Organosilicon defoamer and process for the preparation thereof

Abstract

Highly active defoamer compositions which are storage stable and maintain their defoaming efficiency for extended times even in harsh chemical environments are prepared by an aqueous base-catalyzed condensation of a hydroxy-terminated polyorganosiloxane, a silicone resin bearing hydroxy groups or hydroxy-reactive groups, and hydrophilic silica. The condensation takes place at a temperature of 80°C to less than 130°C, and the reaction viscosity is monitored to determine an appropriate time to add the hydrophilic silica.

Description

WS 12405ORGANOSILICON DEFOAMER AND PROCESS FOR THE PREPARATION THEREOFTECHNICAL FIELD

[0001] The invention is directed to organosilicon defoamer compositions useful for preventing and / or regulating foam in liquid systems, and to a process for the preparation thereof.BACKGROUND

[0002] Foaming occurs in numerous industrial processes, particularly those requiring intense agitation, but also during distillation and other processes. Some illustrative examples involve the pumping and treatment of the so-called “black liquor” associated with the pulping of softwoods and hardwoods, dyeing operations, herbicide formulating, and the use of detergents in machine dishwashing and laundry. In chemical laboratories worldwide, it has been common for many years to add traces of silicone oils, largely linear polydimethylsiloxanes, to inhibit foaming during chemical syntheses. The effectiveness of these silicone oils coupled with their relatively high boiling points facilitates such use, as they are easily separated from the reaction products. However, many chemical processes, including many of those having large-scale uses in industry, involve high temperatures and harsh chemical environments which rapidly degrade simple silicone oils, reducing or even totally eliminating their effectiveness after only a short time. Reducing foaming in the treatment of black liquor is one example of such a problematic defoamer environment, as the liquid is highly corrosive due to its high content of alkali.

[0003] There have been many attempts to improve upon the defoaming ability of silicone- based defoamers to increase their effectiveness and also to enable these defoamers to maintain their defoaming activity over time, even in harsh environments. Some of the prior art attempts to satisfy these goals have involved addition of silicone resins to silicone oils, addition of hydrophobic silica to silicone oils, and absorption of liquid defoamer ingredients by solid particulates such as pyrogenic silica, among many others. Attempts have also been made to partially or fully react some or all of the ingredients in such mixtures, as well as to add non-siliconeWS 12405 components such as oligomeric polyethylene waxes, natural oils and waxes, high molecular weight alcohols, polyoxyalkylene glycol surfactants, and other substances.

[0004] For example, in US patent 9,120,035 B2 are described numerous prior art attempts to increase the efficiency and longevity of silicone-based defoamers, including addition of hydrophobic silica to polysiloxanes by alkali-catalyzed reaction at temperatures greater than 120°C; addition of partly cross-linked siloxanes to such compositions; the use of branched polysiloxanes obtained by hydrosilylation of vinyl-terminal siloxanes with Si-H-functional siloxanes, and the use of anti-foams based on branched polyether / polysiloxane copolymers. The 9,120,035 patent indicates that these prior art formulations do not exhibit sufficient activity or are difficult to handle due to an exceptionally high viscosity. Thus, the 9,120,035 inventors proposed a defoamer containing organopoly siloxanes containing at least one structural unit where adjacent organosiloxy units are linked by a divalent organic radical containing 1-30 carbon atoms, a filler, an organopolysiloxane resin, and a linear or cyclic polydiorganosiloxane. The components were condensed and equilibrated in the presence of highly basic methanolic KOH to produce the final defoamer composition. The synthesis of the organopolysiloxane containing divalent organic radicals is tedious and expensive and thus adds to the cost of the defoamer. There is no description of the storage stability of the defoamer compositions.

[0005] The long felt need to provide improved defoamer compositions and the failures of the prior art to do so is thoroughly discussed in U.S. 10,870,071 B2. The inventors proposed defoamers containing, like U.S. 9,120,035, a defoamer composition containing a polyorganosiloxane having siloxy units linked by a divalent hydrocarbon but also containing ethylenically unsaturated groups, together with fillers and silicone resin is disclosed. Preparation of the polyorganosiloxane is difficult, and the defoamer components are preferably condensed at 150°C using methanolic KOH as a condensation / equilibration catalyst. Foam knockdown time and collapsed foam level were improved compared to products produced according to the prior art, as was long term performance, but the latter is still in need of improvements.

[0006] The inefficiency of prior art defoamers based on organosilicon compositions prepared by heating hydrophilic silica in polydimethylsiloxanes and in general the use ofWS 12405 polydimethylsiloxanes themselves is discussed in US patent publication 2020 / 0165393 Al, which also discusses the failure of prior art technical solutions to balance costs, compatibility, efficiency, and long-term stability. The inventors proposed solving these long existing problems by providing a defoamer compound which is a condensate of an aryl-substituted polysiloxane, and at least one of a wide variety of fillers, including metal soaps, finely ground quartz, PTFE powders, fatty acid amides and other substances, preferably hydrophobic silica and / or one or more silicone resins. Condensation takes place in the presence of methanolic KOH at a relatively high temperature of 150°C, yielding defoamer compositions having viscosities in the range of, for example, 500 mPas to 5500 mPas. The necessity to use relatively expensive aryl-functional polysiloxanes is a disadvantage. The viscosity of the defoamer compositions is also lower than is generally desired. The defoamers were stable in detergent concentrates, but their neat storage stability was not assessed.

[0007] US patent 4,639,489, first filed as JP 59-108450 in 1984, also discusses the inefficiency of prior silicone-based defoamers, and proposed a defoamer containing a reaction product of a non-functional polyorganosiloxane having a viscosity of 20-100,000 mPas, a polyorganosiloxane containing at least one terminal silicon-bonded hydroxyl or alkoxy group, a hydrolyzable silane or condensate thereof or a silicone resin or a condensate of one of the latter compounds with the non-functional polyorganosiloxane or the hydroxyl or alkoxy-functional polyorganosiloxane. The condensation takes place in the presence of a catalyst which is preferably neat KOH or alcoholic KOH, including the use of potassium alkoxylates. These catalysts are highly basic and not only catalyze condensation but also are efficient equilibration catalysts. The condensation was effectuated beginning at a temperature of 130°C to 140°C, followed by reaction with silica at a temperature of 180°C. Defoaming activity, when tested in a one weight percent aqueous solution of Tween™ 80 surfactant, showed a high initial effectiveness which decreased markedly after only 180 seconds. No testing of the composition in highly corrosive environments was made, nor any testing of neat storage stability.

[0008] These references, as well as many others, document a long sought need for a defoaming compositions which exhibits high defoaming activity which extends over a long period of time, and which are cost-effective due to avoidance of costly raw materials and difficult and / orWS 12405 extended process steps in their preparation. In addition, as might be expected, commercially useful defoaming compositions should exhibit an extended shelf life, not only in diluted form in compositions such as detergent concentrates, but also in neat form. The present invention is directed to defoaming compositions which improve upon these considerations all or in part.SUMMARY

[0009] The invention is directed to defoamer compositions for liquid systems, comprising an initial condensation product of a substantially linear OH-terminated polyorganosiloxane and a silicone resin having at least two silicon-bonded hydroxy or alkoxy groups, with hydrophilic silica, added at a later stage, the composition also containing a diluent which is preferably a nonfunctional substantially linear polyorganosiloxane, wherein the condensation catalyst used to prepare the composition is neutralized following the reaction. The defoamer compositions may be prepared by condensation in the presence of an aqueous basic catalyst, preferably aqueous alkali hydroxide, at a temperature in the range of 90°C to less than 130°C, wherein the diluent preferably is added to the reaction in at least two temporally spaced additions.DETAILED DESCRIPTION

