A process for the preparation of a high-hind content conjugated diene polymer
By using commercially available lithium metal particles and ether compounds as catalysts, an anionic polymerization method has solved the problems of high cost of lithium initiators and harsh reaction conditions in existing technologies. This method enables the stable preparation of conjugated diene polymers with high side group content and high-purity products, which are suitable for industrial production.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- LIMING RES INST OF CHEM IND
- Filing Date
- 2023-05-26
- Publication Date
- 2026-06-19
AI Technical Summary
Existing lithium initiators are costly, have low lithium utilization rates, and require harsh reaction conditions in conjugated diene polymerization. The resulting products have high gel content, low vinyl content, complex processes, and are not environmentally friendly.
Commercially available lithium metal particles are used as initiators, and ether compounds are used as catalysts and solvents to carry out anionic polymerization. After the reaction, unreacted lithium metal is directly recovered, and the ether compounds can be reused as catalysts and solvents to control the molecular weight and side group content of the polymer.
Stable preparation of conjugated diene polymers with high side group content has been achieved, with adjustable molecular weight, high product purity, mild reaction conditions, and low raw material cost, meeting the needs of industrial production.
Abstract
Description
Technical Field
[0001] This invention relates to the field of polymer synthesis, and in particular to a method for preparing conjugated diene polymers with high side group content. Background Technology
[0002] When lithium is used as an initiator for conjugated diene polymerization, it mainly appears in the form of metallic lithium, organolithium, and lithium complexes.
[0003] Lithium metal can initiate the polymerization of conjugated dienes in hydrocarbon solvents. US Patent 3317918A discloses a method for preparing polybutadiene by initiating butadiene polymerization in petroleum ether using a lithium dispersion with a particle size of 20 μm as an initiator. This method requires expensive lithium dispersions as initiators, has low lithium utilization, and requires the reaction to be carried out under argon or helium atmospheres. The resulting product has high gel content and low vinyl content.
[0004] Organolithium compounds are currently the most important initiators for the synthesis of industrial polymers using anionic methods. Major industrial products such as styrene-butadiene-styrene block copolymers, medium- and high-vinyl polybutadiene rubbers, and low-cis polybutadiene are all synthesized using butyllithium as an initiator. However, organolithium compounds are expensive, with each mole of initiator costing more than 10 times that of metallic lithium.
[0005] Lithium and polycyclic aromatic hydrocarbons (PAHs) can form homogeneous complexes in ether solvents. Chinese patent CN1070198A discloses a method for preparing an initiator for anionic polymerization. In this method, PAHs and metallic lithium react in a mixed solvent composed of aromatic hydrocarbons and a small amount of ethers or amines to obtain the initiator. This initiator can be used for the polymerization of conjugated dienes or styrene monomers to prepare various homopolymers and copolymers. This method requires prior preparation of the initiator, is complex, the mixed solvent is difficult to recycle, and the product contains carcinogenic PAH impurities. Summary of the Invention
[0006] To address the aforementioned problems, this invention provides a method for preparing a conjugated diene polymer with high side group content. This method uses commercially available lithium metal particles as an initiator and ether compounds as a reaction catalyst and solvent, enabling the commercially available lithium metal particles to directly initiate the polymerization of conjugated dienes. Furthermore, unreacted lithium metal can be reused without further processing.
[0007] The technical solution of the present invention is as follows:
[0008] A method for preparing a conjugated diene polymer with high side group content involves using lithium metal as an initiator and carrying out anionic polymerization of conjugated diene monomers in the presence of ether compounds to obtain the conjugated diene polymer.
[0009] The method for preparing the conjugated diene polymer includes the following steps:
[0010] (1) Under nitrogen protection, add lithium metal initiator and ether compound to the reactor and stir until homogeneous;
[0011] (2) Add a solution of conjugated diene monomer or conjugated diene-ether compound to carry out anionic polymerization reaction;
[0012] (3) The reaction was terminated after polymerization and the conjugated diene polymer was obtained after post-treatment.
[0013] The purity of lithium metal is required to be above 98%, preferably 98.0% to 99.9% lithium metal particles with a diameter and length of 2~6 mm*2~6 mm.
