Special aluminum foil with thickness of 0.01 mm for anti-counterfeit label and preparation method thereof

Abstract

The invention discloses a 0.01 mm-thick aluminum foil special for an anti-counterfeit label and a preparation method of the 0.01 mm-thick aluminum foil, and relates to the field of aluminum foil processing.The preparation method comprises the steps that a 0.24 mm-H14 aluminum foil blank is subjected to four-pass rolling and shearing, and a 0.01 mm-H18 aluminum foil is obtained; and carrying out gradient annealing on the aluminum foil finished product rolled in the fourth pass to obtain the 0.01 mm-0 state thickness aluminum foil special for the anti-counterfeit label. Wherein the process conditions of gradient annealing are as follows: heating: the temperature is increased to 185 DEG C from room temperature within 20 hours; primary heat preservation: preserving heat at 185 DEG C for 25 hours; cooling: reducing the temperature from 185 DEG C to 120 DEG C within 3 hours; and secondary heat preservation: preserving heat at 120 DEG C for 10 hours. The optimized 1235 alloy raw material is selected to prepare the blank, and the specific four-pass rolling process and the gradient annealing process are combined, so that the obtained aluminum foil is few in pinholes, flat in plate shape and smooth in surface and has the good mechanical properties that the tensile strength ranges from 75 MPA to 95 MPA, the transverse elongation is larger than or equal to 1.4%, and the longitudinal elongation is larger than or equal to 2.0%; and the performance requirements of the aluminum foil for preparing the anti-counterfeit label can be met.

Description

Technical Field

[0001] The present invention relates to the field of aluminum foil processing, and specifically to an aluminum foil with a thickness of 0.01 mm for anti-counterfeiting labels and a preparation method thereof. Background Art

[0002] Labels used as product identifiers mainly include electronic labels and anti-counterfeiting labels, both of which can provide specific information for products. Electronic labels identify relevant information of products by storing data, such as name, specification, batch, etc.; anti-counterfeiting labels identify products through unique patterns, codes, etc., enabling consumers or relevant personnel to identify the authenticity and identity of products.

[0003] The core component of ordinary electronic labels such as RFID is the antenna. The etching of RFID antennas requires ensuring high conductivity and signal transmission efficiency. Therefore, the etching width cannot be too narrow, otherwise it will affect the performance. Its etching width is usually between 50 microns and several millimeters. The etching of anti-counterfeiting labels is usually used to make microtext, holographic patterns or other fine anti-counterfeiting features. The etching width of the aluminum foil for anti-counterfeiting labels is generally only a few microns to fifty microns, and the material thickness is 0.01 mm. Therefore, the requirements for the aluminum foil for anti-counterfeiting labels are more stringent.

[0004] Reference 1: Chinese invention patent with application number 202010284539.X.

[0005] Reference 1 discloses an aluminum foil for low-pinhole and high-surface-finish electronic labels and its production process. By controlling the weight percentages of Fe and Si in the total raw materials to satisfy the following relationship: Fe / Si = 2 - 3, Fe + Si ≤ 1%, the produced aluminum foil has a thickness of 0.015 mm ± 5% (i.e., 0.01425 mm - 0.01575 mm), mechanical properties: tensile strength 70 - 80 Mpa, elongation > 9%, and the number of pinholes: 0, meeting the usage requirements of electronic labels. However, since the thickness of the aluminum foil for this electronic label is about 0.015 mm, it cannot be used as an anti-counterfeiting label.

[0006] Moreover, as is well known, the thinner the aluminum foil, the more pinholes there will be, and the tensile strength and elongation will also change. Therefore, during the aluminum foil processing, when its thickness is continuously thinned to 0.01 mm, the phenomenon of increased pinholes will inevitably occur. The aluminum foil prepared in Reference 1 cannot meet the requirements of anti-counterfeiting labels for an aluminum foil thickness of 0.01 mm, a pinhole density ≤ 5 per m 2 and mechanical properties.

[0007] Reference 2: Chinese invention patent with application number 202010717592.4.

[0008] Reference 2 discloses a method for preparing a low-pinhole ultra-wide and ultra-thin aluminum foil, which solves the problem of excessive pinholes in the aluminum foil when the ultra-wide aluminum foil is thinned to 0.0053 mm, and adopts a gradient cooling method. The produced ultra-wide and ultra-thin aluminum foil has ≤800 pinholes / m 2 , and the tensile strength performance is 75-90 MPa.

[0009] Reference 3: A Chinese invention patent with the application number 202010730716.2.

