CA2181416A1

CA2181416A1 - Degreasing process with hydrogen peroxide especially for metal articles

Info

Publication number: CA2181416A1
Application number: CA 2181416
Authority: CA
Inventors: Thierry Sindzingre; Christine Devos; Raymond Soumarmon; Eric Duchateau
Original assignee: CHEMODAL SA; Chemoxal SA; LAir Liquide SA pour lEtude et lExploitation des Procedes Georges Claude
Current assignee: CHEMODAL SA; Chemoxal SA; LAir Liquide SA pour lEtude et lExploitation des Procedes Georges Claude
Priority date: 1995-07-19
Filing date: 1996-07-17
Publication date: 1997-01-20
Also published as: FR2736936A1; JPH09111483A; EP0756023A1; FR2736936B1

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 of an effective quantity of at least one wetting surface-active agent which is stable in an oxidizing medium, as degreasing composition especially for cleaning metal articles.
It relates, furthermore, to a degreasing process making use of this mixture.
Application: industrial degreasing in the engineering industry.

Description

"~. 2181416 The present in~rention relate~ generally to the field of industrial degreasing ~nd cleaning of manu~actured articles and ita subject-matter is chie~ly the use of compositions based on hy.l~ ~ peroxide aa degrea3ing agent eapecially for metal articles.
A mechanical article i5 aubjected to varioua cleaning and degrea ~ing treatments during its manuf acture .
These treatmenta can be carried out either by means o~ aqueoua solutions ( "aqueous process~V ), or by means of solventG ("solvent proces~") .
Petroleum aolvents and ~hlnr;n~ted solvents are prominent among the aolvents currently employed for making use o~ these latter treatments, the laat-mentioned solvents bei~g subdivided into two aubgroups:
chlorinated ~olventa and chloro~luorinated 301vents.
Chlorinated solvents are employed chie~ly for cleaning and degreasin~ of metals at varioua stages:
- degreasing between operations, - final cleanirg, - degreasing before sur$ace treatment, - maintenance cleaning.
Theae solvents in fact offer many advantages in these applications.
In particular they have good degreasing properties, whatever the type of contamination to be cleaned of ~, and are compatible with all materials.
In addition, ~ince their boiling point is relatively low, they can be employed in vapour pharle with a relatively low expenditure of energy.
Finally, they can be employed hot practically without ri k because they do not exhibit any fla3h point .
~Iowever, chlorinated solvents are toxic to man and detrimental to the~ environment, because they are, in particular, suspected of de~troying the ozone layer.
For these reasons, chlorinated solvents are at present aubject to a severe regulation intended to re3trict, or even to prohibit, their uae, in the 2l8l4l6 particular ca3e of chlorofluorinated (CFC) solvents and of 1,1,1-trichloroethane (T111) .
In these conditions the obi ective of the present invention is to solve the tf~'l~n; ~'Al problem 5 consisting of the provision of degrea3ing compositions capable of being employed as a replacement ~or the chlorinated solvents, l~ith the aame effectiveness as the latter but without exhibiting their diæadvantages which were recalled above.
Another objective of the present invention is to solve the technical problem consisting in providing a proce3s allowing the~;e degreasing compositions to be used on an industrial scale.
It has been found, and this constitutes the 15 basis of the present invention, that mixtures consisting of an aqueous solution containing from 3 to 50 % by weight o~ hydLugcul peroxide and o~ an effective quantity of at least one wetting surface-active agent which is stable in an ~Y;~;7;nS medium exhibit very 20 good degreasing properties and can be advantageously employed for cleaning articles, especially metallic one 8 .
Some mixtures Euch as those employed within the scope of the present invention have already been descri~ed generically in document EP 0 351 772.
More precisely,, this prior document describes in a general manner aqueous solutions of hydrogen peroxide containing a 2lurface-active agent o~ any kind, the weight ratio of this surface-active agent to the 3 0 hydrogen peroxide being between approximately 1:1 and 1: 10 000 .
It should be noted that, according to this prior document, the function o~ the surface-active agent is essentially:
- on the one hand, to stabilize the hYdLU~L1 peroxide solution against the catalytic activity of metal ions, and in particular of cupric ions, and - on the other hand, to facilitate the rinsing of metal articles which are treated with a l-yd-uu~
peroxide solution.
~ Iowever, document EP 351 772 does not comprise 5 any indication liable to encourage a person skilled in the art to employ a surface-active agent in general and, a fortiori, a wetting surface-active agent in order to produce a degreaaing composition based on 11YdL US~ peroxide .
Thus, according to a first a3pect, the invention aims to cover the use of a mixture consisting of an aqueous solution cnntr~;n;ns from 3 to 50 % and preferably from 10 % ~o 40 % by weight o hyd~ uge~l peroxide and of an eff~ctive ~uantity of at least one 15 wetting surface-active agent which is stable in an rY;~;7;n~ medium, as degrea3ing composition especially for cleaning metal article3.
Many wetting surface-active agents can be employed within the scope of the present invention in 20 order to improve the degreasing properties of aqueous solutions of ~yd~ouen p~roxide.
These surface-active agents may be anionic, n~n;r~n;r, cationic or a~nphoteric.
~ mong the anionic agents capable of being 25 employed there will be mentioned more particularly the organic mono-, di- and triesters of phosphoric acid, fatty acids and sulphonated e3ters, carboxylated ethoxylated fatty alcohols marketed especially under the name Akypo b}~ the Chemy company, and 30 alkyln~rb~h~ nr~Aulphonates.
Among the nonionic surface-active agents capable of being employed there will be mentioned more particularly:
- the following n~nr~ Yylated derivatives:
alkylpolyglucosides, fatty acid alkanol-amide3 and amine oxides;
- the following alkoxylated derivatives:
alkoxylated alcohols and alkylphenols, copolymers of ethylene and propylene oxides, ethoxylated fatty acids, ethoxylated sorbitan esters, etho~ylated glycerides, alkoxylated amines and amides and alkoxylated derivatives of perfluo~ inated and polyfluorinated alcohols.
Among the cationic surface-active agents capable of being employed there will be mentioned more particularly quaternary ammoniums and amine and imidazoline salts.
