Inhibiting metallic corrosion in aqueous systems

Abstract

The use of polymeric corrosion inhibiting compositions incorporating heterocyclic groups is disclosed. The polymers form a protective barrier on metallic components to aqueous systems and remain substantive on metallic surfaces over a wide pH range. Moreover, the polymers are resistant to oxidizing biocides, and are substantially impervious to repeated or prolonged exposure to corrosive agents.

Description

[0001] The present invention relates to a process for inhibiting corrosion of metallic components in contact with aqueous and non-aqueous systems. More particularly, the invention is directed to introducing oligomeric and polymeric compositions as fluid additives in aqueous systems that are effective corrosion inhibitors over a wide range of pH and render metals passive to repeated attack by oxidants and oxidizing biocides. In addition, the invention relates to a process for applying anti-corrosive coatings to metallic components.

[0002] Metallic components used in industrial processes and heating ventilation and air conditioning (HVAC) operations that are in contact with fluid media such as, for example, cooling water experience three major problems: metal corrosion, deposition of solids and the growth of microorganisms. The three problems are interrelated in that the ability to control one problem often influences the ability to effectively control the remaining problems. The most common method to address the problems is to add a combination of chemical agents and corrosion inhibitors to the fluid media in contact with the metallic components. Polymeric dispersants and phosphonates are commonly used to inhibit the deposit of solids referred to as scale. Biocidal compositions, in particular oxidizing biocides such as chlorine or bromine, are often used to control the deposition and growth of microorganisms. The most challenging problem in the development of new anti-corrosive compositions is providing effective chemical agents which inhibit corrosion and which do not produce an adverse environmental impact themselves or upon treatment with oxidizing biocides.

[0003] Corrosion may be defined as the gradual weight loss of a metallic component through some chemical process or series of chemical reactions. Metals in contact with aqueous systems such as sea water, fresh water and brackish water and exposed to oxidants contained therein such as chlorine, acid, bleach, caustic and dissolved oxygen are prone to corrosion. Metal alloys using more corrosion resistant metals (e.g. Ti, Cr, Ni) are one means of improving corrosion resistance. However, such alloys are costly, difficult to process and manufacture, and experience problems with corrosion at joints, welds, and under repeated exposure to corrosive agents. Inorganic compositions such as chromates, phosphates or zinc compositions and organic compositions such as tolyltriazole (TTA) and benzotriazole (BZT) are corrosion inhibitors applied to metals or added to fluids in contact with metallic components which inhibit or slow down the rate of metal corrosion. Azoles, for example, are film forming compositions that adsorb to metallic surfaces and provide a barrier to contact with an aqueous system. The effectiveness of a particular composition is usually a trade off of its anti-corrosion properties as compared to its inherent limitations such as cost, long term performance and environmental impact. Since metal corrosion occurs under a variety of environmental conditions, specific inhibitor compositions have been developed to provide corrosion resistance for specific situations.

[0004] A common corrosion inhibitor for metals such as copper and its alloys are film forming azoles such as tolyltriazole (TTA) and benzotriazole (BZT). TTA has been usefully employed as a corrosion inhibitor for metallic components manufactured from copper and copper alloys. When such metals, protected with TTA films, are exposed to oxidizing biocides such as chlorine, however, the corrosion protection breaks down. After film breakdown, it is difficult to form new protective films in TTA treated aqueous systems that are periodically or continuously chlorinated. Very high dosages of TTA are frequently applied in an attempt to improve performance, often with limited success. Other problems associated with combining triazoles and oxidizing biocides in aqueous systems include by-products that are less effective corrosion inhibitors, by products which are volatile and that have objectionable odors and halogen containing by products that are toxic to the environment if released from the aqueous system. Moreover, it is believed that the decomposition product of TTA may be more toxic than TTA, which itself is toxic to fish populations. Under the conditions found in cooling water treatment equipment, the decomposition product of TTA is believed to be an N-chlorinated compound, which is relatively volatile and susceptible to removal by stripping in the cooling tower, further reducing the levels of corrosion inhibitor and oxidizing biocide in the system.

[0005] When copper containing metals corrode, excessive concentrations of copper are released and subsequently discharged in to rivers that often serve as reservoirs of cooling water. The toxic effects of copper on fish populations and other organisms in aqueous ecosystems is well established. In addition, excessive concentrations of copper ions can redeposit on mild steel components, setting up a galvanic oxidation-reduction couple leading to severe metal pitting.

[0006] U.S. Pat. No. 4,282,007 discloses a corrosion inhibiting additive for a fuel composition, which is the reaction product of a C15-C30 hydrocarbyl succinic acid anhydride and aminotriazole. However, such fuels contain acidic contaminants from alcohols and the additives are only effective at inhibiting corrosion of metal surfaces exposed to acidic conditions. Accordingly, it would be desirable to provide alternative methods of inhibiting metallic corrosion in aqueous systems that incorporate corrosion inhibitors that are effective over a wide range of pH, that are resistant to oxidizing biocides and that have minimal environmental impact.

[0007] The inventors recognized a need to provide corrosion inhibiting compositions having substantive film forming ability that are effective over a wide pH range in aqueous or non-aqueous systems, that are resistant to oxidizing biocides and that can withstand repeated and prolonged chemical attack by corrosive agents such as chlorine. The inventors discovered polymeric corrosion inhibiting compositions that are products of reactions between anhydrides and heterocycles which are surprisingly effective copper corrosion inhibitors and remain substantive on metallic surfaces over a wide pH range in aqueous and non-aqueous systems, are resistant to oxidizing biocides, and are substantially impervious to repeated or prolonged exposure to corrosive agents.

[0008] The present invention provides a process for inhibiting corrosion of metallic components in contact with an aqueous system comprising the step of adding to the system an effective amount of one or more polymers comprising at least one repeating unit selected from a functionalized imide component of Formula Ia, a functionalized amide component of Formula Ib and combinations of Formulas Ia and Ib: 1

[0009] wherein n is 0 or 1; R and R1 are independently selected from hydrogen, methyl, and C2-C4 alkyl; a heterocycle which comprises unsaturated or aromatic heterocycles having one or more hetero atoms selected from N, O, S and combinations thereof, the heterocycle chemically bonded to a nitrogen atom of Formula 1a or 1b via a hetero atom which is part of the heterocycle or a carbon atom of the heterocycle; R3 is selected from hydrogen, methyl, ethyl, C3-C18 branched and straight chain, alkyl and alkenyl groups; and R4 is selected from H, CH3, C2H5, C6H5 and C3-C18 branched or straight chain alkyl and alkenyl groups.

