WO1997012722A1

WO1997012722A1 - Method and apparatus for working metals

Info

Publication number: WO1997012722A1
Application number: PCT/GB1996/002284
Authority: WO
Inventors: Timothy James Leeman; Paul Scales
Original assignee: Croda International Plc
Priority date: 1995-10-03
Filing date: 1996-09-18
Publication date: 1997-04-10
Also published as: GB9520197D0; GB2305934A; GB2305934B; EP0853526A1

Abstract

A recirculating flow of a non-micellar milky white water-in-oil emulsion is provided to a metal workpiece (4) being subjected to a working operation in a work station (1), the fluid (20) returning from the work station (1) being collected in a tank (8) and its water content replenished by simple addition (21) of water thereto. The direction of circulation of fluid (20) is indicated by arrows (30). During recirculation, the fluid preferably passes through filters (17, 13) to a clean storage tank (14).

Description

METHOD AND APPARATUS FOR WORKING METALS

This invention relates to a method and apparatus for working metals.

In metalworking and metalforming operations, such as cutting, grinding, drawing, blanking, broaching, slotting, milling, threading, drilling, tapping, turning, forming, lobbing, pressing, reaming, spinning, and in rolling, it is usual to use a lubricat ing/coo1 ing fluid. Such fluids serve a number of purposes including, of course, cooling the workpiece and providing lubrication. They also assist in removal of swarf, wear debris and other detritus and generally promote the overall operation.

Because of their obvious suitability as lubricants, neat oils have been used as meta1-working fluids but they are not generally good at cooling the workpiece. In addition, their use can constitute a fire hazard. To overcome these problems, oil-in-water emulsions have been used, and whilst these can provide much better cooling and a much lower fire risk, they are not generally as satisfactory at lubricating. As an alternative, certain water-in-oil emulsions (invert emulsions) have been developed to provide better lubrication whilst at the same time giving good cooling and low fire risk. Particular such emulsions for certain metal working operations are described in our GB-A- 2249556.

When water-in-oil emulsions are used as metal working fluids, quite often water is lost from the emulsions. For example, some of the water may evaporate or be driven off as steam. It is not possible to replace water lost from conventional invert emulsions simply by adding water to the used emulsion, since the added water is not taken up in the emulsion but remains as a separate continuous phase. This is a serious drawback to the use of water-in-oil emulsions since it is desirable for economic and other reasons to recirculate the fluids on a continuous basis without any significant change in their constitution

GB-A-1599715 describes a way of overcoming this problem. Water-in-oil emulsions are used in which the emulsion is micellar, and these emulsions after use can be replenished by adding water which will be taken up in the emulsion. Thus, these micellar emulsions can be used on a recirculating continuous basis by arranging to add water from time to time. In order to form a micellar emulsion of the type used in GB-A-1599715 , it is essential to use emulsifiers capable of providing a stable micellar emulsion These emulsifiers cause the water effectively to be solubilized in the oil. This gives rise to a problem in the use of these emulsions for certain metal working operations .

When metal is rolled, the fluid forms a surface coating on the rolled product. This coating is very important, in that it provides protection. For example on ferrous metals, it provides protection against corrosion However, micellar water-in-oil emulsions of the type described in GB-A-1599715 provide a surface coating which is relatively hydrophilic and thus does not provide such good protection, for example against corrosion. Thus, the surfactants used in the emulsion remain in the essentially oily surface coating, and provide hydrophilicity.

We have now found that certain water-in-oil emulsions can be used as metal working fluids on a continuous recirculation basis, in that they can have their water content easily replenished, and yet do not provide a hydrophilic coating on the worked metal.

According to the present invention, there is provided a method of working metal (by which we also include metal forming operations) which comprises subjecting a metal workpiece to a working operation; providing a recirculated flow of a non-micellar, milky-white, water-in-oil emulsion to the working area; collecting the emulsion and replenishing the water-conten thereof by simple addition of water; and recirculating the replenished emulsion.

In another aspect, the invention provides a work station for working a metal workpiece, which station comprises

(a) metal working means;

(b) a container for metal working fluid;

(c) means for supplying make-up water to the container;

(d) a pump for recirculating said fluid: and

(e) conduit means for recirculating said fluid from said container to the metal working means and back to the container.

