AU4519789A

AU4519789A - Purification of industrial lubricating agents

Info

Publication number: AU4519789A
Application number: AU45197/89A
Authority: AU
Inventors: Gunnar Strom
Original assignee: Alfa Laval Separation AB
Current assignee: Alfa Laval Separation AB
Priority date: 1988-11-21
Filing date: 1989-11-21
Publication date: 1990-06-12
Anticipated expiration: 2009-11-21
Also published as: FI912351A0; FI105273B; NO911912D0; SE8804206D0; DK95591D0; DK95591A; ES2091767T3; ATE142685T1; JPH04501731A; NO911912L; JP2983235B2; AU645004B2; WO1990005768A1; DE68927180T2; NO301080B1; DE68927180D1; EP0451160A1; SE462393B; EP0451160B1

Abstract

Use of polymeric two-phase systems for removing microbial contaminants from industrial lubricating agents, a method of purifying microbial contaminated lubricating agents by mixing the lubricating agent with a polymeric two-phase system, allowing the mixture to separate so as to form a top-phase containing the lubricating agent and a bottom-phase containing at least part of the microbial contaminants, and separating at least a major part of the microbially enriched bottom-phase from the top-phase, a plant for microbial purification of lubricating agents comprising a mixing tank (4) having means (7, 8) for feeding microbially contaminated lubricating agent (S) to the mixing tank, means (13) for feeding a polymeric two-phase system to the mixing tank, a stirrer (5) in the mixing tank, means (9, 10) for feeding the mixture to a separation device (6) for separating the mixture into a top-phase (T) containing lubricating agents, and a bottom-phase (B) containing microbial contaminants, and means (18) for recovering the top-phase of the two-phase system, and a lubricating agent concentrate, in which at least part of the lubricating agent at the same timeforms part of the top-phase component of the polymeric two-phase system.

Description

Purification of Industrial Lubricating Agents

Technical Field

The present invention relates to the technical field industrial lubricating and/or cooling agents, especially su agents for use in metal working. More specifically the inve tion relates to purification of such agents, in the followi referred to as "lubricating agents", as regards microbi contaminants by using polymeric two-phase systems. Background of the Invention

Cutting oils and cutting liquids represent a common ty of industrial lubricating agents which are widely used in t engineering industry in connection with cutting, turnin drilling, grinding and similar machining of materials. The primary function is to increase the useful life of the too by acting as a cooling and lubricating agent between t tools and the work pieces. Cutting oils - as well as lubric ting agents in general - consist of. so-called base oil which may be based on mineral oils or be synthetic or sem synthetic. By "cutting liquids/lubricating liquids we me aqueous emulsions of cutting oils and lubricating oils re pectively.

Rapid microbial growth, primarily of bacteria but al of fungi, often restricts the useful life of the cutti liquids to a few months. Already after such a short time use the bacterial concentration may have increased from ze to the order of 10⁸ cells/ml. The growth of microorganis not only results in a deteriation of the properties of t cutting liquid, but also creates an unpleasant odour. connection with e.g. grinding and turning also airborne ba teria can be spread in aerosol form, thereby creating further problem in the working environment.

Cutting liquids contain a plurality of components, fr bactericidal preparations to anti-foam agents and corrosi inhibitors. Several of these components, together with micro-flora of bacteria and fungi, are considered to capable of causing problems, especially eczema and sk irriation, for industrial workers (Wahlberg, J.E. 1976, Ski influence of oil, Esso Symposium 1976).

Since no practically/economically useful methods pre sently are available for cleaning the cutting liquid when i use, the microbial contamination is usally coped with b simply discarding the entire contaminated cutting liquid an replacing the same with fresh cutting liquid. This procedur does not only cause high costs for the disposal and for th fresh cutting liquid, but it also creates high extra cost caused by the shut-down which is necessary for emptying an cleaning the tanks and the distribution systems for th cutting liquid and for re-filling the systems with fres cutting liquid.

Microbial growth in cutting liquids is thus a grea problem in today's engineering industry and there is a grea need of means for extending the useful 'life of cutting li quids. It may as an example be mentioned, that about 10,00 tons of cutting liquids in 1977 were used only in Sweden, o which about 2,000 tons were emulsion concentrates (LO: Report on Cutting Oils). The costs for the acquisition an disposal were estimated to be of the order of 140 to 20 millions SEK, to which should be added the far higher cost for shut-down in connection with the exchange of cuttin liquid.

Similar problems with microbial contamination occur whe using and disposing of other types of lubricating oils, fo example different kinds of hydraulic oils, used oils, etc.

Derwent Abstract No. 76-65593x/35, JP 51079959 disclose an agent for the treatment of contaminated waste water including used cutting oil, by adsorption of the contami nants. The adsorbent consists of very small complex bodie comprising inorganic particles and an organic polymer. Th inorganic particles may consist of active carbon or certai metal hydroxides.

