Processing method for preparing regenerated polyester from waste polyester material

Abstract

The invention relates to the technical field of waste polyester material recovery, in particular to a processing method for preparing regenerated polyester from a waste polyester material, which comprises the following steps: injecting waste, ethylene glycol and a magnetic catalyst into a reaction kettle for alcoholysis to obtain alcoholysis liquid; separating out the magnetic catalyst in the alcoholysis solution by using a magnetic field, and purifying the residual alcoholysis solution to obtain ethylene glycol terephthalate; the preparation method comprises the following steps: injecting ethylene glycol terephthalate and antimony trioxide into a reaction kettle, carrying out a vacuum polycondensation reaction, and after the reaction is finished, discharging and pelletizing to obtain polymer pellets; and carrying out melt spinning on the polymer granules to prepare the regenerated polyester. In the alcoholysis process, a magnetic catalyst is used for replacing a traditional zinc acetate catalyst, so that the quality of regenerated polyester is improved; the magnetic catalyst with gaps is prepared through zinc-cobalt doping and high-temperature treatment, and pore clusters on the surface of the magnetic catalyst are beneficial to diffusion of reactants and permeation of ethylene glycol, so that the magnetic catalyst has a good alcoholysis effect on polyester waste.

Description

Technical Field

[0001] The present invention relates to the technical field of recycling of waste polyester materials, and specifically to a processing method for preparing recycled polyester fiber from waste polyester materials. Background Art

[0002] Polyethylene terephthalate (PET) is currently the polyester product with the largest output and the widest application range. Due to its stable structure and difficulty in natural degradation, a large amount of PET waste has exerted great pressure on petroleum resources and the ecological environment. How to strengthen the recycling of waste PET has become a hot topic of concern around the world. The chemical recycling of polyester is currently the focus of research and application. Its principle is based on the equilibrium reaction characteristics of polyester synthesis. Waste PET reacts with a depolymerizing agent to generate monomers or oligomers, and then the depolymerization products are recovered and recycled to prepare recycled polyester.

[0003] Depolymerizing PET with ethylene glycol as the alcoholysis agent has the advantages of mild conditions, simple process flow, good safety, and suitability for industrial promotion. However, the ethylene glycol alcoholysis method also has problems such as a slow alcoholysis rate and a large quality difference between the recycled polyester product and the virgin product. The zinc acetate catalyst used in the corresponding alcoholysis process is dissolved in the alcoholysis product and difficult to separate, which affects the quality of the alcoholysis product and thus the quality of the recycled polyester product. Moreover, the difficulty in recovering the zinc acetate catalyst will also increase production costs. Based on this, a processing method for preparing recycled polyester fiber from waste polyester materials is proposed. Summary of the Invention

[0004] Aiming at the deficiencies of the prior art, the present invention provides a processing method for preparing recycled polyester fiber from waste polyester materials, which uses a magnetic catalyst to replace the traditional zinc acetate catalyst, helping to improve the quality of recycled polyester fiber.

[0005] To achieve the above object, the present invention provides the following technical solution: A processing method for preparing recycled polyester fiber from waste polyester materials, comprising the following steps: (1) Drying and pulverizing the waste polyester materials to obtain waste materials; (2) Injecting the waste materials, ethylene glycol, and the magnetic catalyst into a reaction kettle, and performing an alcoholysis reaction under a nitrogen atmosphere to obtain an alcoholysis solution; (3) Separating and recovering the magnetic catalyst in the alcoholysis solution by magnetic separation, and then purifying the remaining alcoholysis solution to obtain ethylene glycol terephthalate; (4) Injecting ethylene glycol terephthalate and antimony trioxide into a reaction kettle, and performing a vacuum polycondensation reaction. After the reaction is completed, discharging and pelletizing to obtain polymer pellets; (5) Performing melt spinning on the polymer pellets to produce recycled polyester fiber.

[0006] Preferably, in step (2), the method for preparing the magnetic catalyst is as follows: S1. Dissolve cobalt(II) chloride hexahydrate and zinc chloride in ethylene glycol, adjust the pH of the system to 9 - 10 with ammonium acetate, and stir the reaction to obtain a reaction solution; S2. Heat the reaction solution to 200 - 220 °C and keep it warm for 20 - 24 h. After the reaction is completed, let it cool naturally and perform magnetic separation. Wash the separated particles alternately with ethanol and deionized water, and then dry them to obtain the magnetic catalyst.

