EP0571246A1 - Process for degreasing of a plurality of objects - Google Patents

Abstract

This process consists in degreasing a plurality of objects (15) with the aid of a degreasing liquid, each object having a surface coated with a layer of fat. The degreasing liquid employed has a higher adhesion tension to the surface of each object than has the fat and it is practically immiscible or only partially miscible with the fat. The operation of degreasing consists in covering the layer of fat with said liquid in order to lift the fat off and suspend it in said liquid; separating the object from the suspension; collecting said suspension in order to separate it into two phases; and recycling the phase (5, 8) consisting essentially of the degreasing liquid. <IMAGE>

Description

The present invention relates to the technical field of the treatment of surfaces of manufactured objects, and, more specifically, to the industrial degreasing of a plurality of objects.

The purpose of degreasing is to remove from the surface of an object all the fatty products and the various soiling it contains, so that this surface, made clean, regains the intrinsic physicochemical properties of the matter which forms it.

This material is generally a metal or a metal alloy, in particular based on copper, iron, aluminum, zinc or even a precious metal such as gold or platinum. It can also be a mineral glass, a ceramic or a plastic.

As the publication recalls: "Comparison of different methods of degreasing metals, Aqueous processes and solvent processes - European chlorinated solvent association - CEFIC - Brussels December 1990 pp. 1-15", degreasing operations are an essential step in all production processes and lead to improved product quality and reliability.

• 1° les procédés de dégraissage à base de solvants chlorés, - au trempé ou en phase vapeur - utilisés dans l'industrie depuis les années 1920 ;
• 2° les procédés aqueux nécessitant des formulations complexes à base d'eau, d'agents de saponification (soude, potasse, silicates, borates ou carbonates) et de tensio-actifs, et une opération de rinçage à l'eau déminéralisée pour l'obtention d'une surface exempte de taches.

According to this publication, degreasing processes essentially fall into two categories:

• 1 ° degreasing processes based on chlorinated solvents, - by quenching or in the vapor phase - used in industry since the 1920s;
• 2 ° aqueous processes requiring complex formulations based on water, saponification agents (soda, potash, silicates, borates or carbonates) and surfactants, and a rinsing operation with demineralized water for the obtaining a stain-free surface.

• (a) les rejets dans l'eau
• (b) les problèmes de déchets
• (c) les émissions atmosphériques
• (d) l'énergie.

The impact of these processes on the environment can be considered by the following themes:

• (a) releases to water
• (b) waste issues
• (c) air emissions
• (d) energy.

With regard to discharges into water, pollution results from poor waste management or, in the case of chlorinated solvents, accidental spills linked to improper storage or handling.

The effluents generated by the aqueous processes can be purified by ultrafiltration and / or distillation and recycled. However, these techniques remain complex, expensive and energy consuming.

With regard to waste, residues from degreasing with chlorinated solvents mainly contain oils and greases. The level of chlorinated solvent in these residues can be lowered by distillation. The highly concentrated final residue must be disposed of in accordance with current legislation - (see reference: Handling of residues and waste of chlorinated solvents Chimie et Industrie, (1988), 522-525.

Degreasing by an aqueous process generates effluents containing the starting chemicals contaminated by the eliminated oils and greases. These effluents must be treated in a treatment plant and the sludge produced poses the problem of their disposal.

With regard to air emissions, the laws in force are becoming very strict and with regard to 1,1,1 trichloroethane, the Montreal Protocol revised in London in 1990 provides for a freeze on uses from 1993 and its prohibition from 2005.

In terms of energy, aqueous processes generally require more energy than processes operating with chlorinated solvents mainly when a drying step is required. If this step can be avoided, the energy consumption of aqueous processes may be lower.

The energy considered above covers the production of the chemical substances used, cleaning proper as well as recycling and disposal of waste.

The publication RE Brunig and JF Fallot, Industrial cleaning current state of the techniques, Oberfläche Surface, N ° 6, 1991, SHZ Fachverlag Zurich, Switzerland, draws attention to the development of legislation regarding cleaning techniques using chlorinated solvents . This is how industrial cleaning with chlorinated solvents will eventually be prohibited in the USA (California) and that in Germany the legislation will impose in the short term an almost perfect sealing of machines using chlorinated solvents.

