Preparation method of waste polyethylene composite material modified asphalt

Abstract

The invention belongs to the field of asphalt material production in constructional engineering, and particularly relates to a preparation method of waste polyethylene composite material modified asphalt. Comprising the following steps: 1) preparing a waste polyethylene composite material: A, preparing isocyanate modified polyethylene; B, preparing anhydride modified polyethylene; C, mixing the isocyanate modified polyethylene and the anhydride modified polyethylene to obtain the waste polyethylene composite material; and 2) mixing the waste polyethylene composite material with matrix asphalt, heating, and shearing to obtain the modified asphalt. According to the method, the modified waste polyethylene is used, so that the cost of the modified asphalt is reduced, and meanwhile, the adverse effect of the waste polyethylene on the natural environment is also reduced.

Description

Technical Field

[0001] The invention belongs to the field of asphalt material production in construction projects, and in particular relates to a method for preparing waste polyethylene composite material modified asphalt. Background Art

[0002] Modified asphalt, as a building material with excellent performance and wide application, plays an important role in highways, bridges, waterproofing projects and other fields. Modifiers are the core components of modified asphalt, which can be divided into three categories: rubber and thermoplastic elastomers, plastics and synthetic resins, and blended polymers. Among them, SBS modified asphalt is the most commonly used type, but SBS is more expensive.

[0003] Polyethylene, as the main component of farmland mulch, is an indispensable material in agricultural production. For example, in areas with arid climate, scarce rainfall, low temperature and short frost-free period, the mulch covering technology of farmland has been widely promoted and applied. However, with the continuous increase in the use of farmland mulch, a large amount of mulch residue has caused serious harm to the quality of cultivated land, agricultural production and human living environment.

[0004] It is worth noting that polyethylene has certain mechanical strength and chemical stability, and it can interact with the aromatic components in asphalt to form a network structure, which helps to improve the high-temperature stability of asphalt. However, polyethylene polymer is a long carbon atom chain, and its non-polar nature directly affects the compatibility of asphalt, so functional groups are inserted into the polymer chain to reduce its crystallization ability and improve the molecular polarity, thereby promoting the compatibility of the polymer with asphalt. It can be seen that polyethylene can be used as an asphalt modifier to prepare modified asphalt with better performance after appropriate modification.

[0005] At present, there are many patent reports on the use of polyethylene to prepare modified asphalt. For example, patent CN202111506729.2 "A functionalized polyethylene asphalt modifier, its preparation method and application" prepares an amino-terminated polyethylene to obtain a functionalized polyethylene asphalt modifier; patent CN202111527132.6 "An epoxy-terminated low-molecular-weight polyethylene asphalt modifier and its preparation method" obtains an epoxy-terminated low-molecular-weight polyethylene asphalt modifier by reducing the molecular weight of polyethylene and adding functional groups to the end of the polyethylene chain; patent CN202110048332.7 "A method for preparing recycled products using waste cross-linked polyethylene and asphalt" grinds the waste cross-linked polyethylene and then uses asphalt as a plasticizer for plasticization to prepare high-performance recycled products; patent CN201410672766.4 "A method for preparing asphalt modified with added polyethylene" grinds polyethylene into fine particles and adds asphalt to reduce preparation time; but there are no patent-related reports on chemically modifying polyethylene by two methods to obtain a composite modifier to prepare modified asphalt.

[0006] In view of this, the present invention is proposed. Summary of the invention

[0007] The purpose of the present invention is to provide a method for preparing asphalt modified by composite materials of waste polyethylene, wherein waste polyethylene is chemically modified to prepare a composite modifier, and the polar groups on the two materials react chemically with the hydroxyl groups in the asphalt, respectively, which can form a more complete network cross-linking structure in the asphalt, and can also reduce the crystallinity of polyethylene in the asphalt, so that the polyethylene modified asphalt has better compatibility and better low-temperature performance. By using the modified waste polyethylene, this method reduces the cost of modified asphalt while also reducing the adverse effects of waste polyethylene on the natural environment.

