Post-treatment method of low-pressure corrosion foil

Abstract

The invention belongs to the technical field of low-pressure corrosion foils, and particularly relates to a post-processing method of a low-pressure corrosion foil. The post-treatment method comprises the following steps: carrying out the following operations on the aluminum foil subjected to corrosion, acid pickling and first water washing: S1, removing an aluminum hydroxide layer blocking a corrosion hole; and S2, soaking in a mixed solution of acid and water with the pH value of 5-6.5 for 2-4 minutes, washing with water for the second time, and then carrying out chip burning treatment. According to the post-treatment method disclosed by the invention, at least 80 days of continuous treatment can be realized without causing blockage of reaction tank equipment, and the prepared low-pressure corrosion foil has relatively high specific volume.

Description

Technical Field

[0001] The present invention belongs to the technical field of low-pressure etching foil, and more specifically, relates to a post-processing method of low-pressure etching foil. Background Art

[0002] Aluminum electrolytic capacitors are energy storage components widely used in the electronic and electrical industry, and corrosion foil is one of the key components in aluminum electrolytic capacitors. The existing technology for preparing low-voltage corrosion foil generally adopts the following steps: aluminum foil pretreatment, corrosion treatment, pickling, water washing, and drying to finally obtain corrosion foil. Among them, the pretreatment of aluminum foil is mainly to remove impurities on the surface of aluminum foil, which is conducive to subsequent corrosion; the corrosion treatment is to make corrosion holes appear on the surface of aluminum foil and increase the surface area of ​​aluminum foil; pickling is to remove excess chloride ions on the surface of aluminum foil caused by corrosion; water washing is to remove excess acid and elute impurities. After the above steps are completed, low-voltage corrosion foil can be obtained by drying. However, the low-voltage corrosion foil formed at this time is easy to get damp during storage, and the aluminum surface is prone to chemical reactions, resulting in poor final performance of the low-voltage corrosion foil and small specific capacity.

[0003] In order to solve the above problems, the prior art generally performs post-treatment (stabilization treatment) on the corrosion foil after pickling and water washing to form an oxide film on the surface of the corrosion foil, which plays a protective role for the corrosion foil. It can effectively prevent moisture or aluminum surface changes within one year, and can increase the specific volume of low-pressure corrosion foil. At present, the common post-treatment method is to use alkaline or weak alkaline substances, and organic acids or inorganic acids can be added to make the pH value of the post-treatment liquid weakly alkaline. The alkaline liquid reacts with the aluminum foil to form aluminum oxide (β-aluminum oxide) or aluminum hydroxide precipitation, and then undergoes high-temperature sintering treatment to convert the aluminum oxide or aluminum hydroxide in the pores of the aluminum foil into γ-aluminum oxide. This γ-aluminum oxide is porous, so the dielectric constant is greater than that of the ordinary aluminum oxide layer, thereby increasing the specific volume of the foil. For example, Chinese patent application CN1967752A discloses a low-voltage anode foil for aluminum electrolytic capacitors and a method for manufacturing the same. The post-treatment method is to soak the etched foil in triethanolamine water after pickling and water washing, and then dry (burn the foil) to obtain a finished etched foil. Compared with the etched foil prepared without post-treatment, the electrostatic capacitance is increased by 5% to 10%, but triethanolamine is a Class 3 carcinogen.

[0004] The current post-treatment method using alkaline or weak alkaline substances to react with aluminum foil for chelation or hydrolysis still has some disadvantages: (1) The chemicals used in the post-treatment method (triethanolamine, ammonia water, etc.) are generally classified as hazardous chemicals, which are not the best choice in terms of hygiene and environmental protection; (2) The cost of chemical reagents involved in the reaction in the post-treatment is relatively high. Since the finished product is obtained after the post-treatment process, the purity of the chemical reagents is also required to be high, generally requiring them to be capacitive pure level, and the price is very expensive; (3) After the inorganic or organic alkaline substances used in the post-treatment react with aluminum, a large amount of sediment will be formed in the reaction tank, which will clog the equipment circulation system over time. If the filtration is not complete, it will also cause appearance defects such as dents on the product surface. Summary of the invention

[0005] The technical problem to be solved by the present invention is to overcome the defects and shortcomings of the prior art post-processing method and provide a post-processing method for low-pressure corrosion foil.

