A car body paint primer, its preparation method and application

Abstract

The application provides a car body paint surface primer and a preparation method and application thereof, and belongs to the technical field of polyurethane primers. In the application, aromatic isocyanate, polyether polyol and hydroxyl acrylate are used as raw materials to prepare a prepolymer with an isocyanate group content of 14% to 18% in a first organic solvent; the prepolymer and polyisocyanate and an organic silicon coupling agent are reacted in a second organic solvent in the presence of carbon black to prepare a primer with an isocyanate group content of 3% to 5%. The primer prepared by the method has excellent adhesion and adhesion effect on different paint surfaces, and can significantly improve the bonding force between the vehicle glass adhesive and the car body paint surface, so that the purpose of sealing and bonding is achieved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of polyurethane primer, in particular to a car body paint surface primer, a preparation method and application thereof. BACKGROUND

[0002] One-component polyurethane glass adhesive has the characteristics of simple operation and room temperature moisture curing, and is widely used in the bonding and sealing of windshields and side windows of various vehicles such as cars, buses, commercial vehicles and rail vehicles. In vehicle assembly production, the glass adhesive needs to form a firm bond to the glass surface and the vehicle body paint surface. This process is generally achieved by using a polyurethane glass adhesive with a primer. The car body paint surface primer, also known as a car paint primer, is applied to the car body paint surface to increase the adhesion between the polyurethane glass adhesive and the car body. Although some paint surfaces can be used without primer, the adaptability of the primer to the paint surface is very limited, and most manufacturers still use car paint primer when assembling the car body glass. When the polyurethane glass adhesive and the car body bond appear defects or debonding, it may cause rain leakage, abnormal noise, glass falling off and other phenomena, and even threaten driving safety. Therefore, the adhesion performance of the car paint primer is crucial.

[0003] A polyurethane glass primer and a preparation method thereof are disclosed in Chinese patent application publication CN113402963A. The polyurethane glass primer includes, by weight: 10-30 parts of a silane-modified polyurethane prepolymer, 1-5 parts of an adhesion promoter, 1-2 parts of a dispersing agent, 1-5 parts of carbon black, 60-85 parts of a solvent, and 0.01-0.2 parts of a catalyst. The silane-modified polyurethane prepolymer is obtained by polymerizing 2-10 parts of a polyol and 4-22 parts of a polyisocyanate, and then end-capping the polymer with a silane coupling agent. The primer has a low solid content, which reduces production costs while ensuring that the adhesion strength does not decrease. However, the adhesion strength still needs to be further improved.

[0004] A method for preparing a water vapor-resistant polyurethane primer is disclosed in Chinese patent application publication CN114381197A. The polyurethane primer is prepared from components I and II, wherein component I is a polyurethane prepolymer that includes a polyisocyanate and at least one polyether polyol; component II contains 0.5%-8% of a silane coupling agent with the formula Y-R1-Si-(OCH3) n X 3-nThe compound of the general formula, X is independently selected from: Cl, CH3O-, C2H5O-, (CH3)2CH-O-, CH3OCH2CH2O-, R1 is an alkylene group having 1-20 carbon atoms, preferably 1-10 carbon atoms, Y is selected from a methacryloxy group, a urea group, a vinyl group, an epoxy group, an alkyl group, an aryl group and an isocyanate group, and n is 1-3. The polyurethane primer is synthesized by combining a prepolymer of a polyether polyol, can greatly improve the surface condition of the wet composite board, and reduce or even eliminate the problem of surface blistering. However, the polyurethane primer composition lacks acrylate substances, which is effective for bonding the composite board, but has poor effect on bonding the body paint surface. SUMMARY

[0005] To solve the above problems, the application provides a preparation method of a body paint surface primer. The body paint surface primer prepared by the preparation method has excellent adhesion and adhesion effect, and can ensure the firm bonding between the polyurethane glass glue and the body paint surface.

