Continuous devulcanization process of an anti-aging butyl reclaimed rubber

Abstract

The application belongs to the field of waste and old rubber recycling and processing, and discloses a continuous devulcanization process of aging-resistant butyl reclaimed rubber, which comprises the following steps: S1: placing waste and old butyl rubber in a water solution containing 0.5-1.5 wt% sodium dodecyl benzene sulfonate to clean, and crushing the waste and old butyl rubber to particles with a particle size of 2-5 mm after removing surface impurities; S2: synchronously feeding the pretreated rubber particles and a composite devulcanization agent into a continuous devulcanization equipment, continuously devulcanizing at 180-220 DEG C, 1.5-2.5 MPa for 30-60 minutes; S3: passing high-purity nitrogen into the devulcanization section at a flow rate of 0.5-1.0 m3 / h to form an inert reaction environment; S4: cooling the devulcanization product to room temperature through a spiral cooling device, and obtaining reclaimed rubber through a 80-120 mesh screen; the application aims to provide a new continuous devulcanization process of aging-resistant butyl reclaimed rubber, solve the problems of poor aging resistance, high antioxidant loss, many oxidation side reactions and low production efficiency in the traditional process, and realize efficient recycling of waste and old butyl rubber and high-performance production of reclaimed rubber.

Description

A continuous desulfurization process for aging-resistant butyl reclaimed rubber Technical Field

[0001] This invention relates to the field of waste rubber recycling technology, specifically a continuous desulfurization process for aging-resistant butyl reclaimed rubber. Background Technology

[0002] Butyl rubber, with its excellent airtightness, chemical resistance, and weather resistance, is widely used in tire inner tubes, pharmaceutical bottle stoppers, and sealing materials. With the development of waste rubber resource utilization technologies, the preparation process of butyl recycled rubber has become a research hotspot in the industry. However, the current desulfurization and regeneration process of waste butyl rubber still faces several technical challenges:

[0003] On the one hand, traditional desulfurization processes, such as dynamic tank desulfurization and single / twin-screw extruder desulfurization, mainly break vulcanization crosslinking bonds through high temperature, mechanical shearing, or chemical reagents. However, it is difficult to precisely control the degree of vulcanization network breakage during the process, which can easily lead to excessive degradation of the rubber backbone, resulting in a decrease in mechanical properties such as tensile strength and elongation at break of the reclaimed rubber. On the other hand, existing processes lack a systematic design to improve the aging resistance of reclaimed rubber, simply adding antioxidants or UV absorbers without addressing the stability of the additives in high-temperature environments. This makes the reclaimed rubber susceptible to aging under the influence of light, oxygen, and heat during long-term use, limiting its application in high-weather-resistance scenarios. In addition, traditional desulfurization equipment often uses a screw-pitch stirring structure, resulting in uneven shear force distribution of the material in the desulfurization section and random vulcanization bond breakage, causing large fluctuations in the performance of the reclaimed rubber. The cleaning process generally uses single-stage spraying or immersion methods, resulting in low utilization of cleaning agents and incomplete removal of impurities, making subsequent processing susceptible to the influence of residual impurities. Therefore, a continuous desulfurization process for aging-resistant butyl reclaimed rubber is proposed, which can achieve directional breakage of the vulcanization network, efficient stabilization of aging-resistant additives, and environmental protection and energy-saving characteristics, so as to improve the comprehensive performance and production efficiency of butyl reclaimed rubber. Summary of the Invention

[0004] This invention aims to provide a novel continuous desulfurization process for aging-resistant butyl reclaimed rubber. By optimizing the compound desulfurizing agent formulation, controlling the inert environment, innovating the equipment structure, and designing environmentally friendly processes, it solves the problems of poor aging resistance, high antioxidant consumption, numerous oxidation side reactions, and low production efficiency in traditional processes, thereby achieving efficient recycling of waste butyl rubber and high-performance production of reclaimed rubber.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] The technical solution provided by this invention is: a continuous desulfurization process for aging-resistant butyl reclaimed rubber, comprising the following steps:

[0007] S1: Wash the waste butyl rubber in an aqueous solution containing 0.5-1.5wt% sodium dodecylbenzenesulfonate to remove surface impurities, and then crush it into particles with a particle size of 2-5mm to obtain pretreated rubber particles.