[0006] Another object of the present invention is to provide a method for preparing a low-pressure etching foil.

[0007] Another object of the present invention is to provide a low-pressure corrosion foil prepared by the preparation method.

[0008] The above-mentioned purpose of the present invention is achieved through the following technical solutions:

[0009] The present invention provides a post-processing method for low-pressure corrosion foil, taking the aluminum foil after corrosion, pickling and first water washing, and performing the following operations:

[0010] S1. Remove the aluminum hydroxide layer that blocks the corrosion holes;

[0011] S2. Soak in a mixed solution of acid and water with a pH of 5 to 6.5 for 2 to 4 minutes, wash with water for the second time, and then perform sintering treatment.

[0012] The present invention first cleans the aluminum foil after corrosion, pickling, and the first water washing treatment to remove the unevenly deposited aluminum hydroxide layer that blocks the corrosion holes, so that the hydration reaction in the next soaking process is more sufficient. The inventor found through research that the aluminum oxide on the surface of the aluminum foil reacts with water in a weak acid environment with a specific pH (pH of 5 to 6.5), and will not quickly generate dense hydrated aluminum oxide to cause pore blockage, thereby hindering the reaction. At the same time, by controlling the soaking time, excessive generation of hydrated aluminum oxide to cause pore blockage is avoided; finally, the corroded foil after soaking and water washing is directly subjected to high-temperature sintering treatment to solidify the holes obtained by corrosion, and at the same time, the hydrated aluminum oxide film is directly converted into γ-type aluminum oxide, forming an oxide layer on the surface of the corroded foil, which plays a protective role and increases the specific volume of the corroded foil.

[0013] If the pH value in the mixed solution is too low, the dissolution rate of the generated hydrated aluminum oxide will be greater than the generation rate, making it difficult to form a film in the subsequent process.

[0014] If the immersion time is too long, the amount of hydrated alumina deposited will be too much, which will block the corrosion holes and reduce the specific volume of the low-pressure corrosion foil; if the immersion time is too short, the deposition of hydrated alumina will be insufficient, which will not protect the low-pressure corrosion foil and increase the specific volume.

[0015] The reaction raw materials used in the present invention are more environmentally friendly and low in cost, and after the reaction, a large amount of sediment will not accumulate in the reaction tank to damage the equipment. The post-treatment method of the present invention can be used for at least 80 days in the reaction tank without causing blockage of the reaction tank equipment; while the conventional alkaline substance can cause serious blockage of the reaction tank after 30 days of continuous reaction, and the reaction cannot be continued.

[0016] Preferably, in the post-treatment method of the low-pressure corrosion foil of the present invention, the immersion time is 3 minutes.

[0017] Preferably, the soaking temperature is 25-50°C.

[0018] Preferably, the acid is a weak acid. When a weak acid is added to water, the pH change is relatively slow, which can play a better buffering role and is more beneficial to the hydration reaction of water and aluminum oxide.

[0019] More preferably, the weak acid is one or more of salicylic acid, oxalic acid, citric acid, tartaric acid or benzoic acid.

[0020] Preferably, the temperature of the sintering treatment is 400-500°C.

[0021] Preferably, the sintering treatment time is 0.5 to 1.5 minutes.

[0022] Preferably, in a post-treatment method for low-pressure corrosion foil, the specific operation of step S1 is as follows: taking the aluminum foil after corrosion, pickling and the first water washing treatment, placing it in water and performing ultrasonic treatment.

[0023] Preferably, in a post-treatment method for low-voltage corrosion foil, the specific operation of step S1 is as follows: taking the aluminum foil after corrosion, pickling, and the first water washing treatment, placing it in water to connect to the negative electrode, and conducting an electric treatment.

[0024] Preferably, the duration of the electrical treatment is 5 to 25 seconds; the current of the electrical treatment is 0.01 to 0.1 A / cm 2 .

