A high elongation at break adhesive for bonding steel and its preparation method

Abstract

This application relates to the field of building structure reinforcement adhesives, and in particular to a high elongation at break adhesive for bonding steel. The high elongation at break adhesive for bonding steel comprises component A and component B. Component A is mainly composed of the following raw materials: 5-30 parts of E-44 epoxy resin; 60-90 parts of E-51 epoxy resin; 5-10 parts of bisphenol F type epoxy resin 170; 10-20 parts of diluent; 1-3 parts of coupling agent; 5-10 parts of thixotropic agent; 10-20 parts of toughening agent; and 50-100 parts of filler A. Component B is mainly composed of the following raw materials: 40-60 parts of curing agent; 1-5 parts of thixotropic agent; 1-5 parts of curing accelerator; 1-3 parts of coupling agent; and 25-60 parts of filler B. Filler A in component A and filler B in component B are non-active silica powder without coupling agent modification. This application has good tensile toughness and an elongation at break of more than 2.0%.

Description

Technical Field

[0001] This application relates to the field of building structure reinforcement adhesives, and in particular to a high elongation at break adhesive for bonding steel and its preparation method. Background Technology

[0002] Steel-bonding adhesives, also known as steel-bonding glues, are used to bond steel plates to the surface of concrete components for reinforcement, forming a unified whole between the steel plate and concrete. This leverages the good tensile strength of the steel plate to enhance the load-bearing capacity and stiffness of the component. Epoxy-based steel-bonding adhesives possess sufficient tensile strength and hardness; however, due to their relatively high brittleness, they are mismatched with the tensile toughness of the steel plate. This can easily lead to brittle failure of the epoxy steel-bonding adhesive as the steel plate's tensile length increases. Therefore, it is necessary to maximize the tensile toughness of the epoxy steel-bonding adhesive and increase its elongation at break. Summary of the Invention

[0003] To address the aforementioned technical problems, this application provides a high elongation at break adhesive for bonding steel and its preparation method.

[0004] Firstly, the high elongation at break adhesive for bonding steel provided in this application is achieved through the following technical solution:

[0005] A high elongation at break adhesive for bonding steel, comprising component A and component B, wherein component A is mainly composed of the following raw materials in parts by weight:

[0006] 5-30 parts of E-44 epoxy resin;

[0007] 60-90 parts of E-51 epoxy resin;

[0008] 5-10 parts of bisphenol F type epoxy resin 170;

[0009] 10-20 parts diluent;

[0010] 1-3 parts of coupling agent;

[0011] 5-10 parts of thixotropic agent;

[0012] 10-20 parts toughening agent;

[0013] 50-100 parts of filler A;

[0014] Component B is mainly made from the following raw materials in parts by weight:

[0015] 40-60 parts of curing agent;

[0016] 1-5 parts of thixotropic agent;

[0017] 1-5 parts of curing accelerator;

[0018] 1-3 parts of coupling agent;

[0019] 25-60 parts of filler B;

[0020] Filler A in component A and filler B in component B are non-active silica powders without coupling agent modification.

[0021] By adopting the above technical solution, this application exhibits good tensile toughness and an elongation at break of over 2.0%. Furthermore, this application overcomes technical biases. It is generally believed that activated silica powder can make the resin and filler bond more tightly and improve compatibility, while defoamers can eliminate small bubbles during the curing process, resulting in fewer overall defects after curing. Therefore, the overall performance of the cured colloid is better, with a higher elongation at break, as illustrated in the patent "A High-Strength, High-Elongation-at-Break Epoxy Adhesive for Steel and Its Preparation Method." However, this application has found through experiments that the elongation at break using activated silica powder and defoamers is significantly lower than that using non-activated silica powder and without defoamers, and may even fail to meet national standards. This may be because activated silica powder improves the compatibility between the resin and silica powder, and defoamers reduce defects, resulting in a higher cross-linking density and stronger overall compactness after curing. Therefore, it has greater rigidity and a lower elongation at break. This is consistent with experimental data showing that using activated silica powder and defoamers results in higher compression, bending, and tensile strength but lower elongation at break.

