FR2736936A1 - PROCESS FOR DEGREASING HYDROGEN PEROXIDE AND APPLICATION TO METALLIC ARTICLES - Google Patents

Abstract

The present invention relates to the use of a mixture consisting of an aqueous solution containing from 3 to 50% by weight of hydrogen peroxide and an effective amount of at least one wetting surfactant, stable in an oxidizing medium, as a degreasing composition, in particular for cleaning metal parts. It also relates to a degreasing process using this mixture. Application: industrial degreasing in the mechanical industry.

Description

The present invention relates generally to the field of degreasing

  and industrial cleaning of manufactured parts and mainly relates to the use of compositions based on hydrogen peroxide as a degreasing agent, in particular for metal parts. During manufacture, a mechanical part undergoes various cleaning and degreasing treatments. These treatments can be carried out either by means of aqueous solutions ("aqueous process") or by means of

  solvents ("solvent process").

  Among the solvents currently used for the implementation of these last treatments, we distinguish between petroleum solvents and chlorinated solvents, the latter being subdivided into two subgroups:

  chlorinated solvents and chlorofluorinated solvents.

  Chlorinated solvents are mainly used for the cleaning and the degreasing of the metals at different stages: - degreasing between operations, - final cleaning, - degreasing before surface treatment,

- cleaning of maintenance.

  These solvents have in fact many

advantages in these applications.

  In particular, they have good degreasing properties, whatever the type of pollution to

  clean, and are compatible with all materials.

  In addition, their boiling point being relatively low, it is possible to use them in the vapor phase with

  a relatively low energy expenditure.

  Finally, they can be used hot virtually without risk because they do not have a flash point.

  However, chlorinated solvents are toxic

  to humans and harmful to the environment, since they are notably suspected of destroying the ozone layer. For these reasons, chlorinated solvents are currently subject to severe regulation intended to limit or even to prohibit their use in the particular case of chlorofluorinated solvents (CFC) and trichloroethane 111 (T111). Under these conditions, the aim of the present invention is to solve the technical problem consisting in the provision of degreasing compositions that can be used as a replacement for chlorinated solvents, with the same efficiency as the latter, but without presenting them.

  the disadvantages mentioned above.

  The present invention also aims to solve the technical problem of providing a method for implementation at scale

  industrial of these degreasing compositions.

  It has been found, and this is the basis of the present invention, that the mixtures consist of an aqueous solution containing from 3 to 50% by weight of hydrogen peroxide and an effective amount of at least one surfactant. wetting, stable in oxidizing medium, have very good degreasing properties and can be advantageously used for cleaning parts

especially metallic.

  Mixtures such as those used in the context of the present invention have already been described in

EP 0 351 772.

  More specifically, this prior document generally describes aqueous solutions of hydrogen peroxide containing any surfactant, the weight ratio of this surfactant to peroxide.

  with hydrogen being between about 1: 1 and 1:10,000.

  It should be noted that, according to this prior document, the surfactant essentially has the following functions: on the one hand, to stabilize the solution of hydrogen peroxide against the catalytic activity of metal ions, and in particular of cupric ions; and on the other hand, to facilitate the rinsing of metal parts treated with a solution of hydrogen peroxide. However, the document EP 351 772 does not include any indication likely to induce the skilled person to use a surfactant in general, and a fortiori a wetting surfactant, to make a composition.

  degreasing agent based on hydrogen peroxide.

  Thus, according to a first aspect, the invention aims to cover the use of a mixture consisting of an aqueous solution containing from 3 to 50% by weight of hydrogen peroxide and an effective amount of at least one wetting surfactant, stable in an oxidizing medium, as a degreasing composition, especially for the cleaning of

metal parts.

  Many wetting surfactants can be used in the context of the present invention to improve the degreasing properties of solutions.

aqueous hydrogen peroxide.

  These surfactants can be anionic,

  nonionic, cationic or amphoteric.

