Preparation method of regenerated extinction cationic dyeable polyester

Abstract

The invention relates to the field of synthesis of regenerated polyester, and discloses a preparation method of regenerated extinction cationic dyeable polyester, which is characterized in that BHET with the polymerization degree of 2-4, a tri-monomer, a stabilizer and an oxidizing agent are subjected to in-situ polymerization to prepare the regenerated extinction cationic dyeable polyester. The problems that the regenerated cationic polyester is poor in color value and unstable in spinning and titanium dioxide and three monomers are easy to self-polymerize and agglomerate to form large-particle gel are solved, and the quality and spinnability of the regenerated extinction cationic dyeable polyester are remarkably improved; according to the method, when the phenyl glycidyl ether and the phosphite ester are combined for use, agglutinated particles are completely not generated in a polyester melt, the DF value of the polyester can be remarkably reduced, the regenerated extinction cationic polyester can be subjected to melt direct spinning, the b value of the extinction cationic polyester can be remarkably reduced, and the yellowing effect of the extinction cationic polyester is remarkably inhibited; the color value of polyester is obviously improved.

Description

A method for preparing recycled matte cationic dyeable polyester Technical Field

[0001] This invention relates to the field of recycled polyester synthesis, and in particular to a method for preparing a recycled matte cationic dyeable polyester. Background Technology

[0002] Polyethylene terephthalate (PET) is a widely used but extremely difficult-to-degrade polymer. Its degradation time under natural conditions is extremely long, leading to serious environmental pollution problems. Therefore, to address these issues, existing technologies have proposed recycling and reuse solutions for PET.

[0003] Currently, PET recycling mainly employs chemical alcoholysis. For example, CN106113319A discloses a recycling process for waste textiles containing polyester. This technology uses ethylene glycol to alcoholyze PET waste, followed by esterification, polycondensation, and multi-stage filtration to obtain recycled polyester. To expand the application range of recycled polyester, existing technologies also provide methods for preparing recycled cationic polyester. For instance, CN107652422B discloses a method for preparing recycled cationic dyeable polyester using waste polyester alcoholysis. This method uses alcoholysis to alcoholyze PET waste and then uses the alcoholysis product to prepare recycled cationic dyeable polyester. Because the diethyl terephthalate (BHET) obtained from the alcoholysis of PET waste is extremely weakly polar, it is difficult for BHET to polymerize with the three monomers, and the three monomers are prone to agglomeration. Therefore, existing methods for preparing recycled cationic dyeable polyester typically first convert BHET into an ester, and then esterify, prepolymerize, and polycondense the BHET ester with the three monomers and polyethylene glycol comonomers.

[0004] Cationic dyeable polyesters suffer from poor opacity, thus conventional techniques typically require the addition of opacifying agents to produce matte or semi-matte cationic dyeable polyesters. However, this invention, when directly synthesizing regenerated matte cationic polyester in situ using BHET, three monomers, and titanium dioxide, revealed significant problems with self-polymerization of the three monomers and agglomeration of titanium dioxide in the reaction system, hindering continuous polymerization and spinning. Furthermore, the regenerated cationic polyester exhibited poor color difference and spinnability. Additionally, this invention, when using the method disclosed in CN107652422B to prepare regenerated matte cationic dyeable polyester, found that the use of titanium dioxide also resulted in agglomerated particles in the polyester product, preventing continuous polymerization. Therefore, providing a method for preparing regenerated matte cationic polyester is of significant importance. Summary of the Invention

[0005] This invention provides a method for preparing recycled matte cationic dyeable polyester. The method involves in-situ polymerization of BHET with a degree of polymerization of 2-4 with three monomers, an ether-type stabilizer, and an oxidant to prepare the recycled matte cationic dyeable polyester. The ether-type stabilizer can reduce the catalytic degradation of polyester by metal salt impurities in BHET and the oxidation of small molecules into colored impurities at high temperatures. It also reduces impurities generated by the self-polymerization of the three monomers in the polyester, improving the color value and spinnability of the recycled matte cationic dyeable polyester. After polymerization onto the polyester, the ether-type stabilizer can form microbranched molecular segments. The spatial confinement effect of these microbranched molecular segments can limit the aggregation and self-polymerization of titanium dioxide and the three monomers, thereby improving the quality of the recycled matte cationic polyester product.

[0006] The specific technical solution of the present invention is as follows: a method for preparing a recycled matte cationic dyeable polyester, comprising the following steps: alcoholystolysis of BHET to prepare a polymeric monomer with a degree of polymerization of 2 to 4; then subjecting the polymeric monomer, ether stabilizer and oxidant to a first esterification reaction to prepare ester one; then adding titanium dioxide and trimonomer to the ester to conduct a second esterification reaction to prepare ester two; then subjecting ester two to a first polycondensation reaction and a second polycondensation reaction, and then performing melt direct spinning to prepare a recycled matte cationic dyeable polyester.

