Method for controlling the brightness of the front and back sides of double zero aluminum foil

Abstract

The present application belongs to the technical field of non-ferrous metal processing, and relates to a method for controlling the brightness of the front and back surfaces of double-zero aluminum foil. The alloy of aluminum plate roughage has a great influence on the brightness of finished aluminum foil. The brightness value of the matt surface of aluminum foil increases with the increase of the reduction rate and the roughness of the roll surface. Before starting the finish rolling, the finish rolling roll is pulled for 15-20 min with aluminum material of the same width or above. The present application strictly controls the process parameters such as alloy type, reduction rate and roll roughness, achieves the purpose of controlling the surface brightness value of the aluminum foil for packaging, better meets the consistent requirements of high-end market on the surface brightness value of aluminum foil, is beneficial to the long-term and consistent needs of packaging market customers for the surface quality of their products, meets the needs of the market of special packaging aluminum foil, and improves the market competitiveness.

Description

Technical Field

[0001] This invention belongs to the field of non-ferrous metal processing technology, and relates to the production process of aluminum foil, and particularly to a method for controlling the brightness of the front and back sides of double-zero aluminum foil. Background Technology

[0002] With the booming development of the packaging industry, aluminum foil with a thickness of less than 0.009mm (hereinafter referred to as double-zero foil) is widely used in packaging composite substrates for industries such as pharmaceuticals, food, beverages, and tobacco. Aluminum foil packaging has characteristics such as sealing, moisture resistance, odorlessness, low air permeability, and good light-blocking properties, and is increasingly used in the packaging field. According to incomplete statistics, the total consumption of aluminum foil for packaging in China reached 1.15 million tons in 2022, indicating a broad market prospect.

[0003] Currently, aluminum foil production typically uses a 4-roll mill. Due to its thinness, double-zero aluminum foil is usually produced by stacking two sheets of aluminum foil of the same thickness. The rolling process uses rolling oil as a lubricant, and the surface of the rolled aluminum foil is coated with a very thin oil film. After being cut into the specifications specified by the customer, it undergoes annealing to remove the oil, and only aluminum foil with a certain degree of plasticity and surface cleanliness can be used for packaging materials.

[0004] After being laminated, the upper and lower surfaces of the double-zero aluminum foil that are in contact with the rolls are called the bright surface; the double-sided surfaces that are not in contact with the rolls are called the matte surface. Because they have not been polished by the rolls, they are darker in brightness. All aluminum foils produced by lamination will have this brightness characteristic.

[0005] During the use of aluminum foil for cigarettes, most of it undergoes a dyeing process. However, due to the inconsistent gloss of the aluminum foil substrate, the color effect of the packaged products after dyeing can vary even with the same dyeing process. This can negatively impact the customer experience and may even lead to unnecessary questions about the authenticity of the products.

[0006] Therefore, many customers require aluminum foil manufacturers to provide aluminum foil with specified brightness values ​​on both sides, and the brightness value fluctuation in the width direction must be ≤3Lx, in order to ensure that the color brightness of the subsequent packaging aluminum foil materials achieves a long-term stable and consistent effect. Summary of the Invention

[0007] This invention discloses a method for controlling the brightness of the front and back sides of a double-zero aluminum foil.

[0008] This invention is only described in the context of the production of 6μm aluminum foil used in cigarette aluminum foil paper where high brightness is required, but this does not limit the scope of protection of this invention.

[0009] Technical solution

[0010] A method for controlling the brightness of both sides of a double-zero aluminum foil, where the alloy of the aluminum sheet raw material has a strong correlation with the brightness of the finished aluminum foil; increasing the reduction rate increases the brightness value of the matte surface; increasing the surface roughness of the rolls increases the brightness value of the front surface; taking the production of 6μm aluminum foil as an example, the method includes the following steps:

[0011] Step 1: Rough rolling

[0012] The pass thickness is 0.24~0.26mm→0.105mm→0.04mm, and the roughness of the roughing roll is Ra:0.32~0.36μm;

[0013] When the required gloss level of the matte finish is 35-41 Lx, the raw material alloy should be 1235.

[0014] When the required gloss level of the matte finish is 41-47 Lx, 8079 alloy is used for the raw material.

[0015] Positive surface brightness has no requirements for the raw material alloy.

[0016] Step 2, intermediate rolling

[0017] The pass thickness is 0.04mm → 0.0135~0.015mm.

