EP0649460B1 - Use of compositions comprising cyclodextrin and fatty substance as aqueous machining fluids - Google Patents

Abstract

PCT No. PCT/FR93/00688 Sec. 371 Date Jan. 6, 1995 Sec. 102(e) Date Jan. 6, 1995 PCT Filed Jul. 5, 1993 PCT Pub. No. WO94/01518 PCT Pub. Date Jan. 20, 1994.An aqueous machining fluid including at least one fatty substance, at least one cyclodextrin and water is disclosed. Also disclosed is a process for making such machining fluid and a process for using the machining fluid to process workpieces, particularly metal pieces, by means of said aqueous machining fluids.

Description

The subject of the present invention is use as an aqueous working fluid of compositions comprising at least one body fatty and at least one cyclodextrin.

It also targets a process for processing parts using such fluids.

The two main functions sought in a cutting fluid are increasing the service life of the tool by a lubricating power and by a power of cooling, and the contribution to obtaining a good surface finish by anti-welding power.

Other qualities are also required of these fluids, such as protection of machined parts and corrosion-resistant machine tool, treatment and proper disposal by simple methods, the absence risks of irritation or toxicity for the user, the absence of an unpleasant smell.

There are two types of machining fluids, for elsewhere well described in the literature, fluids whole machining and aqueous machining fluids.

Whole machining fluids are anhydrous and largely made up of fatty substances. They present generally excellent lubrication characteristics.

However, their use leads to several disadvantages such as high smoke temperature, risk of flammability, problems with dermatoses caused by their handling, the difficulty of their recycling and finally, the very cost of these products.

These drawbacks have favored the development of aqueous machining fluids.

These, thanks to the high specific heat of the water they contain, has a cooling capacity greater than that of whole fluids.

They also have a lubricating power sufficient and low cost.

Furthermore, their tendency to provoke developments corrosion on the workpieces and the tools can be easily contained by use suitable anti-corrosion agents.

Therefore, aqueous fluids are preferred over whole fluids.

Aqueous fluids fall into three categories : soluble fluids, semi-synthetic fluids and synthetic fluids.

Soluble or emulsifiable fluids occur usually in the form of a milky emulsion.

Semi-synthetic fluids are found under the form of a translucent micro-emulsion or pseudo-emulsion, becoming opaque in service.

Finally, synthetic fluids are solutions transparent which, unlike the two categories do not contain mineral oil or synthesis.

As for the first two categories, their formulation requires the presence of emulsifying agents in order to obtain stable and efficient fluids.

The use of these emulsifiers poses a significant problem when reprocessing these fluids. Indeed, they oppose the breaking of the emulsion, an essential step in its recycling. However, metalworking produces a among the most important waste industry, this waste being, moreover, among the most difficult to reprocess.

In addition, some commonly used emulsifiers represent a risk of irritation for the operator.

In order to limit friction between the tool and the chip, increase tool life and contribute an improvement in the surface condition of the parts machined, machining fluids, especially aqueous, can be admixed with various additives such as for example oiling agents, antiwear agents and / or agents extreme pressure.

More specifically, extreme pressure additives (hereinafter referred to as EP) have the role of reducing risks seizure between surfaces, under very severe friction and at high temperatures, by the formation of a protective film regularly removed from surfaces.

These EP compounds are most often compounds organo-sulfur, organo-chlorine, organo-phosphorus chemicals and / or combinations of these compounds, paraffins chlorinated being the main EP additives used. Their use is however limited in practice by corrosion and toxicity risks resulting from the formation of chlorine in the presence of water.

Furthermore, extreme pressure additives, which they are chlorinated, sulfur or phosphorus compounds, have the major disadvantage of being polluting for the environment, which therefore causes costs of high treatment for their elimination.

The object of the invention is to remedy the drawbacks prior art aqueous machining fluids and has for object use as an aqueous working fluid of compositions characterized by the fact that they include at least one fatty substance and at least one cyclodextrin.

In the context of the present invention, the term "fatty substance" means any oil or fat, liquid, solid or pasty at room temperature, whether original vegetable, animal, mineral or synthetic, whether used as is or chemically modified, as well as any extract from one of these fatty substances such as for example phytosterols, cholesterol, undecylenic acid, or still a mixture of several of these compounds.

