Preparation and purification process of high-activity hydroxyl-terminated polybutadiene

Abstract

The application discloses a preparation and purification process of high-activity hydroxyl-terminated polybutadiene and belongs to the technical field of high polymer material preparation. The polybutadiene prepolymer is prepared through an anion polymerization reaction, and an epoxy group is used for end capping reaction to form a hydroxyl-terminated structure; meanwhile, a complexing purifying agent is introduced in the polymerization reaction stage to realize in-situ removal of catalyst residues, low-molecular-weight impurities are removed through a membrane separation technology, and finally, the solvent is removed under low-temperature vacuum conditions to obtain the high-activity hydroxyl-terminated polybutadiene product. The method can significantly improve the hydroxyl-terminated reaction activity and reduce the metal residue content, and has a good industrial application prospect.

Description

Technical Field

[0001] This invention belongs to the field of polymer material preparation technology, specifically, it relates to a preparation and purification process for highly active hydroxyl-terminated polybutadiene. Background Technology

[0002] Hydroxyl-terminated polybutadiene (HTPB) is a liquid rubber material with a telechelic structure. Its molecular chains contain hydroxyl functional groups at both ends, allowing it to crosslink with isocyanates, epoxy resins, or acrylic monomers to form polymers with excellent elasticity, low-temperature resistance, and adhesive properties. Due to its superior physicochemical properties, HTPB is widely used in solid rocket propellant binders, polyurethane elastomers, structural adhesives, anti-corrosion coatings, and sealing materials.

[0003] Currently, HTPB is mainly prepared via free radical oxidative polymerization or anionic polymerization. Free radical polymerization, which uses initiators such as peroxides or hydrogen peroxide to initiate butadiene polymerization, has the advantages of simple equipment and low production cost. However, its chain termination process is highly random, easily forming various chain-end groups with different structures, making it difficult to precisely control the number and distribution of terminal hydroxyl groups. Furthermore, free radical polymerization easily generates peroxide byproducts, carbonyl compounds, and low-molecular-weight byproducts, thereby reducing the reactivity of the terminal hydroxyl groups.

[0004] Another technical approach employs anionic polymerization, using organolithium initiators to polymerize butadiene monomers. This allows for some controllable adjustment of molecular weight, but existing technologies still suffer from uncontrollable chain termination, low end-hydroxyl capping efficiency, and difficulty in completely removing catalyst residues. Furthermore, in traditional processes, polymerization and purification are typically two separate stages. During subsequent washing, extraction, and solvent removal, end-hydroxyl groups easily form complexes with metal ions or undergo side reactions in an oxidizing environment, leading to a decrease in the actual reactivity of the end-hydroxyl groups.

[0005] In recent years, some studies have attempted to obtain hydroxyl-terminated polybutadiene through oxidative pyrolysis or post-functionalization reactions of polybutadiene. However, such methods usually suffer from problems such as uncontrollable molecular chain breakage, wide molecular weight distribution, and difficulty in completely removing oxidation byproducts.

[0006] In view of this, the present invention is proposed. Summary of the Invention

[0007] To solve the above-mentioned technical problems, the basic concept of the technical solution adopted by the present invention is as follows:

[0008] A process for preparing and purifying highly active hydroxyl-terminated polybutadiene includes the following steps:

[0009] Step S1: Under inert gas protection, butadiene monomer is dissolved in an organic solvent to form a polymerization reaction system, and an anionic initiator and a polar structure modifier are added to carry out solution polymerization reaction, so that butadiene monomer undergoes anionic polymerization to form polybutadiene prepolymer with active chain ends;

[0010] Step S2: After the polymerization reaction reaches the preset conversion rate, a hydroxyl end-capping agent containing epoxy groups is added to the polymerization system to cause the active chain end to undergo a ring-opening reaction with the epoxy groups, thereby forming a terminal hydroxyl structure at the end of the polybutadiene molecular chain.

[0011] Step S3: During the end-capping reaction, a complexing purification agent is added to the system to remove residual metal catalysts and polar byproducts in situ through complexation or complexation sedimentation.

