Preparation method, product and application of polyethylene wax asphalt modifier

Abstract

The invention relates to the technical field of road engineering asphalt pavement materials, in particular to a preparation method, a product and application of a polyethylene wax asphalt modifier. The preparation method of the polyethylene wax asphalt modifier comprises the following steps: uniformly mixing polyethylene particles and a cracking catalyst to obtain mixture particles; the mixture particles are fed into a double-screw extruder to be extruded, and micro-cracking liquid glue is obtained; and carrying out high-temperature and high-pressure reaction on the micro-cracked liquid glue to obtain the polyethylene waxy asphalt modifier. The cracking catalyst is prepared by loading nickel on expanded vermiculite powder. The polyethylene waxy asphalt modifier has the advantages that the asphalt viscosity is reduced, the asphalt is modified, the compatibility and storage stability between the asphalt and polyethylene are improved to a great extent, and compared with the common polyethylene cracking technology, the polyethylene waxy asphalt modifier has the advantages that a large amount of energy consumption can be reduced; and the recycling degree of the waste polyethylene plastic can be increased, energy conservation and environmental protection are achieved, and efficient utilization is achieved.

Description

Technical Field

[0001] The invention relates to the technical field of asphalt pavement materials for road engineering, and in particular to a preparation method, product and application of a polyethylene wax asphalt modifier. Background Art

[0002] In recent years, the total mileage of highways has been increasing, which has put forward higher requirements on road quality. In order to improve the quality of road traffic and reduce road diseases, the mainstream method at this stage is to prepare asphalt modifiers with excellent performance and improve road performance by adding high-performance modifiers. Wax prepared from waste plastic particles is a new type of modifier. Because of its low price and good compatibility with asphalt, it is widely used as an organic viscosity-reducing warm mix agent to reduce the mixing temperature of hot mix mixtures. However, at present, waste plastic particles may contain different types of polyethylene due to their complex composition. The use of single-temperature thermal cracking technology may cause some polyethylene in the waste plastic particles to be over-crackered or insufficiently cracked, which will result in poor performance of the produced wax. After adding asphalt, it will affect the low-temperature performance of asphalt and cause road cracking.

[0003] Recycling and granulation of waste plastics is a relatively environmentally friendly means of plastic recycling at this stage. The mechanical recycling method is used to re-extrude, process and transform polyethylene mixed with the original polymer to reduce the overall cost. In the early process of using waste plastics to produce polyethylene wax, the process has been in the exploratory stage. The research on its physical and chemical properties is not in-depth, and the wide range of its application fields has not been recognized, such as its application in cables, coatings, inks, wax products, rubber and other fields. Polyethylene wax is only produced as a by-product in the process of preparing polyethylene at high temperature, but the molecular weight of the output product varies greatly and the quality is uneven. In addition, the production cost is high, which makes small-scale production less effective. From this perspective, further exploration of the production process of polyethylene wax is limited, and it has become a problem to achieve industrialization and commercialization within a certain period of time.

[0004] In the existing invention patents, waste polyethylene particles are used to prepare polyethylene wax, and most of them use high-temperature and high-pressure reactors to produce it by controlling a single temperature. This method can achieve good results by cracking a single type of polyethylene particles, but the composition of waste plastic particles at this stage is complex, mostly a mixture of HDPE (high-density polyethylene), LDPE (low-density polyethylene) and LLDPE (linear low-density polyethylene). If the traditional reactor single-temperature cracking method is used, it is easy to lead to poor product performance, and different types of polyethylene cannot be cracked accurately and controllably. Therefore, it is necessary to further optimize the process of cracking waste polyethylene particles to prepare wax modifiers in order to prepare polyethylene wax asphalt modifiers with excellent performance. Summary of the invention

[0005] Based on the above content, the present invention provides a preparation method, product and application of a polyethylene waxy asphalt modifier.

