FR2783525A1 - Composition for use as antifoaming agent comprising homogeneous mixture of silicone constituent and ester of unsaturated fatty acid and aliphatic alcohol - Google Patents

Abstract

Composition comprises homogeneous mixture of at least a silicone constituent selected from oil, rubber and polyorganosiloxane resin and their mixtures; and at least an ester of 8-18C unsaturated fatty acid and 1-6C aliphatic alcohol. Independent claims are also included for method for making anti-foaming agent containing the composition; and method for cleaning gases using the agent.

Description

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 The present invention relates to compositions based on oil, gum or polyorganosiloxane resin especially useful as anti-foaming agents.

 Silicone oils, gums and resins, generally polydimethylsiloxane, reactive or non-reactive, can be used as antifoaming agent, antiblocking agent, etc., or used in more complex compositions intended, for example, for the formation of silicone elastomers. The viscosity of the oils, gums and silicone resins, which depends on the number of constituent units, can vary in very large proportions. It may be noted that the gums are distinguished from the oils by a high viscosity, e. g. greater than 500,000 mPa.s at 25 ° C. This viscosity, when it is relatively high, may pose problems when the oil, gum or silicone resin is used, either in its direct application which may require its dispersion in a aromatic solvent or its emulsification in water, or in its processing applications.

 Mention may be made of the use of silicone oils as anti-foam agent.

 There are a large number of anti-foam formulations, obtained from a mineral filler, most often silica particles, and silicone oil adsorbed or physically and / or chemically bound to the mineral filler. The antifoam formulations can be divided into two broad categories, aqueous emulsions and dispersible compounds. The formulation of these compounds is generally prepared by mixing the mineral filler with an oil or silicone gum, for example a reactive polydimethylsiloxane oil. or not, then heating the mixture This base compound can be emulsified with water to give an anti-foaming emulsion. It can also be used as is and then it is called dispersible compound. To be useful, an antifoam agent must not only have antifoaming activity but also have appropriate spreading properties, which can be directly influenced by the viscosity.

 Anti-foams based on silicone oil are particularly used as antifoaming agent in the field of gas scrubbing, especially in gas refineries, to trap toxic gases such as H2S and CO2. The most commonly used technology is alkanolamine gas treatment based on the principle of a reaction between a weak base and a weak acid to form a water-soluble salt. In a column where the gas to be washed circulates, a solution of alkanolamine which is then regenerated and recycled is countercurrently flowed. It is necessary to add an antifoaming agent in the alkanolamine solution to limit the Foam formation throughout the installation and especially in the column

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Silicone defoamers of both types (emulsions and dispersible compounds) are used in practice, such as RHODORSIL 454,426R and 422 from RHODIA CHEMISTRY or DOW CORNING DB-31 from Dow Corning. The compounds must be diluted beforehand in a suitable solvent. Silicone antifoam emulsions are often preferred because their aqueous composition is compatible with the gas treatment medium such as alkanolamine solutions. They are also so for their absence of toxic compounds such as solvents, e. g. Aliphatic, aromatic, chlorinated hydrocarbons used to dilute dispersible compounds.

 However, the emulsions have the disadvantage of being very sensitive in terms of stability, and can thus be destabilized by the action of components present in the gases such as liquid hydrocarbons. They are also less thermally stable than dispersible compounds.

 As for the dispersable compounds, their main disadvantage has been seen above, which is to require the use of toxic solvents for their dilution.

 The object of the present invention is to propose a novel means for diluting silicone compounds, which is compatible in particular with aqueous media and which therefore can remedy the main disadvantage of antifoam silicone compounds.

 The present invention more particularly aims its application in the field of antifoam, to overcome both the disadvantages of these emulsions and anti-foam compounds, proposing to use this dilution means for the preparation of new compositions anti-foam silicone that are effective and stable at high temperatures and do not require the use of toxic solvents for their implementation.

 Another object of the invention is to provide such compositions which are directly compatible with aqueous treatment media, especially gas treatment media, such as alkanolamine solutions.

 Yet another object of the invention is to provide such compositions which are particularly easy to implement thanks to an excellent spreadability.

 Yet another object of the invention is to provide such compositions which have increased anti-foam activity at high temperatures.

 One of its aims is to propose such anti-foam compositions which can be used at high temperature by being more stable and more effective than conventional silicone emulsions.

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 Yet another object of the invention is to provide such compositions which are biodegradable.

