Regeneration method of waste nylon engineering plastic and regenerated nylon

Abstract

The invention discloses a regeneration method of waste nylon engineering plastic and regenerated nylon, and belongs to the technical field of waste nylon plastic recycling. According to the method, the waste nylon plastic is converted into oligomer micromolecules through high-pressure pre-depolymerization. Secondly, under the medium-pressure condition, the high-pressure pre-depolymerized small molecules are depolymerized again and purified. Thirdly, carrying out normal-pressure prepolymerization on the purified monomer; and then, under a negative pressure condition, polymerizing the pre-polymerized prepolymer again to prepare the regenerated nylon. Through four stages of high-pressure pre-depolymerization, medium-pressure re-depolymerization and purification, normal-pressure pre-polymerization and negative-pressure re-polymerization, the waste nylon plastic is reversely degraded into a high-purity monomer, and the high-purity monomer is further re-polymerized into high-performance regenerated nylon, so that closed-loop regeneration from a waste material to a primary-quality polymer is realized; and the conversion of engineering plastic recycling from degradation cycle to high-value cycle is promoted.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of recycling waste nylon plastics, and relates to a waste nylon engineering plastic regeneration method and regenerated nylon. BACKGROUND

[0002] Nylon (polyamide) is an important engineering plastic, which is widely used in the fields of automobiles, electronic appliances, machinery manufacturing, textiles, packaging, etc., and has the advantages of high strength, good wear resistance, strong heat resistance, excellent chemical stability, etc. With the acceleration of social industrialization, the consumption of nylon products continues to rise, and a large amount of waste nylon plastics is generated accordingly. If these waste materials are discarded directly without treatment, not only resources will be wasted, but also the ecological environment will be persistently polluted. How to realize efficient recycling and cyclic utilization of waste nylon materials has become an important research topic in the fields of material science and environmental protection engineering.

[0003] The existing nylon recycling methods mainly include mechanical recycling and chemical recycling. Mechanical recycling usually recycles waste nylon into plastic products through processes such as crushing, melting and regranulation. Although it is simple to operate and has low cost, the performance of the material will decrease significantly due to chain segment breakage in the multiple thermal processing processes, and problems such as yellowing and embrittlement are likely to occur, which makes it difficult to meet the recycling needs of high-performance materials. In contrast, chemical recycling can crack polymers into monomers or oligomers from the molecular level, thereby realizing the near-original recovery of material performance, and has higher resource value.

[0004] In the chemical recycling path, high-temperature hydrolysis or ammonolysis depolymerization method has been widely concerned because it can effectively break the amide bond and realize the reverse degradation of the polyamide molecular structure. However, the traditional chemical depolymerization process often has problems such as harsh reaction conditions, high energy consumption, many by-products, complex process steps, etc., which limit its application in industrialization. In addition, the process from monomer recovery to regenerated polymerization in the existing technology usually needs multiple steps of reaction and intermediate separation, which is complicated, low in efficiency, and easy to introduce impurities, affecting the quality of regenerated nylon.

[0005] Especially in the recycling of semi-aromatic nylon (such as nylon 6T, nylon MXD6, etc.), due to the rigid aromatic ring contained in its molecular structure, it has higher thermal stability and hydrolysis resistance, making it more difficult to depolymerize by conventional methods, so there is currently a lack of an efficient, environmentally friendly and economic integrated processing technology to realize the closed-loop recycling of this type of engineering plastic. In order to solve the above problems, it is urgent to develop an efficient, low energy consumption, environmentally friendly and suitable for closed-loop recycling process of various types of nylon. The present application proposes a "one-pot" monomer preparation and regeneration method for waste nylon engineering plastics, especially semi-aromatic nylon, which integrates high-pressure depolymerization, medium-pressure purification, atmospheric pressure prepolymerization and negative pressure repolymerization, realizing efficient and high-purity closed-loop regeneration of nylon materials. This method not only simplifies the process flow and reduces the reaction threshold, but also helps to realize the high-value recycling and recycling of nylon resources, has significant economic benefits and environmental value, and has broad application prospects in promoting plastic circular economy and "carbon neutralization" strategy. SUMMARY

[0006] The present application aims to provide a regeneration method for waste nylon engineering plastics and regenerated nylon to solve the technical problems of complicated process steps, high energy consumption, low purity and performance degradation of the prior art nylon recycling process.

