Elastomer-toughened recycled polyolefin material and method for its production

Abstract

The application discloses an elastomer toughened regenerated polyolefin material and a preparation method thereof, relates to the technical field of polyolefin materials, and comprises the following steps: firstly, melt grafting modification is conducted on regenerated polyolefin, maleic anhydride, styrene and dicumyl peroxide; and then, melt blending is conducted on the regenerated polyolefin, the maleic anhydride, the styrene, the dicumyl peroxide, microcrystalline cellulose grafted elastomer, nitrogen-boron coordination boric acid crosslinking agent and zinc acetate, and extrusion granulation is conducted. The application improves the heterogeneous interface compatibility through grafting modification, forms a double-network synergistic enhancement through dynamic crosslinking of the microcrystalline cellulose grafted elastomer and the nitrogen-boron, and cooperates with zinc acetate to catalyze and improve the crosslinking efficiency, so that the prepared material has high tensile strength, elongation at break and impact toughness, excellent thermal stability and cycle processing performance, and effectively solves the problems of regenerated polyolefin, such as brittleness, poor compatibility, poor mechanical properties and poor cycle processing performance.

Description

Technical Field

[0001] This invention relates to the field of polyolefin materials technology, specifically to an elastomer-toughened recycled polyolefin material and its preparation method. Background Technology

[0002] Recycled polyolefins are the core material for the resource utilization of waste polyolefin plastics, effectively reducing environmental pollution and raw material costs. However, the degradation of molecular chains and the increase of structural defects during the recycling process lead to problems such as high brittleness, poor tensile strength and impact toughness, and severe degradation of mechanical properties, making them unable to directly meet application requirements. Traditional methods of toughening recycled polyolefins by blending with elastomers suffer from technical shortcomings due to the large polarity difference between the non-polar matrix and the elastomer, resulting in poor interfacial compatibility, significant phase separation, and a substantial decrease in tensile strength while toughening. Furthermore, conventional modified materials lack dynamic self-healing and efficient cyclic processing capabilities, have insufficient thermal stability, and experience a sharp decline in performance after repeated heat treatment. In addition, ordinary filler reinforcement is prone to agglomeration, resulting in poor interfacial bonding and failing to achieve a synergistic improvement in strength and toughness.

[0003] Existing technologies cannot simultaneously solve the problems of interfacial compatibility, strength-toughness balance, thermal stability and recyclability of recycled polyolefins, which seriously limits the high-value application and large-scale promotion of recycled polyolefins. There is an urgent need to develop an elastomer-toughened recycled polyolefin material with excellent comprehensive performance. Summary of the Invention

[0004] The purpose of this invention is to provide an elastomer-toughened recycled polyolefin material and its preparation method, so as to solve the problems raised in the prior art.

[0005] To achieve the above objectives, the present invention provides the following technical solution: A method for preparing an elastomer-toughened recycled polyolefin material includes the following steps: S1: adding recycled polyolefin, maleic anhydride, styrene, and dicumyl peroxide into a reaction vessel, heating to 170-180℃ and melting and blending for 5-8 minutes to obtain graft-modified recycled polyolefin. S2: Graft-modified recycled polyolefin, microcrystalline cellulose grafted elastomer, nitrogen-boron coordinated boric acid crosslinking agent, and zinc acetate are added to a reaction vessel, stirred evenly, heated to 170-180℃ for melt blending for 5-10 minutes, and extruded and granulated to obtain elastomer-toughened recycled polyolefin material.

[0006] Furthermore, the recycled polyolefin is recycled polyethylene or recycled polypropylene.

[0007] Furthermore, in the preparation process of graft-modified recycled polyolefin, the mass ratio of recycled polyolefin, maleic anhydride, styrene, and dicumyl peroxide is 100:(1.5-1.7):(1.6-1.8):(0.03-0.05).

[0008] Furthermore, in the preparation process of the elastomer-toughened recycled polyolefin material, the mass ratio of graft-modified recycled polyolefin, microcrystalline cellulose grafted elastomer, nitrogen-boron coordinated boric acid crosslinking agent, and zinc acetate is 100:(10-30):(0.9-1.2):(0.015-0.06).

