Degradation method of cross-linked high polymer material

Abstract

The invention relates to the technical field of polymer degradation, and discloses a degradation method of a cross-linked high-molecular material, which comprises the following steps: adding at least one of dichloroethane, dichloromethane and chloroform and an amphoteric permeation carrier into crushed cross-linked high-molecular material for swelling treatment, and adding anhydrous ferric trichloride for constant-temperature permeation treatment; then adding benzaldehyde and at least one of triphenylphosphine and polyethylene glycol dimethyl ether for in-situ complexing activation to obtain mother liquor to be reacted; carrying out degradation reaction on the mother liquor to be reacted under the condition that the temperature is 85 to 120 DEG C and the pressure is 0.5 to 1.5 MPa and is in periodic gradient fluctuation; and finally, adding a quenching agent into the degradation liquid to terminate the reaction, and separating and purifying to obtain the oligomer. Through the synergistic effect of swelling permeation, in-situ activation and pressure fluctuation physical disturbance, embedding and efficient reaction of a catalytic active center in a three-dimensional network are achieved, and an oligomer product with narrow molecular weight distribution and complete active end group retention is obtained.

Description

Technical Field

[0001] This invention relates to the field of polymer degradation technology, specifically a method for degrading cross-linked polymer materials. Background Technology

[0002] Cross-linked polymer materials are polymer materials with a three-dimensional network structure formed by connecting macromolecular chains through covalent bonds. Cross-linked polymer materials have excellent physical and mechanical properties, thermal stability and chemical solvent resistance, and are widely used in industrial fields such as tire manufacturing, sealing products and aerospace.

[0003] Current technologies for processing cross-linked polymer materials mainly cover physical-mechanical recycling, high-temperature pyrolysis, and chemical solvent degradation. Physical-mechanical recycling processes cross-linked polymer materials into powder or granules for use as fillers through mechanical shearing. High-temperature pyrolysis uses external heating in an oxygen-free environment to break chemical bonds and extract pyrolysis oil and solid products. Chemical solvent degradation uses specific solvents and catalysts to destroy cross-linking points in a pressure vessel, attempting to reduce cross-linked polymer materials to oligomers.

[0004] Because cross-linked polymers have a tight three-dimensional network structure, there is significant mass transfer resistance during the penetration of external catalytic centers and solvent molecules into the cross-linked polymer material. This mass transfer resistance restricts the degradation reaction to occur mainly in the surface region of the cross-linked polymer particles, resulting in uneven degradation and low reaction efficiency. Since a stable cross-linking chemical bond energy needs to be overcome, current technologies typically drive the reaction by significantly increasing the reaction temperature. However, this temperature increase triggers uncontrollable random breakage and deep oxidation of the polymer backbone. Random breakage leads to an excessively wide molecular weight distribution of the degradation products, and the decomposition and deactivation of the active functional groups at the ends of the degradation products. Due to the severely damaged chemical structure and unstable properties of the degradation products, cross-linked polymers cannot be converted into high-value recycled raw materials. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a method for degrading cross-linked polymer materials, aiming to solve the problems of high mass transfer resistance in cross-linked networks, uneven degradation, and loss of product activity due to uncontrolled molecular chain breakage under high temperature conditions.

[0006] To achieve the above objectives, the present invention provides the following technical solution: This invention provides a method for degrading cross-linked polymer materials, comprising the following steps: S1. Add cross-linked polymer material fragments to at least one of dichloroethane, dichloromethane, and chloroform, and add an amphoteric permeable carrier for swelling treatment to obtain a swollen system; S2. Add an iron salt precursor to the swelling system for permeation treatment to obtain a permeation system; S3. Add benzaldehyde and at least one of triphenylphosphine and polyethylene glycol dimethyl ether to the permeation system for in-situ complexation activation to obtain the mother liquor to be reacted. S4. The mother liquor to be reacted is subjected to a degradation reaction under conditions of periodic gradient fluctuation between 85 and 120 degrees Celsius and pressure between 0.5 and 1.5 MPa to obtain a degradation solution. S5. Add a quencher to the degradation solution to terminate the reaction, and obtain the oligomer by separation and purification.

[0007] The core technology of this solution lies in utilizing the synergistic effects of swelling, permeation, in-situ activation, and periodic pressure fluctuations to precisely embed catalytic active centers within the cross-linked network. This mechanism of initiating depolymerization from the inside out is explained below: In the initial stage of the treatment, namely step S1, the amphoteric permeation carrier, due to the polarity difference between its intramolecular hydrophobic carbon chains and polyoxyethylene segments, not only enhances the wettability of the solvent on the polymer surface, but more importantly, assists the solvent in overcoming the physical resistance of the three-dimensional network and entering the interstitial spaces of the cross-linked network. This process causes the originally compact structure to physically swell, thereby providing the necessary free volume for the subsequent migration of active components.

[0008] In the subsequent permeation treatment (step S2), the iron salt precursor, guided by the amphoteric permeation carrier, diffuses into the deeper layers of the fragments along the established swelling channels. This distribution ensures the uniformity of metal ions at the microscopic level, avoiding the drawback of traditional degradation where the catalyst remains only on the surface of the fragments. Building upon the physical permeation, step S3 introduces the activator benzaldehyde, causing the aldehyde oxygen atoms to coordinate with the pre-placed iron ions. With the assistance of triphenylphosphine or polyethylene glycol dimethyl ether, the system constructs high redox potential iron-based complexes in situ within the network. These complexes, distributed within the network, serve as reaction centers, preparing for subsequent chemical bond breaking.

[0009] The deep release of degradation efficiency depends on the dynamic coupling of thermodynamic and mechanical forces in step S4. The periodic gradient pressure fluctuations, acting as a physical disturbance, force frequent relaxation and deformation of the polymer chain segments at the microscopic level. This dynamic change significantly increases the effective collision frequency between the pre-embedded active centers and cross-linking bonds. Within a specific temperature range, iron-based complexes induce directional oxidation or breakage of cross-linking bonds. Compared to thermal degradation relying solely on high temperatures, this invention, through an endogenously driven degradation mode, effectively controls the intensity of the reaction, maintaining low energy consumption while reducing the occurrence of disordered side reactions, ultimately resulting in a product exhibiting oligomer characteristics with a narrow molecular weight distribution and intact active end groups.