[0014] The ether compound simultaneously acts as a reaction catalyst, a side group content regulator, and a solvent, and is one or a mixture of several of the following: diethyl ether, tetrahydrofuran, dioxane, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, and anisole, preferably diethyl ether or tetrahydrofuran.
[0015] The conjugated diene monomer is one or a mixture of butadiene, isoprene, 2,3-dimethylbutadiene and 1,4-dimethylbutadiene, preferably butadiene and isoprene.
[0016] The polymerization reaction temperature is -20~80 ℃, preferably 0~30 ℃; the polymerization reaction time is 0.5~6 h, preferably 1~3 h.
[0017] Step (3) is preferably performed after polymerization, by filtering the reaction solution to remove unreacted lithium metal and adding a terminator to terminate the reaction. After washing with water and drying, a homopolymer or copolymer of conjugated diene can be obtained. The terminator is one or a mixture of methanol, ethanol, and isopropanol, preferably methanol or ethanol.
[0018] The molecular weight and molecular weight distribution of conjugated diene polymers can be effectively controlled by changing the amount of lithium metal and conjugated diene monomers. When the molar ratio of lithium metal to conjugated diene monomers is 10:1 to 1:50, the number average molecular weight of the resulting conjugated diene polymer is 2000 to 20000, the molecular weight distribution index is 1.1 to 1.4, and the side group structure content of the resulting product is 70% to 95%.
[0019] Compared with other lithium-based polymerization processes, the advantages of this invention are that it does not introduce other substances, the metallic lithium and ether compounds in the reaction system can be recycled, only lithium salt waste liquid is generated in the water washing step, and the method is simple to operate, the reaction conditions are mild, the raw material cost is low, no rare gas protection such as argon is required, the metallic lithium can be reused, and it can stably obtain conjugated diene polymers with high side group content of different molecular weights. The products have high purity, stable structure and performance, and meet the needs of industrial production.
[0020] Using the method provided by this invention, conjugated diene polymers of different molecular weights can be stably obtained. When reacting with a fixed amount of feed, depending on the type of conjugated diene used, the resulting product is a colorless, transparent, viscous liquid or a light yellow solid. The molecular weight is stable, and the molecular weight distribution shows a symmetrical single peak. At the same time, the product has good mechanical properties and processing properties. Detailed Implementation
[0021] The present invention will be further illustrated by specific embodiments below.
[0022] Example 1
[0023] Under nitrogen protection, 2 g of lithium metal granules and 100 mL of tetrahydrofuran were added sequentially to a dry, sealed 500 mL three-necked flask. The mixture was stirred thoroughly until homogeneous. After the temperature inside the flask reached 0 °C, 100 g of butadiene-tetrahydrofuran solution with a butadiene content of 25 wt% was added to initiate the polymerization reaction. Throughout the process, the temperature was controlled between 0 and 10 °C. After reacting for 1 h, the reaction solution was filtered and poured into ethanol to recover unreacted lithium metal granules. The reaction solution was washed with water, an antioxidant was added, and then subjected to vacuum distillation using GPC and [other methods]. 1 The prepared polybutadiene was analyzed by H NMR and found to have a number average molecular weight of 3000, a molecular weight distribution index of 1.20, and a vinyl content of 95%.
[0024] Example 2
[0025] Under nitrogen protection, the recovered lithium metal particles from Example 1 and 100 mL of tetrahydrofuran were added sequentially to a dry, sealed 500 mL three-necked flask. The mixture was stirred thoroughly until homogeneous. After the temperature inside the flask reached 0 °C, 100 g of a butadiene-tetrahydrofuran solution with a butadiene content of 25 wt% was added to initiate the polymerization reaction. Throughout the process, the temperature was controlled between 0 and 10 °C. After reacting for 1 h, the reaction solution was filtered and poured into ethanol to recover unreacted lithium metal particles. The reaction solution was washed with water, an antioxidant was added, and vacuum distillation was performed. The resulting polybutadiene was analyzed and found to have a number-average molecular weight of 3200, a molecular weight distribution index of 1.22, and a vinyl content of 95%.
