A process for the preparation of polyisobutylene

Abstract

The application relates to the technical field of high polymer material preparation, and discloses a preparation process of polyisobutene, which comprises the following steps: after the completion of cationic polymerization of isobutene, a polyisobutene solution contained in a polymerization solvent is sequentially subjected to three-step post-treatment: in the first step, Mg-Al type layered double hydroxide is added, stirring and filtration are conducted, and residual halogen anions are removed and acidic substances are neutralized at the same time; in the second step, a prepared stabilizer-diatomite composite is added, and through solid-phase dispersion, a hindered phenolic primary antioxidant and a metal passivator are uniformly distributed and residual metal ions are chelated; in the third step, alpha-tocopherol is added, and a regeneration mechanism of providing hydrogen atoms for a hindered phenolic oxy radical is utilized to delay net consumption of the primary antioxidant; and polymerization solvent is evaporated to obtain a stabilized product. The application realizes universal dehalogenation and synchronous acid neutralization of BF3 and AlCl3 catalyst systems, and significantly improves the utilization rate of the stabilizer and the storage stability of the polyisobutene product.

Description

Technical Field

[0001] This invention relates to the field of polymer material preparation technology, and more specifically, to a preparation process for polyisobutylene. Background Technology

[0002] Polyisobutylene (PIB) is a polymer material prepared by cationic polymerization of isobutylene as the main monomer. It is widely used in lubricant additives, fuel cleaners, and sealing materials. Industrially, cationic polymerization is typically carried out using BF3 complexes (such as BF3·ethyl ether) or Lewis acid catalysts such as AlCl3. After polymerization, three types of harmful components inevitably remain in the polyisobutylene solution: firstly, metal cations or Lewis acidic substances generated by catalyst hydrolysis (residual Al in the AlCl3 system). 3+ The residual fluoroboronic acid substances in the BF3 system can promote the decomposition of hydroperoxides at the residual unsaturated bonds in the polyisobutylene molecular chain, generating alkoxy and peroxy free radicals, thus accelerating the oxidative degradation of polyisobutylene; secondly, the halide anions generated by the catalyst hydrolysis (F in the BF3 system) - The AlCl3 system produces Cl - The catalyst competes with the coordination functional groups of the metal passivator to bind metal ions, thus significantly reducing the chelation and blocking rate of metal ions by the metal passivator; thirdly, the acidic substances (HF, HCl) generated by the hydrolysis of the catalyst accelerate the oxidative degradation of polyisobutylene and speed up the consumption of the stabilizer.

[0003] Existing technologies typically involve adding a combination of hindered phenolic primary antioxidants and metal passivators to polyisobutylene after polymerization and solvent removal to improve storage stability. However, these technologies have the following drawbacks: High molecular weight PIB (number average molecular weight Mn greater than 10,000) is semi-solid to solid at room temperature. When stabilizers are directly added to this high-viscosity system, they are difficult to diffuse uniformly, resulting in uneven distribution and low actual utilization rate; the F generated by the BF3 system... - Cl generated with the AlCl3 system - Due to their different properties, existing anion exchange resin dehalogenation technologies must be tailored to F. - and Cl - Different types of resins were selected, and the resins could only capture halogen anions and could not simultaneously neutralize acidic substances such as HF and HCl; the residual hindered phenolic main antioxidants were continuously consumed in the long-term process of capturing peroxide free radicals, generating inactive hindered phenolic oxygen free radicals, and the effective concentration of the main antioxidants continued to decrease over the storage time.

[0004] The above-mentioned problems combined result in insufficient storage stability of polyisobutylene products, high consumption of stabilizers, and poor process economy and environmental protection. Summary of the Invention

[0005] This invention provides a preparation process for polyisobutylene, which solves the technical problems in related technologies such as the inability to simultaneously remove residual halogen anions and acidic substances in the post-processing of polyisobutylene, the uneven distribution of stabilizers in high-viscosity systems leading to low utilization, and the continuous consumption of hindered phenolic main antioxidants during storage resulting in short effective storage life.

[0006] This invention provides a process for preparing polyisobutylene. After the cationic polymerization step of isobutylene is completed, the polyisobutylene solution contained in the polymerization solvent is used as the post-treatment object, and the following steps one to three are performed sequentially: Step 1: Add layered double hydroxide to the polyisobutylene solution, stir and mix at 15-35℃, filter to remove the solid layered double hydroxide, capture the halogen anions in the polyisobutylene solution through interlayer anion exchange, and at the same time use the hydroxyl groups of the layers to neutralize the residual acidic substances to obtain the dehalogenated and purified polyisobutylene solution. Step 2: Add a stabilizer-diatomaceous earth composite to the dehalogenated and purified polyisobutylene solution obtained in Step 1. The stabilizer-diatomaceous earth composite is a solid dispersion prepared by loading a hindered phenolic main antioxidant and a metal passivator onto the inner wall of the pores of diatomaceous earth. After stirring and dispersing, the metal passivator chelates and coordinates with the residual metal ions in the solution. Step 3: Add tocopherol to the polyisobutylene solution obtained in Step 2, so that it is uniformly dispersed in the polyisobutylene solution in a free state. Tocopherol provides hydrogen atoms to the hindered phenolic radicals to regenerate the hindered phenolic main antioxidant. After Step 3 is completed, evaporate the polymerization solvent to obtain the stabilized polyisobutylene product.

[0007] Preferably, the layered double hydroxide described in step one is a Mg-Al type layered double hydroxide with the general formula: Where x is 0.2-0.4, and the initial interlayer anion is NO3. - The particle size is 5100μm.

[0008] Preferably, in step one, the amount of layered double hydroxide added is 0.5%-3% of the mass of polyisobutylene, the stirring and mixing time is 0.5-2 hours, and the pore size of the filter medium used for filtration is not greater than 5μm.

