MX2008006408A

MX2008006408A - Aqueous dispersions containing ionomer resins and rust-preventive ionomeric coatings made therefrom

Info

Publication number: MX2008006408A
Application number: MXMX/A/2008/006408A
Authority: MX
Inventors: Gordon Anderson Albert; Mahler Walter
Original assignee: E I Du Pont De Nemours And Company
Priority date: 2005-11-22
Filing date: 2008-05-16
Publication date: 2008-09-02

Abstract

The present invention is directed to an aqueous dispersion composition which comprises an ethylene-unsaturated carboxylic acid ionomer resin (A) neutralized with a mixture of ions including at least one divalent metal ion and at least one ammonium ion, (B) a non-water soluble vapor phase corrosion inhibitor, and (C) water. The dispersion exhibits good shelf-life and excellent rust-prevention properties. Durable corrosion resistant ionomeric coatings can be easily formed therefrom, which when applied to metal surfaces and baked, can form a rust-preventive coating layer showing excellent coating adhesion both to the metal surface and to an over coat paint. Such coatings are particularly useful when applied to a vehicle body or part thereof.

Description

AQUEOUS DISPERSIONS CONTAINING IONOMER RESINS AND IONOMERIC PREVENTATIVE WRAP COATINGS MADE TO START FROM THEMSELVES FIELD OF THE INVENTION This invention relates to aqueous dispersion compositions containing ionomer resins and a process for producing the same, and a rust preventative coating made therefrom and treated articles such as vehicle bodies or parts thereof. same treated with them.

BACKGROUND OF THE INVENTION Electrodeposition of rust preventive preparations on automotive metal substrates is widely used in the automotive industry. In this process, a conductive article, such as a car body or a car part is immersed in a bath of an electrodepositable coating composition comprising an aqueous emulsion of a film-forming polymer and the article acts as an electrode in the electrodeposition process. A high voltage electrical current is then passed between the article and a counter electrode in electrical contact with the coating composition until a coating of a desired thickness is deposited on the article. In a typical cathodic coating process, the article to be coated is the cathode and the counter-electrode is the anode. After the electrodeposition process is completed, the resulting coating article is removed from the bath and rinsed with deionized water and then typically cured in an oven at sufficient temperature to form an interlaced finish on the article. Once the electrodeposition rust preventative is applied to the automotive substrate, the vehicle is then coated on the top with a multi-layer automotive exterior finish to provide chip resistance properties and an attractive aesthetic appearance such as gloss and distinction. of image. A disadvantage associated with conventional electrodeposition processes is that the coating defects tend to form on the surface of the coated article, such as holes and cracks, which can compromise the corrosion protective properties of the electrodeposited film and produce other deleterious effects such as surface of rough film. The high-voltage baths required in electrodeposition coating processes use large amounts of electricity and are also expensive to maintain. In addition, multiple rinses with deionized water are undesirable, as they present significant waste management and water treatment problems. Accordingly, there is a desire to eliminate the electrocoating process completely and to find new coating methods and compositions that can replace the electrodeposition process, while still maintaining the desired coating properties for automotive rust preventive sizing finishes such as a high degree of corrosion resistance and paint addition both for preventative rust preventions on the metal surface and to the paint applied on it during exterior automotive finishing operations. Various ionomeric coating compositions comprising aqueous dispersions of ionomer resins made from neutralized ethylene with acrylic acid ions or ethylene-methacrylic acid copolymers have been proposed for preventive treatment of rust from metal surfaces, for example as described in JP 2000 -198949 A2 from Akimoto et al., WO 00/50473 Al from Nakata, et al., And US Patent No. 6,458,897 to Tokita, et al, issued October 1, 2002. However, various properties are required for a coating formed of an ionomer resin dispersion to be a suitable commercial replacement for an electrocoating bath. When trying conventional ionomeric aqueous dispersions, the resulting coating can not provide the level of bath stability and uniformity and corrosion resistance, water impermeability, film smoothness and ease of use required to produce automotive-grade high-performance rust preventive coating. The present invention provides a uniform aqueous dispersion of an ionomer resin with good stability and rust preventative properties that sufficiently meet the high performance requirements of automotive finishes and is therefore suitable as a commercial replacement for conventional electrodeposition sizing currently used in automobile assembly plants. The present invention can also be applied directly on non-chromed metal to provide direct contact protection, which provides substantial savings to the automobile manufacturers, since most of the auto bodies are currently constructed of steel with Zn electrodeposition (galvanized) everywhere except the awning area.

