Continuous desulfurization process of aging-resistant butyl regenerated rubber

Abstract

The invention belongs to the field of waste rubber recovery treatment, and discloses a continuous desulfurization process of anti-aging butyl regenerated rubber, which comprises the following steps: S1, putting waste butyl rubber into an aqueous solution containing 0.5-1.5 wt% of sodium dodecyl benzene sulfonate, cleaning, removing surface impurities, and crushing into particles with the particle size of 2-5mm; s2, synchronously feeding the pretreated colloidal particles and a compound desulfurizer into continuous desulfurization equipment, and continuously desulfurizing for 30-60 minutes under the conditions that the temperature is 180-220 DEG C and the pressure is 1.5-2.5 MPa; s3, introducing high-purity nitrogen at the flow rate of 0.5-1.0 m / h in the desulfurization section to form an inert reaction environment; s4, cooling the desulfurization product to room temperature through a spiral cooling device, and sieving through a 80-120-mesh sieve to obtain reclaimed rubber; the invention aims to provide a brand new continuous desulfurization process for aging-resistant butyl regenerated rubber, the problems of poor aging resistance, high antioxidant loss, more oxidation side reactions, low production efficiency and the like in the traditional process are solved, and efficient recovery of waste butyl rubber and high-performance production of the regenerated rubber are realized.

Description

Technical Field

[0001] The invention relates to the technical field of waste rubber recycling and treatment, in particular to a continuous desulfurization process for aging-resistant butyl regenerated rubber. Background Art

[0002] Butyl rubber is widely used in tire inner tubes, pharmaceutical bottle stoppers, sealing materials and other fields due to its excellent air tightness, chemical corrosion resistance and weather resistance. With the development of waste rubber resource utilization technology, the preparation process of butyl recycled rubber has become a hot research topic in the industry. However, the current desulfurization and regeneration process of waste butyl rubber still faces several technical challenges: On the one hand, traditional desulfurization processes, such as dynamic tank desulfurization and single / twin screw extruder desulfurization, primarily break vulcanized crosslinks through high temperatures, mechanical shearing, or chemical agents. However, it's difficult to precisely control the extent of the vulcanized network breakage during the process, which can easily lead to excessive degradation of the rubber backbone and a decrease in mechanical properties like tensile strength and elongation at break of the reclaimed rubber. On the other hand, existing processes lack a systematic approach to improving the aging resistance of reclaimed rubber, simply adding antioxidants or UV absorbers without addressing the stability of the additives in high-temperature environments. This results in the reclaimed rubber being susceptible to aging due to factors like light, oxygen, and heat during long-term use, limiting its application in applications requiring high weather resistance. Furthermore, conventional desulfurization equipment often utilizes a pitch-type agitator, resulting in uneven shear distribution of the material in the desulfurization section and random rupture of vulcanized bonds, leading to significant fluctuations in the properties of the reclaimed rubber. The cleaning process generally employs a single-stage spray or immersion method, which results in low cleaning agent utilization and incomplete impurity removal, making subsequent processing susceptible to residual impurities. Therefore, a continuous desulfurization process for aging-resistant butyl reclaimed rubber was proposed. This process achieves directional rupture of the vulcanized network, effectively stabilizes the aging-resistant additive, and is environmentally friendly and energy-efficient, thereby improving the overall performance and production efficiency of butyl reclaimed rubber. Summary of the Invention

[0003] The present invention aims to provide a new continuous desulfurization process for aging-resistant butyl regenerated rubber. By optimizing the formula of the composite desulfurizer, controlling the inert environment, innovating the equipment structure and designing an environmentally friendly process, the present invention solves the problems existing in the traditional process, such as poor aging resistance, high antioxidant loss, multiple oxidative side reactions and low production efficiency, thereby achieving efficient recovery of waste butyl rubber and high-performance production of regenerated rubber.

