Copolyesters, processes for their preparation and use

Abstract

This invention relates to the field of polyesters, and discloses a copolyester, its preparation method, and its application. The copolyester contains ester units as shown in formula (I), and the weight ratio of titanium to hafnium in the copolyester is 1.5-2.5:1. The preparation method includes the following steps: (1) under esterification reaction conditions, a diol monomer, a diacid monomer having the structure shown in formula (II), and a titanium-based catalyst are mixed for a first-stage reaction to obtain a prepolymer; (2) under polycondensation reaction conditions, the prepolymer and a modified monomer having the structure shown in formula (III) are subjected to a second-stage reaction; a hafnium-based catalyst is added in the first-stage reaction and / or the second-stage reaction. This copolyester has a low content of cyclic oligomers. When used to prepare polyester fibers, oligomer precipitation does not occur on the spinneret during production, resulting in stable production. The polyester fibers also exhibit high mechanical properties and uniform dyeing. Formula (I); Formula (II); Formula (III).

Description

Technical Field

[0001] This invention relates to the field of polyesters, and more specifically, to a copolyester, its preparation method, and its applications. Background Technology

[0002] Research on thermoplastic polyester elastomers (TPEEs) began in the late 1940s. TPEEs consist of crystalline, high-melting-point polyester blocks as hard segments and amorphous polyether blocks with low glass transition temperatures as soft segments, combining the elasticity of rubber with the strength of engineering plastics. TPEEs comprise an elastomer polyester crystalline phase and an amorphous phase composed of non-crystalline polyester hard segments and polyether soft segments. The crystalline phase is dispersed within the amorphous soft segments and acts as physical crosslinking points. This heterogeneous phase structure gives TPEE elastomers excellent physical and mechanical properties and ease of processing.

[0003] Currently, TPEE elastomer monofilament fibers are widely used in mesh fabrics, nonwoven sports shoes, and other fields. However, due to the wide molecular weight distribution of polyether raw materials, and the significant differences in molecular weight distribution and crown ether content of polyether raw materials from different polymerization processes and manufacturers, TPEE elastomers obtained from polyether raw material polymerization are prone to contain a large amount of cyclic oligomers, including dimers, trimers, pentamers, and cyclic ethers. When the content of cyclic oligomers is higher than 1 wt%, oligomer precipitation is likely to occur on the spinneret during the preparation of monofilament fibers from TPEE elastomers, affecting production stability. At the same time, the tensile strength of the obtained monofilament fibers is relatively low, and the dyeing uniformity is poor. Summary of the Invention

[0004] The purpose of this invention is to overcome the problem in the prior art that the high oligomer content in TPEE elastomers leads to oligomer precipitation on the spinneret during the production of monofilament fibers, affecting production stability. This invention provides a copolyester, its preparation method, and its application. The copolyester has a low content of cyclic oligomers, and when it is used to prepare polyester fibers, oligomer precipitation does not occur on the spinneret during the production process, resulting in stable production. Furthermore, the polyester fibers exhibit high mechanical properties and uniform dyeing.

[0005] To achieve the above objectives, the first aspect of the present invention provides a copolyester containing ester units as shown in formula (I), wherein the weight ratio of titanium to hafnium in the copolyester is 1.5-2.5:1. Formula (I); Wherein, R1 is selected from at least one of C6-C10 arylene, C7-C10 alkylene, and C7-C10 arylene, R I and R II Each is independently selected from hydrogen or C1-C4 alkyl groups, where m is an integer from 2 to 4 and n is an integer from 5 to 40.

[0006] A second aspect of the present invention provides a method for preparing a copolyester, comprising the following steps: (1) Under esterification reaction conditions, a diol monomer, a diacid monomer having the structure shown in formula (II) and a titanium catalyst are mixed to carry out the first stage reaction to obtain a prepolymer; (2) Under polycondensation reaction conditions, the prepolymer and the modified monomer having the structure shown in formula (III) are subjected to a second-stage reaction; A hafnium-based catalyst is added to the first stage reaction and / or the second stage reaction; Formula (II); Formula (III); Wherein, R1 is selected from at least one of C6-C10 arylene, C7-C10 alkylaryl, and C7-C10 aralkyl, R I and R II Each is independently selected from hydrogen or C1-C4 alkyl groups, where m is an integer from 2 to 4 and n is an integer from 5 to 40.

[0007] The third aspect of the present invention provides the application of the copolyester described in the first aspect and / or the copolyester obtained by the preparation method described in the second aspect in the preparation of polyester fibers.

