Low-mooney-viscosity random 1,2-polybutadiene, and method of making and use thereof

Abstract

This invention belongs to the field of synthetic rubber preparation technology, specifically relating to low Mooney viscosity atactic 1,2-polybutadiene, its preparation method, and its applications. The preparation method of the low Mooney viscosity atactic 1,2-polybutadiene includes the following steps: under a protective gas atmosphere, adding a phosphate ester compound to a molybdenum compound, aging and cooling, then adding toluene to obtain a main catalyst; placing a trialkylaluminum alkane solution in an ice-water bath, adding aryloxy ligands dropwise to the container, and reacting in an ice-water bath to obtain a co-catalyst; dissolving butadiene in an alkane solution, adding the co-catalyst, main catalyst, activator, and molecular weight regulator respectively, and carrying out a polymerization reaction to obtain low Mooney viscosity atactic 1,2-polybutadiene. This invention provides a method for preparing low Mooney viscosity atactic 1,2-polybutadiene with high conversion rate; the obtained 1,2-PB has a low Mooney value and a high 1,2-structure content; it can be applied to rubber additives and damping materials to improve their performance.

Description

Technical Field

[0001] This invention belongs to the field of synthetic rubber preparation technology, specifically relating to low Mooney viscosity random 1,2-polybutadiene, its preparation method and application. Background Technology

[0002] High-vinyl polybutadiene rubber (1,2-PB) possesses excellent properties such as high wet skid resistance, low heat generation, low rolling resistance, and aging resistance, making it a suitable rubber material for manufacturing safe and energy-efficient "green" tires. However, 1,2-PB has a high vinyl content and large molecular weight, resulting in a high Mooney viscosity (typically greater than 80), which leads to poor feedability and blendability with other rubbers during processing. Additionally, 1,2-PB exhibits high damping properties and can be used as a sound-absorbing and vibration-damping material after foaming; however, the high Mooney viscosity can negatively impact cell quality and mechanical properties. Low Mooney viscosity (20–40) 1,2-PB can also be used as a rubber additive to improve the processing and mechanical properties of rubber, while also enhancing solvent extraction, wet skid resistance, aging resistance, and damping properties. Therefore, developing a low Mooney viscosity 1,2-PB is of great significance for expanding its application in tires and rubber products.

[0003] CN114591454A discloses an olefin metathesis technology. The polymerization catalyst consists of a main catalyst (a complex of molybdenum compound and phosphate ester or alcohol) and a co-catalyst (a complex of alkylaluminum and phenolic compound). Although it can reduce the molecular weight of 1,2-PB, the metathesis catalyst is expensive, costing tens of thousands of yuan per ton of rubber catalyst, making industrial production difficult. Currently, adjusting the molecular weight and distribution of 1,2-PB is the main method to reduce its Mooney viscosity. Molybdenum-based catalysts are commonly used in the catalytic synthesis of random 1,2-PB, possessing not only high activity but also a high 1,2-structure content of up to 80%. EP0483572A1 discloses a catalytic system using molybdenum compounds substituted with alkyl acids (10-30 carbon atoms) or aromatic carboxylic acids (7-30 carbon atoms) and alkyl-substituted or allyl-substituted phenols to prepare 1,2-PB with a molecular weight of 250,000, but the molecular weight is still high, and the Mooney viscosity is greater than 60.

[0004] US4912182A discloses that modifying trialkylaluminum compounds with allylphenol as an additive can reduce the molecular weight of high-vinyl polybutadiene, bringing it within the range required for industrial applications. However, the product prepared by this catalytic system is syndio-1,2-PB with a melting point of 195–215°C, which is suitable for use as plastics but difficult to apply to rubber.

[0005] CN104530282A discloses a method for preparing random 1,2-polybutadiene, using butadiene as a monomer and employing a catalyst comprising the following components: a) an organophosphate iron compound solution; b) alkyl aluminum and / or hydrogenated alkyl aluminum; c) an electron donor, wherein the electron donor is a phosphorus-containing organic compound and / or a nitrogen-containing organic compound and / or an oxygen-containing organic compound. Although this method improves the conversion rate, the 1,2-structure content is relatively low.

