A method for preparing recycled polyesteramide based on ester-amide exchange reaction

Abstract

This invention relates to a method for preparing recycled polyesteramide based on an ester-amide exchange reaction. The invention first involves ester-amide exchange of waste polyamide to obtain polyamide esters, then purifying the polyamide esters to remove color and impurities, and finally obtaining recycled polyesteramide through vacuum polycondensation and de-alcoholization. Compared with existing technologies, this invention eliminates the need to depolymerize waste polyamide into caprolactam monomers, resulting in lower energy consumption, relatively mild reaction conditions, and simple operation. It can be completed using conventional reaction equipment and has the potential for large-scale production. This invention achieves efficient recycling of waste polyamide and high-value-added regeneration of polyesteramide, providing technical support for the recycling of waste polyamide textiles.

Description

Technical Field

[0001] This invention relates to the field of waste textile recycling, and in particular to a method for preparing recycled polyesteramide based on ester-amide exchange reaction. Background Technology

[0002] Polyamide, also known as nylon, boasts excellent properties, including strength, abrasion resistance, and elasticity, making it the second most widely used synthetic fiber in the textile industry. However, with the rapid development of the polyamide textile industry, the amount of waste polyamide products (such as scraps, offcuts, discarded clothing, carpets, etc.) is increasing year by year. Because it is difficult to degrade in the natural environment, it places enormous pressure on environmental protection. Therefore, developing efficient recycling technologies to achieve the recycling of waste polyamide has become an important way to solve the above problems.

[0003] Due to the complex composition of polyamide materials, which generally contain plasticizers, pigments, and functional additives, separation and purification during recycling are difficult. While the most commonly used physical recycling method is simple and low-cost, the number of recyclable cycles is limited, and each cycle causes micro-degradation of the polyamide. Therefore, the quality of recycled products is poor, and the added value is low. Chemical recycling refers to the degradation of polyamide to form relatively low molecular weight and high-value-added products, representing a potentially high-value recycling method. However, current methods for polyamide chemical recycling mainly involve alcoholysis, ammonolysis, and hydrolysis to depolymerize polyamide into monomers, which are then reused in polyamide polymerization. These routes generally require high temperature and pressure or supercritical conditions, resulting in low monomer recovery rates, high energy consumption, and demanding requirements for reaction equipment.

[0004] Chinese patent CN117888223A discloses a method for preparing high-amino nylon 6 recycled fiber. This method uses mixed waste nylon 6 fibers and the amino-terminated supplement Jinam-6 as raw materials. The process involves crushing, melting and plasticizing, and pelletizing to obtain high-amino nylon 6 recycled chips. These chips are then melted, spun into filaments, stretched, shaped, and wound to obtain the finished product. However, this method falls under the category of physical recycling, and the resulting recycled fiber has limited applicability.

[0005] Chinese patent CN113512193A discloses a method for the alcoholysis regeneration of waste polyamide 6. This method first involves adding an alkyd monomer to waste polyamide 6 under specific temperature and pressure conditions to generate alcoholysis polyamide 6 segments with carboxyl and amino groups at their ends. These segments are then subjected to esterification and amidation reactions under specific conditions to prepare regenerated polyamide 6, which is then melt-spun into regenerated polyamide 6 fibers. However, this method is complex in the regeneration stage and makes it difficult to control the molecular weight of the polyamide 6 segments.

[0006] Chinese patent CN113248705A discloses a method and application for the alcoholysis regeneration of waste polyester-polyamide 6 blended textiles. This method utilizes the alcoholysis of polyester-polyamide 6 blended textiles to obtain amide oligomers and polyester oligomers, which are then reacted with diacids to prepare recycled polyesteramide. However, the reaction system is complex, and the control of the alcoholysis process is highly demanding.

[0007] It is evident that the aforementioned existing technologies generally suffer from problems such as stringent recycling conditions for waste polyamide, complex reaction systems, high equipment requirements, and low molecular weight of the resulting recycled products. Therefore, given the increasingly severe plastic pollution, developing an efficient and simple method for the recycling of waste polyamide has become an important research direction in the textile industry. Summary of the Invention

[0008] The purpose of this invention is to overcome the shortcomings of the existing technology and provide a method for preparing recycled polyesteramide based on ester-amide exchange reaction, thus providing an effective solution for recycling waste polyamide.

