Metal surface polarity group enhancer, preparation method and application thereof and metal surface treatment method

Abstract

The application provides a metal surface polarity group enhancer, a preparation method and application thereof, and a metal surface treatment method. The metal surface polarity group enhancer comprises, in mass fraction, 2-5% of phosphomolybdic acid, 1-3% of potassium fluorotitanate, 0.5-2% of 3-mercaptopropionic acid, and 2-4% of trisodium citrate, and the balance is water. The metal surface polarity group enhancer can increase the number of polar functional groups such as carboxyl groups on the metal surface, thereby enhancing the bonding ability of a coupling agent and the polar groups on the metal surface when the coupling agent is coated on the metal surface to bond the metal and the silicone rubber, and further improving the bonding performance between the metal and the silicone rubber.

Description

Technical Field

[0001] The present invention relates to the technical field of metal surface treatment, in particular to a metal surface polar group enhancer, a preparation method and application thereof, and a metal surface treatment method. Background Art

[0002] Due to its chemical inertness and susceptibility to oxidation, metal surfaces suffer from weak adhesion and easy peeling of the adhesive layer when bonded to silicone rubber. Currently, a coupling agent is applied to the metal surface, with one end of the coupling agent binding to polar groups such as carboxyl groups on the metal surface and the other end binding to organic functional groups on the silicone rubber surface to enhance the adhesion between the metal and silicone rubber. However, due to the extremely small number of polar groups on the metal surface, the adhesion is still not ideal. While traditional metal surface treatment methods, such as pickling and mechanical polishing, can remove surface contaminants, they cannot introduce active functional groups to the metal surface, making it difficult to meet the high-demand bonding requirements.

[0003] Therefore, there is an urgent need for a method that can introduce a large number of polar groups on the metal surface to enhance the adhesion between metal and silicone rubber. Summary of the Invention

[0004] The main purpose of the present invention is to provide a metal surface polar group enhancer and its preparation method and application and metal surface treatment method, so as to solve the problem of poor adhesion between metal and silicone rubber in the prior art.

[0005] In order to achieve the above-mentioned object, according to one aspect of the present invention, a metal surface polar group enhancer is provided, which comprises, by mass fraction, 2-5% phosphomolybdic acid, 1-3% potassium fluorotitanate, 0.5-2% 3-mercaptopropionic acid and 2-4% trisodium citrate, with the balance being water.

[0006] Furthermore, the metal surface polar group enhancer includes, by mass fraction, 3-4% of phosphomolybdic acid, 2-3% of potassium fluorotitanate, 1-2% of 3-mercaptopropionic acid and 2-3% of trisodium citrate, with the balance being water.

[0007] Furthermore, the water includes purified water and / or deionized water, preferably deionized water.

[0008] According to a second aspect of the present invention, a method for preparing the metal surface polar group enhancer provided in the first aspect is provided, comprising the following steps: mixing phosphomolybdic acid, potassium fluorotitanate, 3-mercaptopropionic acid, trisodium citrate and water to obtain the metal surface polar group enhancer.

[0009] According to a third aspect of the present invention, there is provided a use of the metal surface polar group enhancer provided in the first aspect or the metal surface polar group enhancer obtained by the preparation method provided in the second aspect in metal surface treatment.

[0010] According to a fourth aspect of the present invention, a metal surface treatment method is provided, comprising the following steps: first immersing a metal substrate in a metal surface polar group enhancer for immersion treatment, and then sequentially performing pulse electrochemical treatment and ultrasonic-assisted chemical treatment, so that the polar groups in the metal surface polar group enhancer are bonded to the surface of the metal substrate to obtain a metal substrate to be bonded; wherein the metal surface polar group enhancer is the metal surface polar group enhancer provided in the above-mentioned first aspect or the above-mentioned second aspect.

[0011] Furthermore, the soaking treatment temperature is 60 to 80° C., and the soaking treatment time is 20 to 40 minutes.

[0012] Furthermore, the voltage of the pulse electrochemical treatment is 10-15V, the pulse period of the pulse electrochemical treatment is 25-30s, the time of the pulse electrochemical treatment is 30-40min, and the temperature of the pulse electrochemical treatment is 60-80°C.

[0013] Furthermore, the temperature of the ultrasonic-assisted chemical treatment is 60 to 80° C., and the time of the ultrasonic-assisted chemical treatment is 20 to 30 minutes.