SUMMARY OF THE INVENTION The stable aqueous dispersion of the present invention comprises (A) an ionomer resin neutralized with a mixture of ammonium ions and at least one divalent metal cation selected from the group consisting of alkaline earth metals and Zn; (B) a vapor phase corrosion inhibitor not soluble in water; and (C) water. A process for producing the above aqueous dispersion composition and rust preventative coatings made therefrom, and treated articles such as vehicle bodies or parts thereof treated therewith, also form a part of this invention. The ionomer resin used is preferably a copolymer of ethylene-acrylic acid or methacrylic acid having an acid content of 5-40 weight percent.

DETAILED DESCRIPTION OF THE INVENTION In this description, a number of terms and abbreviations are used. The following definitions are provided. "Ionomer" or "ionomer resins" are polymers or copolymers of ethylene and acrylic or methacrylic acid which optionally have been partially or completely neutralized with a base, such as a hydroxide or metal oxide or acetate, ammonium hydroxide or amines. The resulting polymer is capable or behaves as if interlacing between polymer chains was formed under curing conditions, which creates strong flexible films. "Copolymers" means polymers that contain two or more monomers. "Not soluble in water" means a material having a solubility in water at 25 ° C not greater than 2%, preferably not greater than 1%, most preferably not greater than 0.5%. An aqueous dispersion composition and a process for producing the same, and a rust preventative coating made therefrom, and treated articles such as vehicle bodies or parts thereof treated therewith, are explained in detail below. . The aqueous dispersion composition of the present invention comprises a dispersion of at least one film-forming ionomer resin (A), in water. The ionomer resin (A) which forms the aqueous dispersion composition is a polymer comprising a polymer backbone consisting mainly of hydrocarbon, and having carboxyl groups in side chains, wherein at least a part of the carboxyl groups is neutralized with one or more cationic neutralizing agents, the divalent metal cations and / or ammonium ions (NH4 +). Preferably, the ionomer resin (A) used in the present invention is an ethylene-unsaturated carboxylic acid copolymer ("ethylene-acid copolymer"), comprising a partially neutralized product obtained by neutralizing at least a portion of the groups carboxyl contained in the copolymer with a mixture of ammonium ions and divalent metal cations. The ethylene-unsaturated carboxylic acid copolymer constituting the main base structure of the ionomer resin can be a random copolymer of ethylene and unsaturated carboxylic acid or a graft copolymer wherein the unsaturated carboxylic acid is grafted to the main chain comprising polyethylene. In particular, the ethylene-unsaturated carboxylic acid random copolymer is preferable. In addition, this ethylene-unsaturated carboxylic acid copolymer may contain one type of unsaturated carboxylic acid only, or two or more types of unsaturated carboxylic acids. The unsaturated carboxylic acid which is the component component of the ethylene-unsaturated carboxylic acid copolymer includes an unsaturated carboxylic acid having 3-8 carbon atoms or the like. Specific examples of the unsaturated carboxylic acid having 3-8 carbon atoms include acrylic acid, methacrylic acid, maleic acid, fumaric acid, itaconic acid, crotonic acid, isocrotonic acid, citraconic acid, alkylsuccinic acid, mesaconic acid, glutaconic acid, nadic acid, methylnadic acid, tetrahydrophthalic acid and methylhexahydrophthalic acid. Of these, acrylic acid and methacrylic acid are preferable from the point of view of film-forming property. In addition, the unsaturated ethylene-carboxylic acid copolymer may contain a third component in the main base structure such as a softening monomer in addition to ethylene and unsaturated carboxylic acid. This third component includes unsaturated carboxylic acid esters such as methyl (meth) acrylate, methyl (meth) acrylate and isobutyl (meth) acrylate and vinyl esters such as vinyl acetate. If these monomers are included, it is generally desirable that the content be set in the range of 20% by weight or less, preferably 10% by weight or less, since larger amounts tend to cause the melting point of a coating film. fall and heat resistance is unacceptable. Preferably, the ethylene-acid copolymer is a dipolymer (not the third comonomer). As for the unsaturated ethylene-carboxylic acid copolymer, when considering the feasibility of manufacturing an aqueous dispersion, the dispersion stability and the physical properties of the coating film obtained with the aqueous dispersion, it is generally desirable that the copolymer ethylene-unsaturated carboxylic acid has an unsaturated carboxylic acid content of 5-40% by weight, preferably 10-35% by weight and most preferably still 15-25% by weight. In the case of using a copolymer containing an unsaturated carboxylic acid in an amount that is less than the aforementioned range, it is difficult to obtain a composition having good dispersion stability. In the case of using a copolymer containing an unsaturated carboxylic acid in an amount greater than the aforementioned range, a stable dispersion composition can be obtained, however both the test quality to water (waterproof) and mechanical strength of the coated film are reduced. At least a part of the carboxyl groups that the ethylene-unsaturated carboxylic acid copolymer has in the side chain is neutralized with a base, which in the present invention, generally comprises a mixture of ions, particularly a mixture of divalent metal cations and ammonium ions as the neutralizing agent, to form entanglements comprising the association of carboxylic acid anions with various divalent metal cations and ammonium ions. The divalent metal ions, which remain in the film after the film is baked, provide the desired corrosion resistance to the coating formed therein. The ammonium ions dissipate when heated as ammonia and therefore provide the water impermeability desired, especially in comparison with alkali metal ions. As for the divalent metal cations, ferrous alkali metals, such as Mg and Ca, and Zn can be used. Of course, ionomer resins having Zn as the divalent metal cations are preferable at the point that production is easy. It is understood that compounds containing the divalent metal cations, when used at the levels desired herein, will typically cause the aqueous dispersion to coagulate. Therefore, for example, when zinc is used, to avoid coagulation, it is desirable to introduce it into the dispersion as an ammonia (or amine) complex preferably in the presence of excess aqueous ammonia (i.e., by the use of an amount of ammonia in excess of the amount that would be necessary to neutralize the carboxylic acid groups). Failure to complex the divalent cation before contact (i.e., mixing) with the ionomeric resin will generally cause the mixture to coagulate and form a non-usable and inferior coating. Therefore, to form the desired divalent metal (preferably divalent zinc oxide) / ammonium complex, the divalent metal oxide (e.g., zinc oxide) is preferably milled, such as milled in a ball mill, with a large amount of (i.e., excesses) aqueous ammonia (10 to 50 moles of ammonia per each mole of zinc oxide) for a few hours, preferably at least 5 hours, at room temperature. The resulting aqueous paste can then be added to the ionomer resin which may or may not be pre-dispersed with aqueous ammonia. Of course, other techniques can also be used to introduce the divalent metals into the dispersion without coagulation, as will be apparent to those skilled in the art. Since the metal cations remain in the final film, it is preferred to discuss levels of neutralization in terms of the metal ion. As will be appreciated by those skilled in the art, the degree of neutralization preferred by the metal, ie, the preferred ratio of metal ion to carboxylic acid anion, will of course depend on the ethylene-acid copolymers and the ions used and the properties desired. However, the preferred proportion of carboxyl groups neutralized with divalent metal cations to all carboxyl groups that the ethylene-unsaturated carboxylic acid copolymer has in the side chain, i.e., the degree of neutralization by the metal, is generally about 20-100% and preferably 25-50%, whereby a coating having excellent resistance to corrosion is obtained. Since the excess ammonia is preferably used, this typically results in a molar ratio of metal cation to ammonia in the final mixture generally of about 2 to 10 and preferably 10 to 20. As will be appreciated by one skilled in the art based on in the teachings herein, the preferred level of neutralization will depend on the ethylene-acid copolymers and the ions used and the desired properties. In particular, wherein the aqueous dispersion composition of the present invention is used as a rust preventative treatment agent, the above ranges are effective such that a rust preventative layer can be formed having excellent corrosion resistance and resistance to corrosion. Water. The production of ionomer resins used herein can be conducted in accordance with various methods known in the art, for example, a method of copolymerization of ethylene, unsaturated carboxylic acid, and a third component used according to the needs, by a method of polymerization of high pressure radicals, and by neutralizing carboxyl groups of the ethylene-unsaturated carboxylic acid copolymer obtained with a compound having the divalent metal cations and ammonium ions; or a method of polymerization by grafting unsaturated carboxylic acid onto polyethylene, and neutralization of carboxyl groups of the graft copolymer obtained with a compound having divalent metal cations and ammonium ions.