Aqueous polymeric two-phase systems as such have bee known for a long time and have been used in laboratories fo biochemical and microbiological analyses and separations e.g. for separating macro molecules, cell particles and whol cells (e.g. Albertsson P. . 1960, Partition of Cell Particle and Macromolecules, 2nd edition, Almquist & Wiksell, Uppsal Blomquist G. and Strom G. 1984, The Distribution of Mou Fungi Conidies in Polymeric Two-Phase Systems, Work a Health No. 31, Strom G. 1986, Qualitative and Quantitati Analysis of Microorganisms Particularly Fungal Spore Methodological Developments, doctor's thesis, University Umea). However, polymeric two-phase system have found f technical uses.

Polymeric two-phase systems substantially consist two aqueous solutions of polymers having different molecul weights. When the two polymer solutions are mixed in certa proportions, two immiscible aqueous phases are formed. T top-phase substantially contains the low molecular polym and the bottom-phase substantially contains the high molec lar polymer. The water contents in the systems is hig usually between 80-98% depending on. the choice of the pha polymers. In an alternative type of polymeric two-pha systems basically the same result can be obtained by r placing the high molecular polymer with a suitable wate soluble salt, e.g. phosphate buffer.

In polymeric two-phase systems particles or cells a distributed substantially between the top-phase, the inte phase (the interface between the phases) and the botto phase; soluble macromolecules will be distributed between t top and bottom-phases.

In order to simplify the description we will in t following use the expressions "top-phase component" a "bottom-phase component" respectively when referring to thos component/components of the polymeric system, which aft mixing and separation of the system substantially are fou in the top-phase and the bottom-phase respectively.

Objects of the Invention The present invention aims at reducing or eliminatin the above mentioned problems and draw-backs of the prior ar systems for using, handling and getting rid of industria lubricating agents, in particular cutting liquids in th engineering industry.

A special object of the invention is to provide lubri eating agent/cutting liquid systems having a considerabl longer_. seful life than today's systems.

Another special object of the invention is to provide purification process which makes it possible to purify lubri eating liquids microbially while in use, thereby considerabl reducing the shut-down time because of change of liquid.

A further object of the invention is to provide purifi cation methods and means for lubricating liquids which mee high demands on industrial hygien and working environment. A still further object of the invention is to provide a improved analysis method for determining the contents o microbial contaminants in industrial lubricating agents, especially cutting liquids.

A further object of the invention is to provide a lubri eating agent which is also capable of serving as the top phase polymer in a polymeric two-phase system for separatin microbial contaminants from a lubricating agent.

These and other objects and advantages of the inventio will be explained further below. Summary of the Invention

The special features which characterize the inventio are indicated in the appended claims. Different aspects o the invention are indicated in the co-ordinated claims. Pre ferred embodiments of the invention are indicated in th sub-claims.

In summary, it can be said that the invention in it different aspects is founded on the basic concept of utili zing polymeric two-phase systems for separating microbia contaminants from contaminated lubricating agents. In accor dance with the invention the polymeric two-phase system wil be designed in such a manner that there is formed, afte mixing with a lubricating agent and phase separation, a top phase containing lubricant and a bottom-phase containing a least part, of the microbial contaminants, so that at least major part of the microbial contaminants can be remove together with the bottom-phase, which can easily be separate from the top-phase. (For the purposes of this descriptio also the inter-phase is included in the bottom-phase.) One aspect of the invention comprises a method of pur fying microbially contaminated lubricating agents, which characterized by the steps of mixing the lubricating age with a polymeric two-phase system, allowing the mixture separate so as to form a top-phase containg the lubricati liquid and a bottom-phase containing at least a part of t microbial contaminants, and separating at least a major pa of the microbially enriched bottom-phase from the top-phase. Another aspect of the invention consists of a plant fo microbial purification of lubricating liquids. This plant i characterized in that it comprises a mixing tank having mean for feeding microbially contaminated lubricating liquid t the mixing tank, means for feeding at least one of the com ponents of a polymeric two-phase system to the mixing tank at least one stirrer in the mixing tank, means for feedin the mixture to a separation device for separating the mixtur into a top-phase containing lubricating agent and a bottom phase containing microbial contaminants, and means for recir culation of the top-phase of the two-phase system. A further aspect of- the invention consists of a ne lubricating oil concentrate which comprises lubricating oi and optionally conventional additives for lubricating oil and which is characterized in that at least part of th lubricating oil also is included in the top-phase componen of a polymeric two-phase system.

A further aspect of the invention relates to a ne cutting liquid which is characterized in that it consists o an aqeuous emulsion of the cutting oil concentrate accordin to the invention. Short Description of the Drawings

The enclosed drawings show the following: Figure 1 is a schematic presentation of a plant accor ding to the invention adapted for cleaning of industria cutting liquids, wherein the dashed lines illustrate alterna tive embodiments;

Figure 2 is a diagram showing the results of comparativ tests concerning the effect of cutting liquids on the usefu life of twist drilling tools. Description of Preferred Embodiments

The enclosed drawing schematically shows a purificatio plant illustrating how the principle of the cutting liqui cleaning according to the invention may be put into practice The plant comprises a tank 1 for cutting liquid S containin the top-phase component. The cutting liquid S is continuousl being circulated between the tank 1 and work stations (no shown) through inlet conduits 2 and outlet conduits 3 of th tank^'. Suitable distribution conduits, pumps, etc. are use for transporting cutting liquid to and from the work sta tions. This is quite conventional technique and will there fore not be described further in this context.

