Solvent-based coating compositions and packaging articles formed therefrom

Abstract

The invention relates to a solvent-based coating composition and a packaging article formed therefrom. The solvent-borne coating composition comprises i) at least one first hydroxyl-functionalized acrylic resin (also referred to as a high Tg hydroxyl-functionalized acrylic resin); ii) at least one second hydroxyl-functionalized acrylic resin (also referred to as a low Tg hydroxyl-functionalized acrylic resin); iii) at least one amino resin; iv) at least one acidic catalyst; and v) additional additives wherein the first hydroxyl-functionalized acrylic resin has a glass transition temperature of not less than 35 DEG C and the second hydroxyl-functionalized acrylic resin has a glass transition temperature of not more than 20 DEG C. The solvent-based coating composition provided by the invention can be cured within 1-5 seconds at the metal peak temperature of 210-232 DEG C, so that the solvent-based coating composition is suitable for high-speed coating application of packaging products.

Description

Technical Field

[0001] The present invention relates to a solvent-based coating composition. More specifically, the present invention relates to a solvent-based coating composition suitable for high-speed production lines and packaging articles having a coating formed from the coating composition, particularly food cans or beverage cans. Background Art

[0002] At present, competition among manufacturers of packaging articles, especially food cans or beverage cans, is becoming increasingly fierce. In order to achieve higher production efficiency, the production line speed has been increasing year by year in recent years in order to achieve the purpose of reducing the overall cost.

[0003] In high-speed coating production lines for packaging articles, such as coating production lines with a line speed as high as 1000 cans per minute or higher, the cured coating generally has one or more of the following problems. For example, due to the low baking temperature and short baking time, the coating cannot be fully cured, so the formed coating has a low film hardness and is easily scratched during subsequent processing, such as the necking process, and even film peeling and other problems may occur. Moreover, the formed coating cannot withstand more stringent post-processing requirements, such as the high-temperature sterilization and cooking requirements of the food industry, resulting in phenomena such as coating whitening or even peeling after high-temperature sterilization and cooking. In addition, during such high-speed coating, it is very easy for the coating to not fully cover the substrate, resulting in individual substrate exposure points, increasing the risk of rust and can leakage.

[0004] Therefore, there is an urgent need in the market for a coating composition that can be adapted to high-speed production lines for packaging articles, especially food cans or beverage cans. Summary of the Invention

[0005] A first aspect of the present invention provides a solvent-based coating composition, the solvent-based coating composition comprising,

[0006] i) at least one first hydroxy-functionalized acrylic resin (also known as a high-Tg hydroxy-functionalized acrylic resin);

[0007] ii) at least one second hydroxy-functionalized acrylic resin (also known as a low-Tg hydroxy-functionalized acrylic resin);

[0008] iii) at least one amino resin;

[0009] iv) at least one acidic catalyst; and

[0010] v) additional additives,

[0011] Among them, the first hydroxy-functionalized acrylic resin has a glass transition temperature of not less than 35 °C, and the second hydroxy-functionalized acrylic resin has a glass transition temperature of not more than 20 °C. Preferably, the glass transition temperature of the first hydroxy-functionalized acrylic resin is above 40 °C, preferably in the range of 40 - 60 °C; and the glass transition temperature of the second hydroxy-functionalized acrylic resin is in the range of 10 - 18 °C.

[0012] In some embodiments according to the present invention, the first hydroxy-functionalized acrylic resin is present in an amount of at least 15% by weight relative to the total weight of the solvent-based coating composition. Preferably, both the first hydroxy-functionalized acrylic resin and the second hydroxy-functionalized acrylic resin are present in amounts in the range of 15 to 40% by weight relative to the total weight of the solvent-based coating composition. Additionally or alternatively, the mass ratio of the first hydroxy-functionalized acrylic resin to the second hydroxy-functionalized acrylic resin is in the range of 0.8 to 3.5:1, preferably in the range of 0.8 to 1.5:1, more preferably in the range of 1.0 to 1.3:1.

[0013] In some embodiments according to the present invention, the amino resin includes one or more selected from partially etherified amino resins, and the partially etherified amino resins include one or more of partially etherified urea-formaldehyde resins, partially etherified melamine aldehyde resins, and partially etherified benzoguanamine aldehyde resins. In some preferred embodiments according to the present invention, the amino resin includes a combination of a partially etherified urea-formaldehyde resin, a partially etherified benzoguanamine aldehyde resin, and optionally a partially etherified melamine aldehyde resin. More preferably, it includes a combination of an isobutanol-etherified urea-formaldehyde resin and a butanol-etherified benzoguanamine aldehyde resin. Even more preferably, it includes a combination of an isobutanol-etherified urea-formaldehyde resin, a methanol-etherified melamine aldehyde resin, and a butanol-etherified benzoguanamine aldehyde resin.

[0014] In some embodiments according to the present invention, the solvent-based coating composition further comprises at least one epoxy resin, preferably including a low molecular weight epoxy resin with a number average molecular weight of not more than 1000 g / mol.

[0015] The second aspect of the present invention provides a packaging article comprising a substrate and a coating, wherein the coating is formed by curing the solvent-based coating composition of the first aspect above, and wherein the substrate is selected from wood, wood composites, paper, metal, plastic, fabric, ceramic, or any combination thereof.

[0016] Another method of the present invention provides a food or beverage can comprising a metal substrate and a coating, wherein the coating is formed by curing the solvent-based coating composition of the first aspect above.

[0017] In some embodiments of the present invention, when the food or beverage can is a three-piece food or beverage can, the coating is a side seam coating of the food or beverage can, including an inner side seam coating and an outer side seam coating.

[0018] In some embodiments of the present invention, when the food or beverage can is a two-piece food or beverage can, the coating is a dome coating of the food or beverage can, including a dome repair coating.

[0019] The inventors of the present invention surprisingly found that in the presence of an acidic catalyst, a solvent-based coating composition obtained by combining two or more hydroxy-functional acrylates having a specific glass transition temperature and an amino resin as a crosslinking agent (such as a combination of urea-formaldehyde resin and melamine aldehyde resin) is applicable to high-speed production lines of packaging products, especially food cans or beverage cans, and can achieve curing within 1-5 seconds at a metal peak temperature of 210-232 °C, preferably within 1-3 seconds at a metal peak temperature of 210-232 °C, and more preferably within 1-3 seconds at a metal peak temperature of 210 °C. Moreover, the cured coating thus formed can also have good retort resistance, and basically does not turn white or blister after being retorted at 125 °C for 45 minutes, and can meet the high-temperature sterilization requirements of the food metal packaging industry.

[0020] The inventors of the present invention more surprisingly found that after the solvent-based coating composition according to the present invention is stored at room temperature or at a temperature of 45 °C for 6 weeks, preferably after being stored at room temperature and at a temperature of 45 °C for 6 weeks, the coating formed therefrom has no obvious attenuation in performance compared with the coating formed from the newly prepared solvent-based coating composition, and has excellent high-temperature storage stability, which was difficult to foresee before this application.