[0008] In order to achieve the above objectives, the present invention particularly adopts the following technical solutions:

[0009] The present invention provides a method for preparing waste polyethylene composite material modified asphalt, comprising the following steps:

[0010] 1) Preparation of waste polyethylene composite materials:

[0011] A. Preparation of isocyanate-modified polyethylene:

[0012] Under the condition that the hydroxyl-containing acrylate solution is kept at a constant temperature, isocyanate is added to the hydroxyl-containing acrylate solution to obtain an isocyanate modifier;

[0013] Adding waste polyethylene to a solvent, heating the waste polyethylene to dissolve the waste polyethylene, and obtaining a waste polyethylene solution; adding an isocyanate modifier and an initiator to the waste polyethylene solution, heating the solution, cooling the solution, and then pouring the solution into a precipitating agent to precipitate the waste polyethylene, and drying the solution to obtain an isocyanate-modified polyethylene;

[0014] B. Preparation of anhydride modified polyethylene:

[0015] Adding waste polyethylene to a solvent, heating the waste polyethylene to dissolve the waste polyethylene, and obtaining a waste polyethylene solution; adding an organic acid anhydride and an initiator to the waste polyethylene solution, heating the solution, cooling the solution, and then pouring the solution into a precipitating agent to precipitate the waste polyethylene, and drying the solution to obtain anhydride-modified polyethylene;

[0016] C. mixing the isocyanate-modified polyethylene and the anhydride-modified polyethylene to obtain a waste polyethylene composite material;

[0017] 2) Mixing the waste polyethylene composite material and the matrix asphalt, heating and shearing to obtain modified asphalt.

[0018] Preferably, the hydroxyl-containing acrylate includes one or more of 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate and 2,3-dihydroxypropyl acrylate;

[0019] The isocyanate includes one or more of isophorone diisocyanate, toluene diisocyanate, 4,4'-diphenylmethane diisocyanate, hexylmethylene diisocyanate, hexamethylene diisocyanate and p-xylylene diisocyanate;

[0020] The organic acid anhydride includes one or more of acetic anhydride, propionic anhydride, succinic anhydride, maleic anhydride and benzoic anhydride.

[0021] Preferably, the waste polyethylene is waste plastic, preferably, waste agricultural mulch film.

[0022] Preferably, the initiator includes dibenzoyl peroxide and / or dicumyl peroxide; the solvent includes one or more of cyclohexane, toluene and xylene; and the precipitating agent includes one or more of acetone, methanol and isopropanol.

[0023] Preferably, in step A, the volume ratio of hydroxyl-containing acrylate to isocyanate is 0.4-0.6:1;

[0024] By weight, the waste polyethylene is 100 parts, the isocyanate modifier is 5-15 parts, the initiator is 1-3 parts, the dissolving agent is 200-500 parts, and the precipitation agent is 400-700 parts.

[0025] Preferably, in step A, the hydroxyl-containing acrylate solution is placed in a water bath at 30-80° C. and kept at the constant temperature for 5-20 min; and the reaction time of the isocyanate and the hydroxyl-containing acrylate solution is 4-10 h.

[0026] In step A, waste polyethylene is added to a solvent and the temperature is raised to 90-140° C.; an isocyanate modifier and an initiator are added, and the temperature is kept constant at 90-140° C. for 4-12 hours.

[0027] Preferably, in step B, by weight, the waste polyethylene is 100 parts, the anhydride-modified polyethylene is 5-15 parts, the initiator is 1-3 parts, the dissolving agent is 200-500 parts, and the precipitation agent is 400-700 parts.

[0028] Preferably, in step B, waste polyethylene is added to a solvent and heated to 90-140° C.; then anhydride-modified polyethylene and an initiator are added in proportion in 3-5 times, and the mixture is heated to maintain a constant temperature of 90-140° C. and reacted for 2-10 hours.