[0008] A fourth aspect of the present invention provides a polyester fiber prepared by using the copolyester described in the first aspect and / or the copolyester obtained by the preparation method described in the second aspect.

[0009] Through the above technical solution, the copolyester provided by this invention participates in the construction and rearrangement of polyester macromolecular chain segments through the ester unit shown in formula (I), which can effectively change the structure and properties of the polymer. Furthermore, through the synergistic effect between titanium and hafnium elements in a specific ratio, the content of cyclic oligomers in the copolyester can be effectively reduced, resulting in a concentrated molecular weight distribution and high crystallinity of the copolyester. When this copolyester is used to prepare polyester fibers, oligomer precipitation does not occur on the spinneret during the production process, production is stable, and the polyester fibers have high mechanical properties and uniform dyeing, showing significant market potential. Detailed Implementation

[0010] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0011] In a first aspect, the present invention provides a copolyester containing ester units as shown in formula (I), wherein the weight ratio of titanium to hafnium in the copolyester is 1.5-2.5:1, specifically 1.5:1, 2:1, 2.5:1, or any value between the two aforementioned values; Formula (I); Wherein, R1 is selected from at least one of C6-C10 aryl, C7-C10 alkylaryl, and C7-C10 aralkyl groups, R I and R II Each is independently selected from hydrogen or C1-C4 alkyl groups, where m is an integer from 2 to 4 and n is an integer from 5 to 40.

[0012] In this invention, R1 is selected from at least one of C6-C10 arylene groups, for example, C6 arylene, C7 arylene, C8 arylene, C9 arylene, and C10 arylene, which can be, but is not limited to, phenylene or naphthylene; R1 is selected from at least one of C7-C10 alkylene groups, for example, C7 alkylene, C8 alkylene, C9 alkylene, and C10 alkylene, which can be, but is not limited to, tolyl; R1 is selected from at least one of C7-C10 arylene alkyl groups, for example, C7 arylene alkyl, C8 arylene alkyl, C9 arylene alkyl, and C10 arylene alkyl, which can be, but is not limited to, dimethylbenzylene or benzylene. I and R II Each is independently selected from hydrogen or C1-C4 alkyl groups. The C1-C4 alkyl groups can be straight-chain C1-C4 alkyl groups, branched C3-C4 alkyl groups, or C3-C4 cycloalkyl groups. For example, R I and R II Each of these can be hydrogen, methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, cyclopropyl, and cyclobutyl, etc. m is an integer from 2 to 4, specifically 2, 3, or 4; n is an integer from 5 to 40, specifically 5, 10, 20, 30, 40, or any value between the two aforementioned values.

[0013] During their research, the inventors of this invention unexpectedly discovered that by involving the ester unit shown in formula (I) in the construction and rearrangement of polyester macromolecular segments, the structure and properties of the polymer can be effectively altered. Furthermore, through the synergistic effect of titanium and hafnium elements in a specific ratio, the content of cyclic oligomers in the copolyester can be effectively reduced to below 0.5 wt%. When this copolyester is used to prepare polyester fibers, oligomer precipitation does not occur on the spinneret during the production process, resulting in stable production. The prepared polyester fibers exhibit high mechanical properties and uniform dyeing, demonstrating significant market potential.

[0014] According to the present invention, preferably, R1 is a C6-C10 arylene, more preferably a phenylene; R I and R II Each component is independently hydrogen or methyl, more preferably hydrogen; n is an integer from 10 to 25. The inventors have discovered that, under this preferred embodiment, the structure and properties of the polymer can be further modified to improve the polyester properties.

[0015] According to the present invention, preferably, the total content of titanium and hafnium in the copolyester is 40-100 ppm, specifically 40 ppm, 50 ppm, 60 ppm, 70 ppm, 80 ppm, 90 ppm, 100 ppm, or any value between the two aforementioned values. The inventors have found that, under this preferred embodiment, the content of cyclic oligomers in the copolyester can be further reduced, and it exhibits better polyester properties.

[0016] According to the present invention, preferably, the content of the ester unit represented by formula (I) in the copolyester is 20-30 wt%, specifically 20 wt%, 25 wt%, 30 wt%, or any value between the two aforementioned values. The inventors have discovered that by controlling the content of the ester unit represented by formula (I) within the above range, the content of cyclic oligomers in the copolyester can be further reduced, thereby improving the performance of the copolyester.