[0009] Furthermore, the preparation method of the microcrystalline cellulose grafted elastomer includes the following steps: adding microcrystalline cellulose-bromoisobutyrate, n-butyl acrylate, tert-butyl acrylate, copper bromide, and 2,2'-bipyridine to N,N-dimethylformamide, performing a freeze-drain-thaw cycle for degassing and sealing in liquid nitrogen, reacting in an oil bath at 70-75℃ for 10-12 hours, cooling to room temperature, removing the seal, adding tetrahydrofuran to dissolve, adding excess methanol, precipitating the precipitate, collecting the precipitate, washing the precipitate with methanol, repeating the above dissolution-precipitation-washing steps three times, and vacuum drying at 60-65℃ to obtain the microcrystalline cellulose graft copolymer; Microcrystalline cellulose graft copolymer, concentrated hydrochloric acid, and 1,4-dioxane were added to a reaction vessel and heated to 80-85℃ for 20-22 hours for hydrolysis. Excess deionized water was added to precipitate the product, which was then redissolved in tetrahydrofuran. The precipitation-dissolution step was repeated three times, and the product was dried under vacuum at 60-65℃ to obtain microcrystalline cellulose graft elastomer.

[0010] Furthermore, in the preparation process of the microcrystalline cellulose graft copolymer, the molar ratio of microcrystalline cellulose-bromoisobutyrate, n-butyl acrylate, tert-butyl acrylate, copper bromide, and 2,2'-bipyridine is 1:(650-780):(220-350):(0.05-0.06):(0.03-0.04); In the preparation of microcrystalline cellulose grafted elastomer, the mass ratio of microcrystalline cellulose graft copolymer, concentrated hydrochloric acid, and 1,4-dioxane is 1:(0.9-1.1):(20-22).

[0011] Furthermore, the preparation method of the microcrystalline cellulose-bromoisobutyrate includes the following steps: adding microcrystalline cellulose to 1-allyl-3-methylimidazolium chloride, heating to 80-85°C and stirring until the microcrystalline cellulose is completely dissolved, adding N,N-dimethylformamide, stirring evenly, and obtaining a cellulose solution; The cellulose solution was placed in an ice bath, and 2-bromoisobutyryl bromide was added. The reaction was carried out at room temperature for 36-40 hours. Excess deionized water was added, and a precipitate was formed. The precipitate was collected, washed with deionized water until neutral, filtered, and dried under vacuum to obtain microcrystalline cellulose-bromoisobutyrate.

[0012] Furthermore, in the preparation of microcrystalline cellulose-bromoisobutyrate, the mass ratio of microcrystalline cellulose, 1-allyl-3-methylimidazolium chloride, and 2-bromoisobutyryl bromide is 1.5:(40-45):(5.8-6).

[0013] Furthermore, the preparation method of the nitrogen-boron coordinated boric acid crosslinking agent includes the following steps: adding 1,4-phenylene diboronic acid and triethanolamine to methanol, stirring evenly, heating to 40-45℃ for 4-4.5h, vacuum filtering, and vacuum drying at 50-55℃ to obtain the nitrogen-boron coordinated boric acid crosslinking agent.

[0014] Furthermore, in the preparation process of the nitrogen-boron coordinated boric acid crosslinking agent, the molar ratio of 1,4-phenylene diboronic acid and triethanolamine is 1:(2.2-2.5).

[0015] Compared with the prior art, the beneficial effects of the present invention are: 1. This invention uses microcrystalline cellulose grafted elastomer as the core toughening and reinforcing component. Microcrystalline cellulose serves as a rigid physical cross-linking skeleton to construct the primary physical network, thereby improving the modulus and tensile strength of the material. The acrylate soft grafted chains endow the material with excellent rubbery elasticity and high elongation at break. The carboxyl side chains formed after the grafted chains are hydrolyzed can construct a hydrogen bond secondary network, forming a dual-network synergistic reinforcement structure with the physical cross-linking of microcrystalline cellulose. This can not only efficiently absorb impact energy to achieve efficient toughening of recycled polyolefins, but also avoid the strength loss problem caused by traditional elastomer toughening. At the same time, the soft chain segments of the grafted elastomer form sufficient chain entanglement with the polyolefin matrix chain, further optimizing the interphase interface bonding state, eliminating phase interface defects, and improving the uniformity and compatibility of the material's microstructure.

