Melt direct-spinning full matte high and low viscosity pet two-component elastic fibre and preparation method therefor

Abstract

The present invention relates to a melt direct-spinning full matte high and low viscosity PET two-component elastic fibre and a preparation method therefor. A liquid titanium dioxide matting agent containing a specific carrier is added to the elastic fibre, the carrier being a linear polyester or a small molecule ester; either end of the linear polyester independently contains a carboxyl functional group or a hydroxyl functional group, and the molecular weight of the linear polyester is 1800-2500; the small molecule ester is of ABA type or BAB type structure, wherein A is dibasic acid, and B is diol. During preparation of the elastic fibre, in addition to a first and second esterification reaction and a first and second pre-polymerisation reaction of terephthalic acid and ethylene glycol, the prepolymer and the liquid titanium dioxide matting agent are polymerised together to prepare a high viscosity component, the prepolymer is independently polymerised to prepare a low viscosity component, and then the two components are spun together. Using the present method, the viscosity of the high viscosity component can be significantly increased, and the quality and curl shrinkage rate of the elastic fibre are high.

Description

A melt-spun fully matte high- and low-viscosity PET bicomponent elastic fiber and its preparation method Technical Field

[0001] The invention relates to a melt-spun fully matt high- and low-viscosity PET two-component elastic fiber and a preparation method thereof. Background Art

[0002] The application scope of elastic fibers in the modern chemical fiber industry is becoming wider and wider. Especially in recent years, with the rapid development of the theory of bicomponent elastic fibers, we have a deeper understanding of the forming mechanism and elasticity generation mechanism of parallel bicomponent elastic fibers, and the varieties of elastic fibers and original technologies have also made great progress. Starting in the 1970s, DuPont first launched single-component spandex elastic fiber, which quickly became popular in the market for its unique style and characteristics. In the late 1970s, it launched the two-component parallel elastic fiber T800, which uses PBT / PET parallel composite to produce good elastic effect. However, due to the low glass transition temperature (26-42°C) of the PBT component of PBT / PET elastic fiber, the fiber undergoes rapid crystallization under stress, and the elastic recovery rate and shape retention of T800 fiber are poor. In the 21st century, with the successful industrialization of PDO by chemical and biological fermentation methods, PTT polyester has a unique molecular structure and excellent elastic recovery properties. DuPont's T400, PTT / PET two-component elastic fiber, was launched. The PTT / PET two-component parallel composite fiber has excellent elastic recovery rate and shape retention. The fabric will not deform after repeated stretching. Its elastic sustained-release effect overcomes the restraining feeling of spandex elastic fiber. With its excellent resistance to chlorine bleaching and light exposure, it has become the best elastic fiber variety in the fabric industry.

[0003] However, the price of PTT polyester raw materials is high, and PTT / PET two-component fibers are basically used in the category of high-end fabrics. For some fabrics with lower elasticity requirements, the cost-effectiveness is not outstanding. Therefore, the development of two-component elastic fibers has become a key area of ​​development in the industry in the past decade. The latest progress is to utilize the different orientation and crystallization behaviors between different viscosity components of PET polyester, and use high-viscosity PET and low-viscosity PET with a certain viscosity difference for parallel spinning to prepare PET / PET two-component elastic fibers. During the spinning process, the high-viscosity component and the low-viscosity component produce elastic curling due to the different speeds and percentages of transition from the orientation state to the crystallization state, forming a spring-like structure, thus showing a good elastic effect on the fabric. Patents such as CN111101237A, CN101126180A, CN106337212A, CN107964690A, CN101851812A, and CN115613159A respectively disclose a series of methods for preparing parallel composite elastic fibers such as PET / PET, PBT / PET, and PTT / PET, as well as methods for preparing easily dyed or deeply dyed elastic fibers by using modified PET with elasticity retention, such as high-viscosity ECDP, high-viscosity high-shrinkage polyester, high-viscosity disperse dye-easy polyester, high-viscosity CDP cationic polyester, etc., and low-viscosity PET polyester.

[0004] The preparation methods of the above-mentioned elastic fibers are all based on a slice spinning production process in which high-viscosity slices and low-viscosity slices are pre-crystallized and melted by a drying screw, and then formed into a composite spinning box and a composite parallel spinneret. Although the basic parallel composite spinning technology problems have been solved, the slice spinning technology has obvious defects such as long process, high cost, low production capacity, and poor product quality stability.

[0005] Fully matte elastic fiber products are made from fully matte polyester raw materials containing a high content of titanium dioxide matting agent, which is an inorganic powder. The large amount of inorganic powder added significantly increases the level of powder agglomeration, resulting in a significant reduction in the life cycle of pre-polymerization and final polymerization filters. Secondly, the titanium dioxide matting agent contains a certain amount of impurities such as high-valent arsenic oxides and antimony oxides. These impurities exacerbate side reactions during the polymerization process, generating a large amount of non-condensable gas components, resulting in poor product color and a significant increase in vacuum load, which reduces equipment efficiency. Finally, the matting agent in fully matte polyester causes significant dynamic thickening in the late polymerization stage as the polymer viscosity increases. This deteriorates melt flowability, significantly reduces material turnover efficiency on the disc reactor surface, and significantly increases the residence time of the melt on the disc reactor surface, leading to a significant increase in thermal degradation side reactions. This directly causes acetaldehyde production to be several times higher than that produced in normal polymerization reactions, making stable and efficient high-viscosity polymerization difficult. In the prior art, liquid titanium dioxide matting agents are used as matting agents for polyester elastic fibers. The carriers of these liquid titanium dioxide matting agents are typically low-polymerization-degree polyacrylates, medium-molecular-weight PEGs, or inert white oils. These carriers do not react with polyester and are therefore typically injected into the melt line after the polymerization reaction has completed. However, these carriers are not well compatible with polyester and can cause certain side reactions, resulting in a decrease in the hue quality of the polyester.

[0006] Summary of the Invention

[0007] The present invention aims to provide a liquid titanium dioxide matting agent. When the matting agent is used for melt-spinning fully matt high- and low-viscosity PET bicomponent elastic fibers, the viscosity of the high-viscosity polyester melt can be further increased, and the matting agent has good compatibility with the polyester fibers, thereby ensuring the quality of the bicomponent elastic fibers.

[0008] Another object of the present invention is to provide a melt-spun fully matte high- and low-viscosity PET bicomponent elastic fiber, in which the viscosity of the high-viscosity polyester component can reach a very high level, and the hue quality of the elastic fiber is significantly improved, and the curl shrinkage rate is high.

[0009] Another object of the present invention is to provide a method for preparing a melt-spun fully matt high- and low-viscosity PET bicomponent elastic fiber. This preparation method can effectively control the viscosity and flow of the melt when the viscosity of the high-viscosity polyester melt component is very high, significantly reduce the apparent melting point of the melt, greatly reduce the residence time of the matting agent during the reaction process, reduce side reactions, and significantly improve the hue quality of the polyester.

[0010] In order to achieve the above object, the technical solution adopted by the present invention is:

[0011] A liquid titanium dioxide matting agent is used for fully matt PET two-component elastic fiber. The PET two-component elastic fiber contains a first PET component and a second PET component, and the first and second PET components have different viscosities. The liquid titanium dioxide matting agent includes titanium dioxide and a carrier; the carrier is a linear polyester or a small molecule ester; either end of the linear polyester independently contains a carboxyl functional group or a hydroxyl functional group, and the molecular weight of the linear polyester is 1800-2500; the small molecule ester has an ABA type or BAB type structure, wherein A is a dibasic acid and B is a diol.

