A branched butadiene-isoprene copolymer and a method of making

Abstract

This invention relates to the field of rare earth catalytic synthesis of rubber, and discloses a branched butadiene-isoprene copolymer and its preparation method. The preparation method includes the following steps: under a protective atmosphere, a composite branching agent is added to a butadiene and isoprene monomer solution, and then a rare earth catalyst is added to react fully to obtain the butadiene-isoprene copolymer; wherein the composite branching agent is prepared as follows: under a protective atmosphere, alkyl aluminum is added dropwise to a sulfur dichloride solution and reacted fully to obtain the desired composite branching agent; the present invention constructs a sulfur dichloride-alkyl aluminum composite branching agent, which is used in the branched butadiene-isoprene copolymerization reaction to obtain a branched copolymer with high cis structure content, excellent mechanical properties and processing properties.

Description

Technical Field

[0001] This invention relates to the field of rare earth catalytic synthesis of rubber, specifically to a branched butadiene-isoprene copolymer and its preparation method. Background Technology

[0002] Rare-earth-catalyzed butadiene-isoprene copolymers are ideal materials for high-performance tire tread compounds due to their excellent low-temperature resistance, wear resistance, and wet skid resistance. However, butadiene-isoprene copolymers prepared by traditional rare-earth catalysis are mostly linear in structure, resulting in problems such as high solution viscosity and severe cold flow, which greatly inconveniences heat transfer, conveying, spraying, and coagulation processes in industrial production, and also limits their application in high-end rubber products. To address these shortcomings, the industry generally adopts the method of introducing branched structures. By controlling the polymer molecular chain morphology, while maintaining its high cis structure and high molecular weight advantages, the solution viscosity is reduced, processing performance and cold flow resistance are improved, thereby enhancing the overall performance of the polymer.

[0003] For example, CN104650362A discloses a method for preparing a branched polymer, using a nitrile-containing liquid polymer as a branching agent. Although this method can reduce the viscosity of the solution to a certain extent, such branching agents have problems such as high price, difficulty in obtaining raw materials, and limited branching efficiency, making it difficult to accurately control the degree of branching and easily having an adverse effect on the microstructure of the copolymer. CN 104231119A discloses a method for preparing long-chain branched high-cis polybutadiene, and CN104231120B discloses a method for preparing long-chain branched high-cis polyisoprene, both using a dithiol compound branching method. This method uses a free radical mechanism, constructing a long-chain branched structure through in-situ generated free radicals undergoing interchain local crosslinking reactions. However, the highly active free radicals generated are prone to uneven reaction and local crosslinking side reactions in high-viscosity adhesives, affecting the uniformity of product performance.

[0004] Currently used branching agents such as disulfide dichloride and alkyl aluminum have inherent defects. For example, disulfide dichloride, as a compound with special reactivity, has certain applications in rubber vulcanization and other fields. It has a unique chemical structure that can react with rubber molecular chains to form cross-linked structures, thereby improving the physical and mechanical properties of rubber. However, when used as a branching agent in branched rare earth rubber, it generally suffers from defects such as uneven branching, residual impurities, decreased cis structure, and high gel content. For example, US3374191A discloses a method for producing diene polymers with improved performance elastomers, using disulfide dichloride to prepare diene polymers. US5567784A discloses a method for producing diene rubber with reduced cold flow and low inherent odor by polymerizing butadiene with a neodymium catalyst. In this method, butadiene is polymerized under a rare earth catalytic system, and S2Cl2 is applied in the later stage of the polymerization reaction to avoid the unpleasant odor produced by S2Cl2. The resulting cis-butadiene rubber is resistant to cold flow and has a low viscosity. US6737476B1 describes a rubber composition and US8586678B2 describes blends of linear and branched neodymium-catalyzed rubber formulations for golf balls, mentioning the use of S2Cl2 as a branching agent in the preparation of branched rare-earth cis-butadiene rubber. Alkyl aluminum, as a catalyst in rare-earth catalytic systems, plays a crucial role in alkylation, reduction, chain transfer, and stabilizing active centers, and is a key component in regulating polymerization activity and molecular weight distribution. However, relying solely on alkyl aluminum to regulate branching is limited by the structure and concentration of alkyl aluminum, resulting in limited branching effects and an inability to precisely control the degree of branching, thus failing to address the core problem of poor processability in linear copolymers. Summary of the Invention

[0005] This invention addresses the problems existing in the prior art by providing a branched butadiene-isoprene copolymer and its preparation method.

[0006] The technical solution adopted in this invention is: a method for preparing branched butadiene-isoprene copolymer, comprising the following steps: Under a protective atmosphere, a composite branching agent was added to a solution of butadiene and isoprene monomers, followed by the addition of a rare earth catalyst, and the reaction was carried out to obtain a butadiene-isoprene copolymer. The preparation method of the composite branching agent is as follows: Under a protective atmosphere, alkylaluminum is added dropwise to a solution of disulfur dichloride and allowed to react completely to obtain the desired composite branching agent; the molar ratio of alkylaluminum to disulfur dichloride is 0.5 to 4:1.