[0006] Specifically, the application adopts the following technical scheme to achieve the above-mentioned technical effects:

[0007] A preparation method of a body paint surface primer, comprising the following steps:

[0008] S1, preparing a prepolymer: uniformly mixing aromatic isocyanate and a first organic solvent, then adding polyether polyol and hydroxy acrylate, heating and reacting, testing the isocyanate group content to be 14%-18%, and obtaining the prepolymer;

[0009] S2, preparing a primer: uniformly mixing the prepolymer, polyisocyanate, carbon black and a second organic solvent, and grinding; adding an organic silicon coupling agent, stirring uniformly, testing the isocyanate group content to be 3%-5%, and obtaining the primer.

[0010] In the preferred scheme, in step S1, 40-60 parts of the aromatic isocyanate and 10-30 parts of the first organic solvent are uniformly mixed, then 20-40 parts of polyether polyol and 1-10 parts of hydroxy acrylate are added, and heating and reaction are carried out.

[0011] In the preferred scheme, in step S2, 10%-30% of the prepolymer, 5%-20% of the polyisocyanate, 5%-10% of the carbon black and 50%-70% of the second organic solvent are uniformly mixed, in percentage of each raw material accounting for the total mass of all raw materials.

[0012] In the preferred scheme, in step S2, the mass of the added organic silicon coupling agent accounts for 1%-5% of the total mass of all raw materials in step S2.

[0013] In a preferred embodiment, in step S1, the heating reaction refers to a reaction at 60-80℃ for 1.5-2.5h.

[0014] In a preferred embodiment, in step S2, the grinding refers to grinding at a speed of 500-1000rpm for 0.5-1h.

[0015] In a preferred embodiment, the aromatic polyisocyanate includes any one or mixture of any several of toluene diisocyanate, diphenyl methane diisocyanate, xylylene diisocyanate, 2,4-toluene diisocyanate trimer, and polymethylene polyphenyl polyisocyanate.

[0016] In a preferred embodiment, the polyether polyol includes any one or mixture of any several of polypropylene oxide polyol, polyethylene oxide polyol, copolymerized polyol of propylene oxide and ethylene oxide, modified castor oil polyol, and polytetrahydrofuran polyol, and the polyether polyol has a hydroxyl functionality ≥2 and a molecular weight of 400-5000Da.

[0017] In a further preferred embodiment, the polyether polyol includes a mixture of at least two of polypropylene oxide polyol, polyethylene oxide polyol, copolymerized polyol of propylene oxide and ethylene oxide, modified castor oil polyol, and polytetrahydrofuran polyol, and the polyether polyol has a hydroxyl functionality ≥2 and a molecular weight of 400-3000Da.

[0018] In a preferred embodiment, the first organic solvent is any one or mixture of any several of butanone, ethyl acetate, n-butyl acetate, toluene, and xylene.

[0019] In a preferred embodiment, the second organic solvent is any one or mixture of any several of butanone, ethyl acetate, n-butyl acetate, toluene, and xylene.

[0020] In a preferred embodiment, the hydroxyl acrylate includes any one or mixture of any several of hydroxyl-containing acrylate monomer, hydroxyl acrylate resin, and polyacrylate polyol, and the hydroxyl acrylate has a hydroxyl functionality ≥1.

[0021] In a preferred embodiment, the polyisocyanate includes any one or mixture of any several of tris(4-phenyl isocyanate) thiophosphoric acid, triphenyl methane triisocyanate, and dimethyl triphenyl methane tetraisocyanate.

[0022] In a preferred embodiment, the silicone-based coupling agent includes any one or mixture of any several of γ-glycidyl ether oxypropyl trimethoxysilane, 2-(3,4-epoxy cyclohexyl) ethyl trimethoxysilane, mercapto propyl trimethoxysilane, and 3-isocyanate propyl trimethoxysilane.

[0023] The present application also provides a vehicle body paint bottom coating agent prepared according to any one of the above schemes. When the vehicle body paint bottom coating agent is applied to the bonding and sealing between the vehicle glass and the vehicle body paint, it has excellent adhesion and adhesion increasing effect.

