HIGH-VISCOSITY PTT POLYMERIZATION REACTOR AND METHOD FOR PREPARING DIRECT MELT-SPUN HIGH-VISCOSITY PTT/LOW-VISCOSITY PET TWO-COMPONENT ELASTIC FIBER

Abstract

The present disclosure relates to a high-viscosity PTT polymerization reactor and a method for preparing direct melt-spun high-viscosity PTT/low-viscosity PET two-component elastic fiber. A cage disc reactor combinations is designed in the low viscosity zone of the polymerization reactor, a circular channel is designed in the middle portion of the disc reactor combinations, and an agitating shaft is disposed in both the med-high viscosity zone and the high viscosity zone. The cage disc reactor combinations is designed with a material propelling part. The high-viscosity PTT production line comprises a first esterification reactor, a second esterification reactor, a first prepolymerization reactor, a second prepolymerization reactor, and a high-viscosity PTT polymerization reactor. The prepared elastic fiber can reach a fiber strength of 2.63.2 cN/dtex, a crimp shrinkage rate of 25%75%, and a crimp stability of 82%90%.

Claims

1. A high-viscosity PTT polymerization reactor, used to prepare a high-viscosity PTT melt for preparing a high-viscosity PTT/low-viscosity PET two-component elastic fiber, wherein, the high-viscosity PTT polymerization reactor is a horizontal polymerization reactor, and comprises a main body containing a chamber internally, the main body comprises a low viscosity zone, a med-high viscosity zone and a high viscosity zone disposed in sequence along the axial direction of the high-viscosity PTT polymerization reactor, the viscosity of the PTT melt in the low viscosity zone, the med-high viscosity zone and the high viscosity zone increases in sequence; the low viscosity zone and the med-high viscosity zone are both provided with disc reactors combinations, and the high viscosity zone is provided with a plurality of single-disc reactors; the high-viscosity PTT polymerization reactor further comprises a rotating shaft disposed in the front end of the low viscosity zone, a cage disc reactor combinations is designed in the low viscosity zone of the high-viscosity PTT polymerization reactor, and comprises a plurality of disc reactors combinations, and an outer cage frame fixedly connected to outer edges of the disc reactors combinations, and the rotating shaft drives the outer cage frame and the plurality of disc reactors combinations in the low viscosity zone to rotate; there is no agitating shaft disposed in an axial region corresponding to the disc reactors combinations in the low viscosity zone, and a circular channel is designed in the middle portion of the disc reactors combinations; there is an agitating shaft disposed in both the med-high viscosity zone and the high viscosity zone, and the disc reactors in the med-high viscosity zone and the high viscosity zone pass through the agitating shaft; the outer cage frame comprises a cage shaped part with a gear shaped in front end, and a material propelling part extending along the axial direction of the high-viscosity PTT polymerization reactor from each gear bend of the cage shaped part, and the outer cage frame is fixedly connected to the rotating shaft.

2. The high-viscosity PTT polymerization reactor according to claim 1, wherein, the length of the low viscosity zone is half of the length of the high-viscosity PTT polymerization reactor, and the total length of the med-high viscosity zone and the high viscosity zone is half of the length of the high-viscosity PTT polymerization reactor.

3. The high-viscosity PTT polymerization reactor according to claim 1, wherein, the length of the agitating shaft disposed in the med-high viscosity zone and the high viscosity zone is half of the length of the high-viscosity PTT polymerization reactor.

4. The high-viscosity PTT polymerization reactor according to claim 1, wherein, the high-viscosity PTT polymerization reactor further comprises a prepolymer inlet located at the bottom of the front end of the low viscosity zone and a high-viscosity PTT melt outlet located at the bottom of the rear end of the high viscosity zone, wherein the high-viscosity PTT melt outlet is trumpet-shaped.

5. The high-viscosity PTT polymerization reactor according to claim 4, wherein, the cross-section of the material propelling part is in a wedge shape, and the thick end of the wedge is oriented towards the direction of rotation of the disc reactors; and/or, there are 812 material propelling parts.

6. The high-viscosity PTT polymerization reactor according to claim 1, wherein, the disc reactors in the med-high viscosity zone have a plurality of disc combinations, namely a 4-disc combination, a 3-disc combination and a 2-disc combination in sequence from front to rear; in the 2-disc combinations in the med-high viscosity zone, the distances between the disc combinations and between their two discs in each combination gradually increases from front to rear; the total number of disc reactors in the med-high viscosity zone and the high viscosity zone is 2535; there are 812 single-disc reactors in the high viscosity zone, with the diameter of the disc reactors gradually decreasing from front to rear, and the diameter of the last disc reactor is 88%-92% of the diameter of the first disc reactor in the high viscosity zone; the high viscosity zone is further provided with a composite scraper, which comprises an axial scraper for scraping off the melt on the agitating shaft, a wall scraper for scraping off the melt on the inner wall of the high-viscosity PTT polymerization reactor, and a disc scraper for scraping off the melt on the disc reactors, the disc scraper being arranged in two layers and controlling the thickness of material on the disc reactors to not exceed 30 mm.

7. A method for preparing a high-viscosity PTT/low-viscosity PET two-component elastic fiber, the two-component elastic fiber containing a high-viscosity PTT component and a low-viscosity PET component, the viscosity of the high-viscosity PTT component being greater than that of the low-viscosity PET component, wherein, the preparation method comprises steps of preparing a high-viscosity PTT melt and a low-viscosity PET melt separately, and spinning the high-viscosity PTT melt and the low-viscosity PET melt through the same parallel composite spinning assembly to obtain the two-component elastic fiber; the viscosity of the high-viscosity PTT melt is greater than the viscosity of the low-viscosity PET melt; the step of preparing a high-viscosity PTT melt comprises sequentially passing terephthalic acid and 1,3-propanediol through a first esterification reactor and a second esterification reactor for esterification reactions, through a first prepolymerization reactor and a second prepolymerization reactor for prepolymerization reactions to give a PTT prepolymer, and polymerizing the PTT prepolymer in the high-viscosity PTT polymerization reactor to obtain the high-viscosity PTT melt, the high-viscosity PTT polymerization reactor is the high-viscosity PTT polymerization reactor according to claim 1; the step of preparing low-viscosity PET melt comprises sequentially passing terephthalic acid and ethylene glycol through a first esterification reactor and a second esterification reactor for esterification reactions, through a first prepolymerization reactor and a second prepolymerization reactor for prepolymerization reactions to give a PET prepolymer, and polymerizing the PET prepolymer in a low-viscosity PET final polymerization reactor to obtain the low-viscosity PET melt.