Whilst the method and apparatus of the present invention are broadly applicable to all metalworking operations on both ferrous and non-ferrous (eg. aluminium- containing) materials, they are especially useful for rolling ferrous materials.

Metal-working stations often have hydraulically operated parts, and moving parts which have to be lubricated. In accordance with a further feature of the present invention, we have found that the water-in-oil emulsions used in the present invention can also be used as the hydraulic fluid or to lubricate the moving parts (e.g. bearings) , or for both these purposes. This is highly advantageous since it overcomes prior art problems of contamination of a metal-working fluid by lubricating oil and/or hydraulic fluid.

It is important in the present invention that the emulsion is such that it will take up replenishing or condensed water very simply. By this we mean that it is unnecessary to repeat the high shear technique used originally to create the emulsion from the oil and water components. For replenishment, water is added to the water- depleted emulsion and, with minimal treatment, it is readily accepted and the original emulsion state is regained. For most purposes, passage through the recirculating pump for example will suffice to cause the added water to be emulsified, but the replenishment water can be added in other ways if desired, for example to the sump or directly onto the emulsion surface at the storage tank. The rate of water addition will, of course, depend on the operating circumstances and, in particular, on how much water replenishment is required but, bv way of example, a water addition rate of around 201/mιnute to 15m^ of fluid recirculating at about 5001/minute might be used.

As will be described hereafter, the emulsions used in the method of the invention contain, in their initial state, from 207. to 807. more preferably from 30 to 607. by weight water. In use, the water content can drop to less than 57. of the original, and still be made up by directlv adding replenishment water. It is preferred to monitor the water-content of the emulsion periodically during use to keep the water content in the desired range.

The emulsions which we prefer to use in the present invention, described in detaii hereinafter, can be filtered without destruction of the emulsion. This is an unusual feature for water-in-oil emulsions. It is highly advantageous in that it enables the removal of solid debris from the recirculating fluid. This filtration can be effected by, for example, paper catπdge filters to 5 microns, flat bed paper of cloth filters (pressure or vacuum type) , magnetic drum filters, or diatomaceous earth filters.

The emulsifiers used in the emulsions employed in the present invention will support water-in-oil emulsions but not oil-in-water emulsions, in the amount they are u s e d .

One preferred invert emulsion metalworking fluid for use in the present invention is described in GB-A- 2249556. This fluid comprises a continuous oil phase and a water phase dispersed in the oil phase, in which the particle size of the water phase is controlled to a fine distribution but the emulsion is non-micellar and of a milky white appearance. Such an emulsion can be made bv introducing water phase components into oil phase components and urging the water phase components to pass through a shear screen to establish a fine particle size, in the presence of a suitable emulsifier. Bv "fine particle size" we mean having a significant proportion of the volume of the water contained in particles of less than 1 micron in diameter, as measured with laser techniques.

The preferred emulsion preferably generally comprises 40 to 507. oil, 35 - 507. water, about 57. ethylene glycol, about 27. emulsifier (e.g. sorbitan ester) and up to 37. of various other additives such as biocides and corrosion inhibitors. The viscositv of the final emulsion is controlled by selecting the viscosity of the base oil blend and the emulsion particle size. The distribution is controlled by use of a fine, high shear screen during the mixing process and conducting the mixing so that a significant proportion of the volume of the water is distributed in fine, sub-micron particles. The mixing process is described later herein.

In the emulsions which we prefer to use, the majority of water particles are less than 1 micron in size. There are significant percentages of particles, about 207. by volume, having a particle diameter less than 0.4 microns or more generally in the range of 0.1 to 0.4 microns. The volume percent of these small particles will vary with percentage water composition in the emulsion, but it is preferred to have at least 107. of the water volume in particles of less than 0.4 microns diameter. The compositions of invert emulsions preferred for use in the invention, generally comprise the following components :

A. a continuous oil phase;

B. an emulsifier; and

C . a water phase .

