A process for nickel-free closed aluminum with lithium salt

Abstract

The application discloses a process method for lithium-salt nickel-free closed aluminum, which comprises the following parts: a countermeasure for serious powdering of a closed surface, a countermeasure for sticking of a composite film, a countermeasure for discoloration of electrolytic coloring material, and a countermeasure for difficulty in reaching a standard of a weight loss value in closed quality detection. The process method for lithium-salt nickel-free closed aluminum solves the technical problems of serious powdering of a closed surface, sticking of a composite film, easy discoloration of electrolytic coloring material, and difficulty in reaching a standard of a weight loss value in closed quality detection in the prior art.

Description

Technical Field

[0001] This invention relates to the field of chemistry, and more specifically to a process for producing nickel-free closed aluminum with lithium salts. Background Technology

[0002] As my country's policies and regulations increasingly emphasize environmental protection, the control and requirements for nickel-containing wastewater discharge have become increasingly stringent. Nickel-containing wastewater discharged by aluminum anodizing surface treatment companies originates from the electrolytic coloring and sealing processes. In recent years, the vast majority of companies successfully transitioned from the Sn-Ni mixed salt electrolytic coloring process to the environmentally friendly single Sn salt process, essentially solving the nickel-containing wastewater problem in the electrolytic coloring process. Subsequently, research and development have shifted towards nickel-free sealing, leading to the emergence of many new nickel-free sealing environmentally friendly processes.

[0003] Lithium salt sealing processes offer relatively low control temperatures and stable sealing quality, making them a promising new technology among nickel-free sealing methods. However, it has unfortunately not yet been widely adopted in industrial production. The reasons for this can be attributed to the following two aspects:

[0004] (1) The relative costs of lithium salt sealant manufacturers and users are higher than those of traditional nickel-containing sealants. Due to the rapid development of the lithium battery industry required for new energy vehicles, the prices of many lithium-containing chemical products used in the production of lithium salt sealants, such as lithium sulfate (Li2SO4), lithium acetate (CH2COOLi), lithium carbonate (Li2CO3), lithium hydroxide (LiOH) and lithium fluoride (LiF), have been rising steadily. As a result, both lithium salt sealant manufacturers and users have to bear the relative increase in production costs. This unavoidable production cost problem has become a major obstacle to the promotion of lithium salt sealing technology.

[0005] (2) As a new process, lithium salt sealing lacks practical experience in application. Some lithium salt sealing agent manufacturers, especially those whose production and R&D are disconnected, hastily push their products to the market. In the initial application stage, they encounter many serious production and quality problems and cannot help the users solve them in time. As a result, the users are pushed back to the old path of using nickel-containing sealing process. The practical application problems of lithium salt sealing are: serious powdering on the sealing surface, easy adhesion of composite film, "discoloration" of sealing electrolytic coloring material, and difficulty in fully meeting the weight loss value of sealing quality test. Summary of the Invention

[0006] The purpose of this invention is to provide a process for lithium salt nickel-free sealed aluminum to solve the technical problems in the prior art, such as severe powdering on the sealed surface, adhesive bonding of the film, easy discoloration of electrolytic colorants, and difficulty in meeting the sealing quality test values.

[0007] To achieve the above objectives, the present invention provides a process for producing nickel-free closed aluminum with lithium salts, comprising the following measures:

[0008] S1. Severe powdering on the sealed surface: The more Al and K enter or accumulate in the sealing bath, the more precipitates will be formed. Therefore, it is necessary to control the content of Al3+ in the anodizing bath and the content of accumulated K+ in the sealing bath.

[0009] S2. Countermeasures for adhesive bonding of composite membranes: Since the higher the temperature of the hot pure water in the sealing post-treatment, the more serious the adhesive bonding of composite membranes will be, it is necessary to reduce the temperature of the anodizing bath, reduce the concentration of F- in the sealing bath, and reduce the water addition ratio.

[0010] S3. Countermeasures for discoloration of electrolytic colorants: Since discoloration of electrolytic colorants is caused by excessively fast sealing speed, resulting in insufficient filling of the sealing product or overflow of the sealing product from the mold cavity, it is necessary to reduce the concentration of F- in the sealing bath and the sealing temperature.