[0010] Preferably, the raw materials are in the following proportions by weight: The mixture comprises 100 parts of cross-linked polymer fragments; 5000 to 15000 parts of at least one of dichloroethane, dichloromethane, and chloroform; 5.0 to 8.0 parts of an amphoteric permeable carrier; 3.3 to 40.0 parts of an iron salt precursor; 33.3 to 200.0 parts of benzaldehyde; and 3.3 to 10.0 parts of at least one of triphenylphosphine and polyethylene glycol dimethyl ether. This precise proportioning ensures sufficient encapsulation between the solvent and the carrier, allowing the active centers within the fragments to reach the threshold required for the degradation reaction.

[0011] Preferably, in step S1, the swelling treatment is carried out by stirring at 40 to 60 degrees Celsius; the amphoteric permeation carrier is a 2-alkyl imidazoline modified with polyoxyethylene.

[0012] This carrier exhibits a good balance between oleophilic and hydrophilic properties, and its permeation kinetics reach their peak within the specified temperature range, which helps to shorten the time required for swelling equilibrium.

[0013] Preferably, in step S2, the permeation is carried out at a constant temperature of 40 to 60 degrees Celsius for 4 to 6 hours; the iron salt precursor is anhydrous ferric chloride.

[0014] Anhydrous ferric chloride, as the core component, readily reacts with benzaldehyde to form Lewis acid-base reactions. Constant temperature treatment ensures that metal ions completely penetrate to the deepest part of the crushed material.

[0015] Preferably, in step S3, the number-average molecular weight of the polyethylene glycol dimethyl ether is 400; the in-situ complexation activation is carried out by stirring at 20 to 25°C for 2 to 3 hours.

[0016] Polyethylene glycol dimethyl ether with a molecular weight of 400 has suitable molecular size and viscosity, and can effectively enhance the solubility of benzaldehyde in the swollen network under conditions of 20 to 25°C, thus promoting the full progress of the complexation reaction.

[0017] Preferably, in step S4, the temperature is increased to the degradation reaction temperature at a rate of 3 degrees Celsius per minute, the degradation reaction lasts for 2 to 24 hours, and the frequency of the periodic gradient fluctuation is 1.0 to 1.5 times per hour.

[0018] The stepped heating is designed to avoid pressure instability caused by violent solvent vaporization, while the specific fluctuation frequency is to coordinate the period of physical stress change with the rhythm of chemical bond breaking.

[0019] Preferably, the amphoteric permeation support comprises a hydrophobic carbon chain with 12 to 22 carbon atoms, and the addition number of ethylene oxide is 5.0 to 15.0 mol; the preparation method includes: Under nitrogen protection, 1.0 mol of fatty acid and 1.1 to 1.2 mol of diethylenetriamine are reacted at 145 to 165 degrees Celsius for 5 to 8 hours for amidation, and the byproduct water is removed to obtain an intermediate; the temperature is raised to 225 to 245 degrees Celsius, and the reaction is carried out under reduced pressure of -0.08 MPa to -0.095 MPa for 4 to 6 hours to achieve dehydration and ring closure; 0.4% to 0.7% by mass of potassium hydroxide is added to the ring-closed product, and 5.0 to 15.0 mol of ethylene oxide is introduced, and polyetherification modification is carried out at 130 to 150 degrees Celsius, followed by neutralization to obtain the amphoteric permeable carrier.

[0020] This preparation process ensures the precise ratio of hydrophilic and lipophilic segments in the carrier structure, resulting in a carrier that exhibits strong affinity with non-polar rubber materials, thereby stably carrying catalytic components into the matrix.

[0021] Preferably, in step S1, the cross-linked polymer material fragments are sulfur-containing system materials, and at least one of nano-zinc oxide and zinc stearate is added simultaneously in step S1 for anti-poisoning pretreatment. The significance of this is to capture free sulfur or sulfur-containing impurities in the system through pretreatment, preventing them from reacting with iron ions to form precipitates, thereby avoiding the risk of poisoning and deactivation of the catalytic active center.

[0022] Preferably, the crosslinked polymer material fragments are rubber stopper fragments, and in step S1, an additional 5.0 to 10.0 parts by weight of dioctyl phthalate is added. As a plasticizing component, it can effectively insert into the gaps between polymer chains, weaken the interactions between macromolecules, and soften the matrix and assist in swelling.

[0023] Preferably, in step S5, the quenching agent is at least one of anhydrous ethanol and isopropanol; the separation and purification includes: The filtrate is obtained by centrifugation or rapid silica gel column chromatography. The filtrate is then precipitated by adding methanol dropwise. The oligomer is obtained by vacuum drying or vacuum distillation. Post-processing steps efficiently remove inorganic residues and residual iron salts, and a suitable desolventizing method is selected based on the final state of the product to ensure the acquisition of a high-purity oligomer.

[0024] This invention provides a method for degrading cross-linked polymer materials. It has the following beneficial effects: 1. This invention utilizes the oleophilic and hydrophilic balance of the amphoteric permeation carrier to assist the solvent and iron salt precursor in penetrating into the internal network gaps of cross-linked polymer fragments. Due to the establishment of diffusion channels from the inside out, the catalytically active components can be pre-embedded at the microscopic level in the three-dimensional network, which helps to overcome the mass transfer bottleneck of the reaction being limited to the surface of the fragments in traditional degradation methods, improves the depth and uniformity of the degradation process, and lays the foundation for obtaining structurally complete oligomers in the future.

[0025] 2. This invention utilizes the physical disturbance of periodic gradient pressure to induce frequent relaxation and microscopic deformation of cross-linked polymer chain segments during degradation. By leveraging the coupling effect of mechanical force and thermal energy generated by pressure fluctuations, the probability of collision between active centers and cross-linked bonds is increased, allowing the reaction to proceed efficiently under mild conditions of 85 to 120 degrees Celsius. This not only reduces overall energy consumption by lowering the reaction temperature but also effectively suppresses side reactions such as carbonization by avoiding the disorderly destruction of the polymer backbone by high-temperature environments.

