Method for recycling polypropylene waste into high-rigidity and high-toughness polypropylene

Abstract

The invention provides a method for recycling polypropylene waste into a high-rigidity and high-toughness polypropylene polymer, and relates to the technical field of upgrading and recycling of waste plastics. Comprising the following steps: S1, after cleaning and vibratory screening are performed on polypropylene waste, the polypropylene waste is crushed into particles with the particle size being smaller than or equal to 5 mm; s2, drying the granules until the moisture content is less than 0.5%, adding glass fibers accounting for 7-10% of the mass of the granules and an elastomer accounting for 2.3-3% of the mass of the granules at the temperature of 200-230 DEG C and the pressure of 5-15 MPa, and performing melt blending, extrusion and granulation to obtain first polypropylene granules; s3, drying the first polypropylene particles until the moisture content is less than 1%, adding nano calcium carbonate accounting for 15-18% of the mass of the particles and a coupling agent accounting for 2-2.4% of the mass of the particles at the temperature of 200-220 DEG C and the pressure of 10-14 MPa, and performing melt blending, extrusion and granulation to obtain the high-rigidity and high-toughness polypropylene polymer particles. The prepared polypropylene polymer has excellent toughness and rigidity.

Description

Technical Field

[0001] The present invention relates to the technical field of upgrading and recycling waste plastics, and in particular to a method for recycling polypropylene waste into high-rigidity and high-toughness polypropylene polymers. Background Art

[0002] Recycling polypropylene (PP) waste is a key area of ​​resource conservation and environmental protection. Existing technologies struggle to achieve both toughness and rigidity enhancement in recycling processes due to the complex sources, high impurity content, and wide variations in properties. This leads to high processing costs. Therefore, a method for recycling PP waste into high-rigidity and high-toughness PP is urgently needed to achieve high-value-added conversion of PP waste. Summary of the Invention

[0003] (1) Technical problems solved

[0004] In view of the shortcomings of the existing technology, the present invention provides a method for recycling polypropylene waste into high-rigidity and high-toughness polypropylene polymers, which solves the technical problem that the existing recycling process is difficult to simultaneously take into account the toughening and stiffness requirements.

[0005] (2) Technical solution

[0006] To achieve the above objectives, the present invention is implemented through the following technical solutions:

[0007] The present invention provides a method for recycling polypropylene waste into a high-rigidity and high-toughness polypropylene polymer, comprising the following steps:

[0008] S1. After cleaning and vibrating screening, the polypropylene waste is crushed into particles with a particle size of ≤5mm;

[0009] S2, drying the pellets to a moisture content of less than 0.5%, adding 7% to 10% by weight of glass fiber and 2.3% to 3% by weight of an elastomer at a temperature of 200° C. to 230° C. and a pressure of 5 MPa to 15 MPa, and melt-blending and extruding to obtain first polypropylene pellets;

[0010] S3. Dry the first polypropylene particles until the moisture content is less than 1%, add 15% to 18% of the mass of the particles of nano-calcium carbonate and 2% to 2.4% of the mass of the particles of coupling agent at a temperature of 200° C. to 220° C. and a pressure of 10 MPa to 14 MPa, melt-blending and extruding to obtain high-rigidity and high-toughness polypropylene polymer particles.

[0011] The present invention discloses a method for recycling polypropylene waste into a high-rigidity and high-toughness polypropylene polymer. The polypropylene waste is treated with glass fiber, an elastomer, nano-calcium carbonate, and a coupling agent. The synergistic effect of the glass fiber and the elastomer improves the toughness of the prepared polypropylene polymer, while the synergistic effect of the nano-calcium carbonate and the coupling agent improves the rigidity of the prepared polypropylene polymer. The resulting polypropylene polymer exhibits both excellent toughness and rigidity.

[0012] Preferably, the mass ratio of the amount of the granular material to the total amount of the glass fiber, elastomer, nano-calcium carbonate and coupling agent is 100:30.

