MXPA97002371A - Acu coating composition - Google Patents

Abstract

The present invention relates to an aqueous coating composition characterized in that it comprises: at least about 50% by weight of a solvent component, based on the total weight of the coating composition, including at least about 70% by weight of water, based on the total weight of the solvent component and an organic solvent, and at least about 30% by weight of a film-forming component, based on the total weight of the coating composition, including: A) a carboxy addition polymer having an acid number of at least about 165 and a glass transition temperature of not more than about 110 ° C; B) an epoxy resin having an epoxide equivalent by weight of about 1,000 about 5,000, wherein the carboxy addition polymer and the epoxy resin are reacted in the presence of about 0.35 to about 1.0 equivalents of a tertiary amine ria by equivalent of carboxy groups present in the carbo-addition polymer

Description

COMPOSITION OF AQUEOUS COATING BACKGROUND OF THE INVENTION Coatings are applied to the inside of metal food and beverage cans to prevent the contents from coming into contact with the metal surfaces of the containers. The contact of the contents of the can with the metal surface, especially where acidic products such as non-alcoholic beverages, tomato juice or beer are involved, can lead to corrosion of the metal container and contamination and deterioration resulting from the content. The interiors of the cans are typically coated with a thin thermosetting film to protect the inner metal surface from its contents. Synthetic resin compositions which include vinyls, polybutadiene, epoxy resins, inoplast alkyd and oleoresin materials have typically been used as interior coatings for the can. These heat curable resin compositions are usually applied as solutions or dispersions in volatile organic solvents. The ideal coating should have a low content of extractables to avoid contamination of the contents and must be cured quickly to facilitate the manufacture of the can. The cured coating should be highly resistant to a wide variety of food products, under both storage and processing conditions. The inner coating should be substantially free of blisters and should have good adhesion to the metal surface, both during application and after processing. Relatively thick films are required to ensure full coverage of the metal and to protect the metal during the stretching and forming operations. This is especially true for coatings applied to metal substrates used to produce the end of a can, where film weights of approximately 0.775 mg / cm2 (5 mg / in2) to approximately 1395 mg / cm2 are typically required. (9 mg / in.2). The side seam coatings, which are also applied as thick films and require coatings resistant to blistering or blistering, have similar performance characteristics. The coatings used for food cans and the end or end parts of cans are generally applied and cured in films over high speed coating lines (for example, spool or coil coating lines). Modern high-speed coating lines require a coating material that will dry and cure without defects within a few seconds when it is heated very rapidly to maximum metal temperatures of approximately 230 ° C to approximately 300 ° C (approximately 450 ° F to approximately 550 ° F). Due to the fast curing rates involved, attempts to use aqueous coatings in modern spool or roll coating lines have encountered particularly difficult problems in preventing the formation of blisters. Blister formation typically occurs when the curing or hardening temperature passes through the boiling point of water. The formation of blisters becomes more acute when the thickness of the uncured coating layer increases and at higher heating rates and higher maximum metal temperatures. All of these factors may be present during the application of a coating to the ends of the can on a high speed coating line. Compositions in which the material that produces the film is dispersed or dissolved in organic solvents, are generally used in coating applications where a relatively thick coating is required. Due to environmental and economic disadvantages associated with the use of organic solventsHowever, there is an increasing demand for water-based coatings. In addition to being less expensive than organic solvent-based coatings, water-based coatings minimize the environmental impact of organic solvent release and reduce the need to incinerate the curing oven effluents. Unfortunately, under fast, high temperature curing conditions, commonly available water based coatings do not provide satisfactory operation. There is, therefore, a continuing need for water-based coatings, which will allow the formation under high temperature, fast curing conditions of the protective films which are substantially free of blisters.

BRIEF DESCRIPTION OF THE INVENTION The present invention provides an aqueous coating composition capable of forming a hard coating, resistant to hydrolysis and other forms of chemical attack, while minimizing the environmental problems associated with the use of organic solvents. The coating composition can be applied and cured without the formation of blisters at high coating weights and at elevated line speeds to provide a cured, corrosion resistant, elastic film. In addition to the choice of specific components, the achievement of these properties depends on an appropriate balance or balance of solids content, viscosity and water content of the coating composition. The coating composition includes a solvent component and a film forming component. The solvent component includes water and an organic solvent. The film forming component includes a curing agent and the product of the reaction of a carboxy addition polymer and an epoxy resin in the presence of a tertiary amine catalyst. The present invention also provides a method of coating a metal substrate to provide a cured film on at least one surface of the substrate. The method includes the application of the aqueous coating composition on the surface of the metal substrate to form a coating layer. The coated metal substrate is then heated so that the coating layer is cured to form a cured film adhered to the surface of the substrate. The coated metal substrate is typically cured by heating for about 2 to about 20 seconds in an oven at a temperature of about 230 to about 300 ° C. The cured film is substantially free of blisters and typically has a film weight of at least about 0.775 mg / cm2 (5 mg / in.2) and, preferably, about 1.085 mg / cm2 (7 mg / in. .2) to approximately 1395 mg / cm2 (9 mg / in.2). The present invention also provides a composite material which includes a metal substrate having at least one surface covered with a cured film, which is the result of coating the surface of the substrate with the coating composition described above and heating the metal substrate Coated for 2 to 20 seconds at a temperature of 230 to 300 ° C. The cured film preferably has a film weight of at least about 0.775 mg / cm2 (5 mg / in2).