[0026] 3. This invention employs an in-situ complexation activation design of benzaldehyde and iron ions, combined with subsequent quenching and precipitation purification processes, to effectively control the endpoint of the degradation process. This enables the resulting oligomers to maintain a narrow molecular weight distribution and retains the active functional groups at the ends of the polymer chain segments to the maximum extent. This helps to solve the problem of performance degradation of recycled products caused by damage to the chemical structure during conventional violent depolymerization, and improves the applicability of recycled materials in the field of high-value reuse. Attached Figure Description

[0027] Figure 1 The image shows the carbon NMR spectrum of the degradation product from Example 1.

[0028] Figure 2 The images show gel permeation chromatography (GPC) curves of the degradation products from Examples 2 and 3.

[0029] Figure 3 The above are the proton NMR spectra of the degradation products of Examples 2, 3, and 4.

[0030] Figure 4 Gel permeation chromatography (GPC) curves of the degradation products of Examples 5, 6, 7, 8, and 9.

[0031] Figure 5 The image shows the proton NMR spectrum of the degradation product of Example 10. Detailed Implementation

[0032] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0033] Preparation Examples 1-3: Preparation Example 1: This preparation example provides a method for preparing an amphoteric permeable carrier A1, comprising the following steps: Amide reaction: 1.0 mol of lauric acid (C12H24O2) and 1.1 mol of diethylenetriamine were added to a reactor equipped with a stirrer and a water separator. Under nitrogen protection, the temperature was raised to 145°C-155°C, and the reaction was stirred for 5-6 hours. The water byproduct generated in the reaction was removed by the water separator to obtain the lauroyl diethylenetriamine intermediate.

[0034] Cyclization reaction: Continue heating to 225°C-235°C, slowly turn on the vacuum pump, maintain the system pressure between -0.08MPa and -0.095MPa, and react under reduced pressure for 4 hours. During this process, the intermediate undergoes dehydration and cyclization to form 2-undecylimidazoline.

[0035] Polyetherification modification: The above cyclized product was cooled to 125°C, and 0.4%–0.6% by mass of potassium hydroxide (KOH) was added as a catalyst. 5.0 mol of ethylene oxide (EO) was introduced, and the reaction pressure was controlled at 0.25 MPa–0.35 MPa. The reaction temperature was maintained at 130°C–140°C until the pressure inside the reactor no longer decreased.

[0036] Refining: Cool to 60°C, neutralize with phosphoric acid to pH 6.5-7.5, remove trace amounts of water under vacuum to obtain amphoteric osmotic carrier A1.

[0037] Preparation Example 2: This preparation example provides a method for preparing an amphoteric permeable carrier A2, comprising the following steps: Amide reaction: 1.0 mol stearic acid (C18H36O2) and 1.15 mol diethylenetriamine were added to a reaction vessel. Under nitrogen protection, the temperature was raised to 150°C-160°C, and the reaction was stirred for 6-7 hours, continuously removing the generated water.

[0038] Cyclization reaction: Heat to 230°C-240°C, adjust the system pressure to below -0.09MPa, and react under reduced pressure for 5 hours to allow complete intramolecular dehydration and cyclization to generate 2-heptadecylimidazoline.

[0039] Polyetherification modification: The cyclized product was cooled to 130°C, and 0.5% (by mass) of KOH was added. 10.0 mol of ethylene oxide (EO) was introduced, and the reaction pressure was controlled at 0.30 MPa-0.40 MPa, and the reaction temperature was controlled at 135°C-145°C until the pressure was constant.

[0040] Refining: After cooling, the catalyst is neutralized, a small amount of precipitate is removed by filtration, and the amphoteric permeation carrier A2 is obtained by vacuum drying.

[0041] Preparation Example 3: This preparation example provides a method for preparing an amphoteric permeable carrier A3, comprising the following steps: Amide reaction: 1.0 mol of erucic acid (C22H42O2) and 1.2 mol of diethylenetriamine were added to a reaction vessel. Under nitrogen protection, the temperature was raised to 155°C-165°C and the reaction was stirred for 7-8 hours until no more water was separated.

[0042] Cyclization reaction: Heat to 235°C-245°C, keep the system pressure below -0.095MPa, and react under reduced pressure for 6 hours to generate 2-dococarbenylimidazoline.

[0043] Polyetherification modification: The cyclized product was cooled to 135°C, and 0.5%–0.7% (by mass) of KOH was added. 15.0 mol of ethylene oxide (EO) was introduced, and the reaction pressure was controlled at 0.35 MPa–0.45 MPa, while the reaction temperature was maintained at 140°C–150°C.

[0044] Refining: Cool to 80°C, neutralize and dehydrate to obtain amphoteric osmotic carrier A3.

[0045] Examples 1-10: Example 1: This embodiment provides a method for degrading cross-linked polymer materials (nitrile gloves), including the following steps: S1. Anti-poisoning pretreatment and swelling: In a 250mL three-necked reactor equipped with an anchor stirrer, add 150mL of dichloroethane and 3g of shredded nitrile glove fragments (particle size <5mm), turn on the stirrer and set the speed to 60rpm; then add 0.15g of the amphoteric permeable carrier A1 prepared in Example 1 and 0.2g of nano ZnO, and continue stirring at 45℃ for 4 hours to allow the material to fully swell and establish a chemical shielding layer; S2, Precursor Infiltration: Add 100mg of anhydrous ferric chloride to the reactor, increase the stirring speed to 100rpm, and infiltrate at a constant temperature of 45℃ for 4 hours, so that the iron salt precursor enters the cross-linked network under the mediation of carrier A1. S3. In-situ complexation activation: 1g benzaldehyde and 0.1g triphenylphosphine are added dropwise to the reaction vessel and stirred at low speed for 2 hours at 23°C to allow the activator to complex with the pre-embedded iron salt in the rubber grid micro-region, thus obtaining the mother liquor to be reacted. S4. Stress-Coordinated Chain Breaking: Seal the reactor and heat it to 85°C at a rate of 3°C / min. Start the pressure circulation system to make the pressure inside the reactor fluctuate periodically between 0.5MPa and 0.8MPa (fluctuation frequency of 1 time / h). Continue the reaction for 3 hours under this temperature and pressure synergy condition. S5. Product purification: Cool to 40℃, add 5mL of anhydrous ethanol to quench the reaction, then centrifuge the material at 6000rpm for 15 minutes to remove inorganic impurities, add the filtrate to excess methanol to precipitate, and dry under vacuum to obtain 2.4g of pale yellow solid product.