In the case of aqueous processes, in particular industrial cleaning with detergents, it is a question of enacting strict standards, in particular in Germany, to limit water consumption and avoid problems of wastewater treatment in treatment plants. communal.

The object of the present invention is to find an industrial degreasing process which does not have the drawbacks of the two processes mentioned above, in particular as regards the possible impact on the environment.

In the technical field of the petroleum industry, the problem of recovering heavy fractions of petroleum, trapped in porous structures in oil fields, has been the subject of studies, in particular by MV Ostrovky and E. Nestaas in Colloids and Surfaces, 26 (1987) 351-373.

These authors have theoretically studied the mechanical equilibrium of a drop of oil on a solid and flat surface, in the presence of an aqueous phase. Oil can detach from the solid surface if its surface tension multiplied by the cosine of its contact angle, namely its adhesion tension, is less than the adhesion tension of the aqueous phase of this same solid surface. Their laboratory studies showed that the presence of a surfactant in the aqueous phase was essential to obtain the detachment of the oil.

MV Ostrovsky in Colloids and Surfaces, 32 (1988) 173-175 published a theoretical study on the parameters which the surfactants must have in a liquid to detach an oil from a solid, smooth, homogeneous, isotropic and not deformable.

• a/ à recouvrir la couche de corps gras par le liquide de dégraissage, avec éventuellement une action mécanique conjointe notamment ultra-sons, afin de décrocher le corps gras de la surface en le mettant en suspension dans le liquide, la surface de l'objet se recouvrant alors du liquide qui a plus d'affinité pour la surface,
• b/ à séparer ensuite l'objet de ladite suspension afin d'obtenir l'objet avec une surface recouverte d'une mince couche dudit liquide,
• c/ à récupérer la suspension et à la séparer en deux phases distinctes :
  • une première phase comportant essentiellement du corps gras,
  • une deuxième phase comportant essentiellement du liquide de dégraissage,
• d/ à recycler cette deuxième phase à l'étape a/.

The object of the present invention, as indicated above, is obtained by a method of degreasing a plurality of objects using a degreasing liquid, each object having a surface covered at least partially with a layer of a fatty substance, characterized in that said liquid having an adhesion tension greater than that of fatty substances on the surface of each object and being practically immiscible or only partially miscible with the fatty substance, said process consists, for each object:

• a / to cover the layer of fatty substances with the degreasing liquid, possibly with a joint mechanical action, in particular ultrasound, in order to unhook the fatty substance from the surface by suspending it in the liquid, the surface of the object then covering itself with the liquid which has more affinity for the surface,
• b / then separating the object from said suspension in order to obtain the object with a surface covered with a thin layer of said liquid,
• c / recover the suspension and separate it into two distinct phases:
  • a first phase essentially comprising fatty substances,
  • a second phase essentially comprising degreasing liquid,
• d / to recycle this second phase in step a /.

In step a /, the layer of fatty substance is covered with the degreasing liquid by any suitable means and in particular by spraying with a jet or spray or else by immersion of the surface of the object in the degreasing liquid.

The use of a pressurized jet also causes a mechanical action facilitating the release of the layer of fatty substance covering the surface of the object.

It is also possible to agitate each object in the degreasing liquid.

This method has multiple advantages over the known methods of the prior art.

The degreasing liquid being chosen in such a way that it is practically immiscible or only partially miscible with the fatty substance, there is no phenomenon of total dilution of the fatty substance by a solvent as is the case for example with chlorinated solvents.

The fatty substance is collected practically undiluted or very little diluted, which corresponds to a collection of the different layers of the fatty substances of the objects subjected to the process according to the invention.

The degreasing liquid, forming a second phase distinct from that forming the combined fatty substance, is recycled with an excellent recovery yield.

As the fatty substance is practically immiscible with, or very sparingly soluble in, the degreasing liquid, this liquid contains dissolved at equilibrium only a small percentage by weight of fatty substance. There is therefore no significant pollution of the degreasing liquid by the fatty substance.

The degreasing liquid may not contain a surfactant. When the degreasing liquid does not contain a surfactant, this has the advantage of simplifying the formulation of this same liquid.

Advantageously, the degreasing liquid does not contain an organic halogen atom. By organic halogen is meant a halogen entering the chemical formula of an organic compound. Thus, the process avoids all current and future binding legislation on the use of organohalogenated products.

Advantageously, the degreasing liquid comprises benzyl alcohol.

