Melt direct spinning fully-dull high and low viscose PET bicomponent elastic fiber and preparation method thereof

Abstract

The present application relates to a kind of melt direct spinning full-dull high, low viscosity PET bicomponent elastic fiber and its preparation method.The elastic fiber is added with liquid titanium dioxide matting agent containing specific carrier, and the carrier is linear polyester or small molecule esterate;Any end of the linear polyester independently contains carboxyl functional group or hydroxyl functional group, and the molecular weight of the linear polyester is 1800-2500;The small molecule esterate is ABA type or BAB type structure, and A is binary acid, and B is binary alcohol.When preparing the elastic fiber, in addition to carrying out first and second esterification reaction of terephthalic acid and ethylene glycol, first and second prepolymerization, high viscosity component is also prepared by polymerizing prepolymer and liquid titanium dioxide matting agent together, and low viscosity component is prepared by polymerizing prepolymer alone, then the two are spun together.Using this method, the viscosity of high viscosity component can be significantly improved, and the quality and curl shrinkage of elastic fiber are high.

Description

TECHNICAL FIELD

[0001] The present application relates to a kind of melt direct spinning full-dull high, low viscosity PET bicomponent elastic fiber and its preparation method. BACKGROUND

[0002] Elastic fiber is applied in the modernization fiber industry more and more widely, especially in recent years, with the rapid development of bicomponent elastic fiber theory, the forming mechanism and the elastic mechanism of parallel bicomponent elastic fiber have been understood more deeply, and the variety of elastic fiber has made great progress. In the 1970s, DuPont first launched single-component spandex elastic fiber, which quickly swept the market with its unique style and characteristics. In the late 1970s, it launched bicomponent parallel elastic fiber T800, which used PBT / PET parallel composite to produce good elastic effect. However, PBT / PET elastic fiber has a low glass transition temperature (26-42℃) due to the PBT component, and the fiber has a rapid crystallization characteristic under stress. The elastic recovery rate and shape retention of T800 fiber are poor. In the 21st century, with the success of PDO industrialization by chemical and biological fermentation methods, PTT polyester has a unique molecular structure and excellent elastic recovery performance. DuPont T400, PTT / PET bicomponent elastic fiber, has excellent elastic recovery rate and shape retention. Multiple stretch fabrics will not deform, and its elastic release effect overcomes the bondage of spandex elastic fiber. It has excellent chlorine resistance, light resistance and other characteristics, and has become the best elastic fiber variety in the fabric industry.

[0003] But the price of PTT polyester raw materials is high, and PTT / PET bicomponent fiber is basically used in high-end fabric category. For some lower elasticity requirements of fabric, the cost performance is not outstanding, so the development of bicomponent elastic fiber has become the focus of the industry in the past ten years. The latest progress is to use the different orientation and crystallization behavior between different viscosity components of PET polyester, and to use high viscosity PET and low viscosity PET with certain viscosity difference to prepare PET / PET bicomponent elastic fiber. In the spinning process, the high viscosity component and the low viscosity component produce elastic crimping due to the difference in the speed and percentage of the orientation state to the crystalline state, forming a spring-like structure, so it shows good elastic effect on the fabric. Patents CN111101237A, CN101126180A, CN106337212A, CN107964690A, CN101851812A, CN115613159A, etc. respectively disclose a series of PET / PET, PBT / PET, PTT / PET and other parallel composite elastic fiber preparation methods, as well as modified PET with elastic retention such as high-viscosity ECDP, high-viscosity high-shrinkage polyester, high-viscosity disperse dye easy-dyeing polyester, high-viscosity CDP cationic polyester and other methods for preparing easy-dyeing or deep-dyeing elastic fiber with low-viscosity PET polyester.

[0004] The above-mentioned elastic fiber preparation methods are based on high-viscosity chips and low-viscosity chips respectively passing through pre-crystallization, drying screw melting, to composite spinning box and composite parallel spinneret for chip spinning production process. Although it solves the basic parallel composite spinning technology problem, the chip spinning technology has obvious defects such as long process, high cost, low capacity, poor product quality stability, etc.

[0005] The full-dull elastic fiber product adopts full-dull polyester raw material, which contains high content of titanium dioxide duller, and the titanium dioxide in the titanium dioxide duller is inorganic powder. The large amount of addition of inorganic powder will first greatly increase the level of powder agglomeration to form agglomerated particles, resulting in a significant reduction in the service life of the pre-polymer filter and the final polymer filter. Secondly, the titanium dioxide duller contains a certain amount of high-valence arsenic oxide, antimony oxide and other impurities, which will increase the level of side reactions during polymerization, produce a large amount of non-condensable gas components, cause the color of the product to deteriorate, and greatly increase the vacuum load, resulting in a decrease in equipment efficiency. Finally, the duller contained in the full-dull polyester will produce obvious dynamic thickening phenomenon with the increase of the viscosity of the polymer at the late stage of polymerization, the melt flowability becomes poor, the material renewal efficiency on the disc surface of the disc reactor is significantly reduced, the residence time of the melt on the disc surface of the disc reactor is greatly increased, resulting in a significant increase in thermal degradation side reactions, which directly leads to the generation of acetaldehyde in multiple times of the amount generated by normal polymerization, and the high-viscosity polymerization reaction is difficult to be stable and effective. In the prior art, liquid titanium dioxide duller is used as the duller for polyester elastic fiber, the carrier of the liquid titanium dioxide duller is usually low-polymerization polyacrylate, medium-molecular-weight PEG or inert white oil, etc. The above carrier will not react with polyester, so it is usually injected into the melt pipeline after the polymerization reaction is completed. However, the above carrier cannot be well compatible with polyester, and will cause certain side reactions, resulting in a decrease in the color quality of polyester. SUMMARY

[0006] The purpose of the present application is to provide a liquid titanium dioxide duller, which can further improve the viscosity of high-viscosity polyester melt when used in melt direct spinning of full-dull high- and low-viscosity PET bicomponent elastic fiber, can have good compatibility with polyester fiber, and can ensure the quality of bicomponent elastic fiber.

[0007] Another purpose of the present application is to provide a melt direct spinning full-dull high- and low-viscosity PET bicomponent elastic fiber, the viscosity of the high-viscosity polyester component in the elastic fiber can be very high, and the color quality of the elastic fiber is significantly improved, and the crimp shrinkage rate is high.

[0008] Still another purpose of the present application is to provide a preparation method of melt direct spinning full-dull high- and low-viscosity PET bicomponent elastic fiber, which can effectively control the viscous flow of the melt when the viscosity of the high-viscosity polyester melt component is very high, the apparent melting point of the melt is significantly reduced, the residence time of the duller in the reaction process is greatly reduced, the side reactions are reduced, and the color quality of the polyester is significantly improved.

[0009] To achieve the above purposes, the technical solution adopted by the present application is:

[0010] A liquid titanium dioxide delusterant for full delustering PET bicomponent elastic fiber, the PET bicomponent elastic fiber containing a first PET component and a second PET component, the first PET component and the second PET component having different viscosities, the liquid titanium dioxide delusterant comprising titanium dioxide and a carrier; the carrier being a linear polyester or a small molecule esterate; either end of the linear polyester independently containing a carboxyl functional group or a hydroxyl functional group, the linear polyester having a molecular weight of 1800-2500; the small molecule esterate being of ABA type or BAB type structure, A being a dibasic acid, B being a dibasic alcohol.