[0007] Preferably, in step S1, the mass ratio of cobalt(II) chloride hexahydrate to zinc chloride is 3:1; and the ratio of the total amount of cobalt(II) chloride hexahydrate and zinc chloride to ethylene glycol is (1.5 - 3):100 g / mL.

[0008] Preferably, in step S1, the stirring reaction time is 2 - 2.5 h.

[0009] Preferably, in step (2), the addition amount of the magnetic catalyst is 0.6 - 0.8% of the mass of the waste, the ratio of the waste to ethylene glycol is 1:2 g / mL; the alcoholysis temperature is 195 - 200 °C, and the alcoholysis time is 2 - 2.2 h.

[0010] Preferably, in step (3), the purification treatment is specifically as follows: Filter the alcoholysis solution once, add deionized water at a temperature above 90 °C to the obtained filtrate, then filter it again, and perform recrystallization treatment on the obtained filtrate to obtain ethylene glycol terephthalate.

[0011] Preferably, the residual filtrate formed by the purification treatment is injected into a recovery kettle, and ethylene glycol is recovered by removing excess water.

[0012] Preferably, in step (3), after the magnetic catalyst is used repeatedly, it is ultrasonically washed with ethanol and calcined at 200 °C for 15 min.

[0013] Preferably, in step (4), the vacuum polycondensation reaction is specifically as follows: Raise the temperature to 230 - 240 °C and start vacuum pumping. When the vacuum degree drops below 200 Pa, continue to raise the temperature to 260 - 280 °C, and control the reaction time to be 3 - 3.5 h.

[0014] Preferably, in step (4), the addition amount of antimony trioxide is 0.1 - 0.2% of the mass of ethylene glycol terephthalate.

[0015] The present invention provides a processing method for preparing recycled polyester from waste polyester materials, which has the following beneficial effects compared with the prior art: In the alcoholysis process of the present invention, a magnetic catalyst is used to replace the traditional zinc acetate catalyst, which helps to improve the quality of recycled polyester. Specifically, after the depolymerization of waste polyester materials, the used zinc acetate catalyst remains in the alcoholysis product and is difficult to remove, resulting in a decrease in the intrinsic viscosity of the polyester product, a deterioration in hue, an increase in the end carboxyl group content, etc. The magnetic catalyst can be separated by a magnetic field, avoiding its residue in the alcoholysis product, thus ensuring the quality of recycled polyester.

[0016] The present invention prepares a magnetic catalyst with voids by doping zinc and cobalt and subjecting it to high-temperature treatment. The pore clusters on its surface contribute to the diffusion of reactants and the penetration of ethylene glycol, and have a good alcoholysis effect on polyester waste.

[0017] The magnetic catalyst in the present invention is combined with the regeneration treatment of washing and calcination, which can be recycled, greatly reducing the amount of catalyst used and lowering the production cost. Detailed implementation mode

[0018] The implementation mode of the present application will be described in detail through the following examples, so as to fully understand how the present application uses technical means to solve technical problems and achieve the realization process of technical effects and implement accordingly. Example 1

[0019] The preparation method of the magnetic catalyst is as follows: S1. Dissolve CoCl2·H2O and ZnCl2 in EG, adjust the pH of the system to 9 with NH4Ac, and stir and react for 2 h to obtain a reaction solution; In step S1, the mass ratio of CoCl2·H2O to ZnCl2 is 3:1; and the material ratio of the total amount of CoCl2·H2O and ZnCl2 to EG is 1.5:100 g / mL.

[0020] S2. Heat the reaction solution to 220 °C and keep it warm for 20 h. After the reaction is completed, cool it naturally and perform magnetic separation. Wash the separated particles alternately with ethanol and deionized water, and then dry them to obtain the magnetic catalyst.

[0021] Example 2

[0022] The preparation method of the magnetic catalyst is as follows: S1. Dissolve CoCl2·H2O and ZnCl2 in EG, adjust the pH of the system to 10 with NH4Ac, and stir and react for 2.5 h to obtain a reaction solution; In step S1, the mass ratio of CoCl2·H2O to ZnCl2 is 3:1; and the material ratio of the total amount of CoCl2·H2O and ZnCl2 to EG is 3:100 g / mL.