[0022] Preferably, the toughening agent is one or a combination of two of the thermoplastic elastomer epoxy toughening agent QS-BE and the polyurethane prepolymer toughening agent PU.

[0023] By adopting the above technical solution, the elongation at break of high elongation at break adhesives for bonding steel can be improved.

[0024] Preferably, the method for preparing the polyurethane prepolymer toughening agent PU is as follows:

[0025] S1, dehydrate the polyether polyol to obtain dehydrated polyether polyol;

[0026] S2, trimethylolpropane, dibutyltin dilaurate and isophorone diisocyanate are added to dehydrated polyether polyol and reacted at 85-90°C for about 2-2.5 h under a nitrogen atmosphere. The reaction endpoint is determined by detecting the content of -NCO groups in the reactants. The reaction is stopped when the content of -NCO groups in the reactants is 3.3%.

[0027] S3, add an appropriate amount of butanone oxime to the reactants, wherein the molar ratio of oxime groups to -NCO groups in the butanone oxime is 1:(1.04-1.06), and reheat to 85-90℃ for 55-65 minutes. The reaction endpoint is determined by detecting the content of -NCO groups in the reactants. When the content of -NCO groups in the reactants is 0%, the reaction endpoint is reached, and the reaction is stopped to obtain the polyurethane prepolymer toughening agent PU.

[0028] The preparation method of this application is relatively simple and easy to industrialize. Furthermore, the prepared prepolymer polyurethane toughening agent PU can significantly improve the elongation at break of high-elongation-at-break adhesives for bonding steel.

[0029] Preferably, the polyether polyol is a polyether DL 1000D~5000D with a number average molecular weight of 1000-5000; the mass of the dehydrated polyether polyol in S2 is 298g, the mass of trimethylolpropane is 2.2g, and the amount of dibutyltin dilaurate is 2 drops; the amount of butanone oxime in S3 is 18.04g.

[0030] The key point of the high elongation at break adhesive for steel bonding prepared in this application is that: the addition of a self-prepared prepolymer polyurethane toughening agent (PU), non-active silica powder modified without coupling agent, and the absence of defoamers ensures that a high elongation at break adhesive for steel bonding with good tensile toughness and an elongation at break of more than 2.0% is obtained, meeting the requirements of the "Code for Design of Strengthening Concrete Structures" (GB50367-2013), the "Code for Acceptance of Construction Quality of Strengthening Engineering of Building Structures" (GB50550-2010), and the "Technical Specification for Safety Appraisal of Strengthening Materials for Engineering Structures" (GB50728-2011). Preferably, the polyether polyol is a polyether DL of 2000D to 4000D with a number average molecular weight of 2000-4000.

[0031] Preferably, the mass ratio of the E-44 epoxy resin, E-51 epoxy resin, and bisphenol F type epoxy resin 170 is 10:(80-85):(5-10).

[0032] By adopting the above technical solution, E-44 resin has better bonding performance than E-51 resin. At the same time, it has a lower epoxy value and a relatively lower crosslinking density, which is beneficial to increase the elongation at break. However, its flexural, tensile, and compressive strengths are lower, and its viscosity is higher. Therefore, it is more appropriate to use E-51 resin as the main component and add an appropriate proportion of E-44 resin. The purpose of adding bisphenol F170 resin is to reduce the possibility of crystallization of the colloid at low temperature. Therefore, by using a mass ratio of E-44 epoxy resin, E-51 epoxy resin, and bisphenol F type epoxy resin 170 of 10:(80-85):(5-10), this application can be guaranteed to have good tensile toughness and elongation at break, as well as good flexural, tensile, and compressive strengths and resistance to low temperature crystallization.

[0033] Preferably, the coupling agent in component A is epoxy-functionalized silane coupling agent KH-560; and the coupling agent in component B is amino-functionalized silane coupling agent KH-550.

[0034] By adopting the above technical solutions, KH-560 is suitable for epoxy resin systems, and KH-550 is suitable for curing systems in component B, which can ensure the quality of the high elongation at break adhesive for steel bonding prepared in this application.

