JPS6317869B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to novel resin compositions particularly useful in coating compositions. More particularly, the present invention relates to water-based coating compositions, particularly compositions suitable for can coatings, in particular for beverage cans. Furthermore, the invention also relates to a method for producing the novel composition, a method for its use and the coated objects produced. The main use of epoxy resins is as surface coating materials.
Epoxy resins have a highly desirable combination of toughness, flexibility, adhesion and chemical resistance. However, epoxy resins have inherent limitations that have limited their use. Solvent-free coatings are made from extremely low molecular weight epoxy resins. In such coatings, the resin itself functions as a wetting agent and is a vehicle for the necessary pigments or fillers. Due to the lack of solvent, this type of coating is free of pinholes, but is brittle, has poor thermal stability, is relatively expensive, and has a short pot life. Coating compositions using high molecular weight epoxy resins are
It is prepared as a solution and formulated with a solvent medium, hardeners and modifying agents, and often with pigments, opacifiers, etc. Epoxy resins are often in the form of esters, and are obtained by reacting epoxy resins with fatty acids, drying oils, etc. Although suitable for many purposes, epoxy ester-based coatings are susceptible to caustic attack. Ester bonds appear to lack the stability desired for many applications. In recent years, water-based epoxy resin-containing coating compositions have attracted attention due to their ease of handling and cleaning. Many attempts have been made to develop such coatings, with some success in certain applications. One promising field of application for such coatings is soft drink and beer cans. This application always presents a challenge due to taste sensitivity. Conventional can coatings tend to alter the taste of the canned beverage. There are a wide variety of ways to do this, such as the coating components leaking into the drink, the flavor being absorbed by the coating, a chemical reaction, or a combination of these. Chemically stable, having no effect on the taste response, easy to apply, pharmaceutically competitive, and other characteristics that a satisfactory product should have that has not been previously attempted to be developed in the relevant application field. There is great potential for use in industrially important and technically difficult can coatings for water-based coating compositions that provide coatings with . Although the present invention provides a practical beverage can coating composition that meets the long-standing needs of the beverage industry, the present invention also relates generally to coating compositions and This invention relates to modified epoxy resin-based resin materials that can be made. The present invention is characterized in that an epoxy resin is prepared by adding an addition polymerizable monomer and at least 3% by weight of the monomer of benzoyl peroxide or an equivalent free radical generating agent. It broadly relates to methods of modifying epoxy resins by reaction at a range of temperatures. This reaction results in a reaction mixture containing a blend of resin materials including unreacted epoxy resin, the new graft polymer, and an associatively formed but ungrafted addition polymer. Graft polymers have an addition polymer component grafted onto the aliphatic backbone carbons of an epoxy resin to which one or two hydrogen atoms are bonded in the non-grafted state. The grafting that occurs in this reaction appears to have an important influence on the properties of coating compositions made from reaction mixtures of this type. For water-dispersible coatings, the addition polymerizable monomer is, at least in large part, acrylic acid, so that both the grafted polymer and the non-grafted addition polymer are acid-functional. In the presence of an ionizing agent, stable aqueous dispersions can be easily prepared. Such water-dispersible coating rotations are particularly useful in formulating can coatings for preserving products for human consumption. Coatings of this type are often referred to as sanitary coatings, and they are an important and preferred embodiment group of the present invention. The sanitary coating compositions provided by the present invention can be prepared by dispersing acid-functional graft polymers and addition polymers, each of a particular composition, with an aqueous medium ionizing agent. Ionizing agents are generally basic reactive reagents and are termed "leaving" because they are released under curing conditions, ie, during baking. With suitable formulations, the sanitary coatings produced according to the invention are extremely suitable for coating beverage cans, in particular for beer cans. Its notable advantages include:
It is easy to use and has virtually no effect on taste. The present invention is based on the following somewhat surprising discovery. That is, when an epoxy resin and an addition polymerizable monomer are reacted at high temperature in the presence of benzoyl peroxide or an equivalent free radical generating agent in an amount of 3% or more by weight of the monomer, graft and addition polymerization proceed simultaneously. There was found. The graft is 1 to 2 in the non-grafted state of epoxy resin.
occurs on an aliphatic carbon of an aliphatic backbone carbon chain that is attached to a hydrogen atom. The reaction products resulting from this reaction include graft polymers, associatively formed non-grafted addition polymers, and unreacted epoxy resins. Grafting reactions have a great influence on the properties of the resulting reaction products. Therefore, when the addition-polymerizable monomer contains a large amount of acrylic acid, both the grafted polymer and the non-grafted addition polymer produced are carboxylic acid functional and can be easily oxidized in the presence of an ionizing agent. Moreover, it can be stably dispersed in an aqueous medium. In order to be sufficiently dispersed in an aqueous medium, the acid value of the reaction product must be sufficient to keep the polymer dispersed in the dispersion. To obtain optimal curing results, crosslinking agents such as aminoplasts are added to the dispersion. The effect of the grafting reaction according to the invention is significant in the case of water-dilutable coating compositions which have sufficient acid functionality to form stable dispersions. The determination method differs depending on the case. For example, the addition polymer contains carboxylic acid units when formed from acrylic acid-containing polymerizable monomers. To facilitate dispersion, these monomers should represent at least 2% by weight of the graft polymer. However, if the initial reaction mixture contains a small amount of epoxy resin or acrylic acid, this determination method alone is insufficient. Therefore, it is best to combine this determination method with the acid number of the entire reaction mixture, which should be greater than 30 and usually less than 220.
A preferred range is about 45 to 150, more preferably about 80 to about 90 as a binder in sanitary coating compositions. If the starting reaction mixture is predominantly epoxy resin, grafting will occur to a appreciably small extent, but the resulting reactant will be significantly influenced by the new graft polymer. Therefore, the grafting ratio of the addition polymer to the epoxy resin may be 1 1/2 parts by weight per 100 parts by weight of the epoxy resin. Generally, to obtain the benefits of the present invention, the amount of epoxy resin used will be at least 5% by weight, preferably 10% by weight of the starting reactants.
% by weight is sufficient. When the epoxy resin is 40% or more by weight of the starting reactants, excellent binder blends are obtained; when it is 50% or more, preferred binders are obtained. However, for sanitary coating composition binders, the amount of epoxy resin is 60 to 90
It should be % by weight. One of the characteristics of the method of the present invention is the amount of radical generator used in the reaction. The amount of benzoyl peroxide when used at about 110°C to 120°C is at least 3%, preferably 4% by weight of the addition polymerizable monomer. The practically preferable range is 6 to 7%, but about 15% can also be used. When using other free radical generators,
The amount should be adjusted to the active equivalent for this reaction, taking into account the temperature. When the amount of free radical generator is less than 3% by weight, ester-type graft copolymers appear to be formed. When the amount of peroxide-type free radical generator corresponds to at least 3% by weight and not more than 7% by weight of benzoyl peroxide, the grafting mainly involves the addition of 1 to 2 hydrogen atoms in the ungrafted state of the epoxy resin component. Occurs on aliphatic backbone carbons. The use of benzoyl peroxide equivalents in excess of 7% by weight at 110 DEG C. to 120 DEG C. generally increases costs and provides no particular benefit. The reaction is preferably carried out by placing the epoxy components and solvent in a reactor and then slowly adding the monomer mixture, catalyst and solvent over a period of time that easily controls the exotherm, although other methods may be used. You can also do it. For example, the epoxy resin and its solvent are placed in a reactor, then all of the catalyst and a portion of the monomer mixture are added. After the initial reaction initiated by heating, the remaining monomer mixture is added gradually over time. Alternatively, in this manner, some of the catalyst can be left with the monomer mixture and added later. Still another method is to place the monomer mixture, epoxy resin component, and any solvent in a reactor and gradually add the catalyst. Once the reaction product is obtained, it is generally useful to suspend it in an aqueous medium so that it can be readily used in coating compositions. Converting the polymer blend and solvent system into a stable aqueous dispersion requires the use of a base or a mixture of bases. A preferred neutralizing base is dimethylethanolamine, which typically contains 4 to 12
% by weight is used. The amount of base influences the viscosity of the resulting aqueous dispersion and thus influences its application properties. When the amount of base is large, the viscosity increases, and the amount of dilution with water increases to control the viscosity. There are two ways to convert the reaction product blend into an aqueous dispersion. A preferred method for ease of manufacture is to add the product blend along with the solvent to the water and dimethanolamine mixture while mixing. Usually a small amount of solvent (ethylene glycol monobutyl ether) is included in the water to aid solubility. The second method adds water and amine to the product blend and solvent with mixing. Although the aqueous dispersion obtained by this method is preferable in terms of quality, this method is not preferable in terms of equipment. The pH of the aqueous dispersion obtained by the above method is usually 7.5.
