For the described two agitating shaft designs, the following further structures or process steps are applicable.

In some embodiments, the high-viscosity final polymerization reactor further comprises steam feed ports for introducing superheated ethylene glycol steam arranged at the top of the main body corresponding to the rear end of the low-viscosity zone, the rear end of the medium-high-viscosity zone, and the rear end of the high-viscosity zone. The preparation method further comprises steps of metering the superheated ethylene glycol steam with a metering system and introducing the steam into the high-viscosity final polymerization reactor. The steam feed ports are arranged in the final polymerization reactor to achieve regular alcoholysis of gel and carbonized materials produced in the high-viscosity zone during the long-period operation of the device, thereby preventing carbonization on the top of the reactor. Moreover, according to the pressure increase of the spinning assembly, the viscosity of the materials on the discs in the high-viscosity zone are timely reduced and the materials are timely removed, so that the long-period aged and deteriorated materials are depolymerized and removed from the surfaces of the discs, thereby rebuilding the material distribution of the discs and prolonging the operation period of the device.

In some embodiments, the high-viscosity final polymerization reactor is connected to a vacuum pump, wherein the vacuum pump is a liquid ring pump and a chilled water device for cooling gas is arranged at an inlet of the liquid ring pump. In the preparation method, the vacuum pump is controlled to have a gas sucking rate of 200-350 kg/h, the vacuum pump has an ultimate vacuum degree of 50-65 Pa, and in a production state, the vacuum degree in the final polymerization reactor is controlled to be 100-180 Pa.

In the present disclosure, due to the increase of side reactions of materials in the high-viscosity zone and the overall decrease in the efficiency of devolatilization, the amount of volatiles produced in the final polymerization reactor is 2.5-3.2 times that of a conventional polyester unit with the same production capacity. The higher the viscosity at the high-viscosity melt outlet, the higher the amount of non-condensable gas produced. Therefore, the gas sucking rate of the vacuum pump is designed to be 2.0-3.0 times that of a conventional polyester unit with the same production capacity, the ultimate vacuum degree is designed to be 50-65 Pa, and the gas sucking rate is designed to be 200-350 kg/h, and a large-capacity chilled water device is designed at the inlet of the vacuum pump (the liquid ring pump) to capture excess non-condensable acetaldehyde. In order to further maintain production stability, all ethylene glycol produced from the vacuum part of the device must be subjected to formaldehyde removal treatment before entering the system.

In some embodiments, the catalyst is a supported catalyst and comprises a carrier and an active component; the carrier is nano barium sulfate with a particle size of 20-50 nm and a specific surface area of 270-350 m²/g; the nano barium sulfate is prepared by reaction in anhydrous ethylene glycol; the active component comprises a main active component and a secondary active component, the main active component is titanium oxide, and the secondary active component is a mixture of scandium oxide, magnesium oxide, cobalt oxide and zinc oxide.

In some embodiments, the catalyst comprises, in percent by weight, 3.3% to 10.0% of titanium oxide, 8% to 15% of the secondary active component, and 75.0% to 88.7% of nano barium sulfate.

In some embodiments, the catalyst has a particle size of 80-160 nm.

In some embodiments, the catalyst is prepared by precipitating a suspension of the carrier in ethylene glycol, scandium sulfate, magnesium sulfate, cobalt sulfate, zinc sulfate, a compound of titanium, and a precipitant, surface treating with a silane coupling agent, and calcining.

In some embodiments, the scandium sulfate, the magnesium sulfate, the cobalt sulfate, and the zinc sulfate are added in the form of an aqueous solution.

In some embodiments, the compound of titanium is tetrabutyl titanate (TBT) or tetraisopropyl titanate (TPT).

In some embodiments, the precipitant is sodium hydroxide, preferably a solution of sodium hydroxide in ethylene glycol.

In the present disclosure, a high-stability polyester formula is used, PTA and EG are used for esterification and polymerization reaction, and the catalyst used is a self-developed titanium-based solid-phase multi-metal catalyst. During synthesis of the catalyst, firstly, nano-sized barium sulfate is prepared in an ethylene glycol liquid phase, the barium sulfate is controlled to have a particle size of 20-50 nm and a specific surface area of 270-350 m²/g, and the pH of the barium sulfate suspension is controlled to be 7.0-7.1; then, under high-speed stirring, the aqueous solution of scandium sulfate, magnesium sulfate, cobalt sulfate, the zinc sulfate and the solution of sodium hydroxide in ethylene glycol are simultaneously added dropwise, and then the suspension is aged, and the compound of titanium is then added dropwise to the suspension; the suspension is then aged again, and a silane coupling agent is added dropwise to seal the powder surface; after another 10.0 hours of aging, water and low-boiling-point alcohol are distilled off, the pH is adjusted to neutral, and filtering and calcining are performed to obtain the catalyst.

The titanium-based solid-phase multi-metal catalyst is a porous solid-phase catalyst with a large specific surface area. The catalyst has a good dispersion effect in ethylene glycol, overcomes the disadvantage of conventional liquid-phase titanium-based catalysts that are prone to hydrolysis during the esterification polymerization process, has an excellent catalytic effect, and can effectively inhibit the level of side reactions. Compared with traditional antimony-based catalysts, this catalyst can ensure that the high-viscosity melt has better thermal stability and thermal oxygen stability. This catalyst can also ensure that the viscosity drop during melt transfer is reduced by about 12% to 18%, compared with the antimony-based catalysts.