[0014] Furthermore, before the immersion treatment, the metal substrate is also pretreated, and the pretreatment includes the following steps: step A, first immersing the metal substrate in an acidic solution for pickling treatment, and then washing and drying in sequence to obtain a pickled metal substrate; step B, washing the pickled metal substrate with an organic solvent, and then washing and drying in sequence to obtain a pretreated metal substrate.

[0015] Furthermore, the concentration of the acidic solution is 10-15 wt%.

[0016] Furthermore, the acidic solution includes at least one of a hydrochloric acid solution and a sulfuric acid solution, and further comprises a hydrochloric acid solution.

[0017] Furthermore, the pickling treatment time is 10 to 15 minutes.

[0018] Furthermore, the organic solvent includes at least one of acetone, ethanol, and heptane.

[0019] By applying the technical solution of the present invention, the present application uses phosphomolybdic acid, potassium fluorotitanate, 3-mercaptopropionic acid, and trisodium citrate to synergize with each other, so that when the metal surface polar group enhancer is applied to the metal surface treatment, the number of polar functional groups such as carboxyl groups on the metal surface can be increased. Thus, when the coupling agent is coated on the metal surface to bond the metal and silicone rubber, the bonding ability between the coupling agent and the polar groups on the metal surface can be enhanced, thereby improving the bonding performance between the metal and the silicone rubber. In addition, during the metal surface treatment process, the metal surface polar group enhancer can also form a small uneven surface on the metal surface, increasing the contact area between the metal and the coupling agent, thereby further improving the bonding between the metal and the silicone rubber. In addition, the metal surface polar group enhancer also improves the oxidation resistance and corrosion resistance of the metal surface. DETAILED DESCRIPTION

[0020] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present invention will be described in detail below with reference to the embodiments.

[0021] As analyzed in the background technology of this application, the existing technology has the problem of poor adhesion between metal and silicone rubber. In order to solve this problem, this application provides a metal surface polar group enhancer, its preparation method and application, and a metal surface treatment method.

[0022] In a typical embodiment of the present application, a metal surface polar group enhancer is provided. Calculated by mass fraction, the metal surface polar group enhancer includes 2-5% phosphomolybdic acid, 1-3% potassium fluorotitanate, 0.5-2% 3-mercaptopropionic acid and 2-4% trisodium citrate, with the remainder being water.

[0023] The present application utilizes phosphomolybdic acid, potassium fluorotitanate, 3-mercaptopropionic acid, and trisodium citrate to synergize with each other, so that when the metal surface polar group enhancer is applied to the metal surface treatment, the number of polar functional groups such as carboxyl groups on the metal surface can be increased. Thus, when the coupling agent is coated on the metal surface to bond the metal and silicone rubber, the bonding ability between the coupling agent and the polar groups on the metal surface can be enhanced, thereby improving the bonding performance between the metal and the silicone rubber. In addition, during the metal surface treatment process, the metal surface polar group enhancer can also form a tiny uneven surface on the metal surface, increasing the contact area between the metal and the coupling agent, thereby further improving the bonding between the metal and the silicone rubber. In addition, the metal surface polar group enhancer also improves the oxidation resistance and corrosion resistance of the metal surface.

[0024] Specifically, in the metal surface polar group enhancer provided by the present application, the sulfhydryl group in 3-mercaptopropionic acid can form a strong chemical bond with the metal surface, making the metal surface structure more stable, and at the same time, the carboxyl group can further introduce more polar functional groups such as carboxyl groups to the metal surface. Potassium fluorotitanate can form a titanium compound with a nanoporous structure on the metal surface, increases the surface area and the active sites bonded to the polar functional groups, promotes the adsorption and chemical bonding of polar functional groups such as carboxyl groups on the titanium compound, and the polar functional groups bonded on the titanium compound are more excellent in heat resistance and are not easy to decompose at high temperatures. In addition, the addition of potassium fluorotitanate can also improve the uniformity of the metal surface treatment process and enhance the corrosion resistance of the metal surface. And phosphomolybdic acid reacts with the metal surface to form molybdate, which provides more active sites for the chemical bonding of polar functional groups such as carboxyl groups, further increases the number of metal surface polar functional groups, and the molybdate generated by the metal surface can also improve the antioxidant capacity of the metal surface. When phosphomolybdic acid reacts with metal surfaces, it corrodes them, creating tiny uneven surfaces. This increases the contact area between the metal and the coupling agent, further enhancing the adhesion between the metal and silicone rubber. Trisodium citrate, as a chelating agent, forms a stable complex with the reactive groups, protecting the metal surface from excessive oxidation or corrosion. It also provides a stable reaction environment during the bonding process of polar functional groups such as carboxyl groups, promoting their uniform distribution across the metal surface.