[0006] Tang Xueming (Wang Guangxin, Xu Ling, Ma Wenhua, Yang Yuwei, Tang Xueming, Effects of allyl halides on the kinetics of butadiene polymerization catalyzed by Mo(Ⅳ) system, Synthetic Rubber Industry, 1988, 11(5): 380-384) studied the effects of more than 20 polar additives on the polymerization system. The results showed that in the molybdenum catalytic system, the double bonds on allyl halides have similar electronegativity to butadiene, and chain transfer can occur, resulting in excellent molecular weight regulation. The molecular weight can be reduced to below 200,000, and the Mooney viscosity can be reduced to below 40. Among them, the molecular weight regulation ability of allyl halides is: allyl bromide > allyl iodine > allyl chloride. However, after allyl iodine and allyl chloride are added to the catalytic system, iodine and chlorine have a slowing effect on polymerization, which reduces the conversion rate of the system. Although allyl bromide can be used to prepare 1,2-PB with a Mooney viscosity of less than 40 without affecting its activity, the boiling point of allyl bromide is 70°C, which is very close to the boiling point of the solvent oil n-hexane (69°C). This makes it very difficult to remove the solvent oil later, affecting the recycling of the solvent oil and hindering industrial production. Summary of the Invention

[0007] The technical problem to be solved by the present invention is to overcome the above-mentioned defects of the prior art and provide a method for preparing low Mooney viscosity random 1,2-polybutadiene with high conversion rate and high solvent recovery rate; the obtained 1,2-PB Mooney viscosity is 20-40 and the 1,2-structure content is high; it can be applied to rubber additives and damping materials to improve their mechanical properties and processing performance.

[0008] The method for preparing low Mooney viscosity random 1,2-polybutadiene according to the present invention includes the following steps:

[0009] S1. Preparation of the main catalyst

[0010] Under a protective atmosphere, phosphate ester compounds were added to the molybdenum compound, aged at 70–80 °C for 30–60 min, cooled to room temperature, and diluted to obtain the main catalyst.

[0011] The molybdenum compound is a pentavalent molybdenum compound, and more preferably molybdenum pentachloride.

[0012] S2, Preparation of co-catalyst

[0013] Under a protective atmosphere, a trialkylaluminum alkane solution is immersed in an ice-water bath at 0–5°C, and aryloxy ligands are added dropwise to the container while controlling the pressure to not exceed 0.2 MPa. After the addition is complete, the reaction is carried out in the ice-water bath for 4–8 hours to obtain a co-catalyst.

[0014] Preparation of S3, low Mooney viscosity random 1,2-polybutadiene

[0015] Butadiene CH2=CH-CH=CH2(Bd) was dissolved in a solvent, and a co-catalyst, a main catalyst, an activator, and a molecular weight regulator were added respectively. The mixture was polymerized at 50–80 °C for 240–360 min to obtain low Mooney viscosity random 1,2-polybutadiene.

[0016] The diluent used in S1 is toluene or xylene, which is a solvent that has been refluxed with sodium wire. Its function is to remove water from the solvent and improve the conversion rate.

[0017] In S1, the phosphate ester compound is triethyl phosphate or tripropyl phosphate, and the molar ratio of the phosphate ester compound to the molybdenum compound is 2 to 5.

[0018] In S2, the trialkylaluminum is triethylaluminum, tributylaluminum, or tripropylaluminum.

[0019] The preferred dropping speed in S2 is 1 drop / second.

[0020] The aryloxy ligand in S2 is 3-methylphenol; the molar ratio of the aryloxy ligand to trialkylaluminum is 0.8 to 1.2, more preferably 1.

[0021] The trialkylaluminum alkane solution in S2 is preferably a trialkylaluminum n-hexane solution.

[0022] The solvent in S3 is hydrogenated gasoline, n-hexane, or cyclohexane, preferably n-hexane.

[0023] The amount of the main catalyst added in S3, calculated as molybdenum (Mo), has a molar ratio of 1.5 × 10⁻⁶ to butadiene. -4 ~3×10 -4 The amount of co-catalyst added is calculated as aluminum (Al), and the molar ratio of co-catalyst to main catalyst is 8 to 16.

[0024] The activator in S3 is 1-methylnaphthalene, 1-ethylnaphthalene, or 1-propylnaphthalene, and the volume ratio of activator to solvent is 0.1 to 0.17.

[0025] The molecular weight regulator in S3 is 3-bromo-2-methylpropene or trans-1-bromo-2-butene or a mixture of both, and its amount is calculated as bromine. The molar ratio of the molecular weight regulator to the main catalyst is 3 to 10. Preferably, the molecular weight regulator is first dissolved in n-hexane to a concentration of 0.017 mol / mL.

[0026] A low Mooney viscosity atactic 1,2-polybutadiene is prepared by the aforementioned method for preparing low Mooney viscosity atactic 1,2-polybutadiene.

[0027] An application of low Mooney viscosity random 1,2-polybutadiene: used in rubber additives and damping materials to improve their processing and mechanical properties.

[0028] Specifically, the preparation method of the low Mooney viscosity random 1,2-polybutadiene includes the following steps:

[0029] S1. Preparation of the main catalyst

[0030] Under nitrogen protection, pentavalent molybdenum compounds were added to a preparation container, followed by phosphate ester compounds at a molar ratio of 2–5 to molybdenum. The mixture was aged at 70–80°C for 30–60 minutes, cooled to room temperature, and then diluted with sodium wire-reflux-treated toluene or xylene to a molybdenum concentration of 5 × 10⁻⁶. -4 The main catalyst was obtained by applying mol / mL.