[0029] Preferably, in step C, the ratio of anhydride-modified polyethylene to isocyanate-modified polyethylene is 30-70:70-30.

[0030] Preferably, in step 2), by weight, the waste polyethylene composite material prepared by external mixing method accounts for 5-15% of 100 parts of matrix asphalt;

[0031] The waste polyethylene composite material and the matrix asphalt are mixed, heated to 120-170°C and then kept warm, mechanically stirred at a low speed of 100-500r / min for 20-40min, and then sheared at a speed of 2500-5000r / min for 30-120min using a high-speed shearing machine.

[0032] The present invention firstly uses isocyanate and organic anhydride to chemically modify waste polyethylene respectively; then the modified waste polyethylene is blended in a ratio of 30% to 70%: 70% to 30% to obtain a composite modifier; finally, the composite modifier is blended with asphalt to obtain modified asphalt, wherein the polyethylene comes from waste plastics such as waste agricultural mulch. On the one hand, the method provides a feasible technical solution for the resource utilization of waste polyethylene, and on the other hand, it can also reduce the production cost of modified asphalt for roads while improving the performance of modified asphalt.

[0033] Beneficial effects of the present invention:

[0034] 1) The present invention reduces the cost of modified asphalt by using waste polyethylene.

[0035] 2) The present invention improves the compatibility of waste polyethylene with asphalt by chemically modifying the waste polyethylene.

[0036] 3) The present invention chemically modifies waste polyethylene and prepares a composite modifier. The polar groups on the two materials can chemically react with the hydroxyl groups in asphalt, which can form a more complete network cross-linking structure in the asphalt. At the same time, it can also reduce the crystallinity of polyethylene in the asphalt, so that the polyethylene modified asphalt has better compatibility and the prepared modified asphalt has better performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0038] Figure 1 This is a comparison diagram of infrared spectra of waste polyethylene before and after isocyanate chemical modification of the present invention;

[0039] Figure 2 The infrared spectra of waste polyethylene before and after chemical modification with maleic anhydride of the present invention are compared. DETAILED DESCRIPTION

[0040] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0041] First, the present invention is explained as a whole, as follows:

[0042] The object of the present invention is to provide a method for preparing waste polyethylene composite modified asphalt, that is, a method for modifying waste polyethylene and using it to prepare modified asphalt, which can be used to produce waste polyethylene modified asphalt.

[0043] On the one hand, preferably, the technical solution provided by the present invention is divided into two parts, the first part is the preparation of two polyethylene composite modifiers, and the second part is the preparation of waste polyethylene modified asphalt, which is achieved by the following technical measures:

[0044] The materials and specific gravity of the first part of the technical solution are as follows: isocyanate chemically modified waste polyethylene: modifier component H is 2-hydroxyethyl methacrylate (HEMA), modifier component I is isophorone diisocyanate (IPDI), component H:I (volume ratio) = 0.55:1, waste polyethylene is 100 parts, HI modifier is 5-15 parts, initiator is 1-3 parts, solvent is 300 parts, precipitant is 500 parts (wherein, waste polyethylene can be selected from waste agricultural mulch, waste plastic bags and other polyethylene waste; the initiator can be selected from dibenzoyl peroxide (BPO) or diisopropyl peroxide (DCP), etc., the solvent can be selected from cyclohexane, toluene, xylene and other solvents, and the precipitant is ethanol). Maleic anhydride chemically modified waste polyethylene: 100 parts of waste polyethylene, 5-15 parts of modifier, 1-3 parts of initiator, 300 parts of solvent, 500 parts of precipitating agent (waste polyethylene can be waste agricultural mulch, waste plastic bags and other polyethylene waste; the modifier is maleic anhydride, the solvent can be cyclohexane, toluene, xylene and other solvents, and the precipitating agent is acetone). The specific gravity of the composite modifier is isocyanate-modified polyethylene: maleic anhydride-modified polyethylene = 30-70: 70-30.

