Crazing-resistant can lid material

Abstract

The present invention provides aluminum can lid material (CES) and a method for manufacturing CES. [Solution] The CES of the present invention comprises a laminated metal strip having a polymer film coating and beneficially exhibiting crazing resistance. In some cases, the crazing-resistant CES described herein also exhibits low feathering and high abrasion resistance. The laminated metal strip may include a laminated polymer coating on the inward side of the metal strip. The laminated metal strip may further include a pre-treatment coating between the polymer film coating and the metal strip. The CES is formed by laminating a polymer film to one side of a metal strip and annealing the laminated metal strip. In some cases, the polymer film laminated to the metal strip is a polyethylene terephthalate (PET) film.

Description

[Technical Field]

[0001] Cross-reference of related applications This application claims benefit and priority to U.S. Provisional Application No. 63 / 178,313, filed on 22 April 2021, which is incorporated herein by reference in its entirety for all purposes.

[0002] This disclosure generally relates to metalworking, and more specifically to laminated metal strips suitable for use as can lid material, and to the manufacture of the same. [Background technology]

[0003] Certain metal products, such as aluminum beverage cans, may require or benefit from a protective layer between the metal and its contents. For example, beverage cans often require adequate protection between the metal of the can and the beverage it contains to avoid damage to the metal from irritating beverages such as soda and cola, and to prevent undesirable effects on the beverage, such as discoloration or changes in taste.

[0004] In many cases, there are requirements imposed on the protective layer on the inner surface of metal products. For example, the protective layer needs to adhere well to the metal product. Conventional protective layers have been found to exhibit undesirable susceptibility to damage, such as crazing and / or feathering. Therefore, conventional protective layers are ineffective. [Overview of the project]

[0005] In some embodiments, the Disclosure provides a process for preparing a crazing-resistant can lid material, comprising: applying a pretreatment coating to a first side of a metal strip; laminating a polymer film to the first side of the metal strip to form a laminated metal strip, wherein the polymer film is bonded to at least a portion of the pretreatment coating; and annealing the laminated metal strip at an annealing temperature of less than 250°C. In some cases, the can lid material does not exhibit visible crazing. In some cases, the first side of the metal strip corresponds to the inward-facing surface of a can lid formed from the metal strip. In some cases, the metal strip is an aluminum strip. In some cases, the polymer film includes a polyethylene terephthalate film. In some cases, the pretreatment coating includes a polymer or copolymer. In some cases, the annealing temperature is less than 230°C. In some cases, the annealing temperature is higher than 150°C.

[0006] In some embodiments, the Disclosure provides can lid material products prepared by any of the processes described herein. In some cases, the first side of the metal strip corresponds to the outward-facing side of the can lid material product. In some cases, the polymer film has a thickness of less than 50 μm.

[0007] In some embodiments, the Disclosure provides a beverage can having a body portion and an end cap, the end cap being formed from a can lid material prepared according to any of the processes described herein.

[0008] In some embodiments, the disclosure provides can lid materials comprising a metal strip, a pretreatment composition, and a polymer film, wherein the can lid materials do not exhibit visible crazing. In some cases, the can lid materials do not exhibit visible crazing within 24 hours after a strain test, and the strain test comprises applying a 2% strain with a force of 10 N / mm²·s. In some cases, the can lid materials do not exhibit visible crazing under UV light within 24 hours after a strain test, and the strain test further comprises coating the sample with a fluorescent marker. In some cases, the metal strip is an aluminum strip. In some cases, the polymer film comprises polyethylene terephthalate. In some cases, the pretreatment composition is a polymer or copolymer. In some cases, the polymer film exhibits an FTIR absorbance peak intensity ratio (A / B) greater than 0.4, where A represents the first absorbance peak at wavenumbers 1330 cm1–1350 cm1 and B represents the second absorbance peak at wavenumbers 1400 cm1–1420 cm-1. In some cases, the absorbance peak intensity ratio (A / B) is greater than 1.0.

[0009] In some embodiments, the disclosure provides a system comprising a lamination system for receiving a metal strip and coating a polymer film onto a first side of the metal strip, and an annealing furnace located downstream of the lamination system for receiving the laminated metal strip and heating the laminated metal strip at an annealing temperature of less than 250°C. In some cases, the metal strip is an aluminum strip. In some cases, the system further comprises a pretreatment coating application system for coating a pretreatment coating onto the metal strip, and the lamination system is configured to coat the polymer film onto the pretreatment coating. In some cases, the lamination system is coupled to a polyethylene terephthalate film feed section. In some cases, the annealing temperature is less than 230°C. In some cases, the annealing temperature is higher than 150°C.

[0010] In some embodiments, the Disclosure provides a method for evaluating the susceptibility of can lid material to crazing, the method comprising stamping can lid material to create a test sample, applying strain to the test sample to create a stress sample, and observing crazing of the stress sample. In some cases, applying strain includes applying a 2% strain with a force of 10 N / mm²·s. In some cases, observing the stress sample includes irradiating the stress sample with light. In some cases, the method further comprises coating the test sample and / or stress sample with a fluorescent marker, and observing the stress sample includes irradiating the stress sample with UV light.

[0011] This disclosure is described in detail below with reference to the attached drawings. In the drawings, similar numbers indicate similar parts. [Brief explanation of the drawing]

[0012] [Figure 1] This is a schematic diagram of a system for preparing can lid material according to a particular aspect of the present disclosure. [Figure 2] Figure 1 is an enlarged side view of the can lid material. [Figure 3A] This is a sheet of can lid material according to a particular aspect of the present disclosure. [Figure 3B] Figure 3A shows a sheet of can lid material after cutting according to a specific embodiment of this disclosure. [Figure 3C] A set of can lid blanks manufactured from the can lid material sheet shown in Figure 3A, according to a particular aspect of this disclosure, is shown. [Figure 3D] Figure 3C shows a beverage can including a can lid formed from the can lid blank, according to a particular aspect of this disclosure. [Figure 4] This is an equiangular cutout diagram showing multiple layers of a portion of a can lid material, according to a particular aspect of the present disclosure. [Figure 5] This is a flowchart showing the process for preparing can lid material according to a particular aspect of the present disclosure. [Figure 6] This is a schematic diagram of a lamination system according to a particular aspect of this disclosure. [Modes for carrying out the invention]

[0013] This specification describes a process and system for manufacturing can lid material from metal strips, such as aluminum strips. In the process described herein, a polymer film, such as polyethylene terephthalate film, is laminated to the inside of the metal strip. The resulting can lid material can be used, for example, for beverage cans.

[0014] Can lid materials manufactured according to the methods described herein exhibit advantageously improved properties. In particular, the can lid materials exhibit resistance to crazing (as defined below). In some cases, the can lid materials described herein also exhibit low feathering. The methods described herein also provide a more efficient means for applying protective films(s) to metal strips.

[0015] As further described in this disclosure, conventional polymer films (e.g., polyethylene terephthalate) have been found to be highly susceptible to crazing. Conventional polymer films are particularly prone to crazing during the crimping process that joins the can lid material to the can body material. The crimping process has been found to initiate, accelerate, or otherwise exacerbate crazing of the polymer film.

[0016] Furthermore, it was found that process conditions affect the susceptibility of the polymer film to crazing. Specifically, annealing the laminated metal strip at a low temperature reduces the susceptibility of the can lid material produced to crazing. While conventional processes promote high annealing temperatures to produce polymer films with higher adhesion and feathering resistance, the novel process described herein anneals at a relatively low temperature to produce can lid material with good adhesion and crazing resistance. In other words, this disclosure provides a process for producing crazing-resistant can lid material.

[0017] Definition and Description As used herein, the terms “invention,” “the invention,” “this invention,” and “the present invention” are intended to broadly refer to the subject matter of this patent application and all of the following claims. It should be understood that any statements containing these terms do not limit the subject matter described herein or the meaning or scope of the following claims.

[0018] This description refers to alloys identified by aluminum industry names such as "Series" or "7xxx." For an understanding of the most commonly used numbering system for naming and identifying aluminum and its alloys, see "International Alloy Designations and Chemical Composition Limits for Wrought Aluminum and Wrought Aluminum Alloys" or "Registration Record of Aluminum Association Alloy Designations and Chemical Composition Limits for Aluminum Alloys in the Form of Castings and Ingot" (both published by the Aluminum Association).

[0019] Aluminum alloys are described herein by their elemental composition in weight percentage (wt%) based on the total weight of the alloy. In specific examples of each alloy, the remainder is aluminum, and the maximum wt% of the total impurities is 0.15%.