[0010] The defoamer compositions are produced by a condensation reaction between (A), a hydroxy-terminated, substantially linear polyorganosiloxane; (B), a silicone resin; and (C), hydrophilic silica, the reaction preferably being performed in the presence of an aqueous basic catalyst (K), and mediated by (D), a non-functional diluent which is preferably a substantially linear, non-functional polyorganosiloxane which may or may not participate in the condensation reaction. The hydrophilic silica (C) is added following an initial condensation of the hydroxyterminated substantially linear polyorganosiloxane (A) and the silicone resin (B). The progress of this initial condensation reaction is monitored by measuring the viscosity growth of the reaction mixture, and when the appropriate viscosity is reached, the hydrophilic silica is then added. Following the condensation reaction between these required substances, an acid is added to neutralize the basic catalyst. Before or after catalyst deactivation, hydrophobic silica is optionally added.WS 12405[0011 J The condensation reaction optionally further takes place in the presence of an optionally partially capped hydroxy -terminated polyoxyalkylene glycol or triol (E) having at least one free hydroxyl group. The defoamer composition, which is a liquid reaction product of the process described above, may be used as is, e.g. “neat,” or may be supplied in the form of a solution in organic solvent or as a dispersion in water or other liquid, and may contain other post-reaction adjuvants, for example, but not limited to, polyorganosiloxanes and silicone glycols. In the description which follows, all weight percentages are based on the total weight of the defoamer composition unless otherwise specified. By the term “neat” as used herein is meant a composition in pure form, for example as a non-diluted solid or liquid.

[0012] The hydroxy-terminated polyorganosiloxane (A) and non-functional polydiorganosiloxane (D) are substantially linear. By the term “substantially linear” is meant that these components are either wholly linear, without any detectable branching, or are at most lightly branched. In this context, the term “lightly branched” means that the substantially linear polyorganosiloxanes contain less than a total of 10 mole percent of branching T siloxy units RSiO3 / 2 and / or Q siloxy units SiO4 / 2, where R are nonreactive hydrocarbon groups. T units and Q units are well known to those skilled in the art of organosilicon compounds. Preferably, the lightly branched polyorganosiloxanes contain less than a total of 5 mole percent of T or Q units, more preferably less than a total of three mole percent of these units, yet more preferably less than a total of two mole percent of these units, and most preferably none of such units or only an amount of such units which are unavoidable due to impurities in the raw materials from which the organopolysiloxanes are made, or from inadvertent rearrangements which may occur during synthesis of the organopolysiloxanes. During the condensation reaction, branch points may be created due to the reaction conditions, but this is not necessary, is not preferred, and is undesirable. In the discussion which follows, the more detailed description of the polyorganosiloxanes (A) and (D) incorporates the above definitions unless clearly specified to the contrary. The terms “organopolysiloxane” and “polyorganosiloxane” are to be viewed as synonyms.

[0013] Hydroxy-terminated polyorganosiloxanes (A) are polyorganosiloxanes whose organo groups are selected from hydrocarbon groups having 1-30 carbon atoms which are substantially unreactive under the conditions of the condensation reaction used in the preparationWS 12405 of the defoamer compositions. Preferred hydroxy-terminated organopolysiloxanes have the formula:

[0014] HO-[Si(R)2-O-]n-H

[0015] where R are organo groups. Most preferably, the organo groups R are the alkyl groups, cycloalkyl groups, alkenyl groups, cyano-substituted alkyl groups, and aryl groups which are well known to those skilled in the art of silicones, preferably Ci-4 alkyl groups, C5-8 cycloalkyl groups, C2-4 alkenyl groups, and Ce-io aryl groups. The use of arylalkyl groups and aryl groups wherein the aryl ring is substituted with alkyl groups is also possible, and these are also well known to the skilled artisan.

[0016] Preferably, the hydroxy-terminated organopolysiloxane R groups are selected from methyl, ethyl, 1 -propyl, 2-propyl, 1 -butyl, vinyl, allyl, phenyl, benzyl, and naphthenyl groups, more preferably methyl and phenyl groups, and most preferably, methyl groups. The proportion of methyl groups among all R organo groups is preferably greater than 80 mole percent, more preferably, in increasing order of preference, greater than 85, 90, 95, and 98 mole percent. Most preferably, all R organo groups are methyl groups or contain other organo groups only in amounts which are unavoidable due to impurities in the starting materials from which the hydroxyfunctional organopolysiloxanes are produced. In the case of lightly branched organopolysiloxanes (A), it is most preferable that the organopolysiloxanes still contain only two terminal hydroxy groups on average, although it is possible to use lightly branched organopolysiloxanes (A) containing three or more terminal hydroxyl groups so long as the final viscosity of the condensed defoamer composition is within the desired viscosity range. The use of organopolysiloxanes (A) with more than three terminal hydroxy groups on average is not preferred, and it is most preferred that the organopolysiloxanes (A) have two terminal hydroxy groups on average.

[0017] The viscosity of the hydroxy -terminated organopolysiloxane (A) is preferably within the range of 100-50,000 mPas, more preferably in the range of 1000-30,000 mPas, and most preferably in the range of 6000-15,000 mPas. The hydroxy -terminated organopolysiloxanes (A) may comprise but a single organopolysiloxane prepared to have a viscosity within the above ranges, or may comprise two or more organopolysiloxanes which together have a mean viscosityWS 12405 within the above ranges. It is most desirable that all organopolysiloxanes (A) have viscosities, as prepared, within the above ranges. The amount of organopolysiloxanes (A) in the composition can vary within a range of 25-75 weight %, more preferably 30-65 weight percent, yet more preferably between 35-60 weight percent, and most preferably between 45-55 weight percent. An amount of approximately 50 weight percent has been found to be particularly useful.

[0018] The silicone resin (B) employed in the condensation reaction may be a single silicone resin or may be a combination of two or more silicone resins. The silicone resins may be liquid or solid, preferably solid. By the term “silicone resin” is meant a polyorganosiloxane compound with such a large quantity of T groups and Q groups that the molecules are highly and three dimensionally cross-linked to form network-like structures. The definition of silicone resin employed herein is the same definition one skilled in the art would describe to the term. Most preferably, the silicone resins employed are silsesquioxane resins (T resins), MQ resins, MT resins, or MTQ resins. These resins preferably contain less than 30 mole percent of difunctional siloxy groups such as dimethylsiloxy groups, preferably less than 20 mole percent, more preferably less than 10 mole percent, and most preferably no difunctional siloxy groups or a number of difunctional siloxy groups which are unavoidable in the preparation of the silicone resin due to impurities contained in the raw materials or rearrangement reactions which occurred during synthesis.

[0019] The silicone resins useful in the inventive defoamer compositions must be capable of condensation with the hydroxy-functional organopolysiloxane (A), and thus must contain at least two functional groups, on average, which are reactive with the hydroxy group of the organopolysiloxane (A). Most preferably, these functional groups are hydroxy groups or lower alkoxy groups such as methoxy, ethoxy, or butoxy groups. Most preferably, the silicone resins contain at least two reactive functional groups per molecule on average, and broadly, on average, preferably from 2 to 5 or more of such functional groups. Most preferably, the reactive functional groups are hydroxy groups or a mixture of hydroxy and methoxy groups. Resins containing only hydroxy groups as the reactive functional groups, optionally in addition to any inadvertent alkoxy groups inadvertently present due to the method of synthesis of the silicone resins, are most preferred.WS 12405

[0020] The diorganosiloxy D groups, when present, and the monoorgano T groups, when present, have organo groups R which may be the same as those of the hydroxy-functional organopolysiloxane (A), and with the same preferences. Most preferably, the organo groups contained in the silicone resins are lower alkyl groups or vinyl groups, more preferably lower alkyl groups with 1 -4 carbon atoms, and most preferably methyl groups. Thus, the M groups of the MQ and other silicone resins are preferably trimethylsiloxy groups, or dimethylsilanol groups, the latter of which then supply the required hydroxy groups to the silicone resin. It is noted that ethylenically unsaturated groups are included within the category of non-functional groups since these enter into reactions with the other components only with difficulty under the reaction conditions employed.