[0010] Accordingly, the present invention provides a process for inhibiting corrosion of metallic components in contact with an aqueous system comprising the step of adding to the system an effective amount of corrosion inhibiting polymer comprising:

[0011] i) at least one repeating unit selected from a functionalized imide component of Formula Ia, a functionalized amide component of Formula Ib and combinations of Ia and Ib;

[0012] ii) at least one ethylenically unsaturated monomer component selected from maleic anhydride, itaconic anhydride, cyclohex-4-enyl tetrahydrophthalic anhydride, and monomers of Formula II:

[0013] Formula II

CH(R5)=C(R6)(R7)

[0014] wherein R5 is selected from hydrogen, phenyl, methyl, ethyl, C3-C18 branched and straight chain alkyl and alkenyl groups; R6 is independently selected from hydrogen, methyl, ethyl, phenyl, C3-C18 branched and straight chain alkyl and alkenyl groups, OR8 and CH2OR8 groups wherein R8 is acetate, glycidyl, methyl, ethyl, C3-C18 branched and straight chain alkyl and alkenyl groups, and groups having the formula [CH2CH(Ra)O]mRb wherein Ra is hydrogen, methyl, ethyl, and phenyl, m is an integer from 1-20 and Rb is independently hydrogen, methyl, ethyl, phenyl and benzyl; and R7 is independently selected from H, CH3, C2H5, CN, a COR9 group wherein R9 is OH, NH2, OR8 group wherein R8 is a group described previously and a NRcRd group wherein Rc and Rd are the same group or different groups, are parts of a 5-membered or 6-membered ring system, hydrogen, hydroxymethyl, methoxy methyl, ethyl and C3-C18 branched and straight chain alkyl and alkenyl groups branched and straight chain alkyl and alkenyl groups; and

[0015] optionally one or more end groups selected from initiator fragments, chain transfer fragments, solvent fragments and combinations thereof.

[0016] Alternatively, the present invention provides a process for inhibiting corrosion of metallic components in contact with an aqueous system comprising the step of adding to the system an effective amount of corrosion inhibiting polymer of formula III:

[0017] Formula III

(A)x(B)y(C)z

[0018] wherein A is an optional end group component selected from initiator fragments, chain transfer fragments, solvent fragments and combinations thereof; wherein B is a functionalized imide component of Formula Ia, a functionalized amide component of Formula Ib and combinations of Ia and Ib; wherein C is an ethylenically unsaturated monomer component selected from maleic anhydride, itaconic anhydride, cyclohex-4-enyl tetrahydrophthalic anhydride, and monomers of Formula II; and wherein x, y, z are integers values chosen such that (y+z)/x is greater than 2.

[0019] The present invention also provides a process for inhibiting corrosion of metallic components in contact with an aqueous system comprising the step of adding to the system an effective amount of one or more polymers of Formula III:

[0020] Formula III

(A)x(B)y(C)z

[0021] wherein A is an end group component selected from initiator fragments, chain transfer fragments, solvent fragments and combinations thereof; wherein B is a functionalized imide component of Formula Ia, a functionalized amide component of Formula Ib and combinations of Ia and Ib; wherein C is an ethylenically unsaturated monomer component selected from maleic anhydride, itaconic anhydride, cyclohex-4-enyl tetrahydrophthalic anhydride, and monomers of Formula II; and wherein x, y, z are integers values chosen such that (y+z)/x is greater than 2.

[0022] The present invention also provides a process for inhibiting corrosion of metallic components in contact with an aqueous system comprising the step of adding to the system an effective amount of one or more polymers comprising:

[0023] i) one or more end groups selected from initiator fragments, chain transfer fragments, solvent fragments and combinations thereof;

[0024] ii) at least one repeating unit selected from a functionalized imide component of Formula Ia, a functionalized amide component of Formula Ib and combinations of Ia and Ib; and

[0025] iii) at least one unit selected from a functionalized imide component or a functionalized amide component selected from succinimide, glutarimide and combinations thereof, wherein the nitrogen atom of each component of B′ is chemically bonded to a group selected from C1-C18 branched or straight chain alkyl, C1-C18 alkyl or alkenyl substituted aryl, which is in turn chemically bonded to a pendant functional group selected from an amine group, amide group, carboxylic acid group, alcohol group or a group having the formula [CH2CH(Ra)O]mRb wherein Ra is hydrogen, methyl, ethyl, and phenyl, m is an integer from 2-20 and Rb is independently hydrogen, methyl, ethyl, phenyl and benzyl.

[0026] Alternatively, the present invention also provides a process for inhibiting corrosion of metallic components in contact with an aqueous system comprising the step of adding to the system an effective amount of one or more polymers of Formula IV:

[0027] Formula IV

(A)x(B)y(B′)z

[0028] wherein A is an end group selected from initiators fragments, chain transfer fragments, solvent fragments and combinations thereof; wherein B is a functionalized imide component of Formula Ia selected from succinimide, glutarimide and combinations thereof; wherein B′ includes at least one unit selected from a functionalized imide component or a functionalized amide component selected from succinimide, glutarimide and combinations thereof, wherein the nitrogen atom of each component of B′ is chemically bonded to a group selected from C1-C18 branched or straight chain alkyl, C1-C18 alkyl or alkenyl substituted aryl, which is in turn chemically bonded to a pendant functional group selected from an amine group, amide group, carboxylic acid group, alcohol group or a group having the formula [CH2CH(Ra)O]mRb wherein Ra is hydrogen, methyl, ethyl, and phenyl, m is an integer from 2-20 and Rb is independently hydrogen, methyl, ethyl, phenyl and benzyl; and wherein x, y, z are integers values chosen such that (y+z)/x is greater than 2.

[0029] The present invention also provides a process for inhibiting corrosion of metallic components in contact with an aqueous system comprising the step of adding to the system an effective amount of a corrosion inhibiting formulation including one or more corrosion inhibiting polymer compositions and one or more additives selected from the group consisting of biocidal compositions, corrosion inhibiting compositions different from those of the present invention, scale inhibiting compositions, dispersants, defoamers, inert tracers and combinations thereof.