[0020] As used herein, “crazing” specifically refers to the formation and / or propagation of small cracks on or near the surface of a protective layer (e.g., polymer film) on a metal strip, and / or on the opposite surface, for example, during the process of crimping a can lid material onto a can body material. In some cases, the cracks extend through the protective layer (e.g., polymer film), i.e., from the surface of the protective layer to the surface facing the metal strip.

[0021] As used herein, "feathering" refers particularly to the elongation and delamination of a protective layer (e.g., polymer film) on a metal strip at a metal fracture site, such as the opening of a beverage can.

[0022] This application refers to alloy tempers or grades. For an understanding of the most commonly used descriptions of alloy tempers, see "American National Standards (ANSI) H35 on Alloy and Temper Designation Systems". F temper or grade refers to aluminum alloys in the as-made state. O temper or grade refers to aluminum alloys after annealing. T1 temper or grade refers to aluminum alloys that have been cooled from hot working and naturally aged (e.g., at room temperature). T2 temper or grade refers to aluminum alloys that have been cooled from hot working, cold working, and naturally aged. T3 temper or grade refers to aluminum alloys that have been solution-heat treated, cold working, and naturally aged. T4 temper or grade refers to aluminum alloys that have been solution-heat treated and naturally aged. T5 temper or grade refers to aluminum alloys that have been cooled from hot working and artificially aged (at high temperatures). T6 temper or temper refers to aluminum alloy that has been solution-heat treated and artificially aged. T7 temper or temper refers to aluminum alloy that has been solution-heat treated and artificially overaged. T8x temper or temper refers to aluminum alloy that has been solution-heat treated, cold-worked, and artificially aged. T9 temper or temper refers to aluminum alloy that has been solution-heat treated, artificially aged, and cold-worked.

[0023] As used herein, the meanings of "a," "an," or "the" include singular and plural references unless the context explicitly indicates otherwise.

[0024] As used herein, “room temperature” means a temperature between approximately 15°C and approximately 30°C, for example, approximately 15°C, approximately 16°C, approximately 17°C, approximately 18°C, approximately 19°C, approximately 20°C, approximately 21°C, approximately 22°C, approximately 23°C, approximately 24°C, approximately 25°C, approximately 26°C, approximately 27°C, approximately 28°C, approximately 29°C, or approximately 30°C.

[0025] All ranges disclosed herein should be understood to encompass all subranges contained therein. For example, the described range "1 to 10" should be considered to include all subranges between the minimum value "1" and the maximum value "10" (and including the endpoints), i.e., all subranges starting from a minimum value of 1 or greater (e.g., 1 to 6.1) and ending from a maximum value of 10 or less (e.g., 5.5 to 10).

[0026] metal strip This disclosure provides a process and system for manufacturing can lid material from a metal strip. More specifically, the method described herein includes applying a pretreatment coating to a first side of a metal strip and laminating a polymer film to the first side of the metal strip. The composition of the metal strip to which the polymer film is laminated is not limited. The method described herein is particularly well suited to aluminum strips, but is not limited thereto. The polymer film may be applied to any suitable aluminum alloy, for example, a continuous coil of aluminum alloy. Suitable aluminum alloys include, for example, aluminum alloys from the 1xxx series, 2xxx series, 3xxx series, 4xxx series, 5xxx series, 6xxx series, 7xxx series, and 8xxx series.

[0027] As a non-limiting example, exemplary 1xxx series aluminum alloys for use as metal strips may include AA1100, AA1100A, AA1200, AA1200A, AA1300, AA1110, AA1120, AA1230, AA1230A, AA1235, AA1435, AA1145, AA1345, AA1445, AA1150, AA1350, AA1350A, AA1450, AA1370, AA1275, AA1185, AA1285, AA1385, AA1188, AA1190, AA1290, AA1193, AA1198, or AA1199. In some cases, aluminum alloys are at least 99.9% pure aluminum (for example, at least 99.91%, at least 99.92%, at least 99.93%, at least 99.94%, at least 99.95%, at least 99.96%, at least 99.97%, at least 99.98%, or at least 99.99% pure aluminum).

[0028] Non-limiting examples of 2xxx series aluminum alloys for use as metal strips include AA2001, AA2002, AA2004, AA2005, AA2006, AA2007, AA2007A, AA2007B, AA2008, AA2009, AA2010, AA2011, AA2011A, AA2111, AA2111A, AA2111B, AA2012, AA2013, AA2 014, AA2014A, AA2214, AA2015, AA2016, AA2017, AA2017A, AA2117, AA2018, AA2218, AA2618, AA2618A, AA22 19, AA2319, AA2419, AA2519, AA2021, AA2022, AA2023, AA2024, AA2024A, AA2124, AA2224, AA2224A, AA2324, AA2424, AA2524, AA2624, AA2724, AA2824, AA2025, AA2026, AA2027, AA2028, AA2028A, AA2028B, AA2028C, A A2029, AA2030, AA2031, AA2032, AA2034, AA2036, AA2037, AA2038, AA2039, AA2139, AA2040, AA2041, AA2044 , may include AA2045, AA2050, AA2055, AA2056, AA2060, AA2065, AA2070, AA2076, AA2090, AA2091, AA2094, AA2095, AA2195, AA2295, AA2196, AA2296, AA2097, AA2197, AA2297, AA2397, AA2098, AA2198, AA2099, or AA2199.

[0029] Non-limiting examples of 3xxx series aluminum alloys for use as metal strips include AA3002, AA3102, AA3003, AA3103, AA3103A, AA3103B, AA3203, AA3403, AA3004, AA3004A, AA3104, AA3204, AA3304, AA3005, AA3005A, AA3105, AA3105A, AA3105B, A This may include A3007, AA3107, AA3207, AA3207A, AA3307, AA3009, AA3010, AA3110, AA3011, AA3012, AA3012A, AA3013, AA3014, AA3015, AA3016, AA3017, AA3019, AA3020, AA3021, AA3025, AA3026, AA3030, AA3130, or AA3065.

[0030] Non-limiting examples of 4xxx series aluminum alloys for use as metal strips may include AA4004, AA4104, AA4006, AA4007, AA4008, AA4009, AA4010, AA4013, AA4014, AA4015, AA4015A, AA4115, AA4016, AA4017, AA4018, AA4019, AA4020, AA4021, AA4026, AA4032, AA4043, AA4043A, AA4143, AA4343, AA4643, AA4943, AA4044, AA4045, AA4145, AA4145A, AA4046, AA4047, AA4047A, or AA4147.

[0031] Non-limiting examples of 5xxx series aluminum alloys for use as metal strips include AA5182, AA5183, AA5005, AA5005A, AA5205, AA5305, AA5505, AA5605, AA5006, AA5106, AA5010, AA5110, AA5110A, AA5210, AA5310, AA5016, AA5017, AA5018, AA5018A, AA5019, AA5019A, AA51 19, AA5119A, AA5021, AA5022, AA5023, AA5024, AA5026, AA5027, AA5028, AA5040, AA5140, AA5041, AA5042, AA5043, AA5 049, AA5149, AA5249, AA5349, AA5449, AA5449A, AA5050, AA5050A, AA5050C, AA5150, AA5051, AA5051A, AA5151, AA5251, AA5251A, AA5351, AA5451, AA5052, AA5252, AA5352, AA5154, AA5154A, AA5154B, AA5154C, AA5254, AA5354, AA5454, AA5 554, AA5654, AA5654A, AA5754, AA5854, AA5954, AA5056, AA5356, AA5356A, AA5456, AA5456A, AA5456B, AA5556, AA5556A This may include AA5556B, AA5556C, AA5257, AA5457, AA5557, AA5657, AA5058, AA5059, AA5070, AA5180, AA5180A, AA5082, AA5182, AA5083, AA5183, AA5183A, AA5283, AA5283A, AA5283B, AA5383, AA5483, AA5086, AA5186, AA5087, AA5187, or AA5088.

[0032] Non-limiting examples of 6xxx series aluminum alloys for use as metal strips include AA6101, AA6101A, AA6101B, AA6201, AA6201A, AA6401, AA6501, AA6002, AA6003, AA6103, AA6005, AA6005A, AA6005B, AA6005C, AA6105, AA6205, AA6305, AA6006, AA6106, AA6206, AA6 306, AA6008, AA6009, AA6010, AA6110, AA6110A, AA6011, AA6111, AA6012, AA6012A, AA6013, AA6113, AA6014, AA6015 , AA6016, AA6016A, AA6116, AA6018, AA6019, AA6020, AA6021, AA6022, AA6023, AA6024, AA6025, AA6026, AA6027, AA6 028, AA6031, AA6032, AA6033, AA6040, AA6041, AA6042, AA6043, AA6151, AA6351, AA6351A, AA6451, AA6951, AA6053, AA6055, AA6056, AA6156, AA6060, AA6160, AA6260, AA6360, AA6460, AA6460B, AA6560, AA6660, AA6061, AA6061A, AA6 This may include 261, AA6361, AA6162, AA6262, AA6262A, AA6063, AA6063A, AA6463, AA6463A, AA6763, A6963, AA6064, AA6064A, AA6065, AA6066, AA6068, AA6069, AA6070, AA6081, AA6181, AA6181A, AA6082, AA6082A, AA6182, AA6091, or AA6092.

