Background of the Invention

1 Field of the Invention

The present invention relates to novel defoaming agent which can be used for a variety of applications More specifically, the invention comprises a completely aqueous silicone defoaming agent which includes a silicone fluid, silica, non-silicone containing surface active agents silicone containing surface active agents and water The composition has particular use in aqueous pulp defoaming applications

2 Technology Description

The use of silicone containing compositions in paper mill pulp defoaming operations has met with a great deal of commercial success Examples of such materials are described in the following patent publications CA 2048823, US 4,076,648, CA 880850 and US 5,380,464 While these types of materials have significantly advanced the art, they typically require the presence of an organic solvent such as a hydrocarbon (including, for example, mineral oils) Such products may not be ultimately desirable for use in commercial operations because of the presence of the volatile organic solvent which can create environmental concerns and cause the formation of pitch and other deposits on resulting paper because of the presence of solvent This latter concern is independent of the amount of volatiles in the hydrocarbon

Despite the above teachings, there still exists a need in the art for a silicone containing composition having no hydrocarbons which has functionality as a defoaming agent and which demonstrates excellent stability properties

Brief Summary of the Invention

In accordance with the present invention a novel composition demonstrating utility as a defoaming agent is provided The composition comprises an aqueous emulsion of the following components

a) one or more silicone fluids,

b) one or more silicone containing surface active agents

c) one or more non-silicone containing surface active agents and

d) a solid particulate material which is rendered hydrophobic in said one or more silicone fluids

wherein said composition does not contain any hydrocarbons

In particularly preferred embodiments, the amount of solids in the emulsion ranges from about 10 to about 60 percent by weight In addition to the above materials, the emulsion may also include performance enhancing additives such as thickeners, biocides, acids bases and the like

Another embodiment of the present invention comprises a process for reducing the foam tn a foam containing liquid by adding to said foam containing liquid an effective defoaming amount of the above defined novel defoaming composition

A preferred embodiment of this aspect of the present invention is where the foam containing liquid to be treated is Kraft pulp liquor

An object of the present invention is to provide a novel composition which contains no organic solvents and is capable of functioning as a defoaming agent

Still another object of the present invention is to provide a process for reducing the foam of a foam containing liquid by utilizing the novel composition of the present invention

These, and other objects, will readily be apparent to those skilled in the art as reference is made to the drawing and detailed description of the preferred embodiment

Brief Description of the Drawing

The Figure is a graphical representation of the knockdown properties of the inventive material as compared to several commercially available defoamers

Detailed Description of the Preferred Embodiment

In describing the preferred embodiment, certain terminology will be utilized for the sake of clarity Such terminology is intended to encompass the recited embodiment, as well as all technical equivalents which operate in a similar manner for a similar purpose to achieve a similar result

The present invention relates to a multi-component blend composition in aqueous emulsion form which demonstrates excellent defoaming or antifoammg properties

The first component of the blend composition is one or more silicone fluids Such fluids are well known in the art and comprise polyorganosiloxanes having a viscosity ranging from between about 50 to about 30000 centistokes at 25°C These fluids are usually of the formula R _1(a) SιO ₍₄ - _a)/2 , wherein R,, which may be the same or different, are monovalent or halogenated hydrocarbon groups having one to ten carbon atoms Specific examples of such groups include methyl _, ethyl, propyl butyl, octyl tπfluoropropyl, phenyl 2-phenylethyl and vinyl groups, and wherein a has a value between about 0 and about 4, more preferably between about 1 9 to about 2 2 It is particularly preferred that the fluid comprises a trimethylsilyl-terminated polydimethylsiloxane

Alternatively, the fluid may be of the formula R ₂ (b)( 30),SiO ₍ -, i,o: wherein R ₂ is the same as defined above for Ri, R ₃ is a hydrogen atom or R ₂ , and the -OR ₃ group is present at least at the end of a molecular chain of polyorganosiloxane The value of b is between about 0 to about 4 more preferably between about 1 9 and 2 2, and c has a value so as to provide at least one -OR ₃ group per molecule Such an alternative fluid is preferably a hydroxyl-terminated polydimethylsiloxane

Mixtures of silicone fluids can be used to yield a composition having a desirable viscosity More preferred is the use of a fluid or mixtures of fluids having a viscosity ranging from between about 200 to about 2000 centistokes at 25°C, and even more preferred is the use of a fluid or mixtures of fluids having a viscosity of about 1000 centistokes at 25°C