[0046] Example 2: This embodiment provides a method for degrading cross-linked polymer materials (rubber bands), including the following steps: S1. Swelling pretreatment: In a 250mL three-necked reactor, add 100mL of dichloromethane and 1g of rubber band scraps, start stirring at 60rpm; add 0.05g of the amphoteric permeable carrier A2 prepared in Example 2, and stir continuously at 40℃ for 6 hours. S2, Precursor permeation: Add 100mg of anhydrous ferric chloride to the reactor and stir at 40℃ for 4 hours to induce the catalytic center precursor to diffuse into the deeper layers of the network; S3, In-situ complexation activation: Add 0.5g benzaldehyde and 0.1g polyethylene glycol dimethyl ether (Mn=400) to the reactor and stir continuously at 20 to 25°C for 3 hours to carry out intramolecular coordination exchange; S4. Stress-induced chain rupture: Heat to 90℃, adjust the dynamic pressure inside the reactor to fluctuate between 0.6MPa and 1.0MPa (frequency 1.5 times / h), and continue the reaction for 24 hours. S5. Product purification: Isopropanol was added for quenching, and residual iron salts were removed by rapid silica gel column chromatography. The filtrate was precipitated with methanol to obtain 0.43g of viscous solid product.

[0047] Example 3: This embodiment provides a method for degrading cross-linked polymer materials (rubber bands), including the following steps: S1. Swelling pretreatment: The steps are the same as in Example 2; S2, Precursor permeation: Add 200 mg of anhydrous ferric chloride to the reactor and stir at a constant temperature of 40°C for 4 hours; S3. In-situ complexation activation: The steps are the same as in Example 2; S4. Stress-induced chain scission: The temperature is raised to 90°C, and the dynamic pressure inside the reactor is adjusted to fluctuate between 0.6MPa and 1.0MPa, and the reaction is continued for 12 hours; S5. Product purification: The steps are the same as in Example 2, and 0.45g of viscous solid product is obtained.

[0048] Example 4: This embodiment provides a method for degrading cross-linked polymer materials (rubber bands), including the following steps: S1. Swelling pretreatment: The steps are the same as in Example 2; S2, Precursor permeation: Add 400 mg of anhydrous ferric chloride to the reactor and stir at a constant temperature of 40°C for 4 hours; S3. In-situ complexation and activation: The steps are the same as in Example 2; S4. Stress-induced chain rupture: Heat to 90℃, adjust the dynamic pressure inside the reactor to fluctuate between 0.6MPa and 1.0MPa, and continue the reaction for 12 hours. S5. Product purification: The steps are the same as in Example 2, and 0.45g of viscous solid product is obtained.

[0049] Example 5: This embodiment provides a method for degrading cross-linked polymer materials (waste tire particles), including the following steps: S1. Anti-poisoning pretreatment and swelling: In a 500mL high-pressure reactor, add 100mL of dichloroethane and 1g of waste tire particles, and start stirring; add 0.08g of the amphoteric permeable carrier A3 prepared in Preparation Example 3 and 0.1g of zinc stearate, and stir at 60°C for 6 hours. S2, Precursor permeation: Add 100mg of ferric trifluoromethanesulfonate (III), increase the rotation speed to 120rpm, and permeate at 60℃ for 6 hours; S3, In-situ complexation activation: Add 2g benzaldehyde and 0.1g triphenylphosphine sequentially, and stir at room temperature for 2 hours; S4, Stress-Coordinated Chain Breaking: Rapidly heat to 120℃, control the pressure inside the vessel to fluctuate between 1.0MPa and 1.5MPa (frequency 1 time / h), and continue the reaction for 2 hours; S5. Product purification: Centrifuge to remove impurities, add methanol to the filtrate to precipitate, and obtain 0.7g of viscous solid.

[0050] Example 6: This embodiment provides a method for degrading waste tire particles, including the following steps: Steps S1-S3 are the same as in Example 5; S4, Stress-Coordinated Chain Breaking: Heat to 120℃, pressure fluctuation range 1.0-1.5MPa, and continue the reaction for 5 hours; S5. Product purification: The steps are the same as in Example 5, and 0.75g of viscous solid is obtained.

[0051] Example 7: This embodiment provides a method for degrading waste tire particles, including the following steps: Steps S1-S3 are the same as in Example 5; S4, Stress-Coordinated Chain Breaking: Heat to 120℃, pressure fluctuation range 1.0-1.5MPa, continuous reaction for 7 hours; S5. Product purification: The steps are the same as in Example 5, and 0.79g of viscous solid is obtained.

[0052] Example 8: This embodiment provides a method for degrading waste tire particles, including the following steps: Steps S1-S3 are the same as in Example 5; S4, Stress-Coordinated Chain Breaking: Heat to 120℃, pressure fluctuation range 1.0-1.5MPa, and continue the reaction for 10 hours; S5. Product purification: The steps are the same as in Example 5, and 0.83g of viscous solid is obtained.

[0053] Example 9: This embodiment provides a method for degrading waste tire particles, including the following steps: Steps S1-S3 are the same as in Example 5; S4, Stress-Coordinated Chain Breaking: Heat to 120℃, pressure fluctuation range 1.0-1.5MPa, continuous reaction for 24 hours; S5. Product purification: The steps are the same as in Example 5, and 0.9g of viscous solid is obtained.

[0054] Example 10: This embodiment provides a method for degrading cross-linked polymer materials (rubber stoppers), including the following steps: S1. Anti-poisoning pretreatment and softening: In a 500mL reactor, add 100mL of chloroform and 2g of rubber stopper fragments, and start stirring; add 0.12g of carrier A2 prepared in Preparation Example 2, 0.15g of nano ZnO and 0.2g of dioctyl phthalate (DOP) in sequence, and stir continuously at 55℃ for 8 hours. S2, Precursor permeation: Add 200 mg of anhydrous ferric chloride and stir at 55°C for 6 hours to permeate; S3, In-situ complexation activation: Add 3.1g benzaldehyde and 0.15g polyethylene glycol dimethyl ether, and stir at 20 to 25°C for 3 hours; S4. Stress-induced chain rupture: Heat to 100℃, control the pressure inside the reactor to fluctuate between 0.8MPa and 1.2MPa (frequency 1.5 times / h), and continue the reaction for 6 hours; S5. Product purification: Cool and quench, centrifuge and remove solvent by vacuum distillation, and collect 1.5g of viscous solid.

