Direct-vat warm-mixing flame-retardant SBS asphalt modifier as well as preparation method and application thereof

Abstract

The invention relates to the field of road engineering, in particular to a direct-vat warm-mixing flame-retardant SBS asphalt modifier as well as a preparation method and application thereof. The modifier comprises 40-60 parts of a polystyrene branched polymer, a cross-linking agent accounting for 0.2-0.4% of the weight of the polymer, 10-20 parts of biodiesel and 10-20 parts of a composite flame retardant. Wherein the molecular weight of the polystyrene branched polymer is preferably 100,000-150,000, and the polystyrene branched polymer is prepared by introducing a branched structure into a linear styrene-butadiene-styrene block copolymer; the biodiesel takes waste animal or vegetable fat as a raw material; the composite flame retardant contains 30%-50% of an organic phosphate flame retardant and 50%-70% of an inorganic flame retardant. The modifier can be directly added into an asphalt mixture mixing pot, can reduce the production and construction temperature by 20-30 DEG C, improves the high-temperature rut resistance and low-temperature crack resistance of asphalt, is flame-retardant, free of toxic and corrosive gases, low in cost and simple in process, and is suitable for pavement of asphalt pavements of highway tunnels.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of road engineering, in particular to a direct-throwing warm-mixing flame-retardant SBS asphalt modifier, a preparation method and application thereof. BACKGROUND

[0002] At present, warm-mixing flame-retardant asphalt concrete is mainly produced by adding warm-mixing agents and flame-retardant agents in the production process of asphalt mixture or by pre-preparing warm-mixing flame-retardant asphalt. The method of adding warm-mixing agents and flame-retardant agents in the production process of asphalt mixture, such as CN113462176A (a warm-mixing flame-retardant SMA asphalt mixture, a preparation method, application and construction method thereof) uses SBS modified asphalt, aggregate, fiber, 10-50 parts of Sasobit warm-mixing agent and 100-500 parts of flame-retardant agent to prepare warm-mixing flame-retardant SMA asphalt mixture; the method of producing asphalt mixture by pre-preparing warm-mixing flame-retardant asphalt, such as CN108624067A (a warm-mixing flame-retardant asphalt and a preparation method thereof) includes warm-mixing agents, base asphalt and flame-retardant agents, and the warm-mixing agent is prepared by the following method: under the action of a first catalyst, high molecular alkane reacts with halogen element to obtain an intermediate; aromatic oil is mixed with a complex to obtain an aromatic complex component; then the aromatic complex component is mixed with the intermediate and reacts to obtain the warm-mixing agent. The above two methods are based on the technology of wet modified asphalt.

[0003] However, the traditional wet modification process requires large-scale production equipment, has a long production cycle and high energy consumption. In addition, SBS molecules in SBS modified asphalt may crack and separate during high-temperature storage, which reduces the performance of SBS modified asphalt. Conventional SBS modifiers have the problems of high viscosity, poor flowability, difficulty in melting in asphalt, and inability to be used in dry method. This is because the intermolecular force in conventional SBS modifiers is strong, especially the physical crosslinking points formed by the styrene hard segment, which still remain strong when heated, resulting in a particularly high viscosity after melting. In addition, SBS is prone to local overheating under high temperature and high viscosity, leading to material degradation. The existing dry SBS modifier mostly uses a compatibilizer oil to reduce the melt viscosity. The added oil can penetrate between the molecular chains, play a lubricating role, reduce the friction between the chains, and thus reduce the viscosity, so as to realize the dry use of SBS. For example, CN115960432B (a dry SBS modifier, SBS modified asphalt and a preparation method thereof) uses SBS polymer modifier 20-40 parts, polyethylene 20-40 parts, octabromoether 10-15 parts, polyethylene wax 5-15 parts, solubilizer 5-15 parts, and crosslinking agent 2-8 parts. The solubilizer is selected from FCC slurry, furfural extract oil, side-line oil of petroleum atmospheric and vacuum distillation, and waste oil. Since the solubilizer is added to reduce the high-temperature performance of the modified asphalt, polyethylene and polyethylene wax and other materials need to be added in the formula to supplement the high-temperature performance. In addition, in order to solve the problem of asphalt fire resistance, the above two methods use complex types of warm mix agents and flame retardants with high addition amount, which affects the road performance of asphalt mixture, and has high cost, making it difficult to be widely applied.

