High-viscosity cold-mixed and cold-laid asphalt additive and preparation method thereof

Abstract

The invention relates to the technical field of road materials, and discloses a high-viscosity cold-mixed and cold-laid asphalt additive and a preparation method thereof, the additive comprises a basic tackifying system, a crosslinking toughening system and an anti-hydrolysis protection system; the preparation method comprises the following steps: preparing hydrophobic microcapsule coated blocked isocyanate by adopting an interfacial polymerization method, activating a molecular sieve dehumidizer, preparing a chelation protection type catalyst, and finally compounding the components according to a sequence from high temperature to low temperature and from a foundation to a function to obtain the additive. The problem that the performance of a traditional cold-mixed asphalt additive is greatly attenuated in a humid environment is solved, and the cold-mixed asphalt additive is suitable for road maintenance construction in rainy areas and high-humidity environments.

Description

Technical Field

[0001] This invention relates to the field of road materials technology, and more specifically, to a high-viscosity cold-mix asphalt additive and its preparation method. Background Technology

[0002] Cold-mix asphalt technology is a road construction technique performed at room temperature or lower temperatures, with additives being its core material. Traditional cold-mix asphalt additives have the following technical limitations: First, the viscosity-enhancing effect of a single component is limited, making it difficult to balance high viscosity and workability; second, relying on physical blending and lacking chemical cross-linking, they have insufficient high-temperature deformation resistance, poor low-temperature toughness, and slow early strength formation; and third, their performance deteriorates significantly in humid environments.

[0003] Additives containing isocyanate crosslinking components, in particular, face severe water sensitivity issues in humid environments: isocyanate groups react rapidly with water to generate amines and carbon dioxide, leading to a 50-70% reduction in the effective content of the crosslinking agent; carbon dioxide escapes and forms micropores (10-100 μm in diameter), reducing density; and the generated amines further consume the crosslinking agent. Simultaneously, organobismuth and organozinc catalysts hydrolyze and deactivate in humid environments, reducing the crosslinking reaction rate by 5-10 times. This synergistic deterioration of crosslinking agent hydrolysis and catalyst deactivation reduces the crosslinking effect of additives by 50-70% in rainy areas (annual rainfall > 1000 mm), coastal high-humidity environments (relative humidity > 80%), and rainy season construction scenarios, resulting in unstable material performance and difficulty in ensuring construction quality. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention provides a high-viscosity cold-mix asphalt additive and its preparation method.

[0005] A high-viscosity cold-mix asphalt additive, comprising the following components in parts by weight: 30-50 parts of high molecular weight polymer, 10-20 parts of organic amine accelerator, 20-40 parts of modified resin, 5-10 parts of end-capped isocyanate crosslinking agent, 8-15 parts of SEBS elastomer, 0.3-0.8 parts of catalyst, and 1.5-3 parts of molecular sieve desiccant; 60-80% of the end-capped isocyanate crosslinking agent is encapsulated in hydrophobic microcapsules. The hydrophobic microcapsules have end-capped isocyanate as the core material and hydrophobic polyurea or polyurethane as the wall material. The microcapsule particle size is 20-80 μm, the wall thickness is 2-5 μm, and the water vapor permeability of the wall material is less than 0.1 g / (m²·day). The molecular sieve desiccant is a type 3A or 4A molecular sieve micro powder with a pore size of 0.3-0.4 nm and a particle size of 1-5 μm. After activation at 300℃ for 4 hours, its water absorption capacity is 20-25% of its own mass. 70-90% of the catalyst is protected by chelation, which is achieved by forming chelates with organobismuth or organozinc catalysts through β-diketone ligands, or by loading the catalyst onto nano-silica that has been hydrophobically treated with silane coupling agents.

[0006] Preferably, the polymer is selected from styrene-butadiene-styrene block copolymer or ethylene-vinyl acetate copolymer, with a molecular weight of 100,000-300,000; the organic amine accelerator is selected from aliphatic polyamines or aromatic amine compounds, with a functionality of 2-4; and the modified resin is selected from petroleum resin, phenolic resin, rosin resin or a combination thereof, with a softening point of 80-140℃.

[0007] Preferably, the end-capping isocyanate crosslinking agent is selected from the trimer of toluene diisocyanate or hexamethylene diisocyanate, and the end-capping agent is phenolic, caprolactam or butanone oxime, and the end-capping agent removal temperature is 60-120℃; the styrene content of the SEBS elastomer is 20-35%.

[0008] Preferably, the hydrophobic microcapsules are prepared by interfacial polymerization, and the wall material monomers are toluene diisocyanate and hydrophobic polyether polyol. They are reacted in an oil-in-water emulsion system at 55-65°C for 1.5-2.5 hours to form a polyurea-polyurethane copolymer wall material. The encapsulation rate of the hydrophobic microcapsules is greater than 95%, and the core material content is 60-75%.

[0009] Preferably, the chelated protective catalyst is prepared by one of the following methods: reacting an organobismuth catalyst or an organozinc catalyst with β-diketone ligand acetylacetone at a molar ratio of 1:2 to 1:4 at 75-85°C for 0.5-1.5 hours to form a chelate; or loading the catalyst onto nano-silica treated with methyltrimethoxysilane hydrophobicity, with a catalyst loading of 15-25%.

[0010] A method for preparing a high-viscosity cold-mix asphalt additive includes the following steps performed sequentially: Step 1: Preparation of hydrophobic microcapsule-encapsulated end-capsulated isocyanate: The end-capsulated isocyanate and hydrophobic solvent are mixed at a mass ratio of 1:0.1-0.3. Toluene diisocyanate, a wall material monomer, and hydrophobic polyether polyol are added, with a mass ratio of 100 parts end-capsulated isocyanate, 8-15 parts toluene diisocyanate, and 6-12 parts hydrophobic polyether polyol, to obtain an oil phase. The oil phase is added dropwise to an aqueous phase containing a water-soluble emulsifier, and the stirring speed is controlled at 800-1500 rpm to form an oil-in-water emulsion. The mixture is heated to 55-65℃ for interfacial polymerization for 1.5-2.5 hours. After cooling, it is filtered or centrifuged, washed, and dried to obtain hydrophobic microcapsule-encapsulated end-capsulated isocyanate. Step 2, activate the molecular sieve desiccant: heat the 3A or 4A type molecular sieve powder from room temperature to 300℃ at a rate of 5-10℃ / minute, maintain the activation at 300℃ for 4 hours, cool to room temperature under dry nitrogen protection, and store in a sealed container. Step 3, preparation of chelated protective catalyst: react organobismuth catalyst or organozinc catalyst with acetylacetone at a molar ratio of 1:2 to 1:4 under nitrogen protection at 75-85℃ for 0.5-1.5 hours, remove excess ligand and solvent by vacuum distillation to obtain β-diketone chelate catalyst; or support the catalyst on hydrophobically treated nano-silica and dry to obtain supported catalyst; Step 4, compounding and preparing additives: In an environment with relative humidity less than 30% and nitrogen protection, melt and mix the polymer at 100-120℃, add SEBS elastomer for high shear dispersion, add modified resin and mix evenly, cool to 80-90℃ and then add non-encapsulated end-capped isocyanate crosslinking agent, hydrophobic microcapsule encapsulation crosslinking agent, activated molecular sieve powder, organic amine promoter, chelated protective catalyst and non-protected catalyst in sequence, mix evenly and cool to room temperature, and then package and seal.

[0011] Preferably, in step one, the volume ratio of the oil phase to the water phase is 1:2 to 1:4, the preferred interfacial polymerization reaction temperature is 60°C, the preferred reaction time is 2 hours, and after the reaction, the wall material is kept at 60°C for 0.5-1 hours to fully cure; the water-soluble emulsifier is selected from polyvinyl alcohol, sodium dodecyl sulfate or a combination thereof, and the amount used is 0.5-2% of the mass of deionized water.

[0012] Preferably: In step two, after the molecular sieve is activated, it is taken out when cooled to 80-100°C and quickly transferred to a sealed container equipped with dry nitrogen protection to continue cooling to room temperature. The relative humidity of the sealed storage environment is less than 10%; the residual moisture content of the activated molecular sieve is less than 0.5%.

[0013] Preferably: In step four, when adding SEBS elastomer at 100-120℃, the stirring speed is increased to 150-200 rpm, and a high-shear dispersion device is used for mixing for 30 minutes; when adding hydrophobic microcapsule-coated crosslinking agent, the stirring speed is controlled to be less than 100 rpm, and the mixture is mixed for 15-20 minutes; the addition time of activated molecular sieve powder is less than 10 minutes; the chelated protective catalyst is added last, and the mixing time is less than 20 minutes.

[0014] The beneficial effects of this invention are as follows: The additive system employs a three-tiered protective mechanism: physical isolation prevents water molecules from contacting isocyanate groups, thus preventing hydrolysis at its source; activated molecular sieves utilize their 0.3-0.4 nm pore size for selective adsorption of water molecules (kinetic diameter 0.28 nm), capturing free water and ambient humidity within the additive system, achieving a water absorption capacity of 20-25% of their own mass, thus eliminating hydrolysis reactants at a chemical level; and chelated protective catalysts prevent the metal centers of organobismuth / zinc catalysts from contacting water and undergoing hydrolysis through the six-membered ring chelate structure of β-diketone ligands or the physical barrier of hydrophobic supports. This triple protection system works synergistically at different levels, maintaining the additive's crosslinking efficiency at 90% relative humidity, exceeding 85% of that in dry environments. Even with a road surface containing 5% moisture, the crosslinking density still reaches over 80% of that under dry conditions, completely resolving the technical bottleneck of traditional isocyanate-containing additives experiencing a significant decrease in crosslinking efficiency (down to 30-50%) or even failure in humid environments.