[0009] Preferably, the halogen-saturated layered double hydroxide solid obtained from filtration in step one is regenerated and recycled for use in step one by the following steps: elution with a 5%-15% (w / w) Na₂CO₃ aqueous solution at 15-35°C for 13 hours by stirring, followed by filtration to separate the halogen-containing waste liquid to obtain CO₃. 2- Layered double hydroxides; CO3 2-The layered double hydroxide was calcined in air at 400-500℃ for 13 hours to decompose it into mixed metal oxides. These mixed metal oxides were then placed in a 5%-10% NaNO3 aqueous solution and stirred at 15-35℃ for 24 hours to reconstruct NO3 using the structural memory effect. - The layered double hydroxide is filtered and recycled for use in step one.

[0010] Preferably, the method for preparing the stabilizer-diatomaceous earth composite in step two is as follows: a stabilizer solution is prepared by dissolving a hindered phenolic main antioxidant and a metal passivator in an organic solvent, and then mixing and stirring the stabilizer solution with diatomaceous earth powder for 13 hours. The solvent is then removed by evaporation under reduced pressure conditions not exceeding 50°C and not exceeding 0.03 MPa to obtain the stabilizer-diatomaceous earth composite. The diatomaceous earth has a pore size of 0.110 μm, and its dosage is 1%-5% of the mass of polyisobutylene. The total pore volume of the diatomaceous earth is not less than the total volume of the prepared stabilizer solution.

[0011] Preferably, the organic solvent is ethanol, and the amount of solvent used is 5 to 20 times the total mass of the hindered phenolic main antioxidant and the metal passivator.

[0012] Preferably, the hindered phenolic primary antioxidant is pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], and its addition amount is 0.1% to 1.0% of the mass of polyisobutylene.

[0013] Preferably, the metal passivating agent is N,N'-disaccharide-1,2-propanediamine, and its addition amount is 0.05%-0.5% of the mass of polyisobutylene.

[0014] Preferably, the tocopherol mentioned in step three is α-tocopherol, and its addition amount is 0.05% to 0.3% of the mass of polyisobutylene. The mixture is stirred at 15-35°C for 0.5 hours to ensure uniform dispersion in the polyisobutylene solution.

[0015] Preferably, after step three is completed, the polymerization solvent is removed by vacuum evaporation at 40-80°C and 0.005-0.05MPa absolute pressure.

[0016] The beneficial effects of this invention are: the use of Mg-Al type NO3 - Layered double hydroxides simultaneously achieve the effect of F - (BF3 system) and Cl - The universal removal of (AlCl3 system) eliminates the limitation that existing anion exchange resins must be selected separately for different halogens; During dehalogenation, LDH utilizes the hydroxyl groups of the laminations to neutralize acidic substances such as HF and HCl, achieving dehalogenation and acid neutralization in one step. Halogen-saturated LDH is recycled after being eluted and calcined with Na2CO3, resulting in a small amount of halogen-containing waste liquid and a high level of green process. The stabilizer is pre-loaded into the pores of diatomaceous earth and introduced into the polyisobutylene solution as a solid dispersion, overcoming the problems of difficult diffusion and uneven distribution of the stabilizer in high-viscosity polyisobutylene, and significantly improving the actual utilization efficiency. Tocopherol is added separately at the end in a free state, which delays the net consumption of the main antioxidant by regenerating hindered phenolic oxygen radicals, thus extending the effective shelf life of the product.

[0017] In summary, this invention systematically solves the technical problems of dehalogenation and purification, uniform dispersion of stabilizers, and synergistic antioxidant in the post-processing of polyisobutylene through a sequential three-step post-processing process, which significantly improves the storage stability of the product and the economy and environmental friendliness of the process. Attached Figure Description

[0018] Figure 1 This refers to the layered double hydroxide and Cl in Experiment 1 of this invention. - Type anion exchange resin - A bar chart comparing removal rates; Figure 2 This refers to the layered double hydroxide and Cl in Experiment 1 of this invention. - A comparative bar chart showing the effect of different types of anion exchange resins on the pH of the system; Figure 3 This is a bar chart comparing the distribution uniformity of Irganox 1010 in polyisobutylene using the stabilizer-diatomaceous earth composite dispersion method (M-composite) and the melt mixing method (M-melt mixing) in Experiment 2 of this invention. Figure 4 This is a graph showing the change in the residual amount of Irganox 1010 over time during the accelerated aging process at 70°C for polyisobutylene products containing and without α-tocopherol in Experiment 3 of this invention. Figure 5 This is a graph showing the oxidation induction time (OIT) of polyisobutylene products containing and without α-tocopherol during accelerated aging at 70°C in Experiment 3 of this invention. Detailed Implementation

[0019] The subject matter described herein will now be discussed with reference to exemplary embodiments. It should be understood that these embodiments are discussed only to enable those skilled in the art to better understand and implement the subject matter described herein, and changes may be made to the function and arrangement of the elements discussed without departing from the scope of this specification. Various processes or components may be omitted, substituted, or added as needed in the examples. Furthermore, some features described in the examples may be combined in other examples. Example 1

[0020] This embodiment discloses a process for preparing polyisobutylene. The process uses polyisobutylene (number-average molecular weight Mn of 20000) prepared with AlCl3 catalyst and n-hexane as polymerization solvent as the processing material. The process involves taking a 1000g n-hexane solution containing polyisobutylene and sequentially performing the following steps: Step 1: Add Mg-Al type layered double hydroxide with a particle size of 15 μm (x=0.25, initial interlayer anion is NO3) to the polyisobutylene n-hexane solution. - 10g of a compound (1.0% of the mass of polyisobutylene) was stirred and mixed at 15°C for 0.5 hours, allowing the layered double hydroxide to capture residual Cl in the solution through interlayer anion exchange. - Simultaneously, the residual HCl is neutralized by the hydroxyl groups of the layer, restoring the solution system from acidic to neutral. After the mixing and contact are completed, the layered double hydroxide solid is removed by filtration with industrial filter paper with a pore size of 3μm, resulting in a dehalogenated and purified polyisobutylene-n-hexane solution.