[0055] Comparative Examples 1-5: Comparative Example 1: Compared with Example 1, the difference is that the amphoteric permeation carrier A1 prepared in Example 1 was not added in step S1, the isothermal permeation process at 45°C in step S2 was omitted, and the in-situ complexation process in step S3 was directly entered after swelling in step S1. All other steps are the same.

[0056] Comparative Example 2: Compared with Example 1, the difference lies in the type of permeation carrier. The amphoteric permeation carrier A1 in step S1 is replaced by an equal mass of commercially available conventional nonionic surfactant sodium dodecylbenzenesulfonate (SDBS), while the rest are the same.

[0057] Comparative Example 3: Compared with Example 5, the difference is that nano ZnO and zinc stearate were not added in step S1, and anti-poisoning pretreatment at 60°C was not performed. Swelling was carried out directly at room temperature. All other aspects are the same.

[0058] Comparative Example 4: Compared with Example 5, the difference is that the stress-assisted environment in step S4 was changed, the periodic gradient fluctuation of pressure was eliminated, and the pressure inside the vessel was kept constant at 1.2 MPa for static degradation. All other aspects are the same.

[0059] Comparative Example 5: Compared with Example 1, the difference lies in the change of the overall reaction mechanism and steps. Steps S1, S2 and S4 are omitted. The nitrile glove fragments in step S1 are directly mixed with dichloroethane, benzaldehyde and anhydrous ferric chloride at 23°C and normal pressure and stirred continuously for 3 hours. The rest are the same.

[0060] Test Examples 1-5: Test Example 1: Structure verification of nitrile rubber degradation products and carrier penetration performance testing Assembly degradation efficiency evaluation system and nuclear magnetic resonance characterization system.

[0061] The degradation reaction mixtures and residual solids prepared in Example 1, Comparative Example 1, Comparative Example 2 and Comparative Example 5 were used as test objects.

[0062] The undegraded residual solids from Examples 1, 1, 2, and 5 were separated by filtration using qualitative filter paper. The residual solids were then washed three times each with dichloroethane and anhydrous ethanol. The washed residual solids were then dried in a vacuum oven at 80°C for 12 hours until constant weight. The mass of the residual solids was recorded, and the degradation efficiency was calculated based on the initial input amount.

[0063] Take 20 mg of the pale yellow solid product obtained in Example 1 and dissolve it in 0.6 mL of deuterated chloroform. Transfer the dissolved liquid into an NMR tube and place it in a 400 MHz NMR spectrometer. Set the scanning parameters, start the NMR spectrometer, run the carbon spectrum test program, and record and read the data. Spectral data.

[0064] Table 1. Comparison of Degradation Efficiency and Product Molecular Weight of Nitrile Rubber Note: Due to the low degradation efficiency of Comparative Example 5, sufficient amount of solvent-soluble oligomers could not be separated from the reaction mixture, resulting in the inability to obtain the number-average molecular weight and polydispersity index data required for gel permeation chromatography (GPC) testing. This is indicated by "--".

[0065] Figure 1 The image shows the carbon NMR spectrum of the degradation product from Example 1. Figure 1 The figure shows the distribution of characteristic peak signals of the degradation products obtained in Example 1 in the region with a chemical shift of 0-12 ppm.

[0066] By analyzing the experimental data recorded in Table 1 and combining it with... Figure 1 The spectral characteristics shown reveal that the product of Example 1 exhibits distinct aldehyde and carbonyl group signals in the chemical shift range of 0-12 ppm. This signal distribution confirms that the carbon-carbon double bonds in the nitrile rubber molecular chain underwent oxidative breakage under the guidance of the catalytic system. In terms of degradation efficiency, Example 1 significantly outperformed the other control groups, and its product also had a lower number-average molecular weight, indicating a more profound degree of chain scission.

[0067] In Comparative Example 1, without the addition of the amphoteric permeable support A1, the catalytically active precursor struggled to penetrate the dense cross-linked network within the nitrile rubber, resulting in the reaction primarily concentrating on the rubber particle surface, with a degradation efficiency maintained at only around 21.85%. This limitation in penetration depth led to a high degree of polydispersity in the product's molecular weight distribution. In contrast, Example 1, through the coordination of the amphoteric permeable support A1 with metal ions, guided the catalytic centers to migrate into the rubber interior and achieve uniform distribution, thus contributing to an increased reaction probability within the cross-linked network.

[0068] When observing the test results of Comparative Example 2, it can be found that after replacing the carrier with the conventional surfactant sodium dodecylbenzenesulfonate, the degradation efficiency was only 32.73%. This reflects that ordinary surfactants, due to their lack of effective chemical coordination ability, cannot form coordination complexes with penetration-driving force, and have difficulty overcoming the strong polar resistance between nitrile rubber molecular chains, thus limiting the improvement of degradation depth.

[0069] Furthermore, Comparative Example 5, employing a traditional ambient temperature and pressure mixing process without the four-step process, showed a degradation efficiency of only 11.27%. This result not only reflects the impact of the missing in-situ complexation activation step on reaction kinetics but also confirms the importance of the mechanochemical synergistic effect generated by gradient pressure in initiating the degradation reaction of highly polar rubber. Experimental observations suggest that controlling the structure of the amphoteric permeable carrier A1 and coordinating with gradient pressure fluctuations is beneficial for balancing the demands of physical deformation energy and chemical chain scission energy, and is a key factor in achieving efficient conversion of nitrile rubber.

[0070] Test Example 2: Controlled molecular weight distribution of rubber band degradation products and stress synergistic testing 1. Configure a gel permeation chromatography analysis system and prepare a molecular weight standard curve.

[0071] 2. The product mixtures of Examples 2, 3 and Comparative Example 4 after the reaction were selected as analytical samples.

[0072] 3. The reaction solutions of each group were pretreated by passing them through a microporous membrane, and then excess anhydrous ethanol was added for precipitation and separation. The obtained solids were collected and dissolved a second time using tetrahydrofuran. After filtering to remove insoluble components, the filtrate was concentrated to constant weight using a rotary evaporator to obtain the oligomer sample to be tested.

