US20030053927A1

US20030053927A1 - Controlled Rellease of oxygen scavengers in cooling systems

Info

Publication number: US20030053927A1
Application number: US10/270,905
Authority: US
Inventors: Joseph Drozd; Thomas Blakemore; Yu-Sen Chen
Original assignee: Dober Chemical Corp
Current assignee: Dober Chemical Corp
Priority date: 2000-03-31
Filing date: 2002-10-15
Publication date: 2003-03-20

Abstract

Provided are compositions and methods for releasing oxygen scavengers into a coolant. The compositions include a controlled release component and an oxygen scavenger component which includes at least one oxygen scavenger. Methods and devices for releasing oxygen scavengers into a coolant are also provided.

Description

RELATED APPLICATION

This application is a continuation in part of U.S. patent application Ser. No. 09/539,914 filed Mar. 31, 2000 the disclosure of which is incorporated herein in its entirety by reference.[0001]

FIELD OF THE INVENTION

The present invention relates to devices and methods for providing a controlled release of oxygen scavengers to coolant in cooling systems, for example, but not limited to, such systems in internal combustion engines, for example, diesel engines, open circulating cooling systems such as cooling towers, and the like.

BACKGROUND OF THE INVENTION

It is well known that with extended use of a coolant the coolant degrades resulting in a lessening of effectiveness of the coolant which is usually a glycol based composition, for example, propylene glycol or ethylene glycol.

The main cause of coolant degradation, particularly at high temperatures, is oxidation of elements that comprise the coolant. Typically, air enters a cooling system due to “breathing” caused by the heating and cooling cycles in the cooling system which cause the coolant to expand and contract. As the coolant cools, a vacuum is created which draws air into the system.

Coolant degradation, for example, oxidative degradation of a coolant can be reduced or eliminated in some cases by closing the cooling system to an intake of air. However, this approach is not practical in many cooling system applications.

Alternatively, oxidative degradation can be minimized or eliminated by adding to the coolant a substance that will scavenge (e.g. remove) oxygen that enters a cooling system. Since air may enter a cooling system slowly and constantly over a long period of time, it is preferable that protective amounts of oxygen scavenger be introduced slowly into the cooling system in amounts effective to remove or lessen the oxygen concentration.

Therefore, there is a need for compositions, methods and devices for releasing oxygen scavengers and/or oxygen scavengers into the coolant of a cooling system at a controlled rate in order to prevent oxidative degradation of one or more components of a coolant in the cooling system.

SUMMARY OF THE INVENTION

New compositions, methods and devices for providing release, preferably controlled release, of at least one oxygen scavenger into a coolant of a cooling system have been discovered. The present compositions, methods and devices effectively provide for gradual, preferably sustained, and more preferably substantially controlled, release of a oxygen scavenger into a coolant, for example, a liquid coolant. A liquid coolant may include an aqueous phase. The liquid coolant may also include at least one freezing point depressant, such as at least one glycol; a liquid coolant which includes at least one freezing point depressant and does not include an aqueous phase; and the like. Examples of glycols which may serve as freezing point depressants include, without limitation, propylene glycol and ethylene glycol.

The present invention provides for coolant additive compositions which include a controlled release component and a oxygen scavenger component. The present invention also provides for methods for releasing an oxygen scavenger component into a coolant which include the step of contacting an additive composition with a coolant. The controlled release component is effective to reduce the rate of release of the oxygen scavenger component into a coolant in a cooling system. The oxygen scavenger component includes one or more oxygen scavengers. Examples of oxygen scavengers that may be included in the oxygen scavenger component are thiosulfite, thiosulfate, mercaptopropionic acid, bisulfite, hydrosulfite, dithionate, hyposulfite, sulfite, sulfide, stannous, hydroxylamine or hydrazine or mixtures thereof.

Liquid oxygen scavengers such as hydrazine may require a special composition and/or device in order to effectively remove oxygen from a coolant. For example, aryl amine compounds and other compounds disclosed in U.S. Pat. No. 3,983,048 may be useful in this regard.

Examples of hydroxylamines that are useful in accordance with the present invention include, without limitation, hydroxylamine hydrochloride, hydroxylammonium acid sulfate, N,N-diethylhydroxylamine, Hydroxylamine phosphate, N-Ethylhydroxylamine, N,N-Dimethylhydroxylamine, O-Methylhydroxylamine, O-Hexylhydroxylamine, N-Heptylhydroxylamine, N,N-Dipropylhydroxylamine, O-Methyl N,N-diethylhydroxylamine, N-Octylhydroxylamine, O-Ethyl N,N-dimethylhydroxylamine, N,N-Diethylhydroxylamine hydrochloride, N-Methyl N-ethylhydroxylamine, O-Methylhydroxylamine phosphate, N-Butylhydroxylamine, N-Benzylhydroxylamine (β-Benzylhydroxylamine), O-Benzylhydroxylamine (α-Benzylhydroxylamine) and N,N-Diethylhydroxylamine acetate

The rate of release of the oxygen scavenger component may be reduced relative to the rate of release of an identical composition without the controlled release component.

The controlled release component may include, for example, a matrix material and/or a coating material. The matrix material and/or a coating material may be effective to reduce the rate of release of the oxygen scavenger component into the coolant relative to an identical oxygen scavenger component without the provided coating material. In addition, the controlled release component may include one or more polymeric materials. Further, the controlled release component may be partially soluble in the coolant.

The oxygen scavenger component, when released in the coolant, is effective to provide at least one benefit to the coolant and/or cooling system. In one embodiment, the oxygen scavenger component is effective to inhibit degradation of the coolant when the oxygen scavenger component is released into the coolant in a cooling system. For example, the oxygen scavenger component may be effective to inhibit oxidative degradation of the coolant.

In accordance with the present invention, the coolant additive composition may be employed in a cooling system that is a circulating cooling system. In one embodiment, the circulating cooling system is not completely closed.

In one embodiment, the cooling system cools an internal combustion engine, for example, a diesel engine.

The present invention provides for methods of producing the herein described coolant additive compositions. In one embodiment, methods include the step of combining a oxygen scavenger component with a matrix material to form a mixture wherein the matrix material is effective to reduce a rate of release of the oxygen scavenger component into a coolant in a cooling system.

In another embodiment the methods include the steps of: 1) providing a coolant additive composition which includes a oxygen scavenger component; and 2) providing a coating material on the coolant additive composition to form a coated additive composition. The coating material may be partially coolant soluble and effective, when the coated additive composition is contacted with a coolant, to reduce the rate of release of the coolant additive composition into a coolant in a cooling system.

The present invention also provides for combining methods of producing additive compositions, for example, a method which includes the steps of: 1) combining a oxygen scavenger component with a matrix material to form a mixture wherein the matrix material is effective to reduce a rate of release of the oxygen scavenger component into a coolant in a cooling system; 2) providing a coating material on the mixture to form a coated mixture. The matrix material and coating material being effective to reduce the rate of release of the additive composition into a coolant in a cooling system.

The present invention also provides for methods for releasing a oxygen scavenger component into a coolant which include the step of contacting an additive composition produced by a method of the invention with a coolant.

The present invention also provides for coolant additive assemblies. The present invention also provides for methods for releasing a oxygen scavenger component into a coolant which include the step of contacting an additive composition included in a coolant additive assembly with a coolant.

The coolant additive assemblies may include a housing which may include a coolant inlet and a coolant outlet. The housing may include an additive composition disposed within the housing which includes a controlled release component and a oxygen scavenger component. The controlled release component may be effective to reduce the rate of release of the oxygen scavenger component into a coolant in a cooling system.

Commonly assigned U.S. patent application Ser. Nos. 09/939,527; 09/781,842; 09/939,214; 09/939,212; 09/539,914 and U.S. Provisional Patent Application No. 60/360,482 are directed to subject matter somewhat related to the present patent application. The disclosure of each of these co-pending U.S. Patent Applications and Provisional Patent Application is incorporated in its entirety herein by reference.

In addition U.S. Pat. Nos. 6,264,833; 5,024,268; 4,782,891; 5,772,873; 5,803,024; 5,948,248; 6,290,870; 6,010,639; 3,962,109; 3,959,166; RE37,369; 5,895,778; 4,711,735; 3,728,281; 3,808,138; 3,687,610; 3,645,896; 4,079,018; 3,639,263; 3,983,048; 3,843,547; 5,366,651; 4,655,930; 4,026,664 and European Patent Application EP 1170348 are directed to subject matter somewhat related to the present patent application. The disclosure of each of these U.S. Patents and the European Patent Application is incorporated in its entirety herein by reference.