[0007] Furthermore, the alkylaluminum is one or more of trialkylaluminum, hydrogenated alkylaluminum, and chloroalkylaluminum, mixed in any proportion.

[0008] Furthermore, the trialkylaluminum is one of trimethylaluminum, triethylaluminum, and triisobutylaluminum; the hydride alkylaluminum is one of diethylaluminum hydride and diisobutylaluminum hydride; and the chloroalkylaluminum is one of diisobutylaluminum chloride, trichlorotriethylaluminum, and monochlorodiethylaluminum.

[0009] Furthermore, the composite branching agent accounts for 0.1 wt.% to 0.8 wt.% of the monomer mass, wherein the monomer includes butadiene and isoprene; the molar ratio of butadiene to isoprene is 90 to 60: 10 to 40.

[0010] Furthermore, the branched butadiene-isoprene copolymer is reacted at a temperature of 30–70 °C for a time of 1–24 h.

[0011] Furthermore, the mass ratio of the rare earth catalyst (in terms of the number of molar amounts of rare earth atoms) to butadiene-isoprene in the rare earth catalyst is 4.0 × 10⁻⁶. -6 ~1.0×10 -5 mol: 1 g.

[0012] Furthermore, the rare earth catalyst is prepared as follows: Under a protective atmosphere, alkylaluminum, chloride, and rare earth compound are sequentially added to a reactor, followed by the addition of a solvent, and the reaction is carried out until complete. The rare earth compound is one or more of rare earth carboxylates, rare earth acidic phosphoric / phosphonates, alkoxy rare earths, rare earth chloride electron-donating complexes, and rare earth sulfonate electron-donating complexes, mixed in any proportion. The alkylaluminum is one or more of trialkylaluminum and alkyl aluminum hydride, mixed in any proportion. The chloride is one or more of monochlorodiisobutylaluminum, monochlorodiethylaluminum, and trichlorotriethyldialuminum, mixed in any proportion.

[0013] Furthermore, the molar ratio of the alkylaluminum, chloride, and rare earth compound is 10–30:2–3:1.

[0014] Furthermore, the reaction temperature is 30–60 °C, and the reaction time is 20–60 min.

[0015] A branched butadiene-isoprene copolymer, wherein the branched butadiene-isoprene copolymer is obtained by polymerization of butadiene-isoprene monomers under the action of a composite branching agent and a rare earth catalyst.

[0016] The beneficial effects of this invention are: This invention constructs a composite branching agent from disulfide dichloride and alkyl aluminum, using disulfide dichloride as the branching core and alkyl aluminum as the auxiliary branching agent. Their synergistic effect solves the problem of cross-linking easily caused by using disulfide dichloride alone, and also improves the branching efficiency. This composite branching agent is used for branching regulation in rare earth-catalyzed butadiene-isoprene copolymerization, overcoming the limitations of existing branching technologies. Furthermore, it exhibits good compatibility with rare earth catalytic systems, does not damage the activity of the rare earth main catalyst, and does not affect the microstructure of the copolymer, achieving integrated "catalysis-branching" and significantly improving the overall performance of the copolymer.

[0017] The preparation method of this invention is simple and highly controllable. The amount of composite branching agent, the type and ratio of alkyl aluminum can be adjusted within a certain range to regulate the degree of branching of the copolymer, making it suitable for industrial production. Attached Figure Description

[0018] Figure 1 The image shows the Gavey mouth shape for the embodiments and control samples of the present invention, with a rotation speed of 100 r / min.

[0019] Figure 2 The Gavey mouthpiece diagrams for the embodiments and control samples of this invention are shown, with a rotation speed of 70 r / min. Detailed Implementation

[0020] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0021] A method for preparing a branched butadiene-isoprene copolymer includes the following steps: Under a protective atmosphere, a composite branching agent was added to a solution of butadiene and isoprene monomers, followed by the addition of a rare earth catalyst. The reaction was allowed to proceed until a butadiene-isoprene copolymer was obtained. The composite branching agent comprised 0.1 wt.%–0.8 wt.% of the monomers, which included butadiene and isoprene. The molar ratio of butadiene to isoprene was 90–60:10–40. The reaction temperature for branching the butadiene-isoprene copolymer was 30–70 °C, and the reaction time was 1–24 h. The mass ratio of the rare earth catalyst (based on the molar number of rare earth atoms) to butadiene-isoprene was 4.0 × 10⁻⁶. -6 ~1.0×10 -5 mol: 1 g.