[0012] Step S4: Perform membrane separation purification on the reaction system to remove low molecular weight byproducts and unreacted monomers through molecular weight selective permeation;

[0013] Step S5: Solvent removal is performed under an inert atmosphere and low temperature to obtain a highly active hydroxyl-terminated polybutadiene product.

[0014] In a preferred embodiment of the present invention, the anionic initiator is an organolithium initiator, and its dosage is 0.01%-0.5% of the mass of the butadiene monomer. The organolithium initiator is selected from butyllithium, sec-butyllithium, tert-butyllithium, naphthalenelithium, or a combination thereof.

[0015] In a preferred embodiment of the present invention, the polarity modifier is used to adjust the microstructure ratio of polymer segments during butadiene polymerization. The amount of the polarity modifier added is 0.1%-5% of the mass of the butadiene monomer, and the polarity modifier is selected from tetrahydrofuran, dimethoxyethane, diethylene glycol dimethyl ether, or a combination thereof.

[0016] In a preferred embodiment of the present invention, the organic solvent is selected from cyclohexane, n-hexane, toluene, cycloheptane or a mixture thereof, and the role of the solvent in the polymerization system includes reducing the viscosity of the system, improving the mass transfer efficiency and stabilizing the anionic polymerization reaction.

[0017] In a preferred embodiment of the present invention, the end-capping agent is an alcohol compound containing an epoxy group, and the amount added is 0.5%-10% of the mass of the polybutadiene prepolymer. The end-capping agent is selected from epoxy ethanol, epoxy propanol, epoxy butanol, glycidyl ether or a combination thereof.

[0018] In a preferred embodiment of the present invention, the complexing purifier is a polydentate coordination compound, and its addition amount is 0.01%-1% of the mass of the reaction system. The complexing purifier can form a stable complex with metal ions, thereby achieving the removal of catalyst residues.

[0019] In a preferred embodiment of the present invention, the complexing purifying agent is selected from one or more of ethylenediaminetetraacetic acid, diethylenetriaminepentaacetic acid, organophosphonates, or polyhydroxy complexing agents.

[0020] In a preferred embodiment of the present invention, the membrane separation and purification step uses a nanofiltration membrane or an ultrafiltration membrane device for fractional separation. The molecular weight cutoff range of the membrane is 500-2000 Da, and the impurity removal efficiency is improved by elution with a circulating solvent.

[0021] In a preferred embodiment of the present invention, during the membrane separation and purification process, the reaction system circulates in the membrane module at a flow rate of 0.5-2 m / s and maintains a filtration pressure of 0.1-0.5 MPa to achieve effective separation of low molecular weight byproducts and unreacted monomers.

[0022] In a preferred embodiment of the present invention, the membrane separation device has a molecular weight cutoff range of 500-2000 Da, a filtration pressure of 0.1-0.5 MPa, and a circulation flow rate of 0.5-2 m / s.

[0023] Compared with the prior art, the present invention has the following advantages:

[0024] This invention employs anionic polymerization combined with ring-opening of epoxy groups for end-capping. Compared to the random chain termination of traditional free radical polymerization and the conventional end-capping process of anionic polymerization, it can precisely construct terminal hydroxyl structures at the ends of polybutadiene molecular chains, effectively reducing the generation of non-hydroxyl end groups. This allows the product's terminal hydroxyl functionality to reach over 1.88, far exceeding the 1.65 of commercially available conventional products. Simultaneously, the end-capping reaction is carried out entirely in an inert atmosphere, and the purification process avoids side reactions such as complexation of terminal hydroxyl groups with metal ions and air oxidation, ensuring the reactivity of the terminal hydroxyl groups. The reaction rate constant between the product and isocyanate is increased by over 60%, significantly shortening the gelation and curing time of downstream products and improving production efficiency.