[0025] The present invention provides a method for preparing a low-pressure corrosion foil, comprising the following steps:

[0026] (1) Aluminum foil pretreatment;

[0027] (2) the aluminum foil pretreated in step (1) is corroded until the aluminum foil with the desired amount of corrosion is obtained, followed by pickling and first water washing to obtain an aluminum foil that has been corroded, pickled, and first water washed;

[0028] (3) Processing is performed according to any of the above-mentioned post-processing methods to obtain a low-pressure corrosion foil.

[0029] Preferably, in a method for preparing a low-pressure corrosion foil, the pretreatment is to place the aluminum foil in a phosphoric acid aqueous solution with a phosphoric acid mass concentration of 1.5 to 3%.

[0030] Preferably, the pretreatment temperature is 75-90° C.; preferably, the pretreatment time is 30-60 s.

[0031] Preferably, the specific step of pickling is: treating in a sulfuric acid solution with a mass concentration of 1 to 20% for 2 to 4 minutes. Preferably, the temperature of pickling is 50 to 60°C.

[0032] Furthermore, the corrosion is electrochemical corrosion.

[0033] Furthermore, the specific operation of the electrochemical corrosion is:

[0034] Electrical corrosion: The aluminum foil after pretreatment is subjected to electrical corrosion in a mixed acid solution, and then washed with water after corrosion is completed;

[0035] Intermediate treatment: the obtained aluminum foil is passivated in the intermediate treatment solution;

[0036] Water washing: wash the treated aluminum foil with water;

[0037] Repeat the steps from electro-etching to water washing until the desired amount of etched aluminum foil is obtained.

[0038] Furthermore, in the electrochemical corrosion, the mixed acid solution is a mixed solution of hydrochloric acid and sulfuric acid, wherein the mass concentration of the hydrochloric acid is 9% to 13%, and the mass concentration of the sulfuric acid is 0.05% to 0.5%.

[0039] Preferably, in the electrochemical corrosion, the current density of the electrified corrosion is 0.05 to 0.45 A / cm 2 The time of the electrocorrosion is 480 to 660 seconds. Preferably, the temperature of the electrocorrosion is 6 to 45°C.

[0040] Furthermore, the intermediate treatment liquid is a phosphide aqueous solution with a mass concentration of 2-5%, and the treatment condition is 85-90° C. for 15-40 seconds. Preferably, the phosphide includes but is not limited to monoammonium phosphate, diammonium phosphate, and the like.

[0041] Furthermore, the present invention protects the low-voltage etching foil prepared by the method for preparing the low-voltage etching foil.

[0042] The present invention has the following beneficial effects:

[0043] The specific volume enhancement effect of the post-treatment method of the present invention is not significantly different from that of the conventional post-treatment using alkaline solution, but the post-treatment method of the present invention can be continuously treated for at least 80 days without clogging of the reaction tank equipment. In addition, the reagents used in the post-treatment method of the present invention are more environmentally friendly and are conducive to promotion and application. DETAILED DESCRIPTION

[0044] The present invention is further described below with reference to specific examples, but the examples do not limit the present invention in any form. Unless otherwise specified, the reagents, methods and equipment used in the present invention are conventional reagents, methods and equipment in the art.

[0045] Unless otherwise specified, the reagents and materials used in the following examples are commercially available.

[0046] Example 1

[0047] A method for preparing a low-pressure corrosion foil:

[0048] (1) Aluminum foil pretreatment: Aluminum foil with a thickness of 95 μm was treated in a phosphoric acid solution with a mass concentration of 1.5% at 80°C for 30 seconds;

[0049] (2) The aluminum foil after the pretreatment in step (1) is treated according to the following steps to obtain an aluminum foil after corrosion, pickling, and the first water washing treatment:

[0050] Electrical corrosion: The pre-treated aluminum foil is placed in a mixed acid solution, and then subjected to electrical corrosion. After the corrosion, it is washed with water. The mixed acid solution is a mixed solution of hydrochloric acid and sulfuric acid. The mass concentration of hydrochloric acid is 11%, the mass concentration of sulfuric acid is 0.1%, and the current density is 0.4A / cm 2 , the corrosion time is 600s, and the temperature of the galvanic corrosion is 12℃;

[0051] Medium treatment: Place the aluminum foil in a 2% monoammonium phosphate aqueous solution and passivate it at 90°C for 30 seconds;

