Preparation method of desulfurized and activated rubber powder modified asphalt material

Abstract

The invention provides waste tire rubber powder subjected to catalytic hydrodesulfurization-acrylamide / silane synergistic grafting activation and a preparation method of modified asphalt of the waste tire rubber powder. Firstly, waste tire rubber powder is subjected to Fe / Mo catalytic hydrogen desulfurization (H2 is 1-5 MPa, the temperature is 180-200 DEG C, and the time is 30-90 min), so that the crosslinking degree is reduced by more than or equal to 50%, and residual sulfur is less than or equal to 0.5 wt%; then, in an APS / TEMED system at the temperature of 60-90 DEG C, acrylamide (10-40 wt%) and GPTMS (0.5-5 phr) are used for conducting methanol-water dispersion grafting on the desulfurized rubber powder, and the synergic grafting activated rubber powder with N / C larger than or equal to 0.025 is obtained. The modified asphalt comprises the following components in parts by weight: 65-85 parts of matrix asphalt, 10-20 parts of synergistically grafted and activated rubber powder and 0-6 parts of aromatic extract oil (preferably 72: 13: 5). The obtained modified asphalt has a 7-day storage layering index of less than or equal to 5% under the condition of a rubber powder mixing amount of 15 wt%, has a Brookfield viscosity of 1.5-2.5 Pa.s at 180 DEG C, and meets conventional pumping construction requirements; according to the method, deep desulfurization and interface activation are carried out step by step, the rubber powder polarity and asphalt storage stability are remarkably improved, equipment is universal, and the method is suitable for industrial continuous production.

Description

Technical Field

[0001] This invention relates to the field of asphalt materials technology, and in particular to an activated waste tire rubber powder modified asphalt material. Background Technology

[0002] Tire rubber powder (GTR) obtained by mechanical crushing at room temperature is widely used in the modification of road petroleum asphalt. It can significantly improve the high-temperature stability, low-temperature crack resistance and durability of road surfaces, and realize the resource utilization of waste rubber.

[0003] However, GTR is derived from highly vulcanized cross-linked rubber, whose internal S–S / C–S bonds intertwine to form a dense network, and the lack of polar functional groups on the surface makes it difficult for the rubber powder to fully swell in the asphalt melt, and it is prone to agglomeration and sedimentation. The softening point difference after 48 h of heat storage is often greater than 4 °C. At the same time, the viscosity of the system increases sharply when the dosage is high (>15 wt%).

[0004] Existing technologies typically employ chemical desulfurization or surface grafting to improve compatibility: Although methods such as alkali / amine chemical desulfurization, peroxide cracking, and supercritical fluid-microwave synergy can break S–S bonds, they require conditions of ≥250 ℃ or ≥20 MPa, easily damage the C–C main chain and generate volatile byproducts, and have high equipment investment and energy consumption. Although simple surface grafting of acrylamide, maleic anhydride, or plasma etching can introduce polar groups, the polar monomers cannot penetrate deeply because the cross-linking network is not loosened, and the powder cannot achieve sufficient swelling.

[0005] To address the challenges of both interfacial compatibility and storage stratification, existing literature has attempted to introduce oxygen-containing groups onto the surface of the rubber powder or to use sulfur-accelerator composite modifiers. Under high-speed shear, a short-term homogeneous system can be obtained, but the process often requires a variety of additives (accelerators, dispersants, antioxidants, etc.), demanding equipment conditions and complex processes, making it difficult to adapt to the continuous production of conventional asphalt mixing plants.

[0006] Therefore, the industry urgently needs a new process for activating waste tire rubber powder that is temperature- and pressure-mild, can simultaneously achieve deep desulfurization and surface polarity enhancement, and can be directly scaled up in existing shearing equipment, in order to obtain rubber powder modified asphalt with both excellent storage stability and ideal construction viscosity. Summary of the Invention

[0007] To address the shortcomings of low desulfurization efficiency, insufficient surface polarity, easy stratification of modified asphalt, and high energy consumption during high-temperature construction of waste tire rubber powder, this invention provides a method for preparing waste tire rubber powder and its modified asphalt through catalytic hydrogen desulfurization-acrylamide / silane synergistic grafting activation. By combining iron-group catalytic hydrogen desulfurization with amide-silane solution grafting, the method achieves simultaneous improvement in deep desulfurization and surface polarity of the rubber powder, solving the problem that desulfurization and interface modification cannot be simultaneously achieved in existing technologies.