In the shown embodiment the plant comprises a mixin tank 4, in which there is a stirrer 5, and a separator 6. conduit 7, in which there is a shut-off valve 8, inter connects the cutting liquid tank S. with the mixing tank 4 The latter can also be connected to the separator 6 through conduit 9 having a shut-off valve 10. There is further show a supply container 11 for fresh or recovered bottom-phas component and a collection container 12 for- used bottom phase. The supply container 11 is connected to the mixin tank 4 through a conduit 13, and a conduit 14 interconnect the collection container 12 with the bottom part of th separator 6. Fresh bottom-phase component can be supplied t the supply container 11 from a supply (not shown) through conduit having a valve 15. An interconnecting conduit 1 makes it possible, if desired, to re-use bottom-phase fro the container 12 through a (dash-dotted) conduit 16, whic may have a suitable rough filter 17. A return conduit 1 returns purified cutting liquid to the tank 1.

In accordance with the invention, the described plant ca be used i.a. as follows for purifying microbially contamina ted cutting oil circulating through the tank 1. It should i this context especially be noticed that the cleaning can b carried out without any need of interruping the feeding o cutting liquid to the work stations; this means that th circulationg of cutting liquid through the conduits 2 and may continue as usual. Contaminated cutting liquid S is supplied to the mixi tank 4 by opening the valve 8 in the conduit 7. Fresh or r used bottom-phase is supplied to the mixing tank 4 throu the conduit 13. The supply valves are then closed and top^' a bottom-phase components are mixed with the contaminat cutting liquid.

After the mixing has been completed the valve 10 opened and the mixture is transferred to the separator wherein it is allowed to separate into a top-phase T and bottom-phase B. A major or minor part of the microbial co taminants from the top-phase T to the bottom-phase B wi then move into the bottom-phase B, but the cutting liqu will remain in the top-phase T.

After completion of the separation the purified to phase will be returned to the cutting oil tank 1 through t conduit 18. The bottom-phase B together with its microbi contaminants will be discharged through the bottom condu 14. Depending on the particular bottom-phase component whi is used, the bottom-phase B can either be discarded through drain 19 or be returned to the tank 11, preferably aft rough filtering and/or other purification in the devi generally designated 17. Disposal is preferred when t bottom-phase component consists of cheap material, where re-use is preferable when it contains expensive material su as fractionated dextran.

If the bottom-phase component contains inorganic salt such as phosphates and/or sulphates, the re-circulated to phase will also contain a minor amount of the correspondi salt. Such salts may have an unfavourable effect on t properties of the cutting liquid, and it is then preferab to desalt the top-phase before returning it into the tank For this purpose the plant shown in the drawing has be provided with a desalting device 20, which may be based desalting principles which are known per se. Top-phase polymers which are preferred according to t invention are comparatively low molecular hydrophilic pol mers, especially polymers which are not solid at room te perature. However, hydrophilic polymers of higher molecul weight, which are solid at room temperature, can also be use within the scope of the invention. In the latter case it i preferred to also add an inorganic solvent, in which th polymer is soluable. By the addition of solvent it can b achieved that the cutting liquid will not leave any soli residue on evaporation; such a residue may have a detrimenta effect on the utility of the lubricating liquid by leaving hard crust on the machines.

In a preferred embodiment the top-phase component of th two-phase system comprises at least one polyalkylene glycol especially a polyethylene glycol having an average molecula weight of 200-20,000, especially 400-10,000, in particula about 600-4,000.

According to another preferred embodiment it is advan tageous to use, as the top-phase, also other hydrophili polymers which are liquid at room temperature and/or at th temperature of use and which per se are useful in syntheti cutting oils as the single cutting oil component or togethe with other cutting oil components in synthetic or semi-syn thetic cutting oils. Polyoxyalkylene-polyalcohol ethers suc as polyoxyalkyleneglycol ethers, linear polymers of ethylen and/or propylene oxide are a few examples of preferred poly mers, which are capable of simultaneously functioning as cutting liquid and a top-phase component. Such lubricatin liquids may, for example, contain at least about 2% by weight, especially at least 4, often at least 6% by weigh of the polymer, especially at least 7% by weight.

In general, the concentration of the top-phase polymer in the lubricating liquid decreases with increasing molecu lar weight.

In the embodiment, in which also the bottom-phase com ponent contains a polymer, such polymer preferably has higher average molecular weight than the top-phase polymer The bottom-phase polymer preferably has an average molecula weight of at least 40^000., and it* is preferably cross-linked Examples of suitable bottom-phase polymers are polysacchari des, in raw or refined form, especially cross-linked poly saccharides, in particular cross-linked dextran, starch cellulose, polyglucose or cross-linked mono-, di- or olig saccha.rides. Examples of other types of suitable bottom-pha polymers are polyvinyl alcohols of different average molec lar weights. Polyvinyl alcohols can be recovered from t bottom-phase by e.g. precipitation.