Most preferably, the degreasing liquid comprises diacetone alcohol. The liquid can be pure diacetone alcohol or contain additives, in particular a small amount in percentage by weight of methanol or water relative to the total weight of the liquid or alternatively mono- and / or di-methyl phosphoric esters.

Preferably, the degreasing liquid has an adhesion tension equal to or greater than 30 x 10⁻³ N / m; this adhesion tension is in fact generally greater than that of a fatty substance on a metal surface.

The fatty substances capable of being treated by the process can be of any kind, in particular of animal, vegetable, mineral or even synthetic origin.

Preferably, each object is chosen so that its surface has hydrophilic polar groups. This facilitates the departure of the layer of fatty substances having a marked lipophilic character.

Advantageously, the surface to be cleaned is metallic, but it can also be made of mineral glass or ceramic, or even an organic polymer.

Another advantage of the process lies in the fact that in step a /, the degreasing liquid can be maintained at a temperature close to room temperature, for example in a range between 15 ° C and 40 ° C.

On the other hand, it is possible in step c /, to facilitate the separation of the two phases, to provide cooling of the suspension to further reduce, if necessary, the very low solubility of the fatty substance in the degreasing liquid and the very poor solubility of the degreasing liquid in the fatty substance.

It is also possible to solidify by cooling the first phase essentially comprising fatty substance to facilitate its recovery as waste.

Advantageously, the degreasing liquid is chosen so that it can be evaporated at a temperature less than or equal to 100 ° C. under normal pressure. This allows that after step b /, the thin layer of said liquid is evaporated covering the surface of the object.

Preferably, the degreasing liquid is chosen to be miscible with an evaporable solvent at a temperature less than or equal to 100 ° C. under normal pressure.

Thus diacetone alcohol (DA) or 4-hydroxy-4-methyl pentanone-2 which is, in the process according to the invention, one of the preferred degreasing liquids, is miscible with alcohols, esters and water.

In addition, diacetone alcohol has a very low vapor pressure (133 Pa at 20 ° C), 100 times lower than that of the chlorinated solvent T 111, a flash point of + 62 ° C (in closed cup), a good stability in neutral medium, at room temperature and in the presence of metals.

Preferably, the evaporable solvent is chosen from water, acetone, methanol, ethanol or one of their mixtures.

Advantageously, after step b /, the surface of the object covered with a thin layer of degreasing liquid is washed with the evaporable solvent, which has the effect of eliminating this layer of liquid and temporarily replacing it with a layer of solvent. The surface is then dried which gives a surface without fatty substance.

In step c / of the process, a second phase is obtained essentially comprising degreasing liquid. The fatty substance, even if it is practically immiscible with this liquid, can dissolve therein very slightly. Before proceeding to step d / of recycling this second phase, it is preferable to purify it on a pulverulent material with selective adsorption, in particular activated carbon, in order to reduce the fatty substance content or even completely eliminate the fatty substance dissolved in this second phase and obtain degreasing liquid having substantially a composition identical to that which it had before any degreasing.

This purification can also be done by rectification.

Step c / can be carried out by decantation. Two distinct phases are then obtained, one of these phases covering the other, the assembly being contained in a suitable container.

In the case where the first phase based on fatty substances is supernatant above the second phase based on degreasing liquid, it has been surprisingly found that the degreasing of each object could be carried out by immersion of each object in the second phase passing through the first then extracting each object in the opposite direction, passing last through the first phase based on fatty substances. Indeed, the fatty substance rolls or slides on the thin layer of degreasing liquid covering the surface of the object.

In addition to the preceding description, the invention will be better understood with the aid of the following examples in which Example 7 is given with reference to the single figure of the appended schematic drawing.

EXAMPLES

Two different procedures were used to assess the effectiveness of degreasing.

First procedure

A NM 22S stainless steel plate coated with petroleum jelly oil (fully aliphatic oil) is quenched for 15 min. in the solvent tested at room temperature and without using ultrasound. In order to shorten the drying, the plate is quickly rinsed with methanol (this alcohol is a bad degreaser), then dried at room temperature. Ten drops of water are distributed on the two sides of the plate, which gives a total of 20 contact angle measurements determined with the goniometer (This angle is determined according to "Testing Surfaces for Cleanliness, WC Jones, Metal Finishing, October 1985 , p. 13 ").

