Hydroxyl bonding aid, its preparation method and sealant

Abstract

The present invention provides a hydroxyl bonding aid and a preparation method thereof. The bonding aid is mainly prepared by first polymerizing HDI biuret with a monoamino silane coupling agent and a diamino silane coupling agent in sequence, and then reacting with trimethylolpropane and a small molecule diol to obtain a macromolecule having 1 to 4 hydroxyl groups, urethane groups, urea groups and siloxane-carbon bonds. The present invention also provides a polyurethane sealant using the above-mentioned hydroxyl bonding aid. The hydroxyl bonding aid not only participates in the chain extension reaction of polyurethane, and the polyhydroxy molecules therein can play a crosslinking role, improving the bulk strength of the sealant; but also because the bonding aid contains a large number of urethane groups, siloxane structures and a large number of urea groups, thereby improving the bonding strength and low-temperature initial adhesion performance of the polyurethane sealant, shortening the construction period in a low-temperature environment, and even improving the construction quality. For the above-mentioned polyurethane sealant, on the premise of ensuring its bonding performance, the viscosities of each component are relatively small and the workability is good.

Description

Technical Field

[0001] The present invention relates to the technical field of adhesion aids, and specifically relates to a hydroxyl adhesion aid, a preparation method thereof, and a sealant. Background Art

[0002] In existing adhesives, in addition to the adhesive material, there are also adhesion aids used to enhance the adhesion strength and other properties of the adhesive material. For example, Chinese Patent Application CN113896852A discloses an adhesion aid for foam plastics, a preparation method thereof, and an application. The adhesion aid is prepared by reacting a small molecule triol-modified isocyanate with a silane coupling agent; the adhesion aid is directly added to the adhesive material component and then mixed with the curing component during the construction process, making the adhesion performance of the foam plastics more stable.

[0003] Two-component raw material system adhesives are often used in production due to their certain advantageous mechanical properties or service properties. When in use, the two-component raw materials need to be mixed in proportion to achieve their adhesion function. For example, polyurethane sealants. When using two-component adhesives, it is usually necessary to use a glue gun to simultaneously extrude and mix the two components. If the viscosity of the components is relatively high, the user needs to apply a greater force to extrude the components, especially when constructing in winter or at a lower temperature environment, which increases the construction difficulty for the user; moreover, when the component viscosity is relatively high, it is not conducive to the uniform mixing of the two components.

[0004] In addition, during the construction process of adhesives, their curing speed has a great relationship with the ambient temperature. During the construction process in winter or at a lower temperature environment, adhesives in the polyurethane system often exhibit poor initial adhesion performance and low initial adhesion strength, especially when using polyurethane sealants to bond building glass, which is more obvious, resulting in a long construction period and even poor construction quality. Summary of the Invention

[0005] In view of this, it is necessary for the present invention to provide a hydroxyl adhesion aid, a preparation method thereof, and a sealant.

[0006] Specifically, the technical solution provided by the present invention is: A hydroxyl adhesion aid, which is mainly a macromolecular adhesion aid having 1 to 4 hydroxyl groups, urethane groups, urea groups, and silicon-oxygen-carbon bonds prepared by first polymerizing HDI biuret with a monoamino silane coupling agent and a diamino silane coupling agent in sequence, and then reacting with trimethylolpropane and a small molecule diol. Among them, calculated by mole parts: 100 parts of HDI biuret, 20 to 50 parts of the diamino silane coupling agent, 100 to 200 parts of the monoamino silane coupling agent, 20 to 150 parts of the small molecule diol, and 20 to 150 parts of the small molecule triol.

[0007] Among them, "HDI biuret" in this text refers to 1,6 - hexamethylene diisocyanate biuret. "Small - molecule diol" in this text refers to diols with a molecular weight below 155, and "small - molecule triol" refers to triols with a molecular weight below 150.