[0021] Details of one or more embodiments of the present invention are set forth in the following description. Other features, objects, and advantages of the present invention will become apparent from the description and the claims.

[0022] Definition

[0023] As used herein, the terms "without a quantifier", "at least one", and "one or more" are used interchangeably. Thus, for example, a coating composition containing an amino resin can be interpreted to mean that the coating composition contains "one or more" amino resins.

[0024] Where a composition is described as comprising or containing a specific component, it is contemplated that optional components not involved in the present invention are not excluded from the composition, and it is contemplated that the composition may consist of or be composed of the components involved. Or where a method is described as comprising or containing specific process steps, it is contemplated that optional process steps not involved in the present invention are not excluded from the method, and it is contemplated that the method may consist of or be composed of the process steps involved.

[0025] For simplicity, only some numerical ranges are explicitly disclosed herein. However, any lower limit can be combined with any upper limit to form a range not explicitly recited; and any lower limit can be combined with other lower limits to form a range not explicitly recited, and likewise any upper limit can be combined with any other upper limit to form a range not explicitly recited. In addition, although not explicitly recited, every point or single value between the range endpoints is included within the range. Thus, each point or single value can be used as its own lower or upper limit and combined with any other point or single value or with other lower or upper limits to form a range not explicitly recited.

[0026] As used herein, the term "amino resin" refers to a product formed by the polycondensation reaction of an amino compound, i.e., a compound containing at least one primary amine (NH 2 ) functional group and / or amide (-CO-NH 2 ) functional group, with an aldehyde compound, and the product may optionally be partially or fully etherified with a monohydric aliphatic alcohol.

[0027] As used herein, the term "epoxy resin" refers to a compound containing two or more epoxy groups, which includes not only small molecule compounds containing two or more epoxy groups, but also oligomers containing two or more epoxy groups and having a certain degree of polymerization. In one embodiment of the present invention, the epoxy resin is a low molecular weight epoxy resin with a number average molecular weight not exceeding 1000 g / mol.

[0028] As used herein, when referring to the use of "epoxy resin", the term "epoxy equivalent" refers to the mass of resin containing 1 mol of epoxy groups. Generally, the lower the epoxy equivalent, the more epoxy groups contained in the resin and the higher the reactivity. In the examples of the present invention, the epoxy equivalent value of the resin is usually provided by the supplier.

[0029] In the context of the present application, the term "blooming" refers to a color change visible to the naked eye on the surface of a coating after the coating has been subjected to a specific treatment, such as steaming at a temperature of 125°C for 45 minutes or longer (e.g., 1 hour, 2 hours, 5 hours, or 10 hours).

[0030] When it comes to a coating formed from a solvent-based coating composition, the term "no significant attenuation in performance" means that there is no significant decrease in one or more, preferably two or more, and more preferably all of the pencil hardness, retort resistance, and bend resistance of the coating.

[0031] In this document, "coating" has the same meaning as "paint film", both of which are formed after being coated and cured with a solvent-based coating composition.

[0032] In this document, the term "three-piece can" refers to a canned packaging container formed by processing a metal sheet through processes such as crimping, bonding, fusing, or welding, which consists of three parts: a can bottom, a can body (also known as a side wall), and a can lid, and the can body has a seam (also known as a side seam).

[0033] In this document, the term "two-piece can" refers to a metal container composed of two parts: a can lid and an integrally seamless can body with a bottom. The can body of this type of metal container is usually formed into a set shape by a drawing method, so the can body inevitably has a bottom arch part.

[0034] When used in the context of "on the side seam of a three-piece food or beverage can", the term "on..." includes the direct or indirect application of the coating composition to the side seam. Therefore, for example, the coating composition applied on the primer layer on the side seam is considered to be the coating composition coated on the side seam. Similarly, when used in the context of "on the arch bottom of a two-piece food or beverage can", the term "on..." includes the direct or indirect application of the coating composition to the arch bottom. Therefore, for example, the coating composition applied on the primer layer on the arch bottom is considered to be the coating composition coated on the arch bottom and is also regarded as the coating composition retouched on the arch bottom.

[0035] If not otherwise specified, in this application, the terms "first", "second", etc. are used to distinguish different objects, rather than to describe a specific order or primary-secondary relationship.

[0036] When appearing in this specification and claims, the terms "comprising" and "including" and their variants do not have a restrictive meaning.

[0037] The terms "preferred" and "preferably" refer to embodiments of the present invention that can provide certain benefits in certain cases. However, in the same or other cases, other embodiments may also be preferred. Additionally, the description of one or more preferred embodiments does not mean that other embodiments are unavailable, and it is not intended to exclude other embodiments from the scope of the present invention. Detailed Description

[0038] According to a first aspect of the present invention, there is provided a solvent-based coating composition, the solvent-based coating composition comprising: i) at least one first hydroxy-functionalized acrylic resin (also known as a high Tg hydroxy-functionalized acrylic resin); ii) at least one second hydroxy-functionalized acrylic resin (also known as a low Tg hydroxy-functionalized acrylic resin); iii) at least one amino resin; iv) at least one acidic catalyst; and v) additional additives, wherein the first hydroxy-functionalized acrylic resin has a glass transition temperature of not less than 35°C, and the second hydroxy-functionalized acrylic resin has a glass transition temperature of not more than 20°C.

[0039] As described above, in the present invention, in the presence of an acidic catalyst, by combining two or more hydroxy-functionalized acrylic resins having specific glass transition temperatures and pairing with an amino resin as a crosslinking agent (such as a combination of urea-formaldehyde resin and melamine aldehyde resin), an acrylic resin-based solvent-based coating composition suitable for high-speed production lines of packaging products, especially food cans or beverage cans, is obtained. As is well known, coating compositions suitable for packaging products, especially food cans or beverage cans, are usually mainly polyester-based, acrylic resin-based coating compositions are not common, and acrylic resin-based coating compositions have the problem of slow curing speed. The inventors of the present application surprisingly found that the acrylic resin-based solvent-based coating composition according to the present invention having the above composition can achieve curing within 1 to 5 seconds at a metal peak temperature of 210 - 232°C, preferably within 1 to 3 seconds at a metal peak temperature of 210 - 232°C, more preferably within 1 to 3 seconds at a metal peak temperature of 210°C, which was difficult to achieve before the present application. Moreover, the cured coating thus formed can also have good retort resistance, for example, it is substantially non-whitening and non-bubbling after retorting at 125°C for 45 minutes, and can meet the high-temperature sterilization requirements of the food metal packaging industry.

[0040] According to the present invention, the solvent-based coating composition comprises hydroxy-functionalized acrylic resin and amino resin, which, as resin components or part of resin components, constitute the main body of the coating formed by the solvent-based coating composition, so as to provide sufficient mechanical strength for the formed coating.