[0073] 4. Weigh 10 mg of the oligomer sample and dissolve it in 5 mL of chromatographic grade tetrahydrofuran solvent. After passing the solution through a 0.22 μm needle filter, inject it into the gel permeation chromatograph. Set the eluent flow rate to 1.0 mL per minute. Record the relationship between eluent time and signal intensity using a differential refractive index detector. Calculate the number-average molecular weight, weight-average molecular weight, and polydispersity index of the product based on the polystyrene standard curve.

[0074] Table 2. Molecular weight distribution and performance comparison of rubber band degradation products. Note: Because Comparative Example 4 reacted under constant pressure, the cross-linking network was not fully broken, resulting in a large number of incompletely degraded microgel particles in the product. Multiple filtration processes are required before gel permeation chromatography testing.

[0075] Figure 2The figures show the gel permeation chromatography curves of the degradation products in Examples 2 and 3. The figures illustrate the evolution of the product elution peak shifting to the lower molecular weight region as the loading of the catalytic precursor increases.

[0076] Combining the physical parameters recorded in Table 2 with Figure 2 The elution curves shown indicate that both Examples 2 and 3 achieved high degradation efficiencies under different catalyst dosages, and the molecular weight distribution of the products exhibited a relatively regular single-peak pattern. This phenomenon suggests that the active centers entering the rubber interior under the guidance of the amphoteric permeation carrier can induce uniform chain breakage of polyisoprene. Comparing the data differences between Examples 2 and 3 reveals that increasing the iron salt loading in the catalytic system is beneficial for further reducing the number-average molecular weight of the products. This provides experimental evidence for the customized application of the degradation products in fields such as lubricant additives or rubber auxiliaries.

[0077] When evaluating the synergistic effect of the physical field, the test results of Comparative Example 4 showed a significant difference. While maintaining the same chemical composition as Example 3, Comparative Example 4 replaced the periodic gradient pressure with a constant pressure. Experimental data showed that the degradation efficiency of Comparative Example 4 decreased significantly to 38.24%, and the polydispersity index of the product increased to 2.47. This increase in distribution width reflects the uneven stress distribution within the crosslinked network in the absence of pressure fluctuation induction, causing the chain-breaking reaction to occur only in local high-energy regions, making it difficult to achieve synchronous destruction of the entire network.

[0078] Scientific observations suggest that the intervention of gradient compressive stress not only helps to increase the penetration rate of solvents and catalysts into the rubber mesh, but more importantly, it generates mechanochemical shear forces through periodic volume deformation. This physical effect synergizes with the chemical chain-splitting energy generated by the in-situ complexation catalytic center, which helps to reduce the activation energy required for carbon-carbon double bond polarization. A horizontal comparison between Example 3 and Comparative Example 4 confirms that the pressure gradient fluctuation step established in this invention is a core element in ensuring uniform degradation of complex cross-linked systems from the inside out, contributing to the acquisition of high-quality oligomers with narrow molecular weight distribution in a shorter time.

[0079] Test Example 3: End-group chemical characterization and process stability testing of rubber band degradation reaction 1. Prepare the nuclear magnetic resonance hydrogen spectrum testing environment, and use the solid oligomer products prepared in Examples 2, 3 and 4 as the test objects.

[0080] 2. Weigh 15 mg of each oligomer sample and place them in a dry centrifuge tube. Add 0.6 mL of deuterated chloroform to dissolve them completely.

[0081] 3. Transfer the dissolved liquid sample into a standard NMR tube through a long-necked funnel, ensuring that the liquid level meets the detection requirements of the 400MHz NMR spectrometer.

[0082] 4. Start the nuclear magnetic resonance spectrometer and load the proton spectrum test program. Set the cumulative number of scans to 128. Record the signal intensity of each group of samples in the range of chemical shift from 0 to 12 ppm. Then, use professional spectral analysis software to integrate the target characteristic peaks.

[0083] Table 3. Characteristic data of 1H NMR spectrum of rubber band degradation products Note: The relative integral area of ​​the characteristic peak is normalized with reference to the signal area of ​​the chemical shift near 10.1 ppm in Example 2. Due to slight differences in the solubility of the product under different catalyst loadings, the integral area values ​​may fluctuate within a normal range of ±0.05 in repeated experiments.

[0084] Figure 3 The following are the 1H NMR spectra of the degradation products in Examples 2, 3, and 4. Figure 3 The figure shows the changes in the morphology and intensity of the characteristic signal peaks generated at the ends of the product molecular chains under different catalyst concentrations.

[0085] Through the Figure 3 Further analysis of the spectral data revealed a distinct single-peak signal in the low-field region with a chemical shift of approximately 10.1 ppm. This signal is attributed to aldehyde progeny atoms generated after the breakage of the rubber backbone. The presence of this characteristic peak directly confirms the precise attack of the carbon-carbon double bonds in the polyisoprene molecular chain by the in-situ complexation catalytic center in this invention, inducing oxidative shearing. Combined with the quantitative data in Table 3, it can be observed that as the catalytic precursor loading increased from Example 2 to Example 4, the relative integral area of ​​the aldehyde characteristic peak showed an increasing trend, and the calculated degradation rate also increased accordingly. This reflects the good process controllability of the reaction system.

[0086] During the experimental study, it was observed that although the concentration of the catalytic component was varied in Examples 2 to 4, the proton NMR spectra of all products maintained a high degree of consistency in the position of the characteristic peaks, and no disordered byproduct signals appeared. This phenomenon reflects the extremely high selectivity of this chemical transformation pathway in the isoprene rubber system, which helps to maintain the basic properties of the polymer backbone during degradation without excessive oxidation. Compared with traditional acid-base catalytic degradation, which easily produces complex cross-linking byproducts, the present invention utilizes an in-situ activation mechanism of iron salts, which is beneficial for obtaining low molecular weight oligomers while retaining active end groups with further modification potential.

[0087] Further analysis suggests that the formation of these end-group functional groups not only signifies successful main chain breakage but also lays the foundation for the subsequent high-value utilization of the product. For example, the introduction of aldehyde groups helps improve the dispersibility of degradation products in polar solvents and enables further chemical reactions with amines or alcohols. A comparative analysis of Examples 2 to 4 confirms that controlling the catalyst concentration allows for precise adjustment of the degree of chain breakage, and this adjustment process does not alter the core reaction mechanism, demonstrating that the process has a wide operating window and strong technical stability in actual industrial production.

