Beverage can body and manufacturing method therefor, and beverage can and manufacturing method therefor

Abstract

A beverage can body (1), comprising a main body portion (10), with a coating provided on the inner surface of a peripheral wall (101) of the main body portion, wherein the coating is provided with recesses, and is formed by means of spray-coating a slurry on the inner surface of the peripheral wall. The coating comprises a first region, a second region and a third region, which are sequentially arranged in a first direction and are each provided with recesses having a distribution density of 160-4900 / mm2, wherein the distribution density of the second region is 28-1300 / mm2 greater than the distribution density of the first region, and the distribution density of the first region is 25-640 / mm2 greater than the distribution density of the third region. The composition of the slurry includes 20%-30% epoxy resin, 1%-3% phenol formaldehyde resin, 55%-65% deionized water, and 0.1%-0.2% defoamer. The recesses of the coating are structurally stable. When the sealed can body filled with a carbonated beverage is opened, foam spontaneously overflows out of the can body at a relatively high speed with enhanced persistence, thereby improving both the visual effect and mouthfeel of the foam and also fully improving the consumer experience. Further disclosed are a method for manufacturing a beverage can body, a beverage can, and a method for manufacturing a beverage can.

Description

Beverage can and its manufacturing method Technical Field

[0001] This invention relates to the field of food packaging, and particularly to beverage cans and their manufacturing methods. Background Technology

[0002] Currently, the market offers a wide variety of canned beverages, including carbonated drinks and beer, often packaged in metals such as aluminum alloy. The traditional function of metal packaging is to isolate the contents from the external environment, facilitating transportation and preventing spoilage by blocking oxygen and microorganisms. The inner surface of beverage cans typically has a coating, the basic function of which is to protect the metal substrate, forming a complete protective layer that completely isolates the contents from the metal substrate, preventing corrosion, leaks, and other problems. While metal packaging provides excellent sealing for the contents, the growing consumer demand for novelty has led to increasing calls for functional innovations in traditional packaging.

[0003] Traditional metal packaging often contains liquids that contain a certain amount of gas, which is essential for consumers to have a good tasting experience and a direct sensory experience. To enhance the consumer experience, a new type of metal packaging, when containing gaseous liquids, allows the gas to escape spontaneously from the packaging after sufficient settling, manifesting as visible foam, providing a visually appealing experience. This visual experience is primarily due to a special coating structure within the packaging.

[0004] However, this type of packaging has poor control over the gas overflow process. For example, there is a long waiting time for foam to form and overflow after the packaging is opened, and the foam overflow is not persistent. Furthermore, the unpleasant taste of the foam when consumed also reduces the consumer experience. These issues require further improvement. To address these problems, the coating structure can be designed. However, even with a designed coating structure, reliable implementation requires careful consideration. Additionally, ensuring the stability of the coating structure, and thus guaranteeing that the product fully exhibits its effects to consumers, is also a crucial consideration. Summary of the Invention

[0005] To address the aforementioned technical problems, embodiments of the present invention disclose a beverage can, the beverage can comprising:

[0006] The main body, used to contain beverages, includes a peripheral wall. The inner surface of the peripheral wall has a coating with recessed portions. The coating is formed by spraying a slurry onto the inner surface of the peripheral wall. The coating includes a first region, a second region, and a third region arranged sequentially along a first direction. The first region, the second region, and the third region each have a distribution density of 160–4900 particles / mm². 2 In the recessed areas, the distribution density in the second region is 28–1300 more per mm than that in the first region. 2 The distribution density in the first region is 25–640 more per mm than that in the third region. 2 The surface areas of the first, second, and third zones are 4550–18500 mm², respectively. 2 ;

[0007] The slurry, by mass percentage, comprises 20%–30% epoxy resin, 1%–3% phenolic resin, 55%–65% deionized water, and 0.1%–0.2% defoamer, with the epoxy equivalent of the epoxy resin being 3800–6000 g / mol.

[0008] The first direction is the direction from the top of the main body to its bottom.

[0009] By adopting the above technical solution, a coating with a special structural design can be obtained, and the coating structure has high stability, especially the structure of the recessed part is relatively stable. When the beverage can contains a carbonated beverage, when the sealed beverage can is opened, foam will spontaneously overflow from the can, and the overflow speed is fast and the persistence is enhanced. The appearance and taste of the foam are improved, which greatly enhances the consumer's user experience.

[0010] Optionally, the epoxy resin is an epoxy acrylate resin, and the epoxy equivalent of the epoxy acrylate resin is 5000-6000 g / mol.

[0011] Optionally, the slurry may further include 2% to 5% dimethylethanolamine, 3% to 6% ethylene glycol butyl ether, 0.5% to 3% n-butanol, and 0.3% to 0.4% carnauba wax.

[0012] Optionally, the ratio of the mass of the defoamer to the sum of the masses of the epoxy resin and the phenolic resin is less than 1:100.

[0013] Optionally, the slurry comprises, by weight percentage, 23% epoxy resin, 2% phenolic resin, 4% dimethyl ethanolamine, 6% ethylene glycol butyl ether, 2% n-butanol, 62.5% deionized water, 0.32% carnauba wax, and 0.18% defoamer.

[0014] Optionally, the defoamer is an acrylic defoamer or a polyester defoamer.

[0015] Optionally, the first, second, and third regions are evenly distributed along the first direction, and the distribution density of the depressions in the second region is 282–2004 per mm. 2 The distribution density of the depressions in the first region is 227–1272 per mm. 2 The distribution density of the recesses in the third region is 169–1031 per mm. 2 The diameter of the recess is 0.1 to 5.0 μm, and the diameter-to-depth ratio of the recess is 2.0 to 20.0, wherein the diameter-to-depth ratio is the ratio of the diameter of the recess to the depth of the recess.

[0016] Optionally, the diameter-to-depth ratio of the recess in the first region is 4.0 to 8.0, the diameter-to-depth ratio of the recess in the second region is 2.5 to 6.0, and the diameter-to-depth ratio of the recess in the third region is 3.0 to 5.5.

[0017] Optionally, the film thickness of the first region is 3.0–4.5 μm, the film thickness of the second region is 3.5–5.0 μm, and the film thickness of the third region is 2.8–4.0 μm.

[0018] Optionally, the film thickness of the first region is 3.2–3.8 μm, the film thickness of the second region is 3.8–4.5 μm, and the film thickness of the third region is 2.8–3.2 μm, and the film thickness of the second region is greater than or equal to the film thickness of the first region and greater than or equal to the film thickness of the third region.

[0019] According to another specific embodiment of the present invention, a method for manufacturing a beverage can is disclosed, comprising the following steps:

[0020] Slurry spraying: Using a spray gun, slurry is sprayed onto the inner surface of the peripheral wall of the main body at a preset angle of 7 to 20°, wherein the preset angle is the angle between the center line of the spray gun and the normal to the surface of the beverage can.

[0021] Drying to form a coating: The sprayed slurry is dried to form a coating.

[0022] This method allows for the creation of beverage cans with different compartments.

[0023] Optionally, the preset angle is 12 to 20°, and the drying temperature of the slurry is 80 to 100°.

[0024] Optionally, the spray pressure of the spray gun is 480 to 550 psi.

[0025] Optionally, in the drying process of forming the coating, the drying process includes a pre-drying and a subsequent drying, wherein the drying temperature of the pre-drying is 80-100°C and the drying time of the pre-drying is 1-3 min, and the drying temperature of the subsequent drying is 150°C-280°C.

[0026] According to another specific embodiment of the present invention, an embodiment of the present invention discloses a beverage can, including the aforementioned can body and a top cover, the top cover being sealed to the beverage can body, the beverage can being used to contain beverages and to fill carbon dioxide.

[0027] By adopting the above technical solution, beverage cans with a foam effect can be obtained, enriching the consumer's visual experience.

[0028] Optionally, the top cover includes an opening portion, which, when opened, causes foam to overflow from the beverage can within 6 to 15 seconds.

[0029] According to another specific embodiment of the present invention, a method for manufacturing a beverage can is disclosed, comprising the following steps:

[0030] Carbon dioxide is introduced into the liquid storage container containing the beverage;

[0031] Carbon dioxide is introduced into the beverage can to make the gas pressure inside the beverage can equal the gas pressure inside the liquid storage container;

[0032] The beverage is filled into the beverage can using its own weight.