[0008] S2: The pretreated granules and composite desulfurizing agent are simultaneously fed into the continuous desulfurization equipment at a weight ratio of 100:25-40, and continuous desulfurization is carried out for 30-60 minutes at 180-220℃ and 1.5-2.5MPa.

[0009] Composite desulfurizers consist of: desulfurization components and an aging-resistant system;

[0010] The desulfurization components, by weight, include: 5-10 parts sulfur, 3-5 parts accelerator M, 5-8 parts zinc oxide, and 2-4 parts stearic acid;

[0011] Anti-aging system: a synergistic combination of ultraviolet absorber UV-9 and antioxidant 1010 (weight ratio 1:1-2), with a total addition of 10-15 parts by weight, wherein antioxidant 1010 is encapsulated using microencapsulation technology;

[0012] S3: In the desulfurization section, at a rate of 0.5-1.0m 3 High-purity nitrogen gas is introduced at a flow rate of / h to create an inert reaction environment;

[0013] S4: The desulfurization product is cooled to room temperature by a spiral cooling device and then passed through an 80-120 mesh sieve to obtain reclaimed rubber.

[0014] Furthermore, the continuous desulfurization equipment adopts a three-section structure, including a feeding section, a desulfurization section, and a discharge section;

[0015] The desulfurization section has a built-in variable pitch spiral agitator with a rotation speed of 50-100 rpm, which achieves directional breakage of the sulfurization network through shear force gradient distribution.

[0016] Furthermore, the preparation method of microencapsulated antioxidant 1010 is as follows: using urea-formaldehyde resin as the wall material and nano-titanium dioxide and silica composite particles as reinforcing fillers, the core antioxidant is encapsulated by in-situ polymerization to form sustained-release microcapsules with a particle size of 5-10 μm.

[0017] Furthermore, the nitrogen protection system includes a pressure regulating valve and a flow monitoring device to ensure that the oxygen content in the desulfurization section is below 0.5%, effectively suppressing high-temperature oxidation side reactions.

[0018] Furthermore, the cleaning process employs counter-current multi-stage spraying technology, achieving a cleaning agent recycling rate of ≥85%, thus realizing efficient utilization of water resources.

[0019] Furthermore, the synergistic combination of UV absorber UV-9 and antioxidant 1010, through a dual protection mechanism of light shielding and chain termination, improves the weather resistance of reclaimed rubber by more than 40% compared with conventional processes.

[0020] The beneficial effects of this technical solution are:

[0021] (1) This invention achieves a qualitative leap in the performance of reclaimed rubber through a unique anti-aging system and process optimization. On the one hand, the UV absorber UV-9 and microencapsulated antioxidant 1010 in the composite desulfurizer are precisely matched in a ratio of 1:1-2 to form a dual protection mechanism of light shielding and chain termination. After aging for 1000 hours under xenon lamp, the elongation at break is maintained at more than 81%, which is more than 30% higher than the traditional process, effectively solving the industry problem of poor weather resistance of reclaimed rubber. On the other hand, the variable pitch spiral stirring device of the three-stage continuous desulfurization equipment realizes the directional breakage of the vulcanization network. While ensuring desulfurization efficiency, it reduces the mechanical degradation of the main chain. The tensile strength of the reclaimed rubber reaches 12.2-13.0 MPa, the molecular weight distribution is narrower, and the Mooney viscosity fluctuation is controlled within ±5, which greatly improves the processing stability and product applicability of the reclaimed rubber.

[0022] (2) This invention significantly reduces production energy consumption and material loss through process parameter optimization and equipment improvement. The nitrogen protection system precisely controls the flow rate between 0.5-1.0 m³ / h. 3 While ensuring an oxygen content below 0.5%, the process reduces nitrogen consumption costs by 40% and overall energy consumption by 25%-35% compared to traditional processes. The variable-pitch spiral agitator, combined with a high-speed design, shortens desulfurization time from 45 minutes to 30 minutes, increasing production efficiency by 33% while reducing energy consumption per unit of capacity. Furthermore, microencapsulated antioxidant technology reduces antioxidant volatilization loss by 40% at high temperatures, increases cleaning agent recycling rate to 90%, and reduces water consumption by 60%. These multiple measures significantly reduce production costs and improve economic efficiency.

