Aqueous foam quenching compositions

Abstract: Certain silicone antifoam emulsions of low viscosity, exhibit excellent bulk and dilute stability, have high efficiency in non-ionic and anionic foamant systems both at ambient and elevated temperature, and their dilutions with water do not separate wherein these emulsions contain silicone antifoam compounds based on polydimethylsiloxanes and inorganic oxides and are protected against creaming and separation using synthetic protective colloids derived from polyvinylpyrrolidone.

Description: The present invention relates to aqueous, silicone-based, foam control formulations which have low viscosity, are efficient foam control additives, are stable on dilution with water, and produce low actives dilutions in water which are free from oil and non-dispersible particles. These formulations are useful as foam control additives in textile bleaching, washing or dying formulations. BACKGROUND OF THE INVENTION The first step in the preparation of a silicone antifoam emulsion is the preparation of the silicone antifoam compound.This is typically a mixture of a silicone fluid and fine solid particles, frequently silica, that has undergone a heat treatment at 100-300°C for several hours in the presence of catalysts, as described, for example in U.S. Patent Nos 3,235,509 and 3,560,401. Antifoam compounds such as these described above cannot be used easily as such in aqueous systems because they do not disperse easily in water.Water compatibility can be achieved by either blending surfactants in with the antifoam compound (US Patent Nos. 3 984 200 and 4 076 648,and JP 05261206) to produce self-emulsifiable compounds, or by emulsifying the antifoam compound to an oil in water or multiple phase emulsion. The preparation of silicone antifoam emulsions is complicated due to the numerous variables that affect performance. These variables can arise from changes in the composition of the antifoam compound, in the composition and nature of the emulsion, and in the nature of the foaming system. The antifoam emulsion droplet size is one of the most important factors controlling the antifoam activity in a given foaming medium. The antifoam emulsion must also conform to certain quality requirements, such as low viscosity for ease of use, stability to temperatures as high as 50°C, and once diluted with water, the emulsion should be free of unemulsified oil and non-dispersed solid particles. In addition, textile formulators require that the emulsion, when diluted with water, form stable dilutions. Effective antifoam emulsions use thickeners in amounts optimised for the undiluted emulsion to prevent droplet creaming and coalescing. Upon dilution with water, the thickener levels are reduced and are no longer capable of imparting the required stability. A way to overcome this would be to use higher quantities of thickeners but this would result in an unacceptably high emulsion viscosity. Alternatively, the emulsion droplet could be made smaller through processing to achieve the required stability, but then the effectiveness of the antifoam would be reduced. European Patent No 0 769 548 teaches the preparation of silicone antifoam emulsions using alkylpolyglucosides and anionic surfactants as the emulsifiers and xanthan gum as the thickener. German Patent No 42 37 754 teaches the use of linear polyurethane dispersions or emulsions as protective colloids in the preparation of silicone antifoam emulsions, while German Patent No 30 13 923 teaches the use of water soluble molecules having the general formula R 1 { CH 2 CH(R 2 )O}R 3 where R 1 is either an alkyl or alkoxy group, R 2 is either hydrogen or methyl and R 3 is an alkyl group for the preparation of silicone antifoam emulsions. The emulsifiers are non-ionic polyethylene oxide modified triglycerides or alcohol ethoxylates. German Patent No 43 43 185 teaches the use of polyalkylene oxide modified siloxanes as emulsifiers for silicone antifoam compounds that are based on blends of polyalkylene oxide modified siloxanes and hydrophobic silica. EP-A-0 425 592 discloses the use of polyvinylpyrrolidone as a protective colloid in the production of polystyrene. The polyvinypyrrolidone have a K-value of 100-150. SUMMARY OF THE INVENTION Certain silicone antifoam emulsions of low viscosity (<3000 cSt at 25°C), exhibit excellent bulk and dilute stability, have high efficiency in non-ionic and anionic foamant systems both at ambient and elevated temperature, and their dilutions with water do not separate. These emulsions contain silicone antifoam compounds based on polydimethylsiloxanes and inorganic oxides and are protected against creaming and separation by the use of synthetic protective colloids wich are based on polyvinylpyrrolidone. The emulsions according to the invention are defined in claim 1 and comprise polyvinylpyrrolidone polymers having a K-value of 10 to 60. One aspect of the present invention is antifoam emulsions which comprise: (A) polydiorganosiloxane; (B) fine solid particles of inorganic oxide, bearing on the surface thereof a polydiorganosiloxane component; wherein the total amount of polydiorganosiloxane present in components (A) and (B) is 5 wt % to 60 wt % of the emulsion and the weight ratio of the total amount of polydiorganosiloxane present in components (A) and (B) to the amount of said inorganic oxide is 10:1 to 200:1; (C) an organic surfactant dispersing agent selected from the group consisting of non-ionic tetrafunctional block copolymers terminating in primary or secondary hydroxyl groups and mixtures thereof, at 0.1 wt % to 36 wt % of said emulsion; (D) a copolymer of polydimethylsiloxane with polyalkylene oxide, the molecular weight of the polydimethylsiloxane portion being 300 to 100,000 Daltons and the total molecular weight of all polyalkylene oxide present being 100 to 40,000 Daltons, which copolymer is present at 0.1 wt.% to 20 wt.% of said emulsion; (E) a non-ionic surfactant component comprising one or more non-ionic surfactants not conforming to agent (C) nor to copolymer (D) at 1 wt % to 60 wt % of said emulsion; (F) a thickener component at 0.01 wt % to 15 wt % of said emulsion; (G) a protective colloid component derived from polyvinylpyrrolidone at 0.01 wt.% to 10 wt.% of said emulsion; and (H) water at up to 95 wt.