8. The preparation method according to claim 7, wherein, in percent by weight, the two-component elastic fiber contains 35%-65% of high-viscosity PTT component and 65%-35% of low-viscosity PET component; and/or, the high-viscosity PTT melt has an intrinsic viscosity of 0.921.16, and a dynamic viscosity of 3201200 Pa.Math.s; the low-viscosity PET melt has an intrinsic viscosity of 0.450.55, and a dynamic viscosity of 90240 Pa.Math.s.

9. The preparation method according to claim 7, wherein, in the same parallel composite spinning assembly, the high-viscosity PTT melt has a dynamic viscosity of 350800 Pa.Math.s, and the low-viscosity PET melt has a dynamic viscosity of 70220 Pa.Math.s.

10. The preparation method according to claim 7, wherein, the preparation method controls the rotation rate of the rotating shaft in the low viscosity zone to be 0-5.5 rpm; and/or, the preparation method controls the agitation rate of the agitating shaft in the med-high viscosity zone and the high viscosity zone to be 0-3.0 rpm.

11. The preparation method according to claim 7, wherein, the PTT prepolymer introduced into the high-viscosity PTT polymerization reactor has an intrinsic viscosity of 0.2800.350.

12. The preparation method according to claim 7, wherein, when preparing the high-viscosity PTT melt, the preparation method further comprises a step of adding an esterification catalyst to the first esterification reactor before carrying out the esterification reaction, wherein the esterification catalyst is selected from tetrabutyl titanate and tetraisopropyl titanate.

13. The preparation method according to claim 12, wherein, the second esterification reactor used for preparing the high-viscosity PTT melt is a horizontal reactor, and comprises three compartments arranged in sequence from front to rear, and when preparing the high-viscosity PTT melt, the preparation method further comprises a step of adding a catalyst blocking agent to the second compartment from front to rear of the second esterification reactor after the esterification reaction in the first compartment from front to rear of the second esterification reactor has completed, to deactivate the esterification catalyst, where the catalyst blocking agent is selected from trimethyl phosphate and phosphoric acid, and the mass of the catalyst blocking agent accounts for 15-30 ppm of the mass of the high-viscosity PTT melt.

14. The preparation method according to claim 13, wherein, when preparing the high-viscosity PTT melt, the preparation method further comprises a step of adding a polymerization catalyst to the third compartment from front to rear of the second esterification reactor; the polymerization catalyst is prepared by reacting a titanate with a protonic acid under anhydrous conditions, removing alcohol by-products, and dissolving the reaction system in 1,3-propanediol.

15. The preparation method according to claim 14, wherein, the titanate is selected from the group consisting of tetrabutyl titanate, tetraisopropyl titanate, and tetra (2-ethylhexyloxy) titanate; and/or, the protonic acid is selected from the group consisting of formic acid, acetic acid, propionic acid, oxalic acid, malonic acid, succinic acid, citric acid, tripolyphosphoric acid, polyphosphoric acid, and combinations thereof; and/or, the mass ratio of the titanate to the protonic acid is 1:(0.5-2.0); and/or, in the polymerization catalyst, the mass percentage of titanium element is 1.0%-3.0%.

16. The preparation method according to claim 14, wherein, the mass of titanium element in the esterification catalyst accounts for 130 ppm of the mass of the high-viscosity PTT melt; and/or, the mass of titanium element in the polymerization catalyst accounts for 30100 ppm of the mass of the high-viscosity PTT melt.

17.-20. (canceled)

21. The preparation method according to claim 7, wherein, the low-viscosity PET final polymerization reactor is a horizontal polymerization reactor, and the length-to-diameter ratio thereof is (2.22.8):1.0.

22. (canceled)

23. The preparation method according to claim 7, wherein, when preparing the high-viscosity PTT melt, the molar ratio of terephthalic acid to 1,3-propanediol is 1:(1.051.65); and/or, the esterification reaction in the first esterification reactor used for preparing the high-viscosity PTT melt is carried out at 250 C.252 C.; and/or, the esterification reaction in the first esterification reactor used for preparing the high-viscosity PTT melt is carried out at a pressure of 0.71.8 kgf/cm.sup.2.

24. (canceled)

25. A high-viscosity PTT/low-viscosity PET two-component elastic fiber prepared by the preparation method according to claim 7.

26. The high-viscosity PTT/low-viscosity PET two-component elastic fiber according to claim 25, wherein, the two-component elastic fiber has a strength of 2.63.2 cN/dtex, a crimp shrinkage rate of 25%75%, and a crimp stability of 82%90%.

27.-46. (canceled)

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0081] FIG. 1 is a schematic diagram of a polymerization system with two production lines used in an embodiment of the present disclosure;

[0082] FIG. 2 is a schematic inner structure diagram of a high-viscosity PTT polymerization reactor used in an embodiment of the present disclosure;

[0083] FIG. 3 is a schematic diagram of disc reactors and a material propelling part of the high-viscosity PTT polymerization reactor used in an embodiment of the present disclosure;

[0084] FIG. 4 is another schematic inner structure diagram of the high-viscosity PTT polymerization reactor used in an embodiment of the present disclosure;

[0085] FIG. 5 is a schematic structure diagram of the disc reactors and an outer cage frame of the high-viscosity PTT polymerization reactor used in an embodiment of the present disclosure;

[0086] FIG. 6 is a schematic structure diagram of a high-viscosity PTT polymerization reactor used in an embodiment of the present disclosure;

[0087] FIG. 7 is a schematic structure diagram of a composite scraper in the high viscosity zone in the high-viscosity PTT polymerization reactor used in an embodiment of the present disclosure;

[0088] Wherein, 1low viscosity zone, 2med-high viscosity zone, 3high viscosity zone, 4composite scraper, 5disc scraper, 6axial scraper, 7wall scraper, 8agitating shaft, 9disc reactor, 10first esterification reactor, 11second esterification reactor, 12first prepolymerization reactor, 13second prepolymerization reactor, 14high-viscosity PTT polymerization reactor, 15low-viscosity PET final polymerization reactor, 16melt pump, 17prepolymer inlet, 18high-viscosity PTT melt outlet, 19outer cage frame, 20rotating shaft, 21cage shaped part, 22material propelling part, 23supporting seat.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

[0089] The present disclosure is further explained in detail below in combination with specific embodiments; it should be understood that, those embodiments are to explain the basic principle, major features and advantages of the present disclosure, and the present disclosure is not limited by the scope of the following embodiments; the implementation conditions employed by the embodiments may be further adjusted according to particular requirements, and undefined implementation conditions usually are conditions in conventional experiments. In the following embodiments, unless otherwise specified, all raw materials are basically commercially available or prepared by conventional methods in the field.