[0004] In order to achieve the above object, the present invention provides the following technical solutions: The technical solution provided by the present invention is: a continuous desulfurization process for aging-resistant butyl regenerated rubber, comprising the following steps: S1: washing the waste butyl rubber in an aqueous solution containing 0.5-1.5 wt% sodium dodecylbenzene sulfonate, removing surface impurities, and crushing the waste butyl rubber into particles with a diameter of 2-5 mm to obtain pretreated rubber particles; S2: The pretreated rubber particles and the composite desulfurizer are simultaneously added into the continuous desulfurization equipment at a weight ratio of 100:25-40, and desulfurization is carried out continuously at 180-220°C and 1.5-2.5MPa for 30-60 minutes; The composite desulfurizer includes: desulfurization components and aging resistance system; The desulfurization components include, by weight: 5-10 parts of sulfur, 3-5 parts of accelerator M, 5-8 parts of zinc oxide, and 2-4 parts of stearic acid; Anti-aging system: a synergistic combination of ultraviolet absorber UV-9 and antioxidant 1010 (weight ratio 1:1-2), with a total addition amount of 10-15 parts by weight, wherein the antioxidant 1010 adopts microencapsulation coating technology; S3: High-purity nitrogen 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 desulfurized product is cooled to room temperature by a spiral cooling device and then sieved through 80-120 mesh to obtain regenerated rubber.

[0005] Furthermore, the continuous desulfurization equipment adopts a three-stage structure, including a feeding section, a desulfurization section and a discharging section; The desulfurization section is equipped with a variable pitch spiral stirring device with a rotation speed of 50-100 rpm, which realizes the directional fracture of the sulfur network through the shear force gradient distribution.

[0006] Furthermore, the preparation method of microencapsulated antioxidant 1010 is as follows: using urea-formaldehyde resin as the wall material, nano-titanium dioxide and silicon dioxide composite particles as reinforcing fillers, and using in-situ polymerization to coat the core antioxidant to form sustained-release microcapsules with a particle size of 5-10 μm.

[0007] 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 less than 0.5%, effectively suppressing high-temperature oxidation side reactions.

[0008] Furthermore, the cleaning step adopts countercurrent multi-stage spraying technology, and the recycling rate of the cleaning agent is ≥85%, realizing efficient use of water resources.

[0009] Furthermore, the synergistic combination of ultraviolet absorber UV-9 and antioxidant 1010 improves the weather resistance of recycled rubber by more than 40% compared with conventional processes through the dual protection mechanism of light shielding and chain termination.

[0010] The beneficial effects of this technical solution are: (1) The present invention achieves a qualitative leap in the performance of recycled rubber through a unique anti-aging system and process optimization. On the one hand, the ultraviolet absorber UV-9 and the microencapsulated antioxidant 1010 in the composite desulfurizer are precisely matched in a ratio of 1:1-2, forming a dual protection mechanism of light shielding and chain termination. After 1000 hours of xenon lamp aging, the elongation at break is retained at more than 81%, which is more than 30% higher than that of the traditional process, effectively solving the industry problem of poor weather resistance of recycled 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 the desulfurization efficiency, reducing the mechanical degradation of the main chain. The tensile strength of the recycled rubber reaches 12.2-13.0MPa, 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 recycled rubber.

[0011] (2) The present invention significantly reduces production energy consumption and material loss through process parameter optimization and equipment improvement. The nitrogen protection system reduces nitrogen consumption costs by 40% and overall energy consumption by 25%-35% compared with traditional processes by precisely controlling the flow rate at 0.5-1.0 m³ / h while ensuring that the oxygen content is lower than 0.5%. The variable pitch spiral stirring device is combined with a high speed design to shorten the desulfurization time from 45 minutes to 30 minutes, increase production efficiency by 33%, and reduce energy consumption per unit of production capacity instead of increasing. In addition, the microencapsulated antioxidant technology reduces the 40% volatilization loss of antioxidants at high temperatures, increases the recycling rate of cleaning agents to 90%, and reduces water consumption by 60%. Multiple measures are implemented in parallel to significantly reduce the production costs of enterprises and improve economic benefits.