[0004] Therefore, there is an urgent need to develop a new type of warm-mix flame-retardant asphalt technology that can dry-mix SBS and be free of compatibilizers to maintain high-temperature performance, which simplifies the warm-mix flame-retardant additives and reduces the addition amount without compromising the road performance and cost, breaks through the bottleneck of the existing process, meets the demand for large-scale promotion of long and large tunnels, and ensures construction and operation safety. SUMMARY

[0005] To achieve one of the above purposes, the present application provides a direct injection type warm-mix flame-retardant SBS asphalt modifier, its preparation method and application, which not only meets the requirements of warm-mix flame-retardant performance of asphalt mixture, solves the problem that traditional warm-mix flame-retardant asphalt mixture mainly relies on wet modified asphalt technology, but also overcomes the problems of high viscosity, poor flowability, difficulty in melting in asphalt and inability to be directly used, and the problems of complex types of warm-mixing agents and flame-retardants, high addition amount, influence on performance of asphalt mixture, high cost and difficulty in large-scale popularization and application in existing warm-mix flame-retardant asphalt. Based on rich practical experience and professional knowledge in designing and manufacturing such products for many years, and with the use of mechanism, the present application actively makes research and innovation, so as to create a dry warm-mix flame-retardant asphalt modifier and its preparation method, which can be widely applied to tunnel asphalt pavement paving. The technical scheme of the present application is implemented as follows: In the first aspect, the present application provides a direct injection type warm-mix flame-retardant SBS asphalt modifier, which comprises the following components: polystyrene branched polymer, crosslinking agent, biodiesel and composite flame retardant; the polystyrene branched polymer has the following structure:

[0006] wherein a, b, c, d and e are positive integers; The R has the following structure:

[0007] wherein n is a positive integer.

[0008] Specifically, the polystyrene branched polymer is obtained by introducing a polystyrene macromonomer with a branched structure into the molecular structure of a traditional linear styrene-butadiene-styrene (SBS) block copolymer; the branched structure is uniformly dispersed in the form of short branches on the polymer molecular chain, and the molecular weight of the short branch is less than the critical molecular weight at which molecular weight entanglement occurs. As a result, on the one hand, the short branch and the low molecular weight feature significantly reduce the degree of entanglement between polymer molecular chains; on the other hand, the presence of the short branch increases the spacing between polymer molecular chains, thereby reducing the frictional resistance experienced by the molecular chains during relative motion and reducing the intermolecular forces of the polymer. The above changes at the molecular level ultimately improve the activity of the polymer molecular chains, thereby improving the melting speed of the polymer.

[0009] Preferably, the molecular weight of the polystyrene branched polymer is 100-150 thousand.

[0010] Specifically, when the molecular weight of the polystyrene branched polymer is less than 100 thousand, the asphalt modification effect is limited, more amount of polystyrene branched polymer is required, the cost is high, and the cost performance is low; when the molecular weight exceeds 150 thousand, the molecular weight is too large, the melt viscosity is large, it is difficult to achieve rapid melting, and it cannot be directly used.

[0011] Preferably, the molecular weight of R is 1000-3000.

[0012] Further preferably, the melt index (190℃, 2.16kg) of the polystyrene branched polymer is greater than 2.0g / 10min.

[0013] Preferably, the direct warm-mix flame-retardant SBS asphalt modifier comprises, by weight parts, 40-60 parts of polystyrene branched polymer, 0.2%-0.4% of the weight of the polystyrene branched polymer of crosslinking agent, 10-20 parts of biodiesel, and 10-20 parts of composite flame retardant.

[0014] Preferably, the raw material of the biodiesel comprises waste animal fat or waste vegetable fat.

[0015] Preferably, the composite flame retardant comprises organic phosphate flame retardant and inorganic flame retardant, the organic phosphate flame retardant accounts for 30%-50% of the total mass of the composite flame retardant, and the inorganic flame retardant accounts for 50%-70% of the total mass of the composite flame retardant.

[0016] Further preferably, the organic phosphate flame retardant comprises any one of tris(1-oxo-1-phospho-2,6,7-trioxa-bicyclo[2,2,2]octane-4-methylene) phosphate or 1-oxo-4-hydroxymethyl-2,6,7-trioxa-1-phospho-bicyclo[2,2,2]octane phosphate.

