FI100999B - Procedure for degreasing various 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

100999

Degreasing method for various articles

The present invention relates to a degreasing technique for manufactured articles, and in particular to an industrial degreasing of various articles.

The purpose of degreasing is to eliminate all grease products and the various impurities they contain from the surface so that the cleaned surface regains the essential physicochemical properties of the substance from which it is formed.

This substance is generally a metal or alloy, especially based on copper, iron, aluminum, zinc or precious metals such as gold or platinum. It can also be inorganic glass, ceramic or plastic.

As recalled in "Comparaison des differentraise de metraxage des metaux, Procedes aqueux et procedes aux 20 solvants- European chlorinated solvent association- CEFIC-Brussels Decembre 1990 pp. 1-15", it is better quality and reliability of products.

According to this publication, degreasing methods can be divided into essentially two groups: 1 ° degreasing methods based on chlorinated solvents - immersion or gas phase - which have been used in industry since the 1920s.

2 ° aqueous phase processes using complex mixtures of water, saponifiers (sodium, potassium, silicates, borates or carbonates) and surfactants, including a rinsing operation with demineralized water to obtain a spotless surface. The impact of these methods on the environment can be assessed on the following topics: 2 100999 (a) emissions to water (b) waste problems (c) emissions to the atmosphere (d) energy 5

In terms of discharges to water, contamination is often the result of poor waste management or, in the case of cloned solvents, it is often a matter of accidental discharges due to the unsuitability of storage or treatment.

Wastewater generated in aqueous phase processes can be purified by ultrafiltration and / or distillation and recycled.

However, these techniques are complex, expensive, and energy intensive.

As far as waste is concerned, the waste obtained when degreasing with chlorinated solvents contains mainly oils and fats. The pi-20 content of the chlorinated solvent in these wastes can be reduced by distillation. The final residue, which is well concentrated, should be eliminated in accordance with current legislation. (See reference: Manipulation of residues and dechets of solvents in chlorine Chimie et Industrie, (1988), 522-525).

25: Degreasing using the water method produces wastewater that contains initially introduced chemicals contaminated with removed oils and fats. These effluents have to be treated in a water treatment plant and the sludge produced is difficult to eliminate.

With regard to atmospheric emissions, existing legislation is tightening on 1,1,1-trichloroethane, the Montreal Protocol, revised in London in 1990, provides for the substance to remain unchanged from 1993 and to be phased out from 2005 onwards.

Water processes generally require more energy than methods based on chlorinated solvents, mainly when a drying step is required. If this 3 100999 drying step can be avoided, the energy consumption of the water methods may prove to be lower.

The energy consumption considered above includes the production of the chemicals used, the cleaning operation itself and the elimination of waste.

R.E.Brunig and J.F.Fallot, Nettoyage industriel et al. Actuel des techniques, Oberfläche Surface, No. 6, 1991 10 SHZ Fachverlag Zurich, Suisse, draws attention to the development of legislation on cleaning techniques using chlorinated solvents. Thus, industrial cleaning using chlorinated solvents will potentially be banned in the US (California) and in Germany, law 15 will soon require almost complete sealing of machines using chlorinated solvents.

With regard to water methods, in particular industrial cleaning with detergents, strict standards are being drawn up 20, especially in Germany, to limit water consumption and to avoid water treatment problems in municipal water treatment plants.

The object of the present invention is to provide an industrial degreasing method which does not have the disadvantages of the two methods mentioned above, in particular with regard to possible environmental disadvantages.

The recovery of heavy oil fractions trapped in the porous structures of the oilfield-30 road has been studied in the technology of the petrochemical industry, in particular by M.V.Ostrovsky and E.Nestaas in Colloids and Surfaces, 26 (1987) 351-373. These authors have theoretically studied the mechanical equilibrium of an oil silicon on a flat surface in the presence of an aqueous phase. An oil can become detached from a solid surface if its surface tension multiplied by the cosine of its contact angle, i.e. its adhesion stress is lower than the adhesion stress of the aqueous phase of this solid surface. Their laboratory studies have shown that a surfactant in the aqueous phase is necessary to remove the oil.