[0021] The silicone resin may be supplied to the condensation reaction neat or dissolved in a suitable solvent. Since it is not desirable, in general, that the final defoamer composition contain any volatile organic solvents, and to avoid removal of volatile organic solvents during the condensation reaction, which increases cost and complexity, it is most desirable that the silicone resin be supplied as a solution in the hydroxy-functional organopolysiloxane (A), the non-reactive organopolysiloxane diluent (D), or another non-reactive relatively high boiling solvent, such as a non-reactive organopolysiloxane other than the diluent (D) or a higher boiling hydrocarbon, for example a paraffinic solvent or isoparaffinic solvent, such as an ISOPAR ® solvent. The solvent for the silicone resin, when other than a polyorganosiloxane fluid, preferably has a flash point higher than 100 C, more preferably greater than 120 C, yet more preferably greater than 150 C, and most preferably above 200°C. Most preferably, the solvent is a polydiorganosiloxane bearing triorganosilyl terminal groups, more preferably a polydimethylsiloxane terminated by trimethylsilyl groups. A suitable solvent is a trimethylsilyl-terminated polydimethylsiloxane with a viscosity of 50-200 mPas, more preferably about 100 mPas. The viscosity is not overly critical, as long as the viscosity of the condensed defoamer composition falls within the desired viscosity range.

[0022] The weight percentage of the silicone resin in the solvent, when a solvent is used, may range from, for example, 5 weight % to 70 weight %, more preferably 20-60 weight percent. When supplied as a solution in one of components, for example (A) or (D), the percentage may vary as desired, as long as the required amount of resin is present in the reaction mixture. MostWS 12405 preferably, the silicone resin is MQ resin 803, a methyl silicone resin having surface hydroxyl groups, available from Wacker Chemie GmbH, dissolved in a 100 mPas trimethylsilyl-terminated poly dimethylsiloxane fluid at a mass ratio of approximately 1: 1. The amount of neat silicone resin in the reactive composition, is from about 0.5 -30 weight %, more preferably 1-15 weight %, yet more preferably 1.5 - 10 weight %, and most preferably about 2-5 weight %. An amount of 3 weight % has been found to work well. The actual amount will depend upon the viscosity and functionality of the other components, and the amount of diluent (D) and any solvent present, in order that the viscosity of the final defoamer composition is within the desired range.

[0023] The hydrophilic silica (C) is preferably a hydrophilic precipitated silica. Fumed silica having a high concentration of surface silanol groups may also be used, but is not preferred. The silanol hydroxy groups of these silicas are more acidic than the other reactive components, and actively condense with the other components, but also serve to mediate viscosity buildup by lowering condensation catalyst activity. The preferable hydrophilic silicas (C) may be characterized by either their mean particle size or by their BET surface area. The mean particle size is preferably in the range of 100 nm - 20 pm, more preferably 800 nm - 15 pm, and most preferably 2 pm - 10 pm. The preferable BET surface area may be from 50 m2 / g to 400 m2 / g, more preferably 80 m2 / g to about 200 m2 / g. Preferably, the hydrophilic silicas have not been partially hydrophobicized. Suitable partially hydrophobicized silicas are easily dispersed in 50% aqueous methanol. It is most preferable that the hydrophilic silica be added following an increase of viscosity due to the condensation of the hydroxy-functional organopolysiloxane (A) and the silicone resin (B) to a desired viscosity, preferably a viscosity in the range of 2000 mPas to 100,000 mPas, more preferably 4000 mPas to 10,000 mPas, most preferably 6000 mPas to 8000 mPas. The acidic silanol groups enable reaction of the hydrophilic silica with the condensation product of the hydroxy-functional organopolysiloxane (A) and the silicone resin (B). Thus, the hydrophilic silica is not simply a filler, nor is it a simple absorbent or adsorbent for the other components. A preferred hydrophilic silica (C) is Sipernate®38, a colloidal precipitated silica with a mean particle size of about 4.5 pm. The amount of hydrophilic silica (C) is preferably from 1-20 weight percent, more preferably from 2-15 weight percent, and most preferably between 3-6 weight percent. An amount of about 4 weight percent has been found particularly useful.WS 12405

[0024] Hydrophobic silica (C') is optionally added to the composition, either before or after neutralization of the condensation catalyst. Hydrophobic silica is well known to those skilled in the art, and is generally prepared by capping the silanol hydroxy groups of precipitated or pyrogenic silica by reaction with a suitable hydroxy group-reactive hydrophobing agent such as hexamethyldisilazane, trimethylchlorosilane, polyorganosiloxanes, and other hydrophobing agents well known in the art. The number of surface silanol groups is severely reduced or even totally eliminated. Such hydrophobicized silicas float when added to water, even when added to aqueous 50% methanol, and must be dispersed using agitation. Due to the severely decreased number of surface silanol groups, the optional hydrophobic silicas do not react with the other, condensable or condensed ingredients, or do so only to a very small extent. Hydrophobic silica C', when present, is used in an amount up to 30 weight percent of the total weight of the defoamer composition, preferably from 1 - 15 weight percent, and most preferably 3 - 10 weight percent. The BET surface area and particle size ranges are preferably the same as for the hydrophilic silica.

[0025] The non-functional diluent (D) is added to retard the initial progress of the reaction so as to avoid obtaining very high viscosities or even gelling of the reactor. The diluent (D) is a liquid substance in which the remaining components of the reaction mixture and their condensation products are soluble. While high boiling organic solvents may potentially be used as such a diluent, it is preferable that the diluent be a substantially linear polydiorganosiloxane, preferably a trimethylsilyl-terminated polydimethylsiloxane, preferably having a viscosity in the range of 50- 20,000 mPas, more preferably 100-1000 mPas, and most preferably in the range of 100 mPas to 500 mPas. The organo (R) groups of the polydiorganosiloxane are the same, with the same preferences, as those of the hydroxy-functional organopolysiloxane. Since the diluent will not be removed from the defoamer product, it is necessary that the diluent or diluents, despite being essentially non-reactive with the other components and their condensation products, have no severe adverse effects on defoaming activity. By the term “non-functional” is meant that the diluent exhibits very low or preferably no reactivity towards the hydroxy-functional polyorganosiloxane (A), the silicone resin (B), the hydrophilic silica (C), and condensation products thereof. In addition, with respect to the diluent (D), the diluent should not contain acidic groups which might neutralize the alkali metal hydroxide condensation / equilibration catalyst. However, it is unavoidable that the diluent, when it is a linear organopolysiloxane, which isWS 12405 preferred, will equilibrate with other polyorganosiloxane species present in the reaction mixture. Such equilibration, which does not involve reaction between functional groups, is considered to be “non-reactive” as that term is used herein.

[0026] The amount of diluent (D) added during preparation of the defoamer composition is preferably from 25-75 weight percent, more preferably 30-60 weight percent, and most preferably 35-50 weight percent, based on the total weight of the defoamer composition. An amount of about 40 weight percent has proven highly effective. As will be discussed elsewhere, it is very preferable that the diluent be added to the reaction mixture in two or more portions, one portion being present at the start of the reaction or just following the start of the reaction, with an additional portion or additional portions being added later in time. The diluent serves to lower the initial reaction rate and also to lower the final viscosity. Preferably, the diluent is one which is active as a defoamer by itself.