[0007] Preferably, the ether stabilizer is one or more of phenyl glycidyl ether, trimethoxy(3-(glycidyl ether)propyl)silane, bisphenol A bisglycidyl ether, and tetra(phenyl glycidyl ether).

[0008] Preferably, the mass ratio of the ether stabilizer to BHET is 1:5000~10000.

[0009] Preferably, the antioxidant is one or more of phosphite, antioxidant 1010, antioxidant 1076 and antioxidant 1098.

[0010] Preferably, the mass ratio of antioxidant to BHET is 1:100000~300000.

[0011] Preferably, the mass ratio of titanium dioxide to BHET is 0.2~3:100.

[0012] Preferably, the mass ratio of the three monomers to BHET is 1~4:100.

[0013] Preferably, the three monomers are one of isophthalic acid-5-sulfonic acid (SIPA) and sodium dihydroxyethyl isophthalate-5-sulfonate (SIPE).

[0014] As a preferred option, the alcoholysis conditions include: a depolymerization temperature of 220~250 ℃, a pressure of 40-80 Kpa, and a mass ratio of ethylene glycol to BHET of 0.05~0.1:1.

[0015] Preferably, the temperature of the first esterification reaction is 240~260 ℃, the pressure of the first esterification reaction is 0.4~1 bar, and the time of the first esterification reaction is 3~5 h.

[0016] Preferably, the temperature of the second esterification reaction is 210~250 °C, the pressure of the second esterification reaction is 0.05~0.5 bar, and the time of the second esterification reaction is 3~5 h.

[0017] Preferably, the temperature of the first-stage polycondensation is 270~280 ℃, the pressure of the first-stage polycondensation is 700~1200 Pa, and the reaction time of the first-stage polycondensation is 2~5 h.

[0018] Preferably, the temperature of the second-stage polycondensation is 270~280 ℃, the pressure of the second-stage polycondensation is 100~300 Pa, and the reaction time of the second-stage polycondensation is 1~3 h.

[0019] This invention provides a method for preparing recycled matte cationic dyeable polyester. The method uses BHET with a degree of polymerization of 2 to 4, along with three monomers, a stabilizer, and an oxidant, to carry out in-situ polymerization to prepare recycled matte cationic dyeable polyester. This method solves the problems of poor color value, unstable spinning, and easy self-agglomeration and agglomeration of titanium dioxide and three monomers to form large particles of gel in recycled cationic polyester, and significantly improves the quality and spinnability of recycled matte cationic dyeable polyester.

[0020] This invention employs stabilizers and antioxidants. The stabilizer is an ether-type stabilizer, which, after polymerization onto the polyester molecular chain, forms microbranched molecular segments. These microbranched segments create a network-like spatial confinement, restricting the free movement of titanium dioxide in the melt, thereby weakening the agglomeration between titanium dioxide and the three monomers. It also inhibits the self-polymerization of polar three monomers during the polycondensation of non-polar polymers, significantly reducing the formation of large agglomerates. The antioxidant has reducing properties, reducing the catalytic degradation of polyester by metal salt impurities in the recovered BHET and the oxidation of small molecules at high temperatures. It inhibits the oxidation of the three monomers at high temperatures, blocks oxidation chain reactions, significantly reduces colored impurities and yellowing, and significantly improves the color stability of the polyester. The antioxidant also inhibits the dehydration of ethylene glycol to diethylene glycol during esterification, preventing excessive diethylene glycol from lowering the polyester melting point and improving dyeing uniformity.

[0021] Furthermore, the stabilizer and antioxidant in this invention have a synergistic effect. When the phenyl glycidyl ether in the stabilizer and the phosphite in the antioxidant are used in combination, they can significantly reduce the aggregated particles in the polyester melt, significantly reduce the DF value of the polyester, enable the recycled matting cationic polyester to be melt-spun directly, and significantly reduce the b value of the matting cationic polyester, thus significantly inhibiting the yellowing effect of the matting cationic polyester.

[0022] Compared with the prior art, this application has the following technical effects: (1) This method uses BHET with a degree of polymerization of 2~4 with three monomers, stabilizers and oxidants to prepare raw matte cationic dyeable polyester in situ polymerization, which solves the problems of poor color value, unstable spinning and easy self-polymerization and agglomeration of titanium dioxide and three monomers to form large particles of gel, and significantly improves the quality and spinnability of the recycled matte cationic dyeable polyester.

[0023] (2) The stabilizers and antioxidants used in this method have a synergistic effect. When the phenyl glycidyl ether in the stabilizer and the phosphite in the antioxidant are used in combination, no aggregated particles are generated in the polyester melt, the polyester DF value can be significantly reduced, the recycled matting cationic polyester can be melt-spun directly, the b value of the matting cationic polyester can be significantly reduced, and the yellowing effect of the matting cationic polyester can be significantly inhibited.

[0024] (3) This method is simple in process, easy to operate, easy to control and industrialized. Detailed Implementation

[0025] The present invention will be further described below with reference to embodiments.

[0026] To better understand the content of this invention, further explanation is provided below with reference to specific embodiments. It should be understood that the following embodiments are for illustrative purposes only and are not intended to limit the scope of this invention.

