A chemically recycled elastic copolyester material, its preparation method, and the filament fibers prepared therefrom

Abstract

The present invention discloses a chemically recycled elastic copolyester material, its preparation method, and the filament fibers prepared therefrom. The copolyester is prepared from recycled waste PET and bio-based aliphatic diols through alcoholysis, transesterification, and polycondensation reactions. In this copolyester, the content of recycled PET is 63-89 wt%, and the bio-based content is 11-37 wt%. By copolymerizing through transesterification after adding bio-based aliphatic diols, the present invention enables the alcoholysis of waste PET with a small amount of ethanol, effectively saving energy. At the same time, due to the introduction of bio-based components in the copolyester fibers of the present invention, the copolyester material itself contains aliphatic chain segments with different methylene numbers, providing good elasticity for the fiber material. The elasticity of the prepared fibers can be adjusted by changing the content of bio-based components, expanding the application range of recycled PET fibers. The preparation method is simple, the technical route is concise, and the operation is convenient, having very good practical value, economic value, and promotion prospects.

Description

Technical Field

[0001] The present invention relates to the technical fields of PET recycling and chemical fiber, and particularly relates to a chemically recycled elastic copolyester material, a preparation method thereof, and a filament fiber prepared therefrom. Background Art

[0002] Polyethylene terephthalate (PET) is a widely used synthetic polymer material. Due to its excellent physical and chemical properties and cost-effectiveness, it is applied in multiple fields such as packaging materials, textiles, and engineering plastics. PET has good mechanical strength, transparency, chemical stability, and recyclability. However, with the increasing use of PET, the recycling and reuse of waste PET have become an important issue. Among the numerous methods for recycling waste PET, chemical recycling can convert waste PET into high-value-added products and achieve resource recycling, which has received extensive attention in the industry. Chemical recycling decomposes PET into its monomers or chemical raw materials through chemical reactions such as catalysis and hydrolysis, and then re-polymerizes them into new PET or other valuable chemicals. That is, through chemical depolymerization technology, waste PET is depolymerized into monomers or prepared into other functional materials to achieve the recycling and reuse of waste PET. This not only helps to save energy and reduce environmental pollution but also improves the economic efficiency of PET recycling.

[0003] Existing chemical depolymerization methods for waste PET mainly include hydrolysis method, alcoholysis method, ionic liquid method, enzymatic catalytic depolymerization method, etc. Among them, the alcoholysis method is widely used due to its advantages such as high efficiency and high product value. The alcoholysis method includes methanol depolymerization method and ethylene glycol depolymerization method. The methanol depolymerization method uses methanol as the alcoholysis agent, and under the action of a catalyst, PET is depolymerized into dimethyl terephthalate (DMT) and ethylene glycol (EG). The produced DMT is taken out by rectification and then undergoes transesterification and polycondensation reactions with EG to obtain recycled PET. The depolymerization product DMT of the methanol depolymerization method is easy to refine, and high-quality recycled PET can be obtained by re-polymerization with this raw material. However, the refining process of DMT has high energy consumption and high recycling cost, and the flammability and explosiveness of methanol also require higher safety and explosion-proof requirements for the factory, which affects its large-scale use. The ethylene glycol depolymerization method, as the name implies, is a method of depolymerizing PET using methanol as the alcoholysis agent. Compared with the methanol depolymerization method, the advantages of the ethylene glycol depolymerization method are that the reaction does not require high temperature and high pressure and has low energy consumption; and the depolymerization product obtained by the ethylene glycol depolymerization method is (BHET), which can be directly re-polymerized to obtain recycled PET. However, since a large amount of impurities such as dimers and trimers are contained in the depolymerized BHET and will participate in the re-polymerization reaction, in actual production, a large amount of excessive EG needs to be used to participate in the reaction to obtain high-purity BHET, which results in the generation of a large amount of by-product diethylene glycol (DEG), making the subsequent purification process complicated and also increasing the investment and manufacturing cost of the purification equipment, which is obviously far from the original intention of saving energy.