In some embodiments, melt pumps are used to transfer the high-viscosity PET melt and the low-viscosity PET melt, a melt cooler is arranged at an outlet of each melt pump, and in the preparation method, the temperature of the high-viscosity PET melt cooled by the melt cooler is controlled to be 284-286° C.; a filter and a booster pump are arranged between each melt pump and the parallel composite spinning assembly; in the preparation method, the transfer time of the high-viscosity PET melt is controlled to be 25-35 min; and a plurality of static slow-flow mixers are arranged at a front end of a melt pipeline.

In the present disclosure, an ultra-short-process efficient high-viscosity polyester melt transfer design is provided; a large-capacity melt cooler is equipped at the outlet of each melt pump to quickly control the melt temperature to be 284-286° C., and then the melts are transferred to spinning units via filters and booster pumps. The design concept of the ultra-short process is to change the location of the final polymerization reactor from the polymerization device to the top of the spinning device, so that the melts are transferred to the spinning units within the shortest transfer time. The conventional polyester melt transfer time is generally 50-70 min, and the short-process high-viscosity melt transfer requires the transfer time to be reduced to 25-35 min. A more stringent design is that the residual internal stress kinetic energy of the melt must be completely released within this residence time range. Therefore, a special front-end multi-position static slow-flow mixer is designed to quickly achieve the plug flow effect without increasing the residence time.

In some embodiments, the preparation method further comprises a step of introducing a viscosity reducer into the high-viscosity PET melt before the high-viscosity PET melt passes through the filter, wherein the viscosity reducer is selected from the group consisting of poly (ethylene terephthalateco-1,4-cyclohexanedimethylene terephthalate) PETG, cationic dyeable polyester CDP, easy cationic dyeable polyester ECDP, atmospheric pressure boiling dyeing polyester EDDP, polybutylene terephthalate PBT, poly (trimethylene terephthalate) PTT, and combinations thereof.

Further, the amount of the viscosity reducer is 0.2%-3.0%, preferably 0.5%-2.0%, more preferably 0.8%-1.5%, of the total mass of the melt. The addition of the viscosity reducer can greatly reduce the kinematic viscosity of the high-viscosity melt, improve the melt transfer efficiency, and reduce process degradation.

Before the high-viscosity melt is transferred to the filter, an additive injection system is designed to inject the viscosity reducer. The addition of the viscosity reducer can greatly improve the fluidity of the high-viscosity melt, improve the internal stress elimination effect of the high-viscosity melt, and enhance the plug flow effect. It can achieve a more stable spinning effect and improved fiber crimp, without affecting the basic indicators and quality of the final two-component elastic fiber product.

In some embodiments, the preparation method further comprises a step of introducing a solid-phase smoothing agent into the ethylene terephthalate prepolymer before introducing the ethylene terephthalate prepolymer into the high-viscosity final polymerization reactor, and a step of passing the mixture of the solid-phase smoothing agent and the ethylene terephthalate prepolymer through the filter, wherein the solid-phase smoothing agent is in the form of a masterbatch and comprises a polyester matrix and an inorganic powder, and the inorganic powder is selected from the group consisting of talc, montmorillonite, barium sulfate, hydrotalcite, nano-silica and combinations thereof.

Further, the amount of the solid-phase smoothing agent is 0.05%-1.0%, preferably 0.06%-0.8%, more preferably 0.1%-0.5%, of the total mass of the melt.

The solid-phase smoothing agent is an inert powder that can produce a good slip effect. The solid-phase smoothing agent can reduce the rapid thickening effect of the high-viscosity melt, and also can form a vaporization center, accelerate the overflow of small molecular materials, improve the devolatilization efficiency reduce the temperature rise effect during melt transfer, greatly reduce the kinematic viscosity of the high-viscosity melt and improve the melt transfer efficiency. The addition of the solid-phase smoothing agent can generate friction between the fluid surface and the pipe wall, thereby improving the fluidity of the melt and reducing the viscosity of the melt accordingly.

In some embodiments, the preparation method further comprises a step of introducing a heat stabilizer, an antioxidant or a colorant into the second esterification reactor before the second esterification reaction, wherein the heat stabilizer is selected from the group consisting of trimethyl phosphate, triethyl phosphate, triphenyl phosphate, triphenyl phosphite, triglycerol phosphate, and combinations thereof; the antioxidant is selected from the group consisting of Antioxidant 168, Antioxidant 1076, Antioxidant 1010, Antioxidant 1222, benzothiazole antioxidants, and combinations thereof.

The introduction of the heat stabilizer and the antioxidant into the second esterification reactor can improve the thermal stability and oxidation resistance of the high-viscosity PET melt, so that side reactions can be suppressed during the esterification and polymerization process, and the viscosity drop caused by thermal degradation of the high-viscosity melt during the residence time of up to 40 min to 90 min in the melt spinning process can be suppressed, and the intrinsic viscosity level of the melt is ensured to be still high in the spinning manifold, thereby generating sufficient elastic crimp.