[0033] The top cover is sealed to the beverage can body to obtain the beverage can, and the gas pressure inside the beverage can is 0.18 to 0.40 MPa. Attached Figure Description

[0034] Figure 1 shows a schematic diagram of the beverage can body structure according to an embodiment of the present invention;

[0035] Figure 2 shows a 10000X magnified scanning electron microscope image of the coating surface according to an embodiment of the present invention;

[0036] Figure 3 shows a 500X magnified scanning electron microscope image of the coating surface according to an embodiment of the present invention;

[0037] Figure 4 shows another scanning electron microscope image of the coating surface magnified 500X according to an embodiment of the present invention. Detailed Implementation

[0038] The following specific embodiments illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. Although the description of the present invention is presented in conjunction with preferred embodiments, this does not mean that the features of the invention are limited to these embodiments. On the contrary, the purpose of describing the invention in conjunction with embodiments is to cover other options or modifications that may be derived based on the claims of the present invention. To provide a deep understanding of the invention, many specific details will be included in the following description. The invention may also be implemented without using these details. Furthermore, to avoid confusion or obscuring the focus of the invention, some specific details will be omitted in the description. It should be noted that, unless otherwise specified, the embodiments and features in the embodiments of the present invention can be combined with each other.

[0039] It should be noted that in this specification, similar reference numerals and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0040] The terms “first”, “second”, etc., are used only to distinguish descriptions and should not be interpreted as indicating or implying relative importance.

[0041] In the description of this embodiment, it should also be noted that, unless otherwise explicitly specified and limited, the terms "set up," "connected," and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this embodiment based on the specific circumstances.

[0042] To make the objectives, technical solutions, and advantages of the present invention clearer, the embodiments of the present invention will be described in further detail below with reference to the accompanying drawings.

[0043] In the embodiments of this application, "beverage" refers to drinkable liquids, including but not limited to water (such as mineral water, soda water, sparkling water, etc.), tea, coffee, juice, milk, yogurt, carbonated beverages (such as cola, etc.), and alcoholic beverages (such as beer, cocktails, sparkling wine, wine, etc.).

[0044] In embodiments of this application, "recessed portion" refers to a pit on the coating that is recessed relative to a flat surface but does not penetrate the coating.

[0045] In the embodiments of this application, "film thickness" refers to the thickness of the solid coating formed on the inner surface of the tank wall after the slurry has been completely dried and cured. Due to the characteristics of industrial production, the coating on the inner wall of the tank is not absolutely uniformly distributed. In the art, when testing film thickness, according to conventional practice, 3 to 4 points are taken at the same height on the circumference inside the tank, and the film thickness at each point is measured using a scanning electron microscope. The film thickness is usually expressed as a range value; alternatively, the film thickness can also be expressed as an average value, that is, the average value of the film thickness at 3 to 4 measurement points is taken. In the embodiments of this application, the film thickness is expressed as a range value.

[0046] In the embodiments of this application, "can" refers to metal packaging products made of thin metal sheets, including various forms of thin-walled packaging containers made for different uses. Metal packaging products typically consist of a metal can body and a lid. The metal can body includes various forms such as thinned and stretched two-piece cans, three-piece cans, and stamped two-piece cans. Typical lid forms include SOT pull-tab lids, RPT pull-tab lids, and full-opening lids. In this invention, "can" refers to all forms of the aforementioned metal can body and lid, including but not limited to the can body and lid types listed above.

[0047] As shown in Figure 1, a first aspect of the present invention discloses a beverage can 1, which includes a main body 10 for containing a beverage. The main body 10 has a peripheral wall 101, the inner surface of which has a coating (not shown in the figure). The beverage can 1 can be open-topped, and the main body 10 has a top end and a bottom end, the top end being opposite to the bottom end. The bottom end can be a bottom 20 integrally formed with the main body 10, for example, integrally stamped from an aluminum alloy sheet to form a can with an opening. The beverage can can be cylindrical or cuboid, and its shape is not particularly limited. Furthermore, the beverage can can be used with various can lids, such as fully open can lids or half open can lids. For example, the can lid can be one of 202SOT, 202RPT, 206SOT, 206RPT, a large-opening easy-open lid, or a fully open lid, or a lid type with a sealing function not listed above. The can lid can have an opening area of ​​220–400 mm². 2 A can lid with an opening area that accounts for 10% to 29% of the total lid area, or an opening area greater than 1300 mm². 2 For can lids whose opening area accounts for more than 50% of the total lid area, there are no special restrictions.

[0048] The coating of beverage cans has a special structure with recesses that can store gases, such as carbon dioxide. When the can is sealed and contains both beverage and gas, opening the sealed can release foam. However, existing products of this type still have significant room for improvement in terms of the speed, duration, and amount of foam release. The inventors have discovered that by designing the structure of the recesses, these problems can be improved.

[0049] In embodiments of the present invention, the coating is designed to include a first region, a second region, and a third region arranged sequentially along a first direction. The first direction is, for example, direction A shown in FIG1, which is the direction from the top end of the main body 10 to its bottom end (e.g., the bottom 20). Specifically, based on the length of the main body 10 extending in the first direction, the three regions can be equally divided into three parts, that is, each region occupies the same length in the first direction, and the three regions have the same shape; or, the second region extends the longest in the first direction, for example, occupying half of the main body 10, while the first and third regions are the same size.

[0050] Furthermore, the first, second, and third zones have distribution densities ranging from 160 to 4900 individuals / mm². 2 The recessed portion. Preferably, the first, second, and third regions each have a distribution density of 160–2004 particles / mm². 2 The recessed area. Furthermore, the distribution density in the second region is 28–1300 more particles / mm² than that in the first region. 2 The distribution density in the first region is 25–640 more per mm than that in the third region. 2 Furthermore, the distribution density in the second region is 100 to 1500 greater than that in the third region. That is, the distribution of depressions is not uniform across regions one through three; the second region has the highest density, followed by the first region, and the third region has the lowest. Moreover, the surface areas of regions one through three are 4550 to 18500 mm², respectively. 2 .

[0051] Distribution density reflects the sparseness of the distribution of depressions. In a specific embodiment of the present invention, multiple unit regions are selected in the first to third regions, the number of depressions in each unit region is measured, and the result is divided by the area of ​​each unit region to obtain the distribution density of depressions in each unit region. The distribution density of each region is finally represented by a range value, or the average value can be used to represent the distribution density of each region. In the embodiment of the present invention, a range value is chosen to represent the distribution density. Specifically, 4 to 6 unit regions are evenly distributed along the circumference at the same height position in the middle of each region. Each unit region is a square with a side length of 1 to 2 cm. Microscopic images of the unit regions are obtained using a scanning electron microscope (ZEISS GeminiSEM 300, Germany), and the number of depressions in each unit region is measured using image processing software. The distribution density of depressions in each unit region is then calculated based on the number of depressions and the area of ​​the unit region, and the distribution density range of each region is finally obtained. Furthermore, the difference in distribution density between different regions is calculated using an average value. For example, when it is necessary to calculate the difference in distribution density between the first region and the second region, the average distribution density of a unit region is first calculated based on the distribution density of each unit region in the first region and the number of unit regions (sum of distribution densities of unit regions / number of unit regions). Similarly, the average distribution density of a unit region is calculated based on the distribution density of each unit region in the second region and the number of unit regions. The difference between the average distribution densities of unit regions represents the difference in distribution density between the first region and the second region. When the average distribution density of a unit region in the second region is greater than that in the first region, it means that the depressions in the second region are more densely distributed than those in the first region. In a specific embodiment of the present invention, more specifically, the diameter of the bottom is 5.5 to 8.2 cm, the total length of the peripheral wall of the main body in the first direction is 15 cm, the shortest distance between the second region and the bottom is 5 cm, and the shortest distance between the first region and the bottom is 10 cm; or, the total length of the peripheral wall of the main body in the first direction is 20 cm, the shortest distance between the second region and the bottom is 6.8 cm, and the shortest distance between the first region and the bottom is 13.6 cm.