[0027] Example 1: A method for preparing a recycled matte cationic dyeable polyester, comprising the following steps: (1) 100,000 parts of BHET, 10,000 parts of ethylene glycol and 1.5 parts of titanium-silicon composite catalyst are added to a depolymerization reactor and heated to 230°C for stirring. The pressure is controlled at 60 kPa for depolymerization reaction for 3 h to remove 12,000 parts of ethylene glycol to obtain a polymer monomer with a degree of polymerization of 2 to 4; (2) The polymer monomer is added to a first esterification reactor. The temperature of the first esterification reactor is set to 250°C and the pressure is set to 0.8 bar. Then, 10 parts of ether stabilizer (phenyl glycidyl ether) and 0.5 parts of antioxidant (phosphite) are added for the first esterification reaction for 4 h to prepare esterification liquid one; (3) Esterification liquid one is injected into a second esterification reactor. Then, 2,300 parts of titanium dioxide are added and stirred for 0.5 h. Then, 2,000 parts of SIPE are added. The temperatures of the three zones of the second esterification reactor are set as follows: Zone 1: 210°C The second esterification reaction was carried out at ℃, 210 ℃ in zone two and 220 ℃ in zone three, and the pressure was set to 0.1 bar for 4 h to obtain esterified liquid II; (4) the esterified liquid was injected into the polycondensation reactor for a first polycondensation reaction for 3 h, the temperature of the first polycondensation reaction was 270 ℃, and the pressure of the first polycondensation reaction was 1200 Pa; after the first polycondensation reaction was completed, a second polycondensation reaction was carried out for 1.5 h, the temperature of the first polycondensation reaction was 278 ℃, and the pressure of the first polycondensation reaction was 200 Pa; the melt was granulated underwater to make recycled matte cationic polyester chips.

[0028] Example 2: A method for preparing a recycled matte cationic dyeable polyester, comprising the following steps: (1) 100,000 parts of BHET, 10,000 parts of ethylene glycol and 1.5 parts of titanium-silicon composite catalyst are added to a depolymerization reactor and heated to 230°C for stirring. The pressure is controlled at 60 kPa for depolymerization reaction for 3 h to remove 10,000 parts of ethylene glycol to obtain a polymer monomer with a degree of polymerization of 2 to 4; (2) The polymer monomer is added to a first esterification reactor. The temperature of the first esterification reactor is set to 250°C and the pressure is set to 0.8 bar. Then, 10 parts of ether stabilizer (phenyl glycidyl ether) and 0.5 parts of antioxidant (phosphite) are added for the first esterification reaction for 4 h to prepare esterification liquid one; (3) Esterification liquid one is injected into a second esterification reactor. Then, 2,300 parts of titanium dioxide are added and stirred for 0.5 h. Then, 2,000 parts of SIPE are added. The temperatures of the three zones of the second esterification reactor are set as follows: Zone 1: 210°C The second esterification reaction was carried out at ℃, 210 ℃ in zone two and 220 ℃ in zone three, and the pressure was set to 0.1 bar for 4 h to obtain esterified liquid II; (4) the esterified liquid was injected into the polycondensation reactor for a first polycondensation reaction for 3 h, the temperature of the first polycondensation reaction was 270 ℃, and the pressure of the first polycondensation reaction was 1200 Pa; after the first polycondensation reaction was completed, a second polycondensation reaction was carried out for 1.5 h, the temperature of the first polycondensation reaction was 278 ℃, and the pressure of the first polycondensation reaction was 200 Pa; the melt was granulated underwater to make recycled matte cationic polyester chips.

[0029] Example 3: A method for preparing a recycled matte cationic dyeable polyester, comprising the following steps: (1) 100,000 parts of BHET, 10,000 parts of ethylene glycol and 1.5 parts of titanium-silicon composite catalyst are added to a depolymerization reactor and heated to 230°C for stirring. The pressure is controlled at 60 kPa for depolymerization reaction for 3 h to remove 12,000 parts of ethylene glycol to obtain a polymer monomer with a degree of polymerization of 2 to 4; (2) The polymer monomer is added to a first esterification reactor. The temperature of the first esterification reactor is set to 250°C and the pressure is set to 0.8 bar. Then, 10 parts of ether stabilizer (phenyl glycidyl ether) and 0.5 parts of antioxidant (phosphite) are added for the first esterification reaction for 4 h to prepare esterification liquid one; (3) Esterification liquid one is injected into a second esterification reactor. Then, 250 parts of titanium dioxide are added and stirred for 0.5 h. Then, 2,000 parts of SIPE are added. The temperatures of the three zones of the second esterification reactor are set as follows: Zone 1 210°C, Zone 2 210°C, and Zone 2 210°C respectively. The second esterification reaction was carried out at ℃ and 220 ℃ in the third zone, and the pressure was set to 0.1 bar for 4 h to obtain esterified liquid II; (4) The esterified liquid was injected into the polycondensation reactor for a first polycondensation reaction for 3 h, the temperature of the first polycondensation reaction was 270 ℃, and the pressure of the first polycondensation reaction was 1200 Pa; after the first polycondensation reaction was completed, a second polycondensation reaction was carried out for 1.5 h, the temperature of the first polycondensation reaction was 278 ℃, and the pressure of the first polycondensation reaction was 200 Pa; the melt was granulated underwater to make recycled matte cationic polyester chips.