In addition, production can be conducted by supplying predetermined components in an extruder and kneading under melting to drive the reaction or it can be conducted in water or an appropriate organic solvent. Instead of preparing the unsaturated ethylene-carboxylic acid copolymer, Nuclel®, which is a copolymer of poly (ethylene-co-methacrylic acid) sold by DuPont, Wilmington, Delaware, can be used as the starting material. This material is typically sold pre-dispersed in water with ammonia. As for the other components, a compound having desired divalent metal cations that can be used to neutralize the resin include divalent metal oxides or hydroxides or simple water-soluble salts such as zinc, calcium or magnesium acetates, sulfates and nitrates. . A compound having the desired ammonium ions that can be used to neutralize the resin is ammonia (NH3) or aqueous ammonia (which is also referred to herein as "ammonium hydroxide" or "ammonia water"). In addition to the above materials, in order to obtain a coating film with sufficient water resistance with automotive applications (ie, impervious to agents that can cause metal corrosion), the aqueous dispersion also contains a vapor phase corrosion inhibitor. Not soluble in water (B). The vapor phase corrosion inhibitor (B) used in the present invention is vaporizable under ambient conditions to provide corrosion protection to the metal surfaces covered by the coating formed thereon. As used herein, the term "vaporizable" and its variants refers to a solid or liquid that is capable of becoming vapor at least under ambient conditions without the application of heat. For example, the corrosion inhibitor of the present invention can be a vaporizable solid that is capable of sublimation in its vapor, or it can be a vaporizable liquid that is capable of evaporating in its vapor at ambient conditions typical of atmospheric pressure and room temperature ( 20 ° C). If desired, heat may be applied to initiate or accelerate vaporization, but is generally not required if the present vapor of the inhibitor is sufficiently high. Virtually any corrosion inhibitor that is compatible with the ethylene-unsaturated carboxylic acid copolymer material and that is freely contained within the metal surface to which the copolymer is applied is used, provided that the inhibitor is also insoluble in water, so that this material is not leached from the coating film formed from the dispersion when it comes into contact with the atmospheric unit. The corrosion inhibiting composition of the present invention can inhibit both anodic and cathodic reactions by including certain types of corrosion inhibitors, such as organic and inorganic nitrogen compounds, sulfonates, phosphate compounds and combinations thereof. The corrosion inhibitors of the present invention are desirably substantially anhydrous to minimize the exposure of a metal surface that can corrode the unit. The corrosion inhibitors desirably have a vapor pressure of about 10"2 to 10" 5mm Hg at about 20 ° C. That vapor pressure allows the delivery vehicle to release the inhibitor to effect a metal surface next to a corroding article. Desirably, the corrosion inhibiting composition of the present invention may also include more than one vapor phase corrosion inhibitor. For example, corrosion inhibitors having different vapor pressures may be suitably selected to provide a controlled release of the vapor phase inhibitors of the composition over time. In that way, a high vapor pressure corrosion inhibitor offers protection against initial corrosion to an article due to its high release rate while a low vapor pressure corrosion inhibitor offers protection against sustained corrosion due to its release rate slower. Certain useful corrosion inhibitors of the present invention include dicyclohexylamine, hexadecylpyridinium iodide; dodecylbenzylquinolinium bromide; propargylquinolinium bromide; cyclohexylammonium benzoate; dicyclohexylammonium nitrite; benzotriazole; sodium dinoylnaphthalene sulfonate; triethanolamine dinoylnaphthalenesulfonate; ammonium dinoylnaphthalenesulfonate; ethylenediamine dinoylnaphthalene sulfonate; diethylenetriamine dinoylnaphthalene sulfonate and 2-methylpentanediamine dinoylnaphthalene sulfonate; or its salts and combinations thereof. Additional useful corrosion inhibitors include triazoles, and nitrites, nitrates, phosphates, inorganic carbonates and aliphatic and aromatic amines that are believed to migrate to the surface in the presence of water vapor and provide corrosion protection. These corrosion inhibitors can be used suitably in the present invention. These compositions are described, for example, in the patent of E.U.A. No. 4,973,448 (Carison); patent of E.U.A. No. 4,051,066 (Miksic); patent of E.U.A. No. 4,275,835 (Miksic); and patent of E.U.A. No. 5,139,700 (Miksic). Examples of nitrite compounds that are effective as