Halogenation method of butyl rubber

Abstract

The present invention relates to the field of polymer preparation, particularly to a butyl rubber halogenation method, which comprises: (S.1) dissolving butyl rubber in an ionic liquid solvent to form a rubber solution; (S.2) adding composite halide salt and an immobilized deacidification agent into the glue solution; the composite halide salt is composed of transition metal halide and quaternary ammonium salt halide; (S.3) enabling the composite halide salt to uniformly permeate into the butyl rubber at a first reaction temperature, performing pre-halogenation, then heating to a second reaction temperature, and performing deep halogenation; and (S.4) after the reaction is finished, centrifugally separating the immobilized deacidification agent, precipitating to obtain halogenated butyl rubber, and recovering the ionic liquid solvent. A halogen system used in a traditional butyl rubber halogenation process is replaced by the composite halide salt, and meanwhile, a combination of reaction medium reconstruction and reaction process staged strengthening is combined, so that a new green halogenation path independent of halogen simple substances is opened up.

Description

Technical Field

[0001] The present invention relates to the field of polymer preparation, and particularly to a method for halogenating butyl rubber. Background Art

[0002] Butyl rubber itself is a synthetic rubber formed by cationic polymerization of isobutene and a small amount of isoprene as monomers. The highly saturated carbon chain in its molecular structure endows excellent airtightness, aging resistance and damping properties, and is widely used in fields such as tire inner liners, medical bottle stoppers, and damping materials. However, the highly saturated structure of butyl rubber also results in strong chemical inertness, especially with only about 1-3% of double bonds remaining in the molecular chain (derived from isoprene units), which makes it difficult to form a stable co-vulcanization network with other rubbers (such as natural rubber and cis-butadiene rubber) through traditional vulcanization systems, severely limiting its application in complex composite rubber products. For example, in tire manufacturing, if unmodified butyl rubber is directly used as the airtight layer, the insufficient interfacial adhesion with the carcass rubber will lead to delamination failure.

[0003] Halogenated butyl rubber is an important class of modified rubber materials prepared by introducing halogen atoms (such as chlorine or bromine) into the molecular chain of butyl rubber. Through halogenation modification, polar halogen groups (such as -Cl or -Br) are introduced into the molecular chain of butyl rubber. On the one hand, it can significantly enhance the polarity of the molecule, thereby enhancing the adhesion to metal cord or other polar materials; on the other hand, the introduction of halogen can form a cross-linking network through double bonds or halogen substitution sites during the vulcanization process, realizing co-vulcanization with materials such as natural rubber. Industrial practice has proved that after halogenation, butyl rubber (such as brominated butyl rubber or chlorinated butyl rubber) while maintaining the advantage of airtightness, its vulcanization rate can be increased by more than 30%, and the interfacial shear strength with other rubbers is increased to 5-8 times that of the unmodified product, greatly expanding its application scenarios.

[0004] Currently, the mainstream process for producing halogenated butyl rubber in industry is the direct halogenation method based on halogen elements. According to the phase state difference of the reaction system, the existing technologies can be divided into two categories: solution halogenation and gas-phase halogenation. The solution method usually dissolves butyl rubber in a chlorinated hydrocarbon solvent (such as chloroform, dichloroethane) to form a homogeneous rubber solution, and chlorine gas or bromine is introduced at a low temperature of 30-60 °C for halogenation reaction, and the reaction is accelerated by ultraviolet light or a free radical initiator (such as benzoyl peroxide). In addition, some improved technologies attempt to use halogen carriers (such as N-bromosuccinimide) or indirect halogen sources (such as a complex system of ferric trichloride and halogenated hydrocarbon) to regulate the reaction activity, but essentially still rely on the direct supply of halogen elements.

[0005] For example, the patent with application number CN201410265217.5 discloses a method for preparing halogenated butyl rubber, which comprises the following steps: a) reacting a solution containing butyl rubber with a halogenating reagent to obtain a halogenated butyl rubber solution; and b) post-treating the halogenated butyl rubber solution obtained in step a) to recover the halogenated butyl rubber, characterized in that the halogenation reaction in step a) is carried out in the presence of an antioxidant. The present invention also relates to the halogenated butyl rubber obtained by the method of the present invention. Compared with the halogenated butyl rubber having a higher proportion - usually the primary structure / (primary structure + secondary structure) exceeding 10 mol% - of the primary structure obtained by the conventional method of halogenating butyl rubber in the absence of an antioxidant, the halogenated butyl rubber obtained by the method of the present invention has a lower proportion of the primary structure containing a primary halogen atom. Therefore, the halogenation reaction results in a reduced degree of degradation of the butyl rubber.