[0004] When using waste PET to prepare fibers, the most direct problems are the resilience and rebound stability. Traditional elastic RPET staple fibers are obtained by mechanical crimping or composite spinning processes to get crimped elastic fibers. However, the retention of mechanical crimping is limited, and there are problems with different degrees of resilience and crimp in composite spun fibers. In this regard, a method for preparing RPET staple fibers and RPET staple fibers disclosed in Chinese patent application document CN117779237A involves partially alcoholyzing and carboxylating recycled PET, then randomly copolymerizing it with PEG to form a PET-PEG copolymer, and then performing side-by-side composite spinning of the copolymer with a second recycled PET to obtain RPET staple fibers. This method essentially also makes the prepared fibers have a certain elasticity and crimp degree by compounding similar polymers with different molecular weights, so its actual improvement in fiber elasticity is limited. Moreover, precise control is required for the partial alcoholysis of recycled PET, and strict reaction conditions such as temperature, pressure, and catalysts are needed for the carboxylation of the alcoholysis product. This not only makes the process complex, but also has low production efficiency and higher costs. In addition, the carboxylated PET alcoholysis product changes the chemical structure of the original PET alcoholysis product molecules, and the introduction of carboxyl groups increases the intermolecular hydrogen bond force, raising the glass transition temperature (Tg) of the material, resulting in the fibers composite with recycled PET becoming brittle and hard at low temperatures and increasing the subsequent processing difficulty. Furthermore, additional chemical treatment steps require the use of more chemicals and energy, and the by-products generated during the carboxylation process need to be properly treated, all of which will impose a new burden on the environment and cannot truly achieve energy conservation and environmental protection.

[0005] Therefore, how to truly achieve energy conservation and environmental protection in the recycling of waste PET and prepare fiber materials with good elastic recovery rate remains an urgent problem to be solved in the recycling and reuse of waste PET. Summary of the Invention

[0006] Aiming at the problems existing in the above-mentioned recycling of waste PET, such as a large amount of ethylene glycol participating in the reaction in excess during the alcoholysis stage, a large number of by-products being generated, the complex purification process consuming too much energy, and the low elastic recovery rate and poor rebound stability of the fibers prepared from existing waste PET, the present invention provides a chemically recycled elastic copolyester material, its preparation method, and the filament fibers prepared therefrom. By depolymerizing waste PET with a lower amount of EG and then copolymerizing it with a bio-based diol to obtain a recycled copolyester, it not only saves energy and has fewer side reactions, but also the fibers prepared from this recycled copolyester have good elasticity. At the same time, the elastic recovery rate of the prepared fibers can be adjusted by adjusting the addition amount of the bio-based diol. The specific technical solutions are as follows:

[0007] First, the object of the present invention is to provide a chemically recycled copolyester material, which is prepared from recycled waste PET and bio-based aliphatic diols through alcoholysis, transesterification and polycondensation reactions; and in this copolyester, the content of recycled PET accounts for 63-89 wt%, and the bio-based content accounts for 11-37 wt%.

[0008] Preferably, in the aforementioned chemically recycled copolyester material, the bio-based aliphatic diol is any one or more of 1,3-propanediol, 1,4-butanediol or 1,6-hexanediol, which is synthesized by biological fermentation using glycerol or sugar or cellulose as raw materials.

[0009] Preferably, in the aforementioned chemically recycled copolyester material, the molecular structure of the copolyester material is composed of repeating units of two terephthalic acid aliphatic diol esters, one of which is diethylene glycol terephthalate and the other is propylene glycol terephthalate, and the molar ratio of the two is 1-89:99-1.

[0010] Preferably, in the aforementioned chemically recycled copolyester material, its intrinsic viscosity is 0.50-1.2 dL / g and its melting point is 190-250 °C.

[0011] Secondly, the object of the present invention is to provide a preparation method of the aforementioned chemically recycled copolyester material, which includes the following steps:

[0012] 1) PET alcoholysis reaction: The recycled waste PET is cleaned, dried, pulverized and then a small amount of ethylene glycol is added, and an alcoholysis reaction is carried out under the action of an alcoholysis catalyst to obtain a PET alcoholysis product;

[0013] 2) Transesterification reaction: Bio-based aliphatic diol is added to the PET alcoholysis product obtained in step 1), the temperature is controlled, and a transesterification reaction is carried out to obtain a transesterification product;

[0014] 3) Polycondensation reaction: A polycondensation catalyst is added to the PET alcoholysis product obtained in step 2), the temperature and pressure are controlled, and a polycondensation reaction is carried out to obtain the aforementioned chemically recycled copolyester material.

