Aqueous lubricating composition

Abstract

An aqueous lubricating composition for use in plastic forming of metallic substrates, the composition comprising: a) an inorganic particulate solid lubricant. b) an inorganic binder comprising: bl) an alkali metal silicate in the dissolved state; and / or, b2) particulate γ-aluminium oxide; c) at least one dispersant; d) at least one base; and, water.

Description

FIELD OF THE INVENTION

[0001] The present disclosure is directed to an aqueous lubricating composition which is to be used in the plastic forming of metallic substrates, for instance in the superplastic or quick plastic forming of metallic substrates. More particularly, the present disclosure is directed to an aqueous lubricating composition which comprises a particulate solid lubricant and an inorganic binder.BACKGROUND TO THE INVENTION

[0002] The term "superplasticity" is defined as the ability of a polycrystalline material to exhibit, in a generally isotropic manner, very high elongation prior to fracture. Superplastic materials thus demonstrate exceptional ductility when deformed under conducive conditions, the process of which is known as superplastic forming (SPF). Typically the polycrystalline materials are characterized by a crystallite (grain) size of less than 10 µm. And exemplary superplastic polycrystalline materials include metals, intermetallics and alloys, of which particular mention may be made of titanium and aluminum alloys.

[0003] In a typical process of superplastic forming (SPF), a sample of the polycrystalline material to be formed is disposed within a die cavity and then heated to a temperature of at least 50% of the absolute melting temperature of the material, under the even impingement of high pressure gas. The gas serves to exert a controlled strain rate on the heated material, which material thins, deforms and thereby conforms to shape of the die cavity. During superplastic deformation, the polycrystalline material becomes uniformly thinner over the entire die cavity but does not experience necking (localized thinning) which often leads to tensile fracture. Further, during the forming process, the material does not develop internal cavities, which is another common cause of tensile failure.

[0004] Quick plastic forming (QPF) is process which is related to superplastic forming (SPF) in that forming is conducted at elevated temperatures using gas pressure. The temperatures used in quick plastic forming tend to be slightly lower than those used in superplastic forming. Moreover, a much faster forming cycle is attained in quick plastic forming through inter alia process automation, thermal control of both the material and the dies, and the application of higher strain rates than those associated with superplastic forming. Further, quick plastic forming is typically utilized to produce articles of lower complexity than could be obtained if longer cycle times (slower strain rates) were permitted.

[0005] In addition to contacting the dies, the polycrystalline materials to be formed by both quick plastic forming (QPF) and superplastic forming (SPF) will typically be contacted by tools, in particular ferrous tools. The polycrystalline material or workpiece should desirably release cleanly from both the tool(s) and the die in order to maintain its integrity, such as its dimensional accuracy and its surface finish. However, the intimate contact that occurs between the workpiece and both the die and working tool(s) during the forming processes (SPF, QPF) is associated with interatomic forces, specifically adhesion and friction, which can be deleterious. For instance, workpiece adhesion can lead to undesired patterning of the finished workpiece surfaces and to distortion of the workpiece from its desired or, in some cases, permissible dimensions.

[0006] Practitioners in this field have sought to mitigate the problems of adhesion and friction through the coating of the polycrystalline material or workpiece with a lubricant or release agent. For example, US Patent No. 5,819,572 (Krajewski) describes a method of forming a sheet of a superplastic aluminum or titanium alloy by forcing a side of the sheet into conformance with the surface of a shaping tool or die, said method comprising: heating said sheet to a superplastic forming temperature; applying a lubricant to at least one of (a) the surface of the shaping tool or die and (b) said side of said sheet, wherein said lubricant comprises either Mg(OH) 2 or a mixture of Mg(OH) 2 and BN.

[0007] JP2001348585A (Kubota Kabushiki Kaisha) describes a lubricant for high-speed superplastic working, which lubricant comprises: a base oil containing liquid paraffin having a flash point in the range of 190 to 320°C; and, from 10 to 25 wt.% of graphite with respect to the base oil.

[0008] US2016075903A1 (Miller-Jupp et al.) discloses a metal sheet or strip made of aluminum or an aluminium alloy and capable of hot forming or superplastic forming, and having a coating at least partially on one or on both sides of the metal sheet or strip, wherein the coating comprises a lubricant and a protective base material and further wherein: the lubricant is contained in the protective base material; the protective base material is at least in part selectively removable substantially without removing the lubricant; the lubricant comprises graphite, boron nitride, brucite, montmorillonite, mica, muscovite, molybdenum sulfide, polytetrafluoroethylene (PTFE) and / or talcum; and, the protective base material is a polymer matrix comprising polymers of propylene, ethylene, styrene, isobutylene, tetrahydrofurane, methylmethacrylate and / or α-methylstyrene.

[0009] There is considered to remain a need in the art to develop alternative compositions which may be coated upon metallic substrates prior to their being plastically formed and which can limit the adhesion of the metallic substrates to metal-working tools and the friction between said substrates and said tools. It is further desired to provide a lubricating composition that has a viscosity which enables its convenient application by a number of methodologies but which, upon forming a coating on the surface of the metallic substrate provides a coating which is thermally stable at the metal-working (plastic forming) temperatures and dimensionally stable under the associated applied strain rates.STATEMENT OF THE INVENTION

[0010] In accordance with a first aspect of the disclosure, there is provided an aqueous lubricating composition comprising: a) inorganic particulate solid lubricant. b) an inorganic binder comprising: b1) an alkali metal silicate in the dissolved state; and / or, b2) particulate γ-aluminium oxide; c) at least one dispersant; d) at least one base; and, water.

[0011] In certain embodiments, the aqueous lubricating composition comprises, based on the weight of the composition: from 1 to 5 wt.%, preferably from 2 to 5 wt.%, more preferably from 3 to 5 wt.% of a) said inorganic particulate solid lubricant; from 1 to 5 wt.%, preferably from 1 to 4 wt.%, more preferably from 1 to 3 wt.% of b) said inorganic binder; from 0.1 to 5 wt.%, preferably from 0.5 to 2.5 wt.%, more preferably from 0.5 to 2 wt.% of c) said at least one dispersant; from 0.1 to 5 wt.%, preferably from 0.5 to 2.5 wt.%, more preferably from 0.5 to 2 wt.% of d) said at least one base; from 0 to 1 wt.%, preferably from 0.05 to 0.5 wt.%, more preferably from 0.05 to 0.2 wt.% of e) a biocidal agent; and, from 80 to 95 wt.%, preferably from 85 to 95 wt.%, more preferably from 90 to 95 wt.% of water, wherein the composition has a pH of from 7 to 10, preferably from 7 to 9.

[0012] The high water content of the aqueous composition - or concomitantly its low solids content - permits the composition to be applied to a substrate by a number of different techniques. The composition can, in certain embodiments, be applied by printing methods which afford great control on both the volume of the applied composition and the locus of application onto the substrate to be coated.