Examples of silicone fluids useful in association with the present invention are disclosed in U S Patent No 5,380 464 To the extent necessary for completion this patent is hereby incorporated by reference A commercial silicone fluid which may be selected for use in the present invention comprises Rhodorsil® 47-V 1000 centistoke silicone fluid manufactured by Rhόne-Poulenc

The amount of the silicone fluid in the emulsion typically ranges from about 5 to about 50 percent by weight of the emulsion with amounts of about 10 to about 30 percent by weight being more preferred and amounts ranging from about 15 to about 25 percent by weight being most preferred

The second component of the inventive composition comprises one or more silicone containing surface active agents This encompasses any and all silicone containing materials which both includes one or more hydrophobic groups and demonstrates surface active properties Particularly preferred are the use of silicone polymers which include alkoxylate groups such as ethylene oxide, propylene oxide, and mixtures thereof Examples of silicone surface active agents which may be selected for use in the present composition are disclosed in the following patent documents U S 5,104,647, U S 5,017,216, U S 5 145,978, US 5,145,977 and WO 94/22311 To the extent necessary for completion these patents are hereby expressly incorporated by reference

Generally these materials are silicone glycols or polyether modified siloxanes Classes of such materials include the polymerization product of one or more polyalkyl or aryl silicone or siloxane monomers with one or more polyoxyalkyl monomers Specifically useful surface active agents include dimethyl, 3-hydroxypropyl ethoxylated-propoxylated siloxanes and silicones (CAS Registration No 68937-55-3) (the presence of the 3-hydroxypropyl group is considered optional) and the copolymer of polyalkyieneoxide methyl siloxane and polyalkylene oxide monomers (CAS Registration No 71965-38-3) Commercial materials which may be selected as the silicone surface active agent include the Silquest® DA products manufactured by OSi Specialties Inc and the Tegopren line of materials manufactured by Goldschmidt

The amount of the silicone containing surface active agent in the emulsion typically ranges from about 2 to about 20 percent by weight of the emulsion with amounts of about 5 to about 15 percent by weight being more preferred and amounts ranging from about 6 to about 12 percent by weight being most preferred It is believed that the high level of silicone containing surface active agent enables the resulting emulsion to have high temperature stability and superior foam knockdown properties

The third component of the composition is one or more non-silicone containing surface active agents These are any materials which are capable of functioning to emulsify the silicone fluid in an aqueous environment and which do not contain silicone atoms The surface active agents may take the form of either surfactants or protective colloids When selecting a surfactant for use, either anionic cationic, amphotenc, noniomic surfactants or mixtures thereof may be selected

Specific examples of surfactants which may be selected include polyethylene glycol mono- and diesters of mono- or polyunsaturated acids, saturated fatty acids, polyoxyethylene sorbitan monooleate, ammonium lauryl ether sulfate, sodium lauryl ether sulfate octyl phenol ethoxylates (30-50 moles of ethylene oxide), nonyl phenol ethoxylates (30-50 moles of ethylene oxide) sodium lauryl sulfate, and phosphate esters such as ammonium or sodium salts of poly(oxy-1 ,2- ethanedιyl),σ-(nonylphenol)-ω-hydroxy-phosphate, poly(oxy-1 2-ethanedιyl) σ-phenol-< )-hydroxy- phosphate and poly(oxy-1 ,2-ethanedιyl),σ-(octylphenol)-ω-hydroxy-phosphate

Examples of protective colloids which may be selected include polyfvmyl alcohol] ethyl cellulose _, poly[vιnyl pyrollidone], sodium polyacrylate and natural gums such as xanthan gum

In the preferred embodiment, mixtures of surfactants may be selected A particularly efficacious mixture is the combination of sorbitan monostearate (e g , Span 60) with ethoxylated steaπc acid (having 40 moles of ethylene oxide per molecule) A commercial example of this type of surfactant is Myrj 52, sold by ICI Americas

The amount of this third component in the emulsion typically ranges from about 1 to about 10 percent by weight of the emulsion with amounts of about 2 to about 8 percent by weight being more preferred and amounts ranging from about 3 to about 7 percent by weight being most preferred

The fourth component in the emulsion comprises a solid particulate material which is rendered hydrophobic when in a silicone fluid The most preferred solid particulate comprises silica including precipitated, pyrogenic, fumed silica and mixtures thereof The silica selected should ideally have a surface area of greater than about 100 m ² /gram The particle size of the silica typically ranges from about 0 1 to about 20 microns, with a particle size of between about 1 micron and about 15 microns being more preferred