[0008] Based on the above, \(n(\text{HDI biuret})\times3=n(\text{bis - amino silane coupling agent})\times2 + n(\text{mono - amino silane coupling agent})+n(\text{small - molecule diol})+n(\text{small - molecule triol})\), where \(n(\text{HDI biuret})\), \(n(\text{bis - amino silane coupling agent})\), \(n(\text{mono - amino silane coupling agent})\), \(n(\text{small - molecule triol})\) and \(n(\text{small - molecule diol})\) respectively represent the molar fractions of the corresponding raw materials; since 1 molecule of HDI biuret contains 3 isocyanate groups, the dosages of the five are limited in this way, so that the isocyanate groups in HDI biuret are completely reacted and blocked, and the prepared product does not contain isocyanate groups.

[0009] Based on the above, the bis - amino silane coupling agent is N - aminoethyl - γ - aminopropyltrimethoxysilane or N - aminoethyl - γ - aminopropyltriethoxysilane.

[0010] Based on the above, the mono - amino silane coupling agent is bis(3 - trimethoxysilylpropyl)amine, 3 - aminopropyltrimethoxysilane, 3 - aminopropyltriethoxysilane or 3-(phenylamino)propyltrimethoxysilane; preferably bis(3 - trimethoxysilylpropyl)amine.

[0011] Based on the above, the small - molecule diol is ethylene glycol, 1,3 - propanediol, diethylene glycol or triethylene glycol.

[0012] Based on the above, the small - molecule triol is trimethylolpropane or glycerol.

[0013] The present invention provides a preparation method of the above - mentioned hydroxyl bonding aid, including:

[0014] Under inert gas conditions, first, HDI biuret is uniformly mixed with a first solvent to form a first mixture, then the mono - amino silane coupling agent is gradually added dropwise to the first mixture under stirring conditions at 20°C - 25°C until the addition is complete, then continue to react for 30 - 60 min, after that, the bis - amino silane coupling agent is added dropwise, and continue to react for 30 - 60 min after the addition, and then the temperature is raised to 50°C - 70°C and continue to react for 30 - 60 min to prepare a first prepolymer;

[0015] First, uniformly mix the small molecule diol, small molecule triol and the second solvent to form a second mixture. Then, under the conditions of 65°C to 75°C, a rotation speed of 80 to 120 r / min and under the protection of inert gas, add the first prepolymer to the second mixture until the reaction is complete and continue to react for 60 to 120 min to obtain the hydroxyl bonding aid.

[0016] The solid content of the hydroxyl bonding aid is 34% to 36%; during its preparation, when calculating the solid content in the formula, if the solid content is below 34%, evacuate the solvent under vacuum and adjust it to 34% to 36%; if the solid content is above 36%, add the second solvent to adjust the solid content to 34% to 36%.

[0017] Based on the above preparation method, after adding the first prepolymer to the second mixture until the reaction is complete and continuing to react for 60 to 120 min, then add the first catalyst and react for 60 to 90 min, and adjust the solid content to 34% to 36% to obtain the hydroxyl bonding aid. Among them, the addition amount of the first catalyst is 0.01% to 0.06% of the total mass of HDI biuret, monoamino silane coupling agent, diamino silane coupling agent, small molecule triol and small molecule diol, and the first catalyst is dibutyltin dilaurate or dibutyltin dichloride.

[0018] Based on the above, the ratio of the total mass of HDI biuret, the diamino silane coupling agent and the monoamino silane coupling agent to the first solvent is (50 to 100):100.

[0019] Based on the above, the mass ratio of the total mass of the small molecule diol and the small molecule triol to the second solvent is (20 to 50):100.

[0020] The first solvent and the second solvent are respectively butyl acetate, methyl ethyl ketone, toluene or xylene.

[0021] The present invention also provides a polyurethane sealant, the raw materials of which include the above-mentioned hydroxyl bonding aid. Preferably, the polyurethane sealant is a low-density polyurethane sealant.