[0017] Further preferably, the inorganic flame retardant is any one of magnesium hydroxide or aluminum hydroxide.

[0018] In a second aspect, the present application provides a preparation method of the direct warm-mix flame-retardant SBS asphalt modifier of the first aspect, comprising the following steps: S1, the polystyrene branched polymer and the biodiesel are added to a rubber internal mixer, and after internal mixing, the material is discharged and sent to a double-screw extruder for extrusion granulation to obtain a blend; S2, the blend, the crosslinking agent and the composite flame retardant are added to a mixer and uniformly mixed, and then sent to a liquid nitrogen cryogenic pulverizer to be pulverized into powder particles to obtain the direct warm-mix flame-retardant SBS asphalt modifier.

[0019] In a third aspect, the present application provides an application of the direct warm-mix flame-retardant SBS asphalt modifier of the first aspect in asphalt pavement highway tunnel paving engineering.

[0020] Compared with the prior art, the present application has the following advantages: (1) The polystyrene branched polymer is used as a modifier of asphalt to prepare the dry warm-mixing flame-retardant SBS modifier, the activity of the polymer molecular chain is improved, the melting speed of the polymer is increased, the purpose of dry use is achieved, and the high-temperature rutting resistance and low-temperature cracking resistance of the modified asphalt are improved.

[0021] (2) The polystyrene branched polymer has good fluidity during mixing production, low high-temperature viscosity, and can reduce the asphalt mixture production construction temperature by 5-10 DEG C compared to conventional SBS modified asphalt mixture, and has certain warm-mixing effect.

[0022] (3) The waste animal and vegetable oils and fats are used as raw materials to prepare the biodiesel, the production construction temperature of the asphalt mixture is reduced by 10-20 DEG C, the production construction temperature of the asphalt mixture is further reduced by 20-30 DEG C by the synergistic effect of the polystyrene branched polymer, and the warm-mixing effect is realized.

[0023] (4) The composite flame retardant prepared by compounding the organic phosphate flame retardant and the inorganic flame retardant can realize low-dosage and low-cost flame retardation of asphalt, can overcome the defects of large combustion smoke, volatile toxic and corrosive gas of traditional halogen flame retardants, and can improve the defects of large dosage of inorganic flame retardants and influence on the performance of asphalt mixture.

[0024] (5) The direct injection type warm-mixing flame-retardant asphalt modifier prepared by the method can be directly injected into an asphalt mixture mixing kettle, the warm-mixing flame-retardant modification of asphalt is realized in the production process of the asphalt mixture, the process is simple, the cost is low, and the method is convenient for large-scale popularization and application. DETAILED DESCRIPTION

[0025] Embodiments of the present application are described in detail below. The embodiments described below are exemplary and are intended to explain the present application, and cannot be understood as a limitation of the present application.

[0026] It should be noted that the terms "first", "second" are only used for description purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first", "second" can explicitly or implicitly include one or more features. Further, in the description of the present application, unless otherwise specified, the meaning of "a plurality of" is two or more.

[0027] In this paper, the terms "contain", "include" or "comprise" are open expressions, that is, they include the contents indicated by the present application, but do not exclude other contents.

[0028] In this document, the terms "optional," "optionally," or "may" generally mean that the herein described event or circumstance can or can not occur or, in the case of a viewer, that is or can be possible. The description includes instances where the event or circumstance occurs and instances where it does not.

[0029] It should be noted that the conventional SBS modifier needs wet modification, and the SBS molecular chain is prone to breakage under long time high temperature conditions. The present application uses polystyrene branched polymer as an asphalt modifier to prepare a dry warm-mix flame-retardant SBS modifier. Through chemical molecular structure design, short branches are introduced into the molecular chain, the degree of entanglement between the polymer molecular chains is reduced through the short branches, the distance between the polymer molecular chains is increased, the intermolecular force and the melt viscosity of the polymer are reduced, the activity of the polymer molecular chain is improved, and the melting speed of the polymer is increased, achieving the purpose of dry use. The macromolecular polystyrene branched polymer is directly used by dry method and dispersed and dissolved in asphalt to form a three-dimensional network structure, and the high-temperature rutting resistance and low-temperature cracking resistance of the modified asphalt are also improved. Compared with the existing dry SBS modifier preparation technology, no compatibilizer is needed to increase the melt viscosity of SBS, so the high-temperature performance of the modified asphalt will not be reduced, and no additive polyethylene material needs to be added in the formula to supplement the high-temperature performance of the modified asphalt.

