Polyhydroxy polybutadiene liquid rubber and preparation method thereof

Abstract

The invention relates to the technical field of preparation of polyhydroxy polybutadiene liquid rubber, and particularly discloses polyhydroxy polybutadiene liquid rubber and a preparation method thereof.The preparation method comprises the steps that hydroxyl-terminated polybutadiene, a sulfo-polyhydroxy compound and an initiator are weighed, the hydroxyl-terminated polybutadiene is added into an organic solvent, and an HTPB solution is obtained; the preparation method comprises the following steps: adding a sulfo-polyhydroxy compound and an initiator into an organic solvent to obtain an initiator-sulfo-polyhydroxy reagent solution; in a heating reflux state, adding the initiator-sulfo-polyhydroxy reagent solution into the HTPB solution through a peristaltic pump, and reacting to obtain the polyhydroxy polybutadiene liquid rubber. According to the method, HTPB is subjected to in-situ modification through a sulfydryl-alkene click chemistry method on the premise that the low-temperature performance, rheological property, molecular weight and distribution of the adhesive HTPB are not obviously changed, and the high-hydroxyl-value polybutadiene liquid rubber is obtained.

Description

Technical Field

[0001] The present invention relates to the technical field of the preparation of polyhydroxyl polybutadiene liquid rubber, and specifically relates to a polyhydroxyl polybutadiene liquid rubber and a preparation method thereof. Background Art

[0002] Currently, the common methods for preparing polyhydroxyl polyols based on the telechelic liquid rubber containing unsaturated olefins - HTPB are as follows: 1) epoxy - ring opening method; 2) hydroformylation method; 3) ozonolysis method; The above several preparation methods have the following characteristics: 1) The epoxy and ring opening of olefins require a reaction environment of strong acid or strong base; 2) The hydroformylation process requires the use of rhodium and cobalt catalysts to convert olefins into aldehyde groups, and then hydrogenate and reduce the aldehyde groups to polyols in a high-pressure environment; 3) Ozonolysis will form an ozone ring at the position of the olefin double bond, and then the unstable ozone ring is opened and broken to form polyols;

[0003] In summary, the current preparation methods for preparing polyhydroxyl polyols based on the telechelic liquid rubber containing unsaturated olefins - HTPB generally require the use of expensive metal catalysts, high pressure and high temperature, strong acid and strong base environments, and long reaction times. The strong oxidizing property of ozone makes the oxidative cracking process poorly controllable, unable to control the product molecular weight, and the molecular weight distribution is also non-uniform. The above deficiencies make it difficult to realize the in-situ preparation of polyhydroxyl polybutadiene based on industrial-grade HTPB raw materials, and cannot meet the scientific research and production use requirements in specific fields. Summary of the Invention

[0004] In view of the above problems, the first object of the present invention is to provide a preparation method of polyhydroxyl polybutadiene liquid rubber. In this method, the HTPB is in-situ modified by the thiol - ene click chemistry method to obtain a polyhydroxyl polybutadiene liquid rubber with a high hydroxyl value without significantly changing the low-temperature performance, rheological properties, molecular weight and its distribution of the binder HTPB.

[0005] The second object of the present invention is to provide a polyhydroxyl polybutadiene liquid rubber, the molecular weight and its distribution and network structure of which do not deviate significantly from those of the raw material terminal hydroxyl polybutadiene (HTPB).

[0006] The first technical solution adopted by the present invention is: a preparation method of polyhydroxyl polybutadiene liquid rubber, comprising the following steps:

[0007] S1: Weigh terminal hydroxyl polybutadiene, thio polyhydroxyl compound and initiator, add the terminal hydroxyl polybutadiene into an organic solvent to obtain an HTPB solution; add the thio polyhydroxyl compound and initiator into an organic solvent to obtain an initiator - thio polyhydroxyl reagent solution;

[0008] S2: Under the condition of heating under reflux, add the initiator - thio polyhydroxy reagent solution to the HTPB solution through a peristaltic pump, and react to obtain polyhydroxy polybutadiene liquid rubber.

[0009] Preferably, the thio polyhydroxy compound is one of alcohol compounds or polyol compounds substituted by mono-mercapto or multi-mercapto, and polyol acid compounds substituted by mono-mercapto or multi-mercapto.