[0022] Specifically, the raw materials of the polyether component of the polyurethane sealant include the above-mentioned hydroxyl bonding aid. That is, the polyurethane sealant is a two-component raw material sealant, and the polyether component mainly plays a curing role and can also be called a curing component.

[0023] Among them, the polyurethane sealant includes the following raw materials in parts by mass:

[0024] Component A: PAPI (polymethylene polyphenyl isocyanate)

[0025] Component B, namely the polyether component, includes: 100 parts of polyether polyol, 0.5 - 5 parts of the above-mentioned hydroxyl bonding aid, 5 - 30 parts of glass microspheres, 2 - 5 parts of fumed silica, and 0.05 - 0.2 parts of the second catalyst. And the polyether polyol is composed of 3 - 9 parts of small molecule polyether polyol and 91 - 97 parts of polyether polyol 330N. And Component B is mainly obtained by the following method: adding the polyether polyol into a dehydration kettle, dehydrating for 2 - 3 h under the conditions of less than -0.095 MPa and 80°C - 100°C, then cooling to 30°C - 40°C and adding the hydroxyl bonding aid into it and continuing to stir for 0.5 - 1 h under vacuum conditions to remove the solvent therein; adding the glass microspheres, fumed silica, and the second catalyst after dehydration treatment into it and stirring for 10 - 20 min.

[0026] Among them, the small molecule polyether polyol is one or a combination of more than one of YD303, YD304, and YD305, and the second catalyst is dibutyltin dilaurate or dibutyltin dichloride. The glass microspheres are hollow microspheres with a true density of 0.15 g / cm 3 ~0.70 g / cm 3 , and the particle size D90 is between 15 microns and 110 microns. Preferably, the glass microspheres are produced by Zhengzhou Shenglaite Hollow Microsphere New Materials Co., Ltd.

[0027] Mixing the Component A and Component B in the above-mentioned polyurethane sealant evenly according to the molar ratio of the isocyanate group in Component A to the hydroxyl group in Component B of (0.98 - 1.05):1 can achieve curing.

[0028] If the above-mentioned hydroxyl bonding aid is added to Component A, the adhesive component of the polyurethane adhesive, the hydroxyl groups contained in it will react with the isocyanate groups in Component A, which will not only cause the viscosity of Component A to increase, increase the extrusion force during the construction process of Component A, and increase the construction difficulty; but also the storage performance of Component A becomes worse. Adding the above-mentioned hydroxyl bonding aid to Component B, the polyether component, has little effect on the viscosity of Component B. Therefore, the above-mentioned hydroxyl bonding aid should be added to Component B, the curing component of the adhesive, to avoid increasing the viscosity of the component and is beneficial to the construction application of the adhesive.

[0029] The above-mentioned hydroxyl adhesion promoter provided by the present invention is mainly prepared by reacting HDI biuret, diamino silane coupling agent, monoamino silane coupling agent, small molecule diol and small molecule triol. First, the monoamino silane coupling agent is added to react with part of the isocyanate groups in HDI biuret, and then the diamino silane coupling agent is added to better control the reaction and reduce the situation of some overly large molecular chains. Finally, the diol and small molecule triol are added mainly to cap the isocyanate groups, so that the adhesion promoter does not contain isocyanate groups and contains 1-4 hydroxyl groups, a large number of urethane groups, a large number of urea groups and a large number of silicon-oxygen-carbon bonds. This macromolecular adhesion promoter not only helps to improve the bonding strength of the polyurethane adhesive, but also the polyhydroxy molecules (molecules containing more than two hydroxyl groups) in it can play a cross-linking role, which is beneficial to improving the strength of the polyurethane colloid itself in the future. At the same time, since the isocyanate groups are completely capped, its usage method has also changed.