[0023] (3) This invention fully implements the green concept from source to process. The cleaning process uses a low concentration (0.5wt%) cleaning agent combined with countercurrent multi-stage spraying technology, which not only realizes the efficient recycling of water resources and saves up to 150,000 tons of water per year (annual production scale of 10,000 tons of glue), but also controls the residual amount of surfactant to below 0.05%, avoiding pollution to the subsequent vulcanization process. The inert reaction environment protected by nitrogen effectively inhibits the high-temperature oxidation side reaction and reduces the emission of volatile organic compounds (VOCs). The microencapsulated biodegradable urea-formaldehyde resin wall material further reduces the generation of pollutants in the production process. Attached Figure Description

[0024] Figure 1 is a data table of Example 1 of the continuous desulfurization process for aging-resistant butyl reclaimed rubber proposed in this invention;

[0025] Figure 2 is a data table for Example 2 of the continuous desulfurization process for aging-resistant butyl reclaimed rubber proposed in this invention;

[0026] Figure 3 is a data table for Example 3 of the continuous desulfurization process for aging-resistant butyl reclaimed rubber proposed in this invention;

[0027] Figure 4 is a data table for Example 4 of the continuous desulfurization process for aging-resistant butyl reclaimed rubber proposed in this invention;

[0028] Figure 5 is a data table for Example 5 of the continuous desulfurization process for aging-resistant butyl reclaimed rubber proposed in this invention;

[0029] Figure 6 is a data table for Example 6 of the continuous desulfurization process for aging-resistant butyl reclaimed rubber proposed in this invention;

[0030] Figure 7 is a data comparison table of various embodiments of the continuous desulfurization process for aging-resistant butyl reclaimed rubber proposed in this invention. Detailed Implementation

[0031] The technical solutions of 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.

[0032] The specific implementation process is as follows:

[0033] Example 1:

[0034] Please refer to Figures 1 and 7. The present invention provides a baseline process: a continuous desulfurization process for aging-resistant butyl reclaimed rubber, comprising the following steps:

[0035] S1: Place 100 parts by weight of waste butyl rubber in an aqueous solution containing 1.0 wt% sodium dodecylbenzenesulfonate, clean it using a countercurrent multi-stage spray device, with a cleaning agent recycling rate of 85%, and crush it into particles with a particle size of 3 mm.

[0036] S2: Basic desulfurization components by weight: 8 parts sulfur, 4 parts accelerator M, 6 parts zinc oxide, and 3 parts stearic acid;

[0037] Anti-aging system: UV absorber UV-9 (5 parts by weight) and microencapsulated antioxidant 1010 (10 parts by weight, coated with urea-formaldehyde resin, particle size 8μm).

[0038] S3: Add the granules and desulfurizing agent to the three-stage continuous desulfurization equipment at a weight ratio of 100:36. The desulfurization section temperature is 200℃, the pressure is 2.0MPa, and the nitrogen flow rate is 0.8m³ / h. 3 / h, oxygen content 0.3%, variable pitch spiral agitator speed 75 rpm, desulfurization time 45 minutes;

[0039] S4: The desulfurization products are cooled to 25°C by a spiral cooling device and then screened through a 100-mesh sieve;

[0040] Performance testing:

[0041] After 1000 hours of aging, the elongation at break of the xenon lamp retained 81% of its value.

[0042] Tensile strength 12.5 MPa, Mooney viscosity 50;

[0043] Nitrogen consumption: 0.8m 3 / h, with overall energy consumption reduced by 30% compared to traditional processes;

[0044] This embodiment significantly improves the aging resistance and processing stability of reclaimed rubber through the synergistic effect of composite desulfurizing agent and nitrogen protection.

[0045] Synergistic mechanism of aging-resistant system:

[0046] UV-9 (2-hydroxy-4-methoxybenzophenone), an ultraviolet absorber, selectively absorbs 280-320nm ultraviolet light through its conjugated structure, converting light energy into harmless heat energy and inhibiting the photo-induced breakage of rubber molecular chains.

[0047] Microencapsulated antioxidant 1010 (pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid]) is coated with urea-formaldehyde resin wall material. Under desulfurization temperature of 180-220℃, the wall material gradually softens and releases the antioxidant. Compared with the traditional uncoated antioxidant (with a volatilization loss rate of up to 40% in 30 minutes at high temperature), the antioxidant retention rate of this solution is increased to 75%, effectively capturing peroxide free radicals (ROO·) generated during desulfurization and terminating the chain oxidation reaction.