[0021] Step 2: Dissolve 1.0 g of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] (0.1% of the mass of polyisobutylene) and 0.5 g of N,N'-disaccharide-1,2-propanediamine (0.05% of the mass of polyisobutylene) in 7.5 g of ethanol (the amount of ethanol used is 5 times the total mass of the stabilizer 1.5 g, and the volume of ethanol is about 9.5 mL) to prepare a stabilizer ethanol solution; add the above stabilizer ethanol solution to 10 g of diatomaceous earth powder with a pore size of 0.5~2 μm and a pore volume of 1.2 mL / g (1.0% of the mass of polyisobutylene; total pore volume = 10 g). ×1.2mL / g=12mL, which is greater than the stabilizer solution volume of 9.5mL, meeting the requirement that all the solution penetrates into the pores. The mixture is stirred and impregnated at 20℃ for 1 hour, allowing the stabilizer ethanol solution to penetrate into the diatomaceous earth pores by capillary force. Subsequently, the ethanol is removed by vacuum evaporation at 40℃ and an absolute pressure of 0.02MPa, yielding the stabilizer-diatomaceous earth composite. This stabilizer-diatomaceous earth composite is added to the dehalogenated and purified polyisobutylene-hexane solution obtained in step one, and stirred and dispersed at 15℃ for 0.5 hours, ensuring that the diatomaceous earth particles are uniformly suspended in the polyisobutylene solution. The metal passivator reacts with the residual Al in the solution. 3+ Chelation coordination occurs.

[0022] Step 3: Add 0.5g of α-tocopherol (0.05% of the mass of polyisobutylene) to the polyisobutylene solution obtained in Step 2, and stir at 15°C for 0.5 hours to allow α-tocopherol to be uniformly dispersed in the polyisobutylene solution in a free state.

[0023] After processing in steps one through three, n-hexane is removed by vacuum distillation at 40°C and 0.005 MPa to obtain a stabilized polyisobutylene product containing hindered phenolic main antioxidant, metal passivator, α-tocopherol and diatomaceous earth. Example 2

[0024] This embodiment discloses a process for preparing polyisobutylene. The process uses polyisobutylene (number-average molecular weight Mn of 50,000) prepared with BF3·diethyl ether complex catalyst and n-hexane as polymerization solvent as the processing material. The process involves taking a 1000g n-hexane solution containing polyisobutylene and sequentially performing the following steps: Step 1: Add Mg-Al type layered double hydroxide with a particle size of 30 μm (x=0.30, initial interlayer anion is NO3) to the polyisobutylene n-hexane solution. - 15g of (type) polyisobutylene (1.5% of the mass of polyisobutylene) was stirred and mixed at 25°C for 1 hour, allowing the layered double hydroxide to capture residual F in the solution through interlayer anion exchange. - Simultaneously, the residual HF is neutralized using the hydroxyl groups of the layered plates. After mixing and contact, the layered double hydroxide solid is removed by filtration with 3μm industrial filter paper to obtain a dehalogenated and purified polyisobutylene-hexane solution. The halogen-saturated layered double hydroxide solid obtained by filtration is regenerated and recycled in step one according to the following steps: it is added to a 10% (w / w) Na₂CO₃ aqueous solution and stirred and eluted at 25°C for 2 hours to remove CO₃²⁻. 2- Interlayer F - Displacement release; filtration separation of F-containing substances - CO3 is obtained from waste liquid 2- Layered double hydroxides; CO3 2- The layered double hydroxide was calcined at 450°C for 2 hours in air to completely decompose the layered structure into a mixed metal oxide of MgO and Al2O3. After cooling to room temperature, the mixed metal oxide was placed in a 9% (w / w) NaNO3 aqueous solution and stirred and dispersed at 25°C for 3 hours to reconstruct NO3 using the structural memory effect. - Type Mg-Al layered double hydroxide; NO3 recovered by filtration - The layered double hydroxide is recycled for step one.

[0025] Step 2: Dissolve 4.0 g of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate (0.4% of the mass of polyisobutylene) and 1.5 g of N,N'-disalicylate-1,2-propanediamine (0.15% of the mass of polyisobutylene) in 27.5 g of ethanol (the amount of ethanol used is 5 times the total mass of the stabilizer 5.5 g, and the volume of ethanol is about 34.9 mL) to prepare a stabilizer ethanol solution; add the above stabilizer ethanol solution to 30 g of diatomaceous earth powder with a pore size of 1~5 μm and a pore volume of 1.3 mL / g. The 3.0% of polyisobutylene mass (total pore volume = 30g × 1.3mL / g = 39mL, greater than the stabilizer solution volume of 34.9mL) was mixed and stirred at 20℃ for 2 hours; then, the ethanol was removed by vacuum evaporation at 45℃ and an absolute pressure of 0.02MPa to obtain the stabilizer-diatomaceous earth composite; the obtained stabilizer-diatomaceous earth composite was added to the dehalogenated and purified polyisobutylene n-hexane solution obtained in step one, and stirred and dispersed at 25℃ for 1 hour, where the metal passivating agent chelated and coordinated with the residual trace metal ions in the solution.

[0026] Step 3: Add 1.5g of α-tocopherol (0.15% of the mass of polyisobutylene) to the polyisobutylene solution obtained in Step 2, and stir at 25°C for 0.5 hours to allow α-tocopherol to be uniformly dispersed in the polyisobutylene solution in a free state.