[0022] The preparation method of rare earth catalysts is as follows: Under nitrogen protection, rare earth compounds, alkyl aluminum compounds, and chlorides are added sequentially to a reactor, followed by the addition of a solvent, and the reaction is allowed to proceed until complete. The molar ratio of alkyl aluminum compounds, chlorides, and rare earth compounds is 10–30:2–3:1. The reaction temperature is 30–60°C, and the reaction time is 20–60 min. Hydrocarbon solvents are used, preferably one or more of n-hexane, n-pentane, cyclohexane, and n-heptane, with n-hexane being the most preferred.

[0023] The rare earth compound is obtained by mixing one or more of rare earth carboxylates, rare earth acidic phosphorus / phosphonates, alkoxy rare earths, rare earth chloride electron-donating complexes, and rare earth sulfonic acid electron-donating complexes in any proportion; wherein the rare earth carboxylates are preferably neodymium neodecanoate Nd(vers)3, neodymium isooctanoate Nd(EHA)3, and neodymium naphthenate Nd(naph)3. The rare earth acidic phosphorus / phosphonate is preferably neodymium diisooctyl phosphate Nd(P) 204 )3 or tris(2-ethylhexylphosphonic acid-2-ethylhexyl ester)neodymium Nd(P 507 3. Alkoxy rare earth elements are preferably ethoxyneodymium, n-propoxyneodymium, or isopropoxyneodymium. Rare earth chloride electron-donating complexes are preferably neodymium chloride isopropanol (NdCl3·3PriOH) or neodymium chloride tributyl phosphate (NdCl3·3TBP). Rare earth sulfonate electron-donating complexes are preferably neodymium trifluoromethanesulfonate tributyl phosphate Nd(CF3SO3)3·3TBP or neodymium benzenesulfonate N,N-dimethylformamide Nd(C 18 H 29 SO3)3·3C3H7NO.

[0024] Alkyl aluminum is obtained by mixing one or more of trialkyl aluminum and alkyl aluminum hydride in any proportion, preferably triisobutylaluminum Al( i -Bu)3, Hydrogenated diisobutylaluminum Al( i The compounds are alkyl aluminum (Al(oct)3), diethylaluminum hydride (AlEt2H), trioctylaluminum (Al(oct)3), or triethylaluminum (AlEt3). The chloride is one or more of monochlorodiisobutylaluminum, monochlorodiethylaluminum, and trichlorotriethylaluminum, mixed in any proportion. The molar ratio of the alkyl aluminum, chloride, and rare earth compound is 10–30:2–3:1. The reaction temperature is 30–60 °C, and the reaction time is 20–60 min.

[0025] The preparation method of the composite branching agent is as follows: Under a protective atmosphere, alkylaluminum is added dropwise to a solution of disulfide dichloride, and the reaction is allowed to proceed until complete to obtain the desired composite branching agent; the molar ratio of alkylaluminum to disulfide dichloride is 0.5–4:1. The alkylaluminum is one or more of trialkylaluminum, hydride alkylaluminum, and chloroalkylaluminum, mixed in any proportion. Trialkylaluminum is one of trimethylaluminum, triethylaluminum, and triisobutylaluminum; hydride alkylaluminum is one of diethylaluminum hydride and diisobutylaluminum hydride; chloroalkylaluminum is one of diisobutylaluminum chloride, trichlorotriethylaluminum, and dichlorodiethylaluminum.

[0026] The preparation process of the composite branching agent is carried out entirely under high-purity nitrogen protection, using an inert organic solvent, such as anhydrous and oxygen-free n-hexane or cyclohexane, preferably n-hexane, with a dosage of 50–100 mL per 0.1 mol of disulfur dichloride. The reaction is carried out at low temperature (0–5 °C) with stirring for 1–2 h to ensure sufficient complexation, ultimately yielding an orange-red transparent composite branching agent.

[0027] A branched butadiene-isoprene copolymer, wherein the branched butadiene-isoprene copolymer is obtained by polymerization of butadiene-isoprene monomers under the action of a composite branching agent and a rare earth catalyst.

[0028] Example 1 A method for preparing a branched butadiene-isoprene copolymer includes the following steps: Under a nitrogen atmosphere, 1 L of a hexane solution containing 10 g / 100 mL butadiene and isoprene monomers was added to a polymerization reactor, along with 0.1 g of a composite modifier; the molar ratio of butadiene to isoprene was 90:10; then a rare earth catalyst was added. The molar ratio of Nd in the rare earth catalyst to the monomer was 4.0 × 10⁻⁶. -6 The reaction was carried out at 30 °C for 24 h, and the polymer was precipitated in ethanol and dried under vacuum to constant weight to obtain butadiene-isoprene copolymer.