[0006] To achieve the above object, the present invention provides the following solutions:

[0007] One of the technical solutions of the present invention is the use of a cracking catalyst in the preparation of a polyethylene waxy asphalt modifier, wherein the preparation method of the cracking catalyst comprises the following steps:

[0008] Drying and crushing the expanded vermiculite to obtain expanded vermiculite powder (particle size 200-230 mesh);

[0009] Dissolving a nickel salt in water to obtain a nickel nitrate solution;

[0010] The expanded vermiculite powder is immersed in a nickel nitrate solution and mixed evenly, and then naturally precipitated and filtered to obtain an immersed powder;

[0011] The impregnated powder is dried, and then calcined at 300-350° C. for 2.5-3 hours to obtain the cracking catalyst;

[0012] The mass ratio of the expanded vermiculite to the nickel salt and water is 30:26:(30-50).

[0013] The second technical solution of the present invention is a method for preparing a polyethylene waxy asphalt modifier, comprising the following steps:

[0014] Mixing polyethylene particles and the cracking catalyst to obtain mixture particles;

[0015] The mixture particles are fed into a twin-screw extruder for extrusion to obtain a micro-cracked liquid glue;

[0016] The micro-cracked liquid gum is subjected to a high temperature and high pressure reaction to obtain the polyethylene waxy asphalt modifier.

[0017] The third technical solution of the present invention is a polyethylene waxy asphalt modifier prepared according to the preparation method.

[0018] A fourth technical solution of the present invention is the use of the polyethylene waxy asphalt modifier in modified asphalt.

[0019] A fifth technical solution of the present invention is a modified asphalt, the raw materials of which include base asphalt and the polyethylene waxy asphalt modifier.

[0020] The present invention discloses the following technical effects:

[0021] The preparation method of the cracking catalyst and the polyethylene wax asphalt modifier of the invention is simple and easy to prepare on a large scale in industry.

[0022] The polyethylene wax asphalt modifier prepared by the present invention is a block wax product with high yield and excellent performance. The polyethylene wax asphalt modifier prepared by the present invention is used to modify the base asphalt. Without adding other modifiers, the mixing temperature of the asphalt mixture can be effectively reduced. Compared with the base asphalt, the Brookfield viscosity of the modified asphalt at 135°C can be reduced by more than 35%. At the same time, the penetration and softening point of the modified asphalt are significantly increased, and the penetration index is reduced, so that the asphalt not only has good high temperature performance after modification, but also has improved low temperature performance. In short, the polyethylene wax asphalt modifier prepared by the present invention is used to prepare modified asphalt. Without adding other modifiers, the modified asphalt can have good high temperature performance and meet various performance indicators for road use. DETAILED DESCRIPTION

[0023] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but should be understood as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0024] It should be understood that the terms described in the present invention are only for describing a particular embodiment and are not intended to limit the present invention. In addition, for the numerical range in the present invention, it should be understood that each intermediate value between the upper and lower limits of the scope is also specifically disclosed. The intermediate value in any stated value or stated range, and each smaller range between any other stated value or intermediate value in the described range is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded in the scope.

[0025] Unless otherwise indicated, all technical and scientific terms used herein have the same meanings as those generally understood by those skilled in the art. Although the present invention describes only preferred methods and materials, any methods and materials similar or equivalent to those described herein may also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials associated with the documents. In the event of a conflict with any incorporated document, the content of this specification shall prevail.

[0026] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments of the present invention description without departing from the scope or spirit of the present invention. Other embodiments derived from the present invention description will be apparent to the skilled artisan. The present invention description and examples are exemplary only.

[0027] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0028] The present invention provides a cracking catalyst, which can be used to prepare polyethylene wax asphalt modifier with waste plastic particles as the main raw material, and utilizes the second-order gradient cracking technology of a twin-screw extruder + a high-temperature and high-pressure reactor to achieve accurate and efficient cracking of different types of polyethylene in waste plastic particles, thereby obtaining a polyethylene wax asphalt modifier with excellent performance. The gradient cracking technology of the present invention solves the problem that the performance of polyethylene wax is affected by excessive cracking of mixed waste plastic particles in a traditional reactor. The polyethylene wax prepared by the present invention can effectively improve the high and low temperature performance of asphalt without adding other modifiers, and can also significantly reduce the mixing temperature of asphalt.