Preferably, said fatty substance is an ester or a fatty acid salt or a mixture of fatty acid esters and / or fatty acid salts of vegetable origin.

In the context of the invention, the term “ "cyclodextrin" alpha, beta or gamma cyclodextrin, or mixtures thereof, as well as derivatives of these cyclodextrins. It may be recalled that α, β and γ cyclodextrin are macrocycles containing respectively six, seven and eight glucose patterns. The term "derivative" should be understood as including any macrocycle as it has just been defined, in which at least one of the glucose units is substituted, at least in one place, by a group or a molecule which can be of size and very diverse functionality, such as grouping alkylated or hydroxyalkylated, and in particular a group hydroxypropyl, or a mono- or di-saccharide molecule such as a maltose, glucose, fructose or sucrose. The term "derivative" also includes "polymers" of cyclodextrins obtained for example by reaction cyclodextrins with polyfunctional reagents.

Preferably, one implements, within the framework of the invention, at least one cyclodextrin chosen from the group consisting of α-cyclodextrin and β-cyclodextrin and their derivatives. The use of β-cyclodextrin (hereinafter designated BCD) appears particularly advantageous.

The composition used according to the invention as an aqueous working fluid, preferably from 30 to 99% and more preferably still from 50 to 95% of body fatty, and from 0.5 to 95%, preferably from 1 to 70% and more preferably still from 5 to 50% of cyclodextrin, these percentages being expressed in dry / dry weight.

This composition is preferably presented in a concentrated form, to make storage easier and its transport to the places of use. The amount of water present in the composition does not constitute a particularly important parameter and we can even consider preparing the composition according to the invention in the absence of water, the water necessary for the constitution of aqueous machining fluids themselves only added when of the step of preparing said fluids. We prefer however, prepare the composition used in accordance with the invention in the form of a homogeneous suspension or dispersion, with a certain amount of water, usually between 22 and 70% by weight, preferably between 30 and 60% by weight.

The various adjuvants usually used in machining fluids, such as corrosion, thickening agents, defoaming agents, wetting agents, bactericidal agents and / or fungicides and extreme pressure agents can be added, totally or partially, from the preparation of the compositions, or they can be incorporated during the final preparation of aqueous machining fluids.

The aqueous machining fluids used in accordance with the invention are prepared from the compositions described above.

This preparation is carried out by placing under vigorous agitation of the composition for machining fluid, most often after addition of water and if necessary after addition of certain adjuvants if these are not already included in said composition. Time agitation is chosen so as to allow obtaining emulsions. These last come in the form of milky emulsions or microemulsions, in which cyclodextrin plays the role of emulsifier.

Just as for the compositions used according to the invention, the amount of water present in machining fluids, therefore obtained essentially by dilution, adjuvantation and placing under shaking said compositions, does not constitute a particularly important parameter. However, ensure that the working fluids contain sufficient of water to be able to emulsify the material fatty by the compound cyclodextrin.

In addition, the amount of water present in the machining fluids varies depending on the operation at which these fluids are intended for, cutting operations requiring less concentrated fluids than operations deformation for example. Most generally, the amount of water present in the machining fluids according to the invention is between 22% and 99%, preferably between 30 and 99% and more preferably still between 35% and 98%.

One of the advantages of using, according to the invention of a cyclodextrin in the constitution of aqueous machining fluids lies in the fact that it is possible to obtain a substantially lubricating capacity equivalent, while slightly decreasing the amount of fat and correspondingly increasing the amount of water.

The Applicant Company has also noted that, surprisingly and unexpectedly, machining fluids aqueous materials used in accordance with the invention are in the form of a metastable emulsion whose technical performance are however remarkable and whose reprocessing, after use, is greatly facilitated.

In addition, compositions used as machining fluids in accordance with the invention, are perfectly bacteriologically stable without it be obligatory to use the presence of agents bactericides and / or fungicides, unlike aqueous machining fluids and art compositions prior. This is obviously another advantage, not predictable, conferred by the present invention. The risk of skin irritation and allergies often caused by contact with such agents are further, and as a result, greatly reduced or even eliminated.

Finally, another remarkable feature and surprising aqueous machining fluid of the composition comprising at least one gas body and at least one cyclodextrin conform to the invention lies in the fact that it allows significantly reduce the amount of extreme pressure agents present.