Optionally, they may also include:

D. anticorrosion and metal passivation agents;

E. lubricity additives to augment the antifriction and antiwear properties of the oil phase; and

F. other additives, for example of a conventional type for emulsion systems.

The preferred emulsions are now described in detail, with each component type described in turn. The following abbreviations are used in the description: KV - Kinematic viscosity determined in accordance with

ASTM D-445. CA - 7. of aromatic carbon atoms 0^ - 7. of naphthenic carbon atoms Cp - 7. of paraffinic carbon atoms

The C , CN and Cp values herein are determined in accordance with ASTM D-2140. Percentages in the following description are by weight unless otherwise indicated.

A. The continuous oil phase

The oil phase may be based upon mineral oil or its substitutes (po1yalphaolefines , eg. butenes, etc) , natural (eg. vegetable, animal, fish oils) and synthetic esters, or upon a blend of two or more thereof. The oil phase provides the lubricity of the system and is desirably selected for its contribution to the reduction of friction eg. at the tool face or in the roll bite, its thermal stability, its hydrolytic stability, its compatabi 1 i ty with the emulsifier system, the final viscosity of the system, and the compatabi 1 i ty with post-processing treatments. The preferred oils are blends of mineral oils and esters, optionally in the form of blends of mineral oils. We have found those possessing KV values of from 1 to 20 centistokes (1-20 x 10^~6 m2/s) at 40°C to be particularly suitable, and more desirably those with a KV of 3 to 20 cSt (3-20 x 10^-6 m²/s), especially 5 to 15 cSt (5-15 x 10^-6 m²/s) . Most preferred are oils with a KV at 40°C of from 4 to 9 cSt (4 to 9 x IO^"6 m²/s) and especially of from 7-9 cSt, e.g. 8 cSt (7-9 and 8 x IO^-6 m²/s) .

The viscosity of the oil is not critical to the invention and, for example, a viscosity of greater than 20 cSt (20 x 10^~6 m /s) may be desired, for example, up to 60 cSt (60 x IO^-6 m²/s) .

We have further found that mineral oils with a C^ from 1 to 10, Cjvj from 15 to 50 and C_p from 40 to 80 are very suitable. More preferably the oils have a C^ value of from 2 to 5, a Cpj value of from 40 to 50 and a C_p value of from 45 to 60. Most preferred oils are with a C^ value of about 1 to 3 (e.g. 2), a CM value of about 44 to 48 (e.g. 46) and a Cp value of about 50 to 54 (e.g. 52) . From a technical point of view, naphthenic oils (e.g. with a CM, value of 40 or more) are particularly desirable because they are considered to improve emulsion stability, but cost factors may require that an oil with lower naphthenic content be used. In general, it would appear that C^, CM and C_p values are less important than the KV and aniline point of an oil.

Suitable mineral oils generally have an aniline point of from 75 to 120°C, more preferably of from 80 to 90°C and most preferably of 83 to 86°C, especially 84°C. The aniline point is a measure of the solvency of the oil and is determined in accordance with ASTM D-611.

The oil can form up to 607. by weight of the emulsion, e.g. 10 to 607. but more preferably it will constitute from 40 to 507., of the composition.

The emulsion normally has a viscosity of from 10 to 120 cSt (10 to 120 x 10^"6 m²/s) at 40°C, more especially from 15 to 60 cSt (15 to 60 x IO^"6 m²/s) and most preferably from 20 to 50 cSt (20 to 50 x 10^"6 m²/s). The quantity and viscosity of the oil are appropriately selected to achieve the desired viscosity of the emulsion.

When the emulsions are used as hydraulic fluids, we prefer them to have a kinematic viscosity of from 10 to 70 cSt (10 to 70 x 10^~6 m²/s) . Preferably, the viscosity is no more than 60 cSt and is most desirably no more than 50 cSt; the preferred minimum viscosity is 15 cSt, more preferably 20 cSt (60, 50, 15 and 20 x 10^~6 m /s, respectively) .

B . The Emulsi fier

An emulsifier is incorporated to maintain the water phase as a homogenous dispersion of fine particles. The action of the emulsifier is to stabilise the water particles as they form, and in principle a wide range of surfactant types and surfactant blends could achieve such stabilisation, and examples of surfactants are given later. Surfactant systems which are appropriate for specific emulsions and uses may be determined empirically. The one or more surfactants used as the emulsifier system in the emulsion also aid wetting of the emulsion on the workpiece and tool, and increase the flushing ability of the fluid, for instance, in grinding operations where open-s true ture (porous) wheels are used.