[0024] The technical scheme of the present application has the following beneficial effects: the vehicle body paint bottom coating agent prepared by the method in the present application has branched polyether / acrylic acid prepolymers, the adhesion to various paints is ≤1 grade, and the peel adhesion performance to various paints reaches ≥95% cohesive failure. Therefore, the vehicle body paint bottom coating agent prepared in the present application can be effectively attached to the paint surface, significantly improving the adhesion between the polyurethane glass adhesive and the vehicle body paint, and achieving the purpose of sealing and bonding. BRIEF DESCRIPTION OF DRAWINGS

[0025] Figure 1 The result graph of the adhesion test of the bottom coating agent prepared by using Example 1 on a white paint board;

[0026] Figure 2 The result graph of the adhesion test of the bottom coating agent prepared by using Example 2 on a white paint board;

[0027] Figure 3 The result graph of the adhesion test of the bottom coating agent prepared by using Example 3 on a white paint board;

[0028] Figure 4 The result graph of the adhesion test of the bottom coating agent prepared by using Example 4 on a white paint board;

[0029] Figure 5 The result graph of the adhesion test of the bottom coating agent prepared by using Comparative Example 1 on a white paint board;

[0030] Figure 6 The result graph of the adhesion test of the bottom coating agent prepared by using Comparative Example 2 on a white paint board;

[0031] Figure 7 The result graph of the glass adhesive peel adhesion performance test of the bottom coating agent prepared by using Example 1 on a white paint board;

[0032] Figure 8 The result graph of the glass adhesive peel adhesion performance test of the bottom coating agent prepared by using Example 2 on a white paint board;

[0033] Figure 9 The result graph of the glass adhesive peel adhesion performance test of the bottom coating agent prepared by using Example 3 on a white paint board;

[0034] Figure 10 The result graph of the glass adhesive peel adhesion performance test of the bottom coating agent prepared by using Example 4 on a white paint board;

[0035] Figure 11 A graph of the results of testing the glass sealant peeling adhesion properties on a white painted panel for the base coating agent prepared using Comparative Example 1;

[0036] Figure 12 A graph of the results of testing the glass sealant peeling adhesion properties on a white painted panel for the base coating agent prepared using Comparative Example 2;

[0037] Figure 13 A graph of the results of testing the adhesion on a blue painted panel for the base coating agent prepared using Example 1;

[0038] Figure 14 A graph of the results of testing the adhesion on a blue painted panel for the base coating agent prepared using Example 2;

[0039] Figure 15 A graph of the results of testing the adhesion on a blue painted panel for the base coating agent prepared using Example 3;

[0040] Figure 16 A graph of the results of testing the adhesion on a blue painted panel for the base coating agent prepared using Example 4;

[0041] Figure 17 A graph of the results of testing the adhesion on a blue painted panel for the base coating agent prepared using Comparative Example 1;

[0042] Figure 18 A graph of the results of testing the adhesion on a blue painted panel for the base coating agent prepared using Comparative Example 2;

[0043] Figure 19 A graph of the results of testing the glass sealant peeling adhesion properties on a blue painted panel for the base coating agent prepared using Example 1;

[0044] Figure 20 A graph of the results of testing the glass sealant peeling adhesion properties on a blue painted panel for the base coating agent prepared using Example 2;

[0045] Figure 21 A graph of the results of testing the glass sealant peeling adhesion properties on a blue painted panel for the base coating agent prepared using Example 3;

[0046] Figure 22 A graph of the results of testing the glass sealant peeling adhesion properties on a blue painted panel for the base coating agent prepared using Example 4;

[0047] Figure 23 A graph of the results of testing the glass sealant peeling adhesion properties on a blue painted panel for the base coating agent prepared using Comparative Example 1;

[0048] Figure 24 A graph of the results of testing the glass sealant peeling adhesion properties on a blue painted panel for the base coating agent prepared using Comparative Example 2;

[0049] Figure 25 A graph of the results of testing the adhesion of the primer prepared using Example 1 on a yellow paint board;

[0050] Figure 26 A graph of the results of testing the adhesion of the primer prepared using Example 2 on a yellow paint board;

[0051] Figure 27 A graph of the results of testing the adhesion of the primer prepared using Example 3 on a yellow paint board;