[0012] In the present invention, the ABA-type structure refers to the esterification product structure of a small molecule ester with dibasic acid structures at both ends and A and B in the middle. Multiple esterification repeating units may be present in the middle, but the overall molecular weight is still low and does not reach the molecular weight level of a prepolymer. Similarly, the BAB-type structure refers to the esterification product structure of a small molecule ester with diol structures at both ends and A and B in the middle. Multiple esterification repeating units may be present in the middle, but the overall molecular weight is still low and does not reach the molecular weight level of a prepolymer.

[0013] In some embodiments, the carrier has a viscosity of 2 to 20 Pa.s at 25° C. and a viscosity of 1.0 to 8.0 Pa.s at 60° C.

[0014] In some embodiments, the melting point of the small molecule ester is less than or equal to 20°C, and the boiling point is greater than or equal to 290°C.

[0015] In some embodiments, the carrier has a thermal weight loss of less than or equal to 0.2% at 290° C. for 2.0 hours under nitrogen protection.

[0016] The dispersant of the liquid titanium dioxide matting agent of the present invention is a bifunctional linear polyester or a small molecule ester. When the matting agent is used for melt-spinning fully matt high- and low-viscosity PET two-component elastic fibers, the dispersant can participate in the polymerization reaction of polyester synthesis, thereby improving the viscosity and fluidity of the polyester melt and lowering the apparent melting point of the high-viscosity polyester melt. In addition, during the polymerization process of polyester, due to the good compatibility of the liquid titanium dioxide matting agent with the polyester matrix, its residence time is greatly reduced, thereby significantly improving the hue of the high-viscosity fully matt polyester, significantly reducing the film thickness of the high-viscosity melt with fluidity in the high-viscosity area, reducing the material residence time, significantly reducing side reactions, and being more conducive to the formation of a plug flow effect during the melt conveying process. Due to the use of the above-mentioned specific dispersant, the liquid titanium dioxide matting agent of the present invention can be used without the use of any other dispersants or leveling agents or other auxiliary agents. The linear polyester carrier molecule has a double functional group at the end and a molecular weight of 1800 to 2500, which is similar to the average molecular weight of the online PET polyester prepolymer. After mixing with the conventional PET polyester prepolymer, it has the same probability of participating in polymerization and can successfully complete block copolymerization.

[0017] In some embodiments, the liquid titanium dioxide matting agent contains 20%-50% titanium dioxide and 50%-80% carrier in terms of weight percentage.

[0018] In some embodiments, the dibasic acid is selected from one or more of succinic acid, glutaric acid, adipic acid, suberic acid, sebacic acid, neopentanoic acid, 1,4-cyclohexanedicarboxylic acid, and phthalic acid.

[0019] In some embodiments, the diol is selected from one or more combinations of 1,3-butanediol, 1,4-butanediol, pentanediol, hexanediol, nonanediol, octanediol, neopentyl glycol, diethylene glycol, and 1,4-cyclohexanedimethanol.

[0020] In some embodiments, the linear polyester is an oligomer of a dibasic acid and a diol, the dibasic acid is selected from a combination of one or more of succinic acid, glutaric acid, adipic acid, suberic acid, sebacic acid, neopentanedioic acid, 1,4-cyclohexanedicarboxylic acid and phthalic acid, and the diol is selected from a combination of one or more of 1,3-butanediol, 1,4-butanediol, pentanediol, hexanediol, nonanediol, octanediol, neopentyl glycol, diethylene glycol and 1,4-cyclohexanedimethanol.

[0021] In some embodiments, the liquid titanium dioxide matting agent is prepared by dispersing, grinding, and filtering titanium dioxide and a carrier.

[0022] The present invention also provides a method for preparing the liquid titanium dioxide matting agent, which comprises the steps of dispersing, grinding and filtering titanium dioxide and a dispersant to obtain the liquid titanium dioxide matting agent.

[0023] The present invention also provides a method for preparing a fully matt PET two-component elastic fiber, the method comprising the steps of sequentially passing terephthalic acid, ethylene glycol, a catalyst, and an optional modified monomer through a first esterification kettle for a first esterification reaction, a second esterification kettle for a second esterification reaction, a first prepolymerization kettle for a first prepolymerization reaction, and a second prepolymerization kettle for a second prepolymerization reaction to obtain an ethylene terephthalate prepolymer; the method further comprising passing the ethylene terephthalate prepolymer and the aforementioned liquid titanium dioxide matting agent into a high-viscosity final polymerization kettle for a polymerization reaction. , obtaining a matt high-viscosity polyethylene terephthalate melt, and passing the polyethylene terephthalate prepolymer into a low-viscosity final polymerization kettle for polymerization reaction to obtain a low-viscosity polyethylene terephthalate melt, wherein the viscosity of the high-viscosity polyethylene terephthalate melt is greater than the viscosity of the low-viscosity polyethylene terephthalate melt; and spinning the matt high-viscosity polyethylene terephthalate melt and the low-viscosity polyethylene terephthalate melt through the same spinning assembly to obtain the fully matt PET two-component elastic fiber.

[0024] The present invention sequentially conducts a first esterification reaction and a second esterification reaction on terephthalic acid and ethylene glycol, then conducts a first prepolymerization reaction in a first prepolymerization kettle and a second prepolymerization reaction in a second prepolymerization kettle to obtain an ethylene terephthalate prepolymer, and then respectively conducts final polymerization on the prepolymer in a high-viscosity final polymerization kettle and a low-viscosity final polymerization kettle to obtain a high-viscosity polyethylene terephthalate melt and a low-viscosity second polyethylene terephthalate melt, and at the same time, the liquid titanium dioxide matting agent of the present invention is introduced into the high-viscosity final polymerization kettle together with the ethylene terephthalate prepolymer. The final polymerization reaction is carried out in the liquid titanium dioxide matting agent. Since the carrier in the liquid titanium dioxide matting agent has a bifunctional group, it can participate in the final polymerization reaction. Therefore, even if a large amount of matting agent needs to be added to achieve full matting, it will not cause the melt fluidity of the high-viscosity polyethylene terephthalate melt to deteriorate. Furthermore, in the high-viscosity final polymerization kettle for preparing the high-viscosity melt through polymerization, the material renewal efficiency in the polymerization reaction device is still high, which will not cause a significant extension of the material residence time, thereby significantly improving the progress of thermal degradation side reactions, and ensuring the comprehensive quality of the final fully matting PET two-component elastic fiber.

[0025] The method for preparing the fully matt PET two-component elastic fiber of the present invention adopts a six-reactor 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.

[0026] The fully matte PET bicomponent elastic fiber of the present invention comprises a high-viscosity and a low-viscosity bicomponent. The high-viscosity polyethylene terephthalate melt corresponds to the high-viscosity component, while the low-viscosity polyethylene terephthalate melt corresponds to the low-viscosity component. The fully matte PET bicomponent elastic fiber is prepared by a melt-spinning method, in which the melt obtained after polymerization is directly used for spinning, without the melt cooling and slicing steps and then remelting for spinning.

[0027] In some embodiments, the PET bicomponent elastic fiber comprises, by weight, 30% to 70% of a first PET component and 70% to 30% of a second PET component, wherein the first PET component and the second PET component have different viscosities. The first PET component and the second PET component correspond to a high-viscosity component and a low-viscosity component, respectively.

[0028] In some embodiments, the preparation method further comprises the step of introducing a matting agent paste into the second esterification kettle before the esterification reaction. The matting agent paste is prepared by grinding and dispersing titanium dioxide and ethylene glycol. The matting agent paste is a common matting agent paste in the prior art. The amount of the matting agent paste used can be 0.1% to 0.5% of the melt mass, preferably 0.3%.

[0029] In some embodiments, the matt high-viscosity polyethylene terephthalate melt contains 1.6% to 8.0% by mass of titanium dioxide.