[0015] As a preferred technical solution, in the preparation method of the aforementioned chemically recycled copolyester material, in step 1), for the PET alcoholysis reaction, the amount of ethylene glycol added is: the mass ratio of PET to ethylene glycol is 1:0.3-1.0; the alcoholysis catalyst is metal acetate, including one or more of zinc acetate, manganese acetate, magnesium acetate, sodium acetate, lithium acetate, and its addition amount is 0.05-0.1% of the mass of PET; the conditions of alcoholysis are: under a gauge pressure of 0-100 Kpa and a temperature of 180-220 °C, alcoholysis for 1-4 hours.

[0016] As a preferred technical solution, in the preparation method of the aforementioned chemically recycled copolyester material, in step 2), the conditions for the transesterification reaction are: normal pressure, at 190-220°C, for 40-100 minutes of transesterification.

[0017] As a preferred technical solution, in the preparation method of the aforementioned chemically recycled copolyester material, in step 3), for the polycondensation reaction, the polycondensation catalyst used is an organic chelate of titanium, and the titanium content in this organic chelate is not less than 3%; the addition amount of the polycondensation catalyst is that the amount of titanium element added is 2-30 ppm of the mass of PET; the conditions for the polycondensation reaction are: vacuum ≤ 100 Pa, at 240-270°C, for 1-4 hours of polycondensation.

[0018] Furthermore, the purpose of the present invention is to provide an application of the aforementioned chemically recycled copolyester material, specifically for spinning to prepare copolyester filament fibers for textiles or optical fiber sheaths, and adjusting the elastic recovery rate of the copolyester filament fibers by adjusting the amount of bio-based aliphatic diol in the raw materials for preparing the copolyester material.

[0019] For the application of the aforementioned chemically recycled copolyester material, the elastic recovery rate of the prepared copolyester filament fibers ranges from 20% to 85%.

[0020] Advantages of the present invention:

[0021] 1) The chemically recycled elastic copolyester material of the present invention is obtained by alcoholyzing waste PET with a small amount of ethylene glycol (EG) and then adding bio-based aliphatic diol for transesterification and directly carrying out polycondensation reaction. It can complete the recycling of waste PET without using a large amount of EG, solve the problem of excessive use of ethylene glycol in the traditional PET recycling method, reduce the generation of by-products, and do not require purification, effectively saving energy, and truly achieving the effect of converting waste PET into high-value products and realizing resource recycling.

[0022] 2) In the preparation method of the present invention, only a small amount of ethanol needs to be added in the PET alcoholysis stage (the mass ratio of PET to EG is 1:0.3-1.0), avoiding the problems caused by the use of a large amount of excessive EG; in the transesterification reaction stage, taking advantage of the fact that the boiling point of the added bio-based aliphatic diol is higher than that of ethylene glycol, directly partially replacing the diol (EG) in PET depolymerization products such as BHET, dimers, and trimers; in the polycondensation reaction stage, the material after the transesterification reaction directly undergoes random copolymerization to obtain a copolyester material copolymerized from two terephthalic acid aliphatic diol esters; the entire preparation process has a simple process, clear reaction principle, convenient control of reaction conditions, and simple operation, and has good prospects for promotion.

[0023] 3) The preparation method of the present invention uses a bio-based aliphatic diol synthesized by biological fermentation from glycerol, sugar, or cellulose as raw materials, which reduces the carbon footprint of the product in one step. Moreover, in the transesterification reaction stage, the exchanged ethylene glycol can be separated, recovered, and reused for feeding, further achieving the effects of energy conservation and environmental protection. Additionally, by adjusting the addition ratio of the bio-based aliphatic diol, the elastic recovery rate (ranging from 20% to 80%) of the prepared fiber material can be adjusted to meet the elastic requirements of fibers for different uses, expanding the scope of application of PET recycled materials.