[0052] In typical cans and containers, the coating is generally flat relative to the main body; that is, if the main body is cylindrical, the coating on its inner surface is also a flat cylindrical shape. In an embodiment of the present invention, the coating includes a first region, a second region, and a third region arranged sequentially along a first direction. These three regions are respectively provided with a distribution density of 160–4900 particles / mm². 2The recessed portions 102 are distributed on the coating surface as shown in Figures 2-4, forming a series of pits. While the recessed portions 102 are recessed towards the inner surface of the main body, they do not penetrate the coating. Due to the presence of these recessed portions 102, when the beverage can 1 is sealed to contain a carbonated beverage, such as beer filled with carbon dioxide, if the seal of the beverage can 1 is removed, allowing the beverage inside to come into contact with the outside, foam will spontaneously overflow from the can. For example, when the can and lid are fitted together, using the lid to seal the inside of the can, and the can contains carbonated beer, due to the presence of the recessed portions, when the consumer opens the lid, the beer foam will automatically overflow without any further action from the consumer, providing a good visual experience. With the full effect of visual and gustatory stimulation, the product experience is enhanced.

[0053] Specifically, as mentioned above, among the first to third zones, the recessed portion of the second zone has the highest density, followed by the first zone, and the third zone has the lowest, with a certain density gradient among the three zones. Furthermore, each of the first to third zones has a certain surface area. The inventors discovered that this arrangement enhances the foam overflow effect. Specifically, firstly, since the first zone is closest to the top of the can, the gas in the first zone will overflow first. Therefore, ensuring the density of the recessed portion of the first zone guarantees that foam will overflow from the beverage can in the first instance. However, if the density of the first zone is too high, it may lead to excessive foam overflow, affecting the consumer experience. Therefore, the inventors devised a higher density in the second zone, setting the density difference between the second and first zones to 28–1300 foam particles / mm². 2This design ensures that the gas volume in the first zone provides a rapid foam overflow rate, while the larger gas volume in the second zone quickly follows up, preventing the foam overflow process from stopping abruptly. In other words, the first zone guarantees "speed," while the second zone guarantees "persistence." Even when the gas in the first zone is nearly depleted, the gas in the second zone can still ensure sufficient foam overflow. Furthermore, the larger gas volume in the second zone can propel the gas in the first zone to escape fully, ensuring the recessed area functions effectively. With the distribution density gradient, this process can also be performed with greater precision. In addition, the recessed area in the third zone has the lowest distribution density and exhibits a distribution density gradient with both the first and second zones. This is because the inventors considered that the third zone is furthest from the top of the tank, resulting in the slowest gas escape rate. Therefore, its primary function is to "replenish" the overflowing foam. While the gas in the first zone rushes out rapidly and the second zone continues its flow, the gas in the third zone simultaneously moves towards the top, ensuring that the foam always overflows sufficiently and improving the uniformity of the foam overflow process. Furthermore, since there is a certain distance between the second zone and the top, some gas loss may occur as it moves upwards from the second zone, resulting in a less than ideal visual foam effect. The presence of the third zone allows the foam from both zones to overlap, ensuring a proper overflow effect. Moreover, the gradient density design ensures that the third zone can replenish the gas released from the second zone in a timely manner. However, it's crucial that the density of the third zone isn't too high. Otherwise, if only the third zone continues to release gas after the first and second zones have largely released theirs, it will negatively impact the consumer's visual and drinking experience. Therefore, the density gradient between the third zone and the other two zones must be controlled within a reasonable range. Simultaneously, by combining the density design with the surface area of ​​the first to third zones, the number of recesses within each zone is ensured, guaranteeing sufficient gas storage.

[0054] In the embodiments of this invention, the inventors utilize the structural features of the can itself and fully leverage the differences in the internal spatial distribution to design different coating zones. These zones function differently: the first zone maximizes the foam release speed, the second zone enhances the sustainability of foam release, and the third zone increases the amount of foam, ensuring rapid, sufficient, and continuous foam overflow. Furthermore, by combining the distribution density of each zone with the density gradient design between zones, the process can be precisely controlled, ensuring consistency in effects across products and the continuity and smoothness of foam generation throughout the entire process for each individual product. In particular, the can of this invention requires fewer recesses, reducing manufacturing complexity, as the combined functions of the first to third zones also achieve a good foam overflow effect.

[0055] In one specific embodiment of the present invention, the diameter of the recess is 0.1–5.0 μm, and the diameter-to-depth ratio is 2.0–20.0, wherein the diameter-to-depth ratio is the ratio of the diameter of the recess to its depth. Because the recess is quite small, instruments such as scanning electron microscopes and laser confocal microscopes are required during the research process. In an embodiment of the present invention, when measuring the diameter, imaging is required under a scanning electron microscope (ZEISS GeminiSEM 300, Germany), as shown in Figures 2-4. It can be seen that the shape of the recessed portion on the coating surface is approximately circular. Therefore, during the research process, multiple recessed portions are approximated as circular, and the diameter of the recessed portion can be measured. Since the size of the recessed portions varies, the measured diameter is a range, or an average value can be calculated. In this embodiment of the present invention, a range is used to represent the diameter. When measuring the depth, a laser confocal microscope (VK3000) can be used. The distance by which the recessed portion is recessed into the inner surface of the main body relative to the coating surface is the depth of the recessed portion. Further calculation can be performed to obtain the diameter-to-depth ratio of the recessed portion. Since the recessed portions are different, the measured depth is a range, or an average value can be calculated. In this embodiment of the present invention, a range is used to represent the depth, and the diameter-to-depth ratio is also expressed as a range.

[0056] Specifically, when measuring the diameter of the recesses in each zone, a circle is identified on the coating surface at the center or upper-middle position of each zone. This circle is perpendicular to the height direction of the tank, and the recesses fall on this circle. Six to ten points within the recesses falling on this circle are selected as the recesses to be measured, as shown in Figure 2. The surface of each recess is photographed using a scanning electron microscope (ZEISS GeminiSEM 300, Germany). The contour of the recess is extracted using image processing software and approximated as a circle. The diameter of each circle is measured to obtain the diameter range of the recesses in each zone. Further, the internal structure of the 6 to 10 recesses to be measured is obtained using a laser confocal microscope (VK3000). The depth is measured at three average positions along the circumference of each recess, and the average value is taken to obtain the depth of each recess. Then, combined with the diameter, the diameter-to-depth ratio of each recess is calculated to obtain the diameter-to-depth ratio range of the recesses in each zone.

[0057] The inventors discovered that the diameter-to-depth ratio of the recesses also affects their gas storage effectiveness. By setting the diameter-to-depth ratio within a suitable range, the recesses can effectively store a certain amount of gas, and the gas escape rate is appropriate. Combined with the aforementioned design of the distribution density and density gradient, this further ensures the speed and visual effect of foam overflow. Specifically, the diameter design range of the recesses is 0.1–5.0 μm, resulting in relatively uniform dimensions and minimal diameter differences between recesses, which improves the fineness of the foam. Combined with the diameter-to-depth ratio design, this ensures sufficient gas storage and enhances the foam overflow effect.

[0058] The inventors also discovered that, through the comprehensive design of distribution density, diameter, and diameter-to-depth ratio, it is possible to ensure that when the sealed can lid is opened, the foam will not gush out in large quantities instantly, causing a "blowout" phenomenon. On the contrary, this design can ensure that the foam overflow is always a uniform process with appropriate speed and quantity.

[0059] To achieve the aforementioned coating structure design, the inventors explored various methods. However, simultaneously obtaining a specific density of recessed portions, an aspect ratio, and a gradient design across the first to third zones proved challenging. For instance, while certain substances could be used to form the recesses, these substances tend to agglomerate and are prone to denaturation at high temperatures, resulting in highly uneven recess sizes. Some recesses were large, while others were small, exhibiting significant dispersion and uneven distribution. This made it difficult to achieve the desired structure, and it was impossible to realize the different designs across the first to third zones. Furthermore, the recesses were prone to collapse, leading to poor foam overflow. The inventors ultimately discovered that the composition of the slurry sprayed onto the inner surface of the main body's peripheral wall could be specially designed to obtain a coating with the aforementioned structure. Specifically, the slurry, by mass percentage, comprises 20%–30% epoxy resin, 1%–3% phenolic resin, 55%–65% deionized water, and 0.1%–0.2% defoamer.