[0045] The technical solution of the present invention, the first part comprises the following steps:

[0046] 1) preparing a waste polyethylene modifier by reacting 2-hydroxyethyl methacrylate (HEMA) with isophorone diisocyanate (IPDI), placing the IPDI solution in a nitrogen atmosphere under a 40° C. water bath condition, keeping the temperature constant for 10 min, then slowly adding the HEMA solution to the IPDI solution using a pipette in proportion, the reaction time is 6 h, cooling after the reaction, and obtaining a HI modifier for standby use;

[0047] 2) Add the waste polyethylene to the solvent in proportion, heat the oil bath to 120°C, stir and heat until the waste polyethylene is dissolved; then gradually add the HI modifier and initiator in step 1 in proportion, keep the oil bath at a constant temperature of 120°C under a nitrogen protective atmosphere, and react for 6 hours;

[0048] 3) After step 2 is completed, the reaction solution is naturally cooled to room temperature, and the reaction solution is poured into acetone to precipitate the waste polyethylene, and then filtered, air-dried and vacuum-dried, and purified multiple times to obtain modified polyethylene (WPE-g-HI).

[0049] 4) Add waste polyethylene to the solvent in proportion, heat to 130°C in an oil bath, and heat and stir until the polyethylene is completely dissolved; then add maleic anhydride modifier and initiator in proportion in 3-5 times, keep the oil bath at a constant temperature of 130°C under a nitrogen protective atmosphere, and react for 4 hours;

[0050] 5) After step 4 is completed, the reaction solution is naturally cooled to room temperature, poured into acetone to precipitate polyethylene, ultrasonically treated for 20 minutes, then filtered, air-dried and vacuum-dried, and purified multiple times to obtain grafted modified polyethylene (WPE-g-MAH).

[0051] 6) Using a crusher, the two modifiers are chopped up and mixed in proportion to prepare a composite modifier.

[0052] The second part of the technical solution provided by the present invention is the preparation of modified asphalt, which is achieved by adopting the following technical measures:

[0053] The material ratio is: the material ratio of the second part of the technical solution is: 100 parts of base asphalt, and the composite modifier prepared by external mixing method accounts for 5-15%.

[0054] The technical solution of the present invention, the second part comprises the following steps:

[0055] 7) The composite modifier and base asphalt in step 6) are mixed in proportion, heated to 150°C and then kept warm, mechanically stirred at a low speed of 100-500 r / min for 20-40 min, and then sheared at a high-speed shearing machine at a speed of 2500-5000 r / min for 60 min to obtain modified asphalt.

[0056] A further solution is that the solution prepared in steps 1) to 4) can be manually stirred using a glass rod or by low-speed mechanical stirring to achieve a uniform solution.

[0057] A further solution is that the oil bath equipment in steps 2) to 4) is a constant temperature oil bath pot, and other equipment with the same function can also be used. At the same time, its temperature should be appropriately adjusted according to the component structure of the polyethylene. If the molecular weight is large, the insulation temperature can be appropriately increased.

[0058] Example 1

[0059] The present invention uses isocyanate and maleic anhydride to graft-modify waste polyethylene respectively, and mixes them to prepare a composite modifier for modified asphalt. The waste polyethylene sample used is: waste agricultural mulch film.

[0060] The proportions of materials used in Example 1 are as follows:

[0061] Isocyanate chemically modified waste polyethylene: modifier component H is 2-hydroxyethyl methacrylate (HEMA), modifier component I is isophorone diisocyanate (IPDI), component H:I (volume ratio) = 0.55:1, waste polyethylene is 100 parts, HI modifier is 8 parts, initiator is 2 parts, solvent is 300 parts, and precipitant is 500 parts (among which, the initiator is dibenzoyl peroxide (BPO), the solvent is xylene, and the precipitant is acetone).