[0041] In an embodiment according to the present invention, the hydroxy-functionalized acrylic resin comprises at least one first hydroxy-functionalized acrylic resin, and this first hydroxy-functionalized acrylic resin has a relatively high glass transition temperature (Tg), and thus is also referred to as a high-Tg hydroxy-functionalized acrylic resin. The Tg of the first hydroxy-functionalized acrylic resin is not lower than 35 °C, may be at least 36 °C, such as at least 38 °C, such as at least 40 °C. The Tg of the first hydroxy-functionalized acrylic resin may be at most 80 °C, such as at most 70 °C, such as at most 68 °C, such as at most 65 °C, such as at most 62 °C, such as at most 60 °C. In some embodiments, the Tg of the first hydroxy-functionalized acrylic resin may be in the range of 35 to 60 °C, or in the range of 35 to 55 °C, or in the range of 35 to 50 °C, or in the range of 38 to 60 °C, or in the range of 38 to 55 °C, or in the range of 38 to 50 °C, or in the range of 40 to 60 °C, or in the range of 40 to 55 °C, or in the range of 40 to 50 °C. In this document, Tg is measured by differential scanning calorimetry (DSC) according to ASTM D6604-00(2013). All Tg values reported herein are measured in this way. The inventors of the present application have found that in the formulation of solvent-based coating compositions, introducing a certain amount of the first hydroxy-functionalized acrylic resin with a high Tg is beneficial to the retort resistance of the paint film formed therefrom, such that the resulting coating is substantially non-whitening and non-bubbling after being retorted at 125 °C for 45 minutes, and can meet the high-temperature sterilization requirements of the food metal packaging industry.

[0042] In an embodiment according to the present invention, the hydroxy-functionalized acrylic resin further comprises at least one second hydroxy-functionalized acrylic resin, and this second hydroxy-functionalized acrylic resin has a lower glass transition temperature (Tg), and thus is also referred to as a low-Tg hydroxy-functionalized acrylic resin. The Tg of the first hydroxy-functionalized acrylic resin does not exceed 20 °C, can be at most 18 °C, such as at least 17 °C, such as at most 16 °C. The Tg of the second hydroxy-functionalized acrylic resin can be at least 0 °C, such as at least 5 °C, such as at least 8 °C, such as at least 10 °C. In some embodiments, the Tg of the second hydroxy-functionalized acrylic resin can be in the range of 10 to 18 °C, or in the range of 12 to 18 °C, or in the range of 13 to 18 °C, or in the range of 14 to 18 °C, or in the range of 15 to 18 °C, or in the range of 10 to 17 °C, or in the range of 12 to 17 °C, or in the range of 13 to 17 °C, or in the range of 14 to 17 °C, or in the range of 15 to 7 °C, or in the range of 10 to 16 °C, or in the range of 12 to 16 °C, or in the range of 13 to 16 °C, or in the range of 14 to 16 °C, or in the range of 15 to 16 °C. In this document, Tg is measured by the same method as that for the first hydroxy-functionalized acrylic resin above. The inventors of the present application have found that in the solvent-based coating composition according to the present invention, combining a certain amount of the second hydroxy-functionalized acrylic resin with a low Tg with the first hydroxy-functionalized acrylic resin with a high Tg can achieve more favorable coating properties, such as coating impact resistance.

[0043] In some embodiments according to the present invention, the glass transition temperature of the first hydroxy-functionalized acrylic resin is above 40 °C, preferably in the range of 40 - 60 °C; and the glass transition temperature of the second hydroxy-functionalized acrylic resin is in the range of 10 - 18 °C. Thus, it is beneficial to the retort resistance and impact resistance of the resulting coating.

[0044] In an embodiment according to the present invention, the molecular weights of the first and second hydroxy-functionalized acrylic resins can vary depending on the material selection and the desired end application. Optionally, the first and second hydroxy-functionalized acrylic resins can have any suitable number-average molecular weight (Mn). For example, the Mn of the first and second hydroxy-functionalized acrylic resins can be at least 7000 Daltons (Da = g / mol), such as at least 7,500 Da. The Mn of the first and second hydroxy-functionalized acrylic resins can be at most 20,000 Da, such as at most 18,000 Da, such as at most 15,000 Da, such as at most 13,000 Da, or even at most 12,000 Da. The Mn of the first and second hydroxy-functionalized acrylic resins can be from 7000 Da to 20,000 Da, or from 7000 Da to 18,000 Da, or from 7000 Da to 15,000 Da, or from 7000 Da to 13,000 Da, or from 7000 Da to 12,000 Da, or from 8000 Da to 20,000 Da, or from 8000 Da to 18,000 Da, or from 8000 Da to 15,000 Da, or from 8000 Da to 13,000 Da, or from 8000 Da to 12,000 Da, or from 9000 Da to 20,000 Da, or from 9000 Da to 18,000 Da, or from 9000 Da to 15,000 Da, or from 9000 Da to 13,000 Da, or from 9000 Da to 12,000 Da. In some preferred embodiments according to the present invention, the first hydroxy-functionalized acrylic resin and the second hydroxy-functionalized acrylic resin each independently have a number-average molecular weight in the range of 7000 - 12000 g / mol. Herein, Mn is determined by gel permeation chromatography using polystyrene standards according to ASTM D6579-11. All Mn values reported herein are measured in this way. If the molecular weights of the first and second hydroxy-functionalized acrylic resins are too high, the coating composition formulated therefrom is difficult to coat evenly and is not suitable for construction operations; if the molecular weights of the first and second hydroxy-functionalized acrylic resins are too low, the film strength of the coating composition formed after curing is limited. Therefore, in some embodiments according to the present application, it is appropriate for the molecular weights of the first and second hydroxy-functionalized acrylic resins to be within the above range.

[0045] In an embodiment according to the present invention, the hydroxyl values of the first and second hydroxyl-functionalized acrylic resins can vary depending on material selection and the desired end application. Optionally, the first and second hydroxyl-functionalized acrylic resins can have any suitable hydroxyl value (or 'OHN'; also known as hydroxyl value or 'OHV'). The hydroxyl value of the first hydroxyl-functionalized acrylic resin can be at least 40 mg KOH / g, such as at least 50 mg KOH / g, such as at least 60 mg KOH / g, or even at least 70 mg KOH / g. The hydroxyl values of the first and second hydroxyl-functionalized acrylic resins can be at most 100 mg KOH / g, such as at most 95 mg KOH / g, such as at most 90 mg KOH / g, such as at most 85 mg KOH / g. The hydroxyl values of the first and second hydroxyl-functionalized acrylic resins can be from 40 mg KOH / g to 100 mg KOH / g, such as from 50 mg KOH / g to 100 mg KOH / g, such as from 60 mg KOH / g to 100 mg KOH / g, or even from 70 mg KOH / g to 100 mg KOH / g. The hydroxyl values of the first and second hydroxyl-functionalized acrylic resins can be from 40 mg KOH / g to 90 mg KOH / g, such as from 50 mg KOH / g to 90 mg KOH / g, such as from 60 mg KOH / g to 90 mg KOH / g, or even from 70 mg KOH / g to 90 mg KOH / g. The hydroxyl values of the first and second hydroxyl-functionalized acrylic resins can be from 40 mg KOH / g to 80 mg KOH / g, such as from 50 mg KOH / g to 80 mg KOH / g, such as from 60 mg KOH / g to 80 mg KOH / g, or even from 70 mg KOH / g to 80 mg KOH / g. In some embodiments according to the present invention, the first hydroxyl-functionalized acrylic resin and the second hydroxyl-functionalized acrylic resin each independently have a hydroxyl value in the range of 50 - 80 mg KOH / g. As reported herein, the hydroxyl value is the number of milligrams of KOH equivalent to the hydroxyl groups in 1 g of material. Methods well known in the art can be used to determine the hydroxyl value. For example, the hydroxyl value is measured by ISO 4629 titration. If the hydroxyl values of the first and second hydroxyl-functionalized acrylic resins are too high, they will gel too quickly after mixing with the amino resin, which is not suitable for construction operations; if the hydroxyl values of the first and second hydroxyl-functionalized acrylic resins are too low, the curing reaction with the amino resin will be too slow, resulting in a decrease in construction efficiency. Therefore, in some embodiments according to the present application, it is appropriate for the hydroxyl values of the first and second hydroxyl-functionalized acrylic resins to be within the above ranges, which enables the coating composition formulated therefrom to have an appropriate pot life.