[0030] In some embodiments, the preparation method further comprises mixing the ethylene terephthalate prepolymer and the liquid titanium dioxide matting agent in a dynamic mixer before introducing them into the high-viscosity final polymerization kettle. Mixing the two before introducing them into the final polymerization kettle can ensure a more uniform mixing of the two, which is more conducive to uniform dispersion of the liquid titanium dioxide matting agent in the prepolymer.

[0031] In some embodiments, the catalyst is a supported catalyst and includes a carrier and an active component; the carrier is selected from nano-alumina or nano-silicon dioxide, the particle size of the carrier is 10-30 nm and the specific surface area is 200 m 2 / g or more; the active component is a mixture of an oxide of metal M and a carbonate of metal M, and the metal M is selected from a combination of one or more of vanadium, tungsten, zirconium, iron, zinc, calcium, magnesium, aluminum, cobalt and scandium.

[0032] In some embodiments, the metal M is zirconium.

[0033] In some embodiments, the metal M is zirconium and cobalt. Preferably, the mass of elemental cobalt accounts for 4% to 8% of the total mass of elemental zirconium and elemental cobalt.

[0034] When synthesizing polyesters using existing technologies, antimony catalysts such as ethylene glycol antimony, antimony acetate, or titanium catalysts are usually used. Heat stabilizers and antioxidants are also used in the polymerization system. However, heat stabilizers and the above-mentioned antimony catalysts will undergo precipitation reactions during the esterification and polymerization reactions, forming precipitates such as antimony phosphate, which leads to the formation of scale layers on the heat medium coils in the esterification and polymerization reactions. After the synthesis device has been running for a long time, the thickness of the scale layer will continue to increase, resulting in a serious reduction in the heat transfer efficiency of the reactor and a significant shortening of the device operation cycle. Secondly, in the high-viscosity polymerization reaction and melt conveying section carried out in the high-viscosity final polymerization reactor, the reducing byproducts of the high-viscosity melt cracking reaction will also reduce the antimony element, forming antimony metal precipitates, resulting in the formation of antimony white metal scale layers on the melt conveying pipeline and the spinning manifold. Finally, a high proportion of titanium dioxide matting agent is usually added to fully matte polyester. Since traditional titanium dioxide matting agents, such as color pastes, use a large amount of surface coating agents, the coating agents will seriously passivate the catalytic activity of the titanium catalyst, which is not conducive to the stable progress of the polymerization reaction in the high-viscosity zone.

[0035] Based on this, the present invention adopts a supported catalyst, the carrier of which has a large specific surface area, and the active components are oxides and carbonates of metals other than antimony and titanium. The use of this catalyst has mild catalytic conditions, can improve the thermal stability of the melt, enhance the color of high-viscosity polyester melt products, and reduce the level of side reactions. Moreover, since the active component is a compound of an active metal element, it will not undergo precipitation reaction with phosphate radicals in the thermal stabilizer, etc., nor will it be reduced to a metal element by the reducing groups cracked during the high-viscosity polymerization reaction. Therefore, it will not cause the formation of a large amount of scale in the polyester device or the melt conveying section, which is beneficial to the long-term operation of the device.

[0036] In some embodiments, the catalyst contains 94%-97% of the support and 3%-6% of the active component by weight.

[0037] In some embodiments, the catalyst is prepared by precipitating a carrier, a compound containing a metal M element, and a precipitant, surface treating with a silane coupling agent, and calcining; the compound containing a metal M element is selected from a sulfate, chloride, oxide, or hydroxide of the metal M element.

[0038] In some embodiments, the precipitating agent is sodium hydroxide.

[0039] The silane coupling agent may be any conventional silane coupling agent.

[0040] In some embodiments, the amount of the catalyst used is 260 to 600 ppm relative to the mass of the melt.

[0041] In some embodiments, the amount of the catalyst used is 300-450 ppm relative to the mass of the melt.

[0042] In some embodiments, the raw materials of the preparation method further include a Lewis base, and the amount thereof is 60 to 100 ppm relative to the melt.

[0043] In some embodiments, in step 1), the modifying monomer is added, and the modifying monomer is selected from one or more combinations of 1,4-cyclohexanedicarboxylic acid, isophthalic acid, 2,6-naphthalene dicarboxylic acid, phthalic acid, trimellitic anhydride, pyromellitic acid, neopentanoic acid, furandicarboxylic acid, 2,2,4,4-cyclobutanedicarboxylic acid, 1,4-cyclohexanedimethanol, pentaerythritol, neopentyl glycol, hydroquinone, and 2,2,4,4-tetramethyl-cyclobutane dimethanol.

[0044] In some embodiments, the molar amount of the modifying monomer is 0.5% to 8.0% of the molar amount of the terephthalic acid.

[0045] In some embodiments, the molar amount of the modifying monomer is 1.0% to 5.0% of the molar amount of the terephthalic acid.

[0046] In some embodiments, the molar amount of the modifying monomer is 1.5% to 3.0% of the molar amount of the terephthalic acid.

[0047] The polymerization monomers of the present invention may include only terephthalic acid and ethylene glycol, or may be modified by adding the above-mentioned modified monomers. The above-mentioned modified monomers are rigid comonomers with greater steric hindrance, which can improve the curl shrinkage and curl stability of the resulting two-component elastic fiber without changing the basic physical and chemical properties of the high- and low-viscosity melt polymers. In addition, the melting point of the melt can be effectively reduced by 5 to 8°C, while significantly reducing the level of side reactions. Moreover, the above-mentioned modified monomers change the viscosity of the melt, which can effectively reduce the dynamic viscosity of the high-viscosity melt, ensuring that the high-viscosity melt has a better film-forming effect in the first final polymerization kettle, and improving the reaction efficiency of high-viscosity polymerization. During the melt conveying process, the lower dynamic viscosity can improve the kinetic energy release efficiency of the macromolecular curling and quickly form a stable plug flow.

[0048] In some embodiments, the high viscosity final polymerization kettle is a horizontal polymerization kettle, and includes a main body containing a chamber, a feed port, and a discharge port. The main body includes a low viscosity zone, a medium-high viscosity zone, and a high viscosity zone arranged in sequence along the axial direction of the high viscosity final polymerization kettle. The viscosity of the polyethylene terephthalate melt in the low viscosity zone, the medium-high viscosity zone, and the high viscosity zone increases in sequence. The high viscosity final polymerization kettle also includes two stirring shafts arranged in parallel along its axial direction. The two stirring shafts rotate in opposite directions. A plurality of stirrers are provided on the two stirring shafts. The outer periphery of the stirrer is circular. The stirrers on the two stirring shafts are correspondingly arranged and the circular outer peripheries are tangentially in contact. The stirrer in the high viscosity zone is a double-disc type. In the present invention, the double-disc type refers to fixing two adjacent stirrers with circular outer peripheries together to achieve the same rotation of the two to improve the strength of the stirrer, which is conducive to not being easily damaged in a high viscosity melt environment. In the prior art, when synthesizing polyester, the polymerization device in the conventional polymerization kettle is a front-back dual-axis disc reactor, while the high-viscosity final polymerization kettle used to synthesize high-viscosity polyester of the present invention adopts a dual-axis disc reactor (agitator) arranged in parallel. The disc reactors arranged on the dual axes are correspondingly arranged and rotate tangentially in opposite directions. The two can form an efficient shearing effect, so that the disc reactor has a good self-cleaning effect, and can significantly improve the material mass transfer efficiency, accelerate the material renewal rate, and thus greatly shorten the polymerization reaction residence time, effectively reduce the side reaction level, and greatly improve the quality of the high-viscosity full-dull polyester melt. The above-mentioned high-viscosity final polymerization kettle of the present invention can reduce the residence time of the material in the high-viscosity final polymerization kettle to 40% to 55% of that of the ordinary polymerization kettle, and the residence time can be as low as 80 to 120 minutes. In addition, the dual-disc disc reactor is arranged in the high-viscosity zone, which is more helpful to solve the problem of the difficulty in producing high-viscosity full-dull polyester, and can obtain a polyester melt with good quality stability, and greatly reduce the generation of agglomerated particles in the final polycondensation stage, and extend the switching cycle of the filter before the final polymerization kettle.