[0010] Reference 3 discloses a rolling method for ultra-wide and ultra-thin aluminum foil, which successfully batch-rolls finished aluminum foil with a width of 1902 mm and a thickness of 0.0053 mm, meeting the needs of foreign customers for ultra-thin and ultra-wide double-zero aluminum foil. The pinholes of the prepared aluminum foil are 2400-2800, and the elongation is 2.2-2.4%.

[0011] Although the thickness of the aluminum foil prepared in Reference Documents 2 and 3 is less than 0.01 mm, the pinhole rate is relatively high and it is not suitable for making anti-counterfeiting labels either.

[0012] In addition, the prior art also discloses a method for preparing 0.01 mm thick aluminum foil for anti-counterfeiting labels. However, although the domestic process for preparing 0.01 mm anti-counterfeiting aluminum foil labels has made certain progress in technology, there are still problems such as pinhole defects, insufficient mechanical properties, and unsatisfactory surface degreasing effect. Summary of the Invention

[0013] The present invention aims to provide a 0.01 mm thick aluminum foil for anti-counterfeiting labels and its preparation method to meet the special requirements of the existing etched microstructures of anti-counterfeiting labels for the pinhole rate and mechanical properties of materials.

[0014] To solve the above technical problems, the specific solution adopted by the present invention is as follows: A 0.01 mm thick aluminum foil for anti-counterfeiting labels is made from the following raw materials by mass percentage,

[0015] Si: 0.10-0.14%, Fe: 0.35-0.45%, Cu: 0.015-0.02%, Mn: 0.008-0.01%, Mg: 0.0045-0.005%, Zn: 0.028-0.3%, Ti: 0.028-0.03%, the balance being Al and unavoidable impurities, and the single impurity ≤0.03%, and the total impurities ≤0.015%; among them, the mass ratio of Si to Fe is 0.25-0.40.

[0016] A 0.01 mm thick aluminum foil for anti-counterfeiting labels and its preparation method include the following steps:

[0017] S1: Prepare materials according to the raw material ratio described in Claim 1 to prepare a blank with a specification of 1235-H14 and a thickness of 0.24 mm * L;

[0018] S2: First, perform the first pass of rolling on the blank to obtain an aluminum foil with a thickness of 0.121 mm, then perform the second pass of rolling to obtain an aluminum foil with a thickness of 0.051 mm, then perform the third pass of rolling to obtain an aluminum foil with a thickness of 0.021 mm. Double the aluminum foil after the third pass of rolling and apply rolling oil between the aluminum foils during doubling, and then perform the fourth pass of rolling to obtain an aluminum foil with a thickness of 0.01 mm;

[0019] S3: After shearing the aluminum foil after the fourth pass of rolling, perform gradient annealing to obtain the 0.01 mm thick aluminum foil for the anti-counterfeiting label;

[0020] Among them, the process conditions for gradient annealing are

[0021] As a further optimization of the above technical solution, the speed of the first pass is 600 - 700 m / min, the speed of the second pass is 900 - 1000 m / min, the speed of the third pass is 1300 - 1500 m / min, and the speed of the fourth pass is 600 - 700 m / min.

[0022] As a further optimization of the above technical solution, the roll roughness of the first pass is 0.28 - 0.3 um, the roll roughness of the second pass is 0.14 - 0.15 um, the roll roughness of the third pass is 0.14 - 0.15 um, and the roll roughness of the fourth pass is 0.09 - 0.10 um.

[0023] As a further optimization of the above technical solution, the roll crown of the first pass is +0.04 mm, the roll crown of the second pass is +0.06 mm, the roll crown of the third pass is +0.06 mm, and the roll crown of the fourth pass is +0.06 mm.

[0024] As a further optimization of the above technical solution, in step S3, the 0.01 mm thick aluminum foil is sheared into the target size and then gradient annealing is performed to obtain the 0.01 mm thick aluminum foil for the anti-counterfeiting label.

[0025] As a further optimization of the above technical solution, the rolling oil is 80# base oil with a light transmittance of more than 90%. Under the temperature condition of 40 °C, the kinematic viscosity of the rolling oil is 1.5 - 1.7 mm 2 / s; the acid value is 0.0035 mgKOH / g; the closed flash point under standard atmospheric pressure is 80 °C; the dry point is 200 - 240 °C, and the initial boiling point is 208 °C.

[0026] The invention discloses an application of 0.01mm thick aluminum foil in preparing an anti-counterfeiting label, wherein the etching width of the anti-counterfeiting label is less than 50μm.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] The present invention selects optimized 1235 alloy raw materials to prepare blanks, and combines a specific four-pass rolling process and a gradient annealing process to obtain an aluminum foil with few pinholes, a flat plate shape, a smooth surface, and mechanical properties such as a tensile strength of 75MPA to 95MPA, a lateral elongation of ≥1.4%, and a longitudinal elongation of ≥2.0%, which can meet the performance requirements of the aluminum foil required for preparing anti-counterfeiting labels.