[0015] The basic thickening system, through the synergistic effect of the chain entanglement network of polymers, the interfacial adhesion promotion of organic amine accelerators, and the rigid thickening of modified resins, increases the dynamic viscosity of asphalt at 60℃ by 150-200% and the softening point by 12-18℃. Building upon this, the cross-linking toughening system, through the reaction of end-capped isocyanates with the hydroxyl and amino groups in the polymer, resin, and accelerators to form a chemical cross-linking network of urethane or urea bonds, provides high-temperature stability and resistance to deformation. The soft segments of the SEBS elastomer provide deformation capacity, while the hard segments provide physical cross-linking points. The catalyst accelerates the cross-linking reaction and shortens the curing time, further increasing the dynamic viscosity at 60℃ by 30-50% on top of the basic thickening, achieving a total increase of 180-220% and a softening point increase of 15-18℃, thus constructing a dual chemical-physical reinforcing network. This dual network provides resistance to rutting by restricting molecular chain movement at high temperatures through chemical cross-linking points, and provides toughness and deformation capacity in the soft segments of the elastomer at low temperatures. The ductility remains above 100 cm at -10℃ and the elastic recovery rate reaches over 75%, achieving a balance between high-temperature stability and low-temperature toughness.

[0016] Hydrophobic microcapsules remain intact during storage and transportation, protecting the crosslinking agent from moisture erosion. During the mixing of the additive with asphalt and pavement compaction, the microcapsule walls rupture under mechanical shear forces, releasing the crosslinking agent as needed to participate in the reaction, achieving controlled release through encapsulation protection and on-demand release. The chelated protective catalyst remains chelated below 60°C, inhibiting catalytic activity. At the crosslinking reaction initiation temperature (>60°C) or upon encountering strong isocyanate coordinating groups, the chelate structure dissociates, restoring catalyst activity and achieving controlled catalytic release. This spatiotemporally controlled release method ensures the additive maintains good flowability and workability during construction (mixing, transportation, paving), rapidly initiates the crosslinking reaction after compaction, quickly forms early strength, increases compressive strength by 100% within 24 hours, and shortens the time to traffic by 50%.

[0017] The anti-hydrolysis protection technology reduces the porosity of the material from 8-12% under severe hydrolysis to <2%, significantly improving its density. It also significantly improves the stability of construction quality during the rainy season, reducing the performance variation coefficient from 30% to <10%. The effective lifespan of the catalyst is extended by 3-5 times, and the storage stability of additives reaches over 6 months. The material can be stably used in scenarios where traditional cold-mix asphalt is difficult to apply, such as rainy areas (annual rainfall >1000mm), coastal high-humidity environments (relative humidity >80%), rainy season construction, construction under light rain conditions, and pothole repair. This expands the application scope of cold-mix asphalt technology from dry to humid areas, with broad market prospects. Simultaneously, it improves high-temperature rutting resistance by 50%, low-temperature flexural strain by over 80%, fatigue life by 2-3 times, and service life by 1-2 years, comprehensively enhancing the material's overall performance and reliability.

[0018] Compared with traditional single protection methods (such as using only desiccant or only hydrophobic components), the hydrolysis resistance is improved by 3-5 times; for the first time, the controllable release of crosslinking agent and catalyst is realized, which solves the contradiction between construction performance and curing performance; for the first time, multi-component synergistic thickening and chemical crosslinking toughening are organically combined to construct a chemical-physical dual reinforcement network, breaking through the performance limitations of traditional physical blending or single crosslinking systems. Attached Figure Description

[0019] Figure 1 This is a comparison of the relative crosslinking efficiency of three samples under different relative humidity conditions according to the present invention; Figure 2 This is a comparison of the dynamic viscosity of different samples of the present invention at 60°C; Figure 3 This is the viscosity enhancement rate relative to pure asphalt according to the present invention; Figure 4 These are radar images showing the combined high-temperature and low-temperature performance of different samples of this invention; Figure 5This is a comparison of the low-temperature ductility and elastic recovery of different samples of the present invention. Detailed Implementation

[0020] The subject matter described herein will now be discussed with reference to exemplary embodiments. It should be understood that these embodiments are discussed only to enable those skilled in the art to better understand and implement the subject matter described herein, and changes may be made to the function and arrangement of the elements discussed without departing from the scope of this specification. Various processes or components may be omitted, substituted, or added as needed in the examples. Furthermore, some features described in the examples may be combined in other examples.

[0021] Example 1 This embodiment presents a high-viscosity cold-mix asphalt additive, which is composed of the following components in parts by mass: 40 parts of high molecular polymer, 15 parts of organic amine accelerator, 30 parts of modified resin, 8 parts of end-capped isocyanate crosslinking agent, 12 parts of SEBS elastomer, 0.5 parts of catalyst, and 2.2 parts of molecular sieve desiccant; 70% of the end-capped isocyanate crosslinking agent is encapsulated in hydrophobic microcapsules. The hydrophobic microcapsules have end-capped isocyanate as the core material and hydrophobic polyurea as the wall material. The microcapsule particle size is 50 μm, the wall thickness is 3 μm, and the water vapor permeability of the wall material is less than 0.1 g / (m²·day). The molecular sieve desiccant is a type 3A molecular sieve micro powder with a pore size of 0.35 nm and a particle size of 3 μm. After activation at 300°C for 4 hours, its water absorption capacity is 22% of its own mass. 80% of the catalyst is protected by chelation, forming chelates with organobismuth catalysts through β-diketone ligands.

[0022] The high molecular polymer is selected from styrene-butadiene-styrene block copolymer with a molecular weight of 200,000; the organic amine accelerator is selected from aliphatic polyamine with a functionality of 3; the modified resin is selected from petroleum resin with a softening point of 110℃.

[0023] The end-capping isocyanate crosslinking agent is selected from the trimer of toluene diisocyanate, and the end-capping agent is used for end-capping. The end-capping agent removal temperature is 90°C. The styrene content of the SEBS elastomer is 28%.

[0024] The hydrophobic microcapsules were prepared by interfacial polymerization. The wall material monomers were toluene diisocyanate and hydrophobic polyether polyol. They were reacted in an oil-in-water emulsion system at 60°C for 2 hours to form a polyurea-polyurethane copolymer wall material. The hydrophobic microcapsules had a coverage rate of more than 95% and a core material content of 38%.

[0025] The chelated protected catalyst was prepared by reacting an organic bismuth catalyst with β-diketone ligand acetylacetone at a molar ratio of 1:3 at 80°C for 1 hour to form a chelate.

[0026] Example 2 The difference between this embodiment and Embodiment 1 is that the high-viscosity cold-mix asphalt additive is composed of the following components in parts by mass: 30 parts of high molecular weight polymer, 10 parts of organic amine accelerator, 20 parts of modified resin, 5 parts of end-capped isocyanate crosslinking agent, 8 parts of SEBS elastomer, 0.3 parts of catalyst, and 1.5 parts of molecular sieve desiccant; 60% of the terminated isocyanate crosslinking agent is encapsulated in hydrophobic microcapsules. The hydrophobic microcapsules have terminated isocyanate as the core material and polyurethane as the wall material. The microcapsule particle size is 20 μm and the wall thickness is 2 μm. The molecular sieve desiccant is a type 4A molecular sieve micro powder with a pore size of 0.3 nm and a particle size of 1 μm. After activation at 300℃ for 4 hours, its water absorption capacity is 20% of its own mass. 70% of the catalyst is protected by chelation, forming chelates with organozinc catalysts via β-diketone ligands.

[0027] Preferably, the polymer is selected from ethylene-vinyl acetate copolymer with a molecular weight of 100,000; the organic amine accelerator is selected from aromatic amine compounds with a functionality of 2; and the modified resin is selected from phenolic resin with a softening point of 80°C.

[0028] The isocyanate crosslinking agent is selected from the trimer of hexamethylene diisocyanate, and caprolactam-based end-capping agent is used for end-capping. The end-capping agent removal temperature is 60°C. The styrene content of the SEBS elastomer is 20%.

[0029] The hydrophobic microcapsules were prepared by interfacial polymerization. The wall material monomers were toluene diisocyanate and hydrophobic polyether polyol. They were reacted in an oil-in-water emulsion system at 55°C for 1.5 hours to form a polyurea-polyurethane copolymer wall material. The hydrophobic microcapsules had a coverage rate of more than 95% and a core material content of 60%.

[0030] The chelated protected catalyst was prepared by reacting an organozinc catalyst with β-diketone ligand acetylacetone at a molar ratio of 1:2 at 75°C for 0.5 hours to form a chelate.

[0031] Example 3 The difference between this embodiment and Embodiment 1 is that the high-viscosity cold-mix asphalt additive is composed of the following components in parts by mass: 50 parts of high molecular polymer, 20 parts of organic amine accelerator, 40 parts of modified resin, 10 parts of end-capped isocyanate crosslinking agent, 15 parts of SEBS elastomer, 0.8 parts of catalyst, and 3 parts of molecular sieve desiccant. 80% of the end-capped isocyanate crosslinking agent is encapsulated in hydrophobic microcapsules. The hydrophobic microcapsules have end-capped isocyanate as the core material and hydrophobic polyurea as the wall material. The microcapsule particle size is 80 μm and the wall thickness is 5 μm. The molecular sieve desiccant is a type 3A molecular sieve micro powder with a pore size of 0.4 nm and a particle size of 5 μm. After activation at 300℃ for 4 hours, its water absorption capacity is 25% of its own mass. 90% of the catalyst is protected by chelation, and the catalyst is loaded onto nano-silica that has been hydrophobically treated with a silane coupling agent.

[0032] Preferably, the polymer has a molecular weight of 300,000; the organic amine accelerator has a functionality of 4; and the modified resin is selected from a combination of petroleum resin, phenolic resin, and rosin resin, with a softening point of 140°C.

[0033] The isocyanate crosslinking agent used is a butanone oxime-based end-capping agent, and the end-capping agent removal temperature is 120°C; the styrene content of the SEBS elastomer is 35%.

[0034] The hydrophobic microcapsules were prepared by interfacial polymerization. The wall material monomers were toluene diisocyanate and hydrophobic polyether polyol. They were reacted in an oil-in-water emulsion system at 65°C for 2.5 hours to form a polyurea-polyurethane copolymer wall material. The hydrophobic microcapsules had a coverage rate of more than 95% and a core material content of 75%.

[0035] The chelated protected catalyst was prepared by loading the catalyst onto nano-silica that had been hydrophobically treated with methyltrimethoxysilane, with a catalyst loading of 15-25%.