[0049] In some embodiments, the distance between two adjacent stirrers increases successively from the low viscosity zone to the medium-high viscosity zone to the high viscosity zone; the distance between two adjacent stirrers in the high viscosity zone is 8-50 mm.

[0050] In some embodiments, the high viscosity final polymerization kettle further comprises a composite scraper, wherein the composite scraper comprises an axial scraper for scraping the melt on the stirring shaft, a wall scraper for scraping the melt on the inner wall of the high viscosity final polymerization kettle, and a disk scraper for scraping the melt on the stirrer.

[0051] In some embodiments, the axial scraper makes the melt thickness on the stirring shaft no more than 10 mm, the wall scraper makes the melt thickness on the inner wall of the high-viscosity final polymerization reactor no more than 10 mm, and the disk scraper makes the melt thickness on the stirrer no more than 8 mm.

[0052] In the prior art, although scrapers are installed in conventional polymerization reactors, the scraper structure is relatively simple and its function is relatively limited. In the high-viscosity final polymerization reactor of the present invention, by adopting the above-mentioned composite scraper, the material renewal rate on the agitator, the surface of the stirring shaft, and the wall of the polymerization reactor can be effectively controlled, so that the material in these three places does not accumulate too much, effectively suppressing the problems of color degradation and large amounts of acetaldehyde generated during the production of fully matte high-viscosity melt. The disk scraper of the composite scraper of the present invention can control the thickness of the disk melt film, the wall scraper can timely update the material on the wall of the polymerization reactor, and the axial scraper can clean the stirring shaft. By providing the above-mentioned composite scraper, the material residence time in the high-viscosity final polymerization reactor can be controlled to 80 to 120 minutes, which is much lower than the residence time of conventional front and rear dual-axis high-viscosity disc reactors, which are generally around 180 to 300 minutes. The significant reduction in residence time effectively reduces the level of side reactions, which is beneficial to the preparation of high-viscosity fully matte polyester melt. Moreover, due to the parallel dual-axis arrangement, the total volume of the high-viscosity final polymerization reactor of the present invention can be achieved to be about half that of a conventional final polymerization reactor.

[0053] In some embodiments, there are 10-16 agitators in the high viscosity zone.

[0054] In some embodiments, the high-viscosity final polymerization kettle further includes steam inlets located at the top of the medium-high viscosity zone and the high viscosity zone for introducing superheated ethylene glycol vapor. The preparation method further includes the step of metering the superheated ethylene glycol vapor using a metering system and introducing the superheated ethylene glycol vapor into the high-viscosity final polymerization kettle. The polyester melt has a higher viscosity in the medium-high viscosity zone and the high viscosity zone. The steam inlets located in these zones can enhance devolatilization efficiency, ensure good melt film drawing, and control the thickness of the melt film on the plate.

[0055] In some embodiments, the preparation method further includes the steps of passing the matte high-viscosity polyethylene terephthalate melt and the low-viscosity polyethylene terephthalate melt through a filter and a booster pump respectively before passing them through the same spinning assembly, and the preparation method controls the time for conveying the matte high-viscosity polyethylene terephthalate melt from the high-viscosity final polymerization kettle to the spinning assembly to be 30-40 minutes.

[0056] In some embodiments, the high-viscosity final polymerization reactor is disposed on top of the spinning assembly, thereby reducing the conveying distance of the high-viscosity polyester melt synthesized in the high-viscosity final polymerization reactor before spinning.

[0057] In some embodiments, the preparation method further includes the step of adding a viscosity reducer to the matte high-viscosity polyethylene terephthalate melt before the matte high-viscosity polyethylene terephthalate melt passes through a filter; the viscosity reducer is selected from a combination of one or more of polyethylene terephthalate-1,4-cyclohexanedimethanol ester (PETG), cationic dyeable polyester (CDP), cationic dye-easily dyeable polyester (ECDP), normal pressure boiling-dyeable polyester (EDDP), polybutylene terephthalate (PBT), and polypropylene terephthalate (PTT). An auxiliary agent injection system is designed before the high-viscosity melt is conveyed through the filter to inject the viscosity reducer. The addition of the viscosity reducer can significantly 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. This can achieve a more stable spinning effect and an improved fiber curl without affecting the basic indicators and quality of the final two-component elastic fiber product.

[0058] In some embodiments, the preparation method further includes the steps of adding a solid-phase smoothing agent to the ethylene terephthalate prepolymer before the ethylene terephthalate prepolymer is introduced into the high-viscosity final polymerization kettle, and passing the mixture of the solid-phase smoothing agent and the ethylene terephthalate prepolymer through a filter, wherein the solid-phase smoothing agent is in the form of a masterbatch and includes a polyester matrix and an inorganic powder, wherein the inorganic powder is selected from a combination of one or more of talc, montmorillonite, barium sulfate, hydrotalcite, and nano-silica. The addition of the solid-phase smoothing agent can generate friction between the fluid surface and the tube wall, thereby increasing the fluidity of the melt and reducing the viscosity of the melt.

[0059] In some embodiments, the preparation method further comprises the step of mixing the mixture of the solid-phase smoothing agent and the ethylene terephthalate prepolymer through a dynamic mixer before passing the mixture through the filter.

[0060] In some embodiments, the preparation method further comprises the step of using a melt pump to transport the matte high-viscosity polyethylene terephthalate melt from the discharge port of the high-viscosity final polymerization reactor to the spinning assembly, and the outlet of the melt pump is provided with a melt cooler.

[0061] In some embodiments, the preparation method controls the average residence time of the high-viscosity polyethylene terephthalate melt in the high-viscosity zone to be 75-120 minutes, and the temperature of the high-viscosity polyethylene terephthalate melt is lower than 284°C.

[0062] In some embodiments, the preparation method further includes the step of introducing a heat stabilizer and an antioxidant from different positions of the second esterification kettle; the heat stabilizer is selected from a combination of one or more of trimethyl phosphate, triethyl phosphate, triphenyl phosphate, triphenyl phosphite, and triglyceride phosphate; and the antioxidant is selected from a combination of one or more of antioxidant 168, antioxidant 1076, antioxidant 1010, antioxidant 1222, and benzothiazole antioxidants.

[0063] By adding heat stabilizers and antioxidants to the high-viscosity area, that is, the area with the highest melt viscosity, the thermal stability and oxidation resistance of the high-viscosity PET polyester melt can be improved, 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 melt direct spinning process of up to 40 to 90 minutes can be suppressed, and the melt characteristic viscosity level can be ensured to remain high in the spinning box, thereby producing sufficient elastic curl.

[0064] In some embodiments, the difference between the intrinsic viscosity of the matte high-viscosity polyethylene terephthalate melt and the intrinsic viscosity of the low-viscosity polyethylene terephthalate melt is 0.23 to 0.45.

[0065] In some embodiments, the intrinsic viscosity of the matte high-viscosity polyethylene terephthalate melt is 0.68-0.80, and its viscosity at 280-282°C is 550-800 Pa.s; the intrinsic viscosity of the low-viscosity polyethylene terephthalate melt is 0.45-0.55, and its viscosity at 276-277°C is 90-310 Pa.s.

[0066] In some embodiments, the intrinsic viscosity of the second PET component is 0.445 to 0.520; the intrinsic viscosity of the first PET component is 0.645 to 0.750.

[0067] In some embodiments, in the same spinning assembly, the viscosity of the matte high-viscosity polyethylene terephthalate melt is 400-600 Pa.s, and the viscosity of the low-viscosity polyethylene terephthalate melt is 70-280 Pa.s.