[0027] After processing in steps one through three, n-hexane was removed by vacuum distillation at 60°C and 0.01 MPa absolute pressure to obtain a stabilized polyisobutylene product containing hindered phenolic main antioxidant, metal passivator, α-tocopherol and diatomaceous earth. Example 3

[0028] This embodiment discloses a process for preparing polyisobutylene. The process uses high-molecular-weight polyisobutylene (number-average molecular weight Mn of 100,000) prepared with AlCl3 catalyst and methyl chloride (boiling point -24°C) as the polymerization solvent. Since methyl chloride is gaseous at 15-35°C and atmospheric pressure, it is first evaporated after polymerization. Then, 1000g of the resulting polyisobutylene is dissolved in n-hexane. The resulting n-hexane solution is used as the post-treatment object, and the following steps are performed sequentially: Step 1: Add Mg-Al type layered double hydroxide with a particle size of 50 μm (x=0.35, initial interlayer anion is NO3) to the polyisobutylene n-hexane solution. - 25g of (type) polyisobutylene (2.5% of the mass of polyisobutylene) was stirred and mixed at 30°C for 1.5 hours, allowing the layered double hydroxide to capture residual Cl in the solution through interlayer anion exchange. -Simultaneously, the residual HCl is neutralized by the hydroxyl groups of the layer; after mixing and contacting, the layered double hydroxide solid is removed by filtration using a stainless steel filter with a pore size of 5μm, resulting in a dehalogenated and purified polyisobutylene-hexane solution.

[0029] Step 2: Dissolve 8.0 g of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] (0.8% of the mass of polyisobutylene) and 3.0 g of N,N'-disaccharide-1,2-propanediamine (0.3% of the mass of polyisobutylene) in 55.0 g of ethanol (the amount of ethanol is 5 times the total mass of the stabilizer 11.0 g, and the volume of ethanol is approximately 69.7 mL) to prepare a stabilizer ethanol solution; add the above stabilizer ethanol solution to 50 g of diatomaceous earth powder with a pore size of 3-10 μm and a pore volume of 1.5 mL / g. In g (5.0% of the mass of polyisobutylene; total pore volume = 50g × 1.5mL / g = 75mL, greater than the stabilizer solution volume of 69.7mL), the mixture was stirred and impregnated at 25℃ for 3 hours; then, ethanol was removed by vacuum evaporation at 50℃ and an absolute pressure of 0.03MPa to obtain the stabilizer-diatomaceous earth composite; the obtained stabilizer-diatomaceous earth composite was added to the dehalogenated and purified polyisobutylene n-hexane solution obtained in step one, and stirred and dispersed at 30℃ for 1 hour, where the metal passivating agent chelated and coordinated with the residual Al³⁺ in the solution.

[0030] Step 3: Add 2.5g of α-tocopherol (0.25% of the mass of polyisobutylene) to the polyisobutylene solution obtained in Step 2, and stir at 30°C for 0.5 hours to allow α-tocopherol to be uniformly dispersed in the polyisobutylene solution in a free state.

[0031] After processing in steps one through three, n-hexane was removed by vacuum distillation at 75°C and 0.03 MPa to obtain a stabilized polyisobutylene product containing hindered phenolic main antioxidant, metal passivator, α-tocopherol and diatomaceous earth. Example 4

[0032] This embodiment discloses a process for preparing polyisobutylene. After the cationic polymerization step of isobutylene is completed, the polyisobutylene solution contained in the polymerization solvent is used as the post-treatment object, and steps one to three are performed sequentially. After completion, the polymerization solvent is evaporated to obtain a stabilized polyisobutylene product. The polymerization solvent is n-hexane; when using a low-boiling-point solvent such as methyl chloride (CH3Cl, boiling point -24℃) as the polymerization solvent, the methyl chloride must be evaporated first after polymerization, and then the obtained polyisobutylene is dissolved in n-hexane, with the resulting n-hexane solution used as the post-treatment object.

[0033] Step 1: The polyisobutylene solution is dehalogenated and neutralized with acid using layered double hydroxides to obtain a dehalogenated and purified polyisobutylene solution.

[0034] Mg-Al type layered double hydroxides are selected, with the general formula being: (x is 0.30, m is the number of water molecules of crystallization), the LDH powder has a particle size of 30 μm, and the initial interlayer anion is NO3. - Type. The affinity order of the anions in the LDH interlayer is CO3. 2- >> F - > Cl - NO3 - NO3 was selected. - The type is due to NO3 - The affinity for interlayer sites is lower than that for F. - and Cl - Residual F in polyisobutylene solution - or Cl - Interlayer NO3 - Successful replacement achieves efficient dehalogenation; if CO3 is used 2- Type LDH, then F - and Cl - It cannot be replaced and lacks dehalogenation function. LDH to F - and Cl - Both exhibit anion exchange affinity, regardless of whether the residual F in the polyisobutylene solution originates from the BF3 catalyst system. - Cl from the AlCl3 catalyst system - All of them can be captured and fixed in the interlayer through anion exchange, without the need to change different materials according to the type of catalyst system.

[0035] LDH was added to a polyisobutylene solution containing residual halogen anions and acidic substances. The amount of LDH added was 1.5% of the mass of polyisobutylene. The mixture was stirred and mixed at 15-35°C for 1 hour to ensure sufficient contact between the LDH particles and the polyisobutylene solution. This allowed the exchangeable anion sites between the LDH layers to interact with the F in the solution. - or Cl - Anion exchange occurs, capturing and immobilizing halide anions within the LDH interlayer, allowing them to transfer from the polyisobutylene solution to the LDH solid phase. Simultaneously, the hydroxyl groups on the LDH layers neutralize residual acidic substances such as HF and HCl, restoring the polyisobutylene solution from acidic to neutral. After mixing and contact, the LDH solid is removed by filtration using a filter medium with a pore size no larger than 5 μm, yielding a dehalogenated and purified polyisobutylene solution.