[0010] Preferably, the alcohol compounds or polyol compounds substituted by mono-mercapto or multi-mercapto include: one of thioglycerol, thioxylitol, thiosorbitol, thiopentaerythritol, thiopolyvinyl alcohol, thiopolyethylene glycol, thiomannitol, thioerythritol, and thio fatty alcohol.

[0011] Preferably, the polyol acid compounds substituted by mono-mercapto or multi-mercapto include: one of thiocitric acid, thiolactic acid, and thiotartaric acid.

[0012] Preferably, the initiator is a free radical initiator, including one of benzoyl peroxide, lauroyl peroxide, azobisisobutyronitrile, azodiisooctanenitrile, cumene hydroperoxide, tert-butyl hydroperoxide, di-tert-butyl peroxide, dicumyl peroxide, tert-butyl perbenzoate, tert-butyl peroxy pivalate, methyl ethyl ketone peroxide, cyclohexanone peroxide, diisopropyl peroxydicarbonate, dicyclohexyl peroxydicarbonate, and persulfate.

[0013] Preferably, the addition amount of the thio polyhydroxy compound is 10% - 25% of the amount of vinyl substance contained in the hydroxyl-terminated polybutadiene; the mass ratio of the thio polyhydroxy compound to the hydroxyl-terminated polybutadiene is 3.9% - 7.9%.

[0014] Preferably, the organic solvent includes one or more of dichloromethane, acetonitrile, cyclohexane, chloroform, benzene, toluene, o-xylene, dichlorobenzene, trichlorobenzene, and tetrahydrofuran.

[0015] Preferably, the mass fraction of the HTPB solution is 45% - 55%; the mass fraction of the initiator in the initiator - thio polyhydroxy reagent solution is 0.067% - 0.733%; the mass fraction of the thio polyhydroxy compound in the initiator - thio polyhydroxy reagent solution is 1.20% - 2.93%.

[0016] Preferably, step S2 includes: under the condition of heating under reflux at 65°C - 75°C, add the initiator - thio polyhydroxy reagent solution to the HTPB solution through a peristaltic pump, and react for 2.5 h - 4 h to obtain polyhydroxy polybutadiene liquid rubber.

[0017] The second technical solution adopted in the present invention is: a polyhydroxypolybutadiene liquid rubber prepared by the preparation method described in the first technical solution, and the hydroxyl value of the polyhydroxypolybutadiene liquid rubber is 0.72 mmol / g to 3.46 mmol / g.

[0018] Advantages of the above technical solution:

[0019] (1) In the preparation method of a polyhydroxypolybutadiene liquid rubber provided by the present invention, through the thiol-ene click chemistry method, without significantly changing the low-temperature performance, rheological properties, molecular weight and its distribution of the binder HTPB, in-situ modification of HTPB is carried out to obtain a polybutadiene liquid rubber with a high hydroxyl value; the molecular weight and its distribution, and network structure of the polyhydroxypolybutadiene liquid rubber do not deviate significantly from those of the raw material terminal hydroxyl polybutadiene (HTPB).

[0020] (2) The preparation method of a polyhydroxypolybutadiene liquid rubber provided by the present invention is realized by the radical addition reaction between terminal hydroxyl polybutadiene and thio polyhydroxyl compounds. By controlling the addition amount of the radical initiator and the radical transfer path, the generation of by-products such as disulfides caused by the homopolymerization reaction (chain growth process) of mercapto radicals and macromolecular radicals during the reaction is avoided, and the molecular weight and its distribution, and network structure of the prepared polyhydroxypolybutadiene do not deviate significantly from those of the raw material terminal hydroxyl polybutadiene (HTPB): the hydroxyl value of the product PHPB can be adjusted within the range of 0.72 mmol / g to 3.46 mmol / g, the number-average molecular weight can be adjusted within the range of 3500 g / mol to 4970 g / mol, and the molecular weight distribution is between 1.71 and 1.85. Since the thio polyhydroxyl compound greatly reduces the consumption of olefin isomers in the HTPB structure, while obtaining a high-hydroxyl product, the glass transition temperature does not rise sharply, and the rheological properties basically remain unchanged, which has good application prospects in specific fields such as composite solid propellants and liners.