~8.0, and is stable within a storage period of over one year.
That is, the viscosity change is small, there is almost no sedimentation separation, and the application characteristics after storage are also satisfactory. According to a preferred embodiment of the present invention, for producing sanitary coating compositions for soft drink and beer cans, the amount of diepoxy resin is preferably about 80% by weight and the amount of monomer mixture reacted with the epoxy component. should be approximately 20% by weight. The amount of benzoyl peroxide that should be present during the reaction is 6
7% to 7% by weight, preferably 6.7 to 6.8%.
The amount of methacrylic acid in the monomer mixture will be reflected in the acid number of the final reaction product obtained, but for this purpose the acid number will be between 45 and 150, preferably between 80 and 90, most preferably between 80 and 90. It is 85. When using 80 parts diepoxy resin, 20 parts monomer mixture and 6.8 parts benzoyl peroxide as a beverage can coating composition, the preferred monomer composition is 70 parts methacrylic acid to 30 parts styrene and 1 mole. % ethyl acrylate.
In the final reaction product, all of the monomers are copolymerized into the addition polymer, with about 2 1/2 parts by weight grafted onto the aliphatic backbone carbons of the diepoxy resin and the remainder copolymerized into the graft polymer in the reaction mixture. Blended as a polymer. Both the graft and addition polymers thus produced are carboxylic acid functional. Both have sufficient ionization potential to be hydrophilic,
Can be easily blended. Diepoxy/monomer mixture for beverage can coating
When an 80/20 reaction mixture is reacted with a benzoyl peroxide amount of 3%, typically 1 1/2% to 2%
addition copolymers (based on all addition copolymers formed from monomer mixtures) are grafted and have poor dispersibility in water. At a benzoyl peroxide level of 5%, approximately 8% of the addition copolymer is grafted, and 7
% of benzoyl peroxide will result in approximately 12% of the addition copolymer being grafted, while for 9% of benzoyl peroxide approximately 20% will be grafted and 15% of the addition copolymer will be grafted.
With benzoyl peroxide, 40% of the addition copolymer is grafted. 10% addition polymer grafted means that the final reaction product is approximately 82
% graft polymer and about 18% associatively formed addition copolymer. Generally, a good coating composition will have about 1 1/2 parts per 100 parts by weight of epoxy resin component in the graft polymer.
Two parts by weight of addition copolymer should be grafted. If the amount of benzoyl peroxide is sufficient, the amount of addition copolymer grafted is
The number is about 12 copies, but in most cases it is practically 5 copies.
1/2 part is the upper limit, with 2 1/2 to 3 parts being preferred for can coating. The reaction product typically obtained from a reaction mixture of 80/20 diepoxy resin to monomer mixture contains up to 18 1/2 parts of non-grafted addition copolymer. For many coating applications, the presence of higher amounts of addition copolymer can be tolerated and a separately made compatible addition copolymer of preferably identical composition can be added to the reaction product in an amount of non-grafted copolymer. can be added until the total amount is about 40 parts. Similarly, a non-grafted diepoxy resin can also be added, usually in an amount of about 10% by weight of the reaction product. In the case of aqueous dispersions with high epoxy content, the carboxyl content of the reaction product should be at least 2% by weight of the reaction product, measured in -COOH. Dispersion stability favors high carboxyl content, with the practical range generally being at least 5%. Polymer blends with carboxyl content below 2% are useful in solvent media. Hereinafter, each requirement of the present invention will be explained in detail. Epoxy Resins Epoxy resins can be aliphatic or aromatic.
Aromatic epoxies are preferred for can coating compositions suitable for preserving products for human consumption. The most preferred epoxy resins are polyglycidyl ethers of bisphenol A, especially those having a 1,2-epoxy equivalent weight of about 1.3 to 2, preferably 2. The molecular weight is about 350 to about 20,000, preferably about 4,000 to 10,000 for sanitary coating compositions.
Low molecular weight epoxy resins typically have a low epoxy content in the polymeric binder, i.e., from about 10 to about 30% by weight.
selected in the case of Low molecular weight epoxy resin refers to one having a molecular weight of less than 1000. Typically, if the polymer blend is intended to contain epoxy resin at 50 to 90% by weight of total solids, the molecular weight of the epoxy resin will range from about 4,000 to about 10,000.
It is particularly suitable for the production of sanitary coating compositions in which the epoxy resin content is preferably 60% of the total solids content. Although it may be convenient to use a final epoxy resin having the required molecular weight, it is often more practical to use bisphenol A and commercially available bisglycidyl ethers of bisphenol A as starting materials. Bisglycidyl ether of bisphenol A is commonly known as liquid epoxy resin and is available in catalyzed form from the Dow Chemical Company under the trade name DER-333, which contains a complex of ethyl triphenylphosphonium acetate and acetic acid as a catalyst.
It is not only commercially available as Epon829, but also commercially available from Shell Chemical Company under the trade name Epon829, and it is convenient to use these as starting materials.
Uncatalyzed liquid epoxy resins are also commercially available.
It can be used with the addition of a suitable catalyst. The physical properties of the catalyst-added liquid epoxy resin DER-333 manufactured by Dow Chemical Company are as follows. Table 1 Properties of DER-333 epoxy resin Appearance Transparent, viscous liquid Color (Gardner) 1-2 Specific gravity 1.15 Gallon weight 9.65 Non-volatile components (weight) 96±1% Volatile components Xylene Non-volatile components (volume) ) 95% average Viscosity (25℃) 2300-4600 cps. Epoxy equivalent weight ^* 199-202 *Epoxy equivalent weight refers to the number of grams of resin containing 1 gram equivalent weight of epoxy. The starting liquid epoxy resin can be reacted with additional bisphenol A as well as other materials to bring the initial molecular weight of the liquid epoxy resin to a level that is satisfactory for many coating applications. Other polyfunctional aromatic alcohols can be used for glycidyl ether preparation and molecular weight increase. A specific example is bis(4-hydroxyphenyl)
Methane, bisphenol F, 2,2-bis(4'-
Hydroxy-2',3',5',6'-tetrachlorophenyl)propane, tetrachlorobisphenol A, 4,4-bis(hydroxyphenyl)pentanoic acid, diphenolic acid, novolac or low molecular weight phenol-formaldehyde 1,8-bis(hydroxyphenyl)pentadecane, resorcinol, 2,2,5,5-tetrabis(4'-hydroxyphenyl)hexane, and the like. However, in order to simply control the process in practice, the preferred substance for increasing the molecular weight of the starting liquid epoxy resin is bisphenol A. The ratio of bisphenol A to DER-333 for the most preferred molecular weight is 65 to 66.5% DER by weight.