The bottom-phase component may also advantageous comprise a small amount of a suitable agent distributi into the bottom-phase and promoting the transfer of t microbial contaminants from the top-phase to the botto phase. Such agents preferably carry positive electric charg which attract the negative charges on the cell surfaces the bacteria. In such a case the system is preferably kept a pH from neutral to slightly basic so as to expose t charges on the cell surfaces of the bacteria. Examples such charge-exposing agents are hydrophilic polymers co taining positively charged groups,, e.g. DEAE-groups. Su positively charged agents may be present in very low co centrations (the order of magnitude of 10^~2% - 10^_3%) a still have a strong effect. In the embodiment in which the bottom-phase compone contains inorganic salts instead of a high molecular botto phase polymer, these salts may e.g. consist of common buff salts suf as alkali metal phosphates and sulphates and mi tures thereof. The amounts of such salts may vary within co paratively broad limits, the amount i.a. depending^' on t particular salts and the particular top-phase polymer bei used. For example, good results are obtained when using two-phase system comprising phosphate buffer in combinati with low molecular polyetheylene glycol, about 10-20% of ea component.

The lubricating liquids according to the inventi preferably comprise 1-16% by weight of lubricating oi especially about 2-10% by weight of lubricating oil, at lea about 2% by weight of top-phase component, especially least about 4% by weight of top-phase component, and when t top-phase component comprises a low molecular polymer whi is not solid at room temperature, preferably at least abo 8% by weight of the top-phase component, the remainder esse tially consisting of water. The upper limit for the amount o top-phase component is not particularly critical and wil therefore primarily be chosen with regard to practical/econo mical considerations. The use according to the invention of polymeric two phase systems for separating microbial contaminants fro contaminated lubricating liquids can also preferably be use for analysing the separated phase with regard to microbia contaminants. Such an analysis, which preferably will b performed substantially quantitatively or semi-quantitative ly, gives a very rapid and reliable basis for judging th quality of the lubricating liquid and as a guide for deter mining what measures may be necessary to take, for exampl addition of biocideε, exchange of lubricating liquid, etc. A present such analyses are performed by cultivation on suit able nutritions substrates, usually having the form of "sticks" to be dipped into the lubricating liquid. The cul tivation requires several days to be completed and the erro margins are considerable. This is a great drawback becaus the growth of contaminating biomass (which includes both bac teria and fungi) can be very rapid, especially when th contaminants approach critical concentrations. There is thu a great need of an analysis method capable of giving a reli able result within a few hours. When using polymeric two phase systems according to the invention for analyses, reliable response is obtained within a few minutes. Whe performing the analysis it is often desirable to be able t distinguish between live biomass and dead biomass since th latter normally does not reduce the quality of the lubrica ting liquid to any significant degree. This is also possibl to achieve according to the invention by the use of markers which can be split into detectable molecules of live biomass especially fluorescent molecules.

The bottom-phase which is separated in the purificatio method for cutting oils according to the invention can b used for the analysis, but it is preferred to take a specia sample for the analysis. As the bottom-phase it is preferre to use salts of the above indicated type instead of hig molecular polymers. Although it is possible to carry out t separation in a single step, it is preferred to carry o separation in two steps (or possibly more).

Some preferred special embodiments of the invention wi be described in the following part of the specificatio wherein also the results of comparative tests are reported.

As already mentioned the starting point for the use of two-phase technique for continuous purification of cutti liquids is that addition of cutting oil/emulsion concentrat to a two-phase system provides a top-phase in the nature e.g. a cutting liquid/polymer phase which is well separat from a bottom-phase which collects microbial contaminant Examples of factors which may influence the distribution a microbial particle between the top, inter and bottom-phas are, for example, the choice of polymers' - charged/uncharg polymers - the polymer concentration, the choice of pH a the ionic strength.

An important condition for successfully using polym two-phase systems as a continuous purification technique f cutting liquids is that the addition of polymer does n negatively effect the properties of the lubricating liquid regards lubricating and cooling properties, corrosion, tack ness etc. It appears from the tests reported below that t polymer additives used according to the invention do not ha any unfavourable influence on the efficiency of the lubric ting liquids, but on the contrary offers further advantag in certain respects. In these tests cutting liquids accordi to the invention were tested as regards physical and chemic properties and compared with a reference liquid which was t very same cutting liquid without any addition of polyme Further tests were carried out using different bottom-pha polymers, as well as separation tests on cutting liqui containing bacterial cells and spores of mould fungi.

Test of Cutting Liquid With and Without Addition of Polymer (Top-Phase Polymer)

All of the tests were carried out at the Institute f Engineering Research ("Institutet for Verkstadsteknisk fors ning") in Gothenburg. In the test a mixture of 6 kg of Polyethylene glycol 60 (Kebo Lab AB, Solna), suspended in 4 kg water, was added to mixture of 28 1 of water plus 2 1 emulsion concentrate (mine ral oil based, fine emulsion) - Liquid 2. A mixture of 2 1 o emulsion concentrate and 38 1 of water was used as referenc - Liquid 1.