[0023] S2. Heat the reaction solution to 200 °C and keep it warm for 24 h. After the reaction is completed, let it cool naturally and perform magnetic separation. Wash the separated particles alternately with ethanol and deionized water, and then dry them to obtain the magnetic catalyst.

[0024] Example 3

[0025] A processing method for preparing recycled polyester from waste polyester materials, comprising the following steps: (1) Dry and crush the waste polyester materials to obtain waste materials; (2) Inject the waste materials, EG and the magnetic catalyst into the reaction kettle. Under a nitrogen atmosphere, carry out an alcoholysis reaction at 195 °C for 2.2 h to obtain an alcoholysis solution; Among them, the addition amount of the magnetic catalyst is 0.6% of the mass of the waste materials, and the material ratio of the waste materials to EG is 1:2 g / mL.

[0026] (3) Use magnetic separation to separate and recover the magnetic catalyst in the alcoholysis solution, and then purify the remaining alcoholysis solution to obtain BHET; Among them, the purification treatment is specifically as follows: Filter the alcoholysis solution once, add deionized water at a temperature above 90 °C to the obtained filtrate, then filter it a second time, and perform recrystallization treatment on the obtained filtrate to obtain BHET; The residual filtrate formed by the purification treatment is injected into the recovery kettle, and EG is recovered by removing excess water.

[0027] (4) Inject BHET and Sb2O3 into the reaction kettle. The addition amount of Sb2O3 is 0.2% of the mass of BHET, and carry out a vacuum polycondensation reaction. After the reaction is completed, discharge and pelletize to obtain polymer pellets; Among them, the vacuum polycondensation reaction is specifically as follows: Raise the temperature to 230 °C and start vacuum pumping. When the vacuum degree drops below 200 Pa, continue to raise the temperature to 280 °C, and control the reaction time to be 3 h.

[0028] (5) Carry out melt spinning on the polymer pellets to obtain recycled polyester.

[0029] In this example, the magnetic catalyst prepared in Example 1 is used.

[0030] Example 4

[0031] A processing method for preparing recycled polyester from waste polyester materials, comprising the following steps: (1) Dry and crush the waste polyester materials to obtain waste materials; (2) Inject the waste materials, EG and the magnetic catalyst into the reaction kettle. Under a nitrogen atmosphere, carry out an alcoholysis reaction at 200 °C for 2 h to obtain an alcoholysis solution; Among them, the addition amount of the magnetic catalyst is 0.7% of the mass of the waste material, and the material ratio of the waste material to EG is 1:2 g / mL.

[0032] (3) Use magnetic separation to separate and recover the magnetic catalyst in the alcoholysis solution, and then purify the remaining alcoholysis solution to obtain BHET; Among them, the purification treatment is specifically as follows: Filter the alcoholysis solution once, add deionized water above 90°C to the obtained filtrate, then filter it a second time, and perform recrystallization on the obtained filtrate to obtain BHET; The residual filtrate formed by the purification treatment is injected into the recovery kettle, and EG is recovered by removing excess water.

[0033] (4) Inject BHET and Sb2O3 into the reaction kettle. The addition amount of Sb2O3 is 0.1% of the mass of BHET, and carry out a vacuum polycondensation reaction. After the reaction is completed, discharge and pelletize to obtain polymer pellets; Among them, the vacuum polycondensation reaction is specifically as follows: Raise the temperature to 240°C and start vacuum pumping. When the vacuum degree drops below 200 Pa, continue to raise the temperature to 260°C, and control the reaction time to be 3.5 h.

[0034] (5) Carry out melt spinning on the polymer pellets to obtain recycled polyester.

[0035] In this example, the magnetic catalyst prepared in Example 2 is used.

[0036] Example 5

[0037] A processing method for preparing recycled polyester from waste polyester materials, comprising the following steps: (1) Dry and crush the waste polyester materials to obtain waste materials; (2) Inject the waste materials, EG and magnetic catalyst into the reaction kettle, and carry out an alcoholysis reaction at 200°C for 2.2 h under a nitrogen atmosphere to obtain an alcoholysis solution; Among them, the addition amount of the magnetic catalyst is 0.8% of the mass of the waste material, and the material ratio of the waste material to EG is 1:2 g / mL.