[0048] When the two are combined in a 1:2 ratio, the light shielding efficiency (85%) and the antioxidant efficiency (78%) reach the best balance, which is significantly better than using UV-9 alone (72% aging retention rate) or antioxidant 1010 alone (75% aging retention rate).

[0049] The oxygen content in the desulfurization section is controlled at 0.3% (compared to 21% in the open environment of existing technology). Verification using FDS fluid simulation software shows that the nitrogen gas flow forms a vortex under spiral stirring, reducing the oxygen concentration in the dead zone of the equipment to below 0.1%. This fundamentally inhibits the high-temperature reaction between the rubber main chain and oxygen (ΔH = -2800 kJ / mol), reducing the carbonyl index (a measure of oxidation) of the reclaimed rubber from 0.85 in the traditional process to 0.32, and increasing the tensile strength retention rate from 80% to 95%.

[0050] A variable pitch screw (25mm pitch in the feed section → 20mm pitch in the desulfurization section) combined with a rotation speed of 75 rpm reduces the shear rate of the rubber compound in the desulfurization section from 50 s⁻¹ to 20 s⁻¹. -1 Gradient increased to 80s -1 Rheometer testing revealed that under these shear conditions, the disulfide bond (SS) breakage rate reached 85%, while the monosulfide bond (CS) breakage rate was only 30%, maximizing the preservation of the integrity of the rubber main chain. The molecular weight distribution index (PDI) decreased from 2.5 in the traditional process to 1.9, and the scorch time during processing was extended by 15%, improving the controllability of the subsequent vulcanization process.

[0051] Example 2:

[0052] Please refer to Figures 2 and 7. The present invention provides a technical solution for optimizing the formulation of an aging-resistant system: a continuous desulfurization process for aging-resistant butyl reclaimed rubber, comprising the following steps:

[0053] S1-S4: Same as Example 1, except that the anti-aging system consists of UV-9 (3 parts) and microencapsulated antioxidant 1010 (12 parts) in a weight ratio of 1:4;

[0054] Performance testing:

[0055] The elongation at break after xenon lamp aging retained 78%, a decrease of 3.7% compared to Example 1;

[0056] Mooney viscosity 52, tensile strength 12.2 MPa;

[0057] When the weight ratio of UV-9 to antioxidant 1010 increases from 1:2 to 1:4, the reasons for the decrease in aging resistance include:

[0058] The amount of UV-9 added was reduced to 3 parts (accounting for 20% of the aging resistance system), and the absorption rate of 280-320nm ultraviolet rays decreased from 85% to 72%. Some high-energy ultraviolet rays penetrated the adhesive layer and triggered photo-oxidation reaction, resulting in a 1.2-fold increase in the carbonyl index during the early stage of aging (within 200 hours).

[0059] The antioxidant 1010 was increased to 12 parts (accounting for 80% of the aging resistance system), the dispersibility of microcapsules in the rubber compound decreased (the proportion of agglomerated particles >15μm increased from 5% to 18%), the effective action area decreased, and excessive antioxidants were prone to "blooming" during vulcanization (surface precipitation rate reached 1.2%), which damaged the appearance and interfacial bonding of rubber products.

[0060] Example 3:

[0061] Please refer to Figures 3 and 7. The present invention provides an improved microencapsulation technology solution: a continuous desulfurization process for aging-resistant butyl reclaimed rubber, comprising the following steps:

[0062] S1-S4: Same as Example 1, except that the microcapsule preparation uses silane coupling agent modified nano-titanium dioxide and silica composite filler in a mass ratio of 1:1;

[0063] Performance testing:

[0064] The microcapsules have a particle size of 6μm, extending the sustained-release period to 120 minutes.

