, the fully synthetic metalworking fluid comprising said quaternary ammonium salt and its preferred embodiments are also denoted as "fully synthetic metalworking fluid of the invention” or "fully synthetic metalworking fluid according to the invention.”

[0038] DETAILED DESCRIPTION

[0039] In the following, the present invention is described in further detail with respect to further preferred features and embodiments.

[0040] Metalworking process

[0041] (i)

[0042] In the metalworking process of the present invention (I) a metalworking tool processes a workpiece at a processing area of a metalworking machine.

[0043] A "metalworking tool” can be any tool conventionally used in metalworking processes, as, e.g., a tool used for cutting and / or forming workpieces, particularly metallic workpieces. In principle, the metalworking tools are any metalworking tools, preferably those as used in automated metalworking processes. Examples of metalworking tools are, e.g., cutting tools, such as tool bits and milling cutters; stamps, punches, pressing tools and the like. The metalworking tools are preferably made of materials, which are much more durable than the metallic workpiece to be processed.

[0044] A "workpiece” is any metallic part in any form, which is processed with a metalworking tool. A metallic workpiece can consist of a metal or an alloy of metals or may be composed of pre-assembles parts of same of different metals and / or alloys. Preferred workpiece materials are steels, including stainless steels, iron, including cast iron and galvanized iron, titanium, aluminum, nickel, and copper.

[0045] The term "processing” in this context preferably means any process of changing the size, shape, or surface structure of the workpiece, e.g., by cutting and / or forming including welding of the metallic workpiece. "Metalworking processes” in the context of this invention are carried out by use of a metal working machine, and are preferably at least partially, more preferred fully automated metalworking processes. The metalworking processes preferably comprise amongst general machining, also specific processes such as cutting, welding, forming, pressing, reaming, tapping, drilling, broaching, honing, general and centerless grinding and the like. The term ''processing area” of the metalworking machine means the area of the metalworking machine, where the metalworking tool processes the workpiece.

[0046] (H)

[0047] Fully synthetic metalworking fluid is supplied to, e.g., the metalworking machine or parts thereof, the metalworking tool and / or the workpiece, in order to cool and / or lubricate the respective machine, machine parts, tools and workpieces. This typically takes place while processing the workpiece according to (I).

[0048] The term "fully synthetic metalworking fluid” is a commonly used term in the field of metalworking defining that the metalworking fluid does not contain mineral oil. Thus, this term is to be distinguished from mineral oil containing metalworking fluids. However, it is emphasized that any tramp oil that may contaminate the fully synthetic metalworking fluid during metalworking and thus is introduced as contamination, only, are not to be regarded as an ingredient of the fully synthetic metalworking fluid of the invention.

[0049] To the contrary, the present invention aims to separate such tramp oil from the fully synthetic metalworking fluid, because it is typically detrimental to the performance of the fully synthetic metalworking fluid.

[0050] The fully synthetic metal working fluid is preferably obtained from a concentrate comprising the main ingredients of the metalworking fluid by dilution of this concentrate. Therefore, in the present invention it is distinguished between the concentrate of the fully synthetic metalworking fluid and the fully synthetic metalworking fluid itself, the latter one being ready-to-use in the metalworking process of the invention. While during the metal working process of the invention the fully synthetic metal working fluid is equipped with the quaternary ammonium salt as defined herein above and below to break a tramp oil emulsion, it is not necessarily the case that the concentrate of the metal working fluid also needs to contain the quaternary ammonium salt. With other words, the concentrate of the fully synthetic metal working fluid may contain the quaternary ammonium salt as defined herein or be free from such quaternary ammonium salt.

[0051] As long as the metal-working fluid is a fully synthetic metal working fluid, the composition is not particularly limited.

[0052] The concentrate of the fully synthetic metalworking fluid contains at least water and a preferably water-soluble synthetic lubricant.

[0053] The water in the concentrate of the fully synthetic metalworking fluid may be mains water, but is preferably deionized water. The amount of water in the concentrate may vary, but is preferably in the range from 1 .5 to 98.5 wt.-%, more preferred in the range from 5 to 95 wt.-% and most preferred in the range from 10 to 90 wt.-%. Besides water the fully synthetic metalworking fluid contains synthetic lubricants which differ from mineral oil and are preferably water-soluble. Such concentrate is preferably translucent, which might include having a tint, such as a yellow or red tint, or such concentrate might even be clear.

[0054] The water-soluble synthetic lubricants are preferably selected from the group consisting of esters and poly (al ky I ene oxide)s.

[0055] Particularly preferred, the synthetic lubricant or lubricants are selected from the group consisting of poly (alkylene oxide)s. Such poly (alkylene oxide)s are preferably depicted by the formula HO-[AO]m-H, AO being alkylene oxide, preferably ethylene oxide (EO) or propylene oxide (PO),and m being the number of alkylene oxide units. Even more preferred the one or more synthetic lubricants are selected from poly(alkylene oxide) block copolymers, comprising at least one poly (ethylene oxide) block and at least one poly (propylene oxide) block. Most preferred are such poly (alkylene oxide) block copolymers, which comprise at one poly(ethylene oxide) block as a central block, flanked by two poly (propylene oxide) blocks, which can be depicted by the formula HO-[PO]x[EO]y[PO]z-H, wherein x+y+z=m.

[0056] The values of m, x, y, and z in the above formulae HO-[AO]m-H and HO-[PO]x[EO]y[PO]z-H, are not particularly limited and can be calculated from the number average molecular weight of the poly(alkylene oxide)s and the relative amounts of ethylene oxide and propylene oxide, used to form the poly(alkylene oxide)s, respectively. Preferably the number average molecular weight of the poly(alkylene oxide)s range from 1000 to 4000 g / mol, more preferred 1500 to 3500 g / mol and most preferred 2000 to 3000 g / mol. The number average molecular weight of the poly (alky lene oxide)s can be determined by gas permeation chromatography.