The degreasing performance is evaluated by calculating the average. The standard deviation of the measurements gives a idea of the homogeneity of degreasing. This static procedure by simple soaking without using ultrasound has the advantage of only evaluating the suitability of a determined solvent. The use of ultrasound, agitation, sprinkling, a rise in temperature are all factors that increase the effectiveness of degreasing.

Second procedure

A mixture of polar and non-polar oils was used to replace the above petroleum jelly oil. The mixture consists of 50% by volume of vaseline oil, 25% of ELF Aleda EE 40 oil (phosphochlorinated mineral oil), 25% by volume of Etirelf BFE 53 oil (completely chlorine-free oil). A metal plate is degreased by following the above procedure. The degreasing evaluation using this mixture of 3 oils was made by observation of the spreading of the water on the plate. A grading system from 0 to 3 was used:
note = 3: the wetting of the surface (steel, stainless steel or aluminum) is very good.
note = 2: the water spreads fairly well but then, we observe a certain shrinkage
note = 1: the anchorage is only partial
note = 0: the water does not wet the surface. This is the case for a surface coated with the mixture of 3 oils.

Following this second procedure, the tests were carried out on a larger scale (10 liter baths). Ultrasound has sometimes been used. Diacetone alcohol additives have sometimes been added.

The adhesion tensions (TA) were determined at 20 ° C, for petroleum jelly oil and the various solvents indicated in the examples below, and are expressed in milli-Newton per meter.

Example 1

• plaque d'acier enduite de vaseline (TA = 30) :   = 90°
• plaque après 15 min. de dégraissage au T 111 (trichloroéthane, TA = 25 ) :   = 52° ± 11°
• plaque après 15 min. de dégraissage au trichloroéthylène (TA = 26 ) :   = 48° ± 10°
• plaque après 15 min. de dégraissage au trifluorotrichloroéthane F 113 :   = 57° ± 4°
• plaque après 15 min. de dégraissage au methanol (TA = 23 ) :   = 69° ± 9°
• plaque après 15 min. de dégraissage au méthylisobutylcarbinol ( TA = 23 ) :   = 62° ± 8°
• plaque après 15 min. de dégraissage à l'éthylamylcétone ( TA = 28 ) :   = 72° ± 6°
• plaque après 15 min. de dégraissage à la méthylisobutylcétone ( TA = 24 ) :   = 68° ± 6°
• plaque après 15 min. de dégraissage au diacétone-alcool ( TA = 31 ) :   = 56° ± 6°
• plaque après 15 min. de dégraissage à la N-méthylpyrrolidone ( TA = 36 ) :   = 72° ± 8°
• plaque après 15 min. de dégraissage au diméthylsulfoxyde ( TA = 34 ) :   = 66° ± 5°
• plaque après 15 min. de dégraissage à l'alcool benzylique ( TA = 39,5 ) :   = 60° ± 5°

Using the first procedure, various oxygenated solvents were compared to conventional halogenated degreasing solvents.

• Vaseline-coated steel plate (TA = 30): = 90 °
• plate after 15 min. degreasing with T 111 (trichloroethane, TA = 25): = 52 ° ± 11 °
• plate after 15 min. degreasing with trichlorethylene (TA = 26): = 48 ° ± 10 °
• plate after 15 min. degreasing with trifluorotrichloroethane F 113: = 57 ° ± 4 °
• plate after 15 min. methanol degreasing (TA = 23): = 69 ° ± 9 °
• plate after 15 min. degreasing with methylisobutylcarbinol (TA = 23): = 62 ° ± 8 °
• plate after 15 min. degreasing with ethylamyl ketone (TA = 28): = 72 ° ± 6 °
• plate after 15 min. degreasing with methyl isobutyl ketone (TA = 24): = 68 ° ± 6 °
• plate after 15 min. of diacetone-alcohol degreasing (TA = 31): = 56 ° ± 6 °
• plate after 15 min. degreasing with N-methylpyrrolidone (TA = 36): = 72 ° ± 8 °
• plate after 15 min. degreasing with dimethyl sulfoxide (TA = 34): = 66 ° ± 5 °
• plate after 15 min. degreasing with benzyl alcohol (TA = 39.5): = 60 ° ± 5 °

This example clearly shows the very good degreasing properties of halogenated solvents (contact angle of water less than 60 °). Quite unexpectedly, the diacetone alcohol gives very good degreasing at room temperature, with good homogeneity of angular measurements and with an efficiency comparable to halogenated solvents. Benzyl alcohol has given good results, however inferior to those obtained by the use of diacetone alcohol. These two solvents act, because of their adhesion tensions greater than 30, by a mechanism essentially of detergency and not of solubilization as is the case for halogenated solvents.