Finally, betaines will be mentioned more particularly among the amphoteric surface-active agents capable of being employed.
The best results have been obtained by employing nonionic wetting surface-active agents of hydrophilic nature and more particularly ethoxylated sorbitan esters.
The quantity of surface-active agents to be employed depends, of course, on the nature of the surfactant and on the general conditions of use of the degreasing treatment, but can be easily det~ nf~d by a person skilled in the art.
In general, the weight ratio of the surface-active agent to ~yd .g~ l peroxide within the mixtures to be employed will be between 1:10 and 1:1000, pre~erably between 1:30 and 1:100.
The aqueous solution containing hyd~y~ll peroxide may be prepared by diluting a concentrated solution of llydloy~: l peroxide in an aqueous medium.
~thoxylated sorbitan esters employed in a weight ratio of approximately 1:100 with a 35% solution of hydrogen peroxide provide the currently preferred embodiment of the invention when working at 60C.
When operating at 70C the preferred solution includes, as active agent: from 10 to 15 % of the weight of 11YdL~Ye11 peroxide and from 0.3 to 0.5 % of ethoxylated sorbitan esters.
Among the ethoxylated sorbitan esters preferably employed within the scope of the present invention there will be mentioned in particular _ 5 _ 2l8l416 ethoxylated sorbitan ~ -rate and ~ApeC; ~l ly the product marketed under the name M~ln~51n~ 20(~3 by the S eppic company .
In a second aspect the subject-matter of the 5 invention is an a~ueous aolution comprising, as active agent, 10 to 15 % by ~eight of hydrogen peroxide and O . 3 to O . 5 % by weight of ethoxylated sorbitan monolaurate .
In a third aspect, the subject-matter of the lO invention is an ac,ueous solution comprising, as active agent, 30 to 50 % by ~eight of 11YdLV~ peroxide and O . 5 % to l % by weight of ethoxylated sorbitan r~n~ llrate. Such a solution, ready for use, can be employed by being diluted to 1/2, or else without being 15 diluted, as additive in order to readjust the LYdL~Ye11 peroxide assay of the working solution during a degreasing operation.
One or more agent(s) st ~h;l;~;n~ the llydLo~
peroxide may be added to the mixture employed in 20 accordance with the present invention, in order to increase the duration of use of the degreasing composition .
The - ollnrlA which will be mentioned in particular for this purpose are those which have the property of forming complexes with metals, like, for example, ~m;n~ rhoxylic and aminophosphonic compounds, and stabilizers such as sodium stannate and sodium pyrophosphate, which ar~ described in the literature.
.according to a f ourth a~pect, the present application aims to ~over a process for degreasing articles, especially ~etallic ones, characterized in thst it consists:
- in immersing the said articles in a bath including a mixture consisting of an a~ueous solution containing from 3 to 50 % by weight o~ hydrogen peroxide and an e~ective cuantity of ~t leaat one wetting surface-active agent which is atable in an r~;rl;~;n~
medium, at a temperature of between 15 and 100C, preferably between 25 and 90C, for a period of between 5 seconds and 60 minutes, preferably fr~m 5 to 30 minutes, and, - in rinsing the said articles thus treated.
The nature of ~he surface-active agent and the concentrations of l~ydro~el~ peroxide and of ~urface-active agent within the immer3ion bath are such as de f ined above .
The abovementioned immersion of the articles in the bath will advant~geously be ~3rr~l , ; ed by a mechanical action inte~ded to facilitate the contact between the articles and the bath.
This mechanical action may, for example, consist of the uae of jets, of means for agitating the bath or articles, or el~e of the use of ultrasonics.
The temperature and duration conditions of the imTnersion stage depend ~pe~ ly on the concentrations of ilydL~ peroxide and of surface-active agent.
In general, t~le duration of the imTnersion treatment will be proportionally shorter, the higher the bath temperature.
A person slcill ed in the art will have no difficulty in ~et~;n~n~ the appropriate temperature and duration conditions in each particular case.
Dr ~ TION O}i ~TT' PRopERTTT~c OF ~T~ ~TlrTTTT~T.
EMP~OYEn WITT-TT~T ~TTTe 5COPE OF ~T~ TTION
The degreasing properties of the mixturea of hydrogen peroxide and of surface-active agents were demonstrated in the following manner:
Stainless steel panels (10 cm x 10 cm) were contaminated in a controlled manner.
To this end a mixture of oil in hexane is sprayed onto a panel previously placed on a rotating tray .
The centrifugal force due to the rotation of the panel allows the oil mixture to spread on the surface of the latter and the quantity of oil sprayed - 7 - 218141~
must be such that the ]?anel is completely covered and that an exces3 of oil is thrown off at the side.
Both faces of e2ch panel are thus prepared.
Weight measurements before and after 5 contamination showed that the quantity of oil deposited on each face by this me3thod was of the order of 2 mg, which corresponds to a rnnron~ration of 0 . 2 g/m2 .
Thus contaminated, the panels are placed in beakers of sufficient size to enable the panel to lie 10 flat in the beaker.
A support which is clean and inert towards lly~ _11 peroxide is placed between the bottom of the beaker and the panel, 80 as to permit free circulation of the solution to be cested, over the entire surface 15 of the panel.
The hot tests ~ere performed on a steam bath under an exhaust hood.
The bath is heeLted to the desired temperature until the thermal equilibria have been obtained, and 2û the panel is then introduced into it.
The thermal inertia of the latter i6 sufficiently small not to result in a change in temperature when it i8 placed in position.
At the end of each test the treated panel is taken out of the bath and then rinsed with running water and finally dried in a vertical po3ition.
The evaluation of the state of cl~nl; n~l~s of a surface is a tricky problem.
In fact, there is at present no simple, rigorous and abaolute means for quantifying the cleanness of the surface of an article.
A method capable of being employed in order to evaluate the state of c:Leanness of a surface i3 the 80-called '`adhesive tape test".
This method consists in carefully applying a length of adhesive tape to the surface to be tested and in then removing it and bonding it onto a ~heet of white paper.