[0029] The preparation method of the composite branching agent is as follows: Under high-purity nitrogen protection and at 0 °C, trimethylaluminum (AlMe3) was added dropwise to a hexane solution of disulfur dichloride, with a molar ratio of 4:1. The mixture was kept at this temperature and stirred for 1 h to ensure sufficient complexation, resulting in an orange-red transparent composite branching agent.

[0030] The preparation method of rare earth catalysts is as follows: Under nitrogen protection, 0.06 mol trioctylaluminum Al(oct)3, 0.004 mol trichlorotriethylaluminum Al2Et3Cl3, and 0.002 mol neodymium neodecanoate Nd(vers)3 were added sequentially to a dry catalyst reactor, followed by the addition of n-hexane solution to obtain a concentration of 3×10⁻⁶. -5 A rare earth catalyst of mol / ml was aged at 60 °C for 20 min to obtain the rare earth catalyst.

[0031] Example 2 A method for preparing a branched butadiene-isoprene copolymer includes the following steps: Under a nitrogen atmosphere, 1 L of a hexane solution containing 10 g / 100 mL butadiene and isoprene monomers was added to a polymerization reactor, along with 0.1 g of a composite modifier; the molar ratio of butadiene to isoprene was 90:10; then a rare earth catalyst was added. The molar ratio of Nd in the rare earth catalyst to the monomer was 4.0 × 10⁻⁶. -6 The reaction was carried out at 30 °C for 24 h, and the polymer was precipitated in ethanol and dried under vacuum to constant weight to obtain butadiene-isoprene copolymer.

[0032] The preparation method of the composite branching agent is as follows: Under high-purity nitrogen protection and at 0 °C, triisobutylaluminum Al( i -Bu)3 was added dropwise to a hexane solution of disulfide dichloride, wherein triisobutylaluminum Al( i The molar ratio of -Bu)3 and disulfur dichloride was 1:1. The mixture was kept at a constant temperature and stirred for 1 h to ensure sufficient complexation, resulting in an orange-red transparent composite branching agent.

[0033] The preparation method of rare earth catalysts is as follows: Under nitrogen protection, 0.06 mol of triisobutylaluminum (Al) was added sequentially to a dry catalyst reactor. i -Bu)3, 0.004 mol monochlorodiisobutylaluminum Al( i -Bu)2Cl, 0.002 mol neodymium diisooctyl phosphate (Nd(P)) 204 3. Add n-hexane solution to obtain a concentration of 3×10⁻⁶. -5 A rare earth catalyst of mol / ml was aged at 60 °C for 20 min to obtain the rare earth catalyst.

[0034] Example 3 A method for preparing a branched butadiene-isoprene copolymer includes the following steps: Under a nitrogen atmosphere, 1 L of a hexane solution containing 10 g / 100 mL butadiene and isoprene monomers was added to a polymerization reactor, along with 0.1 g of a composite modifier; the molar ratio of butadiene to isoprene was 90:10; then a rare earth catalyst was added. The molar ratio of Nd in the rare earth catalyst to the monomer was 4.0 × 10⁻⁶. -6 The reaction was carried out at 30 °C for 24 h, and the polymer was precipitated in ethanol and dried under vacuum to constant weight to obtain butadiene-isoprene copolymer.

[0035] The preparation method of the composite branching agent is as follows: Under high-purity nitrogen protection and at 0 °C, triethylaluminum (AlEt3) was added dropwise to a hexane solution of disulfur dichloride, with a molar ratio of 3:1. The mixture was kept at this temperature and stirred for 1 h to ensure sufficient complexation, resulting in an orange-red transparent composite branching agent.

[0036] The preparation method of rare earth catalysts is as follows: Under nitrogen protection, 0.06 mol of triethylaluminum (AlEt3), 0.004 mol of diethylaluminum chloride (AlEt2Cl), and 0.002 mol of neodymium chloride (NdCl3·3Pr) were sequentially added to a dry catalyst reactor. i OH, add n-hexane solution, to obtain a concentration of 3×10 -5 A rare earth catalyst of mol / ml was aged at 60 °C for 20 min to obtain the rare earth catalyst.

[0037] Example 4 A method for preparing a branched butadiene-isoprene copolymer includes the following steps: Under a nitrogen atmosphere, 1 L of a hexane solution containing 10 g / 100 mL butadiene and isoprene monomers was added to a polymerization reactor, along with 0.8 g of a composite modifier; the molar ratio of butadiene to isoprene was 80:20; then a rare earth catalyst was added. The molar ratio of Nd in the rare earth catalyst to the monomer was 1.0 × 10⁻⁶. -5 The polymer was reacted at 70 °C for 1 h, precipitated in ethanol, and dried under vacuum to constant weight to obtain butadiene-isoprene copolymer.