The following properties of the two cutting liquids wer studied;

* Effect on the useful tool life in twist drilling * Crevice corrosion

* Effect on copper and aluminum

* Separation of leaking oil

* Foaming

* Sedimentation * Residue after water evaporation, retaining forces.

The machining test was performed using production machi ning data on heat treatment steel (SS 2541-03) and a stabl machine tool.

Machining Test - Twist Drilling Equipment

Work piece material: SIS 2541-03 (260 HB)

Tool material: High speed steel, SIS 2724, φ 6 mm

Numerically-contro1led bed cutter: SAJO VBF 450

Machining Data ^*

Cutting speed 17-35 m/min

Feed: 0.17 mm/r

Depth of bores: 24 mm (4 x d)

Warn-out test: total destruction

Pre-Treatment of Equipment

The work pieces are taken from one charge and are rolle in sequence. They are cut to a size of 200 x 30 x.375 m (about 400 bores/plate) and spot faced.

The tools are normalized with narrow geometric toleran ces and hardness variations.

Procedure The work pieces (2) are clamped into the machine and th test program is designed so as to distribute the machining both plates for each tool, the purpose being to avoid lo unevenness in the material. The cutting speed is varied f different drills in order to obtain a relation between cu ting speed and warn-out time (vT-curve).

Destruction of the tool is seen as vibrations and changing cuttings (the tip melts). This occurs within a f seconds.

The other tests were carried out according to te programs defined in IVF-report 87-03-18, supplementing revision of IVF Result No. 71607.

Results When evaluating these cutting liquid tests the scale 1 and 2 was used. Grade 1 means generally acceptable f engineering products and 2 means increased effect in t respective test.

Liquid 1 Liquid 2 (invention Machining test 1 (2) 2

Corrosion Steel 2 2-

Cast iron 0 2

Attack on metals

Copper 2 2

Aluminum 2 2 Comment. For both tests the same Cu contents, 51.4 mg/1, we measured using atom absorption spectrophotometer after copper plate had been immersed in the liquids for two weeks

Separation of leaking oil 2 layers 2 layers

Comment. Liquid 1 has a turbid border zone, rough emulsio but the border zone is clear for Liquid 2.

Foaming

Foam column

(15 cm), min. 4.4 4.3

Disintegration, min 11.4 13.0 Sedimentation 30%^' 50% Evaporation residue.

This .test could not be carried out because it was not po sible to evaporate Liquid 2 in a drying chamber at 40°C. surface layer prevents evaporation of water. The test results show that the addition, according the invention, of a top-phase polymer to a mineral oil bas fine emulsion results in a plurality of positive effects regards the properties of the cutting liquid. The meta cutting test, which is an indirect measure of the cooling a lubricating properties of the liquid, showed reduced wear the machine tool when using a cutting liquid containing polymer. At a cutting speed of e.g. 22 m/min a useful to life, expressed as the number of holes/drill, of about 28 w recorded for the normal cutting liquid, and a value of 1 for the corresponding polymer/cutting liquid mixture (see v curve in Fig. 2) .

An important property for the useful life of a cutti liquid is the capability of efficiently separating contamin ting leak oil from i.a. hydraulic systems. The comparati tests with and without admixture of polymer -showed a low tendency of leak oil emulgation into the cutting liqu according to the invention, which means that it is easy remove leak oil from the system.

For both types of cutting liquids the attack on t metals copper and aluminum were minimal and the leakage Cu-ions from a copper plate was identical (51.4 mg/1) .

As regards corrosion, the cutting liquid according the invention had an evident anti-corrosive effect on cas iron whereas the effect of the reference liquid was unacce table for engineering products. Both products showed increased effect on steel.

Amine derivatives are often used as corrosion inhibito in cutting liquids. These amines often cause working enviro mental problems. Furthermore, carbon/nitrogen compounds the amine type can readily be used as a substrate by micr organism, thereby promoting the microbial growth. The evide corrosion inhibiting effect when adding a top-phase polym according to the invention can make it possible to complete exclude amine compounds from these products.

The tendency to foaming and foam degradation of cutti liquid products is an important property for the engineeri industry. The results of the comparison between cutti liquid with and without addition of top-phase polymer acco ding to the invention did not show any significant differen as regards foaming.

The addition of polymer to a cutting liquid results in certain increase of viscosity. The effect of this increase viscosity could also be seen in sedimentation tests using fine powder of reduced iron. It was found that 30% of t added amount of iron powder had not sedimented after seconds in a cutting liquid without addition of polymer. T corresponding value for the cutting liquid according to t invention was 50%. It can further be mentioned that inorgan particles, which are' present in .the polymeric two-pha systems, will not be distributed into the top-phase, i.e. t cutting liquid phase. The result is that also inorgan particles in the system will be removed together with micr organisms in the bottom-phase.