[0011] In the present application, ABA type structure refers to both ends of the small molecule esterate being dibasic acid structure, and the middle being esterification product structure of A and B, the middle can have multiple esterification repeating units, but the overall is still at the level of small molecular weight, not reaching the molecular weight level of prepolymers. Similarly, BAB type structure refers to both ends of the small molecule esterate being dibasic alcohol structure, and the middle being esterification product structure of A and B, the middle can have multiple esterification repeating units, but the overall is still at the level of small molecular weight, not reaching the molecular weight level of prepolymers.

[0012] In some embodiments, the carrier has a viscosity of 2-20 Pa.s at 25℃, and a viscosity of 1.0-8.0 Pa.s at 60℃.

[0013] In some embodiments, the small molecule esterate has a melting point less than or equal to 20℃, and a boiling point greater than or equal to 290℃.

[0014] In some embodiments, the carrier has a thermal weight loss less than or equal to 0.2% under nitrogen protection at 290℃ for 2.0 hours.

[0015] The dispersant of the liquid titanium dioxide matting agent of the present application is a linear polyester or a small molecule esterate with bifunctional groups. When the matting agent is used in melt direct spinning full-matt high and low viscosity PET bicomponent elastic fiber, the dispersant can participate in the polymerization reaction of polyester synthesis, which can improve the viscous flow properties of polyester melt and reduce the apparent melting point of high viscosity polyester melt. In the polymerization process of polyester, the liquid titanium dioxide matting agent has good compatibility with the polyester matrix, which greatly reduces the residence time, thereby greatly improving the hue of high viscosity full-matt polyester, significantly reducing the film thickness of high viscosity melt in the high viscosity region, reducing the residence time of the material and significantly reducing the side reaction, which is more conducive to the formation of plug flow effect in the melt conveying process. Due to the use of the above specific dispersant, the liquid titanium dioxide matting agent of the present application can not use any other dispersant or flat flow agent and other auxiliary agents. The linear polyester carrier molecule has bifunctional groups, with a molecular weight of 1800-2500, which is similar to the average molecular weight of in-line PET polyester prepolymer. After mixing with conventional PET polyester prepolymer, it has the same probability of participating in polymerization and can smoothly complete block copolymerization.

[0016] In some embodiments, the liquid titanium dioxide matting agent contains 20%-50% titanium dioxide and 50%-80% carrier by weight percentage.

[0017] In some embodiments, the diacid is selected from a combination of one or more of succinic acid, glutaric acid, adipic acid, suberic acid, sebacic acid, pimelic acid, 1,4-cyclohexane dicarboxylic acid, and phthalic acid.

[0018] In some embodiments, 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-cyclohexane dimethanol.

[0019] In some embodiments, the linear polyester is an oligomer of a diacid selected from a combination of one or more of succinic acid, glutaric acid, adipic acid, suberic acid, sebacic acid, pimelic acid, 1,4-cyclohexane dicarboxylic acid, and phthalic acid, and a diol 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-cyclohexane dimethanol.

[0020] In some embodiments, the liquid titanium dioxide matting agent is prepared by dispersing, grinding, and filtering titanium dioxide and a carrier.

[0021] The application further provides a preparation method of the liquid titanium dioxide matting agent, which comprises the steps of dispersing, grinding and filtering titanium dioxide and a dispersing agent to obtain the liquid titanium dioxide matting agent.

[0022] The application further provides a preparation method of the full-matt PET bicomponent elastic fiber, which comprises the steps of sequentially subjecting terephthalic acid, ethylene glycol, a catalyst and an optional modified monomer to first esterification in a first esterification kettle, second esterification in a second esterification kettle, first prepolymerization in a first prepolymerization kettle and second prepolymerization in a second prepolymerization kettle to obtain terephthalic acid glycol ester prepolymer; the preparation method further comprises the steps of feeding the terephthalic acid glycol ester prepolymer and the aforementioned liquid titanium dioxide matting agent into a high-viscosity final polymerization kettle for polymerization reaction to obtain a high-viscosity polyterephthalic acid glycol ester melt with matting, feeding the terephthalic acid glycol ester prepolymer into a low-viscosity final polymerization kettle for polymerization reaction to obtain a low-viscosity polyterephthalic acid glycol ester melt, wherein the viscosity of the high-viscosity polyterephthalic acid glycol ester melt is higher than that of the low-viscosity polyterephthalic acid glycol ester melt; and spinning the high-viscosity polyterephthalic acid glycol ester melt with matting and the low-viscosity polyterephthalic acid glycol ester melt through the same spinning assembly to obtain the full-matt PET bicomponent elastic fiber.

[0023] In the application, terephthalic acid and ethylene glycol are sequentially subjected to first esterification, second esterification, first prepolymerization in a first prepolymerization kettle and second prepolymerization in a second prepolymerization kettle to obtain terephthalic acid glycol ester prepolymer, and then the prepolymer is subjected to final polymerization in a high-viscosity final polymerization kettle and a low-viscosity final polymerization kettle respectively to obtain high-viscosity polyterephthalic acid glycol ester melt and low-viscosity polyterephthalic acid glycol ester melt respectively, and meanwhile, the aforementioned liquid titanium dioxide matting agent is fed into the high-viscosity final polymerization kettle for final polymerization reaction together with the terephthalic acid glycol ester prepolymer; the carrier in the liquid titanium dioxide matting agent can participate in the final polymerization reaction due to the dual functional groups, so that even if a large amount of matting agent needs to be added for full matting, the melt flowability of the high-viscosity polyterephthalic acid glycol ester melt will not be deteriorated, and the material renewal efficiency of the polymerization reaction device in the high-viscosity final polymerization kettle for preparing high-viscosity melt is still high, which will not significantly prolong the material residence time, thereby significantly improving the thermal degradation side reaction and ensuring the comprehensive quality of the final full-matt PET bicomponent elastic fiber.

[0024] In the preparation method of the full-matt PET bicomponent elastic fiber, a six-kettle device system comprising a first esterification kettle, a second esterification kettle, a first prepolymerization kettle, a second prepolymerization kettle, a high-viscosity final polymerization kettle and a low-viscosity final polymerization kettle is adopted.

[0025] The full-dull PET bicomponent elastic fiber of the present application contains high-viscosity and low-viscosity bicomponents, the high-viscosity polyethylene terephthalate melt corresponds to the high-viscosity component, and the low-viscosity polyethylene terephthalate melt corresponds to the low-viscosity component. The preparation method of the aforementioned full-dull PET bicomponent elastic fiber is a melt direct spinning method, i.e., the melt obtained after polymerization is directly used for spinning without the step of cooling the melt into chips and then melting and spinning again.

[0026] In some embodiments, the PET bicomponent elastic fiber contains 30%-70% of the first PET component and 70%-30% of the second PET component in terms of mass percentage, and the first PET component and the second PET component have different viscosities. The first PET component and the second PET component correspond to the high-viscosity component and the low-viscosity component, respectively.