[0025] Typically but not limitatively, the content of phosphomolybdic acid in the metal surface polar group enhancer, measured by mass fraction, is 2%, 3%, 4%, 5% or a range consisting of any two values; the content of potassium fluorotitanate is 1%, 1.5%, 2%, 2.5%, 3% or a range consisting of any two values; the content of 3-mercaptopropionic acid is 0.5%, 1%, 1.5%, 2% or a range consisting of any two values; the content of trisodium citrate is 2%, 2.5%, 3%, 4% or a range consisting of any two values.

[0026] In order to further increase the number of polar functional groups such as carboxyl groups on the metal surface, as well as further improve the adhesion between the metal and the silicone rubber, and the oxidation resistance and corrosion resistance of the metal surface, the metal surface polar group enhancer preferably includes, by mass fraction, 3-4% phosphomolybdic acid, 2-3% potassium fluorotitanate, 1-2% 3-mercaptopropionic acid, and 2-3% trisodium citrate, with the balance being water.

[0027] In some embodiments, the water in the metal surface polar group enhancer comprises purified water and / or deionized water to further reduce impurities in the metal surface polar group enhancer. To further reduce impurities in the metal surface polar group enhancer, it is further preferred that the water be deionized water.

[0028] In a second typical embodiment of the present application, a method for preparing a metal surface polar group enhancer is provided, comprising the following steps: mixing phosphomolybdic acid, potassium fluorotitanate, 3-mercaptopropionic acid, trisodium citrate and water to obtain a metal surface polar group enhancer.

[0029] In the present application, the mixing method is not specifically limited, and any mixing method commonly used in the technical field can be used. For ease of operation, stirring is the preferred mixing method.

[0030] In a third typical embodiment of the present application, there is provided an application of the metal surface polar group enhancer provided in the first typical embodiment or the metal surface polar group enhancer obtained by the preparation method provided in the second typical embodiment in metal surface treatment.

[0031] In a fourth exemplary embodiment of the present application, a metal surface treatment method is provided, comprising first immersing a metal substrate in a metal surface polar group enhancer for immersion treatment, followed by sequential pulse electrochemical treatment and ultrasonic-assisted chemical treatment, so that the polar groups in the metal surface polar group enhancer bond to the surface of the metal substrate, thereby obtaining a metal substrate to be bonded. The metal surface polar group enhancer is the metal surface polar group enhancer provided in the first or second exemplary embodiment described above.

[0032] This metal surface treatment method first immerses a metal substrate in a metal surface polar group enhancer for immersion treatment, allowing the metal surface polar group enhancer to react with the metal substrate surface, causing the polar groups in the metal surface polar group enhancer to bond to the metal substrate surface. Pulsed electrochemical treatment and ultrasonic-assisted chemical treatment are used to ensure a more complete reaction and a more uniform distribution of polar groups on the metal surface.

[0033] The synergistic effects of phosphomolybdic acid, potassium fluorotitanate, 3-mercaptopropionic acid, and trisodium citrate enable the metal surface polar group enhancer to increase the number of polar functional groups, such as carboxyl groups, on the metal surface when applied to metal surface treatment. This enhances the bonding ability between the coupling agent and the polar groups on the metal surface when the coupling agent is applied to the metal surface to bond the metal to the silicone rubber, thereby improving the adhesion between the metal and the silicone rubber. Furthermore, during the metal surface treatment process, the metal surface polar group enhancer can also create microscopic uneven surfaces on the metal surface, increasing the contact area between the metal and the coupling agent, further enhancing the adhesion between the metal and the silicone rubber. Furthermore, the metal surface polar group enhancer also improves the metal surface's oxidation resistance and corrosion resistance.

[0034] In some embodiments, the immersion treatment temperature is 60-80°C (such as 60°C, 65°C, 70°C, 75°C, 80°C, etc.), and the immersion treatment time is 20-40 minutes (such as 20 minutes, 25 minutes, 30 minutes, 35 minutes, 40 minutes, etc.) to allow the metal surface to further fully react with the metal surface polar group enhancer.