The surfactants may also contribute to the anticorrosive action of the emulsion, preventing attack of the water phase on ferrous metals.

The emulsifier employed may, for example, be selected from one or more of the following types: (I) amphoteric surfactants, for example fatty acid betaine and sultaine derivatives, imidazo1 ine-carboxy1ates , sulphonated-imidazol ines , amphoteric carboxyl and aminO- glycinates and propionates, amine oxides and protein surfactants ;

(II) anionic agents, for example alkylaryl sulphonates, alcohol sulphates, ether sulphates, phosphate esters, sulphosuccinates , sulphosuccinamates , paraffin sulphonates, olefine sulphonates, taurates and isethionates, sarcosinates, fluoroalkyl carboxylates and sulphonates, and salts of fatty acids, for example sodium, potassium, calcium and zinc soaps of lauric and stearic acids;

(III) cationic surfactants, for example fatty acid amines, quaternary ammonium chlorides and quaternary i idazoline derivatives ; and

(IV) non-ionic agents, for example alkoxylates, alkyl phenol ethoxylates and propoxylates , alcohol ethoxylates and propoxylates , amine ethoxylates and propoxylates , ester ethoxylates and propoxylates , castor oil ethoxylate and propoxylate, amide ethoxylates and propoxy1ates , block copolymers of ethylene oxide and propylene oxide, alkanolamides, esters derived from mono and polyhydric alcohols and fatty acids, fluoroalkyl esters, glucosides and ethoxylated derivatives thereof, lanolin and wool wax derivatives .

We have found that blends of surfactants are preferred in order to obtain the balance of properties desired. An ester of a polyhydric alcohol is one component of a preferred blend, specifically a fatty acid ester, eg. a mono-oleate, of a polyol, eg. sorbitol. The ester of the polyhydric alcohol preferably has an acid value of 3 to 10 mgKOH/g and more preferably about 6 to 7 (e.g. 6.5) mgKOH/g, a saponification number of 130 to 180 mgKOH/g, and most preferably of 145 to 155, e.g. 150 mgKOH/g, and a hydroxyl value in the range 180 to 220 and more preferably of about 200 mgKOH/g. The ester, eg. sorbitan monooleate, is added at levels between 1 and 57., and most preferably at about 27. (e.g. 1.75 to 2.257.), of the total composition.

A further component of this surfactant blend is an ethoxylated ester of a polyhydric alcohol, principally a trioleate ester of sorbitol ethoxylated to a preferred ratio of 1 mole of ester to 15 to 25 moles, more preferably 20 moles, of ethylene oxide. Preferred are grades with acid values of up to 5 mgKOH/g and most preferably of about 2 mgKOH/g, a saponification value of 70 to 100 mgKOH/g and most preferably about 90 mgKOH/g, and a hydroxyl number ranging from 30 to 70 mgKOH/g with a value of about 45 being most suitable. The ethoxylated ester may be conveniently added at 0.5 to 27. of the formulation but a level of about 17. (e.g. 0.95 to 1.057.) is most preferred.

A sodium sulphonate is also desirably added as part of the emulsifier package. This is an oil soluble sodium salt of an alkylaryl sulphonic acid and may be conveniently carried in a mineral oil for ease of dispersion. Especially useful are blends of sodium sulphonates in mineral oil containing of from 61 to 637. sodium sulphonate.

The weight average molecular weight of the sulphonate is preferably in the range of from 400 to 600, and preferably is about 420. The SO3 content of the sulphonate is preferably in the range of from 15 to 2 . witn the most preferable SO3 level being about 197. or 207.. The sodium sulphonate normally constitutes from 0.5 to 27. but is more typically included at about 0.87. (e.g. 0.75 to 0.85^*.' by weight of the total composition.

CL The Water Phase

The water phase of the emulsion is normally present at a level of from 30 to 807. by weight of the emulsion and is preferably formulated such that it provides the desired balance of cooling, viscosity, and stability.

Generally these properties are optimised when the water forms about 35 to 507. and especially 407. of the total composition, and this is the preferred level. D. Ant icorrosion and Metal Passivation Agents

Anticorrosion and metal passivation ingredients may also be conveniently included. These are selected on the basis of their performance with the work metals and tools, their contribution to the stability of the emulsion, the viscosity of the system, and thermal stability characteristics. Another important feature is the toxicity of the additive since recent and pending legislation does not permit the use of nitrite, borates, phenols, and agents such as ni trolote tra-ace tic acid.