[0038] The preparation method of the composite branching agent is as follows: Under high-purity nitrogen protection and at 5 °C, diisobutylaluminum chloride Al( i -Bu)2Cl was added dropwise to a hexane solution of disulfide dichloride, wherein diisobutylaluminum chloride Al( iThe molar ratio of -Bu)2Cl and disulfide dichloride was 3:1. The mixture was kept at a constant temperature and stirred for 2 h to ensure sufficient complexation, resulting in an orange-red transparent composite branching agent.

[0039] The preparation method of rare earth catalysts is as follows: Under nitrogen protection, 0.02 mol of diethylaluminum hydride (AlEt2H), 0.006 mol of trichlorotriethylaluminum (Al2Et3Cl3), and 0.002 mol of neodymium chloride tributyl phosphate (NdCl3·3TBP) were sequentially added to a dry catalyst reactor. Hexane solution was then added to obtain a solution with a concentration of 3 × 10⁻⁶. -5 A rare earth catalyst was prepared by aging a mol / ml solution at 30 °C for 60 min.

[0040] Example 5 A method for preparing a branched butadiene-isoprene copolymer includes the following steps: Under a nitrogen atmosphere, 1 L of a hexane solution containing 10 g / 100 mL butadiene and isoprene monomers was added to a polymerization reactor, along with 0.8 g of a composite modifier; the molar ratio of butadiene to isoprene was 80:20; then a rare earth catalyst was added. The molar ratio of Nd in the rare earth catalyst to the monomer was 1.0 × 10⁻⁶. -5 The polymer was reacted at 70 °C for 1 h, precipitated in ethanol, and dried under vacuum to constant weight to obtain butadiene-isoprene copolymer.

[0041] The preparation method of the composite branching agent is as follows: Under high-purity nitrogen protection and at 5 °C, diisobutylaluminum hydride Al( i -Bu)2H was added dropwise to a hexane solution of disulfide dichloride, wherein diisobutylaluminum hydride Al( i The molar ratio of -Bu)2H and disulfur dichloride was 2:1. The mixture was kept at a constant temperature and stirred for 2 h to ensure sufficient complexation, resulting in an orange-red transparent composite branching agent.

[0042] The preparation method of rare earth catalysts is as follows: Under nitrogen protection, 0.02 mol of diisobutylaluminum hydride (Al) was added sequentially to a dry catalyst reactor. i -Bu)2H, 0.006 mol diethylaluminum chloride AlEt2Cl, and 0.002 mol neodymium naphthenate Nd(naph)3 were added to a hexane solution to obtain a concentration of 3×10 -5 A rare earth catalyst was prepared by aging a mol / ml solution at 30 °C for 60 min.

[0043] Example 6 A method for preparing a branched butadiene-isoprene copolymer includes the following steps: Under a nitrogen atmosphere, 1 L of a hexane solution containing 10 g / 100 mL butadiene and isoprene monomers was added to a polymerization reactor, along with 0.8 g of a composite modifier; the molar ratio of butadiene to isoprene was 80:20; then a rare earth catalyst was added. The molar ratio of Nd in the rare earth catalyst to the monomer was 1.0 × 10⁻⁶. -5 The polymer was reacted at 70 °C for 1 h, precipitated in ethanol, and dried under vacuum to constant weight to obtain butadiene-isoprene copolymer.

[0044] The preparation method of the composite branching agent is as follows: Under high-purity nitrogen protection and at 5 °C, diethylaluminum chloride (AlEt2Cl) was added dropwise to a hexane solution of disulfur dichloride, with a molar ratio of 1:1. The mixture was kept at this temperature and stirred for 2 h to ensure sufficient complexation, resulting in an orange-red transparent composite branching agent.

[0045] The preparation method of rare earth catalysts is as follows: Under nitrogen protection, 0.02 mol of triethylaluminum (AlEt3), 0.006 mol of diethylaluminum chloride (AlEt2Cl), and 0.002 mol of neodymium isooctanoate (Nd(EHA)3)3 were added sequentially to a dry catalyst reactor, followed by the addition of n-hexane solution to obtain a concentration of 3 × 10⁻⁶. -5 A rare earth catalyst was prepared by aging a mol / ml solution at 30 °C for 60 min.

[0046] Example 7 A method for preparing a branched butadiene-isoprene copolymer includes the following steps: Under a nitrogen atmosphere, 1 L of a hexane solution containing 10 g / 100 mL butadiene and isoprene monomers was added to a polymerization reactor, along with 0.5 g of a composite modifier; the molar ratio of butadiene to isoprene was 60:40; then a rare earth catalyst was added. The molar ratio of Nd in the rare earth catalyst to the monomer was 8.0 × 10⁻⁶. -5 The reaction was carried out at 50 °C for 14 h, and the polymer was precipitated in ethanol and dried under vacuum to constant weight to obtain butadiene-isoprene copolymer.