[0046] In some embodiments according to the present application, the first hydroxy-functionalized acrylic resin has a significant impact on the retort resistance of the coating and is present in an amount of at least 15% by weight relative to the total weight of the solvent-based coating composition. For example, relative to the total weight of the solvent-based coating composition, the first hydroxy-functionalized acrylic resin may be in an amount of at least 18% by weight, at least 20% by weight, and at most 50 wt%, at most 45 wt%, at most 40 wt%, at most 35 wt%. In a preferred embodiment according to the present application, the amount of the first hydroxy-functionalized acrylic resin, relative to the total weight of the solvent-based coating composition, is in the range of 15 to 40 wt%, preferably in the range of 20 to 40 wt%, more preferably in the range of 20 to 35 wt%. If the amount of the first hydroxy-functionalized acrylic resin used is too low, the retort resistance of the coating cannot be achieved, and the resulting coating is prone to whitening after retort treatment; if the amount of the first hydroxy-functionalized acrylic resin used is too high, it will have an adverse effect on the flexibility of the coating, and the resulting packaging product is prone to cracking during subsequent necking treatment and cannot meet the application requirements. Therefore, in some embodiments according to the present application, it is appropriate that the amount of the first hydroxy-functionalized acrylic resin is within the above range, which enables the coating composition formulated therefrom to have excellent coating properties.

[0047] In some embodiments according to the present application, the second hydroxy-functionalized acrylic resin may be present in the solvent-based coating composition in any suitable amount as needed. In one embodiment according to the present application, the amount of the second hydroxy-functionalized acrylic resin, relative to the total weight of the solvent-based coating composition, is in the range of 15 to 40 wt%, preferably in the range of 20 to 40 wt%, more preferably in the range of 20 to 35 wt%. In some preferred embodiments according to the present application, both the first hydroxy-functionalized acrylic resin and the second hydroxy-functionalized acrylic resin are present in an amount in the range of 15 to 40% by weight relative to the total weight of the solvent-based coating composition.

[0048] In addition, in order to ensure the coating properties of the solvent-based coating composition according to the present invention, the ratio of the first hydroxy-functionalized acrylic resin and the second hydroxy-functionalized acrylic resin is also one of the factors to be considered. The inventors of the present application have found that controlling the mass ratio of the first hydroxy-functionalized acrylic resin and the second hydroxy-functionalized acrylic resin within a certain range is beneficial to the application of the resulting coating composition in the high-speed coating production line of packaging products, so that the resulting coating not only has excellent retort resistance but also shows favorable bend resistance. In some embodiments according to the present invention, the mass ratio of the first hydroxy-functionalized acrylic resin to the second hydroxy-functionalized acrylic resin is in the range of 0.8 to 3.5:1, preferably in the range of 0.8 to 1.5:1, more preferably in the range of 1.0 to 1.3:1.

[0049] In an embodiment according to the present invention, a hydroxy-functional acrylic resin that meets the above performance requirements can be made, for example, by techniques well-known to those of ordinary skill in the art. For example, the hydroxy-functional acrylic resin can be a hydroxy-containing copolymer of ethylenically unsaturated compounds. These copolymers are copolymers of olefin monomers containing hydroxyl groups and olefin monomers without hydroxyl groups. Examples of suitable monomers include vinyl and vinylidene monomers such as styrene, α-methylstyrene, o- and p-chlorostyrene, o-, m- and p-methylstyrene, p-tert-butylstyrene, acrylic acid, (meth)acrylonitrile, acrylic and methacrylic esters having 1 to 8 carbon atoms (such as ethyl acrylate, methyl acrylate, n- or isopropyl acrylate, n-butyl acrylate, 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, isooctyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate and isooctyl methacrylate); diesters of fumaric acid, itaconic acid or maleic acid having 4 to 8 carbon atoms in the alcohol component; (meth)acrylamide; vinyl esters of alkane monocarboxylic acids having 2 to 5 carbon atoms (such as vinyl acetate or vinyl propionate) and hydroxyalkyl esters of acrylic or methacrylic acid having 2 to 4 carbon atoms in the hydroxyalkyl residue (such as 2-hydroxyethyl acrylate or methacrylate, 2-hydroxypropyl acrylate or methacrylate, 4-hydroxybutyl acrylate or methacrylate, trimethylolpropane monoacrylate or methacrylate or pentaerythritol monoacrylate or methacrylate). Mixtures of these monomers can also be used to prepare the hydroxy-functional acrylic resin.

[0050] As an example of the hydroxy-functional acrylic resin, any conventional hydroxy-functional acrylic resin can be used, such as a proprietary acrylate resin purchased from Sherwin-Williams.

[0051] In some embodiments according to the present application, the solvent-based coating composition further comprises an amino resin as a film-forming resin component in addition to the above-mentioned hydroxy-functional resin.

[0052] As described above, amino resins refer to the condensation products of aldehydes (such as formaldehyde, acetaldehyde, crotonaldehyde, and benzaldehyde) and amino compounds containing amino or amide groups (such as urea, melamine, benzoguanamine, or methyloguanamine). Condensation products of other amines and amides can also be used, such as triazines, diazines, triazoles, guanidines, guanamines, and aldehyde condensates of alkyl-substituted and aryl-substituted melamines. Some examples of such compounds are N,N'-dimethylurea, benzourea, dicyandiamide, methylguanidine, ethylguanidine, glycoluril, cyanuric diamide, 2-chloro-4,6-diamino-1,3,5-triazine, 6-methyl-2,4-diamino-1,3,5-triazine, 3,5-diaminotriazole, triaminopyrimidine, 2-mercapto-4,6-diaminopyrimidine, 3,4,6-tris(ethylamino)-1,3,5-triazine, etc. Although the aldehydes used are usually formaldehyde, other aldehydes can also be used, such as acetaldehyde, crotonaldehyde, acrolein, benzaldehyde, furfural, glyoxal, etc., and mixtures thereof. In the presently preferred embodiments of the present invention, melamine-aldehyde resins, benzoguanamine-aldehyde resins, urea-aldehyde resins, or any combination thereof are used as amino resins.

