Preparation method of all-solid waste asphalt modifier

Abstract

The invention provides a preparation method of an all-solid waste asphalt modifier, belongs to the technical field of asphalt modifier preparation, and solves the problems of insufficient rubber powder activation degree, poor multi-component blending compatibility and poor stability in the existing preparation technology. The preparation method comprises the following steps: carrying out first-order activation treatment to generate high-activation glue, carrying out second-order low-temperature compounding and blending, extrusion and water ring granulation, finally carrying out drying treatment to obtain modifier particles, and applying the modifier particles to the preparation processes of cooling, isolating, packaging and the like. According to the method, a double-screw extruder is adopted for two-stage sectional treatment, the method comprises a first-stage activation procedure and a second-stage compounding and blending procedure, and the method is environmentally friendly and suitable for large-scale production.

Description

Technical Field

[0001] This invention belongs to the field of asphalt modifier preparation technology, specifically relating to a method for preparing a solid waste asphalt modifier. Background Technology

[0002] With the rapid development of transportation infrastructure construction in my country, the demand for asphalt for roads has been increasing year by year. Although traditional polymer-modified asphalt such as SBS can effectively improve pavement performance, it has problems such as high cost, non-renewability, and high carbon emissions. In recent years, research on using solid waste as asphalt modifiers has gradually emerged, especially the recycling of waste rubber tire powder and recycled plastics has become a research hotspot.

[0003] The existing technologies disclose composite modified asphalt, its preparation methods, and applications, which employ a CO2 supercritical fluid-carried ionic liquid swelling treatment process and a microwave plasma treatment process to jointly and synergistically treat rubber-plastic mixtures. This method has a relatively complex process route, uses vinyl imidazole ionic liquids and 100-200 mesh ultrafine waste plastic powder as raw materials, resulting in high costs and difficulty in industrialization. Furthermore, it is difficult to achieve deep desulfurization, which limits its effect on improving asphalt performance.

[0004] Furthermore, existing high-viscosity rubber asphalt modifiers and their preparation methods employ a screw extruder to prepare linear activated rubber. This method requires pretreatment of the rubber powder at 50-120℃ for 6-36 hours, resulting in a long pretreatment cycle and impacting production efficiency. During the modification process, activated rubber, olefin polymers, and crosslinking aids are mixed using an internal mixer. In practical applications, it has been found that the activated rubber and polyolefin compounds undergo a crosslinking reaction to form elastomers, which have poor solubility in asphalt. The modifier components cannot be completely dissolved in the asphalt, making it difficult for each component to exert its modification potential. The insoluble portions tend to settle, resulting in poor stability and easy segregation of the modified asphalt. Ordinary extrusion granulation is only suitable for activated rubber with low activation (sol content < 40%). It cannot granulate high-activation rubber (sol content > 50%) or the granules tend to stick together.

[0005] In summary, existing technologies generally suffer from the following drawbacks: 1. Insufficient activation of rubber powder: This results in a low trichloroethylene sol content in the rubber powder, making it difficult to fully realize its modification potential. 2. Poor compatibility of multi-component blending: The rheological behavior of rubber and plastic melts differs greatly, making blending prone to localized overheating or insufficient shear, affecting blend uniformity. 3. Particles are prone to sticking together: Finished particles lack effective anti-sticking measures, resulting in poor storage stability. 4. Poor stability of modified asphalt: The modifier has poor compatibility with the base asphalt, leading to easy segregation. 5. Existing technologies often use only one or two types of solid waste (e.g., only fly ash, single waste polymers), resulting in problems such as limited performance (e.g., inability to simultaneously achieve high-temperature rutting resistance and low-temperature crack resistance), low solid waste utilization rate (often below 50%), and poor compatibility (weak interfacial bonding between inorganic solid waste and asphalt).