-333 to 35 to 33.5% by weight bisphenol A. The following table shows the properties of the final epoxy resin.

[Table] In butyl ether)
The reaction conditions used to increase the molecular weight of liquid epoxy resins and other low molecular weight epoxy resins are a reaction temperature of 175° C. and normal pressure. Although the reaction can be carried out without solvent, it is preferred to use ethylene glycol monobutyl ether at about 15% by weight of the total reactants. Epoxy resins suitable for many coating applications are typically diepoxy resins with molecular weights in the range of about 350 to 20,000. However, for more demanding applications, particularly those where the objective is sanitary coatings, the molecular weight range of the epoxy resin is preferably from about 4,000 to about 10,000. These and other molecular weight measurements of epoxy resins are preferably made by gel permeation chromatography, although other standard means may be used. The epoxy resins used in the invention can also be modified with other condensates, such as phenolic resins, phenols and polyols. Typical examples of modified epoxy resins are epoxidized polybutadiene; glycidyl ether obtained by reacting phenol novolac resin with epichlorohydrin; 4,4'-isopropylidenephenol-epichlorohydrin or 4,4-sec-butylidenediphenol-epichlorohydrin. Reactants with one or more of the following drying oils or fatty acids: beech oil, kukui oil, castor oil (including dehydrated), tung oil, coconut oil, corn oil, cottonseed oil, fish oil (refined), hempseed oil, linseed oil, ostrich oil, perilla oil, poppy seed oil, pumpkin seed oil, safflower oil, sesame oil, soybean oil, sunflower oil, tall oil and walnut oil; 4,4'-isopropylidenediphenol-epichlorohydrin or more Products treated with: allyl ethers of mono-, di- or trimethylolphenols; 4,4'-isopropylidenediphenol-formaldehyde, 4,4'-sec-butylidenediphenol-formaldehyde, melamine formaldehyde and urea-formaldehyde, etc. Examples of commercially available epoxy resins with suitable molecular weights that can be used as is without any molecular weight increase are Dow Chemical products such as DER662, 664, 667, 668 and 669 (each with a calculated average molecular weight of 1275 ; 1850; 3600; 5500; and 9000) and EPON836, 1007 and 1009 etc.
Chemical Company products (each with a calculated average molecular weight of
625; 4500; and 6500). A preferred diepoxy material used in the practice of this invention is prepared by reacting epichlorohydrin with bisphenol A; however, other satisfactory epoxy compounds include the following starting materials with molecular weights adjusted to appropriate ranges: There is: The epoxy resin component is further characterized by its oxirane content. This value is anywhere from zero to about 8%. Zero oxirane content refers to the case where the epoxy groups have completely reacted due to excess bisphenol A, for example. For applications other than good can coating, the epoxy group may not be necessary. The method for measuring the oxirane content is as follows. Measurement of oxirane content Place the weighed sample in a 50 ml Erlenmeyer flask and dissolve in 10 ml of chlorobenzene. To this solution are added 10 ml of tetraethylammonium bromide solution and 2-3 drops of 2% crystal violet indicator glacial acetic acid solution. Then 10ml of the resulting solution
Titrate with standardized 0.1N perchloric acid (HClO ₄ ) to a blue-green end point using a microbiuret.
Oxirane % is calculated from the following formula: Oxirane % = (titration ml x HClO ₄ normal) x 1600 / grams of sample For the above 0.1N HClO ₄ , add 8.5 ml of 72% HClO ₄ to 300 ml.
of glacial acetic acid (99.5%), 20 ml of acetic anhydride was added, the solution was diluted with 1 part of glacial acetic acid and left overnight. It was then standardized with potassium hydrogen phthalate. Tetraethylammonium bromide required for the above measurement is 400 g of tetraethylammonium bromide.
ml of glacial acetic acid (99.5%). Neutralize basic impurities by adding a few drops of 2% crystal violet indicator and standardize the solution.
Titrate with 0.1N HClO ₄ to end point of color change. This measurement method can be applied to any reaction mixture containing the starting epoxy resin and the graft polymer. Addition Polymerizable Monomers In practicing the present invention, a second group of important materials consists of addition polymerizable materials. Addition-polymerizable monomers that react with epoxy resins and free radical generators to form reaction products, including graft polymers, that can be used in the present invention include single monomers and monomers. Any mixture is included within the scope. The selection criteria for materials are the physical properties that can be obtained and the economic efficiency. For example, styrene is useful because it is a filler and is economical. Acrylamide is also interesting because it enhances self-curing properties whether used alone or as part of a mixture. Acrylic acid provides acid functionality. A mixture of three or more monomers currently approved for epoxy-acrylic coatings for beverage can applications, namely styrene, methacrylic acid, and ethyl acrylate, and optionally methyl methacrylate. However, mixtures of methacrylic acid and styrene generally provide much more useful water-dilutable coatings than acid-based ones, providing sufficient acid functionality to form stable aqueous dispersions. Generally, the addition polymerizable monomers used to make the coating compositions according to the invention are also selected from these three types of monomers. The selection may be a single monomer or a mixture of these monomers selected to achieve a particular purpose, eg acid functionality. The first group of monomers used to make coating compositions are acrylic acids. This range includes acrylic acid itself and lower alkyl-substituted acrylic acids, ie, acids having ethylenically unsaturated bonds in the alpha and beta positions of a single carboxylic acid group.
A preferred acrylic acid is methacrylic acid. The second group of monomers refers to commercially available, readily available monomers with vinyl unsaturation and no added functionality. Examples include styrene monomers such as styrene, vinyltoluene, and divinylbenzene. In addition, isoprene, conjugated butadiene, etc. are used. The third group of monomers are alkyl esters of acrylic acid, usually lower alkyl esters, i.e. with 1 to 4 esterifying groups, in accordance with the current regulations applicable to sanitary coatings which can be added in particular to methacrylic acid-styrene. carbon atoms, especially ethyl acrylate. Other useful monomers of this group include C _1-15 alkyl acrylate and methacrylate esters, such as propyl acrylate, isopropyl acrylate, butyl acrylate, isobutyl acrylate, t-butyl acrylate, pentyl acrylate, decyl acrylate, lauryl acrylate, isobornyl acrylate, methyl methacrylate, butyl methacrylate, isobutyl methacrylate,
Examples include hexyl methacrylate, 2-ethylhexyl methacrylate, octyl methacrylate, and nonyl methacrylate. acrylamide,
and acrylonitrile are also used, but not for food grade. Generally, addition monomers that are readily polymerizable under emulsion polymerization conditions are suitable for use, especially those having ethylenically unsaturated bonds. Thus, for example, ethylenically unsaturated substances such as acetylene glycol are also included. If monomer mixtures are used in the production of water-dilutable coatings, the selected monomers other than the acrylic acid monomer should be sufficiently copolymerizable with the acrylic acid monomer; A copolymer that is not itself crosslinked should be formed. A suitable monomer mixture for most water-dilutable coating compositions includes a major proportion of acrylic acid and a minor proportion of a styrenic monomer, usually styrene. For general coating compositions that may be inoculated with food, and for beer can coating compositions in particular, a preferred addition polymerizable monomer mixture is 70 parts by weight methacrylic acid to 30 parts by weight styrene and 1 Made from weight percent ethyl acrylate. Another preferred monomer mixture is a mixture of methacrylic acid, styrene and ethyl acrylate in a ratio of approximately 65:34:1. Free Radical Generator The epoxy resin and the polymerizable monomer are reacted in the presence of a free radical generator, preferably of the peroxide type. Although many free radical generators may be used, benzoyl peroxide is preferred. Commonly usable materials include what are commonly referred to as peroxide type catalysts. This type of free radical generator is generally well known and is generally combined to some extent with a free radical generator and an activator of the free radical generator, such as ultraviolet light, high-energy electron beam, under suitable conditions. It is useful in Typical examples of free radical generators that are widely used in practice include kyumene hydroperoxide, benzoyl peroxide, t-butyl perbenzoate, t-butyl peroxide, lauroyl peroxide, methyl ethyl ketone peroxide, chlorobenzoyl peroxide, etc. There is. Benzoyl peroxide is useful as a free radical generator to initiate and advance graft and addition polymerizations in the practice of this invention. The amount of free radical generation activity is important. In the present invention, this amount is determined at the working temperature, usually between 110°C and 110°C.