[0068] In some embodiments, the same spinning assembly is a composite spinning beam.

[0069] In some embodiments, the composite spinning beam includes a composite spinneret.

[0070] In some embodiments, the high-viscosity region is connected to a vacuum pump, and the preparation method controls the pressure of the high-viscosity region to be 60-75 Pa. This pressure reflects an extremely high vacuum degree.

[0071] In some embodiments, the vacuum pump has a suction capacity of 80 to 150 kg / h.

[0072] Due to the increased side reactions of materials in the high-viscosity zone, the high-viscosity final polymerization reactor of the melt-spinning fully matt high- and low-viscosity bicomponent elastic polyester fiber plant requires rapid devolatilization to quickly remove the generated gaseous components from the polymerization unit. The higher the high-viscosity outlet viscosity, the greater the amount of non-condensable gas generated. Therefore, the vacuum pump of the high-viscosity final polymerization reactor requires a higher vacuum level. The liquid ring pump inlet of this vacuum pump can be designed with a large-capacity chilled water device to capture excess non-condensable acetaldehyde. To further maintain production stability, all ethylene glycol produced in the vacuum section of the plant must undergo formaldehyde removal treatment before entering the system.

[0073] The present invention also provides a fully matt PET two-component elastic fiber prepared by the above preparation method.

[0074] In some embodiments, the curl shrinkage rate of the matt PET bicomponent elastic fiber is 15.0% to 35.0%.

[0075] Due to the application of the above technical solution, the present invention has the following advantages compared with the prior art:

[0076] The dispersant of the liquid titanium dioxide matting agent of the present invention is a bifunctional linear polyester or a small molecule ester. When the matting agent is used for melt-spinning fully matt high- and low-viscosity PET two-component elastic fibers, the dispersant can participate in the polymerization reaction of polyester synthesis, thereby improving the viscosity and fluidity of the polyester melt and lowering the apparent melting point of the high-viscosity polyester melt. In addition, during the polymerization process of polyester, due to the good compatibility of the liquid titanium dioxide matting agent with the polyester matrix, its residence time is greatly reduced, thereby significantly improving the hue of the high-viscosity fully matt polyester, significantly reducing the film thickness of the high-viscosity melt with fluidity in the high-viscosity area, reducing the material residence time, significantly reducing side reactions, and being more conducive to the formation of a plug flow effect during the melt conveying process. Due to the use of the above-mentioned specific dispersant, the liquid titanium dioxide matting agent of the present invention can be used without the use of any other dispersants or leveling agents or other auxiliary agents.

[0077] The present invention sequentially conducts a first esterification reaction and a second esterification reaction on terephthalic acid and ethylene glycol, then conducts a first prepolymerization reaction in a first prepolymerization kettle and a second prepolymerization reaction in a second prepolymerization kettle to obtain an ethylene terephthalate prepolymer, and then respectively conducts a final polymerization of the prepolymer in a high-viscosity final polymerization kettle and a low-viscosity final polymerization kettle to obtain a high-viscosity polyethylene terephthalate melt and a low-viscosity second polyethylene terephthalate melt, and at the same time, the liquid titanium dioxide matting agent of the present invention is introduced into the high-viscosity final polymerization kettle together with the ethylene terephthalate prepolymer. The final polymerization reaction is carried out in the polymerization kettle. The dispersant in the liquid titanium dioxide matting agent can participate in the final polymerization reaction due to its bifunctional group. Therefore, even if a large amount of matting agent needs to be added for full matting, it will not cause the melt fluidity of the high-viscosity polyethylene terephthalate melt to deteriorate. Furthermore, when the high-viscosity melt is prepared by polymerization, the material renewal efficiency in the polymerization reaction device is still high, which will not cause a significant extension of the material residence time, thereby significantly improving the progress of thermal degradation side reactions, and ensuring the overall quality of the final fully matting PET two-component elastic fiber.

[0078] In the present invention, the intrinsic viscosity of the high-viscosity melt at the outlet of the high-viscosity polymerizer can reach 0.68 to 0.80, and its viscosity at 280-282°C is 550 to 800 Pa.s, which is much higher than the viscosity of the high-viscosity melt in the prior art. The difference in intrinsic viscosity between the high-viscosity melt at the outlet of the high-viscosity polymerizer and the low-viscosity melt at the outlet of the low-viscosity polymerizer can reach 0.23 to 0.45, which is much higher than that in the prior art.

[0079] The matte PET bicomponent elastic fiber of the present invention has an intrinsic viscosity of the high-viscosity PET component (the first PET component) of 0.645 to 0.750. The crimp shrinkage of the matte PET bicomponent elastic fiber can reach 35.0%, far higher than that of existing bicomponent elastic fibers.

[0080] The preparation method of the present invention is used for industrial production of two-component elastic fibers, which can achieve a low-viscosity and fully matte melt production capacity of 30,000 to 80,000 tons / year and a high-viscosity and fully matte melt production capacity of 30,000 to 80,000 tons / year. When the product is a melt-spun fully matte PET / PET high-low viscosity two-component elastic fiber, the comprehensive device production capacity is 60,000 to 160,000 tons / year. BRIEF DESCRIPTION OF THE DRAWINGS

[0081] FIG1 is a schematic diagram of a six-reactor polymerization system used in an embodiment of the present invention;

[0082] FIG2 is a schematic structural diagram of a high-viscosity polymerization reactor used in an embodiment of the present invention;

[0083] FIG3 is a schematic structural diagram of a composite scraper used in a high-viscosity polymerization reactor according to an embodiment of the present invention;

[0084] Among them, 1-low viscosity zone, 2-medium and high viscosity zone, 3-high viscosity zone, 4-compound scraper, 5-disk scraper, 6-axial scraper, 7-wall scraper, 8-stirring shaft, 9-stirrer, 10-first esterification kettle, 11-second esterification kettle, 12-first prepolymerization kettle, 13-second prepolymerization kettle, 14-high viscosity final polymerization kettle, 15-low viscosity final polymerization kettle, 16-pump. DETAILED DESCRIPTION

[0085] The above scheme is further described below with reference to specific examples. It should be understood that these examples are intended to illustrate the basic principles, main features, and advantages of the present invention, and the present invention is not limited in scope by the following examples. The implementation conditions used in the examples can be further adjusted according to specific requirements. The implementation conditions not specified are generally those used in routine experiments. Unless otherwise specified in the following examples, all raw materials were purchased commercially or prepared by conventional methods in the art.

[0086] The above embodiments are intended only to illustrate the technical concepts and features of the present invention. Their purpose is to enable those skilled in the art to understand the contents of the present invention and implement them accordingly. They are not intended to limit the scope of protection of the present invention. Any equivalent changes or modifications made in accordance with the spirit of the present invention are intended to be covered by the scope of protection of the present invention.

[0087] As shown in Figure 1, in the embodiment, a six-reactor system is used to prepare fully matt PET bicomponent elastic fibers: 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. The six reactors are connected by necessary piping. A pump 16 and filters A and B are located between the second prepolymerization reactor 13 and the high-viscosity final polymerization reactor 14. In actual production processes, filters A and B are not operated simultaneously. For example, filter A can be operated first, and after the system has been running for a period of time, filter B can be switched to use, at which time filter A can be cleaned.