[0047] The preparation method of the composite branching agent is as follows: Under high-purity nitrogen protection and at 3 °C, diisobutylaluminum hydride Al( i-Bu)2H was added dropwise to a hexane solution of disulfide dichloride, wherein diisobutylaluminum hydride Al( i The molar ratio of -Bu)2H and disulfur dichloride was 2:1. The mixture was kept at a constant temperature and stirred for 1.5 h to ensure sufficient complexation and obtain an orange-red transparent composite branching agent.

[0048] The preparation method of rare earth catalysts is as follows: Under nitrogen protection, 0.04 mol of triethylaluminum (AlEt3), 0.006 mol of trichlorotriethylaluminum (Al2Et3Cl3), and 0.002 mol of neodymium trifluoromethanesulfonate tributyl phosphate (Nd(CF3SO3)3·3TBP) were added sequentially to a dry catalyst reactor, followed by the addition of n-hexane solution to obtain a concentration of 3 × 10⁻⁶. -5 A rare earth catalyst of mol / ml was aged at 50 °C for 30 min to obtain the rare earth catalyst.

[0049] Example 8 A method for preparing a branched butadiene-isoprene copolymer includes the following steps: Under a nitrogen atmosphere, 1 L of a hexane solution containing 10 g / 100 mL butadiene and isoprene monomers was added to a polymerization reactor, along with 0.5 g of a composite modifier; the molar ratio of butadiene to isoprene was 60:40; then a rare earth catalyst was added. The molar ratio of Nd in the rare earth catalyst to the monomer was 8.0 × 10⁻⁶. -5 The reaction was carried out at 50 °C for 14 h, and the polymer was precipitated in ethanol and dried under vacuum to constant weight to obtain butadiene-isoprene copolymer.

[0050] The preparation method of the composite branching agent is as follows: Under high-purity nitrogen protection and at 3 °C, trichlorotriethylaluminum (Al2Et3Cl3) was added dropwise to a hexane solution of disulfide dichloride, with a molar ratio of 4:1. The mixture was kept at this temperature and stirred for 1.5 h to ensure sufficient complexation, resulting in an orange-red transparent composite branching agent.

[0051] The preparation method of rare earth catalysts is as follows: Under nitrogen protection, 0.04 mol of triisobutylaluminum (Al) was added sequentially to a dry catalyst reactor. i -Bu)3, 0.006 mol monochlorodiisobutylaluminum Al( i -Bu)2Cl, 0.002 mol neodymium benzenesulfonate N,N-dimethylformamide Nd(C 18 H 29 SO3)3·3C3H7NO, when added to n-hexane solution, yields a solution with a concentration of 3×10-5 A rare earth catalyst was prepared by aging a mol / ml solution at 50 °C for 30 min.

[0052] Example 9 A method for preparing a branched butadiene-isoprene copolymer includes the following steps: Under a nitrogen atmosphere, 1 L of a hexane solution containing 10 g / 100 mL butadiene and isoprene monomers was added to a polymerization reactor, along with 0.5 g of a composite modifier; the molar ratio of butadiene to isoprene was 60:40; then a rare earth catalyst was added. The molar ratio of Nd in the rare earth catalyst to the monomer was 8.0 × 10⁻⁶. -5 The reaction was carried out at 50 °C for 14 h, and the polymer was precipitated in ethanol and dried under vacuum to constant weight to obtain butadiene-isoprene copolymer.

[0053] The preparation method of the composite branching agent is as follows: Under high-purity nitrogen protection and at 3 °C, diethylaluminum hydride (AlEt2H) was added dropwise to a hexane solution of disulfur dichloride, with a molar ratio of AlEt2H to disulfur dichloride of 3:1. The mixture was kept at this temperature and stirred for 1.5 h to ensure sufficient complexation, resulting in an orange-red transparent composite branching agent.

[0054] The preparation method of rare earth catalysts is as follows: Under nitrogen protection, 0.04 mol of diisobutylaluminum hydride (Al) was added sequentially to a dry catalyst reactor. i -Bu)2H, 0.006 mol trichlorotriethylaluminum Al2Et3Cl3, 0.002 mol tris(2-ethylhexylphosphonic acid-2-ethylhexyl ester)neodymium Nd(P 507 3. Add n-hexane solution to obtain a concentration of 3×10⁻⁶. -5 A rare earth catalyst was prepared by aging a mol / ml solution at 50 °C for 30 min.

[0055] Control Sample 1 A method for preparing a branched butadiene-isoprene copolymer includes the following steps: Under a nitrogen atmosphere, 1 L of a hexane solution containing butadiene and isoprene at a monomer concentration of 10 g / 100 mL was added to the polymerization reactor; the molar ratio of butadiene to isoprene was 90:10; then a rare earth catalyst was added. The molar ratio of Nd in the rare earth catalyst to the monomer was 4.0 × 10⁻⁶. -6 The reaction was carried out at 30 °C for 24 h, and the polymer was precipitated in ethanol and dried under vacuum to constant weight to obtain butadiene-isoprene copolymer.