[0009] In its conceptualization process, the applicant believed that the present invention first performs an ester-amide exchange reaction on waste polyamide to achieve esterification and end-capping, thereby reducing the content of terminal amino groups in the molecular chain. Then, it removes small molecule impurities such as dyes through purification and processing. Finally, it removes excess alcohol compounds to achieve molecular chain growth, thereby omitting the degradation process to generate monomers, reducing energy consumption, extracting the effective components of polyamide, and efficiently repolymerizing to prepare high-value-added polyesteramide.

[0010] The objective of this invention can be achieved through the following technical solutions:

[0011] A method for preparing recycled polyesteramide based on ester-amide exchange reaction, comprising the following steps:

[0012] S1. Add waste polyamide and ester, transesterification catalyst and heat stabilizer to the reaction vessel, purge the air in the reactor with nitrogen, heat and stir to depolymerize, and obtain polyamide ester.

[0013] S2. The polyamide ester obtained in S1 is decolorized, impurities removed, and purified to obtain a high-purity polyamide ester.

[0014] S3. The high-purity polyamide ester obtained in S2 is placed in a reaction vessel and a recycled polyesteramide polymer is obtained by vacuum polycondensation. After cooling and drying, recycled polyesteramide chips are obtained.

[0015] S4. The recycled polyesteramide chips obtained in S3 are dried and then placed in a melt spinning machine to obtain recycled polyesteramide fibers after melt spinning.

[0016] Furthermore, in S1, the weight ratio of the waste polyamide to the esterified product, the transesterification catalyst, and the heat stabilizer is 100:(1-50):(0.1-10):(0.1-10).

[0017] Furthermore, in S1, the waste polyamide is any one of polyamide 6, polyamide 66, and polyamide 56.

[0018] Furthermore, in S1, the esterified product is any one of polyethylene terephthalate, 1,3-propanediol terephthalate, 1,4-butanediol terephthalate, polyethylene isophthalate, 1,3-propanediol isophthalate, and 1,4-butanediol isophthalate.

[0019] Furthermore, in S1, the transesterification catalyst is any one of antimony trioxide, tetrabutyl titanate, isopropyl titanate, zinc acetate, manganese acetate, antimony acetate, and magnesium acetate.

[0020] Furthermore, in S1, the heat stabilizer is any one of triphenyl phosphate, triphenyl phosphite, Irganox 1010, Irganox 168, and Irganox 245.

[0021] Furthermore, in S1, the reaction temperature is 230–280°C, the pressure is 0.1–5 bar, the stirring speed is 50–500 r / min, and the stirring time is 1–3 h.

[0022] Furthermore, in S3, the reaction temperature is 240–280°C, the pressure is 0–100 Pa, and the reaction time is 2–4 h.

[0023] Furthermore, in S4, the specific steps of the melt spinning process include screw extrusion melting, spinneret extrusion, side blowing cooling, bundling and oiling, drawing, and winding.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] (1) This invention is based on an ester-amide exchange reaction. First, waste polyamide is subjected to an ester-amide exchange reaction to achieve esterification and end-capping, reducing the content of terminal amino groups in the molecular chain. Then, it is purified to remove small molecule impurities such as dyes. Finally, excess alcohol compounds are removed to achieve molecular chain growth. This method can efficiently remove residual chemical auxiliaries and pigments without depolymerizing the waste polyamide into caprolactam monomers. The reaction conditions are relatively mild, the operation is simple, and the energy consumption is low. It can efficiently extract the effective components of waste polyamide and efficiently repolymerize it to prepare high-value-added polyesteramide, providing technical support for the establishment of a waste polyamide textile recycling system.

[0026] (2) This invention can be completed based on conventional reaction equipment, and has the characteristics of low cost and easy promotion, and has the potential for large-scale production. Detailed Implementation

[0027] The present invention will now be described in detail with reference to specific embodiments. Any preparation methods, materials, structures, or composition ratios not explicitly described in this technical solution are considered common technical features disclosed in the prior art.

[0028] In this invention, unless otherwise specified, the detection methods for each parameter are as follows.

[0029] Performance tests of recycled polyesteramide fibers in various embodiments of the present invention:

[0030] (1) Strength: Under standard atmospheric conditions, using a constant-rate elongation tester, according to the formula... The strength is calculated using the formula: σ is the breaking strength, measured in centine Newtons per dtex (cN / dtex); F is the breaking force of the specimen, measured in centine Newtons (cN); and T is the linear density of the sample measured in the same laboratory, measured in decitex (dtex). For specific testing principles and methods, please refer to GB / T14344-2008.

