Metal surface polar group reinforcing agent, preparation method and application thereof, and metal surface treatment method

Abstract

The invention provides a metal surface polar group reinforcing agent, a preparation method and application thereof and a metal surface treatment method, and the metal surface polar group reinforcing agent comprises the following components in percentage by mass: 2-5% of phosphomolybdic acid, 1-3% of potassium fluotitanate, 0.5-2% of 3-mercaptopropionic acid, 2-4% of trisodium citrate and the balance of water. The metal surface polar group enhancer can increase the number of polar functional groups such as carboxyl on the metal surface, so that when the metal surface is coated with a coupling agent to bond metal and silicone rubber, the bonding capacity of the coupling agent and the polar groups on the metal surface is enhanced, and the bonding performance between the metal and the silicone rubber is improved.

Description

Technical Field

[0001] The invention relates to the technical field of metal surface treatment, and 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 easy oxidation, the metal surface has weak bonding force and easy peeling of the bonding layer when bonding with silicone rubber. At present, a coupling agent is coated on the metal surface, and one end of the coupling agent is combined with polar groups such as carboxyl on the metal surface, and the other end is combined with organic functional groups on the silicone rubber surface to enhance the adhesion between metal and silicone rubber. However, due to the extremely small number of polar groups on the metal surface, the adhesion is still not ideal. Although traditional metal surface treatment methods, such as pickling and mechanical polishing, can remove surface pollutants, they cannot introduce active functional groups on the metal surface, and it is difficult to meet high-demand bonding applications.

[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 a metal surface treatment method to solve the problem of poor adhesion between metal and silicone rubber in the prior art.

[0005] In order to achieve the above-mentioned purpose, 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, and the balance is water.

[0006] Furthermore, the metal surface polar group enhancer 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.

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

[0008] According to a second aspect of the present invention, there is provided a method for preparing the metal surface polar group enhancer provided in the first aspect, 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 temperature is 60 to 80° C., and the soaking 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 successively washing and drying to obtain the pickled metal substrate; step B, washing the pickled metal substrate with an organic solvent, and then successively washing and drying to obtain the 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 is 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 cooperate with each other, so that when the metal surface polar group enhancer is applied to metal surface treatment, the number of polar functional groups such as carboxyl groups on the metal surface can be increased, so that when the coupling agent is coated on the metal surface to bond the metal and silicone rubber, the bonding ability of 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. 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 in conjunction with the embodiments.

[0021] As analyzed in the background technology of this application, there is a problem of poor adhesion between metal and silicone rubber in the prior art. In order to solve this problem, this application provides a metal surface polar group enhancer and 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, and the balance is water.

[0023] The present application uses phosphomolybdic acid, potassium fluorotitanate, 3-mercaptopropionic acid and trisodium citrate to cooperate with each other, so that when the metal surface polar group enhancer is applied to metal surface treatment, the number of polar functional groups such as carboxyl groups on the metal surface can be increased, so that when the coupling agent is coated on the metal surface to bond the metal and silicone rubber, the bonding ability of 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 thiol 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, increase the surface area and the active sites bonded to the polar functional groups, promote 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 have better 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. The 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 polar functional groups on the metal surface, and the molybdate generated on the metal surface can also improve the antioxidant capacity of the metal surface. When phosphomolybdic acid reacts with the metal surface, it corrodes the metal surface to form a tiny uneven surface, thereby increasing the contact area between the metal and the coupling agent. When the coupling agent bonds the metal to the silicone rubber, the bonding between the metal and the silicone rubber is further improved. As a complexing agent, trisodium citrate forms a stable complex with the reactive group to protect the metal surface from excessive oxidation or corrosion, and can provide a stable reaction environment during the bonding process of polar functional groups such as carboxyl groups, promoting the uniform distribution of polar functional groups on the metal surface.

