Method for modifying pet plastic and application of modified pet plastic in asphalt modification

Abstract

The application discloses a PET plastic modification method and application of modified PET plastic in asphalt modification, and relates to the technical field of road engineering materials.The PET modification method comprises the following steps: (1) PET is subjected to microwave radiation treatment to realize PET depolymerization, and PET oligomer is obtained; and (2) soybean oil is subjected to grafting reaction with the PET oligomer to obtain grafted modified PET; the microwave radiation treatment is carried out under normal pressure, the radiation frequency is 2.45 GHz, and the radiation temperature is 200-300 DEG C.The PET is subjected to depolymerization by using the microwave depolymerization technology, the efficient depolymerization of the PET can be realized under normal pressure in a very short time of 2-10 min, then the PET after the microwave depolymerization is subjected to grafting modification by using soybean oil as raw material, the waste soybean oil raw material can be used, the resource utilization of the waste soybean oil raw material is realized, and the problems of phase separation and performance degradation of the PET modified asphalt material are solved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of road engineering materials, in particular to a modification method of PET plastic and application of modified PET plastic in asphalt modification. BACKGROUND

[0002] Polyethylene terephthalate (PET) is a high molecular material widely used in plastic packaging and textile industries. Due to its good mechanical properties, chemical corrosion resistance and thermal stability, PET plastic is widely used to manufacture beverage bottles, food containers, textile fibers and other products. However, the high molecular weight and polar structure of PET make it difficult to be effectively recycled in waste disposal, and its poor compatibility with non-polar asphalt materials makes it difficult to be directly applied in asphalt modification field.

[0003] In road construction, asphalt is a key component of pavement materials, and its mechanical properties and durability are crucial for improving the service life of roads. In order to improve the performance of asphalt, researchers try to improve its rheological, viscoelastic and anti-aging properties by using modifiers. Traditional asphalt modifiers include polymers (such as SBS, SBR, etc.), rubber powder, etc. However, these materials usually have problems such as high price, unstable modification effect, environmental pollution, etc., so people continue to explore alternative materials. With the improvement of environmental awareness and the progress of resource recycling technology, more and more research focuses on how to apply waste PET plastic to asphalt modification to realize waste resource utilization. However, the molecular structure of PET plastic is complex, especially its high molecular weight and polar molecular chain, which makes it have poor compatibility with asphalt.

[0004] The high molecular weight of PET comes from its long-chain polymer structure, which gives PET plastic good mechanical strength and heat resistance, but also increases the difficulty of material decomposition. In traditional PET degradation technology, methods such as pyrolysis, chemical depolymerization or biodegradation are often used. However, these methods usually require long reaction times and high energy consumption, and may produce harmful by-products, making it difficult to achieve large-scale application. In addition, the compatibility problem of PET material in asphalt is also a key challenge for the application of PET modified asphalt. Asphalt is a complex non-polar compound composed of saturated components, aromatic components, resins and asphaltenes, with weak polarity. Therefore, PET with strong polarity is not easy to disperse in asphalt and is prone to phase separation. This phase separation not only affects the uniformity of modified asphalt, but also causes the deterioration of material performance during high temperature or storage. SUMMARY

[0005] The purpose of the present application is to provide a modification method of PET plastic and application of modified PET plastic in asphalt modification to solve the problems existing in the prior art.

[0006] To achieve the above object, the present application provides the following scheme:

[0007] One of the technical solutions of the present application is to provide a PET modification method based on microwave depolymerization and soybean oil grafting, comprising the following steps:

[0008] (1) Microwave irradiation treatment is performed on PET to realize PET depolymerization, and PET oligomers are obtained;

[0009] (2) Grafting reaction is performed on the PET oligomers and soybean oil to obtain grafting modified PET;

[0010] The microwave irradiation treatment is performed under normal pressure, the irradiation frequency is 2.45 GHz, and the irradiation temperature is 200-300℃.

[0011] As a further preferred embodiment of the present application, the microwave output power during irradiation is 600-800w, and the microwave irradiation treatment time is 2-10min.

[0012] As a further preferred embodiment of the present application, the molecular weight of the PET oligomers is 4000Da-5000Da.

[0013] As a further preferred embodiment of the present application, the grafting reaction is performed at 120-180℃, and the grafting reaction time is 1-3h.