It is expressed as the weight percent of benzoyl peroxide or equivalent based on the total weight of polymerizable monomers at 120°C. It is necessary that the amount is at least 3% by weight, preferably 4% by weight of benzoyl peroxide or its equivalent. Benzoyl peroxide is an expensive material, so no more should be used than necessary to achieve the desired results. A minimal degree of grafting occurs when the amount or equivalent of benzoyl peroxide is about 3% of the monomer. As the amount of free radical generator used increases, grafting onto aliphatic backbone carbons takes place preferentially. When the reaction mixture consists of about 80% by weight of epoxy resin and 20% by weight of polymerizable monomer, using a free radical generator corresponding to 6% to 7% of benzoyl peroxide reduces the amount of starting monomer from about 12% by weight grafts to the aliphatic backbone carbon bonding one to two hydrogen atoms in the ungrafted state of the epoxy. Grafting appears to occur at the alpha aliphatic backbone carbon of the terminal epoxy group, but some grafting also appears to occur at other positions. A schematic diagram of this type of grafting reaction is shown below: [However, x is CH ₃ or H, y is, for example,

[Formula] -CO ₂ H, -CO ₂ Et, etc.] Based on the fact that 12% of the addition polymerizable monomer is grafted to the epoxy resin, it is calculated that all the epoxy resin is grafted. The grafted addition polymer formed from the monomers is found to be 2.4 parts out of 82.4 parts of the graft polymer. That is, the addition polymer component is about 2.9% by weight of the graft polymer.
In reality, a significant proportion of the epoxy resin may be ungrafted, but analysis of free, ungrafted epoxy is difficult. It is possible that as much as 50% of the original ungrafted epoxy remains. Reaction Process The reaction generally involves combining an epoxy resin with about 5% to about 95% addition monomer by weight of the reaction mixture and at least 3% benzoyl peroxide or equivalent free radical generator by weight of the monomer. The method consists of reacting in the presence of Although the reaction can be carried out in the absence of a solvent, a solvent system is usually used for coating production. A preferred solvent system consists of two miscible solvents, one that dissolves the epoxy resin and the other that dissolves the monomer. A preferred technique for carrying out the reaction is to place the epoxy resin in a reactor, heat it, and then
There is a method of slowly adding the polymerizable monomer, solvent, and free radical generator while stirring over a period of time. Since this reaction is exothermic, this technique allows the temperature to be maintained with some degree of control during any reaction step. After the addition to the reactor is complete, the contents within the reactor are maintained at a constant holding temperature for an additional period of time to ensure that the reaction proceeds to the desired extent. The solvent used may be any conventionally known solvent. Solvents such as xylene are satisfactory for the epoxy resin component. Other solvents include benzene,
These include ethylbenzene, toluene and alkoxyalkanols. Alcohols such as methanol, ethanol, propanol and butanol are suitable as the solvent for the monomer, with butanol being particularly preferred. Ethylene glycol monobutyl ether, ethylene glycol monobutyl ether acetate, etc., hexane, mineral spirits, etc. are also suitable. If the final product is used in an aqueous medium, water-soluble substances should be chosen as solvents, such as acetone, butanol, ethanol, propanol, ethylene glycol monoethyl ether, etc. A solvent may also be added into the system during the initial reaction to increase the molecular weight of the catalyzed liquid epoxy resin. The preferred solvent for this purpose is ethylene glycol monobutyl ether, used at 15% by weight of the total reactants. From the viewpoint of can coating efficiency, it is also preferable to use a mixture of ethylene glycol monobutyl ether and n-butyl alcohol in a weight ratio of 40/60. Many solvents are added as viscosity modifiers, while others are added to adjust the reactivity of the monomers. The pressure during the grafting reaction is usually atmospheric pressure,
The pressure may be higher or lower than that. The reaction temperature is preferably maintained at about 80°C to about 130°C;
The temperature can also be maintained within a relatively wide range to control the reactivity of the reaction mixture. Therefore, the operating temperature ranges from about 30°C to about 200°C depending on the desired results and conditions of use.
A range of °C is possible. As mentioned above, the grafting is done simultaneously with the formation of the addition polymer. The proportions of the reactants are usually adjusted so that the oxirane content in the reaction mixture is about 3% or less, although the oxirane content of the binder of the sanitary coating composition is usually between zero and 1%. Although the use of a solvent is optional and the reaction proceeds without a solvent, the amount of solvent is usually about 5 to 30% by weight of the sum of the other ingredients. In short, conventional solvent copolymerization conditions can be used for the graft reaction. Although the monomer and the free radical generator can be added all at once, it is preferable to add them in regular portions to control heat generation. After the monomer addition is complete, the reaction mixture is typically maintained at the reaction temperature for no more than 3 hours to allow complete reaction of the monomers. Reaction Products Under the above reaction conditions, two reaction products are obtained simultaneously in a mutually associated state using at least 3% by weight of monomers, preferably 6 to 7% by weight of benzoyl peroxide. . In the present invention, this is referred to as associative formation. One of the products present in the final reaction mixture is the graft polymer. Under the above conditions, grafting occurs at the aliphatic backbone carbons that have bound one to two hydrogen atoms in the ungrafted state of the epoxy resin. When the free radical generator is about 3% benzoyl peroxide or its equivalent, or less, grafting reactions to aliphatic backbone carbons are less likely to occur than at higher amounts.
Regardless of the conditions, it is clear that as long as the acidic polymerizable monomer is present, some ester-type grafting will occur, but under the operating conditions of the present invention, particularly the preferred conditions, the amount is extremely small. Few. In addition to the graft polymer, the reaction mixture also includes an associatively formed non-graft addition polymer formed from the monomer mixture. Although it is difficult to detect unreacted epoxy resin in the reaction mixture,
Up to about 10% by weight of the resin solids in the reaction mixture may be unreacted epoxy. In some cases, as much as 50% by weight can be unreacted epoxy resin, especially if the epoxy resin accounts for a high percentage of the total reactants. If the epoxy resin is in a small amount, on the order of 5% of the initial reaction mixture, the proportion grafted will be high. Although the grafting ratio of epoxy resin is extremely small, it is extremely important in terms of physical properties. Preferably, the epoxy resin is initially present sufficient to allow sufficient grafting so that the epoxy resin component of the grafted polymer initially represents at least about 5% by weight of the reaction mixture.