[0013] The mass ratio of the amount of the granular material to the total amount of the glass fiber, the elastomer, the nano-calcium carbonate and the coupling agent is controlled so that the prepared polypropylene polymer has both excellent rigidity and toughness.

[0014] Preferably, the mass ratio of the glass fiber to the elastomer is 10:3.

[0015] Preferably, the mass ratio of the nano-calcium carbonate to the coupling agent is 15:2.

[0016] Preferably, the mass ratio of the total amount of the glass fiber and the elastomer to the total amount of the nano-calcium carbonate and the coupling agent is 1:1.3 to 1:2.

[0017] The mass ratio of glass fiber and elastomer is controlled to be 10:3, the mass ratio of nano-calcium carbonate and coupling agent is controlled to be 15:2, and the mass ratio of the total amount of glass fiber and elastomer to the total amount of nano-calcium carbonate and coupling agent is controlled to be 1:1.3 to 1:2, which can take into account the rigidity and toughness of the prepared polypropylene polymer.

[0018] Preferably, the elastomer is selected from polyolefin elastomer and EPDM rubber.

[0019] Preferably, the particle size of the nano calcium carbonate is 50 to 100 nm.

[0020] Preferably, the coupling agent is selected from phthalate coupling agents, silane coupling agents, and maleic anhydride grafted polypropylene coupling agents.

[0021] Preferably, the mass ratio of the total amount of the glass fiber and the elastomer to the total amount of the nano-calcium carbonate and the coupling agent is 1:1.3.

[0022] The mass ratio of the total amount of the glass fiber and the elastomer to the total amount of the nano-calcium carbonate and the coupling agent is controlled to be 1:1.3, so as to take into account both the rigidity and toughness of the prepared polypropylene polymer.

[0023] Preferably, the mass ratio of the total amount of the glass fiber and the elastomer to the total amount of the nano-calcium carbonate and the coupling agent is 1:2.

[0024] The mass ratio of the total amount of the glass fiber and the elastomer to the total amount of the nano-calcium carbonate and the coupling agent is controlled to be 1:2, so as to take into account both the rigidity and toughness of the prepared polypropylene polymer. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0026] Figure 1 It is a schematic diagram of the notch of the specimen prepared for testing the impact strength of the simply supported beam. DETAILED DESCRIPTION

[0027] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention are clearly and completely described. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0028] The embodiments of the present application provide a method for recycling polypropylene waste into high-rigidity and high-toughness polypropylene polymers, thereby solving the technical problem that existing recycling processes are difficult to simultaneously meet the requirements of toughening and stiffening, and achieving the prepared polypropylene polymers with both excellent rigidity and toughness.

[0029] The technical solution in the embodiments of the present application is to solve the above technical problems, and the overall idea is as follows:

[0030] The present invention provides a method for recycling polypropylene waste into a high-rigidity and high-toughness polypropylene polymer, comprising the following steps:

[0031] S1. After cleaning and vibrating screening, the polypropylene waste is crushed into particles with a particle size of ≤5mm;

[0032] S2, drying the pellets to a moisture content of less than 0.5%, adding 7% to 10% by weight of glass fiber and 2.3% to 3% by weight of an elastomer at a temperature of 200° C. to 230° C. and a pressure of 5 MPa to 15 MPa, and melt-blending and extruding to obtain first polypropylene pellets;

[0033] S3. Dry the first polypropylene particles until the moisture content is less than 1%, add 15% to 18% of the mass of the particles of nano-calcium carbonate and 2% to 2.4% of the mass of the particles of coupling agent at a temperature of 200° C. to 220° C. and a pressure of 10 MPa to 14 MPa, melt-blending and extruding to obtain high-rigidity and high-toughness polypropylene polymer particles.