[0033] Non-limiting examples of 7xxx series aluminum alloys for use as metal strips include AA7011, AA7019, AA7020, AA7021, AA7039, AA7072, AA7075, AA7085, AA7108, AA7108A, AA7015, AA7017, AA7018, AA7019A, AA7024, AA7025, A A7028, AA7030, AA7031, AA7033, AA7035, AA7035A, AA7046, AA7046A, AA7003, AA7004, AA7005, A A7009, AA7010, AA7011, AA7012, AA7014, AA7016, AA7116, AA7122, AA7023, AA7026, AA7029, AA7 129, AA7229, AA7032, AA7033, AA7034, AA7036, AA7136, AA7037, AA7040, AA7140, AA7041, AA704 9, AA7049A, AA7149, AA7204, AA7249, AA7349, AA7449, AA7050, AA7050A, AA7150, AA7250, AA705 5, AA7155, AA7255, AA7056, AA7060, AA7064, AA7065, AA7068, AA7168, AA7175, AA7475, AA7076, AA7178, AA7278, AA7278A, AA7081, AA7181, AA7185, AA7090, AA7093, AA7095, or AA7099 may be included.

[0034] Non-limiting examples of 8xxx series aluminum alloys for use as metal strips include AA8005, AA8006, AA8007, AA8008, AA8010, AA8011, AA8011A, AA8111, AA8211, AA8112, AA8014, AA8015, AA8016, AA8017, AA8018, AA8019, AA802 1. May include AA8021A, AA8021B, AA8022, AA8023, AA8024, AA8025, AA8026, AA8030, AA8130, AA8040, AA8050, AA8150, AA8076, AA8076A, AA8176, AA8077, AA8177, AA8079, AA8090, AA8091, or AA8093.

[0035] In some embodiments, the metal strips include AA3104, AA5006, AA5182, or a combination thereof.

[0036] Although aluminum alloy products are described throughout this disclosure, the methods and products are applicable to any metal strip. In some embodiments, the metal strip is aluminum, aluminum alloy, magnesium, magnesium-based materials, titanium, titanium-based materials, copper, copper-based materials, steel, steel-based materials, bronze, bronze-based materials, brass, brass-based materials, composites, sheets used in composites, or any other suitable combination of metals or materials. The products may include monolithic materials as well as non-monolithic materials, such as roll-bonded materials, clad materials, composite materials, or various other materials. In some examples, the metal articles are metal coils, metal strips, metal plates, metal sheets, metal billets, metal ingots, etc.

[0037] Metal strips can be prepared from any suitable alloy of any temper. In certain examples, alloys can be used in tempers F, O, T3, T4, T6, and T8x. Alloys can be manufactured by direct chill casting (including direct chill co-casting), semi-continuous casting, continuous casting (including, for example, the use of a twin-belt caster, twin-roll caster, block caster, or any other continuous caster), electromagnetic casting, hot-top casting, or other casting methods.

[0038] Pre-treatment coating The process described herein, and the can lid material produced therefrom, includes applying a pretreatment coating to a metal strip. More specifically, the process of this disclosure includes applying the pretreatment coating to one side of the metal strip (e.g., a first side) and laminating a polymer film thereon. In other words, the polymer film may be bonded to at least a portion of the pretreatment coating. In some cases, the pretreatment coating is applied to the side of the metal strip corresponding to the inward-facing side of the can lid formed from the metal strip. Thus, the pretreatment coating forms a portion of the product-side of the can lid material.

[0039] As shown in the following example, pretreatment coatings can provide improved feathering performance. In detail, the adhesion between the polymer film and the metal strip can be controlled (e.g., improved) by selecting an appropriate pretreatment coating and controlling process parameters (e.g., the annealing temperature described below).

[0040] In some embodiments, the pretreatment coating is a pretreatment applied to a metal strip, such as a pretreatment suitable for metal strips. In some cases, the pretreatment coating may include a polymer or copolymer, such as a poly(vinylphosphonic acid-co-acrylic acid) copolymer. In some embodiments, a suitable commercial example of a pretreatment that can be used as a pretreatment coating is Addibond 712-CP30 from Solvay (Brussels, Belgium).

[0041] In some embodiments, the pre-treatment coating has an average thickness of 5nm to 100nm. For example, it may have an average thickness of 5nm to 95nm, 5nm to 90nm, 5nm to 85nm, 5nm to 80nm, 5nm to 75nm, 6nm to 100nm, 6nm to 95nm, 6nm to 90nm, 6nm to 85nm, 6nm to 80nm, 6nm to 75nm, 8nm to 100nm, 8nm to 95nm, 8nm to 90nm, 8nm to 85nm, 8nm to 80nm, 8nm to 75nm, 10nm to 100nm, 10nm to 95nm, 10nm to 90nm, 10nm to 85nm, 10nm to 80nm, 10nm to 75nm, 12nm to 100nm, 12nm to 95nm, 12nm to 90nm, 12nm to 85nm, 12nm to 80nm, or 12nm to 75nm.

[0042] Regarding the lower limit, the pre-treatment coating may have an average thickness greater than 5 nm, for example, greater than 6 nm, greater than 8 nm, greater than 10 nm, or greater than 12 nm. Regarding the upper limit, the pre-treatment coating may have an average thickness less than 100 nm, for example, less than 95 nm, less than 90 nm, less than 85 nm, less than 80 nm, or less than 75 nm. Polymer film

[0043] The process described herein and the can lid material produced therefrom include laminating a polymer film onto a metal strip. More specifically, the method of this disclosure includes laminating a polymer film onto a side of the metal strip (e.g., a first side) corresponding to the inward-facing side of the can lid formed from the metal strip. Thus, the polymer film forms part of the product side of the can lid material. As will be further detailed in the following examples, using a polymer film on the inward-facing side of the can lid (as opposed to, for example, lacquer) is beneficially improved in the quality of the can lid product. Furthermore, the polymer film described herein (e.g., produced according to the described process conditions) exhibits reduced feathering. Moreover, laminating a polymer film onto a metal strip is more reproducible and cleaner because impurities are usually rare in polymer films.

[0044] The polymer film is not particularly limited and may include any polymer suitable for the desired use of the can lid material (e.g., as a beverage can). Suitable polymers for the polymer film include, for example, polyethylene, polypropylene, and polyethylene terephthalate (PET). In some cases, the polymer film laminated to the metal strip is a biaxially oriented polymer such as biaxially oriented polyethylene terephthalate (BoPET) film. Suitable commercial suppliers of polymer films for use herein include, for example, Toray Plastics (Front Royal, Virginia), Mitsubishi Polyester Film (Greer, South Carolina), and DuPont Performance Polymers (Wilmington, Delaware).

[0045] In some embodiments, the polymer film further includes a coloring agent, such as a dye or colorant. In other words, the polymer film may be a colored polymer film (e.g., a colored PET film). The coloring agent used in the colored polymer film is not particularly limited. Suitable coloring agents include, for example, titanium dioxide (for example, for producing a white polymer film).

[0046] In some embodiments, the polymer film has an average thickness of 5 μm to 50 μm. For example, 5 μm to 48 μm, 5 μm to 46 μm, 5 μm to 44 μm, 5 μm to 42 μm, 5 μm to 40 μm, 6 μm to 50 μm, 6 μm to 48 μm, 6 μm to 46 μm, 6 μm to 44 μm, 6 μm to 42 μm, 6 μm to 40 μm, 8 μm to 50 μm, 8 μm to 48 μm, 8 μm to 46 μm, 8 μm to 44 μm, 8 μm to 42 It has an average thickness of μm, 8μm~40μm, 10μm~50μm, 10μm~48μm, 10μm~46μm, 10μm~44μm, 10μm~42μm, 10μm~40μm, 12μm~50μm, 12μm~48μm, 12μm~46μm, 12μm~44μm, 12μm~42μm, or 12μm~40μm.

[0047] Regarding the lower limit, the polymer film may have an average thickness greater than 5 μm, for example, greater than 6 μm, greater than 8 μm, greater than 10 μm, or greater than 12 μm. Regarding the upper limit, the polymer film may have an average thickness less than 50 μm, for example, less than 48 μm, less than 46 μm, less than 44 μm, less than 42 μm, or less than 40 μm.