[0065] The tensile strength of the reclaimed rubber was 13.0 MPa, which is 4% higher than that of Example 1;

[0066] The mechanism by which the composite filler of nano-titanium dioxide and silica (mass ratio 1:1) modified with a silane coupling agent (γ-methacryloyloxypropyltrimethoxysilane) improves the performance of microcapsules is as follows:

[0067] The alkoxy group (-OCH3) of the silane coupling agent forms a Si-O-Ti / Si covalent bond with the hydroxyl group (-OH) on the surface of titanium dioxide / silica. The methacryloyloxy group (-C=C-) at the other end undergoes a polycondensation reaction with the aldehyde group (-CHO) of the urea-formaldehyde resin wall material, which increases the interfacial bonding strength between the filler and the wall material from 0.8MPa to 2.5MPa. The breakage rate of the microcapsules under high-speed stirring (100 rpm) is reduced from 15% to 5%, ensuring the slow-release stability of the antioxidant in the desulfurization section (the release rate is reduced from 0.3 mg / min to 0.2 mg / min, and the continuous release time is extended to 120 minutes).

[0068] Modified nano-titanium dioxide (anatase type, 20nm particle size) absorbs ultraviolet light below 380nm during desulfurization, forming a dual protection of "photocatalysis-chain termination" with antioxidant 1010: hole oxidation of adsorbed oxygen generates superoxide radicals (·O2). - It undergoes a disproportionation reaction with peroxy radicals (ROO·) captured by antioxidants, thereby increasing the total antioxidant capacity (TAC) by 20%.

[0069] Uniformly dispersed nanofillers (microcapsules with a particle size of 5-10μm containing 5% modified filler) serve as physical crosslinking points, forming a "nano-reinforced network" with rubber molecular chains. The elastic modulus of reclaimed rubber is increased from 1.2MPa to 1.5MPa, and the stress transfer efficiency of microcapsules during stretching is increased by 30%, thereby achieving a tensile strength of 13.0MPa (compared to 12.5MPa for traditional unmodified microcapsule processes).

[0070] Example 4:

[0071] Please refer to Figures 4 and 7. The present invention provides a technical solution for optimizing nitrogen flow control: a continuous desulfurization process for aging-resistant butyl reclaimed rubber, comprising the following steps:

[0072] S1-S4: Same as Example 1, except that the nitrogen flow rate is adjusted to 0.5m. 3 / h, oxygen content 0.4%;

[0073] Performance testing:

[0074] Tensile strength 12.8 MPa, Mooney viscosity 48;

[0075] Nitrogen consumption was reduced to 0.5m. 3 / h, overall energy consumption is reduced by 35%;

[0076] Change the nitrogen flow rate from 0.8 m 3 / h decreased to 0.5m 3 / h (oxygen content 0.4%) still meets the oxidation inhibition requirements;

[0077] A CFD model of the gas flow in the desulfurization section was established, with a flow rate of 0.5 m³ / s. 3 At a rate of / h, the residence time of nitrogen in the equipment is extended from 80 seconds to 120 seconds, through a gas-solid ratio (0.5m). 3 Based on calculations (per kg of adhesive), nitrogen consumption per unit of adhesive compound is reduced by 37.5%, while the oxygen content remains below 0.5% (the safety threshold). This demonstrates that significant gas costs can be saved while maintaining an inert environment (industrial nitrogen costs approximately 1.2 yuan / m³). 3 The cost of gas per ton of adhesive decreased from 9.6 yuan to 6 yuan.

[0078] According to the Arrhenius equation, when the oxygen content increases from 0.3% to 0.4%, the oxidation reaction rate constant k only increases by 5% (Ea=85kJ / mol, T=473K), while the energy consumption reduction (compressor power decreases by 20%) caused by the reduction in nitrogen flow rate is far greater than the performance impact.

[0079] If existing large-scale desulfurization equipment (capacity 5t / h) adopts 0.5m 3 With a flow rate of / h·kg glue, the total nitrogen requirement is only 2.5m³. 3The nitrogen generator can be used to meet the demand with a small nitrogen generator (power ≤ 5kW) per hour, saving 30% of equipment investment compared with the traditional process (which requires a compressor of 10kW or more), and is especially suitable for promotion by small and medium-sized reclaimed rubber enterprises.

[0080] Example 5:

[0081] Please refer to Figures 5 and 7. The present invention provides a technical solution for optimizing equipment structure: a continuous desulfurization process for aging-resistant butyl reclaimed rubber, comprising the following steps:

[0082] S1-S4: Same as Example 1, except that the screw pitch in the desulfurization section is gradually reduced from 20mm to 15mm, and the stirring speed is adjusted to 100 rpm.

[0083] Performance testing:

[0084] The sulfur network breakage rate increased to 92%, and the molecular weight distribution index was 1.8.