[0057] Besides water and the therein soluble synthetic lubricant, the concentrate of the fully synthetic metalworking fluid may comprise one or more further ingredients, such as acidic compounds and their salts, basic compounds and their salts, polymers, corrosion inhibitors, biocides, antifoam agents, complexing agents, anti-wear additives, stabilizers, lubricating film improvers and extreme pressure additives.

[0058] The acidic compounds and salts thereof are particularly selected from carboxylic acids and salts thereof and phosphonic acids, preferably organophosphonic acids, and salts thereof. Preferably, the concentrate of the fully synthetic metalworking fluid comprises one or more monomeric carboxylic acids from the group consisting of monocarboxylic acids and dicarboxylic acids. Preferably the monocarboxylic acids and dicarboxylic acids comprise 6 to 16 carbon atoms, more preferred 8 to 14 and even more preferred 9 to 12 carbon atoms. Particularly preferred monocarboxylic acids can be depicted by the following formula Rm-COOH, wherein Rmis a linear or branched, preferably branched alkyl group comprising 6 to 16 carbon atoms, more preferred 8 to 14 and even more preferred 9 to 12 carbon atoms, or Rmbeing a poly(alkylene oxide) chain containing ethylene oxide units and / or propylene oxide units, carboxylic acids of the first mentioned type without poly (alkylene oxide) being preferred. Particularly preferred dicarboxylic acids can be depicted by the following formula HOOC-Rd-COOH, wherein Rdis a linear or branched, preferably linear alkylene group comprising 6 to 16 carbon atoms, more preferred 8 to 14 and even more preferred 9 to 12 carbon atoms. Preferably a combination of the monocarboxylic and dicarboxylic acids is employed in the concentrate of the fully synthetic metalworking fluid.

[0059] The metalworking fluids of the invention preferably further comprise phosphonic acids of formula RP-P(0)(0H)2, wherein RP is a linear or branched, preferably linear alkyl group comprising 6 to 16 carbon atoms, more preferred 8 to 14 carbon atoms.

[0060] Any of the afore-mentioned acidic compounds may be in the form of their salts, preferably salts formed by neutralization with primary, secondary or tertiary amines, including amino alcohols.

[0061] Besides the acidic compounds, basic compounds, which are apt to form salts with the acidic compounds may be comprised in the concentrate of the fully synthetic metalworking fluid. Such basic compounds can be inorganic bases such as alkali metal hydroxides, like sodium or potassium hydroxide or organic bases such as amines. Preferred are amines such as primary, secondary or tertiary amines, including amino alcohols.

[0062] Preferred amines can be depicted by the general formula N(R’)(R”)(R”’), wherein R', R” and R’” are independently of each other H or groups of formula (CH2CH2O)PH, with p being 1 , 2, or 3, preferably 1 or 2, with the proviso that at least one of R', R” and R’” is a group of formula (CH2CH2O)PH.

[0063] Depending on the desired pH value of the concentrate of the fully synthetic metalworking fluid, the basic compounds and the acid compounds may form salts with one another.

[0064] The concentrate of the fully synthetic metalworking fluid may further comprise further polymers such as cationic polymers, e.g., as emulsion breakers. Polymers may also include polyvinylalcohols, polyacrylamides and their copolymers with anionic or cationic monomers, polymethacrylic acid and poly acrylic acid and their salts, copolymers comprising methacrylate monomers and / or acrylate monomers, polyethylene imines, polyethylene copolymers and block copolymers containing oxidized alpha-olefines. Furthermore, corrosion inhibitors can be contained in the concentrate of the fully synthetic metalworking fluid, such as sulfonates, amines, alkali carbonates and others.

[0065] Further, biocides such as 1 ,2-benzisothiazolin-3(2H)-one may be contained in the concentrate of the fully synthetic metalworking fluid.

[0066] Besides the above further ingredients, which might be contained in the concentrate of the fully synthetic metalworking fluid, other ingredients which are not explicitly mentioned may also be contained in the concentrate of the fully synthetic metalworking fluid.

[0067] The concentrate of the fully synthetic metalworking fluid preferably contains water-soluble synthetic lubricants in an amount from 10 to 40 wt.-%, more preferably from 15 to 35 wt.-% and most preferably from 20 to 30 wt.-%, based on the total weight of the concentrate.

[0068] In a particularly preferred embodiment of the present invention the concentrate of the fully synthetic metalworking fluid comprises 25 to 50 wt.-% water, 10 to 50 wt.-% of one or more water-soluble synthetic lubricant, 5 to 20 wt.- % of one or more monocarboxylic acids, 1 to 10 wt.-% of one or more dicarboxylic acids, 0 to 5 wt.-% of one or more phosphonic acids, 15 to 35 wt.-% of one or more amines, 0 to 10 wt.-% of one or more polymers, preferably cationic polymers, 0 to 8 wt.-% of one or more corrosion inhibitors, 0 to 5 wt.-% of one or more biocides differing from the one or more quaternary ammonium salts as used in the metalworking process of the present invention, and 0 to 5 wt.-% of the one or more quaternary ammonium salts as used in the metalworking process of the present invention.