Taking the example of manufacturing a resin binder blend for a can coating composition, the reaction product is a 65:34:1 monomer mixture of 80 parts by weight of diepoxy resin to 20 parts by weight of methacrylic acid/styrene/ethyl acrylate. About 6 to 7 monomers in a solvent using as starting material
When formed in the presence of % by weight benzoyl peroxide, about 2 1/2 parts by weight of the 20 parts by weight starting monomer mixture are in the graft polymer and the remaining 17 1/2 parts by weight. Parts by weight are non-grafted copolymer. Since it is difficult to separate the graft polymer from other components in the reaction mixture, it is difficult to measure the molecular weight of the graft polymer itself, and an approximation method must be used at best. According to this, the molecular weight of the graft polymer is in the range of about 5,000 to about 40,000. The grafting rate between the addition polymer component and the epoxy resin component suitable for the coating composition is determined by
The proportion is at least 1 1/2 parts by weight of addition polymer component per 100 parts by weight. There are several documents proving that the graft polymer has the above structure. One important piece of evidence is that the acid number predicted from the simple component mixture approximates the acid number of the final reaction product. This shows that almost no ester was produced during grafting. Furthermore, evidence obtained using carbon-13 NMR spectroscopy confirms that during grafting, there is almost no ester formation due to chemical reaction with the epoxy moiety (model structure). Suitable for coating compositions, the acid value of the reaction product is approximately 30
Acid values suitable for sanitary coating compositions are from about 80 to about 90, preferably around 85. 3 of benzoyl peroxide as a polymerizable monomer
When used in amounts greater than % by weight, grafting occurs selectively on the carbons of the aliphatic backbone of the epoxy component, but at a benzoyl peroxide amount of 3%, almost no grafting occurs on the aliphatic carbons. do not have. The amount of benzoyl peroxide or its equivalent is 6% or more
When increased to a preferred operating amount of 7%, the best results from an economical and production standpoint of the desired graft type are usually obtained. Coating Composition The reaction mixture produced according to the invention can be converted into an aqueous dispersion using essentially conventional methods. The graft polymer is dispersed in deionized water using a leaving base (under coating curing conditions). Such bases include, for example, primary, secondary and tertiary alkyls, alkanols and aromatic amines and mixed alkanol-alkyl amines, in particular mono-ethanolamine, dimethylethanolamine, diethanolamine, triethylamine,
Examples include dimethylaniline and ammonium hydroxide. This operation is usually carried out by adding the amine with a small amount of water, stirring vigorously with heating (if necessary), and then diluting the dispersion with a further amount of deionized water. The amount of water in the final dispersion depends on the required viscosity, which is related to the method of application. The appropriate amount of water for spraying the dispersion is approximately 60% by weight of the dispersion.
are typical amounts, with 10 to 30% by weight of the dispersion being solids and about 70% to 90% being volatiles, ie, base, water and solvent. The base is usually about 2 to 6
%, water is 30-90%, organic solvent is 0-40%,
All percentages are by weight of the sprayable dispersion. The solids content is about 9-29% reaction mixture solids based on the sprayable dispersion and about 1% crosslinker.
~10%. For application methods other than spraying, the composition of the dispersion is
Reaction mixture containing 10-70% solids, including 0.1-16% by weight of crosslinker and 6-39.9% by weight of graft polymer; and 60-90% volatile components, usually including 6-9% organic solvent. 35%, water 25-80%. For ease of application, it is preferred to use organic solvents, usually in a ratio of 1 part by weight of organic solvent to 3 parts by weight of water. The organic solvent may be one or more known solvents, such as n
-butanol, 2-butoxy-ethanol-1,
It may be made from a solvent such as xylene or toluene. Preferably, n-butanol is used in combination with 2-butoxy-ethanol-1 in equal amounts. Aminoplast resins are preferred for crosslinking the graft polymer. The time of addition to the graft polymer may be either before or after neutralization and dilution. Representative examples of aminoplasts include melamine, benzoquanamine, acetoquanamine, and urea resins such as urea formaldehyde. Suitable commercially available water-soluble or water-dispersible aminoplasts are Cymel 301,
Cymel303, Cymel370 and Cymel373 (all melamine-based from American Cyanamid Co., Stanford, CT; e.g., Cymel301 is hexamethoxymethylmelamine)
and Beetle 80 (a methylated or butylated urea manufactured by American Cyanamid). Other suitable aminoplast resins include aldehyde and formoguanamine, ammeline, 2-
Chloro-4,6-diamine-1,3,5-triazine, 2-phenyl-p-oxy-4,6-diamino-1,3,5-triazine, 2-phenyl-
p-oxy-4,6-trihydrazine-1,3,
There are types produced by reaction with 5-triazine and 2,4,6-triethyl-triamino-1,3,5-triazine, etc. 2,4,6-
Mono-, di- or triarylmelamines such as triphenyl-triamino-1,3,5-triazine are preferred. Other aldehydes that react with amino compounds to form resinous materials include crotonaldehyde, acrolein, or aldehyde-forming compounds such as hexamethylene-tetramine, paraldehyde, and the like. A crosslinking agent is required if there is little or no oxirane functionality in the graft polymer. Otherwise, it is desirable to use a crosslinking agent, but the graft polymer is thermally self-crosslinkable. Another method of introducing crosslinking ability into the reaction mixture is to use materials such as acrylamide or its alkyl derivatives or bismaleimide for all or part of the polymerizable monomers in the reaction mixture. The coating compositions of the present invention can be colored and/or opacified with known pigments or opacifying agents. A preferred pigment for many applications, including food applications, is titanium oxide. Generally, the amount of pigment used is a pigment to binder weight ratio of 0.1:1 to 1:1.
That is, the titanium oxide pigment is added to the composition in an amount of about 5 to 40% by weight based on the solids content of the composition. The resulting aqueous coating composition can be applied by any method known in the coatings industry. That is, spray methods, roll methods, dipping methods, flow coating methods, electrodeposition methods, etc. can be applied to either transparent or colored coatings, but the spray method is often preferred. After application to a metal substrate, the coating is approximately 95°C to 235°C
It is thermally cured in the above temperature range. The curing time ranges from 1 to 20 minutes, which is sufficient time to complete curing and volatilize the contained separable components.
Furthermore, the film may be air-dried for a long time at room temperature. For metal plate substrates for beverage containers, especially carbonated beverages such as beer, per ^cm2 of exposed metal surface.
Applied at a rate of 0.078mg to 0.23mg. To achieve this, the thickness of the water dispersion coating applied is 1/10
~1 mil. The present invention will be explained in more detail with reference to Examples below. In this application, unless otherwise specified, all parts and percentages are by weight and temperatures are in degrees Celsius. Example 1 Production of beverage can coating composition Plant batches were produced by the following method. 104,779g of epoxy resin (DER333) was heated to 82°C in a reactor with stirring, to which 53,070g
of bisphenol A was added. The reactor was then heated to 191°C over approximately 2 hours and held at that temperature for an additional 2 hours. Measurements of viscosity and % oxirane were taken periodically. The target oxirane value was about 0.6% and the target viscosity was between Z and Z ₁ (Gardner-Holt) at 25°C. Once these values were obtained, 61,225 g of 2-butoxy-ethanol-1 was added followed by 92,079 g of N-butanol. The molecular weight of the epoxy resin at this point was approximately 5500, based on the oxirane content. In a separate container, the following ingredients were mixed: 29030g methacrylic acid, 18144g styrene,
19958g ethyl acrylate and 4536g benzoyl peroxide. This monomer mixture was gradually added to the reactor containing the epoxy resin at a uniform rate over a period of 2 hours. The reaction temperature was maintained at 118°C.
During this period, samples were taken out periodically to check their viscosity. When the batch was cooled to 85°C and the acid value of the solid content was measured, it was 85. This resin batch was then mixed with 496,681 g of deionized water (resistance of at least 50,000 ohm-cm.) and 25,855 g.
dimethylethanolamine mixture. The temperature of the resulting blend is 50℃
It was hot. After holding this at this temperature for about an hour, the blend was added with 226,795 g of cold deionized water.