[0006] Although the above method dominates in the industry, it still has several key technical defects. First is the high risk and high cost of elemental halogens. Elemental halogens such as chlorine and bromine are highly corrosive and toxic, and special pressure-resistant containers and leakage emergency treatment systems are required for storage and transportation, directly raising production costs and safety inputs. Second is the problem of controlling side reactions. There is competition between the addition and substitution reactions of halogen atoms to double bonds. Especially under high-temperature or high-concentration halogen conditions, over-substitution or allylic halogenation is likely to occur, leading to the rupture or out-of-control crosslinking of rubber molecular chains. Third is the problem of removing residual halogens. The hydrogen halides (such as HBr, HCl) and unreacted elemental halogens remaining in the system after the reaction need to be treated by multiple water washes, vacuum degassing or neutralization. During this process, rubber agglomeration or emulsification may occur. In addition, the halogenated hydrocarbon solvents in the solvent method are difficult to be completely recovered (the actual recovery rate is usually lower than 85%), which not only causes waste of raw materials, but also causes persistent pollution to the environment through volatilization or leakage.

[0007] Therefore, in summary, the existing production technologies of halogenated butyl rubber are still restricted by bottleneck problems such as high dependence on elemental halogens, complex processes, and poor environmental friendliness, and there is an urgent need to develop an efficient, economical and environmentally friendly halogenation technology system. Summary of the Invention

[0008] The present invention aims to overcome the problems of high cost and side reactions caused by the need to use elemental halogens such as chlorine and bromine in the method for halogenating butyl rubber in the prior art. Therefore, a method for halogenating butyl rubber is provided to overcome the above deficiencies.

[0009] To achieve the above invention object, the present invention is realized through the following technical solutions: In the first aspect, the present invention first provides a method for halogenating butyl rubber, comprising the following steps: (S.1) dissolving butyl rubber in an ionic liquid solvent to form a rubber solution; (S.2) adding a composite halide salt and a solid deacidifying agent to the glue solution; The composite halide salt is composed of transition metal halide and quaternary ammonium halide; (S.3) at a first reaction temperature, allowing the composite halogenated salt to uniformly penetrate into the interior of the butyl rubber and perform pre-halogenation, and then raising the temperature to a second reaction temperature for deep halogenation; (S.4) After the reaction is completed, the deacidifying agent is immobilized by centrifugation to obtain the halogenated butyl rubber by precipitation, and the ionic liquid solvent is recovered.

[0010] Existing technologies generally rely on halogens as halogen sources. Their high risk not only leads to rising storage and transportation and operating costs, but also triggers irreversible side reaction chains due to the high activity of halogens in the reaction. That is, when halogen molecules react with the double bonds of butyl rubber, they are prone to over-substitution or allylic halogenation, causing molecular chain breakage or uncontrolled crosslinking. For example, in the traditional bromination process, the violent contact between bromine vapor and butyl rubber will lead to local accumulation of reaction heat, forming an impenetrable byproduct layer (such as crosslinking microdomain), which limits the penetration depth of halogen and shows uneven distribution of halogen content in macroscopic form. The Mooney viscosity of the final product fluctuates by more than ±8 (ASTM D1646 standard), which seriously restricts its application in high-end products. At the same time, the traditional solvent method requires a large amount of chlorinated hydrocarbons to dissolve rubber, and its recovery energy consumption accounts for more than 30% of the total energy consumption, and the environmental problems caused by solvent residues are increasingly becoming a shackle on technological development. However, although existing improved technologies (such as gas-phase radiation halogenation and halogen carrier indirect reaction) attempt to alleviate the above-mentioned defects by optimizing operating conditions, they have not broken through the essential framework of "halogen elements participating in activation reactions", resulting in limited improvement in process efficiency and difficulty in systematically resolving multiple contradictions.

[0011] In response to this systemic problem, the present invention constructs a new halogenation method through the three-in-one technical route of "halogen source substitution + reaction medium reconstruction + process intensification". The creative core of its technical solution lies in completely abandoning the halogen element and designing the synergistic mechanism of composite halide salts and solid-supported deacidification agents. Specifically, the composite halide salt uses transition metal halides (such as FeCl3) as electron transfer catalysts and quaternary ammonium halides (such as tetrabutylammonium bromide) as phase transfer carriers. The two are compounded in a specific proportion to form a "dual-functional activation system". Under the solubility and polarity regulation of ionic liquids (such as 1-butyl-3-methylimidazolium chloride), quaternary ammonium cations are preferentially adsorbed to the hydrophobic micro-regions of the rubber molecular chains through electrostatic action, and the halogen ions (Cl - or Br - ) is transported to the reaction site, while Fe 3+ Transition metal ions such as Fe 3+ / Fe2+ ) Activate the double bond to form a dynamic proton transfer channel. This mechanism enables precise delivery and controlled release of halogen ions at the molecular level, fundamentally avoiding the out-of-control side reactions caused by the direct attack of halogen elements on double bonds in traditional processes. Comparative experiments show that in the composite halogenation system with a molar ratio of FeCl3 / tetrabutylammonium bromide of 1:1, the conversion rate of double bonds can reach 98.5% (only 72% for the traditional bromine method), and the proportion of di-substituted halides in the product decreases from 12 - 18% in the conventional method to less than 2%, significantly improving the halogenation selectivity.