[0016] 2. This invention further introduces a nitrogen-boron coordinated boric acid crosslinking agent as a dynamic covalent bond functional core component, which can form a reversible dynamic crosslinking network with grafted modified recycled polyolefins and microcrystalline cellulose grafted elastomers. The boron-nitrogen coordination bond can be broken and recombined under thermal activation conditions, effectively extending the service life of the material. This crosslinking agent can also act as an interfacial compatibilizer, tightly connecting the polyolefin phase and the elastomer phase, further inhibiting phase separation and improving the compatibility of the system.

[0017] 3. The raw material components of this invention form a synergistic effect. Graft modification improves the interfacial compatibility between multiple phases. The physical crosslinking of microcrystalline cellulose and the dynamic chemical crosslinking of nitrogen-boron form a synergistic dual-network structure. Zinc acetate catalysis and crosslinking reaction form a synergistic effect on reaction efficiency. The recycled polyolefin matrix and bio-based microcrystalline cellulose form a green and environmentally friendly synergistic effect. These multiple synergistic effects ultimately endow the material with excellent comprehensive performance. The resulting elastomer-toughened recycled polyolefin material has high tensile strength, high elongation at break, excellent impact toughness, and heat and aging resistance. Detailed Implementation

[0018] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0019] Example 1: A method for preparing an elastomer-toughened recycled polyolefin material, comprising the following steps: S1: 100g of recycled polyolefin, 1.6g of maleic anhydride, 1.7g of styrene, and 0.04g of dicumyl peroxide are added to a reaction vessel and heated to 170°C for melting and blending for 8 minutes to obtain graft-modified recycled polyolefin. S2: Graft-modified recycled polyolefin, 20g microcrystalline cellulose grafted elastomer, 1g nitrogen-boron coordinated boric acid crosslinking agent, and 0.03g zinc acetate are added to a reaction vessel, stirred evenly, heated to 170℃ for melt blending for 5min, and extruded and granulated to obtain elastomer-toughened recycled polyolefin material.

[0020] The preparation method of microcrystalline cellulose grafted elastomer includes the following steps: 1.5g of microcrystalline cellulose is added to 40g of 1-allyl-3-methylimidazolium chloride, heated to 80℃ and stirred until the microcrystalline cellulose is completely dissolved, N,N-dimethylformamide is added and stirred evenly to obtain a cellulose solution; The cellulose solution was placed in an ice bath, and 5.8 g of 2-bromoisobutyryl bromide was added. The reaction was carried out at room temperature for 36 h. Excess deionized water was added, and a precipitate was formed. The precipitate was collected, washed with deionized water until neutral, filtered, and dried under vacuum to obtain microcrystalline cellulose-bromoisobutyrate.

[0021] 1 mmol of microcrystalline cellulose-bromoisobutyrate, 650 mmol of n-butyl acrylate, 220 mmol of tert-butyl acrylate, 0.05 mmol of copper bromide, and 0.03 mmol of 2,2'-bipyridine were added to N,N-dimethylformamide. The mixture was subjected to a freeze-drain-thaw cycle in liquid nitrogen for degassing and sealing. The mixture was then placed in an oil bath at 70°C for 10 h. After cooling to room temperature, the seal was removed, tetrahydrofuran was added to dissolve the precipitate, and excess methanol was added to precipitate the precipitate. The precipitate was collected, washed with methanol, and the above dissolution-precipitation-washing steps were repeated three times. The mixture was then dried under vacuum at 60°C to obtain the microcrystalline cellulose graft copolymer. 1g of microcrystalline cellulose graft copolymer, 0.9g of concentrated hydrochloric acid, and 20g of 1,4-dioxane were added to a reaction vessel and heated to 80℃ for 20h for hydrolysis. Excess deionized water was added to precipitate the product, which was then redissolved in tetrahydrofuran. The precipitation-dissolution step was repeated three times, and the product was dried under vacuum at 60-65℃ to obtain microcrystalline cellulose graft elastomer.