[0027] The basic catalyst (K) is a catalyst which promotes condensation between silanol hydroxy groups, but whose activity as an equilibrative decomposition catalyst is preferably lower than neat KOH, potassium alkoxylates, or alcoholic KOH such as methanolic KOH. The reason for this is that a buildup of molecular weight by condensation is prevented by a decrease in molecular weight due to equilibration. The basic catalyst is preferably an aqueous alkali metal hydroxide, although other basic catalysts such as aqueous quaternary ammonium hydroxides may also be useful. The alkali metal hydroxide is preferably sodium hydroxide or potassium hydroxide, more preferably potassium hydroxide. The basic catalyst is thus preferably introduced in the form of an aqueous solution, for example as a 45 weight percent solution of potassium hydroxide in water. Once again, the use of an aqueous catalyst is most desirable, as very strong catalysts such as neat potassium hydroxide or methanolic potassium hydroxide are too active as equilibration catalysts, and prevent sufficient buildup of viscosity due to a rapid scissioning of the chains of both reactive and nonreactive polydiorganosiloxanes. It may be possible to find a neat catalyst which has the necessary balance of condensation versus equilibration, and the use of such a catalyst is within the scope of the invention.WS 12405

[0028] The amount of basic catalyst can be readily determined by those skilled in the art based on the rate of viscosity build, which is indicative of the degree of condensation, and the final viscosity or of the viscosity following the initial viscosity build, which is indicative of the decomposition or “equilibration” of the polydiorganosiloxane chains. Preferable amounts are from 0.05 weight % - 2 weight %, more preferably 0.1 weight % - 1 weight %, calculated on the basis of a 45 weight percent solution of potassium hydroxide in water.. An amount of about 0.16 weight percent has been found to be particularly suitable. The amount of basic catalyst might have to be increased or decreased if the starting materials contain acidic or basic substances as impurities, or if other acidic or basic substances are added during the condensation reaction between the hydroxyfunctional polyorganosiloxane (A) and the silicone resin (B).

[0029] The condensation reaction optionally includes a hydroxy-terminated polyoxyalkylene glycol compound, added following an initial condensation of components (A) and (B). Polyoxyalkylene glycols are prepared by the catalyzed ring-opening polymerization of an oxirane such as ethylene oxide, propylene oxide, butylene oxide, or cyclic oxides such as tetrahydrofuran and other compounds which are well known to those skilled in the art. During the polymerization, a single alkylene oxide may be employed, or a plurality of these may be employed. Different alkylene oxides may also be employed at different times to produce block copolymers. These compounds are well known to those skilled in the art and are available in a wide range of molecular weights. Suitable average molecular weights for use in the inventive defoamer compositions are between 400 Da and 3000 Da, more preferably between 800 Da and 2000 Da, and most preferably between 1000 Da and 2000 Da.

[0030] The polyoxyalkylene glycols may be homopolyoxyethylene glycols, but this is not preferred as these molecules tend to be quite hydrophilic. Preferably, the poly oxyalkylene glycols are polyoxypropylene or polyoxybutylene glycols, as homopolymers or optionally as copolymers with oxyethylene groups. The copolymers may be random copolymers, block copolymers, or block random copolymers. All of these are well known to those skilled in the art. The polyoxyalkylene glycol compounds contain at least one free terminal hydroxy group. The terminal hydroxy group may be a primary or secondary hydroxy group. Unmodified polyoxyalkylene glycols (E) contain two terminal hydroxy groups and are suitable and preferred for use in theWS 12405 present invention. However, it is also possible to use polyoxyalkylene glycols (E) which have been end-capped with an ether group such as a methoxy or ethoxy group, a long chain alkyl ether group, or with an ester group such as an acetate, propionate, or laurate group. Other terminal groups are also possible. These other terminal groups may or may not be reactive with the hydroxy groups of the hydroxy-functional organopolysiloxane (A) and silicone resin (B), but most of these end-cap units are preferably nonreactive in this respect. At least one hydroxy-functional terminal group or branch group is necessary in order that the polyoxyalkylene glycol (E) compound can be condensed along with the other raw materials and form part of the defoamer compound which results.

[0031] It is also possible to use, as the poly oxyalkylene glycol compound, a polyoxyalkylated glycerine or trimethylolpropane, especially polyoxyalkylated species of these compounds in which the base triol has been etherified at one hydroxyl group with a single alkyl group, preferably a long chain alkyl group, or esterified with a single long chain carboxylic acid. If not etherified or esterified, the polyoxyalkylated compounds will be a “super glycol” having two hydroxy groups as well as a further hydroxy group. The use of such polyoxyalkylated trihydroxy compounds offers the possibility of further crosslinking and thus some additional control over viscosity buildup. These compounds can be also used in conjunction with conventional and optionally partially end-capped polyoxyalkylene glycols. When polyoxyalkylated trihydroxy compounds where one hydroxyl group is capped are used, it is preferable that the capping be by means of an ether group, which is much more resistant to hydrolysis under harsh conditions than are ester groups. The size of the end group can be used to tailor defoaming activity. Both the hydroxy-terminated polyoxyalkylene compounds described immediately above may be termed “polyoxyalkylene glycols” herein, or may be termed “polyoxyalkylene polyols.”

[0032] The amount of optional hydroxy -terminated poly oxyalkylene glycol (E) is from 1- 20 weight percent, more preferably 2-8 weight percent. Suitable polyoxyalkylene glycols include Bl 1 / 50, a copolymer containing on average 12 oxyethylene and 12 oxypropylene moieties, terminated at one end with a butyl ether group, available from Clariant. Another suitable polyoxyalkylene glycol is D21 / 150 a copolymer containing on average 36 oxyethylene groups and 18 oxypropylene groups, and no end-capping, also available from Clariant. Such poly oxyalkyleneWS 12405 glycols are also manufactured by numerous other companies. The optional, hydroxy-terminated polyoxyalkylene glycols are added to the reaction mixture prior to addition of the hydrophilic silica (C).

[0033] The reaction is terminated by the addition of an acid (F) which neutralizes the basic catalyst (K). While it is theoretically possible to employ strong acids such as sulfuric acid or HC1 for this purpose, it is well known that such strong acids are also equilibration catalysts which promote the chain scission and chain reformation of polysiloxanes. When such strong acids are used, it is very possible to introduce to much acid, which may decrease storage stability by continued equilibration during storage. Thus, it is preferable to employ acids which are not strong acids, such as carboxylic acids. Thus, acids such as oxalic acid, malic acid, acetic acid, and propionic acid are preferred for this use. Acetic acid is most preferred due to its ready availability and low cost. The acid is added at a point in time at which the desired degree of condensation has been achieved and no further condensation or equilibration is desired. This point is generally following addition of the hydrophilic silica and its condensation with the condensation products of the initial reactants. It has been found that in the absence of catalyst neutralization, large changes in viscosity of the defoamer are observed. These changes negatively affect the storage stability and effectiveness of the defoamer compositions.

[0034] By the term “neutralization” and similar terms is meant a partial neutralization, a “full” neutralization which equates to a stoichiometric neutralization, or an “over” neutralization, where acid in excess of the stoichiometric amount is added. In such cases, the excess acid is preferably a weak acid, for example a carboxylic acid. It has been very surprisingly and unexpectedly found, that foam control compositions in which neutralization is less than stoichiometric, preferably having an acid / neat KOH mole ratio in the range of 0.6: 1 to 0.85 : 1 , more preferably 0.65:1 to 0.8: 1, and most preferably about 0.7: 1, exhibit consistently superior storage stability. Storage stability is assessed by noting the change in viscosity over a five week period of storage at 50°C. When the stoichiometry of the neutralization was 0.8, for example, very good storage stability was observed, whereas when a 1: 1 stoichiometry was used, storage stability worsened or was erratic. In any case, it is preferred that the stoichiometry of the acid (calculated on the basis of a monoacid) to base, be in the range of 0.5: 1 to 1.5: 1, more preferably 0.6:1 toWS 124051.3: 1, yet more preferably 0.7:1 to 1.0: 1, and most preferably the neutralization is a partial neutralization as described above.