[0030] The technical solutions in the embodiments of the present application will be described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments of the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the protection scope of the present application.

[0031] The materials used in the present application are all purchased from the market. The polystyrene branched polymer is purchased from Hefei Gengshu New Material Technology Co., Ltd. The sulfur is purchased from Jinhua Jing Sulfur Chemical Co., Ltd. The tris (1-oxo-1-phosphonic acid-2, 6, 7-trioxa-bicyclo [2, 2, 2] octane-4-methylene and 1-oxo-4-hydroxymethyl-2, 6, 7-trioxa-1-phosphonic acid bicyclo [2, 2, 2] octane are purchased from Jiangsu Younuo New Material Co., Ltd. The magnesium hydroxide and aluminum hydroxide are purchased from Suzhou Jiayi Chemical Co., Ltd. The biodiesel is purchased from Sichuan Xinkuanyi Biological Technology Co., Ltd.

[0032] The present application provides a preparation method of a direct injection type warm-mix flame-retardant SBS asphalt modifier, comprising the following steps: (1) The polystyrene branched polymer and the biodiesel are added into a rubber internal mixer, the internal mixing rotor speed is controlled to be 20~40 revolutions per minute, the internal mixing temperature is controlled to be 80~120℃, and the material is discharged after internal mixing for 3~5 minutes, and then the material is sent into a double screw extruder by a feeding screw to be extruded and granulated, so as to obtain a blend; Specifically, the biodiesel is a fatty acid methyl or ethyl ester formed by ester conversion of waste animal fat or waste vegetable fat with methanol or ethanol; (2) The blend, crosslinking agent and composite flame retardant are added into a mixer to mix uniformly, and then are sent into a liquid nitrogen cryogenic pulverizer to be pulverized, to obtain 40-60 mesh powder particles, i.e. the direct-throw warm-mixing flame-retardant SBS asphalt modifier.

[0033] Example 1 The present example provides a preparation method of a direct-throw warm-mixing flame-retardant SBS asphalt modifier, comprising the following steps: (1) 400g polystyrene branched polymer and 100g biodiesel are added into a rubber internal mixer to be mixed, the rotation speed of the internal mixer rotor is controlled to be 20 rpm, the mixing temperature is 80℃, and the mixed material is discharged after 3 minutes of mixing, and then is uniformly fed into a twin-screw extruder to be extruded and granulated, to obtain a blend; The polystyrene branched polymer has a molecular weight of 100,000, the short branched polystyrene has a molecular weight of 1,000, and the polystyrene branched polymer has a melt index of 8.6 kg / 10 min at 190℃ and under a load of 2.16 kg (GB / T 3682-2000, Determination of melt mass-flow rate and melt volume-flow rate of thermoplastics); (2) The blend prepared in step (1), 100g composite flame retardant (30% tri (1-oxo-1-phospho-2, 6, 7-trioxa-bicyclo [2, 2, 2] octane-4-methylene) phosphate organic flame retardant and 70% magnesium hydroxide inorganic flame retardant) and 0.2% sulfur crosslinking agent by weight of the polystyrene polymer are added into a mixer to be mixed, and then are added into a liquid nitrogen cryogenic pulverizer to be frozen and pulverized into 60 mesh powder particles, to obtain the direct-throw warm-mixing flame-retardant SBS asphalt modifier.

[0034] Example 2 The present example provides a preparation method of a direct-throw warm-mixing flame-retardant SBS asphalt modifier, comprising the following steps: (1) 500g polystyrene branched polymer and 150g biodiesel are added into a rubber internal mixer to be mixed, the rotation speed of the internal mixer rotor is controlled to be 30 rpm, the mixing temperature is 100℃, and the mixed material is discharged after 5 minutes of mixing, and then is uniformly fed into a twin-screw extruder to be extruded and granulated, to obtain a blend; The polystyrene branched polymer has a molecular weight of 120,000, and the short branched polystyrene has a molecular weight of 1800, and the polystyrene branched polymer has a melt index of 5.5 kg / 10 min at 190°C and 2.16 kg (GB / T 3682-2000, Determination of melt mass-flow rate and melt volume-flow rate of thermoplastics); (2) The blend prepared in step (1) is mixed with 200 g of a composite flame retardant (40% 1-oxo-4-hydroxymethyl-2,6,7-trioxa-1-phosphabicyclo[2,2,2]octane phosphate organic flame retardant and 60% magnesium hydroxide inorganic flame retardant) and 0.3% by weight of the polystyrene polymer of a sulfur crosslinking agent in a mixer, and after uniform mixing, is frozen and crushed in a liquid nitrogen cryogenic crusher to form 40-mesh powder particles to obtain a direct injection warm-mixing flame-retardant SBS asphalt modifier.