[0029] The first aspect of the present invention provides an application of a cracking catalyst in the preparation of a polyethylene waxy asphalt modifier, wherein the preparation method of the cracking catalyst comprises the following steps:

[0030] Drying and crushing the expanded vermiculite to obtain expanded vermiculite powder (particle size 200-230 mesh);

[0031] Dissolving a nickel salt in water to obtain a nickel nitrate solution;

[0032] The expanded vermiculite powder is immersed in a nickel nitrate solution and mixed evenly, and then naturally precipitated and filtered to obtain an immersed powder;

[0033] The impregnated powder is dried, and then calcined at 300-350° C. for 2.5-3 hours to obtain the cracking catalyst;

[0034] The mass ratio of the expanded vermiculite to the nickel salt and water is 30:26:(30-50).

[0035] In some embodiments of the present invention, the drying is specifically drying at 60° C. for 20-30 min.

[0036] In a preferred embodiment of the present invention, the nickel salt is Ni(NO3)2·6H2O.

[0037] The second aspect of the present invention provides a method for preparing a polyethylene waxy asphalt modifier, comprising the following steps:

[0038] Mixing polyethylene particles and the cracking catalyst to obtain mixture particles;

[0039] The mixture particles are fed into a twin-screw extruder for extrusion to obtain a micro-cracked liquid glue;

[0040] The micro-cracked liquid gum is subjected to a high temperature and high pressure reaction to obtain the polyethylene waxy asphalt modifier.

[0041] In a preferred embodiment of the present invention, the polyethylene particles include high density polyethylene, low density polyethylene and / or linear low density polyethylene.

[0042] The polyethylene particles of the present invention can be waste polyethylene particles such as recycled plastic particles, or unused non-recycled polyethylene particles. In order to save costs, recycled plastic particles are used in the specific embodiment of the present invention.

[0043] In a preferred embodiment of the present invention, the mass ratio of the polyethylene particles to the cracking catalyst is 100:5.

[0044] In a preferred embodiment of the present invention, the parameters of the twin-screw extruder are set as follows: zone 1 temperature 100-120°C, zone 2 temperature 140-160°C, zone 3 temperature 170-190°C, zone 4 temperature 200-220°C, zone 5 temperature 170-190°C, die head temperature 120-160°C, and screw speed 5rpm.

[0045] In the present invention, the temperature gradient of the twin-screw extruder is set to ensure micro-cracking of some polyethylene, so as to cooperate with the precise cracking in the high temperature and high pressure reaction. If the temperature of each zone of the twin-screw extruder is too low, the first-order cracking reaction will be insufficient, and if the temperature is too high, it will cause excessive cracking.

[0046] In a preferred embodiment of the present invention, the high temperature and high pressure reaction is specifically: reacting at 320-360° C. for 15-30 min under an inert atmosphere and a pressure of 0.8-1.6 MPa.

[0047] In the present invention, if the temperature of the high temperature and high pressure reaction is too low, it will cause insufficient cracking of polyethylene, and if the temperature is too high, it will cause excessive cracking to form gas or gasoline, affecting product performance, so the reaction temperature of 320-360°C is selected.

[0048] The invention adopts a twin-screw extruder and a high-temperature and high-pressure reactor for two-step gradient cracking under the protection of inert gas, and obtains a polyethylene wax asphalt modifier with excellent performance by controlling the temperature, pressure and reaction time in the high-temperature and high-pressure reactor under the condition of adding a cracking catalyst.

[0049] In the present invention, the twin-screw extruder plays a role in mixing and micro-cracking, and forms an organic whole by matching the specific temperature, pressure and reaction time in the reactor to prepare polyethylene wax with various performance indicators far superior to those produced by the existing process. At the same time, it can also shorten the reaction time of the traditional cracking method and greatly reduce the energy consumption problem.

[0050] The third aspect of the present invention provides a polyethylene waxy asphalt modifier prepared according to the preparation method.

[0051] The fourth aspect of the present invention provides the use of the polyethylene waxy asphalt modifier in modified asphalt.

[0052] The fifth aspect of the present invention provides a modified asphalt, the raw materials of which include base asphalt and the polyethylene waxy asphalt modifier.

[0053] In a further preferred embodiment of the present invention, the polyethylene wax asphalt modifier is added in an amount of 5% of the mass of the base asphalt.

