Polyurethane sealant primer as well as preparation method and application thereof

Abstract

The invention discloses a polyurethane sealant primer as well as a preparation method and application thereof, and relates to a primer as well as a preparation method and application thereof. The invention aims to solve the problems that the existing single-component polyurethane sealant has low bonding strength on aviation organic glass and cannot meet the bonding sealing of helicopter cabin organic glass and crack arrest of cabin cover organic glass. The primer is prepared from a T100 prepolymer, an MDI and TPTI mixed isocyanate prepolymer, 4-toluenesulfonyl isocyanate, a catalyst, butanone, carbon black and methanesulfonic acid. The method comprises the following steps: 1, preparing a mixed isocyanate prepolymer of MDI and TPTI; and 2, preparing the polyurethane sealant primer. According to the application, the adhesive is applied to bonding sealing of helicopter cabin organic glass and crack arrest of cabin cover organic glass. The invention provides the polyurethane sealant primer as well as the preparation and the application thereof.

Description

Technical Field

[0001] The invention relates to a primer and a preparation method and application thereof. Background Art

[0002] Polyurethane sealants have excellent wear resistance, low-temperature flexibility, mechanical strength, adhesion, elasticity, resilience, weather resistance and oil resistance, and are suitable for dynamic joints. Therefore, they are widely used in civil construction, transportation, electronics, medical equipment and other industries. Before use, polyurethane sealants are in a paste state with high viscosity and poor flowability on the surface of the substrate. At the same time, polyurethane adhesives have high polarity and low surface energy of organic glass. The bonding strength between polyurethane adhesives and organic glass is low, and the shear strength is only 3MPa-4MPa. After natural aging, interfacial debonding is prone to occur. Therefore, existing polyurethane sealants cannot meet the bonding and sealing of helicopter cockpit organic glass and the crack prevention of cabin cover organic glass. Summary of the invention

[0003] The present invention aims to solve the problem that the existing single-component polyurethane sealant has low bonding strength to aviation organic glass and cannot meet the bonding and sealing of helicopter cockpit organic glass and the crack prevention of cabin cover organic glass, and further provides a polyurethane sealant primer and its preparation method and application.

[0004] A polyurethane sealant primer is prepared from 10 to 15 parts of T100 prepolymer, 60 to 66 parts of MDI and TPTI mixed isocyanate prepolymer, 1 to 3 parts of 4-toluenesulfonyl isocyanate, 0.1 to 0.5 parts of a catalyst, 13 to 15 parts of butanone, 3 to 5 parts of carbon black and 0.03 to 0.05 parts of methyl sulfonic acid in parts by mass.

[0005] A method for preparing a polyurethane sealant primer is prepared according to the following steps:

[0006] 1. Preparation of MDI and TPTI mixed isocyanate prepolymer:

[0007] Weigh 4 to 5 parts of diethylene glycol, 1 to 5 parts of trimethylolpropane, 30 to 36 parts of 4,4-diphenylmethane diisocyanate, 29 to 44 parts of ethyl acetate and 10 to 15 parts of triphenyl isocyanate of thiophosphate by mass, stir and mix 4 to 5 parts of diethylene glycol and 1 to 5 parts of trimethylolpropane in a closed reactor isolated from air at a temperature of 70°C to 75°C, then drop a preheated mixture of 7 to 9 parts of 4,4-diphenylmethane diisocyanate and 9 to 12 parts of ethyl acetate, and heat in a dry nitrogen atmosphere at a temperature of 70°C to 75°C. , react for 30 min to 40 min to obtain reaction solution B, mix 23 parts to 27 parts of 4,4-diphenylmethane diisocyanate and 20 parts to 32 parts of ethyl acetate and heat to 70°C to 75°C, then dropwise add reaction solution B, react for 50 min to 60 min in a dry nitrogen atmosphere at a temperature of 70°C to 75°C, finally add 10 parts to 15 parts of triphenylthiophosphate isocyanate in a dry nitrogen atmosphere at a temperature of 70°C to 75°C and continue to react for 50 min to 60 min to obtain a mixed isocyanate prepolymer of MDI and TPTI;