[0060] First, epoxy resin constitutes the main structure of the coating. It possesses excellent adhesive properties, firmly adhering to the surface of aluminum or other metal substrates, ensuring good adhesion between the coating and the can. The epoxy resin coating has a certain degree of hardness and flexibility, able to withstand the mechanical stress that may occur during transportation and stacking, preventing the coating from cracking or peeling off. Epoxy resin also has good chemical stability, ensuring the stability of the coating and the beverage inside the can. In the embodiments of this invention, since it is necessary to form recesses in the coating, and these recesses also need to have specific structural features, the coating preparation process of this invention involves additional reactions compared to ordinary coating preparation processes. This places higher demands on the epoxy resin forming the main structure; it needs to maintain its original performance advantages while also acting as a stable load for the recesses to ensure their functional characteristics. Specifically, the embodiments of this invention use 20% to 30% epoxy resin; within this range, the multiple functions of the epoxy resin can be guaranteed. More specifically, in the embodiments of this invention, the epoxy resin used is epoxy acrylic resin. Compared to other types of epoxy resins, epoxy acrylate resins have better water solubility and are more suitable as a matrix for creating depressions. Furthermore, the epoxy equivalent of the epoxy acrylate resin is 3800–6000 g / mol. Epoxy acrylate resins with a certain epoxy equivalent can ensure the realization of depression and gradient designs, thereby ensuring the overflow rate, continuity, and uniformity of the foam. Even further, the epoxy equivalent of the epoxy acrylate resin is 4000–6000 g / mol. Preferably, the epoxy equivalent of the epoxy acrylate resin is 5000–6000 g / mol. Within this range, the compatibility of the epoxy acrylate resin with water is within a suitable range, which will promote surface unevenness of the coating during subsequent curing, further promoting the formation of depressions.

[0061] Specifically, in the embodiments of this application, the epoxy equivalent is measured as follows:

[0062] Weigh a certain amount of epoxy resin (accurate to at least three decimal places) and place it in a sample conical flask; add 25 ml of methyl ethyl ketone (MEK) to the sample conical flask, and simultaneously add the same volume of MEK to the control blank flask; dissolve the resin on a magnetic stirrer (slight heating is acceptable), and add 50 ml of a cyclohexanone-glacial acetic acid mixed solvent to both the conical flask and the blank flask; add 2.0 ± 0.1 g of CTBA to each conical flask and the blank flask, then add 4 drops of crystal violet indicator to each, and titrate with a 0.1 M perchloric acid-glacial acetic acid solution. The titration endpoint is reached when the color changes from blue through blue-green to emerald green. The epoxy equivalent is calculated using the following formula: EEW = 1000 * M / (AB) * N (Formula 1).

[0063] Wherein, EEW is the epoxy equivalent of the epoxy resin to be tested, A is the number of milliliters of perchloric acid solution consumed by the sample, B is the number of milliliters of perchloric acid solution consumed by the blank sample, N is the equivalent concentration of the perchloric acid solution, and M is the weight of the epoxy resin.

[0064] Secondly, the slurry also contains 1%–3% phenolic resin. This 1%–3% phenolic resin can fully react with 20%–30% epoxy resin. The phenolic resin acts as a crosslinking agent, undergoing a crosslinking reaction with the epoxy acrylic resin under high-temperature baking to form a strong and dense coating. This coating covers the metal surface while simultaneously isolating the metal from the contents of the container. The 1%–3% phenolic resin and 20%–30% epoxy resin ensure sufficient crosslinking, forming a stable coating structure.

[0065] In addition, the 55%–65% deionized water in the slurry is mainly used to adjust the viscosity of the slurry, making it easier to spray. The use of deionized water ensures that no additional impurities or ions are introduced during the spraying process, thereby guaranteeing the quality and consistency of the coating.

[0066] In addition, the slurry specifically contains 0.1% to 0.2% defoamer. Using defoamer can prevent excessive bubbles from affecting the spraying effect during the coating process. However, in the embodiments of the present invention, the defoamer plays an even more important role. During the experiment, the inventors discovered that the defoamer has poor compatibility with the coating matrix. During the curing process of the resin in the coating, it can form dense pits and fine wrinkles of a certain shape on the coating surface, constituting the desired recesses. The dense pits and wrinkles on the coating surface can cause uneven distribution of gas in the beverage within the can, so that when the can lid is opened and the internal pressure is released instantaneously, the gas can be released in a concentrated and rapid manner, generating a large amount of foam. Simultaneously, the defoamer can have better dispersibility in the coating, enabling the generated recesses to achieve a certain distribution density on the coating surface. If other substances are used instead of the defoamer, they may agglomerate within the slurry, making it difficult to achieve the specific distribution density of the recesses. Furthermore, the physicochemical properties of defoamers are relatively stable, which is beneficial for obtaining recesses with a certain diameter-to-depth ratio, thus allowing for the storage of sufficient gas. Defoamers are usually in liquid or soluble form and can be directly added to the slurry without pretreatment, making operation very convenient and beneficial for industrial production. In addition, defoamers have good heat resistance, maintaining their chemical stability under various temperature conditions. This allows them to maintain stable efficacy in both high-temperature and low-temperature applications, especially during the production of slurries and cans, where high-temperature treatment is required. Under these conditions, the defoamer can still maintain its performance and dispersibility, ensuring the stable formation of recesses. The addition of a certain amount of defoamer can facilitate the formation of the aforementioned coating structure design, particularly for creating recesses with specific distribution density, diameter, and diameter-to-depth ratio, greatly aiding in achieving different designs for the first to third zones. Furthermore, it can improve the visual effect of foam overflow in beverage cans.

[0067] Specifically, in embodiments of the present invention, the defoamer is an acrylic defoamer or a polyester defoamer. Acrylic and polyester defoamers have low compatibility with the resin system of the slurry of the present invention, thus ensuring the full formation of the recessed portion.

[0068] In particular, the dosage relationship between resin and defoamer also affects the final structure and performance of the coating. The more defoamer used, the more depressions are generated. However, when the amount of defoamer is too high, the mass ratio of defoamer to resin is too high, which will lead to poor dispersibility of the defoamer, poor coverage of the metal substrate by the coating, and even make the can highly conductive. Therefore, using 20% ​​to 30% epoxy resin, 1% to 3% phenolic resin and 0.1% to 0.2% defoamer can achieve a good match between resin and defoamer. The defoamer can have good dispersibility and generate the required depressions appropriately without affecting the final performance of the coating. Preferably, the mass ratio of defoamer to resin is less than 1:100. Specifically, the mass ratio of defoamer to epoxy resin and phenolic resin is less than 1:100. That is, the ratio of the mass of defoamer to the sum of the masses of epoxy resin and phenolic resin is less than 1:100. This ensures that the distribution density, aspect ratio, coating coverage, and film thickness of the recessed areas are all within a suitable range, guaranteeing the speed, continuity, and appearance of foam overflow. Furthermore, the inventors have also discovered that using defoamer allows the resulting recessed areas to maintain structural stability within the resin system. Whether during subsequent production or transportation, or during storage by the consumer, the structural integrity of the recessed areas is guaranteed, preventing undesirable problems such as collapse.

[0069] In a specific embodiment of the present invention, the first region, the second region, and the third region are evenly distributed along a first direction, that is, the first region to the third region are three regions that are completely identical in spatial range. The distribution density of the recesses in the second region is 282 to 2004 per mm. 2 The distribution density of the depressions in the first region is 227–1272 per mm. 2 The distribution density of the depressions in the third region is 169–1031 per mm. 2 By precisely designing the gradient distribution of the recessed areas, the functionality of the three zones can be maximized, optimizing the generation and overflow of foam from beverage cans. This structure can be achieved using a slurry containing epoxy resin and defoamer.

[0070] In one specific embodiment of the present invention, the slurry further comprises 2%–5% dimethylethanolamine, 3%–6% ethylene glycol butyl ether, 0.5%–3% n-butanol, and 0.3%–0.4% carnauba wax. Dimethylethanolamine can improve the water solubility of the slurry. Ethylene glycol butyl ether and n-butanol are both cosolvents, helping the epoxy acrylate resin to be more miscible with water. The main function of carnauba wax is to provide sufficient slippage to the coating to ensure metal deformation.