[0056] The preparation method of rare earth catalysts is as follows: Under nitrogen protection, 0.06 mol of triisobutylaluminum (Al) was added sequentially to a dry catalyst reactor. i -Bu)3, 0.004 mol monochlorodiisobutylaluminum Al( i -Bu)2Cl, 0.002 mol neodymium neodecanoate Nd(vers)3, added to n-hexane solution, yielded a concentration of 3×10 -5 A rare earth catalyst of mol / ml was aged at 60 °C for 20 min to obtain the rare earth catalyst.

[0057] Control sample 2 A method for preparing a branched butadiene-isoprene copolymer includes the following steps: Under a nitrogen atmosphere, 1 L of a hexane solution containing butadiene and isoprene at a monomer concentration of 10 g / 100 mL was added to the polymerization reactor; the molar ratio of butadiene to isoprene was 80:20; then a rare earth catalyst was added. The molar ratio of Nd in the rare earth catalyst to the monomer was 1.0 × 10⁻⁶. -5 The polymer was reacted at 70 °C for 1 h, precipitated in ethanol, and dried under vacuum to constant weight to obtain butadiene-isoprene copolymer.

[0058] The preparation method of rare earth catalysts is as follows: Under nitrogen protection, 0.02 mol of triisobutylaluminum (Al) was added sequentially to a dry catalyst reactor. i -Bu)3, 0.006 mol monochlorodiisobutylaluminum Al( i -Bu)2Cl, 0.002 mol neodymium neodecanoate Nd(vers)3, added to n-hexane solution, yielded a concentration of 3×10 -5 A rare earth catalyst was prepared by aging a mol / ml solution at 30 °C for 60 min.

[0059] Control sample 3 A method for preparing a branched butadiene-isoprene copolymer includes the following steps: Under a nitrogen atmosphere, 1 L of a hexane solution containing butadiene and isoprene at a monomer concentration of 10 g / 100 mL was added to the polymerization reactor; the molar ratio of butadiene to isoprene was 60:40; then a rare earth catalyst was added. The molar ratio of Nd in the rare earth catalyst to the monomer was 8.0 × 10⁻⁶. -5 The reaction was carried out at 50 °C for 14 h, and the polymer was precipitated in ethanol and dried under vacuum to constant weight to obtain butadiene-isoprene copolymer.

[0060] The preparation method of rare earth catalysts is as follows: Under nitrogen protection, 0.04 mol of triisobutylaluminum (Al) was added sequentially to a dry catalyst reactor. i -Bu)3, 0.006 mol monochlorodiisobutylaluminum Al( i -Bu)2Cl, 0.002 mol neodymium neodecanoate Nd(vers)3, added to n-hexane solution, yielded a concentration of 3×10 -5 A rare earth catalyst was prepared by aging a mol / ml solution at 50 °C for 30 min.

[0061] The performance test results of the butadiene-isoprene copolymers obtained in the embodiments and control groups of the present invention are shown in Table 1. All tests were conducted using existing testing methods.

[0062] Table 1. Test results of the examples and control groups

[0063] As shown in Table 1, the butadiene-isoprene copolymer obtained in the examples has a significantly higher degree of long-chain branching than the control group, indicating that the composite branching agent can significantly improve the branching degree of the copolymer. The gel content of the butadiene-isoprene copolymer obtained in the examples is significantly lower than that of the control group, indicating that its processing performance is significantly improved.

[0064] Figure 1 The figures show Gavey die profiles for Examples 3, 5, 7, and 9 of this invention and Control Sample 1, with extrusion conditions of 100 rpm, barrel temperature of 65°C, and die temperature of 70°C. As can be seen from the figures, the butadiene-isoprene copolymers obtained in these examples exhibit significantly better processing performance than Control Sample 1.

[0065] Figure 2 The figures show Gavey die profiles for Examples 3, 5, 7, and 9 of this invention and Control Sample 1, with extrusion conditions of 70 rpm, barrel temperature of 65 °C, and die temperature of 70 °C. As can be seen from the figures, the butadiene-isoprene copolymers obtained in these examples exhibit significantly better processing performance than Control Sample 1.

[0066] This invention constructs a composite branching agent using disulfide dichloride and alkyl aluminum, which is a stable sulfur-aluminum coordination complex. This composite branching agent uses disulfide dichloride as the branching core and alkyl aluminum as the auxiliary branching agent; their synergistic effect solves the problem of cross-linking easily caused by using disulfide dichloride alone, and also improves the branching efficiency, overcoming the limitations of existing branching technologies.