[0054] The present invention utilizes the porous and heat-resistant characteristics of expanded vermiculite powder to load nickel-based compounds, prepare an improved cracking catalyst, and blend it with waste polyethylene particles. A twin-screw extruder is used to achieve full fusion between polyethylene particles and the catalyst under the protection of oxygen isolation through high temperature and high shear, and obtain a first-order gradient micro-cracking product. The first-order gradient micro-cracking product is put into a high-temperature and high-pressure reactor, and after high temperature and high pressure and short-time cracking, a second-order gradient deep cracking product is obtained. The gradient cracking technology of the twin-screw extruder + high-temperature and high-pressure reactor is used to achieve accurate control of the cracking degree of waste polyethylene particles. Compared with ordinary polyethylene wax, the polyethylene wax (polyethylene wax asphalt modifier) ​​prepared by the present invention not only reduces the viscosity of asphalt, but also plays a modifying role on asphalt, greatly improves the compatibility and storage stability between asphalt and polyethylene, can reduce a large amount of energy consumption compared with ordinary polyethylene cracking technology, and can increase the recycling degree of waste polyethylene plastics, energy saving, environmental protection, and efficient utilization.

[0055] The technical solutions described in the present invention, unless otherwise specified, are all conventional solutions in the art, and the reagents or raw materials used, unless otherwise specified, are purchased from commercial channels or have been disclosed.

[0056] The polyethylene particles used in the embodiments of the present invention are recycled plastic particles produced by Shenxian Kehuan Recycling Resources Co., Ltd., and are mainly composed of HDPE, LDPE and LLDPE. The mass ratio of HDPE, LDPE and LLDPE is between 2:3:5 and 3:4:6.

[0057] The technical solutions provided by the present invention are described in detail below in conjunction with the embodiments, but they should not be construed as limiting the protection scope of the present invention.

[0058] Example 1

[0059] 1. A cracking catalyst, wherein the raw materials are composed of 26 parts of Ni(NO3)2·6H2O, 30 parts of expanded vermiculite and 30 parts of deionized water, calculated by weight.

[0060] The preparation method of the above cracking catalyst comprises the following steps:

[0061] (1) The expanded vermiculite was dried at 110° C. for 2 h, crushed with a crusher for 10 min, ball-milled with a ball mill for 45 min, and dried at 110° C. for 1 h to obtain expanded vermiculite powder with a particle size of 200-230 mesh.

[0062] (2) Dissolve Ni(NO3)2·6H2O in deionized water to obtain a nickel nitrate solution.

[0063] (3) Adding expanded vermiculite powder to nickel nitrate solution and mixing evenly, waiting for natural precipitation for 2 hours, and filtering with filter paper to obtain impregnated expanded vermiculite powder (abbreviated as: impregnated powder).

[0064] (4) The impregnated powder was dried at 60° C. for 30 min, and then placed in a muffle furnace and calcined at 350° C. for 3 h to obtain a cracking catalyst.

[0065] 2. A polyethylene wax asphalt modifier, whose raw materials are composed of 100 parts of polyethylene particles (20 parts of HDPE + 30 parts of LDPE + 50 parts of LLDPE) and 5 parts of cracking catalyst, calculated by weight.

[0066] The preparation method of the above-mentioned polyethylene wax asphalt modifier comprises the following steps:

[0067] 1) Put polyethylene particles and cracking catalyst into a stirrer and stir them thoroughly to obtain mixture particles.

[0068] 2) feeding the mixture particles into a twin-screw extruder, controlling the temperature of each zone of the twin-screw extruder as follows: the temperature of zone 1 is 100° C., the temperature of zone 2 is 140° C., the temperature of zone 3 is 170° C., the temperature of zone 4 is 200° C., the temperature of zone 5 is 170° C., the temperature of the die head is 120° C., controlling the screw speed to 5 rpm, and reacting in the twin-screw extruder for 10 minutes to obtain a micro-cracking liquid glue.

[0069] 3) Select a high-temperature and high-pressure reactor with a volume of 1 L, and add the micro-lysis liquid gel into the reactor in an amount of 10% of the volume of the high-temperature and high-pressure reactor.

[0070] 4) Open the air inlet and exhaust port of the reactor, and introduce 99.999% pure N2 into the reactor for 15 minutes. After exhausting the air in the reactor, close the exhaust port, use the gas cylinder pressure reducing valve to adjust the pressure in the reactor to 1MPa, close the air inlet, turn on the heating device, and increase the temperature to 340°C at a rate of 10°C / min. After reacting for 10 minutes, wait for the instrument temperature to cool down to room temperature before discharging. The product is naturally cooled to room temperature to obtain a polyethylene wax asphalt modifier.