DETAILED DESCRIPTION OF THE INVENTION The coating compositions of this invention are useful for protecting the interior of food and beverage cans. Cans are typically formed of metals such as aluminum, tin, steel or tin-plated steel. The coatings are generally applied to the metal sheets by one of two processes, each of which involves different curing and coating conditions. The coated metal sheets can be manufactured in can bodies or limbs in a final stage of the manufacturing operation. A process, called the baking process by means of sheets or sheets, involves the roll coating of large metal sheets. These sheets are then placed vertically on supports or racks and the supports or racks are typically placed in ovens for approximately 10 minutes to achieve maximum metal temperatures of about 180 ° C to about 205 ° C. In a coating process by means of a reel or coil, the second type of process, large rolls of thin gauge metal (eg steel or aluminum) are unrolled, roller coated, thermally cured and re-wound . During the reel or coil coating process, the total residence time in the curing ovens will vary from about 2 seconds to about 20 seconds with maximum metal temperatures typically ranging from about 230 ° C to about 300 ° C. The aqueous coating composition of the present invention is particularly suitable for use in coating the ends or closures or caps of beverage or food cans, or for coatings of the side seams of cans. The ends of the cans are typically coated by means of rollers on spool or roll coating lines, up to a dry film weight (after curing) of at least about 0.775 mg / cm2 (5 mg / in2) , preferably in an approximate form 1085 mg / cm2 (7 mg / in2) to approximately 1395 mg / cm2 (9 mg / in2), and more preferably in an approximate 1.162 mg / cm2 (7.5 mg / in2) form to approximately 1317 mg / cm2 (8.5 mg / in2). The present coating composition can also be used to coat the interior of the can body, where it is typically applied by means of a baking process by means of sheets or sheets. The present aqueous coating composition can be coated on a metal substrate at a relatively high film weight (eg, 0.775 to 1395 gm / cm2 (5 to 9 mg / in2)). The integrity and thickness of the uncured film can be sustained despite the exposure of the coated substrate to translational forces (e.g., the translational forces generated during the coating of large rolls of thin gauge metal over coating lines of reel or winding, high speed). The coated substrate can then be cured at high coating weights and high line speeds, without the formation of blisters. The use of the present coating composition allows for the formation of a hard, elastic cured film, which is substantially free of defects. Another advantage of the present aqueous coating composition is that, despite differences in the performance requirements between the two processes, the same composition used to form a relatively coarse coating by means of a reel coating or winding process also It can be used to form thinner coatings (for example, a film weight of 0.465-0.62 mg / cm2 (3-4 mg / in.2) through baking processes by means of sheets or sheets. need to develop separate formulations to meet the different requirements of the two application methods.The aqueous coating composition includes at least about 50% by weight and, preferably, at least about 55% by weight of a component of the solvent and at least about 30% by weight of a film-forming component (based on the total weight of the coating composition). The aqueous coating composition preferably has sufficient viscosity and solids content to allow application to a relatively high film weight (eg, 0.775 to 1395 mg / cm2 (5 to 9 mg / in.2) on a metal substrate subjected to to translational forces, such as the forces generated during a coil coating or winding process. The viscosity of the coating composition should also be low enough to avoid the formation of wastes during the curing of the coated substrate. Preferably, the viscosity of the coating composition is from about 13 to about 100 seconds, more preferably in about 20 to about 80 seconds and more preferably in about 30 to about 60 seconds form (Ford vessel or vessel from # 4 to 27). ° C (80 ° F)). Where the coating composition has to be applied through a reel or winding coating process, the composition preferably includes at least about 30% by weight and, more preferably, about 35 to about 45% by weight of the film-forming component and typically has a viscosity of about 30 to about 60 seconds (vessel or container). Ford from # 4 to 27 ° C (80 ° F)). For those applications where a baking process by means of sheets or sheets will be used and a relatively low coating weight is desired (for example, 0.465-0.62 mg / cm2 (3-4 mg / in2)), the composition preferably includes about 35 to about 45% by weight of the film-forming component and typically has a viscosity of about 50 to about 80 seconds (Ford vessel or container of # 4 at 27 ° C (80 ° F)). ). The coating composition is in the form of an aqueous dispersion with the film-forming component substantially present in the particulate form. If the particle size is too large, stability problems with dispersion can be experienced. The typical particle size is from about 0.1 to about 0.6 microns, preferably from about 0.2 to about 0.4 microns and, more preferably, not more than 0.35 microns. The pH of the coating composition is preferably within the range of about 6.0 to about 8.0 and more preferably is about 6.5 to about 7.5. The composition of the solvent includes water and an organic solvent. Preferably, the solvent component includes from about 70 to about 97% by weight, more preferably from about 75 to about 95% by weight of water and even more preferably from about 79 to about 91% by weight of water (based on the total weight of the solvent component). To minimize cost and environmental problems, it is desirable to include as high a percentage of water as possible. Some organic solvent is necessary, however, to prevent the formation of blisters during curing, particularly where the coating is applied on a coil coating or high speed winding line. The solvent component typically includes at least about 3% by weight, preferably at least about 5% by weight and more preferably at least about 8% by weight of the organic solvent (based on the total weight of the solvent component). Preferably the organic solvent is substantially miscible with water and is either in the form of a single polar compound or as a mixture of compounds which may include non-polar components. The solvent is typically capable of dissolving the resins in the film-forming component, whereby dispersion in an aqueous solution is facilitated. Suitable solvents, which are to be used either alone or as part of a mixture, include glycol ethers and alcohols such as alkanols, monoalkyl glycols, and alkyl carbithols (monoalkyl ethers of diethylene glycol). Among the most commonly used solvents are alcohols such as butyl alcohols (for example, n-butanol), 2-butoxyethanol, Butyl Carbitol (diethylene glycol monobutyl ether). Non-polar solvents can also be included as minor constituents of the organic solvent. Suitable non-polar solvents which may be used include: aliphatic and aromatic hydrocarbons, such as naphtha, hepta-no, strong mineral spirits, toluene and the like. The film-forming component includes a carboxy addition polymer and an epoxy resin, which has been reacted together in the presence of a tertiary amine catalyst. A curing agent is then combined with the resulting reaction product. The amounts (% by weight) specified for the carboxy addition