[0035] Example 3 The present embodiment provides a preparation method of a direct injection warm-mixing flame-retardant SBS asphalt modifier, comprising the following steps: (1) 600 g of a polystyrene branched polymer and 200 g of biodiesel are mixed in a rubber internal mixer, the rotation speed of the internal mixer rotor is controlled to be 40 rpm, the mixing temperature is 120°C, and after mixing for 5 minutes, the mixture is discharged, and then uniformly fed into a twin-screw extruder for extrusion and granulation to obtain a blend; The polystyrene branched polymer has a molecular weight of 120,000, and the short branched polystyrene has a molecular weight of 1800, and the polystyrene branched polymer has a melt index of 5.5 kg / 10 min at 190°C and 2.16 kg (GB / T 3682-2000, Determination of melt mass-flow rate and melt volume-flow rate of thermoplastics); (2) The blend prepared in step (1) is mixed with 150 g of a composite flame retardant (50% 1-oxo-4-hydroxymethyl-2,6,7-trioxa-1-phosphabicyclo[2,2,2]octane phosphate organic flame retardant and 50% magnesium hydroxide inorganic flame retardant) and 0.4% by weight of the polystyrene polymer of a sulfur crosslinking agent in a mixer, and after uniform mixing, is frozen and crushed in a liquid nitrogen cryogenic crusher to form 60-mesh powder particles to obtain a direct injection warm-mixing flame-retardant SBS asphalt modifier.

[0036] Comparative Example 1 The present comparative example provides a preparation method of a common warm-mixing flame-retardant SBS asphalt modifier, wherein the polystyrene branched polymer has a short branched polystyrene with a molecular weight of 500, comprising the following steps: (1) 600g polystyrene branched polymer, 200g biodiesel were added to the rubber internal mixer for mixing, the speed of the internal mixer rotor was controlled at 40 rpm, the mixing temperature was 120°C, and the mixed material was discharged after mixing for 5 minutes, then uniformly entered the twin-screw extruder for extrusion and granulation, to obtain a blend; The molecular weight of the polystyrene branched polymer is 150,000, the molecular weight of the short branched polystyrene is 500, and the melt index of the polystyrene branched polymer at 190°C and 2.16 kg (GB / T 3682-2000, Determination of melt mass-flow rate and melt volume-flow rate of thermoplastics) is 0.3 kg / 10 min; (2) The blend prepared in step (1) was mixed with 0.4% sulfur cross-linking machine of the mass of polystyrene polymer, 150g composite flame retardant (50% 1-oxo-4-hydroxymethyl-2,6,7-trioxa-1-phosphacyclo[2,2,2] octane phosphate organic flame retardant and 50% aluminum hydroxide inorganic flame retardant) in a mixer, and then added to a liquid nitrogen cryogenic pulverizer for frozen pulverization after uniform mixing, to obtain a common warm mix flame retardant SBS asphalt modifier.

[0037] Comparative Example 2 This comparative example provides a preparation method of a common warm mix flame retardant SBS asphalt modifier, wherein the molecular weight of the short branched polystyrene of the polystyrene branched polymer is 5000, comprising the following steps: (1) 600g polystyrene branched polymer, 200g biodiesel were added to the rubber internal mixer for mixing, the speed of the internal mixer rotor was controlled at 40 rpm, the mixing temperature was 120°C, and the mixed material was discharged after mixing for 5 minutes, then uniformly entered the twin-screw extruder for extrusion and granulation, to obtain a blend; The molecular weight of the polystyrene branched polymer is 130,000, the molecular weight of the short branched polystyrene is 5000, the branched molecular weight is large, new intermolecular entanglement is formed, the high-temperature viscosity is large, and the melt flowability is poor, and the melt index of the polystyrene branched polymer at 190°C and 2.16 kg cannot be tested;

[0038] (2) The blend prepared in step (1) was mixed with 0.4% sulfur cross-linking machine of the mass of polystyrene polymer, 150g composite flame retardant (50% 1-oxo-4-hydroxymethyl-2,6,7-trioxa-1-phosphacyclo[2,2,2] octane phosphate organic flame retardant and 50% aluminum hydroxide inorganic flame retardant) in a mixer, and then added to a liquid nitrogen cryogenic pulverizer for frozen pulverization after uniform mixing, to obtain a common warm mix flame retardant SBS asphalt modifier.