[0052] Figure 28 A graph of the results of testing the adhesion of the primer prepared using Example 4 on a yellow paint board;

[0053] Figure 29 A graph of the results of testing the adhesion of the primer prepared using Comparative Example 1 on a yellow paint board;

[0054] Figure 30 A graph of the results of testing the adhesion of the primer prepared using Comparative Example 2 on a yellow paint board;

[0055] Figure 31 A graph of the results of testing the glass mastic peel adhesion of the primer prepared using Example 1 on a yellow paint board;

[0056] Figure 32 A graph of the results of testing the glass mastic peel adhesion of the primer prepared using Example 2 on a yellow paint board;

[0057] Figure 33 A graph of the results of testing the glass mastic peel adhesion of the primer prepared using Example 3 on a yellow paint board;

[0058] Figure 34 A graph of the results of testing the glass mastic peel adhesion of the primer prepared using Example 4 on a yellow paint board;

[0059] Figure 35 A graph of the results of testing the glass mastic peel adhesion of the primer prepared using Comparative Example 1 on a yellow paint board;

[0060] Figure 36 A graph of the results of testing the glass mastic peel adhesion of the primer prepared using Comparative Example 2 on a yellow paint board. DETAILED DESCRIPTION

[0061] The technical solutions of the present application are clearly and completely described below in combination with the embodiments, so that those skilled in the art can fully understand the present application. Obviously, the described embodiments are only a part of the preferred embodiments of the present application, rather than all the embodiments. Any equivalent transformation or replacement of the following embodiments made by those skilled in the art without creative labor shall fall within the protection scope of the present application.

[0062] The ordinal numbers used in the present application, such as "first", "second", etc., are only used for description purposes to distinguish similar objects, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features.

[0063] The polyether polyols T-403, DL-1000D, DL-2000D and MN-700 used in the following embodiments are all purchased from Shandong Lansheng Dongda Co., Ltd. The polyether polyols C2010D and C2020 are all purchased from Wanhua Chemical Group Co., Ltd. The polyether polyol A30 (effective ingredient is modified castor oil polyol) is purchased from Shanghai Jingri New Material Technology Co., Ltd. The polyether polyol VORANOL CP450 is a product of Dow Chemical. The hydroxyethyl methacrylate (HEMA) and the hydroxypropyl methacrylate (HPMA) are purchased from Yurui (Shanghai) Chemical Co., Ltd. The hydroxyacrylic resin CFU1955A is purchased from Shandong Kafulei High Polymer Material Co., Ltd. Jinan Branch. The BM-261 is purchased from Bolier Chemical Co., Ltd. The aromatic isocyanate TDI-80 (a product of two isomers of 2,4-toluene diisocyanate and 2,6-toluene diisocyanate mixed in a ratio of 80:20), MDI-100, PM-200 and XR-2005 are purchased from Wanhua Chemical Group Co., Ltd. The polyisocyanate Desmodur RFE (effective ingredient is tris (p-isocyanate phenyl ester) phosphorothioate) is purchased from Covestro Co., Ltd. The JQ-1E (effective ingredient is triphenylmethane triisocyanate) and the JQ-5E (effective ingredient is dimethyl triphenylmethane tetraisocyanate) are purchased from Liaoning Hongshan Chemical Co., Ltd. The silane coupling agent A-Link35 (effective ingredient is 3-isocyanate propyl trimethoxysilane) is produced by American Momentive Hi-Tech Group. The silane coupling agents JH-S189 (3-mercaptopropyl trimethoxysilane), JH-O186 (2-(3,4-epoxy cyclohexyl) ethyl trimethoxysilane) and JH-O187 (γ-glycidyl ether propyl trimethoxysilane) are all purchased from Hubei Jianghan New Material Co., Ltd.

[0064] The detection method of isocyanate group in the following examples refers to the method in HG / T 2409-92 "Determination of Isocyanate Group Content in Polyurethane Prepolymer".