[0090] The embodiments described above are only for illustrating the technical concepts and features of the present disclosure, and are intended to make a person familiar with the technology being able to understand the content of the present disclosure and thereby implement it, and should not limit the protective scope of this disclosure. Any equivalent variations or modifications according to the spirit of the present disclosure should be covered by the protective scope of the present disclosure.

[0091] The present disclosure will be further described in conjunction with the accompanying drawings and preferred embodiments of the present disclosure. In the following embodiments, it should be noted that terms such as orientations front and rear are based on the flow direction of the materials, with the directions in which the material flows first being the front and the direction in which it flows later being the rear. For example, in FIG. 1, the term front refers to the left side of FIG. 1, and the term rear refers to the right side of FIG. 1, therefore, the orientation and positional relationship described in the present disclosure are only for the convenience of describing the disclosure and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, only have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation of the present disclosure.

[0092] As shown in FIG. 1, the preparation of a high-viscosity PTT/low-viscosity PET two-component elastic fiber in an embodiment uses two production lines. The first production line prepares the high-viscosity PTT melt, as shown in the first row of FIG. 1, and this production line comprises a five-reactor system consisting of a first esterification reactor 10, a second esterification reactor 11, a first prepolymerization reactor 12, a second prepolymerization reactor 13, and a high-viscosity PTT polymerization reactor 14. The five reactors are in communication through necessary pipelines, and necessary vacuum systems and the like are in communication with the five reactors. Wherein, a melt pump 16 and filters A and B are provided between the second prepolymerization reactor 13 and the high-viscosity PTT polymerization reactor 14, and in the actual production process, the filters A and B are not turned on at the same time, for example, the filter A may be turned on first, and after the device runs for a period of time, the filter B can be switched to use, at this time, the filter A can be cleaned.

[0093] The second production line prepares the low-viscosity PET melt, as shown in the second row of FIG. 1, and this production line comprises another five-reactor system consisting of a first esterification reactor 10, a second esterification reactor 11, a first prepolymerization reactor 12, a second prepolymerization reactor 13, and a low-viscosity PET final polymerization reactor 15. The five reactors are in communication through necessary pipelines, and necessary vacuum systems and the like are in communication with the five reactors. Wherein, a melt pump 16 and filters A and B are provided between the second prepolymerization reactor 13 and the low-viscosity PET final polymerization reactor 15, and in the actual production process, the filters A and B are not turned on at the same time, for example, the filter A may be turned on first, and after the device runs for a period of time, the filter B can be switched to use, at this time, the filter A can be cleaned.

[0094] For the high-viscosity PTT polymerization reactor 14, as shown in FIG. 6, it is a horizontal polymerization reactor, and comprises a main body containing a chamber internally, the main body comprises a low viscosity zone 1, a med-high viscosity zone 2 and a high viscosity zone 3 disposed in sequence along the axial direction of the high-viscosity PTT polymerization reactor, the viscosity of the PTT melt in the low viscosity zone 1, the med-high viscosity zone 2 and the high viscosity zone 3 increases in sequence; the low viscosity zone 1 and the med-high viscosity zone 2 are both provided with disc reactors 9 combinations, and the high viscosity zone 3 is provided with a plurality of single disc reactors 9.

[0095] As shown in FIGS. 2-6, the high-viscosity PTT polymerization reactor 14 further comprises a rotating shaft 20 disposed in the front end of the low viscosity zone 1, a cage disc reactor combinations is designed in the low viscosity zone 1 of the high-viscosity PTT polymerization reactor 14, and comprises a plurality of disc reactors 9 combinations, and an outer cage frame 19 fixedly connected to outer edges of the disc reactors 9 combinations, and the rotating shaft 20 drives the outer cage frame 19 and the plurality of disc reactors 9 combinations in the low viscosity zone 1 to rotate; there is no agitating shaft disposed in an axial region corresponding to the disc reactors 9 combinations in the low viscosity zone 1, and a circular channel is designed in the middle portion of the disc reactors 9 combinations; there is an agitating shaft 8 disposed in both the med-high viscosity zone 2 and the high viscosity zone 3, and the disc reactors 9 in the med-high viscosity zone 2 and the high viscosity zone 3 pass through the agitating shaft 8.

[0096] The length of the low viscosity zone 1 is half of the length of the high-viscosity PTT polymerization reactor 14, and the total length of the med-high viscosity zone 2 and the high viscosity zone 3 is half of the length of the high-viscosity PTT polymerization reactor 14. The length of the agitating shaft 8 disposed in the med-high viscosity zone 2 and the high viscosity zone 3 is half of the length of the high-viscosity PTT polymerization reactor 14. It should be emphasized that half in the present disclosure is not an exact value of half, but refer to a value roughly or around half, approximately equal to half.

[0097] The high-viscosity PTT polymerization reactor 14 further comprises a prepolymer inlet 17 located at the bottom of the front end of the low viscosity zone 1 and a high-viscosity PTT melt outlet 18 located at the bottom of the rear end of the high viscosity zone 3, wherein the high-viscosity PTT melt outlet 18 is trumpet-shaped.

[0098] As shown in FIGS. 2-5, the outer cage frame 19 comprises a cage shaped part 21 with a gear shaped in front end, and a material propelling part 22 extending along the axial direction of the high-viscosity PTT polymerization reactor 14 from each gear bend of the cage shaped part 21, and the outer cage frame 19 is fixedly connected to the rotating shaft 20. The cross-section of the material propelling part 22 is in a wedge shape, and the thick end of the wedge is oriented towards the direction of rotation of the disc reactors 9. There are 812 material propelling parts 22.