[0014] As a further preferred embodiment of the present application, the carboxyl content in the soybean oil is 1%-10%.

[0015] As a further preferred embodiment of the present application, the soybean oil is treated waste soybean oil, and the treatment includes the steps of water washing, filtering, dewatering and acid treatment.

[0016] As a further preferred embodiment of the present application, the acid treatment temperature is 60℃-80℃.

[0017] As a further preferred embodiment of the present application, the pretreatment of the waste soybean oil specifically includes the following steps:

[0018] a. Water washing: mix water and waste soybean oil, stir uniformly, and then separate the water phase after standing, and repeat the washing several times;

[0019] b. Filtering: after water washing, multi-stage filtering is performed, first removing large particle impurities through a coarse filter screen, and then removing small impurities through a fine filter screen;

[0020] c. Dewatering: the filtered waste soybean oil is heated to 60℃-80℃ and kept for a certain time to remove water.

[0021] d. Acidification treatment: the waste soybean oil after water washing, filtration and dehydration is subjected to acidification treatment, the waste soybean oil is heated to 60-80 DEG C, and an acid aqueous solution with a concentration of 30-50wt% is added to perform acid treatment, the temperature is controlled at 60-80 DEG C, and the acid treatment time is 30-60 min. The acid aqueous solution accounts for 1-15% of the mass of the waste soybean oil.

[0022] As a further preferred embodiment of the present application, in the graft modification treatment, the depolymerized PET and the pretreated soybean oil are mixed according to a mass ratio of 1:1.

[0023] As a further preferred embodiment of the present application, after the completion of the graft reaction, the unreacted waste soybean oil is cleaned by using acetone.

[0024] The acid used in the acidification treatment can be phosphoric acid (H3PO4), hydrochloric acid (HCl), oxalic acid (H2C2O4) or sulfuric acid (H2SO4). The present application preferably uses the relatively mild oxalic acid to perform acidification treatment on the waste soybean oil, so as to effectively remove impurities, reduce the risk of oil emulsification, and improve the treatment effect and the stability of subsequent application.

[0025] The second technical solution of the present application provides a modified PET material prepared by using the above modification method.

[0026] The third technical solution of the present application provides a modified asphalt obtained by mixing the above modified PET material with base asphalt.

[0027] As a further preferred embodiment of the present application, the mass ratio of the modified PET material to the base asphalt is 3% to 10%.

[0028] The present application has the following technical effects:

[0029] The present application uses microwave depolymerization technology to depolymerize PET, and can realize efficient depolymerization of PET in a very short time of 2-10 min under normal pressure, the reaction process is fast and the energy utilization rate is high, thereby avoiding the problems of high energy consumption and long reaction time in the traditional pyrolysis method.

[0030] The present application uses soybean oil as a raw material to graft modify the PET after microwave depolymerization, can use waste soybean oil raw material to realize its resource utilization, effectively improves the polarity problem of PET, makes it more suitable for application in asphalt modification material, has the remarkable characteristics of economic and environmental protection, and the modified PET material of the present application shows excellent storage stability in asphalt, and can effectively solve the problems of phase separation and performance degradation of PET modified asphalt material.

[0031] The application is based on the microwave depolymerization and waste soybean oil grafted modified PET modified asphalt material which has wide application prospects in the field of road construction, can improve the road performance, promote the resource utilization of waste plastics and waste oils, and has important economic and environmental significance. BRIEF DESCRIPTION OF DRAWINGS

[0032] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed to be used in the embodiments will be briefly introduced as follows. Obviously, the drawings in the following description only constitute some embodiments of the present application, and for those skilled in the art, other drawings can also be obtained without creative labor on the basis of these drawings.

[0033] Figure 1 The segregation index of the PET doped modified asphalt of the control group and each treatment group of the present application.

[0034] Figure 2 The modifier distribution comparison in the modified asphalt sample under different test conditions of the present application. DETAILED DESCRIPTION

[0035] The various exemplary embodiments of the present application will now be described in detail, which should not be considered as limiting the present application, but should be understood as a more detailed description of certain aspects, characteristics and embodiments of the present application.

[0036] It should be understood that the terms described in the present application are only for describing the specific embodiments, and are not used to limit the present application. In addition, for the numerical range in the present application, it should be understood that each intermediate value between the upper limit and the lower limit of the range is also specifically disclosed. Each smaller range between any stated value or intermediate value within the stated range, and any other stated value or intermediate value within the stated range, is also included in the present application. The upper limit and the lower limit of these smaller ranges can be independently included or excluded from the range.