In some embodiments, the preparation method further comprises a step of introducing a liquid-phase lubricant into the high-viscosity PET melt before the high-viscosity PET melt passes through the filter, wherein the liquid-phase lubricant is selected from the group consisting of polyethylene glycol with a molecular weight of 8000-20000, polyetheramine with a molecular weight of 10000-20000, poly (butylene glycol) adipate with a molecular weight of 5000-20000, polyacrylate and combinations thereof.

Further, the amount of the liquid-phase lubricant is 0.1%-2.0%, preferably 0.3%-1.5%, more preferably 0.5%-1.0%, of the total mass of the melt.

In some embodiments, a difference between the dynamic viscosity of the high-viscosity PET melt and the dynamic viscosity of the low-viscosity PET melt is 250-700 Pa·s, preferably 450-630 Pa·s. Further preferably, the difference between the intrinsic viscosity of the high-viscosity PET melt and the intrinsic viscosity of the low-viscosity PET melt is 0.30-0.45, and the difference between the dynamic viscosity of the high-viscosity PET melt and the dynamic viscosity of the low-viscosity PET melt is 500-600 Pa·s.

In some embodiments, the preparation method further comprises the step of mixing a mixture of the solid-phase smoothing agent and the ethylene terephthalate prepolymer by a dynamic mixer before the mixture of the solid-phase smoothing agent and the ethylene terephthalate prepolymer passes through the filter.

In some embodiments, the preparation method further comprises a step of filtering the ethylene terephthalate prepolymer in the filter before introducing the ethylene terephthalate prepolymer into the high-viscosity final polymerization reactor and the low-viscosity final polymerization reactor.

In some embodiments, the preparation method further comprises a step of passing the high-viscosity PET melt and the low-viscosity PET melt through filters respectively before the high-viscosity PET melt and the low-viscosity PET melt pass through the same spinning assembly.

In some embodiments, the high-viscosity final polymerization reactor is arranged at the top of the spinning assembly. In this way, the transfer distance of the high-viscosity melt synthesized in the high-viscosity final polymerization reactor before spinning can be reduced.

In some embodiments, the same spinning assembly is a composite spinning manifold.

In some embodiments, the composite spinning manifold comprises a composite spinneret.

The present disclosure further provides a PET two-component elastic fiber prepared by the preparation method described above.

In some embodiments, the PET two-component elastic fiber has a crimp shrinkage rate of 18%-38%.

Due to the application of the described technical solution, the present disclosure has the following advantages compared with the prior art:

In the present disclosure, a six-reactor polymerization device system comprising a first esterification reactor, a second esterification reactor, a first prepolymerization reactor, a second prepolymerization reactor, a high-viscosity final polymerization reactor, and a low-viscosity final polymerization reactor is adopted, and the high-viscosity final polymerization reactor is configured in a double-shaft stirring form with unequal lengths at the front and rear ends, that is, the length of the low-viscosity zone in the high-viscosity final polymerization reactor is unequal to the total length of the medium-high-viscosity zone and the high-viscosity zone, and the length of the low-viscosity zone is controlled to be longer. Moreover, a special disc reactor arrangement and a scraper arrangement are provided in the three zones. In this way, the viscosity of the high-viscosity melt in the high-viscosity final polymerization reactor is significantly improved and the molecular weight distribution of the melt is narrowed. Moreover, the high-viscosity final polymerization reactor and the low-viscosity final polymerization reactor are used to synthesize the high-viscosity melt and the low-viscosity melt, respectively. In this way, the viscosity difference between the high-viscosity melt and the low-viscosity melt can be adjusted effectively, and then the crimp rate and shrinkage rate of the final two-component elastic fiber can be adjusted.

Alternatively, in the present disclosure, the high-viscosity final polymerization reactor may be configured in a double-shaft stirring form with equal length at the front and rear ends, that is, the length of the low-viscosity zone is equal to the total length of the medium-high-viscosity zone and the high-viscosity zone; moreover, a specific disc reactor arrangement and a scraper arrangement are provided in the three zones. In this way, the viscosity of the high-viscosity melt can be improved, thereby effectively adjusting the viscosity difference between the high-viscosity melt and the low-viscosity melt and further adjusting the crimp rate and shrinkage rate of the final two-component elastic fiber.

In the present disclosure, the high-viscosity melt has an intrinsic viscosity of 0.68-0.90, and the low-viscosity melt has an intrinsic viscosity of 0.45-0.64. The viscosity of the high-viscosity melt is much higher than that in the prior art.

The PET two-component elastic fiber of the present disclosure has a crimp shrinkage rate of 38%, which is much higher than that of the existing two-component elastic fiber.