[0029] The ingredients have unique effects:

[0030] 1) The present invention controls the mass percentage of Si to 0.10-0.14% and the mass percentage of Fe to 0.35-0.45%, thereby forming nano-scale Al-Fe-Si intermetallic compounds during the rolling process, inhibiting the extension of microcracks during the rolling process, and synergistically improving the strength with Fe and Si, while inhibiting excessive grain growth. The Si / Fe ratio is controlled at 0.25-0.40, thereby improving rolling stability.

[0031] 2) Fe combines with H in the melt to form FeH2, which reduces the hydrogen content of the aluminum liquid (measured H content ≤ 0.10ml / 100g Al) and reduces the probability of pinhole formation (for every 0.01ml / 100g reduction in hydrogen content, the pinhole density decreases by 2 pinholes / m 2 );

[0032] 3) Fe content of 0.35-0.45% can enhance the mechanical properties of aluminum foil, make the micro-etching edge clearer, and reduce burrs;

[0033] 4) By controlling Cu≤0.02% and Mn≤0.01%, the formation of coarse intermetallic compounds can be avoided and the uniformity of the foil can be improved; Cu≤0.02%: avoid the formation of coarse Al2Cu phase (stress concentration occurs when the size is greater than 500nm) to ensure the uniformity of rolling deformation (finite element simulation shows that the local strain difference is greater than 15% when Cu>0.03%). Mg≤0.005%: prevent MgO inclusions from destroying the continuity of the surface oxide layer (SEM shows that the probability of oxide film rupture increases to 35% when Mg>0.005%). Mg / Zn / Ti≤0.03% can prevent the abnormality of the surface oxide layer during annealing and improve the surface finish of the aluminum foil.

[0034] Four rolling process coordination mechanisms:

[0035] 1) Pass rolling parameter design

[0036] Through the speed gradient, the balance between dynamic recrystallization and work hardening is achieved. In the first two passes (600 - 1000 m / min): The high strain rate (10 3 s -1 -1 level) promotes dislocation multiplication and increases the strength (the grain size is refined to 1.2 μm).

[0037] In the third pass (1300 - 1500 m / min): The low strain rate (10 2 s -1 -1 level) promotes dislocation rearrangement, improves plasticity (the elongation rate is increased to 1.4%), and ensures the flatness of the sheet shape.

[0038] 2) The law of decreasing roll roughness

[0039] The roll roughness decreases from 0.30 μm to 0.10 μm, reducing the friction coefficient in the rolling contact zone from 0.12 to 0.08 and reducing surface scratches.

[0040] 3) The characteristics of the double - combined rolling oil

[0041] Oil with high light transmittance: The light transmittance ≥ 90% ensures the uniformity of the rolling oil film thickness (the film thickness fluctuation ≤ 0.5 μm), avoiding pinholes caused by local lubrication failure.

[0042] Closed - cup flash point control: The flash point of 80°C can inhibit the thermal decomposition of the rolling oil and reduce the carbonized residues (TGA test shows that the residue of the traditional 70°C flash point oil reaches 0.3%, and the residue of the process of the present invention ≤ 0.05%).

[0043] Through the gradient annealing of the present invention, the residual stress is removed, the internal structure of the metal is changed, thereby changing the properties of the material: the longitudinal elongation rate (2.0%) is higher than the transverse (1.4%), obtaining the mechanical properties for preparing the aluminum foil for anti - counterfeiting labels; and it can also remove the residual rolling oil on the surface of the aluminum foil.

[0044] In the annealing furnace, the aluminum foil volatilizes due to heat, diffuses towards the end face of the aluminum foil, and is either burned or the oil and gas are discharged from the furnace with the purging air.

[0045] The aluminum foil products produced by the annealing process (as shown in Table 2) meet the requirements of etching. Brief description of the drawings

[0046] Figure 1 An anti - counterfeiting label made of 0.01 - mm - thick aluminum foil prepared by the method described in this solution. Detailed implementation mode

[0047] The technical solution of the present invention is further elaborated in detail below in conjunction with specific embodiments. The parts of the present invention that are not described and disclosed in detail in the following embodiments should be understood as the prior art known or should be known to those skilled in the art.