[0027] In some embodiments, the preparation method further comprises the step of introducing a dulling agent colorant into the second esterification kettle before the esterification reaction in the second esterification kettle, and the dulling agent colorant is prepared by grinding and dispersing titanium dioxide and ethylene glycol. The dulling agent colorant is a common dulling agent colorant in the prior art. The amount thereof can be 0.1%-0.5% of the mass of the melt, and preferably 0.3%.

[0028] In some embodiments, the dulling high-viscosity polyethylene terephthalate melt contains 1.6%-8.0% of titanium dioxide in terms of mass percentage.

[0029] In some embodiments, the preparation method further comprises the step of mixing the polyethylene terephthalate prepolymer and the liquid titanium dioxide dulling 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 make the mixing more uniform and more conducive to the uniform dispersion of the liquid titanium dioxide dulling agent in the prepolymer.

[0030] In some embodiments, the catalyst is a supported catalyst and comprises a carrier and an active component; the carrier is selected from nano-aluminum oxide or nano-silicon dioxide, the particle size of the carrier is 10-30 nm, and the specific surface area of the carrier is 200 m 2 / g or more; and the active component is a mixture of an oxide of a metal M and a carbonate of the metal M, and the metal M is selected from one or more of vanadium, tungsten, zirconium, iron, zinc, calcium, magnesium, aluminum, cobalt, and scandium.

[0031] In some embodiments, the metal M is zirconium.

[0032] In some embodiments, the metal M is zirconium and cobalt. Preferably, the mass of elemental cobalt accounts for 4%-8% of the total mass of elemental zirconium and elemental cobalt.

[0033] In the prior art, antimony-based catalysts such as ethylene glycol antimony, antimony acetate, or titanium-based catalysts are usually used in the synthesis of polyester. In addition, heat stabilizers and antioxidants are also used in the polymerization system. However, the heat stabilizers and the above-mentioned antimony-based catalysts will precipitate during the esterification and polymerization reaction, forming antimony phosphate and other precipitates, which will form a scale layer in the heat transfer coil part of the esterification and polymerization reaction. The thickness of the scale layer will increase over time, resulting in a significant reduction in the heat transfer efficiency of the reaction kettle and a significant reduction in the operation cycle of the device. In addition, the reducing by-products of the high-viscosity polymerization reaction in the high-viscosity final polymerization kettle, the melt conveying section, and the high-viscosity melt cracking reaction will also reduce the antimony element, forming an antimony metal precipitate, which will cause the formation of an antimony white metal scale layer in the melt conveying pipeline and the spinning box. Finally, full-dull polyester usually contains a high proportion of titanium dioxide opacifier. Since the traditional titanium dioxide opacifier such as color paste uses a large amount of surface coating agent, which will severely passivate the catalytic activity of the titanium-based catalyst, which is not conducive to the stable progress of the high-viscosity polymerization reaction.

[0034] Therefore, the present application uses a supported catalyst. The carrier of the catalyst has a large specific surface area, and the active component is an oxide or carbonate of a metal other than antimony and titanium. The use of the catalyst has mild catalytic conditions, can improve the melt heat stability, enhance the color of the high-viscosity polyester melt product, and reduce the level of side reactions. In addition, since the active component is a compound of an active metal element, it will not precipitate with the phosphate in the heat stabilizer, 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 layer in the polyester device or the melt conveying section, which is conducive to the long-term operation of the device.

[0035] In some embodiments, the catalyst contains 94%-97% of the carrier and 3%-6% of the active component by weight percentage.

[0036] In some embodiments, the catalyst is prepared by precipitation of the carrier, a compound containing metal M element, and a precipitant, surface treatment with a silane coupling agent, and calcination. The compound containing metal M element is selected from the sulfate, chloride, oxide, or hydroxide of the metal M element.

[0037] In some embodiments, the precipitant is sodium hydroxide.

[0038] The silane coupling agent can be any conventional silane coupling agent.

[0039] In some embodiments, the amount of the catalyst used is 260-600 ppm relative to the mass of the melt.

[0040] In some embodiments, the amount of the catalyst used is 300-450 ppm relative to the mass of the melt.

[0041] In some embodiments, the raw material of the preparation method further comprises a Lewis base, and the amount of the Lewis base is 60-100 ppm relative to the melt.

[0042] In some embodiments, in the step 1), the modified monomer is added, and the modified monomer is selected from the group consisting of one or more of 1,4-cyclohexane dicarboxylic acid, isophthalic acid, 2,6-naphthalene dicarboxylic acid, phthalic acid, trimellitic anhydride, pyromellitic acid, glutaric acid, furan dicarboxylic acid, 2,2,4,4-cyclobutane dicarboxylic acid, 1,4-cyclohexane dimethanol, pentaerythritol, neopentyl glycol, hydroquinone, and 2,2,4,4-tetramethyl-cyclobutane dimethanol.

[0043] In some embodiments, the molar amount of the modified monomer accounts for 0.5%-8.0% of the molar amount of the terephthalic acid.

[0044] In some embodiments, the molar amount of the modified monomer accounts for 1.0%-5.0% of the molar amount of the terephthalic acid.

[0045] In some embodiments, the molar amount of the modified monomer accounts for 1.5%-3.0% of the molar amount of the terephthalic acid.

[0046] The polymerized monomer of the present application can only comprise terephthalic acid and ethylene glycol, or the above-mentioned modified monomer can be added for modification. The above-mentioned modified monomer is a rigid co-monomer with greater steric hindrance, which can improve the crimping shrinkage and crimping stability of the final obtained two-component elastic fiber without changing the basic physical and chemical properties of the high and low viscosity melt polymers. In addition, the modified monomer can effectively reduce the melting point of the melt by 5-8°C, significantly reduce the level of side reactions, and change the viscous flow of the melt, effectively reduce the dynamic viscosity of the high viscosity melt, ensure better film formation of the high viscosity melt in the first final polymerization kettle, improve the reaction efficiency of the high viscosity polymerization, and improve the kinetic energy release efficiency of the macromolecular crimping during the melt conveying process, and quickly form a stable plug flow.

[0047] In some embodiments, the high-viscosity final polymerization kettle is a horizontal polymerization kettle, and comprises a main body with a cavity inside, a feeding port, and a discharging port, the main body comprises 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 further comprises two stirring shafts arranged in parallel along the axial direction thereof, the rotation directions of the two stirring shafts are opposite, a plurality of stirrers are arranged on the two stirring shafts, the outer periphery of the stirrers is circular, the stirrers on the two stirring shafts are arranged correspondingly and the circular outer peripheries are tangentially contacted, and the stirrers in the high-viscosity zone are double-disc type. In the present application, the double-disc type refers to fixing and connecting two adjacent stirrers with circular outer periphery together to realize the same rotation of the two, so as to improve the strength of the stirrers and facilitate the non-damage in the high-viscosity melt environment. In the prior art, when synthesizing polyester, the polymerization device in the conventional polymerization kettle is a front-and-back double-shaft disc reactor, and the high-viscosity final polymerization kettle for synthesizing high-viscosity polyester in the present application adopts double-shaft disc reactors (stirrers) arranged in parallel and side by side, the disc reactors arranged on the double shafts are arranged correspondingly and rotate reversely tangentially, the two can form a high-efficiency shearing effect, the disc reactors have good self-cleaning effect, the mass transfer efficiency of the material can be obviously improved, the material renewal speed is accelerated, and then the residence time of the polymerization reaction is greatly shortened, the side reaction level is effectively reduced, and the quality of the high-viscosity full-dull polyester melt is greatly improved. By using the above high-viscosity final polymerization kettle of the present application, the residence time of the material in the high-viscosity final polymerization kettle can be reduced to 40% to 55% of that in the ordinary polymerization kettle, and the residence time can be as low as 80 to 120 minutes. And arranging the double-disc disc reactor in the high-viscosity zone is more helpful to solve the problem of difficult production of high-viscosity full-dull polyester, can obtain polyester melt with good quality stability, and greatly reduces the generation of condensed particles in the final polymerization stage, prolongs the switching period of the filter before the final polymerization kettle.