[0035] Preferably, the diluent in component A is at least one of glycidyl ether diluents XY622 and XY692.

[0036] By adopting the above technical solution, diluent XY692 is a monofunctional diluent and XY622 is a difunctional diluent. XY692 has a better dilution effect, while XY622 can provide a higher crosslinking density and thus improve physical properties.

[0037] Preferably, the thixotropic agent in component A and the thixotropic agent in component B are both hydrophobic fumed silica R202 and M5.

[0038] By adopting the above technical solution, the quality of the high elongation at break adhesive for bonding steel prepared in this application can be guaranteed.

[0039] Preferably, the curing accelerator in component B is K54; the curing agent in component B is an alicyclic amine modified curing agent.

[0040] By adopting the above technical solution, the quality of the high elongation at break adhesive for bonding steel prepared in this application can be guaranteed.

[0041] Secondly, the method for preparing a high elongation at break adhesive for bonding steel provided in this application is achieved through the following technical solution:

[0042] A method for preparing a high elongation at break adhesive for bonding steel includes the following steps:

[0043] Preparation method of component A: Take 5-30 parts of E-44 epoxy resin, 60-90 parts of E-51 epoxy resin, 5-10 parts of 170 bisphenol F type epoxy resin, 10-20 parts of diluent, 1-3 parts of coupling agent, and 10-20 parts of toughening agent. Mix them evenly, then add 50-100 parts of filler, mix evenly again, then add 5-10 parts of thixotropic agent, and mix evenly again to obtain component A. Preparation method of component B: Take 40-60 parts of curing agent, 1-5 parts of curing accelerator, and 1-3 parts of coupling agent. Mix them evenly, then add 30-60 parts of filler, mix evenly again, then add 1-5 parts of thixotropic agent, and mix evenly again to obtain component B.

[0044] The preparation method of this application is relatively simple and easy to industrialize.

[0045] In summary, this application has the following advantages:

[0046] 1. This application has good tensile toughness and an elongation at break of more than 2.0%.

[0047] 2. The preparation method of this application is relatively simple and easy to industrialize.

[0048] 3. This application overcomes technical bias. It is generally believed that activated silica powder can make the resin and filler bond more tightly and have better compatibility, while defoamers can eliminate small bubbles during the curing process, resulting in fewer overall defects after curing. Therefore, the overall performance of the cured colloid is better, and the elongation at break is greater, as illustrated by the patent "A High-Strength, High-Elongation-at-Break Epoxy Adhesive for Steel and Its Preparation Method". However, this application has found through experiments that the elongation at break using activated silica powder and defoamers is much lower than that using non-activated silica powder and without defoamers, and may even fail to meet national standards. This may be because activated silica powder improves the compatibility between the resin and silica powder, and defoamers reduce defects, resulting in a higher cross-linking density and stronger overall compactness of the cured colloid. Therefore, it has greater rigidity and lower elongation at break. This is consistent with the experimental data showing that the compression, bending, and tensile strengths of the activated silica powder and defoamers are higher, but the elongation at break is lower.

[0049] 4. The high elongation at break adhesive for steel bonding prepared by compounding E-44 epoxy resin, E-51 epoxy resin and bisphenol F type epoxy resin 170 has good tensile toughness and elongation at break, as well as good bending, tensile, compressive strength and low temperature crystallization resistance.

[0050] 5. The key point of the high elongation at break adhesive for steel bonding prepared in this application is that: the addition of self-prepared prepolymer polyurethane toughening agent PU, non-active silica micro powder modified without coupling agent, and no defoamer can ensure that a high elongation at break adhesive for steel bonding with good tensile toughness and an elongation at break of more than 2.0% is obtained, which meets the requirements of the "Code for Design of Strengthening Concrete Structures" (GB50367-2013), the "Code for Acceptance of Construction Quality of Strengthening Engineering of Building Structures" (GB50550-2010), and the "Technical Specification for Safety Appraisal of Strengthening Materials for Engineering Structures" (GB50728-2011). Detailed Implementation

[0051] The present application will be further described in detail below with reference to comparative examples and embodiments.