[0030] Accordingly, the present invention provides a process for inhibiting corrosion of metallic components used in the manufacture of equipment associated with aqueous and non-aqueous systems that require corrosion protection. “Aqueous system” refers to any system containing metallic components which contain or are in contact with aqueous fluids on a periodic or continuous basis. The term “aqueous fluids” refers to fluids containing 5 weight percent or more water and includes water-based fluids. Water based fluids refer to fluids containing a minimum of 40 percent by weight water, the remainder being suspended and/or dissolved solids and compounds that are soluble in water. “Non-aqueous system” refers to any system containing metallic components which contain or are in contact with non-aqueous fluids on a periodic or continuous basis. Non-aqueous fluids may be miscible or immiscible in water.

[0031] Typical aqueous systems include, for example, recirculating cooling units, open recirculating cooling units that utilize evaporation as a source of cooling, closed loop cooling units, heat exchanger units, reactors, equipment used for storing and handling liquids, boilers and related steam generating units, radiators, flash evaporating units, refrigeration units, reverse osmosis equipment, gas scrubbing units, blast furnaces, paper and pulp processing equipment, sugar evaporating units, steam power plants, geothermal units, nuclear cooling units, water treatment units, food and beverage processing equipment, pool recirculating units, mining circuits, closed loop heating units, machining fluids used in operations such as for example drilling, boring, milling, reaming, drawing, broaching, turning, cutting, sewing, grinding, thread cutting, shaping, spinning and rolling, hydraulic fluids, cooling fluids, oil production units and drilling fluids. Typical examples of aqueous fluids include fresh water, brackish water, sea water, waste water, mixtures of water and salts (known as brines), mixtures of water and alcohol such as methanol, ethanol and ethylene glycol, mixtures of water and acids such as mineral acids, mixtures of water and bases such as caustic and combinations thereof. Aqueous systems treated using the compositions of this invention may contain dissolved oxygen or may contain no oxygen. The aqueous systems may contain other dissolved gases such as, for example, carbon dioxide, ammonia and hydrogen sulfide.

[0032] In the descriptions that follow, the terms oligomer, polymer and co-polymer are used. Oligomer refers to compositions produced by the polymerization of one or more monomer units wherein the number of monomer units incorporated in the oligomer are between 2 and about 10. Polymer refers to compositions produced by the polymerization of one or more monomer units with no restriction on the number of types of monomer units incorporated in the polymer. Co-polymer refers to compositions produced by the polymerization of two different monomer units with no restriction on the number of either monomer units incorporated in the co-polymer.

[0033] The metallic components in contact with the aqueous system are processed from any metal for which corrosion and/or scaling can be prevented. Typical examples of metals requiring corrosion protection are copper, copper alloys, aluminum, aluminum alloys, ferrous metals such as iron, steels such as low carbon steel, chromium steel and stainless steel, iron alloys and combinations thereof.

[0034] Different types of metal corrosion are encountered in aqueous systems such as, for example, uniform corrosion over the entire metal surface and localized corrosion such as pitting and crevice forming. Often, control of localized corrosion may be the critical factor in prolonging the useful life of the metal components in contact with the aqueous system. Aqueous systems containing significant concentrations (also referred to as “levels”) of anions such as chloride and sulfate are prone to both uniform and localized corrosion. These anions are often present in the aqueous fluids used in the system. Uniform and localized corrosion often result in the failure of the metallic components requiring replacement or extensive repairs and maintenance, both shutting down operation of the aqueous system. Therefore, the present invention provides polymeric compositions for inhibiting corrosion in aqueous systems.

[0035] The corrosion resistant polymer compositions usefully employed in the present invention are substantially resistant or impervious to oxidizing biocides including for example oxidants such as oxygen, ozone and hydrogen peroxide, halogens such as chlorine, bromine, and iodine, combinations of oxidants such as NaOCl and alkali salts of Group VII (Group 17 according to the nomenclature of the International Union of Pure and Applied Chemists) elements, organic compounds such as hydantinoids, cyanuric acid derivatives, substituted cyanuric acid derivatives such as chloro cyanuric acid, alkali and alkaline earth salts of cyanuric acid and cyanuric acid derivatives, and combinations thereof. In addition, the anti-corrosive compositions are substantially resistant or impervious to repeated and prolonged exposure to corrosive agents including for example chlorine, bromine, and iodine; hypochlorite and its alkali metal salts such as sodium hypochlorite; hypochloric acid; chlorous acid; mineral acids such as hydrochloric acid, sulfuric acid and phosphoric acid; perchloric acid, basic compounds such as lye, caustics, bleaches, and ammonia; reducing agents such as sulfides, sulfites and alkali metal sulfides; and combinations thereof.

[0036] The corrosion inhibiting compositions of the present invention are effective in highly acidic or basic aqueous systems, namely, at pH between 0.5 and 14. It is preferred that the corrosion inhibiting compositions are added to the aqueous systems at pH between 6 and 10.

[0037] All polymers and corrosion inhibiting polymer compositions usefully employed in the present invention include at least one repeating unit selected from a functionalized imide component having Formula Ia, a functionalized amide component having Formulas Ib and combinations of Ia and Ib: 2

[0038] Preferably n is 0. Preferably R and R1 are hydrogen. Preferably, R3 is selected from C3-C18 branched and straight chain alkyl groups. Preferably, Preferably, R4 is selected from C3-C18 branched and straight chain alkyl groups.

[0039] Suitable heterocycles usefully employed in accordance with the invention include for example 5 to 7-membered heterocycles having some degree of unsaturation, aromatic heterocycles having at least one hetero atom selected from N, O or S atoms and combinations thereof. The heterocycle is chemically bonded to a nitrogen atom of the imide or amide component via a hetero atom which is part of the heterocycle or a carbon atom of the heterocycle. In addition, suitable heterocycles include for example 5 to 7-membered heterocycles that are fused together to form larger 9 to 14-membered heterocycles having more than one type or combination of N, O or S atoms, isomers of such heterocycles and combinations thereof.

[0040] Preferred heterocyclic groups include for example imidazole, triazole, thiophene, pyrrole, oxazole, azoles, indazoles thiazoles and their respective isomers such as thiazol-4-yl, thiazol-3-yl, and thiazol-2-yl, substituted thiazoles and their respective isomers such as 2-amino thiazol-4-yl, pyrazole, tetrazole, pyridine, pyridazine, pyrimidine, pyrazine, indazoles, triazoles and their respective isomers such as 1, 2, 3-triazole, 1,2,4-triazole, and combinations thereof.