[0007] To achieve the above-mentioned purpose, the technical scheme is adopted as follows:

[0008] In a first aspect, the present application provides a regeneration method for waste nylon engineering plastics, comprising the following steps:

[0009] The waste nylon plastic is put into a reaction kettle, and an alkaline solution and ultrapure water are added, and after high-temperature depolymerization and cooling to room temperature, a mixed aqueous solution of nylon oligomers is obtained;

[0010] The mixed aqueous solution of nylon oligomers is sieved to obtain a clear oligomer solution, an alkaline solution is added to the clear oligomer solution and secondary depolymerization is carried out at medium temperature to obtain a purified product;

[0011] An acidic solution is added to the purified product, and a white precipitated monomer is obtained after filtration;

[0012] The white precipitated monomer is mixed with a diamine solution and a catalyst is added, and pre-polymerization is carried out at room temperature and atmospheric pressure to form a pre-polymer;

[0013] The pre-polymer is heated and the repolymerization of the pre-polymer is completed under negative pressure, and finally a regenerated nylon is obtained.

[0014] Further, in the step of putting the waste nylon plastic into a reaction kettle, adding an alkaline solution and ultrapure water, and cooling to room temperature after high-temperature depolymerization to obtain a nylon oligomer, the mass ratio of the waste nylon plastic, the alkaline solution and the ultrapure water is (0.3-2):(0.05-1):(1-30); and the alkaline solution is a sodium hydroxide solution with a mass concentration of 10%-30%.

[0015] Further, the reaction temperature of the high-temperature depolymerization is 220-320 DEG C, the pressure is 2.2-12.5 MPa, the reaction time is 10-90 min, and the rotation speed of the reaction kettle is 500-1200 r / min.

[0016] Further, in the step of sieving the mixed aqueous solution of the nylon oligomer to obtain a clarified oligomer solution, adding an alkaline solution to the clarified oligomer solution and performing secondary moderate-temperature redispersion to obtain a purified product, the sieving is performed by using a sieve with a mesh size of 10-200, and the mass ratio of the alkaline solution to the clarified oligomer solution is (1-2):50.

[0017] Further, the reaction temperature of the secondary moderate-temperature redispersion is 100-200 DEG C, the pressure is 0.1-2.1 MPa, the reaction time is 30-120 min, and the rotation speed of the reaction kettle is 500-1200 r / min.

[0018] Further, the acid solution is hydrochloric acid; and the addition amount of the acid solution is 1.2-1.5 times the total amount of the alkaline solution.

[0019] Further, the particle size of the white precipitated monomer is 0.64-0.92 mu m.

[0020] Further, the mixing mass ratio of the white precipitated monomer and the diamine solution is 1:0.9; the catalyst is sodium phosphite, and the mass ratio of the white precipitated monomer to the catalyst is 1000:1.

[0021] Further, in the step of heating the prepolymer, completing the repolymerization of the prepolymer under negative pressure, and finally obtaining the regenerated nylon, the reaction temperature is 150-370 DEG C, the negative pressure is-0.1--0.01 MPa, and the reaction time is 120-180 min.

[0022] In the second aspect, the application provides a regenerated nylon prepared by the above-mentioned method for regenerating waste nylon engineering plastic.

[0023] Compared with the prior art, the application has the following beneficial effects:

[0024] The application discloses a regeneration method of waste nylon engineering plastics and regenerated nylon, does not need any catalyst, only uses green and cheap water as a solution, and realizes reverse degradation of the waste nylon plastics into high-purity monomers through four stages of high-pressure depolymerization, medium-pressure purification, normal-pressure prepolymerization and negative-pressure repolymerization, and further realizes re-polymerization into high-performance regenerated nylon, realizes closed-loop regeneration from waste materials to virgin quality polymers, and promotes the transformation of engineering plastic recycling from "degradation cycle" to "high-value cycle". Moreover, the application integrates the multi-step processing process in the traditional chemical recycling into a continuous and controllable one-pot reaction process, omits a large number of intermediate transfer, solvent extraction and other cumbersome steps, significantly reduces the energy consumption and process complexity, and improves the industrialization level of the process. The application is suitable for various types of engineering plastics such as nylon 6, nylon 66 and part of semi-aromatic nylons (such as nylon 6T), especially has good depolymerization and regeneration effect on high-performance nylon materials with stable structure and difficult depolymerization, and has wide raw material adaptability. In addition, the reaction process of the method does not need to use a large amount of toxic organic solvents, only needs simple chemicals such as water, lye and acid adjusting liquid, has few by-products, low environmental pollution, conforms to the principle of green chemistry, and has good environmental friendliness and policy adaptability. Finally, through medium-pressure purification and low-temperature prepolymerization, the obtained regenerated nylon has high purity and complete structure, and has mechanical properties, thermal stability and virgin nylon materials, and even has more excellent heat resistance and crystallization performance in some aspects, and can be widely applied to engineering fields with high material performance requirements. The application can realize whole-process control by using conventional chemical equipment, has stable process, wide raw material sources, and good amplification basis, and provides technical support and implementation path for realizing large-scale and industrialized closed-loop recycling of nylon plastics. BRIEF DESCRIPTION OF DRAWINGS