Cooled to below 32°C. The water dispersion resin had the following properties: NV (non-volatile content) 20%, stable dispersion, PH 7.8, viscosity (Food No. 4 cup) 22 ± seconds. This water dispersion was then mixed with 11,340 g of amino acid. Modified with plastic resin (Cymel 370, manufactured by American Cyanamid). The dispersion was stable. The can coated with the sanitary coating obtained in this example showed excellent properties and was suitable for the carbonated beverage and beer industries. It is noted that the coated cans are particularly inert. That is, it does not impart any undesirable organoleptic properties or haze to the canned beverage. Example 2-20 Effect of compositional changes In Example 1, the amount of benzoyl peroxide used during the reaction was approximately
It was 6.8% by weight. To see the effects of compositional changes, additional experiments were performed with varying proportions of a few monomers in the epoxy resin and monomer mixture. In each case, the amount of benzoyl peroxide was 6.8% in the monomer mixture, and the order of addition of reactants, reaction temperature, pressure, and other operating conditions were the same as in Example 1. Therefore, grafting and addition polymerization operations are
It was carried out at 120℃. The solvent used was an equal mixture of n-butanol and 2-butoxy-ethanol-1. the amounts of reactants used in these additional experiments,
The properties of the epoxy reactants, acid number and oxirane content of the final reaction mixture are shown in the table below. The acid number and oxirane content were measured using a 60% solution of non-volatile matter (NV=
60).

【table】

[Table] Each resin reaction product of Examples 2 to 13 in Table 3 was diluted with deionized water using dimethylethanolamine as a neutralizing and ionizing agent. When these aqueous dispersions were stored at room temperature above 49° C. for a period of over 8 months, no gel or precipitate formed in any of the samples. Slight changes in pH and viscosity were observed. Other examples showed similar properties. These water-dispersed resins were sprayed onto the metal substrate of a tin plate, cured, and evaluated for blistering resistance, coverage, foaming resistance, electrical conductivity, adhesion, coating continuity, etc., and were satisfied in all cases. I got good results. A brief description of these tests will be provided later in the ``General Comments'' section. Table 4 lists the initial viscosity (No. 4 food cup/seconds at 25°C) and pH of the resin reaction products of Examples 2-13 in Table 3. Both physical properties were measured for the aqueous dispersion of each sample. Additionally, Table 4 shows the percentage of neutralization (ionization) by dimethylethanolamine for each sample and the dispersion at approximately 49°C, measured in the same manner as above.
Also record the viscosity and pH after 8 months storage. The resin reaction products produced according to the present invention can be easily stored, transported, formulated, and applied in liquid media, either solvent media or aqueous dispersions. In either case, the reaction product

【table】

[Table] The composition is usually composed of an epoxy resin, preferably an epoxy resin or an addition polymer used as a reactant, for economic reasons or for the purpose of obtaining desired physical properties.
Preferably, an analogue of the non-grafted addition polymer formed during the reaction, or both, can be added to increase the amount. The following examples illustrate increasing amounts of epoxy resin reaction mixtures having different molecular weights. Example 21 Utilization of Solid Epoxy Resin (6500 Molecular Weight) Extending Agent 1150 g of EPon829 epoxy resin was placed in a reactor to which 606 g of bisphenol A and 310 g of 2-butoxy-ethanol-1 were added.
Epom829 epoxy resin has a Gardner color of up to 3, as reported by the manufacturer, Shell Chemical Company.
Density at 20.0°C 114g/cm ³ and epoxy equivalent 193~
203. Calculated average molecular weight is approximately 396. The material was heated to approximately 82°C and it was further heated to 145°C before adding the suphenol. Furthermore, when the temperature was raised to 175°C, the viscosity at this temperature was UV.
Then 170 g of 2-butoxy-ethanol-1
was added, the temperature was raised to 180°C, and the temperature was maintained for 2 hours. Then 826 g of N-butyl alcohol was added. In a separate vessel were mixed 283 g of methacrylic acid, 148 g of styrene, 4 g of ethyl acrylate, and 30 g of benzoyl peroxide (approximately 6.9% of the monomers). 111 g of 2-butoxy-ethanol
1 and this monomer mixture was added to the reactor containing the epoxy resin at 115° C. over a period of 2 hours. After 2 hours, 62 g of N-butyl alcohol was added at 117°C and the whole was mixed for 2 hours at 117°C. Then 339g of Epon 1009 was added and mixed and dissolved with the other ingredients. Epon 1009 epoxy resin is a solid resin with a Gardner-Holdt viscosity of Z ₁ -Z ₂ , a Gardner color of up to 5, and an epoxy equivalent weight of 2500-4000, as reported by the manufacturer, Shell Chemical Company. Calculated average molecular weight is approximately 6500. Thereafter, the temperature of the reaction mixture was brought to 116°C. After diluting the entire resin mixture with water and adding neutralizer to 25% non-volatile content, the emulsion had the following properties: Non-volatile content 26.07% Viscosity (No. 4 food cup) 23 seconds PH 6.90 Neutralization % 50 Acid value (non-volatile content) 74.20 The above water-dilutable composition was applied to tin and aluminum plates such as those used in two-piece cans for carbonated beverages. Spray and bake the coating to cure. The resulting cured film had excellent properties in terms of inertness to flavor, no blistering, and adhesiveness. Example 22 Utilization of solid epoxy resin extender (molecular weight 1850) A reaction mixture containing a graft polymer was prepared in the same manner as in Example 21. The reaction mixture is
Diluted with 339g of DER664 epoxy resin instead of Epon1009. According to the manufacturer, Dow Chemical Company, DER644 epoxy resin has an epoxy equivalent weight of 875−
975, softening point 95℃~105℃ (Dulrance mercury method),
Gardner-Holdt viscosity R-V (40% glycol ether solvent) and gallon weight 9.54
(lbs.). The calculated average molecular weight is 1850. When the epoxy extended reaction mixture was neutralized and dispersed in water, the water diluted composition had excellent application properties and formed an excellent cured coating. The physical properties of the water emulsion are as follows. : Non-volatile content 26.27% Viscosity (No. 4 food cup) 20 seconds PH 6.90 Neutralization % 50 Acid number 74.60 Example 23 Utilization of relatively low molecular weight epoxy resin extender The reaction mixture of Example 21 containing the graft polymer was
Diluted with 339g of DER661 epoxy resin. According to manufacturer Dow Chemical Company, DER661 epoxy resin has an epoxy equivalent weight of 475 to 575 and a softening point of 70°C to
80°C (Dulrance mercury method), Gardner-Holdt viscosity G-J (40% glycol ether solvent) and gallon weight 9.65 lbs/gal. The calculated average molecular weight was 1050. When the epoxy extender reaction mixture was neutralized and dispersed in water, the water diluted composition had excellent properties as applied and in cured coating form. The physical properties of this emulsion are as follows: Non-volatile content 26.14% Viscosity (No. 4 food cup) 29 seconds PH 6.90 Neutralization % 50 Acid number 75.20 The dispersion stability of the emulsions of Examples 21 to 23 was 49
When tested for long periods at °C, virtually no phase separation,
It showed excellent properties with no change in viscosity or PH. Example 24 Study on Grafting Mechanism A polymer blend was obtained by reacting an epoxy resin with an addition polymerizable monomer mixture at a weight ratio of 80:20 in the following manner. First, DER333 liquid epoxy resin is reacted with bisphenol A in a ratio of approximately 65% resin to 35% bisphenol A. In a separate container, mix 65% of the mixture of methacrylic acid, styrene and ethyl acrylate.