[0021] (3) In the research and application fields of composite solid propellants and liners, the low-temperature and rheological properties of the binder determine the application scenarios and process conditions of the propellant and the liner, which are very important performance indicators. Therefore, the present invention provides a method for in-situ modification of HTPB to obtain a polybutadiene liquid rubber with a high hydroxyl value without significantly changing the low-temperature performance, rheological properties, molecular weight and its distribution of the binder HTPB. Due to the feasibility and high efficiency of the thiol-ene click chemistry, the PHPB prepared by this method has broad application prospects in the fields of composite solid propellants and liners.

[0022] (4) The thiol-ene click chemistry used in the present invention has the characteristics of mild reaction conditions and high efficiency, and can react with the vast majority of olefins through free radical addition or Michael addition. These characteristics make it possible to in-situ prepare polyhydroxylated polybutadiene from the three olefin isomers contained in the industrial-grade HTPB binder matrix. Moreover, compared with the preparation of polyhydroxylated polybutadiene liquid rubber by reacting mercaptoethanol with hydroxyl-terminated polybutadiene liquid rubber, the microstructure of the product polyhydroxylated polybutadiene (PHPB) (i.e., the relative content of olefin isomers) will change significantly, and compared with the raw material HTPB, the glass transition temperature of the product will increase significantly and the rheological properties will deteriorate. Without significantly changing the low-temperature properties, rheological properties, molecular weight and its distribution of the binder HTPB, the present invention in-situ modifies HTPB to obtain high-hydroxyl-value polybutadiene liquid rubber, that is, the molecular weight and its distribution and network structure of the prepared polyhydroxylated polybutadiene liquid rubber do not deviate significantly from the raw material hydroxyl-terminated polybutadiene (HTPB). BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a schematic diagram of an ideal stepwise growth chain transfer reaction process in the regulation of the free radical addition reaction path of thiol-ene click chemistry provided by an embodiment of the present invention;

[0024] Figure 2 It is a schematic diagram of the synthesis route of polyhydroxylated polybutadiene provided by an embodiment of the present invention;

[0025] Figure 3 It is an infrared characterization spectrum of polyhydroxylated polybutadiene provided by an embodiment of the present invention;

[0026] Figure 4 It is the glass transition temperature of polyhydroxylated polybutadiene provided by an embodiment of the present invention;

[0027] Figure 5 It is a thermal stability characterization spectrum of polyhydroxylated polybutadiene provided by an embodiment of the present invention;

[0028] Figure 6 It is a rheological property test of polyhydroxylated polybutadiene provided by an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0029] The present invention will be further described below through specific embodiments. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several modifications and improvements can also be made, and these should also be regarded as belonging to the protection scope of the present invention.

[0030] The content not detailedly described in the specification of the present invention belongs to the well-known technology of those skilled in the art.

[0031] The present invention discloses a preparation method of polyhydroxy polybutadiene liquid rubber, which comprises the following steps:

[0032] S1: Weigh hydroxyl-terminated polybutadiene (HTPB), thio polyhydroxy compound and initiator. Add the hydroxyl-terminated polybutadiene (HTPB) into an organic solvent to obtain an HTPB solution; add the thio polyhydroxy compound and the initiator into an organic solvent to obtain an initiator-thio polyhydroxy reagent solution.

[0033] Wherein, before step S1, it also includes determining the amount of vinyl substances contained in the hydroxyl-terminated polybutadiene (HTPB) by nuclear magnetic or infrared quantitative analysis method. The addition amount of the thio polyhydroxy compound is 10% - 25% of the amount of vinyl substances contained in the HTPB; the mass ratio of the thio polyhydroxy compound to the HTPB is 3.9% - 7.9%.

[0034] The HTPB refers to an industrial-grade product obtained by a free radical polymerization method, which contains three kinds of olefin isomer structures of 1,4-cis (cis), 1,2-vinyl (vinyl), and 1,4-trans (trans). The relative content of each olefin isomer is generally not higher than 50%. Among them, the relative content of 1,4-cis is 29% - 37%, the relative content of 1,2-vinyl is 19% - 20%, and the relative content of 1,4-trans is 42% - 49%; the number average molecular weight is 3000 g / mol - 3600 g / mol, and the hydroxyl value is 0.65 mmol / g - 0.8 mmol / g.

