Steric hindrance type amino-terminated polyolefin and preparation method thereof

Abstract

The invention discloses steric hindrance type amino-terminated polyolefin and a preparation method thereof, the structure of the steric hindrance type amino-terminated polyolefin is as follows: # imgabs0 #, in the formula, R1 is-H or-CH3; r2 is-C6H5 or-CN; m is equal to 0-200, n is equal to 0-200, x is equal to 0-200, and m, n and x are not 0 at the same time. According to the preparation method, hydroxyl-terminated polyolefin is taken as a raw material, steric hindrance type amino-terminated polyolefin is prepared through transesterification, and alcohol byproducts are removed through intermittent vacuum, so that accumulation of the byproducts and loss of the raw material in the reaction process are avoided. The method is suitable for various types of hydroxyl-terminated polyolefins, the hydroxyl conversion rate of the obtained steric hindrance type amino-terminated polyolefins is 80% or above, the amino-terminated functionality can reach 1.9 or above, the process steps are few, the refining and purifying process is simple, and the preparation cost is low. The reaction speed of the obtained steric hindrance type amino-terminated polyolefin and isocyanate is moderate, and the steric hindrance type amino-terminated polyolefin has better processing property and can be used for various polyurethane and polyurea materials.

Description

Technical Field

[0001] The present invention relates to the technical field of liquid rubber in polymer materials, in particular to a sterically hindered amino-terminated polyolefin and a preparation method thereof. Background Art

[0002] Hydroxyl-terminated polyolefin liquid rubbers, such as hydroxyl-terminated polybutadiene, hydroxyl-terminated butadiene-styrene copolymers, and hydroxyl-terminated butadiene-acrylonitrile copolymers, are widely used in polyurethanes, adhesives, coatings, and other fields due to their low production costs, exceptional reactivity, and low glass transition temperatures. Due to the low reactivity of hydroxyl groups with isocyanates, heating in the presence of a catalyst is generally required to form a polyurethane structure.

[0003] Amine-terminated polyolefins have a reactivity hundreds of times higher with isocyanates than hydroxyl-terminated polyolefins. They can be used to prepare polyureas at room temperature without catalysts and can also serve as toughening agents for epoxy resins. Based on their reactivity, they can be categorized as highly reactive amino-terminated polyolefins with aliphatic amines as the active group and as sterically hindered, less reactive amino-terminated polyolefins with aromatic amines as the active group. Highly reactive primary amine-terminated polyolefins exhibit high reactivity, making their reaction with isocyanates difficult to control and requiring high processing requirements. They are generally used as toughening agents for epoxy resins, such as Huntsman's HYPRO® ATBN series of amino-terminated butadiene-acrylonitrile copolymers. U.S. Patent No. 4,133,957A indicates that these amino-terminated butadiene-acrylonitrile copolymers are produced by condensing carboxyl-terminated butadiene-acrylonitrile copolymers with alkylamines, rather than using hydroxyl-terminated polyolefins as raw materials. In addition, amino-terminated polyolefins can also be produced by modifying hydroxyl-terminated polyolefins with hydroxyl groups. For example, the article "Synthesis and Characterization of Amine-Terminated Polybutadiene" published in the journal Elastomers in 2011 by the Research Institute of PetroChina Lanzhou Petrochemical Company described a method for preparing fatty amine-terminated polybutadiene by sulfonylation, azidation, and reductive amination of hydroxyl-terminated polybutadiene. However, this method is complex, has high synthesis costs, produces many byproducts, and is difficult to commercialize. Hindered low-activity amino-terminated polyolefins have an aromatic amine terminal amino structure. Due to conjugation and steric hindrance, their reactivity with isocyanates is between that of fatty amine-type high-activity amino-terminated polyolefins and hydroxyl-terminated polyolefins. The reaction rate for forming polyureas is moderate, resulting in good process performance. However, the number of literature and patents related to the preparation of sterically hindered amino-terminated polyolefins is limited.