[0030] Example 4: A method for preparing a recycled matte cationic dyeable polyester, comprising the following steps: (1) 100,000 parts of BHET, 10,000 parts of ethylene glycol and 1.5 parts of titanium-silicon composite catalyst are added to a depolymerization reactor and heated to 230°C for stirring. The pressure is controlled at 60 kPa for depolymerization reaction for 3 h to remove 12,000 parts of ethylene glycol to obtain a polymer monomer with a degree of polymerization of 2 to 4; (2) The polymer monomer is added to a first esterification reactor. The temperature of the first esterification reactor is set to 250°C and the pressure is set to 0.8 bar. Then, 10 parts of ether stabilizer (phenyl glycidyl ether) and 1 part of antioxidant (phosphite) are added for the first esterification reaction for 4 h to prepare esterification liquid one; (3) Esterification liquid one is injected into a second esterification reactor. Then, 2,300 parts of titanium dioxide are added and stirred for 0.5 h. Then, 2,000 parts of SIPE are added. The temperatures of the three zones of the second esterification reactor are set as follows: Zone 1 210°C, Zone 2 210°C, and Zone 2 210°C respectively. The second esterification reaction was carried out at ℃ and 220 ℃ in the third zone, and the pressure was set to 0.1 bar for 4 h to obtain esterified liquid II; (4) The esterified liquid was injected into the polycondensation reactor for a first polycondensation reaction for 3 h, the temperature of the first polycondensation reaction was 270 ℃, and the pressure of the first polycondensation reaction was 1200 Pa; after the first polycondensation reaction was completed, a second polycondensation reaction was carried out for 1.5 h, the temperature of the first polycondensation reaction was 278 ℃, and the pressure of the first polycondensation reaction was 200 Pa; the melt was granulated underwater to make recycled matte cationic polyester chips.

[0031] Example 5: A method for preparing a recycled matte cationic dyeable polyester, comprising the following steps: (1) 100,000 parts of BHET, 10,000 parts of ethylene glycol and 1.5 parts of titanium-silicon composite catalyst are added to a depolymerization reactor and heated to 230°C for stirring. The pressure is controlled at 60 kPa for depolymerization reaction for 3 h to remove 12,000 parts of ethylene glycol to obtain a polymer monomer with a degree of polymerization of 2 to 4; (2) The polymer monomer is added to a first esterification reactor. The temperature of the first esterification reactor is set to 250°C and the pressure is set to 0.8 bar. Then, 5 parts of ether stabilizer (phenyl glycidyl ether) and 0.5 parts of antioxidant (phosphite) are added for the first esterification reaction for 4 h to prepare esterification liquid one; (3) Esterification liquid one is injected into a second esterification reactor. Then, 2,300 parts of titanium dioxide are added and stirred for 0.5 h. Then, 2,000 parts of SIPE are added. The temperatures of the three zones of the second esterification reactor are set as follows: Zone 1 210°C, Zone 2 210°C, and Zone 2 210°C respectively. The second esterification reaction was carried out at ℃ and 220 ℃ in the third zone, and the pressure was set to 0.1 bar for 4 h to obtain esterified liquid II; (4) The esterified liquid was injected into the polycondensation reactor for a first polycondensation reaction for 3 h, the temperature of the first polycondensation reaction was 270 ℃, and the pressure of the first polycondensation reaction was 1200 Pa; after the first polycondensation reaction was completed, a second polycondensation reaction was carried out for 1.5 h, the temperature of the first polycondensation reaction was 278 ℃, and the pressure of the first polycondensation reaction was 200 Pa; the melt was granulated underwater to make recycled matte cationic polyester chips.