[0024] 4) In the chemical recycled elastic copolyester fiber material of the present invention, the transesterification of the bio-based aliphatic diol makes the copolyester material itself contain aliphatic chain segments with different methylene numbers. The helical or folded structural characteristics ([ Figure 5 shown) of the bio-based aliphatic diol molecule itself provide good elastic conditions and stability guarantees for the fiber material. Especially for 1,3-propanediol, the odd-carbon effect formed by its helical folded structure greatly improves the elasticity and stability of the prepared copolyester filament material. Compared with the fiber materials obtained by compounding similar polymers with different molecular weights in the prior art, the elastic ability of the copolyester filament fiber material of the present invention comes from the single matrix material itself, with better resilience stability, upgrading the performance of the PET recycled product, and can replace elastic materials such as PBT and PTT in the applications of textile fibers, optical fiber sheaths, etc.

[0025] Generally speaking, the polyester of the present invention uses waste PET and bio-based diol as raw materials. The entire waste PET recycling process has a simple process flow, a simple technical route, a clear reaction principle, simple operation, and does not require the use of a large amount of EG without generating by-products, and the product does not need to be purified, truly realizing the purpose of saving energy and being environmentally friendly in PET recycling. At the same time, the elasticity and crimp of the copolyester filament fiber material prepared by the present invention come from the matrix material itself, with stable performance and excellent low-temperature resistance, and has very good economic value, practical value, and social benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 is the molecular structure schematic diagram of diethylene glycol terephthalate;

[0027] Figure 2 is the molecular structure schematic diagram of propylene glycol terephthalate;

[0028] Figure 3 is the DSC quantitative analysis result of the copolyester material prepared by the present invention;

[0029] Figure 4 is the physical object of the chemically recycled copolyester filament fiber prepared by the present invention;

[0030] Figure 5It is the molecular conformational diagrams of three diols, namely ethylene glycol, 1,3-propanediol, and 1,4-butanediol. Detailed implementation mode

[0031] To make the objectives, technical solutions, and advantages of the present invention clearer, the following will, in conjunction with the embodiments, clearly and completely describe the technical solutions of the present invention. All the drugs involved in the embodiments are purchased from the market, and those without purity marked are of industrial or reagent grade.

[0032] Example 1

[0033] This example is for preparing a chemically recycled copolyester elastic filament fiber material. This copolyester elastic fiber material is prepared by adding a small amount of ethylene glycol for alcoholysis to the recycled waste PE, then adding the bio-based aliphatic diol 1,3-propanediol (PDO) for transesterification, and then carrying out polycondensation reaction. Its molecular structure is composed of repeating units of two terephthalic acid aliphatic diol esters, namely one is diethylene glycol terephthalate (the molecular structure is as Figure 1 shown), and the other is propylene glycol terephthalate (the molecular structure is as Figure 2 shown). The specific preparation process is as follows:

[0034] 1500 grams of washed and dried PET flakes (bulk density 260 g / L) and 750 grams of EG are added to a 5 L stainless steel reaction kettle with a reflux device, and then 1.2 grams of catalyst zinc acetate is added. Stir and heat up to 195 °C, and carry out depolymerization reaction under normal pressure; after 2.5 hours of reaction time, 563 grams of 1,3-propanediol (PDO) is added, and the transesterification reaction is continued under normal pressure at 215 °C for 80 minutes, and the ethylene glycol distilled out during the transesterification reaction is condensed and received for repeated feeding use. After the transesterification reaction ends, 1 gram of an organic titanium polycondensation catalyst with a titanium content of 3% is added, and the temperature is raised to 235 °C to start vacuum pumping into a low vacuum reaction. After 40 minutes, it enters a high vacuum reaction. Control the reaction temperature at 265 °C, and the residual pressure ≤ 100 Pa. After 95 minutes of high vacuum reaction, stop stirring, introduce nitrogen to relieve the vacuum and extrude the copolyester. The recycled PET content in this copolyester is 67.5 wt%, and the bio-based content is 32.5 wt%. The DSC quantitative analysis results are as Figure 3 shown.