[0031] (2) Elongation: Under standard atmospheric conditions, using a constant-rate elongation tester, according to the formula... The elongation is calculated as follows: ε is the elongation at break (%); E is the elongation value in millimeters (mm); and L0 is the initial length in millimeters (mm). For specific testing principles and methods, please refer to GB / T 14344-2008.

[0032] In the various embodiments of the present invention, the "melt spinning machine" is a multi-functional flexible spinning machine. The process parameters for melt spinning are: spinning temperature 250°C, spinneret temperature 260°C, screw pressure 6.5MPa, metering pump pressure 13MPa, spinning speed 2000m / min, and draw ratio 3.0.

[0033] Example 1

[0034] This embodiment provides a method for preparing recycled polyesteramide based on ester-amide exchange reaction, including the following steps:

[0035] S1. Add 100g of waste polyamide 6, 1g of polyethylene terephthalate, 1g of antimony trioxide and 3g of triphenyl phosphate to the reaction vessel. After purging the air in the reactor with nitrogen, heat to 245℃ and depolymerize for 2h at 0.1 bar pressure and 280r / min stirring speed to obtain polyamide ester.

[0036] S2. The polyamide ester obtained in S1 is decolorized, impurities removed, and purified to obtain a high-purity polyamide ester.

[0037] S3. The high-purity polyamide ester obtained in step S2 is placed in a reaction vessel, and the temperature is gradually increased to 240°C while the pressure is reduced to 20Pa. The reaction is continued for 2 hours under these conditions. The resulting polymer is cooled and dried to obtain recycled polyesteramide chips.

[0038] S4. After drying, the recycled polyesteramide chips obtained in step S3 are placed in a melt spinning machine. They undergo screw extrusion melting, spinneret extrusion, side-blowing cooling, bundling and oiling, drawing, and winding to obtain recycled polyesteramide fibers. The strength of the recycled polyesteramide fibers is 4.3 cN·dtex. -1 The elongation rate is 11%.

[0039] Example 2

[0040] This embodiment provides a method for preparing recycled polyesteramide based on ester-amide exchange reaction, including the following steps:

[0041] S1. Add 100g of waste polyamide 6, 5g of 1,3-propanediol terephthalate, 4g of tetrabutyl titanate and 1g of triphenyl phosphite to the reaction vessel. After purging the air in the reactor with nitrogen, heat to 260℃ and depolymerize for 1.6h at a pressure of 2 bar and a stirring speed of 380r / min to obtain polyamide ester.

[0042] S2. The polyamide ester obtained in S1 is decolorized, impurities removed, and purified to obtain a high-purity polyamide ester.

[0043] S3. The high-purity polyamide ester obtained in step S2 is placed in a reaction vessel, and the temperature is gradually increased to 244°C while the pressure is reduced to 50Pa. The reaction is continued for 2.8 hours under these conditions. The resulting polymer is cooled and dried to obtain recycled polyesteramide chips.

[0044] S4. The recycled polyesteramide chips obtained in step S3 are dried and then placed in a melt spinning machine. After screw extrusion melting, spinneret extrusion, side-blowing cooling, bundling and oiling, drawing, and winding, recycled polyesteramide fibers are obtained. The strength of the recycled polyesteramide fibers is 4.5 cN·dtex. -1 The elongation rate is 14%.

[0045] The preparation method of "1,3-propanediol terephthalate" in this embodiment is as follows: terephthalic acid and 1,3-propanediol (molar ratio 1:1.7) are added to 0.05% tetrabutyl titanate (0.05% of the mass of terephthalic acid), and esterification is carried out at 200°C for two hours to obtain 1,3-propanediol terephthalate.

[0046] Example 3

[0047] This embodiment provides a method for preparing recycled polyesteramide based on ester-amide exchange reaction, including the following steps:

[0048] S1. Add 100g of waste polyamide 6, 10g of 1,4-butanediol terephthalate, 7g of isopropyl titanate and 0.1g of Irganox 1010 to the reaction vessel. After purging the air in the reactor with nitrogen, heat to 275℃ and depolymerize for 1.2h at a pressure of 5 bar and a stirring speed of 450r / min to obtain polyamide ester.