[0025] In order to more clearly illustrate the technical solutions of the embodiments of the application, the following will briefly introduce the drawings needed to be used in the embodiments. It should be understood that the following drawings only show some of the embodiments of the application, and therefore should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can also be obtained without creative labor on the basis of these drawings.

[0026] Figure 1 The process flow chart of the method of the application. DETAILED DESCRIPTION

[0027] In order to enable those skilled in the art to understand the characteristics and effects of the application, the following will make general description and definition on the terms and phrases mentioned in the specification and claims. Unless otherwise specified, all technical and scientific words used in the text are the usual meanings understood by those skilled in the art for the application, and when there is a conflict, the definition in the specification shall prevail.

[0028] The theories or mechanisms described and disclosed herein, whether right or wrong, should not in any way limit the scope of the invention, that is, the contents of the invention can be implemented without being limited by any particular theory or mechanism.

[0029] In this document, all features defined by numerical ranges or percentage ranges, such as numerical values, quantities, contents, and concentrations, are for the sake of brevity and convenience only. Accordingly, descriptions of numerical ranges or percentage ranges should be considered as covering and specifically disclosing all possible sub-ranges and individual numerical values ​​(including integers and fractions) within those ranges.

[0030] In this article, unless otherwise specified, “contains,” “includes,” “containing,” “has,” or similar terms cover the meanings of “composed of” and “mainly composed of,” for example, “A contains a” covers the meanings of “A contains a and others” and “A contains only a.”

[0031] For the sake of brevity, not all possible combinations of the technical features in each implementation scheme or embodiment are described herein. Therefore, as long as there is no contradiction in the combination of these technical features, the technical features in each implementation scheme or embodiment can be combined arbitrarily, and all possible combinations should be considered within the scope of this specification.

[0032] The present invention will now be described in further detail with reference to the accompanying drawings:

[0033] See Figure 1 This invention discloses a method for recycling waste nylon engineering plastics, comprising the following steps:

[0034] S1. Waste nylon plastic is placed in a reactor, and an alkaline solution and ultrapure water are added. After high-temperature depolymerization, the mixture is cooled to room temperature to obtain nylon oligomers.

[0035] In this step, the mass ratio of waste nylon plastic, alkaline solution, and ultrapure water is (0.3–2):(0.05–1):(1–30); the alkaline solution is a sodium hydroxide solution with a mass concentration of 10%–30%. The high-temperature depolymerization reaction temperature is 220℃–320℃, the pressure is 2.2MPa–12.5MPa, the reaction time is 10min–90min, and the rotation speed of the reactor is 500r / min–1200r / min.

[0036] S2, the mixed aqueous solution of nylon oligomers is sieved to obtain a clear oligomer solution. An alkaline solution is added to the clear oligomer solution and a second medium-temperature depolymerization is performed to obtain the purified product (aqueous solution of monomers).

[0037] In this step, the sieving is performed by using a 10-mesh to 200-mesh screen, and the alkaline solution is a sodium hydroxide solution with a mass concentration of 10% to 30%. The mass ratio of the alkaline solution to the clarified oligomer solution is (1 to 2) to 50. The reaction temperature of the secondary medium-temperature redissociation is 100°C to 200°C, the pressure is 0.1 MPa to 2.1 MPa, the reaction time is 30 min to 120 min, and the rotation speed of the reaction kettle is 500 r / min to 1200 r / min.