[0085] Desulfurization time is reduced to 30 minutes, and production efficiency is increased by 33%.

[0086] The effect of gradually reducing the screw pitch in the desulfurization section from 20mm to 15mm (compression ratio 1.33:1) and increasing the rotation speed to 100 rpm on the breakage of the vulcanization network is as follows:

[0087] Actual measurements using a torque sensor showed that the shear force in the feeding section was 20 N·m, increasing to 35 N·m at the end of the desulfurization section, forming a gradient change of 1.75 times. This difference in shear force caused selective breakage of sulfur bonds with different bond energies in the vulcanized rubber: disulfide bonds (bond energy 260 kJ / mol) broke preferentially in the low-shear region, while monosulfide bonds (bond energy 300 kJ / mol) broke in the high-shear region. This avoided the "excessive breakage" (monosulfide bond breakage rate of up to 50%) caused by traditional fixed-pitch equipment (uniform shear force distribution), thus retaining more effective crosslinking points. The crosslinking density of the reclaimed rubber increased from 0.8 mol / m 3 Increased to 1.2 mol / m 3 The vulcanization speed is increased by 10%;

[0088] The high rotation speed (100 rpm) reduces the residence time of the rubber compound in the desulfurization section from 45 minutes to 30 minutes. At the same time, through the tapered screw pitch design, the rubber compound filling rate is increased from 60% to 80%, and the throughput per unit volume is increased by 33%. DSC test shows that the residual amount of vulcanizing agent after 30 minutes of desulfurization (0.8 parts sulfur) is close to that after 45 minutes of desulfurization (0.7 parts sulfur), proving that the desulfurization is maintained while shortening the time.

[0089] Example 6:

[0090] Please refer to Figures 6 and 7. The present invention provides an improved cleaning process: a continuous desulfurization process for aging-resistant butyl reclaimed rubber, comprising the following steps:

[0091] S1: Adopting counter-current three-stage spray technology, the cleaning agent concentration is reduced to 0.5wt%, and the recycling rate is increased to 90%;

[0092] S2-S4: Same as Example 1;

[0093] Performance testing:

[0094] The residual surfactant content is <0.05%, which has no impact on subsequent vulcanization;

[0095] Water consumption is reduced by 65%, meeting environmental protection requirements;

[0096] By employing a counter-current three-stage spray system with a 0.5wt% cleaning agent concentration, a balance between cleaning efficiency and environmental friendliness is achieved. Its technological advantages include:

[0097] Sodium dodecylbenzenesulfonate (SDBS) forms a micelle structure at a concentration of 0.5 wt% (critical micelle concentration of 0.18 wt%). The hydrophilic groups (-SO3Na) encapsulate polar / non-polar impurities such as dust and oil. Through three-stage countercurrent spraying (with the spray volume decreasing by 30% in each stage), the total removal rate reaches 98% (oil impurity residue <0.01%, dust residue <0.05%), which is superior to the 95% removal rate of traditional single-stage spraying. It also avoids the residual surface activity of the colloidal particles caused by high concentrations of cleaning agents (above 2 wt%) (which affects subsequent vulcanization crosslinking).

[0098] After the cleaning wastewater is treated with an ultrafiltration membrane (10kDa molecular weight cutoff) to remove suspended solids, the turbidity drops from 50 NTU to 5 NTU and the conductivity increases from 800 μS / cm to 1200 μS / cm (only soluble salts are added). It can be directly reused in the primary spraying process, with a recycling rate of 90% (compared to only 50% for traditional processes).

[0099] Low concentrations of cleaning agent residue (<0.05%) have no significant effect on the activation effect of vulcanization accelerators (such as CZ). According to vulcanization tester tests, the scorch time (T10) and positive vulcanization time (T90) fluctuate by <5% compared with unwashed rubber particles, which solves the problem of "vulcanization delay" caused by traditional high-concentration cleaning and ensures the quality stability of reclaimed rubber products.

[0100] Please refer to Figure 1-7:

[0101] The xenon lamp aging retention rate of Example 1 reached 81%, which is 30.6% higher than the prior art (62%). The core benefit is the precise 1:2 ratio of UV-9 and microencapsulated antioxidant 1010. The two work through a dual mechanism of "light shielding (absorbing 280-320nm ultraviolet rays) + chain termination (capturing peroxy free radicals ROO·)" to extend the photooxidation induction time of reclaimed rubber from 200 hours in the traditional process to more than 500 hours.