[0048] The invention discloses an aluminum foil with a thickness of 0.01 mm specially used for an anti-counterfeiting label. The aluminum foil is made of the following raw materials in mass percentage: Si: 0.10-0.14%, Fe: 0.35-0.45%, Cu: 0.015-0.02%, Mn: 0.008-0.01%, Mg: 0.0045-0.005%, Zn: 0.028-0.3%, Ti: 0.028-0.03%, the remainder is Al and inevitable impurities, and a single impurity is less than or equal to 0.03%, and the total impurities are less than or equal to 0.015%. The mass ratio of Si to Fe is 0.25-0.40.

[0049] The thickness of the aluminum foil is 0.01mm, and the pinhole density is ≤5 / m 2 , tensile strength is 75MPA~95MPA, lateral elongation ≥1.4%, and longitudinal elongation ≥2.0%.

[0050] The specific steps include:

[0051] S1: Prepare and make billets with specifications of 1235-H14 and 0.24mm*L. The raw material components meet the following mass percentages: Si: 0.10-0.14%, Fe: 0.35-0.45%, Cu: 0.015-0.02%, Mn: 0.008-0.01%, Mg: 0.0045-0.005%, Zn: 0.028-0.03%, Ti: 0.028-0.03%, single impurity ≤0.03% and total impurities ≤0.015%, and the balance is Al.

[0052] The prepared 1235-H14, 0.24mm*L billet is a 1235 alloy after optimizing the content and ratio of Si and Fe. The process of preparing the 1235-H14 alloy billet is a prior art. The main steps of preparing the 1235-H14 alloy billet are briefly described as follows:

[0053] 1) Melting and purification

[0054] Raw material ratio: Mix according to the optimized alloy composition.

[0055] Melting: Melt at 720-750℃ and use 50+60 mesh foam ceramic filter plate for online filtration to reduce inclusions such as Al2O3.

[0056] Degassing: Use Ar gas rotation degassing to reduce the hydrogen content to ≤0.12ml / 100g Al.

[0057] 2) Continuous casting and rolling

[0058] Continuous casting and rolling temperature: 680 - 700 °C, continuous casting and rolling speed 1.0 - 1.5 m / min, obtaining a continuous casting and rolling plate with a thickness of 6 - 8 mm.

[0059] Cold rolling to 0.24 mm:

[0060] Rough rolling: 6 mm → 2 mm (rolling speed 600 - 800 m / min, roll roughness Ra 0.3 μm)

[0061] Intermediate rolling: 2 mm → 0.5 mm (rolling speed 1000 - 1200 m / min, roll roughness Ra 0.15 μm)

[0062] Finish rolling: 0.5 mm → 0.24 mm (rolling speed 1300 - 1500 m / min, roll roughness Ra 0.1 μm).

[0063] 3) Annealing (H14 condition)

[0064] Annealing: Annealing the finish - rolled sheet at 350 - 400 °C for 2 - 4 h to eliminate cold - rolling stress and improve plasticity.

[0065] 4) Surface treatment

[0066] Removing the residual rolling oil from the annealed sheet, cutting it into a size of 0.24 mm × L, thus preparing a blank of 1235 - H14, 0.24 mm * L.

[0067] S2: Passing the blank through the first - pass and second - pass rolling successively to obtain an aluminum foil with thickness changes of 0.24 mm - 0.121 mm - 0.051 mm. Passing the aluminum foil with a thickness of 0.051 mm through the third - pass rolling to obtain an aluminum foil with a thickness of 0.021 mm. Doubling the aluminum foil with a thickness of 0.021 mm and coating rolling oil between the aluminum foils during doubling, and then passing through the fourth - pass rolling to obtain an aluminum foil with a thickness of 0.01 mm;

[0068] Specifically: (as shown in Table 1)

[0069] S201: Feeding the blank with a thickness of 0.24 mm into the aluminum foil roughing mill for the first - pass and second - pass rolling. The first - pass rolling is from 0.24 mm to 0.121 mm, and the speed of the first - pass is 600 - 700 m / min; the second - pass rolling is from 0.121 mm to 0.051 mm, and the speed of the second - pass is 900 - 1000 m / min;

[0070] S202. Then, feed the aluminum foil with a thickness of 0.051 mm into the intermediate rolling mill for the third pass of rolling, reducing the thickness from 0.051 mm to 0.021 mm. The speed of the third pass of rolling is 1300 m / min to 1500 m / min.

[0071] S203. Enter the coil combining process. Feed two coils with a thickness of 0.021 mm into the coil combining machine for double combining (coating a layer of rolling oil in the middle) to form a single coil of (0.021 mm * 2) material. The rolling oil is 80# base oil with a light transmittance of more than 90%. At a temperature of 40 °C, the kinematic viscosity of the rolling oil is 1.5 - 1.7 mm 2 / s; the acid value is 0.0035 mgKOH / g; the closed - cup flash point under standard atmospheric pressure is 80 °C; the dry point is 200 - 240 °C, and the initial boiling point is 208 °C.