[0088] 2 , the high viscosity final polymerization kettle 14 is a horizontal polymerization kettle, and includes a main body containing a chamber, a feed port, and a discharge port. The main body includes a low viscosity zone 1, a medium-high viscosity zone 2, and a high viscosity zone 3 arranged in sequence along the axial direction of the high viscosity final polymerization kettle 14. The viscosity of the polyethylene terephthalate melt in the low viscosity zone 1, the medium-high viscosity zone 2, and the high viscosity zone 3 increases in sequence (the prepolymer material is continuously polymerized from the low viscosity zone 1 to the medium-high viscosity zone 2, and then to the high viscosity zone 3). The high viscosity final polymerization kettle 14 also includes two stirring shafts 8 arranged in parallel along its axial direction. The two stirring shafts 8 rotate in opposite directions. A plurality of stirrers 9 are provided on the two stirring shafts 8. The outer periphery of the stirrer 9 is circular. The stirrers 9 on the two stirring shafts 8 are correspondingly arranged and the circular outer peripheries are tangentially contacted. The stirrer 9 in the high viscosity zone 3 is a double-disc type, that is, two adjacent stirrers 9 are fixedly connected. The stirrers 9 in the low viscosity zone 1 and the medium-high viscosity zone 2 are single-disc type, that is, two adjacent stirrers 9 are not fixedly connected. The distance between two adjacent stirrers 9 increases from the low viscosity zone 1 to the medium and high viscosity zone 2 to the high viscosity zone 3. The distance between two adjacent stirrers 9 in the high viscosity zone 3 is 8-50 mm. There are 10-16 stirrers 9 in the high viscosity zone 3.

[0089] As shown in Figures 2 and 3, the high-viscosity final polymerization kettle 14 also includes a composite scraper 4, which includes an axial scraper 6 for scraping the melt from the stirring shaft 8, a wall scraper 7 for scraping the melt from the inner wall of the high-viscosity final polymerization kettle 14, and a disk scraper 5 for scraping the melt from the stirrer 9. The high-viscosity final polymerization kettle 14 also includes steam feed ports provided at the top of the medium-high viscosity zone 2 and the high viscosity zone 3 for introducing superheated ethylene glycol steam.

[0090] A dynamic mixer and filters A and B can be set between the second prepolymerization kettle 13 and the high-viscosity final polymerization kettle 14; before the dynamic mixer, a liquid titanium dioxide matting agent injection system and a solid phase smoothing agent injection system are set; a filter is set between the second prepolymerization kettle and the low-viscosity final polymerization kettle 15.

[0091] After the high-viscosity final polymerization kettle 14 and before the same spinning assembly, a dynamic mixer and a filter are set; before the dynamic mixer, a viscosity reducer injection system is set; after the low-viscosity final polymerization kettle and before the same spinning assembly, a filter is set.

[0092] Necessary melt pumps, vacuum pumps, etc. can be installed on the pipes connecting the six kettles.

[0093] The same spinning assembly is a composite spinning manifold, and the high-viscosity final polymerization reactor 14 is arranged on the top of the composite spinning manifold to shorten the conveying distance of the high-viscosity melt.

[0094] Example 1

[0095] This embodiment provides a method for preparing a fully matte PET bicomponent elastic fiber, and the specific steps are as follows:

[0096] The liquid titanium dioxide matting agent is composed of 20% titanium dioxide and 80% carrier by weight. The carrier is a binary small molecule ester of succinic acid and 1,3-butanediol with an ABA structure, where A is a succinic acid residue and B is a 1,3-butanediol residue. The carrier has a viscosity of 3.6 Pa.s at 25°C and 1.0 Pa.s at 60°C, and a melting point of -23.7°C. The synthesis method and viscosity control method of the binary ester adopt known techniques from the prior art. The liquid matting agent is prepared by dispersing, grinding, and filtering titanium dioxide and a dispersant.

[0097] The preparation method of the catalyst used in this embodiment is as follows:

[0098] The specific surface area is 260m 2 / g of γ-nano alumina, zirconium sulfate and a precipitant, sodium hydroxide, are subjected to precipitation reaction, filtered, and the obtained solid is surface-treated with a silane coupling agent and then calcined to prepare a catalyst. The active component of the catalyst is a mixture of zirconium oxide and zirconium carbonate. The particle size of the catalyst is about 50nm. In terms of weight percentage, the carrier nano-alumina accounts for 94% and the active component accounts for 6%.

[0099] Using the aforementioned six-reactor polymerization apparatus, terephthalic acid, ethylene glycol, and the aforementioned catalyst were sequentially subjected to an esterification reaction in a first esterification reactor 10 and a second esterification reactor 11, followed by a prepolymerization reaction in a first prepolymerization reactor 12 and a second prepolymerization reactor 13 to produce an ethylene terephthalate prepolymer. Prior to the esterification reaction in the second esterification reactor 11, a conventional matting agent paste was introduced. The paste was prepared by grinding and dispersing titanium dioxide and ethylene glycol, wherein the titanium dioxide accounted for 10 wt% and the ethylene glycol accounted for 90 wt%. The conventional matting agent paste was used in an amount corresponding to 0.3% of the total mass of the spinning melt. The catalyst content in the PET melt was 260 ppm. The ethylene terephthalate prepolymer and the aforementioned liquid titanium dioxide matting agent are then mixed in a dynamic mixer and filtered through a filter before being passed into a high-viscosity final polymerization reactor 14 for polymerization reaction, yielding a matte, high-viscosity polyethylene terephthalate melt. Simultaneously, the ethylene terephthalate prepolymer is separately passed into a low-viscosity final polymerization reactor 15 for polymerization reaction, yielding a low-viscosity polyethylene terephthalate melt. Finally, the matte, high-viscosity melt and the low-viscosity melt are directly passed into a composite spinning manifold at a mass ratio of 5:5 for spinning, yielding a fully matte PET bicomponent elastic fiber, designated FDY, with a specification of 55 dtex / 36 f. The amount of liquid titanium dioxide matting agent used is such that the corresponding titanium dioxide accounts for 1.7% of the total mass of the spinning melt.

[0100] The conditions of the six-reactor polymerization apparatus and the properties of the high-viscosity melt with extinction are shown in Table 1. The intrinsic viscosity is measured by dissolving the melt in a mixed solvent of phenol and tetrachloroethane (3:2 by volume), and the unit is dL / g.

[0101] Example 2

[0102] This example provides a method for preparing a fully matte PET bicomponent elastic fiber. This method is essentially the same as that of Example 1, differing only in that the carrier in the composition of the liquid titanium dioxide matting agent is replaced with a linear polyester of succinic acid and 1,3-butanediol, having a molecular weight of 2000 and a viscosity of 18.0 Pa.s at 25°C and ~6.8 Pa.s at 60°C. The linear polyester synthesis method and molecular weight control method employ known techniques from the prior art.

[0103] Example 3

[0104] This embodiment provides a method for preparing a fully matt PET two-component elastic fiber. The method is basically the same as that in Example 1, except that the catalyst carrier is replaced by nano-silicon dioxide instead of nano-alumina.

[0105] Example 4

[0106] This embodiment provides a method for preparing a fully matte PET bicomponent elastic fiber. The method is basically the same as that of Example 2, except that the active component of the catalyst is partially replaced by a mixture of cobalt oxide and cobalt carbonate instead of a mixture of zirconium oxide and zirconium carbonate. That is, cobalt acetate is also added to the raw materials when synthesizing the catalyst. In the catalyst, the mass of the cobalt element accounts for 6% of the total mass of the cobalt element and the zirconium element.

[0107] Example 5

[0108] This embodiment provides a method for preparing a fully matte PET bicomponent elastic fiber. The method is substantially the same as that of Example 2, except that: a viscosity reducer, PETG, having an intrinsic viscosity of 0.68 (measured in a mixed solvent of phenol and tetrachloroethane in a volume ratio of 3:2), is introduced into a polymerization apparatus via a viscosity reducer injection system, and the amount used is 0.75% of the total mass of the melt; and a solid-phase smoothing agent, nano-barium sulfate polyester masterbatch, is introduced into the polymerization apparatus via a solid-phase smoothing agent injection system, wherein the polyester is PET, the solid-phase smoothing agent has a particle size of 30 to 50 nm, and the amount used is 270 ppm of the total mass of the melt.