[0039] Comparative Example 3 This comparative example provides a preparation method of a common warm-mix flame-retardant SBS asphalt modifier, replacing the polystyrene branched polymer with a conventional linear SBS, comprising the following steps: (1) 600 g of conventional linear SBS, 200 g of biodiesel were added to a rubber internal mixer for internal mixing, the internal mixer rotor speed was controlled at 40 rpm, the internal mixing temperature was 120°C, and after 5 minutes of internal mixing, the mixture was discharged, then uniformly fed into a twin-screw extruder granulator for extrusion granulation to obtain a blend; The conventional linear SBS has a molecular weight of 100,000, no branched structure, and poor fluidity, and its melt index at 190°C, 2.16 kg cannot be tested;

[0040] (2) The blend prepared in step (1) was added to a mixer along with 0.4% sulfur cross-linking machine of the mass of the polystyrene polymer, 150 g of a composite flame retardant (50% 1-oxo-4-hydroxymethyl-2,6,7-trioxa-1-phosphacyclo[2,2,2]octane phosphate organic flame retardant and 50% aluminum hydroxide inorganic flame retardant) for mixing, and after uniform mixing, was added to a liquid nitrogen cryogenic pulverizer for frozen pulverization, and was pulverized into 60-mesh powder particles to obtain a common warm-mix flame-retardant SBS asphalt modifier.

[0041] According to the Technical Guidelines for Dry SBS Modified Asphalt Mixture of Highway Pavement (T / CHTS 20003-2018) and the Test Code for Asphalt and Asphalt Mixture of Highway Engineering (JTG E20-2011), the dry warm-mix flame-retardant asphalt modifier and its asphalt mixture prepared in Examples 1-3 and Comparative Examples 1-3 and the wet SBS modified asphalt (I-D modified asphalt, purchased from Jiangsu Yihu Asphalt Material Co., Ltd.) were evaluated for relevant performance, and the results of the test evaluation are shown in Tables 1 and 2.

[0042] Table 1 Evaluation of dry warm-mix flame-retardant asphalt modifier indexes

[0043] Table 2 Evaluation of flame-retardant performance indexes of dry warm-mix flame-retardant modified asphalt (dry warm-mix flame-retardant modifier: base asphalt = 10:100)

[0044] Table 3 Evaluation of road performance of dry warm-mix flame-retardant asphalt mixture (SMA-13 grading is used, the base asphalt oil stone ratio is 5.5%, and the dry warm-mix flame-retardant modifier content is 0.55% of the mineral aggregate)

[0045] Table 1~Table 3 are the performance test results of the dry warm-mix flame-retardant modifier, modified asphalt and modified asphalt mixture prepared therefrom. From the performance of the dry warm-mix flame-retardant modifier in Table 1, the modifiers prepared in Examples 1~3 have large melt index, fast melting speed in dry mixing dispersibility test and no residual modifier particles; the modifiers prepared in Comparative Examples 2 and 3 have poor flowability, the melt index cannot be tested, and basically no particles melt in the dry mixing dispersibility test; and the modifier prepared in Comparative Example 1 has small molecular weight and branched structure, has small effect on the melt flowability, has a melt index of only 1.6 kg / 10 min, and still has most of the modifier particles remaining in the dry mixing test. From the performance test of the modified asphalt mixture in Table 3, it can also be seen that the asphalt mixtures prepared in Examples 1~3 have a dynamic stability of more than 9000 times / mm at 60℃, a low-temperature beam failure strain of more than 3500 με at -10℃, a porosity of the mixture formed after a temperature drop of 20℃ that is equivalent to that of the wet SBS modified asphalt, excellent warm-mixing effect, and excellent high-temperature anti-rutting and low-temperature anti-cracking performance of the mixture. The asphalt mixtures prepared in Comparative Examples 1~3 have large porosity after a temperature drop, cannot meet the technical requirements, and have poor high-temperature and low-temperature performance of the asphalt mixture, which also cannot meet the technical requirements.