[0072] S204. Roll the double - combined coil of 0.021 mm * 2 in the finishing mill for the fourth pass of rolling, reducing the thickness from 0.021 mm * 2 to 0.01 mm * 2.

[0073] The specific process parameters in the aluminum foil rolling process are shown in Table 1:

[0074] Table 1

[0075] S3: Gradient anneal the aluminum foil with a thickness of 0.01 mm to obtain the 0.01 - mm - thick aluminum foil for the anti - counterfeiting label.

[0076] Specifically, feed the coil of 0.01 mm * 2 to the slitting process for shearing into the target specifications. The sheared aluminum foil is then fed into the annealing furnace for gradient annealing treatment to obtain the 0.01 - mm - thick aluminum foil for the anti - counterfeiting label.

[0077] The process conditions for gradient annealing are shown in Table 2:

[0078] Table 2

[0079] It should be noted that in the present invention, the aluminum foil of the target specifications has a relatively narrow width (width is 280 mm - 750 mm) and a relatively small coil diameter (coil diameter is 300 mm - 450 mm). Therefore, it can be taken out of the furnace after the secondary heat preservation is completed, and there will be no cold drum phenomenon during this process. After taking out of the furnace, the aluminum foil is naturally cooled.

[0080] Figure 1It is a graphic of an anti-counterfeiting label made by a certain electronics factory (Jiangsu Hongtan Electronic Technology) for liquor factories such as Wuliangye. This kind of anti-counterfeiting wine label is generally circular, with two specifications of diameter sizes: 15mm and 22mm. The etching width is relatively narrow (from a few microns to fifty microns). The aluminum foil used for this anti-counterfeiting label has a thickness of 0.01mm and is prepared by the method described in the present invention.

[0081] Example 1

[0082] A preparation method for 0.01mm-thick aluminum foil dedicated to anti-counterfeiting labels, comprising the following steps:

[0083] S1. Prepare materials and ensure that the raw materials meet the following mass percentages: Si: 0.13%, Fe: 0.43%, Cu: 0.018%, Mn: 0.01%, Mg: 0.005%, Zn: 0.3%, Ti: 0.03%, and the balance is Al and unavoidable impurities, and the content of a single impurity ≤ 0.03%, and the total content of impurities ≤ 0.015%; prepare a blank with a specification of 1235-H14 and 0.24mm * L:

[0084] S2. Rolling:

[0085] Feed the blank with a thickness of 0.24mm into the aluminum foil roughing mill for the first and second passes of rolling. In the first pass, roll from 0.24mm to 0.121mm. The speed of the first pass is 650 m / min, the roughness of the roll is Ra0.28 - 0.3um, and the camber of the roll is +0.04mm;

[0086] In the second pass, roll from 0.121mm to 0.051mm. The speed of the second pass is 950 m / min, the roughness of the roll is Ra0.14 - 0.15um, and the camber of the roll is +0.06mm;

[0087] Then feed the aluminum foil with a thickness of 0.051mm into the medium rolling mill for the third pass of rolling, and the thickness is rolled from 0.051mm to 0.021mm. The speed of the third pass of rolling is 1400 m / min, the roughness of the roll is 0.14 - 0.15um, and the camber of the roll is +0.06mm;

[0088] Enter the coiling process. Feed two coils with a thickness of 0.021mm into the coiling machine for double coiling (coat a layer of rolling oil in the middle) to form a double-coiled (0.021mm * 2) coil;

[0089] Roll the double-coiled coil of 0.021mm * 2 in the finishing mill for the fourth pass of rolling, and the thickness is rolled from 0.021mm * 2 to 0.01mm * 2. The speed of the fourth pass is 650 m / min, the roughness of the roll is Ra0.09 - 0.10um, and the camber of the roll is +0.06mm.

[0090] S3. Feed the coil stock of 0.01 mm * 2 to the slitting process for shearing, and then obtain the 0.01 mm thick aluminum foil for anti-counterfeiting labels through gradient annealing treatment.

[0091] The process parameters of gradient annealing are as follows:

[0092] Heating: Raise the temperature from room temperature to 185 °C in 20 h;

[0093] First heat preservation: Keep the temperature at 185 °C for 25 h;

[0094] Cooling: Lower the temperature from 185 °C to 120 °C in 3 h;

[0095] Second heat preservation: Keep the temperature at 120 °C for 10 h.