[0036] Halogen-saturated LDH solids were soaked in a 10% (w / w) Na₂CO₃ aqueous solution and eluted with stirring at 1535°C for 2 hours to remove F₂ from the interlayer. - and Cl - CO3 2-The affinity for LDH interlayer anion exchange sites is significantly higher than that for F. - and Cl - Therefore, the CO3 in the Na2CO3 solution 2- The fixed F can be - and Cl - Displacement releases CO3. 2- Type LDH. Filtration separates the regeneration wastewater containing F⁻ / Cl⁻, and the halogen concentration in the wastewater is much lower than that of the halogen-containing wastewater generated by regenerating anion exchange resin with NaOH solution. Due to CO₃²⁻... 2- It has the highest affinity for interlayer exchange sites, and the resulting CO3 2- Type LDH requires a calcination-reconstruction step to restore its anion exchange capacity: CO32-2000 LDH2000 is used to calcine and rebuild the LDH. 2- LDH was calcined at 450°C for 2 hours in air to completely decompose its layered structure into mixed metal oxides. After cooling to room temperature, the resulting mixed metal oxides were placed in a 9% (w / w) NaNO3 aqueous solution and stirred and dispersed at 15-35°C for 3 hours. The structure memory effect of LDH was then used to reconstruct NO3. - LDH layered structure, NO3 recovered by filtration - Type LDH, used cyclically in step one.

[0037] Step 2: Add the stabilizer-diatomaceous earth composite to the polyisobutylene solution to obtain a polyisobutylene solution with a uniformly distributed stabilizer. The preparation method of the stabilizer-diatomaceous earth complex is as follows: Pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] (molecular weight 1178 g / mol, possessing four active phenolic hydroxyl functional groups, exhibiting superior long-term antioxidant protection compared to monofunctional hindered phenols; the addition amount is 0.4% of the mass of polyisobutylene) and N,N'-disalicylate-1,2-propanediamine (molecular weight 282...) g / mol, Schiff basic metal passivating agent, with better chelating effect on Al³⁺ than oxaloyl aniline; added at 0.15% of polyisobutylene mass) is dissolved together with ethanol (N,N'-disalicylate-1,2-propanediamine has low solubility in n-hexane, so ethanol must be used to ensure complete dissolution of both stabilizers; the amount of solvent is 5 times the total mass of stabilizers) to prepare a stabilizer solution; the above stabilizer solution is then mixed with diatomaceous earth powder (diatomaceous earth is a porous silica mineral with a pore size of 0.1-10 μm, its amount is 3% of the mass of polyisobutylene; the total pore volume of the diatomaceous earth used must not be less than the total volume of the prepared stabilizer solution so that all the stabilizer solution can penetrate into the inner wall of the pores; based on 1000g of polyisobutylene: Irganox The following ingredients were used: 1010 (4.0g), N,N'-dihydrate salicyl-1,2-propanediamine (1.5g, totaling 5.5g), ethanol (27.5g, approximately 34.9mL), and diatomaceous earth (30g). The pore volume was 1.2mL / g, resulting in a total pore volume of 30g × 1.2mL / g = 36mL (≥ 34.9mL), which met the requirement of complete solution penetration into the pores. The mixture was stirred and impregnated for 2 hours to allow the stabilizer solution to penetrate the diatomaceous earth pores via capillary force and be adsorbed onto the pore walls. Subsequently, the ethanol was removed by vacuum evaporation at 45℃ and 0.02MPa (ethanol's boiling point at normal pressure is 78℃, requiring vacuum evaporation at 45℃ for complete removal). This yielded a stabilizer-diatomaceous earth composite with the main antioxidant and metal passivator uniformly loaded onto the inner walls of the diatomaceous earth pores.

[0038] The stabilizer-diatomaceous earth composite was added to the dehalogenated and purified polyisobutylene solution obtained in step one, and stirred and dispersed at 15-35°C for 1 hour to ensure that the diatomaceous earth particles were uniformly suspended in the polyisobutylene solution as a solid dispersion. The stabilizer was pre-fixed uniformly to the inner wall of the diatomaceous earth pores. When the diatomaceous earth particles were uniformly dispersed in the polyisobutylene solution, the main antioxidant and metal passivator were uniformly distributed throughout the polyisobutylene solution along with the diatomaceous earth particles, overcoming the deficiency of uniform diffusion caused by the high viscosity when the stabilizer was directly added to high-viscosity polyisobutylene. After the metal passivator was released from the diatomaceous earth pores into the polyisobutylene solution, it reacted with trace metal ions (such as Al) remaining in the system after step one treatment. 3+ Chelating coordination occurs, locking metal ions in a stable complex, thereby eliminating the catalytic effect of metal ions on the oxidative degradation of polyisobutylene.

[0039] Step 3: Add tocopherol to the polyisobutylene solution to obtain a polyisobutylene solution containing hindered phenolic main antioxidant, metal passivating agent and free tocopherol. After step two is completed, α-tocopherol is added to the polyisobutylene solution at a concentration of 0.15% of the polyisobutylene mass. The mixture is stirred at 15-35°C for 0.5 hours to ensure that the α-tocopherol is uniformly dispersed in a free state within the polyisobutylene solution. Tocopherol must be added after step two for the following reason: the phenolic hydroxyl groups of tocopherol have a certain adsorption affinity for the silanol groups on the surface of diatomaceous earth. If tocopherol and the stabilizer-diatomaceous earth composite are added to the polyisobutylene solution simultaneously, some of the free tocopherol will be adsorbed onto the surface and pores of the composite particles, leading to a decrease in the concentration of free tocopherol in the polyisobutylene solution and a weakening of the synergistic antioxidant effect. Adding tocopherol after the stabilizer-diatomaceous earth composite is completely dispersed in the polyisobutylene solution in step two ensures that the tocopherol is uniformly dispersed in a free state, fully leveraging its synergistic regeneration effect on the main antioxidant.