[0069] In an even more preferred embodiment of the present invention the concentrate of the fully synthetic metalworking fluid comprises 30 to 45 wt.-% water, 15 to 40 wt.-% of one or more water-soluble synthetic lubricant, 8 to 15 wt- % of one or more monocarboxylic acids, 2 to 8 wt.-% of one or more dicarboxylic acids, 0 to 5 wt.-% of one or more phosphonic acids, 20 to 30 wt.-% of one or more amines, 0 to 5 wt.-% of one or more polymers, preferably cationic polymers, 0.1 to 5 wt.-% of one or more corrosion inhibitors, 0.1 to 5 wt.-% of one or more biocides differing from the one or more quaternary ammonium salts as used in the metalworking process of the present invention, and 0 to 5 wt.-%, such as 1 to 4 wt.-% of the one or more quaternary ammonium salts as used in the metalworking process of the present invention.

[0070] In all the embodiments of the concentrate of the fully synthetic metalworking fluid as described in the previous four paragraphs, it is preferred that the one or more water-soluble synthetic lubricants, the one or more monocarboxylic acids, the one or more dicarboxylic acids, the one or more phosphonic acids, the one or more amines, the one or more polymers, preferably cationic polymers, the one or more corrosion inhibitors, the one of more biocides differing from the one or more quaternary ammonium salts as used in the metalworking process of the present invention, and the one or more quaternary ammonium salts as used in the metalworking process of the present invention are selected from those as described herein above.

[0071] As described above, it is possible that the concentrate of the fully synthetic metalworking fluid contains the one or more quaternary ammonium salts as described under (v) above and in more detail under (v) below. In such case the concentrate is "pre-equipped” with the one or more quaternary ammonium salts, thus serving as a biocide. In the diluted ("ready-to-use”) concentrate, i.e. , in the fully synthetic metalworking fluid it may thus be contained prior to the first use, providing the fully synthetic metalworking fluid with an intrinsic demulsifying property in view of emulsified tramp oil in the bulk phase of the fully synthetic metalworking fluid.

[0072] The fully synthetic metalworking fluid ("ready-to-use” fully synthetic metalworking fluid) is preferably obtained by diluting the above-described concentrates thereof with an aqueous medium, preferably water, more preferably deionized water. The final water content of the fully synthetic metalworking fluid as used in the method of the present invention preferably is 10 or 15 to 99 wt.-% water, the content of the water-soluble synthetic lubricant and the further ingredients, if any, automatically result from the dilution rate of the concentrate, which is determined by the final water content.

[0073] The fully synthetic metalworking fluid can also be directly obtained without using a concentrate. In such case the concentrations of the ingredients are those which would result as if a concentrate as described above would have been diluted.

[0074] The concentrates of the fully synthetic metalworking fluid as well as the ready-to-use fully synthetic metalworking fluid can be obtained by simply mixing the ingredients. In case the quaternary ammonium salts as described herein above and below are employed into the concentrates of the fully synthetic metalworking fluid or the ready-to-use fully synthetic metalworking fluid, it is preferred to introduce these by high-shear mixing.

[0075] (Hi)

[0076] In metalworking processes, while carrying out (I) and (II), it is almost unavoidable that oily fluids from leaky systems, corrosion protection oils to protect workpieces and / or gear oils from upstream processing, are contaminating the metalworking fluid, which is preferably recirculated through the machining equipment. The contaminated metalworking fluid reduces the life of the metalworking fluid and metalworking machine including the metalworking tools. Herein, the oily substances which are introduced into the fully synthetic metal working fluid used in the metalworking process of the invention are summarized under the term "tramp oil(s),” also referred to as "foreign oil (s)." The tramp oils are not water-soluble, i.e., they are not soluble in fully synthetic metalworking fluids, while the ingredients of a fully synthetic metalworking fluid, such as the typically used synthetic lubricants are water-soluble. In the context of the present invention the terms "tramp oil” and "tramp oils” mean the same and may contain just one type of oil or a mixture of oils. Tramp oil in the present invention preferably comprises or consists of one or more water-insoluble oils, i.e., one or more oils forming an oil phase as a second phase when introduced into water. Typically, tramp oil comprises a mineral oil or mixture of mineral oils.

[0077] A fully synthetic metalworking fluid, which is not contaminated with tramp oils, is typically and preferable a translucent or even clear aqueous liquid, which does not show any phase-separation of its ingredients. Thus, for the bare eye, a fully synthetic metalworking fluid is a single-phase liquid, which is translucent or even clear.

[0078] However, during the metalworking process, the fully synthetic metalworking fluid takes up tramp oil, thus forming a used, tramp oil containing fully synthetic metalworking fluid. If reused without purification, such used, tramp oil containing fully synthetic metalworking fluid accumulates tramp oil, since from the second and any subsequent uses further portions of tramp oil get into the fully synthetic metalworking fluid.

[0079] The used, tramp oil containing fully synthetic metalworking fluid is collected in a container and preferably analyzed for the presence and / or amount of free and emulsified tramp oil.

[0080] Preferably the container is a so-called sump or a tank of the metalworking machine. Preferably, in a typical metalworking process, the used, tramp oil containing fully synthetic metalworking fluid drops or flows down and is collected in a container, such as the sump or tank of the metalworking machine, and is recirculated.

[0081] The term "free tramp oil” refers to tramp oil, which is free floating at the air-metalworking fluid interface (interface between air and the fully synthetic metalworking fluid). Thus, the free tramp oil is present at the surface of the fully synthetic metal-working fluid, forming a visibly separated phase.

[0082] The term "emulsified tramp oil” refers to the tramp oil which is dispersed in the bulk phase of the fully synthetic metalworking fluid. Thus, emulsified tramp oil, does not freely float at the air-metalworking fluid interface, but is, at the time of analyzing the used, tramp oil containing fully synthetic metalworking fluid, part of the bulk phase.

