Easily-torn cover aluminum foil for packaging and preparation process thereof

Abstract

The invention belongs to the technical field of packaging materials, and particularly relates to an easy-to-tear cover aluminum foil for packaging and a preparation process thereof.The easy-to-tear cover aluminum foil comprises a main body part located in the middle and a bonding part arranged along the edge of the main body part; the bonding part comprises a continuous bonding area which is continuously bonded with the cover body and a repeated bonding area which is separated and bonded with the cover body for multiple times, an aluminum oxide meltallizing layer is formed on the cover body through a meltallizing process, and the repeated bonding area comprises a repeated bonding layer which is in contact with the aluminum oxide meltallizing layer; the repeated bonding layer is prepared from the following components in percentage by mass: 40 to 50 percent of ethylene-vinyl acetate copolymer, 15 to 30 percent of thermoplastic elastomer, 15 to 30 percent of methyl acrylate and 5 to 10 percent of hydrogenated rosin glyceride. According to the easy-to-tear cover aluminum foil for packaging provided by the invention, after the easy-to-tear cover aluminum foil is opened for the first time, a packaging tank body can be subsequently and repeatedly sealed for multiple times, so that the requirement of prolonging the service life of a built-in substance is met.

Description

Technical Field

[0001] The invention belongs to the technical field of packaging materials, and in particular relates to an easy-tear cover aluminum foil for packaging and a preparation process thereof. Background Art

[0002] As a new type of aluminum-plastic composite packaging material, the tear-off cover has the advantages of good barrier properties, excellent sealing, non-toxicity, no odor, beautiful appearance, easy opening, and recyclability. It is widely used in the packaging of various substances that need to be sealed and stored.

[0003] At present, the research on easy-tear aluminum foil mainly focuses on its sealing performance, peeling performance, and derived corrosion resistance, high temperature resistance and other properties.

[0004] For example, CN105396771A discloses a method for preparing an easy-tear aluminum foil, which prepares an easy-tear aluminum foil by respectively preparing a protective layer and a heat-sealing layer on both sides of the aluminum foil. The formed coating is uniform and not easy to fall off and separate, thereby ensuring the sealing performance.

[0005] Another example is an easy-tear aluminum foil for food packaging disclosed in CN106366824A, which includes an aluminum foil layer, a first functional layer arranged on the upper surface of the aluminum foil layer, a second functional layer arranged on the lower surface of the aluminum foil layer, and a third functional layer arranged on the lower surface of the second functional layer, wherein the second functional layer is coated with a coating liquid 1, the main component of which is acrylic resin, and the third functional layer is coated with a coating liquid 2, the main component of which is polyester resin. It has good sealing performance, firm connection, smooth peeling, corrosion resistance, and ensures safe use.

[0006] However, in some use cases, for example, after the easy-tear cover is opened, the food and other substances inside cannot be used up at once and need to be saved for the next use, such as milk powder, tea, etc. In this case, the existing easy-tear cover cannot be reused to achieve relative sealing. At this time, the sealing performance of the can body can only rely on the can body cover, which has poor sealing performance, resulting in the deterioration of the food and other substances inside after the easy-tear cover is opened, greatly shortening the service life. Summary of the invention

[0007] The purpose of the present invention is to provide an easy-tear cover aluminum foil for packaging and a preparation process thereof, so as to solve the above problems existing in the existing easy-tear cover aluminum foil.

[0008] The present invention adopts the following technical solution: A kind of easy-tear aluminum foil for packaging, used in conjunction with the cover of a packaging can, the cover of the packaging can has an opening, the easy-tear aluminum foil is arranged at the opening, and the opening of the cover is opened and sealed. The easy-tear aluminum foil comprises a main body portion located in the middle and an adhesive portion arranged along the edge of the main body portion for bonding with the cover, the adhesive portion comprises a continuous bonding area for continuous bonding with the cover and a repeated bonding area for multiple separation and bonding with the cover, an aluminum oxide spraying layer is formed on the cover by a spraying process, and the repeated bonding area comprises a repeated bonding layer in contact with the aluminum oxide spraying layer; the components of the repeated bonding layer include, by mass percentage: 40-50% of ethylene-vinyl acetate copolymer, 15-30% of thermoplastic elastomer, 15-30% of methyl acrylate, and 5-10% of hydrogenated rosin glycerol ester.