[0040] The phenolic hydroxyl group of α-tocopherol (Toc-OH) donates a hydrogen atom to the hindered phenoxy radical (ArO•), reducing it to the hindered phenol (ArOH) with antioxidant activity, thus regenerating the primary antioxidant. Simultaneously, tocopherol itself transforms into a tocopheryloxy radical (Toc-O•). Due to the resonance delocalization provided by the benzodihydropyran ring structure and the steric hindrance effect of multiple methyl substituents on the ring, Toc-O• exhibits high stability and low reactivity, failing to abstract hydrogen atoms from the polyisobutylene chain to initiate new oxidation chain reactions, ultimately terminating harmlessly. This synergistic effect significantly reduces the net consumption rate of the primary antioxidant, extending the effective protective lifespan of the primary antioxidant and metal passivator for polyisobutylene products.

[0041] After processing in steps one to three, n-hexane is removed by vacuum distillation at 60°C and 0.01 MPa absolute pressure (under these conditions, the boiling point of n-hexane is about 30°C, which can effectively remove it without damaging the added stabilizer), resulting in a stabilized polyisobutylene product containing hindered phenolic main antioxidant, metal passivator, α-tocopherol and diatomaceous earth, which is the target product of this embodiment.

[0042] Experimental verification Experiment 1: Verification of the Simultaneous Dehalogenation and Acid Neutralization Effect of Layered Double Hydroxides 1. Experimental Objective In the verification step one, Mg-Al type NO3 was used. -When treating polyisobutylene solution with layered double hydroxide (LDH), can it simultaneously achieve (1) effective removal of F⁻ and (2) neutralization of acidic substances such as HF? This is compared with commonly used anion exchange resins in the prior art (D201 type strong base anion exchange resin, Cl⁻ type; Cl⁻ type resin uses Cl⁻ as the counterion, and its affinity for F⁻ is higher than that for Cl⁻. It can exchange and adsorb F⁻ in the solution to the resin and release Cl⁻, but what is released is Cl⁻ instead of OH⁻, and it cannot neutralize acidic substances such as HF).

[0043] 2. Preparation of experimental samples Based on the parameters of Example 2: a polyisobutylene (Mn=50000) n-hexane solution prepared by the BF3·diethyl ether complex catalyst system was taken, containing 1000g of polyisobutylene, with an initial F⁻ concentration of 620mg / kg (based on the mass of polyisobutylene), and an initial system pH of 3.2 (determined by the aqueous extract of the solution). The above solution was divided into three equal portions and numbered accordingly: S-Blank: Without adding any dehalogenating reagent, stir directly at 25℃ for 0.5 hours as a blank control with isothermal stirring. S-Resin: Add 10g (1.0% of polyisobutylene mass) of D201 type strong basic anion exchange resin (Cl⁻ type, with Cl⁻ as the counterion, capable of exchanging and adsorbing F⁻ and releasing Cl⁻), stir at 25℃ for 0.5 hours, filter to remove resin, and take the filtrate for analysis. S-LDH: Add Mg-Al type NO₃⁻ with a particle size of 30μm. - 10 g of a layered double hydroxide (1.0% of the mass of polyisobutylene, x=0.30) was stirred at 25°C for 0.5 hours, filtered through 3 μm industrial filter paper, and the filtrate was tested.

[0044] 3. Detection Method (1) F⁻ removal rate: The n-hexane solution of each sample was extracted with deionized water (n-hexane solution: deionized water = 1:1 volume ratio, extracted 3 times), the aqueous phases were combined, and the F⁻ concentration in the aqueous phase was determined by ion chromatography (IC) to calculate the F⁻ removal rate. (2) pH of the system after treatment: The pH of the aqueous phase after the n-hexane solution of each sample was extracted with deionized water was measured at 25℃ using a pH meter (accuracy 0.01).

[0045] 4. Experimental Data

[0046] 5. Results Analysis The F⁻ removal rates of S-resin and S-LDH were similar (94.7% vs. 95.5%), indicating that LDH's F⁻ removal capacity is comparable to that of existing Cl⁻-type anion exchange resins. However, after treatment with S-resin, the pH of the system only increased from 3.2 to 3.4, indicating almost no neutralization effect: Cl⁻-type D201 resin releases Cl⁻ instead of OH⁻ while adsorbing F⁻, and therefore cannot neutralize HF, so the acidity of the system remained essentially unchanged. After S-LDH treatment, the pH of the system increased from 3.2 to 6.8, approaching neutrality, because the Mg-OH / Al-OH hydroxyl groups on the LDH plate directly reacted with HF to neutralize the acidity, which was significantly eliminated.

[0047] LDH simultaneously achieved dehalogenation (95.5% removal rate) and acid neutralization (pH increase from 3.2 to 6.8) in a single-step treatment, while Cl⁻-type anion exchange resins could only remove F⁻ and could not neutralize acidic substances like HF, verifying the technological advantage of step one. Furthermore, Cl⁻-type D201 resin can only be used in the BF⁻ system (F⁻) and is ineffective in the AlCl⁻ system (Cl⁻) (the counterion of Cl⁻-type resins is Cl⁻, which cannot adsorb Cl⁻); while LDH is applicable to both F⁻ and Cl⁻, further demonstrating the versatility of LDH. See Figure 1 and Figure 2 .

[0048] Experiment 2: The effect of the dispersion method of diatomaceous earth composite carrier on the uniformity of stabilizer distribution 1. Experimental Objective The study aimed to verify whether the solid-phase dispersion method of the stabilizer-diatomaceous earth composite used in step two could significantly improve the uniformity of stabilizer distribution in polyisobutylene compared to the existing technology of directly adding the stabilizer to solid polyisobutylene (melt mixing method).