[0053] In some preferred embodiments according to the present invention, the amino resin can be optionally partially etherified. In the field of coatings, amino resins can be etherified with different alcohols, including but not limited to butyl etherified amino resins, isobutyl etherified amino resins, methyl etherified amino resins, and mixed etherified amino resins. When etherified with different alcohols, the activity of the amino resin is significantly different. The inventors of the present application have found that when an isobutanol-etherified urea-formaldehyde resin is combined with a butanol-etherified benzoguanamine aldehyde resin and an optionally methanol-etherified melamine aldehyde resin, the resulting amino resin has appropriate curing activity, and when combined with the above-mentioned hydroxyl-functionalized acrylic resin in the presence of an acidic catalyst, a solvent-based coating composition can be obtained, which is suitable for high-speed production lines of packaging products, especially food cans or beverage cans, and can achieve curing within 1-5 seconds at a metal peak temperature of 210-232 °C, preferably within 1-3 seconds at a metal peak temperature of 210-232 °C, and more preferably within 1-3 seconds at a metal peak temperature of 210 °C. Moreover, the cured coating thus formed can also have good retort resistance, and basically does not turn white or blister after retorting at 125 °C for 45 minutes, and can meet the high-temperature sterilization requirements of the food metal packaging industry.

[0054] Thus, in some preferred embodiments according to the present invention, the amino resin comprises a combination of a partially etherified urea-formaldehyde resin, a partially etherified benzoguanamine resin, and optionally a partially etherified melamine resin, preferably a combination of an isobutanol-etherified urea-formaldehyde resin and a butanol-etherified benzoguanamine resin, and more preferably a combination of an isobutanol-etherified urea-formaldehyde resin, a methanol-etherified melamine resin, and a butanol-etherified benzoguanamine resin.

[0055] The amino resin is commercially available. Non-limiting examples of suitable commercially available amino resins include Cymel 303LF, Cymel 5010, Cyeml U-662, etc. from Allnex.

[0056] The amount of the amino resin may depend on various factors, including, for example, the type of the amino resin, the baking time and temperature, the molecular weight of the hydroxy-functional resin, and the desired coating properties. Relative to the total weight of the coating composition, the amino resin is usually present in an amount of up to 60 wt%, preferably up to 55 wt%, more preferably up to 50 wt%, and is present in an amount of at least 1 wt%, at least 2 wt%, at least 3 wt% or at least 5 wt%. In a preferred embodiment according to the present application, the amount of the amino resin, relative to the total weight of the coating composition, is in the range of 2 to 35 wt%, preferably in the range of 3 to 20 wt%, and more preferably in the range of 5 to 10 wt%. Generally, the desired amount of the amino resin used can usually be selected empirically according to the film-forming performance of the paint film. In a preferred embodiment according to the present invention, the amino resin comprises, relative to the total weight of the coating composition, 0 to 20 wt% of a methanol-etherified melamine-aldehyde resin, preferably 3 to 20 wt% of a methanol-etherified melamine-aldehyde resin; 0 to 10 wt% of a butanol-etherified aryl-substituted melamine-aldehyde resin, preferably 1 to 5 wt% of a butanol-etherified aryl-substituted melamine-aldehyde resin; and 0.1 to 10 wt% of an isobutanol-etherified urea-formaldehyde resin, preferably 1 to 5 wt% of an isobutanol-etherified urea-formaldehyde resin.

[0057] In an embodiment according to the present invention, the solvent-based coating composition may further comprise at least one epoxy resin, preferably a low molecular weight epoxy resin having a number average molecular weight not exceeding 1000 g / mol. The inventors of the present application have found that in the solvent-based coating composition according to the present invention, adding a low molecular weight epoxy resin can increase the adhesion of the paint film to the substrate while ensuring a high solid content and low viscosity of the coating, thereby ensuring the workability of the coating and achieving a better coating coverage effect. Moreover, the application of a specific amount of the low molecular weight epoxy resin can further improve the impact resistance, flexural resistance, and steam resistance of the resulting coating, which was difficult to anticipate before the present application.

[0058] In some embodiments according to the present invention, the epoxy resin comprises at least one bisphenol A type epoxy resin. Preferably, the number average molecular weight of the epoxy resin is in the range of 300 - 500 g / mol, and / or the epoxy equivalent of the epoxy resin is in the range of 200 - 250.

[0059] In the solvent-based coating composition according to the present application, the amount of the epoxy resin can be adjusted according to needs, particularly according to the amount of the hydroxyl-functional resin and / or the amino resin, based on the experience of those skilled in the art. In some embodiments of the present application, the epoxy resin is present in an amount of up to 15 wt%, up to 13 wt%, up to 12 wt%, up to 10 wt%, and at least 0.5 wt%, at least 3 wt%, at least 5 wt%. In some preferred embodiments of the present invention, the amount of the epoxy resin is in the range of 0.1 - 10 wt%, preferably in the range of 0.2 - 8 wt%, more preferably in the range of 2 - 8 wt%, still more preferably in the range of 6 - 8 wt%. These weight percentages are determined based on the total weight of the solvent-based coating composition.

[0060] In an embodiment according to the present invention, the solvent-based coating composition may further comprise at least one acidic catalyst. Examples of the acidic catalyst include, but are not limited to, p-toluenesulfonic acid, benzenesulfonic acid, methanesulfonic acid, dinonylnaphthalenesulfonic acid, dinonylnaphthalenedisulfonic acid, dodecylbenzenesulfonic acid, oxalic acid, maleic acid, phthalic acid, acrylic acid, mono(di)alkyl phosphate, phosphoric acid, mon(di)alkyl pyrophosphate, or a combination thereof.

[0061] In the solvent-based coating composition according to the present application, the amount of the acidic catalyst can be adjusted according to needs, particularly according to the amount of the hydroxyl-functional resin and / or the amino resin, based on the experience of those skilled in the art. In some embodiments of the present application, the acidic catalyst is present in an amount of up to 15 wt%, up to 13 wt%, up to 12 wt%, up to 10 wt%, up to 8 wt%, up to 5 wt%, and at least 0.1 wt%, at least 0.2 wt%, at least 0.5 wt%. In some preferred embodiments of the present invention, the amount of the acidic catalyst is in the range of 0.1 - 10 wt%, preferably in the range of 0.2 - 8 wt%, more preferably in the range of 0.2 - 6 wt%. These weight percentages are determined based on the total weight of the solvent-based coating composition.

[0062] In an embodiment according to the present application, in some embodiments according to the present application, the solvent-based coating composition may contain an organic solvent to further adjust the viscosity of the coating composition. The addition of the organic solvent can increase the evaporation rate of the coating composition and accelerate the formation of the paint film. In some embodiments of the present application, the organic solvent includes ketones (such as acetone, methyl isopropyl ketone, methyl isobutyl ketone, etc.), esters (ethyl acetate, butyl acetate, etc.), aromatic hydrocarbons (toluene, xylene, etc.), aliphatic hydrocarbons (cyclopentane, cyclohexane, etc.) or any combination thereof.