[0004] Patent US4732959A reports on the preparation of polyester polyamines through transesterification of polyester polyols and para-aminobenzoic acid esters in the presence of a catalyst. Patent US6111129A describes the preparation of small diamines through transesterification of small diols in the presence of a tin catalyst. Patents US20090030226A1 and CN101353311A further optimize this process by using auxiliary alcohols such as isobutanol as additives to convert ethyl para-aminobenzoate into isobutyl para-aminobenzoate in situ, reducing sublimation losses of ethyl para-aminobenzoate and producing a series of polyether polyamines. Patent CN116283634A uses ionic liquids as catalysts, replacing the existing tin catalyst, to report methods for the synthesis of a series of small diamines, polyether diamines, and polyester diamines. This type of transesterification reaction features low raw material costs and a simple synthesis process, making it suitable for large-scale industrial production. However, hydroxyl-terminated polyolefins have a higher viscosity than polyethers, and the ethanol byproduct of the transesterification reaction is difficult to discharge from the reaction system through the water separator, resulting in low hydroxyl conversion and low terminal amino functionality of the product. If a vacuum environment is maintained during the reaction, the p-aminobenzoic acid ester will be drawn out of the reaction system, making it difficult to obtain an amino-terminated polyolefin product with high terminal amino functionality and high hydroxyl conversion. Therefore, it is urgent to develop a method for preparing sterically hindered amino-terminated polyolefins with fewer process steps, lower production costs, and higher amino content to promote the application of amino-terminated polyolefins in polymer materials such as polyureas and epoxy resins. Summary of the Invention

[0005] To overcome the shortcomings of the prior art, the present invention provides a hindered amino-terminated polyolefin and a method for preparing the same. The hindered amino-terminated polyolefin has higher reactivity than hydroxyl-terminated polyolefins, can mildly react with isocyanates at room temperature to form polyureas, and exhibits excellent process performance. The preparation method involves using an organometallic compound as a catalyst to carry out an ester exchange reaction between the hydroxyl-terminated polyolefin and p-aminobenzoate in a solvent, ultimately producing the hindered amino-terminated polyolefin.

[0006] The first aspect of the present invention provides a sterically hindered amino-terminated polyolefin, the structure of which is shown below: , Wherein, R1 is -H or -CH3; R2 is -C6H5 or -CN; m=0~200, n=0~200, x=0~200, and m, n, x are not 0 at the same time.

[0007] A second aspect of the present invention provides a method for preparing a sterically hindered amino-terminated polyolefin, comprising the following steps: (1) Under the protection of inert gas, add hydroxyl-terminated polyolefin, p-aminobenzoic acid ester, solvent A and transesterification catalyst into the reactor. (2) heating to the reaction temperature to carry out the reaction and intermittently removing the reaction by-products; (3) After the reaction is completed, sterically hindered amino-terminated polyolefin is obtained through post-treatment.

[0008] Preferably, in step (1), the hydroxy-terminated polyolefin, p-aminobenzoic acid ester, and solvent A are first added, stirred evenly, and heated to 100° C., and then the transesterification catalyst is added.

[0009] Preferably, in step (1), the hydroxyl-terminated polyolefin is one or a mixture of hydroxyl-terminated polybutadiene, hydroxyl-terminated polyisoprene, hydroxyl-terminated polystyrene, hydroxyl-terminated polyacrylonitrile, hydroxyl-terminated butadiene-styrene copolymer, hydroxyl-terminated butadiene-acrylonitrile copolymer, hydroxyl-terminated isoprene-styrene copolymer, and hydroxyl-terminated isoprene-acrylonitrile copolymer. The structure of the hydroxyl-terminated polyolefin is: , Wherein, R1 is -H or -CH3; R2 is -C6H5 or -CN; m=0~200, n=0~200, x=0~200, and m, n, x are not 0 at the same time.

[0010] Preferably, in step (1), the p-aminobenzoic acid ester is a mixture of one or more of methyl p-aminobenzoate, ethyl p-aminobenzoate, and butyl p-aminobenzoate, preferably ethyl p-aminobenzoate. The amount of the p-aminobenzoic acid ester used is 100-200% of the molar amount of the hydroxyl group of the hydroxyl-terminated polyolefin, preferably 120-150%.