M.V.Ostrovsky, in Colloids and Surfaces, 32 5 (1988) 173-175, have published a theoretical study of the parameters of surfactants necessary for the removal of oil from a solid, smooth, homogeneous, isotropic and non-distorted surface.

The object of the present invention is achieved as described above by a degreasing method for various articles using a degreasing solution, each surface of which is at least partially covered with grease, characterized in that said solution has a higher ad-tension than the grease on each article and that the solution is practically immiscible or only partially miscible with the fat, said method comprising for each article: 20 a / covering the fat with a degreasing solution, possibly combined with a mechanical action, in particular the use of ultrasound, to remove the fat from the surface by suspending it in solution; the surface is covered with a solution having a higher affinity for the surface, 25 b / then removing said article from said suspension to obtain an article whose surface is covered with a thin layer of said solution; 30 c / of the recovery and separation of the suspension into two different phases: - a first phase containing mainly fats - a second phase containing mainly a degreasing solution, 35 d / of recycling this second phase to step a /.

In step a), the degreasing layer is covered with a degreasing solution by all suitable means, and in particular by spraying or further immersing the surface of the article in the degreasing solution.

By using a pressurized spray, a mechanical effect is also obtained which facilitates the removal of the grease covering the surface.

It is also possible to shake each object in the degreasing solution.

10 This method has several advantages over known methods representative of the prior art.

Since the degreasing solution is chosen to be practically immiscible or only partially miscible with the degreasing agent, the degreasing agent is not completely soluble in the solvent as is the case with chlorinated solvents.

The fat material is recovered practically undiluted or very slightly diluted, which means that the different fat layers of the objects treated by the method according to the invention can be recovered. The degreaser, which forms a separate phase from the second degreaser, is recycled with very good toluene.

Since the fat is practically insoluble or very slightly soluble in the degreasing solution, this solution has a very small weight percent of dissolved fat at equilibrium. The degreasing solution is thus very slightly contaminated with grease.

The degreasing solution can be present without a surfactant. When the degreasing solution does not contain a surfactant, the preparation of this solution is preferably simplified.

Preferably, the degreasing solution does not contain an organic halogen atom. By organic halogen atom is meant 6,100999 halogens contained in the chemical formula of organic matter. Thus, the method avoids the limitations of current and future legislation regarding the use of organohalogen compounds.

5

Preferably, the degreasing solution contains benzyl alcohol. Most preferably, the degreasing solution contains diacetone alcohol. The solution may be pure diacetone alcohol or may contain additives, in particular a small amount by weight of methanol or water relative to the total weight of the solution, or further mono- and / or dimethyl phosphorus esters.

The degreasing solution preferably has an adhesion stress greater than or equal to 30x10-3 N / m; this is because this ad-15 tensile stress is generally higher than that of the fat on the metal surface.

The fatty substances to be treated by the process can be from any source, in particular from an animal, vegetable, mineral or even synthetic source.

Each article is preferably selected to have hydrophilic polar groups on its surface. This helps to remove the highly lipophilic layer of fat.

25

The surface to be cleaned is preferably metal, but may also be an inorganic glass or ceramic or even an organic polymer.

Another advantage of the method is that in step a) the degreasing solution can be kept at a temperature approaching room temperature, for example 15 ° C-40 ° C.

Conversely, in step c / to facilitate the separation of the two phases, it is possible to design cooling the suspension, if necessary, to reduce the already very low solubility of the degreaser in the degreasing solution and to reduce the already very low solubility of the degreasing solution.

100999

It is also possible to solidify by cooling the first phase, which mainly contains fat, to recover this phase as waste material.

The degreasing solution is preferably selected to evaporate at a temperature less than or equal to 100 ° C at normal pressure. This allows, after step b /, evaporation of said solution covering the surface of the article.

