CONCENTRATED SILICONE ANTIFOAM EMULSION

Abstract

A concentrated silicone-in-water antifoam emulsion and a preparation process and a process for inhibiting foam are described herein.

Claims

1. A silicone-in-water antifoam emulsion EA comprising: at least a first silicone-in-water antifoam emulsion EA1 with a volume mean diameter d.sub.EA1 of greater than or equal to about 6 m comprising: a) at least one silicone antifoam AS comprising from about 0.1% to about 10% by weight of at least one mineral filler C, b) optionally at least one organopolysiloxane B1, c) at least one emulsifier D1, d) at least one additive F1, e) water W1, and at least a second silicone-in-water emulsion E2 with a volume mean diameter d.sub.E2 of less than d.sub.EA1 and wherein the silicone-in-water antifoam emulsion EA comprises a water content of less than about 65% by weight.

2. The silicone-in-water antifoam emulsion EA as claimed in claim 1, wherein the emulsion EA has a viscosity of less than about 6000 mPa.Math.s.

3. The silicone-in-water antifoam emulsion EA as claimed in claim 1, wherein the content of the silicone-in-water emulsion E2 is between about 2% and about 30% relative to the total weight of the silicone-in-water antifoam emulsion EA.

4. The silicone-in-water antifoam emulsion EA as claimed in claim 1, wherein the silicone-in-water emulsion E2 is an emulsion with a volume mean diameter d.sub.E2 of between about 0.01 m and about 6 m.

5. The silicone-in-water antifoam emulsion EA as claimed in claim 1, wherein the silicone-in-water emulsion E2 is a silicone-in-water emulsion with a silicone concentration of greater than or equal to about 35% by weight of the total weight of E2.

6. The silicone-in-water antifoam emulsion EA as claimed in claim 1, wherein the silicone-in-water emulsion E2 comprises from about 35 parts to about 80 parts by weight of at least one organopolysiloxane B2, from about 0.1 parts to about 10 parts by weight of at least one emulsifier D2, from about 0 parts to about 5 parts by weight of at least one additive F2 and from about 5 parts to about 65 parts by weight of water W2 per 100 parts by weight of the sum of the constituents B2, D2, F2 and W2.

7. The silicone-in-water antifoam emulsion EA as claimed in claim 1, wherein the silicone antifoam AS is obtained by polycondensation chemistry.

8. The silicone-in-water antifoam emulsion EA as claimed in claim 1, wherein the silicone antifoam AS is obtained by polyaddition chemistry.

9. The silicone-in-water antifoam emulsion EA as claimed in claim 1, wherein the silicone antifoam AS is obtained by radical chemistry.

10. The silicone-in-water antifoam emulsion EA as claimed in claim 1, wherein the silicone antifoam AS is obtained by mixing various silicone antifoams AS.

11. The silicone-in-water antifoam emulsion EA as claimed in claim 1, wherein the emulsion EA comprises a silicone-in-water antifoam emulsion EA1 with a water content of less than about 65% and a silicone-in-water emulsion E2 with a water content of less than about 65%.

12. The silicone-in-water antifoam emulsion EA as claimed in claim 1, wherein the particle size distribution of the dispersed oily phases is of bimodal type with a percentage of coarse particles/percentage of fine particles ratio of between about 98/2 and about 60/40, the percentage of coarse particles being calculated in the following manner: (weight of silicone antifoam AS+weight of organopolysiloxane B1+weight of emulsifiers D1) of the antifoam emulsion EA1/sum of ((weight of silicone antifoam AS+weight of organopolysiloxane B1+weight of emulsifiers D1) of the antifoam emulsion EA1 and of weight of the emulsion E2) and the percentage of fine particles being the balance to 100%.

13. The silicone-in-water antifoam emulsion EA as claimed in claim 1, wherein the emulsion EA comprises, per 100 parts by weight of antifoam emulsion EA: from about 70 parts to about 98 parts by weight of a silicone-in-water antifoam emulsion EA1 with a volume mean diameter d.sub.EA1 of greater than or equal to about 6 m comprising: a) from about 15 parts to about 55 parts by weight of at least one silicone antifoam AS comprising from about 0.1 to about 10 parts by weight of at least one mineral filler C, b) from about 0 parts to about 25 parts by weight of at least one organopolysiloxane B1, c) from about 0.1 parts to about 12 parts by weight of at least one emulsifier D1 d) from about 0.01 parts to about 5 parts by weight of at least one additive F1 e) from about 3 parts to about 65 parts by weight of water W1, and from about 2 parts to about 30 parts by weight of at least a second silicone-in-water emulsion E2 with a volume mean diameter d.sub.E2 of less than d.sub.EA1.

14. A process for preparing a silicone-in-water antifoam emulsion EA as claimed in claim 1, wherein the process comprises the following steps: a) dispersing, with stirring and at a temperature above about 50 C. and below about 75 C., at least one silicone antifoam AS, optionally at least one organopolysiloxane B1, at least one emulsifier D1 and a portion of the water, until the mixture has been homogenized, b) cooling, with stirring, the mixture obtained at the end of step a) down to a temperature below or equal to about 30 C. and adding the second portion of water, then the additive F1 and stirring until the mixture has been homogenized in order to obtain EA1, c) adding, to EA1, the silicone-in-water emulsion E2 and stirring until the silicone-in-water antifoam emulsion EA has been homogenized.

15. A process of inhibiting foam formation by adding a silicone-in-water antifoam emulsion EA to a liquid surface, wherein the silicone-in-water antifoam emulsion EA, is obtained by the process of claim 14.

16. A process of inhibiting foam formation, the process comprising adding a silicone-in-water antifoam emulsion EA to a liquid surface, wherein the silicone-in-water antifoam emulsion EA is the emulsion EA of claim 1.