[0037] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the present application pertains. Although preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present application. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials in connection with which the documents are concerned. In the event of any conflict between the content of this specification and any document incorporated by reference, the content of this specification will control.

[0038] Many modifications and variations of the specific embodiments of the application can be practiced in accordance with the teachings of the description of the application, which are within the scope of the present application. Other embodiments of the application will be apparent to those skilled in the art from consideration of the specification and practice of the application disclosed herein. The specification and examples of the application are exemplary only.

[0039] As used herein, the terms "comprise", "comprising", "include", "including", "have", "having" and the like are open-ended terms that are intended to mean "including but not limited to".

[0040] It should be noted that the present application does not specifically describe the conventional operation means in the art, and is not the focus of the present application.

[0041] The embodiment of the present application grafts the PET material after microwave radiation depolymerization of waste soybean oil, and uses the modified PET material for asphalt modification treatment to improve the stability of asphalt.

[0042] Example 1

[0043] (1) Microwave depolymerization of PET plastic fragments:

[0044] The recycled PET plastics are sorted, washed to remove surface residues, crushed by a crusher after washing, and then dried to remove residual moisture.

[0045] According to the standard of 30g of PET fragments per portion, 5 portions are weighed respectively, which are respectively treatment groups 1-4 and a control group. Among them, the control group is not treated by microwave radiation (as is), and the treatment groups 1-4 are treated by microwave radiation with a frequency of 2.45GHz (microwave radiation temperature is 200-300℃, and the molecular weight of PET oligomer after microwave depolymerization is 4000Da-5000Da). Specifically:

[0046] Treatment group 1: microwave output power 600w for 5min; treatment group 2: microwave output power 600w for 10min; treatment group 3: microwave output power 800w for 5min; treatment group 4: microwave output power 800w for 10min.

[0047] (2) Pretreatment of waste soybean oil:

[0048] a. Water washing: mix water and waste soybean oil, stir uniformly, and then separate the water phase after standing, and repeat multiple times of washing;

[0049] b. Filtration: after water washing, multi-stage filtration is carried out, first through a coarse filter screen to remove large particles, and then use a fine filter screen to remove small impurities;

[0050] c. Dehydration: heat the filtered waste soybean oil to 80℃ to remove moisture.

[0051] d. Acidification treatment: The waste soybean oil after water washing, filtration and dehydration was heated to 80°C, and an oxalic acid (H2C2O4) aqueous solution with a concentration of 50wt% was added under stirring, the temperature was controlled at 80°C, the amount of the oxalic acid aqueous solution was 10% of the mass of the waste soybean oil, the acid treatment time was 3h, and until the pH of the lower water phase reached 3.5. The upper oil layer was finally collected to remove free fatty acids, gums and other impurities, and improve the purity and stability of the oil.

[0052] (3) Graft modification treatment:

[0053] The waste soybean oil after the pretreatment of step (2) was mixed with the PET product under five different test conditions of step (1) at a ratio of 1:1 at a temperature of 180°C, and reacted for 60min. After the reaction, the mixture was cooled to room temperature, and the precipitate was suspended in 500mL of acetone to wash away the excess unreacted waste soybean oil. After filtration and separation of the product, the product was again placed in 250mL of acetone for secondary cleaning. After cleaning, the product was filtered and reserved, and was then placed in a tray and flattened, and was placed in an oven at 160°C for drying for 1h to obtain the graft modified PET. The graft modified PET after drying was ground to a particle size of 0.3-0.6mm for subsequent preparation of modified asphalt.

[0054] (4) Preparation of PET modified asphalt:

[0055] 15g of the ground graft modified PET of step (3) was weighed, and a certain amount of base asphalt was heated and liquefied in a 150°C oven, and 300g of the liquefied base asphalt was weighed and transferred to a heating table for preheating. The 15g of the graft modified PET was uniformly added to the 300g of the base asphalt, and the amount of the graft modified plastic added was 5%. A controllable temperature high-speed shearing machine was used, the shearing temperature was controlled at 160°C, the shearing rate was 4000r / min, and the shearing time was 60min in total, so as to ensure that the graft modified PET material was fully dispersed in the asphalt matrix to form a uniform composite material, which was the PET modified asphalt.