[0012] Further creativity lies in the gradient temperature design during the reaction process and the micro-nano structure innovation of the immobilized deacidifying agent. By dividing the reaction into two stages: pre-halogenation and deep halogenation, at the low temperature stage, the high diffusivity of the ionic liquid first promotes the uniform penetration of halogen precursors into the interior of the rubber phase to form a preliminary halogenation "framework"; then the temperature is increased to accelerate the proton migration and substitution reaction catalyzed by transition metal ions. At this stage, the mass transfer limitation during the gelation process is broken through by regulating the rotation speed, enabling the final product to have a halogen content of 1.8 - 2.2 mol% (1.2 - 1.6 mol% for the traditional process).

[0013] Therefore, in summary, from the perspective of the integrity of the technical solution, the present invention is not a simple optimization of a single process parameter, but rather through an innovative combination of halogen source substitution (composite halogenated salt), reaction medium reconstruction (ionic liquid), and process intensification (gradient temperature / deacidifying agent coordination), it has opened up a new green halogenation path independent of halogen elements. Its creativity is not only reflected in the breakthrough of core elements, but also in the synergistic amplification effect among various technical features. Among them, the high polarity of the ionic liquid promotes the phase transfer function of quaternary ammonium salts, and the micro-nano structure design of the deacidifying agent further ensures the pH stability of the reaction environment, ultimately forming a self-consistent halogenation cycle system. There is neither a precedent for using a transition metal halide - quaternary ammonium salt complex system in the prior art, nor a process for in-situ deacidification by an immobilized deacidifying agent, and there is a lack of systematic integration of multi-stage reaction temperatures and dynamic mass transfer control. Therefore, the present invention shows significant progressiveness in terms of technical principles, implementation means, and effect indicators, and has outstanding substantive features and industry promotion value.

[0014] Preferably, the ionic liquid solvent is an imidazole chloride substituted by C2 - C8 alkyl groups.

[0015] Selecting an imidazole chloride substituted by C2 - C8 alkyl groups as the ionic liquid solvent is mainly because its unique molecular structure balances solubility, reaction efficiency, and environmental compatibility. The high polarity of short-chain (such as C2 - C4) imidazole chlorides helps to quickly dissolve butyl rubber and break its crystalline region, while the hydrophobic alkyl groups of long-chain (C6 - C8) enhance the compatibility between the rubber and the solvent, reducing the viscosity fluctuation of the rubber solution. The Cl in such ionic liquids -It can dynamically coordinate with transition metals (such as FeCl3) in the composite halide salt, and regulate the slow-release rate of halogen ions by adjusting the alkyl chain length. For example, short chains slowly release halogen during the low-temperature pre-halogenation stage, and long chains accelerate ion dissociation during the high-temperature reaction, thus precisely matching the requirements of the halogenation stage. In addition, the stability of the imidazole ring (decomposition temperature > 250 °C) ensures solvent safety at high temperatures, and its high boiling point and low volatility greatly simplify the recovery process (recovery rate > 99.8%), while Cl - The pre-adsorption on the active sites of rubber effectively inhibits side reactions, comprehensively realizing the unity of efficient halogenation and green process.

[0016] Preferably, the mass concentration of the obtained rubber solution is 5-20%.

[0017] Controlling the rubber solution concentration at 5-20% not only ensures the full dissolution of butyl rubber (the lower limit of 5% avoids molecular chain entanglement and penetrates the crystalline region), but also maintains a reasonable viscosity to balance the mass transfer efficiency (the upper limit of 20% inhibits side reactions caused by overheating). In this range, the best match is formed among the halogen salt permeability, reaction rate, and product uniformity. The side reaction is reduced to less than 1.5%, while the solvent consumption is saved and the recovery rate is increased (> 99%), comprehensively reducing energy consumption and cost by more than 30%.

[0018] Preferably, the transition metal halide includes at least one of FeCl3, ZnCl2, and CuCl2; The quaternary ammonium salt halide is selected from at least one of tetramethylammonium chloride and tetrabutylammonium bromide.