Description

DETAILED DESCRIPTION

[0028] The silicone-in-water antifoam emulsion EA comprising: [0029] at least a first silicone-in-water antifoam emulsion EA1 with a volume mean diameter d.sub.EA1 of greater than or equal to 6 m comprising: [0030] a) at least one silicone antifoam AS comprising from 0.1% to 10% by weight of at least one mineral filler C, [0031] b) optionally at least one organopolysiloxane B1, [0032] c) at least one emulsifier D1, [0033] d) at least one additive F1, [0034] e) water W1, and [0035] at least a second silicone-in-water emulsion E2 with a volume mean diameter d.sub.E2 of less than d.sub.EA1 and characterized in that the silicone-in-water antifoam emulsion EA comprises a water content of less than 65% by weight, preferably less than 60% by weight and preferentially less than 55% by weight.

[0036] The silicone-in-water antifoam emulsion EA is characterized in that it has a viscosity of less than 6000 mPa.Math.s and preferably of less than 3500 mPa.Math.s.

[0037] All the viscosities referred to in the present disclosure correspond to a magnitude of dynamic viscosity at 25 C. termed Newtonian, i.e. the dynamic viscosity which is measured, in a manner known per se, with a Brookfield viscometer, at a shear rate gradient which is low enough for the viscosity measured to be independent of the shear rate gradient.

[0038] According to another embodiment, the silicone-in-water antifoam emulsion EA is characterized in that the content of silicone-in-water emulsion E2 is between 2% and 30% relative to the total weight of the silicone-in-water antifoam emulsion EA, preferably between 2.5% and 30% relative to the total weight of the silicone-in-water antifoam emulsion EA, more preferentially between 4% and 24% and even more preferentially between 6% and 20%.

[0039] According to another embodiment, the silicone-in-water antifoam emulsion EA is characterized in that the silicone-in-water emulsion E2 is an emulsion with a volume mean diameter d.sub.E2 of between 0.01 and 6 m.

[0040] The mean size of the particles is measured by laser particle size analysis. The mean size the particles corresponds to the diameter D[4,3] which is the volume mean diameter. The definition of the volume mean diameter, D[4,3], is well known to those skilled in the art.

[0041] According to another embodiment, the silicone-in-water antifoam emulsion EA is characterized in that the silicone-in-water emulsion E2 is a silicone-in-water emulsion with a silicone concentration of greater than 35% by weight of the total weight of E2.

[0042] According to another preferred embodiment, the silicone-in-water antifoam emulsion EA is characterized in that the silicone-in-water emulsion E2 comprises [0043] from 35 to 80 parts by weight of at least one organopolysiloxane B2, [0044] from 0.1 to 10 parts by weight of at least one emulsifier D2, [0045] from 0 to 5 parts by weight of at least one additive F2 and [0046] from 5 to 65 parts by weight of water W2 per 100 parts by weight of the sum of the constituents B2, D2, F2 and W2.

[0047] The volume mean diameter D[4,3] of the emulsion EA1 is preferably greater than 6 m, preferably between 7 and 150 m and preferentially between 10 and 120 m.

[0048] The fact of adding, to a silicone-in-water antifoam emulsion EA1 with a volume mean diameter d.sub.EA1 of greater than 6 m, a silicone-in-water emulsion E2 with a volume mean diameter d.sub.E2 of less than d.sub.EA1 makes it possible to simultaneously obtain an emulsion that is concentrated in silicone and has a low viscosity. Hence, a productivity saving is obtained, the handling operations and transportation are thereby facilitated, while retaining good antifoaming properties.

[0049] The silicone-in-water antifoam emulsion EA according to the invention simultaneously has a silicone content of greater than 35%, a viscosity of less than 6000 mPa.Math.s, preferably less than 3500 mPa.Math.s, good water dispersibility, good storage stability and good antifoaming properties.

[0050] The silicone emulsion E2 is a silicone-in-water emulsion based on organopolysiloxanes.

[0051] To describe organopolysiloxanes, reference is made to siloxyl units M, D, T and Q. The letter M represents the monofunctional unit of formula (R).sub.3SiO.sub.1/2, the silicone atom being bonded to a single oxygen atom in the polymer comprising this unit. The letter D signifies a difunctional unit (R).sub.2SiO.sub.2/2 in which the silicon atom is bonded to two oxygen atoms. The letter T represents a trifunctional unit of formula (R)SiO.sub.3/2, in which the silicon atom is bonded to three oxygen atoms. The letter Q represents a tetrafunctional unit of formula SiO.sub.4/2, in which the silicon atom is bonded to four oxygen atoms. The symbol R has the same definition as the symbols R.sup.2, R.sup.3 and R.sup.4 defined below. The units M, D and T may be functionalized. Reference is then made to units M, D and T while specifying the specific radicals.

[0052] The silicone-in-water emulsion E2 comprises at least one organopolysiloxane B2, which may be chosen from the group consisting of: [0053] non-reactive organopolysiloxanes which, per molecule, have monovalent organic substituents, which may be identical to or different from one another, bonded to the silicone atoms, and which are chosen from the group consisting of C.sub.1-C.sub.40 alkyl, C.sub.3-C.sub.8 cycloalkyl, C.sub.6-C.sub.10 aryl and C.sub.7-C.sub.50 alkylaryl radicals; [0054] reactive organopolysiloxanes comprising at least two SiOH silanol groups per molecule; [0055] and mixtures thereof.

[0056] In the context of the invention, the term non-reactive is understood to mean an organopolysiloxane which, under the conditions of emulsification, of preparation of the silicone-in-water emulsion and of use, does not react chemically with any of the constituents of the emulsion.

[0057] The non-reactive organopolysiloxane may be an oil or a gum, and preferably has a dynamic viscosity of between 50 and 600 000 mPa.Math.s at 25 C. or a consistency between 200 and 2000 expressed in tenths of a millimeter at 25 C.

[0058] The dynamic viscosity of silicones is measured at 25 C. according to the standard ASTM D 445.