[0049] 2. Preparation of experimental samples Based on the stabilizer formulation of Example 2 (Irganox 1010: 0.4%, N,N'-disaccharide-1,2-propanediamine: 0.15%), two sets of samples were prepared from the same batch of BF3·ethyl ether system polyisobutylene (Mn=50000): M-complex (method of the present invention): Following step two of Example 2, Irganox 1010 (4.0 g) and N,N'-disaccharide-1,2-propanediamine (1.5 g) were dissolved in ethanol (27.5 g) and then loaded onto diatomaceous earth (30 g). After vacuum evaporation of ethanol, a stabilizer-diatomaceous earth complex was obtained. A polyisobutylene n-hexane solution (1000 g polyisobutylene) was added, and the mixture was stirred and dispersed at 25 °C for 1 hour. The n-hexane was then evaporated to obtain a solid polyisobutylene product.

[0050] M-Melting (Control Group, Existing Technology): Solid polyisobutylene (1000g) after hexane removal is heated to 80°C to become molten. Irganox 1010 powder (4.0g) and N,N'-disaccharide-1,2-propanediamine powder (1.5g) are directly added. The mixture is stirred at 200rpm for 1 hour at 80°C using a paddle stirrer. After cooling, solid polyisobutylene product is obtained.

[0051] 3. Detection Method Five locations (locations 1 to 5, approximately 5g per point) were uniformly sampled from top to bottom along the longitudinal section of each sample. The content of Irganox 1010 (mg / kg, based on the mass of polyisobutylene) at each sampling point was determined by high performance liquid chromatography (HPLC). The uniformity of distribution was evaluated using the coefficient of variation (CV = standard deviation / mean × 100%), with a smaller CV indicating a more uniform distribution.

[0052] 4. Experimental Data

[0053] 5. Results Analysis In the M-melted sample, the content of Irganox 1010 showed a clear gradient distribution from top to bottom (2280-5820 mg / kg), with a coefficient of variation (CV) as high as 32.0%, indicating that the solid powder was difficult to diffuse in high-viscosity molten polyisobutylene and the distribution was severely uneven. The stabilizer concentration in the top region (2280 mg / kg) was only 57% of the design value (4000 mg / kg), indicating a serious lack of antioxidant protection.

[0054] In the M-complex sample, the Irganox 1010 content at each location was concentrated between 3890-4090 mg / kg, with a standard deviation of 70 mg / kg and a CV of only 1.8%, which is close to the theoretical uniform distribution (design value 4000 mg / kg).

[0055] This experiment verified the necessity of solid-phase dispersion in step two using the stabilizer-diatomaceous earth composite: dispersion was performed in solution (the viscosity of the polyisobutylene-hexane solution is much lower than that of molten PIB), and the stabilizer was uniformly suspended in the solution along with the diatomaceous earth particles. The uniform distribution of the stabilizer was preserved after the solvent was evaporated. See [link to relevant documentation]. Figure 3 .

[0056] Experiment 3: Effect of α-Tocopherol Synergistic Regeneration on the Storage Stability of Polyisobutylene 1. Experimental Objective The study aimed to verify whether the addition of α-tocopherol in step three could delay the net consumption rate of the main antioxidant Irganox 1010 through the hydrogen transfer and regeneration of hindered phenolic radicals (ArO•), thereby extending the storage stability of polyisobutylene. The effect was quantified using oxidation induction time (OIT) as a comprehensive antioxidant performance indicator.

[0057] 2. Preparation of experimental samples Based on the formulation of Example 2, the following two groups of products were prepared (1000g of polyisobutylene sample was prepared for each group): T-Tocopherol-Free: Follow the complete procedures of Step 1 and Step 2 of Example 2 (Irganox 1010: 0.4%, N,N'-disalicylate-1,2-propanediamine: 0.15%, diatomaceous earth: 3.0%), but do not add α-tocopherol in Step 3. After removing n-hexane by evaporation, solid polyisobutylene product is obtained.

[0058] T-Tocopherol: Follow the complete procedure from step one to step three of Example 2 (add α-tocopherol: 0.15% in step three), and obtain solid polyisobutylene product after removing n-hexane by evaporation.

[0059] Aging test conditions Both groups of samples were placed in a 70℃ constant temperature incubator for accelerated storage aging. Samples were taken every two weeks for a total of five times (weeks 0, 2, 4, 6, and 8). Each sample was approximately 20g, and the following two tests were performed: (1) Residual amount of Irganox 1010: After dissolving the sample in toluene, the content of Irganox 1010 (mg / kg, based on the mass of polyisobutylene) was determined by HPLC (C18 column, methanol / water = 90 / 10 mobile phase, detection wavelength 277nm). (2) Oxidation induction time (OIT): Differential scanning calorimetry (DSC) was used to determine the time (min) from the introduction of oxygen to the start of the exothermic peak in a pure oxygen atmosphere (oxygen flow rate 50mL / min) at 200℃. The larger the OIT value, the stronger the antioxidant capacity.

[0060] 3. Experimental Data

[0061] 4. Results Analysis At week 0, both groups had the same Irganox 1010 content (4000 mg / kg), but the initial OIT (58.3 min) in the T-tocopherol-containing group was higher than that in the T-tocopherol-free group (42.5 min). This difference stemmed from the fact that α-tocopherol itself also possesses phenolic hydroxyl antioxidant activity (α-tocopherol 1500 mg / kg contributes approximately 19% of the amount of phenolic hydroxyl substances), and that α-tocopherol and hindered phenols exhibited a synergistic regenerative effect in the initial stage, resulting in an initial OIT higher than the simple additive expectation. Both groups were compared for aging trends at week 0 using their respective initial OIT as a 100% baseline, with consistent indicator criteria.

[0062] After 8 weeks of accelerated aging at 70℃, the residual amount of Irganox 1010 in the T-tocopherol-free group decreased from 4000 mg / kg to 480 mg / kg, with a consumption rate of 88.0%, and the OIT (occurrence interval) decreased from 42.5 min to 5.2 min (retention rate of 12.2%). In the T-tocopherol-containing group, the residual amount of Irganox 1010 was 1920 mg / kg, with a consumption rate of only 52.0%, and the OIT decreased from 58.3 min to 25.8 min (retention rate of 44.3%). Comparing the two groups, the consumption rate of Irganox 1010 in the tocopherol-containing group decreased by 36 percentage points, while the OIT retention rate increased by 32 percentage points. These two indicators are consistent and mutually corroborating.