[0032] Example 6: A direct spinning method for recycled matte cationic dyeable polyester, comprising the following steps: (1) 100,000 parts of BHET, 10,000 parts of ethylene glycol and 1.5 parts of titanium-silicon composite catalyst are added to a depolymerization reactor and heated to 230°C for stirring. The pressure is controlled at 60 kPa for depolymerization reaction for 3 h to remove 12,000 parts of ethylene glycol to obtain a polymer monomer with a degree of polymerization of 2 to 4; (2) The polymer monomer is added to a first esterification reactor. The temperature of the first esterification reactor is set to 250°C and the pressure is set to 0.8 bar. Then, 10 parts of ether stabilizer (phenyl glycidyl ether) and 0.5 parts of antioxidant (phosphite) are added for the first esterification reaction for 4 h to prepare esterification liquid one; (3) Esterification liquid one is injected into a second esterification reactor. Then, 2,300 parts of titanium dioxide are added and stirred for 0.5 h. Then, 2,000 parts of SIPE are added. The temperatures of the three zones of the second esterification reactor are set as follows: Zone 1: 210°C ℃, Zone 2 210 ℃ and Zone 3 220 ℃, pressure set to 0.1 bar for 4 h of second esterification reaction to obtain esterified liquid II; (4) inject the esterified liquid into the polycondensation reactor for a first polycondensation reaction for 3 h, the temperature of the first polycondensation reaction is 270 ℃, the pressure of the first polycondensation reaction is 1200 Pa; after the first polycondensation reaction is completed, a second polycondensation reaction is carried out for 1.5 h, the temperature of the first polycondensation reaction is 278 ℃, the pressure of the first polycondensation reaction is 200 Pa; the melt is conveyed to the spinning section by the screw, the spinning process parameters are: spinning temperature 285℃, cooling air temperature 28℃, side blowing air speed 0.4m / s, network pressure 0.30 MPa, spinning speed 4000 m / min, oiling rate 0.5%, first-stage stretching ratio is 2.4, the temperature of the stretching process is 90-235℃, and the spinning process is carried out to produce recycled matte cationic dyeable polyester fiber.

[0033] Comparative Example 1: The difference between Comparative Example 1 and Example 1 is that BHET was not depolymerized, and the following steps were performed: (1) 100,000 parts of BHET and 1.5 parts of titanium-silicon composite catalyst were added to the first esterification vessel. The temperature of the first esterification vessel was set to 250 °C and the pressure was set to 0.8 bar. Then, 10 parts of ether stabilizer (phenyl glycidyl ether) and 0.5 parts of antioxidant (phosphite) were added to carry out the first esterification reaction for 4 h to prepare esterification liquid one; (2) Esterification liquid one was injected into the second esterification vessel, and 2,300 parts of titanium dioxide were added and stirred for 0.5 h. Then, 2,000 parts of SIPE were added. The temperatures of the three zones of the second esterification vessel were set as follows: Zone 1 210 °C, Zone 2 210 °C and Zone 3 220 °C. The pressure was set to 0.1 bar to carry out the second esterification reaction for 4 h to obtain esterification liquid two; (3) The esterification liquid was injected into the polycondensation reactor to carry out a first polycondensation reaction for 3 h. The temperature of the first polycondensation reaction was 270 °C. The temperature of the first polycondensation reaction was 278 °C, and the pressure of the first polycondensation reaction was 1200 Pa. After the first polycondensation reaction was completed, the second polycondensation reaction was carried out for 1.5 h. The temperature of the first polycondensation reaction was 278 °C, and the pressure of the first polycondensation reaction was 200 Pa. The melt was granulated underwater to produce recycled matte cationic polyester chips.

[0034] Comparative Example 2: The difference between Comparative Example 2 and Example 1 is that no stabilizer was added, and the following steps were included: (1) 100,000 parts of BHET, 10,000 parts of ethylene glycol and 1.5 parts of titanium-silicon composite catalyst were added to the depolymerization reactor and heated to 230°C for stirring. The pressure was controlled at 60 KPa for depolymerization reaction for 3 h to remove 12,000 parts of ethylene glycol to obtain the polymer monomer. The degree of polymerization of the polymer monomer was 2~4; (2) The polymer monomer was added to the first esterification reactor. The temperature of the first esterification reactor was set to 250°C and the pressure was set to 0.8 bar. Then 0.5 parts of antioxidant (phosphite) were added for the first esterification reaction for 4 h to prepare esterification liquid one; (3) Esterification liquid one was injected into the second esterification reactor. Then 2,300 parts of titanium dioxide were added and stirred for 0.5 h. Then 2,000 parts of SIPE were added. The temperatures of the three zones of the second esterification reactor were set as follows: Zone 1 210°C, Zone 2 210°C and Zone 3 220°C. ℃, pressure set to 0.1 bar for 4 h of second esterification reaction to obtain esterified liquid II; (4) inject the esterified liquid into the polycondensation reactor for a first polycondensation reaction for 3 h, the temperature of the first polycondensation reaction is 270 ℃, the pressure of the first polycondensation reaction is 1200 Pa; after the first polycondensation reaction is completed, a second polycondensation reaction is carried out for 1.5 h, the temperature of the first polycondensation reaction is 278 ℃, the pressure of the first polycondensation reaction is 200 Pa; the melt is granulated underwater to make recycled matte cationic polyester chips.