 Unexpectedly, the Applicant has found that polyorganosiloxane oils, gums and resins can be easily mixed with esters of fatty acids and aliphatic alcohols leading to a homogeneous blend of viscosity lower than the viscosity of the oil, gum or starting resin.

Thus, the present invention firstly relates to a composition comprising a homogeneous mixture of at least one silicone component chosen from oil, gum and polyorganosiloxane resin and mixtures thereof, and at least one fatty acid ester. unsaturated C8 to C18 and aliphatic alcohol C1 to C6
Unexpectedly, a homogeneous mixture is obtained, which is characterized by a certain transparency, and of viscosity lower than the viscosity of the oil, gum or resin alone. It is obvious that the mixture can be made in all proportions depending on the specifications and in particular depending on the desired final viscosity and taking into account other ingredients that may be present, e. g a charge. Thus, an oil, gum or resin + ester mixture according to the invention may comprise from 5 to 95% by weight of ester, in particular from 20 to 80%, preferably from 40 to 80%.

 In the presence of a filler and especially in the case where a suitable oil or gum is used, the composition obtained can be used as an antifoaming agent, especially in the compound form. Remarkably, the compound thus produced has antifoam effectiveness increase with temperature and exceed that of the compound alone without ester, the efficiency gap with the compound alone without ester increasing beyond 40-50 C. This totally unexpected result makes the compositions according to the invention of great interest as an antifoam when the medium to be defoamed is at a high temperature, especially above 40-50 C. In addition, the drop in viscosity of the mixture contributes to improve the spreadability of the composition which is favorable to this type of use. The biodegradable character is an added advantage.

 More particularly, the ester is derived from unsaturated C10-C16, preferably C12-C14, unsaturated fatty acids.

 In a particularly preferred embodiment, the composition comprises an ester selected from the group consisting of myristates (C14), laurates (C12) and mixtures thereof.

In case of mixing, the proportions are not critical

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Preferably, the ester is derived from C1 to C4 aliphatic alcohols, preferably C1 to C2 aliphatic alcohols.

Among the oils, gums and polyorganosiloxane resins that may be used, mention may be made of those comprising or consisting of units of formula
R'3-aRaSiO1 / 2 and R2Si02 / 2 where - a is an integer from 0 to 3 - the radicals R are the same or different and represent a saturated or unsaturated aliphatic hydrocarbon group containing from 1 to 10 carbon atoms; . a polar organic group bonded to silicon via an Si-C or Si-OC bond; an aromatic hydrocarbon group containing from 6 to 13 carbon atoms; the radicals R 'are identical or different and represent. an OH group; . an alkoxy or alkenyloxy group containing from 1 to 10 carbon atoms; an aryloxy group containing from 6 to 13 carbon atoms; . an acyloxy group containing from 1 to 13 carbon atoms; . a cetiminoxy group containing from 1 to 8 carbon atoms; . an amino or amido-functional group containing from 1 to 6 carbon atoms bonded to silicon by an Si-N bond; preferably at least 80% of the radicals R of said oils, gums or resins representing a methyl group.

Among the polyorganosiloxane resins that may be used, mention may be made of those consisting of units of formulas
R Si O3 / 2 (unit T) and / or SiO2 (unit Q) associated with units of formula R'3-a Ra SiO1 / 2 (unit M) and / or R2Si 0212 (unit D) in which a, R and R 'are as defined above.

alkoxyalkylène tels que -CHz-CHz-O-CH3 ; -CH2-CH2-O-CH3 . alcényles tels que vinyle, alkyle, hexényle, décényle, décadiényle These are generally of the MQ, MDQ, TDM, TD, MT type.
Examples of aliphatic or aromatic hydrocarbon radicals R include: alkyl groups such as methyl, ethyl, octyl, trifluoropropyl

alkoxyalkylene such as -CH 2 -CH 2 -O-CH 3; -CH2-CH2-O-CH3. alkenyls such as vinyl, alkyl, hexenyl, decenyl, decadienyl

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 alkenyloxyalkylene such as - (CH2) 3-O-CH2-CH = CH2; - (CH2) 3-OCH2-CH2-O-CH = CH2 aryls such as phenyl.