[0030] The above-mentioned macromolecular adhesion promoter with 1-4 hydroxyl groups is used in the polyurethane sealant provided by the present invention. On the one hand, it participates in the polyurethane chain extension reaction and reacts with a relatively large bonding group into the polyurethane chain segment. And because it contains polyhydroxy molecules (molecules containing more than two hydroxyl groups), it can play a cross-linking role, thereby improving the bulk strength of the final polyurethane sealant; on the other hand, because the adhesion promoter contains a large number of urethane groups, siloxane structures and a large number of urea groups, the bonding strength of the polyurethane sealant to substrates such as glass, stainless steel, and anodized aluminum and the low-temperature initial adhesion performance are improved, the construction period in a low-temperature environment is shortened, and even the construction quality is improved. In addition, for the polyurethane sealant using the above-mentioned hydroxyl adhesion promoter, on the premise of ensuring its bonding performance, the viscosity of each component is relatively small and the workability is good. Specific Embodiments

[0031] The technical solutions of the present invention will be further described in detail below through specific embodiments.

[0032] Examples 1-5

[0033] Examples 1-5 of the present invention and Comparative Example 1 each provide a hydroxyl adhesion promoter, the raw materials of which are composed of the raw materials shown in Table 1 below and dibutyltin dichloride, and the addition amount of dibutyltin dichloride is 0.03% of the total mass of the raw materials shown in Table 1.

[0034] Table 1 Molar ratio table of raw materials for hydroxyl adhesion promoter

[0035]

[0036] Among them, the hydroxyl adhesion promoters provided in Examples 1-5 are mainly prepared by the following steps:

[0037] Step 1: Mix HDI biuret and the first solvent butyl acetate evenly under nitrogen protection to form a first mixture. Then, gradually add bis(3-trimethoxysilylpropyl)amine dropwise to the first mixture under stirring at 25°C. After the addition, continue the reaction for 45 min. Subsequently, continue to gradually add the diamino silane coupling agent to the above substance. After the addition, continue the reaction for 45 min. Then, raise the temperature to 60°C and continue the reaction for 45 min to ensure that bis(3-trimethoxysilylpropyl)amine completely reacts with HDI biuret, and prepare the first prepolymer. The mass ratio of the butyl acetate solvent to the total mass of HDI biuret, N-aminoethyl-γ-aminopropyltrimethoxysilane, and bis(3-trimethoxysilylpropyl)amine is 100:75;

[0038] Step 2: Mix ethylene glycol and trimethylolpropane evenly and dehydrate them at a temperature below -0.095 MPa and 75°C for 90 min. Then, cool down to normal temperature and pressure and add the second solvent butyl acetate to form a second mixture. Slowly add the first prepolymer to the second mixture under the conditions of 70°C, a rotation speed of 100 r / min, and nitrogen protection. After the addition, continue the reaction for 90 min. Then, add dibutyltin dichloride and continue the reaction for 45 min to ensure that the remaining isocyanate groups in HDI biuret completely react with the hydroxyl groups in ethylene glycol and trimethylolpropane. Then, adjust the solid content to 35% to obtain the above-mentioned hydroxyl bonding aid. The weight ratio of the butyl acetate solvent to the total mass of ethylene glycol and trimethylolpropane is 100:35.

[0039] The hydroxyl bonding aid provided in Comparative Example 1 is mainly prepared by the following steps: 1) First, dehydrate trimethylolpropane, and then add HDI biuret and 25% of the total weight of the bonding aid of butyl acetate thereto under an inert atmosphere at 75°C, and stir and react at 300 r / min until the NCO value is stable and unchanged. At this time, add butyl acetate to dilute the product, and the added amount of butyl acetate is 25% of the total weight of the bonding aid; 2) Under an environment below 20°C and a stirring speed of 400 r / min, dropwise add N-aminoethyl-γ-aminopropyltrimethoxysilane to the product diluted in step 1). The dropping time is 45 min. After the addition, continue the reaction for 1.5 h; 3) Continue to add bis(3-trimethoxysilylpropyl)amine to the product in step 2) in batches, keeping the temperature and rotation speed unchanged. After the addition, stir and react for 45 min. At this time, reduce the rotation speed to 300 r / min, raise the temperature to 65°C, and continue to stir for 1.5 h. Then, adjust the solid content to 35% to obtain the said hydroxyl bonding aid.