[0035] Comparative Example 3: The difference between Comparative Example 3 and Example 1 is that no antioxidant was added. The following steps were included: (1) 100,000 parts of BHET, 10,000 parts of ethylene glycol and 1.5 parts of titanium-silicon composite catalyst were added to the depolymerization reactor and heated to 230°C for stirring. The pressure was controlled at 60 KPa for depolymerization reaction for 3 h to remove 12,000 parts of ethylene glycol to obtain the polymer monomer. The degree of polymerization of the polymer monomer was 2~4; (2) The polymer monomer was added to the first esterification reactor. The temperature of the first esterification reactor was set to 250°C and the pressure was set to 0.8 bar. Then 10 parts of ether stabilizer (phenyl glycidyl ether) were added for the first esterification reaction for 4 h to prepare esterification liquid one; (3) Esterification liquid one was injected into the second esterification reactor. Then 2,300 parts of titanium dioxide were added and stirred for 0.5 h. Then 2,000 parts of SIPE were added. The temperatures of the three zones of the second esterification reactor were set as follows: Zone 1 210°C, Zone 2 210°C, and Zone 2 210°C respectively. The second esterification reaction was carried out at ℃ and 220 ℃ in the third zone, and the pressure was set to 0.1 bar for 4 h to obtain esterified liquid II; (4) The esterified liquid was injected into the polycondensation reactor for a first polycondensation reaction for 3 h, the temperature of the first polycondensation reaction was 270 ℃, and the pressure of the first polycondensation reaction was 1200 Pa; after the first polycondensation reaction was completed, a second polycondensation reaction was carried out for 1.5 h, the temperature of the first polycondensation reaction was 278 ℃, and the pressure of the first polycondensation reaction was 200 Pa; the melt was granulated underwater to make recycled matte cationic polyester chips.

[0036] Comparative Example 4: The difference between Comparative Example 4 and Example 1 is that the amount of stabilizer used is too large. The stabilizer is 100 parts, including the following steps: (1) 100,000 parts of BHET, 10,000 parts of ethylene glycol and 1.5 parts of titanium-silicon composite catalyst are added to the depolymerization kettle and heated to 230°C for stirring. The pressure is controlled at 60 KPa for depolymerization reaction for 3 h to remove 12,000 parts of ethylene glycol to obtain the polymer monomer. The degree of polymerization of the polymer monomer is 2~4; (2) The polymer monomer is added to the first esterification kettle. The temperature of the first esterification kettle is set to 250°C and the pressure is set to 0.8 bar. Then 100 parts of ether-type stabilizer (phenyl glycidyl ether) and 0.5 parts of antioxidant (phosphite) are added for the first esterification reaction for 4 h to prepare esterification liquid one; (3) Esterification liquid one is injected into the second esterification kettle and 2,300 parts of titanium dioxide are added and stirred for 0.5 h. h, then add 2000 parts of SIPE, the temperature of the three zones of the second esterification reactor is set as follows: Zone 1 210 ℃, Zone 2 210 ℃ and Zone 3 220 ℃, and the pressure is set as 0.1 bar. The second esterification reaction is carried out for 4 h to obtain esterification liquid II; (4) The esterification liquid is injected into the polycondensation reactor for a first polycondensation reaction for 3 h. The temperature of the first polycondensation reaction is 270 ℃ and the pressure of the first polycondensation reaction is 1200 Pa. After the first polycondensation reaction is completed, the second polycondensation reaction is carried out for 1.5 h. The temperature of the first polycondensation reaction is 278 ℃ and the pressure of the first polycondensation reaction is 200 Pa. The melt is granulated underwater to make recycled matte cationic polyester chips.

[0037] Comparative Example 5: The difference between Comparative Example 5 and Example 1 is that the antioxidant is in excess, and the antioxidant is 5 parts. The steps include: (1) Adding 100,000 parts of BHET, 10,000 parts of ethylene glycol and 1.5 parts of titanium-silicon composite catalyst to the depolymerization reactor and heating to 230°C for stirring, controlling the pressure to 60 KPa for depolymerization reaction for 3 h to remove 12,000 parts of ethylene glycol to obtain the polymerized monomer, and the degree of polymerization of the polymerized monomer is 2~4; (2) Adding the polymerized monomer to the first esterification reactor, setting the temperature of the first esterification reactor to 250°C and the pressure to 0.8 bar, and then adding 10 parts of ether stabilizer (phenyl glycidyl ether) and 5 parts of antioxidant (phosphite) for the first esterification reaction for 4 h to prepare esterification liquid one; (3) Injecting esterification liquid one into the second esterification reactor, and then adding 2300 parts of titanium dioxide and stirring for 0.5 h. h, then add 2000 parts of SIPE, the temperature of the three zones of the second esterification reactor is set as follows: Zone 1 210 ℃, Zone 2 210 ℃ and Zone 3 220 ℃, and the pressure is set as 0.1 bar. The second esterification reaction is carried out for 4 h to obtain esterification liquid II; (4) The esterification liquid is injected into the polycondensation reactor for a first polycondensation reaction for 3 h. The temperature of the first polycondensation reaction is 270 ℃ and the pressure of the first polycondensation reaction is 1200 Pa. After the first polycondensation reaction is completed, the second polycondensation reaction is carried out for 1.5 h. The temperature of the first polycondensation reaction is 278 ℃ and the pressure of the first polycondensation reaction is 200 Pa. The melt is granulated underwater to make recycled matte cationic polyester chips.