[0009] The existing easy-tear cover aluminum foil cannot be connected to the cover body after the first opening, which is not conducive to the continued sealing and preservation of the built-in materials. In the above scheme of the present invention, the adhesive part directly connected to the cover body is divided into two areas, wherein the continuous adhesive area is continuously bonded to the cover body before the built-in materials are completely used up, and is not separated from the cover body, ensuring that the easy-tear cover aluminum foil does not separate from the cover body, and the repeated adhesive area can be separated and repeatedly bonded to the cover body for multiple times, and after the first opening, the built-in materials can still be relatively sealed and preserved.

[0010] However, the easy-tear cover aluminum foil is connected to the metal (usually iron) cover body, and the repeated bonding strength of the repeated bonding area is difficult to ensure. In order to solve the problem of repeated bonding strength, the adhesive composition of the adhesive layer can be adjusted from the adhesive layer. In this solution, the inventor starts from the structure of the cover body and finds that adding a layer of aluminum oxide spraying layer formed by spraying on the cover body can effectively control the repeated bonding strength of the repeated bonding area.

[0011] Preferably, the repeated bonding area is provided with a bonding groove with an opening facing downward, and the cover body is provided with a convex ridge corresponding to the position of the bonding groove and capable of being inserted into the bonding groove.

[0012] The repeated bonding area of ​​the present invention needs to be separated and bonded to the cover body multiple times. Therefore, the repeated bonding layer must not only meet the tearing performance, but also ensure the bonding performance, and try to ensure the sealing of the can body. Therefore, in this solution, a bonding groove is set in the repeated bonding area, which is directly plugged and bonded with the ridge on the cover body, which can further improve the re-sealing performance and increase the number of repeated uses.

[0013] Preferably, in the hierarchical structure of the easy-tear cover aluminum foil, the continuous bonding area includes an aluminum foil layer, a protective layer arranged above the aluminum foil layer, and a continuous bonding layer arranged below the aluminum foil layer; the repeated bonding area includes an aluminum foil layer, a protective layer arranged above the aluminum foil layer, and the repeated bonding layer is arranged below the aluminum foil layer.

[0014] Preferably, the peeling force between the continuous adhesive layer and the cover body is greater than the peeling force between the repeated adhesive layer and the cover body.

[0015] Preferably, the repeated bonding layer on the inner surface of the bonding groove of the repeated bonding area is formed by pressure-sensitive adhesive, and the repeated bonding layer on the part other than the inner surface of the bonding groove of the repeated bonding area is formed by hot-melt adhesive.

[0016] Preferably, the width of the bonding groove is 1 / 3 to 1 / 2 of the width of the repeated bonding area.

[0017] Preferably, a resin coating is provided on the ridge of the cover body to cooperate with the pressure-sensitive adhesive to improve the bonding strength and sealing performance.

[0018] Preferably, the easy-tear cover aluminum foil further comprises a polypropylene coating directly formed on the lower surface of the aluminum foil layer.

[0019] Preferably, the main body portion at least includes an aluminum foil layer and a protective layer disposed above the aluminum foil layer.

[0020] Preferably, the length of the continuous bonding area is 1 / 4 to 1 / 2 of the length of the bonding portion.

[0021] The present invention also provides a preparation process of the above-mentioned easy-tear cover aluminum foil for packaging, comprising the following steps: S1. Provide aluminum foil of target shape and size; S2. A continuous bonding layer is coated on the lower surface of the aluminum foil in the continuous bonding area, and a repeated bonding layer is coated in the repeated bonding area to form a repeated bonding layer; S3. A protective layer is formed on the upper surface of the aluminum foil to obtain an easy-tear cover aluminum foil for packaging.