[0008] The above-mentioned technical objective of this invention is achieved through the following technical solution: a method for preparing desulfurized activated rubber powder modified asphalt material, comprising the following steps in sequence: (1) Preparation of synergistically grafted activated waste tire rubber powder: A) Catalytic hydrogen desulfurization: 20-40 mesh waste tire rubber powder and aromatic extracted oil are mixed at a mass ratio of 1:(0.5-2), and 1-5 wt% of iron group metal catalyst is added. The mixture is reacted under 1-5 MPa hydrogen and 160-200 ℃ for 20-120 min to reduce the crosslinking density of the rubber powder by no less than 50%. B) Solution grafting: Disperse the desulfurized rubber powder obtained in step A) in a methanol-water solvent, add 10-40 wt% acrylamide and 0.5-5 phr γ-glycidylpropoxytrimethoxysilane, and react at 60-90 ℃ in a free radical system for 0.5-3 h. C) Post-treatment: Terminate the reaction and wash until the conductivity is less than 0.2 mS / cm. -1 The activated adhesive powder was dried at 60 ℃ and -0.09 MPa for 6-8 h, then cold-cut, pulverized and passed through a 40-mesh sieve. (2) Preparation of modified asphalt: a) Heat the base bitumen to 170-190 ℃; b) Under shearing conditions of 3000-5000 r / min, add the activated adhesive powder described in step (1) and shear for 15-40 min; c) Insulate the material to allow it to develop, thus obtaining the desulfurized activated rubber powder modified asphalt material.

[0009] Preferably, the iron group metal catalyst described in step (1)A) is an Fe / Mo composite, wherein the mass ratio of Fe to Mo is 4:1 to 6:1.

[0010] Preferably, the catalytic hydrogen desulfurization described in step (1)A) is carried out at a hydrogen pressure of 2-4 MPa and a temperature of 180-200 °C for a reaction time of 40-90 min.

[0011] Preferably, the free radical system described in step (1)B) is an ammonium persulfate / tetramethylethylenediamine initiation system, and the total amount of initiator is 0.5-1.0 wt% of the mass of the adhesive powder.

[0012] Preferably, the acrylamide described in step (1)B) can be replaced with maleic anhydride, N-hydroxyethylacrylamide or a mixture thereof.

[0013] Preferably, the matrix asphalt in step (2) is 65-85 parts and the activated adhesive powder is 10-20 parts.

[0014] Preferably, the base asphalt is No. 70-90 road petroleum asphalt.

[0015] An activated waste tire rubber powder that satisfies the following: a) The crosslinking density is reduced by at least 50% compared to the original rubber powder; b) The surface nitrogen / carbon atom ratio (N / C) ≥ 0.025 and the residual sulfur content ≤ 0.5 wt%; c) Particle D 50 It ranges from 150 to 400 µm.

[0016] A desulfurized activated rubber powder modified asphalt material, comprising 65-85 parts of base asphalt and 10-20 parts of activated rubber powder, with a softening point difference ≤2℃ after standing at 163℃ for 48 h, and a Brookfield viscosity of 1.5-2.5 Pa·s at 180℃.

[0017] Compared with the prior art, the beneficial effects of the present invention are: 1. Synergistic desulfurization and polarization enhancement: Catalytic hydrogen desulfurization effectively breaks S–S / C–S bonds, and the grafting step introduces -CONH- and -Si-O- groups at the chain ends, achieving a crosslinking density reduction of ≥50% and an N / C ratio increase of over 0.03.

[0018] 2. Significantly improved performance of modified asphalt: When the activated rubber powder content is 15 wt%, the asphalt obtained has a 7-day storage stratification index of ≤5%; the viscosity at 180 ℃ is controlled at 1.5–2.5 Pa·s, which meets the requirements of conventional pumping construction.