% of the emulsion. These antifoam emulsions are characterised in that they possess low viscosity, they have excellent bulk and dilute stabilities, their water dilutions do not separate on standing for prolonged periods, they exhibit a strong antifoam effect, and they are freeze/thaw stable. DETAILED DESCRIPTION OF THE INVENTION The polydiorganosiloxane used in the present invention can be either linear or branched. The repeating unit has exclusively the general formula R 1 R 2 SiO 2/2 for the linear type or R 1 SiO 3/2 and R 2 SiO 2/2 for the branched type where each occurrence of R 1 and R 2 denotes a C 1 to C 6 alkyl, aryl, or C 1 to C 6 alkoxy radical, such as methyl, ethyl, propyl, butyl, phenyl, methoxy, ethoxy, or propoxy groups. The end groups of the polymer have the general formula R 3 R 4 R 5 SiO 1/2 , where each occurrence of R 3 , R 4 , and R 5 denotes a C 1 to C 6 alkyl, aryl, or C 1 to C 6 alkoxy and/or hydroxy radical, such as methyl, ethyl, propyl, butyl, phenyl, methoxy, ethoxy, or propoxy groups. For the purpose of the present invention, it is preferred that R 1 , R 2 , R 3 , R 4 and R 5 be methyl radicals. The kinematic viscosity of the polydiorganosiloxane component should be in the 5·10 -5 to 20 m 2 /s (50 to 20,000,000 centistokes)range, preferably between 1·10 -4 and 12 m 2 /s (100 and 12,000,000 centistokes) The concentration of the polydiorganosiloxane component is preferably about 5 to 60% by weight of the emulsion. The finely divided solid particulate component, frequently called "filler", can be either inorganic or organic in nature. Inorganic fine particulate matter suitable for the present invention can be either an inorganic oxide or silicate. Organic particulate matter suitable for the present invention can be a fatty acid amide such as ethylene bis stearamide or a polyethylene wax with a melting point of at least 80°C. Silica is preferred as the particulate material. The silica can be fumed, precipitated or aerogel and in either hydrophilic or hydrophobized form. While silica is preferred in this invention, fine particles of other materials, such as alumina, titania, zirconia, amorphous alumino-silicates or their combinations with each other or with silica can be used. The filler particles should have a specific BET surface area of about 40 to 400 m 2 /g. The filler can be either hydrophilic, that is, untreated, or hydrophobized. The concentration of the filler particles in the antifoam compound should be set so that the ratio of the total amount of the polydiorganosiloxane present in the antifoam compound to the amount of the filler particles is about 10:1 1 to 200:1. The polydiorganosiloxane component and the filler component are combined so that some of the polydiorganosiloxane becomes bound to the surface of the filler particles. The term "bound" is used herein to mean that polydiorganosiloxane is present on, and remains on, the particle surfaces during and following the preparation of the emulsion according to the present invention. The behavior of the polydiorganosiloxane on the particle surfaces is consistent with its being covalently bound thereto, but the actual nature of the attachment of the polydiorganosiloxane to the particle surface is not critical so long as the attachment exists. The attachment of the polydiorganosiloxane to the particle surfaces can be effected either by simply heating the raw materials at 50 - 300°C for a duration of 1-36 hours, or is preferably effected with the aid of a catalyst at a temperature of 100 - 220°C, preferably 150 - 200°C, for a period of 1 - 24 hours, preferably 6 - 18 hours. As reaction catalyst either at least one basic or acidic material may be used. The preferred catalyst is alkali hydroxide, such as KOH, NaOH etc., or alkali silanolate, such as potassium-silanolate or sodium-silanolate. Other basic materials, such as alkali or alkaline earth metal oxides, hydroxides and silanolates; monoalkyl, dialkyl, and trialkyl amines; and tetraalkylammonium hydroxides and silanolates can also be used as catalyst. Typical examples of these catalysts include sodium, potassium, cesium, calcium, magnesium or strontium oxide, hydroxide or silanolate and their combinations. Each alkyl group in an amine catalyst typically can be a C 1 to C 16 alkyl group, such as methyl, ethyl, propyl, butyl, decyl, dodecyl, or hexadecyl, or one of the alkyl groups can be replaced by a phenyl group. The kind of catalysts that can be used in this invention are siloxane equilibration catalyst such as those described in the book Chemistry and Technology of Silicones, by Walter Noll, Academic Press, 1968, Chapter 5. The catalyst is preferably used in an effective amount on the order of 0.1% to 10% by weight of the combined amount of polydiorganosiloxane and filler present, and preferably 0.5% to 5% by weight thereof. To facilitate the emulsification of the antifoam compound there is included in the antifoam agents at least one organic surfactant dispersing agent of a non-ionic difunctional or tetrafunctional, preferably tetrafunctional, block copolymer terminating in primary or secondary hydroxyl groups for assisting in dispersing the antifoam compound in the water of the emulsion. As used herein, "difunctional" and "tetrafunctional", respectively mean disubstituted and tetrasubstituted with said hydroxyl substitution. Surfactants of the difunctional type are well known in the art as exemplified in European Patent No 254,499. The tetrafunctional types are derived from the sequential addition of propylene oxide and ethylene oxide to ethylene diamine. Tetrafunctional block copolymers terminating in hydroxyl groups with a molecular weight of 1600 to 30000 Daltons, preferably from 2000 to 8000 Daltons and most preferably from 3000 to 8000 Daltons, HLB up to 7 and an aqueous cloud point of maximum 35°C are preferred. The concentration of the hydroxyl-terminated organic surfactant dispersing agent can vary between 2% and 60% on the weight of the antifoam emulsion, preferably between 10% and 60% on the weight of the antifoam emulsion. In addition to the hydroxyl-terminated organic surfactant dispersing agent, at least one non-ionic emulsifier component is necessary to produce the antifoam emulsion. Any non-ionic surface active agent can be employed in this invention. The non-ionic surface active agent can be a non-ionic organic surface active agent or a non-ionic siloxane surface active agent. The concentration of the non-ionic surface active agent can vary between 10% and 200% on the weight of the antifoam compound, preferably between 20% and 100% on the weight of the antifoam compound. The non-ionic emulsifier component is comprised of one or more than one non-ionic emulsifiers. Preferably the non-ionic emulsifier is comprised of silicone based and/or organic based surfactants. Useful organic based surfactants include polyoxyethylene-alkyl ethers (alcohol ethoxylates) such as oleochemical alcohol ethoxylates such as lauryl-myristyl alcohol ethoxylates, cetyl-stearyl alcohol ethoxylates, cetyl-oleyl alcohol ethoxylates, petrochemical or synthetic alcohol ethoxylates such as the Ziegler fatty alcohol ethoxylates, the oxo-alcohol ethoxylates, the branched oxo-alcohol ethoxylates, the isotridecyl alcohol ethoxylates, the 2-ethylhexanol ethoxylates, the nonyl phenol ethoxylates and the octyl phenol ethoxylates, ethylene oxide/propylene oxide copolymers, fatty acid alkyl esters and their ethoxylates, glyceryl-lacto esters of fatty acids, such as glyceryl lactooleate, glyceryl fatty acid mono- and di-esters, such as glyceryl monostearate, glyceryl monooleate, glyceryl monolaurate or glyceryl 5-hydroxydecanoate, lactylated fatty acid esters of glycerol and propylene glycol, polyglycerol esters of fatty acids, fatty acid