Unless otherwise expressly noted to the contrary, each of the words “include”, “includes”, “included” and “including,” and the phrase “for example” and abbreviation “e.g. ” as used herein in referring to one or more things or actions means that the reference is not limited to the one or more things or actions specifically referred to.

Each and every feature described herein, and each and every combination of two or more of such features, is included within the scope of the present invention provided that the features included in such a combination are not mutually inconsistent.

Additional aspects and advantages of the present invention are set forth in the following description and claims, particularly when considered in conjunction with the accompanying drawings in which like parts bear like reference numerals.

DETAILED DESCRIPTION OF THE INVENTION

The present invention is directed to the inclusion of an oxygen scavenger component in a coolant, for example, a coolant in a cooling system. The cooling systems, include, but are not limited to boilers, systems in or associated with motors, engines, such as internal combustion engines, for example, in vehicles such as automobiles, planes, trains, trucks and the like, in heavy equipment, including both stationary and mobile equipment, as well as open circulating coolant or cooling systems, such as cooling towers and the like.

In one broad embodiment, the present invention includes an oxygen scavenger component and a controlled release component.

The oxygen scavenger component may be any suitable composition effective for use in a coolant in accordance with the present invention. In one embodiment, the oxygen scavenger component is effective to eliminate or reduce the molecular oxygen concentration in coolants, for example, in aqueous based or glycol based coolants. In another embodiment, the oxygen scavenger component is effective to eliminate or reduce the concentration of oxidative species in coolants, for example, in aqueous based or glycol based coolants. The oxygen scavenger component may be effective to prevent oxidative degradation of components present in solution or in dispersion in the coolant. For example, the oxygen scavenger components may prevent the oxidative degradation of freezing point depressants such as glycols, glycol based freezing point depressants and the like, other coolant additives and mixtures thereof present in the coolant. The oxygen scavenger component selected should be effective, as noted above, and have no substantial or significant detrimental effect on the coolant or the cooling system in which the coolant is used. In one embodiment, an oxygen scavenger component for use in accordance with the present invention is not intended, and preferably does not function, to form a protective complex with metal to protect the metal from degradation, for example, corrosion. Examples of oxygen scavengers which can be included in an oxygen scavenger component include without limitation, thiosulfite, thiosulfate, mercaptopropionic acid, bisulfite, hydrosulfite, dithionate, hyposulfite, sulfite, sulfide, stannous, hydroxylamine and hydrazine and the like and mixtures thereof. In one embodiment, one or more oxygen scavengers employed in an oxygen scavenger component is/are provided as a salt. Examples of oxygen scavenger salts include without limitation alkali metal (e.g., sodium or potassium), alkaline earth metal (e.g., magnesium or calcium) ammonium and the like salts. Any and all combinations of the embodiments disclosed in the present invention are included within the scope of the present invention.

Preferably, an oxygen scavenger component is released over a prolonged period of time, for example, under sustained conditions into a coolant, preferably a liquid coolant. The oxygen scavenger component is effective when released into the coolant to confer or maintain one or more benefits or beneficial properties to the coolant and/or the cooling system in which the coolant is used, in particular, the prevention of coolant degradation. The present invention may also be effective to, for example, prevent corrosion in a cooling system.

Representative coolants include, but are not limited to, liquids, such as substantially an aqueous liquid including at least one freezing point depressant, such as at least one glycol, for example ethylene glycol and/or propylene glycol; substantially a non-aqueous liquid including a freezing point depressant, such as at least one glycol, for example ethylene glycol and/or propylene glycol; and the like.

The coolant may include one or more of the following: (1) a buffering component to maintain a neutral or alkaline pH, including for example, alkali metal salts or sodium phosphates, borates and the like, (2) a cavitation liner pitting inhibitor component, including for example, alkali metal or sodium nitrites, molybdates and the like, (3) a metal corrosion and hot surface corrosion inhibitor component, including for example, alkali metal, salts of nitrates, nitrates and silicates, carboxylic acids, phosphonic acids, phosphonate, pyrophosphate, azoles, sulfonic acids, mercaptobenzothiazoles, metal dithiophosphates and metal dithiocarbonates (one particular corrosion inhibitor that has been found to be highly satisfactory is a phenolic anti-oxidant, 4,4′-methylenebis (2,6-di-tertbutylphenol) that is commercially available under the trademark Ethyl 702 manufactured by Ethyl Corporation), and the like, (4) a defoaming agent component including for example, silicone defoamers, alcohols such as polyethoxylated glycol, polypropoxylated glycol or acetylenic glycols and the like, (5) a hot surface deposition and scale inhibitor component including for example, phosphate esters, phosphino carboxylic acid, polyacrylates, styrene-maleic anhydride copolymers, sulfonates and the like, (6) a dispersing component, including for example, non-ionic and/or anionic surfactants such as phosphate esters, sodium alkyl sulfonates, sodium aryl sulfonates, sodium alkylaryl sulfonates, linear alkyl benzene sulfonates, alkylphenols, ethoxylated alcohols, carboxylic esters and the like, (7) an organic acid, including for example adipic acid, sebacic acid and the like, (8) an anti-gel such as that disclosed by Feldman et al in U.S. Pat. No. 5,094,666, the content of which is incorporated in its entirety herein by reference (for example, such anti-gel additive comprises copolymers of ethylene and vinyl esters of fatty acids with molecular weight of 500-50,000; or Tallow amine salt of phthalic anhydride, used at 0.01-0.2%; or Tallow amine salt of dithio benzoic acid, used at 0.005-0.15%; or 4-hydroxy, 3,5-di-t-butyl dithiobenzoic acid; or ethylene-vinylacetate copolymers) and/or microbiocides, for example, microbiocides used in open circulating cooling water systems of cooling towers, as disclosed by Sherbondy et al. U.S. Pat. No. 5,662,803, wherein the disclosures of which is incorporated in its entirety herein by reference.

In one embodiment, the controlled release component includes a coating or coating material encapsulating an oxygen scavenger component core which enables a reduced rate of release of the oxygen scavenger component into coolant in a cooling system, for example a circulating cooling system. Preferably, the rate of release is reduced relative to that of an identical composition without the coating material. Any type of coating conventionally known in the art which provides controlled-release properties may be used in the present invention.

A coated coolant additive composition may be of any size or any shape to accommodate the circumstance of use. For example, composition may be in the form of a single object, for example a single, puck-shaped, or “doughnut” shaped object. In one embodiment, the composition is present as a plurality of irregular or regular shaped pellets or tablets. Different shapes and sizes, and the various surface to volume ratios provided thereby, can be selected to provide a desired oxygen scavenger component release rate.

The coating or coating material may be soluble or partially soluble in the coolant. The soluble portion of the coating material may be effective, when released into the coolant, to provide a benefit to the coolant. Such coatings are highly advantageous in that they are effective both to reduce the rate of release of the oxygen scavenger component into the coolant and to provide a further benefit to the coolant when solubilized or partially solubilized into the coolant. Alternatively, the controlled release component, for example, a coating material may be substantially insoluble or insoluble in a coolant.

A coating material may constitute about 1% to about 60% of the total coolant additive composition weight. For example, the coating may constitute about 5% to about 48% or about 8% to about 30% of the total coolant additive composition weight.

In one particularly useful embodiment, the coating is a polymer dispersion. The polymer dispersion may have one or more the following properties:

1. Viscosity: The polymer dispersion may be of a low to medium viscosity. When the viscosity is to high, it may become impossible to pump the polymer dispersion through a coating system. This may cause the line and spray gun to become plugged. Also, in this case, the droplets of polymer dispersion may be too thick and difficult to lose moisture. They may not have the desired level of dryness before they reach the tablet surface. Therefore, the polymer may not form a good and homogeneous coating.

It may be noted that reducing the viscosity of a polymer dispersion through dilution with water is not always a viable solution. Often the dilution leads to changes of physical properties for the polymer dispersion and renders the polymer not appropriate for coating applications.

2. Low film forming and glass transition temperatures: Every polymer has its own characteristic film forming temperature and glass transition temperature, T _g. To form a good coating, the polymer may have a film forming temperature lower than the operating temperatures inside the chamber of the drum coater in the coating process. A high T_gmay lead to a brittle and fragile film which may easily peel off. Generally, a polymer with lower film forming temperature and T_gforms better film than those polymers with higher corresponding temperatures.