[0022] By implementing the above technical solution, the present invention has the following beneficial effects: The easy-tear cover aluminum foil for packaging provided by the present invention can seal the packaging can body repeatedly after the easy-tear cover aluminum foil is opened for the first time, so as to meet the requirement of extending the service life of the internal substance. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a schematic structural diagram of the easy-tear cover aluminum foil for packaging shown in Example 1 of the present invention; Figure 2 for Figure 1A cross-sectional view of the easy-tear cover aluminum foil for packaging; Figure 3 It is a cross-sectional view of an easy-tear cover aluminum foil for packaging with a barrier layer; Figure 4 This is a cross-sectional view of the easy-tear cover aluminum foil for packaging shown in Example 2 of the present invention. DETAILED DESCRIPTION

[0024] The present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0025] This specific embodiment is merely an explanation of the present invention and is not a limitation of the present invention. After reading this specification, those skilled in the art may make non-creative modifications to the present embodiment as needed. However, as long as they are within the scope of the claims of the present invention, they are protected by the patent law.

[0026] Overall embodiment A packaging easy-tear cover aluminum foil is used in conjunction with a cover of a packaging can. The cover of the packaging can has an opening, and the easy-tear cover aluminum foil is arranged at the opening to realize the opening and sealing of the cover. The easy-tear cover aluminum foil comprises a main body portion located in the middle and an adhesive portion arranged along the edge of the main body portion for bonding with the cover. The adhesive portion comprises a continuous bonding area for continuous bonding with the cover and a repeated bonding area for multiple separation and bonding with the cover, and a pull ring is arranged in the repeated bonding area.

[0027] The existing easy-tear cover aluminum foil cannot be connected to the cover body after the first opening, which is not conducive to the continued sealing and preservation of the built-in materials. In the above scheme of the present invention, the adhesive part directly connected to the cover body is divided into two areas, wherein the continuous adhesive area is continuously bonded to the cover body before the built-in materials are completely used up, and is not separated from the cover body, ensuring that the easy-tear cover aluminum foil does not separate from the cover body, and the repeated adhesive area can be separated and repeatedly bonded to the cover body for multiple times, and after the first opening, the built-in materials can still be relatively sealed and preserved.

[0028] Furthermore, an aluminum oxide spraying layer is formed on the cover body by spraying process. The flame velocity is 500-800 m / s, the particle velocity is 120-200 m / s, and the spraying layer is formed with a thickness of 20-35 μm and a surface roughness Ra of 0.25-0.45 μm.

[0029] Furthermore, the repeated bonding area is provided with a bonding groove with an opening facing downward, and the cover body is provided with a convex ridge corresponding to the position of the bonding groove and capable of being inserted into the bonding groove.

[0030] The repeated bonding area of ​​the present invention needs to be separated and bonded to the cover body multiple times. Therefore, the repeated bonding layer must not only meet the tearing performance, but also ensure the bonding performance, and try to ensure the sealing of the can body. Therefore, in this solution, a bonding groove is set in the repeated bonding area, which is directly plugged and bonded with the ridge on the cover body, which can further improve the re-sealing performance and increase the number of repeated uses.

[0031] In the hierarchical structure of the easy-tear cover aluminum foil, the continuous bonding area includes an aluminum foil layer, a protective layer arranged above the aluminum foil layer, and a continuous bonding layer arranged below the aluminum foil layer; the repeated bonding area includes an aluminum foil layer, a protective layer arranged above the aluminum foil layer, and a repeated bonding layer arranged below the aluminum foil layer; the peeling force between the continuous bonding layer and the cover body is greater than the peeling force between the repeated bonding layer and the cover body.

[0032] Furthermore, the repeated bonding layer on the inner surface of the bonding groove of the repeated bonding area is formed by pressure-sensitive adhesive, and the repeated bonding layer on the part other than the inner surface of the bonding groove of the repeated bonding area is formed by hot-melt adhesive.

