Waste thermoplastic polyurethane modified asphalt and preparation method thereof

Abstract

The invention relates to the technical field of road building materials, in particular to waste thermoplastic polyurethane modified asphalt and a preparation method thereof. According to the method, waste thermoplastic polyurethane is used as a modifier, and the modified asphalt with excellent high and low temperature performance is prepared through pretreatment, melt blending and shear dispersion processes. The method comprises the following steps: (1) carrying out sorting, cleaning, crushing and surface modification on waste thermoplastic polyurethane; (2) carrying out melt blending on the pretreated waste thermoplastic polyurethane particles and matrix asphalt at a high temperature, and carrying out high-speed shearing to realize uniform dispersion; and (3) optimizing the interface bonding characteristics of the asphalt and the waste thermoplastic polyurethane by virtue of a solubilizer and an interface agent. The low-temperature ductility of the obtained modified asphalt is obviously improved by more than or equal to 50cm, the softening point is improved by more than or equal to 10 DEG C, and the modified asphalt has good storage stability. According to the invention, resource utilization of waste thermoplastic polyurethane is realized, environmental pollution is reduced, the cost of modified asphalt is reduced, and the modified asphalt is suitable for pavement engineering of high-grade highways and extreme climate areas.

Description

Technical Field

[0001] The invention relates to the technical field of road construction materials, in particular to waste thermoplastic polyurethane modified asphalt and a preparation method thereof. Background Art

[0002] As an important road engineering material, asphalt occupies a core position in global infrastructure construction. However, traditional petroleum asphalt has inherent defects such as easy softening at high temperatures, easy brittle cracking at low temperatures, and poor anti-aging performance, which makes it difficult to meet the high modulus, high elastic recovery rate and long life requirements of modern transportation for pavement materials. For this reason, modified asphalt technology came into being, among which polymer modified asphalt has attracted much attention due to its significant improvement in material performance. Although the current mainstream modifier styrene-butadiene block copolymer modified asphalt can improve high temperature performance, it has problems such as high price of the modifier and insufficient UV aging resistance.

[0003] As a high-performance polymer, thermoplastic polyurethane has an elongation at break of 600%-800%, a wear resistance that is 5-10 times that of natural rubber, and excellent oil resistance and weather resistance. According to data from the European Plastics Association, more than 500,000 tons of waste thermoplastic polyurethane (TPU) materials are generated worldwide each year, mainly from shoe materials, automotive interiors, and industrial conveyor belts. Traditional treatment methods are mainly landfill and incineration, which not only releases toxic substances such as benzene and isocyanates, but also produces about 2.8 tons of CO per ton of thermoplastic polyurethane. 2 Equivalent carbon emissions.

[0004] At present, there are also some technologies for polyurethane modified asphalt. The application number is 201710476851.7. The invention name is "A polyurethane modified asphalt and its preparation method". It discloses a technical solution of using polyurethane prepolymer to modify ordinary asphalt and optimizing the compatibility with asphalt with the help of admixtures. The prepared polyurethane modified asphalt has good low-temperature performance, but the essence of this method is physical modification, which will still lead to the separation of the polyurethane modifier and the asphalt, resulting in a shortened service life of the pavement.

[0005] A Chinese patent with authorization announcement number CN116178970B discloses a polyurethane modified asphalt and a preparation method thereof. By enhancing the modification effect of polyurethane asphalt with graphene oxide and organic solvent acetone, an asphalt-based composite material is developed that can take into account the high-temperature performance advantages of asphalt and make up for its insufficient low-temperature performance. However, this method has high economic costs and the organic solvents will cause pollution to the environment.

[0006] The application number is 202111655309.0, and the name of the invention is "A method for preparing polyurethane and SBS composite modified asphalt", which discloses a technical solution of adding styrene-butadiene-styrene block copolymer to base asphalt and stirring to react to obtain an SBS modified asphalt matrix, and then adding polyurethane to the SBS modified asphalt matrix to react to obtain polyurethane and SBS composite modified asphalt, but the method does not involve the recycling of waste thermoplastic polyurethane. Summary of the invention

[0007] In response to the current problems of low resource utilization rate of waste thermoplastic polyurethane materials and insufficient technical reference basis for waste thermoplastic polyurethane modified asphalt, the present application provides a waste thermoplastic polyurethane modified asphalt and a preparation method thereof. Waste thermoplastic polyurethane particles are modified and modified by a silane coupling agent to reduce their surface polarity, and ethylene-vinyl acetate is used as a solubilizer to improve the interfacial bonding characteristics between waste thermoplastic polyurethane and asphalt, thereby preparing waste modified asphalt with excellent high and low temperature properties, expanding the ways to utilize waste resources, reducing environmental pressure, and reducing the production cost of high-performance modified asphalt.