[0035] The thio polyhydroxy compound is any one of alcohol compounds or polyol compounds substituted by monothiol or polythiol, and polyol acid compounds substituted by monothiol or polythiol; examples of alcohol compounds or polyol compounds substituted by monothiol or polythiol include: thioglycerol, thioxylitol, thiosorbitol, thiopentaerythritol, thiopolyvinyl alcohol, thiopolyethylene glycol, thiomannitol, thioerythritol, thio fatty alcohol, etc.; examples of polyol acid compounds substituted by monothiol or polythiol include: thiocitric acid, thiolactic acid, thiotartaric acid, etc.

[0036] The initiator is a free radical initiator, including any one of benzoyl peroxide, lauroyl peroxide, azobisisobutyronitrile, azobis(2,4-dimethylvaleronitrile), cumene hydroperoxide, tert-butyl hydroperoxide, di-tert-butyl peroxide, diisopropylbenzene peroxide, tert-butyl perbenzoate, tert-butyl peroxypivalate, methyl ethyl ketone peroxide, cyclohexanone peroxide, diisopropyl peroxydicarbonate, dicyclohexyl peroxydicarbonate, persulfate.

[0037] The organic solvent includes one or more of dichloromethane, acetonitrile, cyclohexane, chloroform, benzene, toluene, o-xylene, dichlorobenzene, trichlorobenzene, and tetrahydrofuran.

[0038] The mass fraction of the HTPB solution is 45% - 55%; the mass fraction of the initiator in the initiator - thiol polyhydroxy reagent solution is 0.067% - 0.733% (i.e., 0.1 / 150 - 1.1 / 150); the mass fraction of the thiol polyhydroxy compound in the initiator - thiol polyhydroxy reagent solution is 1.20% - 2.93% (i.e., 1.8 / 150 - 4.4 / 150).

[0039] S2: Under the condition of heating and refluxing at 65°C - 75°C, add the initiator - thiol polyhydroxy reagent solution to the HTPB solution through a peristaltic pump (the flow rate of the peristaltic pump is controlled at 0.8 mL / min - 1.4 mL / min), and react for 2.5 h - 4 h to obtain polyhydroxy polybutadiene liquid rubber.

[0040] Step S2 further includes: subjecting the reaction solution to vacuum distillation until a small amount of solvent remains, pouring it into an anti-solvent, fully stirring, washing, and separating, retaining the solid precipitate, then adding an excessive amount of organic solvent (one or more of dichloromethane, acetonitrile, cyclohexane, chloroform, benzene, toluene, o-xylene, dichlorobenzene, trichlorobenzene, and tetrahydrofuran) to dissolve it, performing vacuum distillation, and drying it under vacuum at 55°C - 65°C for 12 h - 24 h to obtain a purified product of polyhydroxy polybutadiene liquid rubber (PHPB); the anti-solvent is an alcohol solvent, such as methanol, ethanol, etc., and the alcohol solvent is pre-cooled at 2°C - 8°C, and the washing and separation operations are repeated 3 times.

[0041] The present invention uses the thiol-ene click chemistry method to in-situ modify HTPB and obtain high-hydroxyl-value polybutadiene liquid rubber without significantly changing the low-temperature properties, rheological properties, molecular weight, and its distribution of the binder HTPB. The ideal step-growth chain transfer reaction process in the regulation of the free radical addition reaction path of the thiol-ene click chemistry is as Figure 1 shown.

[0042] The present invention also discloses a polyhydroxy polybutadiene liquid rubber prepared by the above preparation method. The hydroxyl value of the polyhydroxy polybutadiene liquid rubber is adjustable within the range of 0.72 mmol / g - 3.46 mmol / g, the number-average molecular weight is adjustable within the range of 3500 g / mol - 4970 g / mol, the molecular weight distribution is between 1.71 - 1.85, the glass transition temperature is -82°C - -69°C, and the action sites of the thiol-ene click reaction are two kinds of olefin isomers, namely 1,4-cis (cis) and 1,2-vinyl (vinyl).