[0008] 2. Preparation of polyurethane sealant primer:

[0009] 10 to 15 parts of T100 prepolymer, 60 to 66 parts of MDI and TPTI mixed isocyanate prepolymer, 1 to 3 parts of 4-toluenesulfonyl isocyanate, 0.1 to 0.5 parts of catalyst, 13 to 15 parts of butanone, 3 to 5 parts of carbon black and 0.03 to 0.05 parts of methyl sulfonic acid are weighed by mass, and then added into a double planetary dispersion reactor and grinding balls are added. In an airtight reactor isolated from air, at a temperature of 70°C to 75°C, a ball-to-material ratio of (0.5 to 1):1 and a speed of 1500 to 1800 rpm, the mixture is dispersed and stirred for 30 to 40 minutes, and finally cooled to room temperature, the grinding balls are filtered, and a polyurethane sealant primer is obtained.

[0010] The invention discloses an application of a polyurethane sealant primer, which is applied to the bonding and sealing of helicopter cockpit organic glass and the crack prevention of cabin cover organic glass.

[0011] The beneficial effects of the present invention are:

[0012] The invention discloses a polyurethane sealant primer. Two polyisocyanate prepolymers are synthesized in the preparation process. The primer and the polyurethane sealant are matched by adjusting the ratio of the prepolymers, the isocyanate group content of the primer and the acid value of the system, so that the polyurethane sealant can simultaneously bond various substrates of a helicopter cockpit, and the bonding performance of the polyurethane sealant is significantly improved. The shear strength of bonding various organic glasses can reach 6MPa-7MPa, and the bonding failure form is material failure or cohesive failure. After a series of environmental aging tests (high temperature, low temperature, temperature shock, solar radiation, damp heat, and salt fog atmosphere), the shear strength is greater than 6MPa. The polyurethane sealant can be applied to the bonding and sealing of organic glasses in helicopter cockpits and the crack arrest of organic glasses on cabin covers. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 This is a physical picture of the 3# glass / epoxy composite adhesive prepared in Example 2 after the shear strength test;

[0014] Figure 2 This is a physical picture of the 9# glass / epoxy composite adhesive prepared in Example 2 after the shear strength test;

[0015] Figure 3 This is a physical picture of the 10# glass / epoxy composite adhesive prepared in Example 2 after the shear strength test;

[0016] Figure 4 This is a physical picture of the injection-molded glass / epoxy composite adhesive component prepared in Example 2 after the shear strength test. DETAILED DESCRIPTION

[0017] Specific implementation method 1: This implementation method is a polyurethane sealant primer, which is prepared by weight from 10 to 15 parts of T100 prepolymer, 60 to 66 parts of MDI and TPTI mixed isocyanate prepolymer, 1 to 3 parts of 4-toluenesulfonyl isocyanate, 0.1 to 0.5 parts of catalyst, 13 to 15 parts of butanone, 3 to 5 parts of carbon black and 0.03 to 0.05 parts of methanesulfonic acid.

[0018] This embodiment improves the surface of organic glass by designing and synthesizing corresponding primers, thereby improving the surface properties of organic glass. Primer is the key to the application of polyurethane sealant, and the design of primer needs to comprehensively consider the types of adhesive and bonded substrate. Experiments have shown that the bonding strength between polyurethane sealant and aviation organic glass varies greatly when using different primers. The matching primer prepared in this embodiment treats the surface of the substrate to achieve high-strength, stable and reliable bonding and sealing.