[0102] Example 3 further improved the aging retention rate to 83% because the silane coupling agent-modified nano-TiO2 / SiO2 composite filler enhanced the breakage resistance of the microcapsule wall material (reducing the breakage rate from 15% to 5%), and through the photocatalytic synergistic effect (generating superoxide radicals·O2)... - The total antioxidant capacity was increased by 20%, which verified the potential for optimization of the anti-aging system.

[0103] Example 2 shows that the light shielding ability decreased due to insufficient UV-9 content (only 20%), and the aging retention rate dropped to 78%, which proves the necessity of the 1:1-2 ratio range in claim 1 - this range is the critical value for balancing the "photoprotection-antioxidation" performance. Deviation will lead to the failure of the synergistic effect (the synergistic factor Q drops from 1.8 to 1.2).

[0104] The tensile strength of Examples 1-6 is ≥12.2MPa, which is 20%-27% higher than that of the traditional process (10.2MPa). Among them, Example 3 reaches 13.0MPa, which is due to the interfacial covalent bond between the nanofiller and the rubber matrix (the interfacial bond strength is increased from 0.8MPa to 2.5MPa), which improves the stress transfer efficiency by 30%.

[0105] The Mooney viscosity is stable between 48 and 52 with a standard deviation of ≤ ±2, which is significantly better than the ±8 fluctuation of the traditional process. In Example 4 (low nitrogen flow rate), the Mooney viscosity is 48, which reflects the reduction of mechanical degradation of the rubber main chain under nitrogen protection (the molecular weight distribution index PDI drops from 2.5 to 1.8). The scorch time during processing is extended by 15%, making it more suitable for the vulcanization molding of precision products (such as medical bottle stoppers).

[0106] Example 5, through a variable pitch screw (20mm → 15mm) and a high rotation speed of 100 rpm, increased the vulcanization network breakage rate to 92%, and the disulfide bond (SS) breakage rate (85%) was much higher than that of monosulfide bonds (CS, 30%), maximizing the retention of effective crosslinking points. This technology solved the problem of "excessive breakage" in traditional fixed pitch equipment (monosulfide bond breakage rate 50%), and increased the crosslinking density of reclaimed rubber from 0.8 mol / m³. 3 Increased to 1.2 mol / m 3 The vulcanization speed is increased by 10%, and production efficiency and product quality are improved simultaneously.

[0107] Example 4 (flow rate 0.5m) 3 ( / h) Under the safe threshold of oxygen content still <0.5%, the nitrogen consumption cost was reduced from 9.6 yuan / t glue to 6 yuan / t glue (a reduction of 40%), and the tensile strength was slightly increased to 12.8 MPa. CFD simulation verified that at this flow rate, the residence time of nitrogen in the equipment was extended to 120 seconds, and the gas-solid ratio was optimized to 0.5m. 3 / kg glue, achieving "low consumption and high efficiency" oxidation inhibition, reducing equipment investment for small and medium-sized enterprises (compressor power reduced from 10kW to 5kW).

[0108] Example 5 reduced the desulfurization time from 45 minutes to 30 minutes (increasing production efficiency by 33%), while the residual amount of vulcanizing agent (0.8 parts of sulfur) was close to that of the benchmark process. This proves that the shear force gradient design of the variable pitch screw (20 N·m in the feeding section → 35 N·m in the desulfurization section) can achieve "selective breaking" of the vulcanization bond, avoiding excessive degradation caused by the uniform distribution of shear force in traditional equipment. This improvement increased the annual capacity of a single production line from 10,000 tons to 13,300 tons without increasing energy consumption (only the speed was increased by 25%), breaking through the technical bottleneck of "efficiency-effect".

[0109] Example 6 uses a low-concentration cleaning agent of 0.5 wt% (compared to 2 wt% in the traditional process) and a three-stage countercurrent spraying system to reduce water consumption from 0.5 t / kg of adhesive to 0.42 t / kg of adhesive, increase the cleaning agent circulation rate from 85% to 90%, save 150,000 tons of water annually (for an annual production of 10,000 tons of adhesive), and reduce wastewater treatment costs by 200,000 yuan. At the same time, the residual surfactant content is <0.05% (compared to 0.2% in the traditional process), completely eliminating interference with subsequent vulcanization (scorch time fluctuation <5%), and meeting the clean production requirements for medical-grade reclaimed adhesive.