[0019] This patent selects a combination of specific transition metal halides and quaternary ammonium salt halides due to their synergistic and complementary characteristics in the reaction mechanism: among them, the transition metal halides selected in this application, such as FeCl3 (strong Lewis acid), can dominate the redox cycle of double bond activation and halogen reception (Fe 3+ →Fe 2+ reduces halogen X - to X 0 ); while ZnCl2 (weak acid) can selectively weaken side reactions (such as isomerization); and CuCl2 (medium strong acid) dynamically adjusts the halogen release rate through disproportionation reaction (2Cu 2+ +Cl - →Cu + +CuCl3 - ), forming a multi-stage catalytic network. Moreover, these metal halides can form stable complexes with imidazole chloride salts (such as [FeCl4] - ·[EMIM] + ), avoiding metal ion precipitation and significantly improving the liquid-phase dispersibility.

[0020] In this application, the quaternary ammonium halide selected, such as tetramethylammonium chloride (short chain), has a high dissociation degree and can rapidly release halogen, mainly attacking the dissolution-phase reaction. Tetrabutylammonium bromide (long chain) anchors to the rubber interface through hydrophobic interaction to improve the mass transfer efficiency across the phase. Moreover, the quaternary ammonium cation (R4N + ) weakens the Coulomb attraction between the metal halide anion and the imidazole cation, enhancing the mobility of the halogen active intermediate (such as [FeCl3] - ).

[0021] Therefore, the combination of the two constructs a dual-engine mechanism of "metal catalytic active site + quaternary ammonium salt directional transport channel": Specifically, the transition metal is responsible for activating the double bond and "grabbing" halogen (such as Fe 3+ + Cl - → FeCl3 - → Fe 2+ + Cl 0 ); while the quaternary ammonium salt forms a halogen relay transfer chain through ion pairing (such as N + Br - … FeCl3 - ), effectively improving the unit halogen utilization rate and the uniformity of the product halogen distribution.

[0022] Preferably, the molar ratio of the transition metal halide to the quaternary ammonium halide is 1:0.5 - 2.

[0023] By setting the molar ratio within the range of 1:0.5–2 in this application, it can balance the metal catalytic activity and the halogen transport efficiency. Within this range, the transition metal (such as FeCl3) fully activates the double bond, while the quaternary ammonium salt (such as tetrabutylammonium bromide) synchronously transports halogen directionally, making the halogenation rate and utilization rate reach the optimum. When the ratio of the two is too small, the quaternary ammonium salt is insufficient, the metal active sites are exposed, causing over-activation of the double bond (increasing by-products), and the halogen transport is blocked; while when the ratio of the two is too large, the quaternary ammonium salt excessively covers the metal catalytic sites, thus reducing the reaction rate, and the halogen accumulates locally, easily generating dihalides, and the energy consumption for solvent recovery increases significantly.

[0024] Preferably, in the step (S.2), the supported deacidifying agent is a composite material of metal oxide supported on a mesoporous silica carrier, with a specific surface area ≥ 200 m 2 / g.

[0025] Preferably, a) prepare a mesoporous silica carrier; b) load the mesoporous silica carrier with a metal salt solution by vacuum-assisted impregnation method and calcine it in stages in a CO2 atmosphere to obtain nano-metal oxide; c) perform surface modification on the composite material using a silane coupling agent; d) Add carbon nanotubes to the mill to complete the mechanical strengthening treatment and obtain the supported deacidifying agent.

[0026] What is particularly crucial in this application is that the nano-magnesium oxide / mesoporous SiO2 composite deacidifying agent developed in the present invention realizes in-situ adsorption and conversion of HX gas through pore size engineering and surface modification technology. During its preparation process, staged calcination is carried out under a CO2 atmosphere to control the grain size of metal oxides within 8 - 12 nm, and a chemical grafting interface is formed through APTES silanization treatment, enabling the formation of ≡Si - O - Mg - O - bridge bonds between the deacidifying agent and rubber chains. This structure not only improves the dispersion stability of the deacidifying agent but also catalyzes the reaction between HX and MgO to generate MgCl2 through the interfacial proton transfer path, neutralizing by-products in real-time and stabilizing the pH of the reaction system at 6.5 - 7.2 (the traditional process is 4.0 - 4.8), significantly reducing the energy consumption and wastewater discharge of the degassing process.

[0027] Preferably, 0.01 - 0.1% of hindered amine radical inhibitors based on the mass of the rubber solution are also added in step (S.2).

[0028] Adding 0.01 - 0.1% of hindered amine radical inhibitors can capture free radicals (such as Cl· / Br·) generated during halogenation or high-temperature shearing, cut off the free radical chain reaction, prevent excessive cross-linking or degradation of rubber molecular chains, and at the same time inhibit product yellowing, ensuring the directional progress of the halogenation reaction and the stability of material properties.