[0059] The term gum is used for organopolysiloxane compounds having viscosities conventionally greater than 600 000 mPa.Math.s, which corresponds to a molecular weight of greater than 260 000 g/mol.

[0060] The consistency or penetrability of a gum is determined at 25 C. by means of a penetrometer of PNR12 type or equivalent model allowing a cylindrical head to be applied to the sample under standardized conditions.

[0061] The penetrability of a gum is the depth, expressed in tenths of a millimeter, to which a calibrated cylinder penetrates the sample over one minute.

[0062] For this purpose, a sample of gum is introduced into an aluminum cup 40 mm in diameter and 60 mm tall. The bronze or brass cylindrical head is 6.35 mm in diameter and 4.76 mm long and is borne by a metal rod 51 mm long and 3 mm in diameter which fits onto the penetrometer. This rod is weighted with a 100 g load. The total weight of the assembly is 151.8 g including 4.3 for the cylindrical part and its support rod. The cup containing the sample of gum is placed in the thermostatic bath at 250.5 C. for at least 30 min. The measurement is taken according to the manufacturer's instructions. The values of the depth (V) in tenths of a millimeter and the time (t) in seconds to reach this depth are indicated on the apparatus. The penetrability is equal to 60 V/t expressed in tenths of a millimeter per minute

[0063] The non-reactive organopolysiloxane gums that may be used in accordance with the invention are used alone or as a mixture in an inorganic solvent. This solvent may be chosen from volatile silicones, octamethyl-cyclotetrasiloxane (D4), decamethylcylopentasiloxane (D5), polydimethylsiloxane (PDMS) oils, polyphenyl-methylsiloxane (PPMS) oils or mixtures thereof, so as to avoid the use of organic solvents that are harmful to the environment and to the health of the workers in tire manufacturing workshops.

[0064] Advantageously, the non-reactive organopolysiloxane is a linear non-reactive organopolysiloxane oil which is a linear homopolymer or copolymer. Preferably the linear non-reactive organopolysiloxane oil has a dynamic viscosity in the range from 0.65 to 100 000 mPa.Math.s at 25 C. Examples that may be mentioned include linear organopolysiloxanes: [0065] consisting along each chain: [0066] i) of units of formula R.sup.5R.sup.6SiO.sub.2/2, optionally combined with units of formula (R.sup.5).sub.2SiO.sub.2/2; [0067] ii) of units of formula (R.sup.6).sub.2SiO.sub.2/2, optionally combined with units of formula (R.sup.5).sub.2SiO.sub.2/2, [0068] iii) of units of formula R.sup.5R.sup.6SiO.sub.2/2 and units of formula (R.sup.6).sub.2SiO.sub.2/2, optionally combined with units of formula (R.sup.5).sub.2SiO.sub.2/2, [0069] and blocked at each chain end with a unit of formula (R.sup.7).sub.3SiO.sub.1/2, the R.sup.7 radicals of which, which may be identical or different, are chosen from R.sup.5 and R.sup.6 radicals; [0070] where the R.sup.5 and R.sup.6 radicals, monovalent organic substituents of the various siloxyl units mentioned above, have the following definitions: [0071] a) the R.sup.5 radicals, which may be identical to or different from one another, are chosen from: [0072] 1. linear C.sub.1-C.sub.6 or branched C.sub.3-C.sub.6 alkyl radicals, for instance methyl, ethyl, propyl, isopropyl, butyl, isobutyl, t-butyl, n pentyl or n-hexyl, and [0073] 2. C.sub.3-C.sub.8 cycloalkyl radicals for instance cyclopentyl or cyclohexyl, [0074] b) the R.sup.6 radicals, which may be identical to or different from one another, are chosen from [0075] 1. C.sub.6-C.sub.10 aryl radicals for instance phenyl or naphthyl, [0076] 2. C.sub.7-C.sub.15 alkylaryl radicals for instance tolyl or xylyl, and [0077] 3. C.sub.7-C.sub.15 arylalkyl radicals for instance benzyl.

[0078] The reactive organopolysiloxane may be an oil or a gum, and preferably has a dynamic viscosity of between 50 and 600 000 mPa.Math.s at 25 C. or a consistency of between 200 and 2000, expressed in tenths of a millimeter at 25 C.

[0079] Preferably, the reactive organopolysiloxane of the silicone-in-water emulsion E2 comprises the following siloxyl units:

M.sup.OH=[(OH)(R.sup.2).sub.2SiO.sub.1/2] and D=[R.sup.3R.sup.4SiO.sub.2/2] [0080] wherein: [0081] R.sup.2, R.sup.3 and R.sup.4 are identical or different radicals chosen from the group consisting of: [0082] linear or branched C.sub.1-C.sub.6 alkyl radicals, for instance methyl, ethyl, propyl, isopropyl, butyl, isobutyl, t-butyl, n-pentyl or n-hexyl; [0083] C.sub.3-C.sub.8 cycloalkyl radicals, for instance cyclopentyl or cyclohexyl; [0084] C.sub.6-C.sub.10 aryl radicals for instance phenyl or naphthyl, and [0085] C.sub.7-C.sub.15 alkylaryl radicals for instance tolyl or xylyl.

[0086] The silicone-in-water emulsion E2 also comprises an emulsifier D2. The nature of the emulsifier D2 will be readily determined by a person skilled in the art, the objective being to prepare a stable emulsion. Anionic, cationic, nonionic and zwitterionic surfactants may be used, alone or as a mixture.

[0087] It should be noted that the silicone-in-water emulsion E2 may also comprise protective colloids such as polyvinyl alcohol, as described in patent EP 0946240.