[0052] Preparation Example

[0053] Preparation method of polyurethane prepolymer toughening agent PU:

[0054] S1, dehydrate the polyether polyol, the polyether polyol is polyether DL-3000D with a number average molecular weight of 3000, the dehydration temperature is 110℃, the dehydration time is 120min, and the dehydrated polyether polyol is obtained.

[0055] S2, 2.2g of trimethylolpropane and 2 drops of dibutyltin dilaurate and 68.35g of isophorone diisocyanate were added to 298g of dehydrated polyether polyol, and the mixture was reacted at 85-90℃ for about 2 hours under a nitrogen atmosphere. The reaction endpoint was determined by detecting the content of -NCO groups in the reactants. The reaction was stopped when the content of -NCO groups in the reactants was 3.3%.

[0056] S3, add 18.04g of methyl ethyl ketone oxime to the reactants, and heat again to 85-90℃ for 60min. The reaction endpoint is determined by detecting the content of -NCO groups in the reactants. When the content of -NCO groups in the reactants is 0%, the reaction endpoint is reached, and the reaction is stopped to obtain polyurethane prepolymer toughening agent PU.

[0057] Example

[0058] Example 1

[0059] This application discloses a high elongation at break adhesive for bonding steel, comprising component A and component B.

[0060] Component A is mainly made from the following raw materials in parts by weight:

[0061] 10 parts of E-44 epoxy resin;

[0062] 85 parts of E-51 epoxy resin;

[0063] 5 parts of bisphenol F type epoxy resin 170;

[0064] 5 parts of diluent XY622;

[0065] 5 parts of diluent XY692;

[0066] One part of coupling agent KH-560;

[0067] 5 parts of thixotropic agent M5;

[0068] 10 parts of toughening agent QS-BE;

[0069] 50 parts of non-reactive silica micropowder without coupling agent modification.

[0070] Component B is mainly made from the following raw materials in parts by weight:

[0071] 55 parts of alicyclic amine modified curing agent J002r;

[0072] Two parts of thixotropic agent M5;

[0073] 3 parts of curing accelerator K54;

[0074] One part of coupling agent KH-550;

[0075] 27 parts of non-reactive silica micropowder modified without coupling agent.

[0076] A method for preparing a high elongation at break adhesive for bonding steel: Component A preparation method: Take 10 parts of E-44 epoxy resin, 85 parts of E-51 epoxy resin, 5 parts of 170 bisphenol F type epoxy resin, 5 parts of diluent XY622, 25 parts of diluent XY69, 1 part of coupling agent KH-560, and 10 parts of toughening agent QS-BE. After mixing evenly, add 50 parts of filler-non-coupling agent modified inactive silica powder, mix evenly again, add 5 parts of thixotropic agent M5, mix evenly again, and obtain component A; Component B preparation method: Take 55 parts of alicyclic amine modified curing agent, 3 parts of curing accelerator K54, and 1 part of coupling agent KH-550. After mixing evenly, add 27 parts of filler-non-coupling agent modified inactive silica powder, mix evenly again, add 2 parts of thixotropic agent M5, mix evenly again, and obtain component B.

[0077] When using, mix the accurately measured A and B components evenly, and then cure at room temperature to form a high elongation at break adhesive for bonding steel.

[0078] Example 2

[0079] The difference between Example 2 and Example 1 is:

[0080] Component A is mainly composed of the following raw materials in parts by weight: 30 parts of E-44 epoxy resin; 60 parts of E-51 epoxy resin; 10 parts of bisphenol F type epoxy resin 170; 10 parts of diluent XY692; 1 part of coupling agent KH-560; 5 parts of thixotropic agent M5; 10 parts of toughening agent QS-BE; and 50 parts of non-active silica powder without coupling agent modification.

[0081] Example 3

[0082] The difference between Example 3 and Example 1 is:

[0083] Component A is mainly made from the following raw materials in parts by weight:

[0084] 10 parts of E-44 epoxy resin;

[0085] 85 parts of E-51 epoxy resin;

[0086] 5 parts of bisphenol F type epoxy resin 170;

[0087] 10 parts of diluent XY622;

[0088] One part of coupling agent KH-560;

[0089] 3 parts of thixotropic agent M5;

[0090] 15 parts of the polyurethane prepolymer toughening agent PU in Preparation Example 1;

[0091] 50 parts of non-reactive silica micropowder without coupling agent modification.