[0110] This process meets the stringent standards of "water reuse rate ≥ 85%" and "water consumption per unit product ≤ 0.5t / kg" in the "Guidelines for Green Development of the Rubber Industry". Existing technologies generally have water consumption > 1t / kg and recycling rate < 50%, showing significant environmental advantages.

[0111] The microencapsulation design of antioxidant 1010 (with a wall material of biodegradable urea-formaldehyde resin) reduces the volatilization loss during the desulfurization process from 40% to 25%, and reduces volatile organic compound (VOC) emissions by 15%. Compared with the "blooming pollution" (exudates contaminating the mold and product surface) caused by the traditional direct addition of antioxidants, this technology achieves the dual goals of "clean production - green products".

[0112] This invention addresses four major pain points of existing processes—poor aging resistance, severe oxidation, low efficiency, and high pollution—through a multi-dimensional technological combination of "compound formulation of anti-aging additives + innovative microencapsulation morphology + precise control under nitrogen protection + optimized equipment structure + environmentally friendly upgrade of cleaning processes." The above descriptions are merely embodiments of this invention; well-known technical solutions or characteristics are not elaborated upon here. It should be noted that those skilled in the art can make various modifications and improvements without departing from the technical solutions of this invention, and these should also be considered within the scope of protection of this invention. These modifications will not affect the effectiveness of the invention or the practicality of the patent. The scope of protection claimed in this application should be determined by the content of its claims, and the specific embodiments described in the specification can be used to interpret the content of the claims.

Claims

1. A continuous desulfurization process for aging-resistant butyl reclaimed rubber, characterized in that, Includes the following steps: S1: Wash the waste butyl rubber in an aqueous solution containing 0.5-1.5wt% sodium dodecylbenzenesulfonate to remove surface impurities, then crush it into particles with a particle size of 2-5mm to obtain pretreated rubber granules; S2: Simultaneously feed the pretreated rubber granules and composite desulfurizing agent into a continuous desulfurization equipment at a weight ratio of 100:25-40, and continuously desulfurize for 30-60 minutes at 180-220℃ and 1.5-2.5MPa; The composite desulfurizing agent comprises: a desulfurizing component and an aging-resistant system; the desulfurizing component includes, by weight: 5-10 parts sulfur, and accelerator M. 3-5 parts, zinc oxide 5-8 parts, stearic acid 2-4 parts; The aging-resistant system: a synergistic combination of ultraviolet absorber UV-9 and microencapsulated antioxidant 1010, with a weight ratio of ultraviolet absorber UV-9 to microencapsulated antioxidant 1010 of 1:1-2, and a total addition amount of 10-15 parts by weight; S3: High-purity nitrogen gas is introduced into the desulfurization section at a flow rate of 0.5-1.0 m³ / h to form an inert reaction environment; S4: The desulfurization product is cooled to room temperature by a spiral cooling device and then obtained as regenerated rubber by sieving through an 80-120 mesh sieve; The preparation method of the microencapsulated antioxidant 1010 is as follows: using urea-formaldehyde resin as the wall material and nano-titanium dioxide and silica composite particles as reinforcing fillers, the core antioxidant is encapsulated by in-situ polymerization to form sustained-release microcapsules with a particle size of 5-10 μm.

2. The continuous desulfurization process for aging-resistant butyl reclaimed rubber according to claim 1, characterized in that: The continuous desulfurization equipment adopts a three-section structure, including a feeding section, a desulfurization section, and a discharging section. The desulfurization section has a built-in variable pitch spiral agitator with a rotation speed of 50-100 rpm, which achieves directional breakage of the sulfurization network through shear force gradient distribution.

3. The continuous desulfurization process for aging-resistant butyl reclaimed rubber according to claim 1, characterized in that: The nitrogen protection system includes a pressure regulating valve and a flow monitoring device to ensure that the oxygen content in the desulfurization section is below 0.5%, effectively suppressing high-temperature oxidation side reactions.

4. The continuous desulfurization process for aging-resistant butyl reclaimed rubber according to claim 1, characterized in that: The cleaning process employs counter-current multi-stage spraying technology, with a cleaning agent recycling rate of ≥85%, achieving efficient utilization of water resources.

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