3. Good film forming ability onto tablet surface: In the early stage of coating process, the polymer may have good adherence to the tablet surface, so that the coating film can gradually build up. The polymer particles may pack well without large spaces or holes in between. This can be examined and confirmed under a microscope. The polymer with small particle size will result in better packing. Preferably, the polymer possesses good elasticity; otherwise, the coating may crack, especially upon cooling.

4. Insolubility of the polymer in an operating aqueous system: Typically, an operating aqueous system, has high temperatures. For example, an operating open circulating cooling water system may be about 70 degrees F. to about 150 degrees F., for example, about 80 degrees F. to about 100 degrees F., or about 90 degrees F. to about 95 degrees F. The polymer coatings may remain insoluble and stable in these systems. If the polymer coating dissolves, it may lose the slow release function.

5. Stability of polymer coating in solutions of aqueous systems under operating conditions: Many polymers degrade because they undergo alkaline hydrolysis reaction in operating aqueous system conditions. As degradation or dissolution occurs, the coating is damaged. As a result, the coating forms holes and loses the control of slow release. Subsequently, all chemical ingredients rapidly enter the bulk cooling.

Without wishing to limit the invention to any particular mechanism or theory of operation, it is believed that the release of the oxygen scavenger component from a coolant additive composition which comprises a polymer coating material into the coolant involves three steps: (a) coolant enters the coolant additive composition through the polymer coating; (b) chemical ingredients of the coolant additive composition dissolve in contact with cooling; and (c) the resulting concentrated solution diffuses through the polymer coating back into the bulk of the coolant. The path and size of channels, microscopically, within the polymer coating, which are characteristics of each specific polymer and are closely related to the physical properties of each polymer in coolant at elevated temperatures, may control the kinetics of these actions.

Suitable polymers useful in forming a controlled release component, for example, a coating material include, for example, homopolymers, copolymers and mixtures thereof, wherein the monomer units of the polymers may be derived from ethylenically unsaturated monomers, for example, two different such monomers.

A particularly useful ethylenically unsaturated monomer is compound I with the formula (R ₁) (R₂) (R₃)C—COO—(CH═CH₂), wherein R₁, R₂and R₃are saturated alkyl chains. In one embodiment, R₃of compound I is CH₃, and R₁and R₂of compound I have a total of about 2 to about 15 carbons; such a molecule is also known as a vinylversatate. In a one embodiment, R₃is CH₃, and R₁and R₂have a total of about 5 to about 10 carbons. In another embodiment, R₃is CH₃, and R₁and R₂have a total of 7 carbons., i.e. R₁+R₂═C₇H₁₆.

In one embodiment, each of the R ₁, R₂, and R₃of compound I is a single chemical element. For example, the element may be a hydrogen. Compound I having a hydrogen as the element for R₁, R₂and R₃is known as vinylacetate.

In another embodiment, R ₁of compound I may be a single chemical element, and R₂of compound I may be a saturated alkyl chain.

Other examples of ethylenically unsaturated monomers that may be used in accordance with the present invention include: monoolefinic hydrocarbons, i.e. monomers containing only carbon and hydrogen, including such materials as ethylene, ethylcellulose, propylene, 3-methylbutene-1, 4-methylpentene-1, pentene-1,3,3-dimethylbutene-1, 4,4-dimethylbutene-1, octene-1, decene-1, styrene and its nuclear, alpha-alkyl or aryl substituted derivatives, e.g., o-, or p-methyl, ethyl, propyl or butyl styrene, alpha-methyl, ethyl, propyl or butyl styrene; phenyl styrene, and halogenated styrenes such as alpha-chlorostyrene; monoolefinically unsaturated esters including vinyl esters, e.g., vinyl propionate, vinyl butyrate, vinyl stearate, vinyl benzoate, vinyl-p-chlorobenzoates, alkyl methacrylates, e.g., methyl, ethyl, propyl, butyl, octyl and lauryl methacrylate; alkyl crotonates, e.g., octyl; alkyl acrylates, e.g., methyl, ethyl, propyl, butyl, 2-ethylhexyl, stearyl, hydroxyethyl and tertiary butylamino acrylates, isopropenyl esters, e.g., isopropenyl acetate, isopropenyl propionate, isopropenyl butyrate and isopropenyl isobutyrate; isopropenyl halides, e.g., isopropenyl chloride; vinyl esters of halogenated acids, e.g., vinyl alpha-chlorocetate, vinyl alpha-chloropropionate and vinyl alpha-bromopropionate; allyl and methallyl compounds, e.g., allyl chloride, ally alcohol, allyl cyanide, allyl chlorocarbonate, allyl nitrate, allyl formate and allyl acetate and the corresponding methallyl compounds; esters of alkenyl alcohols, e.g., beta-ethyl allyl alcohol and beta-propyl allyl alcohol; halo-alkyl acrylates, e.g., methyl alpha-chloroacrylate, ethyl alpha-chloroacrylate, methyl alphabromoacrylate, ethyl alpha-bromoacrylate, methyl alpha-fluoroacrylate, ethyl alpha-fluoroacrylate, methyl alpha-iodoacrylate and ethyl alpha-iodoacrylate; alkyl alpha-cyanoacrylates, e.g., methyl alpha-cyanoacrylate and ethyl alpha-cyanoacrylate and maleates, e.g., monomethyl maleate, monoethyl maleate, dimethyl maleate, diethyl maleate; and fumarates, e.g., monomethyl fumarate, monoethyl fumarate, dimethyl fumarate, diethyl fumarate; and diethyl glutaconate; monoolefinically unsaturated organic nitriles including, for example, fumaronitrile, acrylonitrile, methacrylonitrile, ethacrylonitrile, 1,1-dicyanopropene-1, 3-octenonitrile, crotononitrile and oleonitrile; monoolefinically unsaturated carboxylic acids including, for example, acrylic acid, methacrylic acid, crotonic acid, 3-butenoic acid, cinnamic acid, maleic, fumaric and itaconic acids, maleic anhydride and the like. Amides of these acids, such as acrylamide, are also useful. Vinyl alkyl ethers and vinyl ethers, e.g., vinyl methyl ether, vinyl ethyl ether, vinyl propyl ether, vinyl n-butyl ether, vinyl isobutyl ether, vinyl 2-ethylhexyl ether, vinyl-2-chloroethyl ether, vinyl propyl ether, vinyl n-butyl ether, vinyl isobutyl ether, vinyl-2-ethylhexyl ether, vinyl 2-chloroethyl ether, vinyl cetyl ether and the like; and vinyl sulfides, e.g., vinyl beta-chloroethyl sulfide, vinyl beta-ethoxyethyl sulfide and the like. Other useful ethylenically unsaturated monomers are styrene, methyl methacrylate, and methyl acrylate.

The coating material may be a mixture of polymers selected to achieve a desired release rate hardness and/or solubility. In one embodiment, the polymer forming the coating is made up of a copolymer of vinylacetate and vinylversatate. In a one embodiment, about 45% to about 95% by weight of the units are from vinylacetate and about 5% to about 55% by weight of the units are from vinylversatate. In one embodiment, about 65% by weight of the units are from vinylacetate and about 35% by weight of the units are from vinylversatate.

The vinylversatate used may be sold under the trademark VEOVA 10 sold by Shell Chemicals. In one embodiment, the water-based emulsion polymer is a vinylacetate-vinylversatate copolymer, sold under the trademark EMULTEX VV575 sold by Harlow Chemical Co. (England). Additionally, a surfactant may also be added to stabilize the dispersion. In one embodiment, the polymer solid in the dispersion is about 54% to about 56% by weight of active polymer solid.

EMULTEX VV575 is particularly advantageous because it meets all of the six requirements for a good coating as set forth above. That is, it (1) exhibits a viscosity low enough for coating processing without difficulties, for example about 500 to about 1,500 mPa.s (RVT 2-20 at 23° C.), (2) has a film forming temperature of 10 degrees C. and a glass transition temperature, T _g, of 11 degrees C., low enough for forming a good coating, (3) has a fine to medium particle size of 0.37 micron and forms an elastic coating, (4) is insoluble in coolings at operating engine conditions, (5) is stable in coolings at operating engine conditions and (6) gives excellent release rates for ingredients.

In one embodiment, a copolymer which may be used as a coating in accordance with this invention includes acrylate-vinylversatate. For example, NeoCAR 820 sold by Union Carbide may be used for forming coatings.