[0035] The foregoing ingredients are the necessary and, in the case of the hydroxyterminated polyoxyalkylene glycol (E) and hydrophobic silica (C'), optional components which the inventive defoamer is preferably based on. However, it is possible to add further ingredients to further improve defoamer in effectiveness, storage stability, or other properties, such as microbial resistance. For the latter, for example, conventional microbicides can be added and amounts which are conventional for the storage of liquid substances. Viscosity modifiers may also be added. These may increase or decrease the viscosity of the initially formed defoamer composition. These viscosity modifiers may also render the defoamer composition nonNewtonian in its viscosity characteristics. Such viscosity modifiers are well known. Preferably, any viscosity modifier will improve rather than detract from the effectiveness of the defoamer composition.

[0036] Additional known defoamers other than those produced by the process of the invention can also be added. These may include, without limitation, further silicone resin particles which are not condensed into the defoamer compound but are merely mixed in with agitation and may be present in dissolved or particulate form; high molecular weight oils, both natural and synthetic; and polyoxyalkylene ether surfactants, preferably those which also act as defoamers, and are useful in applications such as conventional machine laundering and dishwashing applications. Preferred additional post-condensation additives include silicone glycols, which are polydiorganosiloxanes having polymerized polyoxyalkylene glycol groups attached to the polydiorganosiloxane chain, which provide the compounds with surfactant properties. Such silicone glycols are already used, for example, in the paper industry as defoamers. Similar compounds have been used for years in the production of polyurethane foams, as foam stabilizers. Preferred silicone glycols are PULPSIL® 955S, PULPSIL® 9605 and PULPSIL® 968S, available from Wacker Chemie GmbH, Munich, Germany. The amount of silicone glycol added to the defoamer composition may be from 1-20 weight percent, more preferably 2-8%, these percentages based on the total weight of the defoamer composition without the silicone glycol.WS 12405

[0037] The viscosity of the complete defoamer composition, including any added defoamers as described in paragraph

[0036] is from 4000 - 200,000 mPas, more preferably 20,000 - 100,000 mPas, and most preferably 35,000 - 80,000 mPas. The defoamer compositions preferably contain no other ingredients than those specified herein, and when such other ingredients are present, their individual amounts are preferably less than 20 weight percent relative to the total weight of the defoamer composition, more preferably, in increasing order of preference, less than 15, 10, 5, 3, 2 weight percent.

[0038] The inventive defoamer compositions are preferably prepared by a unique process where the hydroxy-functional polyorganosiloxane (A) and silicone resin (B) condensable components are charged to a reaction vessel along with a first portion of diluent (D), and with aqueous basic catalyst, mixed until homogeneous, and then heated do a reaction temperature which is between 90°C and 130°C, preferably between 100°C and 125°C, and most preferably between 105°C and 120°C. When the temperature of the reaction reaches 100°C, the viscosity of the mixture is monitored with a Brookfield viscometer every 30-60 minutes. In this temperature range, the viscosity increases consistently. Optionally, only a portion of the aqueous basic condensation / equilibrium catalyst may be added initially, further amount being added during the course of the reaction. When the viscosity reaches a viscosity in the range of 4000-20,000 mPas, the hydrophilic silica is added and the reaction temperature maintained until sufficient time for at least partial condensation of the hydrophilic silica with the condensation products of the other ingredients has elapsed, preferably a time period of several hours.

[0039] When the optional polyoxyalkylene glycol is used, it is added following an initial condensation of the hydroxy-functional polyorganosiloxane (A) and silicone resin (B), and allowed sufficient time to at least partially condense with the initially formed condensation product, prior to addition of silica. The time required for this partial condensation may range from 15 minutes, or less, to several, e.g. 3 hours or more, but is preferably between 20 minutes and 90 minutes, and more preferably 30 to 60 minutes. Due to the various condensation reactions which take place sequentially or at least partially sequentially, the resulting product is different from a product prepared by a process in which all condensable reactants are added at once, or in which the order of condensation is changed. Following this condensation of all the ingredients, theWS 12405 reaction mixture is preferably cooled to a lower temperature, preferably in the range of 40-80°C, more preferably about 60°C, and the neutralizing acid is added to inactivate the basic catalyst.

[0040] During the inventive process, in lab scale preparations, all the diluent may be added all at once, or may be added in separate portions over time. However, it has been found, quite surprisingly, that in commercial preparation involving large quantities, it is often necessary to add the diluent in separate portions. By doing so, an initial high condensation rate is achieved, which is not generally possible if all of the diluent is added at the beginning of the reaction. Preferably, the initial portion of diluent, which is present at the beginning or slightly following the beginning of the reaction, is from 20-80 weight percent of the total weight of all the diluent added to the reaction, more preferably from 30-60 weight percent, and most preferably about 50 weight percent. The remaining diluent is preferably added in one separate portion, although it is also possible to add the remaining diluent in more than one portion. The second and any further portions of the diluent are preferably added prior to neutralization. The use of a single diluent addition or multiple, temporaly spaced additions is dictated by the reaction vessel used. While laboratory scale and small industrial reactors may have sufficient heating capacity and agitation to allow for only a single diluent addition, larger scale reactors generally require two or more additions.

[0041] Control of the viscosity during the condensation is extremely important, as well as the use of an aqueous base as the condensation catalyst. Very strong bases such as non-aqueous KOH are effective condensation catalysts, but are also extremely effective equilibration catalysts. As those skilled in the art are aware, “equilibration” in the technology of silicones, refers to random scission of the covalent bonds between adjacent siloxy groups, which then reform, but do not generally result in the same molecular arrangement which existed prior to scission. For example, a relatively high molecular weight linear polydimethylsiloxane, when heated with a highly acidic or basic equilibration catalyst, will equilibrate by bond scission and re-formation to a polydimethylsiloxane having a different molecular weight and molecular weight distribution than did the original. The actual molecular weight achieved is very dependent upon the temperature at which equilibration takes place and the length of time. Ultimately, the final result is generally temperature dependent. Nonaqueous basic catalyst such as KOH cause condensation between the hydroxy groups of the hydroxy-functional polyorganosiloxane (A) and the silicone resin (B), butWS 12405 this same catalyst also causes chain scission and network scission in both of these components. Thus, the molecular weight and hence the viscosity are both affected by the nature of the catalyst and the reaction temperature.