[0071] Preferably, by weight percentage, the slurry comprises 23% epoxy resin, 2% phenolic resin, 4% dimethyl ethanolamine, 6% ethylene glycol butyl ether, 2% n-butanol, 62.5% deionized water, 0.32% carnauba wax, and 0.18% defoamer. This slurry composition, combined with a specific slurry spraying process, can produce a coating with different recessed structures in zones one through three, exhibiting good performance stability. When the beverage can is opened, the gas inside escapes rapidly, producing abundant foam for a better visual experience. The duration of the foam's emergence is also suitable, ensuring both a satisfying visual experience and minimal beverage consumption. Furthermore, the foam is finer and denser, resulting in a superior taste.

[0072] In a specific embodiment of the present invention, a specific coating structure can be obtained through the specific proportions of the components of the slurry. Specifically, the aspect ratio of the recesses in the first region is 4.0–8.0, the aspect ratio of the recesses in the second region is 2.5–6.0, and the aspect ratio of the recesses in the third region is 3.0–5.5. Based on the above coating structure, the inventors further designed the aspect ratio of the recesses in each region. The combination of the distribution density of the recesses in each region and the aspect ratio can further enhance the functional design of each region. Among these, the aspect ratio range of the recesses in the first region is wider because the first region is closest to the tank opening and has a certain gas escape velocity advantage. Therefore, some recesses with relatively small aspect ratios can exist in this region to ensure the gas storage capacity; some recesses with relatively large aspect ratios can also exist in this region to further ensure the gas escape velocity in the first region. Within a certain range of aspect ratio design, the inventors further discovered that the foam produced by beverage cans also has a more delicate texture and is denser, improving the drinking experience of the foam and further enhancing the consumer experience.

[0073] Furthermore, both diameter and depth affect the state of gas molecules. In fact, the diffusion and motion of gases inside a container are not equivalent to those in ordinary environments. Knudsen diffusion occurs within a small spatial area, especially pronounced in microscale or nanoscale systems. This diffusion phenomenon is relatively complex, and the motion of gas molecules is related to multiple factors. As shown in Equation 2, the Knudsen number K... n It is related to λ and L.

[0074] Where λ is the mean free path and L is the characteristic length scale of the fluid, which can be the diameter of the channel, the thickness of the boundary layer, or the pore size in a porous medium.

[0075] Based on the different states and dynamics of gas within the container, the inventors made a more detailed design of the diameter-to-depth ratio. Since the gas in the first zone needs to escape at a faster rate than the other two zones, the inventors designed the diameter-to-depth ratio of the recessed portion in the first zone to be relatively larger. With a larger diameter-to-depth ratio, the structure of the recessed portion is closer to the shape of a "plate." The shallower "plate bottom" ensures rapid gas escape, and also ensures that the gas at the innermost part of the recess can escape quickly, allowing the gas in the first zone's recessed portion to quickly and fully exert its function. The recessed portion in the second zone functions to ensure the continuity of foam overflow. Therefore, compared to the first zone, the diameter-to-depth ratio of the recessed portion in the second zone is smaller. Thus, when the diameter is in the range of 0.1–5.0 μm, the recessed portion in the second zone can be relatively deeper. Unlike the rapid gas escape in the first zone, the gas in the second zone's recessed portion can disperse relatively smoothly and evenly, thereby improving the continuity and uniformity of the foam. The diameter-to-depth ratio of the recessed area in the third zone is relatively moderate, placing it between the first and second zones. This allows gas to escape relatively quickly, compensating for the longer gas travel distance due to its distance from the tank opening, while also ensuring relatively uniform gas escape. Therefore, the combined effect of the three zones can improve foam overflow in terms of speed, continuity, and uniformity.

[0076] In one specific embodiment of the present invention, the diameter-to-depth ratio of the recessed portion in the first region is greater than that in the second and third regions. Further, the diameter-to-depth ratio of the recessed portion in the third region is greater than that in the second region. The inventors set the diameter-to-depth ratio of the recessed portion in the first region to be the largest to ensure the gas escape velocity in the first region. The diameter-to-depth ratio of the recessed portion in the third region is secondary, also considering that the third region has the longest distance; therefore, the diameter-to-depth ratio of the recessed portion in this region is set accordingly to reasonably increase the gas escape velocity in the third region. The diameter-to-depth ratio of the recessed portion in the second region can be the smallest because the gas in the second region does not require a particularly fast escape velocity, and a smaller diameter-to-depth ratio can ensure a larger gas storage capacity.

[0077] Preferably, the diameter-to-depth ratio of the recessed portion in the first region is 4.5–7.5, the diameter-to-depth ratio of the recessed portion in the second region is 2.5–6.0, and the diameter-to-depth ratio of the recessed portion in the third region is 4.0–5.5. This allows for better foam overflow effect in conjunction with the distribution density, resulting in a delicate and creamy foam texture. More preferably, based on this, the diameter-to-depth ratio of the recessed portion in the first region is larger than that in the other two regions.

[0078] In one specific embodiment of the present invention, the film thickness of the first region is 3.0–4.5 μm, the film thickness of the second region is 3.5–5.0 μm, and the film thickness of the third region is 2.8–4.0 μm. The inventors have discovered that by designing the film thickness of each region, the aspect ratio of the recessed portion, and the density of the recessed portion, foam can be generated within a short time after the beverage can is opened. The foam can fully cover the can opening, achieving an excellent visual effect. Furthermore, the duration of the foam is reasonable—neither too short to provide the consumer with sufficient visual enjoyment, nor too long to prevent excessive consumption of the beverage. Simultaneously, this film thickness design also ensures the coating's protective function for the beverage inside.

[0079] In a specific embodiment of the present invention, the film thickness of the first region is 3.2–3.8 μm, the film thickness of the second region is 3.8–4.5 μm, and the film thickness of the third region is 2.8–3.2 μm, with the film thickness of the second region ≥ the film thickness of the first region ≥ the film thickness of the third region. By designing a gradient in film thickness, and further combining it with the aspect ratio and distribution density, the foaming effect of the beverage can can be further guaranteed. Furthermore, the thickness gradient of the coating also facilitates achieving different gradients in aspect ratio and distribution density, making the structure more stable. Preferably, based on the above, the film thickness of the second region > the film thickness of the first region > the film thickness of the third region. Specifically, for example, the film thickness of the first region is 3.2–3.8 μm, the film thickness of the second region is 3.9–4.5 μm, and the film thickness of the third region is 2.8–3.1 μm.

[0080] Specifically, when measuring the film thickness of each zone, a circumferential plane is identified at the middle or upper part of each zone. This circumferential plane is perpendicular to the height direction of the tank. The coating forms a ring shape of varying thickness on this circumferential plane. An average of 3 to 4 points are selected on the ring shape as measurement points. The tank is then cut on the circumferential plane, thus exposing the internal cross-section of the coating. A scanning electron microscope (Germany ZEISS GeminiSEM 300) is used to acquire cross-sectional images. The width of the coating cross-section at each point is measured using image processing software to obtain the film thickness at each point. Finally, the film thickness range is obtained.

[0081] The inventors discovered in process production and laboratory research that there is usually a certain correlation between film thickness and the distribution density of the recesses. In the production process, the control of film thickness can be used as one of the factors to adjust the distribution density. Furthermore, by combining some influencing factors in the process and slurry formulation, the distribution density or the difference between distribution densities can be adjusted to obtain the preset distribution density and the difference between distribution densities, thereby obtaining the desired product.

[0082] The beverage can design of this invention fully considers the factors affecting foam overflow at various levels, and adopts a reasonable structural layout and design. It also takes into account the correlation and influence between various structural features, bringing consumers a dual enjoyment of taste and visual appeal, and enhancing the functionality of the beverage can. Furthermore, this beverage can is particularly suitable for use after storage at low temperatures (e.g., 4–12°C), where foam generation and overflow are better, and the foam has a smoother texture.