[0099] The disc reactors 9 in the med-high viscosity zone 2 have a plurality of disc combinations designs, namely a 4-disc combination, a 3-disc combination and a 2-disc combination in sequence from front to rear; in the 2-disc combinations design in the med-high viscosity zone 2, the distances between the disc combinations and between their two discs in each combination gradually increases from front to rear; the total number of disc reactors 9 in the med-high viscosity zone 2 and the high viscosity zone 3 is 2535; there are 812 single-disc reactors 9 in the high viscosity zone, with the diameter of the disc reactors 9 gradually decreasing from front to rear, and the diameter of the last disc reactor 9 is 88%-92% of the diameter of the first disc reactor 9 in the high viscosity zone 3.

[0100] As shown in FIG. 7, the high viscosity zone 3 is further provided with a composite scraper 4, the composite scraper 4 comprises an axial scraper 6 for scraping off the melt on the agitating shaft, a wall scraper 7 for scraping off the melt on the inner wall of the high-viscosity polymerization reactor 14, and a disc scraper 5 for scraping off the melt on the disc reactors 9, the disc scraper 5 is arranged in two layers and controls the thickness of the material on the disc reactors 9 to not exceed 30 mm.

[0101] As shown in FIG. 6, the length-to-diameter ratio of the high-viscosity PTT polymerization reactor 14 is (3.54.0):1.0.

[0102] As shown in FIG. 1, the second esterification reactor 11 used for preparing the high-viscosity PTT melt is a horizontal reactor, and comprises three compartments arranged in sequence from front to rear. The first esterification reactor 10 and the second esterification reactor 11 used for preparing the high-viscosity PTT melt are both provided with distillation columns at their upper ends. The distillation column at the upper end of the second esterification reactor 11 is disposed in the third compartment from front to rear of the second esterification reactor 11.

[0103] The high-viscosity PTT polymerization reactor 14 further comprises a steam feed inlet for introducing superheated 1,3-propanediol steam at the top of the main body located in the rear end portion of the low viscosity zone 1, the rear end portion of the med-high viscosity zone 2 and the rear end portion of the high viscosity zone 3. The high-viscosity PTT polymerization reactor is connected to a vacuum pump, and the ultimate vacuum degree of the vacuum pump is 6075 Pa, the pumping rate of the vacuum pump is 70220 kg/h, and the vacuum degree in the high-viscosity PTT polymerization reactor 14 is 90140 Pa.

[0104] The high-viscosity PTT polymerization reactor 14 is connected to a vacuum pump, and the vacuum pump is a liquid ring pump, with its inlet being provided with a chilled water device for cooling the gas. The melt pumps transport the high-viscosity PTT melt and the low-viscosity PET melt, with their outlets being provided with melt coolers.

[0105] A dynamic mixer and a filter are arranged downstream of the high-viscosity PTT polymerization reactor 14 and the low-viscosity PET final polymerization reactor 15 and upstream of the same spinning assembly; a viscosity reducer injection system is arranged upstream of the dynamic mixer.

[0106] Necessary melt pumps, vacuum pumps, and conveying pipeline, etc. may be provided on the pipelines connecting the five reactors of the two production lines.

[0107] The same spinning assembly is a composite spinning box, and the high-viscosity PTT polymerization reactor 14 is arranged at the top of the composite spinning box to shorten the conveying distance of the melt, especially the high-viscosity PTT melt. The composite spinning box comprises a spinneret.

Embodiment 1

[0108] This embodiment provided a method for preparing a high-viscosity PTT/low-viscosity PET two-component elastic fiber, which comprises specific steps of:

[0109] The method for preparing a polymerization catalyst used in this embodiment was as follows:

[0110] Tetrabutyl titanate was mixed with acetic acid to carry out an exothermic reaction, with a mass ratio of 1:1, after the reaction, a titanium tetraacetate complex and a large amount of n-butanol byproduct were generated, the reaction system was vacuum purified at 50 C. for 2.0 hours to remove the generated n-butanol, and cooled to room temperature, 1,3-propanediol was injected into the reaction system under agitating to prepare a 1,3-propanediol solution of the polymerization catalyst, the injection amount of 1,3-propanediol was controlled so that the content of titanium element in the polymerization catalyst solution was 1.0%.

[0111] A polymerization device using the two production lines mentioned above was used to synthesize the high-viscosity PTT melt and the low-viscosity PET melt, respectively.

[0112] For the high-viscosity PTT melt production line, the device comprises a pulping reactor, a first esterification reactor (with a distillation column at its upper end), a second esterification reactor (with a three-chamber structure, and a distillation column at its upper end), a first prepolymerization reactor, a second prepolymerization reactor, a high-viscosity PTT polymerization reactor, and supporting vacuum systems and melt transport systems.

[0113] For the low-viscosity PET melt production line, the device comprises a pulping reactor, a first esterification reactor, a second esterification reactor, a first prepolymerization reactor, a second prepolymerization reactor, a low-viscosity PET final polymerization reactor, and supporting vacuum systems and melt transport systems.

Synthesis of High-Viscosity PTT Melt:

[0114] Purified terephthalic acid and 1,3-propanediol were sequentially subjected to esterification reactions in the first esterification reactor and the second esterification reactor, and prepolymerization reactions in the first prepolymerization reactor and the second prepolymerization reactor to give a PTT prepolymer, which was polymerized in the high-viscosity PTT polymerization reactor to give a high-viscosity PTT melt. The molar ratio of purified terephthalic acid to 1,3-propanediol was 1:1.25. The esterification temperature in the first esterification reactor was 250 C.252 C., and the esterification was carried out at a pressure of 0.70.8 kgf/cm.sup.2 (this pressure refers to the actual pressure in the first esterification reactor, which is lower than atmospheric pressure, that is, the reaction the first esterification reactor is in fact carried out under reduced pressure). The esterification temperature in the second esterification reactor was 250 C.252 C., and the esterification was carried out under normal pressure. An esterification catalyst tetrabutyl titanate was added to the first esterification reactor, with a usage amount such that the mass of titanium element was 30 ppm of the mass of the melt. A blocking agent for the esterification catalyst, trimethyl phosphate, is introduced into the second compartment from front to rear of the second esterification reactor, with a mass of 100 ppm of the total mass of the high-viscosity PTT melt, to deactivate the esterification catalyst. The polymerization catalyst prepared above was introduced into the third compartment from front to rear of the second esterification reactor, with a usage amount such that the mass of titanium element was 70 ppm of the mass of the melt. Before the second esterification reaction in the second esterification reactor is carried out, an ordinary titanium dioxide matting agent color paste (prepared by grinding and dispersing titanium dioxide and ethylene glycol, with titanium dioxide accounting for 10 wt % and ethylene glycol accounting for 90 wt %) is added into the second esterification reactor through corresponding pipelines, its usage amount is such that titanium dioxide accounts for 0.32% of the total mass of the melt. The reaction temperature in the first prepolymerization reactor was 250 C., and the vacuum degree was 9.9 kPa; the reaction temperature in the second prepolymerization reactor was 251 C., and the vacuum degree was 1.15 kPa; the temperature at the melt outlet of the high-viscosity PTT polymerization reactor was 252.6 C., and the vacuum degree in the high-viscosity PTT polymerization reactor was 138 Pa. And the steam feed inlet of the high-viscosity PTT polymerization reactor is sprayed with superheated 1,3-propanediol through a steam jet pump, and for the large amount of cyclic dimers generated during the polymerization process, a double polycondensation circulating cooling system is provided to facilitate the cleaning of the vacuum system. The high-viscosity PTT melt discharged ultimately from the melt outlet of the high-viscosity PTT polymerization reactor had an intrinsic viscosity of 0.922, and a dynamic viscosity of 375 Pa.Math.s, where the intrinsic viscosity was determined in a mixed solvent of phenol and tetrachloroethane in a volume ratio of 3:2. The dynamic viscosity was measured at 252 C.

Synthesis of Low-Viscosity PET Melt:

[0115] Purified terephthalic acid and ethylene glycol were sequentially subjected to esterification reactions in the first esterification reactor and the second esterification reactor, and prepolymerization reactions in the first prepolymerization reactor and the second prepolymerization reactor to give a PET prepolymer, which was polymerized in the low-viscosity PET final polymerization reactor to give a low-viscosity PET melt. Both the catalysts for esterification and polymerization were ethylene glycol antimony, and its usage amount was such that the mass of antimony element in it was 210 ppm of the total mass of the PET melt, and this catalyst was added to the reaction system in the first esterification reactor. The first esterification reactor was for esterification under pressurization, and the second esterification reactor was for esterification at atmospheric pressure. Before the second esterification reaction in the second esterification reactor is carried out, an ordinary titanium dioxide matting agent color paste (prepared by grinding and dispersing titanium dioxide and ethylene glycol, with titanium dioxide accounting for 10 wt % and ethylene glycol accounting for 90 wt %) is added into the second esterification reactor through corresponding pipelines, its usage amount is such that titanium dioxide accounts for 0.30% of the total mass of the melt. By adjusting the reaction conditions (including the vacuum degree of the low-viscosity PET final polymerization reactor, the agitating rate of the low-viscosity PET final polymerization reactor, the polymerization temperature of the low-viscosity PET final polymerization reactor, etc., the vacuum degree was controlled at 180200 Pa, the agitating rate was 2.22.5 rpm in the med-high viscosity zone and high viscosity zone; the polymerization temperature ranged from 272 to 273 C.), the resulting low-viscosity PET melt had an intrinsic viscosity of 0.452, and a dynamic viscosity of 90 Pa.Math.s. The intrinsic viscosity was measured in a mixed solvent of phenol and tetrachloroethane in a volume ratio of 3:2. The dynamic viscosity was measured at 270 C.

Spinning:

[0116] Finally, the high-viscosity PTT melt and the low-viscosity PET melt were transported through the melt transport in a mass ratio of 5:5 to the composite spinning box, and then spun through the composite spinning spinneret to obtain a high-viscosity PTT/low-viscosity PET two-component elastic fiber.

[0117] Wherein, the parameters of reaction conditions, high-viscosity PTT melt, and low-viscosity PET melt are shown in Tables 1-5. Wherein, - indicates none. The melt chip performance was tested using GB/T 14190-2017 standard, where the intrinsic viscosity was measured in a mixed solvent of phenol and tetrachloroethylene in a volume ratio of 3:2; moisture, ash content, ferrum content, and agglomerated particles refer to the content of water, ash, Fe element, and agglomerated particles in the polyester in mass fraction, respectively.

Embodiments 2-13

[0118] Embodiments 2-13 provided methods for preparing a high-viscosity PTT/low-viscosity PET two-component elastic fiber, where the specific steps were basically the same as in Embodiment 1, by differing in that when synthesizing the high-viscosity PTT melt, the parameters of the high-viscosity PTT melt were adjusted by adjusting the reaction conditions (including the vacuum degree of the high-viscosity PTT polymerization reactor, the agitating rate in the low viscosity zone, the agitating rate in the med-high viscosity zone and the high viscosity zone, the inlet temperature of the PTT prepolymer melt (PTT low-viscosity melt), and the residence time of material in the polymerization reactor, etc.); when synthesizing the low-viscosity PET melt, the parameters of the low-viscosity PET melt were adjusted by adjusting the reaction conditions (including the vacuum degree of the low-viscosity PET final polymerization reactor, the agitating rate in the low-viscosity PET final polymerization reactor, and the polymerization temperature in the low-viscosity PET final polymerization reactor). Wherein, the parameters of reaction conditions, high-viscosity PTT melt, and low-viscosity PET melt are shown in Tables 1-5.

Embodiment 14

[0119] Embodiment 14 provided A method for preparing a high-viscosity PTT/low-viscosity PET two-component elastic fiber, where the specific steps were basically the same as in Embodiment 1, by differing in that when synthesizing the high-viscosity PTT melt, the parameters of the high-viscosity PTT melt were adjusted by adjusting the reaction conditions (including the vacuum degree of the high-viscosity PTT polymerization reactor, the agitating rate in the low viscosity zone, the agitating rate in the med-high viscosity zone and the high viscosity zone, the inlet temperature of the PTT prepolymer melt (PTT low-viscosity melt), and the residence time of material in the polymerization reactor, etc.); when synthesizing the low-viscosity PET melt, the parameters of the low-viscosity PET melt were adjusted by adjusting the reaction conditions (including the vacuum degree of the low-viscosity PET final polymerization reactor, the agitating rate in the low-viscosity PET final polymerization reactor, and the polymerization temperature in the low-viscosity PET final polymerization reactor). In addition, a viscosity reducer was injected into the system, specifically an amorphous polyester with an intrinsic viscosity of 0.55 (measured using phenol:tetrachloroethylene (in a volume ratio of 3:2)), with a usage amount of 0.5% of the total mass of the melt. Wherein, the parameters of reaction conditions, high-viscosity PTT melt, and low-viscosity PET melt are shown in Tables 1-5.