[0036] Example 4 This embodiment presents a method for preparing a high-viscosity cold-mix asphalt additive, comprising the following steps performed sequentially: Step 1: Preparation of hydrophobic microcapsule-encapsulated end-capsulated isocyanate: End-capsulated isocyanate and hydrophobic solvent are mixed at a mass ratio of 1:0.2. Toluene diisocyanate, a wall material monomer, and hydrophobic polyether polyol are added, with a mass ratio of 100 parts end-capsulated isocyanate, 12 parts toluene diisocyanate, and 9 parts hydrophobic polyether polyol, to obtain an oil phase. The oil phase is added dropwise to an aqueous phase containing a water-soluble emulsifier, and the stirring speed is controlled at 1200 rpm to form an oil-in-water emulsion. The mixture is heated to 60°C for interfacial polymerization for 2 hours. After cooling, it is filtered and separated, washed, and dried to obtain hydrophobic microcapsule-encapsulated end-capsulated isocyanate. Step 2, Activation of molecular sieve desiccant: Heat the 3A type molecular sieve micro powder from room temperature to 300℃ at a heating rate of 8℃ / min, maintain the activation at 300℃ for 4 hours, cool to room temperature under dry nitrogen protection, and store in a sealed container; Step 3, preparation of chelated protective catalyst: The organic bismuth catalyst and acetylacetone were reacted at 80°C for 1 hour under nitrogen protection in a molar ratio of 1:3. Excess ligands and solvents were removed by vacuum distillation to obtain the β-diketone chelating catalyst. Step 4, compound preparation of additives: In an environment with relative humidity less than 30% and nitrogen protection, the polymer is melt-mixed at 110°C, SEBS elastomer is added for high shear dispersion, modified resin is added and mixed evenly, and after cooling to 85°C, non-encapsulated end-capped isocyanate crosslinking agent, hydrophobic microcapsule encapsulation crosslinking agent, activated molecular sieve powder, organic amine promoter, chelated protective catalyst and non-protected catalyst are added in sequence, mixed evenly and cooled to room temperature, and then packaged and sealed.

[0037] In step one, the volume ratio of oil phase to water phase is 1:3, the preferred interfacial polymerization reaction temperature is 60℃, the preferred reaction time is 2 hours, and after the reaction, the wall material is kept at 60℃ for 0.8 hours to fully cure; the water-soluble emulsifier is selected from polyvinyl alcohol, and the amount used is 1% of the mass of deionized water.

[0038] In step two, after the molecular sieve is activated, it is taken out when cooled to 90°C and quickly transferred to a sealed container equipped with dry nitrogen protection to continue cooling to room temperature. The relative humidity of the sealed storage environment is less than 10%; the residual moisture content of the activated molecular sieve is less than 0.5%.

[0039] In step four, when adding SEBS elastomer at 110℃, the stirring speed is increased to 180 rpm, and a high-shear dispersion device is used for mixing for 30 minutes; when adding hydrophobic microcapsule-coated crosslinking agent, the stirring speed is controlled to be less than 100 rpm, and the mixture is mixed for 18 minutes; the addition time of activated molecular sieve powder is less than 10 minutes; the chelated protective catalyst is added last, and the mixing time is less than 20 minutes.

[0040] Example 5 The difference between this embodiment and embodiment 4 is that: End-capped isocyanate and hydrophobic solvent were mixed at a mass ratio of 1:0.1. Toluene diisocyanate, a wall material monomer, and hydrophobic polyether polyol were added, with a mass ratio of 100 parts end-capped isocyanate, 8 parts toluene diisocyanate, and 6 parts hydrophobic polyether polyol, to obtain an oil phase. The oil phase was then added dropwise to an aqueous phase containing a water-soluble emulsifier, and the stirring speed was controlled at 800 rpm to form an oil-in-water emulsion. The mixture was then heated to 55°C for interfacial polymerization for 1.5 hours. The 4A type molecular sieve micro powder was heated from room temperature to 300℃ at a heating rate of 5℃ / min and kept at 300℃ for 4 hours to activate it. The organozinc catalyst was reacted with acetylacetone at a molar ratio of 1:2 under nitrogen protection at 75°C for 0.5 hours. Excess ligands and solvent were removed by vacuum distillation to obtain the β-diketone chelating catalyst. In an environment with relative humidity less than 30% and nitrogen protection, the polymer was melt-mixed at 100°C, SEBS elastomer was added for high-shear dispersion, modified resin was added and mixed evenly, and after cooling to 80°C, non-encapsulated isocyanate crosslinking agent, hydrophobic microcapsule encapsulation crosslinking agent, activated molecular sieve powder, organic amine promoter, chelated protective catalyst and non-protected catalyst were added in sequence.

[0041] The volume ratio of the oil phase to the water phase is 1:2. After the reaction, the wall material is kept at 60°C for 0.5 hours to fully cure. The water-soluble emulsifier is selected from sodium dodecyl sulfate and the amount used is 0.5% of the mass of deionized water.

[0042] The molecular sieve is removed after activation and cooling to 80°C.

[0043] When adding SEBS elastomer at 100℃, the stirring speed was increased to 150 rpm, and the mixture was mixed for 30 minutes using a high-shear dispersion device; when adding hydrophobic microcapsule-coated crosslinking agent, the stirring speed was controlled to be less than 100 rpm, and the mixture was mixed for 15 minutes.

[0044] Example 6 The difference between this embodiment and embodiment 4 is that: End-capped isocyanate and hydrophobic solvent were mixed at a mass ratio of 1:0.3. Toluene diisocyanate, a wall material monomer, and hydrophobic polyether polyol were added, with a mass ratio of 100 parts end-capped isocyanate, 15 parts toluene diisocyanate, and 12 parts hydrophobic polyether polyol, to obtain an oil phase. The oil phase was then added dropwise to an aqueous phase containing a water-soluble emulsifier, and the stirring speed was controlled at 1500 rpm to form an oil-in-water emulsion. The mixture was then heated to 65°C for interfacial polymerization for 2.5 hours. The molecular sieve powder was heated from room temperature to 300℃ at a rate of 10℃ / min and kept at 300℃ for 4 hours to activate it. The catalyst was loaded onto hydrophobically treated nano-silica and dried to obtain the supported catalyst. In an environment with relative humidity less than 30% and nitrogen protection, the polymer was melt-mixed at 120°C, SEBS elastomer was added for high-shear dispersion, modified resin was added and mixed evenly, and after cooling to 90°C, non-encapsulated end-capped isocyanate crosslinking agent, hydrophobic microcapsule encapsulation crosslinking agent, activated molecular sieve powder, organic amine promoter, chelated protective catalyst and non-protected catalyst were added in sequence.

[0045] The volume ratio of oil phase to water phase is 1:4, the preferred interfacial polymerization reaction temperature is 60℃, the reaction time is 2 hours, and after the reaction, the wall material is kept at 60℃ for 1 hour to fully cure; the water-soluble emulsifier is selected from polyvinyl alcohol, sodium dodecyl sulfate or a combination thereof, and the amount used is 2% of the mass of deionized water.

[0046] The molecular sieve is taken out after activation and cooling to 100°C.

[0047] When adding SEBS elastomer at 100-120℃, increase the stirring speed to 200 rpm and mix for 30 minutes using a high-shear dispersion device; when adding hydrophobic microcapsule-coated crosslinking agent, control the stirring speed to less than 100 rpm and mix for 20 minutes.

[0048] Example 7 This embodiment proposes a method for preparing a high-viscosity cold-mix asphalt additive, which includes the following specific implementation steps: This additive is composed of the following components in the following mass ratios: 35 parts of polymer, 15 parts of organic amine accelerator, 30 parts of modified resin, 5 parts of end-capped isocyanate crosslinking agent, 12 parts of SEBS elastomer, 0.6 parts of catalyst, and 2.4 parts of molecular sieve desiccant, with a total mass ratio of 100 parts. 70% of the end-capped isocyanate crosslinking agent is encapsulated in hydrophobic microcapsules, and 80% of the catalyst is chelated for protection. The preparation method includes the following four steps performed sequentially: Step 1: Preparation of hydrophobic microcapsules encapsulating end-capped isocyanates This step involves encapsulating end-capped isocyanates in hydrophobic polyurea or polyurethane microcapsules via interfacial polymerization to form a physical barrier layer that prevents moisture from contacting the isocyanate groups. Compared with existing technologies, the differences in this step are: (1) using hydrophobic polyurea / polyurethane as the wall material instead of ordinary polymer materials, with a water vapor permeability of <0.1g / (m²·day), exhibiting extremely low water permeability; (2) protecting the crosslinking agent during storage and transportation, and rupturing and releasing under the mechanical shearing action of mixing and compaction, achieving "encapsulation protection - release on demand"; (3) precisely controlling the microcapsule particle size (20-80μm) and wall thickness (2-5μm) by controlling the interfacial polymerization reaction conditions, thus balancing the hydrolysis resistance and release performance.

[0049] Specific implementation process: (1) Preparation of aqueous phase: Weigh 0.5-2% (preferably 1%) of water-soluble emulsifier by mass of deionized water, dissolve it in deionized water, and stir until completely dissolved to obtain an aqueous phase solution. The water-soluble emulsifier is selected from polyvinyl alcohol, sodium dodecyl sulfate or a combination thereof, preferably polyvinyl alcohol (degree of polymerization 1700-1800, degree of alcoholysis 87-89%) and sodium dodecyl sulfate in a mass ratio of 3:1, which has a better synergistic emulsification effect and high emulsion stability.

[0050] (2) Preparation of oil phase: The capped isocyanate (core material) and a small amount of hydrophobic solvent are mixed at a mass ratio of 1:0.1-0.3 (preferably 1:0.2) to adjust the viscosity of the oil phase for easy emulsification; the wall material monomer toluene diisocyanate and hydrophobic polyether polyol are added, with a mass ratio of 100 parts of capped isocyanate, 8-15 parts of toluene diisocyanate (preferably 12 parts), and 6-12 parts of hydrophobic polyether polyol (preferably 9 parts), and stirred evenly to obtain the oil phase. The terminating isocyanate is preferably a trimer of toluene diisocyanate termin ...