[0052] Water washing: wash the treated aluminum foil with water;

[0053] Repeat the steps of electro-etching to washing 13 times until the aluminum foil with the required amount of corrosion is obtained; then, pickle treatment is carried out at 55° C. for 3 minutes in a sulfuric acid solution with a mass concentration of 15%, and the first water washing is carried out to obtain the aluminum foil after corrosion, pickling and the first water washing;

[0054] (3) Post-processing:

[0055] S1. After corrosion, pickling and first water washing, the aluminum foil is placed in water and treated with direct current. The aluminum foil is connected to the negative electrode and the graphite plate is connected to the positive electrode. The current density is 0.02A / cm 2 , power-on time 15s;

[0056] S2. Take out the aluminum foil and place it in a reaction tank, soak it in a mixed solution of acid and water at pH 5 at 45°C (the acid is salicylic acid, and the pH is adjusted to 5) for 3 minutes, wash it with water, and then sinter it at 440°C for 1 minute to obtain a low-pressure corrosion foil.

[0057] Using the above post-treatment method, the same reaction tank was treated continuously for 80 days without clogging.

[0058] Example 2

[0059] The difference compared with Example 1 is that in step S2, salicylic acid is added to the mixed solution of acid and water to adjust the pH to 6.5, and the other experimental methods and parameters are consistent with Example 1.

[0060] Using the above post-treatment method, the same reaction tank was treated continuously for 80 days without clogging.

[0061] Example 3

[0062] The difference compared with Example 1 is that in step S2, salicylic acid is replaced by citric acid, and the pH of the mixed solution is adjusted to 5. The other experimental methods and parameters are consistent with Example 1.

[0063] Using the above post-treatment method, the same reaction tank was treated continuously for 80 days without clogging.

[0064] Example 4

[0065] The difference compared with Example 1 is that in step S2, the immersion temperature is 25°C, and the other experimental methods and parameters are consistent with Example 1.

[0066] Using the above post-treatment method, the same reaction tank was treated continuously for 80 days without clogging.

[0067] Example 5

[0068] The difference compared with Example 1 is that in step S2, the immersion temperature is 50°C, and the other experimental methods and parameters are consistent with Example 1.

[0069] Using the above post-treatment method, the same reaction tank was treated continuously for 80 days without clogging.

[0070] Comparative Example 1

[0071] The difference compared with Example 1 is that in step S2, salicylic acid is added to the mixed solution to adjust the pH to 3.5, and the other experimental methods and parameters are consistent with Example 1.

[0072] Comparative Example 2

[0073] The difference compared with Example 1 is that in step S2, salicylic acid is not added to the mixed solution, which is pure water. The aluminum foil is taken out and placed in a reaction tank, immersed in pure water at 45°C (pH 7.5) for 3 minutes, washed with water, and then sintered at 440°C for 1 minute to obtain a low-pressure corrosion foil.

[0074] Comparative Example 3

[0075] The difference compared with Example 1 is that the aluminum foil after being corroded, pickled and washed with water for the first time is not subjected to step S1 but directly subjected to step S2.

[0076] Comparative Example 4

[0077] The difference compared with Example 1 is that in step S2, the immersion time is 6 minutes, and the other experimental methods and parameters are consistent with Example 1.

[0078] Comparative Example 5

[0079] The difference from Example 1 is the post-processing method, and the other experimental methods and parameters are consistent with Example 1.

[0080] The post-treatment of this comparative example is: the aluminum foil after corrosion, pickling and the first water washing is placed in a reaction tank, and then in a weak alkaline solution (concentration of 2mL / L ammonia water + 8g / m 3 The foil was treated in a mixed solution of ammonium dihydrogen phosphate (pH about 8.5) at a temperature of 55°C for 4 minutes, washed with pure water, and then sintered at 440°C for 1 minute to obtain a low-pressure corrosion foil.

[0081] The above post-treatment method was used to continuously treat the same reaction tank for 30 days, and the reaction tank was blocked and the reaction could not proceed. Compared with the embodiment, the conventional method treatment of comparative example 5 was more likely to cause blockage of the reaction tank.

[0082] Comparative Example 6

[0083] The etched foil was not post-processed. The aluminum foil after etching, pickling and the first water washing was fired at 440°C for 1 minute to obtain a low-pressure etched foil.