[0056] The prepared PET modified asphalt was subjected to a storage stability experiment, and a dynamic rheological shearing instrument was used to test the rut factor and the fatigue factor, and then the segregation index was calculated to comprehensively evaluate the performance comparison of the PET modified asphalt prepared by the present application, the unmodified asphalt and the conventional PET modified asphalt in terms of high temperature performance, compatibility and storage stability.

[0057] 1. Rut factor and fatigue factor test:

[0058] First, the cut PET modified asphalt of the example was poured into an aluminum tube with a diameter of 25 mm and a length of 140 mm. Then, the aluminum tube was tightly closed and placed vertically in a holder inside an oven at a temperature of 163°C for 48 hours. Then, the aluminum tube was immediately placed in a refrigerator at -18°C for 6 hours. After the sample hardened due to freezing, each tube sample was cut into three equal parts (top, middle, and bottom), and the samples inside the top and bottom were extracted and placed in an aluminum box with a diameter of 30 mm for storage. Then, the top and bottom samples were placed in an oven at 150°C for 30 min to liquefy the samples, and then dropped to perform rut factor and fatigue factor tests.

[0059] The complex shear modulus G* and phase angle δ of the top and bottom of the five modified asphalts were measured at 64°C using a dynamic rheological shear instrument with a 25 mm spindle, at a frequency of 10 rad / s and a strain value of 12%, and the rut factor was calculated (Formula 1); the complex shear modulus G* and phase angle δ of the top and bottom of the five modified asphalts were measured at 25°C using a dynamic shear rheometer with an 8 mm spindle, at a frequency of 10 rad / s and a strain value of 12%, and the fatigue factor was calculated (Formula 2).

[0060]

[0061] Fatigue factor = G * ·sinδ (2)

[0062] In Formula (1) and Formula (2), G* is the complex shear modulus, which represents the total resistance of the material when repeatedly deformed by shear, including the elastic (recoverable) part and the viscous (non-recoverable) part; δ is the phase angle, which represents a relative index of the amount of recoverable and non-recoverable deformation.

[0063] According to Formula 1 and Formula 2, the rut factor and fatigue factor calculation results obtained from the complex modulus and phase angle at 64°C and 25°C, respectively, are summarized in Table 1 and Table 2.

[0064] Table 1 Rut factor calculation results at 64°C

[0065]

[0066]

[0067] Table 2 Fatigue factor calculation results at 25°C

[0068]

[0069] It can be seen that the rut factor and fatigue factor values are large at the bottom and small at the top. After the storage stability test of the PET modified asphalt, due to the density of the PET modifier being larger than the density of the base asphalt, the PET deposits at the bottom. The rut factor represents the high-temperature rut resistance of the asphalt material, and the larger the rut factor, the stronger the rut resistance of the asphalt material. The bottom value is larger than the top value, indicating that the modified asphalt at the bottom has stronger rut resistance at high temperature. The fatigue factor represents the medium-temperature fatigue resistance of the asphalt material, and the larger the fatigue factor, the stronger the fatigue resistance of the asphalt material. The bottom value is larger than the top value, indicating that the modified asphalt at the bottom has stronger fatigue resistance at medium temperature.

[0070] The compatibility of the PET modified asphalt is analyzed according to the segregation index (formula (3) or formula (4)).

[0071]

[0072] In formula (3) and formula (4), SI is an index for evaluating the storage stability of the PET modified asphalt, (G* / sinδ) is the rut factor, and (G*·sinδ) is the fatigue factor. The segregation index is calculated according to the rut factor and the fatigue factor. The storage stability index of the PET modified asphalt is shown in Table 1. Figure 1

[0073] 2. Stability test:

[0074] Figure 1 The segregation index of the PET doped modified asphalt of the control group and each treatment group is smaller, indicating that the storage stability of the modified asphalt is better.

[0075] According to formula (3), the segregation index of the PET modified asphalt without microwave depolymerization is 61%, the segregation index of the sample with a microwave output power of 600w and a microwave exposure time of 5min is 45%; the segregation index of the sample with a microwave output power of 600w and a microwave exposure time of 10min is 31%; the segregation index of the sample with a microwave output power of 800w and a microwave exposure time of 5min is 15%; and the segregation index of the sample with a microwave output power of 800w and a microwave exposure time of 10min is 7%.