[0034] In some embodiments, polypropylene waste includes at least one of cake, scooped material, and ground material. Cake refers to irregular solid blocks discharged from the start-up valve during the start-up and shutdown of a polypropylene extruder due to poor temperature control and material flow. Scooped material refers to polypropylene, such as long strips, flakes, and debris, that stick together during the water washing and separation of pellets during underwater pelletizing. Ground material refers to polypropylene material that falls to the ground and mixes with ground contaminants during transportation, screening, and packaging. Pretreatment of cake includes: shredding → crushing → cleaning, with a cutter speed of 400-600 rpm; pretreatment of scooped material includes: cleaning → vibratory screening → crushing → secondary cleaning → drying, with a moisture content controlled at ≤0.5%; pretreatment of ground material includes: cleaning → impurity separation → drying, with the cooling time optimized to 20-30 seconds to improve dimensional stability.

[0035] In some embodiments, the cleaning can be performed by any cleaning method known in the art. For example, the cavitation effect of ultrasound and high-frequency mechanical vibration can be used to perform physical cleaning for efficient decontamination, degassing or surface treatment of polypropylene (PP) materials.

[0036] In some embodiments, the particle size of the granular material is 1 mm, 2 mm, 3 mm, 4 mm, 5 mm, or any value therebetween.

[0037] In some embodiments, the glass fiber length is 3 mm, 4 mm, 5 mm, or any value therebetween.

[0038] In some embodiments, the glass fiber has a length of 3 mm to 5 mm, so that the prepared polypropylene polymer has excellent toughness.

[0039] In some embodiments, the amount of glass fiber accounts for 5%, 8%, 9%, 10%, 11%, 12%, 15% or any value therebetween of the mass of the particulate material, and the amount of elastomer accounts for 2%, 3%, 4%, 5% or any value therebetween of the mass of the particulate material.

[0040] In some embodiments, the amount of nano-calcium carbonate added is 10%, 13%, 14%, 15%, 16%, 17%, 20% or any value therebetween of the mass of the granular material, and the amount of coupling agent added is 1%, 2%, 3% or any value therebetween of the mass of the granular material.

[0041] In some embodiments, S2 is melt blended by a twin-screw extruder, illustratively, having an aspect ratio of 44, a nominal diameter of 71 mm, and a rotation speed of 500-600 rpm;

[0042] In some embodiments, a segmented temperature control process is used in S3, for example, 220° C. in the front section and 200° C. in the back section, to ensure uniform dispersion of the nano-calcium carbonate.

[0043] In some embodiments, the pelletizing system for producing the high-strength, high-toughness polypropylene polymer pellets utilizes nitrided steel cutters with a die aperture of 4 mm, producing pellets of 3 to 5 mm in size. The vacuum dehydration system for producing the high-strength, high-toughness polypropylene polymer pellets maintains a vacuum of -0.09 MPa, a moisture content of ≤0.3%, and a uniformity of over 95%. This results in a 2,000 yuan per ton efficiency increase. The impact strength of toughened grades is increased by 40%, while the flexural modulus of stiffer grades is increased by 30%.

[0044] The present invention discloses a method for recycling polypropylene waste into a high-rigidity and high-toughness polypropylene polymer. Glass fiber, an elastomer, nano-calcium carbonate and a coupling agent are selected to process the polypropylene waste. Under the synergistic effect of the glass fiber and the elastomer, the toughness of the prepared polypropylene polymer is improved. Under the synergistic effect of the nano-calcium carbonate and the coupling agent, the rigidity of the prepared polypropylene polymer is improved.

[0045] Preferably, the mass ratio of the amount of the granular material to the total amount of the glass fiber, elastomer, nano-calcium carbonate and coupling agent is 100:30.

[0046] The mass ratio of the amount of the granular material to the total amount of the glass fiber, the elastomer, the nano-calcium carbonate and the coupling agent is controlled so that the prepared polypropylene polymer has both excellent rigidity and toughness.

[0047] Preferably, the mass ratio of the glass fiber to the elastomer is 10:3.