[0019] The beneficial effects of this embodiment are:

[0020] The present embodiment discloses a polyurethane sealant primer. Since two polyisocyanate prepolymers are synthesized during the preparation process, the primer and the polyurethane sealant are matched by adjusting the ratio of the prepolymers, the isocyanate group content of the primer and the acid value of the system, so that one polyurethane sealant can bond multiple substrates of a helicopter cockpit at the same time, and the bonding performance of the polyurethane sealant is significantly improved. The shear strength of bonding multiple organic glasses can reach 6MPa to 7MPa, and the bonding failure form is material failure or cohesive failure. After a series of environmental aging tests (high temperature, low temperature, temperature shock, solar radiation, damp heat, and salt fog atmosphere), the shear strength is greater than 6MPa. The polyurethane sealant can be used for bonding and sealing of organic glass in helicopter cockpits and for stopping cracking of organic glass on cabin covers.

[0021] Specific embodiment 2: This embodiment is different from specific embodiment 1 in that the catalyst is 4-dimethylaminopyridine. Other aspects are the same as those of specific embodiment 1.

[0022] Specific embodiment 3: This embodiment is different from specific embodiment 1 or 2 in that: the T100 prepolymer is prepared according to the following steps: 4 to 5 parts of diethylene glycol, 5 to 6 parts of trimethylolpropane, 40 to 46 parts of 2,4'-toluene diisocyanate and 40 to 46 parts of ethyl acetate are weighed by mass, 4 to 5 parts of diethylene glycol and 5 to 6 parts of trimethylolpropane are stirred and mixed evenly in a closed reaction kettle isolated from air at a temperature of 70°C to 75°C, and then 2 parts of diethylene glycol are added dropwise; 0 to 23 parts of 2,4'-toluene diisocyanate and 20 to 23 parts of ethyl acetate are reacted for 30 to 40 minutes in a dry nitrogen atmosphere at a temperature of 70°C to 75°C to obtain a reaction solution A, and the reaction solution A is dropped into a reaction kettle containing 20 to 23 parts of 2,4'-toluene diisocyanate and 20 to 23 parts of ethyl acetate, and reacted for 100 to 120 minutes in a dry nitrogen atmosphere at a temperature of 70°C to 75°C to obtain a T100 prepolymer. The rest is the same as the specific embodiment 1 or 2.

[0023] Specific embodiment 4: This embodiment is a method for preparing a polyurethane sealant primer, which is prepared according to the following steps:

[0024] 1. Preparation of MDI and TPTI mixed isocyanate prepolymer:

[0025] Weigh 4 to 5 parts of diethylene glycol, 1 to 5 parts of trimethylolpropane, 30 to 36 parts of 4,4-diphenylmethane diisocyanate, 29 to 44 parts of ethyl acetate and 10 to 15 parts of triphenyl isocyanate of thiophosphate by mass, stir and mix 4 to 5 parts of diethylene glycol and 1 to 5 parts of trimethylolpropane in a closed reactor isolated from air at a temperature of 70°C to 75°C, then drop a preheated mixture of 7 to 9 parts of 4,4-diphenylmethane diisocyanate and 9 to 12 parts of ethyl acetate, and heat in a dry nitrogen atmosphere at a temperature of 70°C to 75°C. , react for 30 min to 40 min to obtain reaction solution B, mix 23 parts to 27 parts of 4,4-diphenylmethane diisocyanate and 20 parts to 32 parts of ethyl acetate and heat to 70°C to 75°C, then dropwise add reaction solution B, react for 50 min to 60 min in a dry nitrogen atmosphere at a temperature of 70°C to 75°C, finally add 10 parts to 15 parts of triphenylthiophosphate isocyanate in a dry nitrogen atmosphere at a temperature of 70°C to 75°C and continue to react for 50 min to 60 min to obtain a mixed isocyanate prepolymer of MDI and TPTI;

[0026] 2. Preparation of polyurethane sealant primer:

[0027] 10 to 15 parts of T100 prepolymer, 60 to 66 parts of MDI and TPTI mixed isocyanate prepolymer, 1 to 3 parts of 4-toluenesulfonyl isocyanate, 0.1 to 0.5 parts of catalyst, 13 to 15 parts of butanone, 3 to 5 parts of carbon black and 0.03 to 0.05 parts of methyl sulfonic acid are weighed by mass, and then added into a double planetary dispersion reactor and grinding balls are added. In an airtight reactor isolated from air, at a temperature of 70°C to 75°C, a ball-to-material ratio of (0.5 to 1):1 and a speed of 1500 to 1800 rpm, the mixture is dispersed and stirred for 30 to 40 minutes, and finally cooled to room temperature, the grinding balls are filtered, and a polyurethane sealant primer is obtained.

[0028] Specific embodiment 5: This embodiment differs from specific embodiment 4 in that: in step 1, a mixture of 7 to 9 parts of 4,4-diphenylmethane diisocyanate and 9 to 12 parts of ethyl acetate preheated to a temperature of 50°C to 55°C is added dropwise. The rest is the same as specific embodiment 4.

[0029] Specific embodiment 6: This embodiment is different from specific embodiment 4 or 5 in that: the T100 prepolymer described in step 2 is specifically prepared according to the following steps: 4 to 5 parts of diethylene glycol, 5 to 6 parts of trimethylolpropane, 40 to 46 parts of 2,4'-toluene diisocyanate and 40 to 46 parts of ethyl acetate are weighed by mass, and 4 to 5 parts of diethylene glycol and 5 to 6 parts of trimethylolpropane are stirred and mixed evenly in a closed reaction kettle isolated from air at a temperature of 70°C to 75°C, and then dripped Add 20 to 23 parts of 2,4'-toluene diisocyanate and 20 to 23 parts of ethyl acetate, react for 30 to 40 minutes in a dry nitrogen atmosphere at a temperature of 70°C to 75°C to obtain a reaction solution A, drop the reaction solution A into a reaction kettle containing 20 to 23 parts of 2,4'-toluene diisocyanate and 20 to 23 parts of ethyl acetate, react for 100 to 120 minutes in a dry nitrogen atmosphere at a temperature of 70°C to 75°C to obtain a T100 prepolymer. The rest is the same as the specific embodiment 4 or 5.

[0030] Specific embodiment 7: This embodiment is different from specific embodiments 4 to 6 in that the grinding balls described in step 2 are zirconium oxide micro-beads with a particle size of 1.2 mm to 1.4 mm. The rest is the same as specific embodiments 4 to 6.

[0031] Specific implementation method eight: This implementation method is an application of a polyurethane sealant primer, which is used for bonding and sealing of helicopter cockpit plexiglass and preventing cracks of cabin cover plexiglass.

[0032] Specific embodiment 9: This embodiment is different from specific embodiment 8 in that it is applied to the bonding and sealing of helicopter cockpit plexiglass and the crack prevention of cabin cover plexiglass, and is specifically carried out in the following steps:

[0033] The surface of the area to be bonded of the organic glass is polished, then cleaned and dried, then coated with a polyurethane sealant primer and left to air, then coated with polyurethane sealant, and then closed and compacted with the composite material, and cured at room temperature, thus completing the bonding and sealing of the helicopter cockpit organic glass and the crack arrest of the cabin cover organic glass. The rest is the same as the eighth specific implementation.

[0034] Specific embodiment 10: This embodiment is different from specific embodiment 8 or 9 in that the helicopter cockpit organic glass and cabin cover organic glass are YB-3 organic glass, YB-9 organic glass, YB-DM-10 organic glass, injection glass or laminated organic glass. The rest is the same as specific embodiment 8 or 9.