[0012] (3) The present invention fully implements the green concept from source to process. The cleaning process adopts 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 annually (annual production scale of 10,000 tons of rubber), 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 high-temperature oxidation side reactions and reduces volatile organic compound (VOCs) emissions; the degradable urea-formaldehyde resin wall material used in microencapsulation further reduces the generation of pollutants in the production process. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 This is a data table of Example 1 of a continuous desulfurization process for aging-resistant butyl regenerated rubber proposed by the present invention; Figure 2 This is a data table of Example 2 of a continuous desulfurization process for aging-resistant butyl regenerated rubber proposed by the present invention; Figure 3 This is a data table of Example 3 of a continuous desulfurization process for aging-resistant butyl regenerated rubber proposed by the present invention; Figure 4 This is a data table of Example 4 of a continuous desulfurization process for aging-resistant butyl regenerated rubber proposed by the present invention; Figure 5 This is a data table of Example 5 of a continuous desulfurization process for aging-resistant butyl regenerated rubber proposed by the present invention; Figure 6 This is a data table of Example 6 of a continuous desulfurization process for aging-resistant butyl regenerated rubber proposed by the present invention; Figure 7 The following is a data comparison table of various embodiments of the continuous desulfurization process for aging-resistant butyl regenerated rubber proposed by the present invention. DETAILED DESCRIPTION

[0014] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0015] The specific implementation process is as follows: Example 1: See also Figure 1 and Figure 7 The present invention provides a technical solution of a benchmark process: a continuous desulfurization process for aging-resistant butyl regenerated rubber, comprising the following steps: S1: 100 parts by weight of waste butyl rubber was placed in an aqueous solution containing 1.0 wt% of sodium dodecylbenzene sulfonate, and washed using a countercurrent multi-stage spray device with a cleaning agent recycling rate of 85%, and crushed into particles with a particle size of 3 mm; S2: basic desulfurization components by weight: 8 parts of sulfur, 4 parts of accelerator M, 6 parts of zinc oxide, and 3 parts of stearic acid; Anti-aging system: UV absorber UV-9 (5 parts by weight) and microencapsulated antioxidant 1010 (10 parts by weight, urea-formaldehyde resin coated, particle size 8 μm); S3: Add the rubber particles and desulfurizer in a weight ratio of 100:36 into a three-stage continuous desulfurization equipment. The desulfurization section temperature is 200°C, the pressure is 2.0 MPa, the nitrogen flow rate is 0.8 m³ / h, the oxygen content is 0.3%, the variable pitch spiral stirring speed is 75 rpm, and the desulfurization time is 45 minutes. S4: The desulfurized product is cooled to 25°C by a spiral cooling device and sieved through a 100-mesh screen; Performance testing: After 1000 hours of xenon lamp aging, the elongation at break retention rate is 81%; Tensile strength 12.5MPa, Mooney viscosity 50; Nitrogen consumption is 0.8m³ / h, and the overall energy consumption is reduced by 30% compared with the traditional process; This embodiment significantly improves the aging resistance and processing stability of reclaimed rubber through the synergistic effect of the composite desulfurizer and nitrogen protection; Synergistic mechanism of anti-aging system: The UV absorber UV-9 (2-hydroxy-4-methoxybenzophenone) selectively absorbs 280-320nm ultraviolet rays through its conjugated structure, converting light energy into harmless heat energy, thereby inhibiting the photoinduced breakage of the rubber molecular chain; Microencapsulated antioxidant 1010 (pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate)) is coated with a urea-formaldehyde resin wall material. At desulfurization temperatures of 180-220°C, the wall material gradually softens and releases the antioxidant. Compared to traditional unencapsulated antioxidants (which experience a 40% volatility loss after 30 minutes at high temperatures), this solution increases the antioxidant retention rate to 75%, effectively capturing peroxyl radicals (ROO) generated during the desulfurization process and terminating the chain oxidation reaction. When the two are mixed in a ratio of 1:2, the light shielding efficiency (85%) and antioxidant efficiency (78%) reach the best balance, which is significantly improved compared with the use of UV-9 (aging retention rate 72%) or antioxidant 1010 (aging retention rate 75%) alone; The oxygen content in the desulfurization section is controlled at 0.3% (compared to 21% in an open environment with existing technology). Verified by FDS fluid simulation software, the nitrogen flow forms a vortex under the action of spiral stirring, reducing the oxygen concentration in the equipment's dead corners to below 0.1%. This fundamentally inhibits the high-temperature reaction between the rubber backbone and oxygen (ΔH = -2800 kJ / mol), reducing the carbonyl index (a measure of oxidation level) of the reclaimed rubber from 0.85 in traditional processes to 0.32, and increasing the tensile strength retention rate from 80% to 95%. The variable-pitch screw (pitch 25mm in the feeding section → pitch 20mm in the desulfurization section) combined with a speed of 75 rpm increases the shear rate of the rubber in the desulfurization section from 50s⁻¹ to 80s⁻¹. Rheometer tests found that under these shear conditions, the disulfide bond (SS) rupture rate reached 85%, while the single sulfur bond (CS) rupture rate was only 30%, maximizing the integrity of the rubber main chain. The molecular weight distribution index (PDI) was reduced 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.