[0041] The nitrogen atom constituting the functionalized imide components and functionalized amide components of B further is chemically bonded to an atom that constitutes the heterocycle. In an embodiment wherein the corrosion inhibiting composition is oligomeric or polymeric, the functionalized imide components and functionalized amide components are incorporated in to the backbone of the oligomer or polymer and further include the heterocyclic group.

[0042] In a separate embodiment, the nitrogen atom constituting the functionalized imide components and functionalized amide components of B′ is chemically bonded to a group selected from C1-C18 branched or straight chain alkyl, C1-C18 alkyl or alkenyl substituted aryl, which is in turn chemically bonded to a pendant functional group selected from an amine group, amide group, carboxylic acid group, alcohol group or a group having the formula [CH2CH(Ra)O]mRb wherein Ra is hydrogen, methyl, ethyl, and phenyl, m is an integer from 2-20 and Rb is independently hydrogen, methyl, ethyl, phenyl and benzyl. Preferred examples include C1-C25 alkyl amines such as butyl amine, hexyl amine, octyl amine, decyl amine, dodecyl amine and stearyl amine; octyl amine; and C1-C25 alkyl amides such as hexyl amide, n-octyl amide, decyl amide and stearyl amide.

[0043] Accordingly, this invention provides a process for inhibiting corrosion of metallic components in contact with an aqueous system comprising the step of adding to the system an effective amount of a corrosion inhibiting polymer comprising chemical components A, B and C; wherein A optionally includes one or more end groups selected from initiator fragments, chain transfer fragments, solvent fragments and combinations thereof; wherein B includes at least one repeating unit selected from a functionalized imide component of Formula Ia, a functionalized amide component of Formula Ib and combinations of Ia and Ib; and wherein C represents at least one ethylenically unsaturated monomer component of Formula II. The components A, B and C are arranged randomly within the polymer and can be arranged sequentially in accordance with the invention.

[0044] Component A includes for example any initiator fragment derived from any initiator useful in initiating free radical addition polymerization. Such initiator fragments include, but are not limited to, peroxyesters, such as t-butylperbenzoate, t-amylperoxybenzoate, t-butylperoxy-2-ethylhexonate, butylperacatate and t-butylperoxylmaleic acid; dialkylperoxides such as di-t-butylperoxide, dicumylperoxide and t-butylcumylperoxide; diacylperoxides such as benzoylperoxide, lauroylperoxide and acetylperoxide; hydroperoxides such as cumene hydroperoxides and t-butylhydroperoxide; azo compounds such as azonitriles, azaamidines, cyclic azoamidines, alkylazo compounds such as azodi-tert-octane.

[0045] Component A further includes for example end groups resulting from any chain transfer agent used in controlling the molecular weight of a free radical polymerization. Suitable chain transfer agents include but are not limited to alcohols, alkyl and aromatic thiols, alkyl phosphites, aryl phosphinic acids, alkyl phosphinic acids, hypophosphites, aldehydes, formates, alkylhalides and alkyl aromatic such as toluene, xylenes, and C9-10 alkylaromatics such as Aromatic 100.

[0046] Component B refers to more than one of either a functionalized imide component or a functionalized amide component having respective Formulas Ia and lb. Preferred B components are selected from succinimide, glutarimide and combinations thereof. The nitrogen atom that constitute the imide or amide portion of component B must be chemically bonded to at least one atom of a R2 group which in turn is chemically bonded to a pendant heterocycle. R2 groups consisting of 2 to 8 consecutive atoms between the nitrogen atom of the imide or amide portion of B and the heterocycle are more preferred. R2 groups consisting of 3 to 6 consecutive atoms between the imide or amide portion of B and the heterocycle are most preferred.

[0047] Component C includes ethylenically unsaturated monomers of Formula III. Examples of suitable monomers include (meth)acrylic acid, methyl (meth)acrylate, hydroxy (meth)acrylate, 2-hydroxyethyl acrylate, 2-hydroxy propyl acrylate, butyl (meth)acrylate, 2-ethylhexyl acrylate, decyl acrylate, lauryl (meth)acrylate, isodecyl (meth)acrylate, hydroxyethyl (meth)acrylate, and hydroxypropyl (meth)acrylate; cyclic anhydrides such as maleic anhydride; anhydrides such as itaconic anhydride, and cyclohex-4-enyl tetrahydrophthalic anhydride; olefins such as ethylene, propylene, butylene, isobutylene, di-isobutylene, d-limonene; olefin oligomers such as propylene tetramer (C12-C14) and propylene dimer trimer (C18-C22); &agr;-olefins such as 1-butene, 1-octene and 1-decene, 1-dodecene, 1-tetradecene, 1-hexadecene, 1-octadecene, Gulftene® 20-24, Gulftene® 24-28; styrene, and substituted styrenes such as &agr;-methyl styrene, &agr;-methylstyrene, 4-hydroxystyrene, styrene sulfonic acid; butadiene; vinyl acetate, vinyl butyrate and other vinyl esters; and vinyl monomers such as vinyl chloride, vinylidene chloride; vinyl ethers such as methyl vinyl ether, ethyl vinyl ether, propyl vinyl ether, butyl vinyl ether, isobutyl vinyl ether; allyl ethers such as allyl ether, allyl ethyl ether, allyl butyl ether, allyl gylcidyl ether, allyl carboxy ethyl ether; ethoxy vinyl ethers such as vinyl-2-(2-ethoxy-ethoxy)ethyl ether, methoxyethoxy vinyl ether, vinyl acetate, vinyl formamide and vinyl acetamide, stilbene; divinyl benzene; (meth)acrylic monomers such as (meth)acrylate esters, (meth)acrylamides, and (meth)acrylonitrile. The use of the term “(meth)” followed by another term such as acrylate or acrylamide, as used throughout the disclosure, refers to both acrylates or acrylamides and methacrylates and methacrylamides, respectively. Preferred monomers of component C include ethylene, propylene, isobutylene, di-isobutylene, propylene tetramer (C12-C14), and propylene dimer trimer (C18-C22).

[0048] The corrosion inhibiting compositions usefully employed in the present invention have weight average molecular weights that range from 400 to 20,000. More preferred are compositions having weight average molecular weights that range from 400 to 10,000. Most preferred are compositions having weight average molecular weights that range from 400 to 5,000. Weight average molecular weights of the polymeric compositions were measured by GPC techniques using styrene as a standard.