[0048] Preferably, the mass ratio of the nano-calcium carbonate to the coupling agent is 15:2.

[0049] In some embodiments, the mass ratio of the total amount of the glass fiber and the elastomer to the total amount of the nano-calcium carbonate and the coupling agent is 1:1.3, 1:1.5, 1:2 or any value therebetween.

[0050] The mass ratio of glass fiber and elastomer is controlled to be 10:3, the mass ratio of nano-calcium carbonate and coupling agent is controlled to be 15:2, and the mass ratio of the total amount of glass fiber and elastomer to the total amount of nano-calcium carbonate and coupling agent is controlled to be 1:1.3 to 1:2, which can take into account the rigidity and toughness of the prepared polypropylene polymer.

[0051] Preferably, the elastomer is selected from polyolefin elastomer and EPDM rubber.

[0052] Preferably, the particle size of the nano calcium carbonate is 50 to 100 nm.

[0053] Preferably, the coupling agent is selected from phthalate coupling agents, silane coupling agents, and maleic anhydride grafted polypropylene coupling agents.

[0054] Preferably, the mass ratio of the total amount of the glass fiber and the elastomer to the total amount of the nano-calcium carbonate and the coupling agent is 1:1.3.

[0055] The mass ratio of the total amount of the glass fiber and the elastomer to the total amount of the nano-calcium carbonate and the coupling agent is controlled to be 1:1.3, so as to take into account both the rigidity and toughness of the prepared polypropylene polymer.

[0056] Preferably, the mass ratio of the total amount of the glass fiber and the elastomer to the total amount of the nano-calcium carbonate and the coupling agent is 1:2.

[0057] The mass ratio of the total amount of the glass fiber and the elastomer to the total amount of the nano-calcium carbonate and the coupling agent is controlled to be 1:2, so as to take into account both the rigidity and toughness of the prepared polypropylene polymer.

[0058] The rigidity of polypropylene polymer is well known in the art and can be tested by methods known in the art, for example, a polypropylene tensile strength tester can be used for testing, refer to "GB / T 1040.1-2018 Plastics - Determination of Tensile Properties" and "GB / T 1040.2-2022 Plastics - Determination of Tensile Properties".

[0059] The toughness of polypropylene polymer is well known in the art and can be tested using methods known in the art, for example, using a pendulum-type simple supported beam impact tester, refer to "GB / T 1043.1-2008 Determination of impact properties of plastics by simple supported beam".

[0060] In order to better understand the above technical solution, the above technical solution will be described in detail below in conjunction with specific implementation methods.

[0061] 1. Preparation method

[0062] Example 1

[0063] This embodiment provides a method for recycling polypropylene waste into high-rigidity and high-toughness polypropylene polymer, comprising the following steps:

[0064] S1. After cleaning and vibrating the scooped material, crush it into granules with a particle size of 5 mm;

[0065] S2, after drying the pellets to a moisture content of 0.3%, 100 parts by mass were fed into a twin-screw extruder, and the twin-screw extruder temperature was adjusted to 210°C, the pressure was 10 MPa, and the speed was 550 rpm. Glass fiber with a length of 4 mm and a polyolefin elastomer (POE) accounting for 10% of the mass of the pellets were added, and the mixture was extruded and granulated to obtain first polypropylene pellets;

[0066] S3. Dry the first polypropylene pellets to a moisture content of 0.5%, feed them into a twin-screw extruder, adjust the temperature of the front section of the twin-screw extruder to 220°C, the temperature of the rear section to 200°C, the pressure to 12 MPa, and the rotation speed to 550 rpm, add nano-calcium carbonate with a particle size of 80 nm accounting for 15% of the mass of the pellets and a titanate coupling agent accounting for 2% of the mass of the pellets, blend and extrude into pellets, and obtain high-rigidity and high-toughness polypropylene polymer pellets.