[0035] The obtained copolyester is cut into pellets, dried in a vacuum oven at 110 °C for 20 hours, and then spun and drawn with a Φ20 mm screw spinning experimental machine to obtain copolyester filament fiber 1, as Figure 4 shown.

[0036] Example 2

[0037] This example is also for preparing a chemically recycled copolyester elastic filament fiber material. The same bio-based aliphatic diol, 1,3-propanediol (PDO), is added to the copolyester elastic fiber material for transesterification reaction. The specific steps are as follows:

[0038] 1500 g of washed and dried PET flakes (bulk density 200 g / L) and 500 g of EG are added to a 5 L stainless steel reactor with a reflux device. Then, 1.2 g of zinc acetate catalyst is added. Stir and heat up to 195 °C, and carry out depolymerization reaction under a pressure of 55 Kpa; after 3.5 hours of reaction time, 225 g of 1,3-propanediol (PDO) is added, and transesterification reaction is carried out at 220 °C under normal pressure for 90 minutes, and the ethylene glycol distilled out during the transesterification reaction is condensed and collected. After the transesterification reaction is completed, 1.3 g of an organic titanium polycondensation catalyst with a titanium content of 3% is added, heat up to 230 °C and start vacuum pumping to enter the low vacuum reaction. After 40 minutes, enter the high vacuum reaction. Control the reaction temperature at 263 °C, residual pressure ≤ 100 Pa. After 85 minutes of high vacuum reaction, stop stirring, introduce nitrogen to relieve the vacuum and extrude the copolyester. The recycled content of this copolyester is 85.5%, and the bio-based content is 14.5%.

[0039] The obtained copolyester is cut into pellets, dried in a vacuum oven at 110 °C for 20 hours, and then spun and drawn with a Φ20 mm screw spinning experimental machine to obtain copolyester filament fiber 2.

[0040] Example 3

[0041] This example is also for preparing a chemically recycled copolyester elastic filament fiber material. The same bio-based aliphatic diol, 1,3-propanediol (PDO), is added to the copolyester elastic fiber material for transesterification reaction. The specific steps are as follows:

[0042] 1500 g of washed and dried PET flakes (bulk density 300 g / L) and 1000 g of EG are added to a 5 L stainless steel reactor with a reflux device. Then, 1.2 g of zinc acetate catalyst is added. Stir and heat up to 195 °C, and carry out depolymerization reaction under a pressure of 88 Kpa. After 2.5 hours of reaction time, 455 g of 1,3-propanediol (PDO) is added, and transesterification reaction is carried out at 215 °C under normal pressure for 70 minutes, and the ethylene glycol distilled out during the transesterification reaction is condensed and collected. After the transesterification reaction is completed, 1 g of an organic titanium polycondensation catalyst with a titanium content of 3% is added, heat up to 235 °C and start vacuum pumping to enter the low vacuum reaction. After 40 minutes, enter the high vacuum reaction. Control the reaction temperature at 265 °C, residual pressure ≤ 100 Pa. After 90 minutes of high vacuum reaction, stop stirring, introduce nitrogen to relieve the vacuum and extrude the copolyester. The recycled PET content of this copolyester is 71 wt%, and the bio-based content is 29 wt%.

[0043] The obtained copolyester was cut into pellets, dried in a vacuum oven at 110°C for 20 hours, and then spun and drawn using a Φ20mm screw spinning experimental machine to obtain copolyester filament fiber 3.

[0044] Example 4

[0045] This example is for the preparation of a PET chemically recycled polyester fiber material. In this fiber material, the bio-based aliphatic diol added for the transesterification reaction is 1,4-butanediol (BDO). The specific steps are as follows:

[0046] 1500 g of washed and dried PET flakes (bulk density 260 g / L) and 750 g of EG were added to a 5L stainless steel reaction kettle with a reflux device. Then, 1.2 g of zinc acetate catalyst was added. The mixture was stirred and heated to 195°C, and the depolymerization reaction was carried out under normal pressure for 2.5 hours. After that, 645 g of 1,4-butanediol (BDO) was added, and the transesterification reaction was continued at 220°C under normal pressure for 80 minutes, and the ethylene glycol distilled out during the transesterification reaction was condensed and collected. After the transesterification reaction ended, 1.3 g of an organotitanium polycondensation catalyst with a titanium content of 3% was added. The temperature was raised to 230°C, and the reaction started to be evacuated to a low vacuum. After 40 minutes, it entered the high vacuum reaction. The reaction temperature was controlled at 263°C, and the residual pressure was ≤100 Pa. After 85 minutes of high vacuum reaction, the stirring was stopped, nitrogen was introduced to relieve the vacuum, and the copolyester was extruded. The recycled content of this copolyester was 61 wt%, and the bio-based content was 39 wt%.

[0047] The obtained copolyester was cut into pellets, dried in a vacuum oven at 110°C for 20 hours, and then spun and drawn using a Φ20mm screw spinning experimental machine to obtain copolyester filament fiber 4.

[0048] Example 5

[0049] This example is for the preparation of a PET chemically recycled polyester fiber material. In this fiber material, the bio-based aliphatic diol added for the transesterification reaction is 1,6-hexanediol (HDO). The specific steps are as follows:

[0050] 1500 g of washed and dried PET flakes (bulk density 260 g / L) and 750 g of EG were added to a 5 L stainless steel reactor equipped with a reflux device. Then, 1.2 g of zinc acetate catalyst was added. The mixture was stirred and heated to 195 °C, and the depolymerization reaction was carried out under atmospheric pressure for 2.5 hours. After that, 363 g of 1,6 - hexanediol (HDO) was added, and the transesterification reaction was continued at 210 °C under atmospheric pressure for 80 minutes, and the ethylene glycol distilled out during the transesterification reaction was condensed and collected. After the transesterification reaction ended, 1 g of an organotitanium polycondensation catalyst with a titanium content of 3% was added, and the temperature was raised to 235 °C to start vacuum pumping into a low - vacuum reaction. After 40 minutes, it entered a high - vacuum reaction. The reaction temperature was controlled at 265 °C, and the residual pressure ≤ 100 Pa. After 85 minutes of high - vacuum reaction, the stirring was stopped, nitrogen was introduced to relieve the vacuum, and the copolyester was extruded. The recycled content of this copolyester was 78 wt%, and the bio - based content was 22 wt%.

[0051] The obtained copolyester was cut into pellets, dried in a vacuum oven at 110 °C for 20 hours, and then spun and drawn using a Φ20 mm screw spinning experimental machine to obtain copolyester filament fiber 5.

[0052] Comparative Example 1

[0053] This example was to prepare a PET chemically recycled polyester fiber material. Except for not adding bio - based aliphatic diol for the transesterification reaction, the other components and the preparation process were the same as those in Example 1. Specifically as follows:

[0054] 1500 g of washed and dried PET flakes and 750 g of EG were added to a 5 L stainless steel reactor equipped with a reflux device. Then, 1.2 g of zinc acetate catalyst was added. The mixture was stirred and heated to 195 °C, and the depolymerization reaction was carried out under atmospheric pressure; after 2.5 hours of reaction time, 1 g of an organotitanium polycondensation catalyst with a titanium content of 3% was added, and the temperature was raised to 235 °C to start vacuum pumping into a low - vacuum reaction. After 40 minutes, it entered a high - vacuum reaction. The reaction temperature was controlled at 265 °C, and the residual pressure ≤ 100 Pa. After 95 minutes of high - vacuum reaction, the stirring was stopped, nitrogen was introduced to relieve the vacuum, and the polyester was extruded. The recycled PET content in this polyester was 100 wt%.

[0055] The obtained polyester was cut into pellets, dried in a vacuum oven at 110 °C for 20 hours, and then spun and drawn using a Φ20 mm screw spinning experimental machine to obtain comparative fiber 1.