On the other hand, pure N-methylpyrrolidone and pure dimethylsulfoxide, although thermodynamically capable of detaching the oil from the surface, have not led to good degreasing performance. However, these two solvents can each be part of a degreasing liquid to increase its polarity and thus adapt its adhesion tension to the adhesion tension of the fatty substance on the object to be degreased.

Example 2

• plaque d'acier enduite d'huile de vaseline :   = 90°
• plaque après 15 min. de dégraissage au DA :   = 56° ± 6°
• plaque après 15 min. de dégraissage au DA additivé de 3% de méthanol(% en poids par rapport au poids de DA ) :   = 52° ± 2,5°
• plaque après 7 min. de dégraissage au T 111 à ébullition :   = 61° ± 2,5°
• plaque après 7 min. de dégraissage au T 111 vapeur :   = 63° ± 4,5°
• plaque après 3 min. de dégraissage au T 111 à ébullition, suivi d'un trempage d'une min. dans T 111 à température ambiante, suivi de 3 min. de dégraissage au T 111 vapeur :   = 54° ± 2,5°

The evaluation of the degreasing efficiency was the same as in Example 1. The tests with diacetonalcohol were carried out according to the first procedure (soaking 15 min. In solvent at room temperature). The performance of diacetone alcohol was compared to that of trichloroethane T 111 used hot.

• steel plate coated with vaseline oil: = 90 °
• plate after 15 min. degreasing at DA: = 56 ° ± 6 °
• plate after 15 min. degreasing with DA additive of 3% methanol (% by weight relative to the weight of DA): = 52 ° ± 2.5 °
• plate after 7 min. degreasing at T 111 at boiling point: = 61 ° ± 2.5 °
• plate after 7 min. degreasing with T 111 steam: = 63 ° ± 4.5 °
• plate after 3 min. degreasing with T 111 at boiling point, followed by soaking for one min. in T 111 at room temperature, followed by 3 min. degreasing with T 111 steam: = 54 ° ± 2.5 °

Diacetone alcohol performs better than T 111 at boiling point or T 111 in the vapor phase, which is particularly remarkable since DA is used at room temperature. The diacetone alcohol additive with 3% (w / w) of methanol and used at room temperature is as effective as a boiling T 111 boiling cycle, T 111 soaking cycle at room temperature, T 111 rinsing in the vapor phase. This cycle is commonly used in degreasing machines. It is also much more efficient than just one of the 3 operations.

Example 3

• plaque d'acier enduite d'huile de vaseline :   = 90°
• plaque après 15 min. de dégraissage au DA :   = 56° ± 6°
• plaque après 15 min. de dégraissage dans une lessive aqueuse GL 1740 (à 50°C) :   = 56°,5 ± 10°
• plaque après 15 min. de dégraissage au 2-méthoxy-propanol-1 :   = 61° ± 7,5°
• plaque après 15 min. de dégraissage dans un mélange 2-méthoxy-propanol-l et coupe pétrolière en C₈-C₁₁ :   = 63° ± 10°

Using the first procedure, diacetonalcohol was compared to an aqueous detergent, as well as to new substitutes based on propylene glycol ethers or their mixtures with petroleum fractions.

• steel plate coated with vaseline oil: = 90 °
• plate after 15 min. degreasing at DA: = 56 ° ± 6 °
• plate after 15 min. degreasing in an aqueous detergent GL 1740 (at 50 ° C): = 56 °, 5 ± 10 °
• plate after 15 min. degreasing with 2-methoxy-propanol-1: = 61 ° ± 7.5 °
• plate after 15 min. degreasing in a 2-methoxy-propanol-l mixture and C coupe-C₁₁ petroleum cut: = 63 ° ± 10 °

Despite the good results it gives, the use of an aqueous detergent requires heating (50 ° C) as well as an important rinsing with distilled water due to significant deposits of salts.

Diacetone alcohol, even without methanol additive, is more effective than degreasers based on 2-methoxy-propanol-1.