[0046] This is because the branched polystyrene structure with small or large molecular weight used in Comparative Examples 1~2 has limited modification effect on the conventional linear SBS, cannot reduce the entanglement degree of the SBS molecular chain, improve the flowability, achieve the purpose of dry melting use, and cannot achieve dry modification; specifically, when the molecular weight of the short branched chain is too large, the molecular chain is long, new molecular chain entanglement is formed, and the activity of the molecular chain is poor; when the molecular weight of the branched chain is too small, the distance between the linear macromolecular chains cannot be increased, the flowability is poor, the effect of fast melting cannot be achieved, and dry use cannot be achieved.

[0047] And the conventional linear SBS modifier used in Comparative Example 3 also cannot be used in dry method, and cannot play a role in modifying asphalt. As can be seen from Table 2, compared with the wet SBS modified asphalt, the oxygen index of the modified asphalt prepared in Examples 1~3 and Comparative Examples 1~3 is significantly increased, and has excellent flame-retardant performance.

[0048] The embodiments described above are part of the embodiments of the present application, rather than all the embodiments. The detailed description of the embodiments of the present application is not intended to limit the scope of the claimed application, but only represents selected embodiments of the present application. All other embodiments obtained by a person of ordinary skill in the art based on the embodiments in the present application without creative labor belong to the scope of protection of the present application.

Claims

1. A direct-mix warm-mix flame-retardant SBS asphalt modifier, characterized in that, It comprises the following components: a branched polystyrene polymer, a crosslinking agent, biodiesel, and a composite flame retardant; the branched polystyrene polymer has the following structure: ； Where a, b, c, d, and e are all positive integers; The R has the following structure: ； Where n is a positive integer.

2. The direct-mix warm-mix flame-retardant SBS asphalt modifier according to claim 1, characterized in that, The molecular weight of the polystyrene branched polymer is 100,000 to 150,000.

3. The direct-mix warm-mix flame-retardant SBS asphalt modifier according to claim 1, characterized in that, The molecular weight of R is 1000~3000.

4. The direct-mix warm-mix flame-retardant SBS asphalt modifier according to claim 1, characterized in that, The components, by weight, include: 40-60 parts of branched polystyrene polymer, 0.2%-0.4% of the weight of the crosslinking agent, 10-20 parts of biodiesel, and 10-20 parts of composite flame retardant.

5. The direct-mix warm-mix flame-retardant SBS asphalt modifier according to claim 1, characterized in that, The raw materials for the biodiesel include waste animal fats or waste vegetable oils.

6. The direct-mix warm-mix flame-retardant SBS asphalt modifier according to claim 1, characterized in that, The composite flame retardant includes an organic phosphate flame retardant and an inorganic flame retardant, wherein the organic phosphate flame retardant accounts for 30% to 50% of the total mass of the composite flame retardant, and the inorganic flame retardant accounts for 50% to 70% of the total mass of the composite flame retardant.

7. The direct-mix warm-mix flame-retardant SBS asphalt modifier according to claim 6, characterized in that, The organophosphate flame retardant includes either tris(1-oxo-1-phosphate-2,6,7-trioxabicyclo[2,2,2]octane-4-methylene) phosphate or 1-oxo-4-hydroxymethyl-2,6,7-trioxa-1-phosphate-bicyclo[2,2,2]octane phosphate.

8. The direct-mix warm-mix flame-retardant SBS asphalt modifier according to claim 6, characterized in that, The inorganic flame retardant is either magnesium hydroxide or aluminum hydroxide.

9. A method for preparing a direct-mix warm-mix flame-retardant SBS asphalt modifier as described in any one of claims 1 to 8, characterized in that, Includes the following steps: S1. Add the branched polystyrene polymer and biodiesel to a rubber mixer, mix them, and then feed the mixture into a twin-screw extruder to granulate it to obtain a blend. S2. Add the blend, crosslinking agent and composite flame retardant to the mixer and mix evenly. Then send it to the liquid nitrogen cryogenic pulverizer to pulverize it into powder particles to obtain the direct-dispensing warm-mix flame retardant SBS asphalt modifier.

10. The application of a direct-mix warm-mix flame-retardant SBS asphalt modifier as described in any one of claims 1 to 8 in asphalt pavement and highway tunnel paving projects.

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