[0038] S3, an acid solution is added to the purified product, and a white precipitate monomer is obtained after filtration;

[0039] In this step, the acid solution is hydrochloric acid with the same concentration as the alkaline solution, and the addition amount of the acid solution is 1.2 to 1.5 times the total amount of the alkaline solution. The particle size of the white precipitate monomer is 0.64 μm to 0.92 μm.

[0040] S4, the white precipitate monomer is mixed with a diamine solution and a catalyst is added to perform pre-polymerization at normal temperature and pressure to form a pre-polymer;

[0041] In this step, the mixing mass ratio of the white precipitate monomer to the diamine solution is 1 to 0.9, and the catalyst is sodium phosphite. The mass ratio of the white precipitate monomer to the catalyst is 1000 to 1.

[0042] S5, the pre-polymer is heated to complete the re-polymerization of the pre-polymer under negative pressure, and finally regenerated nylon is obtained.

[0043] In this step, the reaction temperature is 150°C to 370°C, the negative pressure is -0.1 MPa to -0.01 MPa, and the reaction time is 120 min to 180 min.

[0044] The embodiment discloses a regenerated nylon prepared according to the above-mentioned method for regenerating waste nylon engineering plastics. The waste nylon plastics are subjected to high-pressure hydrolysis polymerization to prepare monomers, medium-pressure hydrothermal monomer purification, normal-pressure prepolymerization and negative-pressure one-pot nylon regeneration treatment, so that the closed-loop regeneration of the waste nylon can be realized. Specifically, the polar amide bond existing in the semi-aromatic polyamide (nylon) has reversibility and hydrophilicity, which provides the possibility for the high-pressure depolymerization and recovery of the nylon plastics. First, the waste nylon plastics are converted into oligomer small molecules through high-pressure depolymerization. Second, the high-pressure depolymerization small molecules are subjected to secondary depolymerization and purification under medium-pressure conditions. Third, the purified monomers are subjected to normal-pressure prepolymerization. Subsequently, the prepolymer after the prepolymerization is subjected to secondary polymerization under negative-pressure conditions, so that the regenerated nylon is prepared. The regeneration process is a closed-loop system. Starting from the waste plastics, the stable regenerated nylon with good performance is obtained after the depolymerization, purification, prepolymerization and re-polymerization, so that the full-process closed-loop conversion of'material-monmer-material' is realized, and good industrial adaptability and popularization prospect are achieved.

[0045] The application will be further described in connection with the following specific examples. It should be understood that the examples are only used to illustrate the application and not used to limit the scope of the application. Furthermore, it should be understood that after reading the content of the application, those skilled in the art can make various modifications or changes to the application, and these equivalent forms also fall within the scope defined by the appended claims of the application.

[0046] The following examples use the conventional apparatus in the art. The experimental methods not specified in the following examples are usually carried out according to the conventional conditions or the conditions recommended by the manufacturers. Various raw materials are used in the following examples, and unless otherwise specified, the conventional commercially available products are used, and the specifications are the conventional specifications in the art. In the specification of the application and the following examples, unless otherwise specified, '%' represents the percentage by weight, 'parts' represents the weight parts, and the ratio represents the weight ratio.

[0047] Example 1:

[0048] The embodiment discloses a method for regenerating waste nylon engineering plastics, which comprises the following steps:

[0049] (1) 5 g of waste nylon plastics are weighed and placed in a glass lining of a reaction kettle. A mixed solution of an alkaline solution and ultrapure water is added to the glass lining, and the mass ratio of the waste nylon plastics, the alkaline solution and the ultrapure water is 0.3:0.2:20. The alkaline solution is a sodium hydroxide solution with a mass concentration of 10%. The glass lining is placed in the reaction kettle, and nitrogen is introduced to discharge air;

[0050] (2) Set the temperature 280℃, the pressure 6.9MPa, the rotation speed of the reactor 700r / min and the reaction time 60min, then start the heating program. After the reaction, the reactor is cooled to room temperature under natural conditions;

[0051] (3) The hydrothermal solution obtained in step (2) is passed through a 100 mesh screen to remove particulate impurities. Then the obtained clear solution is added to a 10% sodium hydroxide solution, the mass ratio of sodium hydroxide solution to clear solution is 1:50, and the operation of step (2) is repeated for secondary depolymerization to obtain a purified product; the reaction temperature is 180℃, the pressure is 2.1MPa, the reaction time is 60min, and the rotation speed of the reactor is 700r / min.