Example 4

In this example, we have used a mixture of 3 polar and nonpolar oils. The mixture was used to coat the steel plates but also to pollute the degreasing bath. It consists of 50% by volume of petroleum jelly oil (d = 0.86), 25% by volume of Aleda EE 40 oil (d = 0.896) and 25% by volume of Etirelf BFE 53 oil ( d = 0.935). The first two oils are insoluble in diacetone alcohol. The third is soluble at 60% (by volume relative to the volume of DA) in diacetone alcohol. It is estimated that the mixture of the 3 oils is soluble at only 20% volume / volume in diacetone alcohol. This low solubility in a very unfavorable case where there are very polar oils therefore allows a considerable reduction in the pollution of the degreasing baths.

Tests using the second procedure were performed with the DA.

Vaseline oil tests

• steel plate coated with vaseline oil: note = 0
• after 15 min. degreasing at DA without ultrasound: note = 1.5
• after 5 min. degreasing at DA with ultrasound: note = 2
• after 10 min. degreasing at DA with ultrasound: note = 2.5
• after 15 min. degreasing at DA with ultrasound: note = 3

Tests with the mixture of the 3 oils

• steel plate coated with the mixture of 3 oils: note = 0
• after 15 min. degreasing at DA with ultrasound: note = 2-2.5

On a larger scale (10 cm² steel plates and 10 l baths), diacetone-alcohol leads to very effective results both with petroleum jelly oil and with a polar mixture of 3 oils.

Pollution of the degreasing bath with the mixture of the 3 oils

• steel plate coated with the mixture of 3 oils: note = 0
• after 15 min. degreasing with DA polluted by 3.5% (v / v) of the mixture of the 3 oils and the application of ultrasound: note = 0
• after 15 min. degreasing with DA additive of 3% MeOH (weight / weight): score = 2
• after 15 min. degreasing with DA additive 5% methyl phosphoric ester (by weight relative to the weight of DA) neutralized by triethanolamine and 5% water: note = 2

By adding the diacetone alcohol of methanol or methyl phosphoric ester, we still get a good degreasing even when the bath is polluted by a content of 3.5% by volume of the mixture of the 3 oils (This is equivalent to the degreasing of 3500 plates).

Example 5

The NM 22S stainless steel plates were coated with an oil chosen from three different oils, then degreased with a liquid composition comprising, in percentages by weight, 89% of DA, 10% of water and 1% of a mixture 50/50 by weight of mono- and di-methyl ester of phosphoric acid, neutralized with triethanolamine.

• huile de vaseline :   note = 2 - 3
• mélange des 3 huiles :   note = 2 - 3
• huile MAGNA BDX 68
  ( CASTROL ) :   note = 0

Degreasing is carried out for 5 minutes with ultrasound, according to the first procedure, but the evaluation of the degreasing is made by observing the spreading of the water on the plate in a manner analogous to example 4. The results are The following:

• vaseline oil: score = 2 - 3
• mixture of the 3 oils: note = 2 - 3
• MAGNA BDX 68 oil
  (CASTROL): score = 0

Example 6

Degreasing is carried out in a manner analogous to Example 5, but with a degreasing liquid consisting of 50% by weight of DA and 50% by weight of Dimethylsulfoxide:
- MAGNA BDX 68 oil: note = 2 - 3

Example 7

This example describes, with reference to the single figure, a prototype of a degreasing machine 1 with two baths using diacetone alcohol (DA). The degreasing evaluation tests are carried out according to the second procedure.

This machine 1 comprises a first tank 2 partially filled with the first bath which is in the form of a first oil phase 6 covering a second phase 5 essentially comprising diacetonalcohol (DA).

The supernatant phase 6 overflows into the decanter 4 by forming an oil column 7 whose height in the decanter increases during the successive cleaning of the objects.

This column of oil 7 floats above a layer 8 of DA coming from the overflow of the tank 2 or from the finish of the settling of the phases 5, 6.

A pipe 9, fitted with a pump 10 and a three-way valve 11, connects the bottom of the decanter 4 to the bottom of the tank 2.

This pipe and its pump make it possible to recycle the layer 8 of DA in the second phase 5 of the tank 2 or to direct the oil from column 7 to a pipe 12 for recovering the oil for its subsequent treatment as waste.