polymer, the epoxy resin and the curing agent are expressed as a% by weight based on the total weight of the film-forming component (i.e., the solids content of the coating composition). The resin mixture includes at least about 7% by weight, preferably about 10 to about 40% by weight of the carboxy addition polymer. Even more preferably, the resin mixture includes at least about 15 to about 25% by weight of the carboxy addition polymer. The carboxy addition polymer can be prepared by conventional polymerization processes and is preferably a copolymer of at least one polymerizable ethylenically unsaturated carboxylic acid monomer and at least one copolymerizable nonionic monomer. Suitable ethylenically unsaturated carboxylic acid monomers include acrylic, methacrylic, maleic, fumaric and itaconic acids. The ethylenically unsaturated carboxylic acid monomer is preferably an o-unsaturated carboxylic acid having from 3 to 10 and, more preferably, from 3 to 5 carbon atoms. Acrylic acid and methacrylic acid are particularly preferred. Suitable non-ionic copolymerizable monomers include ethylenically nonionic unsaturated monomers, such as vmyl aromatic compounds and alkyl esters of ethylenically unsaturated carboxylic acids. Included among the most commonly used copolymerizable nonionic monomers are lower alkyl acrylates (eg, ethyl acrylate), lower alkyl methacrylates, styrene, alkyl substituted styrenes, vinyl acetate and acrylonitrile. Preferably, the copolymectable nonionic monomer is selected from the group consisting of styrene and C-alkyl esters of 8 to 13 unsaturated carboxylic acids having 3 to 5 carbon atoms. The weight average molecular weight of the carboxy addition polymer is generally at least about 2,000 and typically does not exceed about 60,000. More preferably, the weight average molecular weight of the addition polymer is from about 5,000 to about 25,000 and even more preferably, from about 7,000 to about 15,000. The carboxy addition polymer has an acid number of at least about 165, typically about 200 to about 350, and preferably about 225 to about 325. The acid number is defined as the amount of potassium hydroxide ( in mg) required to neutralize one gram of polymer (based on solids). Typically, the carboxy addition polymer has a glass transition temperature (T) of not more than about and 110 ° C and, preferably, the glass transition temperature of the carboxy addition polymer is from about 50 to about 100 ° C. If the coating composition includes a relatively large amount of epoxy resin (for example, of at least about 60% by weight based on the total weight of the film-forming component), a carboxy addition polymer having a T Relatively low, ie, from about 50 to about 100 ° C, it is typically employed. The resin mixture also includes at least about 40% by weight, and preferably about 50 to about 90% by weight of the epoxy resin (based on the total weight of the film-forming component). Even more preferably, the resin mixture includes about 60 to about 80% by weight of the epoxy resin. The epoxy resin can be any resin soluble in an organic solvent containing epoxy groups. Preferably, the epoxy resin includes glycidyl polyethers having more than one epoxide group per molecule (i.e., glycidyl polyethers containing an average of more than one epoxy group per molecule). Typically, the glycidyl polyethers have an average of about 2.0 to about 2.5 epoxide groups per molecule. The diglycidyl ethers of the dihydric phenols are particularly suitable for use in the present coating composition. Exemplary dihydric phenols include resorcinol, 1,5-dihydroxy naphthalene and bisphenols, such as Bisphenol A (p, p'-dihydroxy-2,2-diphenylpropane). Bisphenol A is the preferred dihydric phenol. The epoxy resins typically used in the present invention can be derived from the reaction of the dihydric phenol and an epihalohydrin, such as epichlorohydrin. The molecular weight of the initial reaction product can be increased by the reaction with an additional dihydric phenol. Epoxy resins suitable for use in the present invention typically have equivalent epoxide weights of at least about 1,000 and no greater than about 30,000. The upper limit for the epoxy equivalent weight of the epoxy ream is dictated mainly by the viscosity of the resin which can be accommodated by the processing equipment employed to prepare the coating composition. Epoxy resins having an epoxide equivalent weight greater than about 30,000 are generally more viscous than can be handled by conventional processing equipment. The equivalent weight of the epoxide is preferably in the form of about 1,500 to about 10,000. The diglycidyl ethers of Bisphenol A are commonly available in commerce and commercial materials such as Epon 1009F and Epon 1007F (both available from Shell Chemical Company, Houston, TX) are available for use in the present invention. Even more preferably, the epoxy resin includes a diglycidyl ether of Bisphenol A having an epoxide equivalent weight of from about 2,500 to about 8,000. The epoxy resin may include diglydyl ethers of dihydric phenols whose molecular weight has been increased ("enhanced") by the reaction with an additional dihydro phenol or with a diacid. The inclusion of a higher molecular weight epoxy resin improves the flexibility of the coating composition and, in particular, improves the resistance of the coating to cracking during manufacture. It has been found that the incorporation of an epoxy resin which has been improved by the reaction with an aliphatic diacid can reduce the viscosity of the epoxy resin as well as improve the flexibility of the coating formed last from the coating composition. Suitable aliphatic diacids which can be employed to improve the epoxide equivalent weight of the epoxy resin include adipic acid, succinic acid, dimer fatty acid and the like. For example, the epoxy resin may include a diglycidyl ether of Bisphenol A which has been upgraded to an epoxide equivalent weight of from about 2,500 to about 8,000 by reaction with an aliphatic diacid such as adipic acid. The weight of the diacid employed in the improvement will depend on a number of factors, such as the molecular weight of the diacid, the equivalent weight of the epoxy of the starting epoxy resin and the equivalent weight of the desired epoxide for the epoxy resin. Typically, the amount of the diacid used or used to improve the epoxy resin ranges from about 0.5 to about 20% by weight and, preferably, in an approximate form from 1.0 to about 15% by weight of the epoxy resin component. The epoxy resin can also be partially defunctionalized by the reaction with a phosphorus-containing acid or with an organic monoacid. The acid that contains phosphorus is an acid that has a P-OH functionality or an acid that is capable of generating such functionality during the reaction with water (for example, a compound that has a P-O-P functionality). Examples of suitable phosphorus-containing acids include polyphosphoric acid, superphosphoric acid, aqueous phosphoric acid, aqueous phosphorous acid and partial alkyl esters thereof. The organic monoacid is preferably an aromatic carboxylic acid having up to ten carbon atoms or an alkanoic acid with C. a C? F). Examples of suitable organic monoacids include acetic, benzoic, stearic, palmitic and octanoic acids. The epoxy resin is typically defunctionalized by the reaction of up to about 50% of the epoxy groups present with the organic monoacid. Where the epoxy resin is defunctionalized by the reaction with the acid containing the phosphor, up to about 50% of the epoxy groups are typically reacted with the acid.