[0083] Under the aforementioned slurry composition system, the coating's function of protecting the contents of the beverage can is first and foremost guaranteed, and the recesses can also be generated reasonably and appropriately, thus realizing the multiple functions of the beverage can. Through the matching of the various components, a coating suitable for foam generation can be produced efficiently and at low cost, and the foam generation effect can be improved. With a multi-layered design encompassing the recess structure, functional zoning, slurry application process, and slurry formulation, the foam generation performance of the beverage can is perfected, providing consumers with a multifaceted sensory experience.

[0084] A second aspect of the present invention discloses a method for manufacturing a beverage can, comprising the following steps:

[0085] Slurry spraying: Using a spray gun, slurry is sprayed onto the inner surface of the main body of the container at a preset angle of 7 to 20°, wherein the preset angle is the angle between the center line of the spray gun and the normal to the surface of the beverage can.

[0086] Drying to form a coating: The sprayed slurry is dried to form a coating;

[0087] The slurry, by mass percentage, comprises 20%–30% epoxy resin and 0.1%–0.2% defoamer.

[0088] The production process of beverage cans includes: uncoiling aluminum coils, cup rinsing, stretching and trimming, cleaning and drying, base coating and drying, color printing and drying, internal spraying and drying, necking and flanging, optical inspection and photography, and stacking and packaging. Through the above processes, the entire production process from aluminum material to beverage can is completed. Among them, the coating of this invention is formed in the internal spraying and drying steps.

[0089] Specifically, by designing the spray gun angle, a slurry containing 20%–30% epoxy resin and 0.1%–0.2% defoamer can be sprayed, and after drying, a structure with zones one through three can be obtained in one step, with the recesses in zones one through three meeting a certain distribution density range. This method is simple, requiring only the preparation of the slurry and spraying at a set angle, making it suitable for industrial mass production. It is highly efficient and produces products with high uniformity. The distribution and structure of the coating can also be controlled by adjusting the spray gun angle.

[0090] In an embodiment of the invention, by setting the spray gun angle and pressure, three different zones can be formed after spraying as the can rotates and changes from a horizontal to a standing position. Specifically, the can is first placed horizontally and rotated, with the center line of the spray gun forming a certain angle with the normal to the surface of the beverage can. A certain spray gun pressure is set, and the spray gun is inserted into the can for spraying. By setting the relative position of the spray gun and the can, different areas inside the can can exhibit differences in film thickness. After spraying, the can changes from a horizontal to a vertical position. At this time, the wet slurry will flow downwards due to gravity. The can is then placed in an oven for drying at a certain temperature. In particular, the film thickness is related to the angle and pressure, and the flow of the slurry also affects the film thickness to some extent. Therefore, the setting of the relative position of the spray gun and the can, the spray gun angle, and the spray gun pressure must take into account the flow of the slurry in advance, so that the flow of the slurry ultimately results in a film thickness within a preset range, and thus the distribution density of each zone and the difference in distribution density between different zones can also be within a preset range. In addition, the spray gun angle, spray gun pressure, and drying temperature also affect the diameter and depth of the recess. Therefore, to obtain a beverage can with the desired structure, the spraying process should be designed holistically and controlled throughout the entire spraying process.

[0091] In one specific embodiment of the present invention, the preset angle of the spray gun is 12–20°, and the drying temperature of the slurry is 80–100°C. Within this range, regions with appropriate density of recessed portions and aspect ratios can be formed, and the film thickness of each region after drying is also within an appropriate range.

[0092] In one specific embodiment of the present invention, the spray gun's spray pressure is 480–550 psi, which can form a first to a third zone with a gradient distribution. Preferably, the spray gun's spray pressure is 500–550 psi. By setting the spray gun's spray pressure to 500–550 psi, it is further ensured that three zones with corresponding aspect ratio gradients are formed in one pass. By precisely controlling the spray angle and pressure, zones with different recess density and aspect ratios can be obtained, resulting in a suitable coating.

[0093] In one specific embodiment of the present invention, the drying process for forming the coating includes preliminary drying and subsequent drying. The preliminary drying temperature is 80–100°C, and the preliminary drying time is 1–3 minutes. The subsequent drying temperature is 150°C–280°C, until a stable coating is formed. That is, after the slurry is sprayed onto the inner surface of the main body, it is first dried at 80–100°C for 1–3 minutes. At this point, the recessed structure has been stably formed. Subsequently, the drying temperature can be increased to 150°C–280°C for rapid curing to form a stable coating. This staged drying method is beneficial for forming a coating with specific physical properties and also ensures the basic functions of the coating.

[0094] A third aspect of the present invention discloses a method for preparing the above-mentioned slurry, comprising:

[0095] Chain extension reaction: The epoxy equivalent of the base epoxy resin (epoxy equivalent 182–192 g / mol) is increased to 3800–6000 g / mol by reacting with bisphenol A. Specifically, ethylene glycol butyl ether solvent, base epoxy resin, and bisphenol A are added to a reaction vessel, and the temperature is raised. When the temperature reaches 175–185°C, it is held at this temperature for 2–3 hours until the epoxy equivalent reaches 3800–6000 g / mol. Further, the epoxy equivalent can be increased to 4000–6000 g / mol by reacting the base epoxy resin with bisphenol A. Preferably, the epoxy equivalent is increased to 5000–6000 g / mol.

[0096] Grafting reaction: Acrylic acid is grafted onto the chain-extended epoxy resin. Specifically, the chain-extended epoxy resin is cooled to 120–130°C, and n-butanol, acrylic acid, ethyl acrylate, methacrylic acid, styrene, and benzoyl peroxide are premixed. The premixed monomers, including acrylic acid, are then slowly added dropwise at 1–2 kg / min under 120–130°C. After all the monomers, including acrylic acid, have been added, the mixture is kept at this temperature for 1 hour.

[0097] Emulsification: The grafted epoxy acrylate resin was emulsified in water under the action of dimethylethanolamine. Specifically, the grafted epoxy acrylate resin was pumped into a stirred tank, dimethylethanolamine and deionized water were added, and the mixture was stirred for 2 hours to adjust the solid content of the emulsion to 30-35%.

[0098] Diluting. Specifically, the emulsified epoxy acrylic emulsion is diluted with water to reduce its solid content, while a crosslinking agent and defoamer are added, and wax may also be added. The final product's solid content is controlled at 22-26%, and its viscosity range is 18-22 seconds (25°C, Ford cup 4).

[0099] A fourth aspect of the present invention discloses a beverage can, comprising the aforementioned beverage can body, and further comprising a top cover that is sealed to the beverage can body, thereby isolating the beverage inside the can from the external environment. The top cover also has an opening portion, allowing the beverage to come into contact with the outside environment when the opening portion is opened. Specifically, the beverage can contains a beverage and is filled with carbon dioxide.

[0100] Specifically, upon opening the can, foam overflows from the beverage container within 6-15 seconds. Furthermore, the foam overflow is relatively even, avoiding excessive foaming immediately after opening, and the foam overflow is continuous. The foam has a delicate texture, providing a good taste and visual experience. Specifically, the beverage is beer. In particular, this beverage can is especially suitable for opening after standing at 4-12℃ for 24 hours, further enhancing the visual appeal and taste of the foam to better meet consumer needs.

[0101] The fifth aspect of the present invention discloses a method for manufacturing the above-mentioned beverage can, comprising the following steps:

[0102] Since unbottled beverages are stored in separate liquid containers, carbon dioxide is first introduced into the liquid containers containing the beverages.

[0103] Carbon dioxide is introduced into the beverage can to make the gas pressure inside the beverage can equal the gas pressure inside the liquid storage container; the beverage is then filled into the beverage can using its own weight.

[0104] The top cap is sealed to the beverage can body to obtain the beverage can, and the gas pressure inside the beverage can is 0.18–0.40 MPa. After the beverage is filled into the beverage can, there is no need to add additional carbon dioxide to achieve the final gas pressure of 0.18–0.40 MPa inside the beverage can.

[0105] In particular, maintaining the gas pressure inside the can ensures that an appropriate amount of carbon dioxide is stored in the recessed area, that the carbon dioxide is evenly distributed in the recessed area, and that the gas can be fully released after the beverage can is opened.