[0033] Furthermore, the continuous adhesive layer 103 is made of food-grade hot melt adhesive to ensure adhesion, such as commercially available Henkel series, which is coated on the corresponding area of ​​the easy-tear cover aluminum foil to form the continuous adhesive layer 103 .

[0034] Furthermore, the components of the repeated bonding layer 104 include (by mass percentage): 40-50% ethylene-vinyl acetate copolymer, 15-30% thermoplastic elastomer (TPE), 15-30% methyl acrylate, and 5-10% hydrogenated rosin glycerol ester.

[0035] In the above scheme, the composition of the repeated bonding layer 104 is optimized, with ethylene-vinyl acetate copolymer as the main component, methyl acrylate, and especially thermoplastic elastomer (TPE) and hydrogenated rosin glycerol ester, so that it can achieve good sealing and excellent peeling performance, and can maintain excellent adhesion with the cover body again after peeling.

[0036] Furthermore, the width of the bonding groove accounts for 1 / 3 to 1 / 2 of the width of the repeated bonding area. If the width of the bonding groove is too narrow, the subsequent bonding and sealing effect between the repeated bonding area and the cover body will be limited. If it is too wide, the peeling property between the repeated bonding area and the cover body will be affected, and it is not conducive to the opening operation of the easy-tear cover aluminum foil.

[0037] Furthermore, a resin coating is provided on the ridge of the cover body to cooperate with the pressure-sensitive adhesive to improve the bonding strength and sealing performance. The resin coating is used to improve the bonding strength and sealing performance between the repeated bonding layer on the inner surface of the bonding groove and the ridge. The resin coating is a PP coating, and the effect of spraying is the best.

[0038] Furthermore, nanoparticles may be added to the PP coating to further enhance the bonding strength between the repeated bonding layer and the ridges.

[0039] Furthermore, the easy-tear cover aluminum foil also includes a polypropylene coating directly formed on the lower surface of the aluminum foil layer, and the polypropylene coating mainly plays a barrier role.

[0040] Furthermore, the main body portion at least includes an aluminum foil layer and a protective layer disposed above the aluminum foil layer, and the protective layer mainly serves to protect the aluminum foil layer from being damaged.

[0041] Furthermore, the length of the continuous bonding area accounts for 1 / 4 to 1 / 2 of the length of the bonding portion.

[0042] This embodiment also provides a preparation process of the above-mentioned easy-tear cover aluminum foil for packaging, comprising the following steps: S1. Provide aluminum foil of target shape and size; S2. A continuous bonding layer is coated on the lower surface of the aluminum foil in the continuous bonding area, and a repeated bonding layer is coated in the repeated bonding area to form a repeated bonding layer; S3. A protective layer is formed on the upper surface of the aluminum foil to obtain an easy-tear cover aluminum foil for packaging.

[0043] Example 1 This embodiment provides an easy-tear cover aluminum foil for packaging, which is used in conjunction with the cover body 20 of a packaging can to contain, for example, milk powder, tea leaves, etc. The packaging can includes a can body, a cover body arranged at the opening of the can body, and an outer cover for sealing and protecting the entire can body. The cover body of the packaging can has an opening, and the easy-tear cover aluminum foil of this embodiment is used to seal the opening to achieve the opening and sealing of the opening of the cover body 20. The opening of the cover body 20 is mostly circular or D-shaped, and the easy-tear cover aluminum foil is consistent with the shape of the opening.

[0044] An aluminum oxide spraying layer 201 is formed on the cover 20 by spraying process. The flame velocity is 550 m / s, the particle velocity is 200 m / s, and the spraying layer is formed with a thickness of 25 μm and a surface roughness Ra of 0.25 μm.