[0088] Test Example 4: Degradation Kinetics and Anti-poisoning Stability Test of Waste Tires 1. Construct a gel permeation chromatography detection system and establish a molecular weight analysis model for complex rubber components.

[0089] 2. The degradation reaction products prepared in Examples 5, 6, 7, 8, and 9, as well as Comparative Examples 3 and 4, were selected as test subjects.

[0090] 3. Soxhlet extraction was performed on each group of samples using toluene. A continuous 24-hour extraction cycle was used to ensure that the oligomer components generated inside the rubber fragments were fully incorporated into the solvent phase. The extract was filtered through a microporous membrane to remove carbon black and inorganic filler. Excess anhydrous ethanol was then added to the filtrate for precipitation and separation. The resulting solid was placed in a vacuum drying oven at 60°C until constant weight was achieved, preparing the purified oligomers for analysis.

[0091] 4. Weigh 20 mg of the purified oligomer and dissolve it in 4 mL of chromatographic grade tetrahydrofuran. Filter the solution through a 0.45 μm organic filter membrane and inject it into a gel permeation chromatograph. Set the column temperature to 35 °C and the eluent flow rate to 1.0 mL per minute. Record the changes in the differential refractive index signal with the eluent volume, and calculate the number-average molecular weight, weight-average molecular weight, and polydispersity index of the product using the calibration curve.

[0092] Table 4. Degradation kinetics and anti-poisoning stability test data of waste tire pellets Note: Due to the inactivation of the catalytic system in Comparative Example 3 by interference from sulfides, soluble oligomers meeting the detection concentration could not be separated from the extract, so no corresponding molecular weight data was obtained, and is indicated by "--".

[0093] Figure 4 The images show the gel permeation chromatography curves of the degradation products from Examples 5, 6, 7, 8, and 9. Figure 4 The paper demonstrates the stepwise shift of the elution peaks of waste tire degradation products from the high molecular weight region to the low molecular weight region at different reaction times.

[0094] By analyzing the data in Table 4 and combining it with... Figure 4 The peak shift pattern shown reveals that, as the reaction time increases from 2 hours to 24 hours, the number-average molecular weight of the products obtained in Examples 5 to 9 exhibits a clear, phased decreasing trend. This dynamic evolution confirms that the present invention can maintain stable degradation kinetics when processing waste tire particles containing a dense vulcanized network. Even in complex systems with high filler content and high sulfur content, the reaction system still exhibits strong controllability, enabling continuous and uniform shearing of the long polymer chains under the action of the catalytic center.

[0095] In the stability study of sulfur-containing materials, Comparative Example 3 showed a lower degradation efficiency, a stark contrast to Example 8. Free sulfur and sulfur-containing functional groups in waste tires readily coordinate strongly with transition metal centers, leading to the loss of function of catalytic active sites due to poisoning. Examples 5 to 9, by introducing nano-zinc oxide and zinc stearate in step S1, pre-captured and shielded active sulfur species chemically. This targeted protection helps maintain the long-term activity of the catalytic centers. Experimental studies observed that without such anti-poisoning pretreatment, the degradation reaction quickly stalled due to interference from sulfides.

[0096] Furthermore, the data from Comparative Example 4 further confirms the necessity of gradient compressive stress in overcoming steric hindrance. When the periodic pressure pulses were eliminated and constant pressure was used, even with a longer reaction time, the degradation efficiency was still far lower than that of the experimental group in the same period, and the polydispersity index of the product increased to 2.47. This increase in distribution width often indicates that the chain-breaking reaction within the cross-linked network is insufficient and heterogeneous. The micro-deformation induced by periodic stress helps the catalytic component migrate across the sulfurized network to the deeper particles, thereby balancing the physical deformation energy and the chemical chain-breaking energy. Therefore, it can be considered that controlling the addition of sulfur-capturing components and coordinating with dynamic pressure synergistic steps is the core pathway to obtain high-quality oligomers when processing industrial waste tires.

[0097] Test Example 5: Degradation compatibility and product structure characterization of complex systems with high filler content 1. Establish an extraction and separation process and nuclear magnetic resonance detection system for degradation products of high-ash rubber.

[0098] 2. The mixtures of Example 10, Comparative Example 1, and Comparative Example 3 after the reaction were selected as test objects, and the degradation performance of rubber stopper fragments containing large amounts of zinc oxide, clay, and vulcanizing agent was evaluated.

[0099] 3. Each group of samples was subjected to Soxhlet extraction with toluene for 48 hours to overcome the adsorption effect of high-content inorganic filler on polymer components. The extract was centrifuged to remove insoluble inorganic ash, and then excess anhydrous ethanol was added to the clarified liquid for precipitation. The resulting solid product was dried in a vacuum drying oven at 60°C for 18 hours to prepare purified oligomer samples.

[0100] 4. Weigh 15 mg of the purified oligomer and dissolve it in 0.6 mL of deuterated chloroform. Transfer the sample solution to a standard NMR tube and place it in a 400 MHz NMR spectrometer. Set the scanning parameters, start the NMR spectrometer to run the proton NMR test program, and record and read the data. Spectral data.

[0101] Table 5. Data on degradation efficiency and product structure characteristics of high-filler rubber stoppers Note: Due to the inactivation of the catalytic system in Comparative Example 3 by interference from high sulfide content, soluble oligomers meeting the detection concentration could not be separated from the extract. Therefore, no corresponding 1H NMR characteristic peak area data was obtained, and it is indicated by "--".

[0102] Figure 5 The above is the 1H NMR spectrum of the degradation product from Example 10. Figure 5 The figure shows the characteristic signal distribution of the degradation products obtained in Example 10 at a chemical shift of 10.1 ppm.

[0103] By comprehensively analyzing the experimental data in Table 5 and combining them with... Figure 5 The spectral characteristics shown indicate that Example 10, even when treating a rubber stopper system with a filler content as high as 45.3%, still exhibits a clear characteristic peak of aldehyde matrices at a chemical shift of 10.1 ppm. This signal distribution confirms that the present invention can still induce effective breakage of carbon-carbon double bonds under complex operating conditions. Experimental data show that the degradation efficiency of Example 10 reached 74.82%, indicating that the physical shielding layer composed of inorganic minerals and metal oxides did not block the catalytic reaction, and the product was ultimately converted into a soluble oligomer component.