10

The degreasing solution is preferably selected to be miscible with a solvent that is volatile at a temperature less than or equal to 100 ° C at normal pressure.

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

20

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

il The volatile solvent is preferably selected from the group consisting of water, acetone, methanol, ethanol or a mixture thereof.

30

The surface of the article covered with a thin layer of degreasing solution is preferably washed after step b / as a volatile solvent which eliminates this solution layer and replaces it momentarily with a solvent layer. The surface is then dried to obtain a grease-free surface.

In step c / of the process, a second phase is obtained which contains mainly the degreasing solution. The fatty substance may dissolve in this to a very small extent, although it is practically immiscible with this solution. Before proceeding to the recycling of step d / second phase, it is preferably purified with a selectively adsorbed powder, in particular activated carbon, to reduce or completely remove the dissolved fat of the second phase 5 and to obtain a degreasing solution having a substantially similar composition to the degreasing before. This purification can also be performed by redistillation.

10

Step c / can be performed by overflow. In this case, two different phases are obtained, one phase covering the other and stored in a suitable container.

In the case where the first degreasing phase is higher on the degreasing solution, an amazing way has been found to degrease each article by immersing it in the second phase through the first phase and removing the article in the opposite direction, passing through the last first degreasing phase. Namely, the grease material rotates or drains with a thin layer of degreasing solution covering the surface of the article.

In addition to the above description, the following examples will help to better understand the invention, of which Example 7 is given with reference to the accompanying schematic single drawing.

Examples 30 Two different methods were used to evaluate the degreasing efficiency.

35 The first method

A stainless steel plate NM 22S coated with petrolatum oil (completely aliphatic oil) is immersed in the 9 100999 solvent to be tested at room temperature and without the use of ultrasound. To shorten the drying time, the plate is quickly rinsed with methanol (this alcohol is a poor degreaser) and then dried at room temperature. Ten drops of water are placed on each side of the plate, giving a total of 20 contact angle measurements, which measurement is performed with a gonio meter (this angle is determined as in "Testing Surfaces for Cleanliness, WCJones, Metal Finishing, October 1985, p. 13"). described.

10

Degreasing efficiency is evaluated by averaging the results. The standard deviation of the measurement results gives an idea of the homogeneity of degreasing. This static simple immersion method without the use of ultrasounds is practical in assessing the degreasing ability of the solvent alone. By using ultrasound, mixing, spraying, raising the temperature, more factors are obtained that increase the degreasing efficiency.

20

Another method

From the state of the above petrolatum oil, a mixture of polar and 25 non-polar oils was used. The mixture consists of 50% v / v copper linseed oil, 25% ELF Aleda EE 40 oil (phosphorous chlorinated mineral oil), 25% Etirelf BFE 53 oil (completely chlorine-free oil). The metal plate is degreased according to the above method. Degreasing is evaluated using this mixture of three three oils by examining the spread of water on the plate.

A rating system of 0 to 3 was used.

Grade = 3: surface wettability (steel, stainless steel te-35 or aluminum) is very good

Grade = 2: the water spreads quite well but a certain withdrawal is found 10 100999

Grade = 1: baptism is only partial

Rating = 0: water does not wet the surface. This happens when a mixture of these three oils is applied to the surface.

5 In this second method, the tests were performed on a larger scale (10 liter baths). In some cases, ultrasound was used. In certain cases, diacetone alcohol was added.

10

Adhesion stresses (AT) were determined at 20 ° C for petrolatum oil and the various solvents shown in the examples below and are expressed in milli-Newtons per meter.

Example 1 Using the first method, various oxygen-containing solvents were compared with classical halogenated degreasing solvents.