[0048] Examples of appropriate average thicknesses for polymer films include 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, 16 μm, 17 μm, 18 μm, 19 μm, 20 μm, 21 μm, 22 μm, 23 μm, 24 μm, 25 μm, 26 μm, 27 μm, 28 μm, 29 μm, 30 μm, 31 μm, 32 μm, 33 μm, 34 μm, 35 μm, 36 μm, 37 μm, 38 μm, 39 μm, 40 μm, and any thickness in between.

[0049] In some embodiments, the process of the present disclosure includes laminating multiple layers of polymer film onto a metal strip. In these embodiments, each layer of polymer film may independently be a polymer film as described above. In some cases, multiple layers of polymer film are laminated onto a metal strip, and one or more layers are identical (e.g., with respect to composition and / or thickness). In some cases, multiple layers of polymer film are laminated onto a metal strip, and the layers are not identical (e.g., with respect to composition and / or thickness).

[0050] As described above, conventional can lid materials preferably include a heat-treated polymer film (e.g., high-temperature treatment such as pretreatment). High-temperature treatment was considered necessary to provide certain properties such as high adhesion and low feathering. However, conventional heat-treated polymer films are highly susceptible to crazing. Specifically, crazing is observed on or near the surface of the amorphous polymer film (e.g., PET film) laminated to the inward-facing (e.g., product) side of the can lid material. It has been found that heat treatment (e.g., high-temperature treatment) alters the conformation of the polymer film. When the conformation of the polymer film is altered, its susceptibility to crazing can increase. Stress applied to the can lid material (e.g., during the crimping process with the can body material) exacerbates this crazing. Crazing on the inward-facing side of the can lid material is particularly problematic because the product contained in the can (e.g., liquid beverage) can further exacerbate the crazing and / or react with the metal strip. This can affect the integrity and quality of both the can and the product by causing metal to leach out of the metal strip.

[0051] To address the crazing problem, in some embodiments of the processes described herein and in the can lid materials manufactured therefrom, the polymer film does not contain high-temperature treated polymer. In other words, in some embodiments, the conformation of the polymer film is substantially unchanged. In some cases, the polymer film has a similar conformation before and after the manufacture of the can lid material. In some cases, the polymer film has the same conformation before and after manufacture. In some embodiments, this is achieved by preventing or limiting the melting of the polymer film during lamination. In some embodiments, this is achieved by preventing or limiting the exposure of the polymer film to high temperatures, for example, above 200°C, above 210°C, above 220°C, above 230°C, above 240°C, or above 250°C. Using the non-temperature treated polymer films described herein is advantageous in that can lid materials with low susceptibility to crazing are manufactured. That is, can lid materials manufactured according to this disclosure are crazing-resistant. Beneficial in that the can lid material may also exhibit low susceptibility to feathering.

[0052] FTIR trial In some cases, the suitability of a polymer film for can lid material can be evaluated by a Fourier transform infrared spectroscopy (FTIR) test developed by the inventors. FTIR is a technique used in various quantitative analyses to obtain infrared spectra of absorbance or emission of solids, liquids, or gases. In the FTIR test of this disclosure, the FTIR absorbance spectrum of the polymer film is analyzed to determine its suitability for use as a can lid material. Specifically, the FTIR test determines the ratio (A / B) of the absorbance peak intensity at a first wavenumber (A) to the absorbance peak intensity at a second wavenumber (B).

[0053] The FTIR absorbance spectrum can be obtained by a commercially available spectrometer, such as Model 670 manufactured by Varian, Inc. (Palo Alto, California). In some cases, the FTIR spectrometer may include an attenuated total reflection (ATR) attachment, such as a diamond ATR. An example of a commercially available ATR attachment is the GladiATR manufactured by Pike Technologies (Madison, Wisconsin). In some embodiments, the FTIR absorbance spectrum is obtained by measuring at one position on the polymer film. In some embodiments, the FTIR absorbance spectrum is obtained by measuring at multiple positions (e.g., at least 2, at least 3, or at least 4 positions) on the polymer film and averaging the output from the spectra.

[0054] The suitability of the polymer film for the can lid material may be determined by evaluating and comparing the relative intensities of two absorbance peaks. That is, the suitability of the polymer film may be determined from the ratio (A / B) of the FTIR absorbance peak intensity (A) at the first wave number to the absorbance peak intensity (B) at the second wave number. In some cases, the suitability of the polymer film (as used herein) refers to the sensitivity to crazing of the polymer film before and / or after annealing.

[0055] In some embodiments, the first absorbance peak (A) of the FTIR ratio is a peak at a wave number of 1330 cm -1 ~1350 cm -1 For the lower limit, the first absorbance peak (A) may peak at a wave number greater than 1330 cm -1 such as greater than 1332 cm -1 greater than 1334 cm -1 greater than 1336 cm -1 greater than 1338 cm -1 For the upper limit, the first absorbance peak (A) is less than 1350 cm -1 such as less than 1348 cm -1 less than 1346 cm -1 less than 1344 cm -1Less than 1342cm -1 A peak can occur at wavenumbers below a certain level.

[0056] In some embodiments, the first absorbance peak (A) is at wavenumber 1330 cm⁻¹. -1 , 1331cm -1 , 1332cm -1 , 1333cm -1 , 1334cm -1 , 1335cm -1 , 1337cm -1 , 1338cm -1 , 1339cm -1 , 1340cm -1 , 1341cm -1 , 1342cm -1 , 1343cm -1 , 1344cm -1 , 1345cm -1 , 1346cm -1 , 1347cm -1 , 1348cm -1 , 1349cm -1 , or 1345cm -1 , or any wavenumber between them.

[0057] In some embodiments, the second absorbance peak (B) of the FTIR ratio is at 1400 cm⁻¹. -1 ~1420cm -1 The peak occurs at this wavenumber. Regarding the lower limit, the second absorbance peak (B) is at 1400 cm⁻¹. -1 Larger, for example, 1402cm -1 Larger, 1404cm -1 Larger, 1406cm -1 Larger, or 1408cm -1 It can peak at higher wavenumbers. Regarding the upper limit, the second absorbance peak (B) is at 1420 cm⁻¹. -1 Less than, for example, 1418cm -1 Under 1416cm -1 Under 1414cm -1 Less than 1412cm -1 A peak can occur at wavenumbers below a certain level.

[0058] In some embodiments, the second absorbance peak (B) occurs at wavenumber 1400 cm⁻¹. -1 , 1401cm -1 , 1402cm -1 , 1403cm -1 , 1404cm -1 , 1405cm -1 , 1407cm -1 , 1408cm -1 , 1409cm -1 , 1410cm -1 , 1411cm -1 , 1412cm -1 , 1413cm -1 , 1414cm -1 , 1415cm -1 , 1416cm -1 , 1417cm -1 , 1418cm -1 , 1419cm -1 , or 1415cm -1 , or any wavenumber between them.

[0059] Polymer films exhibiting a high FTIR ratio (A / B) are particularly suitable for the can lid materials described herein. In particular, using polymer films having a high FTIR ratio results in can lid materials that are less susceptible to crazing. In some embodiments, the polymer film exhibits an absorbance peak intensity ratio (A / B) greater than 0.4, e.g., greater than 0.5, greater than 0.6, greater than 0.8, greater than 1.0, greater than 1.1, greater than 1.2, greater than 1.3, greater than 1.4, or greater than 1.5. With respect to the upper limit, the absorbance peak intensity ratio (A / B) of the polymer film may be less than 2.0, e.g., less than 1.9, less than 1.8, less than 1.7, or less than 1.6.

[0060] Rakka In some embodiments, can lid material manufactured according to this disclosure includes a lacquer layer. In some cases, for example, the lacquer layer may be applied to the surface of a metal strip, for example, the outward-facing surface. In these embodiments, the lacquer forms a protective layer between the metal strip and the contents of the can lid material (e.g., the contents of a beverage can formed from the can lid material).

[0061] The composition of the lacquer suitable for use in the processes described herein is not particularly limited. In some cases, the lacquer may contain aqueous and / or solvent-based compositions, which may preferably be sprayed, poured, or otherwise applied to the surface of the metal strip. In some embodiments, the lacquer applied to the surface of the metal strip contains an epoxy-based solution. A commercial example of a composition suitable for use as lacquer for this disclosure is a packaging coating manufactured by AkzoNobel (Amsterdam, Netherlands).