-(CHz)3-N(CHZCHZOH}-CHz-CHz-N(CH2CHZOH)z aminofonctionnels tels que -(CH2)3-NH2 : -(CH2)3-NH-(CH2)2NH2 amidofonctionnels tels que -(CH2)3-N-(COCH3)-(CH2)2NH(COCH3) . carboxyfonctionnels tels que -CH2-CH2-S-CH2-COOH
A titre d'exemples de radicaux R', on peut citer les groupes : alkoxy tels que méthoxy, éthoxy, octyloxy alcényloxy tels que vinyloxy, héxényloxy, isopropényloxy . aryloxy tels que phényloxy acyloxy tels que acétoxy cétiminoxy tels que ON=C(CH3)C2H5 aminofonctionnels tels que éthylamino, phénylamino amidofonctionnels tels que méthylacétamido. As examples of polar organic groups R, mention may be made of: hydroxyfunctional groups such as - (CH 2) 3 -OH; - (CH2) 4N (CH2CH2OH) 2;

Amino-functional - (CH 2) 3 -N (CH 2 CH 2 OH) -CH 2 -CH 2 -N (CH 2 CH 2 OH) z - such as - (CH 2) 3 -NH 2 - (CH 2) 3 -NH- (CH 2) 2 NH 4 amidofunctional radicals such as - (CH 2) 3-N- (COCH 3) - (CH 2) 2 NH (COCH 3), carboxyfunctional such as -CH 2 -CH 2 -S-CH 2 -COOH
As examples of R 'radicals, there may be mentioned alkoxy groups such as methoxy, ethoxy, octyloxy alkenyloxy such as vinyloxy, hexenyloxy, isopropenyloxy. aryloxy such as phenyloxy acyloxy such as acetoxy cetiminoxy such as ON = C (CH3) C2H5 aminofunctional such as ethylamino, phenylamino amidofunctional such as methylacetamido.

 As concrete examples of "D units", mention may be made of: (CH 3) 2 SiO; CH3 (CH2 = CH) SiO; CH3 (C6H5) SiO; (C6H5) 2SiO CH3HSIO CH3 (CH2-CH2CH2O) SiO.

(CH3)3SiOi/2 , (CH3)z(OH)SiO,r ; (CH3)z(CH=CHz)SiO,z ; (CH3)zHSiO"z ; (OCH3)3SiOrz ; [O-C(CH3)=CHz]3Si0"z ; [ON=C(CH3)13SiOl/2 ; (NH-CH3)3SiO,z ; (NH-CO-CH3)3SiO,iz. As concrete examples of "M-patterns", mention may be made of:

(CH 3) 3 SiO 1/2, (CH 3) z (OH) SiO, r; (CH 3) z (CH = CH 2) SiO, z; (CH3) zHSiO "z; (OCH3) 3SiOr2; [OC (CH3) = CHz] 3SiO"z; [ON = C (CH3) 13SiO1 / 2; (NH-CH 3) 3 SiO, z; (NH-CO-CH3) 3 SiO, iz.

As concrete examples of "T-patterns", mention may be made of
CH3SiO3 / 2; (CH = CH2) SiO3 / 2; HSi03 / 2
When said oils, gums or resins contain reactive and / or polar radicals R (such as H, vinyl, allyl, hexenyl, aminoalkyl), the latter generally do not represent more than 2% of the weight of the oil or gum and not more than 10% of the weight of the resin.

The viscous polydimethylsiloxane and α, ú-bis (hydroxy) polydimethylsiloxane oils as well as the polydimethylsiloxane, polyphenylmethylsiloxane and α, β-bis (hydroxy) polydimethylsiloxane gums are well-known commercial products.
The viscous polymethylsiloxane resins DT containing from 1 to 2% by weight of silanol functional groups are also commercially available products.

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 In the context of antifoam applications, the compositions according to the invention are then compounds which comprise a filler, in particular a mineral filler. The proportions constituting silicone / filler are in particular from 2 to 15, preferably from 2 to 10.

 The mineral filler is preferably silica.

 It may be precipitated silica or fumed silica, treated or not.

 The precipitated silica is preferably prehydrophobic by conventional treatment with one or more organosilicon compounds. It can also be incorporated untreated and then treated (hydrophobed) in situ with one or more organosilicon compounds. Among these compounds are methylpolysiloxanes such as hexamethyldisiloxane, octamethylcyclotetrasiloxane, methylpolysilazanes such as hexamethyldisilazane, hexamethylcyclotrisilazane, chlorosilanes such as dimethyldichlorosilane, trimethylchlorosilane, methylvinyldichlorosilane, dimethylvinylchlorosilane, alkoxysilanes such as dimethylmethoxysilane. During this treatment, the silicas can increase their starting weight up to a rate of 20%.