Suitable anticorrosives and metal deactivators are thiazole and triazole derivatives, amine and metal sulphonates (that is, salts of alkylaryl sulphonic acid) , and alkanolamines. Particularly preferred are calcium sulphonate for ferrous protection and benzotriazole as a multi-metal corrosion inhibi tor/pas s ivator . These are conveniently added at 0.01 to 5. by weight of the formulation but are incorporated preferably at levels of about 0.057. for the benzotriazole and 0.0257. for the sulphonate .

E. Lubricity Additives

Lubricity additives designed to augment the antifriction and antiwear properties of the oil component can also be used. Extreme pressure (EP) additives may be incorporated to assist in control of the coefficient of friction and load-carrying properties for bearing lubrication and in the rolling process, for example.

Some lubricants, especially those possessing bound chlorine, phosphorus or sulphur, offer high levels of lubricity by formation of a layer of solid lubricant by reaction of the additive with the metal surface. These solid lubricants remain effective at temperatures up to their melting points and are used as EP additives. By careful selection and blending of these EP additives, it is possible to formulate metal working fluids for a wide working range of materials and operations. Additives may be selected from sulphurized fatty oils, elemental sulphur, chlorinated paraffins., chlorinated oils, and sulpho- chlorinated oils, metal di thiocarbamates and phosphorodithioates.

Preferred EP additives are zinc diaryl- and dialkyIdi thio phosphates, and especially preferred is a zinc diaryldithiophosphate containing 3 to 47. zinc, 37. phosphorus and 6 to 7. sulphur. Also preferred are long chain po lysulphides and sulphurized esters.

Other lubricating additives which may also be incorporated are esters, particularly polyol esters of fatty acids, eg. trime thyloylpropane esters.

F . 0the r Additives

It may also be advantageous to add ingredients to preserve the metal working fluid in storage from the effects of frost. Accordingly, anti-freeze agents may be incorporated .

Typically, glycols may be added and a preferred anti-freeze additive is monoethylene glycol incorporated at levels of up to 107., normally 1 to 107.. but about 57. is preferred in the present case.

Although cleanliness and good housekeeping in machine shops do much to avoid bacterial and fungal infection of water based machining fluids, chemical sterilization provides a convenient safeguard against emulsion breakdown brought about by the presence of fungi and aerobic and anaerobic bacteria. Since bactericides vary in their effectiveness, they must be carefully selected. To be acceptable, a biocide must fulfil several requirements. It must produce a persistent biocidal effect under service conditions in which continuous reinfection may occur, and it must be compatible with the total emulsion, particularly with the emulsifier system. The chosen biocide or biocides must also provide acceptable toxicological hazards.

Additionally, the biocide should not significantly detract from the corrosion protection performance of the metal working fluid nor induce foaming in use.

Biocides that may be employed in this system, either solely or in blends, include oxazo1idines , triazine, derivatives including hexahydrotriaz ines , i so thiazo1 inones , 0 and N formal, 0 and N acetals, halogenised acid amines, and an omadine, e.g. sodium-2-pyri thine thio 1-1-oxide also known as sodium omadine or sodium pyrithione.

Preferred however, is a blend of 1,3,5 triazine - 2,3,5 (2H, 4H, 6H) - triethanol and an omadine providing broad spectrum biocidal activity. This is usually included at levels from 0.05 to 0.57. but a preferred dosage is 0.27..

Defoamers may also be conveniently added to improve the flushing ability of the fluid and prevent the formation of froth, which inhibits the removal of swarf and tramp oil from the system. Sequestrants are also possible ingredients where water hardness salts are present at high levels, to prevent their interaction with the emulsifier system and subsequent instability of the emulsion.

The emulsions are preferably made by mixing preblends of (1) the emulsifier and other amphiphilic or oleophilic (but non-oil) components, (2) the water and components soluble therein and, if a blend of oils is being used, (3) the oils. These blends are then agitated at high speed under high shear to form an invert emulsion.

In order that the invention may be more fully understood, the following Examples are given by way of illustration only.