Make with a weight ratio of 34:1. About 6.8% of the benzoyl peroxide of this mixture is added, and this mixture is then gradually added to the epoxy resin within 2 hours at a reaction temperature of about 120°C. After holding at the same temperature for a further 2 hours, a sample of the product is removed for structural evaluation. Carbon-13 NMR spectral analysis shows that the grafting between the addition copolymer and the epoxy resin is due to the aliphatic secondary
occurs only in positions that were previously tertiary backbone carbons (and possibly aliphatic tertiary backbone carbons). To further illustrate such grafting, several different model compounds were each given the configuration of some aliphatic carbon atoms present in the epoxy resin, and the same monomer mixture was grafted under similar grafting conditions as described above. were reacted separately. Carbon 13 NMR spectroscopy shows that the grafting of the model compound onto the aliphatic backbone carbon occurs almost exclusively on the carbon that was the aliphatic secondary carbon at the alpha position of the oxirane group before grafting. This results in
Similar circumstances governing the resin blend reaction products of the present invention are suggested. The acid value of the reaction product was slightly decreased compared to the acid value of the equivalent product calculated based on the total amount of methacrylic acid added to the reactor, and this slight decrease was obtained by carbon-13 spectroscopy. This seems to confirm the findings. Therefore, the conclusion is that other grafting of aliphatic carbon atoms of the epoxy resin backbone may occur, but the proportion is between 1 and 1 in the non-grafted state and aliphatic backbone carbon atoms in the alpha position of the oxirane group. This can be said to be less than what occurs in other skeletal carbons having 2 hydrogen atoms. Example 25 Effect of Different Amounts of Benzoyl Peroxide Used A series of resin blends were made in the same manner as in Example 24, varying the percentage of benzoyl peroxide free radical generator to monomer weight. The weight fraction of the total monomer mixture grafted onto the epoxy resin was approximately estimated by a solvent extraction method. The dispersibility of each blend was observed in an aqueous amine solvent;
The sedimentation resistance (stability) of the obtained dispersion was observed for one week. The observation results are shown in the table below.

【table】

[Table] General Comments In summary, the present invention provides that epoxy resins, addition polymers, and addition polymers are primarily attached to epoxy resins prior to grafting to aliphatic secondary carbons (and possibly tertiary carbons) of the backbone carbons of the epoxy resin. carbon),
That is, providing an associatively formed resin blend of grafted polymers grafting at non-oxirane portions of the molecule. It is most likely that the grafting occurs primarily at the original secondary (methylene) carbon atom in the alpha position of the terminal oxirane group.
In any case, this grafting creates a very permanent bond that significantly affects the properties of the resin blend product and modifies the epoxy resin enough to impart the permanent properties of the addition polymer grafted onto the epoxy resin. is given. Thus, for example, if the graft polymer is rich in carboxyl groups, several parts by weight of the grafted carboxylic acid-containing addition polymer imparting at least 1 part by weight of carboxylic acid groups per 100 parts of starting epoxy resin may be used. If present, it imparts superior properties to the resin blend product for producing water-diluted coating compositions for use inside beverage cans and the like. Such blends have a high degree of resistance to undesired reactions in slightly alkaline aqueous dispersions and precipitation from such dispersions. However, in order to obtain such appropriate proportions of permanent grafting and the concomitant influence on the properties of the associatively formed blend, the addition polymerization should be controlled with respect to the polymerization temperature and the polymerizable monomers. , unusually large amounts of free radical initiators, e.g.
It is necessary to initiate the addition polymerization with 7% by weight of benzoyl peroxide. According to a preferred embodiment of the invention, the invention also relates to the production of resin compositions primarily intended for use in can coatings for products for human consumption, in particular for soft drinks and beer. There are several tests that are performed to determine whether a particular coating composition is satisfactory for these surprising and demanding applications. Some of the more important tests are outlined below. When a coating composition is indicated in this application as being able to be used as a sanitary coating composition, it always means that it can pass a number of these tests. Flavor Test The cured coating within the can shall not impart any appreciable flavor to the contents of the can, nor shall it alter the flavor of the contents of the can in any way. This test is particularly important in the case of beer can coatings. Adhesion Adhesion tests are performed at room temperature and under ambient humidity conditions. Carve three parallel lines 2.54 cm long and 3 mm apart on the test coating panel. Intersect these three similar lines at 90° angles at the same intervals. These lines are usually cut with the tip of a knife or a razor blade. Next, firmly stick a piece of Scotch cellophane tape diagonally across the dice cut in this way. The tape is pulled quickly and continuously and peeled off at a pull angle of approximately 150°. Determine whether the carved area of the panel has been uncovered. If the coating is removed, rate the percentage on a scale of 0 to 10. A rating of zero is a perfect score indicating no removal and a rating of 10 is
Showing 100% removal. Storage Stability Water-dilutable coating compositions must exhibit satisfactory aqueous stability during long-term storage. This is done by first measuring all properties of the coating composition and then remeasuring after storage on samples stored not only at room temperature but also at 50°C. The most important indicators of stability are the absence of gels, the absence of precipitates and the pH.
For example, there is no change. To be approved as a sanitary coating composition, after 12 months storage at room temperature or 50
After 8 months of storage at °C, it is necessary that almost no change in viscosity be observed as evidence that gelation has not occurred. Thermal Stability In some can manufacturing methods, after the coating is applied, the coated metal may be immersed in a solder bath at a temperature in the range of 340°C to 370°C for about 5 seconds or less. The amount of discoloration of the coating indicates the degree of degradation. When using die-forged ends in other can manufacturing processes,
The assembled cans are typically immersed in an acidic copper sulfate bath for 5 minutes to test whether the coating has cracked during the manufacturing process. The presence of cracks is indicated by a small amount of copper deposited on the metal of the can. Water Disinfection Test This test is often performed on a cured film that is sprayed and baked onto the inside surface of two-piece aluminum beverage cans. This test is also used to measure the resistance of a coating to water and water vapor at sterilization temperatures. The coating weight used in the test is 12-16 milligrams per 258 cm ² panel. Two sections, each 3.8 cm x 22.9 cm, were cut after the coating was applied and baked for about 2 minutes at about 218°C. The top 5 cm of each test piece was bent to expose the coated surface. Each test piece is then heated to approximately 94℃
Each strip was half immersed in a water bath over the edge of the water bath. After 1/2 hour immersion, the test pieces were cooled at room temperature under running tap water, dried, and immediately examined for fading and adhesion. Fading (whitening) indicates water absorption during sterilization and is evaluated on a scale of zero to 10, with zero being complete and no fading and 10 being complete whitening. Both immersed surfaces and surfaces exposed only to water vapor are evaluated. An evaluation of whitening in the range of 0 to 2 is acceptable. Adhesion tests were performed in the manner described above on both immersed surfaces and surfaces exposed only to water vapor and were rated on a scale of zero to 10. A score of zero to one is a pass. Enamel Evaluation Test This is a test used by can manufacturers to evaluate the degree of metal exposure in coated cans. Under test conditions, a low voltage is applied between an electrode immersed in a can filled with electrolyte and the can body.
If the can is incompletely coated, there is exposed metal and current can flow through it. The current flow is indicated by an ammeter, and the strength of the current is related to the total surface area of the metal exposed to the electrolyte. Therefore, the magnitude of current flow, as indicated by the milliammeter reading, is a relative measure of the total exposed metal. Generally, each can manufacturer has its own specifications regarding allowable current. According to the test conditions, standardized electrolyte and 6.5cm ²
A coating weight of 2.5 mg per coat is used. For a 340g beverage can, the coating weight is approximately 110 to 120 per can.
mg. Under normal test conditions, a current of less than 25 milliamps is acceptable for most manufacturers as an aluminum beer can. For soft drink cans, the requirements are even more stringent, typically less than 5 milliamps for aluminum soft drink cans. Soft drink cans therefore have a high coating weight, typically 6.5 cm ²
A 340g soft drink with 4.5mg per serving is approx.