corrosion inhibitors include sodium nitrite, dicyclohexylammonium nitrite, diisopropylammonium nitrite and nitronaphthalemonium nitrite. A variety of different classes of useful corrosion inhibitors include primary amines; secondary amines; tertiary amines; diamines; aliphatic polyamines; aldehydes; organic acids; salts of organic aromatic acids; salts of quaternary ammonium compounds; non-aromatic heterocyclic amines; heterocyclic amines; thiols (mercaptans); thioethers; sulfoxides; thiourea and substituted thioureas; substituted thiocarbonyl esters; and combinations thereof. Examples of primary amines useful in the present invention include n-octylamine; n-decylamine; n-tetradecylamine; n-octadecylamine and cyclohexylamine. Examples of secondary amines useful in the present invention include dibutylamine; diamylamine; di-n-octylamine; 3-isopropylamine-1-butyne; 3-benzylamino-l-butyne; and dicyclohexylamine. Examples of tertiary amines useful in the present invention include tributylamine; tri-n-octylamine; and dipiperidinomethane. Examples of diamines useful in the present invention include n-hexadecyl propylenediamine and n-dodecyl-b-methylenediamine. Examples of aldehydes useful in the present invention include cinnamic aldehyde and furfuraldehyde. Examples of aldehydes useful in the present invention include n-caproic acid; n-caprylic acid; 9, 11-octadecadienoic acid and nicotinic acid esters or amides. Examples of heterocyclic amines useful in the present invention include 6-n-ethylpurine; l-ethylamino-2-octadecylimidazoline; 1-hydroxyethyl-2-octadecylimidazoline; diethyl thiophosphate; quinoline; 2-6-dimethylquinoline; acridine; 4-5-diphenylimidazole; benzimidazole; 1-methylbenzimidazole; 1-phenylbenzimidazole and 2-phenylbenzimidazole. Examples of thiols (mercaptans) useful in the present invention include 2-mercaptobenzothiazole. Examples of thioethers useful in the present invention include didecyl sulfide, ethyl-n-octyl sulfide; diphenyl sulfide, phenylbenzyl sulfide; dibenzyl sulfide and xylenol polysulfide. Examples of sulfoxides useful in the present invention include diphenyl sulfoxide; di-p-tolyl sulfoxide and dibenzyl sulfoxide. Examples of thiourea and thioureas useful in the present invention include phenylthiourea and 1-3-diphenylthiourea. Examples of phosphates useful in the present invention include dioctyl thiophosphate and tributyl selenophosphate. The non-water soluble vapor phase corrosion inhibitor is generally used in an amount sufficient to provide the desired level of corrosion resistance for a particular application. Therefore, the amount may vary, according to the intended use. Typically, the amount of corrosion inhibitor used in the dispersion will vary from about 0.1-10% by weight, preferably 1-5% by weight, based on the total weight of neutralized resin. As for the amount of water (C) used to make the aqueous dispersion, when taking into account the ease of production, stability and economic efficiency, it is generally desired to adjust the concentration of solids in the aqueous dispersion to approximately 2-60% by weight, preferably about 5-50% by weight, and most preferably still 10-40% by weight. The aqueous dispersion composition of the present invention can be made by various methods well known in the art. Typically, the aqueous dispersion, which can finally be used as a rust preventative coating composition, is made by introducing ionomer resin (A), neutralizing agents such as ammonia and one or more divalent metal cation complexes, and corrosion inhibitor. of vapor phase not soluble in water (B), and water in a vessel, then stirred at a temperature above the melting temperature of the ionomer resin, typically at about 100-200 ° C, for a time sufficient to heat fuse and uniformly disperse the ionomer resin (A), preferably from about 10 minutes to 2 hours. A suitable aqueous dispersion that can be used by this invention for rust preventive coating of automotive bodies comprises about 5-50% by weight, preferably 5-30% by weight, and most preferably 10-30% by weight based on the weight total of the dispersion, of film-forming ionomer resin, which is preferably an ethylene-acrylic acid copolymer having an acid content of 18-30% by weight, 25-50 mol% of divalent metal cations and 75- 600 mole ammonia based on the carboxyl groups of copolymer, and a vapor phase corrosion inhibitor not soluble in water in an amount of about 1-5% by weight, preferably about 2-3% by weight, based on the total weight of neutralized copolymer. An aqueous dispersion suitable for rust preventative coating preferably also has its average diameter of dispersed particles in the range of about 0.1 μm or less, and preferably 0.05 μm or less and its concentration of solids content in the range of 10-45% in weight, and preferably 15-35% by weight and most preferably 15-30% by weight. A suitable aqueous dispersion typically