[0109] Example 6

[0110] This embodiment provides a method for preparing a fully matte PET bicomponent elastic fiber. The method is basically the same as Example 2, except that: a viscosity reducer: amorphous polyester (NPG) with an intrinsic viscosity of 0.78 (measured in a mixed solvent of phenol and tetrachloroethane in a volume ratio of 3:2) is introduced into the polymerization device through a solid-phase smoothing agent injection system, and its usage is 0.75% of the total mass of the melt; and a polyester masterbatch of talc powder, a solid-phase smoothing agent, is introduced into the polymerization device through the solid-phase smoothing agent injection system, wherein the polyester is PET, the solid-phase smoothing agent has a particle size of 100 to 230 nm, and its usage is 270 ppm of the total mass of the melt.

[0111] Example 7

[0112] This embodiment provides a method for preparing a fully matte PET bicomponent elastic fiber. The method is essentially the same as that of Example 1, except that a viscosity reducer, amorphous polyester (NPG), having an intrinsic viscosity of 0.78 (measured in a 3:2 volume ratio of phenol to tetrachloroethane) is introduced into the polymerization apparatus via a viscosity reducer injection system. The amount of the NPG used is 0.75% of the total mass of the melt.

[0113] Example 8

[0114] This embodiment provides a method for preparing a fully matt PET bicomponent elastic fiber. The method is basically the same as that of Example 2, except that the amount of liquid titanium dioxide matting agent is changed so that the spinning melt contains 8% by mass of titanium dioxide.

[0115] Example 9

[0116] This embodiment provides a method for preparing a fully matte PET bicomponent elastic fiber. The method is basically the same as that of Example 2, except that the copolymerized modified monomer 1,4-cyclohexanedicarboxylic acid is added to the polymerization system together with terephthalic acid and ethylene glycol, and the molar amount of 1,4-cyclohexanedicarboxylic acid is 0.5% of the molar amount of terephthalic acid.

[0117] Comparative Example 1

[0118] This comparative example provides a method for preparing a fully matt PET bicomponent elastic fiber. The method is basically the same as Example 1, except that no liquid titanium dioxide matting agent is introduced into the polymerization system. Only ordinary matting agent paste is introduced into the second esterification kettle, and the amount of titanium dioxide is such that the titanium dioxide accounts for 2.0% of the total mass of the melt.

[0119] Comparative Example 2

[0120] This comparative example provides a method for preparing a fully matt PET two-component elastic fiber. The method is basically the same as that in Example 1, the only difference is that the carrier in the composition of the liquid titanium dioxide matting agent is replaced by a low-polymerization degree polyacrylate.

[0121] Comparative Example 3

[0122] This comparative example provides a method for preparing a fully matt PET bicomponent elastic fiber. The method is basically the same as Example 2, except that the catalyst is replaced with ethylene glycol antimony so that the active metal antimony accounts for 210 ppm of the total mass of the melt.

[0123] The following is Table 1:

[0124] Table 1 Process conditions and product indicators of Examples 1 to 9 and Comparative Examples 1 to 3

[0125] The properties of the ethylene terephthalate prepolymer, high viscosity melt, low viscosity melt, melt in the spinning manifold, and final bicomponent elastic fiber obtained in Examples 1-9 and Comparative Examples 1-3 were tested. The properties of the bicomponent elastic fiber were tested in accordance with the GBT 8960-2015 test standard. The results are shown in Tables 2-4 below.

[0126] Table 2

[0127] Table 3

[0128] Table 4 is shown below:

[0129] Table 4

[0130] As shown in Tables 1-4 above, the present invention, by adding a liquid titanium dioxide matting agent having a specific composition, particularly a specific carrier, to the high-viscosity polymerization process, can increase the viscosity of the high-viscosity component and improve the quality and crimp shrinkage of the resulting bicomponent elastic fiber. Furthermore, the present invention, by utilizing a supported catalyst with a specific composition to catalyze the polymerization, further improves the properties of the high-viscosity component and the resulting bicomponent elastic fiber.

[0131] The above embodiments are intended only to illustrate the technical concepts and features of the present invention. Their purpose is to enable those skilled in the art to understand the present invention and implement it accordingly. They are not intended to limit the scope of protection of the present invention. Any equivalent variations or modifications based on the spirit and essence of the present invention are intended to be encompassed by the scope of protection of the present invention.

Claims

1. A liquid titanium dioxide matting agent, which is used for a fully matte PET two-component elastic fiber, wherein the PET two-component elastic fiber contains a first PET component and a second PET component, wherein the first PET component and the second PET component have different viscosities, and is characterized in that: The liquid titanium dioxide matting agent comprises titanium dioxide and a carrier; the carrier is a linear polyester or a small molecule ester; either end of the linear polyester independently contains a carboxyl functional group or a hydroxyl functional group, and the molecular weight of the linear polyester is 1800-2500; the small molecule ester is an ABA type or BAB type structure, wherein A is a dibasic acid and B is a diol.

2. The liquid titanium dioxide matting agent according to claim 1, characterized in that: The viscosity of the carrier at 25°C is 2 to 20 Pa.s, and the viscosity at 60°C is 1.0 to 8.0 Pa.s; and / or the melting point of the small molecule ester is less than or equal to 20°C, and the boiling point is greater than or equal to 290°C; and / or the thermal weight loss of the carrier at 290°C under nitrogen protection for 2.0 hours is less than or equal to 0.2%.

3. The liquid titanium dioxide matting agent according to claim 1, characterized in that: According to weight percentage, the liquid titanium dioxide matting agent contains 20%-50% titanium dioxide and 50%-80% carrier.

4. The liquid titanium dioxide matting agent according to claim 1, characterized in that: The linear polyester is an oligomer of a dibasic acid and a diol, wherein the dibasic acid is selected from a combination of one or more of succinic acid, glutaric acid, adipic acid, suberic acid, sebacic acid, neopentanedioic acid, 1,4-cyclohexanedicarboxylic acid, and phthalic acid; and / or the diol is selected from a combination of one or more of 1,3-butanediol, 1,4-butanediol, pentanediol, hexanediol, nonanediol, octanediol, neopentyl glycol, diethylene glycol, and 1,4-cyclohexanedimethanol.

5. The liquid titanium dioxide matting agent according to claim 1, characterized in that: The liquid titanium dioxide matting agent is prepared by dispersing, grinding and filtering titanium dioxide and a carrier.

6. A method for preparing a fully matte PET two-component elastic fiber, comprising the steps of subjecting terephthalic acid, ethylene glycol, a catalyst and an optional modified monomer to an esterification reaction in a first esterification kettle and a second esterification kettle, and a prepolymerization reaction in a first prepolymerization kettle and a second prepolymerization kettle to obtain an ethylene terephthalate prepolymer; characterized in that: The preparation method also includes the steps of introducing the ethylene terephthalate prepolymer and the liquid titanium dioxide matting agent described in any one of claims 1 to 5 into a high-viscosity final polymerization kettle for polymerization reaction to obtain a matte high-viscosity polyethylene terephthalate melt, and introducing the ethylene terephthalate prepolymer into a low-viscosity final polymerization kettle for polymerization reaction to obtain a low-viscosity polyethylene terephthalate melt, wherein the viscosity of the high-viscosity polyethylene terephthalate melt is greater than the viscosity of the low-viscosity polyethylene terephthalate melt; and spinning the matte high-viscosity polyethylene terephthalate melt and the low-viscosity polyethylene terephthalate melt through the same spinning assembly to obtain the fully matte PET two-component elastic fiber.