[0025] This invention incorporates a multidentate coordination complexing purifier during the end-capping reaction to achieve in-situ complexation removal of residual metal catalysts, avoiding the damage to the terminal hydroxyl structure caused by subsequent purification in traditional processes. Furthermore, the molecular weight selective separation via nanofiltration / ultrafiltration membranes precisely removes low-molecular-weight byproducts and unreacted monomers. After optimization of the membrane separation's molecular weight cutoff, flow rate, and pressure parameters, the removal rate of low-molecular-weight impurities can reach over 94%, reducing the low-molecular-weight impurity content in the product to below 0.45%, and controlling the residual lithium metal content to below 2.5 ppm, far lower than the over 10 ppm level of traditional processes. This high purity effectively avoids the negative impact of impurities on the product's cross-linking reaction and mechanical properties.

[0026] This invention incorporates a complexing purifying agent into the end-capping reaction system to achieve continuous polymerization-end-capping-in-situ purification. Furthermore, subsequent membrane separation and solvent removal are completed under an inert atmosphere. This process design completely avoids various side reactions of the terminal hydroxyl groups and preserves their reactivity to the maximum extent.

[0027] The specific embodiments of the present invention will now be described in further detail with reference to the accompanying drawings. Attached Figure Description

[0028] In the attached diagram:

[0029] Figure 1 This is a flowchart of the preparation and purification process of a highly active hydroxyl-terminated polybutadiene. Detailed Implementation

[0030] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments will be clearly and completely described below with reference to the accompanying drawings. The following embodiments are used to illustrate the present invention.

[0031] Example 1

[0032] The preparation process using sec-butyllithium as an initiator and glycidol as a capping agent is as follows: Under nitrogen inert gas protection, 1000g of butadiene monomer is added to a high-pressure reactor equipped with a stirring and temperature control device, and 2000mL of cyclohexane is added as an organic solvent. The mixture is stirred thoroughly to completely dissolve the butadiene and form a homogeneous polymerization system. Subsequently, 0.8g of sec-butyllithium is added as an anionic initiator, and 5mL of tetrahydrofuran is added as a polar structure modifier. The temperature of the reaction system is adjusted to 20℃, and the stirring rate is controlled at 300r / min to carry out the anionic solution polymerization reaction. The monomer conversion rate is monitored in real time.

[0033] When the butadiene monomer conversion rate reaches 70%, 20g of glycidol is slowly added dropwise to the reaction system as a hydroxyl end-capping reagent at a dropping rate of 0.5g / min. After the addition is completed, the reaction continues for 2 hours to allow the active chain end of the polybutadiene prepolymer to fully undergo a ring-opening reaction with the epoxy groups of glycidol to form a terminal hydroxyl structure.

[0034] When the end-capping reaction has been underway for 1 hour, 10 g of ethylenediaminetetraacetic acid is added to the system as a complexing and purifying agent. The reaction is continued to be stirred until the end-capping reaction is completed, thereby achieving in-situ complexing and removal of residual metal catalyst and polar by-products.

[0035] After the reaction was completed, the reaction system was transferred to a nanofiltration membrane separation device for purification. The membrane molecular weight cutoff was 1000 Da. The circulation flow rate of the system in the membrane module was controlled at 1.0 m / s, and the filtration pressure was 0.2 MPa. Simultaneously, cyclohexane was used as the elution solvent for cyclic elution. The amount of elution solvent was 1.5 times the system volume. The separation was continued for 4 hours to remove low molecular weight byproducts and unreacted butadiene monomers.

[0036] Finally, the material separated by membrane separation was transferred into a rotary evaporator, where solvent removal was carried out under low-temperature vacuum conditions of nitrogen inert atmosphere, 50°C, and vacuum degree of -0.095MPa for 6 hours to obtain a highly active hydroxyl-terminated polybutadiene product, denoted as HTPB-1.

[0037] Example 2: Preparation process using butyllithium as initiator and epoxy ethanol as end-capping agent

[0038] Under argon protection, 1500g of butadiene monomer was added to the reactor, along with 3500mL of a mixed solvent of n-hexane and toluene (volume ratio 1:1). After stirring to dissolve, 1.2g of n-butyllithium was added as an initiator, and 12mL of dimethoxyethane was added as a polarity modifier. The reaction temperature was adjusted to 25℃, and the polymerization reaction was carried out at a stirring rate of 250r / min.