[0016] Example 2: See also Figure 2 and Figure 7 The present invention provides a technical solution for optimizing the ratio of an aging-resistant system: a continuous desulfurization process for aging-resistant butyl regenerated rubber, comprising the following steps: S1-S4: Same as Example 1, except that the anti-aging system consists of UV-9 (3 parts) and microencapsulated antioxidant 1010 (12 parts), with a weight ratio of 1:4; Performance testing: After xenon lamp aging, the elongation at break retention rate was 78%, which was 3.7% lower than that in Example 1. Mooney viscosity 52, tensile strength 12.2MPa; When the weight ratio of UV-9 to antioxidant 1010 increases from 1:2 to 1:4, the reasons for the decline in aging resistance include: 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 dropped from 85% to 72%. Some high-energy ultraviolet rays penetrated the adhesive layer and triggered photooxidation reactions, causing the carbonyl index growth rate in the early stage of aging (within 200 hours) to accelerate by 1.2 times; When the amount of antioxidant 1010 increases to 12 parts (accounting for 80% of the aging resistance system), the dispersibility of the microcapsules in the rubber compound decreases (the proportion of agglomerated particles >15μm increases from 5% to 18%), the effective action area decreases, and excessive antioxidants are prone to "frosting" during the vulcanization process (the surface precipitation rate reaches 1.2%), which damages the appearance and interfacial bonding strength of the rubber products.