[0096] Example 2

[0097] A preparation method of 0.01 mm thick aluminum foil for anti-counterfeiting labels, comprising the following steps:

[0098] S1. Prepare materials and ensure that the raw materials meet the following mass percentages: Si: 0.13%, Fe: 0.43%, Cu: 0.018%, Mn: 0.01%, Mg: 0.005%, Zn: 0.3%, Ti: 0.03%, and the balance is Al and unavoidable impurities, and the single impurity ≤ 0.03%, and the total impurities ≤ 0.015%; Prepare a blank with a specification of 1235-H14, 0.24 mm * L: S2. Rolling:

[0099] Feed the blank with a thickness of 0.24 mm into the aluminum foil roughing mill for the first and second passes of rolling. The first pass is rolled from 0.24 mm to 0.121 mm, the speed of the first pass is 600 m / min, the roughness of the roll is Ra0.28 - 0.3 um, and the roll crown is +0.04 mm;

[0100] The second pass is rolled from 0.121 mm to 0.051 mm, the speed of the second pass is 900 m / min, the roughness of the roll is 0.14 - 0.15 um, and the roll crown is +0.06 mm;

[0101] Then feed the aluminum foil with a thickness of 0.051 mm into the medium rolling mill for the third pass of rolling, and the thickness is rolled from 0.051 mm to 0.021 mm. The speed of the third pass of rolling is 1300 m / min, the roughness of the roll is Ra0.14 - 0.15 um, and the roll crown is +0.06 mm;

[0102] Enter the coiling process, feed two coils with a thickness of 0.021 mm into the coiling machine for double coiling (coat a layer of rolling oil in the middle), and double coil into a coil stock (0.021 mm * 2);

[0103] The double-layer material with a thickness of 0.021 mm * 2 is coiled and rolled in the finishing mill for the fourth pass. The thickness is rolled from 0.021 mm * 2 to 0.01 mm * 2. The speed of the fourth pass is 600 m / min, the roughness of the roll is Ra0.09 - 0.10 μm, and the camber of the roll is +0.06 mm.

[0104] S3. Send the coil of 0.01 mm * 2 material to the slitting process for shearing, and then obtain the 0.01 mm thick aluminum foil for anti-counterfeiting labels through gradient annealing treatment.

[0105] The process parameters of gradient annealing are as follows:

[0106] Heating: The temperature is raised from room temperature to 185 °C in 20 h.

[0107] Primary heat preservation: Keep the temperature at 185 °C for 25 h.

[0108] Cooling: The temperature is lowered from 185 °C to 120 °C in 3 h.

[0109] Secondary heat preservation: Keep the temperature at 120 °C for 10 h.

[0110] Example 3

[0111] A method for preparing 0.01 mm thick aluminum foil for anti-counterfeiting labels includes the following steps:

[0112] S1. Prepare materials and ensure that the raw materials meet the following mass percentages: Si: 0.13%, Fe: 0.43%, Cu: 0.018%, Mn: 0.01%, Mg: 0.005%, Zn: 0.3%, Ti: 0.03%, and the balance is Al and unavoidable impurities, and the single impurity ≤ 0.03%, and the total impurities ≤ 0.015%; Prepare a blank with a specification of 1235-H14, 0.24 mm * L:

[0113] S2. Rolling:

[0114] Feed the blank with a thickness of 0.24 mm into the aluminum foil roughing mill for the first pass and the second pass of rolling. In the first pass, it is rolled from 0.24 mm to 0.121 mm. The speed of the first pass is 700 m / min, the roughness of the roll is Ra0.28 - 0.3 μm, and the camber of the roll is +0.04 mm;

[0115] In the second pass, it is rolled from 0.121 mm to 0.051 mm. The speed of the second pass is 1000 m / min, the roughness of the roll is 0.14 - 0.15 μm, and the camber of the roll is +0.06 mm;

[0116] Then, an aluminum foil with a thickness of 0.051 mm is fed into the intermediate rolling mill for the third pass of rolling, with the thickness being rolled from 0.051 mm to 0.021 mm. The speed of the third pass of rolling is 1500 m / min, the roughness of the rolling rolls is Ra0.14 - 0.15 um, and the crown of the rolling rolls is +0.06 mm.

[0117] Enter the coil combining process. Two coils with a thickness of 0.021 mm are fed into the coil combining machine for double combining (coating a layer of rolling oil in the middle), and are double combined into a single coil (0.021 mm * 2) material coil.

[0118] The double combined material coil of 0.021 mm * 2 is rolled in the finishing mill for the fourth pass, with the thickness being rolled from 0.021 mm * 2 to 0.01 mm * 2. The speed of the fourth pass is 700 m / min, the roughness of the rolling rolls is Ra0.09 - 0.10 um, and the crown of the rolling rolls is +0.06 mm.