  Among the anionic agents that may be used, mention will be made more particularly of organic mono-, di- and tri-esters of phosphoric acid, sulphonated fatty acids and esters and carboxylated ethoxylated fatty alcohols marketed in particular under the name AKYPO by CHEMY. as well as alkylnaphthalenesulfonates. Among the nonionic surfactants that may be used, mention will be made more particularly of: the following non-alkoxylated derivatives: alkyl polyglucosides, fatty acid alkanol amides, amine oxides; the following alkoxylated derivatives: alkoxylated alcohols and alkylphenols, copolymers of ethylene and propylene oxides, ethoxylated fatty acids, ethoxylated sorbitan esters, ethoxylated glycerides, alkoxylated amines and amides, alkoxylated derivatives of

  perfluorinated and polyfluorinated alcohols.

  Among the cationic surfactants that may be used, mention will be made more particularly of quaternary ammoniums and salts

amine and imidazoline.

  Finally, among the amphoteric surfactants that may be used, mention may be made of

especially betaines.

  The best results have been obtained using hydrophilic nonionic wetting surfactants and more particularly the

ethoxylated sorbitan.

  The amount of surfactants to use depends of course on the nature of the surfactant, and the general conditions of implementation of the degreasing treatment but can be easily determined by the skilled person. In general, the weight ratio between the surfactant and the hydrogen peroxide in the mixtures to be used will be between 1:10 and 1: 1000,

preferably between 1:50 and 1: 200.

  The best results, in terms of degreasing, were obtained with an aqueous solution containing approximately

  % by weight of hydrogen peroxide.

  The aqueous solution containing the hydrogen peroxide can be prepared by dilution in an aqueous medium of a concentrated hydrogen peroxide solution and / or by dissolving in an aqueous medium hydrogen peroxide precursor compounds such as, for example,

  percolated as in particular sodium percarbonate.

  Ethoxylated sorbitan esters used in a weight ratio of about 1: 200 with a 35% hydrogen peroxide solution provide the

  presently preferred embodiment of the invention.

  Among the ethoxylated sorbitan esters preferably used in the context of the present invention,

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  mention will in particular be made of ethoxylated sorbitan monolaurate, and in particular the product marketed under the name

  MONTANOX 20 by the company SEPPIC.

  It is possible to add to the mixture used in accordance with the present invention one or more agent (s) stabilizing hydrogen peroxide, so as to increase the period of use of the degreasing composition. Compounds with the property of forming complexes with metals, for example aminocarboxylic and aminophosphonic compounds and stabilizers such as sodium stannate and sodium pyrophosphate described in the literature, are particularly suitable for this purpose. According to a second aspect, the present application is intended to cover a method for degreasing parts, especially metallic parts, characterized in that it consists in: immersing said parts in a bath comprising a mixture consisting of an aqueous solution containing from 3 to 50% by weight of hydrogen peroxide and an effective amount of at least one wetting surfactant, stable in an oxidizing medium, at a temperature of between 15 and 100 ° C., preferably between 25 ° and 90 ° C., for a period of time between 5 seconds and 60 minutes; and - rinsing said parts thus treated The nature of the surfactant and the concentrations of hydrogen peroxide and surfactant in the immersion bath are such that

previously defined.

  Advantageously, the aforementioned immersion of the parts in the bath will be accompanied by a mechanical action intended to facilitate the contact between the parts and the

bath.

  This mechanical action may for example consist of the use of jets, bath stirring means or

  parts, or in the use of ultrasound.

  The temperature and duration conditions of the immersion step depend in particular on the concentrations

  in hydrogen peroxide and surfactant.

  In general, the duration of the immersion treatment will be shorter as the temperature of the

bath will be high.

  The skilled person will have no difficulty in determining the conditions of temperature and duration

  appropriate in each particular case.

  HIGHLIGHTING THE PROPERTIES OF MIXTURES

  USED IN THE CONTEXT OF THE INVENTION

  The degreasing properties of the mixtures of hydrogen peroxide and surfactants were demonstrated as follows: Stainless steel plates (10 cm × 10 cm) were

  have been polluted in a controlled manner.

  For this purpose, a mixture of oil in hexane is projected on a plate previously arranged on a

plateau set in rotation.