[0011] S4. Solutions for difficulty in meeting the weight loss value of sealing quality test: Since the sealing products of lithium salt sealing can enter deeper membrane pores, although the corrosion marks on the sample surface after the phosphoric acid weight loss test are very slight, the calculated weight loss value is often slightly higher than the standard for building aluminum. Therefore, it is necessary to appropriately reduce the temperature of the anodizing bath and add a hot water washing treatment after lithium salt sealing.

[0012] Furthermore, methods for controlling the Al3+ content in the anodizing bath and the accumulated K+ content in the closed bath include:

[0013] S11. After anodizing, a 2-3 water rinse is required before sealing. The pH value of the water rinse before sealing must be controlled at ≥4. The water rinse before sealing is thorough, which avoids the Al3+ in the anodizing bath from being carried into the sealing bath and also avoids the need to frequently adjust the pH value of the sealing bath with KOH.

[0014] S12. The F- content in the lithium salt sealing additive can be partially replaced by other fluorides that do not contain K, such as KHF2. The cumulative equilibrium value of K+ in the sealing bath is directly proportional to the K content in the lithium salt sealing additive. When there is no K component in the sealing agent, the cumulative equilibrium value of K+ in the bath depends on the pH value of the water wash before sealing. The lower the pH value, the more KOH is needed to adjust the pH value of the sealing bath, so that the cumulative equilibrium value of K+ in the sealing bath tends to increase.

[0015] S13. In the pre-sealing water wash, or directly in the lithium salt sealing tank, add an appropriate amount of a certain A13+ complexing agent that has no negative effect on sealing, in order to reduce the precipitates generated in the sealing tank.

[0016] S14. For enhanced filtration of closed tank liquid, the filter flow rate should be more than 3 times the volume of the closed tank liquid per hour, and the filter medium particle size should be more than 14m. During normal production, the filter should always be in operation, and the filter cloth or filter element should be cleaned and replaced in a timely manner.

[0017] Furthermore, the content of Al3+ in the anodizing bath needs to be controlled in consideration of production costs, and the content of Al3+ in the anodizing bath should be controlled within ≤18g / L.

[0018] Furthermore, methods to reduce the temperature of the anodizing bath, reduce the concentration of F- in the closed bath, and reduce the water addition ratio include:

[0019] S21. Appropriately reduce the temperature of the anodic oxidation bath. The film structure obtained at a low temperature in the anodic oxidation bath will not have film quality problems such as looseness, large pores, or blocked pores. This makes it easier for F- in the lithium salt sealing bath to carry Li+ into the bottom of the deeper pores, and also reduces the difficulty of sealing the shallow surface. The temperature of the anodic oxidation bath is controlled at 18-20°C.

[0020] S22. Appropriately reduce the F- concentration in the sealing tank solution. For sealing ordinary silver-white materials, the F- concentration should be controlled at 0.3-0.5 g / L. For sealing electrolytic coloring materials, especially black materials, in order to prevent the "discoloration" problem, the F- concentration should be controlled to the lower limit.

[0021] S23. Add a certain surfactant that has a lubricating effect and has little or no negative effect on sealing to the lithium salt sealing tank solution or to the hot water in the post-sealing process.

[0022] S24. Select a low-viscosity composite membrane for lithium salt sealing products. The adhesive layer on the surface of the composite membrane is originally a mixture of water, glue, and additives, which is then coated onto a sanded rubber sheet and cured at high temperature. By appropriately reducing the proportion of glue, the viscosity of the composite membrane can be reduced.

[0023] Furthermore, methods for reducing the concentration of F- in the sealing tank solution and the sealing temperature in S3 include:

[0024] S31. Appropriately reduce the F- concentration and sealing temperature of the sealing tank solution; add a certain surfactant to the hot water for the post-sealing treatment of lithium salt. This surfactant has the effect of inhibiting "discoloration" and has little negative effect on sealing.

[0025] S32. To ensure the quality of the extruded substrate and prevent the electrolytic colorant from undergoing a closed "color change", it is advisable to adopt an aging process that appropriately lowers the aging temperature and appropriately extends the aging holding time.