[0006] Therefore, there is an urgent need to develop a process for preparing all-solid-waste asphalt modifiers that can efficiently activate rubber powder, achieve precise blending of various solid waste materials, and ensure product storage stability. Summary of the Invention

[0007] The purpose of this invention is to provide a method for preparing a solid waste asphalt modifier, in order to solve the problems of insufficient activation of rubber powder, poor compatibility of multi-component blending, and poor stability in existing preparation technologies.

[0008] The technical solution of this invention is: a method for preparing a solid waste asphalt modifier, comprising the following steps: Step 1: Raw material pretreatment Remove metallic impurities from waste rubber tire powder; Step 2: First-order activation treatment Waste rubber tire powder with a mesh size of 20-40 after removing metal impurities is added to the first screw system of a twin-screw extruder and subjected to thermomechanical shearing treatment at a temperature of 200℃-280℃. This causes partial desulfurization, chain breaking, and swelling of the rubber powder, resulting in a highly activated rubber with a trichloroethylene sol content of >50%. Step 3: Second-order low-temperature compounding and blending After the high-activation rubber is discharged from the first-stage screw system, it enters the second-stage screw system of the twin-screw extruder, where recycled plastic and 40-80 mesh waste tire rubber powder are added and blended in cooling mode; Step 4: Extrusion and Water Ring Granulation The blended mixture is conveyed to the extruder die by the second-stage screw, and the mixture is continuously extruded in a molten state and enters the water ring granulation device to be cut into spherical or cylindrical particles; Step 5: Drying treatment The cut wet granules are fed into a dryer and dried until the moisture content is <0.1wt% to obtain drying modifier granules. Step Six: Cooling, Isolation and Packaging Add 0.1-0.5% of the release agent by mass to the dried modifier granules, force-cool to room temperature using a blower, then automatically weigh, package, and seal for storage.

[0009] As a further improvement of the present invention, in step two, the screw speed is 60-90 RPM and the thermomechanical shearing treatment time is 3-8 minutes.

[0010] As a further improvement of the present invention, in step two, the thermomechanical shearing treatment temperature is preferably 220℃-260℃, which is more conducive to maintaining the elasticity of the adhesive powder while increasing the sol content.

[0011] As a further improvement of the present invention, in step three, the recycled plastic is one or more of PET, PP, PE, LDPE, and EVA.

[0012] As a further improvement of the present invention, in step three, the temperature in the cooling mode is controlled at 100℃-150℃, and the screw speed of the second-stage screw system is 15-50RPM.

[0013] Second-order low-temperature compounding and blending achieves uniform dispersion of plastic melting and activated rubber powder through low-shear and low-temperature environment, which can avoid degradation of sensitive plastics such as PET caused by high temperature.

[0014] As a further improvement of the present invention, in step four, the die head temperature is set to 100-150℃, the pelletizing speed is 1000-2500RPM, and the mass of a single pellet is controlled to be no more than 0.05g / particle.

[0015] As a further improvement of the present invention, in step five, the drying temperature is 60-80℃ and the drying time is 20-30 minutes.

[0016] As a further improvement of the present invention, in step six, the release agent is silica fume or pyrolysis carbon black, which can be used to prevent particle adhesion, at room temperature ≤35°C.

[0017] The beneficial effects of this invention are as follows: This invention provides a two-stage thermomechanical synergistic modification process based on a twin-screw extruder for preparing high-performance all-solid waste asphalt modifiers. It can improve the activation efficiency of high-proportion waste rubber tire powder and obtain highly activated rubber with a trichloroethylene sol content of more than 50%. At the same time, it can achieve uniform blending of activated rubber powder and recycled plastics (PET, PP, PE, LDPE, EVA). Furthermore, it constructs a continuous production process integrating "activation-compounding-granulation-anti-sticking", which improves the consistency of product quality and industrial feasibility. Therefore, it solves the problem of agglomeration of modifier particles during storage, thereby improving the storage and transportation stability of the product. Attached Figure Description

[0018] Figure 1This is a flowchart illustrating the preparation process of the present invention. Figure 2 This is a graph showing the test results of the highly activated sol content in Example 2 of this invention; Figure 3 The images show photographs and morphological diagrams of the modifier particles obtained in Example 2 of this invention. Detailed Implementation

[0019] The process method of the present invention will be described in detail through specific embodiments. The purpose of the embodiments is to support and explain the claims, and their content is a concretization of the foregoing technical solutions and should be consistent with the content of the technical solutions; the following three specific embodiments further illustrate the technical solutions of the present invention, but should not be construed as limiting the present invention.