As a substitute for silica, the following solid particulate materials may alternatively be selected clay, talc, titanium dioxide, aluminum oxide, zirconium oxide and mixtures of the above Mixtures of the materials of this paragraph with silica are expressly covered by this invention

The amount of this fourth component in the emulsion typically ranges from about 0 5 to about 5 percent by weight of the emulsion

Also optionally present in the emulsion are performance enhancing and stabilizing chemicals which can function to provide specific properties to the final emulsion Examples of such chemicals include bioαdes, acids, bases, dyes, corrosion inhibitors, thickening agents (e g ,

polygalactomannans, polyacrylates and the like), enzymes and the like In practice the amount of these additives is no more than 10 percent by weight of the emulsion

A particularly preferred optional additive is a non-hydrocarbon silicone performance additive These materials provide improved durability or longevity of the defoaming activity Examples of such additives include the PULPSIL® silicone chemicals which are manufactured by Wacker-Chimie The most preferred of such chemicals is PULPSIL® 160C, which, according to the manufacturer is a silicone compound which is a colorless cloudy liquid having a specific gravity at 25°C of 0 99-1 01 g/cm ³ , a Refractive index at 25°C of 1 4020-1 4100, a variable viscosity at 25°C a maximum volatility of 2% at 5g, 2 hours 180°C and a shelf life of 12 months Another useful specialty additive comprises the PULPAID silicone chemicals which are manufactured by Dow Corning Particularly useful is PULPAID 3472 Concentrate which according to the manufacturer is a 100 percent concentrate which is a cream white emulsion which has as active ingredients silica-filled polydimethylsiloxane and silicone organic copolymers This compound has a specific gravity of 1 0, a viscosity of 20,000 - 30,000 cps at 25°C and a flash point greater than 100°C These specialty additive compounds allegedly comply with FDA §§ 176 170, 176 180 and 176 210 and BGA XXXVI In practice, the specialty additives should be present in amounts ranging from about 0 25 to about 10 0 percent by weight of the final emulsion

The final component of the emulsion is the aqueous emulsifying medium, typically water

The emulsion does not contain any hydrocarbons (e g , organic solvents such as kerosene, mineral oils, etc )

The emulsion of the present invention contains between about 10 and about 60 percent solids by weight, with amounts between about 15 and about 50 percent solids by weight being more preferred and amounts between about 20 and about 40 percent solids by weight being most preferred The viscosity of the emulsion typically ranges between about 100 and about 30000 cps as measured by a Brookfteld Viscometer, Spindle #3, 60 rpm, with a viscosity of between about 200 and about 2000 cps being more preferred

Preparation of the inventive emulsion simply comprises a simple sequential mixture of the various components under preferred heating and agitation conditions In practice the solid particulate material is first mixed into the silicone fluid under heat and pressure (2000 psi for homogenization) and agitation sufficient to yield a homogenous material This homogenous material is thereafter added to a vessel containing water and the non-silicone containing surface active agent followed by addition of the silicone containing surface active agent Thereafter optional bases thickening agents, and the like are added and the emulsion is mixed until it is completely homogenous

The above synthesized emulsion may be used in any application where foam reduction is desired such as in personal care products, agricultural applications detergents and cleaners and in paper mill operations A particularly preferred use of the novel composition is in Kraft pulp liquor defoaming

To utilize the emulsion of the present invention to control foam in aqueous foaming systems the above defined emulsion is simply added to an acidic, basic or neutral aqueous foaming (or foam- producing) system Typically, the foam control emulsions of the present invention are added at a concentration of about 10 ppm to about 0 1 percent based on the weight of the foaming system However, the skilled artisan will readily determine optimum concentrations after a few routine experiments

The emulsions of the present invention provide the following advantages as compared to prior art systems which require the presence of hydrocarbons environmentally safe and friendly, easy to process, and, when used in paper mills the emulsion does not contribute to deposit formation It is well known that mineral oils and other hydrocarbons typically present in defoaming agents tackify naturally occumng wood pitch making the colloidal particles more susceptible to agglomeration thereby increasing the probability of the formation of deposits Since there is no hydrocarbon present in the inventive emulsion there is a much reduced risk of deposit formation