[0018] When the finished matte finish brightness is required to be 35-39 Lx, the roughness of a single working roll is selected as Ra: 0.13~0.15μm, and the raw material alloy is 1235;

[0019] When the finished matte finish brightness is required to be 37-41 Lx, the roughness of a single working roll is selected as Ra: 0.15~0.17μm, and the raw material alloy is 1235;

[0020] When the finished matte finish brightness is required to be 41-44 Lx, the roughness of a single working roll is selected as Ra: 0.13~0.15μm, and the raw material alloy is 8079;

[0021] When the finished matte finish brightness is required to be 44-47 Lx, the roughness of a single working roll is selected as Ra: 0.15~0.17μm, and the raw material alloy is 8079;

[0022] Step 3: Double-layer finishing rolling

[0023] The pass thickness is 0.0135-0.015mm → double pass thickness is 0.006mm.

[0024] A. The matte finish brightness is achieved using the following process based on the required brightness range:

[0025] When the finished matte finish brightness is required to be 35-39 Lx, the raw material alloy is 1235, and the finishing rolling passes are 13.5~14.3→double-layer 0.006mm.

[0026] When the finished matte finish brightness is required to be 37-41 Lx, the raw material alloy is 1235, and the finishing rolling passes are 14.3~15.0→double-layer 0.006mm.

[0027] When the finished matte finish brightness is required to be 41-44 Lx, for raw material alloy 8079, the finishing rolling passes are 13.5~14.3→double-layer 0.006mm.

[0028] When the finished matte finish brightness is required to be 44-47Lx, the raw material is 8079 alloy, and the finishing rolling passes are 14.3~15.0→double 0.006mm.

[0029] B. The surface brightness is determined according to the required range using the following process:

[0030] When the required surface brightness is 17-21 Lx, the roughness of the finishing roll should be Ra: 0.09-0.10 μm;

[0031] When the required surface brightness is 21-25 Lx, the roughness of the finishing roll should be Ra: 0.11-0.12 μm;

[0032] When the required surface brightness is 25-29 Lx, the roughness of the finishing roll should be Ra: 0.13-0.14 μm;

[0033] Step 4: Brightness detection, slicing, and annealing.

[0034] In a preferred embodiment of the present invention, in step three, before starting the finishing rolling, the finishing rolls are stretched for 15 to 20 minutes with aluminum material of equal or greater width to avoid affecting the brightness of the positive surface of the aluminum foil.

[0035] In a preferred embodiment of the present invention, the rolling oil temperature used in step three is 40–60°C, preferably 45–48°C.

[0036] In a preferred embodiment of the present invention, the two laminated aluminum foils in step three are uniformly sprayed with 80# base oil.

[0037] The double-zero aluminum foil obtained in step three was measured using a dedicated spectrophotometer, a Konica Minolta CM2500C from Japan, to read the luminance value (Lx, in lux). During measurement, the spectrophotometer must be oriented perpendicular to the rolling line direction.

[0038] If the customer has requirements for the brightness values ​​of both the front and back sides of the packaging aluminum foil, then the front and matte surfaces must be measured simultaneously.

[0039] Products with acceptable surface brightness values ​​are transported to a slitting machine for slitting according to customer requirements, followed by annealing. The surface brightness value of the aluminum foil remains unchanged before and after annealing.

[0040] Beneficial effects

[0041] This invention achieves the goal of controlling the surface brightness value of aluminum foil for packaging by strictly controlling process parameters such as alloy type, pressure ratio, and roll roughness. It better meets the high-end market's consistent requirements for aluminum foil surface brightness value, which is beneficial to the long-term stable and consistent surface quality of packaging products for customers, meets the needs of the specialty packaging aluminum foil market, and enhances market competitiveness. Detailed Implementation

[0042] The present invention will be described in detail below with reference to specific embodiments, so that those skilled in the art can better understand the present invention, but the present invention is not limited to the following embodiments.

[0043] Example 1

[0044] Customer's finished product quality requirements: thickness 6μm±3%, surface gloss value 21~24Lx, matte surface gloss value 37~40Lx; tensile strength 60~90N / mm 2 Elongation ≥ 1.0%; Pinhole count ≤ 200 / m 2 There are no invisible pinholes.

[0045] A method for controlling the brightness of the front and back sides of a double-zero aluminum foil includes the following steps:

[0046] Step 1: Rough rolling

[0047] Select alloy 1235-H14, preferably 0.24 mm thick raw material, and process it into a single foil with a thickness of 0.0143-0.015 mm through two rough rolling passes and one intermediate rolling pass. The rolling pass allocation is as follows:

[0048] 0.24mm → 0.105mm → 0.04mm → (single sheet) 0.0143~0.015mm → (stacked) 2×0.006mm; The parameters of the rolls used in step one are as follows:

[0049] The roughness Ra of the roughing mill work roll is 0.35μm (between 0.34 and 0.36μm), and it is ground with a Japanese Noritake 150# grinding wheel.