[0049] S2. The polyamide ester obtained in S1 is decolorized, impurities removed, and purified to obtain a high-purity polyamide ester.

[0050] S3. The high-purity polyamide ester obtained in step S2 is placed in a reaction vessel, and the temperature is gradually increased to 248°C while the pressure is reduced to 0 Pa. The reaction is continued for 3.2 hours under these conditions. The resulting polymer is cooled and dried to obtain recycled polyesteramide chips.

[0051] S4. After drying, the recycled polyesteramide chips obtained in step S3 are placed in a melt spinning machine. They undergo screw extrusion melting, spinneret extrusion, side-blowing cooling, bundling and oiling, drawing, and winding to obtain recycled polyesteramide fibers. The strength of the recycled polyesteramide fibers is 4.6 cN·dtex. -1 The elongation is 15%.

[0052] The preparation method of "1,4-butanediol terephthalate" in this embodiment is as follows: terephthalic acid and 1,4-butanediol (molar ratio 1:1.7) are added to 0.05% tetrabutyl titanate (0.05% of the mass of terephthalic acid), and esterification is carried out at 200°C for two hours to obtain 1,4-butanediol terephthalate.

[0053] Example 4

[0054] This embodiment provides a method for preparing recycled polyesteramide based on ester-amide exchange reaction, including the following steps:

[0055] S1. Add 100g of waste polyamide 6, 15g of polyethylene isophthalate, 10g of zinc acetate and 5g of Irganox 168 to the reaction vessel. After purging the air in the reactor with nitrogen, heat to 280℃ and depolymerize for 1.8h at a pressure of 4.2 bar and a stirring speed of 200r / min to obtain polyamide ester.

[0056] S2. The polyamide ester obtained in S1 is decolorized, impurities removed, and purified to obtain a high-purity polyamide ester.

[0057] S3. The high-purity polyamide ester obtained in step S2 is placed in a reaction vessel, and the temperature is gradually increased to 252°C while the pressure is reduced to 35Pa. The reaction is continued for 3.6 hours under these conditions. The resulting polymer is cooled and dried to obtain recycled polyesteramide chips.

[0058] S4. After drying, the recycled polyesteramide chips obtained in step S3 are placed in a melt spinning machine. They undergo screw extrusion melting, spinneret extrusion, side-blowing cooling, bundling and oiling, drawing, and winding to obtain recycled polyesteramide fibers. The strength of the recycled polyesteramide fibers is 4.6 cN·dtex. -1 The elongation is 15%.

[0059] Example 5

[0060] This embodiment provides a method for preparing recycled polyesteramide based on ester-amide exchange reaction, including the following steps:

[0061] S1. Add 100g of waste polyamide 6, 20g of 1,3-propanediol isophthalate, 5g of manganese acetate and 8g of Irganox 245 to the reaction vessel. After purging the air in the reactor with nitrogen, heat to 235℃ and depolymerize for 1 hour at a pressure of 2.5 bar and a stirring speed of 470 r / min to obtain polyamide ester.

[0062] S2. The polyamide ester obtained in S1 is decolorized, impurities removed, and purified to obtain a high-purity polyamide ester.

[0063] S3. The high-purity polyamide ester obtained in step S2 is placed in a reaction vessel, and the temperature is gradually increased to 256°C while the pressure is reduced to 100Pa. The reaction is continued for 3.8 hours under these conditions. The resulting polymer is cooled and dried to obtain recycled polyesteramide chips.

[0064] S4. The recycled polyesteramide chips obtained in step S3 are dried and then placed in a melt spinning machine. After screw extrusion melting, spinneret extrusion, side-blowing cooling, bundling and oiling, drawing, and winding, recycled polyesteramide fibers are obtained. The strength of the recycled polyesteramide fibers is 4.2 cN·dtex. -1 The elongation is 12%.

[0065] The preparation method of "1,3-propanediol isophthalate" in this embodiment is as follows: isophthalic acid and 1,3-propanediol (molar ratio 1:1.7) are added to 0.05% tetrabutyl titanate (0.05% of the mass of isophthalic acid), and esterification is carried out at 200°C for two hours to obtain 1,3-propanediol isophthalate.