Embodiment 15

[0120] Embodiment 15 provided A method for preparing a high-viscosity PTT/low-viscosity PET two-component elastic fiber, where the specific steps were basically the same as in Embodiment 1, by differing in that when synthesizing the high-viscosity PTT melt, the parameters of the high-viscosity PTT melt were adjusted by adjusting the reaction conditions (including the vacuum degree of the high-viscosity PTT polymerization reactor, the agitating rate in the low viscosity zone, the agitating rate in the med-high viscosity zone and the high viscosity zone, the inlet temperature of the PTT prepolymer melt (PTT low-viscosity melt), and the residence time of material in the polymerization reactor, etc.); when synthesizing the low-viscosity PET melt, the parameters of the low-viscosity PET melt were adjusted by adjusting the reaction conditions (including the vacuum degree of the low-viscosity PET final polymerization reactor, the agitating rate in the low-viscosity PET final polymerization reactor, and the polymerization temperature in the low-viscosity PET final polymerization reactor). In addition, a viscosity reducer was injected into the system, specifically an amorphous polyester with an intrinsic viscosity of 0.58 (measured using phenol:tetrachloroethylene (in a volume ratio of 3:2)), with a usage amount of 0.8% of the total mass of the melt. Wherein, the parameters of reaction conditions, high-viscosity PTT melt, and low-viscosity PET melt are shown in Tables 1-5.

Comparative Example 1

[0121] This comparative example 1 provided a method for preparing a direct melt-spun high-viscosity PET/low-viscosity PET two-component elastic fiber. This preparation method adopted a six-reactor system consisting of a first esterification reactor, a second esterification reactor, a first prepolymerization reactor and a second prepolymerization reactor connected successively, and a high viscosity final polymerization reactor and a low viscosity final polymerization reactor respectively connected to the second prepolymerization reactor. The high-viscosity PET melt obtained in the high viscosity final polymerization reactor and the low-viscosity PET obtained in the low viscosity final polymerization reactor were simultaneously transported through melt transport to the same spinning assembly for parallel spinning. Wherein, the second esterification reactor was provided with three compartments. The high viscosity final polymerization reactor and the low viscosity final polymerization reactor both adopted a conventional structure in the prior art.

[0122] In particular, terephthalic acid, ethylene glycol and a catalyst ethylene glycol antimony were sequentially subjected to esterification reactions in the first esterification reactor and the second esterification reactor, and prepolymerization reactions in the first prepolymerization reactor and the second prepolymerization reactor to give an ethylene terephthalate prepolymer, and before the second esterification reaction in the second esterification reactor was carried out, an ordinary titanium dioxide matting agent color paste (prepared by grinding and dispersing titanium dioxide and ethylene glycol, with titanium dioxide accounting for 10 wt % and ethylene glycol accounting for 90 wt %) was added into one compartment of the second esterification reactor through corresponding pipelines. Wherein, the molar ratio of terephthalic acid to ethylene glycol was 1:1.25, and the usage amount of catalyst mentioned above was 210 ppm of antimony element in the total mass of the melt; the usage amount of matting agent was such that titanium dioxide accounted for 0.3% of the total mass of the melt. The ethylene terephthalate prepolymer was then introduced into the high viscosity final polymerization reactor and the low viscosity final polymerization reactor for polymerization, to give a high-viscosity PET melt and a low-viscosity PET melt; finally, the high-viscosity PET melt and the low-viscosity PET melt were directly introduced in a mass ratio of 5:5 to the same parallel composite spinning box for spinning, to obtain a PET two-component elastic fiber. Wherein, the parameters of the high-viscosity PBT melt and the low-viscosity PET melt are shown in Tables 3-5.

Comparative Example 2

[0123] This comparative example 2 provided a method for preparing a chip-spun high-viscosity PBT/low-viscosity PET two-component elastic fiber. In particular, a high-viscosity PBT melt chip and a low-viscosity PET melt chip were pre-crystallized and dry screw melted, the two melts were then directly introduced in a mass ratio of 5:5 to the same parallel composite spinning box for spinning, to obtain a chip-spun two-component elastic fiber. The properties of the corresponding chips are shown in Tables 3-5. Wherein, the high-viscosity PBT chip and the low-viscosity PET chip were both obtained commercially, and contained no titanium dioxide matting agents (matting agents cannot be added to the high-viscosity PBT chip).

Comparative Example 3

[0124] This comparative example 3 provided a method for preparing a chip-spun high-viscosity EDDP (disperse atmospheric metachromatic polyester)/low-viscosity PET two-component elastic fiber. In particular, a high-viscosity EDDP melt chip and a low-viscosity PET melt chip were pre-crystallized and dry screw melted, and the two melts were then directly introduced in a mass ratio of 5:5 to the same parallel composite spinning box for spinning, to obtain a chip-spun two-component elastic fiber. The properties of the corresponding chips are shown in Tables 3-5.

TABLE-US-00001 TABLE 1 Test indicators for esterification materials of high-viscosity PTT polyester Agglomerated particles Acid value (mg KOH/g) (5~10 m)/mg Esterification rate PTT First Second First Second First Second production esterification esterification esterification esterification esterification esterification line reactor reactor reactor reactor reactor reactor Embodiment 1 39.52 14.96 0.02 92.8% 97.3% Embodiment 2 38.50 14.91 0.01 92.7% 97.4% Embodiment 3 37.54 13.95 0.03 93.2% 97.7% Embodiment 4 39.06 14.45 0.01 92.5% 97.8% Embodiment 5 39.55 14.95 0.00 92.6% 98.1% Embodiment 6 38.09 13.85 0.01 94.1% 98.4% Embodiment 7 38.60 13.87 0.03 93.7% 98.9% Embodiment 8 39.59 14.48 0.00 93.0% 98.2% Embodiment 9 38.10 14.56 0.02 94.3% 98.4% Embodiment 10 38.65 14.03 0.00 93.7% 98.5% Embodiment 11 38.58 13.65 0.02 93.9% 98.6% Embodiment 12 38.97 13.97 0.00 93.8% 98.2% Embodiment 13 39.25 14.05 0.03 92.9% 98.0% Embodiment 14 38.68 13.88 0.02 93.8% 98.3% Embodiment 15 39.54 14.22 0.00 92.7% 97.8%