[0065] Example 1

[0066] A preparation method of a car body paint primer, comprising the following steps:

[0067] S1, preparing a prepolymer

[0068] Mix 60 kg of aromatic isocyanate PM-200 and 16 kg of butanone, and then fully stir 3 kg of polyether polyol T-403, 20 kg of polyether polyol C2010D and 1 kg of hydroxyethyl methacrylate (HEMA) into the mixture, and then react at 80°C for 1.5 h. The isocyanate group content is 15.7%, and the prepolymer I is prepared. After the prepolymer I, 10 kg of carbon black, 5 kg of Desmodur RFE and 70 kg of xylene are uniformly mixed, the mixture is ground in a sand mill at a speed of 800 rpm for 1 h, 5 kg of silane coupling agent JH-O187 (γ-glycidyl ether propyl trimethoxysilane) is added, and the mixture is uniformly stirred at a speed of 200 rpm. The isocyanate group content is 3.2%, and the primer I is obtained.

[0069] S2, preparing a primer

[0070] After the prepolymer I, 10 kg of carbon black, 5 kg of Desmodur RFE and 70 kg of xylene are uniformly mixed, the mixture is ground in a sand mill at a speed of 800 rpm for 1 h, 5 kg of silane coupling agent JH-O187 (γ-glycidyl ether propyl trimethoxysilane) is added, and the mixture is uniformly stirred at a speed of 200 rpm. The isocyanate group content is 3.2%, and the primer I is obtained.

[0071] Example 2

[0072] A preparation method of a car body paint primer, comprising the following steps:

[0073] S1, preparing a prepolymer

[0074] Mix 40 kg of aromatic isocyanate TDI-80 and 30 kg of ethyl acetate, and then fully stir 5 kg of polyether polyol A30, 20 kg of polyether polyol C2010D and 5 kg of HPMA into the mixture, and then react at 70°C for 1.5 h. The isocyanate group content is 14.6%, and the prepolymer II is prepared. After the prepolymer II, 30 kg of carbon black, 9 kg of JQ-1E and 60 kg of toluene are uniformly mixed, the mixture is ground in a sand mill at a speed of 800 rpm for 1 h, 1 kg of silane coupling agent A-Link35 is added, and the mixture is uniformly stirred at a speed of 200 rpm. The isocyanate group content is 5%, and the primer II is obtained.

[0075] S2, preparing a primer

[0076] After the prepolymer II, 30 kg of carbon black, 9 kg of JQ-1E and 60 kg of toluene are uniformly mixed, the mixture is ground in a sand mill at a speed of 800 rpm for 1 h, 1 kg of silane coupling agent A-Link35 is added, and the mixture is uniformly stirred at a speed of 200 rpm. The isocyanate group content is 5%, and the primer II is obtained. ​​

[0077] Example 3

[0078] A method for preparing a vehicle body paint primer includes the following steps:

[0079] S1. Preparation of prepolymer

[0080] 48 kg of aromatic isocyanate XR-2005 and 10 kg of toluene are thoroughly mixed, then 5 kg of polyether polyol VORANOL CP450 and 35 kg of polyether polyol are added. C2020 and 2 kg of hydroxyl acrylic resin BM-261 were reacted at 70°C for 2 h, and the isocyanate group content was tested to be 18.0%, thus obtaining prepolymer III.

[0081] S2, Preparation of primer

[0082] Mix 15 kg of prepolymer III, 5 kg of carbon black, 20 kg of Desmodur RFE and 57 kg of ethyl acetate evenly, grind in a sand mill at 1000 rpm for 0.5 h, add 3 kg of silane coupling agent JH-O186, stir evenly at 150 rpm, test the isocyanate group content to be 4.1%, and discharge to obtain primer III.

[0083] Example 4

[0084] A method for preparing a vehicle body paint primer includes the following steps:

[0085] S1. Preparation of prepolymer

[0086] 50 kg of aromatic isocyanate MDI-100 and 20g of n-butyl acetate were thoroughly mixed, and then 10kg of polyether polyol MN-700, 10kg of polyether polyol DL-2000D and 10kg of hydroxyl acrylic resin CFU1955A were added. The mixture was reacted at 60℃ for 2.5h. The isocyanate group content was tested to be 14.0%. The product was then discharged to obtain prepolymer IV.