[0017] Example 3: See also Figure 3 and Figure 7 The present invention provides a technical solution for improving microencapsulation technology: a continuous desulfurization process for aging-resistant butyl regenerated rubber, comprising the following steps: S1-S4: Same as Example 1, except that the microcapsules are prepared by using a silane coupling agent to modify nano-titanium dioxide and silicon dioxide composite filler, with a mass ratio of 1:1; Performance testing: The microcapsule particle size is 6 μm, and the sustained-release period is extended to 120 minutes; The tensile strength of the reclaimed rubber is 13.0 MPa, which is 4% higher than that of Example 1; The mechanism of improving the performance of microcapsules by modifying nano-titanium dioxide and silicon dioxide composite filler (mass ratio 1:1) with a silane coupling agent (γ-methacryloxypropyltrimethoxysilane) is as follows: The alkoxy group (-OCH3) of the silane coupling agent forms a Si-O-Ti / Si covalent bond with the hydroxyl group (-OH) on the titanium dioxide / silicon dioxide surface. The methacryloyloxy group (-C=C-) at the other end undergoes a condensation reaction with the aldehyde group (-CHO) of the urea-formaldehyde resin wall material, increasing 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 sustained release stability of the antioxidant in the desulfurization stage (the release rate is reduced from 0.3mg / min to 0.2mg / min, and the sustained release time is extended to 120 minutes). The modified nano-titanium dioxide (anatase type, particle size 20nm) absorbs ultraviolet light below 380nm during the desulfurization process, forming a dual "photocatalytic-chain termination" protection with the antioxidant 1010: the holes oxidize the adsorbed oxygen to form superoxide radicals (・O2⁻), which undergo a disproportionate reaction with peroxyl radicals (ROO・) captured by the antioxidant, increasing the total antioxidant capacity (TAC) by 20%. Evenly dispersed nanofillers (microcapsules with a particle size of 5-10μm containing 5% modified fillers) serve as physical cross-linking points, forming a "nano-reinforced network" with the rubber molecular chains. The elastic modulus of the reclaimed rubber is increased from 1.2MPa to 1.5MPa, and the stress transfer efficiency of the microcapsules during stretching is increased by 30%, thereby achieving a tensile strength of 13.0MPa (the traditional unmodified microcapsule process is 12.5MPa).

[0018] Example 4: See also Figure 4 and Figure 7 The present invention provides a technical solution for optimizing nitrogen flow control: a continuous desulfurization process for aging-resistant butyl regenerated rubber, comprising the following steps: S1-S4: Same as Example 1, except that the nitrogen flow rate is adjusted to 0.5 m³ / h and the oxygen content is 0.4%; Performance testing: Tensile strength 12.8MPa, Mooney viscosity 48; Nitrogen consumption is reduced to 0.5m³ / h, and overall energy consumption is reduced by 35%; Reducing the nitrogen flow rate from 0.8m³ / h to 0.5m³ / h (oxygen content 0.4%) still meets the oxidation inhibition requirements; A CFD model of gas flow in the desulfurization section was established. At a flow rate of 0.5 m³ / h, the nitrogen residence time within the equipment was extended from 80 seconds to 120 seconds. Calculated using a gas-to-solid ratio (0.5 m³ / kg of rubber), nitrogen consumption per unit of rubber was reduced by 37.5%, while the oxygen content remained below 0.5% (the safety threshold). This demonstrates that significant gas cost savings can be achieved while maintaining an inert environment (industrial nitrogen costs approximately 1.2 yuan / m³, reducing the gas cost per ton of rubber from 9.6 yuan to 6 yuan). 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 brought about by the reduction in nitrogen flow (compressor power drops by 20%) far outweighs the performance impact; If existing large-scale desulfurization equipment (with a production capacity of 5t / h) adopts a flow rate of 0.5m³ / h・kg rubber, the total nitrogen demand is only 2.5m³ / h, which can be met by a small nitrogen generator (power ≤5kW). Compared with the traditional process (which requires a compressor of more than 10kW), this process saves 30% of equipment investment and is particularly suitable for promotion by small and medium-sized recycled rubber enterprises.