[0043] Example 1

[0044] Weigh 50.0 g of HTPB, dissolve it fully with 105.0 g of THF to prepare an HTPB solution, transfer the HTPB solution into a two-necked round-bottom flask, and reflux at 70 °C;

[0045] Weigh 3.2 g of thioglycerol and 1.0 g of azobisisobutyronitrile, dissolve them fully with 150 g of THF to prepare an initiator - thiopolyhydroxy reagent solution;

[0046] Slowly add the initiator - thiopolyhydroxy reagent solution to the HTPB solution through a peristaltic pump, the flow rate of the peristaltic pump is 1.2 mL / min, and the reaction time is 3 h;

[0047] After the reaction is completed, distill the reaction solution under reduced pressure at 70 °C until a small amount of solvent remains, then pour it into excessive ice methanol for washing and separation, repeat the operation 3 times, collect the white solid product, dissolve it with excessive THF and then distill it under pressure until no obvious solvent remains, and dry it under vacuum at 60 °C overnight to obtain polyhydroxypolybutadiene liquid rubber (PHPB). The measured hydroxyl value is 1.73 gmmol / g; The synthesis route of polyhydroxypolybutadiene liquid rubber is as Figure 2 shown.

[0048] Perform infrared characterization on the raw material HTPB and the prepared polyhydroxypolybutadiene liquid rubber (PHPB) respectively to obtain the infrared characterization spectra as Figure 3 shown; It can be seen from Figure 3 that compared with the raw material HTPB, the infrared spectrum of PHPB shows the following obvious changes: First, the stretching vibration characteristic peak of the hydroxyl O―H at 3380 cm -1 is significantly strengthened and the peak shape becomes wider, indicating that the product has a polyhydroxy structure. At the same time, the characteristic peak intensity of the stretching vibration of the primary hydroxyl C―O at 1070 cm -1 is strengthened, indicating that the hydroxyl content of PHPB has increased relative to HTPB; The characteristic absorption peaks at 2915 cm -1 and 1440 cm -1 are the characteristic absorption peaks of methylene. Due to the introduction of a mercapto reagent (containing methylene) into the product structure, the intensity of the above two characteristic absorption peaks increases significantly. At the same time, the characteristic absorption peak of methyl at 2980 cm -1 has almost invisible relative intensity attenuation. Infrared characterization proves that PHPB has been successfully prepared.

[0049] Measure the glass transition temperatures of the raw material HTPB, polyhydroxypolybutadiene liquid rubber (PHPB), and mixtures of PHPB and HTPB with different mass ratios (mass ratios are 1:3 and 3:1) respectively by differential scanning calorimetry (DSC) method. The test results are as Figure 4 shown; It can be seen from Figure 4It can be seen that the glass transition temperatures of the raw material HTPB and the product PHPB are -82.2 °C and -69.2 °C respectively. Since a thioether structure is introduced into the side chain of HTPB, and the presence of a large number of hydroxyl groups enhances the hydrogen bond interaction between different main chains, the flexibility and mobility of the PHPB main chain are reduced compared with HTPB, ultimately leading to an increase in the glass transition temperature of PHPB. As the mass fraction of PHPB in the PHPB / HTPB mixture increases, the glass transition temperature rises slowly, and the curve always shows a single step shape, indicating that the mixture has a single glass transition temperature, that is, under different mixing ratio states, PHPB and HTPB are completely miscible and compatible.

[0050] The thermal stabilities of the raw material HTPB and the product polyhydroxypolybutadiene liquid rubber (PHPB) were analyzed by DSC-TG, and the measurement results are as Figure 5 shown; from Figure 5 it can be seen that there is only 1 weight loss step in the thermogravimetric curves of HTPB and PHPB, and the initial weight loss temperature (T 5％ ), the half-weight loss temperature (T 50％ ), and the maximum weight loss rate temperature (T max ) are almost the same, which are 305.2 °C, 454.5 °C, and 374.2 °C respectively, indicating that the introduction of the mercapto reagent does not cause a loss of thermal stability, and the initial decomposition temperature is higher than 300 °C, and PHPB has high thermal stability.