  The centrifugal force due to the rotation of the plate allows the spreading of the oil mixture on the surface of the latter, and the amount of oil projected must be such that the plate is completely covered and that an excess

oil is thrown aside.

  The two faces of each plate are thus prepared. Weight measurements before and after pollution showed that the amount of oil deposited on each side by this method was of the order of 2 mg, which corresponds to

0.2 g / m2.

  The plates thus polluted are arranged in beakers of sufficient size so that the plate can

lay flat in the beaker.

  A clean and inert carrier with respect to the hydrogen peroxide is placed between the bottom of the beaker and the plate, so as to allow free circulation of the solution.

  test, on the entire surface of the plate.

  The hot tests were carried out in a water bath

under a fume hood.

  The bath is heated to the desired temperature until the thermal equilibria are achieved,

then the plate is introduced.

  The thermal inertia of the latter is low enough not to cause variation in

  temperature when it is put in place.

  At the end of each test, the treated plate is removed from the bath, then rinsed with running water and finally

dried in a vertical position.

  Assessment of the state of cleanliness of a surface

is a delicate problem.

  Indeed, to date there is no simple, rigorous and absolute way of quantifying the cleanliness of the

surface of a room.

  A method that can be used to evaluate the state of cleanliness of a surface is the method

called "scotch test".

  This method consists in carefully applying a piece of adhesive tape to the surface to be tested, then to

  remove it and stick it on a sheet of white paper.

  It is assumed that the scotch carried with it all the pollution at the point where it was in contact with the plate. Under these conditions, when the tape is placed on the white sheet, one can visually appreciate its

  change of color by referring to a scale

established.

  However, this method could not be applied in that the oil deposited on the stainless plates is colorless, so that it does not appear

color change of the tape.

  The method that has been used in the context of the invention is a variant of the Scotch test based on the finding that the color of a clean plate

  is lighter than that of a polluted plate.

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  Assuming that the scotch removes any greasy pollution on the surface of the plate, a clear trace should appear, when after being applied to a

  polluted plate, the tape is removed.

  The evaluation of the degreasing action of the bath was therefore carried out by evaluating the trace thus produced. For this purpose we have established a five-level evaluation scale, according to the trace left by the scotch

on plate.

  - Level O: no effect, the plate has kept its original color. Of course, she is very fat to the touch. - Level 1: noticeable effect to a slight color change, but there is still a lot

detectable oil to the touch.

  - Level 2: the layer of oil is imperceptible to the touch, the trace of the tape is still visible, the edge of

the trace being continuous.

  - Level 3: the trace of the tape is invisible in places. - Level 4: the trace of tape is totally invisible.

RESULTS OF REALIZED TESTS

  Preliminary tests have shown the essential role of rinsing in the degreasing process

according to the invention.

  At the end of the bath, the parts are covered with a liquid film containing hydrogen peroxide, surfactant and various materials.

from pollution.

  The latter, which are generally oily and hydrophobic, tend to form associations, for example

  micelles, with surfactant molecules.

9 2736936

  By drying, the water and the hydrogen peroxide evaporate and these micelles are redeposited on the surface of

the room.

  It is therefore particularly important to rinse the immersed parts in the degreasing bath for

get the desired effect.

  Table I gives the results of the various tests which have demonstrated the detergent properties of the mixtures based on hydrogen peroxide and

surfactants.

  The wetting surfactant used in the context of these tests is an ethoxylated sorbitan monolaurate

(product MONTANOX 20).

  Of course, this surfactant is mentioned only as a particular illustrative example and preferred, but as indicated above, the skilled person will be able to find, especially among the surfactant classes mentioned above, other compounds leading to

desired result.

  Test No. 1 was carried out under relatively severe operating conditions, the concentration of hydrogen peroxide being 35% by weight, the temperature

  70 C bath and immersion time of 30 minutes.

  In these conditions the degreasing action is

particularly remarkable.

  Indeed, after rinsing and drying, the test

  mentioned previously shows that the plate is clean.