[0013] It is preferred that constituent a) of the composition comprises or consists of boron nitride. More particularly, constituent a) may comprise or consist of boron nitride having a median volume particle size (Dv50) of from 0.1 to 10 µm.

[0014] Desirably constituent b1) of the composition consists of sodium silicate of the formula (Na 2 O) x ·(SiO 2 ) y , wherein (y / x) is from 3.0 to 3.6. Independently of, or additional to this preference of b1), constituent b2) said particulate γ-aluminium oxide should preferably have: a medium volume particle diameter (Dv50) of from 10 to 50 nm, as determined by laser diffraction; and, or, a surface area of from 50 to 500 m 2< / g as determined by Brunauer Emmett Teller (BET) adsorption analysis in accordance with ASTM D1993-03.

[0015] The selection of compounds for constituent c) may permit the aqueous composition to be applied without significant foaming or even in a foam free manner. It is preferred that constituent c) of the composition comprises at least one compound selected from the group consisting of: carboxymethycellulose (CMC); carboxy-hydroxymethylcellulose; ethoxymethylcellulose; hydroxyethylcellulose; and, hydroxypropylcellulose. Independently of, or desirably additional to the presence of such cellulose ethers, it is preferred that constituent c) comprises at least one polycarboxylate polymer. The or each polycarboxylate polymer should desirably be characterized by: a weight average molecular weight of from 1000 to 200000 daltons; and, or, an equivalent weight per carboxylate group of from 25 to 500 g / eq. It is noted that polyacrylate polymers represent a preferred form of said polycarboxylate polymer.

[0016] Good results have been obtained where the aqueous lubricating composition comprises, based on the weight of the composition: from 1 to 5 wt.% of a) said inorganic particulate solid lubricant, wherein said inorganic particulate solid lubricant comprises boron nitride having a median volume particle size (Dv50) of from 0.1 to 10 µm; from 1 to 5 wt.% of b) said inorganic binder, wherein said inorganic binder comprises: b1) sodium silicate in the dissolved state, said sodium silicate having the formula (Na 2 O) x ·(SiO 2 ) y , wherein (y / x) is from 3.0 to 3.6; and / or, b2) particulate γ-aluminium oxide having a medium volume particle diameter (Dv50) of from 10 to 50 nm, as determined by laser diffraction and a surface area of from 50 to 500 m 2< / g as determined by Brunauer Emmett Teller (BET) adsorption analysis in accordance with ASTM D1993-03; from 0.1 to 5 wt.% of c) a dispersant mixture comprising: c1) at least one polyacrylate polymer having a weight average molecular weight of from 1000 to 200000 daltons and an equivalent weight per carboxylate group of from 25 to 500 g / eq; and, c2) at least one compound selected from the group consisting of: carboxymethycellulose (CMC); carboxy-hydroxymethylcellulose; ethoxymethylcellulose; hydroxyethylcellulose; and, hydroxypropylcellulose; from 0.1 to 5 wt.% of d) at least one base; from 0 to 1 wt.% of e) a biocidal agent; and, from 80 to 95 wt.% of water, wherein the composition has a pH of from 7 to 10.

[0017] In accordance with a second aspect of the present disclosure, there is provided the use of the aqueous waterborne lubricant composition as defined herein above and in the appended claims, or the dried coating obtained therefrom in the plastic forming of metallic substrates.

[0018] A further aspect of the present disclosure provides a method of plastic forming a metallic substrate utilizing at least one solid metal-working tool, the method comprising: i) applying the aqueous lubricating composition as defined herein above and in the appended claims to at least one solid surface of said metallic substrate, which surface or surfaces would, if not coated, directly contact a solid metal-working tool surface during the process; ii) drying the applied aqueous lubricating composition to form a coating on said at least one solid surface of said metallic substrate; (iii) heating the coated metallic substrate formed in step ii) to a first temperature which is from 50 to 90% of the melting temperature of the metallic substrate; iv) whilst maintaining the first temperature of the metallic material, disposing the coated metallic substrate into contact with said at least one metal-working tool and impinging a flow of pressurized inert gas onto the coated metallic substrate to plastically form the coated metallic substrate with said at least one metal-working tool; and, v) cooling the formed, coated metallic substrate and removing said substrate from the metal-working tool.

[0019] In a preferred embodiment, the method is iterative and, as such, further comprises: vi) removing the residual coating from said at least one solid surface of the metallic substrate formed in step v); vii) annealing said metallic substrate obtained in step vi); and, viii) repeating steps i) to v).

[0020] Where the aspects of the disclosure are described above as having certain embodiments, any one or more of those embodiments can be implemented in or combined with any one of the further embodiments, even if that combination is not explicitly described. Expressed differently, the described embodiments are not mutually exclusive, and permutations thereof remain within the scope of this disclosure.DEFINITIONS

[0021] The words "a" and "an" generally carry a meaning of "one or more," unless stated otherwise.

[0022] The terms "comprising", "comprises" and "comprised of" as used herein are synonymous with "including", "includes", "containing" or "contains", and are inclusive or open-ended and do not exclude additional, non-recited members, elements or method steps. If used, the phrase "consisting of" is closed, and excludes all additional elements. Further, the phrase "consisting essentially of" excludes additional material elements, but allows the inclusions of non-material elements that do not substantially change the nature of the invention. For completeness, the term "comprising" encompasses "consisting of".

[0023] When amounts, concentrations, dimensions and other parameters are expressed in the form of a range, a preferable range, an upper limit value, a lower limit value or preferable upper and limit values, it should be understood that any ranges obtainable by combining any upper limit or preferable value with any lower limit or preferable value are also specifically disclosed, irrespective of whether the obtained ranges are clearly mentioned in the context.

[0024] The words "preferable", "preferred", "preferably", "particularly" and "desirably" and synonyms thereof are used frequently herein to refer to embodiments of the disclosure that may afford particular benefits, under certain circumstances. However, the recitation of one or more preferable, preferred, particular or desirable embodiments does not imply that other embodiments are not useful and is not intended to exclude those other embodiments from the scope of the disclosure.

[0025] As used throughout this application, the word "may" is used in a permissive sense - that is meaning to have the potential to - rather than in the mandatory sense.

[0026] As used herein, room temperature is 23°C plus or minus 2°C.

[0027] Viscosities of the composition compositions may be determined using the Brookfield Viscometer, Model RVT at standard conditions of 25°C and 50% Relative Humidity (RH). The viscometer is calibrated using silicone oils of known viscosities, which vary from 5,000 cps to 50,000 cps. A set of RV spindles that attach to the viscometer are used for the calibration. Measurements of the aqueous lubricating compositions are done using the No. 6 spindle at a speed of 20 revolutions per minute for 1 minute until the viscometer equilibrates. The viscosity corresponding to the equilibrium reading is then calculated using the calibration.

[0028] As used herein, number average molecular weight (Mn) and weight average molecular weight (Mw) are determined by gel permeation chromatography (GPC) with tetrahydrofuran (THF) as the eluent in accordance with DIN 55672-1:2007-08. The term polydispersity (PD) is derived from Mw and Mn and is calculated as (Mw / Mn).