[0020] Example 1 The total feed amount of raw materials is 1000kg, of which waste tire rubber powder accounts for 60%, recycled plastic accounts for 10%, LDPE and EVA are selected, LDPE:EVA=2:8, and waste tire rubber powder accounts for 30%.

[0021] Step 1: Raw material pretreatment Remove metallic impurities from waste rubber tire powder; Step 2: First-order activation treatment Waste rubber tire powder with 20 mesh after removing metal impurities is added to the first screw system of a twin-screw extruder. The screw speed is 60 RPM. Thermomechanical shearing is performed at a temperature of 200℃-280℃, preferably 220℃, for 3 minutes. This causes partial desulfurization, chain breaking, and swelling of the rubber powder, resulting in a highly activated rubber with a trichloroethylene sol content of >50%. Step 3: Second-order low-temperature compounding and blending After the high-activation rubber is discharged from the first-stage screw system, it enters the second-stage screw system of the twin-screw extruder, where recycled plastic and 40-mesh waste tire rubber powder are added and blended in cooling mode. The temperature in cooling mode is controlled at 100℃, and the screw speed of the second-stage screw system is 15RPM.

[0022] Step 4: Extrusion and Water Ring Granulation The blended mixture is conveyed to the extruder die head by the second-stage screw. The die head temperature is set to 100℃. The mixture is continuously extruded in a molten state and enters the water ring granulation device. The pelletizing speed is 1000RPM, and it is cut into spherical or cylindrical particles. The mass of a single particle is controlled to be no more than 0.05g / particle. Step 5: Drying treatment The cut wet granules are fed into a dryer at a temperature of 60°C for 20 minutes until the moisture content is less than 0.1 wt%, thus obtaining the drying modifier granules.

[0023] The performance test results of the prepared drying modifier particles are shown in Table 1.

[0024] Step Six: Cooling, Isolation and Packaging Add 0.1% by weight of a release agent (silica fume or pyrolyzed carbon black) to the dried modifier particles. Specifically, add 20wt% modifier particles, 3wt% SBS, 2wt% extractable oil, and 0.15wt% modified asphalt to 90# base asphalt. The performance test results of the modified asphalt are shown in Table 2. Force-cool to room temperature (≤35℃) using a blower, then automatically weigh and package, seal and store. Packaging is done in woven bags lined with plastic film or vacuum aluminum foil bags, with a net weight of 20kg or 25kg per bag.

[0025] Example 2 The total feed amount of raw materials is 1000kg, of which waste tire rubber powder accounts for 60%, recycled plastic accounts for 10%, PP and EVA are selected, PP:EVA=1:9, and waste tire rubber powder accounts for 30%.

[0026] Step 1: Raw material pretreatment Remove metallic impurities from waste rubber tire powder; Step 2: First-order activation treatment Waste rubber tire powder (30 mesh, after removing metal impurities) is added to the first-stage screw system of a twin-screw extruder at a screw speed of 75 RPM. Thermomechanical shearing is performed at a temperature of 200℃-280℃, preferably 240℃, for 5 minutes. This process causes partial desulfurization, chain scission, and swelling of the rubber powder, resulting in a highly activated rubber with a trichloroethylene sol content >50%. The test results for the highly activated rubber sol content are as follows: Figure 2 As shown.

[0027] Step 3: Second-order low-temperature compounding and blending After the high-activation rubber is discharged from the first-stage screw system, it enters the second-stage screw system of the twin-screw extruder, where recycled plastic and 60-mesh waste tire rubber powder are added and blended in cooling mode. The temperature in cooling mode is controlled at 125℃, and the screw speed of the second-stage screw system is 30RPM.