[0038] Comparative Example 6: The difference between Comparative Example 6 and Example 1 is that the second esterification temperature is too high. The following steps are included: (1) 100,000 parts of BHET, 10,000 parts of ethylene glycol and 1.5 parts of titanium-silicon composite catalyst are added to the depolymerization kettle and heated to 230°C for stirring. The pressure is controlled at 60 KPa for depolymerization reaction for 3 h to remove 12,000 parts of ethylene glycol to obtain the polymer monomer. The degree of polymerization of the polymer monomer is 2~4; (2) The polymer monomer is added to the first esterification kettle. The temperature of the first esterification kettle is set to 250°C and the pressure is set to 0.8 bar. Then 10 parts of ether stabilizer (phenyl glycidyl ether) and 0.5 parts of antioxidant (phosphite) are added for the first esterification reaction for 4 h to make esterification liquid one; (3) Esterification liquid one is injected into the second esterification kettle. Then 2,300 parts of titanium dioxide are added and stirred for 0.5 h. Then 2,000 parts of SIPE are added. The temperatures of the three zones of the second esterification kettle are set as follows: Zone 1 250°C, Zone 2 ... ℃, Zone 2 250 ℃ and Zone 3 260 ℃, pressure set to 0.1 bar for 4 h of second esterification reaction to obtain esterification liquid II; (4) inject the esterification liquid into the polycondensation reactor for a first polycondensation reaction for 3 h, the temperature of the first polycondensation reaction is 270 ℃, the pressure of the first polycondensation reaction is 1200 Pa; after the first polycondensation reaction is completed, a second polycondensation reaction is carried out for 1.5 h, the temperature of the first polycondensation reaction is 278 ℃, the pressure of the first polycondensation reaction is 200 Pa; the melt is granulated underwater to make recycled matte cationic polyester chips. Comparative Example 7: The difference between Comparative Example 7 and Example 1 is that: the amount of ethylene glycol is too large, including the following steps: (1) 100,000 parts of BHET, 100,000 parts of ethylene glycol and 1.5 parts of titanium silicon composite catalyst are added to the depolymerization reactor and heated to 230 ℃ for stirring, and the pressure is controlled at 60 KPa for depolymerization reaction 3 h. h Remove 12,000 parts of ethylene glycol to obtain the polymer monomer, the degree of polymerization of the polymer monomer is 2~4; (2) Add the polymer monomer to the first esterification kettle, the temperature of the first esterification kettle is set to 250 ℃, the pressure is set to 0.8 bar, and then add 10 parts of ether stabilizer (phenyl glycidyl ether) and 0.5 parts of antioxidant (phosphite) to carry out the first esterification reaction for 4 h to obtain esterification liquid one; (3) Inject esterification liquid one into the second esterification kettle, then add 2,300 parts of titanium dioxide and stir for 0.5 h, then add 2,000 parts of SIPE, the temperature of the three zones of the second esterification kettle is set to: zone one 210 ℃, zone two 210 ℃ and zone three 220 ℃, the pressure is set to 0.1 bar to carry out the second esterification reaction for 4 h to obtain esterification liquid two; (4) Inject the esterification liquid into the polycondensation reactor to carry out a first polycondensation reaction for 3 h, the temperature of the first polycondensation reaction is 270 ℃, the pressure of the first polycondensation reaction is 1200 Pa; after the first stage of polycondensation reaction, a second stage of polycondensation reaction is carried out for 1.5 h. The temperature of the first stage of polycondensation reaction is 278 ℃ and the pressure of the first stage of polycondensation reaction is 200 Pa; the melt is granulated underwater to produce recycled matte cationic polyester chips.

[0039] Test Example: The properties of the recycled matte cationic polyester chips obtained in Examples 1-5 and Comparative Examples 1-7 were tested. The test methods were in accordance with the methods disclosed in "FZ / T 51019-2021 Polyester Fiber Masterbatch". The test items included intrinsic viscosity, melting point end carboxyl groups, diethylene glycol aggregates, b-value, and melt pressure filtration value (DF value). The test results are shown in Table 1. Table 1 Test Results of Recycled Matte Cationic Polyester Chips As shown in Table 1, the DF values ​​of the recycled matte cationic polyesters obtained in Examples 1-5 are 0.26-0.35, which are comparable to those of the bright cationic polyesters. This indicates that the recycled matte cationic polyesters obtained in this invention have good titanium dioxide distribution in the melt and no agglomerated particles in the melt, which will not cause the melt pressure to rise and can be used for melt direct spinning.

[0040] In Comparative Example 1, the recycled BHET was not depolymerized. The results showed that the resulting recycled matte cationic polyester had a melt DF value of 0.9, 4.8 aggregated particles / mg, and a b-value of 6.5. From the results of Comparative Example 1 and Example 1, it can be seen that the recycled matte cationic polyester obtained by not depolymerizing BHET has a large color difference value, and the high melt pressure makes direct melt spinning impossible. Further analysis revealed that the reason for these phenomena is that the undepolymerized BHET has a high degree of polymerization. The higher the degree of polymerization of BHET, the lower its polarity, which significantly increases the difficulty of polymerization with the three monomers. The three monomers are more prone to self-polymerization. Furthermore, the microbranched network structure formed by the stabilizer and the undepolymerized BHET is more loose, and its spatial confinement effect on the three monomers and titanium dioxide is limited, failing to completely prevent the formation of aggregated particles in the polymer. In addition, the high impurity content in the undepolymerized BHET leads to a high color difference value in the resulting matte cationic polyester.