[0051] (3) Emulsion preparation: In a reactor equipped with a mechanical stirrer, the oil phase is slowly added dropwise to the aqueous phase, and the stirring speed is controlled at 800-1500 rpm (preferably 1200 rpm) to form an oil-in-water (O / W) emulsion. The volume ratio of the oil phase to the aqueous phase is controlled at 1:2 to 1:4 (preferably 1:3), and the emulsification time is 15-30 minutes (preferably 20 minutes) to obtain a uniform emulsion with an oil droplet size of 20-80 μm (preferably 40-60 μm). The dropping rate is controlled at 2-5 mL / min; too fast a rate will result in uneven oil droplet size.

[0052] (4) Interfacial polymerization reaction: While maintaining stirring, heat the reactor to 55-65℃, preferably 60℃. Control the heating rate at 2-5℃ / min (preferably 3℃ / min) to avoid sudden heating that could lead to excessively rapid local reactions. At the oil droplet interface, the isocyanate groups of toluene diisocyanate react with the hydroxyl groups of the polyether polyol to form polyurethane. Simultaneously, the isocyanate groups react with trace amounts of water in the aqueous phase or active hydrogen on the emulsifier to form urea bonds, forming a polyurea-polyurethane copolymer wall material in situ on the oil droplet surface. The reaction time is 1.5-2.5 hours (preferably 2 hours), and the wall material gradually thickens to 2-5 μm (preferably 3-4 μm). During the reaction, maintain a stirring speed of 800-1200 rpm (preferably 1000 rpm) to ensure that the microcapsules are uniformly dispersed and do not aggregate.

[0053] (5) Curing and post-treatment: After the reaction, continue to keep warm at 60℃ for 0.5-1 hour (preferably 0.8 hours) to fully cure the wall material and improve its mechanical strength and density. Cool to room temperature (cooling rate controlled at 5-10℃ / min), and obtain microcapsules by filtration or centrifugation. Centrifugation is preferred (speed 3000-5000 rpm, preferably 4000 rpm, time 10-15 minutes) for better separation effect. Wash with deionized water 2-3 times (preferably 3 times) to remove residual emulsifier and unreacted monomers, and centrifuge after each wash. Vacuum dry at 60℃ for 4-6 hours (preferably 5 hours, vacuum degree 0.09-0.095MPa) until constant weight (the difference between two consecutive weighings <0.1% is considered constant weight) to obtain hydrophobic microcapsule-encapsulated isocyanate, which is a white to pale yellow powder or granules, for later use.

[0054] Step 2: Activate the molecular sieve desiccant This step activates 3A or 4A molecular sieve micropowder to make it a highly efficient selective desiccant, capturing free water and ambient humidity in the additive system and preventing isocyanate hydrolysis from a chemical perspective. Compared with the prior art, the differences in this step are: (1) 3A or 4A molecular sieves with a pore size of 0.3-0.4 nm are selected. Their pore size is slightly larger than the dynamic diameter of water molecules (0.28 nm) but smaller than the molecular size of asphalt components and organic additives, so as to achieve selective adsorption of water molecules without adsorbing other components, avoiding the non-selective reaction and corrosiveness of traditional chemical desiccants (such as calcium oxide and sodium sulfate); (2) High-temperature activation treatment at 300℃ is used to completely remove the pre-adsorbed water in the molecular sieve channels, so that the water absorption capacity reaches 20-25% of its own mass, which is significantly higher than that of conventional desiccants; (3) After activation, it is stored under dry nitrogen protection to prevent re-absorption of moisture and ensure that the desiccant is in the best active state when used.

[0055] Specific implementation process: (1) Molecular sieve selection: Select type 3A or type 4A molecular sieve (micro powder, particle size 1-5μm (preferably 2-3μm), specific surface area 600-800m² / g (preferably 700m² / g). Type 3A molecular sieve has a smaller pore size and higher selectivity, but a slightly slower water absorption rate; type 4A molecular sieve has a slightly larger pore size and a faster water absorption rate, but a slightly lower selectivity. Type 4A molecular sieve is preferred, as it achieves the best balance between water absorption rate and selectivity in cold-mix asphalt additive systems. Its pore size of 0.4nm can efficiently adsorb water molecules (kinetic diameter 0.28nm) and effectively exclude larger organic molecules, and its water absorption rate is 30-50% faster than that of type 3A. Depending on the application requirements, type 3A and type 4A can also be mixed at a mass ratio of 1:1 to balance high selectivity and rapid water absorption.

[0056] (2) Pretreatment: Place the molecular sieve powder in a stainless steel tray and spread it into a thin layer with a thickness of no more than 2 cm (preferably 1-1.5 cm) to ensure uniform heating. The tray is preferably made of 304 stainless steel, which is corrosion resistant and has uniform thermal conductivity. Place the tray in a forced-air drying oven or a muffle furnace. It is preferred to use a forced-air drying oven, which has higher temperature control accuracy (±2℃) and hot air circulation makes the heating more uniform.

[0057] (3) Activation by heating: Slowly increase the temperature from room temperature to 300℃, with the heating rate controlled at 5-10℃ / minute (preferably 8℃ / minute) to avoid damage to the molecular sieve framework structure or crystal cracking caused by sudden heating. Maintain a constant temperature after reaching 300℃. The reason for choosing 300℃ as the activation temperature is that this temperature is sufficient to remove the water adsorbed on the molecular sieve channels and surface (water has a boiling point of 100℃, but there is a capillary coagulation effect in the micropores, requiring a higher temperature for desorption), while not damaging the aluminosilicate framework structure of the molecular sieve (the molecular sieve framework only begins to decompose above 600-800℃). Too low a temperature (<250℃) will lead to incomplete desorption, while too high a temperature (>350℃) will not damage the framework but will increase energy consumption and may cause surface defects.

[0058] (4) Constant temperature activation: Maintain activation at 300℃ for 4 hours (preferably 4 hours). The activation time ensures complete desorption of water from the internal pores of the molecular sieve. If the activation time is too short (<3 hours), incomplete desorption will affect the subsequent water absorption capacity. If the activation time is too long (>5 hours), energy consumption will increase and crystal structure defects may occur. During the activation process, a small amount of dry air or nitrogen (flow rate 50-100 mL / min, preferably dry nitrogen) is introduced to promote the escape of water vapor and accelerate the desorption rate. Ventilation also helps to maintain a uniform atmosphere inside the furnace and avoid excessively high local water vapor concentration.

[0059] (5) Cooling and Storage: After activation, turn off the heating and allow the furnace to cool naturally to 80-100℃ (approximately 1-1.5 hours). Remove the tray and quickly transfer it to a sealed container or glove box equipped with dry nitrogen protection, and continue cooling to room temperature. The cooling process must be carried out in a dry nitrogen or inert atmosphere to prevent the activated molecular sieve from adsorbing moisture from the air (the activated molecular sieve has a very strong affinity for water and can adsorb 5-10% of its own mass of moisture within minutes of exposure to air). After cooling to room temperature, immediately seal and store in an aluminum foil bag or glass bottle with a relative humidity of <10%.

[0060] (6) Quality inspection: Take a small amount of activated molecular sieve and use thermogravimetric analysis (TGA) or Karl Fischer moisture determination to test the residual moisture content. It should be <0.5% (mass percentage); Water absorption capacity test: Expose the activated molecular sieve to a 100% relative humidity environment for 24 hours. The weight gain should reach 20-25% to verify the activation effect.

[0061] When to use: The activated molecular sieve should be removed before use and directly applied to subsequent compounding steps. The time from removing it from the sealed container to adding the additive should be less than 10 minutes to minimize exposure to air.

[0062] Step 3: Preparation of chelated protective catalyst This step modifies the organobismuth / zinc catalyst using chelation protection or support loading techniques to prevent the catalyst from hydrolyzing and deactivating in a humid environment, while maintaining its catalytic activity in a controllable manner.

[0063] Catalytic mechanism: The reaction of isocyanates with hydroxyl or amino groups catalyzed by organobismuth / zinc catalysts follows this mechanism: The metal center (Bi³⁺ or Zn²⁺) activates the carbon atoms in the isocyanate group through coordination, enhancing their electronegativity and making them more susceptible to nucleophilic attack from hydroxyl or amino groups; simultaneously, the metal center forms coordinate or hydrogen bonds with the active hydrogen atoms on the hydroxyl or amino groups, lowering the activation energy and accelerating the reaction. The specific reaction is as follows: (1) Isocyanates react with hydroxyl groups to form urethane bonds: R-NCO+R'-OH→R-NH-COO-R' (catalysts accelerate the reaction rate by 10-50 times) (2) Isocyanate reacts with amino groups to form urea bonds: R-NCO+R'-NH2→R-NH-CO-NH-R' (catalysts accelerate the reaction rate by 5-20 times) In humid environments, the metal-oxygen bonds or metal-carbon bonds of catalysts are prone to hydrolysis with water: M-OR + H2O → M-OH + ROH (M = Bi or Zn). The resulting metal hydroxides or oxides lose their catalytic activity, leading to a significant reduction in the crosslinking reaction rate.

[0064] Compared with the prior art, the differences in this step are: (1) β-diketone ligands (such as acetylacetone) are used to form chelates with the catalyst. The ligands form a stable six-membered ring chelate structure with the metal center through bidentate coordination. The hydrophobic organic groups of the ligands form a protective layer outside the metal center to prevent water molecules from contacting and hydrolyzing. This chelate structure can reversibly dissociate and release catalytic activity when exposed to high temperature (>60℃) or strong coordinating groups such as isocyanates; (2) The catalyst is loaded on nano-silica treated with silane coupling agent to prevent water from contacting the catalyst. At the same time, the nano-carrier provides a large specific surface area to make the catalyst highly dispersed and improve the catalytic efficiency; (3) Both methods achieve "protected storage-controlled release". The catalyst is protected during the storage period of the additive and in a humid environment. After the crosslinking reaction is started, the protective groups detach from the catalyst and restore activity.