[0028] Step 4: Extrusion and Water Ring Granulation The blended mixture is conveyed to the extruder die head by the second-stage screw. The die head temperature is set to 125℃. The mixture is continuously extruded in a molten state and enters the water ring granulation device. The pelletizing speed is 1500RPM, and it is cut into spherical or cylindrical particles. The mass of a single particle is controlled to be no more than 0.05g / particle. Step 5: Drying treatment The cut wet granules were fed into a dryer at 70℃ for 25 minutes until the moisture content was <0.1wt%, yielding dried modifier granules. Photos of the modifier granules and their morphology are shown below. Figure 3 As shown.

[0029] The performance test results of the prepared drying modifier particles are shown in Table 3.

[0030] Step Six: Cooling, Isolation and Packaging Add a release agent equivalent to 0.3% of its mass to the dried modifier particles. The release agent is silica fume or pyrolyzed carbon black. Specifically, in 90# base asphalt, add 20wt% modifier particles, 3wt% SBS, 2wt% extractable oil, and 0.15wt% modified asphalt. The performance test results of the modified asphalt are shown in Table 4. Force-cool to room temperature (≤35℃) using a blower, then automatically weigh and package, seal and store. The packaging form is a woven bag with an inner plastic film lining or a vacuum aluminum foil bag, with a net weight of 20kg or 25kg per bag.

[0031] Example 3 The total feed amount of raw materials is 1000kg, of which waste tire rubber powder accounts for 65%, recycled plastic accounts for 10%, and PET, PE and LDPE are selected, with PET:PE:LDPE=0.5:1.5:8 and waste tire rubber powder accounts for 25%.

[0032] Step 1: Raw material pretreatment Remove metallic impurities from waste rubber tire powder; Step 2: First-order activation treatment Waste rubber tire powder with 40 mesh after removing metal impurities is added to the first screw system of a twin-screw extruder. The screw speed is 90 RPM. Thermomechanical shearing is performed at a temperature of 200℃-280℃, preferably 260℃, for 8 minutes. This causes partial desulfurization, chain breaking, and swelling of the rubber powder, resulting in a highly activated rubber with a trichloroethylene sol content of >50%. Step 3: Second-order low-temperature compounding and blending After the high-activation rubber is discharged from the first-stage screw system, it enters the second-stage screw system of the twin-screw extruder, where recycled plastic and 80-mesh waste tire rubber powder are added and blended in cooling mode. The temperature in cooling mode is controlled at 150℃, and the screw speed of the second-stage screw system is 50RPM.

[0033] Step 4: Extrusion and Water Ring Granulation The blended mixture is conveyed to the extruder die head by the second-stage screw. The die head temperature is set to 150℃. The mixture is continuously extruded in a molten state and enters the water ring granulation device. The pelletizing speed is 2500RPM, and it is cut into spherical or cylindrical particles. The mass of a single particle is controlled to be no more than 0.05g / particle. Step 5: Drying treatment The cut wet granules are fed into a dryer at a temperature of 80°C for 30 minutes until the moisture content is less than 0.1 wt%, thus obtaining the drying modifier granules.

[0034] The performance test results of the prepared drying modifier particles are shown in Table 5.

[0035] Step Six: Cooling, Isolation and Packaging Add a release agent equivalent to 0.5% of its mass to the dried modifier particles. The release agent is silica fume or pyrolyzed carbon black. Specifically, in 90# base asphalt, add 20wt% modifier particles, 3wt% SBS, 2wt% extractable oil, and 0.15wt% modified asphalt. The performance test results of the modified asphalt are shown in Table 6. Force-cool to room temperature (≤35℃) using a blower, then automatically weigh and package, seal and store. The packaging form is a woven bag with an inner plastic film lining or a vacuum aluminum foil bag, with a net weight of 20kg or 25kg per bag.