7. The preparation method according to claim 6, characterized in that: The preparation method further comprises the step of introducing a matting agent paste into the second esterification kettle before the second esterification kettle carries out the esterification reaction, wherein the matting agent paste is prepared by grinding and dispersing titanium dioxide and ethylene glycol; and / or, the matting high-viscosity polyethylene terephthalate melt contains 1.6%-8.0% by mass of titanium dioxide; and / or, the preparation method further comprises the step of mixing the ethylene terephthalate prepolymer and the liquid titanium dioxide matting agent in a dynamic mixer before the two are introduced into the high-viscosity final polymerization kettle; and / or, in terms of mass percentage, the PET two-component elastic fiber contains 30%-70% of a first PET component and 70%-30% of a second PET component, and the viscosity of the first PET component and the second PET component are different.

8. The preparation method according to claim 6, characterized in that: The catalyst is a supported catalyst and includes a carrier and an active component; the carrier is selected from nano-alumina or nano-silicon dioxide, the particle size of the carrier is 10-30nm and the specific surface area is 200m 2 / g or more; the active component is a mixture of an oxide of metal M and a carbonate of metal M, and the metal M is selected from a combination of one or more of vanadium, tungsten, zirconium, iron, zinc, calcium, magnesium, titanium, cobalt and scandium.

9. The preparation method according to claim 8, characterized in that: According to weight percentage, the catalyst contains 94%-97% of carrier and 3%-6% of active component.

10. The preparation method according to claim 8, characterized in that: The catalyst is prepared by precipitating a carrier, a compound containing a metal M element and a precipitant, treating the surface with a silane coupling agent, and calcining; the compound containing a metal M element is selected from sulfates, chlorides, oxides or hydroxides of the metal M element.

11. The preparation method according to claim 6, characterized in that: In the step 1), the modified monomer is added, and the modified monomer is selected from one or more combinations of 1,4-cyclohexanedicarboxylic acid, isophthalic acid, 2,6-naphthalene dicarboxylic acid, phthalic acid, trimellitic anhydride, pyromellitic acid, neopentanoic acid, furandicarboxylic acid, 2,2,4,4-cyclobutanedicarboxylic acid, 1,4-cyclohexanedimethanol, pentaerythritol, neopentyl glycol, hydroquinone, and 2,2,4,4-tetramethyl-cyclobutane dimethanol.

12. The preparation method according to claim 11, characterized in that: The molar amount of the modified monomer accounts for 0.5% to 8.0% of the molar amount of the terephthalic acid.

13. The preparation method according to claim 6, characterized in that: The high-viscosity polymerization kettle is a horizontal polymerization kettle, and includes a main body with a chamber inside, a feed port, and a discharge port. The main body includes a low-viscosity zone, a medium-high-viscosity zone, and a high-viscosity zone arranged in sequence along the axial direction of the high-viscosity polymerization kettle. The viscosity of the polyethylene terephthalate melt in the low-viscosity zone, the medium-high-viscosity zone, and the high-viscosity zone increases in sequence. The high-viscosity polymerization kettle also includes two stirring shafts arranged in parallel along its axial direction. The two stirring shafts rotate in opposite directions. A plurality of stirrers are arranged on the two stirring shafts. The outer circumference of the stirrer is circular. The stirrers on the two stirring shafts are correspondingly arranged and the circular outer circumferences are tangentially contacted. The stirrer in the high-viscosity zone is a double-disc type.

14. The preparation method according to claim 13, characterized in that: From the low viscosity zone to the medium-high viscosity zone to the high viscosity zone, the distance between two adjacent stirrers increases successively; the distance between two adjacent stirrers in the high viscosity zone is 8-50mm.

15. The preparation method according to claim 13, characterized in that: The high viscosity final polymerization kettle also includes a composite scraper, which includes an axial scraper for scraping the melt on the stirring shaft, a wall scraper for scraping the melt on the inner wall of the high viscosity final polymerization kettle, and a disk scraper for scraping the melt on the stirrer; and / or, there are 10-16 stirrers in the high viscosity area.

16. The preparation method according to claim 13, characterized in that: The high viscosity final polymerization kettle also includes steam feed ports arranged at the top of the medium-high viscosity zone and the high viscosity zone for introducing superheated ethylene glycol steam. The preparation method also includes the step of using a metering system to meter the superheated ethylene glycol steam and introducing it into the high viscosity final polymerization kettle.

17. The preparation method according to claim 13, characterized in that: The preparation method also includes the steps of passing the matte high-viscosity polyethylene terephthalate melt and the low-viscosity polyethylene terephthalate melt through a filter and a booster pump respectively before passing the two through the same spinning assembly, and the preparation method controls the time for conveying the matte high-viscosity polyethylene terephthalate melt from the high-viscosity final polymerization reactor to the spinning assembly to be 30-40 minutes.

18. The preparation method according to claim 17, characterized in that: The preparation method further comprises the step of adding a viscosity reducing agent to the matt high-viscosity polyethylene terephthalate melt before the matt high-viscosity polyethylene terephthalate melt passes through a filter; the viscosity reducing agent is selected from a combination of one or more of polyethylene terephthalate-1,4-cyclohexanedimethanol PETG, cationic dyeable polyester CDP, cationic dye-easy polyester ECDP, normal pressure boiling dyeable polyester EDDP, polybutylene terephthalate PBT, and polypropylene terephthalate-1,3-glycol terephthalate PTT; Alternatively, the preparation method further comprises the steps of injecting a solid-phase smoothing agent into the ethylene terephthalate prepolymer before the ethylene terephthalate prepolymer is introduced into the high-viscosity final polymerization kettle, and passing a mixture of the solid-phase smoothing agent and the ethylene terephthalate prepolymer through a filter, wherein the solid-phase smoothing agent is in the form of a masterbatch and comprises a polyester matrix and an inorganic powder, wherein the inorganic powder is selected from a combination of one or more of talc, montmorillonite, barium sulfate, hydrotalcite and nano-silica.

19. The preparation method according to claim 13, characterized in that: The preparation method further comprises the step of using a melt pump to transport the matte high-viscosity polyethylene terephthalate melt from the discharge port of the high-viscosity final polymerization reactor to the spinning assembly, and a melt cooler is provided at the outlet of the melt pump.

20. The preparation method according to claim 13, characterized in that: The preparation method controls the average residence time of the high-viscosity polyethylene terephthalate melt in the high-viscosity zone to be 75-120 minutes, and the temperature of the high-viscosity polyethylene terephthalate melt is lower than 284°C.

21. The preparation method according to claim 13, characterized in that: The preparation method also includes the step of introducing a heat stabilizer and an antioxidant from different positions of the second esterification kettle; the heat stabilizer is selected from a combination of one or more of trimethyl phosphate, triethyl phosphate, triphenyl phosphate, triphenyl phosphite, and triglyceride phosphate; the antioxidant is selected from a combination of one or more of antioxidant 168, antioxidant 1076, antioxidant 1010, antioxidant 1222, and benzothiazole antioxidants.

22. The preparation method according to claim 13, characterized in that: The difference between the intrinsic viscosity of the matte high-viscosity polyethylene terephthalate melt and the intrinsic viscosity of the low-viscosity polyethylene terephthalate melt is 0.23 to 0.

45.

23. The preparation method according to claim 6, characterized in that: The intrinsic viscosity of the matte high-viscosity polyethylene terephthalate melt is 0.68-0.80, and its viscosity at 280-282°C is 550-800 Pa.s; the intrinsic viscosity of the low-viscosity polyethylene terephthalate melt is 0.45-0.55, and its viscosity at 276-277°C is 90-310 Pa.s.

24. The preparation method according to claim 6, characterized in that: The intrinsic viscosity of the second PET component is 0.445-0.520; the intrinsic viscosity of the first PET component is 0.645-0.

750.

25. The fully matt PET bicomponent elastic fiber prepared by the preparation method according to any one of claims 6 to 24.

26. The fully matte PET bicomponent elastic fiber according to claim 25, characterized in that: The curling shrinkage rate of the full-dull PET two-component elastic fiber is 15.0% to 35.0%.

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