DE-A-550 871 describes the use watery emulsions of machining fluid, more particularly it describes a rust inhibition process on metals by the use of oils or materials cutting fat in highly diluted aqueous emulsions, characterized by the fact that before using the cutting oils or fats, add to water used for the emulsion, an original colloidal substance vegetable or animal.

The use of cyclodextrins has already been proposed in whole fluids such as lubricant compositions and in particular cutting oils; so the US Patent No. 3,314,884 granted to MOBIL OIL CORP. claims their use in order to improve performance of these compositions thanks to their complexing properties vis-à-vis the chemical additives introduced therein. In this case, the role of cyclodextrins is to protect complexed additives against anticipated degradation (oxidative or bacteriological) and constitute a means of control their release.

The emulsifying properties of cyclodextrins and in particular forms α, β and γ, have moreover already been described, in particular by K. SHIMADA & al, in NIPPON SHOKUHIN KOGYO GAKKAISHI, vol. 38 No. 1 (1991).

These properties were mainly used for the formulation of cosmetic and food emulsions which must remain stable at temperature ambient over a long period. For these applications cosmetics and food, this stability is guaranteed by the use of thickening agents and / or emulsifiers conventional.

However, it was absolutely not obvious that metastable or even unstable emulsions containing a compound cyclodextrin as an emulsifier can be used as an aqueous working fluid and respond quite fully satisfies the requirements of this application, such as in particular the maintenance of properties, in lubricants, at operating temperatures which can reach 700 ° C at tool and workpiece level machined during the machining operation.

Furthermore, the instability of these emulsions, which results in a separation into two phases at rest, one essentially oily and the other aqueous, has a notable interest in the treatment and recycling of these fluids, which today constitute, as previously stated, a major concern.

In addition, cyclodextrin is harmless total for the manipulator, unlike the emulsifiers conventionally used, and finally use as a fluid machining of compositions comprising at least one fatty substance and at least a cyclodextrin according to the invention proves to be particularly advantageous in difficult machining conditions as they allow to be exonerated in whole or in part from the presence extreme pressure agents whose harmful effects for the environment are notorious.

The aqueous machining fluids used according to the invention are prepared using a simple method that requires no expensive and / or delicate apparatus or technical means, this which constitutes another advantage of the invention.

They can be used in treatment of parts, in particular metal, which consist of machining these parts with simultaneous watering of the active part of the tool by an aqueous machining fluid containing at least one fatty substance and at least one cyclodextrin, then recover the fluid at the end of the operation machining, leave it to rest for the time necessary to that there is separation of the phases, to recover each of the phases, to filter them in order to remove the impurities in suspension and finally to recycle them according to a treatment of appropriate regeneration.

The use as an aqueous working fluid of the compositions comprising at least one gas body and at least one cyclodextrin allows both better refrigeration, better lubrication under conditions difficult machining, recycling costs reduced by the absence, or at least the presence in quantity less significant, sulfur, chlorinated or phosphorous, and has good resistance to development bacterial or fungal.

In addition, the cyclodextrins being derived from materials renewable plants, namely starchy materials, their biodegradability and non-toxicity make them products perfectly tolerated by the environment.

If we also choose an original fatty substance plant or animal, use according to the invention has a biodegradable character.

Use according to the invention finds its application in all machining operations, in particular metals, whether cutting (bar turning operations, milling ...) or deformation (stamping, drawing, rolling ...). It can also be applied to temporary protection operations on the surfaces of objects such as auto parts, piping, frames aluminum, molded articles and others, which consist basically apply a protective coating to them usually in the form of a film or film which can be disposed of at the time of sale or immediately before use.

The invention can be understood even better. using the examples which follow and which show some particularly advantageous embodiments, examples which are however given without any limiting character.

EXAMPLES 1. PREPARATION OF COMPOSITIONS AND AQUEOUS MACHINING FLUIDS

Two compositions are prepared as follows :

• de la β-cyclodextrine, sous agitation, jusqu'à dilution complète, la β-cyclodextrine utilisée étant celle commercialisée par la société demanderesse sous la marque KLEPTOSE,
• une huile, le mélange obtenu étant maintenu sous agitation jusqu'à obtention d'une émulsion,
• un inhibiteur de corrosion, une agitation étant alors maintenue pendant environ quinze minutes.