[0084] Effect example

[0085] Experimental materials: low-pressure etching foils prepared in Examples 1 to 5 and Comparative Examples 1 to 6.

[0086] Specific capacitance test: The specific capacitance of the prepared low-voltage corrosion foil was tested using a 21V small sample formation method.

[0087] Experimental results: The experimental results are shown in Table 1. From the data of Examples 1 to 5 and Comparative Example 6 in Table 1, it can be seen that the post-treatment method provided in the embodiments of the present invention can significantly increase the specific volume of the low-pressure etching foil. Compared with Comparative Example 6, the specific volume of the low-pressure etching foil obtained by the post-treatment of the present invention is increased by 7.95% to 11.36%.

[0088] In comparative example 1, an excess of salicylic acid was added (pH of the mixed solution = 3.5), and in comparative example 2, no salicylic acid was added (pure aqueous solution, pH 7.5). The specific capacity of the low-pressure corrosion foil obtained was significantly reduced to only 90 uf / cm 2 , compared with Example 1, it is reduced by 8.16%.

[0089] Comparative Example 3: No electrical treatment was performed during the post-treatment process. The specific capacitance of the low-pressure corrosion foil prepared was 93 uf / cm 2 , which is significantly lower than that in Example 1.

[0090] Comparative Example 4: Too long an immersion time will result in excessive deposition of hydrated aluminum oxide, blocking the corrosion holes, making the prepared corrosion foil hard, and reducing the specific volume to only 85 uf / cm 2 , the effect is worse than that of Comparative Example 6 (without post-treatment).

[0091] Table 1 Specific volume of low-pressure corrosion foils prepared in different groups

[0092] Group Test voltage(V) <![CDATA[Specific volume (uf / cm 2 )]]> Example 1 21 98 Example 2 21 95 Example 3 21 97 Example 4 21 98 Example 5 21 97 Comparative Example 1 21 90 Comparative Example 2 21 90 Comparative Example 3 21 93 Comparative Example 4 21 85 Comparative Example 5 21 98 Comparative Example 6 21 88

[0093] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be equivalent replacement methods and are included in the protection scope of the present invention.

Claims

1. A post-processing method for low-pressure corrosion foil, characterized in that: After the aluminum foil has been corroded, pickled, and washed for the first time, the following operations are performed: S1. Remove the aluminum hydroxide layer that blocks the corrosion holes; S2. Soak in a mixed solution of acid and water with a pH of 5 to 6.5 for 2 to 4 minutes, wash with water for the second time, and then perform sintering treatment.

2. The post-processing method according to claim 1, characterized in that: The soaking temperature is 25-50°C.

3. The post-processing method according to claim 1, characterized in that: The acid is a weak acid.

4. The post-processing method according to claim 1, characterized in that: The specific operation of step S1 is as follows: the aluminum foil after being corroded, pickled and washed with water for the first time is placed in water and subjected to ultrasonic treatment.

5. The post-processing method according to claim 1, characterized in that: The specific operation of step S1 is as follows: the aluminum foil after being corroded, pickled and washed with water for the first time is placed in water to connect to the negative electrode and then energized.

6. The post-processing method according to claim 5, characterized in that: The duration of the energization treatment is 5 to 25 seconds, and the current is 0.01 to 0.1 A / cm 2 .

7. A method for preparing a low-pressure corrosion foil, characterized in that: (1) Aluminum foil pretreatment; (2) the aluminum foil pretreated in step (1) is corroded until the aluminum foil with the desired amount of corrosion is obtained, followed by pickling and first water washing to obtain an aluminum foil that has been corroded, pickled, and first water washed; (3) A low-pressure corrosion foil is obtained by treating the foil according to any one of the post-treatment methods of claims 1 to 6.

8. The preparation method according to claim 7, characterized in that: The corrosion is electrochemical corrosion.

9. The preparation method according to claim 8, characterized in that: The current density of the electrochemical corrosion is 0.05-0.45A / cm 2 ; The power-on time is 480 to 660 seconds.

10. The low-pressure corrosion foil prepared by the preparation method according to any one of claims 7 to 9.