[0025] Typically but not restrictively, by mass fraction, the content of phosphomolybdic acid in the metal surface polar group enhancer 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, and further improve the adhesion between metal and silicone rubber, and the oxidation resistance and corrosion resistance of the metal surface, the metal surface polar group enhancer preferably includes 3-4% phosphomolybdic acid, 2-3% potassium fluorotitanate, 1-2% 3-mercaptopropionic acid, and 2-3% trisodium citrate, and the balance is water.

[0027] In some embodiments, the water in the metal surface polar group enhancer includes purified water and / or deionized water to further reduce impurities in the metal surface polar group enhancer. In order to further reduce impurities in the metal surface polar group enhancer, it is further preferred that the water is 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, there is no specific limitation on the mixing method, 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 typical embodiment of the present application, a metal surface treatment method is provided, wherein a metal substrate is first 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. The metal surface polar group enhancer is the metal surface polar group enhancer provided in the first typical embodiment or the second typical embodiment.

[0032] The metal surface treatment method first immerses the metal substrate into a metal surface polar group enhancer for immersion treatment, so that the metal surface polar group enhancer reacts with the surface of the metal substrate, so that the polar groups in the metal surface polar group enhancer are bonded to the surface of the metal substrate. Pulse electrochemical treatment and ultrasonic assisted chemical treatment are used to make the reaction more complete and the polar groups more evenly distributed on the metal surface.

[0033] Through the synergy of phosphomolybdic acid, potassium fluorotitanate, 3-mercaptopropionic acid and trisodium citrate, the metal surface polar group enhancer can increase the number of polar functional groups such as carboxyl groups on the metal surface when applied to metal surface treatment, so that 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.

[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 min (such as 20 min, 25 min, 30 min, 35 min, 40 min, 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 10-15V (such as 10V, 11V, 12V, 13V, 14V, 15V, etc.), the pulse period of the pulse electrochemical treatment is 25-30s (such as 25s, 26s, 27s, 28s, 29s, 30s, etc.), the time of the pulse electrochemical treatment is 30-40min (such as 30min, 32min, 34min, 36min, 38min, 40min, 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 20-30min (such as 20min, 22min, 24min, 26min, 28min, 30min, etc.), and the frequency of ultrasonic-assisted chemical treatment is 20KHz-40KHz.

[0037] The conditions of the pulse electrochemical treatment or ultrasound-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 a single drying to obtain a metal substrate to be bonded.

[0039] In some embodiments, the primary drying temperature is 60-80°C (such as 60°C, 60°C, 70°C, 75°C, 80°C, etc.), and the primary drying time is 60-120 minutes (such as 60 minutes, 80 minutes, 100 minutes, 120 minutes, etc.). Too high a temperature will cause the polar functional groups on the metal surface to decompose and oxidize or the metal surface to be thermally damaged, thereby reducing the adhesion between the metal and the silicone rubber; too low a temperature will reduce 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 with water twice and drying twice to obtain the metal substrate after the pickling treatment; step B, washing the metal substrate after the pickling treatment with an organic solvent, and then sequentially washing with water three times and drying three times to obtain the 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 can be fully removed.

[0042] In the above-mentioned pretreatment process, the metal substrate is treated with pickling 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 acid solution or impurities remaining on the surface of the metal substrate are removed by two water washes, and the metal substrate after pickling is obtained after two dryings. The metal substrate after pickling 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 is neutral after the secondary 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, and 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 (eg, 10 minutes, 12 minutes, 14 minutes, 15 minutes, etc.).

[0047] In order to further promote the drying of the metal substrate, the temperature of the secondary drying 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 blower drying. The compressed air drying pressure is further preferably 0.3-0.8 MPa and the temperature is 40-70°C. The preferred temperature of the hot air blower is 60-80°C.

[0050] The beneficial effects of the present application will be further illustrated below in combination with embodiments 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 are added to the remaining 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 oven at 80°C and dried for 60 minutes to obtain a metal sheet to be bonded.