Combustion silica can be used untreated If necessary, it can however be treated as precipitation silica
Siliceous fillers of other mineral fillers such as ground quartz, calcined clays and diatomaceous earth may also be used in addition to or instead of.

 The mineral fillers generally have a specific surface area, measured according to the BET methods, of at least 50 m 2 / g, in particular between 50 and 400 m 2 / g, preferably greater than 70 m 2 / g, and an average particle size of less than 50 m 2 / g. 0.1 micrometer (m) and a bulk density of less than 200 g / liter.

To further facilitate their implementation, and even further increase the effectiveness of anti-foam compositions, the compositions according to the invention may further comprise a nonionic surfactant and in particular a polyalkoxylated linear or branched fatty alcohol. Preferably, this polyalkoxylated fatty alcohol has the general formula:
R1O- [R2O] nH with: - R1 being a C8 to C30 alkyl group, a C6 to C14 aromatic group optionally substituted with C1 to C15 alkyl groups, R2 being optionally branched C2 to C4 alkyl; , preferably C2-n alkyl is between 10 and 100, preferably between 20 and 50.

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 These polyalkoxylated fatty alcohols further promote the dispersion of the compounds in aqueous media (eg gas washing media, such as alkanolamine solutions), are non-volatile, non-toxic and act in synergy with the esters of the invention on the anti-foam efficacy.

C H3-(C H z), -CH z-O-(C H 2-CHz-O)s-H CH3-(CHZ)"-CHZ-O-(CH2-CHZ-O)s-H
La quantité de tensioactif mise en #uvre pourra être comprise entre 0,5 et 8 %, de préférence entre 1 et 5 %, par rapport au mélange constituant silicone + charge + ester. Preferably, R 1 is: - a residue of alcohol R 3 - (CHR 4) m - CH 2, with R 3 and R 4 being a hydrogen atom or a C 1 to C 4 alkyl, preferably R 3 is CH 3 and preferably R 4 is a hydrogen atom, and m is between 1 and 16, preferably between 10 and 12 - or a phenyl residue substituted or not by a C8-C13 alkyl;
By way of example, mention may be made of the following compounds:

C H 3 - (CH z), -CH zO- (CH 2 -CH 2 -O) sH CH 3 - (CH 2) n - CH 2 O- (CH 2 -CH 2 -O) sH
The amount of surfactant used may be between 0.5 and 8%, preferably between 1 and 5%, relative to the silicone + filler + ester component mixture.

 For the preparation of an antifoam compound, it is preferred to use a silicone component which is an oil. In general, oils having a viscosity of between 500 and 10,000 mPa.s at 25 ° C., or mixtures of such oils, are used. As is known per se, however, it is excluded the use of gum especially in mixture with low viscosity oils. It is possible to dilute at room temperature (e.g., 20-30 ° C.) a conventional base compound (silicone component + filler) in an ester formulation according to the invention, in the desired proportions, for example from 5 to 95% by weight of oil + filler compound (relative to the silicone + filler + ester component assembly), especially from 20 to 80%, preferably from 20 to 60%.

 The preparation of the base compound (silicone component + filler) is conventional and may comprise heating the mixture obtained between 60 and 200 ° C., in particular around 150 ° C., for several hours, in particular from 6 to 10 hours, preferably 8 h This heat treatment, especially when it is carried out at a temperature greater than 100 -150 C, also leads to hydrophobicize in situ the mineral filler, so that such a high temperature treatment can be substituted for a treatment with organosilicon compounds. The ester will then be mixed at room temperature as seen above.

 It goes without saying that the invention is intended to apply to all commercial silicone base compounds. It will also be noted that the dilution in the ester can be done in advance or extemporaneously.

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 The present invention therefore also relates to the use of esters according to the invention for the dilution of an oil, resin or polyorganosiloxane gum under the conditions indicated above.

 More particularly, it relates to the use of such esters for the preparation of antifoam compounds from a base compound comprising a filler, in particular silica, and a silicone component, as described above.

 The subject of the present invention is also the process for the preparation of an antifoam compound, in which a conventional base compound (silicone component + filler) is diluted, preferably at room temperature, in an ester formulation conforming to the invention, especially in the proportions indicated above, and optionally incorporation of a surfactant as described above.