[0029] The term "at least a fraction" is used herein in the context of representing an amount of a constituent component specifically encompasses 100% of the defined constituent. The term "at least a fraction" includes: at least 5%; at least 10%; at least 15%; at least 20%; at least 25%; at least 30%; at least 35%; at least 40%; at least 45%; at least 50%; at least 55%; at least 60%; at least 65%; at least 70%; at least 75%; at least 80%; at least 85%; at least 90%; at least 95%; or, 100% of the defined electronic components.

[0030] The term "fraction" per se refers to a numerical quantity which defines a part up to but not including 100 percent or the entirety of the thing in question.

[0031] Unless otherwise stated, the term "particle size" refers to the largest axis of the particle. In the case of a generally spherical particle, the largest axis is the diameter.

[0032] The term "median volume particle size" (Dv50), as used herein, refers to a particle size corresponding to 50% of the volume of the sampled particles being greater than and 50% of the volume of the sampled particles being smaller than the recited Dv50 value. Particle size is determined herein by laser diffraction.

[0033] The term "aqueous lubricating composition" as used herein refers to that composition which actually contacts the metallic substrate. As is known in the art, such contacting can occur in a so-called "bath" which is shaped, sized and disposed to enable at least part of the substrate to be immersed therein. The bath should moreover be sized to allow for movement of the aqueous lubricating composition around and throughout the loaded substrate, which movement can be further enhanced with recirculation and / or ultrasonics. The pH of the composition within the bath, the temperature of the bath, and contact time of the substrate are result effective variables which should be monitored either manually or automatically, whenever possible.

[0034] As used herein, the term "equivalent (eq.") relates, as is usual in chemical notation, to the relative number of reactive groups present in the reaction.

[0035] The term "solid lubricant" as used herein refers to material that is able, in the solid state, to reduce friction between two surfaces sliding against each other.

[0036] The term "binder" is to be understood as any component having the property of introducing cohesion to the composition in which it is incorporated and which makes it possible to provide mechanical characteristics to the said formulation, such as but not limited to compressive strength, tensile strength and adherence.

[0037] The term "hydraulic binder" is to be understood as any binder ingredient which has the property of becoming hydrated in the presence of water, the hydration of which ingredient makes it possible to obtain a solid having mechanical characteristics. The term "hydraulic binder" also denotes hydric binders.

[0038] As used herein, the term "metallic material" means a pure metal, a metal alloy or a metal composite. As used herein, the term "alloy" refers to a substance composed of two or more metals or of a metal and a non-metal which have been intimately united, usually by being fused together and dissolved in each other when molten. The term "X alloy" therefore denotes an alloy of which the metal X is the majority constituent component and wherein X will generally comprise at least 50 wt.% - more typically at least 60 wt.% or at least 70 wt.% - of the alloy, on a metals basis.

[0039] As used herein, the term "inert gas" refers to a gas that is chemically non-reactive under the conditions of use. These gases have a stable electron configuration and do not readily form compounds with other elements or molecules. Inert gases are often used in various processes to create an environment that prevents unwanted chemical reactions, such as oxidation or combustion. Common examples of inert gases include helium, argon, neon, krypton, xenon, and nitrogen.

[0040] As used herein, "(meth)acryl" is a shorthand term referring to "acryl" and / or "methacryl". Thus the term "(meth)acrylamide" refers collectively to acrylamide and methacrylamide.

[0041] The present compositions are defined herein as being "substantially free" of certain compounds, elements, ions or other like components. The term "substantially free" is intended to mean that the compound, element, ion or other like component is not deliberately added to the composition and is present, at most, in only trace amounts which will have no (adverse) affect on the desired properties of the coating. An exemplary trace amount is less than 1000 ppm by weight of the composition. The term "substantially free" encompasses the term "free", the latter term indicating those embodiments where the specified compound, element, ion, or other like component is completely absent from the composition or is not present in any amount measurable by techniques generally used in the art.DETAILED DESCRIPTION OF THE INVENTION

[0042] Referring back, the present disclosure provides an aqueous lubricating composition comprising: a) inorganic particulate solid lubricant; b) an inorganic binder comprising: b1) an alkali metal silicate in the dissolved state; and / or, b2) particulate γ-aluminium oxide; c) at least one dispersant; d) at least one base; and, water.a) Inorganic Particulate Solid Lubricant

[0043] The aqueous lubricating composition of the present disclosure comprises an inorganic particulate solid lubricant.

[0044] The composition may conventionally comprise, based on the weight of the composition, from 1 to 5 wt.% of a) said inorganic particulate solid lubricant. For example, the composition may comprise from 2 to 5 wt.% or from 3 to 5 wt.% of a) said inorganic particulate solid lubricant, based on the weight of the composition.

[0045] There is no particular intention to limit the shape of the particles which may be employed as the inorganic particulate solid lubricant: particles that are fibrous, acicular, spherical, ellipsoidal, cylindrical, bead-like, cubic or platelet-like may be used alone or in combination. Moreover, it is envisaged that agglomerates of more than one particle type may be used.

[0046] There is furthermore no particular intention to limit the size of the particles employed as the inorganic solid lubricant. However, the inorganic particulate solid lubricant may conventionally have a median volume particle size (Dv50), as measured by laser diffraction, of from 0.1 to 50 µm, for example from 0.1 to 20 µm or from 0.1 to 10 µm.

[0047] Exemplary inorganic particulate solid compounds, which may be used alone or in combination as constituent a), include: brucite, montmorillonite; mica; muscovite; talc (hydrated magnesium silicate); molybdenum disulphide; tungsten disulphide; titanium disulphide; zirconium disulphide; molybdenum diselenide; tungsten diselenide; titanium diselenide; zirconium diselenide; molybdenum ditelluride; tungsten ditelluride; titanium ditelluride; zirconium ditelluride; graphite; graphite fluoride; cerium fluoride; calcium fluoride; carbon fibers; carbon black; silicon carbide; silicon nitride; barium oxide; zinc oxide; sodium borate; and, boron nitride.

[0048] Preferably, constituent a) comprises at least one compound selected from the group consisting of: molybdenum disulphide; tungsten disulphide; talc; calcium fluoride; cerium fluoride; and, boron nitride.

[0049] In an important embodiment, constituent a) of the aqueous lubricating composition comprises or consists of boron nitride. Good results have been obtained where constituent a) comprises or consists of boron nitride having a median volume particle size (Dv50) of from 0.1 to 10 µm.b) Inorganic binder

[0050] The aqueous lubricating composition of the present disclosure comprises b) an inorganic binder comprising: b1) an alkali metal silicate in the dissolved state; and / or, b2) particulate γ-aluminium oxide. For completeness, it is preferred that b) said inorganic binder comprises both of b1) and b2).

[0051] The composition may conventionally comprise, based on the weight of the composition, from 1 to 5 wt.% of b) said inorganic binder. For example, the composition may comprise from 1 to 4 wt.% or from 1 to 3 wt.% of b) said inorganic binder, based on the weight of the composition.