[0065] Method 1: β-Diketone chelation protection method Specific implementation process: (1) Raw material preparation: Prepare an organobismuth catalyst or an organozinc catalyst with a purity >95%. The organobismuth catalyst is preferably bismuth octanoate Bi(Oct)3, which has high catalytic activity, low toxicity, and good compatibility with the system in the isocyanate-hydroxy / amino reaction, and its catalytic efficiency is better than that of bismuth neodecanoate; the organozinc catalyst is preferably zinc octanoate Zn(Oct)2, which has moderate catalytic activity and low cost. Considering catalytic efficiency, cost and safety, bismuth octanoate is preferred as the catalyst. Prepare β-diketone ligand acetylacetone (chemical formula CH3COCH2COCH3, molecular weight 100.12) with a purity >99%, preferably analytical grade (purity ≥99.5%). Acetylacetone contains two carbonyl groups, and the methylene hydrogen at the carbonyl α position is acidic (pKa about 9), which can form a stable six-membered ring chelate with metal ions.

[0066] (2) Molar ratio calculation: The molar ratio is determined based on the valence and coordination number of the metals in the catalyst. For trivalent bismuth Bi³⁺, theoretically it can coordinate with 3 acetylacetone molecules to form Bi(acac)3; for divalent zinc Zn²⁺, it can coordinate with 2 acetylacetone molecules to form Zn(acac)2. Considering the reaction equilibrium and the fact that excess ligands promote the chelation reaction, the actual molar ratio is selected as catalyst:acetylacetone = 1:2 to 1:4 (preferably 1:3). This ratio ensures that the chelation reaction proceeds fully (chelation rate > 85%) and avoids the difficulty in removing excess ligands.

[0067] (3) Chelation reaction: In a three-necked flask equipped with a reflux condenser and nitrogen protection, add an organobismuth or organozinc catalyst; add acetylacetone in a calculated molar ratio of 1:2-1:4 (preferably 1:3); add a small amount of anhydrous toluene or anhydrous ethanol as a solvent (solvent to catalyst mass ratio of approximately 1:1 to 2:1, preferably 1.5:1) to assist the reaction and dissolve the product. Anhydrous toluene is preferred as the solvent because its high boiling point (111℃) facilitates reflux, and it is also highly hydrophobic and compatible with the catalyst and ligands. Heat to 75-85℃ (preferably 80℃) under nitrogen protection and stir the reaction. During the reaction, the methylene hydrogen of the acetylacetone molecule is removed (pKa decreases at 80℃ and under the influence of the catalyst metal center), and two oxygen atoms in the form of negative ions (acac⁻) coordinate with the metal center, displacing the original carboxylate ligands (octanoate, neodecanoate) and releasing them into the solution. The reaction time is 0.5-1.5 hours (preferably 1 hour). At a reaction temperature of 80℃, chelation equilibrium can be reached in 1 hour (chelation rate >85%). The stirring speed should be controlled at 200-400 rpm (preferably 300 rpm) to ensure sufficient contact between the reactants.

[0068] (4) Product separation: After the reaction is complete, cool to room temperature (cooling rate 5-10℃ / min). Remove excess acetylacetone (boiling point 140℃) and solvent (toluene boiling point 111℃, ethanol boiling point 78℃) by vacuum distillation. The distillation temperature is controlled at 80-100℃ (preferably 90℃), the vacuum degree is 0.09-0.095MPa (gauge pressure, preferably 0.092MPa), and the distillation time is 1-2 hours (preferably 1.5 hours). The reason for choosing a distillation temperature of 80-100℃ is that acetylacetone and solvent can be effectively evaporated under reduced pressure at this temperature, while avoiding decomposition of the chelating catalyst by avoiding excessively high temperatures (chelates begin to decompose slowly above 120℃). After distillation, a yellow to orange viscous liquid or semi-solid is obtained, which is the β-diketone chelating catalyst. For further purification, wash 2-3 times with anhydrous hexane (1-2 times the mass of the crude product) to remove unreacted catalyst and free carboxylic acid. After each wash, allow the layers to stand or centrifuge (3000 rpm, 5 minutes) and take the lower layer of chelated catalyst phase.

[0069] (5) Structural characterization and quality control: FT-IR spectroscopy was used to detect the absorption peaks of the C=O stretching vibration of the chelate ring at 1520-1580 cm⁻¹ and the C=C stretching vibration at 1380-1420 cm⁻¹, proving the formation of the chelate structure; ¹H-NMR spectroscopy was used to detect the chemical shift of the methylene hydrogen of acetylacetone from δ3.5 ppm to δ5.5 ppm, proving coordination; ICP-OES determination of metal content: bismuth content 18-25% or zinc content 12-18%; chelation rate >85% (unchelated metal ions were determined by titration).

[0070] Step 4: Preparation of additives through compounding Crosslinking reaction pathway and mechanism: The additives undergo the following cross-linking reactions during subsequent mixing, paving, and compaction of asphalt: (1) Decapping of end groups: Under mechanical shearing at 60-120℃, the end groups (such as phenols and caprolactams) of the end-capped isocyanates are released, releasing active isocyanate groups: R-NCO-Cap→R-NCO+Cap↑ (Cap is the end-capping group). The microcapsules rupture under mechanical shearing, and the crosslinking agent in the core material is released to participate in the reaction.

[0071] (2) Catalyst activation: When the chelated protective catalyst is at >60℃ or encounters a strong isocyanate coordinating group, the chelate ligand dissociates and the metal center restores its catalytic activity: M(acac)n+R-NCO→M-NCO complex+nacac⁻ (M=Bi³⁺ or Zn²⁺, acac is an acetylacetone anion).

[0072] (3) Crosslinking reaction: Under the action of a catalyst, the active isocyanate groups react with the hydroxyl and amino groups in the system to form a three-dimensional network structure: - Reaction with hydroxyl groups in polymers and resins: R-NCO+HO-polymer → R-NH-COO-polymer (carbamate bond) - Reaction with amino groups in organic amine accelerators: R-NCO+H2N-accelerator → R-NH-CO-NH-accelerator (urea bond) - The multifunctionality of the crosslinking agent (NCO functionality ≥ 3) enables different polymer chains, resin molecules, and accelerator molecules to be crosslinked and connected through carbamate bonds or urea bonds to form a chemical crosslinking network.

[0073] (4) Molecular sieve dehumidification: The activated molecular sieve continuously adsorbs free water and ambient humidity in the system throughout the process, preventing isocyanate from reacting with water: R-NCO+H2O→R-NH2+CO2↑ (side reaction, the molecular sieve inhibits this reaction).

[0074] (5) Synergistic reinforcement: The chemical cross-linking network and the physical entanglement network of SEBS elastomer work together to provide resistance to deformation by restricting the movement of molecular chains at high temperatures and providing toughness and deformation capacity by providing soft segments of elastomer at low temperatures, forming a chemical-physical dual reinforcement network.

[0075] Specific implementation process: (1) Environmental preparation: The compounding operation shall be carried out in a dry environment with a relative humidity of <30% (preferably <20%). It can be carried out in a clean room equipped with a dehumidifier or in a glove box protected by dry nitrogen. It is preferred to carry out the operation in a clean room (cleanliness level 10,000) equipped with a dehumidifier (dehumidification capacity ≥50L / day) to ensure dryness and avoid the introduction of impurities. Prepare a planetary mixer or twin-screw extruder equipped with a mechanical stirrer, heating device, temperature control system (control accuracy ±2℃) and nitrogen protection interface. A planetary mixer (volume 20-100L, selected according to production scale) is preferred because it has good mixing uniformity, controllable shear force and is suitable for multi-component compounding.

[0076] (2) Preparation of feed ingredients: Weigh the following components according to the formula: 30-50 parts of polymer (based on a total formula of 100 parts, the same below, preferably 37 parts), 10-20 parts of organic amine accelerator (preferably 14 parts), 20-40 parts of modified resin (preferably 28 parts), 8-15 parts of SEBS elastomer (preferably 11 parts), 5-10 parts of end-capped isocyanate crosslinking agent (preferably 7.5 parts, of which 60-80% is microcapsule coated, preferably 70% i.e. 5.3 parts, and 20-40% is non-coated, preferably 30% i.e. 2.2 parts), 0.3-0.8 parts of catalyst (preferably 0.5 parts, of which 70-90% is chelated and protected, preferably 80% i.e. 0.4 parts, and 10-30% is non-protected, preferably 20% i.e. 0.1 parts), and 1.5-3 parts of activated molecular sieve powder (preferably 2 parts). The total preferred formulation of all components is 37 + 14 + 28 + 11 + 7.5 + 0.5 + 2 = 100 parts, which meets the normalization requirements. The preferred polymer is SBS (styrene content 30-32%, molecular weight approximately 150,000), which has better tackifying and high-temperature performance than EVA. The preferred organic amine accelerator is diethylenetriamine (DETA, functionality 3) or triethylenetetramine (TETA, functionality 4), which are liquid at room temperature, easy to add, and have good accelerating effects. The preferred modified resin is a mixture of C5 petroleum resin and phenolic resin in a 2:1 mass ratio, balancing tackifying and cross-linking reactivity. All components should be checked for packaging tightness before use and used immediately after opening.

[0077] (3) First stage - polymer melting and mixing: Add the polymer (preferably SBS) to the stirring container, start the heating system and heat to 100-120℃ (preferably 110℃), with the heating rate controlled at 5-10℃ / min (preferably 8℃ / min). At this temperature, the polymer melts into a viscous flow state (viscosity drops to 10). 4 -10 5 Start the stirrer at 50-80 rpm (preferably 65 rpm) and stir for 10-15 minutes (preferably 12 minutes) to ensure the polymer is fully melted and homogeneous. Visually inspect the melt for transparency, uniformity, and absence of particles. This stage should be carried out under nitrogen protection (nitrogen flow rate 100-200 mL / min) to prevent high-temperature oxidation, discoloration, or molecular chain breakage of the polymer.

[0078] (4) Second stage - Elastomer dispersion: Maintain the temperature at 100-120℃ (preferably 110℃) and add SEBS elastomer (preferably SEBS with 30% styrene content). The melting temperature of SEBS is 150-170℃. At 100-120℃, it is in a softened state but not completely melted, requiring dispersion by high shear force. Increase the stirring speed to 150-200 rpm (preferably 180 rpm) and use a high shear dispersion device (such as a high shear emulsifying head, shear rate 3000-5000 s⁻¹) to mix for 30 minutes (preferably 30 minutes) to fully disperse the SEBS elastomer in the polymer matrix and form a uniform two-phase blend. Microscopic observation (100x optical microscope) should not reveal SEBS agglomerates larger than 50 μm, preferably with a dispersed particle size of 10-30 μm. The dispersion effect affects the low-temperature toughness and elastic recovery performance.