Hard crystalline evaporation residues from a cuttin liquid may have a negative effect on movable machine par and precision tools. The evaporation tests with the miner oil based fine emulsion with addition of polymer according the invention showed that the product could not be evapora ted, probably because a formed surface layer prevented wate from escaping. Other evaporation tests using both mineral oi based and semi-synthetic emulsion concentrates containin polymer according to the invention and water showed that n hard crystalline evaporation residue was formed. In the cas with the mineral oil based concentrate two-phases were ob tained, one consisting of concentrate and the other of th added top-phase polymer.

The fact that polyethylene glycol, after evaporation does not form a homogenous liquid with mineral oil base concentrates does not seem to be of any significant impor tance. ^* Separation Tests

In all of the separation tests the following two type of emulsion concentrates were used; semi-synthetic fin emulsion (5-Star-40, Cincinnati, Millacron) and mineral^' oi based rough emulsion (Multan 94-2, Henkel Kemi) .

Each of the emulsions were tested as follows:

1. 0,6 g of Polyethylene glycol 600 were mixed with 0.2 emulsion concentrate and 3.2 g water having bacterial cell (about 2 x 10⁸ bacterial eelIs/ml) or, alternatively, fung spores (about 5 x 10⁷ spores/ml) suspended therein.

2. 0.8 g Polyethylene glycol 600 was mixed with 0.2 emulsion concentrate and 3.0 g water as above.

3. 0.8 g Polyethylene glycol 600 and 0.1 g Polyethylen glycol 8000 (Carbowax 6000, Union Carbide, New York, USA were mixed with 3.2 g water as above.

A polymer mixture consisting of diethylaminoethyl dex tran (DEAE-dextran) and below listed polymers was added t each of the systems for the separation test: a) Dextran 500 (molecular weight 500,000, Pharmacia Fin Chemicals, Uppsala) b) Dextran (Batch 30-0472-00) c) Dextran (Fraction I) d) Soluble potatoe starch (Kebo Lab AB, Solna) .

The final concentration in the system was 0.001% fo DEAE-dextran and 1% for the other polymers (w/w) .

After mixing and phase separation 1 ml of the top-phas (emulsion + polyethyleneglycol phase) was removed and the diluted in steps of 10**-; thereafter each dilution step wa seeded on culture substrates for fungi and bacteria. Culture Media and Cultivation Conditions

The quantification of the number of fungi, elements wa performed by cultivation on a substrate composed of 2% (w/w of malt extract (Oxoid, L 39), 1.5% Agar (Oxoid, L 28) and 3 mg/1 of streptomycin sulphate (Sigma Chemical Co.). Incuba tion was carried out at room temperature (22°C) during days, after which the number of colony forming units could b determined.

The concentration of bacteria was determined by th cultivation on a substrate composed of 2.4% (w/w) Trypto Glucose Extract Agar (CM 127, Oxoid), 0.2% Casein Hydrolysa (Acid) (L 41, Oxoid) and 50 mg/1 Actidione (Sigma).

The number of colony forming units was determined aft incubation for six days at room temperature.

The results of separation tests performed with differe dextran fractions or soluble starch as the bottom-pha polymer and with the above described composition of the to phase are presented in Tables 1 and 2.

Table 1

Separation of bacterial cells of Bacillus subtilis usi different bottom-phase polymers. The amount of bacteri cells before the separation was 1.6 x 10⁸/ml in Systems 1 a 3 and 1.5 x 10⁸ in System 2. The final concentration of t bottom-phase polymers was 1%. A semi-synthetic fine emulsi (5-Star-40) was used as the emulsion concentrate.

Bottom-phase- Bact. cone, after sep. (Purification effect) polymer a) System 1 (%) System 2 (%) System 3 (%)

Dextran 500 b) - l.OxlO⁷ (93) O.δxlO⁷ (95)

Dx 30-0472-00 b) - l.lxlO⁷ (93) 1.3xl0⁷ (92)

Dx Fraction l b) - 0.9xl0⁷ (94) 0.9xl0⁷ (95)

Starch 1.7xl0⁷ (89) 2.0xl0⁷ (87) 1.5xl0⁷ (91)

a) including 0.001% DEAE-Dextran b) does not form two-phas

In one case a semi-synthetic fine emulsion was us together with the top-phase polymers (Table 1), and in t other case a mineral oil based rough emulsion (Table 2 Together with the bottom-phase polymers also diethylamin ethyl-dextran (DEAE-dextran) was added to a final concentr tion of 0.001%.

The separation of a known amount of bacterial cells fr the top-phases containing the semi-synthetic fine emulsi proved to be very good (87-95%) substantially independent of the type of bottom-phase polymer (Table 1). The effe was enhanced by the presence of the positively substitut diethylamino-ethyl-dextran which is distributed into the bot tom-phase of the system. At the high pH prevailing in th system, negative charges on the cell surfaces of the bacteri will be exposed and the cells attracted to the positivel charged bottom-phase (cutting liquids usually have a pH of 7 9).

Corresponding separations of fungal spores from a mine ral oil based rough emulsion are presented in Table 2. Lik in the case with bacterial cells a very high degree of sepa ration (96-98%) was obtained, enhanced by the presence o DEAE-dextran and the high pH in the system.