[0087] S2, Preparation of primer

[0088] Mix 20 kg of prepolymer IV, 10 kg of carbon black, 15 kg of JQ-5E and 50 kg of methyl ethyl ketone evenly, grind in a sand mill at 500 rpm for 1 hour, add 5 kg of silane coupling agent JH-S189, stir evenly at 100 rpm, test the isocyanate group content to be 4.3%, and discharge to obtain primer IV.

[0089] Comparative Example 1

[0090] A method for preparing a vehicle body paint primer includes the following steps:

[0091] S1. Preparation of prepolymer

[0092] 50 kg of aromatic isocyanate MDI-100 and 30g of n-butyl acetate were thoroughly mixed, and 10kg of polyether polyol MN-700 and 10kg of polyether polyol DL-2000D were added. The mixture was reacted at 60℃ for 2.5h. The isocyanate group content was tested to be 15.0%. The product was then discharged to obtain prepolymer V.

[0093] S2, Preparation of primer

[0094] Mix 20 kg of prepolymer V, 50 kg of butanone, 15 kg of Desmodur RFE and 10 kg of carbon black evenly, grind in a sand mill at 750 rpm for 1 hour, add 5 kg of silane coupling agent JH-O186, stir evenly at 200 rpm, test the isocyanate group content to be 4.5%, and discharge to obtain primer V.

[0095] Comparative Example 2

[0096] A method for preparing a body paint primer includes the following steps: 65 kg of butanone, 20 kg of JQ-1E and 10 kg of carbon black are mixed evenly, ground in a sand mill at 750 rpm for 1 hour, 5 kg of silane coupling agent A-Link35 is added, and stirred evenly at 200 rpm. The isocyanate group content is tested to be 1.0%, and the material is discharged to obtain primer VI.

[0097] Primer performance test

[0098] 1. Test materials

[0099] The substrates used in the tests were white, blue, and yellow painted boards. The main components of the paint were acrylic and / or polyurethane, sourced from PPG Industries, AkzoNobel, and Weixin Paint (Jiangxi) Co., Ltd., respectively. The silicone sealant used in the tests was Hubei Huitian New Materials Co., Ltd.'s 8960H single-component polyurethane silicone sealant.

[0100] 2. Basic performance test of primer

[0101] The basic performance tests were carried out on the primers prepared in Examples 1-4 and Comparative Examples 1-2 according to the general standard, and the main test items included appearance, viscosity, solid content, surface dry time and open time. The basic performance test method of the primer referred to the methods in GB / T 6753.4-1998 "Flow Cup Method for Testing Flow Time of Paints and Varnishes" and GB / T 2793-1995 "Determination of Non-volatile Matter Content of Adhesives". The test results are shown in Table 1.

[0102] Table 1 Basic performance test results of the primer

[0103]

[0104] The open time in Table 1 refers to the time after the primer is opened, which can maintain the basic performance unchanged. From the test results in Table 1, it can be seen that the basic performance of the primer prepared in the examples and comparative examples meets the requirements.

[0105] 3. Adhesion test of the primer on the paint board

[0106] The detection method of the adhesion of the primer referred to the method in GB / T 9286-2021 "Cross-hatch Test for Paints and Varnishes"; the representation of the glass glue peeling failure mode referred to the definition in GB / T 16997-1997 "Representation of Main Failure Modes of Adhesives".

[0107] The primer prepared in Examples 1-4 and Comparative Examples 1-2 was respectively applied on 6 clean paint surfaces, and after drying at room temperature (23±2℃, 50±5% RH) for 24h, a cross-hatch grid was cut with a cross-hatch knife, and then a soft brush was lightly swept, and then a pressure-sensitive adhesive tape was tightly attached to the coating grid. Within 5min after the tape was attached, one end of the tape was held in the air, and the tape was smoothly torn off at an angle of about 60° to the paint surface within 1.0s. The peeling of the coating was observed and recorded, and the results are shown in Figures 1-6 (white paint board), Figures 13-18 (blue paint board), Figures 25-30 (yellow paint board) and Tables 2-4. From these figures, it can be seen that the primer prepared in Examples 1-4 has good adhesion to the paint surface, and the tape cannot tear off the primer film; while the primer prepared in Comparative Examples 1-2 is torn off in a large area, indicating that the primer prepared in the comparative examples has poor adhesion to the paint surface.