[0066] Example 6

[0067] This embodiment provides a method for preparing recycled polyesteramide based on ester-amide exchange reaction, including the following steps:

[0068] S1. Add 100g of waste polyamide 6, 25g of 1,4-butanediol isophthalate, 0.1g of antimony acetate and 10g of triphenyl phosphate to a reaction vessel. After purging the reactor with nitrogen, heat the reactor to 270℃ and depolymerize it for 1.4h at a pressure of 3.4 bar and a stirring speed of 500r / min to obtain the polyamide ester.

[0069] S2. The polyamide ester obtained in S1 is decolorized, impurities removed, and purified to obtain a high-purity polyamide ester.

[0070] S3. The high-purity polyamide ester obtained in step S2 is placed in a reaction vessel, and the temperature is gradually increased to 260°C while the pressure is reduced to 80Pa. The reaction is continued for 3.9 hours under these conditions. The resulting polymer is cooled and dried to obtain recycled polyesteramide chips.

[0071] S4. After drying, the recycled polyesteramide chips obtained in step S3 are placed in a melt spinning machine. They undergo screw extrusion melting, spinneret extrusion, side-blowing cooling, bundling and oiling, drawing, and winding to obtain recycled polyesteramide fibers. The strength of the recycled polyesteramide fibers is 4.7 cN·dtex. -1 The elongation is 16%.

[0072] The preparation method of "1,4-butanediol isophthalate" in this embodiment is as follows: isophthalic acid and 1,4-butanediol (molar ratio 1:1.7) are added to 0.05% tetrabutyl titanate (0.05% of the mass of isophthalic acid), and esterification is carried out at 200°C for two hours to obtain 1,4-butanediol isophthalate.

[0073] Example 7

[0074] This embodiment provides a method for preparing recycled polyesteramide based on ester-amide exchange reaction, including the following steps:

[0075] S1. Add 100g of waste polyamide 6, 30g of polyethylene terephthalate, 9g of magnesium acetate and 6g of triphenyl phosphite to the reaction vessel. After purging the air in the reactor with nitrogen, heat to 250℃ and depolymerize for 2.2h at 1 bar pressure and 400r / min stirring speed to obtain polyamide ester.

[0076] S2. The polyamide ester obtained in S1 is decolorized, impurities removed, and purified to obtain a high-purity polyamide ester.

[0077] S3. The high-purity polyamide ester obtained in step S2 is placed in a reaction vessel, and the temperature is gradually increased to 264°C while the pressure is reduced to 60Pa. The reaction is continued for 3 hours under these conditions. The resulting polymer is cooled and dried to obtain recycled polyesteramide chips.

[0078] S4. The recycled polyesteramide chips obtained in step S3 are dried and then placed in a melt spinning machine. After screw extrusion melting, spinneret extrusion, side-blowing cooling, bundling and oiling, drawing, and winding, recycled polyesteramide fibers are obtained. The strength of the recycled polyesteramide fibers is 4.4 cN·dtex. -1 The elongation rate is 13%.

[0079] Example 8

[0080] This embodiment provides a method for preparing recycled polyesteramide based on ester-amide exchange reaction, including the following steps:

[0081] S1. Add 100g of waste polyamide 6, 34g of 1,3-propanediol terephthalate, 6g of antimony trioxide and 9g of Irganox 1010 to the reaction vessel. After purging the air in the reactor with nitrogen, heat to 230℃ and depolymerize for 2.6h at a pressure of 1.5 bar and a stirring speed of 100r / min to obtain polyamide ester.

[0082] S2. The polyamide ester obtained in S1 is decolorized, impurities removed, and purified to obtain a high-purity polyamide ester.

[0083] S3. The high-purity polyamide ester obtained in step S2 is placed in a reaction vessel, and the temperature is gradually increased to 268°C while the pressure is reduced to 30Pa. The reaction is continued for 2.4 hours under these conditions. The resulting polymer is cooled and dried to obtain recycled polyesteramide chips.

[0084] S4. The recycled polyesteramide chips obtained in step S3 are dried and then placed in a melt spinning machine. After screw extrusion melting, spinneret extrusion, side-blowing cooling, bundling and oiling, drawing, and winding, recycled polyesteramide fibers are obtained. The strength of the recycled polyesteramide fibers is 4.4 cN·dtex. -1 The elongation rate is 13%.

[0085] The preparation method of "1,3-propanediol terephthalate" in this embodiment is as follows: terephthalic acid and 1,3-propanediol (molar ratio 1:1.7) are added to 0.05% tetrabutyl titanate (0.05% of the mass of terephthalic acid), and esterification is carried out at 200°C for two hours to obtain 1,3-propanediol terephthalate.