[0088] As anionic surfactants, mention may be made of the following surfactants: [0089] the alkyl ester sulfonates of formula R.sup.aCH(SO.sub.3M) COOR.sup.b, where R.sup.a represents a C.sub.8-C.sub.20, preferably C.sub.10-C.sub.16, alkyl radical, R.sup.b represents a C.sub.1-C.sub.6, preferably C.sub.1-C.sub.3, alkyl radical and M represents an alkali metal (sodium, potassium, lithium) cation, a substituted or unsubstituted ammonium (methyl-, dimethyl-, trimethyl-, tetramethylammonium, dimethylpiperidinium) cation or a cation derived from an alkanolamine (monoethanolamine, diethanolamine, triethanolamine), [0090] the alkyl sulfates of formula R.sup.cOSO.sub.3M, where R.sup.c represents a C.sub.10-C.sub.24, preferably C.sub.12-C.sub.20, alkyl or hydroxyalkyl radical, M representing a hydrogen atom or a cation having the same definition as above, and also the ethoxylated (EO) and/or propoxylated (PO) derivatives thereof, preferably having from 1 to 20 EO units, [0091] the alkylamide sulfates of formula R.sup.dCONHR.sup.eOSO.sub.3M where R.sup.d represents a C.sub.2-C.sub.22, preferably C.sub.6-C.sub.20, alkyl radical, R.sup.e represents a C.sub.2-C.sub.3 alkyl radical, M representing a hydrogen atom or a cation having the same definition as above, and also the ethoxylated (EO) and/or propoxylated (PO) derivatives thereof, preferably having from 1 to 20 EO units, [0092] the salts of saturated or unsaturated C.sub.8-C.sub.24, preferably C.sub.14-C.sub.20, fatty acids, C.sub.9-C.sub.20 alkylbenzenesulfonates, and also the the ethoxylated (EO) and/or propoxylated (PO) derivatives thereof, preferably having from 1 to 20 EO units, [0093] C.sub.9-C.sub.20 alkylbenzenesulfonates, primary or secondary C.sub.8-C.sub.22 alkyl sulfonates, alkylglycerol sulfonates, the sulfonated polycarboxylic acids described in GB-A-1 082 179, paraffin sulfonates, N-acyl-N-alkyl taurates, monoalkyl and dialkyl phosphates, alkyl isethionates, alkyl succinamates, alkyl sulfosuccinates, sulfosuccinate monoesters or diesters, N-acyl sarcosinates, alkyl glycoside sulfates, polyethoxycarboxylates, the cation being an alkali metal (sodium, potassium or lithium), a substituted or unsubstituted ammonium residue (methyl-, dimethyl-, trimethyl-, tetramethylammonium, dimethylpiperidinium) or an alkanolamine derivative (monoethanolamine, diethanolamine or triethanolamine).

[0094] As nonionic surfactants, mention may be made of poly(alkylene oxide) alkyl or aryl ethers, polyoxyethylene sorbitan hexastearate, polyoxyethylene sorbitan oleate and poly(ethylene oxide) cetyl stearyl ethers. As poly(alkylene oxide) aryl ethers, mention may be made of polyoxyethylene alkylphenols. As poly(alkylene oxide) alkyl ethers, mention may be made of polyethylene glycol isodecyl ether and polyethylene glycol trimethylnonyl ether containing from 3 to 15 ethylene oxide units per molecule.

[0095] As examples of surfactants, mention may also be made of: ionic, nonionic or amphoteric fluorinated surfactants and mixtures thereof, for example: [0096] perfluoroalkyls, [0097] perfluorobetaines, [0098] ethoxylated polyfluoroalcohols, [0099] ammonium polyfluoroalkyls, [0100] surfactants, the hydrophilic part of which contains one or more saccharide units bearing from five to six carbon atoms and the hydrophobic part of which contains a unit of formula R.sup.f(CH.sub.2).sub.n, in which n=2 to 20 and R.sup.f represents a perfluoroalkyl unit of formula C.sub.mF.sub.2m+1, in which m=1 to 10; and [0101] polyelectrolytes having fatty perfluoroalkyl side groups.

[0102] The term fluorinated surfactant is understood to mean, as is perfectly known per se, a compound formed of an aliphatic perfluorocarbon part, comprising at least three carbon atoms, and an ionic, nonionic or amphoteric hydrophilic part. The perfluorocarbon part of at least three carbon atoms may represent either all or only a fraction of the fluorocarbon part of the molecule. There are a large number of references in the literature as regards this type of compound. A person skilled in the art may notably refer to the following references: [0103] FR-A-2 149 519, WO-A-94 21 233, U.S. Pat. No. 3,194,767, the book Fluorinated Surfactants, Erik Kissa, published by Marcel Dekker Inc. (1994) Chapter 4, notably Tables 4.1 and 4.4.

[0104] Mention may be made in particular of the products sold by the company DuPont under the name Zonyl, for example FSO, FSN-100, FS-300, FSD, and also the fluorinated surfactants of the name Forafac distributed by the company DuPont and the products sold under the name Fluorad by the company 3M.

[0105] Among these surfactants, mention may be made in particular of anionic, cationic, nonionic and amphoteric perfluoroalkyl compounds, and among them, more particularly, the surfactants of the Zonyl class sold by DuPont, sold by DuPont under the names Zonyl FSA, Zonyl FSO, Zonyl FSC and Zonyl FSK, respectively.

[0106] The following may also be specified with respect thereto: [0107] Zonyl FSO 100: CAS 65545-80-4, (nonionic) 99% to 100%, the remainder being 1,4-dioxane, [0108] Zonyl FSN: CAS 65545-80-4, 99% to 100%, the remainder being sodium acetate and 1,4-dioxane, [0109] Zonyl FS-300: CAS 65545-80-4, 40%, the remainder being 1,4-dioxane (<0.1%) and water, [0110] Zonyl FSD: CAS 70983-60-7 30%, (cationic), the remainder being hexylene glycol (10%), sodium chloride (3%) and water (57%).