In a turbine homogenizer already containing 80 liters of demineralized water preheated to 30 ° C, the following is successively added:

• β-cyclodextrin, with stirring, until complete dilution, the β-cyclodextrin used being that marketed by the applicant company under the brand KLEPTOSE,
• an oil, the mixture obtained being kept under stirring until an emulsion is obtained,
• a corrosion inhibitor, stirring being then maintained for approximately fifteen minutes.

The compositions thus obtained are presented under the form of concentrated emulsions. From these compositions, two machining fluids A and B are prepared, by dilution with 70 liters of demineralized water for each of the two fluids.

The surface tension is then, the case if necessary, adjusted by adding a tall oil fatty acid saponified with a triethanolamine, so as to obtain a surface tension of about 35 mN / m.

Finally, we add xanthan gum and volume is adjusted with demineralized water.

The formulations of two aqueous fluids, A and B, are collated in Table I. FORMULATIONS MANUFACTURING BRAND A% BY WEIGHT B% BY WEIGHT Mineral oil ENERPAR (BP) 4.07 - Vegetable oil METILOIL A (ATO) - 4.12 β-cyclodextrin KLEPTOSE (ROQUETTE) 1.4 2.04 Corrosion inhibitor LUBRIZOL 5329 (LUBRIZOL) 1.05 1.01 Xanthan gum 0.09 0.09 Tall oil soap (DAUDRUY) - 0.06 Water 93.39 92.68 Surface tension 40 mN / m 35 mN / m

The cutting fluid which will be taken as reference below (REF 1) is an emulsifiable mineral oil which forms with water a milky emulsion stable over time. She is additive anticorrosion, antirust, antifoam and extreme pressure. Its dry matter is 3%.

2. EVALUATION OF THE TECHNICAL PERFORMANCE OF MACHINING FLUIDS

Machining fluids A and B are tested in bar turning.

Bar turning tests are carried out on a lathe MANURHIN automatic single spindle with fixed headstock Combimat type 42.

Operations carried out on a production of 6 hours are as follows: drilling, turning, tapping, chamfer drive, groove drive (1.5 mm), thread, sinking trapezoidal groove and cutting.

For each operation, tolerance criteria are preset regarding the diameter, the thread pitch, the coaxiality, roughness or visual appearance of the parts. Sure the tools, the lifespan by evaluation of the collapse of the cutting edge and wear are measured.

On the shavings, the fragmentation is evaluated; we judge thus, in their appearance, the quality of lubrication and refrigeration. Indeed, depending on whether they are straight and long, tangled, in the form of a large diameter helix, or small diameter propeller, straight and short, arched, spiral, needle or grain, the quality of the parts will be different.

Machined steel is weakly structural steel ally 18 CD4U, supplied by ASCOMETAL.

at. For turning operations, driving trapezoidal, parting off or sinking the throat, the criterion studied was the roughness of the machined parts.

Roughness is measured using a device PERTHEN M4P surface finish.

Results obtained with fluids and the reference oil are collected in the Tables II, III, IV and V.

These results show that, in general, the average values of roughness obtained with the fluids A and B are very close to those obtained with the machining fluid of the prior art. Rolling roughness COMPOSITION ROUGHNESS Ra in µm MINI MAXI AVERAGE REF 1 2.5 7.6 4.2 AT 2.5 5.3 3.3 B 1.8 3.9 2.5 Roughness in trapezoidal driving COMPOSITION ROUGHNESS Ra in µm MINI MAXI AVERAGE REF 1 2.7 10 6.6 AT 4.3 8 6.0 B 5.8 9 7.3 Parting roughness COMPOSITION ROUGHNESS Ra in µm MINI MAXI AVERAGE REF 1 1.9 6.2 3.8 AT 3.6 7.5 5.1 B 1.8 3.8 2.8 Roughness in sinking 15 ° cone COMPOSITION ROUGHNESS Ra an µm MINI MAXI AVERAGE REF 1 4.5 5.6 5.2 AT 4.6 7.4 6.0 B 4 7.5 6.1

b. Chip rating

For each of the operations, the shavings obtained were noted. The description of the appearance of the chips and the ratings have been collated in Table IV. SURGERY BEADING TROLLEY CONCEALING 15 ° THROWING SECTIONING TRAPEZOIDAL PAVING REF 1 DESCRIPTION OF CHIPS propeller of small ice length., propeller cyl. short propeller cyl. short short conical winding propeller cyl. short small to long propeller. propeller cyl. short spiral APPRECIATION bad to acceptable acceptable acceptable acceptable bad to acceptable Well AT DESCRIPTION OF CHIPS propeller cyl. short propeller cyl. short coiled short conical spiral propeller cyl. short spiral APPRECIATION acceptable acceptable acceptable Well acceptable Well B DESCRIPTION OF CHIPS propeller cyl. short propeller cyl. short coiled conical spiral propeller cyl. short spiral APPRECIATION acceptable acceptable acceptable Well acceptable Well