Example 1

Emulsions were prepared from formulations 1,2 and 3, whose compositions are set out in Table 1 below. The emulsions were used in various metal working operations, in accordance with the present invention, with excellent water replenishment characteristics.

Preparation of the Emulsions

The preparation of the emulsions was as follows: pre-blend A is made by mixing the ingredients with gentle agitation at 40° to 50°C until homogenous.

Preblend A is added to the mineral oil component B with agitation at 20 to 25°.

Preblend C is prepared at 20 to 25° and then added to the mixture of A and B at 20 to 30° using a high shear agitator.

The mixing of preblend C, which is essentially the water phase components, into the oil phase previously mixed from preblends A and B is achieved by introducing the water phase to a high speed mixing head (impeller) immersed in the oil phase. The rate of addition of the water phase is preferably 16 litres per minute, with an impeller speed of 970 revolutions per minute. The impeller is surrounded by a screen. The screen is not the usual screen used for making emulsions, which would be a round apertured screen, but is a square holed shear screen, with aperture dimension in the range of 1 to 3mm, most preferably 2mm.

The resultant fluids are non-micellar opaque white emu1 s ions .

Characteristics of the Emulsions

The characteristics of the emulsions are shown in Table 2 below. Corrosion resistance is assessed in accordance with the procedures of IP135. IP135 tests a neat fluid, not an emulsion, but our tests involve an emulsion.

Emulsion stability is assessed by a modified version of IP 290/84. IP 290/94 requires storage of liquid for 1000 hours at ambient temperature but in the modified version the test is accelerated by storing the emulsions for 48 hours at 70^*C. The separation values in Table 2 refer to the amount of oil and water breaking free from the emulsion after the test period.

Table 1

In Table 1 , the content of each component is expressed as the weight percentage based on the total weight of the formulation .

Formulation

Preblend A Sorbi tan ester 1.88 1.88 1.88 Ethoxylated sorbitan ester 1.00 1.00 0.99 Sodium sulphonate (a) 0.80 0.80 0.79 Calcium sulphonate (b) 0.26 0.26 0.26 Zinc diaryldithiophosphate 1.00 1.00 1.08

Preblend B

Mineral seal oil (c) 40.00 14.75

Mineral oil 60 SP 49 / O 6.73 35.00

Preblend C

Water 40. ,36 43. , 07 40. .30

Ethylene glycol 4. ,70 5. .01 4. .70

Benzotriazole 0. .05 0. .05 0. .05

Biocide 0. .20 0. .20 0. .20

(a) The sodium salt of an alkylaryl sulphonic acid.

(b) Included as a corrosion preventative and based upon alkylaryl acids. The salt has a free alkalinity of 45 mg KOH/g and an SO3 content of 6.0 w/w.

(c) Sold as GULFPAR 4p . Table 2

Characteristics of the Emulsions

Formula t ion

Appearance White White White Emulsion Emulsion Emulsion

S.G. at 15.5°C 0.93 0.93 0.93

Kinematic Viscosity at 40°C/cSt 45 22.8 32.7 (IO^"6 m²/s)

Corrosion Protection No Rust No Rust No Rust

Emulsion Stability oil sep oil sep oil sep

3 ml 3 ml 3 ml water sep water sep water sep l ml l ml l ml

Use of the emulsions (including water replenishment) as described in Example 2 gave very similar results to those of Example 2.

Example 2

A non-micellar milky white emulsion was made up as described above from three preblends A, B and C of the following components (the percentages being by weight of the final emuls ion) : Preblend A 7. w/w

Sorbitan ester 2 , . 05 Ethoxylated sorbitan ester 1 , . 0 5 Sodium sulphonate 0 , . 80 Calcium sulphonate 0 . . 26 Zinc diaryldithiophosphate 1 . . 1 0

Preblend B

Paraffinic Mineral oil,

4 cSt at 40°C 32.0

Naphthenic Mineral oil,

8.5 cSt at 40°C 17.69

Antiwear additive 2.00

Preblend C

Water 38.00

Ethyleneglycol 4.80

Benzotrizole 0.05

Biocide 0.20

The emulsion was fed to a rolling mill in the arrangement to be described hereafter with reference to Fig. 1.