has a pH of 7 or more and a viscosity of about 30-2,000 mPa-s, and particularly about 50-1,500 mPa-s, at the time of application for a working capacity. Some other additives may be mixed in the dispersion to provide additional coating attributes, as necessary, within the range in which the object of the present invention has not been altered. For example, some other film-forming and / or interlacing resins such as water-soluble polyester polyols, acrylics and water-soluble covalent corrosion agents such as amino resins and the like. The water-soluble amino resin is used in particular to improve the strength of the coating, and examples thereof include water-soluble melanin resins, hexametoxymelamine, methylolated benzoguanamine resins and methylolated urea resins. Examples of the other components include organic and inorganic thickeners for adjusting viscosity, surface active agents for improving stability, water-soluble polyvalent or monovalent metal salts and other rust-preventive auxiliaries, mold-proofing agents, fungicides, biocides, ultraviolet absorbers, heat stabilizers, foaming agents, other rheology control agents, pigments, fillers and extenders. The aqueous dispersion composition of the present invention is particularly suitable as a rust preventative agent for use in a rust preventative treatment method in which the composition is applied to a metal surface to form a rust preventative layer having excellent strength corrosion and also good adhesion to an overcoat paint, such as automotive sizing, filler or pigmented base coat paint with solid color or flake pigments on which a clear clear protective coating is typically applied to form a finish of base coating / automotive clear coating. That coating is applicable to various types of metallic materials in various ways. Examples of metals to which the rust preventative treatment method is applied include various metals such as zinc electroplated steel, zinc-plated alloy steel electroplated steel, aluminum electroplated steel, aluminum-based alloy steel plated steel, rolled steel in cold and hot rolled steel. The metal surface to which the coating is applied may contain a slight amount of additional elements, such as surface treatments such as chromate processing, phosphoric acid processing, etc. The rust preventive method of the present invention is especially useful on non-electroplated metal, such as zinc, aluminum and aluminum alloys, and the like, which is particularly desirable in the automotive and aircraft industries when metal is used to build vehicle bodies. of motor such as car bodies and trucks. In the rust preventive treatment method of the present invention, the coating of the rust preventative treatment agent can be conducted in any manner of spraying, curtain, flow coating, roller coating, brush coating, dipping and the like. In automotive applications, the immersion method is preferably used. In preventive treatment of rust from automobiles and trucks, it is typically desired to maintain the vehicle body or part thereof in the immersion tank of approximately 1 to 300 seconds, most preferably approximately 1 to 60 seconds, at a bath temperature of 18 to 60 ° C, at atmospheric pressure. After coating the rust preventative treatment agent on the substrate, the agent can be dried spontaneously, but it is preferable to conduct baking. The temperature of the baking is generally about 60-250 ° C, and upon heating for 1 second to 30 minutes, it is generally sufficient to expel the volatile components, so that a rust preventative layer comprising a coating having good resistance to corrosion can be formed. The thickness of the rust preventive layer formed on the substrate is appropriately selected in accordance with the purpose of use of the rust preventive treated metal products, used rust preventative treatment agent, type, thickness or the like of an overcoat paint. -coating and the like, and not particularly limited thereto. Generally, to present sufficient rust preventative capacity without causing breakage in the rust preventive layer when dried after coating the rust preventative treatment agent, it is preferable to coat in a thickness of about 7 to 60 microns, preferably 12 to 36 microns . In the rust preventative treatment method of the present invention, the overcoat paint applied on the rust preventative layer formed with the treatment by the rust preventative treatment agent is preferably a paint comprising, for example, a resin acrylic, an acrylic modified alkyd resin, a toxic resin, a urethane resin, a melamine resin, an ophthalmic acid resin, an amino resin, a polyester resin or a vinyl chloride resin. Of these, a paint comprising a urethane resin, a melamine resin or an acrylic resin is preferable due to its particularly excellent adhesion to the rust preventative layer comprising the rust preventative treatment agent of the present invention.