The reaction between the carboxy addition polymer and the epoxy resin is carried out in the presence of about 0.35 to about 1.0 equivalents and, more preferably, in about 0.5 to about 0.8 equivalents, of a tertiary amine catalyst per equivalent of the carbo-xi groups present in the carboxy addition polymer. Examples of suitable tertiary amines include trialkyl amines (for example, diethyl butyl amine), dialkyl benzyl amines, and cyclic amines such as N-alkyl pyrrolidine, N-alkyl morphol and N, N '-dialkyl piperidine. Tertiary amines containing at least two methyl groups, such as dimethyl ethanolamm, trimethylamine and dimethylbenzyl amine, are preferred. The film-forming component includes at least about 2% by weight of the curing agent (based on the total weight of the film-forming component). More preferably, the film-forming component includes from about 3 to about 45% by weight, and even more preferably from about 5 to about 25% by weight of the curing agent. The curing agent includes an aminoplast resin and / or a fenoplast resin. Preferably, the curing agent includes a fenoplast resin. Fenoplast reams are condensation products of an aldehyde, such as formaldehyde or acetaldehyde, and / or phenol. Suitable fenoplast reams can be derived from an unsubstituted phenol, cresol or other alkyl phenols as well as from dihydric phenols such as Bisphenol A. The mixtures of the phenols can be used to vary and control the properties of the resin of fenoplast. The phenoplast resin preferably includes at least one of a ream of alkylated phenol-formaldehyde and a bisphenol A-formaldehyde resin. The melting point of the fenoplast resin is preferably not greater than about 100 ° C. Alkylated phenol-formaldehyde reams which are suitable for use in the present coating compositions include solid, polymeric resins having a low color and a molecular weight of at least 1000. Such alkylated phenol-formaldehyde resins are typically a base of one or more longer chain alkylated phenols, for example, phenols substituted with an alkyl group having from 4 to 10 carbon atoms. Longer chain, alkylated, representative phenols include t-butylphenol, hexylphenol, octylphenol, t-octylphenol, nonylphenol, decylphenol and dodecylphenol. The film-forming component may also include a hydrophobic addition polymer. The mcorporation of a hydrophobic addition polymer as an additional component in the present coating compositions "can lead to an improvement in the flexibility, adhesion and / or water resistance of the coatings derived from the composition. , the amount of the hydrophobic addition polymer added to the coating composition typically ranges from about 5 to about 35% by weight and preferably from about 10 to about 30% by weight of the film forming component ("solids content") The hydrophobic addition polymer has a relatively high molecular weight and is typically formed by the polymerization of one or more non-ionic monomers (ie, monomers which do not include an ionizable functional group such as a carboxylic acid or an amine). Weighted average molecular weight of the hydrophobic addition polymer is typically at least about 50,000 and preferably at least about 100,000. Polymers of this type can be produced by an emulsion polymerization process. The preparation of addition polymers of this type is described in U.S. Pat. Nos. 4,446,258 and 4,476,262, the description of which is incorporated herein by reference. Preferably, the hydrophobic addition polymer is formed by the emulsion polymerization of one or more ethylenically unsaturated nonionic monomers in the presence of an aqueous dispersion of the epoxy resin / carboxy addition polymer reaction product. The hydrophobic addition polymer is preferably formed from a monomer or monomers which do not include a hydrophilic group, such as a hydroxyl group or an ionizable group. Examples of suitable hydrophobic monomers include ethylenically unsaturated, hydrophobic monomers, such as vinyl aromatics or acrylate or alkyl methacrylate esters. In a preferred embodiment of the invention, the hydrophobic addition polymer is formed by means of the emulsion polymerization of a mixture of styrene and butyl acrylate. The present hydrophobic addition polymer typically has a relatively low T, for example, and a T of not more than about 100 ° C. Preferably, the present hydrophobic addition polymer has a T of not more than about 40 ° C, and more preferably of not more than about 20 ° C. The hydrophobic addition polymers which are in a state similar to that of rubber at room temperature, are highly effective for use in the present coating compositions. An example of a hydrophobic addition polymer which can be employed in the present coating composition is a polymer formed from a 1: 1 mixture of styrene and butyl acrylate and having a calculated T of 3 ° C. Depending on the desired application, the coating composition may include other additives such as lubricants, coalescing solvents, agents for homogeneous and uniform deposition, wetting agents, thickening agents, suspending agents, surfactants, defoamers, adhesion promoters. , corrosion inhibitors, pigments and the like. The coating compositions, which are to be used as a coating for a can, typically include a lubricant such as a long-chain, synthetic, brittle, hard aliphatic wax, an emulsion of car-nauba wax, or a polyethylene / TefIon mixture. The coating composition of the present invention can be prepared by conventional methods. For example, the coating composition can be prepared by adding the epoxy resin to a solution of the carboxy addition polymer in a solvent mixture which includes an alcohol and a small amount of water. During the addition, a layer of inert gas is maintained in the reactor and the solution of the carboxy addition polymer is heated, typically to about 100 ° C. The mixture is maintained at this temperature and stirred until the epoxy resin is dissolved. The tertiary amine (eg, dimethylethanol amine) is then added and the resulting mixture is stirred for a period of time at an elevated temperature. The curing agent, which typically includes a phenoplast resin, is then added and the batch is maintained for about 30 minutes at a temperature of about 90 to 100 ° C. The deionized water is added under maximum stirring to emulsify the resin and at the temperature it is allowed to reduce. Typically, additional deionized water is added at a uniform rate over a period of about one hour while the batch is cooling. The final viscosity is adjusted to the desired value (typically 30-60 seconds (# 4 Ford vessel or vessel at 27 ° C (80 ° F)) by the additional addition of deionized water.The coating composition that is produced can be used as is or other additives (e.g., a lubricant) can be combined to form the final coating composition The present invention also provides a method of coating a metal substrate to provide a substantially continuous film on at least one surface of the substrate. The method includes applying the aqueous coating composition described above on the metal surface to form a coating layer and heating the coated substrate so that the coating layer is cured to form a cured film which adheres to the surface of the substrate. The cured film has a film weight of at least about 0.465 mg / cm2 (3 mg / in2), preferably at least about 0.775 mg / cm2 (5 mg / in2), and is substantially free of blisters. The present coating compositions are typically used to produce cured, blister-free films having film weights of about 1085 mg / cm2 (7 mg / in.2) to about 1395 gm / cm2 (9 mg / in2). The coating composition can be applied to the surface of the substrate using a variety of well-known techniques. For example, the composition can be coated by means of rolls, coated by means of a bar or sprayed on the surface. Where large rolls of a thin gauge metal are going to be coated, it is advantageous to apply the coating composition by means of reverse roll coating. Where large metal sheets are to be coated, the coating composition is directly roller coated typically on the sheets as part of a baking process by means of sheets or sheets. The baking process by means of sheets or sheets is typically used to form a coated metal substrate wherein a relatively low weight of the cured film (e.g., about 0.465-0.62 mg / cm2 (3-4 mg / in. 2)), it is desired. If the coating is applied using a baking process by means of sheets or sheets, the coated metal substrate is typically cured at a temperature from about 180 ° C to about 205 ° C during about 8 to about 10 minutes. In contrast, when the coating is carried out using a coating process by means of a spool or coil, the coated metal substrate is typically cured by heating for approximately 2 to about 20 seconds at a temperature of about 230 ° C. up to about 300 ° C. If the coating process by means of a reel or spool is used to produce the material to be manufactured at the ends of the can, the cured film on the coated metal substrate typically has a film weight of at least about 0.775. mg / cm2 (5 mg / in.2) and preferably, approximately 1085 to approximately 1395 mg / cm2 (7-9 mg / in.2). The present invention can be further described by reference to the following examples. The parts and percentages, unless otherwise designated, are parts and percentages by weight.