[0029] Preferably, the hindered amine radical inhibitors are selected from at least one or a combination of bis(2,2,6,6-tetramethyl-4-piperidyl) sebacate, Chimassorb 944, the polymer of succinic acid and 4-hydroxy-2,2,6,6-tetramethyl-1-piperidinol, 4-hydroxy-1,2,2,6,6-pentamethylpiperidine, and N,N'-bis(2,2,6,6-tetramethyl-4-piperidyl)-1,6-hexanediamine.

[0030] Preferably, the first reaction temperature is 40 - 60 °C, and the pre-halogenation reaction time is 0.5 - 2 hours; The second reaction temperature is 80 - 100 °C, and the deep halogenation reaction time is 1 - 3 hours.

[0031] Therefore, this application has the following beneficial effects: This application replaces the halogen system used in the traditional butyl rubber halogenation process with a composite halogenated salt, and combines the reconstruction of the reaction medium and the staged strengthening of the reaction process to open up a new green halogenation path that does not rely on halogen elements. Specific Embodiments

[0032] The present invention will be further described below in conjunction with specific embodiments. Those of ordinary skill in the art will be able to implement the present invention based on these descriptions. In addition, the embodiments of the present invention described below generally only represent a part of the embodiments of the present invention, rather than all of the embodiments. Therefore, all other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the scope of protection of the present invention.

[0033]

Preparation of Supported Deacidifying Agent

[0034] Step 2: Magnesium salt loading and calcination: Prepare a 0.5 mol / L ethanol solution of magnesium nitrate (Mg(NO3)2); Take 10 g of mesoporous SiO2 and immerse it in the salt solution, impregnate it under vacuum assistance (-0.08 MPa) for 2 hours to ensure full penetration of the pores; after drying at 80 °C in air, place it in a tubular furnace: Stage 1: Heat up to 250 °C at a rate of 2 °C / min under a CO2 atmosphere and hold for 1 hour to decompose residual organic matter; Stage 2: Switch to a N2 / CO2 mixed gas (volume ratio 1:1), heat up to 450 °C at a rate of 5 °C / min and calcine for 3 hours to completely decompose magnesium nitrate into MgO to obtain MgO / SiO2.

[0035] Step 3: Surface modification: Disperse 5 g of MgO / SiO2 in 50 mL of toluene, add 1 g of KH-550 silane coupling agent, reflux and react at 80 °C for 4 hours, centrifuge, wash and dry to enhance surface hydrophobicity.

[0036] Step 4: Mechanical strengthening: Mix the treated composite material with 1 wt% carboxylated carbon nanotubes (CNTs), ball mill (300 rpm × 6 hours), and the specific surface area of the final product is ≥ 550 m 2 / g.

[0037] Preparation of Zinc Oxide / Mesoporous SiO2 Supported Deacidifying Agent Step 1: Preparation of mesoporous silica support: The same as Step 1 above to obtain the mesoporous SiO2 support.

[0038] Step 2: Zinc salt loading and calcination: Prepare a 0.6 mol / L ethanol solution of zinc nitrate (Zn(NO3)2); The impregnation and vacuum treatment are the same as those of MgO / SiO2; Adjustment of the calcination procedure: Stage 1: Pre-calcine at 200 °C for 1 hour under a CO2 atmosphere; Stage 2: Calcinate at 550 °C in a N2 / CO2 mixed gas for 2 hours to produce ZnO / SiO2, with a specific surface area ≈ 400 m 2 / g.

[0039] Step 3: Surface modification: Adopt the same silane treatment process, but use KH-560 epoxy-based silane instead.

[0040] Step 4: Mechanical strengthening: Add 1.5 wt% carbon nanotubes, and increase the ball milling parameters to 400 rpm × 4 hours. The final product has a specific surface area ≥ 380 m 2 / g.

[0041] Example 1 A method for halogenating butyl rubber specifically includes the following steps: (S.1) Preparation of the rubber solution: Dissolve butyl rubber in 1-butyl-3-methylimidazolium chloride (BMIMCl, C4) to form a rubber solution with a mass concentration of 5%.

[0042] (S.2) Mixing of additives: Add a composite halogenated salt accounting for 8% of the mass of butyl rubber, a magnesium oxide / mesoporous SiO2 solid-supported deacidifying agent accounting for 2% of the mass of butyl rubber, and bis(2,2,6,6-tetramethyl-4-piperidyl) sebacate accounting for 0.01% of the mass of the rubber solution to the rubber solution; Among them, the composite halogenated salt is mixed by CuCl2, ZnCl2 and tetramethylammonium chloride (TMACl) in a molar ratio of 1:1:4; the composite halogenated salt is mixed by FeCl3 and tetramethylammonium chloride (TMACl) in a molar ratio of 1:0.5.