[0111] Mention may also be made of: [0112] perfluoroalkyl betaines (amphoteric) such as the product sold by DuPont under the name Forafac 1157, ethoxylated polyfluoroalcohols (nonionic), such as the product sold by DuPont under the name Forafac 1110 D, polyfluoroalkylammonium salts (cationic), such as the product sold by DuPont under the name Forafac 1179, [0113] surfactants in which the hydrophilic part contains one or more saccharide units containing from 5 to 6 carbon atoms (units derived from sugars such as fructose, glucose, mannose, galactose, talose, gulose, allose, altose, idose, arabinose, xylose, lyxose and/or ribose) and in which the hydrophobic part contains a unit of formula R.sup.F(CH.sub.2).sub.n, where n may range from 2 to 20, preferably from 2 to 10, and R.sup.F represents a perfluoroalkyl unit of formula C.sub.mF.sub.2m+1 with m possibly ranging from 1 to 10, preferably from 4 to 8, chosen from those having the characteristics defined above; mention may be made of the monoesters of perfluoroalkylated fatty acids and of sugars such as sucrose, it being possible for the monoester function to be represented by the formula R.sup.F(CH.sub.2).sub.nC(O), where n may range from 2 to 10 and R.sup.F represents a perfluoroalkyl unit of formula C.sub.mF.sub.2m+1 with m possibly ranging from 4 to 8, described in the Journal of the American Oil Chemists' Society (JAOCS), Vol. 69, No. 1, (January 1992) and chosen from those having the characteristics defined above; and [0114] polyelectrolytes having fatty perfluoroalkyl side groups such as polyacrylates having R.sup.F(CH.sub.2).sub.n groups where n may range from 2 to 20, preferably from 2 to 10 and R.sup.F represents a perfluoroalkyl unit of formula C.sub.mF.sub.2m+1 with m possibly ranging from 1 to 10, preferably from 4 to 8, chosen from those having the characteristics defined above; mention may be made of the polyacrylates containing CH.sub.2C.sub.7F.sub.15 groups described in J. Chim. Phys. (1996) 93, 887-898 and chosen from those having the characteristics defined above.

[0115] The amount of emulsifier D2 depends on the type of each of the constituents present and on the very nature of the emulsifier used. As a general rule, the emulsion comprises from 0.1% to 10% by weight of emulsifier relative to the total weight of the emulsion.

[0116] Moreover, in a conventional and nonlimiting manner, use may also be made, in the emulsions, of additives F2 such as film-forming polymers, biocides, rheology modifiers, coalescers, dispersants, acidifying agents, neutralizing agents, bases and/or thickeners, alone or as a mixture.

[0117] The concentrations of such adjuvants are known to those skilled in the art.

[0118] According to another embodiment, the silicone-in-water antifoam emulsion EA is characterized in that the silicone antifoam AS is obtained by polycondensation chemistry.

[0119] Said polycondensation chemistry is well known to those skilled in the art. Without being limiting, mention may be made for example of documents EP 0163541 and EP 2794760.

[0120] According to another embodiment, the silicone-in-water antifoam emulsion EA, is characterized in that the silicone antifoam AS is obtained by polyaddition chemistry.

[0121] Said polyaddition or hydrosilylation chemistry is well known to those skilled in the art. Without being limiting, mention may be made for example of documents EP0434060, U.S. Pat. No. 8,053,480, WO2018224131 and WO2021167728.

[0122] According to another embodiment, the silicone-in-water antifoam emulsion EA, is characterized in that the silicone antifoam AS is obtained by radical chemistry.

[0123] Said radical chemistry is well known to those skilled in the art. Without being limiting, mention may be made for example of document WO2021126195.

[0124] According to another embodiment, the silicone-in-water antifoam emulsion EA, is characterized in that the silicone antifoam AS is obtained by mixing various silicone antifoams AS.

[0125] The mineral filler C of the silicone antifoam AS is a compound chosen from the group comprising silicas, preferably fumed silicas and/or precipitated silicas and/or colloidal silicas, diatomaceous earths, ground quartz, calcium carbonate, hydrated alumina, magnesium hydroxide, carbon black, titanium dioxide, aluminum oxide, vermiculite, zinc oxide, mica, talc, iron oxide, barium sulfate, slaked lime, and mixtures thereof. The mineral filler C of the silicone antifoam AS is preferentially silica.

[0126] It may be treated or untreated precipitated silica or fumed silica. The precipitated silica is preferably made hydrophobic beforehand by conventional treatment with one or more organosilicon compounds. It may be incorporated untreated and then treated (rendered hydrophobic) in situ by one or more organosilicon compounds. Among such compounds are methylpolysiloxanes, such as hexamethyldisiloxane and octamethylcyclotetrasiloxane, methylpolysilazanes, such as hexamethyldisilazane and hexamethylcyclotrisilazane, chlorosilanes, such as dimethyldichlorosilane, trimethylchlorosilane, methyl-vinyldichlorosilane and dimethylvinylchlorosilane, and alkoxysilanes, such as dimethyldimethoxysilane. During this treatment, the silicas may increase their initial weight by up to 20%. The fumed silica may be used untreated. If required, it may, however, be treated like the precipitated silica.

[0127] The mineral fillers C generally have a specific surface area, measured according to the BET methods, of at least 10 m.sup.2/g, notably of between 20 and 300 m.sup.2/g.

[0128] A mixture of fillers C may be used.

[0129] The content of mineral filler C is generally between 0.1% and 10% by weight of the silicone antifoam AS, preferably between 0.5% and 10% by weight of the silicone antifoam AS.

[0130] The silicone antifoam AS or the silicone-in-water antifoam emulsion EA1 may optionally contain polyether silicones to improve the antifoam in properties. The latter are well known to those skilled in the art. By way of illustration which is in no way limiting, reference may be made to documents WO2020228212, EP3423165, EP2563491 and EP2563491.

[0131] According to another embodiment, the silicone-in-water antifoam emulsion EA is characterized in that it comprises a silicone-in-water antifoam emulsion EA1 with a water content of less than 65% and a silicone-in-water emulsion E2 with a water content of less than 65%.