[0048] In some embodiments, the distance between the adjacent two stirrers increases in sequence from the low-viscosity zone to the medium-high-viscosity zone to the high-viscosity zone; and the distance between the adjacent two stirrers in the high-viscosity zone is 8 to 50 mm.

[0049] In some embodiments, the high-viscosity final polymerization kettle further comprises a composite scraper, 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 disc scraper for scraping the melt on the stirrer.

[0050] In some embodiments, the axial scraper makes the thickness of the melt on the stirring shaft not more than 10 mm, the wall scraper makes the thickness of the melt on the inner wall of the high-viscosity final polymerization kettle not more than 10 mm, and the disc scraper makes the thickness of the melt on the stirrer not more than 8 mm.

[0051] In the prior art, although a scraper is arranged in a conventional polymerization kettle, the scraper structure is relatively simple and the effect is limited. In the high-viscosity final polymerization kettle of the present application, the above-mentioned composite scraper is adopted, so that the material renewal rate of the stirrer, the surface of the stirring shaft and the wall surface of the polymerization kettle can be effectively controlled, so that the material at the three places will not accumulate too much, and the problems of color phase deterioration and large amount of acetaldehyde generation in the production process of the full-dull high-viscosity melt can be effectively inhibited. The disc scraper of the composite scraper of the present application can control the thickness of the disc melt film, the wall scraper can timely update the material on the wall of the polymerization kettle, and the axial scraper can clean the stirring shaft. By arranging the above-mentioned composite scraper, the material residence time in the high-viscosity final polymerization kettle can be controlled to be 80-120 min, which is much lower than the residence time of the conventional front-and-back double-shaft high-viscosity disc reactor, which is usually about 180-300 min, and the large reduction of the residence time effectively reduces the level of side reactions, which is beneficial to the preparation of the high-viscosity full-dull polyester melt; and due to the parallel double-shaft arrangement, the total volume of the high-viscosity final polymerization kettle of the present application can be about half of that of the conventional final polymerization kettle.

[0052] In some embodiments, the number of stirrers in the high-viscosity zone is 10-16.

[0053] In some embodiments, the high-viscosity final polymerization kettle further comprises a steam feeding port for feeding superheated ethylene glycol steam arranged at the top of the medium-high-viscosity zone and the high-viscosity zone, and the preparation method further comprises the step of metering the superheated ethylene glycol steam by a metering system and feeding it into the high-viscosity final polymerization kettle. In the medium-high-viscosity zone and the high-viscosity zone, the viscosity of the polyester melt is larger, and the arrangement of the above-mentioned steam feeding port in this area can improve the devolatilization effect in this area, ensure good melt film drawing effect, and control the thickness of the disc melt film at the same time.

[0054] In some embodiments, the preparation method further comprises the step of passing the dull high-viscosity polyethylene terephthalate melt and the low-viscosity polyethylene terephthalate melt through filters and booster pumps respectively before passing them through the same spinning assembly, and the preparation method controls the time for the dull high-viscosity polyethylene terephthalate melt to be transported from the high-viscosity final polymerization kettle to the spinning assembly to be 30-40 min.

[0055] In some embodiments, the high-viscosity final polymerization kettle is arranged at the top of the spinning assembly. In this way, the transportation distance of the high-viscosity polyester melt synthesized by the high-viscosity final polymerization kettle before spinning can be reduced.

[0056] In some embodiments, the preparation method further comprises a step of adding a viscosity reducing agent to the high-viscosity, matt polyethylene terephthalate melt before the high-viscosity, matt polyethylene terephthalate melt passes through the filter; the viscosity reducing agent is selected from a combination of one or more of polyethylene terephthalate-1,4-cyclohexane dimethanol (PETG), cationic dyeable polyester (CDP), cationic dyeable polyester (ECDP), easy dyeing polyester (EDDP), polybutylene terephthalate (PBT), and polytrimethylene terephthalate (PTT). The addition of the viscosity reducing agent can greatly improve the flowability of the high-viscosity melt, improve the stress relief effect of the high-viscosity melt, and improve the plug flow effect, thereby making the spinning process more stable and improving the fiber crimping rate without affecting the basic indicators and quality of the final bicomponent elastic fiber product.

[0057] In some embodiments, the preparation method further comprises a step of adding a solid phase smoothing agent to the polyethylene terephthalate prepolymer before the polyethylene terephthalate prepolymer is fed into the high-viscosity final polymerization kettle, and a step of passing the mixture of the solid phase smoothing agent and the polyethylene terephthalate prepolymer through a filter, wherein the solid phase smoothing agent is in the form of a master batch and comprises a polyester matrix and an inorganic powder selected from a combination of one or more of talc, montmorillonite, barium sulfate, hydrotalcite, and nano-silicon dioxide. The addition of the solid phase smoothing agent can generate friction between the fluid surface and the pipe wall, thereby improving the flowability of the melt and reducing the viscosity of the melt.

[0058] In some embodiments, the preparation method further comprises a step of mixing the mixture of the solid phase smoothing agent and the polyethylene terephthalate prepolymer through a dynamic mixer before the mixture is passed through the filter.

[0059] In some embodiments, the preparation method further comprises a step of using a melt pump to transport the high-viscosity, matt polyethylene terephthalate melt from the discharge port of the high-viscosity final polymerization kettle to the spinning assembly, wherein the outlet of the melt pump is provided with a melt cooler.

[0060] 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 min, and the temperature of the high-viscosity polyethylene terephthalate melt is lower than 284°C.

[0061] In some embodiments, the preparation method further comprises the step of introducing a heat stabilizer and an antioxidant from different locations of the second esterification kettle; the heat stabilizer is selected from the group consisting of one or more of trimethyl phosphate, triethyl phosphate, triphenyl phosphate, triphenyl phosphite, and triglycerol phosphate; the antioxidant is selected from the group consisting of one or more of antioxidant 168, antioxidant 1076, antioxidant 1010, antioxidant 1222, and benzothiazole antioxidant.

[0062] By adding a heat stabilizer and an antioxidant in the high viscosity zone, i.e., the region with the highest melt viscosity, the thermal stability and the antioxidant property of the high viscosity PET polyester melt can be improved, so that the occurrence of side reactions during esterification and polymerization can be inhibited, the viscosity drop caused by thermal degradation of the high viscosity melt during the residence time of up to 40-90 minutes in the melt direct spinning process can be inhibited, and the melt intrinsic viscosity level at the spinning box part can be ensured to be still high, thereby generating sufficient elastic crimping.