[0062] In some embodiments, the lacquer layer has an average thickness of 2 μm to 20 μm. For example, 2 μm to 18 μm, 2 μm to 16 μm, 2 μm to 14 μm, 2 μm to 12 μm, 2 μm to 10 μm, 3 μm to 20 μm, 3 μm to 18 μm, 3 μm to 16 μm, 3 μm to 14 μm, 3 μm to 12 μm, 3 μm to 10 μm, 4 μm to 20 μm, 4 μm to 18 μm, 4 μm to 16 μm, 4 μm to 14 μm, It has an average thickness of 4μm~12μm, 4μm~10μm, 5μm~20μm, 5μm~18μm, 5μm~16μm, 5μm~14μm, 5μm~12μm, 5μm~10μm, 6μm~20μm, 6μm~18μm, 6μm~16μm, 6μm~14μm, 6μm~12μm, or 6μm~10μm.

[0063] Regarding the lower limit, the lacquer layer may have an average thickness greater than 2 μm, for example, greater than 3 μm, greater than 4 μm, greater than 5 μm, or greater than 6 μm. Regarding the upper limit, the lacquer layer may have an average thickness less than 20 μm, for example, less than 18 μm, less than 16 μm, less than 14 μm, less than 12 μm, or less than 10 μm.

[0064] Examples of suitable average thicknesses of the lacquer layer include 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, 16 μm, 17 μm, 18 μm, 19 μm and 20 μm, as well as any thickness in between.

[0065] In some cases, the thickness of the lacquer layer may be expressed in terms of basis weight. In some embodiments, the lacquer layer has a basis weight of 1 g / m 2 ~15 g / m 2 For example, 1 g / m 2 ~14 g / m 2 、1 g / m 2 ~12 g / m 2 、1 g / m 2 ~10 g / m 2 、1 g / m 2 ~8 g / m 2 [[ID=2D]]、1 g / m 2 ~6 g / m 2 、1.5 g / m 2 ~15 g / m 2 、1.5 g / m 2 ~14 g / m 2 、1.5 g / m 2 ~12 g / m 2 、1.5 g / m 2 ~10 g / m 2 、1.5 g / m 2 ~8 g / m 2 、1.5 g / m 2 ~6 g / m 2 、2 g / m 2 ~15 g / m 2 、2 g / m 2 ~14 g / m 2 、2 g / m 2 ~12 g / m 2 、2 g / m 2 ~10 g / m 2 、2 g / m 2 ~8 g / m 2 、2 g / m 2 ~6 g / m 2 、2.5 g / m 2 ~15 g / m 2 、2.5 g / m 2 ~14 g / m 2 、2.5 g / m 2~12g / m 2 2.5g / m 2 ~10g / m 2 2.5g / m 2 ~8g / m 2 2.5g / m 2 ~6g / m 2 , 3g / m 2 ~15g / m 2 , 3g / m 2 ~14g / m 2 , 3g / m 2 ~12g / m 2 , 3g / m 2 ~10g / m 2 , 3g / m 2 ~8g / m 2 , or 3g / m 2 ~6g / m 2 It has a basis weight of [amount].

[0066] Regarding the lower limit, the lacquer layer is 1 g / m 2 Larger, for example, 1.5 g / m 2 Larger, 2g / m 2 Larger 2.5g / m 2 Larger than 3g / m 2 It may have a larger basis weight. Regarding the upper limit, the lacquer layer is 15 g / m². 2 Less than, for example, 14 g / m² 2 Less than 12g / m² 2 Less than 10g / m² 2 Less than 8g / m² 2 Less than 6 g / m² 2 It may have a basis weight of less than .

[0067] An example of a suitable basis weight for a lacquer layer is 1 g / m². 2 1.5g / m 2 , 2g / m 2 2.5g / m 2 , 3g / m 2 3.5g / m 2 4g / m 2 4.5g / m 2 5g / m 2 5.5g / m 2 , 6g / m 2 6.5g / m 2 7g / m 27.5g / m 2 , 8g / m 2 9g / m 2 10g / m 2 , 11g / m 2 12g / m 2 13g / m 2 14g / m 2 15g / m 2 , and any thickness between them.

[0068] In some embodiments, can lid materials manufactured according to this disclosure include an adhesive coating between a metal strip and a lacquer layer. More specifically, the adhesive coating may be applied to the metal strip and the lacquer may be applied thereon. The adhesive coating conveniently fixes the lacquer to the metal strip. In some embodiments, the adhesive coating is a pretreatment applied to the metal strip, e.g., a pretreatment suitable for the metal strip. The adhesive coating between the metal strip and the lacquer layer may be the same as or different from the adhesive coating between the polymer film and the metal strip. Commercial examples of suitable pretreatments that can be used as the adhesive coating between the metal strip and the lacquer include titanium zirconium (Ti-Zr) based pretreatments or chromium (Cr3) based pretreatments, e.g., Bonderite from Henkel Adhesive Technologies (Düsseldorf, Germany).

[0069] Process and system for preparing can lid material In some embodiments, the present disclosure provides a process for preparing can lid material. The process described herein advantageously produces crazing-resistant can lid material. In some embodiments, the process described herein produces laminate can lid material that exhibits high performance in other test parameters, such as an acetic acid test, which can evaluate the corrosion resistance of the laminate to acidic conditions that can cause delamination. These processes involve applying a pretreatment coating to a metal strip, laminating a polymer film to the metal strip, and annealing the laminated metal strip at an annealing temperature (T AThis may include annealing at a temperature of less than 250°C. According to the process of this disclosure, annealing a laminated metal strip may include annealing at a temperature of less than 250°C T A This includes heating up to a certain temperature. Annealing at this temperature prevents the polymer film from becoming amorphous (e.g., due to melting), thereby significantly improving the performance characteristics of the can lid material produced.

[0070] In some embodiments, the metal strip is coated on both sides. In embodiments of this disclosure, the metal strip may be laminated on one side and lacquered on the other. For example, the metal strip may be laminated on the inward side and lacquered on the outward side, but other configurations can also be used. This hybrid laminate / lacquered metal strip allows for improved functional performance on the inside of the can lid material by using a polymer film, while maintaining high decorative and functional performance on the outside of the can lid material by using lacquer.

[0071] In some cases, the laminated metal material is sent directly from the lamination process to the annealing process (e.g., an annealing furnace). In other cases, the laminated metal material is sent directly from the lamination process to the lacquering system and then to the annealing process (e.g., an annealing furnace). In some cases, the laminated metal material is quenched (e.g., air quenching or water quenching) before entering the lacquering system.

[0072] The processes and systems described herein, as well as various additional features and examples thereof, are described with reference to the drawings. In the drawings, similar numbers indicate similar elements, and directional descriptions are used to illustrate exemplary embodiments, but, like the exemplary embodiments, they are not used to limit this disclosure. Elements included in the drawings herein may not be depicted to scale.

[0073] Figure 1 is a schematic diagram of a system 100 for preparing can lid material according to a particular aspect of the present disclosure. A metal strip 102 is sent to a pre-treatment coating system 112, which applies a pre-treatment coating to the metal strip 102. The pre-treatment coating system 112 may be any suitable system for applying a pre-treatment coating to the metal strip 102.

[0074] In some cases, the metal strip 102 may be treated before entering the pretreatment coating system. In some embodiments, the surface of the metal strip 102 may be degreased (for example, using an acidic solution) to clean the surface. In some embodiments, the metal strip 102 may be preheated before entering the pretreatment coating system.

[0075] The pre-treated metal strip 104 is sent to the lamination system 114. The metal strip 102, as the pre-treated metal strip 104, passes through the lamination system 114 to coat the polymer film 120 on one side of the metal strip 102. In some cases, the polymer film can be coated on both sides of the metal strip 102. The lamination system 114 may be any suitable system for laminating the polymer film 120 onto the metal strip 102. In some cases, the lamination system 114 is a hot-melt lamination system. The laminated metal strip 106 exits the lamination system 114, bonding the metal strip 102 with the polymer film 120.

[0076] In some embodiments, the laminated metal strip 106 can be fed into an optional lacquering system 116. The lacquer 124 is applied to the metal strip 102 by the lacquering system 116. The lacquering system 116 may be any suitable system for applying the lacquer 124 to the metal strip 102. The lacquering system 116 may include a furnace for heating and curing the lacquer 124 onto the metal strip 102. In some cases, the lacquering system 116 is located downstream (e.g., after) the lamination system 114. In some cases, the lacquering system 116 is located upstream (e.g., before) the annealing furnace 118. In some cases, the lacquering system 116 is located upstream of either the lamination system 114 or the preheating furnace 112. In some cases, the lacquering system 116 is located downstream of both the lamination system 114 and the annealing furnace 118. In the embodiment shown in Figure 1, the lacquer coating system 116 is located between the lamination system 114 and the annealing furnace 118. The laminated and lacquered metal strip 108 can exit the lacquer coating system 116.