[0104] Degradation stability studies of the high-filler system showed that, in Comparative Example 1, the degradation efficiency decreased to 24.31% in the absence of the amphoteric permeable support A1, and the integral area of ​​the characteristic peak was only about 28% of that in Example 10. This difference reflects that the presence of a large amount of inorganic filler further increases the difficulty for the catalytic active centers to penetrate into the polymer matrix. Example 10 utilized the coordination guiding effect between the support and metal ions, which helped the catalytic component bypass the inorganic barrier and contact the rubber molecular chains. Experimental observations suggest that controlling the polarity partition coefficient of the support molecules is beneficial for maintaining an effective concentration of active sites in a densely filled environment.

[0105] When investigating the anti-poisoning mechanism, it was found that the test data of Comparative Example 3 showed a significant decline, with a degradation efficiency of only 12.54%. Rubber stoppers typically contain a high proportion of accelerators and sulfur-containing vulcanization systems, which can easily lead to the failure of the iron salt catalytic system. Example 10, through the anti-poisoning pretreatment process introduced in step S1, utilizes the synergistic effect of nano-zinc oxide and zinc stearate to pre-neutralize the active sulfur species in the material, thereby protecting the subsequently added catalytic active centers. Comparative experimental results confirm that for industrial waste with high filler content and complex chemical additives, anti-poisoning pretreatment is a prerequisite for ensuring the initiation of the degradation reaction.

[0106] Furthermore, observation of the properties of the product in Example 10 revealed that the degraded substance transformed from an original high-hardness solid into a brownish-yellow viscous liquid. This macroscopic morphological change, coupled with chain-severing signals in the 1H NMR spectrum, provided quantitative and qualitative confirmation. The mechanochemical action generated by gradient compressive stress helps stretch the long rubber chains embedded in the inorganic filler gaps and expose them to the catalytic environment, thereby balancing the steric hindrance created by the solid filler and the mass transfer requirements of the chemical reaction. Therefore, it can be determined that the multi-step process developed in this invention has good adaptability and technical reliability in processing industrial-grade high-filler rubber products.

Claims

1. A method for degrading cross-linked polymer materials, characterized in that, Includes the following steps: S1. Add cross-linked polymer material fragments to at least one of dichloroethane, dichloromethane, and chloroform, and add an amphoteric permeable carrier for swelling treatment to obtain a swollen system; S2. Add an iron salt precursor to the swelling system and perform a permeation treatment to obtain a permeation system; S3. Add benzaldehyde and at least one of triphenylphosphine and polyethylene glycol dimethyl ether to the permeation system for in-situ complexation activation to obtain the mother liquor to be reacted. S4. The mother liquor to be reacted is subjected to a degradation reaction under conditions of 85 to 120°C and a pressure fluctuating periodically between 0.5 and 1.5 MPa to obtain a degradation solution. S5. Add a quencher to the degradation solution to terminate the reaction, and obtain the oligomer by separation and purification.

2. The degradation method for cross-linked polymer materials according to claim 1, characterized in that, The raw materials are as follows by weight: Cross-linked polymer material fragments: 100 parts; At least one of dichloroethane, dichloromethane, and chloroform: 5,000 to 15,000 parts; Amphoteric transdermal carrier: 5.0 to 8.0 parts; Iron salt precursor: 3.3 to 40.0 parts; Benzaldehyde: 33.3 to 200.0 parts; At least one of triphenylphosphine and polyethylene glycol dimethyl ether: 3.3 to 10.0 parts.

3. The degradation method for cross-linked polymer materials according to claim 1, characterized in that, In step S1, the swelling treatment is carried out by stirring at 40 to 60°C; the amphoteric permeation carrier is a 2-alkyl imidazoline modified with polyoxyethylene.

4. The degradation method for cross-linked polymer materials according to claim 1, characterized in that, In step S2, the iron salt is permeated at a constant temperature of 40 to 60°C for 4 to 6 hours; the iron salt precursor is anhydrous ferric chloride.

5. The degradation method for a cross-linked polymer material according to claim 1, characterized in that, In step S3, the number-average molecular weight of the polyethylene glycol dimethyl ether is 400; the in-situ complexation activation is carried out by stirring at 20 to 25°C for 2 to 3 hours.

6. The degradation method for a cross-linked polymer material according to claim 1, characterized in that, In step S4, the temperature is increased to the degradation reaction temperature at a rate of 3°C per minute, the degradation reaction lasts for 2 to 24 hours, and the frequency of the periodic gradient fluctuation is 1.0 to 1.5 times per hour.

7. The degradation method for a cross-linked polymer material according to claim 3, characterized in that, The amphoteric permeation support comprises a hydrophobic carbon chain with 12 to 22 carbon atoms, and the addition number of ethylene oxide is 5.0 to 15.0 mol; the preparation method of the amphoteric permeation support includes the following steps: Under nitrogen protection, 1.0 mol of fatty acid and 1.1 to 1.2 mol of diethylenetriamine were reacted at 145 to 165 °C for 5 to 8 hours to undergo amidation, and the byproduct water was removed to obtain the intermediate. The temperature is raised to 225 to 245°C, and the reaction is carried out under reduced pressure of -0.08 MPa to -0.095 MPa for 4 to 6 hours to achieve dehydration and ring closure. Add 0.4% to 0.7% potassium hydroxide by mass of the cyclic product to the cyclic product, then introduce 5.0 to 15.0 mol of ethylene oxide, and perform polyetherification modification at 130 to 150 °C. The amphoteric permeable carrier is then obtained after neutralization.

8. The degradation method for a cross-linked polymer material according to claim 1, characterized in that, In step S1, the cross-linked polymer material fragments are sulfur-containing materials, and at least one of nano zinc oxide and zinc stearate is added simultaneously in step S1 for anti-poisoning pretreatment.

9. The degradation method for a cross-linked polymer material according to claim 1, characterized in that, The cross-linked polymer material fragments are rubber stopper fragments, and in step S1, an additional 5.0 to 10.0 parts by weight of dioctyl phthalate is added.

10. The degradation method of a cross-linked polymer material according to claim 1, characterized in that, In step S5, the quenching agent is at least one of anhydrous ethanol and isopropanol; the separation and purification includes: The filtrate is obtained by centrifugation or rapid silica gel column chromatography. The filtrate is then added dropwise to methanol for precipitation. The oligomer is obtained by vacuum drying or vacuum distillation.

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