[0071] The polyethylene wax asphalt modifier prepared in this example is used to modify asphalt: 70# base asphalt is preheated to 120°C in a container, 5% by mass (referring to the mass percentage of 70# base asphalt) of the polyethylene wax asphalt modifier is added to the asphalt, and after it is fully dissolved in the asphalt, it is stirred for 15 minutes to obtain modified asphalt Example 1.

[0072] Example 2

[0073] 1. A cracking catalyst, wherein the raw materials are composed of 26 parts of Ni(NO3)2·6H2O, 30 parts of expanded vermiculite and 40 parts of deionized water, calculated by weight.

[0074] The preparation method of the above cracking catalyst comprises the following steps:

[0075] (1) Same as step (1) of Example 1.

[0076] (2) Same as step (2) in Example 1.

[0077] (3) Same as step (3) of Example 1.

[0078] (4) The impregnated powder was dried at 60° C. for 30 min, and then placed in a muffle furnace and calcined at 320° C. for 3 h to obtain a cracking catalyst.

[0079] 2. A polyethylene wax asphalt modifier, whose raw materials are composed of 100 parts of polyethylene particles (20 parts of HDPE + 30 parts of LDPE + 50 parts of LLDPE) and 5 parts of cracking catalyst, calculated by weight.

[0080] The preparation method of the above-mentioned polyethylene wax asphalt modifier comprises the following steps:

[0081] 1) Same as step 1) in Example 1.

[0082] 2) feeding the mixture particles into a twin-screw extruder, controlling the temperature of each zone of the twin-screw extruder to be: 110° C. for zone 1, 150° C. for zone 2, 180° C. for zone 3, 210° C. for zone 4, 180° C. for zone 5, and 130° C. for the die head, controlling the screw speed to 5 rpm, and reacting in the twin-screw extruder for 10 min to obtain a micro-cracking liquid glue.

[0083] 3) Select a high-temperature and high-pressure reactor with a volume of 1 L, and add the micro-lysis liquid gel into the reactor in an amount of 10% of the volume of the high-temperature and high-pressure reactor.

[0084] 4) Open the air inlet and exhaust port of the reactor, and introduce N2 with a purity of 99.999% into the reactor for 15 minutes. After exhausting the air in the reactor, close the exhaust port, use the gas cylinder pressure reducing valve to adjust the pressure in the reactor to 1.2MPa, close the air inlet, turn on the heating device, and increase the temperature to 320°C at a rate of 10°C / min. After reacting for 15 minutes, wait for the instrument temperature to cool down to room temperature before discharging. The product is naturally cooled to room temperature to obtain a polyethylene wax asphalt modifier.

[0085] The polyethylene wax asphalt modifier prepared in this example is used to modify asphalt: 70# base asphalt is preheated to 120°C in a container, 5% by mass of the polyethylene wax asphalt modifier is added to the asphalt, and after it is fully dissolved in the asphalt, stirred for 15 minutes to obtain modified asphalt Example 2.

[0086] Example 3

[0087] 1. A cracking catalyst, wherein the raw materials are composed of 26 parts of Ni(NO3)2·6H2O reagent, 30 parts of expanded vermiculite and 50 parts of deionized water, calculated by weight.

[0088] The preparation method of the above cracking catalyst comprises the following steps:

[0089] (1) Same as step (1) of Example 1.

[0090] (2) Same as step (2) in Example 1.

[0091] (3) Same as step (3) of Example 1.

[0092] (4) The impregnated powder was dried at 60° C. for 30 min, and then placed in a muffle furnace and calcined at 300° C. for 2.5 h to obtain a cracking catalyst.

[0093] 2. A polyethylene wax asphalt modifier, whose raw materials are composed of 100 parts of polyethylene particles (20 parts of HDPE + 30 parts of LDPE + 50 parts of LLDPE) and 5 parts of cracking catalyst, calculated by weight.

[0094] The preparation method of the above-mentioned polyethylene wax asphalt modifier comprises the following steps:

[0095] 1) Same as step 1) in Example 1.