[0042] Applicant has surprisingly and unexpectedly discovered that it is necessary, in order to provide effective defoamers, that very basic catalysts such as KOH must be supplied in aqueous form, which is less reactive than is the same types of catalysts supplied neat or in alcoholic solvent, for example methanol or ethanol. At the same time, the reaction temperature has been found to be exceptionally important. Over the range of 90°C to less than 130°C, there is a smooth and continual viscosity build which indicates that the rate of condensation exceeds the rate of equilibrative decomposition. If the temperature increases beyond 130°C, the resulting defoamer compositions are not nearly as effective. The most preferred temperature range is from 105-120°C. At 125 °C, the rate of decomposition is already higher than desired, and this rate increases markedly as the temperature nears 130°C. At a temperature of 130°C, it is very difficult to obtain the desired viscosity of the initial condensation reaction. Most preferably, the temperature range is from 105°C to 120°C, and is ideally in the range of 110°C to 115°C. The effect of temperature may be seen from Table 1 below, which tablets the viscosity in mPas measured at 110°C for various reaction temperatures and times. Viscosity can be measured by numerous methods which are similar in their results, but for lab samples is conveniently measured with a Brookfield viscometer, spindle #LV 62, while adjusting the speed to reach 50% torque. The viscosity of production samples were measured with an Anton Parr Rheometer, model MCR 302, spindle CP 50-2 or CP 25-2 at a shear rate of 1 sec'1. For large scale reactors, an industrial in-line viscometer can be used to monitor viscosity accurately and effortlessly. For these runs, a mixture of hydroxy-functional polyorganosiloxane (A), silicone resin (B), diluent (D), and aqueous KOH catalyst (K) which is substantially similar to the mixture used in Example 1 is used. No polyoxyalkylene glycol or silica is used.WS 12405

[0043] TABLE 1 - Lab Viscosity Data vs. T at Different temperatures

[0044] As can be seen from the Table, it is possible to effect the condensation efficiently at temperatures as low as 90°C. However, as shown in the Table, these low temperatures are not preferred, as although the viscosity build is slow, and although it is continual, a suitable viscosity can only be reached after an extended reaction time. Such an extended reaction time would increase product cost which is contrary to one of the objects of the invention. At temperatures of 130°C and above, there is an initial rapid build of viscosity, indicating that condensation is rapidly progressing. However, after two hours, the increase in viscosity slows and even decreases, indicating that equilibrative decomposition is dominant. Further heating at such temperatures will actually lower the viscosity rather than increase it. The last four columns of the Table indicate theWS 12405 speed of viscosity growth per hour at different temperatures. Since the condensation speed slows down at a large industrial scale, the optimum temperature range is from 105°C to 120°C, ideally in the range of 110°C - 115°C. In these ranges, not only viscosity grows, but also the speed of this growth accelerates. It can be seen that at temperatures of 130° or higher, the viscosity actually decreases from its maximum rather than increasing.

[0045] The timing of diluent addition is also important. In lab scale preparations, the initial rate of condensation without diluent is very high, and the risk of exceeding the desired viscosity or even the gelling of the reactor is a possibility. Thus, it was found necessary to add a diluent to slow down the condensation reaction. However, it was surprisingly discovered that in large-scale commercial synthesis, for example the synthesis of greater than 100 kg of product, preferably greater than 500 kg of product, and up to 5000 kg or more, the initial reaction rate is considerably lower with respect to the rate obtained in laboratory scale preparations. However, the diluent also serves to reduce the final viscosity of the preparation such that the components can be relatively highly condensed and yet the overall viscosity will not be too high. If the diluent were totally absent, the product would have a very high viscosity, and this high viscosity would negatively impact the following silica addition and dispersing step, resulting in an inhomogeneous silica dispersion which will negatively impact defoaming performance of the finished product. The high viscosity, if it reaches an extreme level, could create operational issues such as gelling the reaction vessel, and associated pipes and pumps, etc. Thus, it is necessary to add a diluent, but in the preferred processes, the diluent is added in several stages such that the initial reactant concentrations are high, promoting a high condensation rate, and upon further addition of the diluent, the reaction rate slows to allow control over viscosity and prevent gelling of the system. The second and any further portions of diluent are added prior to addition of the hydrophilic silica and its condensation with condensable reactants or reaction products in the reactor.

[0046] Thus, invention also pertains to a process for preparation of a defoamer composition which reduces foam in liquid compositions, comprising the steps of:

[0047] 1) condensing in a reactor, a reaction mixture comprising from 25-75 weight percent of a hydroxy-terminated polyorganosiloxane (A) having a viscosity in the range of 100-WS 1240550,000 mPas, 0.5-15 weight percent of a silicone resin (B) having at least two hydroxy-reactive groups on average per molecule, and a diluent (D), preferably a polyorganosiloxane diluent (D), said condensing taking place in the presence of an effective condensation-promoting amount of a basic catalyst, preferably an aqueous basic catalyst, at a temperature in the range of 90°C to less than 130°C, and monitoring the viscosity of the condensing reaction mixture until the viscosity at 110°C is in the range of 2000-100,000 mPas, to form an initial condensate;

[0048] 2) optionally adding a hydroxy-functional polyoxyalkylene glycol compound (E) and condensing the polyoxyalkylene glycol compound (E) with components (A) and (B), or with the initial condensate, to form a further condensate;

[0049] 3) adding from 1 -20 weight percent of hydrophilic silica (C) and further reacting to condense the hydrophilic silica with the initial condensate or with the further condensate; and

[0050] 4) optionally, adding up to 30 weight percent hydrophobic silica, prior to or after step 5), and

[0051] 5) cooling the reaction mixture and adding a neutralizing amount of a carboxylic acid to neutralize the basic catalyst, and

[0052] optionally, 6) adding one or more silicone glycols. In this method, all weight percents are based on the total weight of the defoamer composition after completion of step 5) and optional steps 4) and 6).

[0053] The effectiveness of the inventive defoamer compositions can be assessed by numerous methods, for example a black liquor foam pumping test which measures foam level at various times after defoamer addition, and tests of defoaming ability in detergent formulations.

[0054] The inventive defoamer composition and inventive process for preparation thereof is illustrated by the following Examples and Comparative Examples which are not to be construed as limiting the invention in any manner.

[0055] The inventive defoamer formulations are preferably added to the foaming medium for which foam control is desired, and amounts of from 0.1 ppmw to 1 percent by weight, inWS 12405 particular an amounts of from 1 to 100 ppmw, based on the total weight of the medium to be defoamed.

[0056] Example 1

[0057] To a 1 L three necked flask equipped with a mixer and sparge for nitrogen gas are added 252 g of OH-polymer 12,000, a bis(hydroxy -terminated) poly dimethylsiloxane with a viscosity of 12,000 mPas, 30 g of a 1: 1 weight / weight solution of MQ resin 803, available from Wacker Chemie GmbH, dissolved in a trimethylsilyl-terminated polydimethylsiloxane fluid having a viscosity of 100 mPas, 200 g of a diluent which is a trimethylsilyl-terminated poly dimethylsiloxane with a viscosity of 350, and 0.8 g of aqueous basic catalyst which is a 45 weight percent aqueous solution of KOH. The mixture is stirred until homogenous and then the temperature is increased to a temperature in the range of 110-120°C, with a target temperature of 110°C. The temperature is maintained substantially within this range throughout the process. Once the temperature reaches the 100°C, the viscosity of the reaction mixture is measured every 60 minutes, employing a Brookfield viscometer as described previously, at a temperature of 110°C. The viscosity increases consistently, and after 140 min. increases to a viscosity of 6,470 mPas, at which time 20 g of Sipernat 38, a colloidal precipitated hydrophilic silica are added. Mixing and reaction is continued for two hours at a temperature between 100 and 120°C. After this period of time, the mixture is cooled down to approximately 60°C, and 0.25 g of glacial acetic acid is added and mixed for an additional 30 minutes. The product has a final viscosity of 71,700 mPas, as measured with an Anton Parr Rheometer, spindle CP25-2, at 25°C and a shear rate of 1 sec'1.