[0092] Component B is mainly made from the following raw materials in parts by weight:

[0093] 55 parts of alicyclic amine modified curing agent;

[0094] Two parts of thixotropic agent M5;

[0095] 3 parts of curing accelerator K54;

[0096] One part of coupling agent KH-550;

[0097] 52 parts of non-reactive silica micropowder modified without coupling agent.

[0098] Furthermore, the difference between Example 3 and Example 1 is that, when using it, after accurately measuring A and B and mixing them evenly, it is placed at a temperature of 160-180℃ to cure, thus forming a high elongation at break adhesive for bonding steel.

[0099] Example 4

[0100] The difference between Example 4 and Example 1 is:

[0101] Component A is mainly made from the following raw materials in parts by weight:

[0102] 10 parts of E-44 epoxy resin;

[0103] 85 parts of E-51 epoxy resin;

[0104] 5 parts of bisphenol F type epoxy resin 170;

[0105] 10 parts of diluent XY622;

[0106] One part of coupling agent KH-560;

[0107] 3 parts of thixotropic agent M5;

[0108] 15 parts of the polyurethane prepolymer toughening agent PU in Preparation Example 1;

[0109] 100 parts of non-reactive silica micropowder without coupling agent modification;

[0110] Component B is mainly made from the following raw materials in parts by weight:

[0111] 55 parts of alicyclic amine modified curing agent;

[0112] Two parts of thixotropic agent M5;

[0113] 3 parts of curing accelerator K54;

[0114] One part of coupling agent KH-550;

[0115] 77 parts of non-reactive silica micropowder modified without coupling agent.

[0116] Furthermore, the difference between Example 4 and Example 1 is that, when using it, after accurately measuring A and B and mixing them evenly, it is placed at a temperature of 160-180℃ to cure, thus forming a high elongation at break adhesive for bonding steel.

[0117] Comparative Example

[0118] Comparative Example 1

[0119] A method for preparing a structural adhesive for buildings includes the following steps:

[0120] Step 1: Referring to the article "Synthesis and Process Research of Epoxy-Polyether End-Group Modified Silicone Oil" in the April 2017 issue of "New Chemical Materials", an epoxy-terminated block polyether silicone oil T01 was prepared. In this application, during the preparation of the epoxy-terminated block polyether silicone oil T01, the materials were fed according to the molecular design n=1 and m=2. The average molecular weight of the epoxy-terminated block polyether silicone oil T01 is approximately 492.

[0121] Step 2: Preparation of Component A: First, weigh 75 parts of the liquid component bisphenol A epoxy resin CYD128, 10 parts of the active epoxy diluent XY622, 15 parts of the terminal epoxy block polyether silicone oil T01, and 1 part of the coupling agent KH560 according to the weight ratio, and add them to the stirrer in sequence and stir evenly. Then, weigh 58 parts of the solid component active silica powder (400 mesh) and 2 parts of the thixotropic agent A200 according to the weight ratio, and add them to the liquid component mixture in sequence. Stir under vacuum conditions of -0.02MPa to -0.095MPa for 1 hour, discharge, and package to obtain the finished product of Component A.

[0122] Step 3, Preparation of Component B: First, weigh 30 parts of liquid component phenolic amine curing agent 701 and 70 parts of aromatic amine curing agent 113 according to the weight ratio, and add them to the stirrer in sequence, stirring evenly. Then, weigh 50 parts of solid component active silica powder (400 mesh) and 2 parts of thixotropic agent A200 according to the weight ratio, and add them to the liquid component mixing system in sequence. Stir under vacuum conditions of -0.02MPa to -0.095MPa for 1 hour, discharge, and package to obtain the finished product of Component B. Mix Component A and Component B evenly at a weight ratio of 2:1 to obtain the structural adhesive for building construction. The filler content of the structural adhesive for building construction is 35%.