[0008] The invention provides a waste thermoplastic polyurethane modified asphalt, comprising the following components in parts by weight: 100 parts of base asphalt, 5-10 parts of waste thermoplastic polyurethane, 0.1-0.5 parts of surface modifier, 1-5 parts of solubilizer, and 0.1-1 parts of interface agent.

[0009] Furthermore, the needle penetration of the base asphalt is 65~75dmm.

[0010] Furthermore, the content of waste thermoplastic polyurethane is 5-10% of the content of base asphalt, and the waste thermoplastic polyurethane mainly comes from discarded sports equipment, scrapped automobile sealing strips, waste electronic product sealing rings and other products.

[0011] Waste thermoplastic polyurethane usually exists in the form of particles, fragments, and powder, and may contain impurities such as metals and fibers. The impurities are removed by magnetic separation followed by flotation, and then the surface oil is cleaned with ethanol to ensure that the impurity content does not exceed 0.1%.

[0012] Furthermore, the cleaned waste thermoplastic polyurethane is crushed by low-temperature liquid nitrogen, and a plastic crusher is used to control the particle size of the waste thermoplastic polyurethane particles to be below 0.5 mm.

[0013] Furthermore, the density of the waste thermoplastic polyurethane material is 1.15-1.25 g / cm 3 , the waste thermoplastic polyurethane is pretreated by diol degradation, and the diol is neopentyl glycol.

[0014] Furthermore, the surface modifier is silane coupling agent KH-550, and the dosage is 2-5% of the waste thermoplastic polyurethane. The organophilic end of the silane coupling agent reacts with the polar groups of the polyurethane, such as carbamate, and the hydrophobic end is compatible with the hydrocarbons in the asphalt to form a bridge structure, reduce interface defects, and improve the interface compatibility with the asphalt.

[0015] Furthermore, the solubilizer is ethylene-vinyl acetate copolymer (EVA), and the amount is 1-5% of the matrix asphalt content. The EVA molecular chain contains both non-polar vinyl and polar vinyl acetate groups, which can connect non-polar asphalt hydrocarbons with polar waste thermoplastic polyurethane to promote uniform dispersion. EVA has a low cost, and its coordinated use with waste thermoplastic polyurethane can improve resource utilization, which is in line with the concept of solid waste resource utilization.

[0016] Furthermore, the interface agent is nano-silicon dioxide, and the dosage is 0.1-1% of the matrix asphalt content. Nano-silicon dioxide has a high specific surface area and abundant surface hydroxyl groups, which can form hydrogen bonds or chemical bonds with polar groups in polyurethane, and at the same time combine with non-polar hydrocarbons in asphalt through physical adsorption, acting as a nano-bridge to further reduce phase separation.

[0017] The present invention also provides a method for preparing waste thermoplastic polyurethane modified asphalt, comprising the following steps: (1) pretreatment of waste thermoplastic polyurethane: washing and drying the waste thermoplastic polyurethane and crushing it to a particle size of ≤0.5 mm, pretreating the waste thermoplastic polyurethane with neopentyl glycol, and treating the waste thermoplastic polyurethane particles with a surface modifier to enhance the interface bonding strength between the waste thermoplastic polyurethane and the matrix asphalt; the specific steps of pretreating the waste thermoplastic polyurethane with neopentyl glycol are as follows: pretreating the surface of the waste thermoplastic polyurethane with neopentyl glycol, first, mixing the neopentyl glycol and the waste polyurethane at room temperature in a reactor with a butterfly stirrer at an angle of 45°, and uniformly mixing and stirring at a speed of 200 rpm for 15 minutes; secondly, raising the temperature of the reactor to 120°C, raising the stirrer speed to 300 rpm, and mixing and stirring for 1 hour; finally, turning off the reactor heating device, reducing the speed to 100 rpm and stirring until the temperature drops to room temperature.

[0018] (2) Heating of base asphalt: Heat the base asphalt to 140~160℃ and keep it in a fluid state.

[0019] (3) Melt blending: Add the pretreated waste thermoplastic polyurethane particles into the hot matrix asphalt in step (2) and stir continuously.

[0020] (4) Add a solubilizer and an interfacial agent to the asphalt in step (3) and stir continuously.

[0021] (5) placing the asphalt in step (4) under a high-speed shearing machine for shearing to uniformly disperse the waste thermoplastic polyurethane.

[0022] (6) The asphalt of step (5) is placed in a mixer and stirred to fully swell, thereby obtaining waste thermoplastic polyurethane modified asphalt.

[0023] Furthermore, the cleaning agent used for cleaning the waste thermoplastic polyurethane in step (1) is ethanol.

[0024] Furthermore, the stirring conditions in step (3) are stirring time of 20 to 25 min and stirring rate of 1500 to 1800 r / min.

[0025] Furthermore, the shearing conditions in step (5) are shearing time 25-45 min, shear rate 2500-4000 r / min, and shear temperature 160-180° C., preferably 170° C.