[0119] S3. Gradient annealing: The coil of 0.01 mm * 2 is sent to the slitting process for shearing, and then undergoes gradient annealing treatment to obtain the special anti-counterfeiting label aluminum foil with a thickness of 0.01 mm.

[0120] The process parameters of gradient annealing are as follows:

[0121] Heating: The temperature is raised from room temperature to 185 °C in 20 h.

[0122] First heat preservation: Keep the temperature at 185 °C for 25 h.

[0123] Cooling: The temperature is lowered from 185 °C to 120 °C in 3 h.

[0124] Second heat preservation: Keep the temperature at 120 °C for 10 h.

[0125] Comparative Example 1

[0126] The overall steps of this comparative example are the same as those of Example 1. The difference is that the blank of specification 1235 - H14, 0.24 mm * L selected in this comparative example is made of ordinary 1235 alloy, and the raw material meets the following mass percentages: the sum of the masses of Si and Fe is 0.65%, Cu: 0.05%, Mn: 0.05%, Mg: 0.05%, V: 0.05%, Zn: 0.1%, Ti: 0.06%, and the balance is Al and unavoidable impurities, and the single impurity ≤ 0.03%, and the total impurities ≤ 0.015%; preparing a blank of specification 1235 - H14, 0.24 mm * L:

[0127] The processes of rolling and gradient annealing are the same as those of Example 1, and an aluminum foil with a thickness of 0.01 mm is obtained.

[0128] Comparative Example 2

[0129] This comparative example has the same overall steps as Example 1, except that the annealing process parameters in this comparative example are as follows:

[0130] In the heating stage, the heating rate is 10 °C / hour, and the temperature is raised to 200 °C.

[0131] In the first holding stage, the holding temperature is 200 °C, and the holding time is 22 hours.

[0132] In the cooling stage, the cooling rate is 8 °C / hour, and the temperature is lowered to 120 °C.

[0133] In the second holding stage: hold at 120 °C for 10 hours.

[0134] The processes of preparing the blank and rolling are the same as those in Example 1, and aluminum foil with a thickness of 0.01 mm is obtained.

[0135] Comparative Example 3

[0136] This comparative example has the same overall steps as Example 1, except that the annealing process parameters in this comparative example are as follows:

[0137] In the heating stage, the heating rate is 8 °C / hour, and the temperature is raised to 185 °C.

[0138] In the holding stage, the holding temperature is 185 °C, and the holding time is 24 hours.

[0139] In the cooling stage, the cooling rate is 20 °C / hour, and the temperature is lowered to room temperature.

[0140] The processes of preparing the blank and rolling are the same as those in Example 1, and aluminum foil with a thickness of 0.01 mm is obtained.

[0141] Comparative Example 4

[0142] This comparative example has the same overall steps as Example 1, except that the annealing process parameters in this comparative example are as follows:

[0143] In the heating stage, the heating rate is 11 °C / hour, and the temperature is raised to 220 °C.

[0144] In the holding stage, the holding temperature is 220 °C, and the holding time is 24 hours.

[0145] In the cooling stage, the cooling rate is 20 °C / hour, and the temperature is lowered to 120 °C.

[0146] In the second holding stage: hold at 120 °C for 10 hours.

[0147] The processes of preparing the blank and rolling are the same as those in Example 1, and aluminum foil with a thickness of 0.01 mm is obtained.

[0148] Comparative Example 5

[0149] This comparative example adopts the production process of Reference 1, and changes the inlet thickness and outlet thickness during rolling to roll aluminum foil with a thickness of 0.01 mm.

[0150] The pinhole density and mechanical properties of the aluminum foils prepared in Example 1 and Comparative Examples 1-5 were detected, and the test results are shown in Table 3 below:

[0151] Table 3

[0152] The calculation method of the qualified rate of 50 μm etching in Table 3 is (statistical data): Qualified rate (%) = (Number of qualified products / Total number of inspected products) %.

[0153] Result analysis: As can be seen from Table 3, the pinhole density of the aluminum foil prepared in Example 1 is 3.2 pieces / m 2 , there are no string-shaped aligned pinholes, no honeycomb-shaped pinholes, the tensile strength ≥ 85 MPa, the longitudinal elongation rate ≥ 2.2%, and the transverse elongation rate ≥ 1.5%, meeting the quality requirements of the anti-counterfeiting electronic label foil.

[0154] In Comparative Example 1, with slightly different trace elements, the metallurgical quality fluctuates, resulting in more pinholes and a decrease in the etching qualified rate.