[0039] When the monomer conversion rate reaches 75%, 35g of epoxy ethanol is slowly added dropwise as the end-capping reagent at a dropping rate of 0.4g / min. After the addition is complete, the reaction is allowed to proceed for 2.5h. 1.2h after the end-capping reaction begins, 8g of diethylenetriaminepentaacetic acid is added as a complexing and purifying agent, and the reaction continues until the end-capping is complete.

[0040] The reaction system was fed into an ultrafiltration membrane separation device with a membrane molecular weight cutoff of 800 Da, a circulation flow rate of 0.8 m / s, a filtration pressure of 0.15 MPa, and a mixed solvent as the eluent for 3.5 h of circulation elution. The amount of eluent used was twice the volume of the system.

[0041] The solvent was then removed under an argon atmosphere, at 45°C and a vacuum of -0.090 MPa for 7 hours to obtain the product HTPB-2.

[0042] Example 3: Preparation process using tert-butyllithium combined with naphthene lithium as a composite initiator and glycidyl ether as a capping agent

[0043] Under nitrogen protection, 800g of butadiene monomer was added to the reactor, and 1800mL of cycloheptane was added as a solvent. After stirring and dissolving, a composite initiator (0.3g of tert-butyllithium combined with 0.2g of naphthalene lithium, with a total mass of 0.0625% of butadiene) was added, and 6mL of diethylene glycol dimethyl ether was added as a polarity modifier. The reaction temperature was adjusted to 18℃, and the polymerization reaction was carried out at a stirring rate of 350r / min.

[0044] When the monomer conversion rate reaches 65%, 15g of glycidyl ether is added dropwise as a capping reagent at a dropping rate of 0.3g / min. After the addition is completed, the reaction is carried out for 1.8h. After 0.8h of the capping reaction, 5g of a composite purification agent of organophosphonate and polyhydroxy complexing agent (mass ratio 2:1) is added, and the reaction is continued until the capping is completed.

[0045] Purification was performed using a nanofiltration membrane separation device with a molecular weight cutoff of 1500 Da, a circulation flow rate of 1.5 m / s, a filtration pressure of 0.3 MPa, and elution with cycloheptane as the eluent for 4.5 h. The amount of eluent used was 1.8 times the system volume.

[0046] Finally, the solvent was removed under a nitrogen atmosphere, at 55°C and a vacuum of -0.098 MPa for 5 hours to obtain the product HTPB-3.

[0047] Example 4: Preparation process of high addition amount initiator

[0048] Under nitrogen protection, 1200g of butadiene monomer was added to the reactor, along with 2800mL of cyclohexane as a solvent, 6.0g of sec-butyllithium (0.5% of the mass of butadiene) as an initiator, and 60mL of tetrahydrofuran (5% of the mass of butadiene) as a polarity modifier. The reaction temperature was adjusted to 30℃, and the polymerization reaction was carried out at a stirring rate of 400r / min.

[0049] When the monomer conversion rate reaches 80%, 120g of glycidol (10% of the mass of polybutadiene prepolymer) is added dropwise as a capping agent at a dropping rate of 0.6g / min. After the addition is completed, the reaction is carried out for 3 hours. After 1.5 hours of capping reaction, 39.2g of ethylenediaminetetraacetic acid (1% of the mass of the reaction system) is added as a complexing and purification agent, and the reaction is continued until the capping is completed.

[0050] A nanofiltration membrane separation device was used, with a membrane molecular weight cutoff of 2000 Da, a circulation flow rate of 2.0 m / s, a filtration pressure of 0.5 MPa, and cyclohexane as the eluent for 5 hours of elution. The amount of eluent used was 2.5 times the system volume.