[0077] If the upstream lacquering system 116 is used, the laminated and lacquered metal strip 108 can be sent into the annealing furnace 118. In some cases, if the lacquering system 116 is not used between the lamination system 114 and the annealing furnace 118, the laminated metal strip 106 can be sent into the annealing furnace.

[0078] The annealing furnace 118 may be located downstream (e.g., later) of the lamination system 114 and, optionally, the lacquering system 116. In some cases, the annealing furnace 118 may be located immediately downstream of the lacquering system 116, so that the lacquered laminate metal strips 108 leaving the lacquering system 116 are sent into the annealing furnace 118 before being sent to or coming into contact with other machines or systems.

[0079] The annealing furnace 118 sets the temperature of the lacquered laminated metal strip 108 to an annealing temperature (T A Raise the temperature to ) Annealing temperature T A The melting temperature of polymer film 120 (T m ) may be lower than. In some embodiments, the annealing temperature T A is a temperature of 175°C~250°C, such as 175°C~245°C, 175°C~240°C, 175°C~235°C, 175°C~230°C, 175°C~225°C, 180°C~250°C, 180°C~245°C, 180°C~2 40°C, 180°C~235°C, 180°C~230°C, 180°C~225°C, 185°C~250°C, 185°C~245°C, 185°C~240°C, 185°C~235°C, 185°C~230°C, 185°C~225°C These are temperatures of 190°C~250°C, 190°C~245°C, 190°C~240°C, 190°C~235°C, 190°C~230°C, 190°C~225°C, 195°C~250°C, 195°C~245°C, 195°C~240°C, 195°C~235°C, 195°C~230°C, 195°C~225°C, 200°C~250°C, 200°C~245°C, 200°C~240°C, 200°C~235°C, 200°C~230°C, or 200°C~225°C. Regarding the lower limit, T2 may be higher than 175°C, for example, higher than 180°C, higher than 185°C, higher than 190°C, higher than 195°C, or higher than 200°C. Regarding the upper limit, T A The temperature may be less than 250°C, for example, less than 245°C, less than 240°C, less than 235°C, less than 230°C, or less than 225°C.

[0080] The lacquered laminated metal strip 108 spends time in an annealing furnace 118 of sufficient length to impart to the lacquered laminated metal strip 108 desired properties, including annealing of the metal strip 102 and desired adhesion of the polymer film 120. The time spent in the annealing furnace 118 may be based on the length of the furnace and the speed of the metal strip. In some cases, the time may be in the range of about 2 to about 30 seconds, about 9 to about 15 seconds, about 10 to about 14 seconds, or about 12 seconds. In some cases, the time can be adjusted as needed (e.g., by adjusting the speed of the metal strip) to compensate for temperature changes in the annealing furnace 118.

[0081] After leaving the annealing furnace 118, the can lid material 110 (e.g., annealed, lacquered, and laminated metal strip) may optionally be quenched in air or a quenching fluid (e.g., water), or by applying a coolant to the can lid material 110. The can lid material 110 can be quenched or cooled by other means immediately after leaving the annealing furnace 118.

[0082] In some cases, the can lid material 110 manufactured by system 100 may include a metal strip 102, on which a layer of laminate polymer film 120 is applied to the first side and an optional lacquer layer 124 is applied to the second side, as shown in Figures 1 and 2.

[0083] Figure 2 is an enlarged side view of the can lid material 110 of Figure 1. The can lid material 110 includes a metal strip 102 sandwiched between a laminate polymer film 120 and an optional lacquer layer 124. A pre-treatment coating 202 is sandwiched between the laminate polymer film 120 and the metal strip 102, and between the optional lacquer layer 124 and the metal strip 102.

[0084] Figures 3A to 3D are isometric projections of the can lid material 302 at various stages of manufacturing. In some cases, the can lid material 302 is the can lid material described herein, comprising a laminated polymer film and lacquer.

[0085] Figure 3A shows a sheet of can lid material 302 according to a particular aspect of the present disclosure. The sheet of can lid material 302 may be can lid material 110 shown in Figure 1 or a similar can lid material. Figure 3B shows the sheet of can lid material 302 of Figure 3A after it has been cut. The sheet of can lid material 302 can be cut by die-cutting, punching, or by other means to produce can lid blanks 306 as shown in Figure 3C. Figure 3C shows a set of can lid blanks 306 produced from the sheet of can lid material of Figure 3A. Figure 3D shows a beverage can 310 including the can lid blanks 306 of Figure 3C and a can lid 308 formed by the can body.

[0086] The can lid 308 includes an outward-facing surface (as seen, for example, in Figure 3D) and an inward-facing surface (as seen, for example, facing the inside of the beverage can 310). As described herein, the can lid 308 can be formed such that the laminate polymer film is located on the inward-facing side.

[0087] Conventional crimping processes may be used to form the beverage can shown in Figure 3D from the can lid blank 306 and can body shown in Figure 3C. In some embodiments, the present disclosure provides a method for preparing a beverage can, comprising crimping a can lid blank formed from the can lid material described herein onto a can body. The crimping process may include the steps of placing the can lid blank on the can body and applying a crimping chuck to the can lid. The method may also optionally include the step of crimping the can lid and can body using a crimping roll. The crimping roll may form and / or engage a curl in the can lid, which may press the outer curl against the chuck to form a seal between the can lid and the can body.

[0088] As described above, conventional can lid materials (e.g., those containing amorphous polymer films) exhibit crazing after the crimping process. In contrast, the can lid materials of this disclosure are crazing-resistant. In some embodiments, for example, the can lid materials do not exhibit visible crazing before and / or after the crimping process.

[0089] Figure 4 is an isometric cutaway showing multiple layers of a portion of a can lid material 400 prepared according to this disclosure. The can lid material 400 may include a metal layer 404, such as aluminum (e.g., an aluminum alloy), surrounded by a laminate polymer film 402, and an optional lacquer layer 406. The can lid material 400 may be the can lid material 110 of Figure 1.

[0090] Figure 5 is a flowchart of step 500 for preparing a can lid material according to an embodiment of the present disclosure. Block 502 provides a metal strip. The metal strip may be an aluminum strip suitable for forming a can lid material. Block 503 degreases the surface of the metal strip optionally (e.g., using an acidic solution). Block 504 applies a pretreatment coating to the metal strip. Block 506 laminates the metal strip with a polymer film, e.g., a PET film. Block 508 anneals the laminated metal strip at an annealing temperature T A The metal strips are annealed. In block 510, the annealed metal strips are optionally quenched (for example, in air). In block 512, a wax coating may optionally be applied to one or both sides of the metal strips.

[0091] Figure 6 is a schematic diagram of a lamination system 614 according to a particular aspect of this disclosure. The lamination system 614 may be the lamination system 114 of Figure 1 or another lamination system. Certain elements shown in Figure 6 are shown at an exaggerated scale for illustrative purposes only.

[0092] The lamination system 614 may include a pair of rollers 652 over which the pre-treated metal strip 604 can pass. The pre-treated metal strip 604 may include a metal strip 602 pre-treated by a preheating furnace 112, as shown in Figure 1. In some cases, the pre-treated metal strip 604 includes one or more conversion layers 603.

[0093] As it passes through roller 652, the polymer film 624 is pressed against the pre-treated metal strip 604 to produce a laminated metal strip 606. In some cases, a single laminating system 614 may have an additional set of rollers for providing a second polymer film to the opposite side of the preheated metal strip 604 from the polymer film 624. In some cases, roller 652 may additionally coat the second polymer film to the opposite side of the pre-treated metal strip 604 from the polymer film 624.

[0094] Characteristics of can lid material As described above, the can lid material of this disclosure, for example, the can lid material manufactured according to the process described above, exhibits many advantageously improved properties.

[0095] In some embodiments, the can lid material of this disclosure exhibits low susceptibility to crazing. In other words, this disclosure describes a crazing-resistant can lid material. As stated above, “crazing” refers, in particular, to the formation and / or propagation of small cracks on or near the surface of the protective layer (e.g., polymer film) on the metal strip, for example, during the crimping process of the can lid material onto the can body material. In some embodiments, the can lid material does not exhibit visible crazing. For example, the can lid material may not exhibit visible crazing before and / or after the crimping process.

[0096] In some cases, the can lid materials of this disclosure show improved results in a 2% strain test. The 2% strain test used herein may include an evaluation of the susceptibility of the can lid material to crazing in response to tensile stress. In detail, the strain test can simulate a crimping process in which crazing is particularly problematic. This test may include stamping a sample of the can lid material (e.g., using an automatic press). The sample can be stamped into any shape suitable for tensile strength testing. The stamped sample is then subjected to a tensile strength test of 10 N / mm². 2 Stress is applied by adding a 2% strain in s. The stressed sample is then left, for example, at room temperature for 24 hours, during which time any crazing will be visible.