[0026] Furthermore, in the S31 pilot-scale test of the blocked electrolytic colorant, in order to effectively suppress the "discoloration" and ensure the sealing quality, the F- concentration was 0.25-0.30 g / L, the sealing temperature was 28-30°C, and the concentration of a certain surfactant in the hot water for post-sealing treatment was 0.5-1.5 g / L.

[0027] Furthermore, the methods in S4 for reducing the temperature of the anodizing bath and adding a hot water wash after lithium salt sealing include...

[0028] S41. Appropriately reduce the temperature of the anodic oxidation bath. The film structure obtained at a low temperature in the anodic oxidation bath will not have film quality problems such as looseness, large pores, or blocked pores. This makes it easier for F- in the lithium salt sealing bath to carry Li+ into the bottom of the deeper pores, and also reduces the difficulty of sealing the shallow surface. The temperature of the anodic oxidation bath is controlled at 18-20°C.

[0029] S42. After lithium salt sealing, add a hot water wash treatment, controlling the hot water temperature at 60-70°C. To prevent the "discoloration" problem of the composite film adhesive and electrolytic coloring products, add a small amount of a certain surfactant that has little or no negative effect on sealing to the hot water. The higher the temperature of the hot water after sealing, the lower the weight loss value.

[0030] Furthermore, the relationship between the hot water temperature and weight loss value after sealing in S42 is as follows: film thickness 15-18 μm, sealing pH value 7.8-8.6, sealing time 15-18 min; hot water temperature after sealing 60°C, time 20 min; phosphochromic acid weight loss test is performed on the sample after aging for 120 h.

[0031] Based on the above technical solution, the present invention can produce the following beneficial effects:

[0032] The present invention provides a process for lithium salt nickel-free sealed aluminum. In actual production applications, as long as the quality of the extruded substrate is well controlled, the process parameters of the preceding anodizing process and lithium salt sealing are appropriately adjusted, a hot water washing process is added after sealing, and a certain surfactant is added to the hot water for post-sealing, some application problems of lithium salt sealing can be solved. Attached Figure Description

[0033] Figure 1 This is a graph showing the relationship between the equilibrium concentration of accumulated K in the sealing tank solution and the K content in the sealing agent in this invention.

[0034] Figure 2 This is a graph showing the relationship between the temperature of the hot water and the weight loss value after the closed treatment according to the present invention. Detailed Implementation

[0035] To better understand the purpose, structure, and function of this invention, the following detailed description of a process for producing nickel-free lithium salt-enclosed aluminum is provided in conjunction with the accompanying drawings.

[0036] In the description of this invention, it should be noted that the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0037] This invention discloses a process for lithium salt nickel-free closed aluminum, comprising the following measures:

[0038] S1. Severe powdering on the sealed surface: The more Al and K enter or accumulate in the sealing bath, the more precipitates will be formed. Therefore, it is necessary to control the content of Al3+ in the anodizing bath and the content of accumulated K+ in the sealing bath.

[0039] S2. Countermeasures for adhesive bonding of composite membranes: Since the higher the temperature of the hot pure water in the sealing post-treatment, the more serious the adhesive bonding of composite membranes will be, it is necessary to reduce the temperature of the anodizing bath, reduce the concentration of F- in the sealing bath, and reduce the water addition ratio.

[0040] S3. Countermeasures for discoloration of electrolytic colorants: Since the discoloration of electrolytic colorants is caused by excessively fast sealing speed, resulting in insufficient filling of the sealing product or overflow of the sealing product from the mold hole, it is necessary to reduce the concentration of F- in the sealing bath and the sealing temperature.

[0041] S4. Solutions for difficulty in meeting the weight loss value of sealing quality test: Since the sealing products of lithium salt sealing can enter deeper membrane pores, although the corrosion marks on the sample surface after the phosphoric acid weight loss test are very slight, the calculated weight loss value is often slightly higher than the standard for building aluminum. Therefore, it is necessary to appropriately reduce the temperature of the anodizing bath and add a hot water washing treatment after lithium salt sealing.

[0042] Furthermore, methods for controlling the Al3+ content in the anodizing bath and the accumulated K+ content in the closed bath include:

[0043] S11. After anodizing, a 2-3 water rinse is required before sealing. The pH value of the water rinse before sealing must be controlled at ≥4. The water rinse before sealing is thorough, which avoids the Al3+ in the anodizing bath from being carried into the sealing bath and also avoids the need to frequently adjust the pH value of the sealing bath with KOH.