And emplos Example 1 Addition polymer of Carboxi A A five-liter reactor was equipped with agitator, condenser, heater, and thermometer with inlet for inert gas. A layer of inert gas is introduced into the reactor. The n-butanol (3636 parts) and 403 parts of deionized water are charged to the reactor and the solvent mixture is heated under stirring to reflux (95-97 ° C). In a separate vessel, a monomer premix was prepared from 1160 parts of ethyl acrylate, 1864 parts of acrylic acid, 2480 parts of styrene and 432 parts of 70% benzoyl peroxide. The premix of the monomer was added to the reactor for four hours while maintaining the temperature at 95-97 ° C. After the addition is complete, the batch is cooled to 93 ° C and maintained at this temperature for one hour. After the one hour retention or maintenance period, 31 parts of 70% benzoyl peroxide are added, and the batch is maintained for another two hours at 93 ° C to ensure a complete reaction. The final product had an acid number of 248 and contained 57.9% by weight of non-volatile components.

Examples 2-7 Addition Polymers of Carboxi B-G Using a procedure similar to that described in Example 1, a solution of a carboxy addition polymer (CAP) in 3636 parts of n-butanol and 403 parts of deionized water was prepared from ethyl acrylate, styrene and either acrylic acid or methacrylic acid (the parts by weight of the monomers used to prepare each specific CAP are shown in Table I) with 463 parts of 70% benzoyl peroxide. The final products were characterized as shown in Table I.

Example 8 Coating Composition 1 A reaction vessel was prepared with a stirrer, condenser, heater and thermometer with an inlet for inert gas. An inert gas atmosphere was introduced and 112.6 parts of Epon 828 (Shell Chemical, Houston, TX), 59.4 parts of Bisphenol A, 9.1 parts of diethylene glycol monobutyl ether (Butyl Carbitol) and 0.15 parts of ethyltriphenyl phosphonium iodide were charged to the reactor. The mixture is heated under agitation to 121 ° C and is allowed to have an exotherm to 170-180 ° C. Following the exotherm, the batch is maintained at 155-160 ° C until an epoxy value of 0.050 is achieved. Then 16.0 parts of diethyl glycol monobutyl ether are added. Then 155.0 parts of the solution of the carboxy addition polymer of Example E were added and at the temperature it was allowed to reduce to 96 ° C. The batch is shaken to achieve uniformity. After the batch was uniform, dimethylethanol amine (22.0 parts) was added at a uniform rate and the batch was kept for 30 minutes at 90-98 ° C. An exotherm is immediately observed following the addition of the amine. After the 30 minute retention period, 86.0 parts of t-butylphenol-formaldehyde resin (average degree of polymerization of 6) are added and the batch is stirred for 30 minutes at 90-98 ° C. The heating is then turned off and 103 parts of deionized water are added at a uniform rate to emulsify the resin. The batch is allowed to stand for one hour, then 240 parts of deionized water are added for one hour at a constant speed. The resulting epoxy / acrylate / phenolic composition contained 4.19% by weight of the non-volatile components. The epoxy / acrylate / phenolic composition (100 parts) above is charged to a mixing vessel equipped with an agitator. The deionized water, 7.44 parts, is added under agitation and mixed until uniform. The resulting coating composition had a theoretical nonvolatile component of 39.0% by weight.