[0086] Example 9

[0087] This embodiment provides a method for preparing recycled polyesteramide based on ester-amide exchange reaction, including the following steps:

[0088] S1. Add 100g of waste polyamide 6, 38g of 1,4-butanediol terephthalate, 2g of tetrabutyl titanate and 0.5g of Irganox 168 to the reaction vessel. After purging the air in the reactor with nitrogen, heat to 240℃ and depolymerize for 2.4h at 0.5 bar pressure and 50r / min stirring speed to obtain polyamide ester.

[0089] S2. The polyamide ester obtained in S1 is decolorized, impurities removed, and purified to obtain a high-purity polyamide ester.

[0090] S3. The high-purity polyamide ester obtained in step S2 is placed in a reaction vessel, and the temperature is gradually increased to 272°C while the pressure is reduced to 70 Pa. The reaction is continued for 2.2 h under these conditions. The resulting polymer is cooled and dried to obtain recycled polyesteramide chips.

[0091] S4. The recycled polyesteramide chips obtained in step S3 are dried and then placed in a melt spinning machine. After screw extrusion melting, spinneret extrusion, side-blowing cooling, bundling and oiling, drawing, and winding, recycled polyesteramide fibers are obtained. The strength of the recycled polyesteramide fibers is 4.5 cN·dtex. -1 The elongation rate is 14%.

[0092] The preparation method of "1,4-butanediol terephthalate" in this embodiment is as follows: terephthalic acid and 1,4-butanediol (molar ratio 1:1.7) are added to 0.05% tetrabutyl titanate (0.05% of the mass of terephthalic acid), and esterification is carried out at 200°C for two hours to obtain 1,4-butanediol terephthalate.

[0093] Example 10

[0094] This embodiment provides a method for preparing recycled polyesteramide based on ester-amide exchange reaction, including the following steps:

[0095] S1. Add 100g of waste polyamide 6, 42g of polyethylene isophthalate, 8g of isopropyl titanate and 4g of Irganox 245 to the reaction vessel. After purging the air in the reactor with nitrogen, heat to 265℃ and depolymerize for 2.9h at a pressure of 3.8 bar and a stirring speed of 250r / min to obtain polyamide ester.

[0096] S2. The polyamide ester obtained in S1 is decolorized, impurities removed, and purified to obtain a high-purity polyamide ester.

[0097] S3. The high-purity polyamide ester obtained in step S2 is placed in a reaction vessel, and the temperature is gradually increased to 276°C while the pressure is reduced to 40Pa. The reaction is continued for 3.4 hours under these conditions. The resulting polymer is cooled and dried to obtain recycled polyesteramide chips.

[0098] S4. After drying, the recycled polyesteramide chips obtained in step S3 are placed in a melt spinning machine. They undergo screw extrusion melting, spinneret extrusion, side-blowing cooling, bundling and oiling, drawing, and winding to obtain recycled polyesteramide fibers. The strength of the recycled polyesteramide fibers is 4.7 cN·dtex. -1 The elongation is 16%.

[0099] Example 11

[0100] This embodiment provides a method for preparing recycled polyesteramide based on ester-amide exchange reaction, including the following steps:

[0101] S1. Add 100g of waste polyamide 6, 48g of 1,3-propanediol isophthalate, 0.5g of zinc acetate and 2g of triphenyl phosphate to the reaction vessel. After purging the air in the reactor with nitrogen, heat to 255℃ and depolymerize for 3h at a pressure of 4.8 bar and a stirring speed of 150r / min to obtain polyamide ester.

[0102] S2. The polyamide ester obtained in S1 is decolorized, impurities removed, and purified to obtain a high-purity polyamide ester.

[0103] S3. The high-purity polyamide ester obtained in step S2 is placed in a reaction vessel, and the temperature is gradually increased to 280°C while the pressure is reduced to 10 Pa. The reaction is continued for 2.6 h under these conditions. The resulting polymer is cooled and dried to obtain recycled polyesteramide chips.

[0104] S4. After drying, the recycled polyesteramide chips obtained in step S3 are placed in a melt spinning machine. They undergo screw extrusion melting, spinneret extrusion, side-blowing cooling, bundling and oiling, drawing, and winding to obtain recycled polyesteramide fibers. The strength of the recycled polyesteramide fibers is 4.6 cN·dtex. -1 The elongation is 15%.