In addition, this overcoating paint may comprise coloring pigments such as titanium white or carbon black, extenders such as talc, metallic pigments such as aluminum powder or copper powder, opaque pigments such as coated mica and rust preventative pigments. such as lead red or lead sulfate and the like. The paint may also contain dispersing agents, drying agents, plasticizers, defoaming agents, thickeners, stabilizers and anticaking agents, anti-molds, antiseptic agents, antifreeze agents and the like. The coating formation of the overcoat paint is typically conducted by coating the overcoat paint on the rust preventive layer by conventional coating, drying and curing methods. Typically, overcoating methods for automotive applications include spraying, electrostatic spraying, and the use of high-rotation electrostatic hoods and the like. The drying time and temperature are appropriately adjusted according to the type of the applied overcoat paint, the thickness of the coating and the like. Generally, a drying time of 5-120 minutes for each overcoat layer is adequate, especially in automotive applications, when the drying temperature is in the range of 50-160 ° C. In the rust preventive treated metal products produced by the rust preventative treatment method of the present invention, the coating thickness of the overcoat paint is appropriately determined in accordance with the purpose of the use of the rust preventive treated metal products. , type of overcoat paint used and the like, and is not particularly limited thereto. For example, when automotive bodies or part thereof are coated, after the rust preventative coating layer of the present invention dries, it is generally desired to coat it with a sizing surface applicator to provide a free soft film. of surface imperfections on which, after baking and application of sand, an automotive topcoat finish such as a color basecoat / lightcoat finish is applied, preferably in a wet-on-wet manner and then cured simultaneously in an oven. The overall thickness of the dry and cured mixed multilayer finish is generally about 40-50 microns and preferably 60-100 microns. Preventive rust preventive treated metal products by the rust preventative treatment method of the present invention have a rust preventative layer having excellent water resistance and rust preventative property, and therefore can be suitably used as parts for automobiles, household appliances, building materials or the like. The aqueous dispersion composition has good stability and good shelf life, such that the particle size and viscosity is significantly changed with time of up to one year or more. The coatings formed therefrom have excellent rust preventative properties and provide a high level of adhesion to treated or untreated metals and are strong, flexible, chip resistant and are relatively permeable to moisture and other corrosive agents, and can provide rust preventative coatings that have desirable properties for automotive finishes. The following examples illustrate the invention. All parts and percentages are on a weight basis unless otherwise indicated.