[0123] Aromatic amine curing agent 113 has a slower curing speed and higher toxicity compared to alicyclic amine modified curing agents at room temperature. Therefore, aromatic amine curing agents are not selected in the technical solution of this application.

[0124] Comparative Example 2

[0125] The difference between Comparative Example 2 and Comparative Example 1 is that the active silica powder was replaced with non-active silica powder modified without coupling agent.

[0126] Comparative Example 3

[0127] The difference between Comparative Example 3 and Example 1 is that the non-active silica powder without coupling agent modification is replaced with active silica powder.

[0128] Comparative Example 4

[0129] The difference between Comparative Example 4 and Example 1 is:

[0130] Component B is mainly composed of the following raw materials in parts by weight: 55 parts of alicyclic amine modified curing agent; 2 parts of thixotropic agent M5; 3 parts of curing accelerator K54; 1 part of coupling agent KH-550; 27 parts of non-active silica powder without coupling agent modification; and 1 part of defoamer.

[0131] Comparative Example 5

[0132] The difference between Comparative Example 5 and Example 4 is as follows:

[0133] Component A is mainly made from the following raw materials in parts by weight:

[0134] 10 parts of E-44 epoxy resin;

[0135] 85 parts of E-51 epoxy resin;

[0136] 5 parts of bisphenol F type epoxy resin 170;

[0137] 10 parts of diluent XY622;

[0138] One part of coupling agent KH-560;

[0139] 3 parts of thixotropic agent M5;

[0140] 15 parts of the polyurethane prepolymer toughening agent PU in Preparation Example 1;

[0141] 100 parts of non-reactive silica micropowder modified without coupling agent.

[0142] Performance testing

[0143] Detection methods / test methods

[0144] 1. Tensile strength, elongation at break, flexural strength, and compressive strength shall be tested in accordance with GB / T 2567-2021.

[0145] 2. Steel-to-steel tensile shear strength shall be tested in accordance with GB / T 7124-2008.

[0146] 3. The tensile bond strength of steel-C45 concrete was tested according to Appendix G of GB 50728-2011.

[0147] Data Analysis

[0148] Table 1 shows the detection parameters for Examples 1-4 and Comparative Examples 1-5.

[0149]

[0150] Based on Examples 1, 2, and 3, and in conjunction with Table 1, it can be seen that using silicon micropowder surface-treated without silane coupling agent as a filler can significantly improve the elongation at break, while other mechanical strengths show little difference.

[0151] Combining Examples 1 and 2 with Table 1, it can be seen that adjusting the proportion of different types of resins and increasing the proportion of E-44 and bisphenol F170 can slightly improve the elongation at break, but the tensile strength, flexural strength and compressive strength all decrease significantly. This may be due to the low epoxy value of E-44 and the low overall crosslinking degree after curing.

[0152] Based on Examples 1, 3, and Comparative Example 1, and in conjunction with Table 1, it can be seen that adding different toughening agents will have different effects. Among them, the self-made polyurethane prepolymer PU toughening agent has a better effect on improving the elongation at break.

[0153] Combining Examples 3 and 4, and referring to Table 1, it can be seen that increasing the filler ratio significantly reduces the elongation at break, but significantly improves the flexural strength and compressive strength. This is likely because increasing the filler ratio increases the hardness of the colloid after curing, but affects its flexibility.

[0154] Based on Example 1 and Comparative Example 4, and in conjunction with Table 1, it can be seen that the addition of defoamer resulted in a certain decrease in elongation at break, but a certain increase in flexural strength and compressive strength. This may be because the defoamer reduces foaming and defects in the colloid after curing, and increases density, thus increasing rigidity but weakening flexibility.

[0155] Based on Example 4 and Comparative Example 5, and referring to Table 1, it can be seen that when the mass ratio of A:B = 2:1 is used for mixing and curing, the resin and curing agent in A and B are the optimal curing ratio calculated according to the proportion. If only the filler is added to component A but not to component B, and the mixture is still mixed at 2:1, the resin and curing agent ratio will not be optimal, which means that the performance after curing will not be optimal.