[0022] The preparation method of nitrogen-boron coordinated boric acid crosslinking agent includes the following steps: 1 mmol of 1,4-phenylene diboronic acid and 2.2 mmol of triethanolamine are added to methanol, stirred evenly, heated to 40℃ and reacted for 4 h, filtered under vacuum, and dried under vacuum at 50℃ to obtain nitrogen-boron coordinated boric acid crosslinking agent.

[0023] Example 2: A method for preparing an elastomer-toughened recycled polyolefin material, comprising the following steps: S1: 100g of recycled polyolefin, 1.6g of maleic anhydride, 1.7g of styrene, and 0.04g of dicumyl peroxide are added to a reaction vessel and heated to 170°C for melting and blending for 8 minutes to obtain graft-modified recycled polyolefin. S2: Graft-modified recycled polyolefin, 10g microcrystalline cellulose grafted elastomer, 1g nitrogen-boron coordinated boric acid crosslinking agent, and 0.03g zinc acetate are added to a reaction vessel, stirred evenly, heated to 170℃ for melt blending for 5min, and extruded and granulated to obtain elastomer-toughened recycled polyolefin material.

[0024] The preparation method of microcrystalline cellulose grafted elastomer includes the following steps: 1.5g of microcrystalline cellulose is added to 40g of 1-allyl-3-methylimidazolium chloride, heated to 80℃ and stirred until the microcrystalline cellulose is completely dissolved, N,N-dimethylformamide is added and stirred evenly to obtain a cellulose solution; The cellulose solution was placed in an ice bath, and 5.8 g of 2-bromoisobutyryl bromide was added. The reaction was carried out at room temperature for 36 h. Excess deionized water was added, and a precipitate was formed. The precipitate was collected, washed with deionized water until neutral, filtered, and dried under vacuum to obtain microcrystalline cellulose-bromoisobutyrate.

[0025] 1 mmol of microcrystalline cellulose-bromoisobutyrate, 650 mmol of n-butyl acrylate, 220 mmol of tert-butyl acrylate, 0.05 mmol of copper bromide, and 0.03 mmol of 2,2'-bipyridine were added to N,N-dimethylformamide. The mixture was subjected to a freeze-drain-thaw cycle in liquid nitrogen for degassing and sealing. The mixture was then placed in an oil bath at 70°C for 10 h. After cooling to room temperature, the seal was removed, tetrahydrofuran was added to dissolve the precipitate, and excess methanol was added to precipitate the precipitate. The precipitate was collected, washed with methanol, and the above dissolution-precipitation-washing steps were repeated three times. The mixture was then dried under vacuum at 60°C to obtain the microcrystalline cellulose graft copolymer. 1g of microcrystalline cellulose graft copolymer, 0.9g of concentrated hydrochloric acid, and 20g of 1,4-dioxane were added to a reaction vessel and heated to 80℃ for 20h for hydrolysis. Excess deionized water was added to precipitate the product, which was then redissolved in tetrahydrofuran. The precipitation-dissolution step was repeated three times, and the product was dried under vacuum at 60-65℃ to obtain microcrystalline cellulose graft elastomer.

[0026] The preparation method of nitrogen-boron coordinated boric acid crosslinking agent includes the following steps: 1 mmol of 1,4-phenylene diboronic acid and 2.2 mmol of triethanolamine are added to methanol, stirred evenly, heated to 40℃ and reacted for 4 h, filtered under vacuum, and dried under vacuum at 50℃ to obtain nitrogen-boron coordinated boric acid crosslinking agent.