A polymer forming a coating in accordance with this invention may be made up of a copolymer of vinylacetate and ethylene. In one embodiment, about 45% to about 95% by weight of the units are from vinylacetate and about 5% to about 55% by weight of the units are from ethylene. In another embodiment, about 60% to about 80% by weight of the units are from vinylacetate and about 30% to about 40% by weight of the units are from ethylene. In still another embodiment, about 90% by weight of the units are from vinylacetate and about 10% by weight of the units are from ethylene. A controlled release component of the present invention may advantageously comprise about 5% to about 15% of a vinylacetate-ethylene copolymer.

A copolymer comprising vinylacetate and ethylene may be purchased under the trade name AirFlex 410, sold by Air Products and Chemicals, Inc., Allen Town, Pa., U.S.A. Such copolymer may have a viscosity of about 250 to about 900 cps.

In another embodiment, the polymer for coating is made up of a homopolymer. The monomer unit of the homopolymer may be ethylcellulose. Ethylcellulose may be used for forming coatings is purchased from Dow Chemical sold under the trademark ETHOCEL S10, S20, S45 and S100.

Specific properties of the various ETHOCEL's are determined by the number of anhydrous units in the polymer chain (expressed by the molecular weight or the solution viscosity), and, the degree of ethoxyl substitution (expressed as the percent of hydroxyl group, —OH, in cellulose substituted by ethoxyl group, —OC ₂H₅). ETHOCEL S45 has a solution viscosity of about 41 to about 49 cP and about 48 to about 49.9% ethoxyl content. The viscosity is for a 5% solution in 80/20 toluene/ethanol measured at 25 degrees C. in an Ubbelohde viscometer.

Controlled release components may include a matrix material. The matrix material may be effective to reduce a release rate of the oxygen scavenger component from the coolant additive composition into the coolant, for example, relative to an identical coolant additive composition without the controlled release component. The level of oxygen scavenger component in the circulating coolant is thereby stabilized, maintained or replenished.

It is to be appreciated that a matrix material may comprise a material that is soluble or partially soluble in a liquid coolant. For example, a coolant additive composition in accordance with the present invention may comprise a coolant-soluble matrix material mixed with an oxygen scavenger component, wherein the soluble matrix material provides sustained oxygen scavenger component release by gradually dissolving into the coolant, thereby gradually releasing the oxygen scavenger component located in the matrix material. Preferably, a suitable soluble matrix material dissolves cleanly in the coolant without clogging or otherwise degrading components of the cooling system. In one useful embodiment, the coolant soluble matrix material, when dissolved in the coolant also functions as an additive, that is acts to provide at least one benefit to the coolant. Alternatively, a matrix material may be substantially soluble or substantially insoluble.

The matrix material may be effective to allow the coolant additive composition to be compressed into, and maintain the shape of, for example, a pellet or tablet. Particularly useful such matrix materials include, without limitation, dispersants, polyvinyl pyrrolidone, acrylates, for example, sodium acrylate and sodium polyacrylate, carboxymethylcellulose, metal carboxymethylcelluloses, for example, sodium carboxymethylcellulose, hydroxypropylcellulose, metal hydroxypropylcelluloses, for example, sodium hydroxypropylcellulose, corn starch, microcrystalline cellulose, propylene glycol, ethylene glycol, silicates, for example, sodium silicate and potassium silicate, methacrylate/acrylate copolymers, metal lignosulfonate, for example, sodium lignosulfonate and water.

In one embodiment, the matrix material includes one or more polymeric materials. A suitable polymeric material for use in the compositions of the present invention may remain stable in a high temperature cooling system. In one embodiment, the polymeric material has a melting point in excess of the coolant operating temperature, for example, a melting point in the range of about 50° C. to about 200° C., or, for example, about 120° C. to about 150° C. or higher. In one embodiment, the polymeric material is insoluble or partially soluble in the coolant at the operating temperature of the cooling system.

The matrix material may be a viscous liquid, a gel or a solid. The matrix material, e.g., in a molten form or a soluble form, is combined, for example, mixed with the oxygen scavenger component. After the mixing step, the oxygen scavenger component/matrix mixture is formed into one or more discrete units having irregular or regular shape and size. The polymeric material may be at least partially soluble in the coolant and, in one very useful embodiment, may be useful to provide a benefit to the coolant.

A coolant additive composition comprising a matrix material may be of any size or any shape to accommodate the circumstance of use. For example, composition may be in the form of a single object, for example a single, substantially spherical shaped or puck-shaped, or “doughnut” shaped object. In one embodiment, the composition is present as a plurality of irregular or regular shaped pellets, tablets, etc. Different shapes and sizes and the various surface to volume ratios provided thereby, can be selected to provide a desired oxygen scavenger component release rate.

Without wishing to limit the invention to any mechanism or theory of operation, it is believed that when these discrete units of oxygen scavenger component/matrix material are placed in contact with coolant in a cooling system, the solid polymeric material serves as a physical barrier between the coolant and the oxygen scavenger component to limit the rate of exposure of the oxygen scavenger component to the coolant, and thus reduce the rate of diffusion of the oxygen scavenger component into the coolant.

The polymeric material may include polymer repeating units derived from an olefin component having 2 to about 12 atoms per molecule. Such polyolefins are generally polymers of unsubstituted, aliphatic hydrocarbon olefins of 2 to about 12 carbon atoms, and are more particularly polymers of an unsubstituted, aliphatic hydrocarbon olefin of 2 to about 12 carbon atoms and a substituted, aliphatic hydrocarbon olefin of 2 to about 12 carbon atoms. In one embodiment, the polymeric material is oxidized. In another embodiment, the polymeric material is amidized.

The matrix material may include an aliphatic acid component, for example, as aliphatic acid component which includes aliphatic acid molecules having about 18 or about 28 to about 36 carbon atoms. A particularly useful aliphatic acid component is montanic acid, nominally C ₂₈H₅₆O₂. Suitable aliphatic acid components, for example, montanic acids may have melting points from about 76° C. to about 87° C., for example, about 76° C., to about 81° C. The aliphatic acid component may have a melting point of at least about 80° C. or at least about 82° C. Montanic acids with these characteristics are known, for example, under the trade name S-Wachs.

Other polymeric materials are also capable of forming the controlled release component comprising, for example, a matrix material. These polymeric materials include: ethylcellulose, cellulose, silicones, rubbers, fatty and synthetic surfactants, thermoplastic resins, adsorbents (clays) and mixtures thereof.

Polyolefins may be prepared from unsubstituted, aliphatic hydrocarbon monoolefins, including straight chain and branched chain compounds such as ethylene, propylene and butene-1, isobutene, pentene, hexene, heptene, octene, isobutene, 3-methylbutene-1, 4-methylpentene-1, 4-methylhexene-1, and 5-methylhexene-1.

The polyolefin may contain an unsubstituted, aliphatic hydrocarbon polyene, such as diene or triene, as a monomer unit. Such unsubstituted compounds can be straight chain, branched chain or cyclic compounds. In certain embodiments polyenes of from about 4 to about 12 carbon atoms are employed.

Suitable comonomers for preparing the polyolefins are those utilized to prepare homopolymers as listed above such as propene or butene-1 with ethylene or isobutylene with isoprene and the like. Suitable termonomers are those utilized to prepare homopolymers and copolymers as disclosed above such as propene, ethylene and the like containing up to 15 percent, for example, up to about 10 percent by weight of polyene, for example, a diene such as dicyclopentadiene, 1,3-butadiene, 1,5-cyclooctadiene, 2-ethylidenenorbornene-5, 1,4 hexadiene, 1,4-heptadiene, bicyclo (2.2.1)hepta-2,5-diene and other conjugated and especially non-conjugated dienes with linear or cyclic chains.

Trienes such as isopropylidene cyclopentadiene and the Diels-Alder mono- and di-adducts thereof with cyclopentadiene can be used in place of the diene.

Unsubstituted aliphatic diolefins can also be used for preparing useful polyolefins such as butadiene, isoprene, octadiene, and the like. Especially useful are the various forms of polybutadiene, such as made in emulsion, suspension or solution processes, and random, block, and star block polymers with monomers such as styrene.

In another embodiment, the polymeric material further includes different polymer repeating units derived from an ethylenically unsaturated monomer. In one embodiment, such polymeric material is polyethylene.

In one embodiment, the polymeric material is a copolymer of ethylene and vinyl acetate, for example, a polyethylene/vinyl acetate copolymer sold by Dupont under its trademark ELVAX. Polyethylene/vinyl acetate copolymer is able to withstand very high temperatures. The polymeric material may be a copolymer of ethylene and butylene.