[0051] The rheological properties of the raw material HTPB, the product polyhydroxypolybutadiene liquid rubber (PHPB), and different ratios of PHPB and HTPB mixtures [(PHPB / HTPB = 1:2), (PHPB / HTPB = 1:1), (PHPB / HTPB = 2:1), (PHPB / HTPB = 3:1)] were measured by a rotational viscometer, and the measurement results are as Figure 6 shown; from Figure 6It can be seen that at 40 °C, the apparent viscosity of PHPB is about 3 times that of HTPB, which are 14.08 Pa·s and 4.68 Pa·s respectively. At 50 °C, the apparent viscosity of PHPB is still 2.85 times that of HTPB, which are 8.07 Pa·s and 2.83 Pa·s respectively. By blending PHPB and HTPB in different proportions, the viscosity can be significantly reduced. The viscosity can be reduced to 5.93 Pa·s at 40 °C and 3.64 Pa·s at 50 °C. The viscous flow activation energy of PHPB is 40.08 kJ, which is higher than that of HTPB at 35.64 kJ. This is due to the fact that the higher hydrogen bond density in PHPB causes a decrease in the movement ability of molecular segments. Moreover, when the temperature rises to 80 °C, the apparent viscosity of PHPB finally drops to the same level as that of HTPB. This is because the change in the apparent viscosity of PHPB depends on the strength of the hydroxyl group, that is, the intermolecular hydrogen bond interaction. When the temperature rises and the hydrogen bonds are partially dissociated, the movement ability of the PHPB molecular chain is enhanced and the apparent viscosity decreases. When the temperature condition reaches the state where the hydrogen bonds are completely dissociated, the apparent viscosity of PHPB approaches that of HTPB.

[0052] Example 2

[0053] Weigh 50.0 g of HTPB, and dissolve it thoroughly with 105.0 g of THF to prepare an HTPB solution. Pour the HTPB solution into a two-necked round-bottom flask and reflux at 70 °C.

[0054] Weigh 1.95 g of thio-polyethylene glycol and 0.61 g of benzoyl peroxide, and dissolve them thoroughly with 150 g of THF to prepare an initiator - thio-polyhydroxy reagent solution.

[0055] Slowly drip the initiator - thio-polyhydroxy reagent solution into the HTPB solution through a peristaltic pump. The flow rate of the peristaltic pump is 1.2 mL / min, and the reaction time is 2.5 h.

[0056] After the reaction is completed, distill the reaction solution under reduced pressure at 70 °C until a small amount of solvent remains. Then pour it into excessive ice methanol for washing and separation, and repeat the operation 3 times. Collect the white solid product, dissolve it with excessive THF, and then distill it under pressure until no obvious solvent remains. Dry it in vacuum at 60 °C overnight to obtain polyhydroxy polybutadiene liquid rubber (PHPB).

[0057] Example 3

[0058] Weigh 50.0 g of HTPB, and dissolve it thoroughly with 105.0 g of THF to prepare an HTPB solution. Pour the HTPB solution into a two-necked round-bottom flask and reflux at 70 °C.

[0059] Weigh 3.95 g of thio-citric acid and 1.1 g of tert-butyl hydroperoxide, and dissolve them thoroughly with 150 g of THF to prepare an initiator - thio-polyhydroxy reagent solution.

[0060] The initiator - thio polyhydroxy reagent solution was slowly added dropwise to the HTPB solution through a peristaltic pump at a flow rate of 1.2 mL / min for a reaction time of 2.5 h;

[0061] After the reaction was completed, the reaction solution was distilled under reduced pressure at 70 °C until a small amount of solvent remained, and then poured into excessive ice methanol for washing and separation. The operation was repeated 3 times, and the white solid product was collected. Then it was dissolved in excessive THF and distilled under pressure until no obvious solvent remained, and vacuum dried at 60 °C overnight to obtain polyhydroxy polybutadiene liquid rubber (PHPB).

[0062] The present invention has been described in detail above in combination with specific embodiments and exemplary examples. The above description is exemplary and not exhaustive, and is not limited to the disclosed embodiments; the above description should not be construed as a limitation of the present invention. Those skilled in the art understand that without departing from the spirit and scope of the present invention, various equivalent substitutions, modifications or improvements can be made to the technical solutions and their implementation manners of the present invention, and these all fall within the scope of the present invention; the protection scope of the present invention is subject to the appended claims.