 The antifoam composition according to the invention may in particular be used in the context of gas scrubbing in gas refineries (in particular for the removal of toxic gases such as H 2 S and CO 2), for example at a rate of from 0.5 to 20 g of composition per ton of gas to be treated, the composition being added to the aqueous gas washing solution (weak basic solution, preferably alkanolamine) which will be brought into contact with the gas. The general principle has been described above. The invention also relates to such a method of using the antifoam composition in this application.

The invention will now be described in more detail using embodiments taken as non-limiting examples.
EXAMPLES
EXAMPLE 1 - Antifoam Compound 1 Starting Compounds
Base antifoam compound prepared by mixing: 94.6 parts of trimethylsiloxane-trimmed polydimethylsiloxane oil, viscosity 1000 mPa.s 5.4 parts of BET specific surface area smelting silica 200 m 2 / g
It is heated at 150 ° C. for 7 hours with stirring. After cooling, a mixture of methyl laurate (70%) and methyl mirystate (30%) (hereinafter ester), marketed by NOVANCE under the name ESTOROB CE 12-14, is added.
The quantities used are: base compound / ester. 30/70% by weight

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2 - Characteristics of the antifoam mixture (base compound + ester):. appearance: homogeneous clear liquid. density (25 C): 0.89-0.91. flash point (closed cup): 130 ° C. refractive index (25 C): 1.4210-1.4270. viscosity (25 C): 35 mPa.s (Brookfield) 3 - Antifoam activity
This determination is carried out in an Amine + DOS (Sodium Dioctylsulfosuccinate) medium using a drop test and recycling of the foaming medium according to the AFNOR T-73-412 standard.

The foaming medium has the following composition - MDEA (monodiethanol amine) 40 g - DOS solution at 5 g / l 20 g - distilled water 40 g - antioxidant additive (Norust PA23 distributed by CECA France) 0.05 g Result 1:
In the test procedure, 500 ml of this foaming medium are placed in a 1000 ml test tube and the equivalent of 300 ppm of base compound (silicone oil + silica) is added. The circulation pump is started and the time for which the volume of foam reaches the value of 1000 ml is measured. For temperatures of 80 ° C., an anti-foaming time of 8 minutes has been obtained for the antifoam compound without ester and 15 minutes for the antifoam mixture according to the invention Result 2:
The same application tests as above are carried out with a foaming medium consisting of a DOS solution at 2 g / l. Measurements corresponding to 300 ppm of base compound were measured at different temperatures, and the following results are obtained with respect to the anti-foaming time expressed in minutes:

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<Tb>
<tb> Temperature <SEP> 20 <SEP> C <SEP> 40 <SEP> C <SEP> 60 <SEP> C <SEP> 80 <SEP> C
<tb> (essay)
<tb> Compound <SEP> of <SEP> 1.5 <SEP> 3 <SEP> 4 <SEP> 7
<tb> base
<tb> Mix <SEP> 0.3 <SEP> 4 <SEP> 6 <SEP> 16
<tb> antifoam
<tb> compound <SEP> + <SEP>
<tb> ester
<Tb>
6 - Protocol 3:
The same tests as above are carried out with the only difference that another foaming medium consisting of:

<Tb>
<tb> - <SEP> carbonate <SEP> of <SEP> soda <SEP> anhydrous <SEP> 10 <SEP> g <SEP>
<tb> - <SEP> sulfate <SEP> of <SEP> sodium <SEP> (10H20) <SEP> 30 <SEP> g <SEP>
<tb> - <SEP> Nonylphenol <SEP> (10 <SE> OE) <SEP> 2 <SEP> g
<tb> - <SEP> water <SEP> qsp <SEP> to <SEP> 1000 <SEP> g <SEP>
<Tb>

Measurements are made at a concentration of 300 ppm of base compound and the following results are obtained in terms of antifoaming (in minutes): Temperature (C)

<Tb>
<tb> 20 C <SEP> 80 C
<tb> Compound <SEP> alone <SEP> 3.5 <SEP> 4,5
<tb> Mix <SEP> antifoam <SEP> 0.5 <SEP> 16
<tb> compound <SEP> + <SEP> ester
<Tb>
7 - Conclusions
These results clearly show that the anti-foaming time of the antifoam mixture according to the invention is improved from the moment when the temperature of the test is greater than or equal to 40 C.