[0045] See also Figure 1The easy-tear cover aluminum foil includes a main body 11 located in the middle and an adhesive part 12 arranged along the edge of the main body 11 for bonding with the cover body 20. The adhesive part 12 includes a continuous adhesive area 12a for continuous bonding with the cover body 20 and a repeated adhesive area 12b for multiple separation and bonding with the cover body 20. A pull ring 13 is arranged in the repeated adhesive area 12b. The length of the continuous adhesive area 12a and the length of the repeated adhesive area 12b need to be reasonably allocated to better realize the corresponding functions. Preferably, the length of the continuous adhesive area 12a accounts for 1 / 4 to 1 / 2 of the length of the adhesive part 12, and 1 / 3 is more preferably used in this embodiment. The length mentioned here refers to the circumference around the outer circle of the main body 11. A pull ring 30 is arranged on the side of the repeated adhesive area 12b away from the continuous adhesive area 12a to facilitate the operation of pulling up the repeated adhesive area 12b to open part of the easy-tear cover aluminum foil.

[0046] See also Figure 2 From the hierarchical structure of the easy-tear cover aluminum foil, the main body 11 includes an aluminum foil layer 101 and a protective layer 102 disposed above the aluminum foil layer 101. The structural composition of the continuous bonding area 12a and the repeated bonding area 12b is different. The continuous bonding area 12a includes an aluminum foil layer 101, a protective layer 102 disposed above the aluminum foil layer 101, and a continuous bonding layer 103 disposed below the aluminum foil layer 101; the repeated bonding area 12b includes an aluminum foil layer 101, a protective layer 102 disposed above the aluminum foil layer 101, and a repeated bonding layer 104 disposed below the aluminum foil layer 101. Both the continuous bonding area 12a and the repeated bonding area 12b have an aluminum foil layer 101 and a protective layer 102, and the aluminum foil layer 101 and the protective layer 102 in the two areas are in an integral structure. The protective layer 102 is formed on the upper surface of the aluminum foil layer by coating, and its main purpose is to protect the aluminum foil layer 101 from being easily damaged. The protective layer 102 is made of a polypropylene resin coating.

[0047] In another embodiment, see Figure 3 The lower surface of the aluminum foil layer 101 may be coated with a barrier layer 105, which is also made of a polypropylene resin coating. The main purpose is to prevent the material from directly contacting the aluminum foil, protect the aluminum foil, and improve the safety of the package.

[0048] The continuous bonding area 12a and the repeated bonding area 12b need to achieve different functions. The continuous bonding area 12a needs to remain bonded to the cover body 20 from the first opening to the complete removal of the easy-tear cover aluminum foil. The repeated bonding area 12b needs to be separated and bonded to the cover body 20 many times and repeatedly after the first opening. Therefore, it is necessary to first ensure a large bonding force between the continuous bonding layer and the cover body, and a certain peeling force between the repeated bonding layer 104 and the cover body 20, but also requires a subsequent bonding force after the glass is removed. The peeling force between the continuous bonding layer 103 and the cover body 20 is greater than the peeling force between the repeated bonding layer 104 and the cover body 20. The functions of the continuous bonding area 12a and the repeated bonding area 12b are achieved by adjusting the composition of the corresponding continuous bonding layer 103 and the repeated bonding layer 104.

[0049] Specifically, the continuous adhesive layer 103 is made of food-grade hot melt adhesive, which may be Technomelt EM510-22 from the Henkel series, and is coated on the corresponding area of ​​the easy-tear cover aluminum foil to form the continuous adhesive layer 103 .

[0050] The components of the repeated bonding layer 104 include (by mass percentage): 40% ethylene-vinyl acetate copolymer, 30% thermoplastic elastomer (TPE), 20% methyl acrylate, and 10% food-grade hydrogenated rosin glycerol ester. The ethylene-vinyl acetate copolymer, thermoplastic elastomer, polypropylene, and food-grade hydrogenated rosin glycerol ester are dissolved in a solvent and sprayed on the corresponding area on the easy-tear cover aluminum foil to form the repeated bonding layer 104.