Example 1 Preparation of aqueous dispersion In a 1000 ml bottle is charged 8.6 g of zinc oxide, 20 g of concentrated ammonium oxide, 2.0 g of dicyclohexylamine, and ten high density alumina ceramic grinding stones (Burundum®) 1.27 cm long X 1.27 cm in diameter (manufactured by US Stoneware, East Palestine, OH). The bottle is sealed, placed in a roller mill (manufactured by U. S. Stoneware, East Palestine, OH), and rolled at 53 rpm for 18 hours. Then 800 g of Michem Prime® 4983R (ethylene copolymer / 21% acrylic acid (Nucrel®) at 25% solids in ammonia water manufactured by Michelman, Inc., Cincinnati, OH), 10 g of ammonium hydroxide and 70 g. Water g was added to the bottle. The contents were placed in the roller mill and rolled for 24 hours. The dispersion was filtered through nylon media to give an ionomeric dispersion having 23% solids and 38% neutralization of the carboxylic acid groups by zinc.

Example 2 Preparation of Rust-Preventive Metal Plate Cold-rolled steel plates 7.62 cm X 12.7 cm (32 gauge) (manufactured by ACT Laboratories, Inc., Hillsdale MI) were cleaned by immersing them in a 1: 1 v / v solution prepared from dichloromethane and acetone. After removing the cleaning solvent by air drying, the plates were immersed in the dispersion of Example 1 and then heated in an oven at 95 ° C for 25 to 30 minutes. The plates were then removed from the oven and allowed to cool to room temperature. The thickness of the coating was found to be about 24 microns by the use of a Permascope® ES thickness gauge (manufactured by Twin City Testing Corp., North Tonawanda, NY).