[0059] Example 2

[0060] The difference between Example 2 and Example 1 is that the composition ratio of the metal surface polar group enhancer in step (1) is adjusted, and the metal surface polar group enhancer includes 5% phosphomolybdic acid, 1% potassium fluorotitanate, 2% 3-mercaptopropionic acid, 2% trisodium citrate, and the balance is deionized water. Aluminum metal sheets are used for subsequent metal substrate pretreatment and metal substrate surface treatment.

[0061] Example 3

[0062] The difference between Example 3 and Example 1 is that the composition ratio of the metal surface polar group enhancer in step (1) is adjusted, and the metal surface polar group enhancer includes 3% phosphomolybdic acid, 3% potassium fluorotitanate, 2% 3-mercaptopropionic acid, 2% trisodium citrate, and the balance is deionized water. Stainless steel metal sheets are 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 so that the copper metal sheet is placed in an oven at 120° C. 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, 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, 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 to be bonded and the silicone rubber provided in the test examples and comparative examples is tested as follows: a commercially available silane coupling agent (34T) is coated on the surface of the metal sheet to be bonded, dried at 130°C, and then silicone rubber (model 1551) is poured on the surface of the metal sheet to be bonded, and cured by a heating curing process. After curing, the thickness of the silicone rubber on the copper metal sheet is 2 mm. The tensile shear strength of the bond between metal and silicone rubber is tested with reference to GB / T 13936-2014, and 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, 5 and Comparative Examples 2, 3, 4, 5, 6, it can be seen that when the metal surface polar group enhancer includes 2-5wt% phosphomolybdic acid, 1-3wt% potassium fluorotitanate, 0.5-2wt% 3-mercaptopropionic acid and 2-4wt% trisodium citrate, and the balance is water, after treating the surface of the metal substrate with the metal surface polar group enhancer, and then coating the coupling agent and bonding the silicone rubber, the tensile shear strength of the metal and silicone rubber bonding is relatively large, indicating that the bonding between the metal and the silicone rubber is relatively strong. When the components or proportions of the metal surface polar group enhancer are changed, any component is missing or the component content is not within the above range, the tensile shear strength of the metal and silicone rubber bonding is reduced, indicating that the bonding between the metal and the silicone rubber is reduced.

[0086] It can be seen from the experimental data of Example 1 and Comparative Example 1 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 uses phosphomolybdic acid, potassium fluorotitanate, 3-mercaptopropionic acid and trisodium citrate to cooperate with each other, so that when the metal surface polar group enhancer is applied to metal surface treatment, the number of polar functional groups such as carboxyl groups on the metal surface can be increased, so that when the coupling agent is coated on the metal surface to bond the metal and silicone rubber, the bonding ability of 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 above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope 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, preferably deionized water.

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

5. Use of the metal surface polar group enhancer according to any one of claims 1 to 3 or the metal surface polar group enhancer obtained by the preparation method according to claim 4 in metal surface treatment.

6. A metal surface treatment method, characterized in that: The following steps are involved: First, immersing the 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, thereby obtaining the 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.

7. The metal surface treatment method according to claim 6, 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 10-15V, 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; 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 min.

8. The metal surface treatment method according to claim 6, 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 treatment, then sequentially washing and drying to obtain a metal substrate after pickling treatment; Step B, washing the pickled metal substrate with an organic solvent, and then washing and drying in sequence to obtain a pretreated metal substrate.

9. The metal surface treatment method according to claim 8, characterized in that: The concentration of the acidic solution is 10-15wt%; Preferably, the acidic solution includes at least one of a hydrochloric acid solution and a sulfuric acid solution, more preferably a hydrochloric acid solution; Preferably, the pickling treatment time is 10 to 15 minutes.

10. The metal surface treatment method according to claim 8, characterized in that: The organic solvent includes at least one of acetone, ethanol and heptane.