[0049] Polymers usefully employed according to the invention can be prepared by conventional emulsion, solution or suspension polymerization, including those processes disclosed in U.S. Pat. No. 4,973,409. Solution polymerization is preferred.

[0050] The polymerization of monomers is performed in a suitable solvent and in the presence of an initiator. Suitable solvents include for example water, dioxane, ketones such as 4-methylbutan-2-one, aromatic hydrocarbons such as toluene, xylene and xylene isomers, alcohols such as methanol and ethanol and ethers such as dioxane. Suitable reaction initiators include for example azo(bis)isobutyronitrile (AIBN), organic peroxides such as benzoyl peroxide, di-t-butyl peroxide, hydroperoxides such as t-butyl hydroperoxide and t-amyl hydroperoxide, hydrogen peroxide, sodium perborate, alkali metal persulfates and ammonium persulfate.

[0051] The corrosion inhibiting polymer compositions are easily prepared in two steps. The first step includes for example polymerization of one or more monomers such as maleic anhydride with one or more ethylenically unsaturated monomer units of C such as di-isobutylene. The anhydride portion of the resulting co-polymer is then converted via one or more post polymerization functionalization reactions such as condensation, amidation, imidation, or esterification to afford polymer compositions of Formula 1a or 1b. For example, the anhydride portion of the resulting co-polymer reacts with one or more heterocycles, such as an amino triazole or an amino pyridine via a condensation, to afford polymer compositions of Formula 1a or 1b. Alternatively, the compositions are easily prepared by polymerizing one or more functionalized monomer units of B with one or more ethylenically unsaturated monomer units of C to afford polymer compositions of Formula 1a or 1b.

[0052] The polymer products of either process for the purpose of isolation may be subjected to partial or complete evaporation under reduced pressure. The unpurified reaction products may be used as the polymer composition of the present invention. The reaction products may also be purified. The pruification procedure consists of: a) evaporation of reaction solvent and washing with a water immiscible organic solvent such as ether, followed by evaporation of this solvent or b) evaporation of the reaction solvent, dissolving the polymer product in a suitable solvent and precipitating the polymer with a suitable non-solvent such as toluene or xylenes.

[0053] Polar groups incorporated in the polymers from the heterocyclic groups, the end groups and the amide/imide components strongly adsorb to metallic surfaces. The polymeric nature of the compositions coupled with high numbers of polar anchoring groups provide effective corrosion inhibition for metals and metal alloys by forming films exhibiting superior barrier properties over a broader range of pH, while remaining substantially impervious to corrosive agents present in aqueous systems and maintaining their anti-corrosive effectiveness over repeated additions of oxidizing biocides and corrosive agents such as chlorine for extended time periods.

[0054] The corrosion inhibiting polymer compositions of the invention have the following advantages: improved chlorine resistance, low toxicity and environmental impact as compared to azoles such as TTA and BZT, a wide range of pH stability, formulated in safe and cost effective manner and are detected and monitored at ppm concentrations (also referred to as traceability). Improved chlorine resistance results in lower concentrations of metal ions such Cu2+ discharged in to the aqueous system in compliance with EPA regulatory discharge restrictions, reduced galvanic corrosion, increased useful life of metallic components, reduced levels of polymer required for corrosion protection and elimination of odors associated with azoles. The low toxicity of the polymer compositions results in a lowered environmental impact as evidenced by relatively lower aquatic toxicological profiles. The polymer composition stability in a wide pH range allows for reductions or elimination of caustic providing reduced handling and shipping hazards. The polymers are made from inexpensive, commercially available monomer feedstocks and are easily formulated with other biocides, scale inhibitors and any other required additives known to be useful in treatment of aqueous systems. The heterocyclic group incorporated in the polymer provides a means to monitor low concentrations (ppm levels) of the polymer in the aqueous system via UV-vis absorption or fluorescence techniques, also referred to as traceability. An inert fluorescent tracer can also be incorporated in to the polymer as well to determine and monitor static and dynamic levels of the polymer in the aqueous system. The traceability of the polymers at ppm levels provides a means to detect the polymer concentration in the aqueous system and control the feed or dose rate required, resulting in significant cost performance. In practice, the amount of polymer compositions of Formula 1a or 1b used to treat the aqueous system varies according to the protective function required.

[0055] The polymer compositions of the present invention can preferably be added to the aqueous system at active amounts ranging between 0.1 to 50,000 ppm (0.00001 to 5 weight %), preferably from 1 to 500 ppm, most preferably from 1 to 100 ppm, based on the weight of the aqueous system.

[0056] The polymer compositions of this invention are used to prepare corrosion inhibiting formulations by combining the polymer with one or more additives known to be useful in treating aqueous systems such as for example biocidal compositions, any other corrosion inhibiting composition known in the art, scale inhibiting compositions, dispersants, defoamers, inert fluorescent tracers and combinations thereof.

[0057] To enhance their solubility and compatibility in formulations and fluid media, the corrosion inhibitors of the present invention can be formulated with surfactants, defoamers, co-solvents and hydrotropes or their pH can be altered with suitable acids or bases. Examples of suitable surfactants include but are not limited to Rhodafac® RS 610 or Rhodafac® RE 610 manufactured by Rhodia, Inc. Examples of suitable defoamers include but are not limited to GE silicone antifoam AF60. Suitable co-solvents include for example ethanol, isopropanol, ethylene glycol and propylene glycol. Suitable hydrotropes include Monatrope® 1250A manufactured by Uniqema, and sodium xylene sulfonate.

[0058] Suitable scale inhibitors include for example polyphosphates and polycarboxylic acids and copolymers such as described in U.S. Pat. No. 4,936,987.

[0059] The corrosion inhibitors of the present invention can also be used with other agents to enhance corrosion inhibition of copper, aluminum, mild steel, alloys of these and other metals. Examples of these agents include phosphates or phosphoric acid, polyphosphates such as tetrapotassium pyrophosphate and sodium hexametaphosphate, zinc, tolyltriazole, benzotriazole and other azoles, molybdate, chromate, phosphonates such as 1-hydroxyethylidene-1,1-diphosphonic acid, aminotris(methylene phosphonic acid), hydroxyphosphonoacetic acid and 2-phosphonobutane-1,2,4-tricarboxylic acid, polymeric corrosion inhibitors such as poly(meth)acrylic acid or polymaleic acid and copolymers of acrylic, methacrylic and maleic acid, as well as their alkali metal and alkaline earth metal salts.