[0017] According to the present invention, preferably, the content of cyclic oligomers in the copolyester is less than 0.5 wt%. When the content of cyclic oligomers in the copolyester is controlled within the above range, when it is used to prepare polyester fibers, oligomer precipitation will not occur on the spinneret during the production process, the production is stable, and the polyester fibers have the characteristics of high mechanical properties and uniform dyeing.

[0018] In this invention, the cyclic oligomers in the copolyester mainly refer to dimers, trimers, tetramers, and cyclic ethers. For example, when the copolyester contains terephthalic acid, 1,4-butanediol, and polytetrahydrofuran, its dimer is cyclobis(1,4-butylene terephthalate), its trimer is cyclotris(1,4-butylene terephthalate), its tetramer is cyclotetra(1,4-butylene terephthalate), and its cyclic ether is a crown ether.

[0019] According to the present invention, preferably, the molecular weight distribution index (Mw / Mn) of the copolyester is less than 1.95. The inventors have found that, in this preferred embodiment, the narrow molecular weight distribution of the copolyester improves its uniformity and further enhances its properties.

[0020] In this invention, the titanium and hafnium content in the copolyester can be determined by elemental content detection methods. The testing process for the cyclic oligomer content in the copolyester includes: gas chromatography with HP-5% cyanopropylphenyl and 95% dimethyl polysiloxane as the stationary phase, and the temperature of the vaporization chamber and detector at 300℃ to detect the cyclic oligomer content. The molecular weight distribution index (Mw / Mn) of the copolyester is tested using a PL-GPC 50 gel permeation chromatograph with a column temperature of 40℃, a flow rate of 1.0 mL / min, and chloroform as the mobile phase. In this invention, the method for determining the ester unit represented by formula (I) in the copolyester and its content includes: using infrared spectroscopy and nuclear magnetic resonance spectroscopy to identify the presence of the ester unit represented by formula (I) in the copolyester; simultaneously, the ester unit has a characteristic hydrogen chemical shift in the nuclear magnetic resonance, and the molar ratio of the ester unit is calculated based on the peak area to achieve content determination.

[0021] Secondly, the present invention provides a method for preparing a copolyester, comprising the following steps: (1) Under esterification reaction conditions, a diol monomer, a diacid monomer having the structure shown in formula (II) and a titanium catalyst are mixed to carry out the first stage reaction to obtain a prepolymer; (2) Under polycondensation reaction conditions, the prepolymer and the modified monomer having the structure shown in formula (III) are subjected to a second-stage reaction; A hafnium-based catalyst is added to the first stage reaction and / or the second stage reaction; Formula (II); Formula (III); Wherein, R1 is selected from at least one of C6-C10 arylene groups, such as C6, C7, C8, C9, and C10 arylene groups, which may be, but is not limited to, phenylene or naphthylene; R1 is selected from at least one of C7-C10 alkylene groups, such as C7, C8, C9, and C10 alkylene groups, which may be, but is not limited to, tolyl; R1 is selected from at least one of C7-C10 arylene alkyl groups, such as C7, C8, C9, and C10 arylene alkyl groups, which may be, but is not limited to, dimethylene or benzylene. I and R II Each is independently selected from hydrogen or C1-C4 alkyl groups. The C1-C4 alkyl groups can be straight-chain C1-C4 alkyl groups, branched C3-C4 alkyl groups, or C3-C4 cycloalkyl groups. For example, R I and R IIEach can be independently hydrogen, methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, cyclopropyl, and cyclobutyl, etc.; m is an integer from 2 to 4, specifically 2, 3, or 4; n is an integer from 5 to 40, specifically 5, 10, 20, 30, 40, or any value between the two aforementioned values.

[0022] According to the present invention, there is no particular limitation on the type of titanium catalyst. In order to further improve the reaction efficiency and product yield, and thus further improve the performance of the copolyester, the titanium catalyst is preferably selected from at least one of tetrabutyl titanate, titanium glycolate and isopropyl titanate, and more preferably tetrabutyl titanate.

[0023] According to the present invention, there is no particular limitation on the type of hafnium catalyst. In order to further improve the reaction efficiency and product yield, and thus further improve the performance of the copolyester, the hafnium catalyst is preferably selected from at least one of hafnium acetylacetonate, hafnium oxide and hafnium trifluoromethanesulfonate, and more preferably hafnium acetylacetonate.