[0019] 3. Energy consumption and environmental protection advantages: The process temperature is ≤200 ℃ and the hydrogen pressure is ≤5 MPa, which saves more than 20% energy compared with traditional high temperature thermal cracking desulfurization; there is no strong acid or alkali waste liquid in the whole process, and only controllable H2S tail gas is generated.

[0020] 4. Strong industrial adaptability: All steps can be completed continuously on existing high-pressure autoclaves, glass autoclaves and asphalt high-shear equipment, which facilitates centralized factory production and on-site wet modification.

[0021] In summary, this invention achieves deep activation of waste tire rubber powder and a significant improvement in the performance of modified asphalt through the synergistic design of iron-group catalytic hydrogen desulfurization and amide-silane solution grafting. It has significant advantages such as high desulfurization efficiency, strong interfacial polarity, low energy consumption, and good storage stability, and can be widely used in the fields of heavy traffic pavement of highways, waterproof bonding layers, and bridge deck paving. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the process flow for the preparation method of the present invention. Detailed Implementation

[0023] The following examples further illustrate the preparation method of waste tire rubber powder and its modified asphalt by catalytic hydrogen desulfurization-acrylamide / silane synergistic grafting activation according to the present invention. The following examples are for illustrative purposes only and are not intended to limit the invention; equivalent modifications or substitutions made by those skilled in the art without departing from the concept of the invention fall within the protection scope of the present invention.

[0024] I. Experimental Materials and Equipment 1. Waste tire rubber powder (GTR): Prepared by room temperature mechanical crushing method, with a particle size of 20-40 mesh and a sulfur content of 1.95wt%.

[0025] 2. Fe / Mo catalyst: Analytical grade Fe powder (purity 99.5%, D...) 50 (≈50 nm) is mixed with MoO3 at a mass ratio of 5:1 until homogeneous.

[0026] 3. Chemical reagents: Acrylamide (AAm, 99%), γ-glycidylpropoxytrimethoxysilane (GPTMS, 98%), ammonium persulfate (APS), tetramethylethylenediamine (TEMED), and methanol were all of analytical grade.

[0027] 4. Base asphalt: Grade A road petroleum asphalt No. 70, softening point 46 ℃.

[0028] 5. Main equipment: 5 L magnetically coupled stirring autoclave, 10 L glass-lined reactor, vacuum drying oven, knife-type cold-cut pulverizer, 40 mesh vibrating screen, 3000–5000 r / min high-speed shear emulsifier.

[0029] II. Implementation Examples Example 1 (Benchmark Sample) (1) Catalytic hydrogen desulfurization: 2 kg of GTR and 1.5 kg of high aromatic extract oil were mixed evenly and placed in a 5 L autoclave. After purging with nitrogen three times, 60 g of Fe / Mo catalyst was added. The autoclave was sealed, hydrogen was introduced to 3 MPa, and the temperature was raised to 200℃. The reaction was carried out at a stirring rate of 200 r / min for 60 min. The crosslinking density of the resulting desulfurized rubber powder decreased by 56%.

[0030] (2) Solution grafting: 1 kg of the above desulfurized rubber powder was added to a 10 L reactor, and 3 L of methanol-water (volume ratio 70:30) mixed solvent was added. The mixture was heated to 70 °C and stirred. 200 g (20 wt%) of AAM and 20 g (2 phr) of GPTMS were added. After 5 min, 6 g of APS and 6 g of TEMED were added dropwise to initiate the grafting reaction for 2 h.

[0031] (3) Post-treatment: Terminate the reaction and wash with pure water at 60 °C until the conductivity of the filtrate is less than 0.2 mS / cm. -1 The product was vacuum dried at 60 °C and –0.09 MPa for 8 h, then cold-cut and pulverized before being passed through a 40-mesh sieve to obtain activated rubber powder sample A. Analysis showed that its surface N / C atomic ratio was 0.028 and its residual sulfur content was 0.42 wt%.