[0155] In Comparative Example 2, the annealing process was adjusted, resulting in a tensile strength lower than 80 Mpa. A low tensile strength is likely to cause wrinkling during lamination, which will cause a decrease in the etching yield.

[0156] It can be seen from Comparative Example 3 that shortening the annealing time will cause incomplete degreasing in the middle of the coil. Bubbles will appear during lamination at the places where degreasing is not complete, which does not meet the etching requirements and causes a decrease in the etching qualified rate.

[0157] In Comparative Example 4, by greatly adjusting the annealing process, the tensile strength decreases, resulting in slight adhesion between layers of the aluminum foil, and the qualified rate of etching decreases;

[0158] In Comparative Example 5, adjusting the rolling process will cause fluctuations in pinholes and performance, resulting in a decrease in the subsequent etching qualified rate.

[0159] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to those skilled in the art. The general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to these embodiments shown herein, but rather to the broadest scope consistent with the principles and novel features disclosed herein.

Claims

1. An aluminum foil with a thickness of 0.01 mm for anti-counterfeiting labels, characterized in that, It is made from the following raw materials by mass percentage: Si: 0.10 - 0.14%, Fe: 0.35 - 0.45%, Cu: 0.015 - 0.02%, Mn: 0.008 - 0.01%, Mg: 0.0045 - 0.005%, Zn: 0.028 - 0.3%, Ti: 0.028 - 0.03%, the balance being Al and unavoidable impurities, and the single impurity ≤ 0.03%, and the total impurities ≤ 0.015%; among them, the mass ratio of Si to Fe is 0.25 - 0.

40.

2. A preparation method of a 0.01mm-thick aluminum foil for anti-counterfeiting labels, characterized in that, It includes the following steps: S1: Prepare materials according to the raw material ratio described in Claim 1, and prepare a blank with a specification of 1235-H14 and 0.24mm * L. S2: First perform the first pass rolling on the blank to obtain an aluminum foil with a thickness of 0.121mm, then perform the second pass rolling to obtain an aluminum foil with a thickness of 0.051mm, then perform the third pass rolling to obtain an aluminum foil with a thickness of 0.021mm, double-join the aluminum foil after the third pass rolling and coat rolling oil between the aluminum foils during double-joining, and perform the fourth pass rolling to obtain an aluminum foil with a thickness of 0.01mm. S3: Cut the aluminum foil after the fourth pass rolling and then perform gradient annealing to obtain the 0.01mm thick aluminum foil for anti-counterfeiting labels. Among them, the process conditions of gradient annealing are as follows in the table:

3. The preparation method of a 0.01mm-thick aluminum foil dedicated for anti-counterfeiting labels according to claim 2, characterized in that, The speed of the first pass is 600 - 700 m / min, the speed of the second pass is 900 - 1000 m / min, the speed of the third pass is 1300 - 1500 m / min, and the speed of the fourth pass is 600 - 700 m / min.

4. The preparation method of a 0.01mm-thick aluminum foil dedicated for anti-counterfeiting labels according to claim 2, characterized in that, The roll roughness of the first pass is 0.28 - 0.3um, the roll roughness of the second pass is 0.14 - 0.15um, the roll roughness of the third pass is 0.14 - 0.15um, and the roll roughness of the fourth pass is 0.09 - 0.10um.

5. The preparation method of a 0.01mm-thick aluminum foil dedicated for anti-counterfeiting labels according to claim 2, characterized in that, The roll crown of the first pass is +0.04mm, the roll crown of the second pass is +0.06mm, the roll crown of the third pass is +0.06mm, and the roll crown of the fourth pass is +0.06mm.

6. The preparation method of a 0.01mm-thick aluminum foil dedicated for anti-counterfeiting labels according to claim 2, characterized in that, In step S3, the 0.01mm thick aluminum foil is cut into the target size and then gradient annealing is performed to obtain the 0.01mm thick aluminum foil for anti-counterfeiting labels.

7. The preparation method of a 0.01mm thick aluminum foil for anti-counterfeiting labels according to claim 2, characterized in that, The rolling oil is 80# base oil with a light transmittance of over 90%. Under the temperature condition of 40°C, the kinematic viscosity of the rolling oil is 1.5 - 1.7 mm 2 / s; the acid value is 0.0035 mgKOH / g; the closed flash point under standard atmospheric pressure is 80°C; the dry point is 200 - 240°C, and the initial boiling point is 208°C.

8. Use of an aluminum foil with a thickness of 0.01 mm as described in claim 1 in the preparation of anti-counterfeiting labels, characterized in that, The etching width of the anti-counterfeiting label < 50μm.

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