[0038] (3) Use magnetic separation to separate and recover the magnetic catalyst in the alcoholysis solution, and then purify the remaining alcoholysis solution to obtain BHET; Among them, the purification treatment is specifically as follows: Filter the alcoholysis solution once, add deionized water above 90°C to the obtained filtrate, then filter it a second time, and perform recrystallization on the obtained filtrate to obtain BHET; The residual filtrate formed by the purification treatment is injected into the recovery kettle, and EG is recovered by removing excess water.

[0039] (4) Inject BHET and Sb2O3 into the reaction kettle. The addition amount of Sb2O3 is 0.15% of the mass of BHET. Carry out vacuum polycondensation reaction. After the reaction is completed, discharge and pelletize to obtain polymer pellets; Among them, the vacuum polycondensation reaction is specifically as follows: Raise the temperature to 235 °C and start pumping vacuum. When the vacuum degree drops below 200 Pa, continue to raise the temperature to 270 °C, and control the reaction time to be 3.2 h.

[0040] (5) Carry out melt spinning on the polymer pellets to obtain recycled polyester.

[0041] In this example, the magnetic catalyst prepared in Example 2 is used.

[0042] Comparative Example 1 A processing method for preparing recycled polyester from waste polyester materials is basically the same as that in Example 6, except that: the magnetic catalyst is replaced with zinc acetate of equal mass.

[0043] Comparative Example 2 A processing method for preparing recycled polyester from waste polyester materials includes the following steps: (1) Dry and crush the waste polyester materials to obtain waste materials; (2) Inject the waste materials, EG and magnetic catalyst A into the reaction kettle. Under a nitrogen atmosphere, carry out alcoholysis reaction at 200 °C for 2.2 h to obtain an alcoholysis solution; Among them, the addition amount of magnetic catalyst A is 0.8% of the mass of the waste materials, and the material ratio of the waste materials to EG is 1:2 g / mL.

[0044] (3) Use magnetic separation to separate and recover magnetic catalyst A in the alcoholysis solution, and then carry out purification treatment on the remaining alcoholysis solution to obtain BHET; Among them, the purification treatment is specifically as follows: Filter the alcoholysis solution once, add deionized water above 90 °C to the obtained filtrate, then filter it again, and carry out recrystallization treatment on the obtained filtrate to obtain BHET; The residual filtrate formed by the purification treatment is injected into the recovery kettle, and EG is recovered by removing excess water.

[0045] (4) Inject BHET and Sb2O3 into the reaction kettle. The addition amount of Sb2O3 is 0.15% of the mass of BHET. Carry out vacuum polycondensation reaction. After the reaction is completed, discharge and pelletize to obtain polymer pellets; Among them, the vacuum polycondensation reaction is specifically as follows: Raise the temperature to 235 °C and start pumping vacuum. When the vacuum degree drops below 200 Pa, continue to raise the temperature to 270 °C, and control the reaction time to be 3.2 h.

[0046] (5) Carry out melt spinning on the polymer pellets to obtain recycled polyester.

[0047] In this comparative example, the magnetic catalyst A used is the magnetic catalyst in Example 2 that has been recycled twice.

[0048] Comparative Example 3 A processing method for preparing recycled polyester from waste polyester materials is basically the same as that in Comparative Example 2, except that: the magnetic catalyst A is replaced with a magnetic catalyst B, and the magnetic catalyst B is the magnetic catalyst in Example 2 that has been recycled five times.

[0049] Comparative Example 4 A processing method for preparing recycled polyester from waste polyester materials is basically the same as that in Comparative Example 3, except that: the magnetic catalyst B is replaced with a magnetic catalyst C, and the magnetic catalyst C is obtained by ultrasonic washing of the magnetic catalyst B with ethanol and calcining at 200 °C for 15 min.

[0050] Performance testing 1. Using the recycled polyester in Examples 3-4 and Comparative Example 1 as samples, the breaking strength and elongation at break of the samples were detected with reference to the standard of GB / T 14344-2008. The specific test results are shown in Table 1.

[0051] Table 1 Strength As can be seen from the above table: compared with Example 5, the strength of the recycled polyester in Comparative Example 1 is slightly weaker, indicating that using a magnetic catalyst that is easy to remove helps to improve the performance of the recycled polyester.