[0052] (4) Add hydrochloric acid to the purified product obtained in step (3), the amount of hydrochloric acid added is 1.4 times the total amount of sodium hydroxide solution added, and then filter to obtain white precipitated monomers, the particle size of the white precipitated monomers is 0.72μm.

[0053] (5) Mix the monomers obtained in step (4) with a diamine solution at a mass ratio of 1:0.9, and add sodium phosphite as a catalyst, the mass ratio of white precipitated monomers to catalyst is 1000:1, and pre-polymerization is carried out at normal temperature and pressure.

[0054] (6) The pre-polymerization product in step (5) is subjected to temperature elevation and pressure reduction, the reaction temperature is 290℃, the negative pressure is -0.08MPa, and the reaction time is 120min, to complete the re-polymerization of the pre-polymer. Finally, regenerated nylon is obtained. The depolymerization and re-polymerization of waste nylon are realized, and the dehydration rate of re-polymerization is about 16.8%.

[0055] Example 2:

[0056] (1) Weigh 5g of waste nylon plastic into the glass lining of the reactor. Add a mixture of alkaline solution and ultrapure water to the glass lining, the mass ratio of waste nylon plastic, alkaline solution and ultrapure water is 1:0.1:10, and the alkaline solution is a 15% sodium hydroxide solution. Put the glass lining into the reactor and introduce nitrogen to remove air;

[0057] (2) Set the temperature 300℃, the pressure 11.8MPa, the rotation speed of the reactor 1000r / min and the reaction time 70min, then start the heating program. After the reaction, the reactor is cooled to room temperature under natural conditions;

[0058] (3) The hydrothermal solution obtained in step (2) is passed through a 150-mesh sieve to remove particulate impurities. The obtained clear solution is then added to a 15% sodium hydroxide solution, and the mass ratio of the sodium hydroxide solution to the clear solution is 1:50. The operation of step (2) is repeated to perform secondary depolymerization to obtain a purified product. The reaction temperature is 190°C, the pressure is 1.1 MPa, the reaction time is 80 min, and the rotation speed of the reaction kettle is 900 r / min.

[0059] (4) Hydrochloric acid is added to the purified product obtained in step (3), and the amount of hydrochloric acid added is 1.5 times the total amount of sodium hydroxide solution added. After filtration, white precipitated monomers are obtained, and the particle size of the white precipitated monomers is 0.84 μm.

[0060] (5) The monomers obtained in step (4) are mixed with a diamine solution at a mass ratio of 1:0.9, and sodium phosphite is added as a catalyst. The mass ratio of the white precipitated monomers to the catalyst is 1000:1, and the pre-polymerization is performed at normal temperature and pressure.

[0061] (6) The pre-polymerization product in step (5) is subjected to temperature elevation and pressure reduction. The reaction temperature is 300°C, the negative pressure is -0.05 MPa, and the reaction time is 180 min. The re-polymerization of the pre-polymer is completed. Finally, regenerated nylon is obtained. The depolymerization and re-polymerization of waste nylon are realized, and the dehydration rate of the re-polymerization is about 17.6%.

[0062] Example 3:

[0063] (1) 5 g of waste nylon plastic is weighed into a glass lining in a reaction kettle. An alkaline solution and ultrapure water mixture is added to the glass lining, and the mass ratio of the waste nylon plastic, the alkaline solution, and the ultrapure water is 1.8:0.7:25. The alkaline solution is a 20% sodium hydroxide solution. The glass lining is placed in the reaction kettle, and nitrogen is introduced to remove air;

[0064] (2) The temperature is set to 310°C, the pressure is 12.6 MPa, the rotation speed of the reaction kettle is 1200 r / min, and the reaction time is 50 min. After the heating program is started, the reaction kettle is cooled to room temperature under natural conditions after the reaction is completed;

[0065] (3) The hydrothermal solution obtained in step (2) is passed through a 90-mesh sieve to remove particulate impurities. The obtained clear solution is then added to a 20% sodium hydroxide solution, and the mass ratio of the sodium hydroxide solution to the clear solution is 2:50. The operation of step (2) is repeated to perform secondary depolymerization to obtain a purified product. The reaction temperature is 170°C, the pressure is 0.8 MPa, the reaction time is 100 min, and the rotation speed of the reaction kettle is 1000 r / min.