[0051] The solvent was removed for 7 hours under a nitrogen atmosphere, at 60°C and a vacuum of -0.095 MPa to obtain the product HTPB-4.

[0052] Example 5: Preparation process of low-addition initiator

[0053] Under argon protection, 2000g of butadiene monomer was added to the reactor, along with 5000mL of n-hexane as a solvent, 0.2g of butyllithium (0.01% of the mass of butadiene) as an initiator, and 2mL of dimethoxyethane (0.1% of the mass of butadiene) as a polarity modifier. The reaction temperature was adjusted to 15℃, and the polymerization reaction was carried out at a stirring rate of 200r / min.

[0054] When the monomer conversion rate reaches 60%, 10g of glycidol (0.5% of the mass of polybutadiene prepolymer) is added dropwise as a capping agent at a dropping rate of 0.2g / min. After the addition is complete, the reaction is allowed to proceed for 1.5h. After 0.5h of capping reaction, 0.702g of diethylenetriaminepentaacetic acid (0.01% of the mass of the reaction system) is added as a complexing and purifying agent, and the reaction continues until capping is complete.

[0055] An ultrafiltration membrane separation device was used, with a membrane molecular weight cutoff of 500 Da, a circulation flow rate of 0.5 m / s, a filtration pressure of 0.1 MPa, and n-hexane as the eluent for 3 hours of circulation elution. The amount of eluent used was 1 times the system volume.

[0056] The solvent was removed for 8 hours under an argon atmosphere, at 40°C and a vacuum of -0.085 MPa, to obtain the product HTPB-5.

[0057] Experimental Example

[0058] Experiment Example 1: Product Performance Testing

[0059] The highly active hydroxyl-terminated polybutadiene products prepared in Examples 1-5 above, as well as commercially available conventional hydroxyl-terminated polybutadiene products (referred to as control samples), underwent comprehensive performance testing. The testing methods followed relevant national standards and industry testing specifications for polymer materials. The test indicators included hydroxyl-terminated functionality, number-average molecular weight (Mn), molecular weight distribution (PDI), residual lithium metal, viscosity (25℃), reactivity (reaction rate with isocyanate), and low molecular weight impurity content. The test results are shown in Table 1 below.

[0060] Sample number Terminal hydroxyl functionality Number average molecular weight (Mn) / Da Molecular weight distribution (PDI) Lithium metal residue / ppm Viscosity (25℃) / mPa・s Reaction rate constant k / (L・mol⁻¹・s⁻¹) Low molecular weight impurity content / % HTPB-1 1.92 3250 1.15 2.1 1250 0.085 0.35 HTPB-2 1.90 3120 1.18 1.8 1180 0.082 0.42 HTPB-3 1.89 3380 1.16 2.3 1320 0.084 0.38 HTPB-4 1.91 2860 1.20 2.5 980 0.079 0.45 HTPB-5 1.88 3550 1.17 1.9 1450 0.083 0.40 control sample 1.65 3080 1.42 15.6 1380 0.052 2.15

[0061] Experiment Example 2: Effect of Different Purification Methods on Product Performance

[0062] To verify the superiority of the in-situ complexation combined with membrane separation purification process of the present invention, three sets of comparative experiments were set up with reference to the basic reaction system of Example 1: in-situ complexation purification only (comparative group 1), membrane separation purification only (comparative group 2), and traditional water washing combined with extraction purification (comparative group 3). The other preparation conditions were completely consistent with those of Example 1. The metal residue and terminal hydroxyl reactivity of each group of products were detected, and the results are shown in Table 2 below:

[0063] Purification method Lithium metal residue / ppm Reaction rate constant k / (L・mol⁻¹・s⁻¹) Terminal hydroxyl functionality In-situ complexation and binding membrane separation (this invention) 2.1 0.085 1.92 In-situ complexation purification only (control group 1) 8.5 0.068 1.85 Membrane separation purification only (Control group 2) 6.2 0.072 1.87 Traditional water washing combined with extraction and purification (comparative group 3) 10.8 0.058 1.72

[0064] As can be seen from the results in Tables 1 and 2 above, when only a single purification method is used, the metal residue is significantly higher than that of the combined purification process of the present invention, and the reactivity and functionality of the terminal hydroxyl groups are reduced. The traditional water washing combined with extraction purification process has the worst metal removal effect. At the same time, due to the complexation of terminal hydroxyl groups with metal ions and air oxidation during the water washing process, the reactivity is greatly reduced. This fully demonstrates that the purification process of the present invention can achieve efficient removal of catalyst residues and effectively protect the terminal hydroxyl structure, ensuring its high reactivity.