[0058] Example 2

[0059] To a 1 L three-necked flask equipped with a mixer and spurge for nitrogen gas are added 252 g of OH-polymer 12,000, a bis(hydroxy -terminated) poly dimethylsiloxane with a viscosity of 12,000 mPas, 200 g of a diluent which is a trimethylsilyl-terminated polydimethylsiloxane with a viscosity of 350 mPas, 30 g of a 1: 1 weight / weight solution of MQ resin 803 (available from Wacker Chemie GmbH) dissolved in a trimethylsilyl-terminated poly dimethylsiloxane fluid having a viscosity of 100 mPas, and 0.8 g of aqueous basic catalystWS 12405 which is a 45 weight percent aqueous solution of KOH. The mixture is stirred until homogeneous and the temperature is raised to a temperature in the range of 110-120°C with a target temperature of 110°C. Once the temperature reaches 100°C, the viscosity is measured and monitored by a Brookfield viscometer every 60 minutes with spindle LV 62 and the speed adjusted to reach a torque of 50%. The viscosity of the mixture increases consistently, and after 120 minutes, the viscosity increases to 5,838 mPas. At this point, 9.5 g of Polyglycol Bl 1 / 50 (available from Clariant) is added with continued heating and agitation for 30 minutes, following which 20 g of Sipernat® 38 hydrophilic silica (available from Evonik), is added and the mixture stirred for two hours within the temperature range of 100-120°C. The mixture is cooled to approximately 60°C, and 0.25 g of glacial acetic acid is added and mixed for an additional 30 minutes to neutralize the catalyst. The final product has a viscosity of 61,880 mPas, measured as in Example 1.

[0060] Example 3

[0061] To a 1 L three-necked flask equipped with a mixer and spurge for nitrogen gas are added 252 g of OH-polymer 12,000, a bis(hydroxy -terminated) poly dimethylsiloxane with a viscosity of 12,000 mPas, 200 g of a diluent which is a trimethylsilyl-terminated polydimethylsiloxane with a viscosity of 350 mPas, 30 g of a 1: 1 weight / weight solution of MQ resin 803 (available from Wacker Chemie GmbH) dissolved in a trimethylsilyl-terminated poly dimethylsiloxane fluid having a viscosity of 100 mPas, and 0.8 g of aqueous basic catalyst which is a 45 weight percent aqueous solution of KOH. The mixture is stirred until homogeneous and the temperature is raised to a temperature in the range of 110-120°C with a target temperature of 110°C. Once the temperature reaches 100°C, the viscosity is measured and monitored by a Brookfield viscometer every 60 minutes with spindle LV 62 and the speed adjusted to reach a torque of 50%. The viscosity of the mixture increases consistently, and after 120 minutes, the viscosity increases to 5,090 mPas. At this point, 9.9 g of Polyglycol D21 / 150 (available from Clariant) is added with continued heating and agitation for 30 minutes, following which 20 g of Sipernat® 38 hydrophilic silica (available from Evonik), is added and the mixture stirred for two hours within the temperature range of 100-120°C. The mixture is cooled to approximately 60°C, and 0.25 g of glacial acetic acid is added and mixed for an additional 30 minutes to neutralize the catalyst. The final viscosity of the sample is 47,770 mPas, measured as in Example 1.WS 12405

[0062] Example 4

[0063] To a 1 L three-necked flask equipped with a mixer and spurge for nitrogen gas are added 232 g of OH-polymer 12,000, a bis(hydroxy -terminated) poly dimethylsiloxane with a viscosity of 12,000 mPas, 184 g of a diluent which is a trimethylsilyl-terminated poly dimethylsiloxane with a viscosity of 350 mPas, 27.6 g of a 1 : 1 weight / weight solution of MQ resin 803 (available from Wacker Chemie GmbH) dissolved in a trimethylsilyl-terminated poly dimethylsiloxane fluid having a viscosity of 100 mPas, and 0.7 g of aqueous basic catalyst which is a 45 weight percent aqueous solution of KOH. The mixture is stirred until homogeneous and the temperature is raised to a temperature in the range of 110-120°C with a target temperature of 110°C. Once the temperature reaches 100°C, the viscosity is measured and monitored by a Brookfield viscometer every 60 minutes with spindle LV 62 and the speed adjusted to reach a torque of 50%. The viscosity of the mixture increases consistently, and after 120 minutes, the viscosity increases to 5,916 mPas. At this point, 36.8 g of Polyglycol D21 / 150 (available from Clariant) is added with continued heating and agitation for 30 minutes, following which 20 g of Sipernat 38 hydrophilic silica (available from Evonik), is added and the mixture stirred for two hours within the temperature range of 100-120°C. The mixture is cooled to approximately 60°C, and 0.25 g of glacial acetic acid is added and mixed for an additional 30 minutes to neutralize the catalyst. The final viscosity of the sample is 81,280 mPas, measured as in Example 1.

[0064] The rheological characteristics of Examples 1-4 are measured by Dynamic Mechanical Analysis using an Anton Paar Model MCR 302 rotational rheometer equipped with Rheoplus software in an oscillatory mode to perform amplitude and frequency sweeps under controlled conditions. A cone and plate geometry using a 50 mm cone with a 2° angle is used at 25°C for all tests. For each test sequence, the respective sample is loaded onto the plate and access sample trimmed at the measurement gap setting. Prior to measurement, a 60 s rotational pre-shear at 5 s'1is followed by a 60 s relaxation interval to remove residual sample stress. An amplitude (strain) sweep is performed at from 0.01 to 100% strain (Ramp Log, 5 pts / decade) at 5% strain, with a test period of 30 minutes.WS 12405

[0065] The viscoelastic behavior is evaluated by plotting storage modulus G’, loss modulus G” and damping factor tan 8 as a function of strain and frequency. With damping factors which are generally greater than 1 the inventive foam control agents maintain flowable behavior under high strain and high-frequency. The changes in tan 8, A tan 8 represent the changes in tan 8 between 1 rad / s and 100 rad / s, and are presented in Table 2 below.

[0066] TABLE 2Rheology of Examples 1-4

[0067] One measure of the efficiency of a defoamer is the “foam knockdown”, which is the “instantaneous performance” of the defoamer, or the time at which the foam of a foaming system reaches a minimum following addition of the defoamer. In general, a very short knockdown time is desirable. However, in addition to a relatively short knockdown time, a much more important consideration is the long-term performance of the foam control agent. One suitable apparatus for determining defoamer performance is a thermostatted dual wall 1000 mL glass beaker having a bottom outlet in communication with a gear pump, the output of the gear pump being directed into the liquid surface near the top of the beaker. In the testing which follows, the apparatus is maintained at a temperature of 80 - 90 °C by circulation of thermostatted water between the outer and inner walls of the beaker, 400 mL of a synthetic black liquor mimicking natural black liquor from a chemical pulp process are recirculated at a rate of 1.1 L / min, and a sample of foam control agent is added at the point in time when the foam level in the apparatus has reached a height of 45 mm. The level of liquid in the apparatus and the height of foam can beWS 12405 measured visually, or automatically through the use of LED light sources and receivers on opposite sides of the beaker.

[0068] In these tests, the shorter the foam collapse time tl and the lower the foam level hl , the better the rapid response of the defoamer. Long-term performance is assessed by measuring the time interval t2 required to return from the lowest foam level to a foam level of 50 mm. The synthetic black liquor was prepared by mixing 85.94 weight percent of deionized water with eight weight percent of Indulin C, 4.16 weight percent sodium carbonate, 1.51 weight percent of sodium hydroxide in pellet form, 0.2 weight percent sodium sulfate, 0.1 weight percent tall oil, and 0.09 weight percent caustic soda.

[0069] Table 3 below shows that by condensing additional and optional polyglycols, the foam knock down tl and long term persistence t2 of the final samples both improved. Simple mixing with corresponding polyglycol negatively impacted foam knock down tl. The impact of condensing additional polyglycol is positive yet primary, and fine tuning the dosage may be necessary to optimize performance.