[0106] The following will describe a more specific implementation method.

[0107] Examples 1-4 are beverage cans with coatings.

[0108] (1) Example 1

[0109] Example 1 is obtained by applying a slurry to the inner surface of the tank body and preparing a coating, specifically including the following steps.

[0110] Slurry spraying: Using a spray gun, at a preset angle of 12° and a spray pressure of 480 psi, the slurry is sprayed onto the inner surface of the container body. By weight percentage, the slurry composition includes: 23% epoxy acrylate resin, 2% phenolic resin, 4% dimethyl ethanolamine, 6% ethylene glycol butyl ether, 2% n-butanol, 62.5% deionized water, 0.4% carnauba wax, and 0.1% defoamer. The epoxy equivalent of the epoxy polypropylene resin is 5000 g / mol.

[0111] Drying to form a coating: The sprayed slurry is dried, first at 95°C for 3 minutes, and then at 250°C to form a coating.

[0112] The coating of Example 1 has three regions evenly distributed in a first direction, namely the first region to the third region, each region having a surface area of ​​7958 mm². 2 The structural characteristics of the depressions in the first to third zones were statistically analyzed, and the results are shown in Table 1.

[0113] It should be noted that in each embodiment and comparative example, the maximum thickness of the coating, the density of the recessed portion, and the diameter-to-depth ratio were all measured by selecting multiple representative points in the coating and taking range values.

[0114] Table 1:

[0115] The distribution density in the second region is 208 more per mm than that in the first region. 2 The distribution density in the first region is 183 more per mm than that in the third region. 2 The diameter of the recessed portion is 0.1–5.0 μm.

[0116] The method for testing the density of the depressions is as follows: Four evenly distributed unit regions are drawn at the same height in the center of each zone along the circumference. Each unit region is a square with a side length of 1 cm. Microscopic images of the unit regions are acquired using a scanning electron microscope (ZEISS GeminiSEM 300, Germany). The number of depressions in each unit region is measured using image processing software. The density of the depressions in each unit region is then calculated based on the number of depressions and the area of ​​the unit region, ultimately yielding the distribution density range for each zone. Furthermore, the difference in distribution density between different regions is represented by the difference in the average distribution density of the unit regions.

[0117] The method for measuring and calculating the diameter-to-depth ratio of the recess is as follows: First, measure the diameter of the recess. Identify a circle on the coating surface at the center of each zone, perpendicular to the height of the can. Recesses fall on this circle. Take six points within the recesses falling on this circle as the recesses to be measured. Use a scanning electron microscope (ZEISS GeminiSEM 300, Germany) to photograph the surface of each recess. Extract the contour of the recess using image processing software, approximating it as a circle. Measure the diameter of each circle to obtain the diameter range of the recesses in each zone. Next, measure the depth of the recess. Use a laser confocal microscope (VK3000) to obtain the internal structure of the six recesses to be measured. Measure the depth at three average locations along the circumference of each recess and take the average value to obtain the depth of each recess. Finally, calculate the diameter-to-depth ratio. The diameter-to-depth ratio of each recess is calculated from the diameter, thus obtaining the diameter-to-depth ratio range of the recesses in each zone.

[0118] The film thickness is measured as follows: a circumferential plane is identified at the center of each zone, perpendicular to the height of the tank. The coating forms a ring shape of varying thickness on this circumferential plane. Three points are taken on average on the ring shape as measurement points. The tank is then cut along the circumferential plane, exposing the internal cross-section of the coating. A scanning electron microscope (ZEISS GeminiSEM 300, Germany) is used to acquire cross-sectional images. The width of the coating cross-section at each point is measured using image processing software to obtain the film thickness at each point. Finally, the film thickness range is obtained.

[0119] The measurement methods for the following embodiments and comparative examples are the same as those in Embodiment 1.

[0120] (2) Example 2

[0121] The only difference between Example 2 and Example 1 is that the spray gun angle is 15°, the pressure is 500 psi, and the mass percentage of carnauba wax and defoamer in the slurry is 0.35%. All other aspects are the same as in Example 1.

[0122] The coating of Example 2 has three regions evenly distributed in a first direction, namely the first region to the third region, each region having a surface area of ​​7958 mm². 2 The structural characteristics of the depressions in the first to third zones were statistically analyzed, and the results are shown in Table 2.

[0123] Table 2:

[0124] The distribution density in the second region is 225 more per mm than that in the first region. 2 The distribution density in the first region is 339 more per mm than that in the third region.2 The diameter of the recessed portion is 0.1–5.0 μm.

[0125] (3) Example 3

[0126] The difference between Example 3 and Example 1 is that the spray gun angle is 18°, the pressure is 550psi, the sprayed slurry is dried at 80°C, and the slurry contains 0.32% carnauba wax and 0.18% defoamer by mass, and the epoxy equivalent of the epoxy polypropylene resin is 5500 g / mol. All other aspects are the same as in Example 1.

[0127] The coating of Example 3 has three regions evenly distributed in a first direction, namely the first region to the third region, each region having a surface area of ​​7958 mm². 2 The structural characteristics of the depressions in the first to third zones were statistically analyzed, and the results are shown in Table 3.

[0128] Table 3:

[0129] The distribution density in the second region is 764 more per mm than that in the first region. 2 The distribution density in the first region is 380 more per mm than that in the third region. 2 The diameter of the recessed portion is 0.1–5.0 μm. Furthermore, the film thickness in the second region is greater than or equal to the film thickness in the first region, which in turn is greater than or equal to the film thickness in the third region.

[0130] (4) Example 4

[0131] The only difference between Example 4 and Example 1 is that the epoxy equivalent of the epoxy polypropylene resin is 3800 g / mol. All other aspects are the same as in Example 1.

[0132] The coating of Example 4 has three regions evenly distributed in a first direction, namely the first region to the third region, each region having a surface area of ​​7958 mm². 2 The structural characteristics of the depressions in the first to third zones were statistically analyzed, and the results are shown in Table 4.

[0133] Table 4:

[0134] The distribution density in the second region is 92 more per mm than that in the first region. 2 The distribution density in the first region is 84 more per mm than that in the third region. 2 The diameter of the recessed portion is 0.1–5.0 μm.

[0135] Comparative Examples 1 and 2 are beverage cans with coatings.

[0136] (1) Comparative Example 1

[0137] The only difference between Comparative Example 1 and Example 1 is that the spray gun angle is 7°, the pressure is 450 psi, the sprayed slurry is dried at 100°C, and the slurry contains 0.42% carnauba wax and 0.08% defoamer by mass. All other aspects are the same as in Example 1.

[0138] The coating of Comparative Example 1 has three regions evenly distributed in a first direction, namely the first region to the third region, each region having a surface area of ​​7958 mm². 2 The structural characteristics of the depressions in the first to third zones were statistically analyzed, and the results are shown in Table 5.

[0139] Table 5:

[0140] The distribution density in the second region is 52 more per mm than that in the first region. 2 The distribution density in the first region is 27 more per mm than that in the third region. 2 The diameter of the recessed portion is 0.1–5.0 μm.

[0141] (2) Comparative Example 2

[0142] The only difference between Comparative Example 2 and Example 1 is that the carnauba wax content in the slurry is 0.16% and the defoamer content is 0.34%. All other aspects are the same as in Example 1.

[0143] The coating of Comparative Example 2 has three regions evenly distributed in the first direction, namely the first region to the third region, each region having a surface area of ​​7958 mm². 2 The structural characteristics of the depressions in the first to third zones were statistically analyzed, and the results are shown in Table 6.