In addition, they have an extremely long shelf life, with the emulsion demonstrating stability for greater than 30 days, more preferably greater than 90 days and most preferably greater than 180 days being possible This stability is demonstrated even at high storage temperatures (i e greater than about 40°C)

The invention is described in greater detail by the following non-limiting examples

Example 1

Approximately 91 parts of a 1000 centistoke silicone fluid is added to a vessel and the vessel is heated to 120°F Approximately 9 parts of silica is added to the vessel and it is mixed until the lumps in the vessel disappear The contents are then homogenized at 2000 psi to yield what is defined as the silicone base

In a separate vessel 1 5 parts of ethoxylated steaπc acid (having 40 moles of ethylene oxide per mole of molecule) and 3 0 parts of sorbitan monostearate are added to 62 75 parts of water and the mixture is heated to 150°F and mixed and held at this temperature for 30 minutes 23 025 parts of the silicone base are then pumped into this mixture followed by the addition of 6 975 parts of a silicone surfactant which is a dimethyl, 3-hydroxypropyl ethoxylated-propoxylated siloxane and/or silicone (CAS Registration No 68937-55-3) and the contents are mixed for 30 minutes 2 5 parts of a polyacrylate dispersant diluted with 50 percent water is added and the mixture is mixed for 30 minutes 0 150 parts of NaOH (50% solution) are then added the mixture is agitated for 30 minutes and the vessel contents are allowed to cool to about 90-100°F 0 100 parts of a biocide which is a 20% solution of 1 ,2-benzιsothιazolιn-3-one in dipropylene glycol are then added and the entire vessel contents are mixed until homogenous If it is necessary to modify the pH and viscosity of the final product a polyacrylate dispersant (Colloid 1560, Rhόne-Poulenc Inc ) and NaOH may be added to the mixture

The resulting product is a creamy white liquid having a specific gravity of between about 0 98 and 1 02 The viscosity of the material at 25°C is between about 800 and 1300 cps as measured by a

Brookfield Viscometer, Spindle #3, 60 rp , the pH is between 7 5 and 9 0 and the percent solids is 35 percent

Test Data

To determine the usefulness of the above composition as a pulp defoamer the following procedure is performed 400 mis of black liquor from a paper mill located in the Southeast part of the United States is heated to 85°C The liquor is transferred into a laboratory "Foam-Cel" foam tester and the rheostat on the tester is activated to 80% to 100% of line voltage (120 volts), thereby starting the pump of the tester This causes the foam in the black liquor to rise When the foam level reaches 24 cm, a specific aliquot of defoaming chemical is added to the tester The level of foam is measured on a periodic basis (every 15 seconds) until the foam level reaches its upper limit (28 cm) and the rheostat is turned off The first reading, which occurs at the time of aliquot addition, is referred to the "Knockdown" time

The following emulsion materials are tested to determine their effectiveness

Sample A - Example 1 Composition (400 μl aliquot)

Sample B - Commercial product made by Nottingham Chemical (400 μl aliquot) Sample C - Commercial product made by Basso (530 μl aliquot)

Sample D - Commercial product made by Callaway Chemical (400 μl aliquot) Sample E - Commercial product made by Henkel Chemical (400 μl aliquot)

The tests are conducted in triplicate Results are shown in the attached table All height measurements are in centimeters and all time measurements are in seconds

The Figure depicts this data in graphical form except the results for Sample B, which are omitted

The above data demonstrates that the inventive composition of the present invention provides excellent defoaming properties These properties include excellent knockdown and maintenance of a low foam height for extended periods of time In addition, because they are completely solvent- free, they are more environmentally desirable compositions and will not contribute to the formation of organic deposition because they do not contain volatile organic solvents or hydrocarbons

Example 2

To 100 parts of the composition of Example 1 are added about 3 5 parts of either PULPAID 3472, manufactured by Dow Corning, or PULPSIL® 160-C manufactured by Wacker-Chimie The resulting compositions are tested using the above Test Data procedures While the initial knockdown values for these two compositions are comparable to those of the Example 1 composition, the foam height remains at a low value for extended periods of time This phenomenon is particularly seen at times of between 60 seconds and 120 seconds after addition of the emulsion composition This Example demonstrates that an even better performance can be obtained by the addition of small amounts of specialty additives to the emulsion

Having described the invention in detail and by reference to the preferred embodiments thereof, it will be apparent that modifications and variations are possible without departing from the scope of the appended claims