[0040] Examples 1 to 5 and Comparative Example 1 each also provide a polyurethane sealant, and its raw materials are as follows:

[0041] Component A: PAPI

[0042] Component B: It includes 8 parts of polyether polyol YD305, 92 parts of polyether polyol 330n, 4.5 parts of the adhesion promoter provided in Examples 1 - 5, 18 parts of glass microbeads HL42, 3 parts of fumed silica, and 0.12 part of dibutyltin dilaurate by mass; the treatment process of this Component B is as follows: Add polyether polyol YD305 and 330n to a dehydration kettle, and dehydrate at a temperature below -0.095 MPa and 90 °C for 2.5 h. Then cool down to 35 °C and add the adhesion promoters provided in Examples 1 - 5 respectively, and continue to stir under vacuum conditions for 45 min to remove the solvent. Then add the dehydrated glass microbeads, fumed silica, and dibutyltin dilaurate, and stir for 15 min to obtain Component B.

[0043] The A and B components in the polyurethane adhesive can be cured by uniformly mixing them in a mass ratio of 100:874.

[0044] Comparative Examples 2 - 6 each provide a polyurethane sealant, in which the adhesion promoters provided in Examples 1 - 5 are respectively added to the A component of the polyurethane sealant provided in the above Examples 1 - 5, and not added to the B component, and other components and processes remain unchanged.

[0045] Examples 6 - 8

[0046] The raw materials of the hydroxyl adhesion promoter provided in Examples 6 - 8 of the present invention consist of those shown in Table 2 and the catalyst dibutyltin dilaurate, and the addition amount of dibutyltin dilaurate is 0.03% of the total mass of the raw materials shown in Table 2.

[0047] Table 2 Molar ratio table of raw materials of hydroxyl adhesion promoter

[0048]

[0049] The preparation method of the hydroxyl adhesion promoter provided in Examples 6 - 8 is basically the same as that of the hydroxyl adhesion promoter provided in Examples 1 - 5, and the main differences are as follows:

[0050] In Example 6, the first solvent used is xylene, and its ratio to the total mass of HDI biuret, N - aminoethyl - γ - aminopropyltriethoxysilane, and 3 - aminopropyltrimethoxysilane is 100:80; the second solvent used is xylene, and its mass ratio to the total mass of triethylene glycol and glycerol is 100:30.

[0051] In Example 7, the first solvent used is toluene, and its ratio to the total mass of HDI biuret, N - aminoethyl - γ - aminopropyltriethoxysilane, and 3 - aminopropyltriethoxysilane is 100:100; the second solvent used is toluene, and its ratio to the total mass of diethylene glycol and glycerol is 100:20.

[0052] The first solvent used in Example 8 was methyl ethyl ketone, and its ratio to the total mass of HDI biuret, N-(2-aminoethyl)-3-aminopropyltriethoxysilane, and 3-(phenylamino)propyltrimethoxysilane was 100:75; the second solvent used was methyl ethyl ketone, and its ratio to the total mass of 1,3-propanediol and glycerol was 100:50.

[0053] Examples 6 to 8 each further provided a polyurethane sealant, the raw materials of which included:

[0054] Component A: PAPI

[0055] Component B: By mass, 7 parts of polyether polyol YD304, 93 parts of polyether polyol 330n, 4 parts of the above-mentioned hydroxyl bonding aid provided in Examples 6 to 8, 17 parts of glass microspheres HS38, 4 parts of fumed silica, and 0.15 parts of dibutyltin dilaurate. The treatment process of Component B was basically the same as the corresponding treatment processes provided in Examples 1 to 5.