[0062] Maleic anhydride chemically modified waste polyethylene: 100 parts of waste polyethylene, 10 parts of modifier, 3 parts of initiator, 300 parts of solvent, and 500 parts of precipitating agent (the modifier is maleic anhydride, the solvent can be xylene, and the precipitating agent is acetone).

[0063] The ratio of the composite modifier is isocyanate modified polyethylene: maleic anhydride modified polyethylene = 50:50.

[0064] The steps for preparing the composite modifier are as follows:

[0065] 1) preparing a waste polyethylene modifier by reacting 2-hydroxyethyl methacrylate (HEMA) with isophorone diisocyanate (IPDI), placing the IPDI solution in a nitrogen atmosphere under a 40° C. water bath condition, keeping the temperature constant for 10 min, then slowly adding the HEMA solution to the IPDI solution using a pipette in proportion, the reaction time is 6 h, cooling after the reaction, and obtaining a HI modifier for standby use;

[0066] 2) Add the waste polyethylene to the solvent in proportion, heat the oil bath to 120°C, stir and heat until the waste polyethylene is dissolved; then gradually add the HI modifier and initiator in step 1 in proportion, keep the oil bath at a constant temperature of 120°C under a nitrogen protective atmosphere, and react for 6 hours;

[0067] 3) After step 2 is completed, the reaction solution is naturally cooled to room temperature, and the reaction solution is poured into acetone to precipitate the waste polyethylene, and then filtered, air-dried and vacuum-dried, and purified multiple times to obtain modified polyethylene (WPE-g-HI).

[0068] 4) Add waste polyethylene to the solvent in proportion, heat to 130°C in an oil bath, and heat and stir until the polyethylene is completely dissolved; then add maleic anhydride modifier and initiator in proportion in 5 times, keep the oil bath at a constant temperature of 130°C under a nitrogen protective atmosphere, and react for 4 hours;

[0069] 5) After step 4 is completed, the reaction solution is naturally cooled to room temperature, poured into acetone to precipitate polyethylene, ultrasonically treated for 20 minutes, then filtered, air-dried and vacuum-dried, and purified multiple times to obtain grafted modified polyethylene (WPE-g-MAH).

[0070] 6) Use a crusher to chop the two modifiers and mix them in proportion to obtain a composite modifier.

[0071] In this example, infrared spectroscopy tests were performed on two types of waste polyethylene before and after chemical modification. The results are as follows: Figure 1 , 2 As shown, Figure 1 Comparison of infrared spectra of waste polyethylene before and after isocyanate chemical modification shows that two new infrared characteristic peaks can be found in the infrared spectrum of isocyanate chemical modification: 1728cm -1 The carbonyl absorption peak of HEMA is 2270 cm -1 It is the infrared characteristic peak of -NCO, which shows that isocyanate has been successfully grafted onto polyethylene. Figure 2 Comparison of infrared spectra of waste polyethylene before and after chemical modification with maleic anhydride revealed that at 1712 cm -1 A new characteristic absorption peak appeared, which corresponds to the carbonyl group (C=O) in maleic anhydride. -1 and 1866cm -1 There are two characteristic absorption peaks at , which are the symmetrical and asymmetrical carbonyl (C=O) stretching vibrations of the five-membered ring anhydride. This proves that maleic anhydride has also been successfully grafted onto waste polyethylene.

[0072] Example 2

[0073] Isocyanate chemically modified waste polyethylene: modifier component H is 2-hydroxyethyl methacrylate (HEMA), modifier component I is isophorone diisocyanate (IPDI), component H:I (volume ratio) = 0.55:1, waste polyethylene is 100 parts, HI modifier is 15 parts, initiator is 3 parts, solvent is 400 parts, and precipitant is 600 parts (among which, the initiator is dibenzoyl peroxide (BPO), the solvent is xylene, and the precipitant is acetone).