 Additional tests were carried out on defoaming mixtures that had been stored at ambient temperature for three months and it was confirmed that the antifoam activity of these was well preserved.

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This new antifoam composition therefore has very interesting properties that can be applied in refineries where the gases are purified with amines.

EXAMPLE 2 Evaluation of Antifoam Activity According to a Bubble Test of a Gas (Nitrogen) in a Foaming Solution According to the AFNOR Standard T-73-412
The foaming medium consists of: - MDEA 400.0 g - Distilled water 599.5 g - Norust PA23 0.5 g Procedure:
350 ml of foaming medium preheated to 70 ° C. are introduced into a glass column maintained at this temperature.

The foaming is then ensured by a current of nitrogen (flow = 35 l / h) in the liquid and the injection of the antifoam solution is carried out when the height of the foam in the column reaches 50 cm.
The anti-foaming time is then measured to obtain a foam height of 30 cm. Each dose of antifoam corresponds to a concentration of 50 ppm of silicone material.

The evaluated products are: 1- commercially available silicone emulsion containing 30% of active material, composed on the one hand of a silicone compound comprising 27.6 parts of trimethylsiloxyl-terminated polydimethylsiloxane oil of viscosity 100 mPa.s and 2.4 parts of BET surface combustion silica of 200 m 2 / g and, on the other hand, 35.5 g of a 10% aqueous solution of polyvinyl alcohol, and QSP in water to reach 100 g 2 -a composition A comprising : 97.5 g of silicone / fatty ester compound mixture described in Example 1 according to the ratio
30/70 - 2.5 g Genapol X050 nonionic surfactant marketed by the company
Hoechst. The composition of this surfactant is as follows:
CH3 (CH2) 11CH2O [CH2CH2O] 5H (tridecyl ether having on average 5 polyoxyethylene groups)
Composition A is used in 30% solution in water.

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Results:

<Tb>
<tb> Product <SEP> used <SEP> (SEP dose) = <SEP> 50 <SEP> emulsion <SEP> Composition <SEP> A
<tb> ppm)
<tb> Anti-foaming time <SEP><SEP> 60 <SEP>><SEP> 180 <SEP>
<tb> (min)
<Tb>
Conclusion: This result shows the greater antifoam effectiveness of the composition described in the invention comprising a silicone compound, a fatty acid ester and a nonionic surfactant.

Claims (22)