[0052] The alkali metal silicate may be represented by the formula (M 2 O) x ·(SiO 2 )y, wherein: M is the alkali metal; and, (y / x) defines the molar ratio of M 2 O to SiO 2 . The alkali metal (M) is herein typically selected from the group consisting of: lithium; potassium; and, sodium.

[0053] It is preferred that the alkali metal silicate is sodium silicate and, more particularly, sodium silicate of the formula (Na 2 O) x ·(SiO 2 ) y , wherein (y / x) is from 1.0 to 3.8. In an important embodiment, the alkali metal silicate is sodium silicate of the formula (Na 2 O) x· (SiO 2 ) y , wherein (y / x) is from 3.0 to 3.6 or from 3.2 to 3.5. Reference may be made to sodium silicate having CAS Registry Number 1344-09-8 and CAS Registry Number 1344-00-9.

[0054] The term "γ-aluminium oxide" (γ-Al 2 O 3 , γ-alumina) reference aluminium oxide which is substantially in the gamma crystal form, as determined by x-ray crystallography. The γ-aluminium oxide having utility in the present disclosure is desirably characterized by a medium volume particle diameter (Dv50) of from 10 to 50 nm, for example from 10 to 30 nm as determined by laser diffraction. Independently of, or additional to this particle size characterization, the γ-aluminium oxide may have a surface area of from 50 to 500 m 2< / g, preferably from 100 to 450 m 2< / g as determined by Brunauer Emmett Teller (BET) adsorption analysis in accordance with ASTM D1993-03.c) Dispersant

[0055] The aqueous lubricating composition of the present disclosure comprises from 0.1 to 5 wt.%, based on the weight of the composition of c) at least one dispersant. The aqueous composition may preferably comprise from 0.5 to 2.5 wt.%, for example from 0.5 to 2 wt.% of c) said least one dispersant.

[0056] The term "dispersant" as used herein refers to a compound that promotes uniform separation of colloidal particles and that does not promote foaming. In certain embodiments, the total amount of dispersant c) included in the composition should be from 5 to 40 wt.%, for example from 10 to 40 wt.% of the total amount by weight of components a) and b).

[0057] A dispersant may in certain embodiments be capable of absorbing liquid - such as, but not limited to, water - of physically swelling and thereby altering the liquid viscometric and flow properties. A dispersant may therefore also function as a thickening agent and serve to keep the particulate components of the aqueous composition - in particular the solid lubricant - in a dispersed form, typically by creating a continuous phase matrix. The dispersant may further function to modify the drying characteristics of the composition.

[0058] It is mentioned, in particular, that the or each dispersant included in the composition may be thixotropic. In accordance with its standard definition, a thixotrope is a substance which - either per se or when dispersed in solvent, herein water - exhibits a viscosity that decreases when a stress is applied, such as when stirred.

[0059] Without intention to limit the present invention, said at least one dispersant should be selected from the group consisting of: carboxyl vinyl polymers; polyvinylpyrrolidone (PVP) polymers and copolymers, such as PVP / vinyl acetate co-polymers; polycarboxylates; cellulose derivatives; non-cellulosic polysaccharides, such as arabinogalactans, alginate, pullulan, chitin, chitosan, guar gum, gum tragacanth, gum arabic, agar, carrageenan, xanthan gum, gellan, welan gum, rhamsan gum, curdlan gum, scleroglucan gum and tamarind gum; and, proteins, such as caseine, collagen and albumin.

[0060] It is preferred herein that constituent c) comprises at least one cellulose derivative. The term "cellulose derivative" references a cellulose of which the constituent hydroxy groups have been reacted with a suitable reagent. For instance, at least a fraction of the hydroxyl groups may have been acylated, esterified, etherified or grafted to. Exemplary cellulose esters having utility herein, alone or in combination, include: cellulose acetate; cellulose butyrate; cellulose propionate; cellulose nitrate; cellulose sulfate; cellulose phosphate; cellulose acetate propionate; cellulose acetate butyrate; and, cellulose acetate phthalate. Exemplary cellulose ethers, having utility herein, alone or in combination include: carboxymethylcellulose; methylcellulose; ethylcellulose; hydroxyethylcellulose; hydroxypropylcellulose; hydroxybutylcellulose; and, ethoxymethylcellulose. Further exemplary cellulose derivatives, having utility herein alone or in combination, include celluloses grafted with styrene, (meth)acrylic acid, (meth)acrylate, ε-caprolactone, lactide and glycolide. It is noted, for completeness, that combinations of distinct cellulose derivatives - such as combinations of cellulose ethers and cellulose ester - may have utility in the present disclosure.

[0061] In an embodiment of the present disclosure, constituent c) comprises at least one compound selected from the group consisting of: carboxymethycellulose (CMC); carboxy-hydroxymethylcellulose; ethoxymethylcellulose; hydroxyethylcellulose; and, hydroxypropylcellulose. In a particularly preferred embodiment, constituent c) comprises at least one carboxymethyl cellulose.

[0062] A preferred carboxymethyl cellulose may be characterized by at least one of: a viscosity of from 100 to 10000 mPa.s when added to water at a 2 wt.%, as determined at 25°C; and, a substitution of from 0.50 to 0.95 carboxymethyl groups per anhydroglucose unit. Suitable commercially available carboxymethyl celluloses include 9M31F, 9M8F, and 7LF available from Aqualon Company.

[0063] In further embodiment of the present disclosure, which is not mutually exclusive to the provision of cellulose derivatives therein, constituent c) comprises at least one polycarboxylate polymer. The or each polycarboxylate polymer may be unmodified but is preferably hydrophobically modified. Modification by the incorporation of linear alkyl side chains may be mentioned in particular in this regard. For completeness, the term polycarboxylate polymer includes the salts thereof, of which alkali metal salts may be mentioned as being exemplary.

[0064] Preferably constituent c) comprises at least one polycarboxylate polymer having a weight average molecular weight of from 1000 to 200000 daltons, for example from 1000 to 100000 daltons or from 1000 to 20000 daltons. Independently of, or addition to this molecular weight preference, it is preferred that the or each polycarboxylate polymer is characterized by an equivalent weight per carboxylate group of from 25 to 500 g / eq., for example from 25 to 250 g / eq. or from 25 to 150 g / eq.

[0065] Exemplary polycarboxylate polymers may be selected from the group consisting of: poly(meth)acrylates; polymaleates; polyaspartates; polylactates; polyitaconates; copolymers of the aforementioned polymers; and, mixtures thereof. A preference may be noted for the use of polyacrylate polymers and more particularly hydrophobically modified polyacrylate polymers. Commercial examples of suitable polyacrylate polymers include those sold under trade names: Carbopol ®< , available from Lubrizol.; Acrysol ®< ICS-1, available from Dow; and, Sokalan ®< , available from BASF.d) Base

[0066] In order to provide stability and rust resistance, the aqueous lubricating composition of the present disclosure comprises d) at least one base. For example, the aqueous composition may comprise, based on the weight of the composition, from 0.1 to 5 wt.% of d) said at least one base. And the aqueous lubricating composition may preferably comprise from 0.5 to 2.5 wt.%, for example from 0.5 to 2 wt.% of d) said least one base, based on the weight of the composition.