[0056] The polyurethane sealant could be cured by uniformly mixing Component A and Component B in a mass ratio of 100:838.

[0057] Performance testing

[0058] Density test method: The polyurethane sealants provided in Examples 1 to 8 and Comparative Examples 1 to 6 were cured for 5 days under standard conditions of 23°C and 50% RH, and then uniformly mixed according to their respective mixing ratios of Component A and Component B, and scraped into thin slices of 2 mm × 40 mm × 40 mm. After curing for 7 days under standard conditions of 23°C and 50% RH, their densities were measured by the drainage method respectively. The results are shown in Table 3.

[0059] Viscosity test method: The polyurethane sealants provided in Examples 1 to 8 and Comparative Examples 1 to 6 were stored in a sealed manner, cured for 24 hours under standard conditions of 23°C and 50% RH respectively, and then the viscosities of their Component A and Component B were measured using a rotary viscometer respectively, and the viscosity of Component A was measured after curing for 10 days. The results are shown in Table 3.

[0060] Shearing strength test method: After curing the polyurethane sealants provided in Examples 1-8 and Comparative Examples 1-6 under standard conditions of 23°C * 50% RH for 5 days, they were respectively mixed evenly according to the mixing ratios of their respective Component A and Component B. Then, using their respective mixtures, a corresponding sealant with a thickness of 1 mm and a bonding area of 25 mm × 12.5 mm was coated on the surface of an anodized aluminum sheet with a size of 25 mm × 100 mm × 2 mm that had been treated with a toluene dilution solution of silane coupling agent KH550. And it was pasted onto a glass with a size of 50 mm × 40 mm × 6 mm that had been treated with a toluene dilution solution of silane coupling agent KH550. At the same time, it was cured for 7 days under standard conditions of 23°C × 50% RH and under low-temperature conditions of -5°C, and its shearing strength was tested. The results are shown in Table 3.

[0061] Table 3 Performance Results of Polyurethane Sealants

[0062]

[0063] As can be seen from Table 3: Compared with the polyurethane sealant provided in Comparative Example 1, the standard-condition shearing strength of the polyurethane sealants provided in Examples 1-5 is relatively larger. This shows that the hydroxyl bonding aid provided in this example is beneficial to enhancing the bonding strength and bulk strength of the polyurethane sealant.

[0064] From the perspective of low-temperature shearing strength, the low-temperature shearing strength of the polyurethane sealants provided in Examples 1-5 is much higher than that of Comparative Examples 1-6. This shows that the amino bonding aid provided in this example, when applied in Component B, is beneficial to enhancing the initial adhesion strength of the polyurethane sealant under low-temperature conditions, increasing the construction performance in a low-temperature environment, and is beneficial to shortening the construction period.

[0065] From the analysis of the viscosities of the components, the viscosities of Component A of the polyurethane sealants provided in Examples 1-5 and Comparative Example 1 basically do not change, but the viscosity of Component B is much smaller than that of Component B in Comparative Example 1. From this, it can be seen that the viscosities of the components of the polyurethane sealant provided in the examples of the present invention are relatively small, which is beneficial to construction. From the comparison of the viscosities of the components of the polyurethane sealants provided in Examples 1-5 and Comparative Examples 2-6, it can be known that when the hydroxyl bonding aid provided in the examples of the present invention is added to Component A of the sealant, the viscosity of Component A will increase significantly, and it will cause the storage of Component A to deteriorate; when added to Component B, its viscosity changes little. Therefore, for the low-density polyurethane sealant using the bonding aid provided in the examples of the present invention, on the premise of ensuring the bonding performance of the sealant, the viscosities of the components are relatively small and the workability is good.

[0066] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them; although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that it is still possible to modify the specific implementation manners of the present invention or perform equivalent replacements for some technical features; without departing from the spirit of the technical solutions of the present invention, they should all be covered within the scope of the technical solutions claimed by the present invention.