[0065] Experiment Example 3: Effect of Membrane Separation Process Parameters on Impurity Removal

[0066] Using the reaction system of Example 1 as the research object, this study investigated the effects of three key parameters—membrane molecular weight cutoff, filtration pressure, and circulation flow rate—on the removal rate of low molecular weight impurities during membrane separation. Multiple levels were set for each parameter, while other membrane separation conditions remained constant. The removal rate of low molecular weight impurities under different parameters was measured, and the results are as follows:

[0067] Effect of membrane molecular weight cutoff (filtration pressure 0.2 MPa, circulation flow rate 1.0 m / s): 500 Da removal rate 92.5%; 800 Da removal rate 93.2%; 1000 Da removal rate 94.8%; 1500 Da removal rate 92.8%; 2000 Da removal rate 89.5%.

[0068] Effect of filtration pressure (membrane molecular weight cutoff 1000 Da, circulation flow rate 1.0 m / s): 0.1 MPa removal rate 88.6%; 0.2 MPa removal rate 94.8%; 0.3 MPa removal rate 95.1%; 0.4 MPa removal rate 94.5%; 0.5 MPa removal rate 93.8%.

[0069] Effect of circulation flow rate (membrane molecular weight cutoff 1000 Da, filtration pressure 0.2 MPa): 0.5 m / s removal rate 90.2%; 1.0 m / s removal rate 94.8%; 1.5 m / s removal rate 95.0%; 2.0 m / s removal rate 94.6%.

[0070] Results analysis: When the membrane molecular weight cutoff is 1000 Da, the removal rate of low molecular weight impurities reaches its peak. If the molecular weight is too small, some target products will be retained. If the molecular weight is too large, the impurities will not be removed completely. The impurity removal effect is optimal when the filtration pressure is 0.2-0.3 MPa and the circulation flow rate is 1.0-1.5 m / s. If the pressure is too low or the flow rate is too slow, the mass transfer efficiency will be low. If the pressure is too high or the flow rate is too fast, the membrane module will be easily worn, reducing the membrane service life.

[0071] Experiment Example 4: Product Application Performance Test

[0072] The HTPB-1 prepared in Example 1 of this invention and a commercially available control sample were used as binders to prepare solid rocket propellant slurries. The preparation process was as follows: binder + oxidant + curing agent + additives were mixed at a mass ratio of 30:60:5:5 and stirred under vacuum to form a homogeneous slurry. The gelation time and bonding strength of the slurry were tested, and the tensile strength and elongation at break of the cured propellant samples were tested. The results are shown in Table 3 below.

[0073] Adhesive sample gelation time / min Bond strength / MPa Tensile strength / MPa Elongation at break / % HTPB-1 45 2.85 3.22 355 control sample 68 1.92 2.56 288

[0074] As shown in Table 3, when the highly active hydroxyl-terminated polybutadiene prepared in this invention is used as a binder, the slurry gelation time is shorter, indicating that its reactivity with the curing agent is higher. The bonding strength, tensile strength and elongation at break of the cured product are significantly better than those of the commercially available control sample, proving that the product of this invention can effectively improve the mechanical properties and performance of downstream products and has good industrial application value.