In another embodiment, the polymeric material is polypropylene, for example polypropylene wax , e.g., having a molecular weight of about 500,000. Such polypropylene is sold under the trademark Coathylene PY 0787F. Other ethylenically unsaturated monomers include ethylene-propylene copolymers ranging in molecular weight from about 200,000 to about 300,000; ethylene-ethylacrylate polymers ranging in molecular weight from about 200,000 to about 300,000. A polyisobutylene ranging in molecular weight from approximately about 60,000 to about 135,000 may be. Repeating units derived from an ethylenically unsaturated monomer used to form the polymeric material includes: monoolefinic hydrocarbons, i.e. monomers containing only carbon and hydrogen, including such materials as ethylene, propylene, 3-methylbutene-1, 4-methylpentene-1, pentene-1,3,3-dimethylbutene-1, 4,4-dimethylbutene-1, octene-1, decene-1, styrene and its nuclear, alpha-alkyl or aryl substituted derivatives, e.g., o-, - or p-methyl, ethyl, propyl or butyl styrene, alpha-methyl, ethyl, propyl or butyl styrene; phenyl styrene, and halogenated styrenes such as alpha-chlorostyrene; monoolefinically unsaturated esters including vinyl esters, e.g., vinyl acetate, vinyl propionate, vinyl butyrate, vinyl stearate, vinyl benzoate, vinyl-p-chlorobenzoates, alkyl methacrylates, e.g., methyl, ethyl, propyl, butyl, octyl and lauryl methacrylate; alkyl crotonates, e.g., octyl; alkyl acrylates, e.g., methyl, ethyl, propyl, butyl, 2-ethylhexyl, stearyl, hydroxyethyl and tertiary butylamino acrylates, isopropenyl esters, e.g., isopropenyl acetate, isopropenyl propionate, isopropenyl butyrate and isopropenyl isobutyrate; isopropenyl halides, e.g., isopropenyl chloride; vinyl esters of halogenated acids, e.g., vinyl alpha-chloroacetate, vinyl alpha-chloropropionate and vinyl alpha-bromopropionate; allyl and methallyl compounds, e.g., allyl chloride, ally alcohol, allyl cyanide, allyl chlorocarbonate, allyl nitrate, allyl formate and allyl acetate and the corresponding methallyl compounds; esters of alkenyl alcohols, e.g., beta-ethyl allyl alcohol and beta-propyl allyl alcohol; halo-alkyl acrylates, e.g., methyl alpha-chloroacrylate, ethyl alpha-chloroacrylate, methyl alphabromoacrylate, ethyl alpha-bromoacrylate, methyl alpha-fluoroacrylate, ethyl alpha-fluoroacrylate, methyl alpha-iodoacrylate and ethyl alpha-iodoacrylate; alkyl alpha-cyanoacrylates, e.g., methyl alpha-cyanoacrylate and ethyl alpha-cyanoacrylate and maleates, e.g., monomethyl maleate, monoethyl maleate, dimethyl maleate, diethyl maleate; and fumarates, e.g., monomethyl fumarate, monoethyl fumarate, dimethyl fumarate, diethyl fumarate; and diethyl glutaconate; monoolefinically unsaturated organic nitriles including, for example, fumaronitrile, acrylonitrile, methacrylonitrile, ethacrylonitrile, 1,1-dicyanopropene-1, 3-octenonitrile, crotononitrile and oleonitrile; monoolefinically unsaturated carboxylic acids including, for example, acrylic acid, methacrylic acid, crotonic acid, 3-butenoic acid, cinnamic acid, maleic, fumaric and itaconic acids, maleic anhydride and the like. Amides of these acids, such as acrylamide, are also useful. Vinyl alkyl ethers and vinyl ethers, e.g., vinyl methyl ether, vinyl ethyl ether, vinyl propyl ether, vinyl n-butyl ether, vinyl isobutyl ether, vinyl 2-ethylhexyl ether, vinyl-2-chloroethyl ether, vinyl propyl ether, vinyl n-butyl ether, vinyl isobutyl ether, vinyl-2-ethylhexyl ether, vinyl 2-chloroethyl ether, vinyl cetyl ether and the like; and vinyl sulfides, e.g., vinyl beta-chloroethyl sulfide, vinyl beta-ethoxyethyl sulfide and the like can also be included as can diolefinically unsaturated hydrocarbons containing two olefinic groups in conjugated relation and the halogen derivatives thereof, e.g., butadiene-1,3; 2-methylbutadiene-1,3, 2,3-dimethylbutadiene-1,3; 2-methylbutadiene-1,3; 2,3-dimethylbutadiene-1,3; 2-chlorobutadiene-1,3; 2,3-dichloro-butadiene-1,3; and 2-bromo-butadiene-1,3 and the like. Mixtures of the foregoing compounds can also be employed. Particularly useful monomer compositions also include styrene, methyl methacrylate, methyl acrylate, vinyl acetate, mixtures of styrene and acrylonitrile, and mixtures of styrene and various maleates.

In one embodiment, the matrix material may be a mixture of polymers selected to achieve a desired release rate, hardness and/or solubility. Such mixtures may include, for example, polyethylene/polypropylene, and/or ethylene/butylene. The controlled matrix material may further serve as a structural agent to the coolant additive composition by retaining the shape of the composition.

To form an oxygen scavenger component/matrix coolant additive composition in accordance with the present invention, an oxygen scavenger component may be physically mixed with the matrix material in molten form and allowed to solidify in a mold. In another example a solid (e.g., a powder) oxygen scavenger component may be mixed with a solid (e.g., a powder) matrix component and the mixture is pressed into a shape, for example a pellet.

In one embodiment, the matrix material may be a one-component or multiple component cure. For example, a monomer with catalyst or a two part polymer, such as an epoxy or urethane, that is mixed with the oxygen scavenger component and will polymerize and harden to a solid.

In one embodiment, a controlled release component, for example a matrix material is partially soluble in the coolant. The controlled release component may include a portion which is soluble in the coolant and is effective when released into the coolant, for example, when solubilized into the coolant, to provide a benefit to the coolant. Thus, the matrix material may be effective not only to reduce the release rate of the oxygen scavenger component into the coolant, but in addition, can also act as an additional additive component in that the coolant is provided with a benefit when the soluble portion of the controlled release component is released into the coolant.

In accordance with the present invention, the controlled release component may be a matrix material and/or a coating material. In one embodiment of the invention, the coolant additive composition of the present invention includes an outer coating material which encases the discrete units of oxygen scavenger component/matrix material. The polymeric material or materials used to produce the controlled release component (e.g. matrix material and/or coating material) can be selected or chosen so that a portion of the polymeric material or materials in the controlled release component is soluble in the coolant. The materials included within the controlled release component can be customized to provide the desired degree of coolant solubility and a desirable benefit to the coolant when the soluble portion is solubilized in the coolant. Such partially soluble controlled release components are included within the scope of the present invention. If the coating material is coolant-insoluble, the coating may be sufficiently porous, or breakable when exposed to high temperature coolant, to allow the coolant to penetrate or break the coating and contact the oxygen scavenger component/matrix material encased therein.

If both a matrix material and a coating material are present, the release rate of the oxygen scavenger component from the coolant additive composition may be reduced relative to an identical coolant additive composition without one of the matrix material and the coating material.

In one embodiment, the coolant additive composition is layered. For example, the innermost core of the coolant additive composition may be a mixture of an oxygen scavenger component and a first matrix material. The next layer of the coolant additive composition may be a mixture of an oxygen scavenger component and a matrix material different from the first. Alternatively, the next layer may be a mixture of the oxygen scavenger component and the matrix material of the first layer, but having a different mixture ratio. The coolant additive composition of the present invention may include more than one layer to achieve a varied release pattern. In one embodiment, the coolant additive composition comprises more than two layers. In another embodiment, the coolant additive composition comprises more than three layers. Such layered coolant additive composition provides for a variable release profile, for example, a pattern of release varying between low and high. For example, the coolant additive composition may include an outer layer structured to provide a minimal, low level rate of oxygen scavenger release and an inner layer structured to provide a relatively higher rate of oxygen scavenger release.

Other arrangement schemes may serve to vary the release pattern of the oxygen scavenger component. For example, an additive composition of the present invention may comprise an oxygen scavenger component which is mixed with a matrix material which is then formed into discrete pellets, which are then mixed with another matrix material and then formed into a unitary object sized and shaped to be placed within a coolant line of a cooling system.