[0043] (S.3) Hierarchical halogenation reaction: Pre-halogenation: Stir and react at 40 °C for 0.5 hour to uniformly penetrate the composite halogenated salt into the rubber interior; Deep halogenation: Raise the temperature to 80 °C and continue to react for 1 hour to complete the halogen substitution and obtain chlorinated butyl rubber.

[0044] (S.4) Product separation and solvent recovery: Centrifuge to separate the solid-supported deacidifying agent, precipitate the chlorinated butyl rubber by alcohol precipitation, and test the halogen content after drying; the ionic liquid solvent is purified by distillation and recycled.

[0045] Example 2 A method for halogenating butyl rubber specifically includes the following steps: (S.1) Preparation of rubber solution: Dissolve butyl rubber in 1-ethyl-3-methylimidazolium chloride (EMIMCl, C2) with a rubber solution concentration of 20%.

[0046] (S.2) Mixing of additives: Add a composite halide salt accounting for 10% of the mass of butyl rubber, a magnesium oxide / mesoporous SiO2 supported deacidifying agent accounting for 3% of the mass of butyl rubber, and Chimassorb 944 accounting for 0.1% of the mass of the rubber solution to the rubber solution; Among them, the composite halide salt is a mixture of CuCl2, ZnCl2 and tetrabutylammonium bromide (TBABr) in a molar ratio of 1:1:4.

[0047] (S.3) Stepwise halogenation reaction: Pre-halogenation: Stir and react at 60 °C for 2 hours to uniformly permeate the composite halide salt into the interior of the rubber; Deep halogenation: Raise the temperature to 100 °C and continue the reaction for 3 hours to complete halogen substitution and produce bromobutyl rubber.

[0048] (S.4) Product separation and solvent recovery: Centrifuge to separate the supported deacidifying agent, precipitate bromobutyl rubber by alcohol precipitation, and test the halogen content after drying; The ionic liquid solvent is purified by distillation and recycled.

[0049] Example 3 A method for halogenating butyl rubber specifically includes the following steps: (S.1) Preparation of rubber solution Dissolve butyl rubber in 1-hexyl-3-methylimidazolium chloride (HMIMCl, C6) with a rubber solution concentration of 12%.

[0050] (S.2) Mixing of additives Add a composite halide salt accounting for 12% of the mass of butyl rubber, a zinc oxide / mesoporous SiO2 supported deacidifying agent accounting for 1% of the mass of butyl rubber, and N,N'-bis(2,2,6,6-tetramethyl-4-piperidyl)-1,6-hexanediamine accounting for 0.055% of the mass of the rubber solution to the rubber solution; Among them, the composite halide salt is a mixture of ZnCl2 and TBABr in a molar ratio of 1:1.

[0051] (S.3) Stepwise halogenation reaction: Pre-halogenation: Stir and react at 50 °C for 1.2 hours to uniformly permeate the composite halide salt into the interior of the rubber; Deep halogenation: Raise the temperature to 90 °C and continue the reaction for 2 hours to complete halogen substitution (such as chlorination or bromination).

[0052] (S.4) Product separation and solvent recovery: Centrifuge to separate the supported deacidifying agent, precipitate halogenated butyl rubber by alcohol precipitation, and test the halogen content after drying; The ionic liquid solvent is purified by distillation and recycled.

[0053] Example 4 A method for halogenating butyl rubber specifically includes the following steps: (S.1) Preparation of rubber solution Dissolve butyl rubber in 1-butyl-3-methylimidazolium chloride (BMIMCl, C4) to form a rubber solution with a mass concentration of 8%.

[0054] (S.2) Mixing of additives: Add a composite halogenated salt accounting for 10% of the mass of butyl rubber, a magnesium oxide / mesoporous SiO2 supported deacidifying agent accounting for 5% of the mass of butyl rubber, and 4-hydroxy-1,2,2,6,6-pentamethylpiperidine accounting for 0.03% of the mass of the rubber solution into the rubber solution; Among them, the composite halogenated salt is mixed by FeCl3, CuCl2 and tetramethylammonium chloride (TMACl) in a molar ratio of 3:1:6.

[0055] (S.3) Hierarchical halogenation reaction: Pre-halogenation: Stir and react at 450 °C for 1.5 hours to uniformly penetrate the composite halogenated salt into the rubber interior; Deep halogenation: Raise the temperature to 85 °C and continue to react for 1.8 hours to obtain chlorinated butyl rubber.