monoglyceridyl citrates, fatty acid polyoxyethylene esters with 10-40 moles of ethylene oxide, such as polyoxyethylene 40 monostearate, polyoxyethylene dioleate, polysorbate 20, polysorbate 60, polysorbate 65, polysorbate 80, propylene glycol mono- and diesters of fatty acids, fatty acid sorbitan mono- and di-esters, such as sorbitan monooleate or sorbitan monostearate, sucrose fatty acid esters, diacetyl tartaric acid esters of monoglycerides, acetic acid esters of monoglycerides, and lecithin. Nonionic surface active agents and / or methods for their preparation which are useful in this invention are well known in the art as witnessed for example by McCutcheon's Detergents and Emulsifiers, 1975 Annual, McCutcheon Division M.C. Publishing Co., Ridgewood, N.J. the disclosure of which is incorporated herein by reference thereto. It is preferred in this invention to combine at least two emulsifiers, one with a low HLB (2-6) and another with a high HLB (6-20). Low HLB emulsifiers are, for example, propylene glycol monostearate, glyceryl monooleate, sorbitan monostearate, sorbitan tristearate or glyceryl lacto-palmitate. High HLB emulsifiers are, for example, glyceryl monolaurate, polyoxyethylene (40) monostearate, polysorbate 60, polysorbate 65, polysorbate 80 or decaglycerol monooleate. Illustrative commercial examples of the high HLB non-ionic organic surface active agents are the MYRJ surfactants of ICI United States Inc., the TERGITOL surfactants of Union Carbide Corporation, and the like. Illustrative commercial examples of the low HLB non-ionic organic surface active agents include, e.g., certain ATMOS, ATMUL, ARLACEL, ATPET, SPAN, TWEEN, and BRIJ surfactants of ICI, and the like. The silicone based emulsifiers which can be used in this invention preferably include at least one copolymer of polydimethylsiloxane with one or a combination of several polyalkylene oxides. This copolymer can have a comb-type structure or an A-B or A-B-A type structure. The molecular weight of the polydimethylsiloxane part of the block copolymer should be about 300-100,000 Daltons. The polyalkylene oxide part of the silicone based copolymer comprises preferably one or both of polyethylene oxide and polypropylene oxide. The molecular weight of the polyalkylene oxide blocks in the silicone based emulsifier component is about 100-40,000 Daltons. The ratio of the polyethylene and polypropylene oxide blocks in the copolymer is preferably about 0-60 %, respectively. The concentration of the silicone polyether copolymer can vary between 0.1% by weight and 20% by weight on the weight of the final emulsion. It is also possible to include a polyalkylene oxide component, which is preferably polypropylene glycol, as solvent. The concentration of this component should be about 5-50% of the final composition. The molecular weight of the polypropylene glycol is about 500-10,000 Daltons, preferably about 500-2000 Daltons. To stabilise the antifoam emulsion, at least one thickener component should be present. Rheology modifiers or thickeners of usefulness in the present invention are polycarboxylate materials. These have at least 60% by weight of segments with the general formula wherein A, Q, and Z are each selected from the group consisting of hydrogen, methyl, carboxy, COOM, carboxymethyl, hydroxy, and hydroxymethyl, M is hydrogen, alkali metal, ammonium or substituted ammonium and t is from 30 to 400. Preferably A is hydrogen or hydroxy, Q is hydrogen or carboxy and Z is hydrogen. Suitable polymeric polycarboxylates include polymerised products of unsaturated monomeric acids, e.g., acrylic acid, maleic acid, maleic anhydride, fumaric acid, itaconic acid, aconitic acid, mesaconic acid, citraconic acid, and methylenemolanic acid. The copolymerisation with lesser amounts of monomeric materials comprising no carboxylic acid, e.g., vinylmethyl, vinylmethylethers, styrene, 1,9-decadiene, ethylene is desirable to the use of the polycarboxylates in the foam control agents of the present invention. Particularly useful polycarboxylate thickener components are copolymers of methyl vinyl ether with maleic anhydride. Copolymers of methyl vinyl ether with maleic anhydride based thickeners are large molecular weight, cross-linked polymer resins of maleic anhydride and its derivatives. These materials are hydrophilic, water-swellable and extremely effective thickeners in aqueous or polar solvent based liquids. Typical commercial copolymers of methyl vinyl ether with maleic anhydride based thickeners which are useful include the STABILEZE products of ISP. These products are available in powdered form, such as STABILEZE 06 or STABILEZE QM. The copolymers of methyl vinyl ether with maleic anhydride based thickeners work effectively if they are allowed to hydrolyse and then be neutralised with a basic material. If neutralised to about pH 5-11, preferably 6-9, the copolymers of methyl vinyl ether with maleic anhydride thickeners give high viscosity and gel structure to aqueous or polar solvent based liquids which can stabilise emulsions. Based on these requirements a neutralising agent should be added to the emulsion in a concentration which is necessary to set the pH of the antifoam emulsion close to neutral (pH 6 to 9), if a copolymer of methyl vinyl ether with maleic anhydride based thickener is used. As neutralising agent various types of basic materials can be used. Typical useful neutralising agents are alkali and ammonium hydroxides, carbonates, hydrogen carbonates, acetates or alkaline earth oxides, hydroxides, carbonates, acetates or any other alkali or alkaline earth salts which can neutralise maleic acid. Organic amine bases including monoalkyl, dialkyl, trialkyl amines, tetraalkylammonium hydroxides, monoethanolamine, diethanolamine, triethanolamine (TEA), aminomethylpropanol, aminomethylpropanediol, diisopropanolamine (DIPA), aminomethyl propanol, tromethamine, sodium hydroxymethyl glycinate, and tetrahydroxypropyl ethylenediamine can also be used as neutralising agents. A polysaccharide type thickener can also be used instead of or preferably, in addition to the polycarboxylate based thickeners in the foam control compositions of this invention. Useful polysaccharides include non-ionic unmodified polysaccharides such as microcrystalline cellulose (trade names: AVICELL, MICROQUICK, FMC Corporation), wheat, corn, and rice starch, gum arabic, gum tragacanth, and guar flour, non-ionic modified polysaccharides such as starch products examples of which include the hot-water-soluble heat-treated starches ("British gum"; trade names: DIATEX, DIAMALT), and the cold-water-soluble heat-treated swelling starches (trade names : DIATEX SL, DIAMALT), the non-ionic starch ethers and starch esters (trade names : SOLVITOSE H and H4, AVEBE; TEXOGUM 3013, DIAMALT), the gum resins (trade names : KARAGUM SUPER, DIAMALT; LAMEGUM, CHEM. FABRIK GRÜNAU ; NAFKA KRISTALLGUMMI, AVEBE), the galactomannans such as carob flour, and guar derivatives (trade names : SOLVITOSE, AVEBE ; POLYGUM, POLYMER INDUSTRIES ; DIAGUM, DIAMALT), and the cellulose derivatives such as the methyl, ethyl, hydroxyethyl, hydroxypropyl, hydroxypropyl methyl, and hydroxyethyl methyl derivatives of cellulose (trade names include : CELLOSIZE, Union Carbide ; NATROSOL MR, Hercules), and anionic polysaccharides such as alginates ( trade names include : ALGINATE, SFC ; KELTEX, KELCO ; DIALGIN, DIAMALT), biopolysaccharides such as xanthan (trade names include: KELZAN, Kelco ; RHODOPOL, Rhone-Poulenc), and carboxymethylated polysaccharides such as anionic starch ethers (trade names include : MONAGUM V, DIAMALT ; SOLVITOSE C5, AVEBE), anionic etherified seed flours such as those based on guar, and carboxymethylcelluloses and their sodium salts (trade names include: CMC Cellulose Gum, Hercules ; COURLOSE, British Cellanese ; TYLOSE C600, Hoechst). Particularly useful polysaccharides for the present invention are the anionic polysaccharides and especially the carboxymethylcelluloses and their sodium salts. These materials do not require a neutralisation step, however, it is important that they be well dispersed in the aqueous phase of the emulsion to be effective. To further stabilise the antifoam emulsion it is necessary to use one or more than one protective colloids which are based on polyvinylpyrrolidone. Protective colloids that are particularly useful in this invention are polymers of polyvinylpyrrolidone, copolymers of polyvinylpyrrolidone and polyalkylatedvinylpyrrolidone, copolymers of polyvinylpyrrolidone with vinyl esters, and copolymers of polyvinylpyrrolidone with vinyl acetate. Such polymers are commercially available under the trade names of KOLLIDON, LUVISKOL, Albigen A, COLLACRAL, LUVISKOL VA, and DIVERGAN from BASF, PVP/VA from General Aniline and Film Corporation, PVP, ANTARON, and GANTREZ AN from ISP. Especially useful are the copolymers of polyvinylpyrrolidone and poly(alkylatedvinylpyrrolidone). Polyvinylpyrrolidone and poly(alkylatedvinylpyrrolidone) have the general structure : where R 6 and R 7 can be either hydrogen or an alkyl group. In the case where R 6 and R 7 are both hydrogen, the structure corresponds to polyvinylpyrrolidone. Polyvinylpyrrolidone polymers are available in several molecular weight grades, ranging from low, 2500 Daltons, to very high molecular weight, 3000000 Daltons. There are different methods for the determination of the molecular weight such as light scattering, osmometry, NMR spectroscopy, ebulliometry, and size exclusion chromatography. By the use of these methods, anyone of three molecular weight parameters can be measured, namely the number average, viscosity average, and weight average molecular weights. Each of these characteristics can yield a different value for the same polymer. It is for this reason that, conventionally, molecular weights for polyvinylpyrrolidone polymers are expressed by their "K-values", which are based on kinematic viscosity measurements. The K-values assigned to different grades of polyvinylpyrrolidone polymers represent a function of the average molecular weight, the degree of polymerisation, and the intrinsic viscosity. The K-values are derived from viscosity measurements and are calculated according to Fikentscher's formula. The higher the K-values the higher the molecular weight of the corresponding polyvinylpyrrolidone polymer. Commercially available polyvinylpyrrolidone polymers have K-values ranging from 10 to 130. Polyvinylpyrrolidone polymers that are useful as protective colloids according to the invention have K-values of 10 to 60. In the case where R 6 and R 7 are either hydrogen or alkyl groups, lipophilic groups are introduced into the polyvinylpyrrolidone structure resulting in the formation of linear copolymers of the heterocyclic monomer and long chain alpha-olefins. These copolymers are commonly called poly(alkylated vinyl pyrrolidone) polymers and have molecular weights that range from 7000 Daltons up to 20000 Daltons. Poly(alkylated vinylpyrrolidone) polymers particularly useful are those modified with alkyl groups having either 16 or 20 carbon atoms. The relative amounts of the rheology modifiers (thickeners) and protective colloids that can be used are such that their combined effect does not result in the viscosity of the final antifoam emulsion to exceed 3·10 3 m 2 /s (3000 cSt). Thus, the rheology modifiers are present in not more than 15%, preferably not more than 7% in the final antifoam emulsion, whereas the protective colloids are present in not more than 10%, preferably not more than 5% in the final antifoam emulsion. A preservative can also be present to prevent microbial growth. Examples of such products are UCARCIDE 250 (glutaraldehyde) from Union Carbide, KATHON CG/ICP from Rohm and Haas. If the antifoam concentrate is to be used in food applications then any food preservative, such as acetic acid, sorbic acid, lactic acid, propionic acid, benzoic acid and their salts or parabens and their combinations can be used. The concentration of the biocide depends on the strength of the biocide and the extent of protection demanded from it. Typically a biocide will be used at levels ranging from 1.5 to 0.05% in the final antifoam emulsion. An additive can be used to protect the antifoam emulsion in case it experiences temperatures lower than 0°C. Such an additive typically is referred to as a freeze/thaw additive. Typical freeze/thaw additives are monohydric or polyhydric alcohols such as methanol, ethanol, propanol, ethylene glycol, propylene glycol, dipropylene glycol, glycerol, isopropyl alcohol, 1-methoxy-2-propanol. The amount of the freeze/thaw additive to be used can vary between 0.5 and 10% in the final antifoam emulsion, preferably 1 to 5% in the final antifoam emulsion. A freeze/thaw additive that is particularly useful is propylene glycol. Manufacture The preparation of the antifoam emulsion is a two-step process. In the first step of the preparation an antifoam compound is made by blending and reacting the polydiorganosiloxane, particulate filler, and catalyst components. A possible way of addition is starting with the polydiorganosiloxane, adding the fine solid particles under intensive mixing, and finally blending the catalyst, if any. The sequence of addition is, however, not critical. After a homogeneous mixture is obtained, it is heated to 50°-300° C for several hours. During heating the blend can be mixed. After this heating step, during which a reaction can take place between the surface hydroxyl groups of the filler and the polyorganosiloxane under the influence of the catalyst, the antifoam compound is cooled to ambient temperature and stored until further use. A process to prepare the antifoam emulsion is as follows : (a) the preparation of Blend A, said Blend comprising antifoam compound, non-ionic emulsifier, and protective polyvinylpyrrolidone based colloid; (b) the preparation of Blend B, said Blend comprising Blend A, non-ionic emulsifier, and water; and (c) the preparation of Blend C, said Blend comprising water, Blend B, thickener, protective