Example 9 Coating Composition 2 A 1 liter reaction vessel was equipped as described in Example 8 and charged 247 parts of the carboxy addition polymer prepared in Example E. The resulting mixture is heated with stirring to about 100 ° C under a gas atmosphere. inert. Epoxy resin 'Epon 1009F (Shell Chemical) is added; Houston, TX; 138 parts) to the reaction vessel and the mixture is stirred at 100 ° C until the epoxy resin dissolves. After the batch was uniform, stirring was continued until the batch was 96 ° C. Di-ethylethanol amine (32.0 parts) was then added at a uniform rate and the resulting mixture was stirred for thirty minutes at a time. temperature of 90-98 ° C. Then add the resin of t-butylphenol-formaldehyde (average degree of polymerization of 6, 68.8 parts.) The batch is left at rest thirty minutes at 90-98 ° C and added 94 parts of deionized water under maximum agitation to emulsify the resin, then allow the temperature to be reduced to 80-82 ° C while the batch is allowed to stand for sixty minutes.The heating is switched off and deionized water is added (200 parts ) at a uniform rate for one hour and the batch is allowed to cool The resulting epoxy / acrylate / phenolic composition had a non-volatile content of 43.1% by weight The epoxy / acrylate / phenolic composition (100 parts) It is loaded into a container and mixed equipped with an agitator. The deionized water (13.4 parts) is added under stirring and mixed until uniform to produce a theoretical, non-volatile component coating composition of 38.0% by weight.

Examples 10-31 Coating Compositions 3-20 Using a procedure similar to that described in either Examples 8 and 9, coating compositions 3-20 were prepared from a t-butylphenol-formaldehyde resin (average degree of polymerization of 6) and addition polymers of carboxy and the epoxy resins indicated in Table II. Two of the epoxy resins used, Epon 1009F and Epon 1007F, were obtained from a commercial source. Epon 1009F (Shell Chemical Company, Houston, TX) is an epoxy resin derived from Bisphenol A and epichlorohydrin having an epoxide equivalent weight of about 3000 and an epoxy value of 0.026-0.043. Epon 1007F (Shell Chemical Company, Houston, TX) is an epoxy resin derived from Bisphenol A and epichlorohydrin having an epoxide equivalent weight of 1700-2300 and an epoxy value of 0.043-0.059. The other epoxy resins were obtained by reacting a commercial epoxy resin (Epon 828) with Bisphenol A. Epon 828 (Shell Chemical Company, Houston, TX) is an epoxy resin derived from Bisphenol A and epichlorohydrin having an equivalent weight of epoxide of 185-192 and an epoxy value of 0.52-0.54. The epoxy resin H is an epoxy resin having an epoxy value of 0.038 and was obtained by reacting Epon 828 and Bisphenol A (in a weight ratio of 64.80 / 35.20) using the procedure described in Example 8. The epoxy resin M is an epoxy resin having an epoxy value of 0.050 and was obtained by reacting Epon 828 and Bisphenol A (in a weight ratio of 65.65 / 34.35) as described in Example 8. Epoxy resin L is an epoxy resin having an epoxy value of 0.115 and was obtained by reacting Epon 828 and Bisphenol A (in a weight ratio of 70.25 / 29.75) using the procedure described in example 8. In in each case, the carboxy addition polymer and the epoxy resin were reacted by heating after the addition of the dimethyl-ethanolamine catalyst (0.65 equivalents per equivalent of the carboxy groups present in the carboxy addition polymer). The t-butylphenol formaldehyde resin was then added followed by dilution with water as described in Examples 8 and 9 to form an intermediate coating composition. Coating compositions based on either Epon 1009F or Epon 1007F were prepared in an n-butanol / water solvent system according to the procedure described in Example 9. Coating compositions based either on Epoxy Resin H, the Epoxy Resin M, or the Epoxy Resin L, were prepared in a Butyl Carbitol / n-butanol / water solvent system according to the procedure described in Example 8. The% by weight of the non-volatile components ( solids), the viscosity, pH and particle size for each of the intermediate coating compositions are shown in Table III. The above described intermediate coating compositions are diluted with water (where necessary) to obtain a final coating composition having a viscosity and weight% solids within the desired ranges (viscosity of about 30 to about 60 seconds ( Ford vessel or container # 4 at 27 ° C (80 ° F), approximately 30 to approximately 45% by weight solids.) Using a properly sized rod coater, each of the coating compositions 1-20 was applied to the aluminum metal panels to form a "blister panel." The blister panels were cured by baking for 10 seconds in an oven at 232.22 ° C (450 ° F) (maximum metal temperature of 232.22 ° C (450 ° F)) to produce cured coated metal panels that have a cured film weight of 1162 mg / cm2 to 1.24 mg / cm2 (7.5 to 8.0 mg / in2). were evaluated to verify the formation of blisters. The results of these evaluations are summarized in Table II. The results shown in Table II demonstrate that the aqueous coating compositions of the present invention are capable of being applied to high coating weights and cured at high line speeds without the formation of blisters to provide a cured, elastic film .

Determinations of the Size of the Particle The measurement of the average particle size of the polymer dispersions reported in Table III is carried out using a Spectronic 20 Bausch & Lomb 33-39-61-62. Almost half a drop of the coating composition under evaluation was added to 50 ml of distilled water. The sampling cell of the spectrophotometer was filled from 1/4 to 1/2 filling with the resulting solution. The solution was then further diluted by adding distilled water to fill approximately 3/4 parts of the cell. After agitation of the cell to produce a homogenous solution, the percent transmittance of the diluted solution is measured at a wavelength of 375 millimicrons. The concentration of the dispersed polymer in the solution is then adjusted so that the solution had an optical density between 0.50 and 0.54 to 375 millimicrons. The optical density of the solution was then measured at 375, 450. 500 and 550 millimicrons. For each solution the logarithm of the optical density was plotted against the logarithm of the wavelength and the average particle size was determined from the slope of the graph, where Log (OD375) - Log (OD550) Pending = 0.167 Average particle size = Antilog [0.055 - 0.2615 (Pending)].