[0056] (S.4) Product separation and solvent recovery: Centrifugally separate the supported deacidifying agent, precipitate the chlorinated butyl rubber by alcohol precipitation, test the halogen content after drying; the ionic liquid solvent is purified by distillation and recycled.

[0057] Example 5 A method for halogenating butyl rubber specifically includes the following steps: (S.1) Preparation of rubber solution: Dissolve butyl rubber in 1-octyl-3-methylimidazolium chloride (OMIMCl, C8) to form a rubber solution with a mass concentration of 15%.

[0058] (S.2) Mixing of additives: Add a composite halogenated salt accounting for 9% of the mass of butyl rubber, a magnesium oxide / mesoporous SiO2 supported deacidifying agent accounting for 5% of the mass of butyl rubber, and a polymer of succinic acid and 4-hydroxypiperidine alcohol accounting for 0.08% of the mass of the rubber solution into the rubber solution; among them, the composite halogenated salt is mixed by CuCl2, tetramethylammonium chloride (TMACl) and tetrabutylammonium bromide (TBABr) in a molar ratio of 2.5:1:1.

[0059] (S.3) Hierarchical halogenation reaction: Pre-halogenation: Stir and react at 55 °C for 1 hour to uniformly penetrate the composite halogenated salt into the rubber interior; Deep halogenation: Raise the temperature to 95 °C and continue to react for 2.5 hours to complete halogen substitution.

[0060] (S.4) Product separation and solvent recovery: Centrifugally separate the supported deacidifying agent, precipitate the halogenated butyl rubber by alcohol precipitation, and test the halogen content after drying; the ionic liquid solvent is purified by distillation and recycled.

[0061] Example 6 A method for halogenating butyl rubber specifically includes the following steps: (S.1) Preparation of rubber solution: Dissolve butyl rubber in 1-ethyl-3-methylimidazolium chloride (EMIMCl, C2) to form a rubber solution with a mass concentration of 18%.

[0062] (S.2) Mixing of additives: Add a composite halogenated salt accounting for 10% of the mass of butyl rubber, a zinc oxide / mesoporous SiO2 supported deacidifying agent accounting for 3.5% of the mass of butyl rubber, and a mixture of bisdecyl sebacate + Chimassorb944 (1:1) accounting for 0.07% of the mass of the rubber solution to the rubber solution; Among them, the composite halogenated salt is mixed by FeCl3, ZnCl2 and tetrabutylammonium bromide (TBABr) in a molar ratio of 1:1:2.4.

[0063] (S.3) Stepwise halogenation reaction: Pre-halogenation: Stir and react at 42 °C for 0.8 hours to uniformly permeate the composite halogenated salt into the rubber interior; Deep halogenation: Raise the temperature to 88 °C and continue to react for 1.5 hours to complete halogen substitution (such as chlorination or bromination).

[0064] (S.4) Product separation and solvent recovery: Centrifugally separate the supported deacidifying agent, precipitate the halogenated butyl rubber by alcohol precipitation, and test the halogen content after drying; the ionic liquid solvent is purified by distillation and recycled.

[0065] Comparative Example 1 Comparative Example 1 is the same as Example 1 in other conditions, the difference is that: toluene is used to replace the ionic liquid to dissolve butyl rubber into a 5% rubber solution.

[0066] Comparative Example 2 Comparative Example 2 is the same as Example 1 in other conditions, the difference is that: the supported deacidifying agent is omitted.

[0067] Comparative Example 3 Comparative Example 3 is the same as Example 1 in other conditions, the difference is that: the pre-halogenation temperature in the stepwise halogenation reaction is 30 °C.

[0068] Comparative Example 4 Comparative Example 4 is the same as Example 1 in other conditions, the difference is that: the pre-halogenation stage is cancelled and directly react at 80 °C for 4 hours.

[0069] Test the halogenated butyl rubber prepared in the examples and comparative examples, and the test results are shown in Table 1 below.

[0070] Table 1 Number Halogen content (wt%) Retention rate of tensile strength Yellowing index ΔE Gel fraction (%) Example 1 5.2 97％ 1.2 0.3 Example 2 14.8 96％ 0.8 0.8 Example 3 10.1 98％ 1.0 0.5 Example 4 8.5 97％ 1.4 0.2 Example 5 13.6 95％ 1.5 0.9 Example 6 12.3 96％ 1.1 0.7 Comparative Example 1 3.1 88％ 2.5 1.8 Comparative Example 2 7.9 60％ 3.4 0.3 Comparative Example 3 4.3 82％ 1.8 0.9 Comparative Example 4 6.7 75％ 2.3 1.5 As can be seen from the data in the above table, in the embodiments of the present application, the halogen content is stably within the target range of 5-15 wt% (for example, it reaches 14.8 wt% in Example 2), and the distribution is uniform (double bond residue < 5%). In the comparative examples, due to parameter overrun, the content is insufficient (such as < 5 wt% in Comparative Examples 1 and 4) or the distribution is uneven, verifying the key role of the molar ratio of the composite halogenated salt and the staged temperature-controlled halogen.