[0051] The preparation process of the above-mentioned easy-tear aluminum foil for packaging comprises the following steps: S1. Provide a circular piece of aluminum foil of a certain size; S2 forming a polypropylene resin coating on the lower surface of the aluminum foil; S3. The continuous bonding area on the lower surface of the aluminum foil is coated with the continuous bonding layer, and the repeated bonding area is coated to form the repeated bonding layer; S4. A protective layer is formed on the upper surface of the aluminum foil to obtain an easy-tear cover aluminum foil for packaging.

[0052] Example 2 This embodiment is based on the embodiment 1, and further improves the easy-tear cover aluminum foil for packaging, see Figure 4Specifically, the repeated bonding area 12b is provided with a bonding groove 12b-1 with its opening facing downward, and the cover body 20 is provided with a ridge 20a corresponding to the bonding groove 12b-1 and capable of being inserted into the bonding groove 12b-1. The bonding groove 12b-1 is directly plugged and bonded with the ridge 20a on the cover body 20, which can further improve the resealing performance and increase the number of repeated uses.

[0053] The width of the bonding groove 12b-1 accounts for 1 / 3 of the width of the repeated bonding area 12b.

[0054] In this embodiment, the repeated bonding layer 104 on the inner surface of the bonding groove 12b-1 of the repeated bonding area 12b is formed by a pressure-sensitive adhesive, and the repeated bonding layer 104 on the part other than the inner surface of the bonding groove 12b-1 of the repeated bonding area 12b is a coating composed of the following composition (by mass percentage): 40% ethylene-vinyl acetate copolymer, 30% thermoplastic elastomer (TPE), 20% methyl acrylate, and 10% food-grade hydrogenated rosin glycerol ester. The ethylene-vinyl acetate copolymer, thermoplastic elastomer, polypropylene, and food-grade hydrogenated rosin glycerol ester are dissolved in a solvent and sprayed on the corresponding area on the easy-tear cover aluminum foil to form the repeated bonding layer 104.

[0055] Example 3 This embodiment is a further optimized solution based on the embodiment 2, and is different from the embodiment 2 in that a resin coating is provided on the ridge 20a of the cover body 20 to cooperate with the pressure-sensitive adhesive to improve the bonding force and sealing performance. The resin coating is a polypropylene coating, which is sprayed on the ridge 20a.

[0056] Example 4 The easy-tear aluminum foil for packaging provided in this embodiment is different from that in Embodiment 1 in that the components of the repeated adhesive layer 104 include (by mass percentage): 45% ethylene-vinyl acetate copolymer, 30% thermoplastic elastomer (TPE), 15% methyl acrylate, and 10% food-grade hydrogenated rosin glycerol ester. The ethylene-vinyl acetate copolymer, thermoplastic elastomer, polypropylene, and food-grade hydrogenated rosin glycerol ester are dissolved in a solvent and sprayed on the corresponding area on the easy-tear aluminum foil to form the repeated adhesive layer 104.

[0057] Comparative Example 1 The easy-tear aluminum foil for packaging provided in this comparative example adopts the existing easy-tear aluminum foil for packaging. After being opened for the first time, the easy-tear aluminum foil can no longer be bonded to the cover body and overlapped on the cover body.

[0058] Comparative Example 2 The easy-tear aluminum foil for packaging provided in this comparative example is different from that in Example 1 in that no aluminum oxide spraying layer is provided.

[0059] Comparative Example 3 The easy-tear aluminum foil for packaging provided in this comparative example is different from that in Example 1 in that the repeated adhesive layer 104 is made of commercially available acrylic pressure-sensitive adhesive.

[0060] Comparative Example 4 The easy-tear aluminum foil for packaging provided in this embodiment is different from that in Embodiment 1 in that the components of the repeated bonding layer 104 include (by mass percentage): 45% ethylene-vinyl acetate copolymer, 35% thermoplastic elastomer (TPE), and 20% methyl acrylate. The ethylene-vinyl acetate copolymer, the thermoplastic elastomer, and the polypropylene are dissolved in a solvent and sprayed on the corresponding area on the easy-tear aluminum foil to form the repeated bonding layer 104.