[0031] S2, Preparation of co-catalyst

[0032] Trialkylaluminum was dissolved in n-hexane solution under nitrogen protection, and the molar concentration of trialkylaluminum was 4.2 × 10⁻⁶. - 4 mol / mL, place in an ice-water bath, control the temperature at 0-5℃, add 3-methylphenol dropwise to the container at a rate of 1 drop / second, control the pressure to not exceed 0.2MPa, after the addition is complete, place the container in an ice-water bath to react for 4-8 hours to obtain the co-catalyst;

[0033] Preparation of S3, low Mooney viscosity random 1,2-polybutadiene

[0034] Butadiene (Bd) was dissolved in a solvent, and a co-catalyst, main catalyst, activator, and molecular weight regulator were added separately. The polymerization reaction was carried out at 50–80 °C for 240–360 min to obtain low Mooney viscosity random 1,2-polybutadiene. The Mooney viscosity could be further adjusted by modifying the polymerization temperature, the amount of catalyst, activator, and molecular weight regulator.

[0035] The principle behind adjusting the molecular weight of allyl bromide lies in the inductive effect of bromine, which makes the electronegativity of its double bond close to that of the double bond in butadiene. This allows allyl bromide to coordinate with the active center, leading to chain transfer and a decrease in molecular weight. However, the boiling point of allyl bromide is close to that of the alkane solvent used, making solvent recovery difficult. Using compounds containing a bromo-allyl structure but with a larger molecular weight seems to be an effective way to solve the azeotropic problem with the solvent. However, the large molecular weight of bromo-allyl compounds results in significant steric hindrance, leading to weak coordination ability and poor molecular weight adjustment when used as molecular weight regulators.

[0036] The present invention discloses a method for preparing low Mooney viscosity random 1,2-polybutadiene rubber, wherein 3-bromo-2-methylpropene or trans-1-bromo-2-butene or a mixture of the two are used as molecular weight regulators, a phosphate ester compound (triethyl phosphate or tripropyl phosphate or a mixture of the two) and a pentavalent molybdenum compound (molybdenum pentachloride) are used as the main catalyst, a conjugated compound is used as the activator, and 3-methylphenol monosubstituted trialkylaluminum is used as the cocatalyst. By controlling the steric hindrance and electron cloud density of the active center through ligands and activators, the coordination ability of the active center with the above molecular weight regulators is improved, thereby improving the molecular weight regulation ability without reducing the polymerization activity.

[0037] Compared with the prior art, the beneficial effects of the present invention are:

[0038] (1) The method for preparing low Mooney viscosity random 1,2-polybutadiene of the present invention has high conversion rate and strong molecular weight adjustment capability.

[0039] (2) The 1,2-polybutadiene prepared by the method of the present invention has a low Mooney value, low viscosity, low molecular weight, and high random 1,2-structure.

[0040] (3) The molecular weight regulator used in this invention does not form an azeotrope with the solvent and does not affect the recycling of the solvent.

[0041] (4) The 1,2-polybutadiene prepared by the method of the present invention can be applied to rubber additives and damping materials to improve the processing performance and mechanical properties of rubber. Attached Figure Description

[0042] Figure 1 This is a GPC diagram of 1,2-polybutadiene prepared in Comparative Example 1 and Examples 1, 4-6 of the present invention.

[0043] Figure 2 These are FTIR images of the 1,2-polybutadiene prepared in Comparative Example 2 and Examples 2-4 of this invention. Detailed Implementation

[0044] The preferred embodiments of the present invention will now be described in detail with reference to specific examples. It should be understood that the following examples are given for illustrative purposes only and are not intended to limit the scope of the invention. Those skilled in the art can make various modifications and substitutions to the present invention without departing from its spirit and essence.

[0045] Unless otherwise specified, the experimental methods used in the following examples are conventional methods.

[0046] Unless otherwise specified, all materials and reagents used in the following examples are commercially available. The density of triethyl phosphate, calculated as relative density (g / mL, 20 / 4℃), is 1.06817. The density of tripropyl phosphate, calculated as density, is 1.012 g / mL (25℃). All amounts of the main catalyst are calculated as molybdenum (Mo), the co-catalyst as aluminum (Al), and the molecular weight regulator as bromine (Br). The density of 3-methylphenol in S2 in the examples is 1.038 g / cm³. 3 The butadiene concentration is 1.3 g / mL. The addition of the butadiene according to molar or volume ratio is determined based on the reagent condition and to ensure compliance with the formulation.