When used for industrial production of a two-component elastic fiber, the preparation method of the present disclosure can achieve a low-viscosity melt capacity of 30,000 to 80,000 tons/year and a high-viscosity melt capacity of 30,000 to 80,000 tons/year. When the product is melt-spun high-viscosity PET/low-viscosity PET two-component elastic fiber, the overall device capacity is 60,000 tons/year to 160,000 tons/year.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of a six-reactor polymerization system used in an embodiment of the present disclosure;

FIG. 2 is a schematic structural diagram of a high-viscosity final polymerization reactor in a first design in an embodiment of the present disclosure;

FIG. 3 is a schematic structural diagram of a high-viscosity final polymerization reactor in a second design in an embodiment of the present disclosure;

FIG. 4 is a schematic structural diagram of a combined scraper of the final polymerization reactor used in an embodiment of the present disclosure;

wherein, 1. low-viscosity zone; 2. medium-high-viscosity zone; 3. high-viscosity zone; 4. combined scraper; 5. disc scraper; 6. axial scraper; 7. wall scraper; 8. agitating shaft; 9. disc reactor; 10. first esterification reactor; 11. second esterification reactor; 12. first prepolymerization reactor; 13. second prepolymerization reactor; 14. high-viscosity final polymerization reactor; 15. low-viscosity final polymerization reactor; 16. melt pump; 17. steam feed port.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The above solutions are further described in conjunction with specific embodiments below. It should be understood that these embodiments are used to illustrate the basic principles, main features and advantages of the present disclosure, and the present disclosure is not limited by the scope of the following embodiments. The implementation conditions used in the embodiments can be further adjusted according to specific requirements, and the implementation conditions not specified are usually the conditions in conventional experiments. In the following embodiments, unless otherwise specified, all raw materials are purchased from commercial sources or prepared by conventional methods in the art.

The above embodiments are only for illustrating the technical concept and features of the invention, and their purpose is to enable people familiar with this technology to understand the content of the invention and implement it accordingly, but not to limit the scope of the present disclosure. Any equivalent changes or modifications made according to the spirit of the present disclosure should fall within the scope of the present disclosure.

The present disclosure is further described below in conjunction with the accompanying drawings and the preferred embodiments of the present disclosure. In the following embodiments, it should be noted that directions referred to as terms “front” and “rear” are based on the flow direction of the material, the direction in which the material flows first is the front, and the direction in which the material flows later is the rear. For example, in FIG. 2, the term “front” refers to the left side in FIG. 2, and the term “rear” refers to the right side in FIG. 2. Therefore, the orientation and positional relationship described in the present disclosure are only for the convenience of describing the present disclosure and simplifying the description, rather than indicating or implying 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 on the present disclosure.

As shown in FIG. 1, during the preparation of PET two-component elastic fiber in an embodiment, a six-reactor device system, comprising a first esterification reactor 10, a second esterification reactor 11, a first prepolymerization reactor 12, a second prepolymerization reactor 13, a high-viscosity final polymerization reactor 14, and a low-viscosity final polymerization reactor 15, is adopted. The sixe reactors are connected to each other by necessary pipelines, and a necessary vacuum system and the like is connected to the six reactors. Pumps 16 and filters A and B are arranged between the second prepolymerization reactor 13 and the high-viscosity final polymerization reactor 14 or the low-viscosity final polymerization reactor 15. In an 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 running for a period of time, the device is switched to the filter B, and then the filter A may be cleaned.

For the high-viscosity final polymerization reactor 14, its first design is a double-shaft stirring design with unequal lengths at front and rear ends. As shown in FIG. 2, the high-viscosity final polymerization reactor 14 comprises a main body containing a chamber internally. The main body comprises a low-viscosity zone 1, a medium-high-viscosity zone 2, and a high-viscosity zone 3 which are arranged in sequence along an axial direction of the high-viscosity final polymerization reactor 14, and the viscosity of the PET melt in the low-viscosity zone 1, the medium-high-viscosity zone 2, and the high-viscosity zone 3 increases in sequence; the length of the low-viscosity zone 1 is three-fifths of the length of the high-viscosity final polymerization reactor 14, and the length of the medium-high-viscosity zone 2 and the high-viscosity zone 3 is two-fifths of the length of the high-viscosity final polymerization reactor 14; the high-viscosity final polymerization reactor 14 further comprises two agitating shafts 8, one of which is arranged in the low-viscosity zone 1 and the other is arranged in the medium-high-viscosity zone 2 and the high-viscosity zone 3, and the central axes of the two agitating shafts 8 are located on a same straight line; the length of the agitating shaft 8 arranged in the low-viscosity zone 1 is three-fifths of the length of the high-viscosity final polymerization reactor 14, and the length of the agitating shaft 8 arranged in the medium-high-viscosity zone 2 and the high-viscosity zone 3 is two-fifths of the length of the high-viscosity final polymerization reactor 14; the high-viscosity final polymerization reactor 14 further comprises a trumpet-shaped high-viscosity melt outlet arranged at a rear end of the high-viscosity zone 3.

Each of the two agitating shafts 8 is provided with a plurality of disc reactors 9; the disc reactors 9 in the low-viscosity zone 1 are in a three-to ten-disc combination design, the front end of the low-viscosity zone 1 is in a ten-to six-disc combination design, the rear end of the low-viscosity zone 1 is in a five-to three-disc combination design, and the number of disc reactors 9 in the low-viscosity zone 1 is 35 to 55; the high-viscosity final polymerization reactor 14 further comprises two round distribution plates arranged at the most front end of the low-viscosity zone 1, and each distribution plate has six spokes by which the distribution plate is divided into six equal parts, wherein sieve plates are arranged in three equally divided fan-shaped areas which are distributed at intervals, and a large number of round holes with a diameter of 1-5 cm are distributed in each sieve plate. The distribution plates can control the material to prevent the short circuit of low-viscosity materials so that the melt has more uniform molecular weight distribution.