[0026] The above one or more technical solutions in the embodiments of the present invention have at least one of the following technical effects: the present invention uses waste thermoplastic polyurethane to modify the matrix asphalt, improves the high and low temperature performance of road asphalt, and thus enhances the service life of the road surface. Waste thermoplastic polyurethane has high stability and is not easily compatible with asphalt. The phase separation between waste thermoplastic polyurethane and asphalt is reduced by silane coupling agent, EVA and nano-silicon dioxide. In addition, the modifier originally comes from waste thermoplastic polyurethane in daily production, which realizes the resource utilization of waste thermoplastic polyurethane and has significant economic and environmental benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is the dispersion diagram of the waste thermoplastic polyurethane modified asphalt obtained in Example 1.

[0028] Figure 2 This is the dispersion diagram of the waste thermoplastic polyurethane modified asphalt obtained in Example 2.

[0029] Figure 3 This is the dispersion diagram of the waste thermoplastic polyurethane modified asphalt obtained in Example 3.

[0030] Figure 4 This is the dispersion diagram of the waste thermoplastic polyurethane modified asphalt obtained in Example 4. DETAILED DESCRIPTION

[0031] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific embodiments of the present invention are described in detail below in conjunction with the accompanying drawings. In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention can be implemented in many other ways different from those described below, and those skilled in the art can make similar improvements without violating the connotation of the present invention, so the present invention is not limited by the specific embodiments disclosed below.

[0032] Example 1

[0033] (1) Pretreatment of waste thermoplastic polyurethane: The waste thermoplastic polyurethane was washed with ethanol, dried and crushed to a particle size of ≤0.5 mm, and the waste thermoplastic polyurethane particles were pretreated with neopentyl glycol at 150°C for 3 hours; the waste thermoplastic polyurethane particles were treated with a surface modifier with a mass ratio of 3% of the waste thermoplastic polyurethane.

[0034] (2) Heating of base asphalt: Heat the base asphalt to 150°C and keep it warm for 1 hour to keep it in a fluid state.

[0035] (3) Melt blending: Add 6% of the mass of the matrix asphalt pre-treated waste thermoplastic polyurethane particles into the hot asphalt and stir for 20 min at a stirring rate of 1800 r / min.

[0036] (4) Add 2% of the mass of solubilizer and 0.3% of the interface agent to the base asphalt in step (3) and stir with a glass rod for 3 minutes.

[0037] (5) The asphalt obtained in step (4) was sheared on a high-speed shearing machine with a shearing time of 30 min, a temperature of 170° C., and a shearing rate of 3000 r / min.

[0038] (6) The asphalt of step (5) is placed in a mixer and stirred for 20 minutes at a rate of 1800 r / min to allow it to fully swell, thereby obtaining waste thermoplastic polyurethane modified asphalt.

[0039] Depend on Figure 1 It can be seen that the waste thermoplastic polyurethane is distributed in the asphalt in filamentous and granular forms, indicating that the distribution uniformity still needs to be improved.

[0040] Example 2

[0041] Compared with Example 1, except that the solubilizer added in step (4) is 4% of the mass of the base asphalt, the other operating steps are the same.

[0042] Depend on Figure 2 It can be seen that the waste thermoplastic polyurethane is mainly distributed in the asphalt in a granular form, indicating that the distribution uniformity is good, and the modification of asphalt by the waste thermoplastic polyurethane shows good dispersion stability.

[0043] Example 3

[0044] Compared with Example 1, except that the interface agent added in step (4) is 0.8% of the mass of the base asphalt, the other operating steps are the same.

[0045] Depend on Figure 3 It can be seen that the waste thermoplastic polyurethane is mainly distributed in the asphalt in the form of fibers and small particles, indicating that the distribution uniformity needs to be improved. The waste thermoplastic polyurethane is sheared and dispersed to form fibers. The dispersion stability of the waste thermoplastic polyurethane in asphalt is average.

[0046] Example 4

[0047] Compared with Example 1, except that the waste thermoplastic polyurethane particles added in step (3) account for 9% of the base asphalt, the remaining operating steps are the same.

[0048] Depend on Figure 4 It can be seen that waste thermoplastic polyurethane is mainly distributed in asphalt in the form of fibers and large particles, indicating that the distribution uniformity needs to be improved.

[0049] Comparative Example 1

[0050] Compared with Example 1, no surface modifier, solubilizer and interface agent were added, and the remaining steps were the same.

[0051] Comparative Example 2

[0052] Compared with Example 1, no solubilizer and interface agent are added, and the remaining steps are the same.

[0053] Comparative Example 3

[0054] Compared with Example 1, no surface modifier was added, and the remaining steps were the same.