[0044] S12. The F- content in the lithium salt sealing additive can be partially replaced by other fluorides that do not contain K, such as KHF2. The cumulative equilibrium value of K+ in the sealing bath is directly proportional to the K content in the lithium salt sealing additive. When there is no K component in the sealing agent, the cumulative equilibrium value of K+ in the bath depends on the pH value of the water wash before sealing. The lower the pH value, the more KOH is needed to adjust the pH value of the sealing bath, so that the cumulative equilibrium value of K+ in the sealing bath tends to increase.

[0045] S13. In the pre-sealing water wash, or directly in the lithium salt sealing tank, add an appropriate amount of a certain A13+ complexing agent that has no negative effect on sealing, in order to reduce the precipitates generated in the sealing tank.

[0046] S14. For enhanced filtration of closed tank liquid, the filter flow rate should be more than 3 times the volume of the closed tank liquid per hour, and the filter medium particle size should be more than 14m. During normal production, the filter should always be in operation, and the filter cloth or filter element should be cleaned and replaced in a timely manner.

[0047] Furthermore, the content of Al3+ in the anodizing bath needs to be controlled in consideration of production costs, and the content of Al3+ in the anodizing bath should be controlled within ≤18g / L.

[0048] Furthermore, methods to reduce the temperature of the anodizing bath, reduce the concentration of F- in the closed bath, and reduce the water addition ratio include:

[0049] S21. Appropriately reduce the temperature of the anodic oxidation bath. The film structure obtained at a low temperature of the anodic oxidation bath will not have film quality problems such as looseness, large pores, and poor pore flow. This makes it easier for F- in the lithium salt sealing bath to carry Li+ into the bottom of the deep pores. It also reduces the difficulty of sealing shallow surfaces. The temperature of the anodic oxidation bath should be controlled at 18-20°C.

[0050] S22. Appropriately reduce the F- concentration in the sealing tank solution. For sealing ordinary silver-white materials, the F- concentration should be controlled at 0.3-0.5 g / L. For sealing electrolytic coloring materials, especially black materials, in order to prevent the "discoloration" problem, the F- concentration should be controlled to the lower limit.

[0051] S23. Add a certain surfactant that has a lubricating effect and has little or no negative effect on sealing to the lithium salt sealing tank solution or to the hot water in the post-sealing process.

[0052] S24. Select a low-viscosity composite membrane for lithium salt sealing products. The adhesive layer on the surface of the composite membrane is originally a mixture of water, glue, and additives, which is then coated onto a sanded rubber sheet and cured at high temperature. By appropriately reducing the proportion of glue, the viscosity of the composite membrane can be reduced.

[0053] Furthermore, methods for reducing the concentration of F- in the sealing tank solution and the sealing temperature in S3 include:

[0054] S31. Appropriately reduce the F- concentration and sealing temperature of the sealing tank solution; add a certain surfactant to the hot water for the post-sealing treatment of lithium salt. This surfactant has the effect of inhibiting "discoloration" and has little negative effect on sealing.

[0055] S32. To ensure the quality of the extruded substrate and prevent the electrolytic colorant from undergoing a closed "color change", it is advisable to adopt an aging process that appropriately lowers the aging temperature and appropriately extends the aging holding time.

[0056] Furthermore, in the S31 pilot-scale test of the blocked electrolytic colorant, in order to effectively suppress the "discoloration" and ensure the sealing quality, the F- concentration was 0.25-0.30 g / L, the sealing temperature was 28-30°C, and the concentration of a certain surfactant in the hot water for post-sealing treatment was 0.5-1.5 g / L.

[0057] Furthermore, the methods in S4 for reducing the temperature of the anodizing bath and adding a hot water wash after lithium salt sealing include...

[0058] S41. Appropriately reduce the temperature of the anodic oxidation bath. The film structure obtained at a low temperature of the anodic oxidation bath will not have film quality problems such as looseness, large pores, or blocked pores. This makes it easier for F- in the lithium salt sealing bath to carry Li+ into the bottom of the deeper pores, and also reduces the difficulty of sealing the shallow surface. The low temperature of the anodic oxidation bath is 18-20°C.