[0132] According to another embodiment, the silicone-in-water antifoam emulsion EA is characterized in that the particle size distribution of the dispersed silicone phases is of bimodal type with a percentage of coarse particles/percentage of fine particles ratio of between 98/2 and 60/40, the percentage of coarse particles being calculated in the following manner: (weight of silicone antifoam AS+weight of organopolysiloxane B1+weight of emulsifiers D1) of the antifoam emulsion EA1/sum of ((weight of silicone antifoam AS+weight of organopolysiloxane B1+weight of emulsifiers D1) of the antifoam emulsion EA1 and of weight of solids of the emulsion E2) and the percentage of fine particles being the balance to 100%.

[0133] Preferably, percentage of coarse particles/percentage of fine particles ratio of the antifoam emulsion EA is between 98/2 and 70/30.

[0134] According to another embodiment, the silicone-in-water antifoam emulsion EA is characterized in that its comprises, per 100 parts by weight of antifoam emulsion EA: [0135] from 70 to 98 parts by weight of a silicone-in-water antifoam emulsion EA1 with a volume mean diameter d.sub.EA1 of greater than or equal to 6 m comprising: [0136] a) from 15 to 55 parts by weight of at least one silicone antifoam AS comprising from 0.1 to 10 parts by weight of at least one mineral filler C, [0137] b) from 0 to 25 parts by weight of at least one organopolysiloxane B1, [0138] c) from 0.1 to 12 parts by weight of at least one emulsifier D1, [0139] d) from 0.01 to 5 parts by weight of at least one additive F1, [0140] e) from 3 to 65 parts by weight of water W1, and [0141] from 2 to 30 parts by weight of at least a second silicone-in-water emulsion E2 with a volume mean diameter d.sub.E2 of less than d.sub.EA1.

[0142] The organopolysiloxane B1 may be identical to or different from B2 and may be reactive or non-reactive as described for B2.

[0143] The emulsifier D1 may be identical to or different from D2. It may be a protective colloid such as polyvinyl alcohols or nonionic, anionic or cationic surfactants, alone or as a mixture.

[0144] The additive F1 may be identical to or different from F2.

[0145] Another subject of the present invention relates to a process for preparing a silicone-in-water antifoam emulsion EA, characterized in that it comprises the following essential steps: [0146] a) dispersing, with stirring and at a temperature above 50 C. and below 75 C., at least one silicone antifoam AS, optionally at least one organopolysiloxane B1, at least one emulsifier D1 and a portion of the water, until the mixture has been homogenized, [0147] b) cooling, with stirring, the mixture obtained at the end of step a) down to a temperature below or equal to 30 C. and adding the second portion of water, then the additive F1 and stirring until the mixture has been homogenized in order to obtain EA1, [0148] c) adding, to EA1, the silicone-in-water emulsion E2 and stirring until the silicone-in-water antifoam emulsion EA has been completely homogenized.

[0149] More particularly, the invention relates to a process for inhibiting foam formation by adding a silicone-in-water antifoam emulsion EA, to the liquid surface.

[0150] Other advantages and features of the present invention will become apparent on reading the following examples given by way of illustration that is in no way limiting.

EXAMPLES

[0151] In the examples below, various silicone antifoams AS, polydimethylsiloxane silicone oils B1, silicone-in-water emulsions E2 and emulsifiers D1 were used to prepare silicone-in-water antifoam emulsions EA according to the invention. Unless otherwise mentioned, throughout the present document, the % are expressed as % by weight.

Raw Materials Used

[0152] Various commercial antifoams AS with a silica content C of between 0.5% and 10% were used: [0153] Silcolapse 825, sold by Elkem Silicones, is a silicone antifoam AS obtained from polycondensation chemistry as described in EP0163541; [0154] Silcolapse 120, sold by Elkem Silicones, is a silicone antifoam AS as described in U.S. Pat. No. 3,383,327; [0155] Silcolapse 490, sold by Elkem Silicones, is a silicone antifoam AS obtained from polycondensation chemistry as described in EP0163541.

[0156] Bluesil FLD 47V350, sold by Elkem Silicones, is a non-reactive polydimethylsiloxane silicone oil B1 with a viscosity 350 mPa.Math.s.

[0157] Bluesil FLD 48V135000, sold by Elkem Silicones, is a reactive (,-dihydroxy) polydimethylsiloxane silicone oil B1 with a viscosity 135 000 mPa.Math.s.

[0158] Various commercial emulsions E2 were used: [0159] Bluesil Emul 872, sold by Elkem Silicones, is an emulsion E2 of 47V350 non-reactive polydimethylsiloxane silicone oil B2 containing 61% solids and having a volume mean diameter D[4,3] of 0.16 m; [0160] Bluesil Emul 284, from Elkem Silicones, is an emulsion E2 of 48V135000 reactive (,-dihydroxy) polydimethylsiloxane silicone oil B2 containing 51% solids and having a volume mean diameter D[4,3] of 0.26 m.

[0161] Radiasurf 7145, sold by Oleon, is an emulsifier D1: Sorbitan monostearate.

[0162] Myrj S40, sold by Croda, is an emulsifier D1: PEG-40 stearate.

[0163] Rhodasurf ROX, sold by Solvay, is an emulsifier D2: ethoxylated branched alcohol.

[0164] Proxel GXL, sold by Lonza, is an additive F1: solution containing 20% of 1,2-benzisothiazolin-3-one.

Characterization of the EmulsionsMeasurement Methods:

[0165] The solids content is expressed as % of residue and is measured using a halogen moisture analyzer (1 g105 C.60 min).

[0166] The viscosity of the emulsion is measured at the start and after 1 month at 40 C. using a Brookfield (A4V20) viscometer.

[0167] The particle size distribution PSD is measured with a Mastersizer 3000 Laser Granulometer from Malvern. D[4,3] corresponds to the volume mean diameter and is expressed in m.