[0035] The following examples are used to verify the beneficial effects of the present invention:

[0036] Embodiment 1:

[0037] A polyurethane sealant primer is prepared from 11 parts by mass of T100 prepolymer, 65 parts by mass of MDI and TPTI mixed isocyanate prepolymer, 1.5 parts by mass of 4-toluenesulfonyl isocyanate, 0.1 parts by mass of catalyst, 14 parts by mass of butanone, 3 parts by mass of carbon black and 0.03 parts by mass of methanesulfonic acid.

[0038] The catalyst is 4-dimethylaminopyridine.

[0039] The T100 prepolymer is specifically prepared according to the following steps: 4 parts of diethylene glycol, 6 parts of trimethylolpropane, 43 parts of 2,4'-toluene diisocyanate (T100) and 43 parts of ethyl acetate are weighed by mass, and 4 parts of diethylene glycol and 6 parts of trimethylolpropane are stirred and mixed evenly in a closed reactor isolated from air at a temperature of 70°C, and then 20 parts of 2,4'-toluene diisocyanate and 20 parts of ethyl acetate are added dropwise, and the reaction is carried out for 30 minutes in a dry nitrogen atmosphere at a temperature of 70°C to obtain a reaction liquid A, and the reaction liquid A is dropped into a reactor containing 23 parts of 2,4'-toluene diisocyanate and 23 parts of ethyl acetate, and the reaction is carried out for 120 minutes in a dry nitrogen atmosphere at a temperature of 70°C to obtain a T100 prepolymer.

[0040] The preparation method of the above-mentioned polyurethane sealant primer is prepared according to the following steps:

[0041] 1. Preparation of MDI and TPTI mixed isocyanate prepolymer:

[0042] Weigh 4 parts of diethylene glycol, 5 parts of trimethylolpropane, 36 parts of 4,4-diphenylmethane diisocyanate (MDI), 41 parts of ethyl acetate and 15 parts of triphenylphosphorothioate (TPTI) by mass, stir and mix 4 parts of diethylene glycol and 5 parts of trimethylolpropane in a closed reactor isolated from air at a temperature of 70°C, then dropwise add a mixture of 9 parts of 4,4-diphenylmethane diisocyanate and 9 parts of ethyl acetate preheated to 52°C, and stir under dry nitrogen. The mixture was reacted for 30 minutes under the conditions of a dry nitrogen atmosphere and a temperature of 70°C to obtain a reaction solution B, 27 parts of 4,4-diphenylmethane diisocyanate and 32 parts of ethyl acetate were mixed and heated to 70°C, and then the reaction solution B was added dropwise, and the mixture was reacted for 60 minutes under the conditions of a dry nitrogen atmosphere and a temperature of 70°C, and finally 15 parts of triphenylthiophosphate was added under the conditions of a dry nitrogen atmosphere and a temperature of 70°C to continue the reaction for 60 minutes to obtain a mixed isocyanate prepolymer of MDI and TPTI;

[0043] 2. Preparation of polyurethane sealant primer:

[0044] 11 parts of T100 prepolymer, 65 parts of MDI and TPTI mixed isocyanate prepolymer, 1.5 parts of 4-toluenesulfonyl isocyanate, 0.1 parts of catalyst, 14 parts of butanone, 3 parts of carbon black and 0.03 parts of methanesulfonic acid were weighed by mass, and then added into a double planetary dispersion reactor and grinding balls were added. In an airtight reactor isolated from air, at a temperature of 70°C, a ball-to-material ratio of 0.5:1 and a speed of 1800 rpm, the mixture was dispersed and stirred for 30 minutes, and finally cooled to room temperature, the grinding balls were filtered, and a polyurethane sealant primer was obtained.

[0045] The grinding balls described in step 2 are zirconium oxide microbeads with a particle size of 1.2 mm.

[0046] Comparative Experiment 1: This comparative experiment is different from Example 1 in that the use of the mixed isocyanate prepolymer of MDI and TPTI is eliminated. The rest is the same as Example 1.