[0026] Example 3
[0027] Under nitrogen protection, 1 g of lithium metal granules and 100 mL of tetrahydrofuran were added sequentially to a dry, sealed 500 mL three-necked flask. The mixture was stirred thoroughly until homogeneous. After the temperature inside the flask reached 0 °C, 200 g of butadiene-tetrahydrofuran solution with a butadiene content of 25 wt% was added to initiate the polymerization reaction. Throughout the process, the temperature was controlled between 0 and 10 °C. After reacting for 1 h, the reaction solution was filtered and poured into ethanol to recover unreacted lithium metal granules. The reaction solution was washed with water, an antioxidant was added, and then subjected to vacuum distillation using GPC and [other methods]. 1 The prepared polybutadiene was analyzed by H NMR and found to have a number average molecular weight of 11,000, a molecular weight distribution index of 1.33, and a vinyl content of 95%.
[0028] Example 4
[0029] Under nitrogen protection, 2 g of lithium metal granules and 100 mL of tetrahydrofuran were added sequentially to a dry, sealed 500 mL three-necked flask. The mixture was stirred thoroughly until homogeneous. After the temperature inside the flask reached 0 °C, 25 g of isoprene was added to initiate the polymerization reaction. Throughout the process, the temperature was controlled between 0 and 10 °C. After reacting for 1 h, the reaction solution was filtered and poured into ethanol to recover unreacted lithium metal granules. The reaction solution was washed with water, an antioxidant was added, and then subjected to vacuum distillation using GPC and [other methods]. 1 The prepared polyisoprene was analyzed by H NMR and found to have a number-average molecular weight of 4000, a molecular weight distribution index of 1.30, and a side group content of 90%.
[0030] Example 5
[0031] Under nitrogen protection, 2 g of lithium metal granules and 100 mL of diethyl ether were added sequentially to a dry, sealed 500 mL three-necked flask. The mixture was stirred thoroughly until homogeneous. After the temperature inside the flask reached 0 °C, 100 g of butadiene-diethyl ether solution with a butadiene content of 25 wt% was added to initiate the polymerization reaction. Throughout the process, the temperature was controlled between 0 and 10 °C. After 1 h of reaction, the reaction solution was filtered and poured into ethanol to recover unreacted lithium metal granules. The reaction solution was washed with water, an antioxidant was added, and vacuum distillation was performed. GPC analysis of the obtained polybutadiene revealed a number-average molecular weight of 3000, a molecular weight distribution index of 1.25, and a vinyl content of 75%.
[0032] Example 6
[0033] Under nitrogen protection, 2 g of lithium metal granules and 100 mL of ethylene glycol dimethyl ether were added sequentially to a dry, sealed 500 mL three-necked flask. The mixture was stirred thoroughly until homogeneous. After the temperature inside the flask reached 0 °C, 100 g of a butadiene-ethylene glycol dimethyl ether solution with a butadiene content of 25 wt% was added to initiate the polymerization reaction. Throughout the process, the temperature was controlled between 0 and 10 °C. After 1 h of reaction, the reaction solution was filtered and poured into ethanol to recover unreacted lithium metal granules. The reaction solution was washed with water, an antioxidant was added, and vacuum distillation was performed. GPC analysis of the obtained polybutadiene revealed a number-average molecular weight of 3000, a molecular weight distribution index of 1.30, and a vinyl content of 70%.
[0034] Example 7
[0035] Under nitrogen protection, 20 g of lithium metal granules and 1000 mL of tetrahydrofuran were added sequentially to a dry, sealed 2 L reactor. The mixture was stirred thoroughly until homogeneous. After the reactor temperature reached 0 °C, 250 g of butadiene was added to initiate the polymerization reaction. Throughout the process, the temperature was controlled between 0 and 10 °C. After 1 h of reaction, the reaction solution was filtered and poured into ethanol to recover unreacted lithium metal granules. The reaction solution was washed with water, an antioxidant was added, and then subjected to vacuum distillation. The resulting polybutadiene was analyzed and found to have a number-average molecular weight of 3100, a molecular weight distribution index of 1.19, and a vinyl content of 95%.