colloid. The order of addition of the different materials in step (a) is not narrowly critical. However, it is preferred that the protective colloid be added last as a blend with a non-ionic surfactant. Blend A is mixed till fully homogeneous. The temperature of mixing is not critical, it can range from 5°C to 100°C, but it is preferred that it be between 5°C and 45°C. In a second step, Blend B is prepared, said blend comprising Blend A, non-ionic emulsifier, water and optionally, freeze/thaw additive. The order of addition of the different materials is not critical. It is preferred however, that Blend A be added first. Blend B is mixed till fully homogeneous. The temperature of mixing can range from 5°C to 80°C, but it is preferred that it be between 25°C and 65°C. In the third step, the final emulsion is prepared, said final emulsion comprising Blend B, thickener, protective colloid, optional preservative, and neutralising agent. The order of addition of the different materials is not narrowly critical. However, it is preferred that Blend B be added first. The temperature of mixing is not narrowly critical, it can range from 5°C to 80°C, but it is preferred that it be between 15°C and 65°C. Mixing throughout the different steps can be effected with any appropriate means to ensure homogeneity. It is preferred that the type of mixers used are those in which turbulent flow conditions prevail. Examples of such mixers include turbine agitated vessels, pipes, jet mixers, sparged systems, high-speed shear mixers, rotor-stator mixers, and static mixers with a high Re number. The final emulsion can be further treated with high shear devices as a colloid mill, valve homogeniser, ultrasonic homogeniser, or sonolator. TEST METHODS The viscosity of the antifoam emulsion was measured using a Brookfield LV viscometer equipped with spindle No 3 at a rotational speed of 30 rpm. A sample was accepted if the viscosity was below 1.5·10 -3 m 2 /s (1500 cSt) preferably below 1·10 -3 m 2 /s (1000 cSt). The quality ofthe emulsion diluted to 3% as received in water, e.g., 3 g of the emulsion mixed with 97g of water, was tested by visual observation. The diluted emulsion was observed in transparent light. The quality of the emulsion was acceptable if no particles larger than a few tenths of a millimetre could be observed and when no unemulsified oil developed immediately and after standing for 30 min. Each emulsion was subjected to shaking, using a Burrell wrist-action shaker for 30 seconds in order to measure the foam height one minute after the shaking stopped. This was repeated ten times. The foam height is the addition of the individual foam heights. The amount of antifoam emulsion added was such that it resulted in 150 ppm of silicone fraction in the foamant liquor which was a 0.5% aqueous solution of sodium dodecyl sulfonate. EXAMPLES Example 1 The following thickeners/protective colloids were investigated : Thickener/Protective Colloid Abbreviation CARBOPOL 934 ( polycarboxylate ) A BLANOSE 9M31XF (cellulose derivative) B PVP K-30 (polyvinylpyrrolidone) C ANTARON V-216 (polyvinylpyrrolidone) D STABILEZE QM (methyl vinyl ether with maleic anhydride) E CARBOPOL 981 ( polycarboxylate ) F BLANOSE 7L2C (cellulose derivative) G AVICELL CL611 (microcrystalline cellulose) H MICROQUICK WC 595 (microcrystalline cellulose) I NATROSOL 250LR (cellulose derivative) J CELLOSIZE QPO9H (cellulose derivative) K ACUSOL 830 (polycarboxylate emulsion) L 100g polydimethylsiloxane having a viscosity of 5·10 -4 m 2 /s (500 cSt) at 25°C, and 3g of finely divided fumed amorphous silica having an average particle size of 7 millimicrometers and a BET surface area of 325 m 2 /g were blended together. Into this blend, 0.04% of K + as potassium silanolate was well dispersed. The resulting mixture was heated to 150°C for 5 hours and then cooled to ambient to provide a silicone antifoam compound. 5.33g of a homogeneous blend of cetyl-stearyl alcohol ethoxylates of high (16.2) and low HLB (6) blended at a ratio so that the overall HLB of the system was 9.3 were mixed with 40.63g of the antifoam compound prepared above followed by the addition of a certain amount (weight A) of thickener/protective colloid polymer. A few minutes later, 155.15g of a blend of thickener/protective colloid (weight B) and water was added, followed by 0. 1g of neutralising agent and 0.12g PIROR P-840 preservative. The aqueous antifoam compositions so prepared are listed below along with the identified thickener and protective colloid, their respective weights and viscosity of the finished emulsion. In the Table below TEA stands for triethanolamine : Thickener/Protective Colloid Neutralising agent Weight A/gr Weight B/gr Viscosity/cSt, 25°C A,G NaOH 0.3 2.03 1550 A,G NaOH 0.2 2.04 1200 A,G NaOH 0.1 2.04 1000 A,H NaOH 0.1 2.01 1300 A,H NaOH 0.11 1.65 1000 A,H,G NaOH 0.3 3.2 16700 A,I NaOH 0.25 2.03 2400 G,J NaOH 2.02 2.03 176 A,J TEA 0.32 2.24 2000 I,C,J TEA 4.01 3.37 130 F,G,C TEA 1.92 2.15 1300 Example 2 75.04g of a polydimethylsiloxane having a viscosity of 1·10 -4 m 2 /s (100 cst) at 25°C, 251.01g of a polydimethylsiloxane having a viscosity of 5·10 -4 m 2 /s (500 cSt) at 25°C and 50.50g of a finely divided fumed hydrophobic silica having an average particle size of 7nm and a BET surface area of 260m 2 /g were mixed under high shear until the silica was well dispersed. 50.09g of a polydimethylsiloxane having a viscosity of 3.5·10 -4 m 2 /s (350 cSt) at 25°C, 75.54g of a polydimethylsiloxane having a viscosity of 12 m 2 /s (12 million cSt) at 25°C and 5.07g of 10% by weight solution of KOH in isopropanol were mixed in. The mixture was heated under shear at 165°C for 36h and then cooled to ambient. 50g of this antifoam compound and 50g of the antifoam compound prepared as described in Example 1 were mixed until homogeneous. This blend was added with mixing to a blend of 0.15g of thickener F of example 1, 0.75g of thickener G of example 1, 26.54g of the blend of cetyl-stearyl alcohols of Example 1, and 363.04g of water that had been prepared in advance at 60°C. After a few minutes, the blend was diluted with 500.19 g of water, neutralised with 2.09g of TEA and preserved with 0.54g of PIROR P-840 preservative. This aqueous antifoam composition had a viscosity of 1.1·10 -3 m 2 /s (1100 cst) total foam height of 154 mm, and had good appearance when diluted 3% in water. Example 3 The same procedure and raw materials as in Example 2 were employed with the exception that the antifoam compound was replaced by a blend of the antifoam compound prepared in Example 2 with a mixture of oxygenated hydrocarbons, primarily aliphatic alcohols and aliphatic ethers having a density of 0.84 g/ml at 20°C and a hydroxyl value of 55 mgKOH/g and a tetra-functional block copolymer derived from the sequential addition of propylene oxide and ethylene oxide to ethylenediamine having an average molecular weight of 3600 Daltons in a ratio of 10:3:3 respectively so that the amount of silicone antifoam compound was proportionately kept the same