[0024] According to the present invention, preferably, the weight ratio of the titanium-based catalyst to the hafnium-based catalyst is 3.5-5.5:1, specifically 3.5, 4.5:1, 5.5:1, or any value between the two aforementioned values. The inventors have found that, under this preferred embodiment, the synergistic effect between the titanium-based catalyst and the hafnium-based catalyst in a specific ratio can further reduce the content of cyclic oligomers in the copolyester, thereby improving the mechanical properties and dyeing uniformity of the copolyester product. More preferably, the weight ratio of the titanium-based catalyst to the hafnium-based catalyst is 3.5-4.6:1.

[0025] According to the present invention, in order to further improve the mechanical properties and dyeing uniformity of the copolyester product, preferably, R1 is a C6-C10 arylene, more preferably a phenylene; R I and R II Each is independently hydrogen or methyl, with hydrogen being more preferred.

[0026] According to the present invention, in order to further improve the mechanical properties and dyeing uniformity of the copolyester product, preferably, the number average molecular weight of the modified monomer is 1000-2000, specifically 1000, 1500, 2000, or any value between the two aforementioned values.

[0027] According to the present invention, preferably, in the modified monomer, the content of the component with a number average molecular weight less than 500 is less than 3 wt%, the content of the component with a number average molecular weight greater than 8000 is less than 2 wt%, the content of the component with a number average molecular weight greater than or equal to 800 and less than or equal to 2500 is greater than 35 wt%, and the cyclic ether content is less than 0.2 wt%. The inventors have found that, under this preferred embodiment, the modified monomer has a narrow molecular weight distribution and high uniformity, which can further reduce the content of cyclic oligomers in the copolyester, thereby further improving the performance of the copolyester. The modified monomer with the above characteristics can be obtained commercially or prepared in-house. Exemplarily, it can be obtained by distillation purification of a modified monomer with a wide molecular weight distribution.

[0028] According to the present invention, the diol monomer can be any diol. In order to further improve its mechanical properties and dyeing uniformity while reducing the content of copolyester oligomers, preferably, the diol monomer is a diol having the structure shown in formula (IV). Formula (IV); Wherein, R2 is a C2-C10 alkylene group, for example, R2 is ethylene, propyleneene, butylene, pentylene, hexylene, heptylene, octylene, nonylene, or decylene, and more preferably a C2-C4 alkylene group. Exemplarily, the diol monomer can be ethylene glycol, propylene glycol, or butanediol, and more preferably butanediol.

[0029] For example, when the diol monomer is 1,4-butanediol, the dicarboxylic acid monomer is terephthalic acid, and the modifying monomer is polytetrahydrofuran, the prepared copolyester may contain the segments shown in formula (V). Formula (V).

[0030] According to the present invention, in order to further improve the mechanical properties and dyeing uniformity of the copolyester while reducing the content of copolyester oligomers, preferably, the molar ratio of the diol monomer to the diacid monomer is 2.5-3:1, specifically 2.5:1, 2.6:1, 2.7:1, 2.8:1, 2.9:1, 3:1, or any value between the two aforementioned values; the weight of the modified monomer is 200-250g compared to 1000g of the diol monomer, specifically 200g, 210g, 220g, 230g, 240g, 250g, or any value between the two aforementioned values; the weight of the titanium catalyst is 0.2-0.6g, specifically 0.2g, 0.3g, 0.4g, 0.5g, 0.6g, or any value between the two aforementioned values.

[0031] According to the present invention, preferably, in step (1), the conditions for the esterification reaction include at least: a temperature of 210-230°C, specifically 210°C, 220°C, 230°C, or any value between the two aforementioned values; an absolute pressure of 60-100 kPa, specifically 60 kPa, 80 kPa, 100 kPa, or any value between the two aforementioned values; and the conditions for the termination of the esterification reaction process include at least: the amount of water produced is greater than 90% of the theoretical amount of water produced.

[0032] According to the present invention, in order to further improve the product performance of copolyester, preferably, in step (2), the second stage reaction includes: performing a prepolymerization reaction on the prepolymer and the modified monomer to obtain a prepolymerization product, and performing a final polymerization reaction on the prepolymerization product.