Claims

1. A preparation method of polyhydroxyl polybutadiene liquid rubber, characterized in that, It includes the following steps: S1: Weigh hydroxy-terminated polybutadiene, thiol polyhydroxy compound and initiator. Add the hydroxy-terminated polybutadiene into an organic solvent to obtain an HTPB solution; add the thiol polyhydroxy compound and the initiator into an organic solvent to obtain an initiator-thiol polyhydroxy reagent solution. S2: Under the condition of heating and refluxing, add the initiator-thiol polyhydroxy reagent solution to the HTPB solution through a peristaltic pump, and react to prepare a polyhydroxy polybutadiene liquid rubber.

2. The preparation method of the polyhydroxyl polybutadiene liquid rubber according to claim 1, characterized in that, The thiol polyhydroxy compound is one of alcohol compounds or polyol compounds substituted with mono-mercapto or multi-mercapto, or polyol acid compounds substituted with mono-mercapto or multi-mercapto.

3. The preparation method of the polyhydroxyl polybutadiene liquid rubber according to claim 2, characterized in that, The alcohol compounds or polyol compounds substituted with mono-mercapto or multi-mercapto include one of thioglycerol, thiomannitol, thiosorbitol, thiopentaerythritol, thiopolyvinyl alcohol, thiopolyethylene glycol, thiomannitol, thioerythritol, and thiol fatty alcohol.

4. The preparation method of the polyhydroxyl polybutadiene liquid rubber according to claim 2, wherein The polyol acid compounds substituted with mono-mercapto or multi-mercapto include one of thiocitric acid, thiolactic acid, and thiotartaric acid.

5. The preparation method of the polyhydroxyl polybutadiene liquid rubber according to claim 1, characterized in that, The initiator is a free radical initiator, including one of benzoyl peroxide, lauroyl peroxide, azobisisobutyronitrile, azodiisooctanenitrile, cumene hydroperoxide, tert-butyl hydroperoxide, di-tert-butyl peroxide, dicumyl peroxide, tert-butyl peroxybenzoate, tert-butyl peroxypivalate, methyl ethyl ketone peroxide, cyclohexanone peroxide, diisopropyl peroxydicarbonate, dicyclohexyl peroxydicarbonate, and persulfate.

6. The preparation method of the polyhydroxyl polybutadiene liquid rubber according to claim 1, wherein, The addition amount of the thiol polyhydroxy compound is 10% - 25% of the amount of vinyl substance contained in the hydroxy-terminated polybutadiene; the mass ratio of the thiol polyhydroxy compound to the hydroxy-terminated polybutadiene is 3.9% - 7.9%.

7. The preparation method of the polyhydroxyl polybutadiene liquid rubber according to claim 1, wherein, The organic solvent includes one or more of dichloromethane, acetonitrile, cyclohexane, chloroform, benzene, toluene, o-xylene, dichlorobenzene, trichlorobenzene, and tetrahydrofuran.

8. The preparation method of the polyhydroxyl polybutadiene liquid rubber according to claim 1, wherein, The mass fraction of the HTPB solution is 45% - 55%; the mass fraction of the initiator in the initiator-thiol polyhydroxy reagent solution is 0.067% - 0.733%; the mass fraction of the thiol polyhydroxy compound in the initiator-thiol polyhydroxy reagent solution is 1.20% - 2.93%.

9. The preparation method of the polyhydroxypolybutadiene liquid rubber according to claim 1, characterized in that, The step S2 includes: Under the condition of heating and refluxing at 65°C - 75°C, add the initiator-thiol polyhydroxy reagent solution to the HTPB solution through a peristaltic pump, and react for 2.5 h - 4 h to prepare a polyhydroxy polybutadiene liquid rubber.

10. A polyhydroxyl polybutadiene liquid rubber prepared by the preparation method according to any one of claims 1 to 9, characterized in that, The hydroxyl value of the polyhydroxy polybutadiene liquid rubber is 0.72 mmol / g - 3.46 mmol / g.

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