[0096] 2) feeding the mixture particles into a twin-screw extruder, controlling the temperature of each zone of the twin-screw extruder to be: 120° C. for zone 1, 160° C. for zone 2, 190° C. for zone 3, 220° C. for zone 4, 190° C. for zone 5, and 140° C. for the die head, controlling the screw speed to 5 rpm, and reacting in the twin-screw extruder for 10 min to obtain a micro-cracking liquid glue.

[0097] 3) Select a high-temperature and high-pressure reactor with a volume of 1 L, and add the micro-lysis liquid gel into the reactor in an amount of 10% of the volume of the high-temperature and high-pressure reactor.

[0098] 4) Open the air inlet and exhaust port of the reactor, and introduce N2 with a purity of 99.999% into the reactor for 15 minutes. After exhausting the air in the reactor, close the exhaust port, use the gas cylinder pressure reducing valve to adjust the pressure in the reactor to 0.8MPa, close the air inlet, turn on the heating device, and increase the temperature to 360°C at a rate of 10°C / min. After reacting for 10 minutes, wait for the instrument temperature to cool down to room temperature before discharging. The product is naturally cooled to room temperature to obtain a polyethylene wax asphalt modifier.

[0099] The polyethylene wax asphalt modifier prepared in this example is used to modify asphalt: 70# base asphalt is preheated to 120°C in a container, 5% by mass of the cracked wax modifier is added to the asphalt, and after it is fully dissolved in the asphalt, it is stirred for 15 minutes to obtain modified asphalt Example 3.

[0100] Example 4

[0101] The only difference from Example 1 is that the reaction temperature of the reactor in step 4) is 320° C., and the remaining steps and parameters are the same as those in Example 1.

[0102] Example 5

[0103] The only difference from Example 1 is that the reaction temperature of the reactor in step 4) is 300°C and the reaction time is 20 min. The remaining steps and parameters are the same as those in Example 1.

[0104] Comparative Example 1

[0105] The only difference from Example 1 is that in the process of preparing the polyethylene wax asphalt modifier, step 2) is omitted, and the reaction time of the reactor in step 4) is 20 minutes.

[0106] Comparative Example 2

[0107] The only difference from Example 1 is that in the process of preparing the polyethylene wax asphalt modifier, step 2) is omitted, and in step 4), the air pressure in the reactor is 1.2 MPa, the reaction temperature is 320° C., and the reaction time is 25 min.

[0108] Comparative Example 3

[0109] The only difference from Example 1 is that in the process of preparing the polyethylene wax asphalt modifier, step 2) is omitted, and in step 4), the air pressure in the reactor is 0.8 MPa, the reaction temperature is 360° C., and the reaction time is 20 min.

[0110] Comparative Example 4

[0111] The only difference from Example 1 is that in the process of preparing the polyethylene wax asphalt modifier, step 2) is omitted, and the reaction temperature of the reactor in step 4) is 320° C. and the reaction time is 20 min.

[0112] Comparative Example 5

[0113] The only difference from Example 1 is that in the process of preparing the polyethylene wax asphalt modifier, step 2) is omitted, and the reaction temperature of the reactor in step 4) is 300° C. and the reaction time is 30 min.

[0114] The penetration, softening point, ductility and viscosity changes of the modified asphalt prepared in the above examples and comparative examples were analyzed and tested. The analysis and testing tests were strictly carried out in accordance with the specific requirements and steps of the "Test Procedure for Asphalt and Asphalt Mixtures in Highway Engineering" (JTGE20-2011). The results are shown in Table 1.

[0115] Table 1

[0116]

[0117]

[0118] As can be seen from Table 1, the penetration of Examples 1-5 is significantly lower than that of the base asphalt, and the softening point is significantly higher than that of the base asphalt, indicating that the use of the gradient controllable technology of the present invention (twin-screw extruder + second-order gradient cracking technology of high-temperature and high-pressure reactor) to prepare the polyethylene wax modifier has a significant improvement on the high-temperature performance of asphalt. The 10°C elongation is increased to a certain extent compared to the base asphalt, indicating that it has an improvement on the low-temperature performance of asphalt. The Brookfield viscosity at 135°C is significantly reduced compared to the base asphalt, indicating that it has a great effect on the warm mix of asphalt.