[0033] According to the present invention, preferably, the conditions for the pre-condensation reaction include at least: a temperature of 230-245°C, specifically 230°C, 240°C, 245°C, or any value between the two aforementioned values; an absolute pressure of 0-4 kPa, specifically 0 Pa, 2 kPa, 4 kPa, or any value between the two aforementioned values; and a time of 45-60 min, specifically 45 min, 50 min, 60 min, or any value between the two aforementioned values. The conditions for the final condensation reaction include at least: a temperature of 235-255°C, specifically 235°C, 245°C, 255°C, or any value between the two aforementioned values; an absolute pressure of 0-100 Pa, specifically 0 Pa, 50 Pa, 100 Pa, or any value between the two aforementioned values; and the conditions for the termination of the condensation reaction process include at least: the stirring power reaching a preset value. The inventors have found that, under this preferred embodiment, the product of the esterification reaction has a better condensation effect, improving the structural and performance stability of the copolyester.

[0034] In this invention, both the first-stage reaction and the second-stage reaction are carried out under stirring conditions, with the stirring speed controlled at 25-40 rpm.

[0035] It should be noted that the preset stirring power in this invention is 130-200% of the rated power of the reactor used. Different reactors have different rated power values.

[0036] According to a particularly preferred embodiment of the present invention, a method for preparing a copolyester is provided, the method comprising the following steps: (1) Under the conditions of temperature of 210-230℃ and absolute pressure of 60-100kPa, a diacid monomer with the structure shown in formula (II), a diol monomer with the structure shown in formula (IV) and a titanium catalyst are mixed and subjected to esterification reaction to obtain a prepolymer. (2) Under the conditions of temperature of 230-245℃ and absolute pressure of 0-4kPa, the prepolymer and the modified monomer having the structure shown in formula (III) are subjected to a prepolymerization reaction to obtain a prepolymerization product. The prepolymerization product is subjected to a final polymerization reaction under the conditions of temperature of 235-255℃ and absolute pressure of 0-100Pa. A hafnium catalyst is added in the esterification reaction and / or the prepolymerization reaction. Formula (II); Formula (III); Formula (IV); Wherein, R1 is a C6-C10 arylene, R2 is a C2-C4 alkylene, and R I and R II Each is independently selected from hydrogen or C1-C4 alkyl groups, where m is an integer from 2 to 4 and n is an integer from 5 to 40; The titanium-based catalyst is tetrabutyl titanate, and the hafnium-based catalyst is hafnium acetylacetonate. The weight ratio of the titanium-based catalyst to the hafnium-based catalyst is 3.5-5.5:1. The modified monomer is polytetrahydrofuran. Among the modified monomers, the content of the component with a number average molecular weight less than 500 is less than 3 wt%, the content of the component with a number average molecular weight greater than 8000 is less than 2 wt%, the content of the component with a number average molecular weight greater than or equal to 800 and less than or equal to 2500 is greater than 35 wt%, and the cyclic ether content is less than 0.2 wt%. The molar ratio of the dicarboxylic acid monomer to the diol monomer is 2.5-3:1; the weight of the modified monomer is 200-250g compared to 1000g of the diol monomer, and the weight of the titanium catalyst is 0.2-0.6g.

[0037] In the preferred embodiments described above, the copolyester cyclic oligomers obtained have a low content. When the copolyester is used to prepare polyester fibers, oligomer precipitation will not occur on the spinneret during the production process, resulting in stable production. Furthermore, the polyester fibers exhibit high mechanical properties and uniform dyeing, demonstrating significant market potential.

[0038] Thirdly, the present invention provides the application of the copolyester described in the first aspect and / or the copolyester obtained by the preparation method described in the second aspect in the preparation of polyester fibers.

[0039] When the copolyester provided by this invention is used to prepare polyester fibers, oligomer precipitation will not occur on the spinneret during the production process, resulting in stable production. The polyester fibers produced have high mechanical properties and uniform dyeing, and have significant market prospects.

[0040] Fourthly, the present invention provides a polyester fiber prepared by using the copolyester described in the first aspect and / or the copolyester obtained by the preparation method described in the second aspect.

[0041] In this invention, the method for preparing polyester fibers is not limited, and any method for preparing polyester fibers can be used. For example, the method for preparing polyester fibers includes the following steps: adding copolyester to a screw extruder to extrude nascent filaments, which are then cooled in a cold water bath, stretched by stretching rollers, heat-set in an oven and setting rollers, and wound to obtain polyester fibers.

[0042] According to the present invention, preferably, the extruder temperature is 240-250℃, specifically 240℃, 245℃, 250℃, or any value between the two aforementioned values; the extrusion die temperature is 240-250℃, specifically 240℃, 245℃, 250℃, or any value between the two aforementioned values; the cold water bath temperature is 15-20℃, specifically 15℃, 18℃, 20℃, or any value between the two aforementioned values; the draw ratio is 3-4 times, specifically 3 times, 3.5 times, 4 times, or any value between the two aforementioned values; the oven temperature is 100-105℃, specifically 100℃, 103℃, 105℃, or any value between the two aforementioned values; and the setting roller temperature is 150-170℃, specifically 150℃, 160℃, 170℃, or any value between the two aforementioned values.