[0083] In some literature a third "type of tramp oil” is discussed, namely "dispersed tramp oil” that is dispersed mechanically throughout the metalworking fluid. This type of tramp oil is characterized in that it will, given enough time, separate and typically rise to the surface. Contrary, the emulsified tramp oil is dispersed in a manner that the dispersion / emulsion is stable over an extended period of time. In the present invention, it is not distinguished between "dispersed tramp oil” and "emulsified tramp oil”, both are summarized under the term "emulsified tramp oil”, in distinction to the "free tramp oil”. Simply said, free trump oil is floating on the surface of the fully synthetic metalworking fluid, while emulsified tramp oil is in the bulk phase at the time of monitoring the metalworking fluid.

[0084] Therefore, according to the present invention, the sum of free tramp oil and emulsified tramp oil constitutes the total amount of tramp oil present in the used, tramp oil containing fully synthetic metalworking fluid.

[0085] The term "analyzing the fully synthetic metal working fluid for the presence and / or amount of free and emulsified tramp oil” does not necessarily mean a quantification of the amounts of free tramp oil and emulsified tramp oil.

[0086] In the present invention, it is preferred to analyze the metalworking fluid's composition collected in the container with respect to the occurrence of a phase separation. If there is a phase separation, the phase which accumulates at the surface of the metalworking fluid is preferably removed, preferably by skimming the surface of the metalworking fluid.

[0087] While not preferred, it is even possible to carry out the metalworking process of the invention, without analyzing the fully synthetic metal working fluid for the presence and / or amount of free and emulsified tramp oil. Such operation may, e.g., be carried out experience-based, if the amount of tramp oil getting into the fully synthetic metalworking fluid can be estimated in a specific set-up. In such case an experience-based addition of the one or more quaternary ammonium salts can be carried out.

[0088] Preferably, analyzing the fully synthetic metal working fluid for the presence and / or amount of free and / or emulsified tramp oil, preferably at least emulsified tramp oil is carried out.

[0089] In first approximation, the presence of free tramp oil can be visibly detected by the bare eye, since it is floating as a separate phase, e.g., a film or layer on the surface of the used, tramp oil containing fully synthetic metalworking fluid.

[0090] Again, in first approximation, the presence of emulsified tramp oil can be visibly detected by the bare eye, since it influences the clarity of the bulk phase of the fully synthetic metalworking fluid. If directly compared with the fully synthetic metalworking fluid before any use, a fully synthetic metalworking fluid, which contains emulsified tramp oil shows at least a slight turbidity. To better evaluate the presence of free tramp oil or emulsified tramp oil by the bare eye, but also for more elaborated analysis, samples can be taken from the container wherein the metalworking fluid is collected. Such samples can be transferred to transparent containers, such as glass containers, like glass cylinders to better compare the samples with fresh, i.e. unused fully synthetic metalworking fluid.

[0091] Besides the analysis of the mere presence of free tramp oil and emulsified tramp oil with the bare eye, other means are available to determine changes of the composition of the fully synthetic metalworking fluid. A simple method is the refractometric measurement of concentration by means of a hand-held refractometer. The dependency of the light refraction on the concentration of a water-dissolved or emulsified substance is exploited using this instrument. Generally, the Abbe refractometer principle is used, so that the measurement is not made directly at the refraction angle, but rather at the angle of total reflection, which is also dependent on substance and concentration. This dependency makes it necessary to use product-specific calibration curves, which can be very quickly produced for a series of concentrations. The instruments, which are particularly suitable for use in practical operation because they are very easy to apply in an operational area, are either calibrated in °Brix (distilled water is equal to 0 °Brix, a 50 wt.-% solution of saccharose equals to 50 °Brix) or are calibrated directly to volume percent related to conventional mineral oil emulsions. In case of highly contaminated emulsions the measurement range of the refractometer may become limiting. However, in such case dilutions with water at a weight ratio of 1 :1 to 1 : 10 are expedient in the case of very high concentrations. Commercially available refractometers are, e.g., portable ("handheld”) refractometers having a rugged construction and automatic temperature compensation mechanism under the tradename VEE GEE BTX-1 (0-32%), from Star Metal Fluids LLC (Arizona USA). The changes in the refractive index of the used, tramp oil containing fully synthetic metalworking compared to a fresh fully synthetic metalworking fluid can be determined and give a semi-quantitative measurement of the amount of emulsified tramp oil.

[0092] In principle any methods commonly used to determine free and / or emulsified tramp oil can be used in the context of the present invention. Such methods are, e.g., IR spectroscopy and determination of the neutralization number, making use standard calibration curves obtained by knowing the possible types of tramp oil for the respective process. Some methods are, e.g., described and / or referred to in EP 0 543 057 A1 (Title: "Method for determining the oil content in oil- in-water emulsions”).

[0093] Analyzing can be carried out with optical means continuously or in time intervals, preferably fixed time intervals.

[0094] (v)

[0095] To purify the fully synthetic metal working fluid at least partially from emulsified tramp oil, one or more of the quaternary ammonium salts as defined herein below are added to the used, tramp oil containing fully synthetic metalworking fluid, preferably to the bulk phase of the used, tramp oil containing fully synthetic metalworking fluid. Preferably, the addition of the one or more of the quaternary ammonium salts is carried out at least once during the metalworking process.