[0027] Example 3: A method for preparing an elastomer-toughened recycled polyolefin material, comprising the following steps: S1: 100g of recycled polyolefin, 1.6g of maleic anhydride, 1.7g of styrene, and 0.04g of dicumyl peroxide are added to a reaction vessel and heated to 170°C for melting and blending for 8 minutes to obtain graft-modified recycled polyolefin. S2: Graft-modified recycled polyolefin, 30g microcrystalline cellulose grafted elastomer, 1g nitrogen-boron coordinated boric acid crosslinking agent, and 0.03g zinc acetate are added to a reaction vessel, stirred evenly, heated to 170℃ for melt blending for 5min, and extruded and granulated to obtain elastomer-toughened recycled polyolefin material.

[0028] The preparation method of microcrystalline cellulose grafted elastomer includes the following steps: 1.5g of microcrystalline cellulose is added to 40g of 1-allyl-3-methylimidazolium chloride, heated to 80℃ and stirred until the microcrystalline cellulose is completely dissolved, N,N-dimethylformamide is added and stirred evenly to obtain a cellulose solution; The cellulose solution was placed in an ice bath, and 5.8 g of 2-bromoisobutyryl bromide was added. The reaction was carried out at room temperature for 36 h. Excess deionized water was added, and a precipitate was formed. The precipitate was collected, washed with deionized water until neutral, filtered, and dried under vacuum to obtain microcrystalline cellulose-bromoisobutyrate.

[0029] 1 mmol of microcrystalline cellulose-bromoisobutyrate, 650 mmol of n-butyl acrylate, 220 mmol of tert-butyl acrylate, 0.05 mmol of copper bromide, and 0.03 mmol of 2,2'-bipyridine were added to N,N-dimethylformamide. The mixture was subjected to a freeze-drain-thaw cycle in liquid nitrogen for degassing and sealing. The mixture was then placed in an oil bath at 70°C for 10 h. After cooling to room temperature, the seal was removed, tetrahydrofuran was added to dissolve the precipitate, and excess methanol was added to precipitate the precipitate. The precipitate was collected, washed with methanol, and the above dissolution-precipitation-washing steps were repeated three times. The mixture was then dried under vacuum at 60°C to obtain the microcrystalline cellulose graft copolymer. 1g of microcrystalline cellulose graft copolymer, 0.9g of concentrated hydrochloric acid, and 20g of 1,4-dioxane were added to a reaction vessel and heated to 80℃ for 20h for hydrolysis. Excess deionized water was added to precipitate the product, which was then redissolved in tetrahydrofuran. The precipitation-dissolution step was repeated three times, and the product was dried under vacuum at 60-65℃ to obtain microcrystalline cellulose graft elastomer.

[0030] The preparation method of nitrogen-boron coordinated boric acid crosslinking agent includes the following steps: 1 mmol of 1,4-phenylene diboronic acid and 2.2 mmol of triethanolamine are added to methanol, stirred evenly, heated to 40℃ and reacted for 4 h, filtered under vacuum, and dried under vacuum at 50℃ to obtain nitrogen-boron coordinated boric acid crosslinking agent.

[0031] Comparative Example 1: A method for preparing an elastomer-toughened recycled polyolefin material, comprising the following steps: S1: 100g of recycled polyolefin, 1.6g of maleic anhydride, 1.7g of styrene, and 0.04g of dicumyl peroxide are added to a reaction vessel and heated to 170°C for melting and blending for 8 minutes to obtain grafted modified recycled polyolefin. S2: Graft-modified recycled polyolefin, 1g of nitrogen-boron coordinated boric acid crosslinking agent, and 0.03g of zinc acetate are added to a reaction vessel, stirred evenly, heated to 170℃ for melt blending for 5min, and extruded and granulated to obtain an elastomer-toughened recycled polyolefin material.

[0032] The remaining steps are the same as in Example 1.