The mill was operated on a continuous basis for 3,500 hours, during which time the emulsion was continually pumped to the rolls. Periodically, the used emulsion was tested for water content, and fresh water added to bring the water content back to the original level. The emulsion easily took up the fresh water, without requiring the mechanical agitation and shear used in the original preparation. From the tank, the emulsion was recirculated to the rolls.

The rolled ferrous metal was found to be coated with a hydrophobic oily coating which gave protection against corrosion.

Examples 3 and 4

Example 2 was repeated with the following two emulsions, made from the preblends A, B and C as described above :

Example 3 Example 4

Preblend A 7. w/w 7. w/w

Sorbi tan ester 2.16 1.75 Ethoxylated sorbitan ester 1.16 0.95 Sodium sulphonate 0.9 0.74 Calcium sulphonate 0.27 0.22 Zinc diaryldithiophosphate 1.21 0.99

Preblend B

Paraffinic Mineral oil, 4 cSt at 40°C 35.00 28.10 Naphthenic Mineral oil, 8.5 cSt at 40°C 10.76 22.73 Antiwear additive 3.00 5.00

Preblend C

Water 40.00 35.00

Ethyleneglycol 5.10 4.20 Benzotrizole 0.08 0.06 Biocide 0.36 0.26 The emulsions were non-micellar, milky white, water-in-oil emulsions. In use, the results were essentially the same as in Example 2. Water replenishment was excellent .

Example 5

The emulsion of Example 1 was used on a creep feed grinding operation using a similar recirculation system to that of Fig. 1. where water is added back to the emulsion at the coolant pump inlet.

Exam le 6

An emulsion was made up as previously described from the following three preblends A, B and C:

Preblend A w/w

Sorbi tan ester 2 , . 0 5 Ethoxylated sorbitan ester 1 , . 0 5 Sodium sulphonate 0 . . 8 0 Calcium sulphonate 0 . . 26 Zinc diaryldithiophosphate 1 . . 1 0

Preblend B

Paraffinic Mineral oil,

4 cSt at 40°C 32.0

Naphthenic Mineral oil,

8.5 cSt at 40°C 17.17

Antiwear additive 2.50

Preblend C

Water 38.00

Ethyleneglycol 4.60

Benzotrizole 0.06

Biocide 0.41 The emulsion was a stable non-micellar, milky whi te fluid .

Samples of the emulsion were then heated to 60°C with stirring to reduce their water contents to 357., 297., 87. and 0.57., respectively.

Addition of appropriate quantities of water, and mild agitation using a magnetic stirrer, returned the emulsions in each case to their original state.

Examp 1e 7

An emulsion was made by mixing the preblends A and

B:

Preblend A 7. w/w

Naphthenic Mineral oil 8.5 cSt at 40°C 45.50 Sorbitan ester 0.27 Tertiary amine 0.60 Lubr izol 5162 4.70 Multi-functional Additive Package

Preblend B

Water 42.50

Ethylene Glycol 5.90

Disodium Tetra-Borate

Decahydrate 0.12

Sodium phosphate 0.33

Benzotriazole 0.02

Biocide 0.06

Samples of the emulsion were then heated to 60°C with stirring to reduce their water contents to 357., 29% 87. and 0.57. respectively. Upon the addition of replenishment water with mild agitation, the stability of the emulsions was lost and a separate water layer formed.

In order that the invention may be more fully understood, reference is made to the accompanying drawings, in which:

Fig. 1 is a schematic diagram of an embodiment of multiroll mill recirculating oil system of the invention, and

Fig. 2 is a schematic diagram of an embodiment of a recirculating oil system of the invention for a metalworking process.

Referring to Fig. 1, there is shown a multiroll mill 1 comprising a multiplicity of rolls 2 in a housing 3. A strip of metal 4 is shown passing through the mill. In operation, fluid sprays 5 are provided onto the rolls 2 and the strip 4. and excess fluid falls under gravity to a collector 6 below the mill 1. Collector 5 connects to a mill sump tank 7 which in turn is connected to a dirty/return tank 8 by a line 9. Line 9 includes a filter 17 upstream of tank 8. Means 21 are provided to supply water to tank 8, and means to agitate (not shown) the tank content.