Viscosity Measurements For the purposes of this application, the viscosity of the Ford vessel or container # 4 was determined using a slightly modified version of ASTM D-1200-54, which is the procedure used to determine the viscosity of paints, varnishes and coatings. related liquid materials. The process is carried out with a vessel or container for viscosity of the Ford # 4 effluent (available from Scientific Instrument Co., Detroit, MI). The liquid material (as a solution or dispersion) and the Ford vessel or vessel of # 4 are brought to a constant temperature of 27 ° C (80 ° F). The hole in the bottom of the vessel or vessel for measuring the viscosity is closed and the liquid material to be tested is then poured into the vessel to determine the viscosity to a slight overflow of the vessel or inner vessel. After any excess material is allowed to flow into the outer vessel, the hole in the bottom of the vessel or container is opened. The time interval required for the occurrence of the first break in the flow of the material flowing from the orifice is measured using a chronograph. Viscosity is reported as the time elapsed until the appearance of the first break in the stream. In some cases, the viscosity was determined using a Brookfield viscometer Model LVF (Brookfield Engineering Laboratories, Inc.). The Brookfield viscosity meter measures the torque required to rotate a spindle head immersed in the coating composition at a given angular velocity. Viscosity is reported in units of centipoise.

RESISTANCE TO THE FORMATION OF AMPOLLAS The coating composition to be evaluated (100-150 g) is placed in a 258.3 g (9 oz) jar and stirred for 20 seconds with a plastic support attached to a high speed motor. The coating composition was coated by means of a bar on an aluminum panel to form a "blister panel" having a coating of a thickness of 1,162-1.24 mg / cm2 (7.5-8.0 mg / in2). A "blister panel" is coated only in the middle part of the panel. This makes it possible for a greater amount of heat to be applied to the coating and increases the severity of the blister test. The coated ampoule panel is dried exposed to ambient air for 5 seconds and then immediately placed in a coating oven with a coil or spool with a maximum metal temperature of 10 seconds at 232.22 ° C (450 ° F). After removal of the oven, the cured coated panel is turned off in water and the blisters are inspected visually. The resistance of the coating to the formation of the ampoules is evaluated on a pass / fail scale.

Example 32 Coating Composition 25 An inert gas atmosphere is introduced into a reaction vessel equipped with a stirrer, condenser, heater, thermometer and a gas inlet. The vessel was loaded with 572.4 parts of the coating composition 6 (described in Example 13) and stirring is started. Deionized water (159.8 parts) is added and the resulting mixture is stirred until uniform. Then styrene (25.6 parts) and butyl acrylate (25.6 parts) are added and the atmosphere of inert gas is converted to an inert gas spray. The mixture is heated to 75 ° C and the gas spray is again converted to an inert gas atmosphere. Benzoin (0.51 parts) is added and the mixture is heated. When the temperature of the mixture reaches 80 ° C, a solution of 30% hydrogen peroxide (2.56 parts) is added and the resulting mixture is treated at 83-86 ° C for 2 hours. Then add additional portions of styrene (12.8 parts) and benzoin (0.13 parts) and the batch is stirred for 5 minutes. Another portion of the 30% hydrogen peroxide solution (0.64 parts) is added and the reaction mixture is maintained at 83-86 ° C for 4 hours. The resulting coating composition included the t-butylphenol-formaldehyde resin, the reaction product formed from the epoxy resin H and the carboxy addition polymer A (as described in Example 13), and an addition polymer hydrophobic styrene / butyl acrylate. The hydrophobic styrene / butyl acrylate addition polymer had a calculated T g of 3 ° C.

Example 33 Addition polymer of Carboxi H The acrylic acid (2542 parts), the styrene (748 parts) and the ethyl acrylate (2208 parts) were reacted according to the procedure described above for the preparation of the carboxy addition polymers BG in the Examples 2-7. The resulting carboxy addition polymer ("H") had an acid number of 339 and a solids content of 57.0% by weight.

Example 34 Coating Composition 26 An inert gas atmosphere was introduced into a reaction vessel equipped with a stirrer, condenser, heater, thermometer and a gas inlet. The vessel was then loaded with 498.1 parts of Epon 828 (Shell Chemical, Houston, TX), Bisphenol A (268.1 parts), Butyl Carbitol (57.4 parts) and ethyltrife-nilphosphonium iodide (0.65 parts). The mixture is heated with stirring at 130 ° C and is allowed to develop the exotherm at 170-180 ° C. Following the exotherm, the batch is allowed to stand at 155-160 ° C until an epoxy value of 0.041 is obtained. The temperature is allowed to reduce to 145-150 ° C and diethylene glycol monobutyl ether (57.3 parts) is added followed by adipic acid (8.8 parts) and tri-n-butyl amine (0.5 parts). The reaction mixture is then maintained at 145-150 ° C until an epoxy value of 0.025 is obtained. The temperature of the reaction mixture is then allowed to reduce to about 135 ° C while diethylene glycol monobutyl ether (177.2 parts) is added. A solution of the carboxy addition polymer H (175.4 parts) prepared according to the procedure described in Example No. 33 was added. The resulting mixture is stirred at 102 ° C until the batch was uniform. After the batch has become uniform, di-ethylethanolamine (27.0 parts) is added at a uniform rate over a period of 7 minutes. The resulting mixture was maintained at 95-100 ° C for 30 minutes. A mixture of bisphenol A-formaldehyde resin (average degree of polymerization of about 2) was added and the resulting mixture is stirred until all of the solids have dissolved. Then deionized water (1067 parts) is added for 2 hours and the resulting coating composition is allowed to cool to room temperature. The invention has been described with reference to several preferred and specific techniques and modalities. It should be understood, however, that many variations and modifications can be made as long as the spirit and scope of the invention is not affected.

TABLE I CARBOXI ADDICTION POLYMERS Theoretical T calculated based on the "amount of < Either monomer in the terpoly "according to the formula 1% monomer weight A% monomer weight B% monomer weight + + T (terpolymer) T (homopolymer A) T (homopolymer B) T (homopolymer in" where the% by weight of each The monomer is based on the total weight of the three monomers in the terpolymer, the TS are "expressed in degrees Kel and T (homopolymer X) is the T of a hmopolymer formed of a monomer" X "" given TABLE II COMPOSITIONS OF COATING SUBSTITUTE SHEET (RULE 26) TABLE III PHYSICAL CONSTANTS OF INTERMEDIATE COATING COMPOSITIONS SUBSTITUTE SHEET (RULE 26) TABLE IV OOMPCWEH1ES OF THE SOLVENT OF THE COMPOSITION OF COATING AND FINAL SOLIDS SUBSTITUTE SHEET (RULE 26) 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.