[0074] Maleic anhydride chemically modified waste polyethylene: 100 parts of waste polyethylene, 8 parts of modifier, 2 parts of initiator, 400 parts of solvent, and 600 parts of precipitating agent (the modifier is maleic anhydride, the solvent can be xylene, and the precipitating agent is acetone).

[0075] The ratio of the composite modifier is isocyanate modified polyethylene: maleic anhydride modified polyethylene = 50:50.

[0076] The steps for preparing the composite modifier are as follows:

[0077] 1) preparing a waste polyethylene modifier by reacting 2-hydroxyethyl methacrylate (HEMA) with isophorone diisocyanate (IPDI), placing the IPDI solution in a nitrogen atmosphere under a 60° C. water bath condition, keeping the temperature constant for 5 minutes, then slowly adding the HEMA solution to the IPDI solution using a pipette in proportion, the reaction time is 4 hours, cooling after the reaction, and obtaining a HI modifier for standby use;

[0078] 2) Add the waste polyethylene to the solvent in proportion, heat the oil bath to 110°C, and stir and heat until the waste polyethylene is dissolved; then gradually add the HI modifier and initiator in step 1 in proportion, keep the oil bath at a constant temperature of 110°C under a nitrogen protective atmosphere, and react for 4 hours;

[0079] 3) After step 2 is completed, the reaction solution is naturally cooled to room temperature, and the reaction solution is poured into acetone to precipitate the waste polyethylene, and then filtered, air-dried and vacuum-dried, and purified multiple times to obtain modified polyethylene (WPE-g-HI).

[0080] 4) Add waste polyethylene to the solvent in proportion, heat to 135°C in an oil bath, and heat and stir until the polyethylene is completely dissolved; then add maleic anhydride modifier and initiator in proportion in 4 times, keep the oil bath at a constant temperature of 135°C under a nitrogen protective atmosphere, and react for 3 hours;

[0081] 5) After step 4 is completed, the reaction solution is naturally cooled to room temperature, poured into acetone to precipitate polyethylene, ultrasonically treated for 20 minutes, then filtered, air-dried and vacuum-dried, and purified multiple times to obtain grafted modified polyethylene (WPE-g-MAH).

[0082] 6) Use a crusher to chop the two modifiers and mix them in proportion to obtain a composite modifier.

[0083] In this example, infrared spectroscopy tests were performed on two types of waste polyethylene before and after chemical modification, and the results were as follows: Figure 1 , 2 As shown, Figure 1 Comparison of infrared spectra of waste polyethylene before and after isocyanate chemical modification shows that two new infrared characteristic peaks can be found in the infrared spectrum of isocyanate chemical modification: 1728cm -1 The carbonyl absorption peak of HEMA is 2270 cm -1 It is the infrared characteristic peak of -NCO, which shows that isocyanate has been successfully grafted onto polyethylene. Figure 2 Comparison of infrared spectra of waste polyethylene before and after chemical modification with maleic anhydride revealed that at 1712 cm -1 A new characteristic absorption peak appeared, which corresponds to the carbonyl group (C=O) in maleic anhydride. -1 and 1866cm -1There are two characteristic absorption peaks at , which are the symmetrical and asymmetrical carbonyl (C=O) stretching vibrations of the five-membered ring anhydride. This proves that maleic anhydride has also been successfully grafted onto waste polyethylene.

[0084] Example 3

[0085] Isocyanate chemically modified waste polyethylene: modifier component H is 2-hydroxyethyl methacrylate (HEMA), modifier component T is toluene diisocyanate (TDI), component H:T (volume ratio) = 0.45:1, waste polyethylene is 100 parts, HI modifier is 8 parts, initiator is 2 parts, solvent is 300 parts, and precipitant is 500 parts (among which, the initiator is dibenzoyl peroxide (BPO), the solvent is xylene, and the precipitant is acetone).