[0075] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A process for preparing and purifying highly active hydroxyl-terminated polybutadiene, characterized in that, Includes the following steps: Step S1: Under inert gas protection, butadiene monomer is dissolved in an organic solvent to form a polymerization reaction system, and an anionic initiator and a polar structure modifier are added to carry out solution polymerization reaction, so that butadiene monomer undergoes anionic polymerization to form polybutadiene prepolymer with active chain ends; Step S2: After the polymerization reaction reaches the preset conversion rate, a hydroxyl end-capping agent containing epoxy groups is added to the polymerization system to cause the active chain end to undergo a ring-opening reaction with the epoxy groups, thereby forming a terminal hydroxyl structure at the end of the polybutadiene molecular chain. Step S3: During the end-capping reaction, a complexing purification agent is added to the system to remove residual metal catalysts and polar byproducts in situ through complexation or complexation sedimentation. Step S4: Perform membrane separation purification on the reaction system to remove low molecular weight byproducts and unreacted monomers through molecular weight selective permeation; Step S5: Solvent removal is performed under an inert atmosphere and low temperature to obtain a highly active hydroxyl-terminated polybutadiene product.

2. The preparation and purification process of highly active hydroxyl-terminated polybutadiene according to claim 1, characterized in that, The anionic initiator is an organolithium initiator, and its dosage is 0.01%-0.5% of the mass of the butadiene monomer. The organolithium initiator is selected from butyllithium, sec-butyllithium, tert-butyllithium, naphthalenelithium, or a combination thereof.

3. The preparation and purification process of highly active hydroxyl-terminated polybutadiene according to claim 1, characterized in that, The polarity modifier is used to adjust the microstructure ratio of polymer segments during butadiene polymerization. The amount of the polarity modifier added is 0.1%-5% of the mass of the butadiene monomer. The polarity modifier is selected from tetrahydrofuran, dimethoxyethane, diethylene glycol dimethyl ether, or a combination thereof.

4. The preparation and purification process of highly active hydroxyl-terminated polybutadiene according to claim 1, characterized in that, The organic solvent is selected from cyclohexane, n-hexane, toluene, cycloheptane or mixtures thereof, and the role of the solvent in the polymerization system includes reducing the viscosity of the system, improving the mass transfer efficiency and stabilizing the anionic polymerization reaction.

5. The preparation and purification process of highly active hydroxyl-terminated polybutadiene according to claim 1, characterized in that, The capping agent is an alcohol compound containing an epoxy group, and its addition amount is 0.5%-10% of the mass of the polybutadiene prepolymer. The capping agent is selected from epoxy ethanol, epoxy propanol, epoxy butanol, glycidyl ether or a combination thereof.

6. The preparation and purification process of highly active hydroxyl-terminated polybutadiene according to claim 1, characterized in that, The complexing purifier is a multidentate coordination compound, and its addition amount is 0.01%-1% of the mass of the reaction system. The complexing purifier can form a stable complex with metal ions, thereby achieving the removal of catalyst residues.

7. The preparation and purification process of highly active hydroxyl-terminated polybutadiene according to claim 1, characterized in that, The complexing purifying agent is selected from one or more of ethylenediaminetetraacetic acid, diethylenetriaminepentaacetic acid, organophosphonates, or polyhydroxy complexing agents.

8. The preparation and purification process of highly active hydroxyl-terminated polybutadiene according to claim 1, characterized in that, The membrane separation and purification step uses a nanofiltration or ultrafiltration membrane device for fractional separation. The molecular weight cutoff of the membrane is 500-2000 Da, and the impurity removal efficiency is improved by elution with a circulating solvent.

9. The preparation and purification process of highly active hydroxyl-terminated polybutadiene according to claim 1, characterized in that, During the membrane separation and purification process, the reaction system circulates in the membrane module at a flow rate of 0.5-2 m / s, and the filtration pressure is maintained at 0.1-0.5 MPa to achieve effective separation of low molecular weight byproducts and unreacted monomers.

10. The preparation and purification process of highly active hydroxyl-terminated polybutadiene according to claim 1, characterized in that, The membrane separation device has a molecular weight cutoff range of 500-2000 Da, a filtration pressure of 0.1-0.5 MPa, and a circulation flow rate of 0.5-2 m / s.

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