[0060] In addition, the corrosion inhibitors may also be used with other agents such as scale inhibitors and dispersants. Examples of these agents include poly(meth)acrylic acid, polymaleic acid, copolymers of acrylic, methacrylic or maleic acid, phosphonates as previously described, and chelants such as nitrilotriacetic acid or ethylenediamine tetraacetic acid, as well as their metal salts. The agents described may be applied in a single formulation or applied separately.

[0061] The polymer compositions of the invention are usefully employed as fluid additives such as coolants, antifreezes, metal working fluids, lubricants, brake fluids, transmission fluids, aircraft de-icing fluids, fluids for polishing electronic devices (e.g. in chemical mechanical planarization (CMP) processes), soldering additives, anti-abrasive compounds, direct metal treatment fluids, cleaning agents and detergents for photographic processes, anti-corrosive coatings, caulks, sealants and pressure sensitive adhesives in contact with metallic components.

[0062] In a preferred embodiment, corrosion inhibiting compositions are usefully employeded in accordance with the present invention as fluid additives in contact with metallic components.

[0063] In an alternative embodiment, the corrosion inhibiting composition are usefully employed as anti-corrosive coatings by techniques which are well known in the coatings art. First, if the composition is an elastomeric coating, caulk, sealant or pressure sensitive adhesive composition is to be pigmented, at least one pigment is well dispersed in an aqueous medium under high shear such as is afforded by a COWLES® mixer or, for more viscous compositions such as caulks and sealants, a high intensity mixer or mill. Then the waterborne polymer is added under lower shear stirring along with other elastomeric coating, caulk, sealant or pressure sensitive adhesive adjuvants as desired. Alternatively, the aqueous emulsion polymer may be included in the pigment dispersion step. The aqueous composition may contain conventional elastomeric coating, caulk, sealant or pressure sensitive adhesive adjuvants such as, for example, tackifiers, pigments, emulsifiers, coalescing agents, buffers, neutralizers, thickeners or rheology modifiers, humectants, wetting agents, biocides, plasticizers, antifoaming agents, colorants, waxes, and anti-oxidants.

[0064] The solids content of the aqueous coating composition may be from about 10% to about 85% by volume. The viscosity of the aqueous composition may be from 0.05 to 2000 Pa.s (50 cps to 2,000,000 cps), as measured using a Brookfield viscometer; the viscosities appropriate for different end uses and application methods vary considerably.

[0065] The oligomeric and polymeric corrosion inhibiting compositions may be applied by conventional application methods such as, for example, brushing and spraying methods such as, for example, roll coating, dipping doctor-blade application, printing methods, an aerosol, air-atomized spray, air-assisted spray, airless spray, high volume low pressure spray, air-assisted airless spray, caulk guns, and trowels.

[0066] In addition to metals, the polymeric corrosion inhibiting compositions may be applied to substrates including but not limited to for example, plastic including sheets and films, wood, previously painted surfaces, cementitious substrates, asphaltic substrates or the like, with or without a prior substrate treatment such as an acid etch or corona discharge or a primer.

[0067] The following examples are presented to illustrate the invention and the results obtained by the test procedures.

[0068] Abbreviations

[0069] AA=acrylic acid

[0070] BA=butyl acrylate

[0071] MMA=methyl methacrylate

[0072] AN=acrylonitrile

[0073] EHA=2-ethylhexyl acrylate

[0074] DI water=deionized water

EXAMPLES AND COMPARATIVE EXAMPLES

[0075] Preparation of Corrosion Inhibiting Compositions.

Example 1

[0076] Preparation of Polymer Containing Succinic Anhydride and Diisobutyl Groups (P1).

[0077]

[0078] A 1.8 L reactor was charged with 150.8 g of maleic anhydride flakes, 485 g of dry reagent grade xylenes, 179.4 g diisobutylene and 0.3 g of p-toluene sulfonic acid. The reactor was sealed. It was flushed with nitrogen and a vacuum of-15 psig. was established. Heating to 160° C. was started and the initiator feed was prepared by dissolving 27.5 g of di-t-butylperoxide in 90 g of xylenes. When the reactor temperature had reached 160° C. the initiator solution was fed for 15 minutes at 2 g/min. Heating is stopped and the reaction is exothermic to 175° C. and 32 psig. The remaining initiator solution is added at 1 g/min for 85 min. During this time the reactor is maintained at 175-180° C. with stirring at 160 rpm. After the initiator feed is the heating is continued for 30 min. The reaction mixture is cooled and the reactor is drained at room temperature and pressure. This procedure gives 928 g of solution containing 35.2% solids. This solution (P1) is used for the functionalization process.

Example 2

[0079] Preparation of Polymer Containing Succinic Anhydride Groups (P2).

[0080] To a 1-liter, 4-neck flask equipped with mechanical stirrer, a reflux condenser topped with nitrogen inlet, and a thermocouple, was added 200 g of maleic anhydride and 200 g of technical grade xylenes. After flushing the reactor with an inert gas, the contents are heated to 60° C. to dissolve the maleic anhydride and then 1.00 g of n-octylamine (NOA) is added. The stirred reactor contents are heated to reflux (140-145° C.) and 20.0 g of di-t-butylperoxide (DBP) in 167 g of xylenes is gradually added over two hours. The solution was maintained under reflux for two hours. The reactor is modified for vacuum distillation and xylenes are distilled off to obtain a solution of P2 at the desired concentration.

Example 3

[0081] Functionalization of P2-synthesis of A.

[0082] To a solution of 50 g of P2 in 45 g dioxane heated to 60° C. is slowly added a solution of 26.2 g of 3-amino-1,2,4-triazole in 30 g of a 1:1 dioxane/methanol mixture. The reaction is heated at 60° C. for 90 minutes. After cooling, the reaction mixture is concentrated to 45% solids and the pH is adjusted to 6 to give A.

Example 4

[0083] Functionalization of P2-synthesis of B.

[0084] To a solution of 40 g of P2 in 30 g dioxane heated to 60° C. is slowly added a slurry of 13.6 g of 3-aminoindazole in 106 g of dioxane. The reaction is heated at 60° C. for 120 minutes. After cooling, the reaction mixture is concentrated to 50% solids and the pH is adjusted to 7 to give B.

Example 5

[0085] Functionalization of P1-synthesis of C.