[0097] In some cases, a 2% strain test may be performed on aged samples to maximize their sensitivity to crazing. For example, the can lid material of the sample may be heated in an furnace for several days (e.g., 2, 3, or 4 days) at a temperature 10°C lower than the glass transition temperature of the polymer film.

[0098] In some cases, the crazing may be visible on the can lid material, for example, to the naked eye. In some cases, the crazing is visible with the help of a light source. For example, light may be shone onto the sample at a flat angle to the sample from the direction of the camera (e.g., parallel to the sample). In some embodiments, the light source may be visible light shone onto the sample. In some embodiments, the light source may be UV light shone onto the sample. To facilitate observation using a UV light source, the sample may be coated with a fluorescent marker. For example, the sample may be covered with a fluorescent marker (e.g., FBP-914 from MET-L-CHEK (Santa Monica, California)) for 10 minutes and then washed off with water. Fluorescence can significantly increase the visibility of the crazing under UV light.

[0099] In some embodiments, the can lid material does not show visible crazing after strain testing. In some embodiments, the can lid material does not show visible crazing under light after strain testing. In some embodiments, the can lid material does not show visible crazing under UV light after strain testing.

[0100] In some embodiments, the can lid materials of this disclosure exhibit improved adhesion. In some cases, for example, the can lid materials of this disclosure exhibit improved results in a 3% acetic acid test. As used herein, the 3% acetic acid test may involve evaluating the coating's resistance to a diluted acidic medium at approximately 100°C for 30 minutes. This test may involve cutting cross-hatch marks onto a sample, placing the sample in a 3% acetic acid solution at approximately 100°C for 30 minutes, and then removing the sample to cool. After cooling, an additional series of cross-cuts are made on each sample, and adhesive tape is placed over the cross-hatch areas before and after the acid bath and carefully removed at an angle of approximately 60° for 0.5 to 1 second. Using the test results (e.g., based on the presence and strength of delamination), it can be determined whether the metal strip is acceptable or unacceptable, taking into account the desired specifications. The degree of delamination is observed and evaluated on a scale of 1 (minimal delamination) to 5, to the extent that delamination occurs. When used herein, a sample passes the 3% acetic acid test if it shows little to no delamination.

[0101] Conventional metal strips (e.g., metal strips with a lacquer layer applied to the outer surface) often perform poorly in the 3% acetic acid test. In some cases, the annealed laminate can lid materials disclosed herein yield more favorable results in the 3% acetic acid test (e.g., no or minimal delamination) than standard lacquered can lid materials. In some embodiments, the can lid materials disclosed herein pass the 3% acetic acid test with minimal delamination. In some cases, the annealed laminate can lid materials disclosed herein pass the 3% acetic acid test without any delamination.

[0102] In some embodiments, the can lid material of this disclosure exhibits reduced feathering. In some cases, for example, the can lid material of this disclosure exhibits improved results in a standard feathering test. As used herein, a standard feathering test may be performed on a can lid and may include immersing the can lid in a bath of deionized water at approximately 75°C for 30 minutes, rinsing the can lid with cold deionized water, returning the can lid to room temperature, and then immediately opening the tab on the can lid. Feathering can be observed and measured on a score panel or at the outlet opening. In some cases, the feathering test may be performed on a flat metal sheet, for example, a flat sheet of can lid material. In such cases, the feathering test may be performed by immersing the sample in deionized water at 80°C for 40 minutes, then cooling the sample to room temperature, cutting the sample, and separating the metal strip by pulling it away from the cut. In any feathering test, the amount of feathering can be measured, and can lid material exhibiting a maximum feathering amount of less than 0.7 mm is considered to pass the test.

[0103] In some examples, the can lid materials described herein pass standard feathering tests. In some embodiments, the can lid materials exhibit a maximum feathering amount of less than 0.7 mm, for example, less than 0.6 mm, less than 0.5 mm, less than 0.4 mm, less than 0.3 mm, or less than 0.2 mm. This feathering amount may be located at a specific indicated position along the opening of the open can lid. The amount of feathering of the film also depends on the design of the cutting, forming, and punching tools for the product.

[0104] Examples The following embodiments are helpful in further illustrating the present invention, but do not constitute any limitation of the invention. Rather, various embodiments, modifications, and equivalents thereof may be used, and such may be suggested to those skilled in the art without departing from the spirit of the invention, as can be seen by reading this specification.

[0105] Example 1: Can Lid Material Several samples of can lid material were prepared according to the disclosed method. The samples were prepared using AA5182 aluminum alloy with a thickness of 0.208 mm as a metal strip. Each sample tested is shown in Table 1. Each sample was pretreated as shown in Table 1, and the can lid material was prepared by laminating a 12 μm polymer film to the first side (inside) and annealing at the annealing temperature.

[0106] Various tests were conducted to evaluate the performance of the above sample can lid material. Several tests were performed to evaluate the susceptibility of the can lid material to crazing. Each sample was tested according to the above FTIR test, and each sample was tested from the middle of the sheet. The FTIR ratio (A / B) was approximately 1340 cm². -1 The absorbance peak intensity (A) is approximately 1409 cm⁻¹. -1 The absorbance peak intensity (B) was calculated by comparison. The 2% strain test described above was performed to observe crazing. The strain test was performed on samples 1-22 as an aged example. For samples 9-24, after the 2% strain test, the samples were coated with MET-L-CHEK (Santa Monica, California) fluorescent marker FBP-914 for 10 minutes and washed with water. To better show crazing, the samples were irradiated with UV light. The results of these tests are shown in Table 2. [Table 1] [Table 2]

[0107] As the above sample demonstrates, aged can lid material is more prone to crazing as the annealing temperature increases. This demonstrates that a lower annealing temperature is beneficial for providing crazing resistance.

[0108] Furthermore, to evaluate the susceptibility of the lid material to aging, several samples (Samples 4, 5, 7, 12, 15, 22, 23, and 24) were selected for additional crazing tests. In this test, the lid material was subjected to a seaming process. Lids prepared from the sample lid material were placed on empty can bodies (AA3104, 0.33 mm) and seamed using a laboratory seamer (Stiller DV10PS-SD). To seam the lid to the body, the edges of the lid were curled and compressed around the periphery of the body. After seaming, the cans were stored for 24 hours. Then, the lids at this seam were covered with a fluorescent marker for 10 minutes, washed, and illuminated under UV light to observe crazing. The results of this test are shown in Table 3.

[0109] Furthermore, to evaluate the susceptibility of the can lid material to corrosion, a filling test corrosion evaluation was performed on several samples (Samples 4, 12, and 22). Lids prepared from the sample can lid material were placed on the can body (AA3104, 0.33 mm) and crimped using a laboratory seamer (Stiller DV10PS-SD). Various beverages were filled into the cans. The cans were then stored upside down for 6 months, with the seam between the lid and the body covered with beverage. These cans were evaluated for corrosion at 3 and 6 months. As reported in Table 3, no corrosion was observed. [Table 3]

[0110] As the above sample demonstrates, aged can lid material is more prone to crazing as the annealing temperature increases. This further demonstrates that lower annealing temperatures can beneficially impart crazing resistance, which is advantageous for downstream commercial processes.

[0111] To evaluate adhesion, each sample was tested according to the 3% acetic acid test described above, and the test was performed from the middle of the sheet. The degree of delamination was evaluated on a scale from 1 (minimal delamination) to 5, up to the point where delamination was observed. To evaluate feathering, the above test was performed by immersing the sample in demineralized water at 80°C for 40 minutes. Feathering was evaluated at the middle of the sheet, and each sample was evaluated twice. The results of these tests are shown in Table 4. [Table 4]

[0112] The above samples demonstrated excellent adhesion and low susceptibility to feathering. Embodiment

[0113] Where used below, any reference to a series of embodiments should be understood as a disjunctive reference to each of those embodiments (for example, “Embodiments 1-4” should be understood as “Embodiments 1, 2, 3, or 4”).

[0114] Embodiment 1 is a process for preparing a crazing-resistant can lid material, comprising: applying a pretreatment coating to a first side of a metal strip; laminating a polymer film to the first side of the metal strip to form a laminated metal strip, wherein the polymer film is bonded to at least a portion of the pretreatment coating to form the laminated metal strip; and annealing the laminated metal strip at an annealing temperature of less than 250°C.

[0115] Embodiment 2 is a step described in any of the preceding or succeeding embodiments, wherein the can lid material does not exhibit visible crazing.