[0067] In certain embodiments, which are not intended to be mutually exclusive of the preferred weight ranges given above, the added amount of base should be such that the aqueous lubricating composition has a pH of from 7 to 10, for example from 7 to 9.

[0068] Typically the or each base included in the composition will be selected from the group consisting of: alkali metal alkoxides; ammonia; quaternary ammonium hydroxide compounds having the general formula (NR a< 4 ) +< (OH) -< , wherein each R a< is independently selected from C 1 -C 4 alkyl; aliphatic, aromatic or mixed aliphatic-aromatic monoamines having the general formula N(R b< )(R c< )(R d< ) wherein: R b< is C 1 -C 12 alkyl, C 1 -C 12 hydroxyalkyl, C 2 -C 12 alkoxyalkyl, C 3 -C 18 cycloalkyl, C 2 -C 12 alkenyl, C 6 -C 10 aryl, C 7 -C 18 aralkyl or C 7 -C 18 alkylaryl; and, R c< and R d< are independently selected from hydrogen, C 1 -C 12 alkyl, C 1 -C 12 hydroxyalkyl, C 2 -C 12 alkoxyalkyl, C 3 -C 18 cycloalkyl, C 2 -C 12 alkenyl, C 6 -C 10 aryl, C 7 -C 18 aralkyl or C 7 -C 18 alkylaryl; aliphatic, aromatic or mixed aliphatic-aromatic polyamines wherein two or more amino groups - N(R c< )(R d< ), which amino groups may be the same or different and of which R c< and R d< are as defined above, are linked by an alkylene, hydroxyalkylene, alkoxyalkylene, cycloalkylene, alkenylene, arylene, aralkylene or alkylarylene group; C 1 -C 9 heterocyclic amines; C 1 -C 9 heteroaryl amines; basic amino acids, such as arginine and lysine; and, amino sugars.

[0069] Suitable alkali metal alkoxides will conventionally be selected from aliphatic, aromatic or araliphatic alkoxides of lithium, sodium or potassium. Non-limiting examples thereof are lithium, sodium or potassium methoxide, ethoxide, n-propoxide, isopropoxide, n-butoxide, sec-butoxide, tert-butoxide, n-pentoxide, isopentoxide, hexoxide, amyl alkoxide, 3,7-dimethyl-3-octoxide, phenoxide, 2,4-di-tert-butylphenoxide, 2,6-di-tert-butylphenoxide, 3,5-di-tert-butylphenoxide and 2,4-di-tert-butyl-4-methylphenoxide. Preference is given to using the aliphatic (C 1 -C 4 )alkoxides, in particular methoxides, ethoxides, n-propoxides, isopropoxides, n-butoxides, sec-butoxides and tert-butoxides of sodium, potassium or lithium.

[0070] Without intention to limit the present disclosure, suitable basic amines - which may be included alone or in combination in the aqueous lubricating compositions - include: methyl amine; dimethylamine; trimethylamine; ethyl amine; diethylamine; triethylamine; cyclohexylamine; dimethylcyclohexylamine; ethanolamine; 2-(diethylamino)ethanol; N,N-dimethylethanolamine, 2,2'-dihydroxydiethylamine (diolamine); N-methylpiperidine; pyridine; 2,6-dimethylpyridine; 2,4,6-trimethylpyridine; quinoline; piperazine; pyrrolidone; 1-(2-hydroxylethyl)pyrrolidine; morpholine; N-methylmorpholine; 4-(2-hydroxyethyl)morpholine; bis(2-(N,N'-dimethylamino)ethyl)ether; bis-(t-butylaminoethyl)ether, 1,2-bis-(t-butylaminoethoxy)ethane; 1,2-bis-(t-butylaminoethoxyethoxy)ethane; bis[2-(isopropylamino)propyl]ether; 1,2-[2-isopropylamino)-propoxy]ethane; aniline; N-methylaniline; 4-methylaniline; 4-hydroxylaniline; pyrrole; pyrimidine; imidazole; quinazoline; purine; pyrazole; and, triazole.

[0071] In an important embodiment, the composition may comprise ammonia (NH 3 ) as a base, either independently or in combination with other of the listed bases. For completeness, the constituent weight of ammonia included in the composition is to be calculated on the basis of NH 3 . The ammonia will be present in the aqueous compositions of the present disclosure as an ammonia solution NH 3 (aq) which encompasses weakly basic solutions of ammonia in water which may referred to in the art as ammonium hydroxide, ammonia water, ammonia liquor, aqua ammonia, aqueous ammonia, or simply ammonia. While the term "ammonium hydroxide" suggests a base with the composition [NH 4 +< ][OH -< ], it is virtually impossible to isolate samples of NH 4 OH, insomuch as these ions do not comprise a significant fraction of the total amount of ammonia in an ammonia solution, except in the case of extremely dilute ammonia solutions.e) Biocidal Agent

[0072] The aqueous lubricating composition may in certain circumstances comprise e) a biocidal agent. Typically the aqueous lubricating composition may comprise, based on the weight of the composition, from 0 to 1 wt.% of e) said biocidal agent. In certain exemplary embodiments, the aqueous lubricating composition comprises from 0.05 to 0.5 wt.% or from 0.05 to 0.2 wt.% of e) said biocidal agent, based on the weight of the composition.

[0073] The biocidal agent acts to destroy, deter, render harmless or exert a controlling effect on microorganisms within the composition and on the substrates to which the composition is applied. The biocidal agent may be formaldehyde-based or non-formaldehyde, the former group including compounds which hydrolyze to formaldehyde.

[0074] Exemplary biocidal agents, which may be used alone or in combination in the present composition, include: triazine compounds, such as 1,3,5-tris-(2-hydroxyethyl)hexahydro-s-triazine, 1,3,5-tris-(3-hydroxypropyl) hexahydro-s-triazine, 1,3,5-tricyclohexylhexahydro-1,3,5-triazine, N-cyclopropyl-1,3,5-triazine-2,4,6-triamine and trimethyl-1,3,5-triazine-1,3,5-triethanol; dithiocarbamates; iodopropynylbutylcarbamate; 4,4-dimethyloxazolidine; 7-ethyl bicyclooxazolidine; bicyclic oxazolidines; 4-(2-nitrobutyl)-morpholine; 4,4'-(2-ethyl-2-nitrotrimethylene)dimorpholine; N,N'-Methylene-bis-morpholine; 1,2-benzisothiazolin-3-one; 2-methyl-4-isothiazolin-3-one; 5-chloro-2-methyl-4-isothiazolin-3-one; 2-methyl-4-isothiazolin-3-one; n-butyl benzisothiazolinone; octylisothiazolinone; dichloro-octylisothiazolinone; dibromo-octylisothiazolinone; 2-bromo-2-nitro-1,3-propanediol; phenolics, such as o-phenylphenol and p-chloro-m-cresol and their corresponding sodium and / or potassium salts; sodium pyrithione; zinc pyrithione; 1-(3-chloroallyl)-3,5,7-triaza-1-azoniaadamantane chloride; chlorothalonil; carbendazim; diiodomethyltolylsulfone; 2,2-dibromo-3-nitrilopropionamide (DBNPA); glutaraldehyde; ethylenedioxy methanol; phenoxyethanol; tetramethylol acetylenediurea; 2,6-dimethyl-m-dioxan-4-ol acetate; dimethylol-dimethyl-hydantoin; and, tris(hydroxymethyl)nitromethane. A preference may be noted for the use of a biocidal agent comprising at least one triazine compound.Adjunct Ingredients