[0019] Embodiment 5: See also Figure 5 and Figure 7 The present invention provides a technical solution for optimizing the equipment structure: a continuous desulfurization process for aging-resistant butyl regenerated rubber, comprising the following steps: S1-S4: Same as Example 1, except that the pitch of the desulfurization section is gradually reduced from 20 mm to 15 mm, and the stirring speed is adjusted to 100 rpm; Performance testing: The vulcanization network breakage rate is increased to 92%, and the molecular weight distribution index is 1.8; Desulfurization time is shortened to 30 minutes, and production efficiency is increased by 33%; The pitch of the desulfurization section is gradually reduced from 20mm to 15mm (compression ratio 1.33:1), and the speed is increased to 100 rpm. The impact on the fracture of the vulcanization network is as follows: Measurements using a torque sensor show shear force of 20 N·m in the feed section, increasing to 35 N·m at the end of the desulfurization section, resulting in a 1.75-fold gradient. This differential shear force selectively breaks sulfur bonds of varying energies in the vulcanized rubber: disulfide bonds (bond energy 260 kJ / mol) preferentially break in the low-shear zone, while single sulfur bonds (bond energy 300 kJ / mol) break in the high-shear zone. This avoids the "excessive breakage" (single sulfur bond breakage rate of 50%) caused by traditional fixed-pitch equipment (uniform shear force distribution), thereby retaining more effective crosslinking points. The crosslink density of the reclaimed rubber increases from 0.8 mol / m³ to 1.2 mol / m³, accelerating the vulcanization rate by 10%. The high rotation speed (100 rpm) shortens the residence time of the rubber in the desulfurization section from 45 minutes to 30 minutes. At the same time, the gradual pitch design increases the rubber filling degree from 60% to 80%, and the unit volume processing capacity increases by 33%. DSC tests show that the residual vulcanizing agent after 30 minutes of desulfurization (0.8 parts of sulfur) is close to that of the 45-minute process (0.7 parts of sulfur), proving that the desulfurization is maintained thoroughly while shortening the time.

[0020] Example 6: See also Figure 6 and Figure 7 The present invention provides a technical solution for improving a cleaning process: a continuous desulfurization process for aging-resistant butyl regenerated rubber, comprising the following steps: S1: Using countercurrent three-stage spraying technology, the cleaning agent concentration is reduced to 0.5wt%, and the recycling rate is increased to 90%; S2-S4: Same as Example 1; Performance testing: The residual amount of surfactant is less than 0.05%, which has no effect on subsequent vulcanization; Water consumption is reduced by 65%, meeting environmental protection requirements; The use of countercurrent three-stage spraying + 0.5wt% cleaning agent concentration achieves a balance between cleaning efficiency and environmental protection. Its technical advantages include: Sodium dodecylbenzenesulfonate (SDBS) forms micelle structures at a concentration of 0.5wt% (critical micelle concentration 0.18wt%). The hydrophilic groups (-SO3Na) encapsulate polar and non-polar impurities such as dust and oil. Through three-stage countercurrent spraying (the spray volume decreases by 30% at 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 active surface of the micelle particles caused by high-concentration cleaning agents (above 2wt%), which affects subsequent vulcanization and cross-linking. After the washing wastewater passes through an ultrafiltration membrane (molecular weight cut-off 10kDa) to remove suspended solids, the turbidity drops from 50NTU to 5NTU, and the conductivity increases from 800μS / cm to 1200μS / cm (only soluble salts increase). It can be directly reused for primary spraying, with a recycling rate of 90% (compared to only 50% in traditional processes). Low-concentration cleaning agent residues (<0.05%) have no significant effect on the activation effect of vulcanization accelerators (such as CZ). Through vulcanization instrument testing, the scorch time (T10) and positive vulcanization time (T90) fluctuate by <5% compared with the unwashed rubber particles, solving the "vulcanization delay" problem caused by traditional high-concentration cleaning and ensuring the quality stability of recycled rubber products.

[0021] See also Figure 1-7 : The xenon lamp aging retention rate of Example 1 reached 81%, an increase of 30.6% over the existing technology (62%). The core benefit is the precise 1:2 ratio of UV-9 and microencapsulated antioxidant 1010. The two extend the photooxidation induction time of the reclaimed rubber from 200 hours in the traditional process to more than 500 hours through the dual mechanism of "light shielding (absorbing 280-320nm ultraviolet rays) + chain termination (capturing peroxyl free radicals ROO・)".

[0022] Example 3 further increases the aging retention rate to 83%. This is because the nano-TiO2 / SiO2 composite filler modified with a silane coupling agent enhances the damage resistance of the microcapsule wall material (the damage rate is reduced from 15% to 5%), and increases the total antioxidant capacity by 20% through the photocatalytic synergistic effect (generating superoxide radicals・O2⁻), verifying the optimization space for the aging resistance system.