Tank 8 has a side wall 10 which acts as a weir and over which fluid 20 spills to line 1 1. Line 1 1 includes a pump 12 and filter 13 and communication to a clean storage tank 14. Outlet 15 from tank 14 communicates with pump 16 which supplies fluid to the mill sprays 5.

In operation, the fluid 20 is a non-micellar, milky white water-in-oil emulsion in accordance with the invention. This is pumped to the rolls 2 and metal workpiece 4. The spent fluid, which will usually be of reduced water content, then flows to the dirty/return tank 8 where fresh water is added to regenerate the emulsion. The fluid is filtered upstream 17 and downstream 13 of tank 8 and returned to the clean tank 14 for re-use. The direction of flow of fluid 20 is shown by arrows 30.

Referring to Fig. 2, there is shown a machine tool 40 in which metal working is effected. Coolant fluid is stored in a sump 41 and circulated by pumps 42 and lines 43 through the tool 40. A fluid rehydration unit 44 is connected by lines 45 to sump 41, with pumps 46 in lines 45. The directions of fluid flow are indicated by the arrow heads 47.

In operation, the coolant fluid is a non-micellar, milky white water- in-oil emulsion in accordance with the present invention. This is pumped from sump 41 through lines 43 to the machine tool 40 and then returned to the sump as indicated by arrows 47 on lines 43. During its passage through the machine tool 40, the fluid will normally lose water. To compensate for this, the fluid in the sump is continuously or intermittently (as required) pumped along lines 45 to rehydration unit 44. Here, water is added and the emulsion is then returned to sump 41 by line 45 in the flow direction indicated by the arrows 47.

Claims

C LA I M S :

1. A method of working metal, which comprises:

(a) subjecting a metal workpiece to a working operation at a work station;

(b) providing to the station a recirculating flow of a non- micellar, milky white water-in-oil emulsion;

(c) collecting the emulsion from the work station and replenishing the water content thereof by simple addition of water; and

(d) recirculating the replenished emulsion to the work station.

2. A method according to claim 1, wherein the collected emulsion is filtered to remove solids.

3. A method according to claim 1 or 2, wherein the working operation is rolling.

4. A method according to claim 1,2 or 3, wherein the work station comprises hydraulic fluid means and/or lubricated moving parts, and wherein the said emulsion is also utilised as the hydraulic fluid and/or as the lubricant for the moving parts.

5. A method according to any of claims 1 to 4, wherein the particle size of the water phase in the emulsion is controlled to a fine distribution.

6. A method according to claim 5, wherein the particle size is controlled so that at least 10. of the volume of the water in the emulsion is in particles of less than 0.4 micron diameter.

7. A method according to claim 6, wherein at least 207. of the volume of the water is in particles of less than 0.4 microns in diameter.

8. A method according to any preceding claim in which the peak average diameter of the water particles in the emulsion is less than 1 micron.

9. A method according to any preceding claim, wherein the kinetic viscosity of the emulsion is in the range 10 to 70 cSt at 40°C.

10. A method according to any preceding claim, wherein the emulsion includes at least one of a mono-oleate ester of sorbitol, an ethoxylated trioleate ester of sorbitol and an oil soluble sodium salt of an alkylaryl sulphonic acid, as an emuls i fier .

11. A method according to any preceding claim, wherein the emulsion comprises at least one EP additive.

12. A method according to claim 11, wherein the EP additive is a po1ysulphide .

13. A method according to any preceding claim, wherein the water content of the emulsion is from 30 to 60. by we ight .

14. A method working metal substantially as herein described with reference to Fig. 1 of the accompanying drawings, or as described in any of Examples 2 to 6.

15. A work station for working a metal workpiece, which station comprises

(a) metal working means;

(b) a container of metal working fluid, said working fluid comprising a non-micellar, milky white water-in-oil emul sion ; (c) means for supplying make-up water to the container;

(d) a pump for circulating said fluid; and

(e) conduit means for cycling said fluid from said container to the metal working means and back to the container.

16. A work station for working a metal workpiece, substantially as herein described with reference to Fig. 1 or Fig. 2 of the accompanying drawings.

17. The use of a non-micellar, milky white water-in- oil emulsion for cooling and lubrication of a metal workpiece during metalworking thereon, including replenishment of the water content of the emulsion during recirculation thereof.