In one embodiment, a coolant additive composition of the present invention may further include a release enhancer component to increase the release rate. A release enhancer component may be selected from wicking materials, surfactants, for example, non-ionic surfactants, e.g., polyoxyethylene-polyoxypropylene block copolymers and the like, and mixtures thereof. Such wicking materials may include, without limitation, cotton and polyester fibers and mixtures thereof. The fibers provide a wicking mechanism for exposing coolant to inner portions of the coolant additive composition.

In one embodiment, a coolant additive composition of the present invention may further include a reinforcement component to reinforce the structure of the coolant additive composition, making it less susceptible to erosion by flowing coolant. Such a component may include, for example, fibers, for example, cotton, polyester and/or fiberglass fibers.

Release-enhancer components and reinforcement components may be added to the matrix material and or coating material. For example, one or more of these components may be added to a matrix material prior to, or during, mixing of the matrix material with the oxygen scavenger component.

The rate of release of the oxygen scavenger component may be adjusted by the relative percentage of matrix material to oxygen scavenger component. For example, more matrix material content in the coolant additive composition generally may reduce the rate of oxygen scavenger component release. In one embodiment, the matrix material constitutes about 1% to about 99% of the total coolant additive composition weight. In a one embodiment, the matrix material constitutes about 25% to about 70%. For example, the matrix material may constitute about 50% of the total coolant additive composition weight.

In the embodiment of the present invention in which the composition comprises a coated oxygen scavenger component/matrix material composition, the rate at which the oxygen scavenger component is to be released may be adjusted by the thickness of the coating and/or the relative percent of matrix material content to oxygen scavenger component. For example, the coating material may constitute about 1% to about 50% of the total coolant additive composition weight. For example, the coating may constitute about 8% to about 25% of the total coolant additive composition weight. In addition, the matrix material may constitute about 5% to about 90% of the total coolant additive composition weight, for example, about 15% to about 70% of the total coolant additive composition weight.

The coolant additive composition may include a die release agent. Suitable die release agents include, for example, calcium stearate, magnesium stearate, zinc stearate, stearic acid, propylene glycol, ethylene glycol, polyethylene glycol, polypropylene glycol, polyoxypropylene-polyoxyethylene block copolymers, microcrystalline cellulose, kaolin, attapulgite, magnesium carbonate, fumed silica, magnesium silicate, calcium silicate, silicones, mono-and dicarboxylic acids and corn starch.

The coolant additive compositions of the present invention may be in the form of a single object, for example a single, puck-shaped, or “doughnut” shaped object. In one embodiment, the composition is present as a plurality of irregular or regular shaped pellets, tablets, etc. Different shapes and sizes and the various surface to volume ratios provided thereby, can be selected to provide a desired oxygen scavenger component release rate.

In one embodiment, the coolant additive composition is in the form of a cylindrical tablet. The tablet may be of any size and any shape. For example, the tablet may be about 9 mm length×about 9 mm diameter. Alternatively, the tablet may be substantially cubical with all sides being about 9 mm. In yet another embodiment, the coolant additive composition is a flat puck with a central aperture. The puck may have, for example, an outside diameter of about 8 cm, an inside diameter of about 5 cm and a height of about 3 cm.

In one embodiment, release of an oxygen scavenger component into a coolant in a cooling system may be achieved by use of a container which includes a casing, for example, a coolant-insoluble and coolant-impermeable casing, having or defining a substantially hollow interior. The casing has at least one opening. The casing may have any suitable shape and size, which are often chosen to be compatible with the particular application involved. The casing, for example, may have a generally cylindrical shape, a generally bowl shape or any of a large number of other shapes. The casing may have one or more curved and/or planar walls or it can have all curved or planar walls. Further aspects of containers that may be used in accordance with the present invention are included in U.S. patent application Ser. No. 09/939,527 which is incorporated in its entirety herein by reference.

The coolant additive composition provided within a container of the invention comprises at least one oxygen scavenger effective when released into the coolant to confer or maintain one or more benefits or beneficial properties to the coolant and/or the cooling system in which the coolant is used. The coolant additive composition may be provided in the form of a liquid, gel, paste or solid particles, for example, beads, tablets, pellets or grains, and the like, as well as mixtures thereof, within the casing. A coolant additive composition of the invention can advantageously further comprise a coating material that at least partially surrounds or encapsulates or coats the oxygen scavenger component, as discussed elsewhere herein. Such coating material may be provided in order to at least assist in controlling, or to control, the release of oxygen scavenger component from the casing, as desired. The coating material may be either coolant-soluble or coolant insoluble. The coating on the oxygen scavenger component may be such as to allow or permit at least some release of oxygen scavenger component from the casing into the coolant.

The coolant additive compositions of the present invention may be provided within a container and may include a matrix material. The matrix material, if any, should be such as to allow or permit release of the oxygen scavenger component from the casing into the coolant. The matrix material advantageously is effective to at least assist in controlling, or to control, the release of the oxygen scavenger component into the coolant.

In one embodiment, the oxygen scavenger component is present in the casing and no matrix material and no coating material are employed. In another embodiment, the oxygen scavenger component is present in the casing and both a matrix material and a coating material are employed.

In one embodiment, a container for use in the present invention may include a coolant-permeable element or elements such as a polymer-containing membrane, for example, a polymer-coated membrane, in order to achieve enhanced oxygen scavenger component release control. The membrane may be suitably coated, impregnated or otherwise associated, for example, by spray coating, dip coating and the like, with a polymer material. Suitable polymer materials include without limitation, coolant insoluble materials which have no significant detrimental effect on the coolant being treated, on the oxygen scavenger components in the casing or on the performance of the present container. Examples of such coating materials include those listed by Mitchell et al U.S. Pat. No. 6,010,639, the disclosure of which is incorporated in its entirety herein by reference. One useful polymer material is polyethylene vinyl acetate copolymer. In addition, or alternatively, a retention member(s) of the coolant-permeable element or elements can be coated, impregnated, or otherwise associated with a material, for example, a coolant-insoluble polymer material, such as those disclosed in Mitchell et al U.S. Pat. No. 6,010,639, to at least assist in controlling or to control, release of the oxygen scavenger composition from the casing, as desired.

In a one embodiment, a coating material can also be used to coat an aforementioned membrane of the invention. Moreover, a preferred release rate for oxygen scavenger component through the membrane can be provided by adjusting the coating thickness to produce the preferred release rate. Suitable film forming polymers may include, for example, homopolymers, copolymers, and mixtures thereof, wherein the monomer units of the polymers may be derived from ethylenically unsaturated monomers or cellulose derivatives.

A coating material is applied to the membrane by any suitable method. Certain methods include dipping, spray coating, and drum or pan coating. In one embodiment, a coating material is spray-coated onto the membrane in an amount ranging from about 1% to about 95% by weight of the membrane.

The container of the present invention may be filled with an oxygen scavenger component through the opening or openings of the casing or otherwise.

The containers of the invention, for example, the casings of the containers, may include one or more coolant-impermeable cap members or coolant-impermeable plugs, which can be detachable or removable from the casing or the remainder of the casing, for example, to facilitate filling the interior space of the casing with coolant additive composition.

In one embodiment of the present invention wherein the casing is substantially cylindrical shaped and the opening or openings are located at the end or ends of the casing, one or both ends of the casing may include a cap member, with at least one of the cap members being removable to allow the casing or cartridge to be filled or refilled with coolant additive composition. Another open end of the casing, if desired, may include a cap member that is permanently sealed thereto, for example, during manufacture, for example, during injection molding of the container. Whenever the cap or plug is attached by threading or screwing it onto the casing, screw threads can be applied to the respective pieces during or after molding with suitable dies or within the mold. The cap member can alternatively be applied to the casing by a press fit. In this case, suitable tolerances to make a snap fit between the casing and the end piece can be provided, for example, to the plastic injection molds used to make the respective pieces. The end piece can also be formed integrally with the casing, e.g., during injection molding.

The cap or end piece used to close at least one end of the casing containing the oxygen scavenger component typically is provided with at least one opening to permit release of oxygen scavenger component therethrough, and to provide fluid communication between the coolant located exterior to the container and the coolant additive composition disposed within the casing interior. Whenever an end piece is formed integrally with the casing, the opening can be provided therein during or after formation of the casing, for example, by injection molding.