[0096] The one or more quaternary ammonium salts have the following general formula

[0097] [N+(R1)(R2)(R3)(R4)]nXn-, wherein residues R1, R2, R3and R4are selected from araliphatic and aliphatic hydrocarbon residues, with the proviso that two of residues R1, R2, R3and R4are hydrocarbon groups with 1 to 4 carbon atoms and the other two of these residues are hydrocarbon residues with 6 to 20 carbon atoms, Xn- being an n-valent anion, and n being 1 , 2 or 3.

[0098] An "araliphatic residue” is a residue which contains an aryl group but is bound to the nitrogen atom of the quaternary ammonium salt via a carbon atom which does not belong the aryl group, namely an alkylene group, such as a methylene group.

[0099] Preferably, R1is an araliphatic residue containing 7 to 16 carbon atoms, such as preferably a benzyl residue or an alkyl group containing 8 to 20, more preferred 10 to 18 and most preferred 10 to 16 carbon atoms.

[0100] Preferably, R2and R3are independently of each other alkyl groups having 1 , 2, 3 or 4 carbon atoms, preferably 1 , 2, or 3, even more preferred 1 or 2 and most preferred 1 carbon atom (methyl).

[0101] Preferably R4is an alkyl group containing 8 to 20, more preferred 10 to 18 and most preferred 10 to 16 carbon atoms

[0102] The n-valent anion Xn- is preferably selected from halogenide, such as chloride; or hydrogen carbonate and carbonate or the anion of a carboxylic acid, the carboxylic acid preferably having 1 to 3 carbon atoms, such as formic acid, acetic acid or propionic acid. From the viewpoint of corrosion prevention, it is preferred that the n-valent anion Xn- is selected from hydrogen carbonate, carbonate ions and the anions of carboxylic acids.

[0103] In a very preferred embodiment R1is a benzyl residue or an alkyl group containing 8 to 20 carbon atoms, R2and R3are independently of each other methyl or ethyl, preferably methyl, R4is an alkyl group containing 8 to 20, more preferred 10 to 18, and in case of n = 1 , X- is halogen, such as a chloride, hydrogen carbonate and the anion of a carboxylic acid; and in case of n = 2, X2’ is carbonate. Adding of the above one or more quaternary ammonium salts is carry out, if the presence of a detrimental amount of emulsified tramp oil is expected by experience obtained from the specific metalworking process, or preferably determined in (iv), and most preferably, if the emulsified tram oil exceeds a pre-set amount. In the metalworking process of the present invention adding the one or more quaternary ammonium salts is preferably carried out at least once.

[0104] As described above, the presence of tramp oil in fully synthetic metalworking might be tolerated up to some extent, depending on the composition of the fully synthetic metalworking fluid itself, but also the area of application, i.e. the type of the metalworking process.

[0105] Thus, the term "if the emulsified tram oil exceeds a pre-set amount” means that it might not be necessary to add the quaternary ammonium salt as defined above or any preferred embodiment thereof immediately after the occurrence of even a small amount of tramp oil. However, if the amount of emulsified tramp oil exceeds a tolerated amount ("pre-set amount”) the one or more of the quaternary ammonium salts are to be added to demulsify the emulsified tramp oil at least partially.

[0106] Preferably, the fully synthetic metalworking fluid is reused for several times. More specific, the fully synthetic metalworking fluid is preferably recirculated. In such cases, the container wherein the used, tramp oil containing fully synthetic metalworking fluid is collected, also serves to store the same for reuse. To accomplish this, the container is preferably directly or indirectly connected with means supplying the fully synthetic metalworking fluid to at least one of the metalworking machine, the metalworking tool and the workpiece.

[0107] If the composition is reused without adding the one or more quaternary ammonium salts of the above formula, tramp oil will accumulate from one use to the next use until the amount exceeds the pre-set amount, meaning that the detrimental effects of the tramp oil in the metalworking process jeopardize the quality of the metalworking process, the quality of the processed workpieces, the lifespan of the metalworking tool and / or the metalworking machine.

[0108] The quaternary ammonium salts of the above formula may be added undiluted as 100%-substance, but is preferably added diluted, more preferably dissolved, most preferably diluted or dissolved in a preferably aqueous medium, more preferably water. They can be added continuously or batchwise. Preferably they are added to the bulk phase of the used, tramp oil containing fully synthetic metalworking fluid. The quaternary ammonium salts of the above formula are typically added to the used, tramp oil containing fully synthetic metalworking fluid, while said fluid is in the above-mentioned container, such as sump or tank. Preferably, it is added in a part of the bulk phase of the used, tramp oil containing fully synthetic metalworking fluid. This has the advantage that free tramp oil present at the air-metalworking fluid interphase is not excessively agitated, thus avoiding the incorporation of a part of the free tramp oil into the bulk phase. It is particularly preferred that the quaternary ammonium salts of the above formula are introduced into the bulk phase of the used, tramp oil containing fully synthetic metalworking fluid under application of shear forces, preferably high-shear forces to guarantee a good distribution of the quaternary ammonium salts throughout the bulk phase of metalworking fluid. The shear forces are preferably employed prior to adding the quaternary ammonium salts to the bulk phase of the fully synthetic metalworking fluid, e.g., by a high shear mixing pump which may supply the metalworking fluid with the quaternary ammonium salt diluted and / or dissolved in an aqueous medium.

[0109] After the step of adding the quaternary ammonium salt of the above formula to the metal working fluid, and before removing the tramp oil from the surface of the metal working fluid, it is preferred to give the quaternary ammonium salt supplemented metal working fluid some time to develop an optimal splitting effect by allowing a good incorporation of the quaternary ammonium salt into the bulk phase of the metal working fluid. The time range for such intermediate step is preferably in the range from 1 min to 24 hours, more preferred in the range from 5 min to 12 hours, even more preferred in the range of 15 min to 8 hours, most preferred in the range from 30 min to 4 hours, such as 45 min to 2 hours.