[0086] To a solution of 10 g P1 (45% solid) in 30 mL of xylenes, is slowly added 1.68 g of 3-amino-1,2,4-triazole and the mixture is heated under reflux for 4 h. The xylene is removed under reduced pressure, and the crude product is washed with water (3×100 mL) to give 5.8 g of C.

Example 6

[0087] Functionalization of P1-synthesis of D and E.

[0088] To a solution of 20 g of P-1 (45% solids) in 20 mL of xylenes is slowly added 3.36 g of 3-amino-1,2,4-triazole. The reaction mixture is heated under reflux for 4 h and then allowed to cool to room temperature. The xylene layer is decanted and the xylene removed under reduced pressure to obtain 1.1 g of D. The residue is washed with water on a suction filter to obtain 9.8 g of E.

Example 7

[0089] Functionalization of P1-synthesis of F and G.

[0090] To 5.0 g of 4(1-H-imidazole-1-yl)-aniline is added slowly a mixture of 16 g (45% solids) P1 and 16 mL xylene. The reaction mixture is heated under reflux for 4 hours, then allowed to cool to room temperature. The xylene layer is decanted and the xylene is removed under reduced pressure to obtain 2.0 g of F. The precipitate is dissolved into 300 mL acetone and then the solvents are removed under reduced pressure to obtain 9.2 g of G.

[0091] Corrosion Resistance Testing

[0092] The following procedure was utilized to determine the corrosion resistance of the polymer compositions of the invention under conditions of chlorination. This test places emphasis on the ability of the corrosion inhibiting polymer compositions to resist penetration of chlorine through the adsorbed film on a copper surface.

[0093] Formulation Stock Solution:

[0094] A stock solution was prepared containing 1000 ppm of phosphoric acid (as PO43−, 1.21 g of 85% H3PO4), 625 ppm of 1-hydroxyethylidene-1,1-disphosphonic acid (as PO43−, 1.13 g of 60% HEDP, Dequest® 2010, Solutia) and 625 ppm of Acumer® 2000 copolymer supplied at 39.5% actives by Rohm and Haas Company (1.58 g). To complete the stock solution, water was added to the mixture to afford a total weight of 998 g. The pH was adjusted to 10.5 and then 1000 ppm tetrapotassium pyrophosphate (as P43−, 1.74 g of TKPP) was added. The pH of the final mixture was adjusted to 11.0.

[0095] Polymer Stock Solution:

[0096] Each polymer was prepared as 1000 ppm (as actives) in an appropriate solvent (water, methanol or isopropanol).

[0097] Preparation of a Test Solution:

[0098] To a container was added the following:

[0099] (a) 125 mL of an aqueous solution containing 500 ppm NaCl, 200 ppm CaCl2 (as CaCO3), 100 ppm MgCl2 (as CaCO3), 400 ppm total alkalinity (as CaCO3), adjusting the solution to pH 7.0;

[0100] (b) 1 mL of formulation stock solution; and

[0101] (c) 0.38 g of polymer stock solution (resulting in 3 ppm actives)

[0102] wherein the solution is maintained at pH 7.0.

[0103] Preparation of Test Apparatus:

[0104] Stainless steel reference electrode-sand with 600 grit SiC paper, rinse with water, rinse with isopropanol, rinse with water, towel dry.

[0105] 18 gauge copper working electrode-sand with 600 grit SiC paper, since with the water, rinse with isopropanol, rinse with water, rinse with acetone then air dry.

[0106] Two stainless steel wires and one copper wire were inserted into the container containing 125 mL of test solution, anchoring the wires through a lid on top of the container. The copper wire is bent into a loop so that the volume/surface area of water to copper is 264 mL/in2. The test solution was stirred at 300 rpm at room temperature for 18 h. After 18 h, 5 ppm NaOCl was added (as Cl2). After 30 minutes, corrosion rate was measured as mil per year (mpy) using an EG&G Princeton Applied Research Potentiostat/Galvanostat Model 273.

[0107] For test without chlorine, the above procedure was used with the following conditions substituted where appropriate: NaCl (1000 ppm), Ca/Mg (100 ppm/50 ppm as CaCO3), volume/surface area 492 mL/in2, 4 h polymer film formation time (unstirred). 1 TABLE I CORROSION INHIBITING COMPOSITIONS AND COMPARATIVE EXAMPLES mpy mpy (3 ppm) Example Sample (3 ppm) with NaOCl Comparative None 3.42 3.09 Comparative Cobratec 0.05 1.24 TT-100 PMC Comparative Cobratec 0.02 2.16 99 PMC 3 A — 5.10 4 B — 4.01 5 C — 2.13 6 D — 0.88 E — 2.70 7 F — 0.50 G — 2.05

[0108] As Table I shows, the best performance in terms of corrosion resistance and chlorine resistance was obtained for Examples 6 and 7. The Examples performed better than TTA, BZT with regard to chlorine resistance (Comparative examples 1 and 2). Overall, most of the examples were comparable to TTA and BZT in terms of chlorine resistance, confirming that they are attractive alternatives to TTA and BZT.

Claims

1. A process for inhibiting corrosion of metallic components in contact with an aqueous system comprising the step of adding to the system an effective amount of one or more polymers comprising:

i) at least one repeating unit selected from a functionalized imide component of Formula Ia, a functionalized amide component of Formula Ib and combinations of Ia and Ib:

3

wherein n is 0 or 1; R and R1 are independently selected from the group consisting of hydrogen, methyl, and C2-C4 alkyl; a heterocycle comprising unsaturated or aromatic heterocycles having one or more hetero atoms selected from the group N, O, S and combinations thereof, the heterocycle chemically bonded to a nitrogen atom via a hetero atom which is part of the heterocycle or a carbon atom of the heterocycle; R3 is selected from the group consisting of hydrogen, methyl, ethyl, C3-C18 branched and straight chain, alkyl and alkenyl groups; and R4 is selected from the group consisting of H, CH3, C2H5, C6H5 and C3-C18 branched and straight chain alkyl groups and C3-C18 alkenyl groups;

ii) at least one ethylenically unsaturated monomer component selected from maleic anhydride, itaconic anhydride, cyclohex-4-enyl tetrahydrophthalic anhydride, and monomers of Formula II:

Formula II

CH(R5)=C(R6)(R7)

wherein R5 is selected from hydrogen, phenyl, methyl, ethyl, C3-C18 branched and straight chain alkyl and alkenyl groups; R6 is independently selected from hydrogen, methyl, ethyl, phenyl, C3-C18 branched and straight chain alkyl and alkenyl groups, OR8 and CH2OR8 groups wherein R8 is acetate, glycidyl, methyl, ethyl, C3-C18 branched and straight chain alkyl and alkenyl groups, and groups having the formula [CH2CH(Ra)O]mRb wherein Ra is hydrogen, methyl, ethyl, and phenyl, m is an integer from 1-20 and Rb is independently hydrogen, methyl, ethyl, phenyl and benzyl; and R7 is independently selected from H, CH3, C2H5, CN, a COR9 group wherein R9 is OH, NH2, OR8 group wherein R8 is a group described previously and a NRcRd group wherein Rc and Rd are the same group or different groups, are parts of a 5-membered or 6-membered ring system, hydrogen, hydroxymethyl, methoxy methyl, ethyl and C3-C18 branched and straight chain alkyl and alkenyl groups branched and straight chain alkyl and alkenyl groups; and

iii) optionally one or more end groups selected from initiator fragments, chain transfer fragments, solvent fragments and combinations thereof.

2. The process according to claim 1, wherein the weight average molecular weight of the polymer is from 400 to 20,000 and the pH of the aqueous system is from 6 to 10.

3. The process according to claim 1, wherein the amount of polymer added to the aqueous system is from 1 to 500 ppm, based on the weight of the aqueous system.

4. The process according to claim 1, wherein the polymer is added to the aqueous system on a periodic or a continuous basis.

5. The process according to claim 1, wherein the polymer is added to the aqueous system as formulation with one or more additives selected from the group consisting biocidal compositions, corrosion inhibitor compositions known in the art, scale inhibiting compositions, dispersants, defoamers, inert fluorescent tracers and combinations thereof.

6. The process according to claim 1, wherein the polymer comprises a functionalized imide component of Formula 1a selected from succinimide, glutarimide and combinations thereof; wherein the heterocycle is selected from the group consisting of imidazole, thiophene, pyrrole, oxazole, thiazoles and their respective isomers, substituted thiazoles and their respective isomers, pyrazole, tetrazole, pyridine, pyridazine, pyrimidine, pyrazine, triazoles and their respective isomers and combinations thereof; and wherein the ethylenically unsaturated monomer component is selected from the group consisting of maleic anhydride, itaconic anhydride, cyclohex-4-enyl tetrahydrophthalic anhydride, ethylene, propylene, butylene, isobutylene, di-isobutylene, propylene tetramer (C12-C14), propylene dimer trimer (C18-C22), 1-butene, 1-octene, 1-decene; styrene, &agr;-methyl styrene, hydroxy styrene, styrene sulfonic acid, butadiene; vinyl acetate, vinyl butyrate, vinyl esters, vinyl chloride, vinylidene chloride, stilbene, divinyl benzene, (meth)acrylic acid, C3-C18 (meth)acrylate esters, C3-C18 (meth)acrylamides and (meth)acrylonitrile.

7. The process according to claim 1 wherein one or more of the polymers is of formula III:

(A)x(B)y(C)z

wherein A is an optional end group component selected from initiator fragments, chain transfer fragments, solvent fragments and combinations thereof; wherein B is a functionalized imide component of Formula Ia, a functionalized amide component of Formula Ib and combinations of Ia and Ib; wherein C is an ethylenically unsaturated monomer component selected from maleic anhydride, itaconic anhydride, cyclohex-4-enyl tetrahydrophthalic anhydride, and monomers of Formula II; and wherein x, y, z are integers values chosen such that (y+z)/x is greater than 2.

8. The polymer according to claim 7 wherein A is selected from the group consisting of dialkyl peroxides, alkyl hydroperoxides, n-dodecyl isopropyl alcohol, alkyl phosphonates, alkyl phosphites, aryl phosphinic acids, alkyl phosphinic acids, hypophosphites, aldehydes, formates, toluene, xylenes, C9-C10 alkylaromatics, and Aromatic 100; wherein the heterocycle attached to B is selected from the group consisting of imidazole, triazole and their respective isomers, thiophene, pyrrole, oxazole, thiazoles and their respective isomers, pyrazole, substituted thiazoles and their respective isomers, tetrazole, pyridine, pyridazine, pyrimidine, pyrazine, and combinations thereof; and wherein C is selected from the group consisting of maleic anhydride, itaconic anhydride, cyclohex-4-enyl tetrahydrophthalic anhydride, ethylene, propylene, butylene, isobutylene, di-isobutylene, propylene tetramer (C12-C14), propylene dimer trimer (C18-C22), 1-butene, 1-octene, 1-decene; styrene, cc-methyl styrene, hydroxy styrene, styrene sulfonic acid, butadiene; vinyl acetate, vinyl butyrate, vinyl esters, vinyl chloride, vinylidene chloride, stilbene, divinyl benzene, (meth)acrylic acid, C3-C18 (meth)acrylate esters, C3-C18 (meth)acrylamides and (meth)acrylonitrile.

9. The process according to claim 1 wherein one or more of the polymers is of formula IV:

Formula IV

(A)x(B)y(B′)z

wherein A is an end group selected from initiators fragments, chain transfer fragments, solvent fragments and combinations thereof; wherein B is a functionalized imide component of Formula Ia selected from succinimide, glutarimide and combinations thereof; wherein B′ includes at least one unit selected from a functionalized imide component or a functionalized amide component selected from succinimide, glutarimide and combinations thereof, wherein the nitrogen atom of each component of B′ is chemically bonded to a group selected from C1-C18 branched or straight chain alkyl, C1-C18 alkyl or alkenyl substituted aryl, which is in turn chemically bonded to a pendant functional group selected from an amine group, amide group, carboxylic acid group, alcohol group or a group having the formula [CH2CH(Ra)O]mRb wherein Ra is hydrogen, methyl, ethyl, and phenyl, m is an integer from 2-20 and Rb is independently hydrogen, methyl, ethyl, phenyl and benzyl; and wherein x, y, z are integers values chosen such that (y+z)/x is greater than 2.

10. The process according to claim 9 wherein the group attached to B′ is an C1-C18 branched or straight chain alkyl amine and the pendant heterocycle attached to B is selected from the group consisting of imidazole, triazole and their respective isomers, thiophene, pyrrole, oxazole, thiazoles and their respective isomers, pyrazole, substituted thiazoles and their respective isomers, tetrazole, pyridine, pyridazine, pyrimidine, pyrazine, and combinations thereof.