[0043] According to the present invention, preferably, the polyester fiber has a tensile strength higher than 39 MPa and an elongation at break higher than 550%. The inventors have found that, under this preferred embodiment, the polyester fiber exhibits good mechanical properties. More preferably, the polyester fiber has a tensile strength higher than 45 MPa and an elongation at break higher than 600%.

[0044] In this invention, the tensile strength and elongation at break of polyester fibers are tested in accordance with GB / T 14344-2022 Test Method for Tensile Properties of Chemical Fiber Filaments.

[0045] According to the present invention, preferably, the coefficient of kinetic friction of the polyester fiber is not higher than 0.2. The inventors have found that, under this preferred embodiment, the polyester fiber can improve its abrasion resistance and extend its service life while simultaneously improving its mechanical properties and dyeing uniformity. More preferably, the coefficient of kinetic friction of the polyester fiber is not higher than 0.1.

[0046] In this invention, the dynamic friction coefficient of polyester fiber is tested according to the method in ASTM D3108-07 Standard Test Method for Coefficient of Friction of Fiber Yarns in Solid Materials.

[0047] In this invention, the dyeing uniformity of polyester fibers is tested in accordance with the "Test Method for Dyeing Uniformity of Polyester Filament" (GB / T 6508-2015).

[0048] The present invention will be described in detail below with reference to embodiments, but this does not limit the scope of the invention.

[0049] In the following examples, polytetrahydrofurans with number-average molecular weights of 1000 and 2000 were purchased from Hangzhou Sanlong New Materials Co., Ltd. Tetrabutyl titanate was purchased from Sinopharm Group, analytical grade; hafnium acetylacetonate was purchased from Shanghai Aladdin Biochemical Technology Co., Ltd., analytical grade. Unless otherwise specified, all other raw materials and reagents were commercially available.

[0050] In the following examples, the titanium and hafnium content in the copolyester can be determined by elemental content detection methods. The testing process for the content of cyclic oligomers in copolyesters includes: using gas chromatography with HP-5% cyanopropylphenyl and 95% dimethylpolysiloxane as the stationary phase, and setting the temperature of the vaporization chamber and detector to 300℃ to detect the content of cyclic oligomers; The molecular weight distribution index (Mw / Mn) of the copolyester was determined using a PL-GPC 50 gel permeation chromatograph at a column temperature of 40℃, a flow rate of 1.0 mL / min, and chloroform as the mobile phase. The melt flow index of the copolyester was determined according to GB / T 3682-2000, "Determination of Melt Mass Flow Rate and Melt Volume Flow Rate of Thermoplastic Plastics," at a temperature of 230℃ and a weight of 2.16 kg. The method for determining the content of the ester unit represented by formula (I) in the copolyester included: using infrared spectroscopy and nuclear magnetic resonance spectroscopy to identify the presence of the ester unit represented by formula (I) in the copolyester; simultaneously, the ester unit exhibited a characteristic hydrogen chemical shift in the nuclear magnetic resonance, and the molar ratio of the ester unit was calculated based on the peak area to determine the content. The tensile strength and elongation at break of the copolyester were tested according to GB / T 528-2009 Determination of tensile stress-strain properties of vulcanized rubber or thermoplastic rubber; the coefficient of dynamic friction of the polyester fiber was tested according to the method in GB / T 14344-2022 Test method for tensile properties of chemical fiber filaments; and the dyeing uniformity of the polyester fiber was tested according to GB / T 6508-2015 Test method for dyeing uniformity of polyester filaments.