[0110] By adding the quaternary ammonium salts to the used, tramp oil containing fully synthetic metalworking fluid, the emulsified tramp oil is at least partially demulsified (breaking of the emulsion), the thus formed free tramp oil migrates, associated with at least part of the quaternary ammonium salts, to air-metalworking fluid, thus floating on the surface.

[0111] The quaternary ammonium salts as used in the metalworking process of the present invention are found to be highly effective in breaking the emulsion of the emulsified tramp oil in the metalworking fluids, even in addition to, e.g., commercially used polymeric emulsion breakers, if such are used at all.

[0112] Furthermore, it was found that the quaternary ammonium salts used in the metalworking process of the invention are apt to act as biocides, thus preventing or inhibiting the growth of microorganisms, particularly bacteria. While at least a part of the quaternary ammonium salts is discharged from the bulk phase in the process of breaking the emulsion and the subsequent removal of free tramp oil, at least a part of the quaternary ammonium salts remains in the bulk phase, thus providing biocidal activity.

[0113] (vi) The free tramp oil resulting from breaking the emulsion of emulsified tramp oil accumulates at an air-metalworking fluid interface and is removed thereof, thus forming an at least partially purified fully synthetic metalworking fluid.

[0114] Removal of the free tramp oil resulting from breaking the emulsion of emulsified tramp oil from the air-metalworking fluid interface, i.e., from the surface of the at least partially purified bulk phase is accompanied by the removal of the free tramp oil, which does not origin from the emulsified tram oil.

[0115] The removal of the free tramp oil (originally free and formed by breaking the emulsion of emulsified tramp oil) from the air-metalworking fluid interface can be carried out by any conventionally applied means, such as skimming the surface. The advantage of the present invention lays in the removal of both, the originally free tramp oil and the free tramp oil originating from emulsified tramp oil in one simple stage such as skimming the surface, without the need of using installed equipment such as filters or using energy consuming separators such as centrifuges. At the same time the fully synthetic metalworking fluid is supplemented with the above described one or more quaternary ammonium salts, which possess biocidal activity.

[0116] The accumulated free tramp oil to be removed, e.g., by skimming, typically contains some of the quaternary ammonium salt(s), which are responsible for the separation of the previously emulsified tramp oil from the metalworking fluid and the migration of this part of the tramp oil to the surface. Consequently, part of the quaternary ammonium salt is likewise removed from the metalworking fluid by the removing process. Furthermore, even if removing, such as skimming is not carried out continuously but in time intervals, the quaternary ammonium salts are associated with the tramp oil and the bulk phase of the metalworking fluid is at least partially depleted from the quaternary ammonium salt, which was added. Thus, preferably an amount of quaternary ammonium salts exceeding the amount necessary to sufficiently break the emulation is added.

[0117] (v / 7)

[0118] Preferably, (vi) is followed by (vii), i.e., the thus obtained at least partially purified fully synthetic metalworking fluid is recirculated and resupplied to at least one of the metalworking machine, the metalworking tool and the workpiece according to (ii), and (iii) to (vi), or (iii) to (vii) are repeated. In such case the above-mentioned container (preferably sump or tank) preferably has an outlet to withdraw the at least partially purified metalworking fluid, which is preferably connected by one or more tubes with means supplying the fluid to at least one of the metalworking machine, the metalworking tool and the workpiece.

[0119] Thus, the metalworking process of the invention is preferably a metalworking process, wherein a plurality of workpieces is processed continuously, while reusing an at least partially purified fully synthetic metalworking fluid. To compensate any losses of the fully synthetic metalworking or its ingredients during such metalworking process, the at least partially purified fully synthetic metalworking fluid can be supplemented by fresh fully synthetic metalworking fluid or any ingredients which are depleted from the fully synthetic metalworking fluid in the metalworking process.

[0120] Method of Removing Emulsified Tramp Oil from Fully Synthetic Metalworking Fluids

[0121] The invention also relates to a method of removing emulsified tramp oil from its emulsion in a fully synthetic metalworking fluid at least partially, by

[0122] (a) adding one or more quaternary ammonium salts as defined above to the fully synthetic metalworking fluid containing emulsified tramp oil, thus breaking the emulsion at least partially to form free tramp oil accumulating at the air-metalworking fluid interface,

[0123] (b) removing the free tramp oil resulting from breaking the emulsion of emulsified tramp oil at the airmetalworking fluid interface at least partially.

[0124] Steps (a) and (b) of this method are preferably conducted as described under (v) and (vi) above. Thus, they can be conducted as part of the metalworking process of the invention or independent thereof.

[0125] If steps (a) and (b) are conducted as part of the metalworking process of the invention, all details as disclosed for (v) and (vi), including the composition and ingredients of the fully synthetic metalworking fluids and the structure of the quaternary ammonium salts apply likewise for the method of at least partially removing emulsified tramp oil from its emulsion in a fully synthetic metalworking fluid. Thus, the respective parts of the description, as well as the preferred and further preferred embodiments are valid in the method of removing tramp oil, too.

[0126] Of course, fully synthetic metalworking fluids contaminated with emulsified tramp oil can also be purified separately. Again, all details as disclosed for (v) and (vi), including the composition and ingredients of the fully synthetic metalworking fluids and the structure of the quaternary ammonium salts apply likewise for the method of at least partially removing emulsified tramp oil from its emulsion in a fully synthetic metalworking fluid. Thus, the respective parts of the description, as well as the preferred and further preferred embodiments are valid in the method of removing tramp oil, too.