[0011] Preferably, in step (1), the solvent A is a mixture of one or more of toluene, mixed xylene, and mesitylene, preferably mixed xylene. The amount of the solvent A used is 10-200% by weight of the hydroxyl-terminated polyolefin, preferably 10-100%.

[0012] Preferably, in step (1), the transesterification catalyst is one or a mixture of stannous octoate, stannous oxalate, dibutyltin dilaurate, dioctyltin dilaurate, dibutyltin di-2-methylhexanoate, dioctyltin dilaurylmercaptoacetate, tetraisopropyl titanate, tetrabutyl titanate, and tetra-2-ethylhexyl titanate, preferably tetraisopropyl titanate or tetrabutyl titanate. The amount of the transesterification catalyst used is 0.5-10% of the number of hydroxyl groups in the hydroxy-terminated polyolefin, preferably 1-2%.

[0013] Preferably, in step (2), the reaction temperature is 160-220°C, preferably 180-200°C; the reaction time is 2-48 hours, preferably 8-24 hours. During the reaction, negative pressure is applied at regular intervals to remove the alcohol by-products generated by the reaction; the negative pressure interval is 10 minutes to 2 hours, and each time lasts 1-10 minutes, preferably 1 hour and 2 minutes; the negative pressure is 0-10 kPa, preferably 0-5 kPa.

[0014] Preferably, in step (3), after the reaction is completed, the temperature is lowered to room temperature, solvent B is added to dissolve the reaction solution to obtain a glue solution, and the ester exchange catalyst is removed by washing with water. The glue solution is vacuum dried to obtain a sterically hindered amino-terminated polyolefin. The solvent B is a mixture of one or more of toluene, n-hexane, and cyclohexane, preferably n-hexane. The amount used is 100-400% of the weight of the hydroxyl-terminated polyolefin, preferably 100-200%. The water washing is performed by using 100-200% of the volume of the glue solution in deionized water, mixing and stirring the glue solution uniformly, standing and separating the layers, and removing the aqueous phase. This is repeated 2-3 times. The drying temperature is preferably 80-130°C, and the drying time is 1-3 hours.

[0015] Compared with the prior art, the advantage of the present invention is that it provides a method for preparing a sterically hindered amino-terminated polyolefin by an ester exchange method, wherein the method adopts a process for removing alcohol by-products by intermittent vacuum, thereby avoiding the accumulation of by-products and the loss of para-aminobenzoate raw materials during the reaction process, and adopts a small amount of toluene solvent to reduce the viscosity of the reaction system and assist in the removal of alcohol by-products. The sterically hindered amino-terminated polyolefin product is directly prepared using industrially produced hydroxyl-terminated polyolefin as a raw material. The method is applicable to various types of hydroxyl-terminated polyolefins, and can obtain a sterically hindered amino-terminated polyolefin product with a hydroxyl conversion rate of more than 80%. The product amino functionality can reach more than 1.9, the process steps are few, the refining and purification process is simple, and the preparation cost is low. The obtained sterically hindered amino-terminated polyolefin has a moderate reaction speed with isocyanate, has good process performance, and can be used for a variety of polyurethane and polyurea materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 The sterically hindered amino-terminated polyolefin prepared in Example 1 1 H NMR spectrum; Figure 2 The sterically hindered amino-terminated polyolefin prepared in Example 1 13 C NMR spectrum; Figure 3 This is the infrared absorption spectrum of the hindered amino-terminated polyolefin prepared in Example 1. DETAILED DESCRIPTION

[0017] The present invention is further described below with reference to specific examples.

[0018] The number average molecular weight was determined according to GJB 1965-1994, the amine value was determined by perchloric acid titration, and the terminal amino functionality was calculated by multiplying the number average molecular weight by the amine value.