Table 2

Separation of mould fungi spores of Penicillium brevicompac tum using different bottom-phase polymers. The amount o fungal spores before separation was 4 x 10⁷/ml (Systems 1 an 3) and 3.8 x 10⁷ in System 2. The final concentration of th bottom-phase polymers was 1%. A mineral oil based roug emulsion (Multan 94-2) was used as the emulsion concentrate.

a) including 0.001% DEAE-Dextran b) Does not form two phase

In summary it appears from the tests that the top-phas polymers according to the invention with excellent result can be included in cutting liquids and at the same tim function as the top-phase in a two-phase system for microbia cleaning of the cutting liquid.

As regards dextran, a broad range of fractions, fro finely fractioned Dextran 500 (molecular weight 500,000) t more unfractionated (and consequently cheaper) raw dextra have been tested and found to be very useful. When using hig molecular dextran it has been found to be especially adva tageous with a top-phase concentration of about 19% (w/w) Polyethylene glycol 600 or, alternatively, about 12.5% Pol ethylene glycol 600 + 2.5% Polyethylene glycol 8000. In^' t latter case it is suitable to use a semi-synthetic cutti liquid concentrate.

When purifying these systems the amount of dextran m be about 1%, resulting in a bottom-phase volume making about 3-5% of the total system. As mentioned dextran may be replaced by other hi molecular polymers, e.g. soluble starch, glucogen or sy thetic polyglucose, as the bottom-phase polymer.

In tests using soluble starch, Polyethylene glycol 6 (16% solution) was mixed with soluble starch to a fin concentration of 1%. Like in the dextran case the botto phase volume was small compared to the total system. contrast to dextran soluble starch gives a more gel-li bottom-phase.

High molecular polyethylene glycols (mw > 1000), whi are crystalline at room temperature, are not* soluble in concentrate based on mineral oil only, but is highly solubl in synthetic emulsion concentrates. Evaporation tests using mixture of 2.5% (weight/weight) of Polyetheylene glycol 80O (Carbovax 6000), 5% (w/w) of semi-synthetic emulsion co centrate (fine emulsion), and 12.5% (w/w) of Polyethyle glycol 600 did not produce any crystalline residue.

As mentioned above the bottom-phase polymer may consis of unfractionated or substantially unfractionated raw dex tran. Such raw dextran preferably has a molecular weight o 5-40 millions, and it is preferably used in mixture with small amount of positively charged polymer such as DEAE dextran. Raw dextran is the presently preferred material fo the bottom-phase polymer since it is both cheap and effi cient. It is especially preferred to use raw dextran whic has been substituted with a small amount of positively char ged groups, e.g. DEAE groups, in which case it is not neces sary to add any separate charged polymer when there is a nee thereof. Also raw fractions of other polysaccharides can b used in corresponding manner. The polymer contents can be a low as_. about 0.01%.

It has especially been found that the combination o this type of bottom-phase polymer (raw dextran etc. ) with th above mentioned "dual-function" top-phase polymer (whic itself serves both as a top-phase polymer and as a cuttin oil) results in both excellent separation results and supe rior cutting liquid . properties, as is illustrated by th following test.

Top-Phase Polymer As Synthetic Cutting Liquid

A synthetic cutting liquid was prepared by mixing th following components in water to the indicating concentra tions.

Emkarox VG 680W 6 % (a polyoxyalkylene glycol ether from ICI)

Synperonic T/701 0.1 %

(a foam inhibitor from ICI)

Phosphate buffer to pH about 7 Water q.*s.

The utility of the obtained cutting liquid was tested i machining tests and was rated as category 2, which means hig class cutting liquid.

The utility of the cutting liquid as a top-phase syste for purification according to the invention was tested a follows:

Bacterial cells and fungal spores were added (in th above described manner) to the above cutting liquid to simu late a microbially contaminated cutting liquid. Raw dextra (molecular weight 5-40 millions, final concentration 0.1% with added DEAE-dextran (final concentration 0.01%) was use as the bottom-phase polymer. The top and bottom-phases wer mixed and allowed to separate; 97-99% of the bacteria an about 99%₍ of the fungi were transferred into the bottom-phas and separated.

Microbial Analysis of Contaminated Cutting Liquid A presently preferred embodiment of the analysis metho according to the invention for quantification of the mic bial contamination of cutting liquids will now be descri as an illustrative but non-limiting example. The results the analysis can e.g. be used for judging the quality of used cutting liquid.