A composition comprising a homogeneous mixture of at least one silicone component selected from oil, gum and polyorganosiloxane resin and mixtures thereof, and at least one unsaturated C 8 to C 18 fatty acid ester and C 1 to C 18 aliphatic alcohol. C6 2. Composition according to claim 1, characterized in that the ester is derived from unsaturated fatty acids C10 to C16, preferably C12 to C14.  3. Composition according to claim 2, characterized in that it comprises an ester selected from the group consisting of myristates, laurates and mixtures thereof 4. Composition according to one of claims 1 to 3, characterized in that the ester is derived from aliphatic alcohols C1 to C4, preferably C1 to C2.  5. Composition according to one of claims 1 to 4, characterized in that the composition comprises from 5 to 95% by weight of ester, in particular from 20 to 90%, preferably from 40 to 80%.  6. Composition according to one of claims 1 to 5, characterized in that it comprises a filler, preferably a mineral filler.  7. Composition according to Claim 6, characterized in that it constitutes an antifoam compound obtainable by mixing, on the one hand, at least one unsaturated C8 to C18 fatty acid ester and aliphatic alcohol. C1 to C6 and secondly, the product of a mixture of silicone component and filler, preferably by heating this mixture between 60 and 200 C for several hours 8. Composition according to claim 6 or 7, characterized in that the proportion constituting silicone / filler is from 2 to 15, preferably from 2 to 10 9. Composition according to one of claims 6 to 8, characterized in that the filler comprises silica, preferably selected from the group consisting of silica precipitation, fumed silica, treated or not.  10. Composition according to one of claims 1 to 9, characterized in that the oil, gum or polyorganosiloxane resin comprises or consists of units of formula R'3-aRaSiO1 / 2 and R2Si02 / 2 formulas where - a is an integer from 0 to 3 - the radicals R are identical or different and represent <Desc / Clms Page number 14>  . a saturated or unsaturated aliphatic hydrocarbon group containing from 1 to 10 carbon atoms; . a polar organic group bonded to silicon via an Si-C or Si-O-C bond; . an aromatic hydrocarbon group containing from 6 to 13 carbon atoms; the radicals R 'are identical or different and represent. an OH group; . an alkoxy or alkenyloxy group containing from 1 to 10 carbon atoms; . an aryloxy group containing from 6 to 13 carbon atoms; . an acyloxy group containing from 1 to 13 carbon atoms; . a cetiminoxy group containing from 1 to 8 carbon atoms; . an amino or amido-functional group containing from 1 to 6 carbon atoms bonded to silicon by an Si-N bond; preferably at least 80% of the radicals R of said oils, gums or resins representing a methyl group.  11. Composition according to one of claims 1 to 10, characterized in that the polyorganosiloxane resin consists of patterned formulas. R Si O3 / 2 (unit T) and / or SiO2 (unit Q) associated with units of formula R'3-a Ra SiOi / 2 (unit M) and / or R2Si O2 / 2 (unit D) in which formulas a is an integer from 0 to 3; the radicals R are identical or different and represent a saturated or unsaturated aliphatic hydrocarbon group containing from 1 to 10 carbon atoms; a polar organic group bonded to silicon via an Si-C or Si-O-C bond; . an aromatic hydrocarbon group containing from 6 to 13 carbon atoms; the radicals R 'are identical or different and represent. an OH group; . an alkoxy or alkenyloxy group containing from 1 to 10 carbon atoms; . an aryloxy group containing from 6 to 13 carbon atoms; . an acyloxy group containing from 1 to 13 carbon atoms; . a cetiminoxy group containing from 1 to 8 carbon atoms; an amino-or amido-functional group containing from 1 to 6 carbon atoms, bonded to silicon by an Si-N bond, <Desc / Clms Page number 15>  preferably at least 80% of the radicals R of said resins representing a methyl group.  12. Composition according to one of claims 1 to 11, characterized in that it comprises a nonionic surfactant, preferably selected from polyalkoxylated fatty alcohol derivatives.  13. Composition according to claim 9, characterized in that the fatty alcohol derivative corresponds to the following formula: R1O- [R2O] nH with: - R1 being a C8 to C30 alkyl group, a C6 to C14 aromatic group optionally substituted with C1 to C15 alkyl groups, R2 being optionally branched C2 to C4 alkyl; , preferably C2-n alkyl is between 10 and 100, preferably between 20 and 50.  14. Composition according to claim 13, characterized in that R1 is - a residue of alcohol R3- (CHR4) m -CH2, with R3 and R4 being a hydrogen atom or a C1-C4 alkyl, preferably R3 is CH 3 and preferably R 4 is a hydrogen atom, and m is between 1 and 16, preferably between 10 and 12 - or a phenyl residue substituted or not by a C 8 -C 13 alkyl.  15. Composition according to claim 14, characterized in that it comprises a fatty alcohol chosen from: CH3- (CH2) 11-CH2-O- (CH2-CH2-O) 8 -H CH3- (CH2) 11-CH2-O- (CH2-CH2-O) 5 -H 16. Composition according to any one of claims 12 to 15, characterized in that, relative to the rest of the composition, the surfactant is present between 0.5 and 8%, preferably between 1 and 5%.  17. A process for the preparation of an antifoam compound, in which a base compound comprising a silicone component and a filler is mixed together and on the other hand a C8 to C18 unsaturated fatty acid ester. and C1 to C6 aliphatic alcohol.  18. The method of claim 17, characterized in that the ester is as defined in any one of claims 2 to 4 <Desc / Clms Page number 16> 19. The method of claim 17 or 18, characterized in that the base compound is obtainable by mixing a silicone component, preferably an oil as defined in claim 10, and a filler, preferably silica, and heating the mixture between 60 and 200 C for several hours, preferably a silicone component / charge ranging from 2 to 15.  20. Process according to any one of claims 17 to 19, characterized in that further incorporates a nonionic surfactant, preferably a polyalkoxylated linear or branched fatty alcohol as defined in any one of claims 13 to 16. .  Anti-foaming compound obtainable by carrying out the process according to any one of claims 17 to 20. 22. A method of washing gases, in which the gases to be washed are brought into contact with an aqueous washing solution, preferably an alkanolamine solution, added with an antifoam agent, characterized in that Antifoam agent comprises a composition according to any one of claims 1 to 16 or 21.