[0033] Comparative Example 2: A method for preparing an elastomer-toughened recycled polyolefin material, comprising the following steps: S1: 100g of recycled polyolefin, 1.6g of maleic anhydride, 1.7g of styrene, and 0.04g of dicumyl peroxide are added to a reaction vessel and heated to 170°C for melting and blending for 8 minutes to obtain graft-modified recycled polyolefin. S2: Add grafted modified recycled polyolefin, 20g microcrystalline cellulose grafted elastomer, and 0.03g zinc acetate to a reaction vessel, stir evenly, heat to 170℃ for melt blending for 5min, and extrude and granulate to obtain elastomer-toughened recycled polyolefin material.

[0034] The remaining steps are the same as in Example 1.

[0035] Comparative Example 3: A method for preparing an elastomer-toughened recycled polyolefin material, comprising the following steps: S1: 100g of recycled polyolefin, 1.6g of maleic anhydride, 1.7g of styrene and 0.04g of dicumyl peroxide are added to a reaction vessel and heated to 170°C for melting and blending for 8 minutes to obtain grafted modified recycled polyolefin. S2: Graft-modified recycled polyolefin, 20g microcrystalline cellulose grafted elastomer, and 1g nitrogen-boron coordinated boric acid crosslinking agent are added to a reaction vessel, stirred evenly, heated to 170℃ for melt blending for 5min, and extruded and granulated to obtain elastomer-toughened recycled polyolefin material.

[0036] The remaining steps are the same as in Example 1.

[0037] Comparative Example 4: A method for preparing an elastomer-toughened recycled polyolefin material, comprising the following steps: S1: 100g of recycled polyolefin, 1.6g of maleic anhydride, 1.7g of styrene and 0.04g of dicumyl peroxide are added to a reaction vessel and heated to 170°C for melting and blending for 8 minutes to obtain grafted modified recycled polyolefin. S2: Graft-modified recycled polyolefin, 20g microcrystalline cellulose, 1g nitrogen-boron coordinated boric acid crosslinking agent, and 0.03g zinc acetate are added to a reaction vessel, stirred evenly, heated to 170℃ for melt blending for 5min, and extruded and granulated to obtain an elastomer-toughened recycled polyolefin material.

[0038] The microcrystalline cellulose has a particle size of 40 μm.

[0039] The remaining steps are the same as in Example 1.

[0040] Performance testing: Tensile properties: According to GB / T 1040.1-2018, a universal testing machine was used for testing, with a tensile rate of 50 mm / min, to detect tensile strength and elongation at break; Impact strength: The impact strength was tested according to GB / T 1043.1-2018; Thermal stability: TGA test, under nitrogen atmosphere, heating rate of 10℃ / min, record the 5% thermogravimetric temperature; Cyclic processing performance: Tensile strength retention rate was tested after three hot extrusion injection molding cycles.

[0041] The performance test results are shown in the table below.

[0042]

[0043] Conclusion: The elastomer-toughened recycled polyolefin material prepared by this invention has both environmental friendliness and mechanical properties.

[0044] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within the present invention.

Claims

1. A method for preparing an elastomer-toughened recycled polyolefin material, characterized in that: Includes the following steps: S1: Add recycled polyolefin, maleic anhydride, styrene, and dicumyl peroxide into a reaction vessel, heat to 170-180℃ and melt-blend for 5-8 minutes to obtain grafted modified recycled polyolefin. S2: Graft-modified recycled polyolefin, microcrystalline cellulose grafted elastomer, nitrogen-boron coordinated boric acid crosslinking agent, and zinc acetate are added to a reaction vessel, stirred evenly, heated to 170-180℃ for melt blending for 5-10 minutes, and extruded and granulated to obtain elastomer-toughened recycled polyolefin material.

2. The method for preparing an elastomer-toughened recycled polyolefin material according to claim 1, characterized in that: In the preparation of graft-modified recycled polyolefin, the mass ratio of recycled polyolefin, maleic anhydride, styrene, and dicumyl peroxide is 100:(1.5-1.7):(1.6-1.8):(0.03-0.05).

3. The method for preparing an elastomer-toughened recycled polyolefin material according to claim 1, characterized in that: In the preparation of elastomer-toughened recycled polyolefin materials, the mass ratio of graft-modified recycled polyolefin, microcrystalline cellulose grafted elastomer, nitrogen-boron coordinated boric acid crosslinking agent, and zinc acetate is 100:(10-30):(0.9-1.2):(0.015-0.06).