[0144] Table 6:

[0145] Beer filled with carbon dioxide was poured into the beverage cans of Examples 1 to 4 and Comparative Examples 1 and 2, with a gas pressure of 0.29 MPa inside the cans. The examples and comparative examples were stored at 8°C for 24 hours before being opened. The following were measured: the fastest foam overflow time, the total foam overflow time, the foam persistence, the average foam overflow amount, and the conductivity value. The taste of the foam was also professionally evaluated. In this embodiment and comparative example, the beverage cans are equipped with easy-open lids. "Fastest foam overflow time after opening" refers to the time from opening the lid to foam overflowing from the lid's pull ring opening; "Total foam overflow time" refers to the time from foam overflowing from the lid's pull ring opening to foam stopping overflowing; "Average foam overflow amount" refers to the amount of gas escaping from the can, calculated using the mass difference before and after opening; "Foam persistence (foam retention, referring to national standard GB4927-2008)" refers to the lifespan of foam from its formation to its disappearance; "Foam taste evaluation" compares the taste of the embodiment and comparative example based on the fineness and density of the foam. "☆☆☆☆☆" represents a very fine and smooth foam, with the flavor compounds of beer detectable; "☆☆☆☆" represents a relatively fine but less smooth foam, with the flavor compounds of beer detectable; "☆☆☆" represents a low degree of fineness and lack of smoothness, with the flavor compounds of beer detectable; and "☆☆" represents low foam fineness and smoothness, and poor flavor. "Coating conductivity value" (refer to national standard GB / T 9106.1-2019, for beverage cans used to hold beer, the individual conductivity value should be ≤75 and the average conductivity value should be ≤35). During the test, an electrolyte [1% (m / v) sodium chloride solution] is added to the beverage can, with the liquid level 3mm away from the can opening. The coating integrity tester with a minimum reading value of no more than 0.1mA is used to test the coating inside the can, and the current value is read at the 4th second.

[0146] The results are shown in Table 7.

[0147] Table 7:

[0148] Examples 1-4 yielded stable and gradient coating structures, resulting in faster foam overflow, longer duration, moderate foam overflow volume, and improved foam taste, allowing for the consumption of flavor compounds. Foam persistence was also enhanced. As shown in Table 5, with a lower defoamer content, the density of the recessed areas in Comparative Example 1 was generally lower than in the examples, leading to insufficient gas storage in the recessed areas. Therefore, as shown in Table 7, the speed and duration of foam emergence were affected. Comparative Example 2 used a larger amount of defoamer during coating preparation. While this resulted in a zoned coating and increased density in the recessed areas, it also led to a higher coating conductivity, failing to meet national standards and classifying it as an unqualified beverage can product. The coating would react with the acidic or alkaline components of the liquid inside the can, compromising the chemical stability of the liquid and compromising food safety. Furthermore, the sealed beverage cans from Examples 1-4 were stored at 8°C for 15 days before being opened and tested under the same conditions. Compared to opening after 24 hours of storage, there were no significant changes in the fastest foam overflow time, total foam overflow time, average foam overflow amount, foam persistence, and foam taste evaluation after opening, indicating that the coating structure is relatively stable and the product stability and consistency are good. Specific test results are shown in Table 8.

[0149] Table 8:

[0150] While the present invention has been illustrated and described with reference to certain preferred embodiments, those skilled in the art should understand that the above description is a further detailed explanation of the invention in conjunction with specific embodiments, and should not be construed as limiting the specific implementation of the invention to these descriptions. Various changes in form and detail can be made by those skilled in the art, including several simple deductions or substitutions, without departing from the spirit and scope of the invention.

Claims

1. A beverage can, characterized in that, The beverage can includes: The main body, for containing beverages, includes a peripheral wall. The inner surface of the peripheral wall has a coating, and the coating has recessed portions. The coating is formed by spraying a slurry onto the inner surface of the peripheral wall. The coating includes a first region, a second region, and a third region sequentially arranged along a first direction. The first region, the second region, and the third region each have a distribution density of 160–4900 particles / mm². 2 In the recessed portion, the distribution density of the second region is 28–1300 more per mm than that of the first region. 2 The distribution density of the first region is 25 to 640 more per mm than that of the third region. 2 The surface areas of the first region, the second region, and the third region are 4550–18500 mm², respectively. 2 ; The slurry comprises, by mass percentage, 20%–30% epoxy resin, 1%–3% phenolic resin, 55%–65% deionized water, and 0.1%–0.2% defoamer, wherein the epoxy equivalent of the epoxy resin is 3800–6000 g / mol. Wherein, the first direction is the direction from the top end of the main body to its bottom end.

2. A beverage can as described in claim 1, characterized in that, The epoxy resin is an epoxy acrylate resin, and the epoxy equivalent of the epoxy acrylate resin is 5000-6000 g / mol.

3. A beverage can as described in claim 2, characterized in that, The slurry also contains 2% to 5% dimethylethanolamine, 3% to 6% ethylene glycol butyl ether, 0.5% to 3% n-butanol, and 0.3% to 0.4% carnauba wax.

4. A beverage can as described in claim 1, characterized in that, The ratio of the mass of the defoamer to the sum of the masses of the epoxy resin and the phenolic resin is less than 1:

100.

5. A beverage can as described in claim 1, characterized in that, The slurry comprises, by weight percentage, 23% epoxy resin, 2% phenolic resin, 4% dimethyl ethanolamine, 6% ethylene glycol butyl ether, 2% n-butanol, 62.5% deionized water, 0.32% carnauba wax, and 0.18% defoamer.

6. A beverage can as described in claim 1, characterized in that, The defoamer is an acrylic defoamer and a polyester defoamer.

7. A beverage can as described in claim 1, characterized in that, The first, second, and third regions are evenly distributed along the first direction, and the distribution density of the depressions in the second region is 282–2004 per mm. 2 The distribution density of the depressions in the first region is 227–1272 per mm. 2 The distribution density of the recesses in the third region is 169–1031 per mm. 2 The diameter of the recess is 0.1 to 5.0 μm, and the diameter-to-depth ratio of the recess is 2.0 to 20.0, wherein the diameter-to-depth ratio is the ratio of the diameter of the recess to the depth of the recess.

8. A beverage can as described in claim 7, characterized in that, The diameter-to-depth ratio of the recessed portion in the first region is 4.0 to 8.0, the diameter-to-depth ratio of the recessed portion in the second region is 2.5 to 6.0, and the diameter-to-depth ratio of the recessed portion in the third region is 3.0 to 5.

5.

9. A beverage can as described in claim 7, characterized in that, The film thickness of the first region is 3.0–4.5 μm, the film thickness of the second region is 3.5–5.0 μm, and the film thickness of the third region is 2.8–4.0 μm.

10. A beverage can as described in claim 9, characterized in that, The film thickness of the first region is 3.2–3.8 μm, the film thickness of the second region is 3.8–4.5 μm, and the film thickness of the third region is 2.8–3.2 μm, and the film thickness of the second region is greater than or equal to the film thickness of the first region and greater than or equal to the film thickness of the third region.

11. A method for manufacturing a beverage can as described in any one of claims 1 to 10, characterized in that, Includes the following steps: Slurry spraying: Using a spray gun, slurry is sprayed onto the inner surface of the peripheral wall of the main body at a preset angle of 7 to 20°, wherein the preset angle is the angle between the center line of the spray gun and the normal to the surface of the beverage can. Drying to form a coating: The sprayed slurry is dried to form a coating.

12. The manufacturing method as described in claim 11, characterized in that, The preset angle is 12 to 20°, and the drying temperature of the slurry is 80 to 100°C.

13. The manufacturing method as described in claim 11, characterized in that, The spray gun has a spray pressure of 480–550 psi.

14. The manufacturing method as described in claim 11, characterized in that, In the drying process of forming the coating, the drying process includes a pre-drying and a subsequent drying. The pre-drying temperature is 80-100°C and the pre-drying time is 1-3 minutes. The subsequent drying temperature is 150°C-280°C.

15. A beverage can comprising a beverage can body as claimed in any one of claims 1 to 10, and a top cover, the top cover being sealed to the beverage can body, the beverage can being used to contain a beverage and to fill with carbon dioxide.

16. The beverage can as described in claim 15, characterized in that, The top cover includes an opening section; when the opening section is opened, foam overflows from the beverage can within 6 to 15 seconds.

17. A method for manufacturing a beverage can as described in claim 15 or 16, characterized in that, Includes the following steps: Carbon dioxide is introduced into the liquid storage container containing the beverage; Carbon dioxide is introduced into the beverage can to make the gas pressure inside the beverage can equal the gas pressure inside the liquid storage container; The beverage is filled into the beverage can using its own weight. The top cover is sealed to the beverage can body to obtain the beverage can, and the gas pressure inside the beverage can is 0.18 to 0.40 MPa.

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