[0067] Examples 2-6

[0068] The difference between Examples 2-6 and Example 1 is that the total amount of glass fiber and POE used as raw materials for preparing high-rigidity and high-toughness polypropylene polymer particles is different in mass ratio to the total amount of nano-calcium carbonate and titanate coupling agent, as shown in Table 1. Other aspects are the same as Example 1.

[0069] Table 1 Amount of raw materials used in the preparation of Examples 2-6 Example 2 Example 3 Example 4 Example 5 Example 6 Pellets 100 copies 100 copies 100 copies 100 copies 100 copies Total amount of glass fiber, POE, nano calcium carbonate, and titanate coupling agent 30 servings 30 servings 30 servings 30 servings 30 servings Glass fiber and POE mass ratio 10:3 10:3 10:3 10:3 10:3 The mass ratio of nano calcium carbonate and titanate coupling agent 15:2 15:2 15:2 15:2 15:2 Mass ratio of total amount of glass fiber and POE to total amount of nano calcium carbonate and titanate coupling agent 1：1 1：1.5 1：2 1：0.8 1：2.5

[0070] Comparative Example 1

[0071] The difference between this comparative example and Example 1 is that no glass fiber is added, and the amount of POE added is 13% of the mass of the pellets. Other details are the same as in Example 1. The specific amounts are shown in Table 2.

[0072] Comparative Example 2

[0073] The difference between this comparative example and Example 1 is that POE is not added, and the amount of glass fiber added accounts for 13% of the mass of the granular material. Other contents are the same as in Example 1. The specific amounts are shown in Table 2.

[0074] Comparative Example 3

[0075] The difference between this comparative example and Example 1 is that no nano calcium carbonate is added, and the amount of titanate coupling agent added is 17% of the mass of the granular material. Other aspects are the same as Example 1. The specific amounts are shown in Table 2.

[0076] Comparative Example 4

[0077] The difference between this comparative example and Example 1 is that no titanate coupling agent is added, and the amount of nano calcium carbonate added accounts for 17% of the mass of the granular material. Other details are the same as in Example 1. The specific amounts are shown in Table 2.

[0078] Table 2 Amount of raw materials used in the preparation of Comparative Examples 1-4 fiberglass POE Nano calcium carbonate Titanate coupling agent Comparative Example 1 0 13% 15% 2% Comparative Example 2 13% 0 15% 2% Comparative Example 3 10% 3% 0 17% Comparative Example 4 10% 3% 17% 0

[0079] 2. Test Method

[0080] The properties of the high-rigidity and high-toughness polypropylene polymer particles prepared in Examples 1-6 and Comparative Examples 1-4 were tested using the following test methods:

[0081] 1 Simply supported beam impact strength

[0082] 1.1 Prepare the sample

[0083] 1.1.1 Sample preparation

[0084] According to ISO 2818: 1994, the high-rigidity and high-toughness polypropylene polymer particles prepared in Examples 1-6 and Comparative Examples 1-4 were made into sample plates with a length*width*thickness of 80±2 mm*10±0.2 mm*4±0.2 mm.

[0085] 1.1.2 Sample inspection

[0086] The specimen plate should be free of distortion and have perpendicular, parallel surfaces. Surfaces and edges should be free of scratches, pits, dents, and flash. Visually inspect the specimen using a ruler, square, and flat plate, and measure with a micrometer to confirm compliance. If one or more of the observed and measured specimens do not meet the requirements, the specimen should be discarded or processed to the appropriate size and shape.

[0087] 1.1.3 According to ISO2818:1994, the specimen is machined into Figure 1 The shape and depth shown are A-type notches with a bottom radius of r. N =0.25mm±0.05mm and at right angles to the main axis.

[0088] 1.2 Maintain the specimen at a constant temperature of 23°C and 50% humidity for 24 hours. Then, test the specimen at 23°C and 50% humidity. Use a Ceast Model 6967 pendulum impact tester in accordance with the standard "GB / T 1043.1-2008 Plastics - Determination of Impact Properties of Simply Supported Beams." Place the specimen on the tester's support, with the impact blade facing the center of the specimen. Carefully position the notched specimen so that the center of the notch lies directly on the impact plane. Release the pendulum and record the impact energy absorbed by the specimen. The test results are shown in Table 3.