[0075] The aqueous lubricating compositions of the present disclosure may further comprise adjuvants and additives that can impart improved properties to these compositions. The adjuvants and additives may, for instance, impart one or more of: enhanced boundary lubrication; reduced drying time; reduced corrosiveness; improved stability; and, longer shelf-life of the compositions. Such adjuvants and additives can be used in such combination and proportions as desired, provided they do not adversely affect the nature and essential properties of the composition. While exceptions may exist in some cases, these adjuvants and additives should not in toto comprise more than 5 wt.% of the total weight of the aqueous lubricating composition.

[0076] Included among such adjuvants and additives are: oils; anti-wear additives; corrosion inhibitors; antioxidants; free fatty acids, which may act to create a reacted layer for boundary lubrication; optical brighteners, in particular where confirmation of deposition of the solid lubricants under illumination may be required; and, tackifiers.

[0077] The addition of oils may serve to form an oily surface on the substrate surface after drying of the aqueous compositions and can compensate for reduced lubricating performance in those regions of the workpieces that are characterized by non-uniform film deposition of the solid lubricant. Further, in those embodiments of the composition where the aqueous lubricating composition is applied at an elevated temperature, this is typically effected by heating the lubricant with steam tubes: the addition of oil to the aqueous lubricating composition can inhibit adhesion of the solid particulate lubricant to the heating tubes.

[0078] The oils may be used alone or in combination and may be selected from mineral oils, animal oils, animal fats, plant oils and synthetic oils. However, the or each added oil should typically be characterized by at least one of and preferably all of: a flash point in the range from 150 to 300°C; a melting point of from -20 to 20°C; and, a viscosity of from 5 to 100 centistokes stokes as determined at 40°C.

[0079] A melting point in excess of 20°C can lead to a diminished emulsifiability and re-emulsifiability by the oil in the waterborne lubricant and thus to a tendency for treatment bath stability to be reduced. An oily component having a melting point below -20°C will typically have a reduced flash point. Likewise, a viscosity below 5 centistokes will typically be associated with a low flash point, which leads to the post-working generation of large amounts of gas and hence an ignition risk. Equally, when the viscosity of the added oil is below 5 centistokes, slip between solid lubricant particles is diminished and the lubrication performance tends to decline. Conversely, a viscosity in excess of 100 centistokes usually leads to a diminished emulsifiability and re-emulsifiability of the oily component in the waterborne lubricant.

[0080] Tackifiers are utilized to improve transfer rates of the lubricant and ensure the applied and dried lubricating composition remains in place to provide the needed lubrication. The or each tackifying resin included in the composition is preferably characterized by: a softening point of from 70 to 150°C.; and, a viscosity at 150°C of less than 2000 Pa.s.

[0081] Exemplary tackifying resins which may be used alone or in combination in the present invention include: aliphatic and cycloaliphatic petroleum hydrocarbon resins; aromatic petroleum hydrocarbon resins and the hydrogenated derivatives thereof; aliphatic / aromatic petroleum derived hydrocarbon resins and the hydrogenated derivatives; polycyclopentadiene resins, hydrogenated polycyclopentadiene resins and aromatic modified hydrogenated polycyclopentediene resins; terpenes, aromatic terpenes and hydrogenated terpenes; polyterpenes, aromatic modified polyterpenes and terpene phenolics; copolymers of α-methylstyrene and a further vinyl aromatic monomer; and, gum rosins, gum rosin esters, wood rosins, wood rosin esters, tall oil rosins, tall oil rosin esters and hydrogenated rosin esters.Preparation of the Aqueous Compositions

[0082] The aqueous lubricating compositions are formulated by simple mixing of the various components as well as any adjunct ingredients. Whilst the order of mixing of the components is not intended to be limited, that order should be selected to ensure that a stable, homogeneous dispersion is formed. For example, it may be prudent to first form an aqueous dispersion of the solid lubricants, dispersants and inorganic binder, to which dispersion is then added the further components under agitation. Alternatively, it may be advantageous for particulate components and polymeric components to be pre-prepared as independent aqueous dispersions - at a solids contents of from 45 to 60 wt.%, for example - to facilitate their admixture with other components of the compositions. Soluble components may also be added as one or more pre-prepared solution or may be added in solid form but under mixing conditions which ensure that the components are in dissolved form in the final aqueous lubricating composition.

[0083] If necessary, the aqueous lubricating compositions may be prepared well in advance of their application. However, in an interesting alternative embodiment, a concentrated composition may first be obtained by mixing components with only a fraction of the water that would be present in the composition as applied: the concentrated composition may then be diluted with the remaining water shortly before its application. It is considered that such concentrated compositions may be prepared and stored as either single-package concentrates - that can be converted by dilution with water only - or as multi-part concentrates, two or more of which must be combined and diluted to form a complete working composition according to the invention. Any dilution can be effected simply by the addition of water, in particular deionized and / or demineralized water, under mixing. The aqueous lubricating composition might equally be prepared within a rinse stream whereby one or more streams of the concentrate(s) is injected into a continuous stream of water.

[0084] Without specific intention to limit the amount of water included in the aqueous lubricating compositions, it is preferred that said compositions contain from 80 to 95 wt.%, preferably from 85 to 95 wt.% and more preferably from 90 to 95 wt.%, based on the weight of the composition, of water. In an alternative but not mutually exclusive characterization, the aqueous lubricating composition may be defined by a viscosity of from 0.005 to 1 Pa.s (50 cps to 1000 cps), as measured using a Brookfield viscometer at 25°C.Methods and Applications

[0085] Prior to applying the compositions to a metallic substrate, it is often advisable to pre-treat the relevant surfaces to remove foreign matter there from: this step can, if applicable, facilitate the subsequent adhesion of the compositions thereto. Such treatments are known in the art and can be performed in a single or multi-stage manner constituted by, for instance, the use of one or more of: an etching treatment with an acid suitable for the substrate and optionally an oxidizing agent; sonication; plasma treatment, including chemical plasma treatment, corona treatment, atmospheric plasma treatment and flame plasma treatment; immersion in a waterborne alkaline degreasing bath; treatment with a waterborne cleaning emulsion; treatment with a cleaning solvent, such as acetone, carbon tetrachloride or trichloroethylene; and, water rinsing, preferably with deionized or demineralized water. In those instances where a waterborne alkaline degreasing bath is used, any of the degreasing agent remaining on the surface should desirably be removed by rinsing the substrate surface with deionized or demineralized water.