[0119] The needle penetration of comparative examples 1-5 is significantly improved compared with the base asphalt, and the softening point is improved compared with the base asphalt, but the effect is not obvious, indicating that the polyethylene wax modifier prepared by the traditional reactor cracking technology has little effect on improving the high-temperature performance of asphalt. The 10°C ductility is reduced to a certain extent compared with the base asphalt, indicating that it has an adverse effect on the low-temperature performance of asphalt.

[0120] It can be concluded from the above results that since the waste plastic particles used in the embodiment are mixed with three different types of polyethylene (HDPE+LDPE+LLDPE), the traditional high temperature and high pressure reactor is used to crack them, and there will be a phenomenon of excessive cracking of some polyethylene particles. Due to excessive cracking, the polyethylene wax modifier produced has an adverse effect on the performance of asphalt. The modified asphalt prepared by the polyethylene wax asphalt modifier of the present invention can effectively improve the high temperature performance of asphalt while meeting the "Technical Specifications for Highway Asphalt Pavement Construction" under the premise of effectively reducing the mixing temperature and meeting the "Technical Specifications for Highway Asphalt Pavement Construction". At the same time, the low temperature performance is also improved to a certain extent. Therefore, the method of gradient cracking of polyethylene particles using a twin-screw extruder + high temperature and high pressure reactor can achieve accurate and controllable full cracking of waste polyethylene particles mixed with a variety of polyethylenes, thereby preparing a polyethylene wax modifier with good appearance and excellent performance.

[0121] The embodiments described above are only descriptions of the preferred modes of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. Use of a cracking catalyst in the preparation of a polyethylene waxy asphalt modifier, characterized in that: The preparation method of the cracking catalyst comprises the following steps: Drying and crushing the expanded vermiculite to obtain expanded vermiculite powder; Dissolving a nickel salt in water to obtain a nickel nitrate solution; The expanded vermiculite powder is immersed in a nickel nitrate solution and mixed evenly, and then naturally precipitated and filtered to obtain an immersed powder; The impregnated powder is dried, and then calcined at 300-350° C. for 2.5-3 hours to obtain the cracking catalyst; The mass ratio of the expanded vermiculite to the nickel salt and water is 30:26:(30-50).

2. The use of the cracking catalyst according to claim 1 in the preparation of a polyethylene waxy asphalt modifier, characterized in that: The nickel salt is Ni(NO3)2·6H2O.

3. A method for preparing a polyethylene waxy asphalt modifier, characterized in that: The following steps are involved: Mixing polyethylene particles and the cracking catalyst described in claim 1 or 2 to obtain mixture particles; The mixture particles are fed into a twin-screw extruder for extrusion to obtain a micro-cracked liquid glue; The micro-cracked liquid gum is subjected to a high temperature and high pressure reaction to obtain the polyethylene waxy asphalt modifier.

4. The method for preparing the polyethylene waxy asphalt modifier according to claim 3, characterized in that: The polyethylene particles include high-density polyethylene, low-density polyethylene and / or linear low-density polyethylene.

5. The method for preparing the polyethylene waxy asphalt modifier according to claim 3, characterized in that: The mass ratio of the polyethylene particles to the cracking catalyst is 100:

5.

6. The method for preparing the polyethylene waxy asphalt modifier according to claim 3, characterized in that: The parameters of the twin-screw extruder are set as follows: zone 1 temperature 100-120°C, zone 2 temperature 140-160°C, zone 3 temperature 170-190°C, zone 4 temperature 200-220°C, zone 5 temperature 170-190°C, die head temperature 120-160°C, and screw speed 5rpm.

7. The method for preparing the polyethylene waxy asphalt modifier according to claim 3, characterized in that: The high temperature and high pressure reaction is specifically: reacting at 320-360° C. for 15-30 minutes under an inert atmosphere and a pressure of 0.8-1.6 MPa.

8. The polyethylene waxy asphalt modifier prepared according to the preparation method according to any one of claims 3 to 7.

9. Use of the polyethylene waxy asphalt modifier as claimed in claim 8 in modified asphalt.

10. A modified asphalt, characterized in that: The raw materials include base asphalt and the polyethylene waxy asphalt modifier described in claim 8.

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