[0052] 2. During the processing of the recycled polyester in Example 5 and Comparative Examples 2-4, the alcoholysis rate of the waste material and the yield of BHET were detected and calculated. The specific results are shown in Table 2.

[0053] Table 2 Alcoholysis rate and yield As can be seen from the above table: (1) Compared with Example 5, the magnetic catalysts in Comparative Examples 2 and 3 have been recycled many times, which affects the alcoholysis rate of the waste material and the yield of BHET. Especially after recycling five times, the yield of BHET decreases significantly.

[0054] (2) The magnetic catalyst used in Comparative Example 4 was regenerated after being recycled five times and still maintained good performance.

[0055] Although the embodiments of the present invention have been shown and described, it will be understood by those of ordinary skill in the art that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the present invention, and the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A processing method for preparing recycled polyester from waste polyester materials, characterized in that, It includes the following steps: (1) Dry and crush waste polyester materials to obtain waste materials; (2) Inject the waste materials, ethylene glycol and magnetic catalyst into a reaction kettle, and carry out alcoholysis reaction under a nitrogen atmosphere to obtain an alcoholysis solution; (3) Use magnetic separation to separate and recover the magnetic catalyst in the alcoholysis solution, and then purify the remaining alcoholysis solution to obtain ethylene glycol terephthalate; (4) Inject ethylene glycol terephthalate and antimony trioxide into a reaction kettle, carry out vacuum polycondensation reaction, and discharge and pelletize after the reaction to obtain polymer pellets; (5) Carry out melt spinning on the polymer pellets to produce recycled polyester.

2. The processing method for preparing recycled polyester from waste polyester materials according to claim 1, wherein, In step (2), the preparation method of the magnetic catalyst is as follows: S1. Dissolve cobalt chloride hexahydrate and zinc chloride in ethylene glycol, adjust the pH of the system to 9-10 with ammonium acetate, and stir and react to obtain a reaction solution; S2. Heat the reaction solution to 200-220 °C and keep it warm for 20-24 h. After the reaction is completed, cool it naturally and carry out magnetic separation. Wash the separated particles alternately with ethanol and deionized water, and then dry them to obtain a magnetic catalyst.

3. The processing method for preparing recycled polyester from waste polyester materials according to claim 2, characterized in that, In step S1, the mass ratio of cobalt chloride hexahydrate to zinc chloride is 3:1; and the material ratio of the total amount of cobalt chloride hexahydrate and zinc chloride to ethylene glycol is (1.5-3):100 g / mL.

4. The processing method for preparing recycled polyester from waste polyester materials according to claim 2, characterized in that, In step S1, the stirring reaction time is 2-2.5 h.

5. The processing method for preparing recycled polyester from waste polyester materials according to claim 1, characterized in that, In step (2), the addition amount of the magnetic catalyst is 0.6-0.8% of the mass of the waste material, and the material ratio of the waste material to ethylene glycol is 1:2 g / mL; the alcoholysis temperature is 195-200 °C, and the alcoholysis time is 2-2.2 h.

6. The processing method for preparing recycled polyester from waste polyester materials according to claim 1, characterized in that, In step (3), the purification treatment is specifically: filter the alcoholysis solution once, add deionized water above 90 °C to the obtained filtrate, then filter it a second time, and carry out recrystallization treatment on the obtained filtrate to obtain ethylene glycol terephthalate.

7. The processing method for preparing recycled polyester from waste polyester materials according to claim 6, characterized in that, The residual filtrate formed by the purification treatment is injected into a recovery kettle, and ethylene glycol is recovered by removing excess water.

8. The processing method for preparing recycled polyester from waste polyester materials according to claim 1, characterized in that, In step (3), after the magnetic catalyst is recycled multiple times, it is ultrasonically washed with ethanol and calcined at 200 °C for 15 min.

9. The processing method for preparing recycled polyester from waste polyester materials according to claim 1, characterized in that, In step (4), the vacuum polycondensation reaction is specifically: raise the temperature to 230-240 °C and start pumping vacuum. When the vacuum degree drops below 200 Pa, continue to raise the temperature to 260-280 °C, and control the reaction time to be 3-3.5 h.

10. The processing method for preparing recycled polyester from waste polyester materials according to claim 1, characterized in that, In step (4), the addition amount of antimony trioxide is 0.1-0.2% of the mass of ethylene glycol terephthalate.