It will be appreciated by those of skill in the art that release of an oxygen scavenger component into a cooling system utilizing a container of the present invention is provided, and the release rate may be substantially controlled by several factors. The following factors, as well as others, may also have an effect on the performance and effectiveness of the containers of the present invention. For example, where a membrane is used, a desired oxygen scavenger component release rate may be obtained by appropriate selection of: the number and type of membrane layers; membrane thickness; membrane composition; surface area of the membrane; membrane pore size, if any; the presence, type and amount, if any, of polymer associated with, e.g., coated, on a support member or membrane and/or retention member; and the presence, type and amount, if any, of the matrix material in and/or coating on the oxygen scavenger component, if any. The rate of release may also be influenced by the number and size of openings in the casing, the type and form of oxygen scavenger in the coolant additive composition, solubility of the oxygen scavenger, coolant temperature, and velocity of coolant through the coolant line, viscosity of oxygen scavenger component and/or coolant additive composition, surface tension and membrane wetting ability of the oxygen scavenger, operating temperature and the like factors.

Contemplated within the invention is a method for releasing an oxygen scavenger component at a controlled rate into a liquid coolant. The method comprises placing a coolant in contact with a coolant additive composition. In one embodiment, a coolant contacts a coolant additive composition which is contained in a container or cartridge as described herein. The container or cartridge configuration described herein preferably permits a release, preferably a controlled release, of oxygen scavenger component from the casing interior into the coolant. It is contemplated that, in some configurations, coolant is permitted to flow around and encircle the casing containing the oxygen scavenger component. However, even in these configurations, release of oxygen scavenger component is preferably sustained and/or controlled, for example, by passive diffusion, rather than by forced flow of coolant through the casing.

A oxygen scavenger component for use in a container or cartridge of the invention may be provided as a liquid, gel, paste or as particles, for example, beads, tablets, pellets, grains, coated versions of these, and the like, as well as mixtures thereof. The particles have a physical size large enough to prevent passage through the coolant-permeable components of the invention as described elsewhere herein.

A solid coolant additive composition of the present invention may be shaped and sized in a manner that facilitates its handling, and conveniently is molded in the form of a pellet or tablet having a spherical or irregular shape. It may be large enough to avoid passing through porous components, if any, used to retain the oxygen scavenger component composition in the casing of the container.

Such tablets or pellets can break apart upon exposure to coolant, however, in certain embodiments, the fragmented particles are retained by a porous component, with dissolution occurring inside the vessel.

In one embodiment, a concentrated solution of oxygen scavenger is formed within the container, which is permitted to pass, e.g., diffuse through a membrane as desired for combining with the coolant. The rate of diffusion is controlled by parameters including flow rate and temperature of the coolant, pore size, orifice diameter, the presence or absence of a coating material on the porous membrane, the presence or absence of a membrane, the inclusion of a plug between the membrane and oxygen scavenger material to further restrict release, oxygen scavenger component solubility and the presence or absence of a coating material and/or matrix material, and the like. Each dimension of length, width and thickness of the particle may be in the range from about {fraction (1/32)} inch to about 3 inch. Suitable binders may be used, as known in the art, and include water-soluble acrylates, cellulosics, polyglycols, and silicates. The coolant additive composition may include one or more additional materials used, for example, to strengthen, stabilize and/or otherwise enhance the composition.

A device of the present invention can be placed in a coolant filter, either upstream or downstream of the filter medium, or it can be provided in a substantially fixed position in a coolant line, either upstream or downstream of a coolant filter.

The invention will now be described with reference to certain examples. These examples are non-limiting and serve only to illustrate certain aspects of the present invention.

EXAMPLES

Example 1

Oxygen Scavenger Added to a Commercial Coolant at Specified Intervals

A commercial coolant based on propylene glycol was placed in a sealed, stainless steel vessel and stirred and heated to simulate operation of an internal combustion engine. Periodically the vessel and coolant were cooled and air was bubbled through the vessel to introduce oxygen in the coolant. Coolant samples were removed periodically and analyzed for test parameters indicative of coolant degradation (pH, reserve alkalinity, glycol oxidation products and corrosion inhibitors). In this first experiment, the values for these parameters at the end of the test were similar to those of coolant used in a diesel engine for 200,000 to 300,000 miles. The coolant was no longer considered suitable for use. [0112]
In a second experiment, the same type of coolant was subjected to these same conditions except that the vessel was kept sealed and no air was allowed to enter the system. In this case, coolant degradation was not detectable. [0113]
In a third experiment, the same type of coolant was again subjected to the same conditions as described for the first experiment except that sodium sulfite, an oxygen scavenger, was added to the coolant at specified intervals. Coolant samples were removed periodically and analyzed for test parameters indicative of coolant degradation. The values for these parameters at the end of the test showed much less degradation of the coolant than in the first experiment. These results demonstrate that use of an oxygen scavenger in an engine coolant has the beneficial effect of decreasing the degradation of the coolant. [0114]

Example 2

Forming a Coolant Additive Composition/Matrix Material Composition

One or more oxygen scavenger additive(s) in solid form, for example, powder or granules, or in liquid form are mixed with a matrix material comprising molten polyethylene wax. The materials are mixed only long enough to distribute the oxygen scavenger additive(s) somewhat uniformly throughout the molten wax. The pellets or granules are not dissolved into the molten wax, but retain substantially their original pellet or granular form. While in the molten state, the oxygen scavenger additive/polyethylene wax mixture is then deposited into a mold to form a flat puck-shaped form, the puck-shaped form having a central hole an outside diameter of 8 cm, an inside diameter of 5 cm and a height of 3 cm. The mixture is allowed to solidify while in the mold and then the solid puck-shaped composition is removed from the mold. Alternately, the molten oxygen scavenger additive/polyethylene wax mixture is cooled to form small pellets, which can be considered pastilles. [0115]

Example 3

Forming a Coated Coolant Additive Composition

A mixture of sodium sulfite and carboxymethyl cellulose is compressed into pellets of about {fraction (1/32)} inch to about {fraction (1/16)} inch in diameter. The pellets are placed onto a rotating pan inside a drum coater chamber. While the pan is rotated, a dispersion of commercially available ethylene/vinyl acetate copolymer is pumped and sprayed through a nozzle onto the surfaces of the forms. The spray rate is maintained at about 15 grams of dispersion per minute. The spray pattern is controlled to give a good mist of copolymer droplets. [0116]
At the same time, through a very slightly reduced pressure, a stream of warm air of about 40° C. is passed through the chamber to remove the water vapor from the polymer mist (or small droplets), before and after they reach the composition surfaces. [0117]
With time, the copolymer gradually forms a layer of coating on each of the forms. After all copolymer dispersion is sprayed to reach the desired thickness of coating, the resulting coated forms are allowed to stay on the rotating pan for a few more minutes, then are decanted from the pan into a container for storage. [0118]
Alternately, the solid which includes an oxygen scavenger additive is coated with the copolymer in a spray drum coater. [0119]

Example 4

Forming a Coolant Additive Composition/Matrix Material Composition

The puck-shaped oxygen scavenger additive/matrix material composition of Example 2 is coated with a coating material by placing a plurality of such puck-shaped forms onto a rotating pan inside a drum coater chamber. While the pan is rotated, a dispersion of commercially available ethylene/vinyl acetate copolymer is pumped and sprayed through a nozzle onto the surfaces of the forms. The spray rate is maintained at about 15 grams of dispersion per minute. The spray pattern is controlled to give a good mist of copolymer droplets. [0120]
At the same time, through a very slightly reduced pressure, a stream of warm air of about 40° C. is passed through the chamber to remove the water vapor from the polymer mist (or small droplets), before and after they reach the composition surfaces. [0121]
With time, the copolymer gradually forms a layer of coating on each of the forms. After all copolymer dispersion is sprayed to reach the desired thickness of coating, the resulting coated forms are allowed to stay on the rotating pan for a few more minutes, then are decanted from the pan into a container for storage. [0122]
Alternately, the pastilles noted in Example 1 are coated with the copolymer in a spray drum coater. [0123]

Example 5

Method of Using a Coolant Additive Composition/Matrix Material Composition

Several oxygen scavenger additive/matrix material composition puck-shaped forms of Example 2 are placed into a coolant filter canister assembly during manufacture of the canister. In use, the coolant filter canister is placed in fluid communication with a circulating aqueous-based coolant system in a vehicle spark-ignited engine. Once connection has been made and fluid communication is established between the cooling system and the canister, the coolant is circulated when the engine is running, allowing the aqueous-based coolant to contact the oxygen scavenger additive/matrix material composition forms disposed in the canister. Upon contact with the forms, the high temperature coolant will diffuse into and out of the polymer matrix material sufficiently to release the oxygen scavenger additive into the coolant. The released oxygen scavenger additive dissolves in the circulating coolant. The gradual release of oxygen scavenger additive, for example, at a substantially uniform rate, continues during each circulation of coolant through the filter canister until, eventually, all oxygen scavenger additive is depleted from the polymer matrix material. In this example, the canister includes filtering media for filtering coolant exiting the canister and preventing larger particulate oxygen scavenger additive from entering the coolant system. The spent matrix material form is removed from the circulating system by simply removing and properly disposing the filter canister and thereafter replacing the canister with another new filter canister containing oxygen scavenger additive/matrix material composition forms produced in accordance with the present invention. [0124]