[0066] (4) adding hydrochloric acid to the purified product obtained in step (3), the amount of hydrochloric acid added being 1.2 times the total amount of sodium hydroxide solution added; and then filtering to obtain white precipitated monomers, the particle size of the white precipitated monomers being 0.80 μm.

[0067] (5) mixing the monomers obtained in step (4) with a diamine solution at a mass ratio of 1:0.9, and adding sodium phosphite as a catalyst, the mass ratio of white precipitated monomers to catalyst being 1000:1, and pre-polymerizing at normal temperature and pressure.

[0068] (6) pre-polymerization product in step (5) is subjected to temperature elevation and pressure reduction, the reaction temperature being 350°C, the negative pressure being -0.02 MPa, and the reaction time being 160 min, to complete the re-polymerization of the pre-polymer. Finally, regenerated nylon is obtained. Depolymerization and re-polymerization of waste nylon are realized, and the re-polymerization dehydration rate is about 18.7%.

[0069] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. The present application can be variously changed and modified by those skilled in the art. Any modification, equivalent replacement, improvement, etc. within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for recycling waste nylon engineering plastics, characterized in that, The method comprises the following steps: The waste nylon plastic is put into a reaction kettle, and an alkaline solution and ultrapure water are added, and after high-temperature depolymerization, the mixture is cooled to room temperature to obtain a nylon oligomer aqueous solution; The nylon oligomer aqueous solution is sieved to obtain a clear oligomer solution, an alkaline solution is added to the clear oligomer solution, and secondary depolymerization is carried out at a medium temperature to obtain a purified product; An acidic solution is added to the purified product, and a white precipitate monomer is obtained after filtration; The white precipitate monomer is mixed with a diamine solution and a catalyst is added, and pre-polymerization is carried out at normal temperature and pressure to form a pre-polymer; The pre-polymer is heated, and re-polymerization of the pre-polymer is completed under negative pressure, and finally a regenerated nylon is obtained.

2. The method according to claim 1, wherein In the step of putting the waste nylon plastic into the reaction kettle, adding the alkaline solution and the ultrapure water, and cooling the mixture to room temperature after high-temperature depolymerization to obtain the nylon oligomer, the mass ratio of the waste nylon plastic, the alkaline solution and the ultrapure water is (0.3-2):(0.05-1):(1-30); the alkaline solution is a sodium hydroxide solution with a mass concentration of 10%-30%.

3. The method according to claim 2, wherein the waste nylon engineering plastic is nylon 6. The reaction temperature of the high-temperature depolymerization is 220-320℃, the pressure is 2.2-12.5 MPa, the reaction time is 10-90 min, and the rotation speed of the reaction kettle is 500-1200 r / min.

4. The method according to claim 1, wherein In the step of sieving the nylon oligomer aqueous solution to obtain a clear oligomer solution, adding an alkaline solution to the clear oligomer solution, and carrying out secondary depolymerization at a medium temperature to obtain a purified product, a sieve with a mesh size of 10-200 is used for sieving, and the mass ratio of the alkaline solution to the clear oligomer solution is (1-2):

50.

5. The method according to claim 4, wherein the waste nylon engineering plastic is nylon 6. The reaction temperature of the secondary depolymerization at a medium temperature is 100-200℃, the pressure is 0.1-2.1 MPa, the reaction time is 30-120 min, and the rotation speed of the reaction kettle is 500-1200 r / min.

6. The method according to claim 1, wherein the waste nylon engineering plastic is nylon 6. The acidic solution is hydrochloric acid. The amount of the acidic solution added is 1.2-1.5 times the total amount of the alkaline solution added.

7. The method according to claim 1, wherein the waste nylon engineering plastic is nylon 6. The particle size of the white precipitate monomer is 0.64-0.92 μm.

8. The method according to claim 1, wherein the waste nylon engineering plastic is nylon 6. The mixing mass ratio of the white precipitate monomer to the diamine solution is 1:0.9; the catalyst is sodium phosphite, and the mass ratio of the white precipitate monomer to the catalyst is 1000:

1.

9. The method according to claim 1, wherein the waste nylon engineering plastic is nylon 6. In the step of heating the pre-polymer and completing the re-polymerization of the pre-polymer under negative pressure to finally obtain a regenerated nylon, the reaction temperature is 150-370℃, the negative pressure is -0.1 to -0.01 MPa, and the reaction time is 120-180 min.

10. A regenerated nylon prepared by the method for regenerating waste nylon engineering plastic according to any one of claims 1-9.

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