[0055] Comparative Example 4

[0056] Compared with Example 1, the waste thermoplastic polyurethane particles were treated with a surface modifier in an amount of 4% by mass of the waste thermoplastic polyurethane; the added solubilizer was 4% by mass of the base asphalt, and the added interface agent was 0.8% by mass of the base asphalt.

[0057] The basic properties of waste thermoplastic polyurethane modified asphalt were tested.

[0058] The waste thermoplastic polyurethane modified asphalt obtained in the examples and comparative examples was subjected to basic index tests, and the results are shown in Table 1.

[0059] Table 1

[0060]

[0061] As can be seen from Table 1, the addition of waste thermoplastic polyurethane reduces the penetration of asphalt, while increasing the ductility, softening point and viscosity, among which the increase in viscosity is particularly obvious. This is because the hard segments in the waste thermoplastic polyurethane tend to combine with the polar components in the asphalt, and the soft segments are entangled with the non-polar oil components to form an interface structure of "hard segment anchoring-soft segment extension", which significantly enhances the low-temperature performance of asphalt.

[0062] In addition, the softening point difference index of Comparative Example 1 is higher than the maximum value specified in the specification, which proves that the compatibility of waste thermoplastic polyurethane and asphalt is not ideal. Comparative Examples 2 and 3 respectively introduced polyurethane surface modifiers and asphalt solubilizers. It can be seen that although the compatibility of asphalt has been improved, the synergistic effect of the two can more efficiently optimize the interfacial properties of waste thermoplastic polyurethane and asphalt. Comparative Example 4 added the highest dosage of surface modifier, solubilizer and interface agent. Although this group of experiments achieved good compatibility, it can be seen from the high values ​​of viscosity and softening point that the hardness of the modified asphalt is also significantly increased, which is not conducive to on-site construction.

[0063] The results of Examples 1 and 4 show that increasing the amount of waste thermoplastic polyurethane added will increase the viscosity and softening point of the modified asphalt.

[0064] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing waste thermoplastic polyurethane modified asphalt, which is used to prepare modified asphalt: characterized in that: The components of the modified asphalt are specifically as follows in parts by weight: Base asphalt: 100 parts; Waste thermoplastic polyurethane: 5-10 parts; Surface modifier: 0.1~0.5 parts; Solubilizer: 1~5 parts; Interface agent: 0.1~1 part; The preparation method of the modified asphalt comprises the following specific steps: (1) Pretreatment of waste thermoplastic polyurethane: the waste thermoplastic polyurethane is cleaned, dried and then crushed to a particle size of ≤0.5 mm, the waste thermoplastic polyurethane is pretreated with neopentyl glycol, and the waste thermoplastic polyurethane particles are treated with a surface modifier; (2) Heating the base asphalt: Heat the base asphalt to 140-160°C and keep it in a fluid state; (3) melt blending: adding the pretreated waste thermoplastic polyurethane particles into the hot matrix asphalt in step (2) and stirring continuously; (4) adding a solubilizer and an interfacial agent to the asphalt in step (3) and stirring continuously; (5) placing the asphalt in step (4) under a high-speed shearing machine for shearing to uniformly disperse the waste thermoplastic polyurethane; (6) The asphalt of step (5) is placed in a mixer and stirred to fully swell, thereby obtaining waste thermoplastic polyurethane modified asphalt.

2. The method for preparing waste thermoplastic polyurethane modified asphalt according to claim 1, characterized in that: The needle penetration of the base asphalt is 65~75dmm.

3. The method for preparing waste thermoplastic polyurethane modified asphalt according to claim 1, characterized in that: The density of the waste thermoplastic polyurethane material is 1.15-1.25 g / cm 3 , the waste thermoplastic polyurethane is pretreated by diol degradation, and the diol is neopentyl glycol.

4. The method for preparing waste thermoplastic polyurethane modified asphalt according to claim 1, characterized in that: The surface modifier is silane coupling agent KH-550.

5. The method for preparing waste thermoplastic polyurethane modified asphalt according to claim 1, characterized in that: The solubilizing agent is ethylene-vinyl acetate copolymer.

6. The method for preparing waste thermoplastic polyurethane modified asphalt according to claim 1, characterized in that: The interface agent is nano silicon dioxide.

7. The method for preparing waste thermoplastic polyurethane modified asphalt according to claim 1, characterized in that: The cleaning agent used for cleaning the waste thermoplastic polyurethane in step (1) is ethanol.

8. The method for preparing waste thermoplastic polyurethane modified asphalt according to claim 1, characterized in that: The stirring conditions in step (3) are a stirring time of 20 to 25 min and a stirring rate of 1500 to 1800 r / min.

9. The method for preparing waste thermoplastic polyurethane modified asphalt according to claim 1, characterized in that: The shearing conditions in step (5) are shearing time 25-45 min, shear rate 2500-4000 r / min, and shear temperature 160-180°C.

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