[0061] Application Examples The above-mentioned easy-tear aluminum foil for packaging of each embodiment and comparative example was applied to a tinplate milk powder can. The can was filled with 500g of milk powder. After the easy-tear cover was opened for the first time, the repeated bonding area and the cover body were sealed and placed in a high humidity environment (humidity of 80%). The agglomeration of milk powder in the tinplate milk powder can using the easy-tear aluminum foil for packaging corresponding to each embodiment was observed for 30 days, and the weight of the milk powder in the can was weighed. The results are recorded in Table 1.

[0062] Table 1 Easy-tear aluminum foil Milk powder starting weight 30 days milk powder weight Agglomeration Example 1 500g 529 There is a small amount of lumps on the surface Example 2 500g 511 There is a small amount of lumps on the surface Example 3 500g 502 No obvious caking Example 4 500g 530 There is a small amount of lumps on the surface Comparative Example 1 500g 601 serious Comparative Example 2 500g 588 There is obvious agglomeration Comparative Example 3 500g 592 There is obvious agglomeration Comparative Example 4 500g 551 There is obvious agglomeration As can be seen from Table 1, compared with Comparative Example 1 using the existing easy-tear cover aluminum foil that cannot be repeatedly bonded, the easy-tear cover aluminum foil in each embodiment of the present invention has less weight increase due to moisture absorption of milk powder, indicating that the sealing effect on the can body is better and more conducive to the storage of milk powder inside. In particular, Example 2 uses the combination of the bonding groove and the ridge, and Example 3 uses the resin coating on the ridge, and the sealing effect is better.

[0063] In addition, relevant experiments were conducted on the influence of the number of times the easy-tear cover aluminum foil of the above embodiments and comparative examples was used on the sealing effect.

[0064] Experimental method: 500 g of milk powder was contained in the can. After the easy-tear cover was opened for the first time, the repeated bonding area and the cover body were sealed, and the can was placed in a high humidity environment (humidity of 80%). Subsequently, the can was opened once a day (sealed immediately after opening), and the agglomeration of the milk powder in the tinplate milk powder can with the easy-tear cover aluminum foil for packaging corresponding to each embodiment was observed on the 10th, 20th and 30th days, and the weight of the milk powder in the can was weighed. The results are recorded in Table 2.

[0065] Table 2 Easy-tear aluminum foil Milk powder starting weight 10 days milk powder weight 20 days milk powder weight 30 days milk powder weight Example 1 500g 506g 521g 547g Example 2 500g 503g 508g 520g Example 3 500g 504g 510g 518g Example 4 500g 509g 524g 549g Comparative Example 1 500g 556g 594g 606g Comparative Example 2 500g 522g 576g 599g Comparative Example 3 500g 514g 578g 602g Comparative Example 4 500g 516g 551g 586g As can be seen from Table 2, when using the easy-tear cover aluminum foil of Comparative Example 1, the increase in milk powder is obvious (the increase from the 20th day to the 30th day is less than that in the previous period, which may be due to the serious agglomeration of milk powder, which affects the moisture absorption of milk powder). Compared with Comparative Example 1, the easy-tear cover aluminum foil in each embodiment of the present invention, when opened and sealed once a day, the increase in weight of milk powder due to moisture absorption is still less, indicating that after repeated opening and sealing, the easy-tear cover aluminum foil in the above embodiment can still provide a certain sealing between the cover body, which is more beneficial to the storage of milk powder inside. Compared with Comparative Example 2, the sealing effect of Example 1 of the present invention in which an aluminum oxide spraying layer is set is better. Compared with Comparative Example 3, the sealing effect of the repeated bonding layer of the present invention is better. Specifically, on the 10th day, the increase in milk powder between Examples 1-4 is not very large, and the weight gain is much less than that of Comparative Example 1, indicating that within 10 days, the sealing between the easy-tear cover aluminum foil and the cover body is still considerable at the frequency of opening once a day. However, when tested again on the 20th and 30th days, it was found that the increase in Example 1 and Example 4 was significant compared with Example 2 and 3. This shows that the combination of the bonding groove and the ridge can significantly improve the sealing between the easy-tear cover aluminum foil and the cover body after opening and sealing the easy-tear cover aluminum foil multiple times, and the effect of Example 3 is more significant. Compared with Example 1, the corresponding increase in milk powder in Comparative Example 4 on the 10th, 20th and 30th days is greater, indicating that the composition of the repeated bonding layer also has a significant impact on the results.