4. The method for preparing an elastomer-toughened recycled polyolefin material according to claim 1, characterized in that: The preparation method of the microcrystalline cellulose grafted elastomer includes the following steps: adding microcrystalline cellulose-bromoisobutyrate, n-butyl acrylate, tert-butyl acrylate, copper bromide, and 2,2'-bipyridine to N,N-dimethylformamide, performing a freeze-drain-thaw cycle in liquid nitrogen for degassing and sealing, reacting in an oil bath at 70-75℃ for 10-12 hours, cooling to room temperature, removing the seal, adding tetrahydrofuran to dissolve, adding excess methanol, precipitating the precipitate, collecting the precipitate, washing the precipitate with methanol, repeating the above dissolution-precipitation-washing steps three times, and vacuum drying at 60-65℃ to obtain the microcrystalline cellulose graft copolymer; Microcrystalline cellulose graft copolymer, concentrated hydrochloric acid, and 1,4-dioxane were added to a reaction vessel and heated to 80-85℃ for 20-22 hours for hydrolysis. Excess deionized water was added to precipitate the product, which was then redissolved in tetrahydrofuran. The precipitation-dissolution step was repeated three times, and the product was dried under vacuum at 60-65℃ to obtain microcrystalline cellulose graft elastomer.

5. The method for preparing an elastomer-toughened recycled polyolefin material according to claim 4, characterized in that: In the preparation of microcrystalline cellulose graft copolymer, the molar ratio of microcrystalline cellulose-bromoisobutyrate, n-butyl acrylate, tert-butyl acrylate, copper bromide, and 2,2'-bipyridine is 1:(650-780):(220-350):(0.05-0.06):(0.03-0.04). In the preparation of microcrystalline cellulose grafted elastomer, the mass ratio of microcrystalline cellulose graft copolymer, concentrated hydrochloric acid, and 1,4-dioxane is 1:(0.9-1.1):(20-22).

6. The method for preparing an elastomer-toughened recycled polyolefin material according to claim 1, characterized in that: The preparation method of the microcrystalline cellulose-bromoisobutyrate includes the following steps: adding microcrystalline cellulose to 1-allyl-3-methylimidazolium chloride, heating to 80-85℃ and stirring until the microcrystalline cellulose is completely dissolved, adding N,N-dimethylformamide, stirring evenly to obtain a cellulose solution; The cellulose solution was placed in an ice bath, and 2-bromoisobutyryl bromide was added. The reaction was carried out at room temperature for 36-40 hours. Excess deionized water was added, and a precipitate was formed. The precipitate was collected, washed with deionized water until neutral, filtered, and dried under vacuum to obtain microcrystalline cellulose-bromoisobutyrate.

7. The method for preparing an elastomer-toughened recycled polyolefin material according to claim 6, characterized in that: In the preparation of microcrystalline cellulose-bromoisobutyrate, the mass ratio of microcrystalline cellulose, 1-allyl-3-methylimidazolium chloride, and 2-bromoisobutyryl bromide is 1.5:(40-45):(5.8-6).

8. The method for preparing an elastomer-toughened recycled polyolefin material according to claim 1, characterized in that: The preparation method of the nitrogen-boron coordinated boric acid crosslinking agent includes the following steps: adding 1,4-phenylene diboronic acid and triethanolamine to methanol, stirring evenly, heating to 40-45℃ for 4-4.5h, vacuum filtering, and vacuum drying at 50-55℃ to obtain the nitrogen-boron coordinated boric acid crosslinking agent.

9. The method for preparing an elastomer-toughened recycled polyolefin material according to claim 8, characterized in that: In the preparation of nitrogen-boron coordinated boric acid crosslinking agent, the molar ratio of 1,4-phenylene diboronic acid and triethanolamine is 1:(2.2-2.5).

10. The recycled polyolefin material prepared by the method for preparing an elastomer-toughened recycled polyolefin material according to any one of claims 1-9.

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