[0059] S42. After lithium salt sealing, add a hot water wash treatment, controlling the hot water temperature at 60-70°C. To prevent the "discoloration" problem of the composite film adhesive and electrolytic coloring products, add a small amount of a certain surfactant that has little or no negative effect on sealing to the hot water. The higher the temperature of the hot water after sealing, the lower the weight loss value.

[0060] Furthermore, the relationship between the hot water temperature and weight loss value after sealing in S42 is as follows: film thickness 15-18 μm, sealing pH value 7.8-8.6, sealing time 15-18 min; hot water temperature after sealing 60°C, time 20 min; phosphochromic acid weight loss test is performed on the sample after aging for 120 h.

[0061] It is understood that, as described through some embodiments, various changes or equivalent substitutions can be made to these features and embodiments by those skilled in the art without departing from the spirit and scope of the invention. Furthermore, under the teachings of this invention, modifications can be made to these features and embodiments to adapt to specific circumstances and materials without departing from the spirit and scope of the invention. Therefore, this invention is not limited to the specific embodiments disclosed herein, and all embodiments falling within the scope of the claims of this application are within the protection scope of this invention.

Claims

1. A process for producing nickel-free lithium-ion sealed aluminum, characterized in that, Including the following measures: S1: Measures to address severe powdering on sealed surfaces, including controlling Al content in the anodizing bath. 3+ The content and control of K accumulation in the closed tank solution + The content; specific The process includes the following steps: S11: Perform 2-3 water rinses after anodizing and before sealing, with the pH value of the pre-sealing rinse controlled at ≥4; S12: In the lithium salt sealing additive, partially replace KHF2 with a potassium-free fluoride; S13: Add an appropriate amount of Al, which has no negative effect on sealing, to the pre-sealing rinse or directly to the lithium salt sealing bath solution. 3+ Complexing agent, Al in the anodic oxidation bath solution 3+ The content should be controlled within ≤18g / L; S14: Strengthen the filtration of the closed tank liquid, with the filter flow rate being more than 3 times the volume of the closed tank liquid per hour, the filter medium particle size being more than 14μm, and the filter should always be kept running during normal production, and the filter cloth or filter element should be cleaned and replaced in a timely manner. S2: Measures to address the adhesive issues when applying composite films include lowering the temperature of the anodizing bath and reducing the amount of fluoride (F) in the sealed bath. - Reduce the concentration and decrease the water ratio; specific The steps include: S21: Controlling the temperature of the anodizing bath solution at 18-20℃; S22: Sealing the F in the bath solution. - The concentration is controlled at 0.3-0.5 g / L. For electrolytic colorants, the F- concentration is controlled at the lower limit. S23: Add a surfactant with lubricating effect and little or no negative effect on sealing to the lithium salt sealing tank or the hot water after the sealing process. S24: Adjust the adhesive ratio of the composite film, reduce the adhesive ratio to reduce the viscosity of the composite film, and perform high-temperature curing at 38°C. S3: Measures to address discoloration of enclosed electrolytic colorants, including reducing the F content of the enclosed bath solution. - Concentration and sealing temperature; specific Includes the following steps: S31: Appropriately reduce the F of the sealing tank solution. - The concentration and sealing temperature are controlled, and a surfactant with inhibitory "discoloration" effect and minimal negative impact on sealing is added to the hot water after lithium salt sealing. The sealing electrolytic colorant, to effectively inhibit "discoloration" while ensuring sealing quality, [F...] - The concentration is 0.25-0.30 g / L, the sealing temperature is controlled at 28-30℃, and the concentration of a certain surfactant in the hot water after sealing is controlled at 0.5-1.5 g / L; S32: The aging process of appropriately reducing the aging temperature and appropriately extending the aging holding time is adopted to ensure the quality of the extruded substrate; S4: Measures to address the difficulty in achieving the required weight loss value in the sealing quality test include appropriately reducing the temperature of the anodizing bath and adding a hot water wash after lithium salt sealing; specifically, the following steps are included: S41: Control the temperature of the anodizing bath at 18-20℃; S42: Add a hot water wash after lithium salt sealing, controlling the hot water temperature at 60-70℃, and adding a small amount of surfactant with little or no negative effect on sealing to the hot water.

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