The amount will be 160-200 mg. The following properties are often evaluated in spray coating compositions for two-piece dishes. Wettability The composition on the coated surface must have the ability to form a continuous wet film. This is an important consideration regarding the bottom wall surface of the two-piece can that is furthest from the spray gun. Blistering resistance A large amount of coating weight may be required, such as in the case of a single coating on a two-piece tin plate. Usually, the wet film concentration is highest in the periphery. Because the film thickness in this area is large, blistering, which is rupture of the film surface due to evaporation of liquid, tends to occur. Foaming properties When applied by airless spray at 70Kg/ ^cm2 , the coating must not foam on the can. When foaming occurs, film discontinuities and rough surfaces occur. Water-dispersed sanitary coating compositions made according to embodiments of the present invention can pass many of the above tests. These coating compositions have particularly good application properties by spraying, either by air or airless equipment. Excellent atomization can be obtained regardless of the nozzle type or pressure. That is, excellent spray coatings can be obtained in the pressure range of 0.14 Kg/cm ² to 1050 Kg/cm ² . The coating material produced according to the present invention is applied to tin plate, aluminum, primer-coated metal, ABS plastic, polyolefin, polyester, polyamide, etc. at a rate of 1 to 10 mg/in per 340 g can, i.e., 50 to 300 mg per 340 g can. Applied in quantity. Generally, within this range, the continuity of the coating film is excellent. Furthermore, these compositions have excellent application properties so that during their use there are no problems such as blistering, sagging, solvent erosion, foaming and overflow. A common problem with water-dilutable coatings is odor in spray equipment, but the compositions made according to the present invention do not have such problems. Although the above examples generally represent preferred embodiments of the invention, other preferred embodiments may also provide superior coating compositions. That is, following the method of Example 21, with the addition of additional diluent (in addition to the epoxy resin diluent), and addition polymerization of the same monomers used in that example, very satisfactory results were obtained. Coatings can be obtained at low cost. The amount added is approximately 40% of the non-grafted addition polymer in the mixture.
% or less, but even higher amounts may be acceptable in some cases. A similar effect is obtained when the diluent is an addition polymer alone, ie, when no non-grafted epoxy resin is added to the reaction mixture. Although the above compositions have generally been described using liquid media, the binder can also be prepared in the absence of a solvent, cooled, and ground into a powdered product. These powders can be used by adding an amine and dispersing them in a solvent medium or an aqueous medium at the time of use. The amount of the free radical generator benzoyl peroxide has been expressed on the basis of the polymerizable monomer, but is preferably in the range of 0.6 to 5% by weight based on the total amount of the reaction mixture. While this invention has been described in detail with respect to preferred embodiments, it is intended to be illustrative and not limiting, and many variations in composition and method operation will be apparent to those skilled in the art within the scope of the invention. You can make it happen.

Claims (1)

[Scope of Claims] 1. (a) a graft polymerized diepoxy resin having a carboxylic acid functional graft polymerization moiety and an epoxy group at the molecular end; (b) a non-grafted carboxylic acid functional addition polymer; A composition comprising an associatively formed resin blend (c), wherein the grafted diepoxy resin (a) has an average of 1 or 2 hydrogen atoms bonded to an aliphatic backbone carbon atom in the non-grafted state. Molecular weight 350 to 20000
A carboxylic acid functional monomer (b1) derived from acrylic acid or methacrylic acid is added to the aliphatic skeleton carbon atoms of the diepoxy resin (a1), and the non-grafted addition polymer (b) ) is a non-graft addition polymerization of a carboxylic acid functional monomer (b1), the resin blend (c) contains a non-grafted diepoxy resin (a1), and the resin blend (c)
The total epoxy resin component (a, a1) in the resin blend (c) is at least 5% by weight of the resin blend (c), and the resin blend (c) is at least 2% by weight of the resin blend (c).
contains carboxylic acid units and has an acid value of 30 to 220.
and the grafting ratio of the addition polymerized component grafted to the graft polymerized diepoxy resin (a) to the diepoxy resin component is at least 1.5% by weight of the total diepoxy resin component (a, a1) in the resin blend (c). ,
Optionally resin blend (c) is 0.1-16% by weight of
A coating resin composition comprising an aminoplast crosslinking agent. 2 Diepoxy resin component (a1) is 350 to 20000
2. The composition of claim 1, wherein the composition is an aromatic epoxy resin having a molecular weight in the range of . 3. The composition according to item 1 above, wherein the addition polymer component contains copolymerized units of acrylic acid and styrene. 4. The composition according to item 1 above, wherein the diepoxy resin component (a1) is a reaction product of epichlorohydrin and bisphenol A. 5. The composition according to item 1, wherein the addition copolymer (b) is formed from copolymer units of methacrylic acid and styrene in a blending ratio of 60:39 to 80:19.5. 6. The resin composition according to item 1 above, wherein the diepoxy resin component and the non-grafted diepoxy resin component in the graft polymerized diepoxy resin account for 60-90% of the resin blend (c). 7. Through the reaction of the diepoxy resin (a1) and the addition polymerizable monomer (b1), (a) a graft-polymerized diepoxy resin having a carboxylic acid functional graft polymerization moiety and an epoxy group at the molecular terminal; b) a non-grafted carboxylic acid functional addition polymer; It is a reaction product with phenol A and has an average molecular weight of 350-20000, and the addition polymerizable monomer (b1) has an ethylenically unsaturated bond, and an addition polymer can be obtained by copolymerization. a mixture comprising a large amount of methacrylic acid, a small amount of styrene and a smaller amount of lower alkyl ester of acrylic acid or methacrylic acid; While stirring, the temperature is only 110℃.
While maintaining the reaction temperature at 120° C., the benzoyl peroxide or an equivalent peroxide-type free radical generator for the reaction is gradually added in the presence of at least 3% by weight based on the monomer mixture (b1). In addition, the reaction involves a first solvent that is a solvent for the diepoxy resin (a1);
The reaction is carried out in the presence of a solvent system that is miscible with the first solvent and also contains a second solvent that is a solvent for the monomer mixture (b1), whereby one or two hydrogen atoms are grafted in a non-grafted state. It is formed by copolymerization of a graft polymer (a) in which an ethylenically unsaturated monomer (b1) is grafted onto the aliphatic skeleton carbon atoms of a diepoxy resin (a1) having A reaction mixture (c) is obtained associatively formed with a non-grafted addition polymer (b), and the reaction mixture (c) contains a non-grafted diepoxy resin (a1), and the total amount in the reaction mixture is Epoxy resin component (a,
a1) is at least 5% by weight of the reaction mixture (c), and said reaction mixture (c) contains copolymerized carboxylic acid units imparting carboxyl groups corresponding to at least 2% by weight, based on its solids content. and the acid value is 30-220, and the grafting ratio of the addition polymerization component grafted into the graft polymerized diepoxy resin (a) to the diepoxy resin component is higher than the total epoxy resin component (a) in the reaction product (c). , a1) is at least 1.5% by weight of
Optionally the reaction mixture (c) is 0.1-16% by weight of
A method for producing a coated resin composition, characterized in that it contains an aminoplast crosslinking agent. 8. The method according to item 7, wherein the diepoxy resin component of the graft polymer (a) and the non-grafted diepoxy resin account for 60 to 90% by weight of the solid content of the reaction mixture (c).