[0086] Propionic anhydride chemical modification of waste polyethylene: 100 parts of waste polyethylene, 10 parts of modifier, 3 parts of initiator, 300 parts of solvent, and 500 parts of precipitating agent (the modifier is propionic anhydride, the solvent can be xylene, and the precipitating agent is acetone).

[0087] The ratio of the composite modifier is isocyanate modified polyethylene: propionic anhydride modified polyethylene = 50:50.

[0088] The steps for preparing the composite modifier are as follows:

[0089] 1) Prepare a waste polyethylene modifier by reacting 2-hydroxyethyl methacrylate (HEMA) with toluene diisocyanate (TDI), place the TDI solution in a nitrogen atmosphere under a 40°C water bath, keep the temperature constant for 10 minutes, then slowly add the HEMA solution to the TDI solution using a pipette according to proportion, react for 6 hours, cool after the reaction, and prepare the HT modifier for use;

[0090] 2) Add the waste polyethylene to the solvent in proportion, heat the oil bath to 120°C, stir and heat until the waste polyethylene is dissolved; then gradually add the HT modifier and initiator in step 1 in proportion, keep the oil bath at a constant temperature of 120°C under a nitrogen protective atmosphere, and react for 6 hours;

[0091] 3) After step 2 is completed, the reaction solution is naturally cooled to room temperature, and the reaction solution is poured into acetone to precipitate the waste polyethylene, and then filtered, air-dried and vacuum-dried, and purified multiple times to obtain modified polyethylene (WPE-g-HT).

[0092] 4) Add waste polyethylene to the solvent in proportion, heat to 130°C in an oil bath, and heat and stir until the polyethylene is completely dissolved; then add propionic anhydride (PA) modifier and initiator in proportion in 5 times, keep the oil bath at a constant temperature of 130°C under a nitrogen protective atmosphere, and react for 4 hours;

[0093] 5) After step 4 is completed, the reaction solution is naturally cooled to room temperature, poured into acetone to precipitate polyethylene, ultrasonically treated for 20 minutes, then filtered, air-dried and vacuum-dried, and purified multiple times to obtain grafted modified polyethylene (WPE-g-PA).

[0094] 6) Use a crusher to chop the two modifiers and mix them in proportion to obtain a composite modifier.

[0095] In this example, infrared spectra of waste polyethylene before and after two chemical modifications were tested. By comparing the infrared spectra of waste polyethylene before and after isocyanate chemical modification, it can be found that two new infrared characteristic peaks can be found on the infrared spectrum of isocyanate chemical modification: 1728cm -1 The carbonyl absorption peak of HEMA is 2270 cm -1 It is the infrared characteristic peak of -NCO, which shows that isocyanate has been successfully grafted onto polyethylene. By comparing the infrared spectra of waste polyethylene before and after chemical modification with propionic anhydride, it can be found that at 1712cm -1 A new characteristic absorption peak appeared, which corresponded to the carbonyl group (C=O) in propionic anhydride, thus proving that propionic anhydride had also been successfully grafted onto waste polyethylene.

[0096] Please note that the technical features of the above embodiments can be combined arbitrarily. In order to make the description concise, all possible combinations of the technical features in the above embodiments are not described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification. The above embodiments only express several implementation methods of the present application, and their descriptions are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that for ordinary technicians in this field, without departing from the concept of the present application, several variations and improvements can be made, which all belong to the scope of protection of the present application. Therefore, the scope of protection of the patent in this application shall be based on the attached claims.