[0063] In a preferred embodiment according to the present application, if present, the solvent may, for example, account for at least 0.1 wt%, at least 1 wt%, at least 3 wt%, at least about 5 wt%, at least about 6 wt%, at least about 7 wt%, at least about 8 wt%, at least about 9 wt%, at least about 10 wt% of the total weight of the coating composition. In a preferred embodiment according to the present application, if present, the solvent may, for example, account for at most 60 wt%, at most about 55 wt%, at most about 52 wt% of the total weight of the coating composition. Generally, the desired amount of the solvent is usually selected empirically according to the film-forming performance of the paint film.

[0064] In some embodiments according to the present invention, in addition to the above solvents, the additional additives in the solvent-based coating composition may also include those commonly used in coating compositions. These additives do not adversely affect the coating composition or the cured coating obtained therefrom. Suitable additives include, for example, those reagents that can improve the processing performance or manufacturing performance of the composition, enhance the aesthetic feeling of the composition, or improve the specific functional properties or characteristics of the coating composition or the cured composition obtained therefrom (such as adhesion to the substrate). According to specific needs, the additives that can be included in the film-forming composition include, for example but not limited to, anti-skinning agents, driers, film-forming aids, coupling agents, pigments, fillers, anti-settling agents, anti-migration aids, antibacterial agents, anti-mold agents, lubricants, wetting agents, biocides, plasticizers, defoamers, colorants, waxes, antioxidants, anti-corrosion agents, rheology modifiers, dispersants, adhesion promoters, UV stabilizers, leveling agents or combinations thereof. The content of each optional component is sufficient to achieve its intended purpose, but preferably, such content does not adversely affect the coating composition or the cured coating obtained therefrom. Preferably, the additional additives include pigments, fillers, thickeners, anti-settling agents, dispersants, wetting agents, film-forming aids, coupling agents, fungicides, anti-mold agents or any combination thereof.

[0065] In some embodiments according to the present invention, the total amount of the additional additives is in the range of about 0 wt% to about 10 wt% relative to the total weight of the coating composition, preferably in the range of about 0.1 wt% to about 8 wt%.

[0066] In a specific embodiment according to the present application, the solvent-based coating composition comprises, relative to the total weight of the solvent-based coating composition,

[0067] i) 15-40% by weight of at least one first hydroxy-functionalized acrylic resin;

[0068] ii) 15-40% by weight of at least one second hydroxy-functionalized acrylic resin;

[0069] iii) 2-35% by weight of at least one amino resin;

[0070] iv) 3-15% by weight of at least one epoxy resin;

[0071] v) 0.1-5% by weight of at least one acidic catalyst; and

[0072] vi) 0-50 wt% of additional additives, the additional additives including at least one solvent, at least one pigment, at least one filler, at least one thickener, at least one dispersant, at least one wetting agent, at least one film-forming aid, at least one coupling agent, at least one bactericide, at least one mildew-proof agent or any combination thereof.

[0073] The preparation of the solvent-based coating composition of the present application can be achieved by any suitable mixing method well-known to those of ordinary skill in the art. For example, the coating composition can be made as follows: adding the hydroxy-functionalized resin, amino resin, acidic catalyst, solvent, and other additional additives (if any) to a container, and then stirring the resulting mixture evenly to form a solvent-based coating composition.

[0074] The inventors of the present invention have found that the Ford Cup No. 4 viscosity of the solvent-based coating composition according to the present invention is in the range of 20-30 seconds at 25 °C, and thus it is sprayable, which is particularly excellent for applications in food or beverage cans. Since the solvent-based coating composition according to the present invention is easy to apply, the coating formed by the solvent-based coating composition according to the present invention can be used as a side seam coating for three-piece food or beverage cans, including an internal side seam coating and an external side seam coating; and / or the coating formed by the solvent-based coating composition according to the present invention can be used as a dome coating for two-piece food or beverage cans, including a dome repair coating.

[0075] The inventors of the present invention have found that the solid content of the solvent-based coating composition according to the present invention is in the range of 32-36% by weight, preferably in the range of 33-36% by weight, which is higher than the existing coating compositions commonly used in the field of coating packaging products such as food or beverage cans. Therefore, it can fully cover the substrate, thereby avoiding the risk of individual exposed points of the substrate, substrate corrosion, and can leakage caused by insufficient coating coverage of the substrate.

[0076] The inventors of the present invention have also found that the solvent-based coating composition according to the present invention has particularly excellent curing performance. In some embodiments according to the present invention, the solvent-based coating composition can achieve curing within 1 to 5 seconds at a metal peak temperature of 210 - 232 °C, preferably within 1 to 3 seconds at a metal peak temperature of 210 - 232 °C, more preferably within 1 to 3 seconds at a metal peak temperature of 210 °C, which was difficult to achieve prior to this application. Therefore, the solvent coating composition according to the present invention is particularly suitable for high-speed production lines of packaging products, especially food or beverage cans, which is conducive to improving industrial production efficiency.

[0077] In addition, the solvent-based coating composition according to the present invention has particularly excellent high-temperature storage stability. For example, in some embodiments according to the present invention, after the solvent-based coating composition according to the present invention is stored at room temperature or at a temperature of 45 °C for 6 weeks, preferably after being stored at room temperature and at a temperature of 45 °C for 6 weeks, the coating formed therefrom has no obvious attenuation in performance compared with the coating formed from the newly prepared solvent-based coating composition. Thus, it can be seen that the solvent-based coating composition according to the present invention not only has excellent curing performance, but also maintains excellent high-temperature storage stability, which is particularly surprising because for those skilled in the art, it is usually a difficult problem to ensure the thermal storage stability of the product while increasing the curing speed.

[0078] In some specific embodiments according to the present invention, the coating formed after the solvent-based coating composition according to the present invention is cured at a metal peak temperature of 210 °C for 1 - 3 seconds has one or more, preferably all, of the following properties:

[0079] The pencil hardness is B or above, preferably F or above;

[0080] After being steamed at a temperature of 125 °C for 45 minutes, it is basically non-whitening, preferably non-whitening;

[0081] The bend resistance according to ASTM D3281 is 20% or above.

[0082] In some specific embodiments according to the present invention, after the solvent-based coating composition according to the present invention is stored at room temperature or at a temperature of 45 °C for 6 weeks, preferably after being stored at room temperature and at a temperature of 45 °C for 6 weeks, the coating formed therefrom has no obvious attenuation in performance compared with the coating formed from the newly prepared solvent-based coating composition.

[0083] Therefore, on the other hand, the present invention relates to a packaging product, comprising a substrate and a coating, wherein the substrate is selected from wood, wood composites, paper, metal, plastic, fabric, ceramics or any combination thereof, and wherein the coating is formed by curing the above-mentioned solvent-based coating composition.

[0084] Yet another aspect of the present invention relates to a food or beverage can, which comprises a metal substrate and a coating, wherein the coating is formed by curing the above solvent-based coating composition. In some embodiments of the present invention, when the food or beverage can is a three-piece food or beverage can, the coating is the side seam coating of the food or beverage can, including an inner side seam coating and an outer side seam coating. In some other embodiments of the present invention, when the food or beverage can is a two-piece food or beverage can, the coating is the dome coating of the food or beverage can, including a dome repair coating.