[0032] (4) Preparation of modified asphalt: 2 kg of base asphalt was heated to 180 °C, and sample A (with an admixture of 15 wt% of the asphalt mass) was added. The sample was sheared at high speed at 4000 r / min for 30 min to obtain modified asphalt sample AM.

[0033] Example 2 (Sample under minimum conditions) The steps of Example 1 were repeated, but the desulfurization conditions were changed to: hydrogen pressure 1 MPa, temperature 180℃, and reaction time 45 min. The grafting amounts were changed to: AAm 100 g (10 wt%) and GPTMS 5 g (0.5 phr). Finally, activated rubber powder sample B (N / C=0.026, crosslinking degree decreased by 52%) and modified asphalt sample BM were obtained.

[0034] Example 3 (High Limit Condition Sample) The steps of Example 1 were repeated, but the desulfurization conditions were changed to: hydrogen pressure 5 MPa, temperature 220℃, and reaction time 75 min. The grafting amounts were changed to: AAm 400 g (40 wt%) and GPTMS 50 g (5 phr). Finally, activated rubber powder sample C (N / C = 0.034, crosslinking degree decreased by 65%) and modified asphalt sample CM were obtained.

[0035] Example 4 (Catalyst Replacement) The steps of Example 1 were repeated, but the Fe / Mo catalyst was replaced with an Fe / Ni catalyst (mass ratio 5:1), while other conditions remained unchanged. Finally, activated rubber powder sample D (N / C=0.029) and modified asphalt sample DM were obtained.

[0036] Example 5 (Grafted Monomer Replacement) The steps of Example 1 were repeated, but AAm was replaced with 250 g (25 wt%) of maleic anhydride (MAH), the amount of GPTMS remained the same, and other conditions remained unchanged. Finally, activated rubber powder sample E (O / C=0.095, degree of crosslinking decreased by 58%) and modified asphalt sample EM were obtained.

[0037] III. Comparative Example

[0038] IV. Performance Testing and Result Analysis 1. Key properties of activated rubber powder and modified asphalt All test methods were performed in accordance with the "Test Procedures for Asphalt and Asphalt Mixtures in Highway Engineering" (JTG E20-2011).

[0039] Table 1 Key properties of activated rubber powder and modified asphalt

[0040] Results analysis: Comparative example FM (desulfurization only): Although the softening point increased slightly (68 ℃), the softening point difference increased to 12.5℃ after 48 h and the storage resistance was only 3 days, indicating that the lack of grafting led to insufficient surface polarity, and the rubber powder was prone to re-aggregation and sedimentation.

[0041] Comparative Example GM (grafted only): The cross-linked network did not loosen, the softening point was 67.6 ℃, and both storage stability and viscosity deteriorated, proving that simple grafting cannot replace the contribution of desulfurization to swelling-development.

[0042] Comparative example HM (untreated adhesive powder): worst in all indicators, representing the baseline of current technology.

[0043] Example DM (Fe / Ni catalysis): Equivalent to the benchmark AM in all metrics, verifying the dependent claim that “iron group catalysts are interchangeable”.

[0044] Example EM (MAH monomer): still maintains a softening point ≥70 ℃ and a softening point difference of ≤1.5 ℃ after 48 h, proving that the storage stability and construction requirements can still be met after replacing the amide monomer, supporting the "replaceable amide functional monomer" variant design.

[0045] Synergistic effect conclusion: Only when "Fe-H2 directional desulfurization" and "amide / silane grafting" coexist can a balance be achieved in terms of desulfurization depth, surface polarity, and interfacial bonding, thereby simultaneously improving high-temperature performance, thermal storage stability, and elastic recovery, while maintaining low construction viscosity. The absence of any one of these components will prevent the achievement of the comprehensive performance indicators.

[0046] 2. Road performance simulation test To verify the applicability of this invention under actual road conditions, AC-13 dense-graded asphalt mixture (with aggregate gradation meeting the relevant requirements of JTG E20-2011) was used for testing, with a target void ratio of 4.0% ± 0.5% and an optimal asphalt content of 4.8% (mass fraction). Asphalt samples AM (reference), BM (lower limit), CM (upper limit), DM (Fe / Ni), EM (MAH variant), and comparative samples FM (desulfurization only), GM (grafting only), and HM (virgin rubber powder) were used. All other mixing, compaction, and curing conditions were consistent to eliminate interference from differences in mix proportions and molding.