It is assumed that the a&esive tape has entrained with it all the contamination at the spot where it has been in contact with the panel. In these conditions, when the a&esive tape is placed on the white sheet, the change in its colour can be as6essed visually by referring to a preestablished scale.
It has not been possible, however, to apply this method in the case where the oil deposited onto the stainless panels is colourless, with the result that no change is seen in the colour of the a&esive tape .
The method which has been employed within the scope of the invention is an alternative form of the adhesive tape test, baaed on the finding of the fact that the colour of a clean panel is lighter than that of a contaminated panel.
Assuming that the a&esive tape removes all greasy contamination at the surface of the panel, a light trace should appear when the a&esive tape is 2 0 removed af ter having been applied to a contaminated panel .
The evaluation of the degreasing action of the bath has therefore been performed using the evaluation of the trace thus produced.
To this end, a five-level evaluation scale has been es~hl;Rh~d as a function of the trace left by the a&esive tape on the panel.
- Level 0: no effect, the panel has retained its original colour. It is, of course, very greasy to 3 0 the touch .
- Level 1: perceptible effect with a slight change in colour, but m~ch oil still remains detectable to the touch.
- Level 2: the oil coating is imperceptible to the touch, the trace of the a&esive tape is still visible, the edge of the trace being continuous.
- Level 3: the trace of the adhesive tape is invisible in places.