[0105] The preparation method of "1,3-propanediol isophthalate" in this embodiment is as follows: isophthalic acid and 1,3-propanediol (molar ratio 1:1.7) are added to 0.05% tetrabutyl titanate (0.05% of the mass of isophthalic acid), and esterification is carried out at 200°C for two hours to obtain 1,3-propanediol isophthalate.

[0106] Example 12

[0107] This embodiment provides a method for preparing recycled polyesteramide based on ester-amide exchange reaction, including the following steps:

[0108] S1. Add 100g of waste polyamide 6, 50g of 1,4-butanediol isophthalate, 3g of manganese acetate and 7g of triphenyl phosphite to the reaction vessel. After purging the air in the reactor with nitrogen, heat to 270℃ and depolymerize for 2.8h at a pressure of 3 bar and a stirring speed of 320r / min to obtain polyamide ester.

[0109] S2. The polyamide ester obtained in S1 is decolorized, impurities removed, and purified to obtain a high-purity polyamide ester.

[0110] S3. The high-purity polyamide ester obtained in step S2 is placed in a reaction vessel, and the temperature is gradually increased to 272°C while the pressure is reduced to 90 Pa. The reaction is continued for 4 hours under these conditions. The resulting polymer is cooled and dried to obtain recycled polyesteramide chips.

[0111] S4. After drying, the recycled polyesteramide chips obtained in step S3 are placed in a melt spinning machine. They undergo screw extrusion melting, spinneret extrusion, side-blowing cooling, bundling and oiling, drawing, and winding to obtain recycled polyesteramide fibers. The strength of the recycled polyesteramide fibers is 4.8 cN·dtex. -1 The elongation is 18%.

[0112] The preparation method of "1,4-butanediol isophthalate" in this embodiment is as follows: isophthalic acid and 1,4-butanediol (molar ratio 1:1.7) are added to 0.05% tetrabutyl titanate (0.05% of the mass of isophthalic acid), and esterification is carried out at 200°C for two hours to obtain 1,4-butanediol isophthalate.

[0113] Example 13

[0114] This embodiment provides a method for preparing recycled polyesteramide based on ester-amide exchange reaction, including the following steps:

[0115] S1. Add 100g of waste polyamide 6, 50g of 1,4-butanediol isophthalate, 3g of manganese acetate and 7g of triphenyl phosphite to the reaction vessel. After purging the air in the reactor with nitrogen, heat to 250℃ and depolymerize for 2.8h at a pressure of 3 bar and a stirring speed of 320r / min to obtain polyamide ester.

[0116] S2. The polyamide ester obtained in S1 is decolorized, impurities removed, and purified to obtain a high-purity polyamide ester.

[0117] S3. The high-purity polyamide ester obtained in step S2 is placed in a reaction vessel, and the temperature is gradually increased to 272°C while the pressure is reduced to 90 Pa. The reaction is continued for 4 hours under these conditions. The resulting polymer is cooled and dried to obtain recycled polyesteramide chips.

[0118] S4. After drying, the recycled polyesteramide chips obtained in step S3 are placed in a melt spinning machine. They undergo screw extrusion melting, spinneret extrusion, side-blowing cooling, bundling and oiling, drawing, and winding to obtain recycled polyesteramide fibers. The strength of the recycled polyesteramide fibers is 4.7 cN·dtex. -1 The elongation rate is 14%.

[0119] The preparation method of "1,4-butanediol isophthalate" in this embodiment is as follows: isophthalic acid and 1,4-butanediol (molar ratio 1:1.7) are added to 0.05% tetrabutyl titanate (0.05% of the mass of isophthalic acid), and esterification is carried out at 200°C for two hours to obtain 1,4-butanediol isophthalate.

[0120] Example 14

[0121] This embodiment provides a method for preparing recycled polyesteramide based on ester-amide exchange reaction, including the following steps:

[0122] S1. Add 100g of waste polyamide 6, 50g of 1,4-butanediol isophthalate, 3g of manganese acetate and 7g of triphenyl phosphite to the reaction vessel. After purging the air in the reactor with nitrogen, heat to 230℃ and depolymerize for 2.8h at a pressure of 3 bar and a stirring speed of 320r / min to obtain polyamide ester.