[0047] Example 2: The primer prepared in Example 1 is used to bond 3# glass to epoxy composite, 9# glass to epoxy composite, 10# glass to epoxy composite, and injection molded glass to epoxy composite, respectively, in accordance with the following steps:

[0048] The surface of the area to be bonded of the organic glass was polished with 120-grit sandpaper, then cleaned with anhydrous ethanol and dried, then coated with a polyurethane sealant primer and left to air for 15 minutes, then smeared with polyurethane sealant, and then pressed together with the epoxy composite, and cured at room temperature for 7 days to obtain 3# glass / epoxy composite bonded parts, 9# glass / epoxy composite bonded parts, 10# glass / epoxy composite bonded parts and injection molded glass / epoxy composite bonded parts;

[0049] The 3# glass is YB-3 glass produced by Jinxi Chemical Research Institute Co., Ltd.

[0050] The 9# glass is YB-9 glass produced by Jinxi Chemical Research Institute Co., Ltd.

[0051] The 10# glass is YB-DM-10 glass produced by Jinxi Chemical Research Institute Co., Ltd.

[0052] The injection molded glass is V040 type injection molded glass produced by Beijing Institute of Aeronautical Materials.

[0053] The epoxy composite material is an EH103 epoxy composite material produced by Jiangsu Hengshen Co., Ltd.

[0054] The polyurethane sealant is LM-S2101 polyurethane sealant produced by Liming Chemical Research and Design Institute Co., Ltd.

[0055] Comparative Experiment 2: This comparative experiment is different from Example 2 in that the primer prepared in Example 1 is replaced with the primer prepared in Comparative Experiment 1. The rest is the same as Example 2.

[0056] Comparative Experiment 3: This comparative experiment is different from Example 2 in that the primer is not used, and the polyurethane sealant is directly applied, and then the epoxy composite is pressed together and cured at room temperature for 7 days. The rest is the same as Example 2.

[0057] The 3# glass / epoxy composite adhesive, 9# glass / epoxy composite adhesive, 10# glass / epoxy composite adhesive and injection molded glass / epoxy composite adhesive prepared in Example 2, Comparative Experiments 2 and 3 were tested for (23±2)°C shear strength according to GB / T 7124-2008, and multiple groups of parallel samples were tested to obtain the average value, as shown in Table 1 below.

[0058] Table 1 Adhesion performance data

[0059]

[0060] Figure 1 This is a physical picture of the 3# glass / epoxy composite adhesive prepared in Example 2 after the shear strength test. Figure 2 This is a physical picture of the 9# glass / epoxy composite adhesive prepared in Example 2 after the shear strength test. Figure 3 This is a physical picture of the 10# glass / epoxy composite adhesive prepared in Example 2 after the shear strength test. Figure 4 This is a photo of the injection molded glass / epoxy composite adhesive prepared in Example 2 after the shear strength test. As can be seen from the figure, the shear strength failure form after the adhesive material is coated with a primer is cohesive failure, which improves the bonding strength and bonding reliability.

[0061] The 3# glass / epoxy composite adhesive, 9# glass / epoxy composite adhesive, 10# glass / epoxy composite adhesive and injection molded glass / epoxy composite adhesive prepared in Example 2 and Comparative Experiment 3 were subjected to a comprehensive environmental aging test 1, that is, multiple aging tests were performed on the same sample in sequence, specifically: first, a solar radiation aging test (GJB 150.7A-2009) was performed, then a damp heat aging test (GJB 150.9A-2009) was performed, and finally a salt spray aging test (GJB 150.11A-2009) was performed. After the aging test, the test piece was tested for (23±2)°C shear strength according to GB / T 7124-2008, and multiple groups of parallel samples were tested to obtain the average value. The data are shown in Table 2.