[0127] Removing the free tramp oil resulting from breaking the emulsion of emulsified tramp oil at the air-metalworking fluid interface at least partially goes along with at least partially removing free tramp oil which was present at the air-metalworking fluid interface prior to breaking the emulsion.

[0128] Use of Quaternary Ammonium Salts Further subject matter of the invention is the use of one or more quaternary ammonium salts as defined for the metalworking process of the invention in a fully synthetic metalworking fluid to demulsify emulsified tramp oil from the bulk phase of the fully synthetic metalworking fluid at least partially.

[0129] The fully synthetic metalworking fluid, its ingredients and composition are the same as described herein above. Thus, any embodiments, including more specific embodiments as described for the fully synthetic metalworking fluid and its ingredients, particularly the quaternary metal salts employed therein, are also embodiments which further specify the use of the invention.

[0130] Fully Synthetic Metalworking Fluid Containing Quaternary Ammonium Salts

[0131] The invention further provides a fully synthetic metalworking fluid containing the quaternary ammonium salts as defined above. Such fully synthetic metalworking fluid is equipped with the intrinsic ability to demulsify and separate tramp oil which may unintentionally get into in the fully synthetic metalworking fluids, such as corrosion protection oils or gear oils, from the metalworking fluid.

[0132] Any embodiments, including more specific embodiments as described for the fully synthetic metalworking fluid and its ingredients, particularly the quaternary metal salts employed therein, are also embodiments which further specify the fully synthetic metalworking fluid of the invention.

[0133] The fully synthetic metalworking fluid can be prepared directly or by diluting a concentrate thereof as described above. Both, the concentrate and the ready-to-use metalworking fluid can be prepared by conventionally mixing the ingredients. However, it is preferred that the quaternary ammonium salts are preferably incorporated by high- shear mixing.

[0134] In the following the invention will be further explained by examples and experimental results.

[0135] EXPERIMENTAL PART

[0136] Preparation of a Fully Synthetic Metalworking Fluid A concentrate of a metalworking fluid was prepared by mixing 380 parts by weight (pbw) of water, with 200 pbw of a mixture of synthetic lubricants containing poly (alkyleneoxide) blockcopolymers, 110 pbw of a mixture of branched monocarboxylic acids comprising 9 to 10 carbon atoms, 30 pbw of a mixture of linear alpha, omega-dicarboxylic acids comprising 10 to 12 carbon atoms, 5 parts by weight of an Cs-alkylphosphonic acid, 250 pbw of a mixture of primary and tertiary amines as defined in the general part of the application and 16 pbw of a mixture of a cationic polymer, a corrosion inhibitor and a biocide.

[0137] The thus prepared concentrate of a metalworking fluid was diluted with water in that 5 pbw of the concentrate were diluted by deionized water to get 100 pbw of a ready-to-use fully synthetic metalworking fluid.

[0138] Simulation of a Contamination

[0139] Into the ready-to-use fully synthetic metalworking fluid, as prepared above, an amount of 1 to 5 pbw of a tramp oil (gear oil) was mixed into 100 pbw of the metalworking fluid by stirring to form a contaminated fully synthetic metalworking fluid.

[0140] Free Tramp Oil Determination

[0141] A sample (approx. 150 mL) of the above contaminated fully synthetic metalworking fluid was homogenized by shaking in a sampling flask. Directly after homogenization, 100 mL of the thus obtained emulsion was transferred to a shaking cylinder with measurement scale (in mL) and let rest for 1 hour. After 1 hour the mL amount of the upper phase, floating on the lower phase was determined. This phase was considered the amount of free tramp oil.

[0142] Emulsified Tramp Oil Determination

[0143] A sample (approx. 350 mL) of the above tramp oil contaminated fully synthetic metalworking fluid was homogenized by shaking in a sampling flask. Directly after homogenization, 100 mL of the thus obtained emulsion was transferred to a first 300 mL-Erlenmeyer-flask with measurement scale (in mL). A second and a third 300 mL-Erlenmeyer-flask were filled the same way.

[0144] The second flask was supplemented with an amount of 0.5 mL of a 28 wt.-% solution of a quaternary ammonium chloride as used in the metalworking process of the invention in water (with R1= benzyl residue, R2= R3= methyl, R4= Ci2-i6-alkyl; and X’ = Cl ) and the thirds flask was supplemented with an amount of 1.0 mL of the aforementioned quaternary ammonium chloride solution in water.

[0145] All three flasks were homogenized by vigorously stirring and let rest for a 1 hour.

[0146] After 1 hour the mL amount of the upper phase, floating on the lower phase was determined and compared to that of the first Erlenmeyer flask to which no quaternary ammonium salt was added. The phase formed is the amount of free tramp oil (as found in the first Erlenmeyer flask) plus free tramp oil originating from the emulsified tramp oil by demulsifying the same with the quaternary ammonium salt.

[0147] The addition of a rather low amount of quaternary ammonium salts (second Erlenmeyer flask) already leads to a visible removal of emulsified tramp oil from the bulk phase (the bulk phase becomes less turbid), while the larger amount of quaternary ammonium salts (third Erlenmeyer flask) lead to a high purification of the bulk phase from emulsified tramp oil.

[0148] In practice, the combined amounts of free tramp oil can easily be skimmed off by use of a conventional oil skimmer, thus allowing the at least partial removal of original free tramp oil and such free tramp oil formed by demulsifying the emulsified tramp oil. As in the above testing environment, in practice, there is preferably a time gap between the addition of the quaternary ammonium salt and the tramp oil removal step (skimming step) in order allow for sufficient mixing to develop the desired effect.