[0050] Step 2, intermediate rolling

[0051] The 0.04mm thick material obtained from the rough rolling process is then subjected to intermediate rolling to achieve a thickness of 0.04mm (single sheet) → 0.0143~0.015mm (stacked) → 2×0.006mm.

[0052] For single-pass milling, the roll surface roughness is selected as Ra: 0.17μm (between 0.16 and 0.17μm); grinding is performed using a Japanese Noritake 220# grinding wheel;

[0053] Step 3, Double-layer finishing rolling

[0054] a. The single zero aluminum foil obtained in step 2 above is subjected to the fourth pass (0.0143~0.015mm)×2→(stack rolling)0.006mm×2 on a finishing mill to obtain an aluminum foil with a thickness of 0.006mm×2.

[0055] b. The surface roughness of the finishing rolls used in this step is between Ra: 0.11μm (0.105~0.115μm), and grinding is performed using a Japanese brand Noritake 320# grinding wheel;

[0056] c. Because the surface roughness of the new finishing roll is in an unstable state, before the new roll is produced, it is necessary to arrange to use materials of the same or greater width for about 15 to 20 minutes to pull the roll to avoid the unstable state of the positive surface brightness.

[0057] d. The two overlapping aluminum foils are uniformly sprayed with 80# base oil commonly used in the market to effectively ensure uniform brightness and color consistency of the matte surface;

[0058] e. The oil temperature during the double rolling process is set at 45-48℃;

[0059] Finishing rolling blanking inspection results:

[0060] Thickness 5.9–6.1 μm, gloss value of the front surface 21.5–24 Lx, gloss value of the matte surface 37.5–40 Lx; pinhole count ≤200 / m 2 There are no visible pinholes, and the brightness and pinhole size meet the quality requirements of the finished product.

[0061] Step 4: Brightness re-inspection, slitting, and annealing.

[0062] The double-zero aluminum foil obtained in step 3 is cut according to the plan requirements, and then re-inspected after cutting; during measurement, the reading direction of the spectrophotometer is required to be perpendicular to the rolling line direction;

[0063] Products that pass the brightness test will continue to be cut; those that fail will need to be recut into other specifications.

[0064] After slitting, the products undergo annealing and degreasing to restore the mechanical properties of the aluminum foil, thus meeting the surface quality and processing performance requirements of packaging aluminum foil.

[0065] The brightness values ​​of the aluminum foil surface after exiting the furnace are as follows: 21.3~23.9Lx for the front surface and 37.5~40Lx for the matte surface, which is consistent with the inspection of the fine rolling blank and meets the brightness requirements of the finished product.

[0066] Example 2

[0067] Customer's finished product quality requirements: thickness 6μm±3%, surface gloss value 25~28Lx, matte surface gloss value 35~38Lx; tensile strength 60~90N / mm 2 Elongation ≥ 1.0%; Pinhole count ≤ 200 / m 2 There are no invisible pinholes.

[0068] A method for controlling the brightness of the front and back sides of a double-zero aluminum foil includes the following steps:

[0069] Step 1: Rough rolling

[0070] Select alloy 1235-H14, preferably 0.24 mm thick raw material, and process it into a single foil with a thickness of 0.0135-0.0143 mm through two rough rolling passes and one intermediate rolling pass. The rolling pass allocation is as follows:

[0071] 0.24mm → 0.105mm → 0.04mm → (single sheet) 0.0135~0.0143mm → (stacked) 2×0.006mm; The parameters of the rolls used in step one are as follows:

[0072] The roughness Ra of the roughing mill work roll is 0.35μm (between 0.34 and 0.36μm), and it is ground with a Japanese Noritake 150# grinding wheel.

[0073] Step 2, intermediate rolling

[0074] The 0.04mm thick material obtained from the rough rolling process is then subjected to intermediate rolling of 0.04mm → (single sheet) 0.0135~0.0143mm → (stack rolling) 2×0.006mm.

[0075] For single-pass milling, the roll surface roughness is selected as Ra: 0.14μm (between 0.135 and 0.145μm); grinding is performed using a Japanese Noritake 220# grinding wheel.

[0076] Step 3, Double-layer finishing rolling

[0077] a. The single zero aluminum foil obtained in step 2 above is subjected to the fourth pass (0.0135~0.0145mm)×2→(stack rolling)0.006mm×2 on a finishing mill to obtain an aluminum foil with a thickness of 0.006mm×2.