[0019] Example 1

[0020] Under a nitrogen atmosphere, 1180 g of hydroxyl-terminated polybutadiene (hydroxyl value 0.84 mmol / g, number-average molecular weight 2900 g / mol, containing 0.99 mol of hydroxyl groups), 199 g of ethyl p-aminobenzoate (1.20 mol), and 200 g of mixed xylene were added sequentially to a 2L Schlenk flask equipped with a reflux condenser and a water separator. The mixture was stirred and heated to 100°C. Under a nitrogen stream, 3.4 g of tetrabutyl titanate (0.01 mol) was added, and heating continued to 180°C. After reacting for 30 minutes, the liquid in the water separator was drained and vacuumed for 1 minute. The reaction was continued for 1 hour, the liquid in the water separator was drained, and vacuumed for 1 minute. This operation was repeated 12 times, for a total reaction time of 12.5 hours. The reaction mixture was cooled to room temperature and poured into a water washing kettle. 2 L of n-hexane was added for dissolution, and then washed three times with deionized water. The organic phase was vacuum dried at 120° C. for 2 hours to obtain 1200 g of amino-terminated polybutadiene product with a number average molecular weight of 3230 g / mol, an amine value of 0.61 mmol / g, an amino-terminated functionality of 1.97, a hydroxyl conversion rate of 81%, and a residual amount of small molecules such as ethyl p-aminobenzoate less than 1%. The product structure is shown below:

[0021] Attachment Figures 1-3 are respectively the sterically hindered amino-terminated polybutadiene prepared in Example 1 1 H NMR spectrum, 13 The C NMR spectrum and infrared absorption spectrum clearly characterize the structure of the product amino-terminated polybutadiene. Figure 1 As shown in Figure 2, the chemical shift of H NMR spectrum is within 4.75~5.75ppm, which is the characteristic peak of the double bond structure of the polybutadiene main chain. The peak at 4.0~4.5ppm is the characteristic peak of amino group and a small amount of unconverted hydroxyl group. Figure 3 As shown, 1604 cm -1 and 1622 cm -1 The peak is the characteristic peak of CN stretching vibration of benzene ring.

[0022] Example 2

[0023] Under a nitrogen atmosphere, 1180 g of hydroxyl-terminated polybutadiene (hydroxyl value 0.84 mmol / g, number-average molecular weight 2900 g / mol, containing 0.99 mol of hydroxyl groups), 199 g of ethyl p-aminobenzoate (1.20 mol), and 200 g of mixed xylene were added sequentially to a 2L Schlenk flask equipped with a reflux condenser and a water separator. The mixture was stirred and heated to 100°C. Under a nitrogen stream, 3.4 g of tetrabutyl titanate (0.01 mol) was added, and heating to 200°C was continued. After 30 minutes of reaction, the liquid in the water separator was drained and vacuumed for 5 minutes. The reaction was continued for 1 hour, the liquid in the water separator was drained, and vacuumed for 5 minutes. This process was repeated six times, for a total reaction time of 6.5 hours. The reaction mixture was cooled to room temperature and poured into a water washing kettle. 2 L of n-hexane was added for dissolution, and then washed three times with deionized water. The organic phase was vacuum dried at 120° C. for 2 hours to obtain 1190 g of amino-terminated polybutadiene product with a number average molecular weight of 3200 g / mol, an amine value of 0.61 mmol / g, an amino-terminated functionality of 1.95, a hydroxyl conversion rate of 80%, and a residual amount of small molecules such as ethyl p-aminobenzoate less than 1%. The product structure is shown below:

[0024] Example 3

[0025] Under a nitrogen atmosphere, 890 g of hydroxy-terminated butadiene-acrylonitrile copolymer (hydroxyl value 0.56 mmol / g, number-average molecular weight 3400 g / mol, containing 0.50 mol of hydroxyl groups), 125 g of ethyl p-aminobenzoate (0.75 mol), and 300 g of mixed xylene were added sequentially to a 2L Schlenk flask equipped with a reflux condenser and a water separator. The mixture was stirred and heated to 100°C. Under a nitrogen stream, 1.7 g of tetrabutyl titanate (0.005 mol) was added, and heating continued to 180°C. After reacting for 30 minutes, the liquid in the water separator was drained and vacuumed for 1 minute. The reaction was continued for 1 hour, the liquid in the water separator was drained, and vacuumed for 1 minute. This operation was repeated 16 times, for a total reaction time of 16.5 hours. The reaction mixture was cooled to room temperature and poured into a water washing kettle. 2 L of toluene was added for dissolution, and the mixture was washed three times with deionized water. The organic phase was vacuum dried at 120° C. for 2 hours to obtain 910 g of an amino-terminated butadiene-acrylonitrile copolymer product. The product had a number average molecular weight of 3690 g / mol, an amine value of 0.46 mmol / g, an amino terminal functionality of 1.70, a hydroxyl conversion rate of 89%, and a residual amount of small molecules such as ethyl p-aminobenzoate less than 1%. The product structure is shown below:

[0026] Example 4

[0027] Under a nitrogen atmosphere, a 2L Schlenk flask equipped with a reflux condenser and a water separator was charged with 1090 g of a hydroxy-terminated butadiene-styrene copolymer (hydroxyl value 0.46 mmol / g, number-average molecular weight 5000 g / mol, containing 0.50 mol of hydroxyl groups), 125 g of ethyl p-aminobenzoate (0.75 mol), and 200 g of mixed xylene. The mixture was stirred and heated to 100°C. Under a nitrogen stream, 1.7 g of tetrabutyl titanate (0.005 mol) was added, and heating continued to 180°C. After reacting for 30 minutes, the liquid in the water separator was drained and vacuumed for 1 minute. The reaction was continued for 1 hour, the liquid in the water separator was drained, and vacuumed for 1 minute. This process was repeated 12 times, for a total reaction time of 12.5 hours. The reaction mixture was cooled to room temperature and poured into a water washing kettle. 2 L of n-hexane was added for dissolution, and then washed three times with deionized water. The organic phase was vacuum dried at 120° C. for 2 hours to obtain 1130 g of amino-terminated butadiene-styrene copolymer. The copolymer had a number average molecular weight of 5310 g / mol, an amine value of 0.36 mmol / g, an amino terminal functionality of 1.91, a hydroxyl conversion rate of 83%, and a residual amount of small molecules such as ethyl p-aminobenzoate less than 1%. The product structure is shown below:

[0028] Example 5

[0029] Under a nitrogen atmosphere, to a 2L Schlenk flask equipped with a reflux condenser and a water separator were added 1020 g of hydroxyl-terminated polyisoprene (hydroxyl value 0.97 mmol / g, number-average molecular weight 2000 g / mol, containing 0.99 mol of hydroxyl groups), 199 g of ethyl p-aminobenzoate (1.20 mol), and 300 g of mixed xylene. The mixture was stirred and heated to 100°C. Under a nitrogen stream, 6.4 g of dibutyltin dilaurate (0.01 mol) was added, and heating continued to 180°C. After reacting for 30 minutes, the liquid in the water separator was drained and the mixture was evacuated for 2 minutes. The reaction was continued for 1 hour, the liquid in the water separator was drained, and the mixture was evacuated for 2 minutes. This procedure was repeated 12 times, for a total reaction time of 12.5 hours. The reaction mixture was cooled to room temperature and poured into a water washing kettle. 2 L of n-hexane was added for dissolution, and then washed three times with deionized water. The organic phase was vacuum dried at 120° C. for 2 hours to obtain 1050 g of amino-terminated polyisoprene product with a number average molecular weight of 2300 g / mol, an amine value of 0.74 mmol / g, an amino-terminated functionality of 1.71, a hydroxyl conversion rate of 88%, and a residual amount of small molecules such as ethyl p-aminobenzoate less than 1%. The product structure is shown below:

[0030] Comparative Example 1

[0031] Under a nitrogen atmosphere, 1180 g of hydroxyl-terminated polybutadiene (hydroxyl value 0.84 mmol / g, number average molecular weight 2900 g / mol, containing 0.99 mol of hydroxyl groups), 102 g of p-aminobenzoic acid (1.36 mol), 2 g of p-toluenesulfonic acid (0.012 mol), 2 g of hydroquinone (0.018 mol) and 1000 mL of toluene were added in sequence to a 2L Schlenk flask equipped with a reflux condenser and a water separator. The mixture was stirred and heated to 110°C. After reacting for 16 hours, the reaction mixture was cooled to room temperature and poured into a water washing kettle. After dissolving in 2 L of toluene, the mixture was washed three times with deionized water. The organic phase was vacuum dried at 120°C for 2 hours to obtain 1180 g of amino-terminated polybutadiene product with a number average molecular weight of 3130 g / mol, an amine value of 0.39 mmol / g, a terminal amino functionality of 1.22, and a hydroxyl conversion rate of 50%.

[0032] Comparative Example 2

[0033] Under a nitrogen atmosphere, 1180 g of hydroxyl-terminated polybutadiene (hydroxyl value 0.84 mmol / g, number average molecular weight 2900 g / mol, containing 0.99 mol of hydroxyl groups), 199 g of ethyl p-aminobenzoate (1.20 mol), and 0.47 g of tetraisopropyl titanate (0.04 w %) were added sequentially to a 2 L three-necked flask equipped with a reflux condenser, a water separator, and a nitrogen intubation. The mixture was heated, purged with nitrogen, and stirred. The mixture was distilled at 220 ° C for 30 min, then the temperature was raised and controlled at 240 ° C for 4 h. The reaction mixture was cooled to room temperature and poured into a water washing kettle. After dissolution with 2 L of n-hexane, the mixture was washed three times with deionized water. The organic phase was vacuum dried at 120 ° C for 2 h to obtain 1200 g of amino-terminated polybutadiene product with a number average molecular weight of 3010 g / mol, an amine value of 0.28 mmol / g, an amino terminal functionality of 0.84, and a hydroxyl conversion rate of 35%.

[0034] Comparative Example 3

[0035] Under a nitrogen atmosphere, a 2L Schlenk flask equipped with a reflux condenser and a water separator was charged with 1180 g of hydroxyl-terminated polybutadiene (hydroxyl value 0.84 mmol / g, number-average molecular weight 2900 g / mol, containing 0.99 mol of hydroxyl groups), 199 g of ethyl p-aminobenzoate (1.20 mol), and 200 g of mixed xylene. The mixture was stirred and heated to 100°C. Under a nitrogen flow, 3.4 g of tetrabutyl titanate (0.01 mol) was added, and the mixture was heated to 180°C for 12 hours while continuously applying vacuum. The reaction mixture was cooled to room temperature and poured into a water washing kettle. After dissolution with 2 L of n-hexane, the mixture was washed three times with deionized water. The organic phase was vacuum-dried at 120°C for 2 hours to yield 1180 g of amino-terminated polybutadiene with a number-average molecular weight of 3060 g / mol, an amine value of 0.47 mmol / g, an amino functionality of 1.44, and a hydroxyl conversion of 59%.

[0036] Comparative Example 4

[0037] Under a nitrogen atmosphere, 1180 g of hydroxy-terminated polybutadiene (hydroxyl value 0.84 mmol / g, number average molecular weight 2900 g / mol, containing 0.99 mol of hydroxyl groups), 199 g of ethyl p-aminobenzoate (1.20 mol), 89 g of 1-butanol (1.20 mol) and 200 g of mixed xylene were added in sequence to a 2L Schlenk flask equipped with a reflux condenser and a water separator. The mixture was stirred and heated to 100°C. 3.4 g of tetrabutyl titanate (0.01 mol) was added under a nitrogen flow, and the mixture was continued to be heated to 180°C. The reaction was carried out for 12 hours, and vacuum was continuously applied. The reaction mixture was cooled to room temperature and poured into a water washing kettle. After dissolving in 2 L of n-hexane, the mixture was washed three times with deionized water. The organic phase was vacuum dried at 120° C. for 2 hours to obtain 1210 g of amino-terminated polybutadiene product with a number average molecular weight of 3140 g / mol, an amine value of 0.49 mmol / g, an amino-terminated functionality of 1.54, and a hydroxyl conversion rate of 63%.