[0047] Test method: (1) Rutting test: According to JTG E20-2011 T0719, under 60 ℃ and 0.7 MPa load, record the rutting depth and dynamic stability (DS, times / mm) for 45 min.

[0048] (2) Freeze-thaw splitting strength ratio (TSR): Performed according to JTG E20-2011 T0729.

[0049] (3) Low-temperature crack resistance of beam bending: According to JTG E20-2011 T0715, the peak strain ε_B (με) was measured at –10 ℃.

[0050] (4) Four-point bending fatigue: According to JTG E20-2011 T0739, under the conditions of 15 ℃, 10 Hz and constant strain of 250 με, the number of cycles N_f until the stiffness decreases by 50% is tested.

[0051] (5) Supplement: Hamburg rutting (water damage and rutting resistance coupled): according to AASHTO T324, at 50 ℃, record the rutting depth and spalling inflection point up to 20,000 wheel loads.

[0052] Experimental results: Table 2 Results of road performance simulation test (AC-13, optimal asphalt-aggregate ratio 4.8%)

[0053] Results Analysis and Technical Effects: 1. High-Temperature Rutting Resistance: AM's DS is 10,500 cycles / mm, approximately 320% higher than HM and approximately 133% higher than FM. CM further improves to 12,000 cycles / mm. AM, BM, CM, and DM all meet the rutting resistance requirements for heavy traffic sections.

[0054] 2. Water damage resistance: AM's TSR is 90%, significantly higher than HM (74%) and GM (80%). The Hamburg rutting thickness is still less than 7 mm after 20,000 cycles, and there is no early spalling inflection point, indicating that the improved interfacial polarity is effective in resisting spalling.

[0055] 3. Fatigue and low-temperature crack resistance: AM's N_f = 2.4 × 10 5 ε_B = 3,100 με, representing improvements of approximately 300% and 72% compared to HM, respectively. The further improvement in CM indicates that, while ensuring desulfurization depth, the elasticity / toughness gains from amide / silane grafting can delay fatigue cracking and improve low-temperature deformation capacity.

[0056] 4. Replaceability Verification: DM (Fe / Ni) is equivalent to AM in all road-use performance indicators, supporting the dependent claim of "equivalent iron group catalysts". Although EM (MAH) is slightly lower than AM, it still meets the engineering application thresholds of TSR≥85% and DS≥8,000 cycles / mm, supporting the variant design of "replaceable amide functional monomers".

[0057] Overall Conclusion: Compared with desulfurization only (FM), grafting only (GM), and untreated (HM), the "Fe-H2 directional desulfurization + amide / silane synergistic grafting" system of this invention achieves significant improvements in four key road performance characteristics: high-temperature rutting resistance, water loss resistance, fatigue life, and low-temperature crack resistance. Specifically, AM achieves DS≥10,000 times / mm, TSR≥90%, and N_f≥2.4×10 without increasing the application viscosity. 5 The result of ε_B≥3,000 με verifies that the performance improvement at the material level also applies to the mixture level, meeting the comprehensive performance requirements of heavy traffic pavement.

[0058] In summary, the test results of the specific implementation methods show that neither catalytic hydrogen desulfurization nor solution grafting alone can produce modified asphalt materials that possess both storage stability and excellent road performance. The sample treated only with desulfurization (FM) exhibited poor thermal storage stability, with a softening point difference of 12.5℃ after 48 hours; the sample treated only with grafting (GM) showed unsatisfactory properties across the board, with a softening point difference of 15.1℃ after 48 hours.