Steel plate coated with 20 - Vaseline (AT = 30): 90 ° plate 15 min. after use for degreasing T 111 (trichloroethane, AT = 25): 52 ° ± 11 ° plate 15 min. after use of trichlorethylene for degreasing (AT = 26): 48 ° ± 10 ° 25 - plate 15 min. after use of trifluorotichloroethane F 113 for degreasing: 57 ° ± 4 plate for 15 min. after using methanol for degreasing (AT = 23): 69 ° ± 9 ° plate 15 min. after use of methylisobutylcarbinol for degreasing (AT = 23): 62 ° ± 8 ° plate for 15 min. after using degreaser. ethylamylacetone (AT = 28): 72 ° ± 6 ° plate for 15 min. after use of methyl isobutylacetone for degreasing (AT = 24): 68 ° ± 6 ° 35 plate for 15 min. after use of diacetone alcohol for degreasing (AT = 31): 56 ° ± 6 ° plate 15 min. after use for degreasing with N-methylpyrrolidone (AT = 36): 72 ° ± 8 ° plate for 15 min. after use of 11 100999 dimethyl sulphoxide for degreasing (AT = 34): 66 ° ± 5 ° plate for 15 min. after use of benzyl alcohol for degreasing (AT = 39.5): 60 ° ± 5 ° 5 These examples easily show the very good degreasing properties of halogenated solvents (water contact angle is less than 60 °). In a very unexpected way, diacetone alcohol gives very good degreasing at room temperature, good homogeneity of angular determinations and efficiency comparable to halogenated solvents. Benzyl alcohol gave good results, but worse than those obtained using diacetone alcohol. The two solvents act with an adhesion stress of more than 30, by a mechanism which is mainly a washing effect and not by dissolving as is the case with halogenated solvents.

In contrast, N-methylpyrrolidone pure and dimethyl sulfoxide pure, although thermodynamically suitable for removing oil from the surface, did not give good results in degreasing. However, the two solvents may each be included in the degreasing solution to increase this polarity and thus to adjust this adhesion stress to the adhesion stress of the grease on the cleaned surface.

Example 2

Determination of the degreasing efficiency was performed as in Example 1. Tests with diacetone alcohol were performed as in the first method (immersion in solvent for 15 min at room temperature). The effectiveness of diacetone alcohol was compared to trichloroethane T 111, which was used hot.

- steel plate coated with Vaseline oil: 90 ° - plate 15 min. after using DA for degreasing 35: 56 ° ± 6 ° plate 15 min. after use of DA with 3% by weight of methanol for degreasing: 52 ° ± 2.5 ° - plate 7 min. after use for degreasing boiling T 111: 61 ° ± 2.5 ° 100999 plate 7 min. after use for degreasing T 111 steam: 63 ° ± 4.5 ° - plate 3 min. after using degreasing boiling T 111 followed by immersion for 1 min. time T 5 111 at room temperature, followed by degreasing for 3 min.

for time T 111 with steam: 54 ° ± 2.5 °

Diacetone alcohol is more effective than boiling T 111 or T 111 in the vapor phase, which is particularly significant because 10 DA is used at room temperature. Diacetone alcohol to which 3% (w / w) methanol has been added when used at room temperature is as effective as boiling T 111 immersion, T 111 immersion at room temperature, T 111 steam phase rinsing cycle. Such a cycle is commonly used in degreasing machines. It is, on the other hand, much more effective than any of these three operations alone.

Example 3 Using the first method, diacetone alcohol has been compared to an aqueous detergent as well as to new propylene glycol ether derivatives or mixtures thereof with petroleum fractions.

- steel plate with Vaseline oil applied: 90 ° - same plate 15 min. after using DA for degreasing: 56 ° ± 6 ° - same plate 15 min. after degreasing with GL 1740 (50 ° C): 56.5 ° ± 10 ° - same plate after 15 min after degreasing with 2-methoxypropanol-1: 61 ° ± 7.5 ° 30 - same plate 15 min. after degreasing with a mixture of 2-methoxypropanol-1 and a C8-Cii petroleum fraction: 63 ° ± 10 °

Although the water detergent gives good results, it requires heating (50 ° C) and rinsing with a large amount of distilled water due to the significant precipitation of salts.