[0089] 2 Tensile strength

[0090] 2.1 Sample preparation

[0091] In accordance with GB / T 1040, the high-rigidity and high-toughness polypropylene polymer particles prepared in Examples 1-6 and Comparative Examples 1-4 were made into dumbbell-shaped specimen plates with a total length of ≥150 mm, a gauge length (parallel section) of 50 mm, a width of 10 mm, and a thickness of 4±0.2 mm.

[0092] 2.2 Sample testing

[0093] The sample plates were tested using a tensile strength testing machine model 5566 produced by Instron in accordance with the standard “GB / T 1040.1-2018 Determination of tensile properties of plastics”. The test results are shown in Table 3.

[0094] 3 Flexural modulus

[0095] 3.1 Sample preparation

[0096] According to the provisions of ISO2818, the high-rigidity and high-toughness polypropylene polymer particles prepared in Examples 1-6 and Comparative Examples 1-4 were made into specimens with a length l*width b*thickness h of 80±2 mm*10±0.2 mm*4±0.2 mm.

[0097] 3.2 Sample inspection

[0098] The specimen must not be twisted, opposing surfaces must be parallel, adjacent surfaces must be perpendicular, and all surfaces and edges must be free of scratches, pits, depressions, and flash. Using a ruler, gauge, and flat plate, visually inspect the specimen for compliance with the above requirements and measure with a vernier caliper. Before testing, specimens that fail to meet one or more of the above requirements should be rejected or processed to the acceptable size and shape.

[0099] 3.3 The sample plates were tested using an Instron 5566 flexural modulus testing machine in accordance with the standard GB / T 1040.1-2018 Plastics - Determination of Tensile Properties. The test results are shown in Table 3.

[0100] 3. Test Results

[0101] The test results of the above embodiments and comparative examples are shown in Table 3.

[0102] Table 3 Test results of examples and comparative examples Simple supported beam impact strength / kJ / m² Tensile strength / MPa Flexural modulus / MPa Example 1 25 32 1800 Example 2 26 33 1445 Example 3 23 31 1810 Example 4 22 30 1820 Example 5 27 34 1430 Example 6 15 20 1890 Comparative Example 1 10 9 1832 Comparative Example 2 12 11 1790 Comparative Example 3 26 33 850 Comparative Example 4 23 30 910

[0103] According to Table 1, Table 2 and Table 3, it can be seen from Comparative Example 1 and Comparative Example 2 that when glass fiber and POE are present at the same time, the prepared polypropylene polymer has higher simply supported beam impact strength and tensile strength, and the polypropylene polymer prepared without any of the two components has lower simply supported beam impact strength and tensile strength. Therefore, glass fiber and POE have a synergistic effect in improving the toughness of the polypropylene polymer of the present application; it can be seen from Comparative Example 3 and Comparative Example 4 that when nano calcium carbonate and titanate coupling agent are present at the same time, the flexural modulus of the prepared polypropylene polymer is lower. The flexural modulus of the polypropylene polymer prepared without any of the two components is low. Therefore, nano-calcium carbonate and titanate coupling agent have a synergistic effect in improving the rigidity of the polypropylene polymer of the present application. As can be seen from Examples 1, 3, and 4 compared with Examples 2, 5, and 6, when the mass ratio of glass fiber to POE is 10:3 and the mass ratio of nano-calcium carbonate to titanate coupling agent is 15:2, the mass ratio of the total amount of glass fiber and POE to the total amount of nano-calcium carbonate and titanate coupling agent is 1:1.3 to 1:2, which can take into account both the rigidity and toughness of the prepared polypropylene polymer.