This machine 1 also includes a second tank 3 partially filled with a bath 13 of DA which receives the objects or parts to be degreased only after their successive passage in phases 5 and 6 of the first tank 2.

The degreasing path, by immersion of the objects, is shown by the dotted line 14 for an object 15.

The first bath removes most of the oil. This settles on the surface of the DA and is found in the upper phase of the settling tank 4. A good part of the pollution of the first bath is thus eliminated. However, some polar oils are soluble in DA. To have a very good degreasing, the installation is completed by the second bath 13 of clean DA which is used for finishing the degreasing and whose service life is very high.

• Dégraissage 10 min. seulement dans le premier bain :   note = 0,5
• Dégraissage 5 min. (premier bain) + 5 min. (deuxième bain) :   note = 2,5

The first DA bath is polluted with 3.5% by volume of the mixture of the 3 oils.

• Degreasing 10 min. only in the first bath: note = 0.5
• Degreasing 5 min. (first bath) + 5 min. (second bath): note = 2.5

This degreasing process at room temperature is therefore particularly effective. In addition, it causes very slow pollution of the degreasing baths. In extreme pollution conditions, it is still effective.

Claims (20)

Method for degreasing a plurality of objects (15) using a degreasing liquid, each object having a surface at least partially covered with a layer of a fatty substance, characterized in that said liquid having an adhesion tension greater than that of the fatty substance on the surface of each object and being practically immiscible or only partially miscible with the fatty substance, said process consists, for each object: a / to cover the layer of fatty substances with the degreasing liquid, possibly with a joint mechanical action, in particular ultrasound, in order to unhook the fatty substance from the surface by suspending it in the liquid, the surface of the object then covering itself with the liquid which has more affinity for the surface, b / then separating the object from said suspension in order to obtain the object with a surface covered with a thin layer of said liquid, c / recover the suspension and separate it into two distinct phases: - a first phase (6,7) essentially comprising fatty substances, - a second phase (5.8) essentially comprising degreasing liquid, d / to recycle this second phase in step a /. Method according to claim 1, characterized in that the degreasing liquid does not contain a surfactant. Process according to either of Claims 1 and 2, characterized in that the degreasing liquid does not contain an organic halogen atom. Method according to one of claims 1 to 3, characterized in that the degreasing liquid comprises diacetone alcohol. Method according to one of claims 1 to 3, characterized in that the degreasing liquid comprises benzyl alcohol. Method according to one of claims 1 to 5, characterized in that the degreasing liquid has an adhesion tension equal to or greater than 30.10⁻³ N / m. Method according to one of Claims 1 to 6, characterized in that each object has a surface which has hydrophilic polar groups. Method according to one of claims 1 to 7, characterized in that said surface is metallic. Method according to one of claims 1 to 7, characterized in that said surface is made of mineral glass or ceramic. Method according to one of Claims 1 to 7, characterized in that the said surface is made of an organic polymer. Method according to one of claims 1 to 10, characterized in that step a / is carried out at a temperature of the degreasing liquid maintained between 15 and 40 ° C. Process according to one of Claims 1 to 11, characterized in that the degreasing liquid can be evaporated at a temperature less than or equal to 100 ° C under normal pressure. Method according to claim 12, characterized in that after step b / the thin layer of said liquid is evaporated covering the surface of the object. Method according to one of claims 1 to 12, characterized in that the degreasing liquid is miscible with an evaporable solvent at a temperature less than or equal to 100 ° C under atmospheric pressure. Process according to Claim 14, characterized in that the evaporable solvent is chosen among water, acetone, methanol, ethanol or one of their mixtures. Method according to claim 14 or 15, characterized in that after step b / the surface of the object covered with a thin layer of said liquid is washed with the evaporable solvent, then dried in order to obtain a surface without fatty substances . Method according to one of claims 1 to 16, characterized in that the second phase comprising essentially liquid is purified on a pulverulent material with selective adsorption, in particular activated carbon, before being recycled in step a / of the method. Method according to one of claims 1 to 17, characterized in that step a / is carried out by immersion of the object in the degreasing liquid. Method according to one of claims 1 to 18, characterized in that the separation of step c / is carried out by decantation. Method according to claim 19, characterized in that step a / of degreasing is carried out by immersing each object in the second phase covered by the first phase and the separation of step b / by extracting each object from the second phase then the first phase.

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