[0086] After said cleaning and / or degreasing, the aqueous lubricating composition is applied to the substrate. The composition may be applied at ambient temperature or the temperature of the aqueous compositions may be elevated prior to application to, for instance, a temperature in the range from 30°C to 90°C, for instance from 30°C to 70°C.

[0087] To produce a double-face plated sheet, it is conventional commercially that an operating bath as hereinbefore described is prepared and the aqueous lubricating composition is applied to the substrate by, without limitation, immersion and dipping. The contact time of the aqueous lubricating composition is not critical but should be sufficient to allow the temperature of the substate to equilibrate with the temperature of the composition in the operating bath. Exemplary contact times are from 1 minute to 15 minutes, for instance from 2 to 10 minutes.

[0088] Alternative techniques which may be used to apply the aqueous lubricating composition to either a singular surface or multiple surfaces of a substrate include but are not limited to: printing, including screen printing; painting; brushing; flow coating; roll coating; wiping; air-atomized spraying; air-assisted spraying; airless spraying; high-volume low-pressure spraying; and, air-assisted airless spraying.

[0089] At the conclusion of the application step, the article is dried using, for instance, ambient air drying, circulating warm air, forced air drying or infrared heating. The surface temperature of the substrate is controlled during drying: the peak metal temperature (PMT) need not exceed 150°C and should, more particularly, be in the range from 100 to 125°C, for example 100 to 120°C.

[0090] The above-described treatment should yield a protective coating over the metal substrate, said coating preferably having a coating weight of from 1 to 50 g / m 2< , preferably from 1 to 40 g / m 2< or from 5 to 40 g / m 2< . The type of metal working to be performed, the degree of working and the substrate surface roughness will be determinative of the optimal thickness of the dried coating. Generally, however, when the dried coating is too thin, contact can occur between the working tools and the substrate itself and seizure will then be prone to occur. When the dried coating is too thick, a fraction of the coating may not be drawn into the interface between the working tool and the metallic substrate: this fraction would thus constitute a waste of the waterborne lubricant. Moreover, excess coating may also associated with necking and eventual breaks in the metallic substrate due to excessive slippage between the substrate and the working tool.

[0091] There is no intention to limit the base metallic substrate to which the aqueous lubricating composition may be applied. Conventionally, however, the metallic substrates will be superplastically formable of which non-limiting examples include: aluminium alloys, such as Al 2004, A17475 and 5083; titanium alloys, such as Timetal 550 (IMI550), Ti 6-4, Ti 3-2.5, Ti 6-6-2, Ti 6-2-4-2, Ti 6-2-4-6, and Ti 6-2-2-2-2; microduplex stainless steels; and Inconel alloys, such as Inconel 625. It will be recognized that each material has characteristic properties, such as ideal temperatures and strain rates for superplastic forming, flow stresses for superplastic forming and mechanical properties after forming.

[0092] The initial form of the metallic substrate to which the aqueous lubricating composition is applied also need not be limited, save to say that the form must be appropriate for tools to be utilized and the target shape or form to be attained after forming. Whilst more complex initial forms are certainly not precluded, conventional stock forms in which the metal and alloy substrates may be provided include: sheets; plates; cuboids; spheres; annuli; solid cylinders; tubes; and, wires.

[0093] As noted above, the present disclosure also provides for the use of the aqueous waterborne lubricant composition or the dried film obtained therefrom in the forming of metallic substrates, in particular the superplastic forming or quick plastic forming of metallic substrates.

[0094] The present disclosure further provides a process for the plastic forming of a metallic substrate utilizing at least one solid metal-working tool, said process comprising the steps of: i) applying the aqueous lubricating composition as defined herein above to at least one solid surface of said metallic substrate, which surface or surfaces would, if not coated, directly contact a solid metal-working tool surface during the process; ii) drying the applied aqueous lubricating composition to form a coating on said at least one solid surface of said metallic substrate; (iii) heating the coated metallic substrate formed in step ii) to a first temperature which is from 50 to 90% of the melting temperature of the metallic substrate; iv) whilst maintaining the first temperature of the metallic material, disposing the coated metallic substrate into contact with said at least one metal-working tool and impinging a flow of pressurized inert gas onto the coated metallic substrate to plastically form the coated metallic substrate with said at least one metal-working tool; and, v) cooling the formed, coated metallic substrate and removing said substrate from the metal-working tool.

[0095] It is acknowledged that the plastic forming of the metallic substrate may be an iterative process. As such, the above-described method may include the following further steps: vi) removing the residual coating from said at least one solid surface of the formed metallic substrate formed in step v); vii) annealing said metallic substrate obtained in step vi); and, viii) repeating steps i) to v).

[0096] In an embodiment, step vi) comprises the treatment of the residual film with an alkaline degreaser. It is particularly preferred that step vi) does not comprise the treatment of the residual film with an acidic pickling liquor.

[0097] In the event that the residual coating attained is not removed prior to annealing, carbon, sulphur, phosphorus and other components of the coating may infiltrate into the metallic substrate, thereby impairing the corrosion resistance and mechanical strength of that substrate. Further, the residual coating would not present a surface to which the aqueous lubricating composition would adhere in the second (and further) iterations of step i) above.

[0098] Various features and embodiments of the disclosure are described in the following example, which is intended to be representative and not limiting.EXAMPLES

[0099] The following commercial products are used in the Examples: all ingredients not mentioned hereinbelow are obtainable from Sigma Aldrich. Carbopol EZ-3:Hydrophobically modified, crosslinked acrylic copolymer, available from Lubrizol.Finnfix 2Sodium carboxymethylcellulose dispersant, available from CP Kelko.Finnfix 10000:Sodium carboxymethylcellulose dispersant, available from CP Kelko.Acticide GR:1,3,5-tris-(2-hydroxyethyl)hexahydro-s-triazine, biocidal agent, available from Thor.Boron nitride S1-SF:Particulate boron nitride solid lubricant, available from Esk.γ-alumina:Available from Merck.