[0035] In some embodiments, the voltage of the pulse electrochemical treatment is 10-15 V (such as 10 V, 11 V, 12 V, 13 V, 14 V, 15 V, etc.), the pulse period of the pulse electrochemical treatment is 25-30 s (such as 25 s, 26 s, 27 s, 28 s, 29 s, 30 s, etc.), the time of the pulse electrochemical treatment is 30-40 min (such as 30 min, 32 min, 34 min, 36 min, 38 min, 40 min, etc.), and the temperature of the pulse electrochemical treatment is 60-80 ° C (such as 60 ° C, 65 ° C, 70 ° C, 75 ° C, 80 ° C, etc.);

[0036] In some embodiments, the temperature of ultrasonic-assisted chemical treatment is 60-80°C (such as 60°C, 65°C, 70°C, 75°C, 80°C, etc.), the time of ultrasonic-assisted chemical treatment is 20-30 min (such as 20 min, 22 min, 24 min, 26 min, 28 min, 30 min, etc.), and the frequency of ultrasonic-assisted chemical treatment is 20 KHz to 40 KHz.

[0037] The conditions of the pulse electrochemical treatment or ultrasonic-assisted chemical treatment are controlled within the above range to further promote the full reaction between the metal and the metal surface polar group enhancer and to make the transition layer generated on the metal surface and the polar functional groups more evenly distributed.

[0038] In some embodiments, after the pulse electrochemical treatment and the ultrasonic-assisted chemical treatment are completed, the metal substrate is further subjected to post-treatment, and the post-treatment includes the following steps: removing the metal substrate from the metal surface polar group enhancer, washing the surface of the metal substrate with deionized water once to remove unreacted residues; placing the washed metal substrate in an oven for drying to obtain a metal substrate to be bonded.

[0039] In some embodiments, the primary drying temperature is 60-80°C (e.g., 60°C, 60°C, 70°C, 75°C, 80°C, etc.), and the primary drying time is 60-120 minutes (e.g., 60 minutes, 80 minutes, 100 minutes, 120 minutes, etc.). Excessively high temperatures can cause decomposition and oxidation of polar functional groups on the metal surface or thermal damage to the metal surface, thereby reducing the adhesion between the metal and the silicone rubber; excessively low temperatures can slow the drying rate.

[0040] In some embodiments, the metal substrate is pretreated before the immersion treatment, and the pretreatment includes the following steps: step A, first immersing the metal substrate in an acidic solution for pickling treatment, and then sequentially washing it with water twice and drying it twice to obtain a pickled metal substrate; step B, washing the pickled metal substrate with an organic solvent, and then sequentially washing it with water three times and drying it three times to obtain a pretreated metal substrate.

[0041] In step A, when the metal substrate is immersed in the acidic solution, it is ensured that the acidic solution can completely cover the surface of the metal substrate so that impurities on the metal surface are fully removed.

[0042] During the above-mentioned pretreatment process, the metal substrate is pickled to remove impurities on the surface to prevent the impurities from affecting the subsequent reaction between the metal and the metal surface polar group enhancer. The acidic solution or impurities remaining on the surface of the metal substrate are removed by two water washes, and the metal substrate is obtained after the pickling treatment after the second drying. The pickled metal substrate is then washed with an organic solvent to remove grease and other organic impurities. The organic solvent or organic impurities remaining on the surface of the metal substrate are removed by three water washes, and the pretreated metal substrate is obtained by three dryings.

[0043] The metal substrate is pretreated to remove impurities on the metal surface, and then immersed in a metal surface polar group enhancer for metal surface treatment, thereby further improving the reactivity of the metal surface.

[0044] In order to further ensure that the acidic solution remaining on the surface of the metal substrate is fully removed, it is preferred that the metal surface be neutral after the second water washing.

[0045] In order to further remove impurities on the surface of the metal substrate, the concentration of the acidic solution in step A is preferably 10-15wt% (such as 10wt%, 11wt%, 12wt%, 13wt%, 14wt%, 15wt%, etc.); the acidic solution preferably includes any one or more of hydrochloric acid solution and sulfuric acid solution, more preferably hydrochloric acid solution.

[0046] In order to further allow the metal substrate to fully react with the acidic solution to remove impurities on the metal surface, the pickling treatment time is preferably 10 to 15 minutes (such as 10 minutes, 12 minutes, 14 minutes, 15 minutes, etc.).