[0168] The ease of use of the emulsions is estimated by filtration through a 250 m nylon screen.

[0169] In order to estimate the dispersibility of the emulsion, a drop of emulsion is dropped from a pipette into a cylindrical tube 4.5 cm high and 1.4 cm in diameter that is filled with 3 ml of deionized water. The number of complete inversions needed for total dispersibility is quantified. The emulsion is considered to be dispersible if the number of complete inversions is less than 10 and preferably less than 5.

[0170] Regarding the storage stability, it is verified visually every two months. The number of months at the end of which phase separation is observed is recorded.

[0171] The antifoaming properties are verified using a recirculation test. 800 ml of detergent solution (aqueous solution containing 3 g/l of sodium dodecyl benzene sulfonate and C12-C18 fatty alcohol ethoxylated on average 7 times) are pumped in recirculation through a specimen of 2 liters at a flow rate of 200 l/h at 60 C. As soon as the foam level reaches the graduation H1 in ml, 50 mg of antifoaming emulsion are injected, and the foam level is monitored over time. First the foam level drops, and the reading of its low point (H2 in ml) makes it possible to calculate the shock effect (1(H2/H1)), expressed as a percentage.

[0172] Compositions and characteristics of the emulsions EA obtained from a single silicone antifoam AS.

TABLE-US-00001 TABLE 1 Example 1 Composition of according Antifoam Emulsion Comparative to the EA (g) Example 1 invention Antifoam Emulsion EA1 Silcolapse 825 (silicone 155 154 antifoam AS) Bluesil 47V350 (silicone oil B1) 210 110 Radiasurf 7145 (emulsifier D1) 66.9 49.5 Myrj S40 (emulsifier D1) 23 16.6 Water W1 442 394 Proxel GXL (additive F1) 1.4 1.4 Bluesil Emul 872 (E2) 0 176 Total weight EA (g) 898.3 901.5 % coarse particles 100 75 % fine particles 25 Characteristics PSD type monomodal bimodal D[4,3] m 90 54 Initial viscosity A4V20 (mPa .Math. s) >10 000 270 Solids content % 51 48 Filtration through 250 m screen no yes Water dispersibility (number of >20 1 inversions) Viscosity after 1 month at 40 C. >10 000 1410 A4V20 (mPa .Math. s) Phase separation after x months 4 months >12 months

[0173] Example 1 according to the invention: A glass container equipped with an anchor stirrer is charged with 154 g of Silcolapse 825 AS, 110 g of Bluesil 47V350 B1, 49.5 g of Radiasurf 7145 D1, 16.6 g of Myrj S40 D1 and 65.1 g of deionized water W1 (first portion). Stirring is carried out at 60 rpm for 45 min while heating to reach a temperature of 65 C. so as to melt the emulsifiers and homogenize the mixture. The stirring is then increased to 150 rpm for 20 minutes before cooling the mixture to 30 C., at which temperature 329 g of deionized water W1 (second portion) are added over one hour at a speed of 10 rpm while continuing the cooling down to room temperature. The stirring speed is increased to 50 rpm for 25 minutes. Then 176 g of Bluesil Emul 872 emulsion E2 are added over 15 minutes. Lastly, 1.4 g of Proxel GXL F1 are added and the stirring is continued for 15 minutes.

[0174] The concentrated silicone-in-water antifoam emulsion obtained is a white emulsion having a bimodal particle size distribution, a volume mean diameter [D(4,3)] of 54 m, a solids content of 48% and a viscosity of 270 mPa.Math.s, namely 37 times lower than comparative example 1 at a comparable solids content.

[0175] Unlike comparative example 1, the emulsion is more filtered without difficulty through a 250 m screen and it is dispersible. Its viscosity after one month at 40 C. is much less than 3500 mPa.Math.s.

[0176] Comparative example 1: The procedure of example 1 was followed except for the addition of Bluesil Emul 872 E2 and with the amounts of each ingredient mentioned in table 1. In the absence of Bluesil Emul 872 emulsion E2, the emulsion obtained has a monomodal particle size distribution, the volume mean diameter [D(4,3)] is 90 m, the viscosity is greater than 10 000 mPa.Math.s for a comparable solids content to example 1 according to the invention. Unlike example 1 according to the invention, the emulsion cannot be filtered through a 250 m screen, its dispersibility is poor and phase separation is observed after 4 months.

[0177] Compositions and characteristics of the emulsions EA obtained from a mixture of 2 silicone antifoams AS.

TABLE-US-00002 TABLE 2 Example 2 Example 3 Example 4 Example 5 Composition of according according according according Antifoam Emulsion Comparative to the to the to the to the EA (g) Example 2 invention invention invention invention Antifoam Emulsion EA1 Silcolapse 825 153 155 155 154 156 (silicone antifoam AS) Silcolapse 120 113 117 117 120 127 (silicone antifoam AS) Bluesil 47V350 85.9 77.4 51.8 35 0 (silicone oil B1) Radiasurf 7145 66 65 60.1 57.6 52.3 (emulsifier D1) Myrj S40 22 21.8 20.7 19.1 17.3 (emulsifier D1) Water W1 454 440 412 391 376 Proxel GXL 1.4 1.4 1.4 1.4 1.4 (additive F1) Bluesil Emul 872 0 25.1 88.3 131 174 (E2) Total weight EA 895.3 902.7 906.3 909.1 904 (g) % coarse 100 97 88 83 77 particles % fine particles 0 3 12 17 23 Characteristics PSD type monomodal bimodal bimodal bimodal bimodal D[4,3] m 69 34 31 23 13 Initial viscosity >10 000 5350 2670 1460 1050 A4V20 (mPa .Math. s) Solids content % 49.3 49.6 50.2 50.9 49.6 Filtration no yes yes yes yes through 250 m screen Water >20 5 4 3 3 dispersibility (number of inversions) Viscosity after 1 >10 000 690 430 2330 2180 month at 40 C. A4V20 (mPa .Math. s) Phase separation 6 months >12 months >12 months >12 months >12 months after x months Antifoaming 89% 90% 88% 89% 91% property: shock effect %