[0023] In Example 2, the light shielding ability is reduced due to the insufficient proportion of UV-9 (only 20%), and the aging retention rate drops 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 "light protection-antioxidation" efficacy. Deviation will lead to the failure of the synergistic effect (the synergistic factor Q drops from 1.8 to 1.2).

[0024] The tensile strengths of Examples 1-6 are all ≥12.2 MPa, which are 20%-27% higher than those of the traditional process (10.2 MPa). Among them, Example 3 reaches 13.0 MPa. This is due to the covalent bond between the nanofiller and the rubber matrix (the interfacial bonding strength is increased from 0.8 MPa to 2.5 MPa), which improves the stress transfer efficiency by 30%.

[0025] 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. The Mooney viscosity of Example 4 (low nitrogen flow) is 48, reflecting that the mechanical degradation of the rubber main chain is reduced under nitrogen protection (the molecular weight distribution index PDI is reduced from 2.5 to 1.8), and the scorch time during processing is extended by 15%, which is more suitable for vulcanization molding of precision products (such as medical bottle stoppers).

[0026] In Example 5, a variable-pitch helix (pitch 20 mm → 15 mm) and a high speed of 100 rpm were used to increase the vulcanization network breakage rate to 92%, and the disulfide bond (SS) breakage rate (85%) was much higher than that of the single sulfur bond (CS, 30%), thereby retaining the effective cross-linking points to the maximum extent. This technology solves the problem of "excessive breakage" in traditional fixed-pitch equipment (single sulfur bond breakage rate of 50%), increases the cross-linking density of the reclaimed rubber from 0.8 mol / m³ to 1.2 mol / m³, accelerates the vulcanization speed by 10%, and simultaneously improves production efficiency and product quality.

[0027] In Example 4 (flow rate 0.5 m³ / h), while the oxygen content is still below the safety threshold of <0.5%, the nitrogen consumption cost is reduced from 9.6 yuan / t rubber to 6 yuan / t rubber (a 40% reduction), and the tensile strength is slightly increased to 12.8 MPa. CFD simulation verification shows that at this flow rate, the residence time of nitrogen in the equipment is extended to 120 seconds, and the gas-solid ratio is optimized to 0.5 m³ / kg rubber, achieving "low-consumption and high-efficiency" oxidation inhibition, reducing equipment investment for small and medium-sized enterprises (compressor power is reduced from 10 kW to 5 kW).

[0028] Example 5 shortens the desulfurization time from 45 minutes to 30 minutes (a 33% increase in production efficiency). Meanwhile, the residual sulfurizing agent (0.8 parts of sulfur) is close to that of the baseline process. This demonstrates that the shear force gradient design of the variable-pitch helix (20 N·m in the feed section → 35 N·m in the desulfurization section) can achieve "selective breaking" of sulfide bonds, avoiding excessive degradation caused by the uniform distribution of shear force in traditional equipment. This improvement increases the annual production capacity of a single production line from 10,000 tons to 13,300 tons without increasing energy consumption (only the rotational speed is increased by 25%), breaking through the technical bottleneck of "efficiency-effectiveness".

[0029] In Example 6, by using a 0.5wt% low-concentration cleaning agent (2wt% in the traditional process) and three-stage countercurrent spraying, the water consumption was reduced from 0.5t / kg of rubber to 0.42t / kg of rubber, and the cleaning agent circulation rate was increased from 85% to 90%. This saved 150,000 tons of water annually (annual production of 10,000 tons of rubber), and reduced the sewage treatment cost by 200,000 yuan. At the same time, the residual amount of surfactant was less than 0.05% (0.2% in the traditional process), completely eliminating interference with subsequent vulcanization (scorch time fluctuation was less than 5%), thus meeting the clean production requirements of medical-grade recycled rubber.

[0030] This process complies with 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". The water consumption of existing technologies is generally greater than 1t / kg and the recycling rate is less than 50%, which has significant environmental advantages.