Test results The adhesion of the coating was determined by cutting the coating with a shaving knife to create a design in crossed diagonals with cut lines separated by 2 mm. Five lines were cut in each direction to form 16 frames. A piece of Scotch tape was pressed on the cross-line design and pulled at a 90 degree angle. The perfect adhesion resulted in no loss of coating within the 16 frames and a score of 16/16 is given. The loss of all the frames gets a score of 0/16. The coating of Example 2 had an adhesion score of 16/16. The corrosion resistance was determined by placing coated steel sheets prepared in Example 2 in a 3% sodium chloride solution for 10 days and noting the appearance of rust. Prior to the corrosion test, the edges of the coated steel panels were painted with an oil-based alkyd paint. The coatings prepared as in example 2 having 12 microns or more thick did not show corrosion.

Some other modifications, alterations, additions or substitutions of the components of the methods and compositions of this invention will be apparent to those skilled in the art without departing from the spirit and scope of this invention. This invention is not limited by the illustrative embodiments set forth herein, but rather is defined by the following claims. It is noted that in relation to this date, the best method known to the applicant to carry out the aforementioned invention, is that which is clear from the present description of the invention.

Claims

CLAIMS Having described the invention as above, the content of the following claims is claimed as property: 1. An aqueous dispersion composition characterized in that it comprises: (A) an ionomer resin neutralized or partially neutralized with a mixture of divalent metal ions and ions of ammonium, (B) a vapor phase corrosion inhibitor not soluble in water and (C) water. 2. The aqueous dispersion according to claim 1, characterized in that the ionomer resin is an ethylene-unsaturated carboxylic acid copolymer having an acid content of 5-40% by weight. 3. The aqueous dispersion according to claim 1, characterized in that the ionomer resin is a copolymer of ethylene-acrylic or methacrylic acid having an acid content of 10-35% by weight. 4. The aqueous dispersion according to claim 1, characterized in that the divalent metal ion is selected from the group consisting of Zn. 5. The aqueous dispersion according to claim 1, characterized in that the dispersion has a solids content of 10 to 45% by weight. 6. A process for producing an aqueous dispersion composition characterized in that it comprises a step of mixing: (A) an ionomer resin neutralized with a mixture of ions comprising at least one divalent metal ion and at least one ammonium ion , (B) at least one vapor phase inhibitor not soluble in water, and (C) water; and heating the mixture for a time and temperature sufficient to uniformly melt and disperse the ionomer resin in water. The process according to claim 6, characterized in that the ionomer resin is an ethylene-unsaturated carboxylic acid copolymer having an acid content of 10-35% by weight. The process according to claim 6, characterized in that the ionomer resin is a copolymer of ethylene-acrylic or methacrylic acid having an acid content of 10-35% by weight. The method according to claim 6, characterized in that the divalent metal ion is selected from the group consisting of Zn. The process according to claim 6, characterized in that the dispersion has a solids content of 10-45% by weight. 11. An ionomeric coating composition, characterized in that it comprises the aqueous dispersion according to any of claims 1 to 5. 12. The ionomeric coating composition according to claim 11, characterized in that the composition also contains pigments, fillers, extenders. and / or other usual additives. 13. A metal substrate characterized in that it is treated with rust preventive coated with a dry and cured layer of the composition according to claim 1. 14. The metal product treated with rust preventive according to claim 13, characterized because the metallic product comprises a steel plate electroplated with zinc, an electroplated steel plate with zinc-based alloy, a steel plate electroplated with aluminum, a cold rolled steel plate, an aluminum plate or an aluminum alloy plate. aluminum. 15. A vehicle body or part thereof characterized in that it is coated with a dry and cured layer of the composition according to claim

1.