[0071] At the same time, the tensile strength retention rate of the embodiments is ≥ 95% (it reaches 98% in Example 3), which is significantly better than 60-88% of the comparative examples, proving that the supported deacidifying agent (MgO / ZnO-SiO2) and the hindered amine inhibitor can synergistically inhibit acid-catalyzed degradation and free radical oxidation.

[0072] In addition, the yellowness index ΔE of the embodiments is all ≤ 1.5 (for example, it is only 0.8 in Example 2), while in the comparative examples, due to insufficient inhibitor, ΔE increases and serious yellowing occurs; finally, the gel fraction of the embodiments of the present application is all < 1% (as low as 0.2% in Example 4), while in the comparative examples, due to out-of-control crosslinking, there is a certain increase, indicating that the synergistic inhibition system (inhibitor + deacidifying agent) in the present application effectively blocks side reactions.

[0073] The above data comprehensively show that the composite halogenated salt ratio, the staged halogenation process, the ionic liquid solvent system, and the synergistic combination of the deacidifying agent / inhibitor defined in the claims are indispensable technical features, solving the pain points of uneven halogen distribution, high by-products, and performance degradation in traditional halogenation processes, and having outstanding creativity and practicality.

Claims

1. A method for halogenating butyl rubber, characterized in that, It includes the following steps: (S.1) Dissolve butyl rubber in an ionic liquid solvent to form a rubber solution; (S.2) Add a composite halide salt and a supported deacidifying agent to the rubber solution; The composite halide salt is composed of a transition metal halide and a quaternary ammonium salt halide; (S.3) At the first reaction temperature, make the composite halide salt uniformly penetrate into the interior of the butyl rubber and carry out pre-halogenation, and then raise the temperature to the second reaction temperature for deep halogenation; (S.4) After the reaction is completed, centrifuge to separate the supported deacidifying agent, precipitate to obtain halogenated butyl rubber, and recover the ionic liquid solvent.

2. The halogenation method of butyl rubber according to claim 1, wherein the ionic liquid solvent is an imidazole-based chloride salt substituted by C2-C8 alkyl groups.

3. The halogenation method of butyl rubber according to claim 1 or 2, wherein the mass concentration of the rubber solution is 5-20%.

4. The halogenation method of butyl rubber according to claim 1, wherein the transition metal halide includes at least one of FeCl3, ZnCl2, and CuCl2; the quaternary ammonium salt halide is selected from at least one of tetramethylammonium chloride and tetrabutylammonium bromide.

5. The halogenation method of butyl rubber according to claim 1 or 4, wherein the molar ratio of the transition metal halide to the quaternary ammonium salt halide is 1:0.5-2.

6. The halogenation method of butyl rubber according to claim 1, wherein In the step (S.2), the immobilized deacidifying agent is a composite material in which a metal oxide is supported on a mesoporous silica support, and the specific surface area is ≥ 200 m 2 / g.

7. The halogenation method of butyl rubber according to claim 6, wherein the preparation method of the supported deacidifying agent includes the following steps: a) Prepare a mesoporous silica support; b) Load the mesoporous silica support with a metal salt solution by vacuum-assisted impregnation method and calcine it in stages in a CO2 atmosphere to obtain a nano-metal oxide; c) Modify the surface of the composite material with a silane coupling agent; d) Add carbon nanotubes for milling to complete the mechanical strengthening treatment to obtain the supported deacidifying agent.

8. The halogenation method of butyl rubber according to claim 1 or 4 or 6, wherein a hindered amine free radical inhibitor accounting for 0.01-0.1% of the mass of the rubber solution is also added in the step (S.2).

9. The halogenation method of butyl rubber according to claim 8, wherein the hindered amine free radical inhibitor is selected from at least one or a combination of bis(2,2,6,6-tetramethyl-4-piperidyl) sebacate, Chimassorb 944, the polymer of succinic acid and 4-hydroxy-2,2,6,6-tetramethyl-1-piperidinol, 4-hydroxy-1,2,2,6,6-pentamethylpiperidine, and N,N'-bis(2,2,6,6-tetramethyl-4-piperidyl)-1,6-hexanediamine.

10. The halogenation method of butyl rubber according to claim 1, wherein the first reaction temperature is 40-60 °C, and the pre-halogenation reaction time is 0.5-2 hours; the second reaction temperature is 80-100 °C, and the deep halogenation reaction time is 1-3 hours.