[0036] The test results of Examples 1-3 show that the preparation method provided by the present invention also has the following advantages: 1. “All solid waste” resource utilization: All raw materials used in this invention come from industrial solid waste, realizing the resource utilization of solid waste. Moreover, the raw materials are inexpensive and widely available, and have significant economic, environmental and social benefits. 2. The twin-screw two-stage temperature control process is adopted, which first activates at high temperature and then blends at low temperature. This ensures that the rubber powder is fully activated (sol content > 50%) and avoids thermal degradation of plastic components, thereby improving the blending quality. 3. Excellent product performance: The modifier has good compatibility with the base asphalt, significantly improving the high-temperature stability, low-temperature crack resistance and fatigue life of asphalt. Through water ring granulation, the particle size is controllable and the surface is dense. 4. Reasonable anti-sticking design for granules: Introducing silica fume or pyrolysis carbon black as a release agent, and combining it with air cooling process, the combination of external release agent and air cooling provides dual protection to effectively prevent granules from clumping during transportation and storage. 5. High yield and stable quality: This method has a high raw material conversion rate, with an overall yield of >98.5% (based on the total mass of the feed), small batch-to-batch differences, and can achieve material modification entirely through thermomechanical action without the use of catalysts, fillers or other additives, thus meeting the needs of engineering applications.

Claims

1. A method of preparing a full-solid waste asphalt modifier, characterized by: The method comprises the following steps: Step 1, raw material pretreatment Remove metal impurities from waste rubber tire crumbs; Step 2, first-order activation treatment After removing metal impurities, 20-40 mesh waste rubber tire crumbs are added to the first-stage screw system of a double-screw extruder, and heat mechanical shearing treatment is performed at a temperature of 200-280°C to cause partial devulcanization, chain scission and swelling of the crumbs, thereby generating highly activated glue with a trichloroethylene sol content of >50%; Step 3, second-order low-temperature compounding and blending After the highly activated glue is discharged from the first-stage screw system, it is added to the second-stage screw system of a double-screw extruder, and recycled plastic and 40-80 mesh waste tire crumbs are added for blending under a temperature reduction mode; Step 4, extrusion and water ring granulation The blended mixture is transported to the extruder die by the second-stage screw, and the mixture is continuously extruded in a molten state and enters the water ring granulation device to be cut into spherical or cylindrical particles; Step 5, drying treatment The cut wet particles are sent to a dryer, and the moisture content is reduced to <0.1wt% after drying, thereby obtaining dry modifier particles; Step 6, cooling, isolation and packaging 0.1-0.5% of an isolating agent corresponding to the mass of the dry modifier particles is added, and forced air cooling is performed to room temperature using a blower, and then automatic weighing and packaging are performed, and the package is sealed and stored.

2. The method for preparing a full-solid waste asphalt modifier according to claim 1, characterized in that: In step 2, the screw rotation speed is 60-90 RPM, and the heat mechanical shearing treatment time is 3-8 minutes.

3. The method of claim 1, wherein the method is characterized by: In step 2, the heat mechanical shearing treatment temperature is preferably 220-260°C.

4. The method of claim 1, wherein the method is characterized by: In step 3, the recycled plastic is one or more of PET, PP, PE, LDPE and EVA.

5. The method of claim 1, wherein the method is characterized by: In step 3, the temperature reduction mode temperature is controlled at 100-150°C, and the screw rotation speed of the second-stage screw system is 15-50 RPM.

6. The method of claim 1, wherein the method is characterized by: In step 4, the die temperature is set to 100-150°C, the cutting speed is 1000-2500 RPM, and the mass of a single particle is controlled to be not more than 0.05g / particle.

7. The method of claim 1, wherein the method is characterized by: In step 5, the drying temperature is 60-80°C, and the drying time is 20-30 minutes.

8. The method of claim 1, wherein the method is characterized by: In step 6, the isolating agent is silica ash or pyrolysis carbon black, and the room temperature is ≤35°C.

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