[0063] In some embodiments, the difference between the intrinsic viscosity of the high viscosity matt polyethylene terephthalate melt and the intrinsic viscosity of the low viscosity polyethylene terephthalate melt is 0.23-0.45.

[0064] In some embodiments, the intrinsic viscosity of the high viscosity matt polyethylene terephthalate melt is 0.68-0.80, and the viscosity thereof 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 the viscosity thereof at 276-277°C is 90-310 Pa.s.

[0065] In some embodiments, the intrinsic viscosity of the second PET component is 0.445-0.520, and the intrinsic viscosity of the first PET component is 0.645-0.750.

[0066] In some embodiments, in the same spinning assembly, the viscosity of the high viscosity matt polyethylene terephthalate melt is 400-600 Pa.s, and the viscosity of the low viscosity polyethylene terephthalate melt is 70-280 Pa.s.

[0067] In some embodiments, the same spinning assembly is a composite spinning box.

[0068] In some embodiments, the composite spinning box comprises a composite spinneret.

[0069] In some embodiments, the high viscosity zone is connected to a vacuum pump, and the preparation method controls the pressure of the high viscosity zone to be 60-75 Pa. This pressure represents an extremely high vacuum degree.

[0070] In some embodiments, the vacuum pump has a pumping capacity of 80-150 kg / h.

[0071] Due to the increase of the side reaction of the high viscosity zone material, the high viscosity final polymerization kettle of the melt direct spinning full-dull high and low viscosity bicomponent elastic polyester fiber device needs rapid devolatilization effect, the generated gas phase components are quickly guided out of the polymerization device, the higher the high viscosity outlet viscosity, the higher the non-condensable gas production, therefore, the vacuum pump of the high viscosity final polymerization kettle needs higher vacuum kettle. The liquid ring pump inlet of the vacuum pump can be designed with a large capacity refrigerated water device to capture excess non-condensable acetaldehyde, and in order to further maintain the stability of production, the ethylene glycol extracted from the vacuum part of the device must be fully de-aldehyde treated before entering the system.

[0072] The application also provides a full-dull PET bicomponent elastic fiber prepared by the above preparation method.

[0073] In some embodiments, the full-dull PET bicomponent elastic fiber has a crimp shrinkage of 15.0%-35.0%.

[0074] Due to the use of the above technical solution, the application has the following advantages compared with the prior art:

[0075] The dispersant of the liquid titanium dioxide matting agent of the application is a bifunctional linear polyester or a small molecule esterate, which can participate in the polymerization reaction of polyester synthesis when the matting agent is used for melt direct spinning full-dull high and low viscosity PET bicomponent elastic fiber, so that the viscous flow property of the polyester melt is improved, and the apparent melting point of the high viscosity polyester melt is reduced. In the polymerization process of the polyester, due to the good compatibility of the liquid titanium dioxide matting agent with the polyester matrix, the residence time is greatly reduced, thereby the color of the high viscosity full-dull polyester can be greatly improved, the film thickness of the high viscosity melt in the high viscosity zone is obviously reduced, the residence time of the material is reduced, the side reaction is obviously reduced, and the formation of the plug flow effect in the melt conveying process is more beneficial. Due to the use of the above specific dispersant, the liquid titanium dioxide matting agent of the application can not use any other dispersant or flat flow agent and other auxiliary agents.

[0076] The present application sequentially carries out first esterification reaction and second esterification reaction on terephthalic acid and ethylene glycol, and then carries out first prepolymerization in a first prepolymerization kettle and second prepolymerization in a second prepolymerization kettle to obtain terephthalic acid glycol ester prepolymer, and then carries out final polymerization on the prepolymer in a high-viscosity final polymerization kettle and a low-viscosity final polymerization kettle respectively to obtain high-viscosity polyethylene terephthalate glycol melt and low-viscosity second polyethylene terephthalate glycol melt respectively. Meanwhile, the aforementioned liquid titanium dioxide matting agent is introduced into the high-viscosity final polymerization kettle together with the terephthalic acid glycol ester prepolymer to carry out final polymerization reaction. The dispersant in the liquid titanium dioxide matting agent can participate in the final polymerization reaction due to its bifunctional groups, so that even if a large amount of matting agent needs to be added for full extinction, the melt flowability of the high-viscosity polyethylene terephthalate glycol melt will not deteriorate, and the material renewal efficiency of the polymerization reaction device is still high when preparing high-viscosity melt, so that the material residence time will not be significantly prolonged, and the thermal degradation side reaction is significantly improved, thereby ensuring the comprehensive quality of the final full-extinction PET bicomponent elastic fiber.

[0077] In the present application, the intrinsic viscosity of the high-viscosity melt at the outlet of the high-viscosity polymerization kettle can reach 0.68-0.80, and the viscosity at 280-282℃ is 550-800 Pa.s, which is much higher than the viscosity of the high-viscosity melt in the prior art. The difference between the intrinsic viscosity of the high-viscosity melt at the outlet of the high-viscosity polymerization kettle and the low-viscosity melt at the outlet of the low-viscosity polymerization kettle can reach 0.23-0.45, which is much higher than the prior art.

[0078] In the full-extinction PET bicomponent elastic fiber of the present application, the intrinsic viscosity of the high-viscosity PET component (first PET component) can reach 0.645-0.750. The crimp shrinkage of the full-extinction PET bicomponent elastic fiber can reach 35.0%, which is much higher than the existing bicomponent elastic fiber.

[0079] The industrial production of bicomponent elastic fiber by using the preparation method of the present application can realize low-viscosity full-extinction melt capacity of 30-80 thousand tons / year, high-viscosity full-extinction melt capacity of 30-80 thousand tons / year, and when the product is melt direct spinning full-extinction PET / PET high-low-viscosity bicomponent elastic fiber, the comprehensive device capacity is 60-160 thousand tons / year. BRIEF DESCRIPTION OF DRAWINGS

[0080] Figure 1 It is a schematic diagram of the six-kettle polymerization system used in the embodiment of the present application;

[0081] Figure 2 It is a structural schematic diagram of the high-viscosity final polymerization kettle used in the embodiment of the present application;

[0082] Figure 3 It is a structural schematic diagram of the composite scraper of the high-viscosity final polymerization kettle used in the embodiment of the present application;

[0083] 1 - low viscosity zone, 2 - medium-high viscosity zone, 3 - high viscosity zone, 4 - composite doctor blade, 5 - disc doctor blade, 6 - axial doctor blade, 7 - wall doctor blade, 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

[0084] The above scheme is further described in combination with specific examples; it should be understood that these examples are used to illustrate the basic principles, main features and advantages of the present application, and the present application is not limited in scope by the following examples; the implementation conditions used in the examples can be further adjusted according to specific requirements, and the implementation conditions not specified are usually the conditions in conventional experiments. In the following examples, all raw materials are commercially available or prepared by conventional methods in the art.

[0085] The above examples are only for illustrating the technical concept and characteristics of the present application, the purpose is to enable those skilled in the art to understand the content of the present application and to implement it, and it cannot limit the protection scope of the present application. Any equivalent changes or modifications made in accordance with the spirit and essence of the present application should be covered within the protection scope of the present application.