[0038] Comparing Comparative Examples 1-4 with Example 1, amino-terminated polyolefins can only be obtained at relatively low hydroxyl conversion rates using either direct esterification or transesterification processes suitable for polyethers. Therefore, the process of the present invention clearly offers advantages such as high hydroxyl conversion rates and high amino-terminated functionality, making it suitable for the preparation of hindered amino-terminated polyolefins.

[0039] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not limitations on the implementation methods of the present invention. For ordinary technicians in the relevant field, other different forms of changes or modifications can be made based on the above description. It is impossible to list all the implementation methods here. All obvious changes or modifications derived from the technical solution of the present invention are still within the scope of protection of the present invention.

Claims

1. A sterically hindered amino-terminated polyolefin having the following structure: ， in, R1 is -H or -CH3; R2 is -C6H5 or -CN; m=0~200, n=0~200, x=0~200, and m, n, x are not 0 at the same time.

2. A method for preparing a sterically hindered amino-terminated polyolefin, comprising the following steps: (1) Under the protection of inert gas, add hydroxyl-terminated polyolefin, p-aminobenzoic acid ester, solvent A and transesterification catalyst into the reactor. (2) heating to the reaction temperature to carry out the reaction and intermittently removing the reaction by-products; (3) After the reaction is completed, sterically hindered amino-terminated polyolefin is obtained through post-treatment.

3. The preparation method according to claim 2, characterized in that In step (1), the hydroxyl-terminated polyolefin is one or a mixture of hydroxyl-terminated polybutadiene, hydroxyl-terminated polyisoprene, hydroxyl-terminated polystyrene, hydroxyl-terminated polyacrylonitrile, hydroxyl-terminated butadiene-styrene copolymer, hydroxyl-terminated butadiene-acrylonitrile copolymer, hydroxyl-terminated isoprene-styrene copolymer, and hydroxyl-terminated isoprene-acrylonitrile copolymer.

4. The preparation method according to claim 2, characterized in that The structure of the hydroxyl-terminated polyolefin is: ， Wherein, R1 is -H or -CH3; R2 is -C6H5 or -CN; m=0~200, n=0~200, x=0~200, and m, n, x are not 0 at the same time.

5. The preparation method according to claim 2, characterized in that In step (1), the p-aminobenzoic acid ester is a mixture of one or more of methyl p-aminobenzoate, ethyl p-aminobenzoate, and butyl p-aminobenzoate, preferably ethyl p-aminobenzoate.

6. The amount of the p-aminobenzoic acid ester is 100-200% of the molar amount of the hydroxyl group of the hydroxyl-terminated polyolefin, preferably 120-150%.

7. The preparation method according to claim 2, characterized in that In step (1), the transesterification catalyst is one or a mixture of stannous octoate, stannous oxalate, dibutyltin dilaurate, dioctyltin dilaurate, dibutyltin di-2-methylhexanoate, dioctyltin dilaurylmercaptoacetate, tetraisopropyl titanate, tetrabutyl titanate, and tetra-2-ethylhexyl titanate, preferably tetraisopropyl titanate and tetrabutyl titanate.

8. The preparation method according to claim 2, characterized in that In step (2), the reaction temperature is 160-220°C, preferably 180-200°C.

9. The preparation method according to claim 2, characterized in that In step (2), during the reaction process, negative pressure is applied to remove alcohol by-products generated by the reaction at regular intervals; the negative pressure interval is 10 minutes to 2 hours, and each time lasts 1 to 10 minutes, and the negative pressure is 0 to 10 kPa, preferably 0 to 5 kPa.

10. The preparation method according to claim 2, characterized in that In step (3), after the reaction is completed, the temperature is lowered to room temperature, solvent B is added to dissolve the reaction solution to obtain a glue solution, and the ester exchange catalyst is removed by washing with water. The glue solution is vacuum dried to obtain a sterically hindered amino-terminated polyolefin.

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