A pre-determined amount of a polymeric two-phase sys according to the invention was added to a test bottle havi a sealable, preferably "pipette shaped" stopper. A bott holding a total of about 50 ml can e.g. be charged with 20 of the system in advance, sealed and delivered to the use When taking a sample an aliquote (20 ml) of a cutting liqu sample is "pipetted" into the bottle, which is then shaken as to mix the phases and then allowed to separate with t bottle turned upside down. The bottle may preferably be co pressible and have a suitable visible volume scale. T separation is normally very good . already after 10 to seconds, but it is preferred to allow the separation proceed for a few minutes. Already at this stage it is po sible to get a good idea of the degree of microbial contam nation of the cutting liquid by turbidimetric-reading of t bottom-phase (which substantially consists of salt solutio e.g. phosphate buffer pH aboi:-; 6.8) and comparison with standard curve for a corresp-Λding system, prepared in manner known per se. It is, however, preferable to make further separation step in which the bottom-phase from t first step (e.g. 10 ml of bottom-phase), which is rich biomass, is mixed with a suitable polymer for a second pha system (e.g. 4 g of polypropylene glycol having a molecul weight of about 425). Since in the preferred embodime (separation in a bottle which is turned upside down), t bottom-phase from the first separation is located closest the opening of the bottle, which preferably is "pipette sh ped", the transfer and metering to the second system can done very conveniently. Also this second separation can carried out in a pre-prepared bottle designed similarly the first bottle. The second bottle is shaken so as to m the phases well, then allowed to rest until the phases ha separated (normally the same separation times as for t first separation are preferred) , and a predetermined amoun of the biomass-enriched bottom-phase is taken out for tur bidimetric analysis and comparison with a standard curv (which expression also includes a specific mathematica relation or any other relation for quantification of th measured value which has been determined in advance) . Befor the reading, the sample may optionally be diluted with e.g particle-free water (in the given specific example e.g. 2 m sample plus 2 ml of particle-free water) . If desired, th amount of live biomass can be determined in the above indi cated manner, e.g. by using fluorescinediacetate (FDA) as marker.

Hiαh-Concentration of Diluted Polymer Solutions The -separation method according to the invention ca also advantageously be used for making used cutting liquid or other lubricating liquids such as.waste oil disposable. A present, the disposal of e.g. synthetic or semi-syntheti cutting liquids is a very costly process because it is ver difficult to concentrate diluted polymer mixtures (and th polymer cannot be disposed of just anywhere) .- The disposa costs can often be as high as the purchase price. Accordin to the invention this problem can be easily remided by strongly concentrating the polymer, e.g. in the followin way. A used-up cutting liquid containing about 7 % by weigh of Emkarox (see above) as the top-phase polymer is mixed wit about 60% phosphate buffer (bottom-phase) to a final concen tration of 25% and allowed to separate (from a minute to a hour or so). A very concentrated and easily separable polyme top-phase is formed (e.g. 35-50%, total volume about 5% o the cutting liquid volume), which can be destructed, wherea the aqueous phase usually can be disposed of directly.

Claims

1. Use of polymeric two-phase systems for purification industrial lubricating agents from microbial contaminant the lubricating agent optionally comprising a polymer whi also is part of the polymeric two-phase system and preferab forms the top-phase polymer of the polymeric two-phase sy tem.

2. Use according to claim 1, characterized in that the lubricating agent is a cutti fluid.

3. A method of separating microbial contaminants fr contaminated lubricating agents, especially cutting fluids, characterized by the steps of mixing the lubricating age with a polymeric two-phase system,' allowing the mixture separate so as to form a top-phase containing the lubricati agent and a bottom-phase containing at least part of t microbial contaminants, and separating at least a major pa of the microbially enriched bottom-phase from the top-phase

4. A method according to claim 3, characterized by the step of determining the contents microbial contaminants in the separated bottom-phase.

5. A plant for microbial purification of industrial lubr cating agents, characterized in that it comprises a mixing tank (4) havi means (7, 8) for feeding microbially contaminated lubricati liquid (S) to the mixing tank, means (13) for feeding least the bottom-phase component of a polymeric two-pha system to the mixing tank so as to form such a two-pha system in the tank, at least one stirrer (5) in the mixi tank, means (9, 10) for feeding the mixture to a separati device' (6) for separating- the mixture Into a top-phase ( containing lubricating liquid and a bottom-phase (B) conta ning microbial contaminants, and means (18) for recoveri the top-phase of the two-phase system, the plant optional being connected to a central tank (1) in a distributio system for lubricating liquid in such a manner that micro bially contaminated lubricating liquid can be withdrawn fro the central tank to the plant, purified therein and reci^'rcu lated to the central tank without interruption of the circu lation of lubricating liquid in the central tank.

6. A lubricating agent concentrate comprising lubricatin oil and optionally conventional additives lubricating agents characterized in that at least part of the lubricating oi also is part of the top-phase component in a polymeric two phase system.

7. A lubricating agent concentrate according to claim 6, characterized in that the top-phase component comprises comparatively low molecular hydrophilic polymer which is no solid at room temperature, a hydrophilic polymer which i solid at room temperature, together with a preferably organi solvent for the polymer, a polyoxyalkyleneglykol ether or preferably linear polymer of ethylene and/or propylene oxide

8. A lubricating agent concentrate according to claim 6 o 7, characterized in that the lubricating oil forms the enti top-phase component of the polymeric two-phase system a preferably consists of a polyoxyalkyleneglykol ether or preferably linear polymer of ethylene and/or propylene oxid

9. A lubricating agent concentrate according to any one claims 6 to 8, characterized in that the lubricating agent is an industri cutting oil.

10. A cutting fluid, characterized in -that it- is an aqueous emulsion of a lubr cating agent concentrate according to any one of claims 6-9.