[0047] In order to further promote the drying of the metal substrate, the secondary drying temperature in step A is preferably 70-80°C (such as 70°C, 72°C, 74°C, 76°C, 78°C, 80°C, etc.)

[0048] In order to further remove organic impurities on the surface of the metal substrate, the organic solvent preferably includes any one or more of acetone, ethanol, and heptane.

[0049] In order to further improve the drying efficiency, the preferred tertiary drying method is compressed air drying or hot air drying. The preferred compressed air drying pressure is 0.3-0.8 MPa and the temperature is 40-70°C. The preferred hot air drying temperature is 60-80°C.

[0050] The beneficial effects of the present application will be further illustrated below with reference to examples and comparative examples.

[0051] Example 1

[0052] This embodiment provides a metal surface treatment method, the steps are as follows:

[0053] (1) Preparation of metal surface polar group enhancer:

[0054] Calculated by mass fraction, 2% of phosphomolybdic acid, 3% of potassium fluorotitanate, 0.5% of 3-mercaptopropionic acid, and 4% of trisodium citrate were added to the remaining amount of deionized water in sequence, and stirred evenly to obtain a metal surface polar group enhancer for later use.

[0055] (2) Pretreatment of metal substrate

[0056] The copper metal sheet was pickled in a 15wt% hydrochloric acid solution for 10 minutes. After the pickling treatment, the metal sheet was taken out, washed with deionized water until neutral, and dried in a 70°C oven for 40 minutes. The dried copper metal sheet was first washed with acetone to remove grease or other organic impurities on the surface, then washed with deionized water, and then dried with a 60°C hot air blower to obtain a pretreated copper metal sheet.

[0057] (3) Surface treatment of metal substrate

[0058] The pretreated copper metal sheet is immersed in the metal surface polar group enhancer prepared in step (1), the immersion temperature is 80°C, and the immersion time is 20 minutes; then the temperature is kept constant at 80°C, and a pulse electrochemical treatment is performed for 30 minutes under the conditions of a voltage of 15V and a pulse period of 30 seconds; then an ultrasonic-assisted chemical treatment is performed for 20 minutes, and the frequency of the ultrasonic-assisted chemical treatment is 25KHz; the copper metal sheet is taken out of the metal surface polar group enhancer, the surface of the metal sheet is washed with deionized water, and then the copper metal sheet is placed in an 80°C oven and dried for 60 minutes to obtain a metal sheet to be bonded.

[0059] Example 2

[0060] Example 2 differs from Example 1 in that the composition ratio of the metal surface polar group enhancer in step (1) is adjusted to include, by mass, 5% phosphomolybdic acid, 1% potassium fluorotitanate, 2% 3-mercaptopropionic acid, and 2% trisodium citrate, with the remainder being deionized water. Aluminum metal sheets are used for subsequent metal substrate pretreatment and metal substrate surface treatment.

[0061] Example 3

[0062] Example 3 differs from Example 1 in that the composition ratio of the metal surface polar group enhancer in step (1) is adjusted to include, by mass, 3% phosphomolybdic acid, 3% potassium fluorotitanate, 2% 3-mercaptopropionic acid, and 2% trisodium citrate, with the remainder being deionized water. Stainless steel sheets were used for subsequent metal substrate pretreatment and metal substrate surface treatment.

[0063] Example 4

[0064] The difference between Example 4 and Example 1 is that the component ratio of the metal surface polar group enhancer in step (1) is adjusted, calculated by mass fraction, so that the metal surface polar group enhancer includes 4% phosphomolybdic acid, 2% potassium fluorotitanate, 1% 3-mercaptopropionic acid, 3% trisodium citrate, and the balance is deionized water.

[0065] Example 5

[0066] The difference between Example 5 and Example 1 is that the component ratio of the metal surface polar group enhancer in step (1) is adjusted, calculated by mass fraction, so that the metal surface polar group enhancer includes 3% phosphomolybdic acid, 2.5% potassium fluorotitanate, 1.5% 3-mercaptopropionic acid, 2.5% trisodium citrate, and the balance is deionized water.

[0067] Example 6

[0068] The difference between Example 6 and Example 1 is that the drying temperature in the metal substrate surface treatment in step (3) is adjusted, and the copper metal sheet is placed in a 120° C. oven and dried for 30 minutes to obtain the copper metal sheet to be bonded.