[0047] Example 1

[0048] The method for preparing the low Mooney viscosity random 1,2-polybutadiene includes the following steps:

[0049] S1. Preparation of the main catalyst

[0050] Under nitrogen protection, molybdenum pentachloride was added to a preparation container, followed by triethyl phosphate to achieve a molar ratio of phosphate ester to molybdenum of 2. The mixture was aged at 70°C for 30 minutes, cooled to room temperature, and then diluted with toluene treated with sodium wire reflux to a molybdenum concentration of 5 × 10⁻⁶. -4 The main catalyst was obtained by applying mol / mL.

[0051] S2, Preparation of co-catalyst

[0052] Under nitrogen protection, 10 mL of a triisobutylaluminum solution in n-hexane (aluminum molar concentration of 4.2 × 10⁻⁶) was added. -4 Place 0.43 mL of 3-methylphenol (mol / mL) in an ice-water bath, control the temperature at 0℃, and slowly add 0.43 mL of 3-methylphenol dropwise to the container, controlling the pressure to not exceed 0.2 MPa. After the addition is complete, place the container in an ice-water bath to react for 4 hours to obtain the co-catalyst.

[0053] Preparation of S3, low Mooney viscosity random 1,2-polybutadiene

[0054] Butadiene (Bd) was dissolved in a hexane solution, and a co-catalyst, a main catalyst, 1-methylnaphthalene, and a hexane solution of 0.017 mol / mL 3-bromo-2-methylpropene were added. The polymerization reaction was carried out at 50 °C for 240 min to obtain low Mooney viscosity random 1,2-polybutadiene.

[0055] The molar ratio of the main catalyst to butadiene is 1.5 × 10⁻⁶. -4 The molar ratio of the co-catalyst to the main catalyst is 6; the volume ratio of 1-methylnaphthalene to n-hexane is 0.1; and the molar ratio of 3-bromo-2-methylpropene to the main catalyst is 3.

[0056] Example 2

[0057] The method for preparing the low Mooney viscosity random 1,2-polybutadiene includes the following steps:

[0058] S1. Preparation of the main catalyst

[0059] Under nitrogen protection, molybdenum pentachloride was added to a preparation container, followed by triethyl phosphate to achieve a molar ratio of phosphate ester to molybdenum of 3. The mixture was aged at 70°C for 30 minutes, cooled to room temperature, and then diluted with toluene treated with sodium wire reflux to a molybdenum concentration of 5 × 10⁻⁶. -4 The main catalyst was obtained by applying mol / mL.

[0060] S2, Preparation of co-catalyst

[0061] Under nitrogen protection, 10 mL of a triisobutylaluminum solution in n-hexane (aluminum molar concentration of 4.2 × 10⁻⁶) was added. -4 Place 0.43 mL of 3-methylphenol (mol / mL) in an ice-water bath, control the temperature at 0℃, and slowly add 0.43 mL of 3-methylphenol dropwise to the container, controlling the pressure to not exceed 0.2 MPa. After the addition is complete, place the container in an ice-water bath to react for 4 hours to obtain the co-catalyst.

[0062] Preparation of S3, low Mooney viscosity random 1,2-polybutadiene

[0063] Butadiene (Bd) was dissolved in a hydrogenated gasoline solution, and a co-catalyst, a main catalyst, 1-ethylnaphthalene, and a hexane solution of 0.017 mol / mL 3-bromo-2-methylpropene were added. The polymerization reaction was carried out at 70 °C for 300 min to obtain low Mooney viscosity random 1,2-polybutadiene.

[0064] The molar ratio of the main catalyst to butadiene is 2 × 10⁻⁶. -4 The molar ratio of the co-catalyst to the main catalyst is 10; the volume ratio of 1-methylnaphthalene to n-hexane is 0.13; and the molar ratio of 3-bromo-2-methylpropene to the main catalyst is 5.

[0065] Example 3

[0066] The method for preparing the low Mooney viscosity random 1,2-polybutadiene includes the following steps:

[0067] S1. Preparation of the main catalyst

[0068] Under nitrogen protection, 1 g of molybdenum pentachloride was added to the preparation container, followed by triethyl phosphate to achieve a molar ratio of 5:1. The mixture was aged at 70°C for 30 min, cooled to room temperature, and then diluted with toluene that had undergone sodium wire reflux treatment to a molybdenum concentration of 5 × 10⁻⁶. -4 The main catalyst was obtained by applying mol / mL.

[0069] S2, Preparation of co-catalyst

[0070] Under nitrogen protection, 10 mL of a triisobutylaluminum solution in n-hexane (aluminum molar concentration of 4.2 × 10⁻⁶) was added. -4 Place 0.43 mL of 3-methylphenol (mol / mL) in an ice-water bath, control the temperature at 5°C, and slowly add 0.43 mL of 3-methylphenol dropwise to the container, controlling the pressure to not exceed 0.2 MPa. After the addition is complete, place the container in an ice-water bath for 4 hours to react and obtain the co-catalyst.