[0056] Comparative Example 2

[0057] In this example, instead of using waste PET as raw material, commercially available purified terephthalic acid (from Hengli Petrochemical (Dalian) Co., Ltd., purity 99.5%) and 1,3 - propanediol (PDO) were used as raw materials to prepare a polyester fiber material. Specifically as follows:

[0058] 1200 g of terephthalic acid and 1041 g of 1,3-propanediol (PDO) were added to a 5 L stainless steel reactor equipped with a reflux device. 1 g of tetrabutyl titanate as a catalyst was added. The mixture was stirred and heated to 220 °C, and the esterification reaction was carried out under atmospheric pressure. After 2 hours of reaction, the temperature was raised to 235 °C and then evacuated to enter the low-vacuum reaction. After 40 minutes, it entered the high-vacuum reaction. The reaction temperature was controlled at 265 °C, and the residual pressure was ≤100 Pa. After 90 minutes of high-vacuum reaction, the stirring was stopped, nitrogen was introduced to relieve the vacuum, and the product polytrimethylene terephthalate polymer was extruded. The regenerated PET content of this polyester was 0 while the bio-based content was 37%.

[0059] The obtained polymer was cut into pellets, dried in a vacuum oven at 110 °C for 20 hours, and then spun and drawn using a Φ20 mm screw spinning experimental machine to obtain Comparative Fiber 2.

[0060] Effect Example 1

[0061] In this implementation, the strength (cN / dtex), elongation at break (%), 10% elongation elastic recovery (%), intrinsic viscosity of the copolyester used to prepare the fiber (phenol / tetrachloroethane = 3 / 2, dL / g), and melting point (°C) of the filament fibers prepared in Examples 1 to 5 and Comparative Examples 1 to 5 were detected. Among them: the detection methods of tensile strength, elongation at break, and elastic recovery rate all refer to GB / T 14344-2008; the detection methods of the intrinsic viscosity and melting point of polyester materials refer to GB / T 14190-2017. The detection results are shown in Table 1.

[0062] Table 1. Detection Results of the Performance of Each Fiber Material

[0063] Test Items Strength (cN / dtex) Elongation at Break (%) Intrinsic Viscosity (dL / g) Melting Point (°C) Elastic Recovery Rate at 10% Elongation (%) Example 1 3.7 39 0.93 227 83 Example 2 3.2 33 0.84 231 71 Example 3 3.4 35 0.87 232 77 Example 4 3.3 31 0.99 225 42 Example 5 1.8 42 0.74 212 36 Comparative Example 1 3.8 24 0.69 246 11 Comparative Example 2 3.1 38 0.90 228 85

[0064] It can be seen from the detection results in Table 1 that compared with the regenerated PET fiber (Comparative Example 1), the elastic recovery rate, tensile yield strength, and elongation at break of the copolyester filament fiber prepared in the present invention have been greatly improved. Especially, the 10% elongation elastic recovery rate has increased by 2 - 7 times, and the effect is very significant; compared with the polytrimethylene terephthalate fiber (Comparative Example 2), the strength of the copolyester filament fiber of the present invention is superior to that of the polytrimethylene terephthalate fiber. Especially, the copolyester fiber prepared by chain exchange with 1,3-propanediol has an elastic recovery rate and elongation at break similar to those of the polytrimethylene terephthalate fiber, showing very good mechanical and textile fiber properties, and can replace elastic materials such as PBT and PTT in the fields of textile fibers and optical fiber sheaths.

[0065] Effect Example 2

[0066] This example is to investigate the effect of the bio-based content in the copolyester on the elasticity of the filament fiber material. The copolyester filament fiber material prepared in Example 1 is used as the basis for investigation. For each fiber material participating in the investigation, except for the different bio-based contents, the other components and preparation methods are the same as those in Example 1. In this example, the strength, elongation at break, and 10% elastic recovery rate of each copolyester filament fiber are used as the investigation indicators, and the detection methods are the same as those in Effect Example 1. The bio-based content and test results of the polyester filament fibers participating in the investigation are shown in Table 2.