The disc reactors 9 in the medium-high-viscosity zone 2 are in a four-disc combination design, a three-disc combination design and a two-disc combination design in sequence from front to rear; the medium-high-viscosity zone 2 is also provided with a wall scraper 7 for removing the melt from an inner wall of the high-viscosity final polymerization reactor 14; the number of disc reactors 9 in the medium-high-viscosity zone 2 is 15 to 25; the disc reactors 9 in the high-viscosity zone 3 are in a two-disc combination design, and 5 to 8 two-disc combinations are arranged in the high-viscosity zone 3; the total number of disc reactors 9 in the medium-high-viscosity zone 2 and the high-viscosity zone 3 is 25 to 35.

As shown in FIG. 4, a combined scraper 4 is also arranged in the high-viscosity zone 1, and the combined scraper 4 comprises an axial scraper 6 for removing the melt from the agitating shaft, a wall scraper 7 for removing the melt from the inner wall of the high-viscosity final polymerization reactor 14 and a disc scraper 5 for removing the melt from an agitator; in the two-disc combination design in the high-viscosity zone 3, the spacing between the disc combinations and the spacing between the two discs in each combination gradually increase from front to rear.

For the high-viscosity final polymerization reactor 14, its second design is a design of providing front and rear shafts with equal length. As shown in FIG. 3, the high-viscosity final polymerization reactor 14 is a horizontal polymerization reactor and comprises a main body containing a chamber internally. The main body comprises a low-viscosity zone 1, a medium-high-viscosity zone 2, and a high-viscosity zone 3 which are arranged in sequence along an axial direction of the high-viscosity final polymerization reactor 14, and the viscosity of the PET melt in the low-viscosity zone 1, the medium-high-viscosity zone 2, and the high-viscosity zone 3 increases in sequence; the length of the low-viscosity zone 1 is half of the length of the high-viscosity final polymerization reactor 14, and the length of the medium-high-viscosity zone 2 and the high-viscosity zone 3 is half of the length of the high-viscosity final polymerization reactor 14;

the high-viscosity final polymerization reactor 14 further comprises two agitating shafts 8, one of which is arranged in the low-viscosity zone 1 and the other is arranged in the medium-high-viscosity zone 2 and the high-viscosity zone 3, and the central axes of the two agitating shafts 8 are located on a same straight line; the length of the agitating shaft 8 arranged in the low-viscosity zone 1 is half of the length of the high-viscosity final polymerization reactor 14, and the length of the agitating shaft 8 arranged in the medium-high-viscosity zone 2 and the high-viscosity zone 3 is half of the length of the high-viscosity final polymerization reactor 14; the high-viscosity final polymerization reactor 14 further comprises a trumpet-shaped high-viscosity melt outlet arranged at a rear end of the high-viscosity zone 3.

Each of the two agitating shafts 8 is provided with a plurality of disc reactors 9; the disc reactors 9 in the low-viscosity zone 1 are in a design of multiple multi-disc combinations; the high-viscosity final polymerization reactor 14 further comprises two round distribution plates arranged at the most front end of the low-viscosity zone 1, and each distribution plate has six spokes by which the distribution plate is divided into six equal parts, wherein sieve plates are arranged in three equally divided fan-shaped areas which are distributed at intervals, and a large number of round holes with a diameter of 1-5 cm are distributed in each sieve plate.

The disc reactors 9 in the medium-high-viscosity zone 2 are in a design of 8 to 10 double-disc combinations; the disc reactors 9 in the high-viscosity zone 3 are in a single-disc design and the number of disc reactors 9 in the high-viscosity zone 3 is 6 to 15; the disc reactors 9 in the high-viscosity zone 3 adopt a reinforced design.

As shown in FIG. 4, a combined scraper is also arranged in the high-viscosity zone 3, and the combined scraper 4 comprises an axial scraper 6 for removing the melt from the agitating shaft 8, a wall scraper 7 for removing the melt from an inner wall of the high-viscosity final polymerization reactor 14, and a disc scraper 5 for removing the melt from an agitator; the wall scraper 7 is in a spiral shape that rotates along the axial direction; the axial scraper 6 and the disc scraper 5 are arranged between the disc reactors 9; the wall scraper 7 is arranged at an outer edge of the disc reactor 9; from front to rear, the spacing between the disc scraper 5 and the adjacent disc reactor 9 and the spacing between the wall scraper 7 and the inner wall of the high-viscosity final polymerization reactor 14 gradually decrease; diameters of the disc reactors 9 in the high-viscosity zone 3 decrease in sequence from front to rear, and the diameter of the last disc reactor 9 in the high-viscosity zone 3 is 85% of the diameter of the first disc reactor 9 in the high-viscosity zone 3.

The high-viscosity final polymerization reactor 14 further comprises steam feed ports 17 for introducing superheated ethylene glycol steam arranged at the top of the main body corresponding to the rear end of the low-viscosity zone 1, the rear end of the medium-high-viscosity zone 2, and the rear end of the high-viscosity zone 3.