[0086] As shown in Figure 1 When preparing full-dull PET bicomponent elastic fiber in the examples, a six-kettle device system of first esterification kettle 10, second esterification kettle 11, first prepolymerization kettle 12, second prepolymerization kettle 13, high viscosity final polymerization kettle 14 and low viscosity final polymerization kettle 15 is used. The six kettles are connected through necessary pipelines. Among them, a pump 16 and filters A and B are arranged between the second prepolymerization kettle 13 and the high viscosity final polymerization kettle 14. In actual production process, filters A and B are not opened at the same time, for example, filter A can be opened first, and after the device runs for a period of time, filter B is switched to use, at this time, filter A can be cleaned.

[0087] Among them, as shown in Figure 2As shown in the figure, the high-viscosity final polymerization kettle 14 is a horizontal polymerization kettle, and comprises a main body with a chamber inside, a feeding port, and a discharging port. The main body comprises 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 further comprises two stirring shafts 8 arranged in parallel along the axial direction thereof. The rotating directions of the two stirring shafts 8 are opposite. A plurality of stirrers 9 are arranged on the two stirring shafts 8. The outer periphery of the stirrers 9 is circular. The stirrers 9 on the two stirring shafts 8 are correspondingly arranged and the circular outer peripheries thereof are tangentially contacted. The stirrers 9 in the high-viscosity zone 3 are double-disc type, i.e., the adjacent two 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, i.e., the adjacent two stirrers 9 are not fixedly connected. From the low-viscosity zone 1 to the medium-high-viscosity zone 2 to the high-viscosity zone 3, the spacing between the adjacent two stirrers 9 increases in sequence. The spacing between the adjacent two stirrers 9 in the high-viscosity zone 3 is 8-50 mm. The number of the stirrers 9 in the high-viscosity zone 3 is 10-16.

[0088] As shown in the figure, Figure 2 and 3 The high-viscosity final polymerization kettle 14 further comprises a composite scraper 4. The composite scraper 4 comprises an axial scraper 6 for scraping the melt on the stirring shaft 8, a wall scraper 7 for scraping the melt on the inner wall of the high-viscosity final polymerization kettle 14, and a disc scraper 5 for scraping the melt on the stirrer 9. The high-viscosity final polymerization kettle 14 further comprises a steam feeding port arranged at the top of the medium-high-viscosity zone 2 and the high-viscosity zone 3 for feeding superheated ethylene glycol steam.

[0089] A dynamic mixer and filters A and B can be arranged between the second prepolymerization kettle 13 and the high-viscosity final polymerization kettle 14. A liquid titanium dioxide delusterant injection system and a solid-phase smoothing agent injection system are arranged before the dynamic mixer. A filter is arranged between the second prepolymerization kettle and the low-viscosity final polymerization kettle 15.

[0090] A dynamic mixer and a filter are arranged after the high-viscosity final polymerization kettle 14 and before the same spinning assembly. A viscosity reducer injection system is arranged before the dynamic mixer. A filter is arranged after the low-viscosity final polymerization kettle and before the same spinning assembly.

[0091] Necessary melt pumps, vacuum pumps, etc. can be arranged on the pipes connecting the six kettles.

[0092] The same spinning assembly is a composite spinning box. The high-viscosity final polymerization kettle 14 is arranged at the top of the composite spinning box to shorten the conveying distance of the high-viscosity melt.

[0093] Example 1

[0094] The embodiment provides a preparation method of full-dull PET bicomponent elastic fiber, and the specific steps are as follows.

[0095] The composition of the liquid titanium dioxide matting agent is as follows in terms of percentage by weight: 20% of titanium dioxide and 80% of carrier, wherein the carrier is a binary small molecule ester compound of succinic acid and 1,3-butanediol, and the structure of the binary small molecule ester compound is ABA type, wherein A is a succinic acid residue and B is a 1,3-butanediol residue. The viscosity of the carrier at 25 DEG C is 3.6 Pa.s, the viscosity at 60 DEG C is 1.0 Pa.s, and the melting point is -23.7 DEG C. The synthesis method and viscosity control method of the binary ester compound adopt known technologies in the prior art. The liquid matting agent is prepared by dispersing, grinding and filtering titanium dioxide and a dispersing agent.

[0096] The preparation method of the catalyst used in the embodiment is as follows:

[0097] γ-nano-alumina with a specific surface area of 260 m 2 / g, zirconium sulfate and a precipitator sodium hydroxide are subjected to a precipitation reaction, filtration, surface treatment of the obtained solid by using a silane coupling agent, and calcination, so as to prepare the catalyst. The active component of the catalyst is a mixture of zirconium oxide and zirconium carbonate, the particle size of the catalyst is about 50 nm, and according to percentage by weight, the carrier nano-alumina accounts for 94%, and the active component accounts for 6%.

[0098] The terephthalic acid, ethylene glycol and the aforementioned catalyst are sequentially subjected to esterification reaction in the first esterification kettle 10 and the second esterification kettle 11, and pre-polymerization reaction in the first pre-polymerization kettle 12 and the second pre-polymerization kettle 13, so as to obtain terephthalic acid glycol ester pre-polymer. Before the esterification reaction in the second esterification kettle 11, the ordinary matting agent color paste prepared by grinding and dispersing titanium dioxide and ethylene glycol is introduced into the second esterification kettle 11, wherein the content of titanium dioxide is 10 wt%, and the content of ethylene glycol is 90 wt%. The amount of the ordinary matting agent color paste is 0.3% of the total mass of the spinning melt. The content of the catalyst in the PET melt is 260 ppm. Then, the terephthalic acid glycol ester pre-polymer and the aforementioned liquid titanium dioxide matting agent are mixed by using a dynamic mixer, filtered by using a filter, and introduced into the high-viscosity final polymerization kettle 14 for polymerization reaction, so as to obtain a high-viscosity terephthalic acid glycol ester melt with extinction. At the same time, the terephthalic acid glycol ester pre-polymer is introduced into the low-viscosity final polymerization kettle 15 for polymerization reaction, so as to obtain a low-viscosity terephthalic acid glycol ester melt. Finally, the high-viscosity terephthalic acid glycol ester melt with extinction and the low-viscosity terephthalic acid glycol ester melt are directly introduced into a composite spinning box for spinning, so as to obtain full-dull PET bicomponent elastic fiber, which is FDY with a specification of 55 dtex / 36 f. The amount of the liquid titanium dioxide matting agent is 1.7% of the total mass of the spinning melt.

[0099] The conditions of the six-kettle polymerization device and the properties of the high viscosity melt with extinction are shown in Table 1. The intrinsic viscosity is measured in a mixed solvent of phenol and tetrachloroethane (3:2 by volume) and the unit is dL / g.

[0100] Example 2

[0101] This example provides a method for preparing a full-extinction PET bicomponent elastic fiber. The method is basically the same as that of Example 1, except that the carrier in the composition of the liquid titanium dioxide extinction agent is replaced by a linear polyester of succinic acid and 1,3-butanediol, which has a molecular weight of 2000, a viscosity of 18.0 Pa.s at 25°C, and a viscosity of ~6.8 Pa.s at 60°C. The synthesis method and molecular weight control method of the linear polyester use known techniques in the prior art.