[0067] This invention yields a branched butadiene-isoprene copolymer. A composite branching agent is added to the reaction system at the initial stage of the polymerization reaction for branching control in rare earth-catalyzed butadiene-isoprene copolymerization. The composite branching agent exhibits good compatibility with the rare earth catalytic system, without damaging the activity of the rare earth main catalyst or affecting the microstructure of the copolymer. This achieves integrated catalysis and branching, significantly improving the overall performance of the copolymer. The addition of alkyl aluminum in the composite branching agent eliminates the poisoning effect of disulfide dichloride alone on the monomers. The branching agent is uniformly dispersed in the polymerization solution, resulting in a copolymer with high cis-1,4-structure content, excellent mechanical properties, and processing performance, meeting the needs of industrial production and high-end applications.

[0068] The present invention discloses a method for preparing branched butadiene-isoprene copolymers. The introduced long branches can significantly improve the melt strength of the polymer under high shear, reduce extrusion swell and die swell, improve filler dispersibility, and significantly improve processability. The preparation method is simple and highly controllable. By adjusting the amount of composite branching agent and the type and ratio of alkyl aluminum, the degree of branching of the copolymer can be precisely controlled, making it suitable for industrial production.

Claims

1. A method for preparing a branched butadiene-isoprene copolymer, characterized in that, Includes the following steps: Under a protective atmosphere, a composite branching agent was added to a solution of butadiene and isoprene monomers, followed by the addition of a rare earth catalyst, and the reaction was carried out to obtain a butadiene-isoprene copolymer. The preparation method of the composite branching agent is as follows: Under a protective atmosphere, alkylaluminum is added dropwise to a solution of disulfur dichloride and allowed to react completely to obtain the desired composite branching agent; the molar ratio of alkylaluminum to disulfur dichloride is 0.5 to 4:

1.

2. The method for preparing a branched butadiene-isoprene copolymer according to claim 1, characterized in that, The alkylaluminum is obtained by mixing one or more of trialkylaluminum, hydrogenated alkylaluminum and chloroalkylaluminum in any proportion.

3. The method for preparing a branched butadiene-isoprene copolymer according to claim 1, characterized in that, The trialkylaluminum is one of trimethylaluminum, triethylaluminum, and triisobutylaluminum; the hydride alkylaluminum is one of diethylaluminum hydride and diisobutylaluminum hydride; the chloroalkylaluminum is one of diisobutylaluminum chloride, trichlorotriethylaluminum, and monochlorodiethylaluminum.

4. The method for preparing a branched butadiene-isoprene copolymer according to claim 1, characterized in that, The composite branching agent accounts for 0.1 wt.% to 0.8 wt.% of the monomer mass, wherein the monomers include butadiene and isoprene; the molar ratio of butadiene to isoprene is 90 to 60: 10 to 40.

5. The method for preparing a branched butadiene-isoprene copolymer according to claim 1, characterized in that, The branched butadiene-isoprene copolymer is reacted at a temperature of 30–70 °C for a time of 1–24 h.

6. The method for preparing a branched butadiene-isoprene copolymer according to claim 1, characterized in that, The mass ratio of rare earth catalyst to butadiene-isoprene in the rare earth catalyst, measured by the number of rare earth atoms in moles, is 4.0 × 10⁻⁶. -6 ~1.0×10 -5 mol: 1 g.

7. The method for preparing a branched butadiene-isoprene copolymer according to claim 1, characterized in that, The rare earth catalyst is prepared as follows: Under a protective atmosphere, alkylaluminum, chloride, and rare earth compound are sequentially added to a reactor, followed by the addition of a solvent, and the mixture is allowed to react fully to obtain the product. The rare earth compound is one or more of rare earth carboxylates, rare earth acidic phosphorus / phosphonates, alkoxy rare earths, rare earth chloride electron-donating complexes, and rare earth sulfonic acid electron-donating complexes, mixed in any proportion. The alkylaluminum is one or more of trialkylaluminum and alkyl aluminum hydride, mixed in any proportion. The chloride is one or more of diisobutylaluminum chloride, diethylaluminum chloride, and triethylaluminum trichlorochloride, mixed in any proportion.

8. The method for preparing a branched butadiene-isoprene copolymer according to claim 7, characterized in that, The molar ratio of the alkylaluminum, chloride, and rare earth compound is 10–30:2–3:

1.

9. The method for preparing a branched butadiene-isoprene copolymer according to claim 7, characterized in that, The reaction temperature is 30–60 °C, and the reaction time is 20–60 min.

10. The branched butadiene-isoprene copolymer obtained by any one of the preparation methods described in claims 1 to 9, characterized in that, The branched butadiene-isoprene copolymer is obtained by polymerization of butadiene-isoprene monomers under the action of a composite branching agent and a rare earth catalyst.

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