TABLE-US-00002 TABLE 2 Test indicators for materials in the high-viscosity PTT second prepolymerization reactor Prepolymer intrinsic Agglomerated particles viscosity (IV) (5~10 m)/mg Embodiment 1 0.336 0.84 Embodiment 2 0.337 0.66 Embodiment 3 0.333 0.85 Embodiment 4 0.340 0.59 Embodiment 5 0.338 0.46 Embodiment 6 0.336 0.61 Embodiment 7 0.339 0.77 Embodiment 8 0.341 0.08 Embodiment 9 0.338 0.12 Embodiment 10 0.338 0.02 Embodiment 11 0.340 0.05 Embodiment 12 0.337 0.04 Embodiment 13 0.334 0.03 Embodiment 14 0.340 0.06 Embodiment 15 0.339 0.02 Note The intrinsic viscosity was measured using a mixed solvent of phenol and tetrachloroethane (3:2).

TABLE-US-00003 TABLE 3 Test indicators for high-viscosity PTT polyester chips Items Carboxyl Agglomerated Intrinsic Titanium terminal particles Melting Hue Ferrum viscosity dioxide group 10 m 5~10 m Moisture point L value B value Ash content Unit dl/g % mol/t /mg /mg % 0 C. % % Embodiment 1 0.922 0.32 14.3 0.02 0.05 0.15 228.3 81.5 3.89 0.03 Embodiment 2 0.921 0.33 13.9 0.00 0.02 0.13 228.3 81.8 4.15 0.03 Embodiment 3 0.919 0.33 14.6 0.01 0.04 0.12 228.5 80.7 4.03 0.03 Embodiment 4 0.923 0.33 13.8 0.03 0.06 0.15 228.2 80.9 3.66 0.02 Embodiment 5 0.921 0.32 14.2 0.01 0.03 0.14 228.3 81.2 4.22 0.03 Embodiment 6 0.919 0.32 14.5 0.00 0.04 0.16 228.5 81.5 3.75 0.02 Embodiment 7 0.953 0.33 13.3 0.03 0.04 0.16 228.5 81.6 3.96 0.03 Embodiment 8 0.982 0.33 11.2 0.04 0.05 0.17 228.3 80.9 4.28 0.02 Embodiment 9 1.021 0.33 11.0 0.04 0.06 0.16 228.4 81.3 4.56 0.02 Embodiment 10 1.050 0.32 10.7 0.03 0.03 0.13 228.5 80.8 4.69 0.02 Embodiment 11 1.082 0.33 11.0 0.02 0.03 0.15 228.5 81.5 4.88 0.03 Embodiment 12 1.101 0.33 10.7 0.03 0.05 0.13 228.3 80.5 5.15 0.02 Embodiment 13 1.123 0.33 10.9 0.01 0.04 0.15 227.9 80.7 5.42 0.03 Embodiment 14 1.022 0.32 11.2 0.00 0.02 0.15 228.4 81.1 4.52 0.03 (0.5% viscosity reducer added) Embodiment 15 1.052 0.33 10.9 0.02 0.04 0.14 228.1 80.9 4.70 0.02 (0.8% viscosity reducer added) Comparative 0.731 0.30 23.8 0.00 0.00 0.16 258.6 82.7 4.62 0.00 example 1 (PET/PET) Comparative 1.122 0.00 15.6 0.04 0.06 0.12 224.8 88.4 6.05 0.04 example 2 (PBT/PET) Comparative 0.803 0.30 22.7 0.00 0.01 0.25 246.5 80.6 6.27 0.01 example 3 (EDDP/PET) Note: The intrinsic viscosity was measured using a mixed solvent of phenol and tetrachloroethane (3:2); in Comparative example 1, the chip refers to the high-viscosity PET chip; in Comparative example 2, the chip refers to the high-viscosity PBT chip; in Comparative example 3, the chip refers to the high-viscosity EDDP chip.

TABLE-US-00004 TABLE 4 Physical and chemical indicators of low-viscosity PET polyester chips Items Carboxyl Agglomerated Intrinsic Titanium terminal particles Melting Hue Ferrum viscosity dioxide group 10 m 5~10 m Moisture point L value B value Ash content Unit dl/g % mol/t /mg /mg % 0 C. % % Embodiment 1 0.452 0.30 28.3 0.00 0.00 0.18 259.2 84.3 2.89 0.00 Embodiment 2 0.471 0.30 27.9 0.00 0.00 0.18 259.7 84.8 3.15 0.00 Embodiment 3 0.492 0.30 27.6 0.00 0.00 0.16 258.5 83.7 3.03 0.01 Embodiment 4 0.510 0.31 27.2 0.00 0.00 0.15 259.2 83.9 3.26 0.00 Embodiment 5 0.532 0.30 27.8 0.00 0.00 0.19 259.4 84.0 3.24 0.00 Embodiment 6 0.553 0.32 27.5 0.00 0.00 0.17 258.5 84.5 3.15 0.02 Embodiment 7 0.550 0.30 27.3 0.00 0.00 0.16 258.3 83.8 3.51 0.00 Embodiment 8 0.552 0.30 27.2 0.00 0.00 0.17 259.8 84.6 3.08 0.00 Embodiment 9 0.550 0.30 27.5 0.00 0.00 0.18 259.4 84.3 3.03 0.00 Embodiment 10 0.548 0.32 27.2 0.00 0.00 0.18 258.8 84.1 3.29 0.01 Embodiment 11 0.552 0.30 29.0 0.00 0.00 0.15 259.2 84.5 3.05 0.00 Embodiment 12 0.549 0.31 28.2 0.00 0.00 0.19 259.6 83.7 2.89 0.00 Embodiment 13 0.553 0.30 27.3 0.00 0.00 0.17 258.9 84.3 3.07 0.00 Embodiment 14 0.550 0.30 27.8 0.00 0.00 0.18 259.7 84.1 3.15 0.02 (0.5% viscosity reducer added) Embodiment 15 0.551 0.30 27.6 0.00 0.00 0.18 259.1 83.5 2.94 0.00 (0.8% viscosity reducer added) Comparative 0.473 0.30 28.2 0.00 0.00 0.16 259.5 84.8 2.99 0.00 example 1 Comparative 0.471 0.30 28.3 0.00 0.00 0.18 259.3 84.2 3.24 0.01 example 2 Comparative 0.473 0.31 29.0 0.00 0.00 0.16 259.7 84.5 3.18 0.00 example 3 Note: The intrinsic viscosity was measured using a mixed solvent of phenol and tetrachloroethane (3:2).