[0102] Example 3

[0103] This example provides a method for preparing a full-extinction PET bicomponent elastic fiber. The method is basically the same as that of Example 1, except that the carrier of the catalyst is replaced by nano-silicon dioxide.

[0104] Example 4

[0105] This example provides a method for preparing a full-extinction 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, i.e., cobalt acetate is added to the raw materials during the synthesis of the catalyst, and in the catalyst, the mass of cobalt element accounts for 6% of the total mass of cobalt element and zirconium element.

[0106] Example 5

[0107] This example provides a method for preparing a full-extinction PET bicomponent elastic fiber. The method is basically the same as that of Example 2, except that a viscosity reducer PETG with an intrinsic viscosity of 0.68 (measured in a mixed solvent of phenol and tetrachloroethane at a volume ratio of 3:2) is introduced into the polymerization device through a viscosity reducer injection system, and the amount of the viscosity reducer is 0.75% of the total mass of the melt; and a solid-phase smoothing agent, nano-barium sulfate polyester granules, is introduced into the polymerization device through a solid-phase smoothing agent injection system, where the polyester is PET, the particle size of the solid-phase smoothing agent is 30-50 nm, and the amount of the solid-phase smoothing agent is 270 ppm of the total mass of the melt.

[0108] Example 6

[0109] The present example provides a preparation method of full-dull PET bicomponent elastic fiber. The method is basically the same as that of Example 2, except that a viscosity reducer, amorphous polyester (NPG) with an intrinsic viscosity of 0.78 (measured in a mixed solvent of phenol:tetrachloroethane at a volume ratio of 3:2) is introduced into the polymerization device through a solid-phase smoothing agent injection system, and the amount of the viscosity reducer is 0.75% of the total mass of the melt.

[0110] Example 7

[0111] The present example provides a preparation method of full-dull PET bicomponent elastic fiber. The method is basically the same as that of Example 1, except that a viscosity reducer, amorphous polyester (NPG) with an intrinsic viscosity of 0.78 (measured in a mixed solvent of phenol:tetrachloroethane at a volume ratio of 3:2) is introduced into the polymerization device through a viscosity reducer injection system, and the amount of the viscosity reducer is 0.75% of the total mass of the melt.

[0112] Example 8

[0113] The present example provides a preparation method of full-dull PET bicomponent elastic fiber. The method is basically the same as that of Example 2, except that the amount of liquid titanium dioxide duller is changed so that the spinning melt contains 8% titanium dioxide by mass.

[0114] Example 9

[0115] The present example provides a preparation method of full-dull PET bicomponent elastic fiber. The method is basically the same as that of Example 2, except that the copolymerization modifier monomer 1,4-cyclohexane dicarboxylic acid is added to the polymerization system together with terephthalic acid and ethylene glycol, and the molar amount of 1,4-cyclohexane dicarboxylic acid is 0.5% of the molar amount of terephthalic acid.

[0116] Comparative Example 1

[0117] The present comparative example provides a preparation method of full-dull PET bicomponent elastic fiber. The method is basically the same as that of Example 1, except that no liquid titanium dioxide duller is introduced into the polymerization system, and only a common duller colorant is introduced into the second esterification kettle, and the amount of the colorant is such that the titanium dioxide accounts for 2.0% of the total mass of the melt.

[0118] Comparative Example 2

[0119] The present comparative example provides a preparation method of full-dull PET bicomponent elastic fiber. The method is basically the same as that of Example 1, except that the carrier in the composition of the liquid titanium dioxide duller is replaced by low-polymerization-degree polyacrylate.

[0120] Comparative Example 3

[0121] This comparative example provides a preparation method of full-dull PET bico- elastic fiber, which is basically the same as example 2, the difference is that the catalyst is replaced by ethylene glycol antimony, and the active metal antimony accounts for 210 ppm of the total mass of the melt.

[0122] The following is Table 1:

[0123] Table 1 Process conditions and product indicators of examples 1-9 and comparative examples 1-3

[0124]

[0125]

[0126]

[0127] The properties of the terephthalic acid ethylene glycol prepolymers, high viscosity melts, low viscosity melts and melts in the spinning box obtained in examples 1-9 and comparative examples 1-3, and the properties of the final bico-elastic fiber were tested, wherein the properties of the bico-elastic fiber were tested according to the test standard of GBT 8960-2015, and the results are shown in Tables 2-4.

[0128] Table 2

[0129]

[0130] Table 3

[0131]

[0132]

[0133] Table 4 is as follows:

[0134] Table 4

[0135]

[0136]

[0137] From the above Tables 1-4, it can be seen that by adding the liquid titanium dioxide matting agent of specific composition, especially the specific carrier, in the high viscosity polymerization process, the viscosity of the high viscosity component can be improved, and the quality and crimp shrinkage of the final bico-elastic fiber can be improved. In addition, by using the specific composition of the supported catalyst to catalyze polymerization, the properties of the high viscosity component and the final bico-elastic fiber are further improved.

[0138] The above examples are only for illustrating the technical concept and characteristics of the present application, and the purpose is to enable those skilled in the art to understand the content of the present application and to implement it, and cannot limit the protection scope of the present application. Any equivalent changes or modifications made according to the spirit and essence of the present application shall be covered within the protection scope of the present application.

Claims

1. A method for preparing a fully matte PET bicomponent elastic fiber, the method comprising the steps of sequentially passing terephthalic acid, ethylene glycol, a catalyst, and optional modified monomers through a first esterification reactor and a second esterification reactor for esterification reaction, and a first prepolymerization reactor and a second prepolymerization reactor for prepolymerization reaction, to obtain a ethylene glycol terephthalate prepolymer; characterized in that: The preparation method further includes the steps of passing the polyethylene terephthalate prepolymer and liquid titanium dioxide matting agent into a high-viscosity final polymerization reactor for polymerization reaction to obtain a matte high-viscosity polyethylene terephthalate melt; and passing the polyethylene terephthalate prepolymer into a low-viscosity final polymerization reactor 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 bicomponent elastic fiber. The liquid titanium dioxide matting agent comprises titanium dioxide and a carrier; the carrier is a linear polyester or a small molecule ester; each 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, where A is a diacid and B is a diol. The small molecule ester has a melting point of less than or equal to 20°C and a boiling point of greater than or equal to 290°C. The liquid titanium dioxide matting agent contains 20%-50% titanium dioxide by weight percentage. 50%-80% of the carrier.

2. The method for preparing fully matte PET bicomponent elastic fiber according to claim 1, characterized in that: The viscosity of the carrier is 2-20 Pa·s at 25°C and 1.0-8.0 Pa·s at 60°C. And / or, the thermal weight loss of the carrier at 290°C for 2.0 hours under nitrogen protection is less than or equal to 0.2%.

3. The method for preparing fully matte PET bicomponent elastic fiber according to claim 1, characterized in that: The linear polyester is an oligomer of a diacid and a diol, wherein the diacid is selected from one or more combinations of succinic acid, glutaric acid, adipic acid, octanoic acid, sebacic acid, neoglutaric acid, 1,4-cyclohexanedicarboxylic acid, and phthalic acid; and / or, the diol is selected from one or more combinations of 1,3-butanediol, 1,4-butanediol, pentanediol, hexanediol, nonanediol, octanediol, neopentanediol, diethylene glycol, and 1,4-cyclohexanediethanol.