Claims

1. A method for preparing waste polyethylene composite modified asphalt, comprising the following steps: 1) Preparation of waste polyethylene composite materials: A. Preparation of isocyanate-modified polyethylene: Under the condition that the hydroxyl-containing acrylate solution is kept at a constant temperature, isocyanate is added to the hydroxyl-containing acrylate solution to obtain an isocyanate modifier; Adding waste polyethylene to a solvent, heating the waste polyethylene to dissolve the waste polyethylene, and obtaining a waste polyethylene solution; adding an isocyanate modifier and an initiator to the waste polyethylene solution, heating the solution, cooling the solution, and then pouring the solution into a precipitating agent to precipitate the waste polyethylene, and drying the solution to obtain an isocyanate-modified polyethylene; B. Preparation of anhydride modified polyethylene: Adding waste polyethylene to a solvent, heating the waste polyethylene to dissolve the waste polyethylene, and obtaining a waste polyethylene solution; adding an organic acid anhydride and an initiator to the waste polyethylene solution, heating the solution, cooling the solution, and then pouring the solution into a precipitating agent to precipitate the waste polyethylene, and drying the solution to obtain anhydride-modified polyethylene; C. mixing the isocyanate-modified polyethylene and the anhydride-modified polyethylene to obtain a waste polyethylene composite material; 2) Mixing the waste polyethylene composite material and the matrix asphalt, heating and shearing to obtain modified asphalt.

2. The preparation method according to claim 1, characterized in that The hydroxyl-containing acrylate includes one or more of 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate and 2,3-dihydroxypropyl acrylate; The isocyanate includes one or more of isophorone diisocyanate, toluene diisocyanate, 4,4'-diphenylmethane diisocyanate, hexylmethylene diisocyanate, hexamethylene diisocyanate and p-xylylene diisocyanate; The organic acid anhydride includes one or more of acetic anhydride, propionic anhydride, succinic anhydride, maleic anhydride and benzoic anhydride.

3. The preparation method according to claim 1, characterized in that The waste polyethylene is waste plastic, preferably waste agricultural mulch film.

4. The preparation method according to claim 1, characterized in that The initiator includes dibenzoyl peroxide and / or dicumyl peroxide; the solvent includes one or more of cyclohexane, toluene and xylene; and the precipitating agent includes one or more of acetone, methanol and isopropanol.

5. The preparation method according to claim 1, characterized in that In step A, the volume ratio of hydroxyl-containing acrylate to isocyanate is 0.4-0.6:

1. By weight, the waste polyethylene is 100 parts, the isocyanate modifier is 5-15 parts, the initiator is 1-3 parts, the dissolving agent is 200-500 parts, and the precipitation agent is 400-700 parts.

6. The preparation method according to claim 1, characterized in that In step A, the hydroxyl-containing acrylate solution is placed in a water bath at 30-80° C. and kept at the constant temperature for 5-20 minutes; the reaction time of the isocyanate and the hydroxyl-containing acrylate solution is 4-10 hours; In step A, waste polyethylene is added to a solvent and the temperature is raised to 90-140° C.; an isocyanate modifier and an initiator are added, and the temperature is kept constant at 90-140° C. for 4-12 hours.

7. The preparation method according to claim 1, characterized in that In step B, by weight, the waste polyethylene is 100 parts, the anhydride-modified polyethylene is 5-15 parts, the initiator is 1-3 parts, the dissolving agent is 200-500 parts, and the precipitation agent is 400-700 parts.

8. The preparation method according to claim 1, characterized in that In step B, waste polyethylene is added to a solvent and heated to 90-140° C.; then anhydride-modified polyethylene and an initiator are added in proportion in 3-5 times, and the temperature is kept constant at 90-140° C. for 2-10 hours.

9. The preparation method according to claim 1, characterized in that In step C, the ratio of anhydride-modified polyethylene to isocyanate-modified polyethylene is 30-70:70-30.

10. The preparation method according to claim 1, characterized in that In step 2), by weight, 100 parts of the matrix asphalt and the waste polyethylene composite material prepared by the external blending method account for 5-15%; The waste polyethylene composite material and the matrix asphalt are mixed, heated to 120-170°C and then kept warm, mechanically stirred at a low speed of 100-500r / min for 20-40min, and then sheared at a speed of 2500-5000r / min for 30-120min using a high-speed shearing machine.

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