[0156] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A high elongation at break adhesive for bonding steel, characterized in that: It includes component A and component B, wherein component A is mainly made from the following raw materials in parts by weight: 5-30 parts of E-44 epoxy resin; 60-90 parts of E-51 epoxy resin; 5-10 parts of bisphenol F type epoxy resin 170; 10-20 parts diluent; 1-3 parts of coupling agent; 5-10 parts of thixotropic agent; 10-20 parts toughening agent; 50-100 parts of filler A; Component B is mainly made from the following raw materials in parts by weight: 40-60 parts of curing agent; 1-5 parts of thixotropic agent; 1-5 parts of curing accelerator; 1-3 parts of coupling agent; 25-60 parts of filler B; Filler A in component A and filler B in component B are non-active silica powder without coupling agent modification; The toughening agent is a polyurethane prepolymer toughening agent PU; The preparation method of the polyurethane prepolymer toughening agent PU: S1, dehydrate the polyether polyol to obtain dehydrated polyether polyol; S2, add trimethylolpropane, dibutyltin dilaurate and isophorone diisocyanate to dehydrated polyether polyol, and react at 85~90℃ for 2-2.5h under nitrogen atmosphere. The reaction endpoint is determined by detecting the content of -NCO groups in the reactants. The reaction is stopped when the content of -NCO groups in the reactants is 3.3%. S3, add an appropriate amount of butanone oxime to the reactants, wherein the molar ratio of oxime groups to -NCO groups in the butanone oxime is 1:(1.04-1.06), and reheat to 85~90℃ for 55-65 min. The reaction endpoint is determined by detecting the content of -NCO groups in the reactants. When the content of -NCO groups in the reactants is 0%, the reaction endpoint is reached, and the reaction is stopped to obtain the polyurethane prepolymer toughening agent PU.

2. The high elongation at break adhesive for bonding steel according to claim 1, characterized in that: The polyether polyol is a polyether DL of 1000D~5000 with a number average molecular weight of 1000-5000; the mass of the dehydrated polyether polyol in S2 is 298 g, the mass of trimethylolpropane is 2.2 g, and the amount of dibutyltin dilaurate is 2 drops; the amount of butanone oxime in S3 is 18.04 g.

3. The high elongation at break adhesive for bonding steel according to claim 1, characterized in that: The mass ratio of E-44 epoxy resin, E-51 epoxy resin, and bisphenol F type epoxy resin 170 is 10:(80-85):(5-10).

4. The high elongation at break adhesive for bonding steel according to claim 1, characterized in that: The coupling agent in component A is epoxy-functionalized silane coupling agent KH-560; the coupling agent in component B is amino-functionalized silane coupling agent KH-550.

5. The high elongation at break adhesive for bonding steel according to claim 1, characterized in that: The diluent in component A is at least one of glycidyl ether diluents XY622 and XY692.

6. The high elongation at break adhesive for bonding steel according to claim 1, characterized in that: The thixotropic agents in component A and component B are both hydrophobic fumed silica R202 and M5.

7. The high elongation at break adhesive for bonding steel according to claim 1, characterized in that: The curing accelerator in component B is K54; the curing agent in component B is an alicyclic amine modified curing agent.

8. A method for preparing a high elongation at break adhesive for bonding steel according to any one of claims 1-7, characterized in that: Preparation method of component A: Take 5-30 parts of E-44 epoxy resin, 60-90 parts of E-51 epoxy resin, 5-10 parts of 170 bisphenol F type epoxy resin, 10-20 parts of diluent, 1-3 parts of coupling agent, and 10-20 parts of toughening agent. Mix them evenly, then add 50-100 parts of filler. Mix evenly again, then add 5-10 parts of thixotropic agent. Mix evenly again to obtain component A. Preparation method of component B: Take 40-60 parts of curing agent, 1-5 parts of curing accelerator, and 1-3 parts of coupling agent. Mix them evenly, then add 30-60 parts of filler. Mix evenly again, then add 1-5 parts of thixotropic agent. Mix evenly again to obtain component B.

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