[0123] S2. The polyamide ester obtained in S1 is decolorized, impurities removed, and purified to obtain a high-purity polyamide ester.

[0124] S3. The high-purity polyamide ester obtained in step S2 is placed in a reaction vessel, and the temperature is gradually increased to 272°C while the pressure is reduced to 90 Pa. The reaction is continued for 4 hours under these conditions. The resulting polymer is cooled and dried to obtain recycled polyesteramide chips.

[0125] S4. After drying, the recycled polyesteramide chips obtained in step S3 are placed in a melt spinning machine. They undergo screw extrusion melting, spinneret extrusion, side-blowing cooling, bundling and oiling, drawing, and winding to obtain recycled polyesteramide fibers. The strength of the recycled polyesteramide fibers is 4.6 cN·dtex. -1 The elongation rate is 14%.

[0126] The preparation method of "1,4-butanediol isophthalate" in this embodiment is as follows: isophthalic acid and 1,4-butanediol (molar ratio 1:1.7) are added to 0.05% tetrabutyl titanate (0.05% of the mass of isophthalic acid), and esterification is carried out at 200°C for two hours to obtain 1,4-butanediol isophthalate.

[0127] Table 1 Performance indicators of recycled polyesteramide fibers

[0128]

[0129] As can be seen from the data in Table 1, Examples 1-14 provided by this invention can efficiently and easily achieve the recycling and regeneration of waste polyamide. The prepared recycled polyesteramide fibers have good physical properties, with a strength of 4.2-4.8 cN·dtex. -1 The elongation is 11-18%.

[0130] The above description of the embodiments is provided to enable those skilled in the art to understand and use the invention. It will be apparent to those skilled in the art that various modifications can be made to these embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present invention is not limited to the above embodiments, and any improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the invention should be within the protection scope of the present invention.

Claims

1. A method for preparing recycled polyesteramide based on ester-amide exchange reaction, characterized in that, Includes the following steps: S1. Waste polyamide is heated and stirred under nitrogen to depolymerize with esterified polyamide, transesterification catalyst, and heat stabilizer to obtain polyamide esterified polyamide. S2. The polyamide ester obtained in S1 is purified to obtain a high-purity polyamide ester. S3. The high-purity polyamide ester obtained in S2 is subjected to vacuum polycondensation to obtain recycled polyesteramide, which is then cooled and dried to obtain recycled polyesteramide chips. S4. The recycled polyesteramide chips obtained in S3 are melt-spun to obtain recycled polyesteramide fibers. In S1, the waste polyamide is any one of polyamide 6, polyamide 66, and polyamide 56; In S1, the esterified product is any one of polyethylene terephthalate, 1,3-propanediol terephthalate, 1,4-butanediol terephthalate, polyethylene isophthalate, 1,3-propanediol isophthalate, and 1,4-butanediol isophthalate. In S1, the heat stabilizer is any one of triphenyl phosphate, triphenyl phosphite, Irganox 1010, Irganox 168, and Irganox 245; In S1, the weight ratio of the waste polyamide to the esterified product, the transesterification catalyst, and the heat stabilizer is 100:(1-50):(0.1-10):(0.1-10).

2. The method for preparing recycled polyesteramide based on ester-amide exchange reaction according to claim 1, characterized in that, In S1, the transesterification catalyst is any one of antimony trioxide, tetrabutyl titanate, isopropyl titanate, zinc acetate, manganese acetate, antimony acetate, and magnesium acetate.

3. The method for preparing recycled polyesteramide based on ester-amide exchange reaction according to claim 1, characterized in that, In S1, the reaction temperature for heating, stirring, and depolymerization is 230~280 ℃, and the pressure is 0.1~5 bar.

4. The method for preparing recycled polyesteramide based on ester-amide exchange reaction according to claim 1, characterized in that, In S1, the stirring speed is 50~500 r / min, and the stirring time is 1~3 h.

5. The method for preparing recycled polyesteramide based on ester-amide exchange reaction according to claim 1, characterized in that, In S3, the vacuum polycondensation reaction temperature is 240~280 ℃, the pressure is 0~100 Pa, and the reaction time is 2~4 h.

6. The method for preparing recycled polyesteramide based on ester-amide exchange reaction according to claim 1, characterized in that, In S4, the specific steps of the melt spinning process include screw extrusion melting, spinneret extrusion, side blowing cooling, bundling and oiling, drawing, and winding.

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