13 100999

Example 4 In this example, we have used a mixture of three polar and non-polar oils. The mixture has been used to coat steel sheets but also to contaminate degreaser-5 leachate. The mixture consists of 50% v / v petrolatum oil (d = 0.86), 25% v / v Aleda EE 40 oil (d = 0.896) and 25% v / v Etirelf BFE 53 (d = 0.935). The first two oils are insoluble in diacetone alcohol. The third oil is 60% soluble (volume per volume of diacetone alcohol-10 hol) in diacetone alcohol. The mixture of the three oils is considered to be only 20% v / v soluble in diacetone alcohol. This poor solubility in the disadvantage that the oils are very polar greatly reduces the contamination of the degreasing solution.

15

Experiments with DA have been performed using the second method. Tests with Vaseline oil 20 - Vaseline oil coated steel plate: grade = 0 - degreasing DA: 11a 15 min. time without ultrasound: grade = 1.5 25 - degreasing DA: 11a 5 min. time with ultrasound: grade = 2 - - degreasing DA: 11a 10 min. time with ultrasound: grade = 2.5 - degreasing with DA 15 min. time 30 with ultrasound: grade = 3

Tests with a mixture of three oils 35 - steel plate coated with a mixture of three oils: grade = 0 - degreasing DA: 11a 15 min. time with ultrasound: grade = 2-2.5 5 14 100999

On a larger scale (10 m ^ steel plate and 10 l baths), diacetone alcohol gives very competitive results for petrolatum as well as for a mixture of three oils.

Contamination of degreasing solution using a mixture of three oils 10 - steel plate coated with a mixture of three oils: grade = 0 - degreasing 15 min. using ultrasound of DA contaminated with 3.5% (v / v) of a mixture of three oils: grade = 0 15 - degreasing 15 min. for DA with 11% MeOH (w / w): grade = 2 - degreasing 15 min. for 5 hours with the addition of 5% phosphorus methyl ester (w / w weight) neutralized with triethanol-20 amine and 5% water: grade = 2

When methanol or phosphorus methyl ester is added to the diacetone alcohol, good degreasing is still achieved, even though the bath is 3.5% contaminated with a mixture of three oils (this 25 corresponds to degreasing of 3500 plates).

Example 5

Stainless MM 22S blade plates were coated with three different oils, and then degreased with a solution consisting of 89% by weight, 89% DA, 10% water and a 50/50 mixture of 1% phosphoric acid mono- and dimethyl ester by weight neutralized. triethanolamine.

Degreasing is performed for 5 minutes under ultrasound using the first method, but the degreasing is evaluated by observing the spread of water on the plate in the same way as in Example 4. The results are as follows: - Vaseline oil: grade = 2-3 „100999 - mixture of three oils: grade = 2-3 - MAGNA BDX 68 (CASTROL) oil: grade = 0

Example 6 5 Degreasing is carried out in the same way as in Example 5, but with a degreasing solution consisting of 50% by weight of DA and 50% by weight of dimethyl sulfoxide: - MAGNA BDX 68 oil: grade = 2-3 Example 7 This example illustrates with reference to the only image a prototype of a two-bath degreaser 1 using diacetone alcohol (DA). Degreasing efficiency tests are performed according to another method.

This device 1 comprises a first basin 2 partially filled with a first bath consisting of a first oil phase 6 which covers a second phase 5 consisting essentially of diacetone alcohol.

20

The above phase 6 flows over to the billing basin 4, forming an oil column 7, the height of which in the billing basin increases with successive washes.

This oil column 7 floats on top of the DA layer 8 coming from the overflow of the basin 2 or the final stage of the overflow of the phases 5,6.

The piping 9, which is equipped with a pump 10 and a three-branch valve-30 brick 11, connects the lower part of the downspout 4 to the bottom of the basin 2.

; This piping and its pump make it possible to recycle the DA layer 8 into the second phase 5 of the basin 2 or to bring the oil of the column 7 into the oil collection pipeline for further treatment 35.