[0079] (5) Third stage - Resin addition: Maintain the temperature at 100-120℃ (preferably 110℃), add the modified resin (preferably a blend of C5 petroleum resin and phenolic resin, with a softening point of 110-120℃, and completely melted at 110℃). Reduce the stirring speed to 80-100 rpm (preferably 90 rpm), and continue mixing for 20-30 minutes (preferably 25 minutes) to ensure the resin is uniformly dispersed in the polymer-elastomer matrix. In this stage, the resin forms partial compatibility with the polymer and elastomer, establishing a ternary blend system, and the matrix viscosity further increases to 10. 5 -10 6 Pa·s. When the mixing is complete, take a sample. The system should be a uniform pale yellow to yellow viscous liquid, without particles or stratification.

[0080] (6) Fourth stage - cooling and crosslinking agent addition: the temperature of the mixture is reduced to 80-90℃ (preferably 85℃) at a rate of 5-10℃ / min (preferably 8℃ / min). After the temperature drops to 80-90℃, add the following in sequence: ① Non-encapsulated isocyanate crosslinking agent (accounting for 20-40% of the total crosslinking agent, preferably 30%, preferably caprolactam-capsulated TDI trimer), add slowly to prevent local high concentration from causing local rapid reaction, add over 3-5 minutes (preferably 4 minutes), after adding, reduce the stirring speed to 60-80 rpm (preferably 70 rpm) and mix for 10 minutes to make the crosslinking agent uniformly dispersed; ② Hydrophobic microcapsule encapsulating crosslinking agent (accounting for 60-80% of the total crosslinking agent, preferably 70%, the product prepared in step one), the microcapsules are in powder or granular form, add in batches (3-5 batches, preferably 4 batches), add over 5-10 minutes (preferably 8 minutes), control the stirring speed <100 rpm (preferably 80 rpm) to avoid excessive shearing and damage to the microcapsule wall material, mix for 15-20 minutes (preferably 18 minutes) to make the microcapsules uniformly dispersed. The reason for controlling the temperature at 80-90℃ is that the decapping rate of the isocyanate end groups is relatively slow and the degree of decapping is limited at this temperature (the decapping rate constant of caprolactam end groups at 85℃ is about 0.01 min⁻¹, the decapping rate in 10 minutes is <10%, and the decapping temperature range of the end groups is 60-120℃, with large-scale decapping only occurring under the high temperature and mechanical action of mixing and compaction). At the same time, the system maintains sufficient fluidity (viscosity 10). 5 -10 6 Pa·s) facilitates mixing and subsequent pumping.

[0081] (7) Fifth stage - Molecular sieve addition: Maintain the temperature at 80-90℃ (preferably 85℃), quickly remove the activated molecular sieve powder (4A type molecular sieve prepared in step two) from the nitrogen-protected container, and immediately add it to the stirring container. The molecular sieve is in the form of fine powder with a density of about 2.0 g / cm³, which is easily airborne. It is added using a closed feeding method (such as a screw feeder) or through a feeding funnel under nitrogen protection. Immediately after adding the powder, increase the stirring speed to 120-150 rpm (preferably 135 rpm) and disperse it for 15-20 minutes (preferably 18 minutes) using a high-speed dispersion device (shear rate 2000-3000 s⁻¹) to ensure that the molecular sieve powder is evenly dispersed in the additive without agglomeration. The addition time of the molecular sieve is <10 minutes (from the opening of the sealed container to the completion of mixing, preferably <8 minutes) to minimize the time the molecular sieve is exposed to air (to avoid adsorbing moisture from the air, which would reduce its activity). The dispersion effect can be checked by microscopic observation; there should be no molecular sieve agglomerates larger than 10 μm.

[0082] (8) Sixth stage - Accelerator addition: Maintain the temperature at 80-90℃ (preferably 85℃), and add an organic amine accelerator (preferably diethylenetriamine DETA or triethylenetetramine TETA, which is a pale yellow liquid at room temperature with a viscosity of about 30-50 mPa·s). Add the accelerator slowly over a period of 3-5 minutes (preferably 4 minutes), while stirring at a speed of 80-100 rpm (preferably 90 rpm) and mixing for 10-15 minutes (preferably 12 minutes) to ensure uniform dispersion of the accelerator. After the accelerator is added, its amino group can react with a small amount of desealed isocyanate groups to form urea bonds (R-NCO+R'-NH2→R-NH-CO-NH-R'). However, due to the limited degree of desealing of the end-capping groups at 80-90℃ (desealing rate <10%, free NCO content <0.5%), and the fact that the reaction rate constant between the accelerator's amino group and isocyanate at 85℃ is about 0.1L / (mol·min), the degree of pre-reaction is low (pre-crosslinking degree <3%) under short time (12 minutes) and low NCO concentration conditions. This does not affect the product's flowability (viscosity is still in the range of 20-100 Pa·s) and subsequent crosslinking performance (crosslinking activity retention rate >95%).

[0083] (9) Seventh stage - catalyst addition: Maintain the temperature at 80-90℃ (preferably 85℃) and add the catalyst last. First, add the chelated protective catalyst or supported catalyst (accounting for 70-90% of the total catalyst, preferably 80%, which is the bismuth octoate chelated catalyst or bismuth octoate supported catalyst prepared in step three), in liquid, semi-solid or powder form (chelated catalyst is a yellow viscous liquid, supported catalyst is a yellow powder), add slowly, with a feeding time of 2-3 minutes (preferably 2.5 minutes), stirring speed of 60-80 rpm (preferably 70 rpm), and mix for 5-10 minutes (preferably 8 minutes); then add a small amount of unprotected catalyst (accounting for 10-30% of the total catalyst, preferably 20%, which is bismuth octoate raw material), with a feeding time of 1-2 minutes (preferably 1.5 minutes), and mix for 5-10 minutes (preferably 8 minutes). The catalyst is added last because it catalyzes the reaction between isocyanates and hydroxyl / amino groups (increasing the catalytic rate constant by 10-50 times). Adding it too early would lead to excessive cross-linking during the compounding process, affecting product flowability and storage stability. The chelated protective catalyst's catalytic activity is not fully released at 80-90℃ (the chelate is stable at <60℃, but partially dissociates at 80-90℃, with catalytic activity only 10-20% of fully activated). Combined with limited decapping of the end groups (decapping rate <10%) and short mixing time (<20 minutes), the pre-cross-linking degree is <5% (gel time test shows that the gel time of the mixed product is still >100 hours when stored at 25℃), ensuring good pumpability. After uniform mixing, the viscosity should be within the pumpable range (20-100 Pa·s, preferably 40-60 Pa·s, measured at 25℃).

[0084] (10) Cooling and Packaging: Turn off the heating and allow the product to cool naturally or in a water bath to 40-50°C (preferably 45°C) under nitrogen protection (nitrogen flow rate 100-200 mL / min), then cool to room temperature (20-30°C, preferably 25°C). Once qualified, immediately transfer the product to aluminum foil bags, tin cans, or plastic drums under dry nitrogen or dry air protection (dew point temperature < -40°C) and seal the packaging.

[0085] Experimental verification Experiment 1: Test of hydrolysis resistance and crosslinking efficiency under humid conditions 1. Experimental Objective The protective effect of the triple anti-hydrolysis protection system (hydrophobic microcapsule encapsulation + molecular sieve dehumidification + chelation protection of catalyst) of the present invention on crosslinking agents and catalysts under different relative humidity environments was verified. It was demonstrated that the crosslinking efficiency of the additive can be maintained at more than 85% in a dry environment under a relative humidity of 90%, thus confirming the inhibitory effect of the triple protection system on the hydrolytic deactivation of isocyanate crosslinking agents and catalysts.

[0086] 2. Preparation of experimental samples According to the formulation and preparation method of this embodiment, the following three additive samples were prepared: Sample A (Sample of this invention): A complete formulation containing a triple anti-hydrolysis protection system, consisting of 37 parts of polymer, 14 parts of organic amine accelerator, 28 parts of modified resin, 11 parts of SEBS elastomer, 7.5 parts of end-capped isocyanate crosslinking agent (70% of which is in the form of hydrophobic microcapsule coating), 0.5 parts of catalyst (80% of which is in the form of chelation protection), and 2 parts of activated molecular sieve powder.

[0087] Sample B (partial protection comparison sample): contains only molecular sieve desiccant, without microcapsule encapsulation crosslinking agent and chelation protective catalyst, and other components and preparation process are the same as Sample A.

[0088] Sample C (unprotected control sample): It does not contain any hydrolysis protection measures, uses ordinary end-capped isocyanate crosslinking agent and ordinary catalyst, and does not contain microcapsules, molecular sieves and chelation protection. Other components and preparation process are the same as those of sample A.

[0089] The three samples were mixed with No. 70 road petroleum asphalt at a ratio of 6% (by mass) and subjected to high-speed shear mixing at 80°C for 30 minutes to obtain modified asphalt samples A1, B1, and C1.

[0090] 3. Experimental conditions Test environment: A constant temperature and humidity chamber was used to control different relative humidity environments. The temperature was set at 25℃, and the relative humidity was set at 30% (dry environment control), 60% (medium humidity), 75% (high humidity), and 90% (high humidity). The samples were placed under each humidity condition for 24 hours before testing.

[0091] Testing equipment: Fourier transform infrared spectroscopy (FT-IR) was used to determine the NCO residue content, dynamic shear rheometer (DSR) was used to determine the crosslinking density, and gel permeation chromatography (GPC) was used to determine the crosslinking network structure.

[0092] 4. Experimental Procedure (1) Sample pretreatment: The prepared modified asphalt samples A1, B1 and C1 were coated on polytetrafluoroethylene plates to make thin film samples with a thickness of 2 mm. Twelve parallel samples were prepared for each sample (4 humidity conditions × 3 parallel samples).