[0071] Preparation of S3, low Mooney viscosity random 1,2-polybutadiene

[0072] Butadiene (Bd) was dissolved in cyclohexane solution, and a co-catalyst, a main catalyst, 1-propylnaphthalene, and a 0.017 mol / mL hexane solution of 3-bromo-2-methylpropene were added. The polymerization reaction was carried out at 80 °C for 360 min to obtain low Mooney viscosity random 1,2-polybutadiene.

[0073] The molar ratio of the main catalyst to butadiene is 3 × 10⁻⁶. -4 The molar ratio of the co-catalyst to the main catalyst is 12; the volume ratio of 1-methylnaphthalene to n-hexane is 0.17; and the molar ratio of 3-bromo-2-methylpropene to the main catalyst is 10.

[0074] Example 4

[0075] The method for preparing the low Mooney viscosity random 1,2-polybutadiene includes the following steps:

[0076] S1. Preparation of the main catalyst

[0077] Under nitrogen protection, 1 g of molybdenum pentachloride was added to the preparation container, followed by tripropyl phosphate to achieve a molar ratio of tripropyl phosphate to molybdenum pentachloride of 2. The mixture was aged at 80°C for 60 min, cooled to room temperature, and then diluted with toluene that had undergone sodium wire reflux treatment to a molybdenum concentration of 5 × 10⁻⁶. -4The main catalyst was obtained by applying mol / mL.

[0078] S2, Preparation of co-catalyst

[0079] Under nitrogen protection, 10 mL of a triethylaluminum solution in n-hexane (aluminum molar concentration of 4.2 × 10⁻⁶) was added. -4 Place 0.43 mL of 3-methylphenol (mol / mL) in an ice-water bath, control the temperature at 5°C, and slowly add 0.43 mL of 3-methylphenol dropwise to the container, controlling the pressure to not exceed 0.2 MPa. After the addition is complete, place the container in an ice-water bath for 8 hours to react and obtain the co-catalyst.

[0080] Preparation of S3, low Mooney viscosity random 1,2-polybutadiene

[0081] Butadiene (Bd) was dissolved in a hexane solution, and a co-catalyst, a main catalyst, 1-methylnaphthalene, and a hexane solution of 0.017 mol / mL trans-1-bromo-2-butene were added. The polymerization reaction was carried out at 60 °C for 240 min to obtain low Mooney viscosity random 1,2-polybutadiene.

[0082] The molar ratio of the main catalyst to butadiene is 1.5 × 10⁻⁶. -4 The molar ratio of the co-catalyst to the main catalyst is 8; the volume ratio of 1-methylnaphthalene to n-hexane is 0.1; and the molar ratio of trans-1-bromo-2-butene to the main catalyst is 3.

[0083] Example 5

[0084] The method for preparing the low Mooney viscosity random 1,2-polybutadiene includes the following steps:

[0085] S1. Preparation of the main catalyst

[0086] Under nitrogen protection, 1 g of molybdenum pentachloride was added to the preparation container, followed by tripropyl phosphate to achieve a molar ratio of tripropyl phosphate to molybdenum pentachloride of 3. The mixture was aged at 70°C for 60 min, cooled to room temperature, and then diluted with xylene that had undergone sodium wire reflux treatment to a molybdenum concentration of 5 × 10⁻⁶. -4 The main catalyst was obtained by applying mol / mL.

[0087] S2, Preparation of co-catalyst

[0088] Under nitrogen protection, 10 mL of a tripropylaluminum solution in n-hexane (aluminum molar concentration of 4.2 × 10⁻⁶) was added. -4 Place 0.52 mL of 3-methylphenol (mol / mL) in an ice-water bath, control the temperature at 2℃, and slowly add 0.52 mL of 3-methylphenol dropwise to the container, controlling the pressure to not exceed 0.2 MPa. After the addition is complete, place the container in an ice-water bath for 8 hours to react and obtain the co-catalyst.

[0089] Preparation of S3, low Mooney viscosity random 1,2-polybutadiene

[0090] Butadiene (Bd) was dissolved in a hexane solution, and a co-catalyst, a main catalyst, 1-methylnaphthalene, and a hexane solution of 0.017 mol / mL trans-1-bromo-2-butene were added. The polymerization reaction was carried out at 70 °C for 240 min to obtain low Mooney viscosity random 1,2-polybutadiene.

[0091] The molar ratio of the main catalyst to butadiene is 2 × 10⁻⁶. -4 The molar ratio of the co-catalyst to the main catalyst is 12; the volume ratio of 1-methylnaphthalene to n-hexane is 0.13; and the molar ratio of trans-1-bromo-2-butene to the main catalyst is 5.