Claims

1. A hydroxyl bonding aid, characterized in that: It is mainly a macromolecular adhesion promoter with 1 to 4 hydroxyl groups, urethane groups, urea groups and silicon-oxygen-carbon bonds prepared by first polymerizing HDI biuret with monoamino silane coupling agent and diamino silane coupling agent in sequence, and then reacting with small molecule triol and small molecule diol. Among them, by mole fraction: 100 parts of HDI biuret, 20 to 50 parts of the diamino silane coupling agent, 100 to 200 parts of the monoamino silane coupling agent, 20 to 150 parts of the small molecule diol, 20 to 150 parts of the small molecule triol; the small molecule triol is trimethylolpropane or glycerol.

2. The hydroxyl bonding aid according to claim 1, wherein: The amounts of substance of HDI biuret, the diamino silane coupling agent, the monoamino silane coupling agent, the small molecule diol and the small molecule triol are represented by n(HDI biuret), n(diamino silane coupling agent), n(monoamino silane coupling agent), n(small molecule diol) and n(small molecule triol) respectively, and n(HDI biuret)×3 = n(diamino silane coupling agent)×2 + n(monoamino silane coupling agent) + n(small molecule diol) + n(small molecule triol).

3. The hydroxyl adhesion promoter according to claim 1 or 2, characterized in that: The monoamino silane coupling agent is bis(3-trimethoxysilylpropyl)amine, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane or 3-(phenylamino)propyltrimethoxysilane.

4. The hydroxyl adhesion promoter according to claim 1 or 2, characterized in that: The diamino silane coupling agent is N-aminoethyl-γ-aminopropyltrimethoxysilane or N-aminoethyl-γ-aminopropyltriethoxysilane.

5. The hydroxyl bonding aid according to claim 1 or 2, characterized in that: The small molecule diol is ethylene glycol, 1,3-propanediol, diethylene glycol or triethylene glycol.

6. A preparation method of the hydroxyl adhesion promoter according to any one of claims 1 to 5, comprising: Under the condition of inert gas, first uniformly mix HDI biuret with the first solvent to form a first mixture, then gradually drop the monoamino silane coupling agent into the first mixture under the stirring condition of 20°C to 25°C until the dropping is completed, then continue to react for 30 to 60 min, and then drop the diamino silane coupling agent. After the dropping is completed, continue to react for 30 to 60 min, and then raise the temperature to 50°C to 70°C and continue to react for 30 to 60 min to prepare a first prepolymer; First uniformly mix the small molecule diol, the small molecule triol and the second solvent to form a second mixture, and then add the first prepolymer to the second mixture under the conditions of 65°C to 75°C, a rotation speed of 80 to 120 r / min and inert gas protection until the reaction is completed and continue to react for 60 to 120 min to obtain the hydroxyl adhesion promoter.

7. The preparation method according to claim 6, characterized in that: It also includes adding the first prepolymer to the second mixture until the reaction is completed and continuing the reaction for 60 to 120 minutes, then adding the first catalyst and reacting for 60 to 90 minutes, and adjusting the solid content to 34% to 36% to obtain the hydroxyl bonding aid. Among them, the addition amount of the first catalyst is 0.01% to 0.06% of the total mass of HDI biuret, monoamino silane coupling agent, diamino silane coupling agent, small molecule triol and small molecule diol, and the first catalyst is dibutyltin dilaurate or dibutyltin dichloride.

8. The preparation method according to claim 6 or 7, characterized in that: The mass ratio of the total mass of HDI biuret, the diamino silane coupling agent and the monoamino silane coupling agent to the mass of the first solvent is (50 to 100):

100.

9. The preparation method according to claim 6 or 7, characterized in that: The mass ratio of the total mass of the small molecule diol and the small molecule triol to the mass of the second solvent is (20 to 50):

100.

10. A polyurethane sealant, characterized in that: Its raw materials include the hydroxyl bonding aid according to any one of claims 1 to 5.

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