[0059] By combining catalytic hydrogen desulfurization with amide / silane synergistic grafting, the prepared modified asphalt materials (AM, BM, CM) exhibit both excellent thermal storage stability (softening point difference ≤2℃ after 48 hours) and suitable work viscosity (1.5-2.5 Pa·s). Compared with materials prepared from untreated, desulfurized, or grafted rubber powders, the asphalt mixtures prepared using the complete two-step method show significant improvements in high-temperature rutting resistance, water loss resistance, fatigue life, and low-temperature crack resistance.

[0060] Furthermore, experimental results also demonstrate that modified asphalt materials that meet engineering application requirements can still be prepared by using Fe / Ni composites instead of Fe / Mo composites as catalysts (DM), or by using maleic anhydride instead of acrylamide as graft monomers (EM).

[0061] This specific embodiment is merely an explanation of the present invention and is not intended to limit the invention. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they are within the scope of the claims of the present invention.

Claims

1. A method for preparing desulfurized activated rubber powder modified asphalt material, characterized in that, The steps are as follows: (1) Preparation of synergistically grafted activated waste tire rubber powder: A) Catalytic hydrogen desulfurization: 20-40 mesh waste tire rubber powder and aromatic extracted oil are mixed at a mass ratio of 1:(0.5-2), and 1-5 wt% of iron group metal catalyst is added. The mixture is reacted under 1-5 MPa hydrogen gas and 160-200 ℃ for 20-120 min, so that the crosslinking density of the rubber powder is reduced by no less than 50%. B) Solution grafting: Disperse the desulfurized rubber powder obtained in step A) in a methanol-water solvent, add 10-40 wt% acrylamide and 0.5-5 phr γ-glycidylpropoxytrimethoxysilane, and react at 60-90 ℃ in a free radical system for 0.5-3 h. C) Post-treatment: Terminate the reaction and wash until the conductivity is less than 0.2 mS / cm. -1 The activated adhesive powder was dried at 60 ℃ and -0.09 MPa for 6-8 h, then cold-cut, pulverized and passed through a 40-mesh sieve. (2) Preparation of modified asphalt: a) Heat the base bitumen to 170-190 ℃; b) Under shearing conditions of 3000-5000 r / min, add the activated adhesive powder described in step (1) and shear for 15-40 min; c) Insulate the material to allow it to develop, thus obtaining the desulfurized activated rubber powder modified asphalt material.

2. The method according to claim 1, characterized in that, The iron group metal catalyst mentioned in step (1)A) is an Fe / Mo complex, wherein the mass ratio of Fe to Mo is 4:1 to 6:

1.

3. The method according to claim 1, characterized in that, The catalytic hydrogen desulfurization described in step (1)A) is carried out at a hydrogen pressure of 2-4 MPa and a temperature of 180-200 °C for a reaction time of 40-90 min.

4. The method according to claim 1, characterized in that, The free radical system described in step (1)B) is an ammonium persulfate / tetramethylethylenediamine initiation system, and the total amount of initiator is 0.5-1.0 wt% of the mass of the adhesive powder.

5. The method according to claim 1, characterized in that, The acrylamide mentioned in step (1)B) can be replaced with maleic anhydride, N-hydroxyethylacrylamide or a mixture thereof.

6. The method according to claim 1, characterized in that, The matrix asphalt mentioned in step (2) is 65-85 parts, and the activated adhesive powder is 10-20 parts.

7. The method according to claim 6, characterized in that, The base asphalt is No. 70-90 road petroleum asphalt.

8. An activated waste tire rubber powder, characterized in that, Prepared by the method described in step (1) of claim 1, and satisfying the following: a) The crosslinking density is reduced by no less than 50% compared to the original rubber powder; b) The surface nitrogen / carbon atom ratio (N / C) ≥ 0.025 and the residual sulfur content ≤ 0.5 wt%; c) Particle D 50 It ranges from 150 to 400 µm.

9. A desulfurized activated rubber powder modified asphalt material, characterized in that, The material is prepared by the method according to any one of claims 1 to 7, comprising 65-85 parts of base bitumen and 10-20 parts of activated rubber powder, and has a softening point difference of ≤2℃ when left to stand at 163℃ for 48 h, and a Brookfield viscosity of 1.5-2.5 Pa·s at 180℃.

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