[0051] Example 1 (1) Add 3 kg of terephthalic acid (PTA), 4.5 kg of 1,4-butanediol (BDO), 1.45 g of tetrabutyl titanate and 0.32 g of hafnium acetylacetonate to the reactor and carry out the esterification reaction at a temperature of 210-230℃ and an absolute pressure of 60-100 kPa. (2) After the water output from the esterification reaction reaches 95% of the theoretical value, 1 kg of polytetrahydrofuran with a number average molecular weight of 1000 is added (in polytetrahydrofuran, the percentage content of the component with molecular weight Mn < 500 is less than 3wt%, the percentage content of the component with molecular weight Mn > 8000 is less than 2wt%, the cyclic ether content is less than 0.2wt%, and the percentage content of the component with molecular weight 800 ≤ Mn ≤ 2500 is greater than 35wt%). Then, a pre-condensation reaction is carried out at a temperature of 245℃ and an absolute pressure of 0-4kPa for 60min; then a final condensation reaction is carried out at a temperature of 255℃ and a vacuum < 100Pa. After the stirring current reaches the rated value, the material is discharged to obtain TPEE elastomer. (3) The TPEE elastomer slices are added to the screw extruder to obtain the nascent filament, wherein the extruder temperature is 240℃ and the extrusion die temperature is 250℃; the nascent filament is cooled in a cold water bath, stretched by a stretching roller, and heat-set in an oven and a setting roller, and then wound to obtain TPEE monofilament, wherein the cold water bath temperature is 18℃, the stretching ratio is 3.0 times, the oven temperature is 100℃, and the heat-setting roller temperature is 160℃.

[0052] Example 2 (1) Add 3 kg of terephthalic acid (PTA), 4.5 kg of 1,4-butanediol (BDO) and 1.45 g of tetrabutyl titanate to the reactor and carry out the esterification reaction at a temperature of 210-230℃ and an absolute pressure of 60-100 kPa. (2) After the water output from the esterification reaction reaches 95% of the theoretical value, 1 kg of polytetrahydrofuran with a number average molecular weight of 2000 (in polytetrahydrofuran, the percentage content of the component with molecular weight Mn < 500 is less than 3 wt%, the percentage content of the component with molecular weight Mn > 8000 is less than 2 wt%, the cyclic ether content is less than 0.2 wt%, and the percentage content of the component with molecular weight 800 ≤ Mn ≤ 2500 is greater than 35 wt%) and 0.32 g of hafnium acetylacetone are added. The pre-condensation reaction is carried out for 45 min at a temperature of 230℃ and an absolute pressure of 0-4 kPa. Then, the final condensation reaction is carried out at a temperature of 242℃ and a vacuum < 100 Pa. After the stirring current reaches the rated value, the material is discharged to obtain TPEE elastomer. (3) The TPEE elastomer slices are added to the screw extruder to obtain the nascent filament, wherein the extruder temperature is 250℃ and the extrusion die temperature is 250℃; the nascent filament is cooled in a cold water bath, stretched by a stretching roller, and heat-set in an oven and a setting roller, and then wound to obtain TPEE monofilament, wherein the cold water bath temperature is 18℃, the stretching ratio is 4.0 times, the oven temperature is 100℃, and the heat-setting roller temperature is 160℃.

[0053] Example 3 (1) Add 3 kg of terephthalic acid (PTA), 4.5 kg of 1,4-butanediol (BDO) and 2.41 g of tetrabutyl titanate to the reactor and carry out the esterification reaction at a temperature of 210-230℃ and an absolute pressure of 60-100 kPa. (2) After the water output from the esterification reaction reaches 95% of the theoretical value, 1 kg of polytetrahydrofuran with a number average molecular weight of 1000 (in polytetrahydrofuran, the percentage content of the component with molecular weight Mn < 500 is less than 3 wt%, the percentage content of the component with molecular weight Mn > 8000 is less than 2 wt%, the cyclic ether content is less than 0.2 wt%, and the percentage content of the component with molecular weight 800 ≤ Mn ≤ 2500 is greater than 35 wt%) and 0.54 g of hafnium acetylacetone are added. The pre-condensation reaction is carried out for 60 min at a temperature of 230℃ and an absolute pressure of 0-4 kPa. Then, the final condensation reaction is carried out at a temperature of 235℃ and a vacuum < 100 Pa. After the stirring current reaches the rated value, the material is discharged to obtain TPEE elastomer. (3) The TPEE elastomer slices are added to the screw extruder to obtain the nascent filament, wherein the extruder temperature is 250℃ and the extrusion die temperature is 250℃; the nascent filament is cooled in a cold water bath, stretched by a stretching roller, and heat-set in an oven and a setting roller, and then wound to obtain TPEE monofilament, wherein the cold water bath temperature is 18℃, the stretching ratio is 4.0 times, the oven temperature is 100℃, and the heat-setting roller temperature is 160℃.