[0069] Comparative Example 1

[0070] The difference between Comparative Example 1 and Example 1 is that the metal sheet is only subjected to the metal sheet pretreatment of step (2), and the metal surface polar group enhancer is not used for the subsequent metal sheet surface treatment of step (3).

[0071] Comparative Example 2

[0072] The difference between Comparative Example 2 and Example 1 is that the phosphomolybdic acid in the metal surface polar group enhancer is removed, so that the metal surface polar group enhancer contains 5% potassium fluorotitanate, 0.5% 3-mercaptopropionic acid, 4% trisodium citrate, and the balance is deionized water, calculated by mass fraction.

[0073] Comparative Example 3

[0074] The difference between Comparative Example 3 and Example 1 is that potassium fluorotitanate in the metal surface polar group enhancer is removed, so that the metal surface polar group enhancer contains 5% phosphomolybdic acid, 0.5% 3-mercaptopropionic acid, 4% trisodium citrate, and the balance is deionized water, calculated by mass fraction.

[0075] Comparative Example 4

[0076] The difference between Comparative Example 4 and Example 1 is that the 3-mercaptopropionic acid in the metal surface polar group enhancer is removed, so that the metal surface polar group enhancer contains 2.5% phosphomolybdic acid, 3% potassium fluorotitanate, 4% trisodium citrate, and the balance is deionized water, calculated by mass fraction.

[0077] Comparative Example 5

[0078] The difference between Comparative Example 5 and Example 1 is that the component ratio of the metal surface polar group enhancer in step (1) is adjusted, calculated by mass fraction, so that the metal surface polar group enhancer includes 1% phosphomolybdic acid, 0.5% potassium fluorotitanate, 5% 3-mercaptopropionic acid, 2% trisodium citrate, and the balance is deionized water.

[0079] Comparative Example 6

[0080] The difference between Comparative Example 6 and Example 1 is that the component ratio of the metal surface polar group enhancer in step (1) is adjusted, calculated by mass fraction, so that the metal surface polar group enhancer includes 7% phosphomolybdic acid, 0.5% potassium fluorotitanate, 0.1% 3-mercaptopropionic acid, 1% trisodium citrate, and the balance is deionized water.

[0081] Test example

[0082] The adhesion between the metal sheet samples provided in the Examples and Comparative Examples and the silicone rubber was tested as follows: a commercially available silane coupling agent (34T) was applied to the surface of the metal sheet and dried at 130°C. Silicone rubber (Type 1551) was then poured onto the surface of the metal sheet and cured by heating. After curing, the silicone rubber had a thickness of 2 mm on the copper sheet. The tensile shear strength of the metal-silicone rubber bond was tested in accordance with GB / T 13936-2014. The results are shown in Table 1.

[0083] Table 1

[0084] Tensile shear strength (MPa) Example 1 4.1 Example 2 5.2 Example 3 4.8 Example 4 5.5 Example 5 5 Example 6 2.7 Comparative Example 1 0.5 Comparative Example 2 1 Comparative Example 3 1.8 Comparative Example 4 1 Comparative Example 5 2.5 Comparative Example 6 2.8

[0085] From the experimental data of Examples 1, 2, 3, 4, and 5 and Comparative Examples 2, 3, 4, 5, and 6, it can be seen that when the metal surface polar group enhancer includes 2-5 wt% phosphomolybdic acid, 1-3 wt% potassium fluorotitanate, 0.5-2 wt% 3-mercaptopropionic acid, and 2-4 wt% trisodium citrate, with the balance being water, the tensile shear strength of the metal-silicone rubber bond is greater when the metal substrate surface is treated with the metal surface polar group enhancer, then coated with a coupling agent, and bonded to the silicone rubber, indicating strong adhesion between the metal and the silicone rubber. When the components or ratios of the metal surface polar group enhancer are varied, such that any component is missing or the component content is outside the above range, the tensile shear strength of the metal-silicone rubber bond decreases, indicating reduced adhesion between the metal and the silicone rubber.

[0086] From the experimental data of Example 1 and Comparative Example 1, it can be seen that after the metal substrate surface is treated with the metal surface polar group enhancer, the tensile shear strength of the metal-silicone rubber bond is significantly increased, indicating that the bonding between the metal and the silicone rubber is significantly enhanced.