The high-viscosity final polymerization reactor 14 is connected to a vacuum pump, wherein the vacuum pump is a liquid ring pump and a chilled water device for cooling gas is arranged at an inlet of the liquid ring pump. Melt pumps are used to transfer the high-viscosity PET melt and the low-viscosity PET melt, and a melt cooler is equipped at the outlet of each melt pump.

After the second prepolymerization reactor and before the high-viscosity final polymerization reactor, a dynamic mixer and a filter are arranged; and before the dynamic mixer, a solid-phase smoothing agent injection system is arranged.

After the high-viscosity final polymerization reactor and the low-viscosity final polymerization reactor and before the same spinning assembly, a dynamic mixer and a filter are arranged; and before the dynamic mixer, a viscosity reducer injection system is arranged.

Necessary melt pumps, vacuum pumps, transfer pipelines, and the like may be installed on pipelines connecting the six reactors.

The same spinning assembly is a composite spinning manifold, and the high-viscosity final polymerization reactor is arranged at the top of the composite spinning manifold, thereby shortening the transfer distance of the melt, especially the high-viscosity melt. The composite spinning manifold comprises a spinneret.

Example 1

This example provides a preparation method for a PET two-component elastic fiber, and the specific steps are as follows.

The catalyst used in this example is prepared as follows.

Sulfuric acid and barium hydroxide or barium acetate were used to react in anhydrous ethylene glycol to prepare a suspension of barium sulfate nanoparticles in ethylene glycol, and the generated acetic acid was removed by vacuum purification (when the raw material was barium acetate). The barium sulfate nanoparticles had a particle size of 20-50 nm and a specific surface area of 270-350 m²/g. The pH of the suspension of barium sulfate nanoparticles in ethylene glycol was adjusted to 7.0-7.1; then, under high-speed stirring, a mixed aqueous solution of scandium sulfate, magnesium sulfate, cobalt sulfate and zinc sulfate and a solution of sodium hydroxide in ethylene glycol were then simultaneously added dropwise to the suspension in ethylene glycol; after added completely, the suspension was then aged for 8.0 hours, and then a compound of titanium (tetrabutyl titanate or isopropyl titanate) was added dropwise to the aged suspension within 5.0 hours, and the suspension was then further aged for 6.0 hours; finally, a silane coupling agent was added dropwise to the suspension to seal the powder surface; then, the suspension was further aged for 10.0 hours, water and low-boiling-point alcohol were distilled off, the pH of the suspension was adjusted to neutral, the suspension was then filtered and the resulting product was heat-set in a muffle furnace at 480-525° C. to obtain a supported catalyst. In the catalyst, barium sulfate nanoparticles were used as a carrier and scandium oxide, magnesium oxide, cobalt oxide, zinc oxide and titanium oxide were used as active components. The catalyst comprised, in percent by weight, 3.3% to 10.0% of titanium oxide, as well as oxides of scandium, magnesium, cobalt and zinc acting as secondary active components; the content of the oxides (secondary active components) was 8% to 15% of the total solid-phase components of the catalyst, and the content of the barium sulfate carrier was 75.0% to 88.7% of the total solid phase.

The described six-reactor polymerization device was used. Terephthalic acid, ethylene glycol, and the described catalyst sequentially passed through the first esterification reactor and the second esterification reactor for esterification reaction and then the first prepolymerization reactor and the second prepolymerization reactor for prepolymerization reaction to obtain an ethylene terephthalate prepolymer, and before second esterification reaction in the second esterification reactor, a common titanium dioxide matting agent color paste (prepared by grinding and dispersing titanium dioxide and ethylene glycol, where the titanium dioxide accounted for 10 wt % and the ethylene glycol accounted for 90 wt %), a heat stabilizer, an antioxidant, and a colorant were separately fed into different cells of the second esterification reactor by corresponding pipelines, where the flow rate of terephthalic acid was 2500-25000 kg/h, the flow rate of ethylene glycol was 1000-10000 kg/h, based on the titanium element, the amount of the catalyst was 8-12 ppm of the total mass of the melt, the amount of the titanium dioxide in the matting agent was 0.3% of the total mass of the melt, and the addition amounts of the heat stabilizer, the antioxidant and the colorant were 20 ppm, 50 ppm and 1 ppm respectively relative to the molar amount of terephthalic acid. Then, the ethylene terephthalate prepolymer was respectively introduced into the high-viscosity final polymerization reactor and the low-viscosity final polymerization reactor for polymerization to obtain a high-viscosity PET melt and a low-viscosity PET melt, respectively. Finally, the high-viscosity PET melt and the low-viscosity PET melt were directly introduced, at a mass ratio of 5:5, to the same parallel composite spinning manifold to be spun, thus obtaining a PET two-component elastic fiber.

The group experiments in Example 1 included 1-1, 1-2 to 9-1, 9-2, and the data are shown in Table 1 below.

The condition setting of the six-reactor polymerization device and the properties of the high-viscosity PET melt and the low-viscosity PET melt are shown in Table 1 below. Each melt was first dissolved in a mixed solvent of phenol and tetrachloroethane (v/v: 3:2) and then tested for its intrinsic viscosity in dL/g.