[0085] Examples

[0086] The present invention is illustrated by the following examples. It should be understood that the specific examples, materials, amounts and procedures are to be broadly interpreted in accordance with the scope and spirit of the present invention as set forth herein. Unless otherwise stated, all parts and percentages are by weight and all molecular weights are weight average molecular weights. Unless otherwise stated, all chemicals used are commercially available from, for example, Sigma-Aldrich, St. Louis, Missouri.

[0087] Test methods

[0088] Viscosity : According to ISO 2431, the DIN viscosity cup method was used to determine the viscosity of the composition. Using a fully filled BYK-Gardner Din viscosity cup #4, the viscosity was measured at 25 °C and reported in seconds (s).

[0089] Pencil hardness : ASTM D3363 was used to evaluate the pencil hardness. The data was reported as the pencil hardness at which the last successful test was performed before the coating cracked. Thus, for example, if the coating did not crack when tested with a 2H pencil but cracked when tested with a 3H pencil, the coating was reported to have a pencil hardness of 2H.

[0090] Sterilization resistance : The coating system to be tested was placed in a 2% citric acid solution and autoclaved at 125 °C for 45 minutes, and the degree of whitening before and after autoclaving was determined. The anti-whitening property indicates the ability of the coating to resist attacks by various solutions. Generally, the whitening is measured by the amount of water absorbed into the coated film. When the film absorbs water, it usually becomes opaque or appears whitened. The whitening is usually determined visually and includes four grades: no obvious whitening, slight whitening, more obvious whitening, and obvious whitening.

[0091] Flexural endurance : The bend resistance of the coating was evaluated according to ASTM D3281.

[0092] Storage stability:The wet sample of the solvent-based coating composition according to the present invention is stored at specific temperatures (e.g., room temperature and 45 °C) for 6 months, and then the coating formed from the stored sample is subjected to the above pencil hardness, steam resistance, and bend resistance tests to determine its storage stability.

[0093] Material

[0094] The first hydroxy-functionalized acrylate, self-made, product number SWA-0025, glass transition temperature 40 °C, hydroxyl value 55 - 65 mg KOH / g, acid value 10 mg KOH / g;

[0095] The second hydroxy-functionalized acrylate, self-made, product number SWA-0027, glass transition temperature 15 °C, hydroxyl value 55 - 65 mg KOH / g, acid value 10 mg KOH / g;

[0096] Amino resin 1: methylated melamine-aldehyde resin, Cymel 303LF purchased from Allnex;

[0097] Amino resin 2: butylated aryl-substituted melamine-aldehyde resin, Cymel 5010 purchased from Allnex;

[0098] Amino resin 3: isobutylated urea-formaldehyde resin, Cymel U662 purchased from Allnex;

[0099] Acidic catalyst: dodecylbenzenesulfonic acid (DDBSA), commercially available from Allnex;

[0100] Epoxy resin: E44, commercially available from Nanya;

[0101] High Tg polyester resin: ES660 commercially available from Skybon, Tg 71 °C;

[0102] Low Tg polyester resin: ES720 commercially available from Skybon, Tg 71 °C;

[0103] Control solvent-based coating composition, 3310-802 / A from PPG Industries.

[0104] Coating composition and coating properties

[0105] Add the first hydroxy-functionalized acrylate, the second hydroxy-functionalized acrylate, amino resin 1, amino resin 2, amino resin 3, epoxy resin, acidic catalyst, organic solvents (such as n-butanol and / or solvent naphtha No. 100), and other additives in the amounts shown in Table 1 below into a mixing container and mix them, and then stir at 800 - 1000 rpm until uniform, thereby obtaining a solvent-based coating composition with a solid content in the range of 34% ± 2% and an initial viscosity (Ford 4#) at 25 °C in the range of 25 ± 2 seconds.

[0106] Table 1: Composition of the solvent-based coating composition

[0107]

[0108] Note: The content of the first hydroxy acrylate resin in Comparative Example 1 is relatively low, and the amino resin is a combination of three amino resins; Comparative Example 2 is a coating composition using only urea-formaldehyde resin as the amino resin; Comparative Examples 3 and 4 are coating compositions prepared by combining a combination of a hydroxy polyester with a high Tg and a hydroxy polyester with a low Tg with urea-formaldehyde resin or melamine aldehyde resin, respectively.

[0109] As can be seen from the results in Table 1, in the presence of an acidic catalyst, a solvent-based coating composition obtained by combining a hydroxy-functionalized acrylate resin with a high Tg and a hydroxy-functionalized acrylate resin with a low Tg and matching with an amino resin as a crosslinking agent can achieve curing within 2 seconds at a metal peak temperature of 210 °C. Moreover, the cured coating thus formed can also have good retort resistance, and basically does not turn white after retorting at 125 °C for 45 minutes, and thus can be applicable to the coating of high-speed production lines for packaging products and can meet the high-temperature sterilization requirements of the food metal packaging industry.

[0110] In addition, in order to verify the storage thermal stability of the coating composition of the present invention, the coating composition of Example 1 according to the present invention and the coating composition of the benchmark product 3310 - 802 / A of PPG Company were stored at room temperature and at a temperature of 45 °C for 6 months respectively, and then the obtained coating compositions were formed into films, and the above pencil hardness, retort resistance and bend resistance tests were carried out on the formed coatings to determine their storage stability. The test results are summarized in Table 2 below.

[0111]

[0112] After the solvent-based coating composition according to the present invention is stored at room temperature and at a temperature of 45 °C for 6 weeks, the coatings formed therefrom, compared with the coatings formed from the newly prepared solvent-based coating composition, have no obvious attenuation in performance (including pencil hardness, retort resistance and bend resistance), and have extremely high high-temperature storage stability.

[0113] Although the present invention has been described with reference to numerous embodiments and examples, those of ordinary skill in the art will recognize, based on the disclosure of the present invention, that other embodiments can be designed without departing from the scope and spirit of the present invention.

Claims

1. A solvent-based coating composition, the solvent-based coating composition comprising: i) at least one first hydroxy-functionalized acrylic resin (also known as a high Tg hydroxy-functionalized acrylic resin); ii) at least one second hydroxy-functionalized acrylic resin (also known as a low Tg hydroxy-functionalized acrylic resin); iii) at least one amino resin; iv) at least one acidic catalyst; and v) additional additives, wherein, the first hydroxy-functionalized acrylic resin has a glass transition temperature of not less than 35 °C, and the second hydroxy-functionalized acrylic resin has a glass transition temperature of not more than 20 °C.

2. The solvent-based coating composition according to claim 1, wherein, the glass transition temperature of the first hydroxy-functionalized acrylic resin is above 40 °C, preferably in the range of 40 - 60 °C; and the glass transition temperature of the second hydroxy-functionalized acrylic resin is in the range of 10 - 18 °C.