[0092] Example 6

[0093] The method for preparing the low Mooney viscosity random 1,2-polybutadiene includes the following steps:

[0094] S1. Preparation of the main catalyst

[0095] Under nitrogen protection, 1 g of molybdenum pentachloride was added to the preparation container, followed by tripropyl phosphate to achieve a molar ratio of 5:1. The mixture was aged at 70°C for 60 min, cooled to room temperature, and then diluted with toluene treated with sodium wire reflux to a molybdenum concentration of 5 × 10⁻⁶. -4 The main catalyst was obtained by applying mol / mL.

[0096] S2, Preparation of co-catalyst

[0097] Under nitrogen protection, 10 mL of a triisobutylaluminum solution in n-hexane (aluminum molar concentration of 4.2 × 10⁻⁶) was added. -4 Place 0.34 mL of 3-methylphenol (mol / mL) in an ice-water bath, control the temperature at 2℃, and slowly add 0.34 mL of 3-methylphenol dropwise to the container, controlling the pressure to not exceed 0.2 MPa. After the addition is complete, place the container in an ice-water bath for 4 hours to react and obtain the co-catalyst.

[0098] Preparation of S3, low Mooney viscosity random 1,2-polybutadiene

[0099] Butadiene (Bd) was dissolved in a hexane solution, and a co-catalyst, a main catalyst, 1-methylnaphthalene, and a hexane solution of 0.017 mol / mL trans-1-bromo-2-butene were added. The polymerization reaction was carried out at 80 °C for 240 min to obtain low Mooney viscosity random 1,2-polybutadiene.

[0100] The molar ratio of the main catalyst to butadiene is 3 × 10⁻⁶. -4The molar ratio of the co-catalyst to the main catalyst is 16; the volume ratio of 1-methylnaphthalene to n-hexane is 0.17; and the molar ratio of trans-1-bromo-2-butene to the main catalyst is 10.

[0101] Example 7

[0102] The method for preparing the low Mooney viscosity random 1,2-polybutadiene includes the following steps:

[0103] Solvent recovery

[0104] Butadiene polymerization was carried out under the conditions of Example 1. After polymerization, polybutadiene was precipitated with ethanol, and the remaining solution was fractionated. After removing the foremilk, the fraction collected at 61–76°C was used to remove impurities such as ethanol and molecular weight regulators, as well as insoluble substances. The fractionated solvent was then distilled with sodium wire to further remove water and ethanol from the hexane, and this recovered solvent was kept for later use.

[0105] S1. Preparation of the main catalyst

[0106] Under nitrogen protection, 1 g of molybdenum pentachloride was added to the preparation container, followed by tripropyl phosphate to achieve a molar ratio of 5:1. The mixture was aged at 70°C for 60 min, cooled to room temperature, and then diluted with toluene treated with sodium wire reflux to a molybdenum concentration of 5 × 10⁻⁶. -4 The main catalyst was obtained by applying mol / mL.

[0107] S2, Preparation of co-catalyst

[0108] Under nitrogen protection, 10 mL of a triisobutylaluminum solution in n-hexane (aluminum molar concentration of 4.2 × 10⁻⁴ mol / mL) was placed in an ice-water bath at 2 °C. 0.43 mL of 3-methylphenol was slowly added dropwise to the container while controlling the pressure to not exceed 0.2 MPa. After the addition was complete, the container was placed in an ice-water bath for 4 h to react and obtain the co-catalyst.

[0109] Preparation of S3, low Mooney viscosity random 1,2-polybutadiene

[0110] Butadiene (Bd) was dissolved in a recovered hexane solution, and a co-catalyst, a main catalyst, 1-methylnaphthalene, and a hexane solution of 0.017 mol / mL trans-1-bromo-2-butene were added. The polymerization reaction was carried out at 80 °C for 240 min to obtain low Mooney viscosity random 1,2-polybutadiene.

[0111] The molar ratio of the main catalyst to butadiene is 3 × 10⁻⁶. -4 The molar ratio of the co-catalyst to the main catalyst is 16; the volume ratio of 1-methylnaphthalene to n-hexane is 0.17; and the molar ratio of trans-1-bromo-2-butene to the main catalyst is 10.

[0112] This embodiment illustrates that the molecular weight regulator used in this invention does not affect solvent recycling.

[0113] Example 8

[0114] The method for preparing the low Mooney viscosity random 1,2-polybutadiene includes the following steps:

[0115] S1. Preparation of the main catalyst

[0116] Under nitrogen protection, 1 g of molybdenum pentachloride was added to the preparation container, followed by triethyl phosphate to achieve a molar ratio of 5:1. The mixture was aged at 70°C for 30 min, cooled to room temperature, and then diluted with toluene that had undergone sodium wire reflux treatment to a molybdenum concentration of 5 × 10⁻⁶. -4 The main catalyst was obtained by applying mol / mL.