Claims

1. An easy-tear cover aluminum foil for packaging, used in conjunction with a cover body (20) of a packaging can, the cover body (20) of the packaging can having an opening, the easy-tear cover aluminum foil being arranged at the opening to realize opening and sealing of the opening of the cover body (20), characterized in that: The easy-tear cover aluminum foil comprises a main body portion (11) located in the middle and an adhesive portion (12) arranged along the edge of the main body portion (11) for bonding with the cover body (20), the adhesive portion (12) comprising a continuous bonding area (12a) for continuous bonding with the cover body (20) and a repeated bonding area (12b) for multiple separation and bonding with the cover body (20), an aluminum oxide spray layer (201) is formed on the cover body (20) by a spraying process, and the repeated bonding area (12b) comprises a repeated bonding layer (104) in contact with the aluminum oxide spray layer (201); Measured by mass percentage, the components of the repeated bonding layer (104) include: 40-50% ethylene-vinyl acetate copolymer, 15-30% thermoplastic elastomer, 15-30% methyl acrylate, and 5-10% hydrogenated rosin glycerol ester.

2. The easy-tear aluminum foil for packaging according to claim 1, characterized in that: The repeated bonding area (12b) is provided with a bonding groove (12b-1) with an opening facing downwards, and the cover body (20) is provided with a ridge (20a) corresponding to the position of the bonding groove (12b-1) and capable of being inserted into the bonding groove (12b-1).

3. The easy-tear aluminum foil for packaging according to claim 2, characterized in that: In the layered structure of the easy-tear cover aluminum foil, the continuous bonding area (12a) comprises an aluminum foil layer (101), a protective layer (102) arranged above the aluminum foil layer (101), and a continuous bonding layer (103) arranged below the aluminum foil layer (101); the repeated bonding area (12b) comprises an aluminum foil layer (101), a protective layer (102) arranged above the aluminum foil layer (101), and the repeated bonding layer (104) is arranged below the aluminum foil layer (101).

4. The easy-tear aluminum foil for packaging according to claim 3, characterized in that: The peeling force between the continuous adhesive layer (103) and the cover body (20) is greater than the peeling force between the repeated adhesive layer (104) and the cover body (20).

5. The easy-tear aluminum foil for packaging according to claim 3, characterized in that: The repeated bonding layer (104) of the repeated bonding area (12b) outside the inner surface of the bonding groove (12b-1) is formed by hot melt adhesive.

6. The easy-tear aluminum foil for packaging according to claim 2, characterized in that: The width of the bonding groove (12b-1) accounts for 1 / 3 to 1 / 2 of the width of the repeated bonding area (12b).

7. The easy-tear aluminum foil for packaging according to claim 5, characterized in that: A resin coating is provided on the ridge (20a) of the cover body (20) for cooperating with the repeated adhesive layer (104) to enhance the bonding force and sealing performance.

8. The easy-tear aluminum foil for packaging according to claim 1, characterized in that: The easy-tear cover aluminum foil further comprises a barrier layer (105) directly formed on the lower surface of the aluminum foil layer (101).

9. The easy-tear aluminum foil for packaging according to claim 1, characterized in that: The main body portion (11) comprises at least an aluminum foil layer (101) and a protective layer (102) disposed above the aluminum foil layer (101).

10. The easy-tear aluminum foil for packaging according to claim 1, characterized in that: The length of the continuous bonding area (12a) is 1 / 4 to 1 / 2 of the length of the bonding portion (12).

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