as in Example 2. This aqueous antifoam composition had a viscosity of 1.34·10 -3 m 2 /s (1340 cSt), total foam height of 59 mm, good appearance when diluted 3% in water and its dilution with water was stable for 3 days at ambient. Example 4 283.5g of a polydimethylsiloxane having a viscosity of 1.25·10 -2 m 2 /s (12500 cSt) at 25°C were mixed with 15.00g of a hydrophobic silica having an average agglomerate size of 5 micrometers and a BET surface area of 90 m 2 /g and 1.50 g of KOH and heated to 150°C for 16h and then cooled to ambient to provide a silicone antifoam compound. A blend of 20.19g of this antifoam compound and 8.13g of a tetra-functional block copolymer derived from the sequential addition of propylene oxide and ethylene oxide to ethylenediamine having an average molecular weight of 3600 Daltons was blended at ambient with a blend of 0.12g D 0.96g of a silicone modified with polyethylene oxide groups having a molecular weight of 7800 Daltons and an estimated HLB of 10 and 0.06g of a silicone modified with polyalkylene oxide groups having a molecular weight of 12500 Daltons and an estimated HLB of 12. The blend was heated to 50°C and mixed with 53.73g of a blend of cetyl-stearyl alcohol ethoxylates of high (16.2) and low HLB (6) blended at a ratio so that the overall HLB of the system was 9.3, water and propylene glycol at a ratio of 10:75:25 respectively. The blend was cooled down and 64.76g of a blend of thickeners E and G of example 1 and water at a ratio of 0.3:2.3:97.4 was mixed in. 54.02g of water and 0.11g of PIROR P-840 preservative were subsequently mixed in. This aqueous antifoam composition had a viscosity of 8.6·10 -4 m 2 /s (860 cSt) and good appearance when diluted 3% in water. Example 5 40.03g of the antifoam compound of Example 2 were mixed at 50°C with 2.02g of a water insoluble polyethylene oxide modified siloxane having a molecular weight of 10000 Daltons, 2.02g of a water insoluble polyalkylene oxide modified siloxane having a molecular weight of 46000 Daltons and 4.02g of a water insoluble polyalkylene oxide modified siloxane having a molecular weight of 23000 Daltons. 4.04g of water were then added followed by 2.03g of thickener B of example 1, 146.04g of water and 0.14g of KATHON LX. This aqueous antifoam composition had a viscosity of 1·10 -3 m 2 /s (1000 cSt) and was freeze / thaw stable. Example 6 40.6g of the antifoam compound of Example 2 were mixed at 50°C with 2.02g of a water insoluble polyethylene oxide modified siloxane having a molecular weight of 10,000 Daltons, 4.03g of a water insoluble polyalkylene oxide modified siloxane having a molecular weight of 46000 Daltons and 2.00g of a water insoluble polyalkylene oxide modified siloxane having a molecular weight of 23,000 Daltons. 16.02g of water were then added followed by 2.43g of thickener L of example 1 and 0.23g of morpholine, 133.61g of water and 0.11g of KATHON LX. This aqueous antifoam composition had a viscosity of 1·10 -3 m 2 /s (1000 cSt). Example 7 4.57g of a stearic acid ester modified with 40 ethylene oxide units having an HLB of 16.9, 12.72 of sorbitan monostearate having an HLB of 4.7, and 15g of water were mixed at 85°C till fully homogeneous. 40.78g of the antifoam compound of Example 2 were slowly added and thoroughly mixed in. 1g of thickener L of example 1 was mixed in and the blend was diluted with 127.32g of water and 0.14g of KATHON LX. This aqueous antifoam composition had a viscosity of 1.7·10 -4 m 2 /s (170 cSt). Example 8 534.25g of a polydimethylsiloxane of viscosity 1.25·10 -2 m 2 /s (12,500 cSt) at 25°C, 60.13g of a hydrophobic silica having an average agglomerate size of 5 micrometers, an average primary particle size of 18 nm and a BET surface area of 90 m 2 /g and 6.02g of KOH were mixed and heated to 150°C for 16 hours and then cooled to ambient to produce an antifoam compound. To 1.14g of a blend of a silicone modified with polyethylene oxide groups having a molecular weight of 7800 Daltons and an estimated HLB of 10 and a poly(alkylatedvinylpyrrolidone) having an average molecular weight of 7300 Daltons and a relative viscosity of 1.009 as a 0.1% solution in toluene used in a ratio of 90.4:9.6 prepared at ambient was added a blend of 20.18g of the antifoam compound prepared above and 8.03g of a tetra-functional block copolymer derived from the sequential addition of propylene oxide and ethylene oxide to ethylenediamine having an average molecular weight of 3600 Daltons and the two mixed initially at ambient and then at 50°C. To this blend were added at 50°C 52.67g of a blend of a stearic acid ester modified with 40 ethylene oxide units having an HLB of 16.9 and sorbitan monostearate having an HLB of 4.7 blended at such a ratio so as to have an overall HLB of 9.5, propylene glycol and water blended at a ratio of 8.2:15.3:76.5 prepared in advance at 60°C. This mixture was then cooled down and 64.29g of a blend of a copolymer of methyl vinyl ether and maleic anhydride crosslinked with 1,9-decadiene having an average particle size of less than 75micrometers a sodium salt of a carboxymethylcellulose having a sodium content of between 7 and 8.9% and water at a ratio of 0.3:2.3:97.4 that had been prepared at 60°C and then cooled down were added and mixed in. 54.7g of water were then added followed by 0.12g of PIROR P-840. The aqueous antifoam composition so obtained had a viscosity of 4.84·10 -4 m 2 /s (484 cSt). Example 9 447.68g of a polydimethylsiloxane of viscosity 1.25·10 -2 m 2 /s (12500 cSt) at 25°C, 50.20g of a hydrophobic silica having an average agglomerate size of 5micrometers, an average primary particle size of 18 nm and a BET surface area of 90 m 2 /g and 25.03g of a 10% solution of KOH in isopropanol were mixed and heated to 150°C for 16 hours to produce an antifoam compound. To 1.13g of a blend of a silicone modified with polyethylene oxide groups having a molecular weight of 7800 Daltons and an estimated HLB of 10 and a poly(alkylatedvinylpyrrolidone) having an average molecular weight of 7300 Daltons and a relative viscosity of 1.009 as a 0.1% solution in toluene used in a ratio of 90.4:9.6 prepared at ambient was added a blend of 20.13g of the antifoam compound prepared above, 8.09g of a tetra-functional block copolymer derived from the sequential addition of propylene oxide and ethylene oxide to ethylenediamine having an average molecular weight of 3600 Daltons and 8.04g of a mixture of oxygenated hydrocarbons, primarily aliphatic alcohols and aliphatic ethers having a density of 0.84 g/ml at 20°C and a hydroxyl value of 55 mgKOH/g and mixed initially at ambient and then at 50°C. To this blend were added at 50°C 53.61g of a blend of cetyl-stearyl alcohol ethoxylates of high (16.2) and low HLB (6) blended at a ratio so that the overall HLB of the system was 9.3, propylene glycol and water blended at a ratio of 10: 15:75 prepared in advance at 60°C. This mixture was then cooled down and 64.53g of a blend of a copolymer of methyl vinyl ether and maleic anhydride crosslinked with 1,9-decadiene having