Chips obtained with machining fluids A and B are of at least equivalent quality and often better than that of the shavings obtained with the machining fluid of the prior art.

The good quality of the chips obtained with the machining fluids A and B clearly demonstrates the completely satisfactory refrigeration and lubrication of these.

vs. For threading and tapping operations, the nets obtained were evaluated.

TAP THREAD REF 1 NET DESCRIPTION low pull-out on flanks low pull-out on flanks APPRECIATION good enough good enough AT NET DESCRIPTION low pull-out on flanks low pull-out on flanks APPRECIATION good enough good enough B NET DESCRIPTION low pull-out on flanks low pull-out on flanks APPRECIATION good enough good enough

Regarding the appearance of threaded and tapping, after examination of the workpiece under a microscope, the machining fluids A and B are completely revealed comparable to those of the prior art.

d. We can still compare the machining fluids A and B and machining fluids according to art previous in actual production and by main operations.

The real production values are collated in Table VIII. NUMBER OF FACTORY PARTS PRODUCTION INDEX INCIDENTS REF 1 40 100% Tool dead in tapping AT 35 88% Tool dead in tapping B 73 182.5% Tool dead in trapezoidal groove driving

Table VIII highlights the number of parts machined until the death of one of the tools, as well as the nature of the faulty tool and gives a classification in lackluster performance of machining fluids A and B with respect to the reference machining fluid.

The values by main operations are collated in Table IX.

We therefore note that on the criterion of ruptures of tools fluid A, in comparison fluid according to the prior art, allows gains of 1.5 throat sinking productivity, and good results in drilling.

We also note that, still on the criterion tool ruptures, fluid B, comparatively machining fluid according to the prior art, allows productivity gains in drilling, tapping, 1.5 throat driving and part cutting, and performance equivalent in stock removal.

3. PROCESSING OF MACHINING FLUIDS

Machining fluids according to the invention have the advantage present spontaneous phase separation after storage for a few days.

This is illustrated by the curves presented in FIG. 1, obtained for two aqueous machining fluids: fluid B, the composition of which has already been given in table I, and fluid C, the composition of which is as follows: % in weight ENERPAR mineral oil (BP) 4.07 β-cyclodextrin KLEPTOSE (ROQUETTE FRERES) 1 LUBRIZOL 5329 (LUBRIZOL) 1.05 Xanthan gum 0.09 Water 93.79

The method of preparation of this fluid C is identical to that of fluids A and B.

Thus, we observe on the curve relating to the fluid B that after 20 days at rest, 80% of the volume of this fluid consists of an aqueous phase, on which therefore floats a concentrated oil / BCD emulsion.

Similarly, the curve relating to the fluid C shows that after 20 days at rest, the aqueous phase represents 50% of the volume of this fluid.

Each of the phases can therefore be easily collected to be filtered.

The concentrated supernatant emulsion is then broken according to known means: it can be a chemical means (emulsion breaker such as sulfuric acid), mechanical, enzymatic and / or thermal.

Thus, the supernatant emulsions of fluids B and C were added 1.5% of pure sulfuric acid, then heated to 118 ° C for 15 minutes and finally subjected to a centrifugal action (SORVALL RC5C centrifuge - 1200 m / s2), which allowed total recovery of the oil.

The oil thus recovered can possibly be reused in the same application.

4. ASSESSMENT OF THE MICROBIOLOGICAL STABILITY OF MACHINING FLUIDS

In addition to the technical performance and the ease of reprocessing of machining fluids, their stability vis-à-vis microorganisms has been studied. This stability was followed on fluids A and B which contain no preservative, put into service for about six months.

The aqueous machining fluid taken as reference is obtained by diluting an adjuvanted paraffinic oil extreme pressure and containing a preservative. Her dry matter is 5% (REF 2).