[0178] Examples 2 to 5 according to the invention: The procedure of example 1 was followed with the amounts of each ingredient mentioned in table 2. A mixture of 2 silicone antifoams AS is used instead of just one. White emotions are obtained having a bimodal particle size distribution, a volume mean diameter [D(4,3)] between 34 and 13 m, a viscosity of less than 6000 mPa.Math.s for a solids content close to 50%, namely a viscosity 2 to 10 times lower than comparative example 2 at a comparable solids content. All the emulsions can be filtered through a 250 m screen, have a good dispersibility, namely less than or equal to 5 inversions, and a viscosity after one month at 40 C. of less than 6000 mPa.Math.s. No phase separation is observed after 12 months of storage, while exhibiting good antifoaming properties: the shock effect measured is greater than 89%.

[0179] Comparative example 2: The procedure of examples 2 to 5 was followed except for the addition of emulsion E2 and with the amounts of each ingredient mentioned in table 2. The emulsion obtained is a very viscous white paste having a monomodal particle size distribution. The volume mean diameter is 70 m, the viscosity is greater than 10 000 mPa.Math.s for a comparable solids content to examples 2 to 5 according to the invention. Unlike examples 2 to 5 according to the invention, the emulsion cannot be filtered through a 250 m screen, its dispersibility is poor (>20 inversions) and phase separation is observed after 6 months.

[0180] Compositions and characteristics of the emulsions EA obtained from a emulsions E2 of different volume mean diameter.

TABLE-US-00003 TABLE 3 Example 6 Example 7 Example 8 Example 9 Composition of according according according according Antifoam Emulsion Comparative to the to the to the to the EA (g) Example 3 invention invention invention invention Antifoam Emulsion EA1 Silcolapse 490 199 194 195 196 194 (silicone antifoam AS) Bluesil 48V135000 95.3 67.9 66.6 67 38.4 (silicone oil B1) Radiasurf 7145 32.3 29 29.3 29.1 26.2 (emulsifier D1) Myrj S40 10.6 9.7 9.7 9.7 8.8 (emulsifier D1) Water W1 176 140 145 137 107 Proxel GXL 0.8 0.8 0.8 0.8 0.8 (additive F1) Bluesil Emul 284 71.4 127 (E2) E2 D[4,3] = 3.5 m 62.3 E2 D[4,3] = 5.5 m 68.2 Total weight EA (g) 514 509.6 508.7 511 502.2 % coarse particles 100 88 90 87 78 % fine particles 0 12 10 13 22 Characteristics PSD type monomodal bimodal bimodal bimodal bimodal D[4,3] m 18 12.1 4.8 5.9 4.5 Initial viscosity 9950 1330 2250 3070 4300 A4V20 (mPa .Math. s) Solids content % 66.3 66.4 66.4 66 66.2 Filtration through no yes yes yes Yes 250 m screen Water dispersibility 9 2 2 3 3 Viscosity after 1 >10 000 2000 3320 4230 5150 month at 40 C. A4V20 (mPa .Math. s)

Preparation of the Emulsions E2:

[0181] Bluesil Emul 284 emulsion: E2 D[4,3]=3.5 m A glass container equipped with an anchor stirrer is charged with 195 g of Bluesil FLD 48V135000 oil B2, 16.1 g of Rhodasurf ROX D2 and 6.5 g of deionized water W2 (first portion). Stirring is carried out at 30 rpm for 20 minutes, then 134 g of deionized water W2 (second portion) is added over 15 minutes. When all the water has been incorporated, the stirring is maintained for 15 min at 100 rpm, and 0.5 g of Proxel GXL F2 is added. The silicone oil-in-water emulsion obtained is a white emulsion having a volume mean diameter [D(4,3)] of 3.5 m and a solids content of 58.5%.

[0182] Bluesil Emul 284 emulsion: E2 D[4,3]=5.5 m

[0183] A glass container equipped with an anchor stirrer is charged with 177 g of Bluesil FLD 48V135000 oil B2, 9.6 g of Rhodasurf ROX D2 and 9.0 g of deionized water W2 (first portion). Stirring is carried out at 40 rpm for 10 minutes, then 157 g of deionized water W2 (second portion) is added over 20 minutes. When all the water has been incorporated, the stirring is maintained for 15 min at 100 rpm, and 0.5 g of Proxel GXL F2 is added. The silicone oil-in-water emulsion obtained is a white emulsion having a volume mean diameter [D(4,3)] of 5.5 m and a solids content of 51.6%.

[0184] Examples 6 to 9 according to the invention: The procedure of example 1 was followed with the amounts of each ingredient mentioned in table 3. Emulsions E2 having different volume mean diameters are used. White emulsions are obtained having a bimodal particle size distribution, a volume mean diameter [D(4,3)] of between 12.3 and 4.5 m, a viscosity of less than 6000 mPa.Math.s for a solids content close to 66%, namely a viscosity 2 to 7 times lower than comparative example 3 at a comparable solids content. All the emulsions can be filtered through a 250 m screen, have a good dispersibility, namely less than or equal to 5 inversions, and a viscosity after one month at 40 C. of less than 6000 mPa.Math.s.

[0185] Comparative example 3: The procedure of examples 6 to 9 was followed except for the addition of emulsion E2 and with the amounts of each ingredient mentioned in table 3. The emulsion obtained is a viscous white paste having a monomodal particle size distribution. The volume mean diameter is 70 m, the viscosity is 9950 mPa.Math.s for a comparable solids content to examples 6 to 9 according to the invention. Unlike examples 6 to 9 according to the invention, the emulsion cannot be filtered through a 250 m screen, its dispersibility is poor (9 inversions).