[0117] S2, Preparation of co-catalyst

[0118] Under nitrogen protection, 10 mL of a triisobutylaluminum solution in n-hexane (aluminum molar concentration of 4.2 × 10⁻⁶) was added. -4 Place 0.43 mL of 3-methylphenol (mol / mL) in an ice-water bath, control the temperature at 5°C, and slowly add 0.43 mL of 3-methylphenol dropwise to the container, controlling the pressure to not exceed 0.2 MPa. After the addition is complete, place the container in an ice-water bath for 4 hours to react and obtain the co-catalyst.

[0119] Preparation of S3, low Mooney viscosity random 1,2-polybutadiene

[0120] Butadiene (Bd) was dissolved in a hexane solution, and a co-catalyst, a main catalyst, 1-methylnaphthalene, a hexane solution of 0.017 mol / mL 3-bromo-2-methylpropene, and 1-bromo-2-butene were added. The polymerization reaction was carried out at 80 °C for 240 min to obtain low Mooney viscosity random 1,2-polybutadiene.

[0121] The molar ratio of the main catalyst to butadiene is 3 × 10⁻⁶. -4 The molar ratio of the co-catalyst to the main catalyst is 12; the volume ratio of 1-methylnaphthalene to n-hexane is 0.17; the molar ratio of 3-bromo-2-methylpropene to the main catalyst is 5; and the molar ratio of 1-bromo-2-butene to the main catalyst is 5.

[0122] Comparative Example 1

[0123] A method for preparing 1,2-polybutadiene includes the following steps: using tributyl phosphate, which has relatively high steric hindrance, as a ligand, with the remaining proportions and polymerization conditions the same as in Example 1, and polymerizing at 60°C for 240 min to obtain 1,2-polybutadiene rubber. This comparative example illustrates that the substituent chain length of the phosphate ester ligand has a significant impact on the coordination ability of the active center and the molecular weight regulator; when the carbon chain length of the substituent is greater than or equal to 4, the molecular weight regulation ability weakens.

[0124] Comparative Example 2

[0125] A method for preparing 1,2-polybutadiene includes the following steps: using triisobutyl phosphate as a ligand, with other configuration and polymerization conditions the same as in Example 1, polymerization is carried out at 60°C for 240 min to obtain 1,2-polybutadiene rubber. This comparative example illustrates that triisobutyl phosphate and tri-n-butyl phosphate have similar effects; neither can effectively improve the coordination ability of the active center and the molecular weight modifier.

[0126] Comparative Example 3

[0127] A method for preparing 1,2-polybutadiene includes the following steps: using triphenyl phosphate as a ligand, with the remaining configuration and polymerization conditions the same as in Example 1, polymerization is carried out at 60°C for 240 min to obtain 1,2-polybutadiene rubber. This comparative example illustrates that when triphenyl phosphate is used as a ligand, the ability of the molecular weight modifier to adjust the molecular weight is further weakened, and the conversion rate decreases.

[0128] Comparative Example 4

[0129] A method for preparing 1,2-polybutadiene includes the following steps: using trimethyl phosphate ligand, without the activator 1-methylnaphthalene, and with the remaining preparation and polymerization conditions the same as in Example 1, polymerization is carried out at 60°C for 240 min to obtain 1,2-polybutadiene rubber. This comparative example illustrates that the conjugation effect between the activator and the active center can improve the molecular weight regulation ability of the molecular weight regulator.

[0130] Comparative Example 5

[0131] A method for preparing 1,2-polybutadiene includes the following steps:

[0132] S1. Preparation of the main catalyst

[0133] Under nitrogen protection, molybdenum pentachloride was added to a preparation container, followed by triethyl phosphate to achieve a molar ratio of phosphate ester to molybdenum of 3. The mixture was aged at 70°C for 30 minutes, cooled to room temperature, and then diluted with toluene treated with sodium wire reflux to a molybdenum concentration of 5 × 10⁻⁶. -4 The main catalyst was obtained by applying mol / mL.

[0134] S2, Preparation of co-catalyst

[0135] Under nitrogen protection, 10 mL of a triisobutylaluminum solution in n-hexane (aluminum molar concentration of 4.2 × 10⁻⁶) was added. -4 Place 0.43 mL of 3-methylphenol (mol / mL) in an ice-water bath, control the temperature at 0℃, and slowly add 0.43 mL of 3-methylphenol dropwise to the container, controlling the pressure to not exceed 0.2 MPa. After the addition is complete, place the container in an ice-water bath to react for 4 hours to obtain the co-catalyst.

[0136] Preparation of S3, low Mooney viscosity random 1,2-polybutadiene

[0137] Butadiene (Bd) was dissolved in n-hexane solution, and a co-catalyst and a main catalyst were added separately. The mixture was then polymerized at 60°C for 240 min to obtain 1,2-polybutadiene. The molar ratio of the main catalyst to butadiene was 2 × 10⁻⁶. -4 The molar ratio of the co-catalyst to the main catalyst is 10.