TABLE 1

Process conditions and viscosity of Example 1

Low-
Intrinsic
Vacuum degree
High-
Stirring speed
Intrinsic

Vacuum degree of
viscosity
viscosity
of high-
viscosity
of agitating
viscosity
Intrinsic viscosity

Intrinsic
low-viscosity final
melt outlet
of low-
viscosity final
melt outlet
shaft in high-
of high-
difference between

viscosity of
polymerization
temperature/
viscosity
polymerization
temperature/
viscosity
viscosity
high-viscosity and

No.
prepolymer
reactor/Pa
° C.
melt
reactor/Pa
° C.
zone/rpm
melt
low-viscosity melts

1-1
0.260
158.0
282.1
0.471
98.5
286.2
2.66
0.742
0.281

1-2
0.261
178.6
281.5
0.549
97.0
286.0
2.66
0.742
0.193

2-1
0.265
164.6
282.4
0.473
104.2
286.0
2.62
0.760
0.277

2-2
0.265
183.4
279.8
0.548
105.0
285.8
2.62
0.762
0.214

3-1
0.269
169.3
282.2
0.469
109.8
285.7
2.58
0.785
0.286

3-2
0.269
198.5
279.3
0.550
110.2
285.3
2.58
0.786
0.236

4-1
0.275
175.6
282.7
0.502
115.0
285.5
2.54
0.801
0.279

4-2
0.275
206.3
277.9
0.460
116.0
285.7
2.54
0.803
0.343

5-1
0.279
182.8
281.7
0.505
122.6
285.8
2.48
0.825
0.280

5-2
0.278
212.0
277.6
0.458
122.5
285.4
2.48
0.826
0.368

6-1
0.286
191.5
281.9
0.503
131.5
285.3
2.50
0.842
0.279

6-2
0.286
220.3
277.2
0.462
131.9
285.1
2.50
0.843
0.381

7-1
0.293
202.7
281.4
0.547
132.7
284.4
2.37
0.868
0.301

7-2
0.293
225.6
277.0
0.466
132.0
284.3
2.37
0.868
0.402

8-1
0.306
206.2
281.6
0.552
125.2
284.7
2.28
0.872
0.320

8-2
0.306
232.4
276.8
0.460
126.8
284.7
2.28
0.873
0.413

9-1
0.310
212.8
281.2
0.550
122.8
284.2
2.21
0.893
0.343

9-2
0.310
236.8
276.6
0.462
122.0
284.2
2.21
0.895
0.433

When the corresponding high-viscosity and low-viscosity PET melts in Example 1 were transferred to the spinneret and spun into fibers, the melt indicators and viscosity difference are shown in Table 2 below. The fiber properties of the present disclosure were all tested in accordance with the GBT8960-2015 test standard.

TABLE 2

Process conditions and viscosity at the spinning manifold in Example 1

Viscosity

Temperature
Intrinsic
Temperature
Intrinsic
difference

of low-
viscosity
of high-
viscosity
between high-

viscosity
of low-
viscosity
of high-
viscosity

melt (at
viscosity
melt (at
viscosity
and low-

spinning
melt (at
spinning
melt (at
viscosity melts

manifold)/
spinning
manifold)/
spinning
(at spinning

No.
° C.
manifold)
° C.
manifold)
manifold)

1-1
275.8
0.463
288.2
0.678
0.215

1-2
275.5
0.535
289.0
0.676
0.141

2-1
275.7
0.459
288.8
0.682
0.223

2-2
275.8
0.531
288.6
0.685
0.154

3-1
275.6
0.457
288.8
0.697
0.240

3-2
275.3
0.537
289.5
0.694
0.157

4-1
275.7
0.485
289.2
0.709
0.224

4-2
276.2
0.450
289.7
0.707
0.257

5-1
275.7
0.492
288.2
0.719
0.227

5-2
275.6
0.447
288.6
0.721
0.274

6-1
275.9
0.490
288.7
0.740
0.250

6-2
275.2
0.451
289.1
0.743
0.292

7-1
275.4
0.534
288.4
0.749
0.215

7-2
276.0
0.455
289.3
0.752
0.302

8-1
275.6
0.539
288.7
0.769
0.230

8-2
276.1
0.449
288.9
0.773
0.324

9-1
276.2
0.537
288.8
0.788
0.251

9-2
276.3
0.450
289.2
0.785
0.335

The properties of the composite elastic fiber obtained by spinning the corresponding high-viscosity and low-viscosity PET melts in Example 1 are shown in Table 3.