4. The method for preparing fully matte PET bicomponent elastic fiber 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.

5. The method for preparing fully matte PET bicomponent elastic fiber according to claim 1, characterized in that: The preparation method further includes a step of introducing a matting agent paste into the second esterification reactor before the esterification reaction is carried out in the second esterification reactor, 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.

6. The method for preparing fully matte PET bicomponent elastic fiber according to claim 1, characterized in that: The preparation method further includes a step of mixing the ethylene terephthalate prepolymer and the liquid titanium dioxide matting agent in a dynamic mixer before introducing them into a high-viscosity final polymerization reactor.

7. The method for preparing fully matte PET bicomponent elastic fiber according to claim 1, characterized in that: The PET bicomponent elastic fiber contains 30%-70% of a first PET component and 70%-30% of a second PET component by weight percentage, wherein the first PET component and the second PET component have different viscosities.

8. The method for preparing fully matte PET bicomponent elastic fiber according to claim 1, characterized in that: The catalyst is a supported catalyst, comprising a support and an active component; the support is selected from nano-alumina or nano-silica, with a particle size of 10-30 nm and a specific surface area of ​​200 m². 2 / g or more; the active component is a mixture of oxides and carbonates of metal M, wherein metal M is selected from one or more combinations of vanadium, tungsten, zirconium, iron, zinc, calcium, magnesium, titanium, cobalt and scandium.

9. The method for preparing fully matte PET bicomponent elastic fiber according to claim 8, characterized in that: The catalyst contains 94%-97% support and 3%-6% active component by weight percentage.

10. The method for preparing fully matte PET bicomponent elastic fiber according to claim 8, characterized in that: The catalyst is prepared by precipitation of a support, a compound containing the metal element M, and a precipitant, surface treatment with a silane coupling agent, and calcination; the compound containing the metal element M is selected from sulfates, chlorides, oxides, or hydroxides of the metal element M.

11. The method for preparing fully matte PET bicomponent elastic fiber according to claim 1, characterized in that: In 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-naphthalenedicarboxylic acid, phthalic acid, trimellitic anhydride, pyromellitic acid, neopentyl dicolic acid, furanyl dicarboxylic acid, 2,2,4,4-cyclobutanedicarboxylic acid, 1,4-cyclohexanediethanol, pentaerythritol, neopentyl glycol, hydroquinone, and 2,2,4,4-tetramethyl-cyclobutanediethanol.

12. The method for preparing fully matte PET bicomponent elastic fiber according to claim 11, characterized in that: The molar amount of the modified monomer accounts for 0.5%-8.0% of the molar amount of the terephthalic acid.

13. The method for preparing fully matte PET bicomponent elastic fiber according to claim 1, characterized in that: The high-viscosity final polymerization reactor is a horizontal polymerization reactor, which includes a main body containing a cavity, a feed inlet, and a discharge outlet. The main body includes a low-viscosity zone, a medium-high viscosity zone, and a high-viscosity zone arranged sequentially along the axial direction of the high-viscosity final polymerization reactor. The viscosity of the polyethylene terephthalate melt in the low-viscosity zone, the medium-high viscosity zone, and the high-viscosity zone increases sequentially. The high-viscosity final polymerization reactor also includes two stirring shafts arranged parallel to its axial direction. The two stirring shafts rotate in opposite directions. Multiple stirrers are arranged on the two stirring shafts. The outer circumference of the stirrers is circular. The stirrers on the two stirring shafts are arranged accordingly and their circular outer circumferences are tangentially in contact. The stirrer in the high-viscosity zone is a double-disc type.

14. The method for preparing fully matte PET bicomponent elastic fiber 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 agitators increases sequentially; in the high viscosity zone, the distance between two adjacent agitators is 8-50mm.

15. The method for preparing fully matte PET bicomponent elastic fiber according to claim 13, characterized in that: The high-viscosity final polymerization reactor 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 reactor, and a disc scraper for scraping the melt on the agitator; and / or, there are 10-16 agitators in the high-viscosity zone.

16. The method for preparing fully matte PET bicomponent elastic fiber according to claim 13, characterized in that: The high-viscosity final polymerization reactor also includes a steam inlet 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 using a metering system to meter the superheated ethylene glycol vapor and introduce it into the high-viscosity final polymerization reactor.

17. The method for preparing fully matte PET bicomponent elastic fiber according to claim 13, characterized in that: The preparation method further includes 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. The preparation method controls the time for the matte high-viscosity polyethylene terephthalate melt to be transported from the high-viscosity final polymerization reactor to the spinning assembly to be 30-40 minutes.

18. The method for preparing fully matte PET bicomponent elastic fiber according to claim 17, characterized in that: The preparation method further includes the step of adding a viscosity reducer to the matte high-viscosity polyethylene terephthalate melt before it passes through a filter; the viscosity reducer is selected from one or more combinations of polyethylene terephthalate-1,4-cyclohexanediol ester PETG, cationic dyeable polyester CDP, cationic dye-easily dyeable polyester ECDP, atmospheric pressure boiling-dyeing polyester EDDP, polybutylene terephthalate PBT, and poly(1,3-propanediol) ester PTT. Alternatively, the preparation method may further include the steps of injecting a solid phase smoothing agent into the polyethylene terephthalate prepolymer before passing it into the high-viscosity final polymerization reactor, and the step of passing a mixture of the solid phase smoothing agent and the polyethylene 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 one or more combinations of talc, montmorillonite, barium sulfate, hydrotalcite, and nano-silica.

19. The method for preparing fully matte PET bicomponent elastic fiber according to claim 13, characterized in that: The preparation method further includes the step of using a melt pump to transport the matte high-viscosity polyethylene terephthalate melt from the outlet of the high-viscosity final polymerization reactor to the spinning assembly, wherein the outlet of the melt pump is equipped with a melt cooler.

20. The method for preparing fully matte PET bicomponent elastic fiber 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 min, and the temperature of the high-viscosity polyethylene terephthalate melt to be below 284℃.

21. The method for preparing fully matte PET bicomponent elastic fiber according to claim 13, characterized in that: The preparation method further includes the step of introducing a heat stabilizer and an antioxidant from different positions in the second esterification reactor; the heat stabilizer is selected from one or more combinations of trimethyl phosphate, triethyl phosphate, triphenyl phosphate, triphenyl phosphite, and triglycerides; the antioxidant is selected from one or more combinations of antioxidant 168, antioxidant 1076, antioxidant 1010, antioxidant 1222, and benzothiazole antioxidants.

22. The method for preparing fully matte PET bicomponent elastic fiber 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 method for preparing fully matte PET bicomponent elastic fiber according to claim 1, 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 method for preparing fully matte PET bicomponent elastic fiber according to claim 1, 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 matte PET bicomponent elastic fiber prepared by the method of any one of claims 1 to 24.

26. The fully matte PET bicomponent elastic fiber according to claim 25, characterized in that: The crimp shrinkage rate of the fully matte PET bicomponent elastic fiber is 15.0% to 35.0%.

Images