an average particle size of less than 75 micrometers a sodium salt of a carboxymethylcellulose having a sodium content of between 7 and 8.9% and water at a ratio of 0.3:2.3:97.4 that had been prepared at 60°C and then cooled down were added and mixed in. 45.81g of water were then added followed by 0.12g of PIROR P-840 and 0.08g of triethanolamine. The aqueous antifoam composition so obtained had a viscosity of 1.812·10 -3 m 2 /s (1812 cSt). Example 10 To 1.13g of a blend of a silicone modified with polyethylene oxide groups having a molecular weight of 7800 Daltons and an estimated HLB of 10 and a poly(alkylatedvinylpyrrolidone) having an average molecular weight of 7300 Daltons and a relative viscosity of 1.009 as a 0.1% solution in toluene used in a ratio of 90.3:9.7 prepared at ambient was added a blend of 20.16g of the antifoam compound of example 8, 8.02g of a tetra-functional block copolymer derived from the sequential addition of propylene oxide and ethylene oxide to ethylenediamine having an average molecular weight of 3600 Daltons and 0.2g of sodium lauryl ether phosphate and mixed initially at ambient and then at 50°C. To this blend were added at 50°C 53.61 g of a blend of cetyl-stearyl alcohol ethoxylates of high (16.2) and low HLB (6) blended at a ratio so that the overall HLB of the system was 9.3, propylene glycol and water blended at a ratio of 10:15:75 prepared in advance at 60°C. This mixture was then cooled down and 64.29g of a blend of a copolymer of methyl vinyl ether and maleic anhydride crosslinked with 1,9-decadiene having an average particle size of less than 75micrometers a sodium salt of a carboxymethylcellulose having a sodium content of between 7 and 8.9% and water at a ratio of 0.3:2.3:97.4 that had been prepared at 60°C and then cooled down were added and mixed in. 53.81g of water were then added followed by 0.12g of PIROR P-840. The aqueous antifoam composition so obtained had a viscosity of 8.36·10 -4 m 2 /s (836 cSt). Example 11 To 1.15g of a blend of a silicone modified with polyethylene oxide groups having a molecular weight of 7800 Daltons and an estimated HLB of 10 and a poly(alkylatedvinylpyrrolidone) having an average molecular weight of 7300 Daltons and a relative viscosity of 1.009 as a 0.1% solution in toluene used in a ratio of 90.3:9.7 prepared at ambient was added a blend of 20.22g of the antifoam compound of example 2 and 8.03g of a mixture of oxygenated hydrocarbons, primarily aliphatic alcohols and aliphatic ethers having a density of 0.84 g/ml at 20°C and a hydroxyl value of 55 mgKOH/g and mixed initially at ambient and then at 50°C. To this blend were added at 50°C 53.61g of a blend of cetyl-stearyl alcohol ethoxylates of high (16.2) and low HLB () blended at a ratio so that the overall HLB of the system was 9.3, propylene glycol and water blended at a ratio of 10:15:75 prepared in advance at 60°C. This mixture was then cooled down and 64.34g of a blend of a copolymer of methyl vinyl ether and maleic anhydride crosslinked with 1,9-decadiene having an average particle size of less than 75micrometers a sodium salt of a carboxymethylcellulose having a sodium content of between 7 and 8.9% and water at a ratio of 0.3:2.3:97.4 that had been prepared at 60°C and then cooled down were added and mixed in. 53.61g of water were then added followed by 0.2g of triethanolamine and 0.11g ofPIROR P-840. The aqueous antifoam composition so obtained had a viscosity of 1.54·10 -3 m 2 /s (1540 cSt). Example 12 To 1.13g of a blend of a silicone modified with polyethylene oxide groups having a molecular weight of 7800 Daltons and an estimated HLB of 10, a poly(alkylatedvinylpyrrolidone) having an average molecular weight of 7300 Daltons and a relative viscosity of 1.009 as a 0.1% solution in toluene and a silicone modified with polyalkylene oxide groups having a molecular weight of 12500 Daltons and an estimated HLB of 12 used in a ratio of 85:9.7:5.3 prepared at ambient was added a blend of 20.14g of the antifoam compound of example 4 and 8.03g of a tetra-functional block copolymer derived from the sequential addition of propylene oxide and ethylene oxide to ethylenediamine having an average molecular weight of 3600 Daltons and mixed initially at ambient and then at 50°C. To this blend were added at 50°C 53.81g of a blend of cetyl-stearyl alcohol ethoxylates of high (16.2) and low HLB (6) blended at a ratio so that the overall HLB of the system was 9.3, propylene glycol and water blended at a ratio of 10:15:75 prepared in advance at 60°C. This mixture was then cooled down and 65.41g of a blend of a copolymer of methyl vinyl ether and maleic anhydride crosslinked with 1,9-decadiene having an average particle size of less than 75micrometers, a hydroxyethylcellulose polymer whose 5% aqueous solution has a viscosity of about 140 cSt at 25°C and water at a ratio of 0.3:3.1:96.6 that had been prepared at 60°C and then cooled down were added and mixed in. 53.74g of water were then added followed by 0.12g of PIROR P-840. The aqueous antifoam composition so obtained had a viscosity of 2.0·10 -4 m 2 /s (200 cSt) and a foam control of 29 mm. Example 13 To 1.13g of a blend of a silicone modified with polyethylene oxide groups having a molecular weight of 7800 Daltons and an estimated HLB of 10, a poly(alkylatedvinylpyrrolidone) having an average molecular weight of 7300 Daltons and a relative viscosity of 1.009 as a 0.1% solution in toluene and a silicone modified with polyalkylene oxide groups having a molecular weight of 12500 Daltons and an estimated HLB of 12 used in a ratio of 85:9.7:5.3 prepared at ambient was added a blend of 20.08g of the antifoam compound example 4 and 8.04g of a tetra-functional block copolymer derived from the sequential addition of propylene oxide and ethylene oxide to ethylenediamine having an average molecular weight of 3600 Daltons and mixed initially at ambient and then at 50°C. To this blend were added at 50°C 53.85g of a blend of cetyl-stearyl alcohol ethoxylates of high (16.2) and low HLB (6) blended at a ratio so that the overall HLB of the system was 9.3, propylene glycol and water blended at a ratio of 10:15:75 prepared in advance at 60°C. This mixture was then cooled down and 64.47g of a blend of a copolymer of methyl vinyl ether and maleic anhydride crosslinked with 1,9-decadiene having an average particle size of less than 75micrometers, a microcrystalline cellulose polymer whose 2.6% aqueous solution has an initial viscosity of about 1.0·10 -4 m 2 /s (100 cSt) at 25°C and water at a ratio of 0.3:2.5:97.5 that had been prepared at 60°C and then cooled down were added and mixed in. 53.89g of water were then added followed by 0.12g of PIROR P-840. The aqueous antifoam composition so obtained had a viscosity of 9.7·10 4 m 2 /s (970 cSt) and a foam control of 28 mm. Example 14 To 1.13g of a blend of a silicone modified with polyethylene oxide groups having a molecular weight of 7800 Daltons and an estimated HLB of 10, a poly(alkylatedvinylpyrrolidone) having an average molecular