[0093] (2) Humidity exposure: The film samples were placed in constant temperature and humidity chambers with relative humidity of 30%, 60%, 75% and 90%, respectively, and the temperature was maintained at 25℃ for 24 hours.

[0094] (3) Crosslinking curing: After 24 hours of humidity exposure, the sample was taken out and immediately cured in a 60℃ oven for 48 hours to simulate the crosslinking curing process after actual construction.

[0095] (4) Determination of residual isocyanate content: The intensity of the characteristic absorption peak (2270 cm⁻¹) of the isocyanate group (NCO) was measured by FT-IR after curing. The lower the residual NCO content, the more complete the crosslinking reaction. The NCO conversion rate was calculated as (initial NCO peak intensity - residual NCO peak intensity) / initial NCO peak intensity × 100%.

[0096] (5) Crosslinking density determination: The crosslinking density was determined by swelling method combined with the Flory-Rehner equation. The cured sample was swollen in toluene until equilibrium (72 hours), the swelling ratio Q was determined, and the crosslinking density was calculated according to the formula, where is the polymer volume fraction at swelling equilibrium, is the solvent molar volume, and is the Flory-Huggins action parameter.

[0097] (6) Gel content determination: Soxhlet extraction method was used. The solidified sample was refluxed in toluene for 24 hours. After extraction, the sample was vacuum dried to constant weight. Gel content = (mass after extraction / mass before extraction) × 100%. Gel content reflects the integrity of the cross-linked network.

[0098] (7) Gel time determination: Under the same humidity conditions, the modified asphalt sample was coated into a thin layer on a 60℃ constant temperature plate. Every 5 minutes, the sample surface was touched with a glass rod, and the time it took for the sample to change from a flowing state to a non-flowing gel state was recorded. The shorter the gel time, the faster the crosslinking rate.

[0099] (8) Crosslinking efficiency calculation: Based on the crosslinking density of each sample under a relative humidity of 30% (dry environment) (defined as 100%), the relative crosslinking efficiency under other humidity conditions is calculated as (crosslinking density under this humidity / crosslinking density under 30% humidity) × 100%.

[0100] 5. Experimental Results Table 1. Crosslinking performance parameters of three samples under different relative humidity conditions.

[0101] Note: The relative crosslinking efficiency is calculated based on the crosslinking density of each sample under 30% relative humidity (100%).

[0102] Figure 1 Comparison of relative crosslinking efficiency of three samples under different relative humidity conditions.

[0103] 6. Analysis and Summary (1) Significantly improved hydrolysis resistance: From Table 1 and Figure 1 As can be seen, under high humidity conditions of 90% relative humidity, the relative crosslinking efficiency of sample A (the present invention) is 87.0%, significantly higher than the design target of 85%, while that of sample B (partially protected) is only 54.9%, and that of sample C (unprotected) drops even further to 32.7%. This fully demonstrates the synergistic effect of the triple anti-hydrolysis protection system. Hydrophobic microcapsule encapsulation, molecular sieve dehumidification, and chelation protection of the catalyst are all indispensable. Single or partial protection measures are difficult to maintain stable crosslinking efficiency under high humidity conditions.

[0104] (2) High crosslinking density retention rate: During the process of increasing the relative humidity from 30% to 90%, the crosslinking density of sample A increased from 3.85 × 10⁻⁶. -4 The mol / cm³ decreased only to 3.35 × 10⁻⁶. -4 The crosslinking density of sample C decreased by only 13.0% from mol / cm³; while the crosslinking density of sample C decreased from 3.52×10 -4 The mol / cm³ decreased significantly to 1.15×10 -4 The decrease of 67.3% in mol / cm³ indicates that the isocyanate crosslinking agent and catalyst underwent severe hydrolysis and deactivation under unprotected conditions.

[0105] (3) Changes in gel time and gel content: Sample A gelled for 48 minutes at 90% humidity, only 13 minutes longer than 35 minutes at 30% humidity, and the gel content decreased from 94.2% to 89.7%; while Sample C gelled for more than 180 minutes at 90% humidity, and the gel content decreased to 52.8%, indicating that the crosslinking reaction was severely hindered and the crosslinking network was incomplete. This further verifies that the triple anti-hydrolysis protection system can effectively protect the isocyanate crosslinking agent and catalyst, maintaining a fast crosslinking rate and high crosslinking integrity in a humid environment.

[0106] (4) NCO conversion rate analysis: Sample A still achieved an NCO conversion rate of 88.3% at 90% humidity, indicating that most of the isocyanate groups participated in the cross-linking reaction rather than the hydrolysis reaction; Sample C had an NCO conversion rate of only 48.5%, which means that more than 50% of the NCO groups were deactivated due to hydrolysis, resulting in a significant reduction in the effective content of the cross-linking agent.

[0107] Experiment 2: Rheological Properties and Low-Temperature Toughness Testing of Chemical-Physical Dual-Reinforcement Networks 1. Experimental Objective The performance advantages of the chemical-physical dual reinforcement network constructed by the present invention through multi-component synergistic thickening and chemical cross-linking toughening are verified. It is demonstrated that the additive increases the dynamic viscosity of asphalt at 60℃ by 180-220%, increases the softening point by 15-18℃, maintains the ductility at -10℃ above 100cm, and achieves an elastic recovery rate of over 75%, thus confirming the significant improvement of the dual reinforcement network in terms of high-temperature deformation resistance and low-temperature toughness.

[0108] 2. Preparation of experimental samples According to the formulation and preparation method of this embodiment, the following four additive samples were prepared: Sample D (Sample of this invention): Complete formulation, containing a basic thickening system (37 parts of polymer, 14 parts of organic amine accelerator, and 28 parts of modified resin) + a crosslinking toughening system (11 parts of SEBS elastomer, 7.5 parts of end-capped isocyanate crosslinking agent, and 0.5 parts of catalyst) + an anti-hydrolysis protection system (70% of microencapsulation crosslinking agent, 80% of chelation protection catalyst, and 2 parts of activated molecular sieve).

[0109] Sample E (physical blend comparison sample only): Contains only the basic tackifying system and SEBS elastomer, without crosslinking agents or catalysts. Tackification and toughening are achieved through physical blending. The components are 48.5 parts of polymer, 14 parts of organic amine accelerator, 28 parts of modified resin, and 9.5 parts of SEBS elastomer.

[0110] Sample F (chemical crosslinking comparison sample only): Contains basic tackifying system and crosslinking agent / catalyst, but does not contain SEBS elastomer. The components are: 45 parts polymer, 14 parts organic amine accelerator, 28 parts modified resin, 10.5 parts end-capped isocyanate crosslinking agent, 0.5 parts catalyst, and 2 parts activated molecular sieve.

[0111] Sample G (Basic Comparative Sample): Contains only the basic tackifying system, without crosslinking agents, catalysts, or SEBS elastomer. The components are 50 parts of polymer, 20 parts of organic amine accelerator, and 30 parts of modified resin.

[0112] Four samples were mixed with No. 70 road petroleum asphalt at a ratio of 6% (by mass) and subjected to high-speed shear mixing at 80°C for 30 minutes to obtain modified asphalt samples D1, E1, F1, and G1, as well as a pure asphalt blank sample H. All samples were tested after curing in a 60°C oven for 48 hours.

[0113] 3. Experimental conditions Testing equipment: Dynamic shear rheometer (DSR) for determining dynamic viscosity and complex modulus, automatic softening point tester (ring and ball method) for determining softening point, low temperature ductility tester for determining ductility, and elastic recovery tester for determining elastic recovery rate.

[0114] Test temperatures: High-temperature rheological properties test temperature 60℃ (simulating high-temperature road surface in summer), low-temperature toughness test temperature -10℃ (simulating low-temperature environment in winter).

[0115] Testing standards: The tests shall be conducted in accordance with the industry standard JTGE20 of the Ministry of Transport of China, "Test Procedures for Asphalt and Asphalt Mixtures in Highway Engineering".

[0116] 4. Experimental Procedure (1) Dynamic viscosity test: The dynamic viscosity of each sample was determined by DSR at 60℃ and 10rad / s angular frequency. Each sample was tested 3 times and the average value was taken. The viscosity increase rate was calculated as (modified asphalt viscosity - pure asphalt viscosity) / pure asphalt viscosity × 100%.

[0117] (2) Complex modulus test: DSR was used to perform frequency scanning (0.1-100 rad / s) at 60℃ to determine the complex shear modulus and phase angle, and to analyze the viscoelastic properties of the material.

[0118] (3) Softening point test: The softening point was determined using the ring and ball method, with a heating rate of 5℃ / minute, and the temperature of the steel ball when it fell was recorded. The softening point reflects the high-temperature stability of the material.

[0119] (4) Rutting factor test: The rutting factor (60℃, 10rad / s) is calculated based on the DSR test results. The higher the parameter, the better the high temperature rutting resistance.

[0120] (5) Low temperature ductility test: In a water bath at -10℃, the ductility (length stretched to breakage) of the sample is measured at a stretching rate of 5cm / min. The greater the ductility, the better the low temperature toughness.

[0121] (6) Elastic recovery test: In a 10℃ water bath, stretch the sample to 20cm and hold for 5 minutes, then cut it off. Record the length of the sample shrinkage after 1 hour, and calculate the elastic recovery rate = (20cm - residual length) / 20cm × 100%.

[0122] (7) Storage modulus and loss modulus test: The storage modulus (elastic response) and loss modulus (viscous response) were measured by DSR at -10℃ and 10rad / s to analyze the low-temperature viscoelastic properties of the material.

[0123] 5. Experimental Results Table 2. High-temperature rheological properties and low-temperature toughness parameters of different samples

[0124] Note: The viscosity increase rate is calculated based on pure asphalt sample H.

[0125] Table 3 Viscoelastic properties of different samples at 60℃ and -10℃

[0126] Note: The smaller the phase angle, the higher the elastic component, and the smaller the phase angle, the higher the elastic ratio.

[0127] Figure 2 Comparison of dynamic viscosity of different samples at 60℃; Figure 3 : Viscosity increase relative to pure asphalt; Figure 4 Radar charts showing the combined high and low temperature performance of different samples; Figure 5 Comparison of low-temperature ductility and elastic recovery of different samples.