3. The solvent-based coating composition according to claim 1, wherein, the number average molecular weights of both the first hydroxy-functionalized acrylic resin and the second hydroxy-functionalized acrylic resin are higher than 7000 g / mol, and the number average molecular weight is determined by GPC.

4. The solvent-based coating composition according to claim 1, wherein, the first hydroxy-functionalized acrylic resin and the second hydroxy-functionalized acrylic resin each independently have a number average molecular weight in the range of 7000 - 12000 g / mol, and the number average molecular weight is determined by GPC.

5. The solvent-based coating composition according to any one of claims 1 to 4, wherein, the first hydroxy-functionalized acrylic resin and the second hydroxy-functionalized acrylic resin each independently have a hydroxyl value in the range of 50 - 80 mg KOH / g resin.

6. The solvent-based coating composition according to any one of claims 1 to 4, wherein, the first hydroxy-functionalized acrylic resin is present in an amount of at least 15% by weight relative to the total weight of the solvent-based coating composition, and preferably, both the first hydroxy-functionalized acrylic resin and the second hydroxy-functionalized acrylic resin are present in amounts in the range of 15 - 40% by weight relative to the total weight of the solvent-based coating composition.

7. The solvent-based coating composition according to any one of claims 1 to 4, wherein, the mass ratio of the first hydroxy-functionalized acrylic resin to the second hydroxy-functionalized acrylic resin is in the range of 0.8 to 3.5:1, preferably in the range of 0.8 to 1.5:1, more preferably in the range of 1.0 to 1.3:

1.

8. The solvent-based coating composition according to any one of claims 1 to 4, wherein, the amino resin includes one or more selected from partially etherified amino resins.

9. The solvent-based coating composition according to claim 8, wherein, The partially etherified amino resin includes one or more selected from butanol-etherified urea-formaldehyde resin, methanol-etherified melamine-aldehyde resin, and butanol-etherified phenylated melamine-aldehyde resin. Preferably, it includes a combination of butanol-etherified urea-formaldehyde resin and butanol-etherified phenylated melamine-aldehyde resin. More preferably, it includes a combination of butanol-etherified urea-formaldehyde resin, methanol-etherified melamine-aldehyde resin, and butanol-etherified phenylated melamine-aldehyde resin.

10. The solvent-based coating composition according to claim 1, wherein, the amino resin is present in a total amount of 2 to 35% by weight based on the total weight of the solvent-based coating composition.

11. The solvent-based coating composition according to claim 10, wherein, the amino resin comprises, based on the total weight of the coating composition, 0 to 20% by weight of methanol-etherified melamine-aldehyde resin, preferably 3 to 20% by weight of methanol-etherified melamine-aldehyde resin; 0 to 10% by weight of butanol-etherified aryl-substituted melamine-aldehyde resin, preferably 1 to 5% by weight of butanol-etherified aryl-substituted melamine-aldehyde resin; and 0.1 to 10% by weight of butanol-etherified urea-formaldehyde resin, preferably 1 to 5% by weight of butanol-etherified urea-formaldehyde resin.

12. The solvent-based coating composition according to any one of claims 1 to 11, wherein, the solvent-based coating composition further comprises at least one epoxy resin.

13. The solvent-based coating composition according to claim 12, wherein, the epoxy resin comprises at least one bisphenol A type epoxy resin.

14. The solvent-based coating composition according to claim 12, wherein, the number average molecular weight of the epoxy resin is in the range of 300 - 500 g / mol, and / or the epoxy equivalent of the epoxy resin is in the range of 200 - 250.

15. The solvent-based coating composition according to any one of claims 1 to 4, wherein the at least one acidic catalyst is selected from the group consisting of p-toluenesulfonic acid, benzenesulfonic acid, methanesulfonic acid, dinonylnaphthalenesulfonic acid, dinonylnaphthalenedisulfonic acid, dodecylbenzenesulfonic acid, oxalic acid, maleic acid, phthalic acid, acrylic acid, mono(di)alkyl phosphate, phosphoric acid, mon(di)alkyl pyrophosphate, or a combination thereof.

16. The solvent-based coating composition according to any one of claims 1 to 12, wherein, the solvent-based coating composition comprises, based on the total weight of the solvent-based coating composition, i) 15 - 40% by weight of at least one first hydroxy-functionalized acrylic resin; ii) 15 - 40% by weight of at least one second hydroxy-functionalized acrylic resin; iii) 2 - 35% by weight of at least one amino resin; iv) 3 - 15% by weight of at least one epoxy resin; v) 0.1 - 5% by weight of at least one acidic catalyst; and vi) 0 - 50% by weight of additional additives, said additional additives comprising at least one pigment, at least one solvent, at least one filler, at least one anti - settling agent, at least one thickener, at least one dispersant, at least one wetting agent, at least one film - forming aid, at least one coupling agent, at least one bactericide, at least one mildew - proof agent or any combination thereof.

17. The solvent - based coating composition according to any one of claims 1 to 16, wherein, the viscosity of the coating composition in a No. 4 Ford cup at 25 °C is in the range of 20 - 30 seconds.

18. The solvent - based coating composition according to any one of claims 1 to 16, wherein, the solid content of the coating composition is in the range of 32 - 36% by weight.

19. The solvent - based coating composition according to any one of claims 1 to 16, wherein, the solvent - based coating composition can be cured within 1 - 5 seconds at a metal peak temperature of 210 - 232 °C, preferably within 1 - 3 seconds at a metal peak temperature of 210 - 232 °C, more preferably within 1 - 3 seconds at a metal peak temperature of 210 °C.

20. The solvent - based coating composition according to any one of claims 1 to 16, wherein, the coating formed after curing the solvent - based coating composition for 1 - 3 seconds at a metal peak temperature of 210 °C has one or more, preferably all, of the following properties: pencil hardness of B or above, preferably F or above; basically no whitening after steaming at 125 °C for 45 minutes, preferably no whitening; flexural resistance according to ASTM D3281 of 20% or above.

21. The solvent - based coating composition according to any one of claims 1 to 16, wherein, after storing the solvent - based coating composition at room temperature or at 45 °C for 6 weeks, preferably after storing at room temperature and at 45 °C for 6 weeks, the performance of the coating formed therefrom shows no obvious attenuation compared with the coating formed from the newly prepared solvent - based coating composition.

22. A packaging product comprising a substrate and a coating, wherein, the substrate is selected from wood, wood composites, paper, metal, plastic, fabric, ceramics or any combination thereof, and wherein the coating is formed by curing the solvent - based coating composition according to any one of claims 1 to 21.

23. A food or beverage can comprising a metal substrate and a coating, wherein, the coating is formed by curing the solvent - based coating composition according to any one of claims 1 to 21.

24. The food or beverage can according to claim 23, wherein, when the food or beverage can is a three - piece food or beverage can, the coating is the side - seam coating of the food or beverage can, including an internal side - seam coating and an external side - seam coating.

25. The food or beverage can according to claim 23, wherein, when the food or beverage can is a two - piece food or beverage can, the coating is the dome coating of the food or beverage can, including a dome repair coating.

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