[0067] Table 2. Effect of Bio-based Content on the Elasticity of Copolyester Filament Fibers

[0068]

[0069] It can be seen from the results in Table 2 that the effect of the bio-based content on the elasticity of the copolyester filament fibers is very obvious. As the bio-based content in the filament fibers increases, the elasticity of the fibers becomes better, the strength and elastic recovery rate increase. The elasticity of the prepared fibers can be adjusted by adjusting the bio-based content, expanding the application range of recycled PET fibers. However, after the bio-based content exceeds 37 wt%, the elongation at break and elastic recovery rate level off, and the fiber strength shows a downward trend. Therefore, it is optimal to control the bio-based content within 11 wt% - 37 wt%.

[0070] For those skilled in the art, it is obvious that the present invention is not limited to the details of the above exemplary embodiments, and without departing from the spirit or basic characteristics of the present invention, the present invention can be implemented in other specific forms. Therefore, from any point of view, the embodiments should be regarded as exemplary and non-limiting. In addition, it should be understood that although this specification is described according to the embodiments, it does not only contain one technical solution. This narrative way of the specification is only for clarity. Those skilled in the art should regard the specification as a whole, and the technical solutions in the embodiments can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A chemically regenerated copolyester filament fiber, characterized in that: The copolyester filament fiber is prepared by alcoholysis, chain exchange and polycondensation reaction using recycled waste PET and bio-based aliphatic diol as raw materials; The bio-based aliphatic diol is any one or more of 1,3-propylene glycol, 1,4-butanediol or 1,6-hexanediol; The preparation method of the chemically regenerated copolyester filament fiber comprises the following steps: 1) PET alcoholysis reaction: After the recycled waste PET is crushed, cleaned and dried, a small amount of ethylene glycol is added, and alcoholysis reaction is carried out under the action of alcoholysis catalyst to obtain PET alcoholysis product; the amount of ethylene glycol added is: the mass ratio of PET to ethylene glycol is 1:0.3~1.0; 2) Chain exchange reaction: adding bio-based aliphatic diol to the PET alcoholysis product obtained in step 1), controlling the temperature, and performing chain exchange reaction to obtain a chain exchange product; the recycled PET content in the chain exchange product accounts for 63-89wt% and the bio-based content accounts for 11-37wt%; 3) Polycondensation reaction: adding a polycondensation catalyst to the PET alcoholysis product obtained in step 2), controlling the temperature and pressure, and performing a polycondensation reaction to obtain a chemically regenerated copolyester material; 4) Spinning: Spinning the copolyester material to prepare filament fibers for textile or optical fiber sheathing, and adjusting the elastic recovery rate of the copolyester filament fibers by adjusting the amount of bio-based aliphatic diol used as a raw material for preparing the copolyester material.

2. The chemically regenerated copolyester filament fiber according to claim 1, characterized in that: The bio-based aliphatic diol is synthesized by biological fermentation using glycerol, sugar or cellulose as raw materials.

3. The chemically regenerated copolyester filament fiber according to claim 1, characterized in that: In step 1), The alcoholysis catalyst is a metal acetate, including one or more of zinc acetate, manganese acetate, magnesium acetate, sodium acetate, and lithium acetate, and the addition amount thereof is 0.05-0.1% of the mass of PET; The conditions for alcoholysis are: 0-100Kpa, 180-220°C, and alcoholysis for 1-4 hours.

4. The chemically regenerated copolyester filament fiber according to claim 1, characterized in that: In step 2), the chain exchange reaction conditions are: normal pressure, 190-220° C., and chain exchange for 40-100 minutes.

5. The chemically regenerated copolyester filament fiber according to claim 1, characterized in that: In step 3), the polycondensation reaction uses a polycondensation catalyst which is an organic chelate of titanium, and the titanium content in the organic chelate is not less than 3%; The amount of the polycondensation catalyst added is 2 to 30 ppm of the titanium element based on the mass of PET; The polycondensation reaction conditions are: vacuum ≤ 100 Pa, 240-270° C., and polycondensation for 1-4 hours.

6. The chemically regenerated copolyester filament fiber according to claim 1, characterized in that: The recycled copolyester material has an intrinsic viscosity of 0.50-1.2 dL / g and a melting point of 190-250°C.

7. The chemically regenerated copolyester filament fiber according to claim 1, characterized in that: In step 4), the elastic recovery rate of the copolyester filament fiber is in the range of 20 to 85%.

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