[0076] Firstly, compared with the PET modified asphalt without microwave depolymerization, the segregation index of the PET modified asphalt after microwave depolymerization is significantly reduced, which can obviously improve the storage stability of the modified asphalt. Secondly, the segregation index has a linear relationship with the microwave output power and the microwave exposure time, and the best microwave treatment condition can be obtained as a microwave output power of 800w and a microwave exposure time of 10min. Similarly, the segregation index calculated by formula (4) is consistent with the above.

[0077] 3. Compatibility test: ​

[0078] The distribution of PET plastic in the top and bottom samples of the five modified asphalts was observed using dark field fluorescence microscopy:

[0079] The modified asphalt sample was dropped into the center of the glass slide by heating and liquefying, then covered with a glass slide and uniformly pressed into a thin layer, and then cooled to room temperature. A purple excitation light source with a wavelength of 435 mm was used, and a high-resolution camera and an optical image acquisition system were used to obtain the image. The distribution of the modifier in the modified asphalt sample under different test conditions is shown in Figure 2 .

[0080] When PET modified asphalt is observed by dark field fluorescence microscopy, the distribution of the modifier in the asphalt can be directly observed. The modifier PET emits obvious fluorescence, and the asphalt itself does not emit light. First, the PET modified asphalt without microwave depolymerization (as received) has obvious agglomerates or uneven distribution of the modifier in the asphalt, indicating poor compatibility. For the top of the sample with a microwave output power of 600 w and a microwave exposure time of 5 min, it appears chain-like, and the bottom appears clumpy, with some modifier aggregation. Similarly, for the two types of samples with a microwave output power of 600 w and 800 w and a microwave exposure time of 5 min, the modifier also has a clumpy aggregation phenomenon, but it is improved compared to the above-mentioned sample. For the sample with a microwave output power of 800 w and a microwave exposure time of 10 min, the PET particles on the top and bottom are smaller and have better dispersibility, and can be more uniformly distributed in the asphalt, thereby improving the compatibility.

[0081] The present application can realize efficient depolymerization of PET in a very short time of 2-10 min under normal pressure conditions, significantly improving the degradation efficiency. Moreover, the present application uses treated waste soybean oil to graft modify the PET after microwave depolymerization, which can effectively improve the phase separation and performance degradation problems in the storage process of traditional PET modified asphalt. The present application follows the concept of environmental protection and regeneration, uses waste PET plastic and waste soybean oil, not only reduces plastic pollution and waste oil disposal problems, but also provides high-performance modified asphalt materials for road construction, with significant environmental and economic benefits.

[0082] The above-described embodiments are only preferred modes of the present application and do not limit the scope of the present application. Without departing from the design spirit of the present application, various modifications and improvements to the technical solutions of the present application made by those skilled in the art shall fall within the protection scope determined by the claims of the present application.

Claims

1. A method for PET modification based on microwave depolymerization and soybean oil grafting, characterized by, The method is used for preparing graft modified PET for asphalt modification, and comprises the following steps: (1) PET is subjected to microwave radiation treatment to realize PET depolymerization, and PET oligomer is obtained; (2) Soybean oil is subjected to graft reaction with the PET oligomer to obtain graft modified PET; The microwave radiation treatment is carried out under normal pressure, the radiation frequency is 2.45 GHz, and the radiation temperature is 200-300 DEG C; The molecular weight of the PET oligomer is 4000 Da-5000 Da; The microwave radiation treatment is carried out for 2-10 min; The graft reaction is carried out at 120-180 DEG C, and the graft reaction is carried out for 1-3 h; The carboxyl content in the soybean oil is 1%-10%.

2. The PET modification method according to claim 1, characterized in that, The soybean oil is treated waste soybean oil, and the treatment comprises the steps of water washing, filtration, dehydration and acid treatment.

3. The PET modification method according to claim 2, characterized in that, The acid treatment is carried out at 60 DEG C-80 DEG C.

4. A modified PET material, characterized in that, The modified PET material is prepared by the modification method in any one of claims 1-3.

5. A modified bitumen characterized in that, The modified PET material is mixed with base asphalt.

6. The modified bitumen of claim 5, wherein, The mass ratio of the modified PET material to the base asphalt is 3% to 10%.

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