[0078] b. The surface roughness of the finishing rolls used in this step is between Ra: 0.13 and 0.14 μm, and grinding is performed using a Japanese brand Noritake 320# grinding wheel;

[0079] c. Since the surface of the new finishing roll is in an unstable state, before formal production, arrange to use material of the same or greater width to pull the roll for about 15 to 20 minutes to avoid the unstable state of the positive surface brightness.

[0080] d. During the stacking process, 80# base oil is sprayed evenly between the two aluminum foils to ensure uniform brightness and color consistency of the matte surface.

[0081] e. The oil temperature during the double rolling process is set at 45-48℃.

[0082] Finishing rolling blanking inspection results:

[0083] Thickness 5.9–6.15 μm, gloss value of the front surface 25.5–28 Lx, gloss value of the matte surface 35.5–38 Lx; pinhole count ≤200 / m 2 There are no visible pinholes, and the brightness and pinhole size meet the quality requirements of the finished product.

[0084] Step 4: Brightness re-inspection, slitting, and annealing.

[0085] The double-zero aluminum foil obtained in step 3 is cut according to the plan requirements, and then re-inspected after cutting.

[0086] During measurement, the reading direction of the spectrophotometer must be perpendicular to the rolling line direction.

[0087] Products that pass the brightness test will continue to be slit; those that fail will need to be recut into other specifications.

[0088] After slitting, the products undergo annealing and degreasing to restore the mechanical properties of the aluminum foil, thus meeting the surface quality and processing performance requirements of packaging aluminum foil.

[0089] The brightness values ​​of the aluminum foil surface after exiting the furnace are as follows: 25.2~27.9Lx for the front surface and 35.5~38Lx for the matte surface, which is consistent with the inspection of the fine rolling blank and meets the brightness requirements of the finished product.

[0090] Example 3

[0091] Customer's finished product quality requirements: thickness 6μm±3%, surface gloss value 21~24Lx, matte surface gloss value 44~47Lx; tensile strength 60~90N / mm 2 Elongation ≥ 1.0%; Pinhole count ≤ 200 / m 2 There are no invisible pinholes.

[0092] A method for controlling the brightness of the front and back sides of a double-zero aluminum foil includes the following steps:

[0093] Step 1: Rough rolling

[0094] Alloy 8079-H14 is selected, preferably with a thickness of 0.24 mm. The raw material is subjected to two rough rolling passes and one intermediate rolling pass to produce a single foil with a thickness of 0.0143–0.015 mm. The rolling pass allocation is as follows:

[0095] 0.24mm → 0.105mm → 0.04mm → (single sheet) 0.0143~0.015mm → (stacked) 2×0.006mm; The parameters of the rolls used in step one are as follows:

[0096] The roughing mill work roll surface roughness Ra: 0.35μm (between 0.34 and 0.36μm); grinding with a Japanese Noritake 150# grinding wheel;

[0097] Step 2, intermediate rolling

[0098] The 0.04mm thick material obtained from the rough rolling process is then rolled into 0.04mm (single sheet) 0.0143~0.015mm (stacked) 2×0.006mm.

[0099] For single-pass milling, the roll surface roughness is selected as Ra: 0.17μm (between 0.16 and 0.17μm); grinding is performed using a Japanese Noritake 220# grinding wheel;

[0100] Step 3, Double-layer finishing rolling

[0101] a. The single zero aluminum foil obtained in step 2 above is subjected to the fourth pass (0.0143~0.015mm)×2→(stack rolling)0.006mm×2 on a finishing mill to obtain an aluminum foil with a thickness of 0.006mm×2.

[0102] b. The surface roughness of the finishing rolls used in this step is between Ra: 0.12 (0.11~0.12μm), and grinding is performed using a Japanese brand Noritake 320# grinding wheel;

[0103] c. Since the surface of the new precision roll is in an unstable state during the initial production stage, before formal production, arrange to use material of the same or greater width to pull the roll for about 15 to 20 minutes to avoid the unstable state of the positive surface brightness.

[0104] d. During the stacking process, 80# base oil is sprayed evenly between the two aluminum foils to ensure uniform brightness and color consistency of the matte surface;

[0105] e. The oil temperature during the double rolling process is set at 45-48℃;

[0106] Finishing rolling blanking inspection results:

[0107] Thickness 5.85–6.15 μm, surface gloss value 21.5–24 Lx, surface gloss value 44.5–47 Lx; pinhole count ≤200 / m 2 There are no visible pinholes, and the brightness and pinhole size meet the quality requirements of the finished product.

[0108] Step 4: Brightness re-inspection, slitting, and annealing.

[0109] The double-zero aluminum foil obtained in step 3 is cut according to the plan requirements, and then re-inspected after cutting.