This device 1 also comprises a second basin 3 filled with a DA bath 13, into which objects are degreased 16 100999 only after they have taken turns in phases 5 and 6 of the first basin 2.

The degreasing by immersion is illustrated by 5 dotted lines 14 on the object 15.

The first bath removes most of the oil. This floats on the surface of the DA and ends up in the top phase of the billing basin 4. Thus, a large part of the impurities of the bath can be eliminated. However, certain polar oils are soluble in DA. In order to achieve very good degreasing, a second bath 13 has been added to the apparatus with pure DA, which is used to finish degreasing and has a very long service life.

15

The first DA bath is contaminated with 3.5% by volume of a mixture of three oils.

- degreasing 10 min. only in the first bath: grade = 0.5 20 - degreasing 5 min. (first bath) + 5 min. (second bath): rating = 2.5 This room temperature degreasing is therefore very effective. In addition, degreasing baths are well contaminated hi-25 again. When it comes to very large amounts of pollution, it still proves to be effective.

30 35

Claims (20)

A process for degreasing various articles (15) using a degreasing liquid, each article being at least partially covered by a grease layer, characterized in that said liquid has a higher adhesion stress than the grease substance on the surface of each article. and that the liquid is practically immiscible or only partially miscible with the fatty substance, while said method for each subject comprises: it forms a suspension in the liquid, the surface of the article being covered by the liquid having a greater affinity for the surface, b) separating the article from said suspension to obtain an article having a surface covered by a thin layer of (c) the suspension is utilized and separated into two different phases: - a first phase (6,7), which mainly consists of the fatty substance 25. a second phase (5,8), which mainly consists of the degreasing liquid, (d) the second phase is recirculated in step a). 30 Process according to claim 1, characterized in that the degreasing solution does not contain a surfactant. »« 3. A process according to claim 1 or 2, characterized in that the stripping solution does not contain an organic halogen atom. Process according to any of claims 1-3, characterized in that the degreasing solution contains diacetone alcohol. 2, 100999 Process according to any of claims 1-3, characterized in that the degreasing solution contains benzyl alcohol. 5 Process according to any one of claims 1-5, characterized in that the degreasing solution has an adhesion stress equal to or greater than 30x10l 3 N / m. Process according to any of claims 1-6, characterized in that the polar hydrophilic groups are present on the surface of each object. Method according to any of claims 1-7, characterized in that said surface consists of metal. 15 Method according to any of claims 1-7, characterized in that said surface consists of inorganic glass or ceramic. 20 Method according to any of claims 1-7, characterized in that said surface consists of an organic polymer. 11. A process according to any one of claims 1-10, characterized in that step a) is carried out at a temperature of 15-40 ° C of the degreasing liquid. Process according to any of claims 1 to 11, characterized in that the degreasing liquid is evaporable at a temperature lower than or equal to 100 ° C. Process according to claim 12, characterized in that after step b) the thin layer of said liquid covering the surface of the article is evaporated. 35 Process according to any one of claims 1-12, characterized in that the degreasing liquid is miscible with a solvent which is evaporable at a temperature lower than or equal to 100 ° C at normal pressure. 22 100999 Process according to Claim 14, characterized in that the evaporable solution is selected from a group consisting of water, acetone, methanol, ethanol or any mixture thereof. 5 Method according to claim 14 or 15, characterized in that after step b) the article covered with a thin layer of said solution is washed with the evaporable solvent and then dried the article to provide a surface free of grease. Process according to any of claims 1-16, characterized in that the substantially liquid containing the second phase is cleaned with a powdery agent having selective adsorption, especially active koi, before it is recirculated in step a) of the process. Process according to any of claims 1-17, characterized in that step a) is carried out by immersing the object 20. degreasing liquid. Method according to any of claims 1-18, characterized in that the separation in step c) is carried out so that the phases are allowed to stand and separate. 25 20. A method according to claim 19, characterized in that degreasing step a) is carried out by immersing each article in the second phase covered by the first phase and the separating step b) is performed by removing each article 30 from the second phase and then from the first phase.