[0138] The 1,2-polybutadiene prepared in the above examples and comparative examples was analyzed for copolymer composition sequence distribution and microstructure using nuclear magnetic resonance spectroscopy and infrared spectroscopy. The molecular weight and molecular weight distribution index of the copolymers were analyzed using gel permeation chromatography, and the Mooney viscosity of the polymers was analyzed using a Mooney viscometer. The 1,2-structure content was determined based on 738, 911, and 967 cm⁻¹. -1 The peaks are the characteristic peaks of the cis-1,4, 1,2, and trans-1,4 structures, respectively, and their peak areas were calculated. All contents mentioned are mass contents. Mn is the number-average molecular weight, and ML is the ML100(1+4) Mooney viscosity. The results are shown in Table 1.

[0139] Table 1 Test Results

[0140] project Polymerization conversion rate / % 1,2-Structure Content / % Mn ML Example 1 85 90 21.2 38 Example 2 90 85 18.5 35 Example 3 95 82 13.2 20 Example 4 82 93 20.8 38 Example 5 88 88 15.5 32 Example 6 92 83 12.3 20 Example 7 84 90 20.5 37 Example 8 87 87 17.5 32 Comparative Example 1 76 91 33.2 88 Comparative Example 2 75 88 34.1 87 Comparative Example 3 ＜65 92 38.3 90 Comparative Example 4 86 89 25.1 60 Comparative Example 5 88 85 45 85

[0141] Of course, the above description is only a preferred embodiment of the present invention and should not be considered as limiting the scope of the embodiments of the present invention. The present invention is also not limited to the above examples, and all equivalent changes and improvements made by those skilled in the art within the scope of the present invention should fall within the patent coverage of the present invention.

Claims

1. A method for preparing low Mooney viscosity random 1,2-polybutadiene, characterized in that: Includes the following steps: S1. Preparation of the main catalyst Under a protective atmosphere, molybdenum compounds and phosphate ester compounds were mixed, aged at 70–80°C for 30–60 min, cooled to room temperature, and diluted to obtain the main catalyst. S2, Preparation of co-catalyst Under a protective atmosphere, an alkane solution of trialkylaluminum was added dropwise to a container at 0–5 °C with an aryloxy ligand, and the pressure was controlled not to exceed 0.2 MPa. After the addition was completed, the mixture was reacted in an ice-water bath for 4–8 h to obtain a co-catalyst. Preparation of S3, low Mooney viscosity random 1,2-polybutadiene Butadiene was dissolved in a solvent, and a co-catalyst, a main catalyst, an activator, and a molecular weight regulator were added respectively. Polymerization was carried out at 50~80℃ for 240~360 min to obtain low Mooney viscosity random 1,2-polybutadiene. The amount of the main catalyst added in S3 is calculated as molybdenum, and the molar ratio of the main catalyst to butadiene is 1.5 × 10⁻⁶. -4 ~3×10 -4 The amount of co-catalyst added is calculated based on aluminum, and the molar ratio of co-catalyst to main catalyst is 8–16. The activator in S3 is 1-methylnaphthalene, 1-ethylnaphthalene, or 1-propylnaphthalene, and the volume ratio of the activator to the solvent is 0.1 to 0.

17. The molecular weight regulator in S3 is 3-bromo-2-methylpropene, trans-1-bromo-2-butene, or a mixture of the two, and its addition amount is calculated as bromine. The molar ratio of the molecular weight regulator to the main catalyst is 3 to 10.

2. The method for preparing low Mooney viscosity random 1,2-polybutadiene according to claim 1, characterized in that: In S1, the phosphate ester compound is triethyl phosphate or tripropyl phosphate, and the molar ratio of the phosphate ester compound to the molybdenum compound is 2 to 5.

3. The method for preparing low Mooney viscosity random 1,2-polybutadiene according to claim 1, characterized in that: In S2, the trialkylaluminum is triethylaluminum, tributylaluminum, or tripropylaluminum.

4. The method for preparing low Mooney viscosity random 1,2-polybutadiene according to claim 1, characterized in that: The aryloxy ligand in S2 is 3-methylphenol; the molar ratio of the aryloxy ligand to trialkylaluminum is 0.8 to 1.

2.

5. The method for preparing low Mooney viscosity random 1,2-polybutadiene according to claim 1, characterized in that: The solvent in S3 is hydrogenated gasoline, n-hexane, or cyclohexane.

6. A low Mooney viscosity random 1,2-polybutadiene, characterized in that: It is prepared by the method for preparing low Mooney viscosity random 1,2-polybutadiene according to any one of claims 1-5.

7. An application of the low Mooney viscosity random 1,2-polybutadiene according to claim 6, characterized in that: Used in rubber additives and damping materials.

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