[0116] Embodiment 3 is the process described in any of the preceding or succeeding embodiments, wherein the first side of the metal strip corresponds to the inward side of the can lid formed from the metal strip.

[0117] Embodiment 4 is the process described in any of the preceding or succeeding embodiments, wherein the metal strip is an aluminum strip.

[0118] Embodiment 5 is a step described in any of the earlier or later embodiments, wherein the polymer film includes a polyethylene terephthalate film.

[0119] Embodiment 6 is a step described in any of the preceding or succeeding embodiments, wherein the pretreatment coating includes a polymer or copolymer.

[0120] Embodiment 7 is the process described in any of the preceding or succeeding embodiments, wherein the annealing temperature is less than 230°C.

[0121] Embodiment 8 is the process described in any of the preceding or succeeding embodiments, wherein the annealing temperature is higher than 150°C.

[0122] Embodiment 9 is a can lid material product prepared according to the steps described in any of the preceding or subsequent embodiments.

[0123] Embodiment 10 is a can lid product according to any of the preceding or succeeding embodiments, wherein the first side of the metal strip corresponds to the outward-facing side of the can lid product.

[0124] Embodiment 11 is a can lid material product according to any of the earlier or later embodiments, wherein the polymer film has a thickness of less than 50 μm.

[0125] Embodiment 12 is a beverage can including a body portion and an end cap, wherein the end cap is formed from a can lid material prepared according to the process described in any of the preceding or subsequent embodiments.

[0126] Embodiment 13 is a can lid material comprising a metal strip, a pretreatment composition, and a polymer film, wherein the can lid material does not exhibit visible crazing.

[0127] Embodiment 14 is a can lid material according to any of the preceding or succeeding embodiments, wherein the can lid material does not show visible crazing within 24 hours after the strain test, and the strain test includes applying a 2% strain with a force of 10 N / mm²·s.

[0128] Embodiment 15 is a can lid material according to any of the earlier or later embodiments, wherein the can lid material does not show visible crazing under UV light within 24 hours after the strain test, and the strain test further includes coating the sample with a fluorescent marker.

[0129] Embodiment 16 is a can lid material according to any of the preceding or succeeding embodiments, wherein the metal strip is an aluminum strip.

[0130] Embodiment 17 is a can lid material according to any of the earlier or later embodiments, wherein the polymer film contains polyethylene terephthalate.

[0131] Embodiment 18 is a can lid material according to any of the earlier or later embodiments, wherein the pretreatment composition is a polymer or copolymer.

[0132] Embodiment 19 is a can lid material according to any of the preceding or succeeding embodiments, wherein the polymer film exhibits an FTIR absorbance peak intensity ratio (A / B) greater than 0.4, where A exhibits a first absorbance peak at wavenumbers of 1330 cm1 to 1350 cm1, and B exhibits a second absorbance peak at wavenumbers of 1400 cm1 to 1420 cm-1.

[0133] Embodiment 20 is a can lid material according to any of the earlier or later embodiments, wherein the absorbance peak intensity ratio (A / B) is greater than 1.0.

[0134] Embodiment 21 is a system comprising a lamination system for receiving a metal strip and applying a polymer film to a first side of the metal strip, and an annealing furnace located downstream of the lamination system for receiving the laminated metal strip and heating the laminated metal strip at an annealing temperature of less than 250°C.

[0135] Embodiment 22 is the system according to any of the earlier or later embodiments, wherein the metal strip is an aluminum strip.

[0136] Embodiment 23 is a system according to any of the earlier or later embodiments, further comprising a pretreatment coating application system for applying a pretreatment coating to the metal strip, wherein the lamination system is configured to apply the polymer film to the pretreatment coating.

[0137] Embodiment 24 is a system according to any of the earlier or later embodiments, wherein the lamination system is coupled to a polyethylene terephthalate film supply unit.

[0138] Embodiment 25 is a system according to any of the earlier or later embodiments, wherein the annealing temperature is less than 230°C.

[0139] Embodiment 26 is a system according to any of the preceding or succeeding embodiments, wherein the annealing temperature is higher than 150°C.

[0140] Embodiment 27 is a method for evaluating the susceptibility of a can lid material to crazing, the method comprising stamping the can lid material to create a test sample, applying strain to the test sample to create a stress sample, and observing the crazing of the stress sample.

[0141] Embodiment 28 is a method according to any of the preceding or succeeding embodiments, wherein applying strain involves applying a 2% strain with a force of 10 N / mm²·s.

[0142] Embodiment 29 is a method of any of the preceding or subsequent embodiments, wherein observing the stress sample includes irradiating the stress sample with light.

[0143] Embodiment 30 further includes coating the test sample and / or the stress sample with a fluorescent marker, and observing the stress sample is a method according to any of the preceding or succeeding embodiments, which includes irradiating the stress sample with UV light.

Claims

1. A process for preparing a crazing-resistant can lid material, The pretreatment coating is applied to the first side of the metal strip, The process involves laminating a polymer film to the first side of the metal strip to form a laminated metal strip, wherein the polymer film is adhered to at least a portion of the pretreatment coating to form the laminated metal strip. Annealing the laminated metal strip at an annealing temperature of less than 250°C. The process including the above.

2. The process according to claim 1, wherein the can lid material does not exhibit visible crazing.

3. The process according to claim 1, wherein the first side of the metal strip corresponds to the inward side of the can lid formed from the metal strip.

4. The step according to claim 1, wherein the metal strip is an aluminum strip.

5. The step according to claim 1, wherein the polyester film comprises a polyethylene terephthalate film.

6. The step according to claim 1, wherein the pretreatment coating comprises a polymer or copolymer.

7. The process according to claim 1, wherein the annealing temperature is less than 230°C.

8. The process according to claim 1, wherein the annealing temperature is higher than 150°C.

9. A can lid material product prepared according to the process described in claim 1.

10. The can lid material product according to claim 9, wherein the first side of the metal strip corresponds to the outward side of the can lid material product.

11. The can lid material product according to claim 9, wherein the polymer film has a thickness of less than 50 μm.

12. A beverage can having a main body and an end cap, wherein the end cap is formed from a can lid material prepared according to the process described in claim 1.

13. metal strip, Pretreatment composition, and A can lid material containing a polymer film, The can lid material does not exhibit visible crazing.

14. The can lid material did not show any visible crazing within 24 hours after the strain test, and the strain test was 10 N / mm ２ - The can lid material according to claim 13, which includes applying a 2% strain with a force of s.

15. The can lid material according to claim 14, wherein the can lid material does not show visible crazing under UV light within 24 hours after the strain test, and the strain test further comprises coating the sample with a fluorescent marker.

16. The can lid material according to claim 13, wherein the metal strip is an aluminum strip.

17. The can lid material according to claim 13, wherein the polymer film contains polyethylene terephthalate.

18. The can lid material according to claim 13, wherein the pretreatment composition is a polymer or copolymer.

19. The polymer film exhibits an FTIR absorbance peak intensity ratio (A / B) greater than 0.4, where A is 1330 cm⁻¹. －１ ~1350cm －１ It shows the first absorbance peak at wavenumber B, where B is at 1400 cm⁻¹. －１ ~1420cm －１ The can lid material according to claim 13, which exhibits a second absorbance peak at a wavenumber.

20. The can lid material according to claim 19, wherein the absorbance peak intensity ratio (A / B) is greater than 1.

0.

21. A lamination system for receiving a metal strip and applying a polymer film to the first side of the metal strip, An annealing furnace located downstream of the lamination system to receive laminated metal strips and heat the laminated metal strips at an annealing temperature of less than 250°C. A system equipped with these features.

22. The system according to claim 21, wherein the metal strip is an aluminum strip.

23. The system according to claim 21, further comprising a pretreatment coating application system for applying a pretreatment coating to the metal strip, wherein the lamination system is configured to apply the polymer film to the pretreatment coating.

24. The system according to claim 21, wherein the lamination system is coupled to a polyethylene terephthalate film supply unit.

25. The system according to claim 21, wherein the annealing temperature is less than 230°C.

26. The system according to claim 21, wherein the annealing temperature is higher than 150°C.

27. A method for evaluating the susceptibility of can lid material to crazing, The process involves stamping the can lid material to create a test sample, The process involves applying strain to the aforementioned test sample to create a stress sample, Observe the crazing of the stress sample mentioned above. The method, including the method described above.

28. Applying strain results in a value of 10 N / mm ２ The method according to claim 27, comprising applying a 2% strain with a force of s.

29. The method according to claim 27, wherein observing the stress sample includes irradiating the stress sample with light.

30. The method according to claim 27, further comprising coating the test sample and / or the stress sample with a fluorescent marker, wherein observation of the stress sample includes irradiating the stress sample with UV light.

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