[0128] 6. Analysis and Summary (1) Significantly improved dynamic viscosity: As shown in Table 2, the dynamic viscosity of sample D (the present invention) reached 685 Pa·s at 60℃, which is 214% higher than that of pure asphalt (218 Pa·s), falling within the target range of 180-220%. In contrast, sample G (basic viscosity enhancement) only increased by 127%, sample E (physical blending) by 161%, and sample F (chemical crosslinking) by 181%. This demonstrates the dual enhancement effect of multi-component synergistic viscosity enhancement and chemical crosslinking toughening, and the viscosity improvement produced by the synergistic effect of the two far exceeds that of a single mechanism.

[0129] (2) Significantly enhanced high-temperature stability: The softening point of sample D reached 66.3℃, which is 17.8℃ higher than that of pure asphalt (48.5℃), meeting the target range of 15-18℃. The rutting factor increased from 1.82kPa in pure asphalt to 4.78kPa, an increase of 163%, indicating a significant enhancement in high-temperature deformation resistance. The cross-linking points formed by the chemical cross-linking network at high temperatures effectively restrict the movement of molecular chains and prevent flow deformation, while the hard segments (styrene blocks) of the SEBS elastomer provide additional physical cross-linking points. The two work synergistically to construct a chemical-physical dual-reinforcement network.

[0130] (3) Excellent low-temperature toughness: Sample D achieved a ductility of 115 cm at -10℃, far exceeding the target value of 100 cm, while the ductility of sample F, which only contains chemical crosslinking, was only 42 cm. This fully demonstrates the key role of SEBS elastomer in low-temperature toughness. The soft segments (ethylene-butene blocks) of SEBS maintain flexibility at low temperatures, providing deformation capability and avoiding the brittleness problem of purely chemical crosslinking systems at low temperatures. The elastic recovery rate of sample D reached 78%, exceeding the target of 75%, indicating that the material can recover quickly after deformation and has excellent fatigue resistance.

[0131] (4) Viscoelastic performance balance: As shown in Table 3, the phase angle of sample D at 60℃ is 77.5°, which is lower than that of pure asphalt (85.2°), indicating that the increased proportion of elastic components optimizes the viscoelastic balance of the material. At -10℃, the value of sample D is 0.393, which is lower than that of pure asphalt (0.545), indicating that the material maintains a high elastic ratio at low temperatures and is less prone to brittle fracture. The storage modulus (185.2 MPa) is significantly higher than that of pure asphalt (52.3 MPa), indicating that the elastic response of the material is enhanced, and it can store and release deformation energy, thus improving fatigue resistance.

[0132] (5) Dual-enhancement network synergy effect: from Figure 4 The radar chart clearly shows that sample D (this invention) achieved 100% of the baseline in all performance indicators, while other samples had significant shortcomings in certain indicators. Sample E (physical blend) showed good low-temperature toughness (ductility 59.1%, elastic recovery 66.7%), but insufficient high-temperature performance (rutting factor only 70.7%); sample F (chemical crosslinking) showed good high-temperature performance (rutting factor 86.8%), but poor low-temperature toughness (ductility only 36.5%). Only sample D, through the synergistic effect of the chemical crosslinking network and the physical entanglement network of SEBS elastomer, achieved a balance between high-temperature stability and low-temperature toughness, constructing a true chemical-physical dual-reinforcing network.

[0133] The embodiments of the present invention have been described above. However, the embodiments are not limited to the specific implementation methods described above. The specific implementation methods described above are merely illustrative and not restrictive. Those skilled in the art can make more equivalent embodiments under the guidance of the present embodiments, and all of them are within the protection scope of the present embodiments.

Claims

1. A high-viscosity cold-mix asphalt additive, characterized in that, Composed of the following components in parts by mass: 30-50 parts of high molecular weight polymer, 10-20 parts of organic amine accelerator, 20-40 parts of modified resin, 5-10 parts of end-capped isocyanate crosslinking agent, 8-15 parts of SEBS elastomer, 0.3-0.8 parts of catalyst, and 1.5-3 parts of molecular sieve desiccant; 60-80% of the end-capped isocyanate crosslinking agent is encapsulated in hydrophobic microcapsules. The hydrophobic microcapsules have end-capped isocyanate as the core material and hydrophobic polyurea or polyurethane as the wall material. The microcapsule particle size is 20-80 μm, the wall thickness is 2-5 μm, and the water vapor permeability of the wall material is less than 0.1 g / (m²·day). The molecular sieve desiccant is a type 3A or 4A molecular sieve micro powder with a pore size of 0.3-0.4 nm and a particle size of 1-5 μm. After activation at 300℃ for 4 hours, its water absorption capacity is 20-25% of its own mass. 70-90% of the catalyst is protected by chelation, which is achieved by forming chelates with organobismuth or organozinc catalysts through β-diketone ligands, or by loading the catalyst onto nano-silica that has been hydrophobically treated with silane coupling agents.

2. The high-viscosity cold-mix asphalt additive according to claim 1, characterized in that, The polymer is selected from styrene-butadiene-styrene block copolymer or ethylene-vinyl acetate copolymer, with a molecular weight of 100,000-300,000; the organic amine accelerator is selected from aliphatic polyamines or aromatic amine compounds, with a functionality of 2-4; the modified resin is selected from petroleum resin, phenolic resin, rosin resin or a combination thereof, with a softening point of 80-140℃.

3. The high-viscosity cold-mix asphalt additive according to claim 1, characterized in that, The end-capping isocyanate crosslinking agent is selected from the trimer of toluene diisocyanate or hexamethylene diisocyanate, and is end-capped with phenol, caprolactam or butanone oxime end-capping agents, with the end-capping agent removal temperature being 60-120℃; the styrene content of the SEBS elastomer is 20-35%.

4. The high-viscosity cold-mix asphalt additive according to claim 1, characterized in that, The hydrophobic microcapsules are prepared by interfacial polymerization. The wall material monomers are toluene diisocyanate and hydrophobic polyether polyol. They are reacted in an oil-in-water emulsion system at 55-65°C for 1.5-2.5 hours to form a polyurea-polyurethane copolymer wall material. The encapsulation rate of the hydrophobic microcapsules is greater than 95%, and the core material content is 60-75%.

5. The high-viscosity cold-mix asphalt additive according to claim 1, characterized in that, The chelated protective catalyst is prepared by one of the following methods: reacting an organobismuth catalyst or an organozinc catalyst with β-diketone ligand acetylacetone at a molar ratio of 1:2 to 1:4 at 75-85°C for 0.5-1.5 hours to form a chelate; or loading the catalyst onto nano-silica treated with methyltrimethoxysilane hydrophobicity, with a catalyst loading of 15-25%.

6. A method for preparing a high-viscosity cold-mix asphalt additive according to any one of claims 1-5, characterized in that, This includes the following steps performed sequentially: Step 1: Preparation of hydrophobic microcapsule-encapsulated end-capsulated isocyanate: The end-capsulated isocyanate and hydrophobic solvent are mixed at a mass ratio of 1:0.1-0.

3. Toluene diisocyanate, a wall material monomer, and hydrophobic polyether polyol are added, with a mass ratio of 100 parts end-capsulated isocyanate, 8-15 parts toluene diisocyanate, and 6-12 parts hydrophobic polyether polyol, to obtain an oil phase. The oil phase is added dropwise to an aqueous phase containing a water-soluble emulsifier, and the stirring speed is controlled at 800-1500 rpm to form an oil-in-water emulsion. The mixture is heated to 55-65℃ for interfacial polymerization for 1.5-2.5 hours. After cooling, it is filtered or centrifuged, washed, and dried to obtain hydrophobic microcapsule-encapsulated end-capsulated isocyanate. Step 2, activate the molecular sieve desiccant: heat the 3A or 4A type molecular sieve powder from room temperature to 300℃ at a rate of 5-10℃ / minute, maintain the activation at 300℃ for 4 hours, cool to room temperature under dry nitrogen protection, and store in a sealed container. Step 3, preparation of chelated protective catalyst: react organobismuth catalyst or organozinc catalyst with acetylacetone at a molar ratio of 1:2 to 1:4 under nitrogen protection at 75-85℃ for 0.5-1.5 hours, remove excess ligand and solvent by vacuum distillation to obtain β-diketone chelate catalyst; or support the catalyst on hydrophobically treated nano-silica and dry to obtain supported catalyst; Step 4, compounding and preparing additives: In an environment with relative humidity less than 30% and nitrogen protection, melt and mix the polymer at 100-120℃, add SEBS elastomer for high shear dispersion, add modified resin and mix evenly, cool to 80-90℃ and then add non-encapsulated end-capped isocyanate crosslinking agent, hydrophobic microcapsule encapsulation crosslinking agent, activated molecular sieve powder, organic amine promoter, chelated protective catalyst and non-protected catalyst in sequence, mix evenly and cool to room temperature, and then package and seal.

7. The preparation method according to claim 6, characterized in that, In step one, the volume ratio of oil phase to water phase is 1:2 to 1:4, the interfacial polymerization reaction temperature is 60℃, the reaction time is 2 hours, and after the reaction, the wall material is kept at 60℃ for 0.5-1 hours to fully cure; the water-soluble emulsifier is selected from polyvinyl alcohol, sodium dodecyl sulfate or a combination thereof, and the amount used is 0.5-2% of the mass of deionized water.

8. The preparation method according to claim 6, characterized in that, In step two, after the molecular sieve is activated, it is cooled to 80-100℃ and taken out. It is then quickly transferred to a sealed container equipped with dry nitrogen protection and cooled to room temperature. The relative humidity of the sealed storage environment is less than 10%; the residual moisture content of the activated molecular sieve is less than 0.5%.

9. The preparation method according to claim 6, characterized in that, In step four, when adding SEBS elastomer at 100-120℃, the stirring speed is increased to 150-200 rpm, and a high-shear dispersion device is used to mix for 30 minutes; when adding hydrophobic microcapsule coating crosslinking agent, the stirring speed is controlled to be less than 100 rpm, and the mixture is mixed for 15-20 minutes. The activated molecular sieve powder is added within 10 minutes; the chelated protective catalyst is added last, and the mixing time is less than 20 minutes.

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