  The following four tests (n 2 to 5) were conducted to highlight the role of each of the

  constituents of the degreasing bath.

  In these tests, the temperature of the bath is 70-

   C and the immersion time of 15 minutes.

  A bath consisting only of distilled water is

totally ineffective (test 3).

  Hydrogen peroxide alone

  than at a relatively average result (test 4).

  Similarly, the surfactant used alone provides

  a poor result (trial 5).

  On the other hand, the combination of hydrogen peroxide

  surfactant proves to be quite effective (test n 2).

  The following tests (Nos. 6, 7 and 8) highlight the influence of the bath temperature on the degreasing action. The results obtained show that the temperature of the bath is an important factor for obtaining the desired result, and that there exists for a predetermined duration of treatment a threshold value below

  which treatment loses its effectiveness.

  In the case of the surfactant used in these tests, this threshold is between 50 and 70 C, for a duration

immersion, 15 minutes.

  The 60 C test appears to be a relatively satisfactory compromise between the duration of the treatment and the temperature of the bath for use in

the mechanical industry.

  The following tests (n 9 to 14) highlight the influence of immersion time in the bath, on

the degreasing action.

  The results obtained show that immersion time is an important factor in obtaining the desired result, and that, for a predetermined bath temperature, there is a threshold value below

  which treatment loses its effectiveness.

  Tests Nos. 9 to 12 carried out between 80 and 87 ° C show that the minimum time to reach an acceptable level of cleanliness is approximately 2.5 minutes. Tests Nos. 13 and 14 show that a satisfactory result can be obtained for a bath temperature

  90 C and immersion time of 2.5 minutes.

  Thus, it is possible in the context of the invention to reduce the duration of the immersion whenever necessary, but in this case, the bath temperature must be increased to achieve

desired result.

  The following tests (Nos. 15 to 17) have shown that it is still possible to simultaneously reduce the immersion time and the temperature of the bath when the immersion treatment is assisted by a treatment such as the use of ultrasound. Thus, one can still obtain good results under these conditions for a duration of immersion of the order

  1 minute and a bath temperature of about 70 C.

  The following test (No. 18) shows that the concentration of surfactant is an important factor in obtaining the desired result and that there exists, for a predetermined immersion time and a bath temperature, a threshold value below of which the

treatment loses its effectiveness.

  In the case where the surfactant is an ethoxylated sorbitan monolaurate, an optimum surfactant concentration is 3.5 g / l under conditions

  suitable for use on an industrial scale.

  Similarly, test No. 19 shows that the concentration of hydrogen peroxide is an important factor for obtaining the desired result and under the above conditions, a concentration threshold value of about 35%

seems appropriate.

  Test No. 20 has shown that good results can be obtained using a peroxide bath

  of hydrogen obtained by dissolution of perhydrated compounds.

  In this test sodium percarbonate (2Na 2 CO 3,

3H202) was used.

  The interest of these compounds is to accumulate the action

  hydrogen peroxide with that of a basic solution.

  This may be advantageous in that the fats saponify in an alkaline medium to produce

soluble compounds in water.

  As part of this test, a concentration of sodium percarbonate of about 140 g / l allows to drive

to excellent results.

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  In order to evaluate the stability of the solution, the concentration of hydrogen peroxide and the pH were

measured regularly.

  The results obtained show that the pH of the bath remains substantially constant before and after cleaning at a

value of about 2.5.

  On the other hand, the hydrogen peroxide titer increases slightly during treatment probably due to the fact that evaporation tends to concentrate the

peroxide solution.

  However this phenomenon is relatively negligible. The process according to the present invention

has many advantages.

  For the most part, it should be noted that this process can be easily implemented on existing installations, practically without pollution, since the usable chemical agents are

generally biodegradable.