[0149] Results

[0150] The above results confirm the ability of the quaternary ammonium salts to remove emulsified tramp oil at least partially from fully synthetic metalworking fluids by converting it to free tramp oil which can easily be removed from the surface of the fully synthetic metalworking fluid. At the same time, the at least one quaternary ammonium salt serves as a biocide and prevents or inhibits microbial growth.

Claims

CLAIMS1 . A metalworking process, wherein(i) a metalworking tool processes a workpiece at a processing area of a metalworking machine;(ii) a fully synthetic metalworking fluid is supplied to at least one of the metalworking machine, the metalworking tool and the workpiece;(ill) the fully synthetic metalworking fluid takes up tramp oil, thus forming a used, tramp oil containing fully synthetic metalworking fluid;(iv) the used, tramp oil containing fully synthetic metalworking fluid is collected in a container and preferably analyzed for the presence and / or amount of free and / or emulsified tramp oil;(v) one or more quaternary ammonium salts of formula[N+(R1)(R2)(R3)(R4)]nXn-, wherein residues R1, R2, R3and R4are selected from araliphatic and aliphatic hydrocarbon residues, with the proviso that two of residues R1, R2, R3and R4are hydrocarbon groups with 1 to 4 carbon atoms and the other two of these residues are hydrocarbon residues with 6 to 20 carbon atoms, Xn- being an n-valent anion, and n being 1, 2 or 3, are added to the used, tramp oil containing fully synthetic metalworking fluid, if emulsified tramp oil is present or exceeds a pre-set amount, thus at least partially breaking the emulsion of emulsified tramp oil in the fully synthetic metalworking fluid forming free tramp oil; and(vi) the free tramp oil resulting from breaking the emulsion of emulsified tramp oil accumulates at an air-metalworking fluid interface and is removed thereof to form an at least partially purified fully synthetic metalworking fluid.

2. The metalworking process according to claim 1, characterized in that (vi) is followed by (vii) recirculating and resupplying the at least partially purified fully synthetic metalworking fluid to at least one of the metalworking machine, the metalworking tool and the workpiece according to (II) and repeating (ill) to (vi), or (ill) to (vii).

3. The metalworking process according to claim 1 or 2, wherein in (iv) the container is a sump of the metalworking machine or a tank.

4. The metalworking process according to one or more of claims 1 to 3, wherein in (iv) analyzing for the presence and / or amount of free and / or emulsified tramp oil is carried out, preferably by means of the bare eye or a refractometer.

5. The metalworking process according to one or more of claims 1 to 4, wherein the residues contained in the quaternary ammonium salt are defined as followsR1is an araliphatic residue or an alkyl group containing 8 to 20, more preferred 10 to 18 and most preferred 10 to 16 carbon atoms;R2and R3are independently of each other alkyl groups having 1 , 2, 3 or 4 carbon atoms, preferably 1 , 2, or 3, even more preferred 1 or 2 and most preferred 1 carbon atom;R4is an alkyl group containing 8 to 20, more preferred 10 to 18 and most preferred 10 to 16 carbon atoms; the n-valent anion Xn- is preferably selected from halogenide, preferably chloride, hydrogen carbonate, carbonate and the anion of a carboxylic acid, even more preferred from hydrogen carbonate, carbonate ions, and anions of carboxylic acids; and n being 1 or 2.

6. The metalworking process according to one or more of claims 1 to 5, whereinR1is a benzyl residue or an alkyl group containing 8 to 20 carbon atoms,R2and R3are independently of each other methyl or ethyl, preferably methyl,R4is an alkyl group containing 8 to 20, more preferred 10 to 18, and in case of n = 1 , X- is halogen, such as a chloride, hydrogen carbonate or the anion of a carboxylic acid; and in case of n = 2, X2’ is carbonate.

7. The metalworking process according to one or more of claims 1 to 6, wherein the fully synthetic metal working fluid contains water and a water-soluble synthetic lubricant; and does not contain a mineral oil.

8. The metalworking process according to one or more of claims 1 to 7, wherein the quaternary ammonium salt is added to the bulk phase of the used, tramp oil containing fully synthetic metalworking fluid undiluted as 100%-substance, diluted or dissolved, more preferably dissolved, most preferably diluted or dissolved under high-shear mixing.

9. The metalworking process according to one or more of claims 1 to 8, wherein in (vi) the combined free tramp oil being originally present and the tramp oil resulting from breaking the emulsion of emulsified tramp oil and is removed from the air-metalworking fluid interface, preferably by skimming.

10. A method of removing emulsified tramp oil from its emulsion in a fully synthetic metalworking fluid at least partially, by(a) adding one or more quaternary ammonium salts as defined in claims 1 , 5 and 6 to the fully synthetic metalworking fluid containing emulsified tramp oil, thus breaking the emulsion at least partially to form free tramp oil accumulating at the air-metalworking fluid interface,(b) removing the free tramp oil resulting from breaking the emulsion of emulsified tramp oil at the airmetalworking fluid interface at least partially.

11. The method of removing emulsified tramp oil according to claim 10, wherein in (b) the free tramp oil resulting from breaking the emulsion of emulsified tramp oil is removed with at least part of free tramp oil which was present at the air-metalworking fluid interface prior to breaking the emulsion.

12. The method of removing emulsified tramp oil according to claim 10 or 11 , wherein removing is performed by skimming the air-metalworking fluid interface.

13. Use of one or more quaternary ammonium salts as defined in claims 1 , 5 and 6, in a fully synthetic metalworking fluid to demulsify emulsified tramp oil from the bulk phase of the fully synthetic metalworking fluid at least partially.