[0087] It can be seen from the experimental data of Examples 1 and 6 that, compared with Example 1, when the drying temperature in Example 6 is too high, functional group decomposition and metal damage occur, so the tensile shear strength of the metal-silicone rubber bond is reduced, and the bonding between the metal and the silicone rubber is reduced.

[0088] From the above description, it can be seen that the above embodiments of the present invention achieve the following technical effects:

[0089] The present application utilizes phosphomolybdic acid, potassium fluorotitanate, 3-mercaptopropionic acid, and trisodium citrate to synergize with each other, so that when the metal surface polar group enhancer is applied to the metal surface treatment, the number of polar functional groups such as carboxyl groups on the metal surface can be increased. Thus, when the coupling agent is coated on the metal surface to bond the metal and silicone rubber, the bonding ability between the coupling agent and the polar groups on the metal surface can be enhanced, thereby improving the bonding performance between the metal and the silicone rubber. In addition, during the metal surface treatment process, the metal surface polar group enhancer can also form a tiny uneven surface on the metal surface, increasing the contact area between the metal and the coupling agent, thereby further improving the bonding between the metal and the silicone rubber. In addition, the metal surface polar group enhancer also improves the oxidation resistance and corrosion resistance of the metal surface.

[0090] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A metal surface polar group enhancer, characterized in that: Calculated by mass fraction, the metal surface polar group enhancer includes 2-5% phosphomolybdic acid, 1-3% potassium fluorotitanate, 0.5-2% 3-mercaptopropionic acid and 2-4% trisodium citrate, and the balance is water.

2. The metal surface polar group enhancer according to claim 1, characterized in that Calculated by mass fraction, the metal surface polar group enhancer includes 3-4% phosphomolybdic acid, 2-3% potassium fluorotitanate, 1-2% 3-mercaptopropionic acid and 2-3% trisodium citrate, and the balance is water.

3. The metal surface polar group enhancer according to claim 1 or 2, characterized in that The water includes purified water and / or deionized water.

4. The metal surface polar group enhancer according to claim 3, characterized in that The water is deionized water.

5. The method for preparing the metal surface polar group enhancer according to any one of claims 1 to 4, characterized in that: The following steps are involved: Phosphomolybdic acid, potassium fluorotitanate, 3-mercaptopropionic acid, trisodium citrate and the water are mixed to obtain the metal surface polar group enhancer.

6. Use of the metal surface polar group enhancer according to any one of claims 1 to 4 or the metal surface polar group enhancer obtained by the preparation method according to claim 5 in metal surface treatment.

7. A metal surface treatment method, characterized in that: The following steps are involved: First, the metal substrate is immersed in a metal surface polar group enhancer for immersion treatment, and then pulse electrochemical treatment and ultrasonic-assisted chemical treatment are performed in sequence, so that the polar groups in the metal surface polar group enhancer are bonded to the surface of the metal substrate, thereby obtaining a metal substrate to be bonded; Wherein, the metal surface polar group enhancer is the metal surface polar group enhancer according to any one of claims 1 to 4.

8. The metal surface treatment method according to claim 7, characterized in that: The soaking temperature is 60-80°C and the soaking time is 20-40 minutes. And / or, the voltage of the pulse electrochemical treatment is 10-15 V, the pulse period of the pulse electrochemical treatment is 25-30 s, the time of the pulse electrochemical treatment is 30-40 min, and the temperature of the pulse electrochemical treatment is 60-80° C.; And / or, the temperature of the ultrasonic-assisted chemical treatment is 60-80° C., and the time of the ultrasonic-assisted chemical treatment is 20-30 minutes.

9. The metal surface treatment method according to claim 7, characterized in that: Before the immersion treatment, the metal substrate is pretreated, and the pretreatment includes the following steps: Step A, first immersing the metal substrate in an acidic solution for pickling, then sequentially washing with water and drying to obtain a pickled metal substrate; In step B, the pickled metal substrate is washed with an organic solvent, and then washed with water and dried in sequence to obtain a pretreated metal substrate.

10. The metal surface treatment method according to claim 9, characterized in that: The concentration of the acidic solution is 10-15 wt%; And / or, the acidic solution includes at least one of a hydrochloric acid solution and a sulfuric acid solution; And / or, the pickling treatment time is 10 to 15 minutes.

11. The metal surface treatment method according to claim 9, characterized in that: The acidic solution is a hydrochloric acid solution.

12. The metal surface treatment method according to claim 9, characterized in that: The organic solvent includes at least one of acetone, ethanol and heptane.