[0104] It should be noted that, in this document, relational terms such as first and second, etc., are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply the existence of any such actual relationship or order between these entities or operations. Moreover, the terms "comprises," "comprising," or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article, or device comprising a series of elements includes not only those elements, but also other elements not explicitly listed, or elements inherent to such process, method, article, or device. In the absence of further limitations, an element defined by the phrase "comprising a ..." does not exclude the presence of other identical elements in the process, method, article, or device comprising the element.

[0105] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present invention.

[0106] The present invention uses the above-described embodiments to illustrate the detailed process flow of the present invention. However, the present invention is not limited to the above-described detailed process flow, that is, it does not mean that the present invention must rely on the above-described detailed process flow to be implemented. Those skilled in the art should understand that any improvements to the present invention, equivalent replacements of various raw materials in the products of the present invention, addition of auxiliary ingredients, and selection of specific methods, etc., are all within the scope of protection and disclosure of the present invention.

Claims

1. A method for recycling polypropylene waste into high-rigidity and high-toughness polypropylene polymer, characterized in that: The steps include: S1. After cleaning and vibrating screening, the polypropylene waste is crushed into particles with a particle size of ≤5mm; S2, after drying the pellets to a moisture content of less than 0.5%, adding glass fiber accounting for 7% to 10% of the pellets mass at a temperature of 200°C to 230°C and a pressure of 5MPa to 15MPa, 2.3% to 3% of an elastomer are melt-blended, extruded and granulated to obtain first polypropylene particles; S3. Dry the first polypropylene particles to a moisture content of less than 1%, add 15% to 18% of the mass of the particles of nano-calcium carbonate and 2% to 2.4% of the mass of the particles of coupling agent at a temperature of 200° C. to 220° C. and a pressure of 10 MPa to 14 MPa, melt-blending and extruding to obtain high-rigidity and high-toughness polypropylene polymer particles.

2. The method for recycling polypropylene waste into high-rigidity and high-toughness polypropylene polymer according to claim 1, characterized in that: The mass ratio of the amount of the granular material to the total amount of the glass fiber, elastomer, nano-calcium carbonate and coupling agent is 100:

30.

3. The method for recycling polypropylene waste into high-rigidity and high-toughness polypropylene polymer according to claim 1, characterized in that: The mass ratio of the glass fiber to the elastomer is 10:

3.

4. The method for recycling polypropylene waste into high-rigidity and high-toughness polypropylene polymer according to claim 1, wherein: The mass ratio of the nano calcium carbonate to the coupling agent is 15:

2.

5. The method for recycling polypropylene waste into high-rigidity and high-toughness polypropylene polymer according to claim 1, characterized in that: The mass ratio of the total amount of the glass fiber and the elastomer to the total amount of the nano-calcium carbonate and the coupling agent is 1:1.3 to 1:

2.

6. The method for recycling polypropylene waste into high-rigidity and high-toughness polypropylene polymer according to claim 1, characterized in that: The elastomer is selected from polyolefin elastomer and EPDM rubber.

7. The method for recycling polypropylene waste into high-rigidity and high-toughness polypropylene polymer according to claim 1, characterized in that: The particle size of the nano calcium carbonate is 50-100 nm.

8. The method for recycling polypropylene waste into high-rigidity and high-toughness polypropylene polymer according to claim 1, wherein: The coupling agent is selected from phthalate coupling agent, silane coupling agent, and maleic anhydride grafted polypropylene coupling agent.

9. The method for recycling polypropylene waste into high-rigidity and high-toughness polypropylene polymer according to claim 1, wherein: The mass ratio of the total amount of the glass fiber and the elastomer to the total amount of the nano-calcium carbonate and the coupling agent is 1:1.

3.

10. The method for recycling polypropylene waste into high-rigidity and high-toughness polypropylene polymer according to claim 1, characterized in that: The mass ratio of the total amount of the glass fiber and the elastomer to the total amount of the nano-calcium carbonate and the coupling agent is 1:2.

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