[0031] The microencapsulated design of antioxidant 1010 (with a wall material of biodegradable urea-formaldehyde resin) reduces volatilization losses during the desulfurization process from 40% to 25%, and reduces volatile organic compound (VOC) emissions by 15%. Compared with the traditional direct addition of antioxidants that causes "frosting pollution" (precipitates contaminating the mold and product surface), this technology achieves the dual goals of "clean production and green products."

[0032] The present invention solves the four major pain points of the existing process, namely poor aging resistance, severe oxidation, low efficiency and high pollution, through a multi-dimensional technical combination of "compounding of aging-resistant additives + innovation of microencapsulation morphology + precise control of nitrogen protection + equipment structure optimization + environmentally friendly upgrade of cleaning process".

[0033] The above is only an embodiment of the present invention, and common knowledge such as the specific technical solutions or characteristics in the solution is not described in detail here. It should be pointed out that for those skilled in the art, without departing from the technical solution of the present invention, several variations and improvements can be made, which should also be regarded as the scope of protection of the present invention, and these will not affect the effect of the implementation of the present invention and the practicality of the patent. The scope of protection required by this application shall be based on the content of its claims, and the specific implementation methods and other records in the description can be used to interpret the content of the claims.

Claims

1. A continuous desulfurization process for aging-resistant butyl regenerated rubber, characterized in that: The following steps are involved: S1: washing the waste butyl rubber in an aqueous solution containing 0.5-1.5 wt% sodium dodecylbenzene sulfonate, removing surface impurities, and crushing the waste butyl rubber into particles with a diameter of 2-5 mm to obtain pretreated rubber particles; S2: The pretreated rubber particles and the composite desulfurizer are simultaneously added into the continuous desulfurization equipment at a weight ratio of 100:25-40, and desulfurize continuously for 30-60 minutes at 180-220℃ and 1.5-2.5MPa; The composite desulfurizer comprises: a desulfurization component and an anti-aging system; The desulfurization components include, by weight: 5-10 parts of sulfur, 3-5 parts of accelerator M, 5-8 parts of zinc oxide, and 2-4 parts of stearic acid; The anti-aging system is a synergistic combination of ultraviolet absorber UV-9 and antioxidant 1010 (weight ratio 1:1-2), with a total addition amount of 10-15 parts by weight, wherein the antioxidant 1010 adopts microencapsulation coating technology; S3: High-purity nitrogen is introduced into the desulfurization section at a flow rate of 0.5-1.0m³ / h to form an inert reaction environment; S4: The desulfurized product is cooled to room temperature by a spiral cooling device and then sieved through 80-120 mesh to obtain regenerated rubber.

2. The continuous desulfurization process for aging-resistant butyl regenerated rubber according to claim 1, characterized in that: The continuous desulfurization equipment adopts a three-stage structure, including a feeding section, a desulfurization section and a discharging section; The desulfurization section is equipped with a variable pitch spiral stirring device with a rotation speed of 50-100 rpm, which realizes the directional fracture of the sulfurized network through the shear force gradient distribution.

3. The continuous desulfurization process for aging-resistant butyl regenerated rubber according to claim 1, characterized in that: The preparation method of the microencapsulated antioxidant 1010 is as follows: using urea-formaldehyde resin as the wall material and nano-titanium dioxide and silicon dioxide composite particles as reinforcing fillers, the core antioxidant is coated by in-situ polymerization to form sustained-release microcapsules with a particle size of 5-10 μm.

4. The continuous desulfurization process for aging-resistant butyl regenerated 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 lower than 0.5%, effectively suppressing high-temperature oxidation side reactions.

5. The continuous desulfurization process for aging-resistant butyl regenerated rubber according to claim 1, characterized in that: The cleaning step adopts countercurrent multi-stage spraying technology, and the recycling rate of the cleaning agent is ≥85%, thereby achieving efficient use of water resources.

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