~ g - Level 4: the trace of the a&esive tape is completely invisible.
R~qULTS OF T~ T~!cTS r~RRT~!n O~JT

Pr~l ;m;n::~ry tests have 3hown the crucial role of the rinsing in the degreasing process in accordance wi th the invention .
In fact, on lea~ing the bath, the articles are covered with a liquid film containing hydLuye:ll peroxide, surfactant and various materials originating f rom the contamination .
The latter, which are generally greaay and hydrophobic, tend to fo~m micelles with the surfactant molecules.
On dyeing, the water and 1~YdLO~ peroxide evaporate and these micelles are redeposited at the surface of the article.
It i9 therefore particularly important to rinse 2 0 the articles immersed i~l the degreasing bath to obtain the des ired ef f ec t .
The results of the various tests which have demonstrated the detergent properties of the mixtures based on 1~YdL~ ~ peroxide and surfactants are reported 2 5 in Table I .
The wetting urface-active agent employed within the scope of ~hese tests is an ethoxylated sorbitan r~ lrate (product ~ontanox 20(1~)).
Thia surfactant is, of course, mentioned only by way of particular andl preferred illustrative example but, as indicated above, a person skilled in the art will be capable of finding other compounds producing the required result, e~pecially among the classes of surfactants referred to above.
Test No. 1 was carried out in relatively severe operating conditions, the hydL~gt:~l peroxide concentration being 35 9~ by weight, the temperature of the bath 70C and the im~ersion period 30 minutes.

2~8~416 ~ - 10 -In these condition3 the degreasing action is particularly rOEarkable.
In fact, after rinsing and drying, the abovOEentioned test sho1,rs that the panel is clean.
The following four tests (No. 2 to 5) were carried out to dOEonstrate the role of each of the constituents of the degreasing bath.
In these tests, the bath tOEperature is 70-75C
and the immersion period 15 minute3.
A bath con3i3ting solely of distilled water is completely ineffective (test No. 3) .
Hyd~ ~y~ peroxide employed by itself produces only a relatively average result (test No. 4) .
Similarly, the ,surface-active agent employed by itself yields a mediocre result (test No. 5) .
On the other hand, the hydrogen peroxide-surfactant combination is found to be fully effective (test No. 2) .
The following tests (No.6, 7 and 8) demonstrate 2 0 the ef f ect of the bath tOEperature on the degreasing ac tion .
The results obtained show that the temperature of the bath is an impc~rtant factor for obtaining the rec~uired result and that, in the case of a 25 prede~; nf.d duration of treatment, there is a threshold value below which the treatment loses its ef f ectiveness .
In the case of the surface-active agent employed in these tests, this threshold lies between 50 30 and 70C in the case of an immersion period of 15 minutes .
The test at 60"C i3 found to be a relatively satisfactory r( ,_l ~e between the treatment period and the tempera ture of the bath f or use in the 35 mechanical industry.
The following tests (No. 9 to 14) demonstrate the influence of the pe~^iod of immersion in the bath on the degreasing action.
.

~ 11 2181416 The results obtained 8how that the immersion period is an important factor for obtaining the recuired result and that, for a predet~ n~d bath temperature, there is a threshold value below which the 5 treatment 103es its eff-ctivenesa.
Tests No. 9 to 12, carried out between 80 and 87C, show that the minimum period enabling an acceptable level of cleanness to be obtained i3 approximately 2 . 5 minutes .
Tests No. 13 and 14 show that a satisfactory result can be obtained at a bath temperature of 90C
and an immersion period of 2 . 5 minutes .
Thus, within the scope of the invention the immersion period can be reduced every time that this is 15 found necessary, but, in this case, the bath temperature must be increased to arrive at the required result .
The following tests (No. 15 to 17) have shown that it i3 still posaible to reduce the immersion 20 period and the bath temperature simultaneously when the immersion treatment is assisted by a treatment such as the use of ultrasonics.
Thus, good results can still be obtained in these conditions with an immersion period of the order 25 of l minute and a bath temperature of the order o 70 C.
The following test (No. 18) shows that the concentration of surface-active agent is an important factor for obtaining th~ required result and that, for 30 a predet~rm;nP~ immersion period and bath temperature, there is a threshold value below which the treatment loses its effectiveness.
In the case where the 8urface-active agent is an ethoxylated sorbitan monolaurate, an optimum 35 concentration of surfactant is 3.5 g/l in the treatment conditions that can be employed on an industrial scale.
Tests No. 19 and! 20 show that the concentration o~ l"~d~ ~yc:ll peroxide which is necessary to obtain the required result depends on the bath temperature.