TABLE I

  TEST Concentration Concentration Temperature Duration Note in H202 in surfactant (OC) (Mn) (% by weight) (g / t)

1 35 3.5 70 30 4

2 35 3.5 70 15 3

3 0 0 75 15 0

4 35 0 75 15 2

0 3.5 75 15

6 35 3.5 50 15 1 +

7 35 3.5 90 15 4-

8 35 3.5 60 15 3+

9 35 3.5 80 2 1+

35 3.5 85 2.5 3+

11 35 3.5 85 2 1

12 35 3.5 87 2, 5 3+

13 35 3.5 90 2 3

14 35 3.5 90 2, 25 4-

35 3.5 81 1 4-

16 35 3.5 76 1 3+

17 35 3.5 70 1 3 +

18 35 1.5 60 15 2

19 15 3.5 60 15 2

3.5 60 15 4

- 1 61

b

Claims (10)

  1. Use of a mixture consisting of an aqueous solution containing from 3 to 50% by weight of hydrogen peroxide and an effective amount of at least one wetting surfactant, stable in an oxidizing medium, as a particular degreasing composition for cleaning metal parts.   2. Use according to claim 1, characterized in that the surfactant (s) surfactant (s) mentioned above (s) is (are) chosen from the group consisting of mono, di and organic esters of phosphoric acid, sulphonated fatty acids and esters, ethoxylated carboxylated fatty alcohols as well as alkylnaphthalenesulfonates, alkyl polyglucosides, fatty acid alkanol amides, amine oxides; alkoxylated alcohols and alkylphenols, copolymers of ethylene and propylene oxides, ethoxylated fatty acids, ethoxylated sorbitan esters, ethoxylated glycerides, alkoxylated amines and amides, alkoxylated derivatives of perfluorinated and polyfluorinated alcohols, ammoniums quaternary salts, amine and imidazoline salts, and betaines. 3. Use according to claim 1 or 2, characterized in that the surfactant (s) surfactant (s) mentioned above (s) is (are) chosen from nonionic surfactants of character hydrophilic and   particularly from ethoxylated sorbitan esters.   4. Use according to one of claims 1 to 3,   characterized in that the weight ratio of the surfactant (s) to the hydrogen peroxide in said mixture is from 1:10 to 1: 1000, preferably between 1:50 and 1: 200.   5. Use according to one of claims 1 to 4,   characterized in that the aforementioned aqueous solution   comprises 35% by weight of hydrogen peroxide.   6. Use according to one of claims 1 to 5,   characterized in that the aqueous solution containing the hydrogen peroxide is prepared by dilution in a 2736936   aqueous medium of a solution of concentrated hydrogen peroxide and / or by dissolution in an aqueous medium of hydrogen peroxide precursor compounds as per example sodium percarbonate.   7. Process for degreasing parts, especially metallic parts, characterized in that it consists in: immersing said parts in a bath comprising a mixture consisting of an aqueous solution containing from 3 to 50% by weight of hydrogen peroxide and of an effective amount of at least one wetting surfactant, stable in an oxidizing medium, at a temperature of between 15 and 100 ° C., preferably between 25 ° and 90 ° C., for a duration of between 5 seconds and 60 minutes; and   - Rinsing said parts thus treated.   8. Method according to claim 6, characterized in that the aforementioned immersion of the parts in the bath is accompanied by a mechanical action to facilitate contact between the parts and the bath as in particular the use of ultrasound.   9. The method of claim 7 or 8, characterized in that the (or) surfactant (s) surfactant (s) above (s) is (are) chosen from the group comprising mono, di and tri organic esters of phosphoric acid, sulphonated fatty acids and esters, ethoxylated carboxylated fatty alcohols as well as alkylnaphthalenesulfonates, alkyl polyglucosides, fatty acid alkanol amides, amine oxides; alkoxylated alcohols and alkylphenols, copolymers of ethylene and propylene oxides, ethoxylated fatty acids, ethoxylated sorbitan esters, ethoxylated glycerides, alkoxylated amines and amides, alkoxylated derivatives of perfluorinated and polyfluorinated alcohols, ammoniums quaternary salts, amine and imidazoline salts, and betaine.   10. Method according to one of claims 7 to 9,   characterized in that the said surfactant (s) surfactant (s) is (are) selected from among the A 16 2736936   nonionic surfactants with a hydrophilic nature and   especially from ethoxylated sorbitan esters.