[0063] The above data validates the synergistic regeneration mechanism of α-tocopherol: α-tocopherol transfers hydrogen atoms to the hindered phenoxy radical (ArO•) generated by Irganox 1010, regenerating ArOH; the generated tocopheroxy radical (Toc-O•) is stabilized due to benzodihydropyran ring resonance and steric hindrance of the methyl group, preventing chain oxidation. Through this regeneration cycle, α-tocopherol delays the net consumption of Irganox 1010, allowing polyisobutylene to maintain higher antioxidant activity during long-term storage. See Figure 4 and Figure 5 .

[0064] The embodiments of the present invention have been described above. However, the embodiments are not limited to the specific implementation methods described above. The specific implementation methods described above are merely illustrative and not restrictive. Those skilled in the art can make more equivalent embodiments under the guidance of the present embodiments, and all of them are within the protection scope of the present embodiments.

Claims

1. A process for preparing polyisobutylene, wherein after the cationic polymerization step of isobutylene is completed, a polyisobutylene solution contained in the polymerization solvent is used as the post-treatment object, characterized in that, Perform the following steps one through three in sequence: Step 1: Add layered double hydroxide to the polyisobutylene solution, stir and mix at 15-35℃, filter to remove the solid layered double hydroxide, capture the halogen anions in the polyisobutylene solution through interlayer anion exchange, and at the same time use the hydroxyl groups of the layers to neutralize the residual acidic substances to obtain the dehalogenated and purified polyisobutylene solution. Step 2: Add a stabilizer-diatomaceous earth composite to the dehalogenated and purified polyisobutylene solution obtained in Step 1. The stabilizer-diatomaceous earth composite is a solid dispersion prepared by loading a hindered phenolic main antioxidant and a metal passivator onto the inner wall of the pores of diatomaceous earth. After stirring and dispersing, the metal passivator chelates and coordinates with the residual metal ions in the solution. Step 3: Add tocopherol to the polyisobutylene solution obtained in Step 2, so that it is uniformly dispersed in the polyisobutylene solution in a free state. Tocopherol provides hydrogen atoms to the hindered phenolic radicals to regenerate the hindered phenolic main antioxidant. After Step 3 is completed, evaporate the polymerization solvent to obtain the stabilized polyisobutylene product.

2. The preparation process of polyisobutylene according to claim 1, characterized in that, The layered double hydroxide mentioned in step one is a Mg-Al type layered double hydroxide, with the general formula: Where x is 0.2-0.4, and the initial interlayer anion is NO3. - The particle size is 5100μm.

3. The preparation process of polyisobutylene according to claim 1, characterized in that, In step one, the amount of layered double hydroxide added is 0.5% to 3% of the mass of polyisobutylene, the stirring time is 0.5 to 2 hours, and the pore size of the filter medium used for filtration is no greater than 5 μm.

4. The preparation process of polyisobutylene according to claim 2, characterized in that, The halogen-saturated layered double hydroxide solid obtained from the filtration in Step 1 is regenerated and recycled for use in Step 1 by the following steps: It is eluted with a 5%-15% (w / w) Na₂CO₃ aqueous solution at 15-35°C with stirring for 13 hours, and the halogen-containing waste liquid is separated by filtration to obtain CO₃. 2- Layered double hydroxides; CO3 2- The layered double hydroxide was calcined in air at 400-500℃ for 13 hours to decompose it into mixed metal oxides. These mixed metal oxides were then placed in a 5%-10% NaNO3 aqueous solution and stirred at 15-35℃ for 24 hours to reconstruct NO3 using the structural memory effect. - The layered double hydroxide is filtered and recycled for use in step one.

5. The preparation process of polyisobutylene according to claim 1, characterized in that, The method for preparing the stabilizer-diatomaceous earth composite in step two is as follows: a stabilizer solution is prepared by dissolving the hindered phenolic main antioxidant and the metal passivator in an organic solvent, mixing and stirring the stabilizer solution with diatomaceous earth powder for 13 hours, and then evaporating and removing the solvent under reduced pressure conditions not exceeding 50°C and not exceeding 0.03MPa to obtain the stabilizer-diatomaceous earth composite. The diatomaceous earth has a pore size of 0.110μm, and the amount used is 1%-5% of the mass of polyisobutylene. The total pore volume of the diatomaceous earth is not less than the total volume of the prepared stabilizer solution.

6. The preparation process of polyisobutylene according to claim 5, characterized in that, The organic solvent is ethanol, and the amount of solvent used is 5-20 times the total mass of the hindered phenolic main antioxidant and the metal passivator.

7. The preparation process of polyisobutylene according to claim 5, characterized in that, The hindered phenolic primary antioxidant is pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], and its addition amount is 0.1%-1.0% of the mass of polyisobutylene.

8. The preparation process of polyisobutylene according to claim 5, characterized in that, The metal passivating agent is N,N'-disalicylate-1,2-propanediamine, and its addition amount is 0.05%~0.5% of the mass of polyisobutylene.

9. The preparation process of polyisobutylene according to claim 1, characterized in that, The tocopherol mentioned in step three is α-tocopherol, and its addition amount is 0.05%-0.3% of the mass of polyisobutylene. It is stirred at 15-35℃ for 0.5 hours to make it uniformly dispersed in the polyisobutylene solution.

10. The preparation process of polyisobutylene according to claim 1, characterized in that, After step three is completed, the polymerization solvent is removed by vacuum evaporation at 40-80℃ and 0.005-0.05MPa absolute pressure.

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