[0036] Comparative Example 1
[0037] Under argon protection, 8 g of lithium metal granules and 400 mL of petroleum ether were added sequentially to a dry, sealed 1 L reactor. The mixture was stirred thoroughly until homogeneous. Once the reactor temperature reached 40 °C, 100 g of butadiene was added to initiate the polymerization reaction. Throughout the process, the temperature was controlled between 40 and 50 °C. After 6 hours of reaction, the reaction solution was filtered and poured into ethanol to stop the reaction. The reaction solution was washed with water, an antioxidant was added, and vacuum distillation was performed, but no polybutadiene product was obtained.
[0038] Compared with US3317918A, replacing the lithium dispersion in US3317918A with lithium metal does not produce polybutadiene.
[0039] Comparative Example 2
[0040] Under nitrogen protection, 2 g of lithium metal granules and 100 mL of cyclohexane were added sequentially to a dry, sealed 500 mL three-necked flask. The mixture was stirred thoroughly until homogeneous. After the temperature inside the flask reached 0 °C, 100 g of a butadiene-cyclohexane solution with a butadiene content of 25 wt% was added to initiate the polymerization reaction. Throughout the process, the temperature was controlled between 0 and 10 °C. After reacting for 1 h, the reaction solution was filtered and poured into ethanol to recover unreacted lithium metal granules. The reaction solution was washed with water, an antioxidant was added, and vacuum distillation was performed, but no polybutadiene product was obtained.
[0041] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. For those skilled in the art, other variations or modifications can be made based on the above description. It is impossible to exhaustively list all the implementation methods here. All obvious variations or modifications derived from the technical solutions of the present invention are still within the protection scope of the present invention.
Claims
1. A method for preparing a conjugated diene polymer with high side group content, wherein lithium metal is used as an initiator, and the conjugated diene monomer undergoes anionic polymerization in the presence of an ether compound to obtain the conjugated diene polymer; The lithium metal has a diameter and length of 2~6 mm and a purity of 98.0%~99.9%. The conjugated diene polymer has a number average molecular weight of 2000-20000, a molecular weight distribution index of 1.1-1.4, and a side group structure content of 70%-95%.
2. The process for preparing a conjugated diene polymer according to claim 1, characterized in that, Includes the following steps: (1) Under nitrogen protection, add lithium metal initiator and ether compound to the reactor and stir until homogeneous; (2) Add conjugated diene monomers or conjugated diene-ether compounds to a solution for anionic polymerization; (3) The reaction was terminated after polymerization and the conjugated diene polymer was obtained after post-treatment.
3. The method for preparing the conjugated diene polymer according to claim 1, characterized in that, The ether compound is one or a mixture of several of the following: diethyl ether, tetrahydrofuran, dioxane, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, and anisole.
4. The method for preparing the conjugated diene polymer according to claim 3, characterized in that, The ether compound is diethyl ether or tetrahydrofuran.
5. The method for preparing the conjugated diene polymer according to claim 1, characterized in that, The conjugated diene monomer is one or a mixture of several of butadiene, isoprene, 2,3-dimethylbutadiene and 1,4-dimethylbutadiene.
6. The method for preparing the conjugated diene polymer according to claim 5, characterized in that, The conjugated diene monomers are butadiene and isoprene.
7. The method for preparing the conjugated diene polymer according to claim 1, characterized in that, The polymerization reaction temperature is 0~30 ℃.
8. The method for preparing the conjugated diene polymer according to claim 1, characterized in that, The polymerization reaction time is 0.5~6 h.
9. The method for preparing the conjugated diene polymer according to claim 8, characterized in that, The polymerization reaction time is 1~3 hours.
10. The method for preparing the conjugated diene polymer according to claim 2, characterized in that, Step (3) involves filtering the reaction solution after polymerization to remove unreacted lithium metal and adding a terminator to terminate the reaction. After washing with water and drying, homopolymer or copolymer products of conjugated dienes can be obtained.
11. The method for preparing the conjugated diene polymer according to claim 10, characterized in that, The terminating agent is one or a mixture of methanol, ethanol, and isopropanol.
12. The method for preparing the conjugated diene polymer according to claim 11, characterized in that, The terminating agent is methanol or ethanol.
13. The method for preparing the conjugated diene polymer according to claim 1, characterized in that, The molar ratio of lithium metal to conjugated diene monomer is 10:1 to 1:50.