[0110] During measurement, the reading direction of the spectrophotometer must be perpendicular to the rolling line direction.

[0111] Products that pass the brightness test will continue to be slit; those that fail will need to be recut into other specifications.

[0112] After slitting, the products undergo annealing and degreasing to restore the mechanical properties of the aluminum foil, thus meeting the surface quality and processing performance requirements of packaging aluminum foil.

[0113] The brightness values ​​of the aluminum foil surface after exiting the furnace are as follows: 21.3~23.9Lx for the front surface and 44.5~47Lx for the matte surface, which is consistent with the inspection of the fine rolling blank and meets the brightness requirements of the finished product.

[0114] The above description is merely an embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural or procedural transformations made using the present invention specification, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A method for controlling the brightness of both sides of a double-zero aluminum foil, wherein the alloy of the aluminum sheet blank and the matte brightness of the finished aluminum foil have a significant impact; increasing the reduction rate increases the matte brightness value; increasing the surface roughness of the rolls increases the brightness value of the front surface; characterized in that, The finished thickness of the double-zero aluminum foil is 6μm, and the process includes the following steps: Step 1: Rough rolling The pass thickness is 0.24~0.26mm→0.105mm→0.04mm, and the roughness of the roughing roll is Ra: 0.32~0.36μm; When the finished matte finish requires a brightness of 35-41 Lx, 1235 alloy should be selected for the raw material. When the finished matte finish requires a brightness of 41-47 Lx, 8079 alloy should be selected for the raw material. Step 2, intermediate rolling The pass thickness is 0.04mm → 0.0135~0.015mm. When the finished matte finish brightness is required to be 35-39 Lx, the roughness of a single working roll is selected as Ra: 0.13~0.15μm, and the raw material alloy is selected as 1235; When the finished matte finish brightness is required to be 37-41 Lx, the roughness of a single working roll is selected as Ra: 0.15~0.17μm, and the raw material alloy is selected as 1235; When the finished matte finish brightness is required to be 41-44 Lx, the roughness of a single working roll is selected as Ra: 0.13~0.15μm, and the raw material alloy is selected as 8079; When the finished matte finish brightness is required to be 44-47 Lx, the roughness of a single working roll is selected as Ra: 0.15~0.17μm, and the raw material alloy is selected as 8079; Step 3: Double-layer finishing rolling The pass thickness is 0.0135–0.015 mm → double pass thickness is 0.006 mm. A. The matte finish brightness is achieved using the following process based on the required brightness range: When the finished matte finish brightness is required to be 35-39 Lx, the raw material alloy is 1235, and the finishing rolling passes are 13.5~14.3μm→double-layer 0.006mm. When the finished matte finish brightness is required to be 37-41 Lx, the raw material alloy is 1235, and the finishing rolling passes are 14.3~15.0μm→double-layer 0.006mm. When the finished matte finish brightness is required to be 41-44 Lx, the raw material alloy is 8079, and the finishing rolling passes are 13.5~14.3μm→double-layer 0.006mm. When the finished matte finish brightness is required to be 44-47 Lx, the raw material alloy is 8079, and the finishing rolling passes are 14.3~15.0μm→double-layer 0.006mm. B. The surface brightness is determined according to the required range using the following process: When the surface brightness of the finished product is required to be 17-21 Lx, the roughness of the finishing roll should be selected as Ra: 0.09-0.10 μm; When the surface brightness of the finished product is required to be 21-25 Lx, the roughness of the finishing roll should be selected as Ra: 0.11-0.12 μm; When the surface brightness of the finished product is required to be 25-29 Lx, the roughness of the finishing roll should be selected as Ra: 0.13-0.14μm; Step 4: Brightness detection, slicing, and annealing.

2. The method for controlling the brightness of the front and back sides of double-zero aluminum foil according to claim 1, characterized in that: In step three, before starting the finishing rolling, the finishing roll is stretched for 15 to 20 minutes with aluminum material no less than the width of the finishing roll to avoid the unstable surface roughness of the new roll affecting the stability of the brightness of the positive surface of the aluminum foil.

3. The method for controlling the brightness of the front and back sides of double-zero aluminum foil according to claim 1, characterized in that: The rolling oil used in step three has a temperature of 40–60°C.

4. The method for controlling the brightness of the front and back sides of double-zero aluminum foil according to claim 3, characterized in that: The rolling oil used in step three has a temperature of 45–48°C.

5. The method for controlling the brightness of the front and back sides of a double-zero aluminum foil according to claim 1, characterized in that: In step three, the two overlapping aluminum foils are uniformly sprayed with 80# base oil.