Test 20 in particular shows that it is possible to employ 15% solutions o~ ~202 if the bath temperature is increased to 70C and that, after an immersion for approximately 5 minutes, the result obtained is rated 5 3+.
To evaluate the stability of the solution, the hydrogen peroxide concentration and the pH have been measured at regular intervals.
The results obtained show that the pH of the 10 bath remains appreciably constant before and after cleaning, at a value of approximately 2 . 5 .
On the other hand, the hyd~ ~/y~l peroxide assay increases slightly during the treatment, probably because of the fact that evaporation tends to 15concentrate the peroxide solution.
However, this pl~- r~ is relatively negligible .
The process in accordance with the present invention of f ers many advantages .
Most importantly, it is appropriate to note that this process can be easily implemented on existing plants, practically without contamination, insofar as the chen~ical agents that can be employed are generally biodegradable .
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Claims

1. Use of a mixture consisting of an aqueous solution containing from 3 to 50 % and preferably from 10 to 40 % by weight of hydrogen peroxide and of an effective quantity of at least one wetting surface-active agent which is stable in an oxidizing medium, as degreasing composition especially for cleaning metal articles.

2. Use according to Claim 1, characterized in that the abovementioned wetting surface-active agent (s) is are) chosen from the group including the organic mono-, di- and triesters of phosphoric acid, fatty acids and sulphonated esters, carboxylated ethoxylated fatty alcohols and alkylnaphthalenesulphonates, alkylpolyglucosides, fatty acid alkanolamides and 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, quaternary ammoniums, amine and imidazoline salts and betaines.

3. Use according to Claim 1 or 2, characterized in that the abovementioned wetting surface-active agent(s) is (are) chosen from nonionic surfactants of hydrophilic nature and in particular from ethoxylated sorbitan esters.

4. Use according to one of Claims 1 to 3, characterized in that the weight ratio of the surface-active agent(s) to the hydrogen peroxide within the said mixture is between 1:10 and 1:1000, preferably between 1:30 and 1:100.

5. Use according to one of Claims 1 to 4, characterized in that the abovementioned aqueous solution includes 35 % by weight of hydrogen peroxide.

6. Use according to one of Claims 1 to 4, characterized in that the abovementioned aqueous solution includes from 10 to 15 % by weight of hydrogen peroxide and 0.3 to 0.5 % of ethoxylated sorbitan esters.

7. Aqueous solution comprising, as active agent, 10 to 15 % by weight of hydrogen peroxide and 0.3 to 0.5 % by weight of ethoxylated sorbitan monolaurate.

8. Aqueous solution comprising, as active agent, 30 to 50 % by weight of hydrogen peroxide and 0.5 % to 1 % by weight of ethoxylated sorbitan monolaurate.

9. Process for degreasing articles, especially metallic ones, characterized in that it consists:
- in immersing the said articles in a bath including a mixture consisting of an aqueous solution containing from 3 to 50 % by weight of hydrogen peroxide and of an effective quantity of at least one wetting surface-active agent which is stable in an oxidizing medium, at a temperature of between 15 and 100°C, preferably between 25 and 90°C, for a period of between 5 seconds and 60 minutes, preferably from 5 to 30 minutes, - in rinsing the said articles thus treated.

10. Process according to Claim 9, characterized in that the abovementioned immersion of the articles in the bath is accompanied by a mechanical action intended to facilitate the contact between the articles and the bath, like, in particular, the use of ultrasonics.

11. Process according to one of Claims 9 and 10, characterized in that the bath is a solution such as defined in Claim 5 at a temperature of approximately 60°C.

12. Process according to one of Claims 9 and 10, characterized in that the bath is a solution such as defined in Claim 7 and that the operating temperature is approximately 70°C.

13. Process according to one of Claims 9 and 10, characterized in that the bath is a solution such as defined in Claim 8, diluted by a half and that the operating temperature is approximately 70°C.