[0108] 4. Peeling adhesion test of the primer on the paint board to the glass glue

[0109] The base coating agent prepared in 6 clean paint coating examples 1-4 and comparative examples 1-2, respectively, was dried at room temperature (23±2℃, 50±5%RH) for 10 min, and then glass glue was applied. The test was performed according to the test method specified in Appendix A of HG / T 4363-2012 "Single-component polyurethane adhesive for automobile window glass". The test results are shown in Tables 2-4. As can be seen from the figures, in examples 1-4, the adhesive tape was torn and damaged during the glass glue peeling process, the base coating agent adhered firmly, and all reached 100% CF cohesive failure; in comparative example 1, during the glass glue peeling process, except for reaching 100% cohesive failure on the blue paint board, it could not reach more than 90% cohesive failure on the white paint board and yellow paint board; in comparative example 2, the glass glue peeling process was basically interfacial failure, and the base coating agent could not adhere stably to the paint surface. Figures 7-12 (white paint board), Figures 19-24 (blue paint board), Figures 31-36 (yellow paint board), and Tables 2-4. As can be seen from the figures, in examples 1-4, the adhesive tape was torn and damaged during the glass glue peeling process, the base coating agent adhered firmly, and all reached 100% CF cohesive failure; in comparative example 1, during the glass glue peeling process, except for reaching 100% cohesive failure on the blue paint board, it could not reach more than 90% cohesive failure on the white paint board and yellow paint board; in comparative example 2, the glass glue peeling process was basically interfacial failure, and the base coating agent could not adhere stably to the paint surface.

[0110] Table 2 Test results of adhesion and peeling adhesion on white paint board

[0111]

[0112]

[0113] Table 3 Test results of adhesion and peeling adhesion on blue paint board

[0114] Blue paint Rating Interfacial / cohesive failure Example 1 ≤1 100% CF Example 2 ≤1 100% CF Example 3 ≤1 100% CF Example 4 ≤1 100% CF Comparative Example 1 ≤1 100% CF Comparative Example 2 ≥4 90% AF, 10% CF

[0115] Table 4 Test results of adhesion and peeling adhesion on yellow paint board

[0116] Yellow paint Rating Interfacial / cohesive failure Example 1 ≤1 100% CF Example 2 ≤1 100% CF Example 3 ≤1 100% CF Example 4 ≤1 100% CF Comparative Example 1 ≥2 20% AF, 80% CF Comparative Example 2 ≥4 90% AF, 10% CF

[0117] In Table 2-4, CF represents cohesive failure in the adhesive layer, and AF represents interfacial failure between the primer and the paint surface. As can be seen from the data in Table 2-4, when the primers prepared in Examples 1-4 are used, the paint surface adhesion is all ≤1 grade on the same paint surface; when the primer prepared in Comparative Example 1 is used, the adhesion is ≤1 grade on the blue paint surface, and ≥2 grade on other paint surfaces; and when the primer prepared in Comparative Example 2 is used, the adhesion is ≥4 grade on all paint surfaces. In the glass adhesive peeling adhesion test, when the primers prepared in Examples 1-4 are used, the failure mode of the glass adhesive is all cohesive failure of more than 95%; and when the primers prepared in Comparative Examples 1-2 are used, the glass adhesive shows different degrees of debonding. That is, on the basis of meeting the basic performance of the primer, the primer prepared in the present application has excellent adhesion and bonding capacity on a variety of paint surfaces, the primer prepared in Comparative Example 1 can only achieve excellent adhesion and bonding capacity on a small part of the paint surface, and the primer prepared in Comparative Example 2 can hardly meet the requirements of the vehicle manufacturer for adhesion and bonding performance. Therefore, the primer prepared by the method of the present application has more excellent paint surface adhesion and adhesion-increasing effect. Using the primer to brush on the vehicle body paint surface can effectively increase the bonding firmness of the polyurethane glass adhesive and the vehicle body substrate, and provides better protection for the safety of the vehicle.