Having described the invention as above, property is claimed as contained in the following

Claims (24)

R E I V I N D I C A C I O N S

1. An aqueous coating composition, characterized in that it comprises: at least about 50% by weight of a solvent component (based on the total weight of the coating composition), which includes about 70 to about 97% by weight of water ( based on the total weight of the solvent component) and at least about 3% by weight of an organic solvent (based on the total weight of the solvent component); and at least about 30% by weight of a film forming component (based on the total weight of the coating composition) which includes: A) at least about 7% by weight of a carboxy addition polymer having an acid number of at least about 165 and a glass transition temperature of not more than about 110 ° C; B) at least about 40% by weight of an epoxy resin; and C) at least about 2% by weight of a curing agent which includes an aminoplast resin or a fenoplast resin; the weight% of the carboxy addition polymer, the epoxy resin and the curing agent is based on the total weight of the component forming the film; wherein the carboxy addition polymer and the epoxy resin have been reacted in the presence of about 0.35 to about 1.0 equivalents of a tertiary amine per equivalent of carboxy groups present in the carboxy addition polymer.

2. An aqueous coating composition, characterized in that it comprises: a solvent component including water and an organic solvent; and a film-forming component including: A) a product formed by reacting a carboxy addition polymer and an epoxy resin in the presence of a tertiary amine, the carboxy addition polymer has an acid number of at least about 165 and a glass transition temperature of not more than about 110 ° C; and B) a phenoplast resin; wherein the component forming the film includes at least about 7% by weight of the carboxy addition polymer, at least about 40% by weight of the epoxy resin, and at least about 2% by weight of the fenoplast resin ( based on the total weight of the component that forms the film).

3. An aqueous coating composition, characterized in that it comprises a film forming component including: A) a product formed by reacting a carboxy addition polymer and an epoxy resin in the presence of a tertiary amine, wherein the addition polymer of carboxy has a glass transition temperature of not more than about 110 ° C; and B) a phenoplast resin having a melting point of no more than about 100 ° C.

4. The composition according to claim 3, characterized in that it also comprises a solvent component which includes water and an organic solvent.

5. "The composition according to any of claims 1, 2 or 3, characterized in that the carboxy addition polymer is a copolymer of at least one ethylenically unsaturated carboxylic acid and at least one copolymerizable nonionic monomer.

6. The composition according to claim 5, characterized in that the carboxy addition polymer is a copolymer of acrylic acid, styrene and ethyl acrylate or a copolymer of methacrylic acid, styrene and ethyl acrylate.

7. The composition according to any of claims 1, 2 or 3, characterized in that the carboxy addition polymer has an acid number of from about 200 to about 350.

8. The composition according to claims 1, 2 or 3, characterized in that the carboxy addition polymer has a vitreous transition temperature of about 50 ° C to about 100 ° C.

9. The composition according to any of claims 1, 2 or 3, characterized in that the carboxy addition polymer has a weight average molecular weight of from about 2,000 to about 25,000.

10. The composition according to any of claims 1, 2 or 3, characterized in that the coating composition has a viscosity of about 13 to about 100 seconds (Ford vessel or container of # 4 at 27 ° C (80 ° F)) .

11. The composition according to any one of claims 1, 2 or 4, characterized in that the organic solvent includes an alkanol, a monoalkyl glycol or a monoalkyl ether of diethylene glycol.

12. The composition according to any one of claims 1, 2 or 3, characterized in that the phenoplast resin includes an alkylated phenol-formaldehyde resin or a bisphenol A-formaldehyde resin.

13. The composition according to claim 12, characterized in that the phenoplast resin includes an alkylated phenol-formaldehyde resin having a melting point of not more than about 100 ° C.

14. The composition according to any of claims 1, 2 or 3, characterized in that the epoxy resin includes a glycidyl polyether of Bisphenol A.

15. The composition according to any of claims 1, 2 or 3, characterized in that the epoxy resin has an epoxide equivalent weight of from about 1,000 to about 10,000.

16. The composition according to any of claims 1, 2 or 3, characterized in that it also comprises a lubricant.

17. The composition according to any of claims 1, 2 or 3, characterized in that the aqueous coating composition is an aqueous dispersion.

18. The composition according to any of claims 1, 2 or 3, characterized in that the tertiary amine includes at least two methyl groups.

19. The composition according to any of claims 1, 2 or 3, characterized in that it also comprises a hydrophobic addition polymer.

20. The composition according to claim 19, characterized in that the hydrophobic addition polymer has a T of not more than about 100 ° C.

21. The composition according to claim 19, characterized in that the hydrophobic addition polymer has a weight average molecular weight of at least about 50,000.

22. A method of coating a metal substrate, characterized in that it comprises: a) applying an aqueous coating composition according to any of claims 1-21 on at least one surface of the metal substrate to form a coating layer on the surface; and b) heating the coated metal substrate in such a way that the coating layer is cured to form a substantially continuous cured film adhering to the surface of the substrate, wherein the cured film has a thickness of at least about 0.775 mg / cm2 ( 5 mg / in.2) and is substantially free of blisters.

23. The method according to claim 22, characterized in that it comprises heating the coated metal substrate for about 2 to about 20 seconds at a temperature of about 230 ° C to about 300 ° C.

24. A composite material, characterized in that it comprises a metal substrate having at least one surface covered with a cured film, which is from about 0.775 to about 1395 mg / cma (5-9 mg / in.2) thick, wherein the Cured film is formed: (i) by coating the surface of the substrate with the aqueous coating composition of any of claims 1-21; and (ii) heating the coated metal substrate for about 2 to about 20 seconds at a temperature of about 230 ° C to about 300 ° C.