Example 6

Method of Using a Coated Oxygen Scavenger Containing Coolant Additive Composition

Coated additive composition produced according to the method of example 2 is packed into a reservoir or housing connected, e.g., along and in the fluid communication with an engine cooling system line. An aqueous coolant is pumped through the cooling system line and through the packed reservoir. Upon contact with the high temperature coolant, the coating of the composition in the reservoir begins to soften and break, allowing the coolant to contact the oxygen scavenger additive encased therein. The oxygen scavenger additive is released into the coolant providing benefits thereto. [0125]
As an alternative to the coated additive composition disclosed above, the ethylene/vinyl acetate copolymer coating is replaced with a partially soluble coating material. Upon contact with the high temperature coolant, the coating of the cylindrical forms in the reservoir partially dissolves, releasing a portion of the coating into the coolant to provide at least one benefit to the coolant. In addition, the coolant is able to penetrate the partially solubilized coating to contact the coolant additive encased therein. [0126]

Example 7

Method of Using a Coated Oxygen Scavenger Containing Coolant Additive Composition/Matrix Material Composition

Coated oxygen scavenger additive/matrix material composition produced according to the method of example 3 is packed into a reservoir or housing connected, e.g., along and in the fluid communication with an engine cooling system line. An aqueous coolant is pumped through the cooling system line and through the packed reservoir. Upon contact with the high temperature coolant, the coating of the composition in the reservoir begins to soften and break, allowing the coolant to contact the oxygen scavenger additive/matrix material encased therein. The oxygen scavenger additive in the matrix material is released into the coolant providing benefits thereto. [0127]
As an alternative to the coated additive/matrix material composition disclosed above, the ethylene/vinyl acetate copolymer coating is replaced with a partially soluble coating material. Upon contact with the high temperature coolant, the coating of the cylindrical forms in the reservoir partially dissolves, releasing a portion of the coating into the coolant to provide at least one benefit to the coolant. In addition, the coolant is able to penetrate the partially solubilized coating to contact the oxygen scavenger component/matrix material encased therein. The oxygen scavenger additive in the matrix material is released into the coolant, providing benefits thereto. [0128]
While the present invention has been described with respect of various specific examples and embodiments, it is to be understood that the invention is not limited thereto and that it can be variously practiced within the scope of the following claims. [0129]

Claims

What is claimed is:

1. A coolant additive composition comprising:

a controlled release component and an oxygen scavenger component wherein the controlled release component is effective to reduce the rate of release of the oxygen scavenger component into a coolant in a cooling system.

2. The additive composition of claim 1 wherein the oxygen scavenger component is not effective to form a protective complex with metal.

3. The additive composition of claim 1 wherein the rate of release is reduced relative to an identical composition without the controlled release component.

4. The additive composition of claim 1 wherein the oxygen scavenger component is effective to inhibit oxidative degradation of the coolant when the oxygen scavenger component is released into the coolant.

5. The additive composition of claim 1 wherein the cooling system is a circulating cooling system.

6. The additive composition of claim 5 wherein the circulating cooling system is not completely closed.

7. The additive composition of claim 1 wherein the cooling system cools an internal combustion engine.

8. The additive composition of claim 1 wherein the oxygen scavenger component is selected from the group consisting of thiosulfite, thiosulfate, mercaptopropionic acid, bisulfite, hydrosulfite, dithionate, hyposulfite, sulfite, sulfide, stannous, hydroxylamine and hydrazine or mixtures thereof.

9. The additive composition of claim 1 wherein the coolant is glycol-based.

10. The additive composition of claim 1 wherein the controlled release component is partially soluble in the coolant.

11. The additive composition of claim 1 wherein the controlled release component includes a matrix material.

12. The additive composition of claim 1 wherein the controlled release component includes a coating material.

13. The additive composition of claim 1 wherein the controlled release component includes both a matrix material and a coating material.

14. A method of producing a coolant additive composition, comprising the step of:

combining an oxygen scavenger component with a matrix material to form a mixture wherein the matrix material is effective to reduce a rate of release of the oxygen scavenger component into a coolant in a cooling system.

15. The method of claim 14 wherein the rate of release of the oxygen scavenger component into the cooling system is reduced relative to an identical additive composition without the matrix material.

16. The method of claim 14 wherein the oxygen scavenger component is effective to inhibit oxidative degradation of the coolant when the oxygen scavenger component is released into the coolant.

17. The method of claim 14 wherein the matrix material comprises a polymeric material.

18. The method of claim 14 which further comprises providing a coating material, the coating material being effective to reduce the rate of release of the oxygen scavenger component into the coolant relative to an identical oxygen scavenger component without the provided coating material.

19. The additive composition of claim 14 wherein the oxygen scavenger component is selected from the group consisting of thiosulfite, thiosulfate, mercaptopropionic acid, bisulfite, hydrosulfite, dithionate, hyposulfite, sulfite, sulfide, stannous, hydroxylamine and hydrazine or mixtures thereof.

20. The method of claim 14 wherein the cooling system cools an internal combustion engine.

21. A method of producing an additive composition comprising the steps of:

providing a coolant additive composition which includes an oxygen scavenger component; and

providing a coating material on the additive composition to form a coated additive composition, the coating material being partially coolant soluble and effective, when the coated additive composition is contacted with a coolant, to reduce the rate of release of the additive composition into a coolant in a cooling system.

22. The method of claim 21 wherein the rate of release of the additive composition is reduced relative to an identical additive composition without the coating material.

23. The method of claim 21 wherein the oxygen scavenger component is effective to inhibit oxidative degradation of the coolant when the oxygen scavenger component is released into the coolant.

24. The additive composition of claim 21 wherein the oxygen scavenger component is selected from the group consisting of thiosulfite, thiosulfate, mercaptopropionic acid, bisulfite, hydrosulfite, dithionate, hyposulfite, sulfite, sulfide, stannous, hydroxylamine and hydrazine or mixtures thereof.

25. The additive composition of claim 21 wherein the cooling system cools an internal combustion engine.

26. A coolant additive assembly comprising:

a housing including a coolant inlet and a coolant outlet; and

an additive composition disposed within the housing including a controlled release component and an oxygen scavenger component wherein the controlled release component is effective to reduce the rate of release of the oxygen scavenger component into a coolant in a cooling system.

27. The additive assembly of claim 26 wherein the rate of release of the oxygen scavenger component into the coolant is reduced relative to an identical additive composition without the controlled release component.

28. The additive assembly of claim 26 wherein the controlled release component is partially soluble in the coolant.

29. The additive assembly of claim 26 wherein the oxygen scavenger component is effective to inhibit oxidative degradation of the coolant when the oxygen scavenger component is released into the coolant.

30. The additive assembly of claim 26 wherein the controlled release component comprises a coating on the oxygen scavenger component.

31. The additive assembly of claim 26 wherein the controlled release component comprises a matrix material.

32. The additive assembly of claim 31 wherein the matrix material comprises a polymeric material and is substantially coolant insoluble or is partially coolant soluble.

33. The additive assembly of claim 26 wherein the controlled release component comprises a coating on the oxygen scavenger component and a matrix material.

34. The additive composition of claim 26 wherein the oxygen scavenger component is selected from the group consisting of thiosulfite, thiosulfate, mercaptopropionic acid, bisulfite, hydrosulfite, dithionate, hyposulfite, sulfite, sulfide, stannous, hydroxylamine and hydrazine or mixtures thereof.

35. The additive composition of claim 26 wherein the cooling system cools an internal combustion engine.

36. A method for releasing an oxygen scavenger component into a coolant comprising contacting the additive composition of claim 1 with a coolant.

37. The method of claim 36 wherein the oxygen scavenger removes molecular oxygen from the coolant.

38. A method for releasing an oxygen scavenger component into a coolant comprising contacting the additive composition produced by the method of claim 14 with a coolant.

39. A method for releasing an oxygen scavenger component into a coolant comprising contacting the additive composition produced by the method of claim 21 with a coolant.

40. A method for releasing an oxygen scavenger component into a coolant comprising contacting an additive composition included in an assembly of claim 26 with a coolant.