[0118] The above-described examples are merely preferred embodiments of the present application and are not intended to limit the protection scope of the present application. The present application can have various modifications and changes for any skilled person in the art. Any simple equivalent changes and modifications made according to the protection scope and content of the present application should be included in the protection scope of the present application.

Claims

1. A method for preparing a primer for automotive paint, characterized in that, Includes the following steps: S1. Preparation of prepolymer: Aromatic polyisocyanate and first organic solvent are mixed evenly, then polyether polyol and hydroxy acrylate are added, heated to react, and the isocyanate group content is tested to be 14%~18% to obtain prepolymer; S2. Preparation of primer: Mix the prepolymer, polyisocyanate, carbon black and second organic solvent evenly and grind them; add organosilicon coupling agent, stir evenly, and test that the isocyanate group content is 3%~5% to obtain primer.

2. The method for preparing the vehicle body paint primer according to claim 1, characterized in that, In step S1, 40-60 parts of the aromatic polyisocyanate and 10-30 parts of the first organic solvent are mixed evenly by mass, and then 20-40 parts of polyether polyol and 1-10 parts of hydroxy acrylate are added and heated to react.

3. The method for preparing the vehicle body paint primer according to claim 1, characterized in that, In step S2, based on the percentage of each raw material to the total mass of all raw materials, 10% to 30% of the prepolymer, 5% to 20% of the polyisocyanate, 5% to 10% of the carbon black, and 50% to 70% of the second organic solvent are mixed evenly; 1% to 5% of the organosilicon coupling agent is added and stirred evenly.

4. The method for preparing the vehicle body paint primer according to claim 1, characterized in that, The heating reaction mentioned in step S1 refers to reacting at 60~80℃ for 1.5~2.5h; or / and in step S2, grinding refers to grinding at a speed of 500~1000rpm for 0.5~1h.

5. The method for preparing the vehicle body paint primer according to claim 1, characterized in that, The aromatic polyisocyanate includes any one or a mixture of several of toluene diisocyanate, diphenylmethane diisocyanate, phenyl dimethylene diisocyanate, 2,4-toluene diisocyanate trimer, and polymethylene polyphenyl polyisocyanate; or / and the polyether polyol includes any one or a mixture of several of polypropylene oxide polyol, polyethylene oxide polyol, propylene oxide and ethylene oxide copolymer polyol, modified castor oil polyol, and polytetrahydrofuran polyol, and the polyether polyol has a hydroxyl functionality ≥2 and a molecular weight of 400~5000 Da.

6. The method for preparing the vehicle body paint primer according to claim 1, characterized in that, The first organic solvent is any one or a mixture of several of butanone, ethyl acetate, n-butyl acetate, toluene, and xylene; or / and the second organic solvent is any one or a mixture of several of butanone, ethyl acetate, n-butyl acetate, toluene, and xylene.

7. The method for preparing the vehicle body paint primer according to claim 1, characterized in that, The hydroxy acrylate includes any one or a mixture of several hydroxyl-containing acrylate monomers and hydroxyl acrylic resins, and the hydroxyl functionality of the hydroxy acrylate is ≥1.

8. The method for preparing the vehicle body paint primer according to claim 1, characterized in that, The polyisocyanate includes any one or a mixture of several of the following: tri(4-phenylisocyanate) thiophosphate, triphenylmethane triisocyanate, and dimethyltriphenylmethane tetraisocyanate; or / and the organosilicon coupling agent includes any one or a mixture of several of the following: γ-glycidoxypropyltrimethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3-mercaptopropyltrimethoxysilane, and 3-isocyanatepropyltrimethoxysilane.

9. The vehicle body paint primer prepared by the preparation method according to any one of claims 1 to 8.

10. The application of the vehicle body paint primer prepared by the preparation method according to any one of claims 1 to 8 in the bonding and sealing between vehicle glass and vehicle body paint.

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