[0041] Comparative Examples 2 and 3 represent technical solutions without stabilizers and antioxidants, respectively. The results showed that stabilizers have a highly significant effect on the formation of aggregated particles and the increase in DF value. Antioxidants also have a certain effect on the formation of aggregated particles and DF value, but the effect is relatively small. Antioxidants, on the other hand, have a significant effect on reducing the polyester b-value. Furthermore, the results from Comparative Examples 1, 2, 3, and Example 1 indicate that stabilizers, antioxidants, and BHET depolymerization must all meet certain conditions simultaneously to ensure that the recycled matte cationic polyester melt is completely free of aggregated particles, thus fully meeting the requirements for melt spinning.

[0042] Comparative Examples 4 and 5 employed techniques with excessive stabilizers and antioxidants. The results showed that excessive stabilizer led to the formation of aggregated particles in the regenerated matte cationic polyester melt, resulting in a significant increase in the DF value and b-value. This is because excessive stabilizer causes over-branching, leading to reduced melt fluidity, the formation of gels in the polymerization system by the three monomers, and significant yellowing of the polyester. Excessive anti-stabilizers, on the other hand, inhibited catalyst activity, making polyester polycondensation and thickening difficult.

[0043] Comparative Example 6 investigated the effect of excessively high esterification temperature on melt pressure increase. When the esterification temperature is too high, titanium dioxide is prone to agglomeration, and side reactions such as self-polymerization are likely to occur after the addition of the three monomers. Ultimately, the number of agglomerated impurities in the melt increases, and the melt pressure rises.

[0044] Comparative Example 7 investigated the amount of ethylene glycol used during the depolymerization of BHET. The results showed that adding excessive ethylene glycol during depolymerization led to problems such as lower acid value after esterification, longer polymerization residence time, difficulty in thickening during polycondensation resulting in lower product viscosity, increased agglomerates leading to increased melt pressure, and a yellowish polyester color.

[0045] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Any simple modifications, alterations, and equivalent transformations made to the above embodiments based on the technical essence of the present invention shall still fall within the protection scope of the present invention.

Claims

1. A method for preparing a recycled matte cationic dyeable polyester, characterized in that, Includes the following steps: BHET is alcoholyzed to produce a polymerizable monomer with a degree of polymerization of 2-4. The polymerizable monomer, ether stabilizer, and oxidant are then subjected to a first esterification reaction to produce ester one. Titanium dioxide and three monomers are then added to the ester to conduct a second esterification reaction to produce ester two. Ester two is then subjected to a first polycondensation reaction and a second polycondensation reaction, and the melt is directly spun to produce a recycled matte cationic dyeable polyester.

2. The preparation method according to claim 1, characterized in that, The ether-type stabilizer is one or more of phenyl glycidyl ether, trimethoxy(3-(glycidyl)propyl)silane, bisphenol A bisglycidyl ether, and tetra(phenyl glycidyl ether).

3. The preparation method according to claim 1 or 2, characterized in that, The mass ratio of ether stabilizer to BHET is 1:5000~10000.

4. The preparation method according to claim 1, characterized in that, The antioxidant is one or more of the following: phosphite, antioxidant 1010, antioxidant 1076, and antioxidant 1098.

5. The preparation method according to claim 1 or 4, characterized in that, The mass ratio of antioxidant to BHET is 1:100000~300000.

6. The preparation method according to claim 1, characterized in that, The mass ratio of titanium dioxide to BHET is 0.2~3:

100.

7. The preparation method according to claim 1, characterized in that, The mass ratio of the three monomers to BHET is 1~4:100, and the three monomers are one of SIPA, SIPE and SIPE.

8. The preparation method according to claim 1, characterized in that, The alcoholysis conditions include: depolymerization temperature of 220~250 ℃, pressure of 40-80 Kpa, and a mass ratio of ethylene glycol to BHET of 0.05~0.1:

1.

9. The preparation method according to claim 1, characterized in that, The temperature of the first esterification reaction is 240~260 ℃, the pressure of the first esterification reaction is 0.4~1 bar, and the time of the first esterification reaction is 3~5 h; the temperature of the second esterification reaction is 210~250 ℃, the pressure of the second esterification reaction is 0.05~0.5 bar, and the time of the second esterification reaction is 3~5 h.

10. The preparation method according to claim 1, characterized in that, The temperature of the first-stage polycondensation is 270~280 ℃, the pressure of the first-stage polycondensation is 700~1200 Pa, and the reaction time of the first-stage polycondensation is 2~5 h; the temperature of the second-stage polycondensation is 270~280 ℃, the pressure of the second-stage polycondensation is 100~300 Pa, and the reaction time of the second-stage polycondensation is 1~3 h.

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