The number of aerobic germs, mold, yeast, anaerobic bacteria and anaerobic bacteria sulfatoréductrices was evaluated. The values are gathered in table X.

This table shows the good stability vis-à-vis the microorganisms of the machining fluids A and B.

5. EVALUATION OF THE EXTREME-PRESSURE CHARACTERISTICS OF THE MACHINING FLUIDS

New machining fluids according to the invention are prepared in a manner identical to that used for fluids A and B.

The formulation of these fluids is given below: FORMULATIONS BRAND D% wt E% wt F% wt G% wt Vegetable oil METILOIL (ATO) 1.79 1.62 - 4.12 Milk fat extract - - 1.75 * - β-cyclodextrin KLEPTOSE B ROQUETTE 0.88 0.8 3.25 * 2.04 Corrosion inhibitor LUBRIZOL 5323 0.26 0.23 0.60 0.6 Xanthan gum 0.039 0.035 0.09 0.09 Tall-oil soap DAUDRUY 0.026 0.023 - 0.06 Extreme pressure agent Chlorinated paraffin ANGLOMOL 40 (LUBRIZOL) - 0.27 - 0.69 Water 97 97 94.3 92.4

The extreme pressure characteristics of D fluids to G, as well as fluid B, are evaluated according to the method FALEX (ASTM D3233 standard). The test is to rotate a steel shaft at 290 rpm between two blocks V-shaped stationary, the assembly being immersed in the formulation to be tested. A load is applied to the V-shaped blocks, this charge steadily increasing with an increment of 250 lbs and being kept constant for 1 minute at each increment. The seizure load obtained makes it possible to evaluate the lubricating properties of the formulation tested and its resistance to deterioration.

The performance of fluids B, D, E, F and G are collated in Table XII.

The two references used here are, on the one hand, the extreme pressure adjuvant cutting fluid REF 1, and on the other hand, the extreme pressure adjuvant cutting fluid defined in point 4, and whose dry matter is now 3%. (REF 3). REF 1 REF 3 B D E F G TEST 1 (in lbs) 2,200 1,600 1,550 1,800 1,600 1,600 1,950 TEST 2 (in lbs) 2,100 1,650 1,550 1,850 1,500 1,500 1,850

On reading these results, it can be seen that the aqueous machining fluids B, D and F, which do not are not additive extreme pressure, have performances perfectly similar to those of cutting fluids according to the prior art REF 1 and REF 3 with extreme pressure additives.

We also note that for a dry matter given (around 7%), the additive as an extreme pressure agent of fluid G does not bring remarkable improvement performance compared to that of fluid B.

Finally, it should be noted that the absence of adjuvants extreme pressure in fluids, constitutes an additional advantage because these do not develop no offensive odors after prolonged rest of a few days, characteristic odors from cutting fluids extreme pressure additives.

Claims (7)

1. Use as aqueous machining fluid of a composition comprising at least one fatty substance and at least one cyclodextrin.
2. Use according to claim 1, characterised by the tact that the composition comprises from 5 to 99.5%, preferably from 30 to 99% and still more preferably from 50 to 95% of fatty substance, and from 0.5 to 95%, preferably from 1 to 70% and still more preferably from 5 to 50% of cyclodextrin, these percentages being expressed by weight on a dry basis.
3. Use according to anyone of claims 1 and 2, characterised by the fact that the composition contains an amount of water comprised between 22 and 99%, preferably between 30 and 99% and still more preferably between 35 and 98%.
4. Use according to anyone of claims 1 to 3, characterised by the fact that the composition is prepared by vigorous stirring after addition of water and eventually after addition of some additives, of at least one fatty substance and of at least one cyclodextrin.
5. Use according to anyone of claims 1 to 4, characterised by the fact that the composition is in the form of an emulsion.
6. Process for processing worked pieces, notably metallic pieces, characterised by the fact that the step of machining of the worked pieces is carried out with simultaneous flooding of the active part of the tool with a composition such as used according to anyone of claims 1 to 5.
7. Process according to claim 6, characterised by the fact that the used composition is recovered as machining fluid at the end of the machining operation, that said composition is allowed to stand for the time necessary for separation of the phases to take place, that each of the phases is recovered, filtered in order to remove the suspended impurities and finally recycled according to an appropriate regeneration processing.

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