weight of 7300 Daltons and a relative viscosity of 1.009 as a 0.1% solution in toluene and a silicone modified with polyalkylene oxide groups having a molecular weight of 12500 Daltons and an estimated HLB of 12 used in a ratio of 85:9.7:5.3 prepared at ambient was added a blend of 20.09g of the antifoam compound of example 4 and 8.06g of a tetra-functional block copolymer derived from the sequential addition of propylene oxide and ethylene oxide to ethylenediamine having an average molecular weight of 3600 Daltons and mixed initially at ambient and then at 50°C. To this blend were added at 50°C 53.49g of a blend of cetyl-stearyl alcohol ethoxylates of high (16.2) and low HLB (6) blended at a ratio so that the overall HLB of the system was 9.3, propylene glycol and water blended at a ratio of 10:15:75 prepared in advance at 60°C. This mixture was then cooled down and 63.82g of a blend of a copolymer of methyl vinyl ether and maleic anhydride crosslinked with 1,9-decadiene having an average particle size of less than 75micrometers, a cellulose polymer modified with ethylene oxide groups and whose 5% aqueous solution has a viscosity of about 1.2·10 -4 m 2 /s (120 cSt) at 25°C and water at a ratio of 0.3:1.6:98.1 that had been prepared at 60°C and then cooled down were added and mixed in. 54.13g of water were then added followed by 0.11g of PIROR P-840. The aqueous antifoam composition so obtained had a viscosity of 2.8·10 -4 m 2 /s (280 cSt) and a foam control of 30 mm. Example 15 To 1.14g of a blend of a silicone modified with polyethylene oxide groups having a molecular weight of 7800 Daltons and an estimated HLB of 10, a poly(alkylatedvinylpyrrolidone) having an average molecular weight of 7300 Daltons and a relative viscosity of 1.009 as a 0.1% solution in toluene and a silicone modified with polyalkylene oxide groups having a molecular weight of 12500 Daltons and an estimated HLB of 12 used in a ratio of 85:9.7:5.3 prepared at ambient was added a blend of 20.13g of the antifoam compound of example 4 and 8.04g of a tetra-functional block copolymer derived from the sequential addition of propylene oxide and ethylene oxide to ethylenediamine having an average molecular weight of 3600 Daltons and mixed initially at ambient and then at 50°C. To this blend were added at 50°C 53.94g of a blend of cetyl-stearyl alcohol ethoxylates of high (16.2) and low HLB (6) blended at a ratio so that the overall HLB of the system was 9.3, propylene glycol and water blended at a ratio of 10:15:75 prepared in advance at 60°C. This mixture was then cooled down and 64.3g of a blend of a sodium salt of a carboxymethylcellulose having a sodium content of between 7 and 8.9%, a crosslinked acrylic acid polymer whose 0.2% aqueous mucilage has a viscosity of 3 p·s (3000 cP) at 20°C, and water at a ratio of 2.3:0.3:97.4 that had been prepared at 60°C and then cooled down were added and mixed in. 52.54g of water were then added followed by 0.11g of triethanolamine and 0.13g of PIROR P-840. The aqueous antifoam composition so obtained had a viscosity of 8.4·10 -4 m 2 /s (840 cSt) and a foam control of 35 mm.

Claims: A silicone antifoam emulsion comprising polydiorganosiloxane, an inorganic oxide and a synthetic protective colloid based on polyvinylpyrrolidone polymer having a K-value of 10 to 60. An antifoam emulsion according to claim 1 comprising: (A) polydiorganosiloxane; (B) fine solid particles of inorganic oxide, bearing on the surface thereof a polydiorganosiloxane component; wherein the total amount of polydiorganosiloxane present in components (A) and (B) comprises 5 wt % to 60 wt % of the emulsion and the weight ratio of the total amount of polydiorganosiloxane present in components (A) and (B) to the amount of said inorganic oxide is 10:1 to 200:1; (C) an organic surfactant dispersing agent selected from the group consisting of non-ionic tetrahydroxy-substituted block copolymers terminating in primary or secondary hydroxyl groups and mixtures thereof, at 0.1 wt % to 36 wt % of said emulsion; (D) a copolymer of polydimethylsiloxane with polyalkylene oxide, the molecular weight of the polydimethylsiloxane portion being 300 to 100,000 Daltons and the total molecular weight of all polyalkylene oxide present being 100 to 40,000 Daltons, at 0.1 wt.% to 20 wt.% of said emulsion; (E) a non-ionic surfactant component comprising one or more non-ionic surfactants not conforming to agent (C) nor to copolymer (D) at 1 wt % to 60 wt % of said emulsion; (F) a thickener component at 0.01 wt % to 15 wt % of said emulsion; (G) a protective colloid component based on polyvinylpyrrolidone polymer having a K-value of 10 to 60 at 0.01 wt.% to 10 wt.% of said emulsion; and (H) water comprising up to 95 wt.% of the emulsion. An antifoam emulsion according to Claim 2 wherein the protective colloid has the structure wherein each R 6 and R 7 can be either hydrogen or an alkyl group. An antifoam emulsion according to Claim 3 wherein the protective colloid has a molecular weight of between 2500 Daltons and 3,000,000 Daltons. An antifoam emulsion according to Claim 3, wherein each R 6 and R 7 can be either hydrogen or a C 1 -C 6 alkyl group. An antifoam emulsion according to Claim 3, wherein R 6 and R 7 are alkyl groups having either 16 or 20 carbon atoms. An antifoam emulsion according to Claim 2 wherein said polydiorganosiloxane comprises polydimethylsiloxane having a viscosity at 25°C of 5 - 10 -5 to 20 m 2 /s (50 to 20,000,000 cSt) and component (B) comprises finely divided hydrophobic silica having an average particle size of from 1 to 20 micrometers and a BET surface area of at least 40 m 2 /g. An antifoam emulsion according to Claim 2 wherein the organic surfactant dispersing agent is a non-ionic tetrahydroxy-substituted block copolymer terminating in primary or secondary hydroxyl groups and having a molecular weight of 1600 to 30,000 Daltons and a 1% aqueous cloud point of 15-100°C. An antifoam emulsion according to Claim 8 wherein said organic surfactant dispersing agent has a molecular weight of 2000 to 8000 Daltons. An antifoam emulsion according to Claim 8 wherein said organic surfactant dispersing agent has a 1 % aqueous cloud point of maximum 35°C. A method of making an antifoam emulsion comprising: (a) the preparation of Blend A, said Blend comprising an antifoam compound made by blending and reacting polydiorganosiloxane, particulate filler and catalyst component, non-ionic emulsifier and synthetic protective colloid based on polyvinylpyrrolidone polymer having a K-value of 10 to 60; (b) the preparation of Blend B, said Blend comprising Blend A, non-ionic emulsifier, and water; and (c) the preparation of Blend C, said Blend comprising water, Blend B, thickener, synthetic protective colloid base on polyvinylpyrrolidone polymer having a K-value of 10 to 60.

Inventors: SANE DANIEL YVES, SPYROPOULOS KONSTANTINOS, SANE, DANIEL YVES, SPYROPOULOS, KONSTANTINOS
Applicants: GEN ELECTRIC, GENERAL ELECTRIC COMPANY
Application year: 1998
Main classification: B01D19
IPC codes: B01D19