[0070] TABLE 3Evaluation of defoamer performance of condensation samples with additional polyglycolThe evaluation was carried out by the synthetic black liquor pumping test described before. The sample was pre-dispersed in ICP (from Sigma Aldrich) at 16 wt. %. The sample dispersion was added and tested at a dosage of 25 pL in 400 mL (thus the absolute dosage of the compound is lOppm)WS 12405[0071 J A further test to evaluate defoamer efficiency is a Contifoam Activity Count (AKZ) test, which simulates defoamer performance of products in industrial mixers. A glass beaker having a volume of approximately 1000 ml is used for this test. The beaker is surrounded by 4 spacedWS 12405 apart light sources and receivers which measure the height of the foam generated by a central mixer consisting of two twirling-sticks. After stirring an aqueous solution containing a foaming surfactant and the defoamer being tested for 30 seconds at 1200 RPM, and the foam collapsing phase is recorded via light detectors to achieve an activity count number which is the area below the foam curve and correlates to the foam collapsing time (knock-down). The AKZ number is calculated by the equation AKZ = 25 x (tl + t2 +t3 + t4). The lower the AKZ number, the faster is the foam knockdown.

[0072] For testing purposes, a 5 wt. % sample of the defoamer is dissolved in methylethylketone (MEK) solvent. For the foaming surfactant, Mersolat® detergent in a concentration of four weight percent in water is employed. 200 mL of the foamable detergent solution is added to the test beaker at room temperature along with 2 ml of the defoamer dispersion in MEK and the central mixer is turned on for 30 seconds to generate foam. At a time tO, foam height is recorded and the times at which the foam reaches sensors 1, 2, 3, and 4 are noted. These times: tl, t2, t3, and t4 are then used to calculate the AKZ number. In the following table, activity counts from Inventive Examples 1-4 and also of mixtures of the foam control agent from Example 1 with corresponding additional polyglycol are determined. In addition, activity counts for the individual polyglycols alone and the methylethylketone solvent are also determined.

[0073] TABLE 4Activity Counts of Defoamers and Individual IngredientsWS 12405

[0074] Comparative Example 1

[0075] Comparative Example 1 is a further commercially available competitive defoamer.

[0076] The efficiency of Inventive Example 1 as compared with Comparative Example1 and is assessed by the black liquor foam test previously described, but with the defoamer concentration being 25 ppmw. The various were added in the form of a 20% dispersion in Solvent DI 10 from ExxonMobil. The results are presented in the Table below.

[0077] TABLE 5Defoamer Evaluation at 25 ppmwWS 12405

[0078] As shown in the Table, at a concentration of 25 ppmw, the inventive defoamer exhibited the quickest foam knockdown time tl and also the longest long term performance t2. The foam levels hl were virtually the same. The combination of foam collapse time tl, foam level hl, and long-term performance t2 show that the defoamer of Inventive Example 1 is surprisingly and unexpectedly much better than the foam control of the composition of Comparative Example 1.

[0079] As required, detailed embodiments of the present invention are disclosed herein; however, it is to be understood that the disclosed embodiments are merely exemplary of the invention that may be embodied in various and alternative forms. The figures are not necessarily to scale; some features may be exaggerated or minimized to show details of particular components. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a representative basis for teaching one skilled in the art to variously employ the present invention.

[0080] While exemplary embodiments are described above, it is not intended that these embodiments describe all possible forms of the invention. Rather, the words used in the specification are words of description rather than limitation, and it is understood that various changes may be made without departing from the spirit and scope of the invention. Additionally, the features of various implementing embodiments may be combined to form further embodiments of the invention.

Claims

WS 12405WHAT IS CLAIMED IS:

1. A condensed defoamer composition for defoaming liquid compositions, comprising a base- catalyzed condensation product of reactants comprising:(A) from 25-75 weight percent of a hydroxy -terminated polyorganosiloxane having a viscosity in the range of 100-50,000 mPas;(B) from 0.5-15 weight percent of a silicone resin bearing at least two hydroxy - reactive groups on average per molecule; and(C) from 1-30 weight percent of a hydrophilic silica bearing condensable groups, in which the condensation of components (A), (B) and (C) takes place in the presence of a basic catalyst (K) and from 25-75% by weight of a non-reactive diluent (D), and(F) an acid to neutralize the aqueous base (K), wherein the defoamer composition has a viscosity in the range of 4,000 - 200,000 mPas, the weight percentages are based on the total weight of components (A) - (D), and total 100%, and the defoamer composition reduces foaming in foamable liquid compositions.

2. The defoamer composition of claim 1, wherein the condensed defoamer composition further comprises condensed moieties from a hydroxy-functional polyoxyalkylene glycol compound (E).

3. The defoamer composition of claims 1 or 2, wherein a silicone glycol is added to the defoamer composition in an amount of from 1-20 weight percent of the total weight of the condensed defoamer composition and silicone glycol.

4. The defoamer composition of claims 1 or 2, further comprising up to 30 weight percent, preferably 1-15 weight percent, and more preferably 3-10 weight percent, based on the total weight of the defoamer composition, of hydrophobic silica.

5. The defoamer composition of claims 1 or 2, wherein the silica having condensable groups is a non-hydrophobicized hydrophilic silica.WS 124056. The defoamer composition of claim 2, wherein the hydroxy-functional polyoxyalkylene glycol is condensed following an initial condensation of the hydroxy-terminated polyorganosiloxane (A) and silicone resin (B).

7. The defoamer composition of claims 1 or 2, wherein the diluent (D) comprises a polyorganosiloxane.

8. A process for preparation of the condensed defoamer composition of claim 1, comprising the steps of:1) condensing in a reactor, a reaction mixture comprising from 25-75 weight percent of a hydroxy -terminated polyorganosiloxane (A) having a viscosity in the range of 100- 50,000 mPas, and 0.5-15 weight percent of a silicone resin (B) having at least two hydroxy-reactive groups on average per molecule, said condensing taking place in the presence of an effective condensation-promoting amount of a basic catalyst and from 25 - 75 wt. % of a non-reactive diluent (D) at a temperature in the range of 80°C to less than 130°C, and monitoring the viscosity of the reaction mixture until a target viscosity in the range of 2000-100,000 mPas at 110°C is reached, to form an initial condensate;2) optionally adding a hydroxy-functional polyoxyalkylene glycol compound (E) and condensing the polyoxyalkylene glycol compound (E) with components (A) and (B), and / or with the initial condensate, to form a further condensate;3) adding from 1-30 weight percent of hydrophilic silica (C) and further reacting to condense the hydrophilic silica with the initial condensate or with the further condensate;4) optionally, adding up to 30 weight percent hydrophobic silica, prior to or after step 5);5) cooling the reaction mixture and adding an acid to neutralize the basic catalyst to form a condensed defoamer composition; andWS 124056) optionally adding a silicone glycol to the condensed defoamer composition.

9. The process of claim 8, wherein from 20-80 wt. % of the total amount of diluent (D) is present proximate the beginning of step (1), and the remainder is added at a later time.

10. The process of claim 8, wherein the diluent (D) is a polyorganosiloxane.

11. The process of claim 8, wherein at least step (1) takes place at a temperature of from 110°C to 115°C.

12. The process of claim 8, wherein the target viscosity of step (1) is from 4,000-20,000 mPas.

13. The process of claim 8, wherein the catalyst (K) comprises aqueous KOH.

14. The use of the condensed defoamer composition of claim 1 or the condensed defoamer composition prepared by the process of claim 8 as a defoamer in a foamable liquid composition.

15. The use of the condensed defoamer composition of claim 1 or the condensed defoamer composition prepared by the process of claim 8 as a defoamer in a black liquor composition.

Images