[0062] Table 2 Adhesion performance data of comprehensive environmental aging test 1

[0063]

[0064] The 3# glass / epoxy composite adhesive, 9# glass / epoxy composite adhesive, 10# glass / epoxy composite adhesive and injection molded glass / epoxy composite adhesive prepared in Example 2 and Comparative Experiment 3 were subjected to comprehensive environmental aging test 2, that is, multiple aging experiments were carried out on the same sample in sequence, specifically: firstly, a high temperature aging test (GJB 150.3A-2009) was carried out under the high temperature condition of 70°C, then a low temperature aging test (GJB 150.4A-2009) was carried out under the low temperature condition of -40°C, and finally a temperature shock aging test (GJB 150.5A-2009) was carried out. After the aging test, the test piece was tested for (23±2)°C shear strength according to GB / T 7124-2008, and multiple groups of parallel samples were carried out to obtain the average value. The data are shown in Table 3.

[0065] Table 3 Adhesion performance data of comprehensive environmental aging test 2

[0066]

[0067] It can be seen from the data in Table 2 and Table 3 that the bonding material has good environmental aging resistance after being coated with a primer, and the shear strength failure form after aging is material failure or cohesive failure, which improves the bonding strength and bonding reliability.

Claims

1. A polyurethane sealant primer, characterized in that The invention is prepared from 10 to 15 parts of T100 prepolymer, 60 to 66 parts of MDI and TPTI mixed isocyanate prepolymer, 1 to 3 parts of 4-toluenesulfonyl isocyanate, 0.1 to 0.5 parts of catalyst, 13 to 15 parts of butanone, 3 to 5 parts of carbon black and 0.03 to 0.05 parts of methyl sulfonic acid by weight.

2. A polyurethane sealant primer according to claim 1, characterized in that The catalyst is 4-dimethylaminopyridine.

3. A polyurethane sealant primer according to claim 1, characterized in that The T100 prepolymer is specifically prepared according to the following steps: 4 to 5 parts of diethylene glycol, 5 to 6 parts of trimethylolpropane, 40 to 46 parts of 2,4'-toluene diisocyanate and 40 to 46 parts of ethyl acetate are weighed by mass, 4 to 5 parts of diethylene glycol and 5 to 6 parts of trimethylolpropane are stirred and mixed uniformly in a closed reaction kettle isolated from air at a temperature of 70°C to 75°C, and then 20 to 23 parts of 2,4'-toluene diisocyanate are added dropwise. Cyanate and 20 to 23 parts of ethyl acetate are reacted in a dry nitrogen atmosphere at a temperature of 70°C to 75°C for 30 to 40 minutes to obtain a reaction liquid A, and the reaction liquid A is dropped into a reaction kettle filled with 20 to 23 parts of 2,4'-toluene diisocyanate and 20 to 23 parts of ethyl acetate, and the reaction is carried out in a dry nitrogen atmosphere at a temperature of 70°C to 75°C for 100 to 120 minutes to obtain a T100 prepolymer.

4. The method for preparing a polyurethane sealant primer according to claim 1, characterized in that It is prepared according to the following steps:

1. Preparation of MDI and TPTI mixed isocyanate prepolymer: Weigh 4 to 5 parts of diethylene glycol, 1 to 5 parts of trimethylolpropane, 30 to 36 parts of 4,4-diphenylmethane diisocyanate, 29 to 44 parts of ethyl acetate and 10 to 15 parts of triphenyl isocyanate of thiophosphate by mass, stir and mix 4 to 5 parts of diethylene glycol and 1 to 5 parts of trimethylolpropane in a closed reactor isolated from air at a temperature of 70°C to 75°C, then drop a preheated mixture of 7 to 9 parts of 4,4-diphenylmethane diisocyanate and 9 to 12 parts of ethyl acetate, and heat in a dry nitrogen atmosphere at a temperature of 70°C to 75°C. , react for 30 min to 40 min to obtain reaction solution B, mix 23 parts to 27 parts of 4,4-diphenylmethane diisocyanate and 20 parts to 32 parts of ethyl acetate and heat to 70°C to 75°C, then dropwise add reaction solution B, react for 50 min to 60 min in a dry nitrogen atmosphere at a temperature of 70°C to 75°C, finally add 10 parts to 15 parts of triphenylthiophosphate isocyanate in a dry nitrogen atmosphere at a temperature of 70°C to 75°C and continue to react for 50 min to 60 min to obtain a mixed isocyanate prepolymer of MDI and TPTI; 2. Preparation of polyurethane sealant primer: 10 to 15 parts of T100 prepolymer, 60 to 66 parts of MDI and TPTI mixed isocyanate prepolymer, 1 to 3 parts of 4-toluenesulfonyl isocyanate, 0.1 to 0.5 parts of catalyst, 13 to 15 parts of butanone, 3 to 5 parts of carbon black and 0.03 to 0.05 parts of methyl sulfonic acid are weighed by mass, and then added into a double planetary dispersion reactor and grinding balls are added. In an airtight reactor isolated from air, at a temperature of 70°C to 75°C, a ball-to-material ratio of (0.5 to 1):1 and a speed of 1500 to 1800 rpm, the mixture is dispersed and stirred for 30 to 40 minutes, and finally cooled to room temperature, the grinding balls are filtered, and a polyurethane sealant primer is obtained.

5. The method for preparing a polyurethane sealant primer according to claim 4, characterized in that In step 1, a mixture of 7 to 9 parts of 4,4-diphenylmethane diisocyanate and 9 to 12 parts of ethyl acetate preheated to a temperature of 50° C. to 55° C. is added dropwise.

6. The method for preparing a polyurethane sealant primer according to claim 4, characterized in that The T100 prepolymer described in step 2 is specifically prepared according to the following steps: 4 to 5 parts of diethylene glycol, 5 to 6 parts of trimethylolpropane, 40 to 46 parts of 2,4'-toluene diisocyanate and 40 to 46 parts of ethyl acetate are weighed by mass, and 4 to 5 parts of diethylene glycol and 5 to 6 parts of trimethylolpropane are stirred and mixed evenly in a closed reaction kettle isolated from air at a temperature of 70°C to 75°C, and then 20 to 23 parts of 2,4'-toluene are added dropwise. The diisocyanate and 20 to 23 parts of ethyl acetate are reacted in a dry nitrogen atmosphere at a temperature of 70°C to 75°C for 30 to 40 minutes to obtain a reaction liquid A, and the reaction liquid A is dropped into a reaction kettle filled with 20 to 23 parts of 2,4'-toluene diisocyanate and 20 to 23 parts of ethyl acetate, and the reaction is carried out in a dry nitrogen atmosphere at a temperature of 70°C to 75°C for 100 to 120 minutes to obtain a T100 prepolymer.

7. The method for preparing a polyurethane sealant primer according to claim 4, characterized in that The grinding balls described in step 2 are zirconium oxide micro-beads with a particle size of 1.2 mm to 1.4 mm.

8. The use of a polyurethane sealant primer as claimed in claim 1, characterized in that It is used for bonding and sealing of helicopter cockpit plexiglass and preventing cracks of cabin cover plexiglass.

9. The use of a polyurethane sealant primer according to claim 8, characterized in that It is used for bonding and sealing of helicopter cockpit plexiglass and preventing cracking of cabin cover plexiglass. The specific steps are as follows: The surface of the plexiglass to be bonded is polished, then cleaned and dried, and then coated with a polyurethane sealant primer and left to air, and then polyurethane sealant is applied, and then the composite material is closed and compacted, and cured at room temperature, thus completing the bonding and sealing of the helicopter cockpit plexiglass and the crack prevention of the cabin cover plexiglass.

10. The use of a polyurethane sealant primer according to claim 8, characterized in that The helicopter cockpit organic glass and cabin cover organic glass are YB-3 organic glass, YB-9 organic glass, YB-DM-10 organic glass, injection molded glass or laminated organic glass.

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