TABLE-US-00005 TABLE 5 Control data of high-viscosity PTT polymerization reactor and related indicators of high-viscosity PTT and low-viscosity PET Agitating Viscosity rate in Intrinsic difference Temperature Temperature med-high viscosity Viscosity between high Vacuum at low Agitating at high- viscosity at high of low viscosity PTT degree in viscosity rate in low viscosity and high viscosity viscosity melt and low polymerization PTT melt viscosity melt viscosity PTT melt PET viscosity PET No. reactor/Pa inlet/ C. zone/rpm outlet/ C. zones/rpm outlet melt melt Embodiment 1 138.0 250.4 4.2 252.6 2.35 0.922 0.452 0.470 Embodiment 2 136.6 250.2 4.2 252.4 2.35 0.921 0.471 0.450 Embodiment 3 139.3 250.2 4.2 252.3 2.35 0.919 0.492 0.427 Embodiment 4 135.6 250.0 4.2 252.5 2.35 0.923 0.510 0.413 Embodiment 5 139.8 250.7 4.2 252.3 2.35 0.921 0.532 0.389 Embodiment 6 137.5 250.8 4.2 252.3 2.35 0.919 0.553 0.366 Embodiment 7 132.7 250.2 4.4 252.6 2.42 0.953 0.550 0.403 Embodiment 8 129.2 250.0 4.4 252.8 2.42 0.982 0.552 0.430 Embodiment 9 126.8 250.3 4.5 252.7 2.45 1.021 0.550 0.470 Embodiment 10 120.5 250.2 4.6 252.9 2.45 1.050 0.548 0.502 Embodiment 11 117.6 250.5 4.6 252.7 2.48 1.082 0.552 0.530 Embodiment 12 115.2 250.3 4.8 252.8 2.48 1.101 0.549 0.552 Embodiment 13 112.8 250.0 4.8 252.8 2.48 1.123 0.553 0.570 Embodiment 14 127.3 250.3 4.5 252.6 2.45 1.022 0.550 0.472 Embodiment 15 122.5 250.1 4.6 252.7 2.45 1.052 0.551 0.501 Comparative 158.5 279.3 5.2 284.5 2.78 0.731 0.473 0.258 example 1 Comparative Not Not Not Not Not 1.122 0.471 0.651 example 2 involved involved involved involved involved (purchased chip) Comparative Not Not Not Not Not 0.803 0.473 0.330 example 3 involved involved involved involved involved

[0125] The properties of the composite elastic fibers obtained by spinning the high-viscosity melt and the low-viscosity PET melt corresponding to Embodiments 1-15 and Comparative Examples 1-3 are shown in Table 6, where the fiber variety is FDY and the specification is 83 dtex/36f. The fiber properties in the present disclosure were tested according to GBT 8960-2015 testing standard.

TABLE-US-00006 TABLE 6 Physical and chemical indicators of PTT/PET two-component composite elastic fibers Boiling Denier Oil Yarn water Crimp count/ Strength/ Elongation/ content/ evenness shrinkage shrinkage Interlacing No. Specification dtex cN/dtex % % CV/% rate/% rate/% point Embodiment 1 83/36 83.2 2.84 30.74 1.45 1.34 18.42 51.5 4 Embodiment 2 83/36 82.6 2.82 31.10 1.47 1.36 18.35 49.6 4 Embodiment 3 83/36 83.4 2.82 31.51 1.51 1.35 18.28 48.1 4 Embodiment 4 83/36 82.7 2.85 30.18 1.44 1.38 18.24 46.2 4 Embodiment 5 83/36 82.9 2.83 30.63 1.49 1.33 18.14 41.8 4 Embodiment 6 83/36 82.6 2.84 31.90 1.43 1.35 18.11 38.4 4 Embodiment 7 83/36 83.5 2.90 31.32 1.48 1.34 18.24 45.6 4 Embodiment 8 83/36 82.9 2.92 30.16 1.53 1.37 18.15 47.3 4 Embodiment 9 83/36 83.1 2.95 30.77 1.44 1.28 18.03 51.7 4 Embodiment 10 83/36 83.3 2.93 30.55 1.46 1.35 17.96 56.4 5 Embodiment 11 83/36 83.5 2.98 30.42 1.45 1.29 18.21 59.8 4 Embodiment 12 83/36 82.8 3.05 30.03 1.45 1.34 18.08 62.6 4 Embodiment 13 83/36 83.6 3.22 29.89 1.42 1.37 17.97 65.3 5 Embodiment 14 83/36 83.2 2.92 30.52 1.47 1.35 18.12 62.7 4 Embodiment 15 83/36 83.4 2.96 30.39 1.44 1.33 18.03 63.9 4 Comparative 83/36 82.9 2.89 26.88 1.32 1.19 13.52 26.5 4 example 1 (PET/PET) Comparative 83/36 82.7 2.72 33.39 1.57 1.34 15.20 37.2 4 example 2 (PBT/PET) Comparative 83/36 83.1 2.68 29.55 1.40 1.42 16.54 30.3 4 example 3 (EDDP/PET)

[0126] It can be seen that the present disclosure utilizes two different polyester production lines to produce a high-viscosity PTT polyester and a low-viscosity PET polyester, respectively, the two melts of different viscosities are then transported to the same parallel composite spinning assembly through melt transport, after which the high-viscosity PTT/low-viscosity PET two-component elastic fiber is prepared, achieving the preparation of direct melt-spun high-viscosity PTT/low-viscosity PET parallel elastic fiber, the obtained fiber has excellent performance.

[0127] The embodiments described above are only for illustrating the technical concepts and features of the present disclosure, and are intended to make a person familiar with the technology being able to understand the content of the present disclosure and thereby implement it, and should not limit the protective scope of this disclosure. Any equivalent variations or modifications according to the spirit of the present disclosure should be covered by the protective scope of the present disclosure.