[0100] Aqueous lubricating compositions were prepared by mixing the ingredients given in Table 1 herein below. Whilst ammonia is added and mixed as an aqueous solution (25%, aq.) and sodium silicate is added and mixed as an aqueous solution (40%, aq.), the values in Table 1 reflect the amount of each ingredient on a compounds basis. Table 1Ingredient Example 1 (wt.%) Example 2 (wt.%) Example 3 (wt.%) Comparative Example 1 (wt.%) Water93.7292.4093.0694.36Boron nitride S1-SF3.643.643.643.64Carbopol EZ-31.151.151.151.15Blend of Finnfix 2, Finnfix 100000.450.450.450.45Ammonia (NH 3 .)0.300.300.300.301,3,5-tris-(2-hydroxyethyl)-s-triazine0.100.100.100.10Sodium silicate0.640.32γ-alumina1.960.98

[0101] The aqueous compositions of Table 1 were independently applied to aluminium alloy (Al3003) panels by bar coating to a wet film thickness of 75 microns. The panels were then placed in an oven set at 100°C for 60 minutes to evaporate the constituent water and 30 minutes at 450°C to remove the organic constituents. The adhesion of the dried coatings to the panels were evaluated in accordance with ASTM D3359-23 Standard Test Methods for Rating Adhesion by Tape Test. The results of this test are provided in Table 2 herein below. Table 2Tested Condition Example 1 Example 2 Example 3 Comparative Example 1 ASTM D3359 Classification1B1B2B0BEvaluation of AdhesionAcceptableAcceptableGoodPoor

[0102] In view of the foregoing description and examples, it will be apparent to those skilled in the art that equivalent modifications thereof can be made without departing from the scope of the claims.

Claims

1. An aqueous lubricating composition comprising: a) an inorganic particulate solid lubricant. b) an inorganic binder comprising: b1) an alkali metal silicate in the dissolved state; and / or, b2) particulate γ-aluminium oxide; c) at least one dispersant; d) at least one base; and, water.

2. The aqueous lubricating composition according to claim 1 comprising, based on the weight of the composition: from 1 to 5 wt.% of a) said inorganic particulate solid lubricant; from 1 to 5 wt.% of b) said inorganic binder; from 0.1 to 5 wt.% of c) said at least one dispersant; from 0.1 to 5 wt.% of d) said at least one base; from 0 to 1 wt.% of e) a biocidal agent; and, from 80 to 95 wt.% of water, wherein the composition has a pH of from 7 to 10.

3. The aqueous lubricating composition according to claim 1 comprising, based on the weight of the composition: from 2 to 5 wt.%, preferably from 3 to 5 wt.% of a) said inorganic particulate solid lubricant; from 1 to 4 wt.%, preferably from 1 to 3 wt.% of b) said inorganic binder; from 0.5 to 2.5 wt.%, preferably from 0.5 to 2 wt.% of c) said at least one dispersant; from 0.5 to 2.5 wt.%, preferably from 0.5 to 2 wt.% of d) said at least one base; from 0.05 to 0.5 wt.%, preferably from 0.05 to 0.2 wt.% of e) said biocidal agent; and, from 85 to 95 wt.%, preferably from 90 to 95 wt.% of water, wherein the composite has a pH of from 7 to 9.

4. The aqueous lubricating composition according to any one of claims 1 to 3, wherein constituent a) comprises or consists of boron nitride.

5. The aqueous lubricating composition according to any one of claims 1 to 3, wherein constituent a) comprises or consists of boron nitride having a median volume particle size (Dv50) of from 0.1 to 10 µm.

6. The aqueous lubricating composition according to any one of claims 1 to 5, wherein constituent b1) consists of sodium silicate of the formula (Na2O)x·(SiO2)y, wherein (y / x) is from 3.0 to 3.6.

7. The aqueous lubricating composition according to any one of claims 1 to 6, wherein the particulate γ-aluminium oxide has: a medium volume particle diameter (Dv50) of from 10 to 50 nm, as determined by laser diffraction; and / or; a surface area of from 50 to 500 m2 / g as determined by Brunauer Emmett Teller (BET) adsorption analysis in accordance with ASTM D1993-03.

8. The aqueous lubricating composition according to any one of claims 1 to 7, wherein constituent c) comprises at least one compound selected from the group consisting of: carboxymethycellulose (CMC); carboxy-hydroxymethylcellulose; ethoxymethylcellulose; hydroxyethylcellulose; and, hydroxypropylcellulose.

9. The aqueous lubricating composition according to any one of claims 1 to 8, wherein constituent c) comprises at least one polycarboxylate polymer.

10. The aqueous lubricating composition according to claim 9, wherein the or each polycarboxylate polymer has: a weight average molecular weight of from 1000 to 200000 daltons; and / or, an equivalent weight per carboxylate group of from 25 to 500 g / eq.

11. The aqueous lubricating composition according to any one of claims 1 to 10, wherein constituent d) comprises ammonia.

12. The aqueous lubricating composition according to claim 1 comprising, based on the weight of the composition: from 1 to 5 wt.% of a) said inorganic particulate solid lubricant, wherein said inorganic particulate solid lubricant comprises boron nitride having a median volume particle size (Dv50) of from 0.1 to 10 µm; from 1 to 5 wt.% of b) said inorganic binder, wherein said inorganic binder comprises: b1) sodium silicate in the dissolved state, said sodium silicate having the formula (Na2O)x·(SiO2)y, wherein (y / x) is from 3.0 to 3.6; and / or, b2) particulate γ-aluminium oxide having a medium volume particle diameter (Dv50) of from 10 to 50 nm, as determined by laser diffraction and a surface area of from 50 to 500 m2 / g as determined by Brunauer Emmett Teller (BET) adsorption analysis in accordance with ASTM D1993-03; from 0.1 to 5 wt.% of c) a dispersant mixture comprising: c1) at least one polyacrylate polymer a weight average molecular weight of from 1000 to 200000 daltons and an equivalent weight per carboxylate group of from 25 to 500 g / eq; and, c2) at least one compound selected from the group consisting of: carboxymethycellulose (CMC); carboxy-hydroxymethylcellulose; ethoxymethylcellulose; hydroxyethylcellulose; and, hydroxypropylcellulose; from 0.1 to 5 wt.% of d) at least one base; from 0 to 1 wt.% of e) a biocidal agent; and, from 80 to 95 wt.% of water, wherein the composition has a pH of from 7 to 10.

13. Use of the aqueous waterborne lubricant composition as defined in any one of claims 1 to 12 or the dried coating obtained therefrom in the plastic forming of metallic substrates.

14. A method of plastic forming a metallic substrate utilizing at least one solid metal-working tool process comprising: i) applying the aqueous lubricating composition as defined in any one of claims 1 to 12 to at least one solid surface of said metallic substrate, which surface or surfaces would, if not coated, directly contact a solid metal-working tool surface during the process; ii) drying the applied aqueous lubricating composition to form a coating on said at least one solid surface of said metallic substrate; (iii) heating the coated metallic substrate formed in step ii) to a first temperature which is from 50 to 90% of the melting temperature of the metallic substrate; iv) whilst maintaining the first temperature of the metallic material, disposing the coated metallic substrate into contact with said at least one metal-working tool and impinging a flow of pressurized inert gas onto the coated metallic substrate to plastically form the coated metallic substrate with said at least one metal-working tool; and, v) cooling the formed, coated metallic substrate and removing said substrate from the metal-working tool.

15. The method according to claim 14 further comprising: vi) removing the residual coating from said at least one solid surface of the formed metallic substrate formed in step v); vii) annealing said metallic substrate obtained in step vi); and, viii) repeating steps i) to v).

Images