TABLE 3

Physical and chemical indicators of PET/PET two-component composite elastic fibers in Example 1

Viscosity
Denier
Strength/
Elongation/
Oil
Yarn evenness
Boiling water
Crimp shrinkage
Interlacing

No.
difference
count/dtex
cN/dtex
%
content/%
CV/%
shrinkage/%
rate/%
point

1-1
0.215
55.7
2.85
31.55
1.62
1.27
19.65
30.2
6

1-2
0.141
55.7
2.89
33.25
1.58
1.26
22.56
22.5
6

2-1
0.223
55.7
2.92
31.27
1.60
1.24
18.78
31.8
5

2-2
0.154
55.7
2.93
33.16
1.61
1.25
21.84
23.7
6

3-1
0.240
55.7
2.95
31.58
1.59
1.26
18.42
33.3
6

3-2
0.157
55.7
2.97
33.92
1.55
1.22
18.51
23.5
6

4-1
0.224
55.7
3.01
31.43
1.53
1.18
18.82
31.5
6

4-2
0.257
55.7
3.05
30.69
1.59
1.23
18.15
35.2
6

5-1
0.227
55.7
3.07
31.64
1.54
1.19
18.35
32.4
5

5-2
0.274
55.7
3.10
30.26
1.61
1.18
17.88
37.5
6

6-1
0.250
55.7
3.11
31.08
1.53
1.25
18.22
34.4
6

6-2
0.292
55.7
3.08
28.35
1.55
1.21
17.73
37.9
6

7-1
0.215
55.7
3.13
31.81
1.61
1.24
18.64
29.6
6

7-2
0.302
55.7
3.12
27.66
1.57
1.26
17.55
39.6
5

8-1
0.230
55.7
3.15
31.45
1.52
1.16
18.66
32.6
6

8-2
0.324
55.7
3.16
25.87
1.57
1.25
17.35
42.3
5

9-1
0.251
55.7
3.15
31.07
1.61
1.18
18.23
34.1
6

9-2
0.215
55.7
3.18
24.09
1.64
1.22
17.32
43.1
6

Example 2

This example provides a preparation method for a PET two-component elastic fiber and this method is basically the same as that of Example 1, except that: a solid-phase smoothing agent was also introduced to a solid-phase smoothing agent injection system, the solid-phase smoothing agent was specifically polyester masterbatch of talc with a particle size of 100 to 250 nm, and the amount of the solid-phase smoothing agent was 0.25% relative to the total mass of the melt; the different intrinsic viscosities of the high-viscosity melt and the low-viscosity melt were controlled, and the intrinsic viscosity of the high-viscosity melt was controlled within a range of 0.80 to 0.90. The corresponding device condition setting and melt properties are shown in Table 4 below. When the high-viscosity and low-viscosity PET melts were transferred to the spinneret and spun into fibers, the melt indicators and viscosity difference are shown in Table 5 below. Nos. 10-1, 10-2 and 10-3 correspond to Example 2.

Example 3

This example provides a preparation method for a PET two-component elastic fiber and this method is basically the same as that of Example 2, except that: a viscosity reducer was also introduced to a viscosity reducer injection system, the viscosity reducer was specifically PETG with an intrinsic viscosity of 0.58, tested using a mixed solvent of phenol and tetrachloroethane (v/v: 3:2), and the amount of the viscosity reducer was 0.5% relative to the total mass of the melt; the different intrinsic viscosities of the high-viscosity melt and the low-viscosity melt were controlled, and the intrinsic viscosity of the high-viscosity melt was controlled within a range of 0.80 to 0.90. The corresponding device condition setting and melt properties are shown in Table 4 below. When the high-viscosity and low-viscosity PET melts were transferred to the spinneret and spun into fibers, the melt indicators and viscosity difference are shown in Table 5 below. Nos. 11-1, 11-2 and 11-3 correspond to Example 3.

Example 4

This example provides a preparation method for a PET two-component elastic fiber and this method is basically the same as that of Example 1, except that: a liquid-phase lubricant was also introduced to a liquid-phase lubricant injection system, the liquid-phase lubricant was specifically poly (butylene glycol) adipate with a molecular weight of 10000, and the amount of the liquid-phase lubricant was 0.25% relative to the total mass of the melt; the different intrinsic viscosities of the high-viscosity melt and the low-viscosity melt were controlled, and the intrinsic viscosity of the high-viscosity melt was controlled within a range of 0.80 to 0.90. The corresponding device condition setting and melt properties are shown in Table 4 below. When the high-viscosity and low-viscosity PET melts were transferred to the spinneret and spun into fibers, the melt indicators and viscosity difference are shown in Table 5 below. Nos. 12-1, 12-2 and 12-3 correspond to Example 4.

TABLE 4

Process conditions and viscosity of Examples 2-4

Vacuum degree

Low-

of high-
High-

Vacuum degree of
viscosity

viscosity final
viscosity
Viscosity
Viscosity difference

low-viscosity final
melt outlet
Viscosity of
polymerization
melt outlet
of high-
between high-

polymerization
temperature/
low-viscosity
reactor
temperature/
viscosity
viscosity and low-

No.
Additive type
reactor (Pa)
° C.
melt
(Pa)
° C.
melt
viscosity melts

10-1
Solid-phase
158.0
282.1
0.461
145.5
286.2
0.802
0.341

10-2
smoothing agent
158.6
281.5
0.463
128.0
286.0
0.855
0.392

10-3
(0.25%)
154.6
282.4
0.463
104.2
286.0
0.902
0.439

11-1
Viscosity reducer
163.4
279.8
0.455
145.0
285.8
0.805
0.350

11-2
(0.5%)
169.3
282.2
0.456
129.8
285.7
0.853
0.397

11-3

168.5
279.3
0.453
110.2
285.3
0.899
0.446