[0054] Example 4 (1) Add 3.1 kg of terephthalic acid (PTA), 4.4 kg of 1,4-butanediol (BDO), 1.12 g of tetrabutyl titanate and 0.32 g of hafnium acetylacetonate to the reactor and carry out the esterification reaction at a temperature of 210-230℃ and an absolute pressure of 60-100 kPa. (2) After the water output from the esterification reaction reaches 95% of the theoretical value, 1.1 kg of polytetrahydrofuran with a number average molecular weight of 1000 is added (in polytetrahydrofuran, the percentage content of the component with molecular weight Mn < 500 is less than 3 wt%, the percentage content of the component with molecular weight Mn > 8000 is less than 2 wt%, the cyclic ether content is less than 0.2 wt%, and the percentage content of the component with molecular weight 800 ≤ Mn ≤ 2500 is greater than 35 wt%). Then, a pre-condensation reaction is carried out at a temperature of 245℃ and an absolute pressure of 0-4 kPa for 60 min; then a final condensation reaction is carried out at a temperature of 255℃ and a vacuum < 100 Pa. After the stirring current reaches the rated value, the material is discharged to obtain TPEE elastomer. (3) The TPEE elastomer slices are added to the screw extruder to obtain the nascent filament, wherein the extruder temperature is 240℃ and the extrusion die temperature is 250℃; the nascent filament is cooled in a cold water bath, stretched by a stretching roller, and heat-set in an oven and a setting roller, and then wound to obtain TPEE monofilament, wherein the cold water bath temperature is 18℃, the stretching ratio is 3.0 times, the oven temperature is 100℃, and the heat-setting roller temperature is 160℃.

[0055] Example 5 Polyester fibers were prepared according to the method of Example 1, except that in step (1), the amount of tetrabutyl titanate was replaced with 2.9g and the amount of hafnium acetylacetonate was replaced with 0.64g.

[0056] Example 6 Polyester fibers were prepared according to the method of Example 1, except that in step (1), tetrabutyl titanate was replaced with isopropyl titanate and hafnium acetylacetonate was replaced with hafnium oxide.

[0057] Example 7 Polyester fibers were prepared according to the method of Example 2, except that in step (2), the polytetrahydrofuran with a number average molecular weight of 2000 (in polytetrahydrofuran, the percentage content of the component with molecular weight Mn < 500 is less than 3 wt%, the percentage content of the component with molecular weight Mn > 8000 is less than 2 wt%, the cyclic ether content is less than 0.2 wt%, and the percentage content of the component with molecular weight 800 ≤ Mn ≤ 2500 is greater than 35 wt%) was replaced with polytetrahydrofuran with a number average molecular weight of 1000 (in polytetrahydrofuran, the percentage content of the component with molecular weight Mn < 500 is 5 wt%, the percentage content of the component with molecular weight Mn > 8000 is 10 wt%, the cyclic ether content is 0.5 wt%, and the percentage content of the component with molecular weight 800 ≤ Mn ≤ 2500 is 25 wt%).

[0058] Example 8 Polyester fibers were prepared according to the method of Example 2, except that in step (2), polytetrahydrofuran with a number average molecular weight of 2000 was replaced with polytetrahydrofuran with a number average molecular weight of 2000 (in polytetrahydrofuran, the percentage content of the component with a molecular weight Mn < 500 is 5wt%, the percentage content of the component with a number average molecular weight Mn > 8000 is 15wt%, the cyclic ether content is less than 0.4wt%, and the percentage content of the component with a number average molecular weight 800 ≤ Mn ≤ 2500 is 22wt%).

[0059] Comparative Example 1 (1) Add 3 kg of terephthalic acid (PTA), 4.5 kg of 1,4-butanediol (BDO) and 2.17 g of tetrabutyl titanate to the reactor and carry out the esterification reaction at a temperature of 210-230℃ and an absolute pressure of 60-100 kPa. (2) After the water output from the esterification reaction reaches 95% of the theoretical value, add 1 kg of polytetrahydrofuran with a number average molecular weight of 1000 (in polytetrahydrofuran, the percentage content of the component with a molecular weight Mn < 500 is less than 3wt%, the percentage content of the component with a number average molecular weight Mn > 8000 is less than 2wt%, the cyclic ether content is less than 0.2wt%, and the percentage content of the component with a number average molecular weight 800 ≤ Mn ≤ 2500 is greater than 35wt%), and then perform a pre-condensation reaction for 60 min at a temperature of 245℃ and an absolute pressure of 0-4 kPa; then perform a final condensation reaction at a temperature of 255℃ and a vacuum < 100 Pa. After the stirring current reaches the rated value, the material is discharged, and TPEE elastomer is produced. (3) The TPEE elastomer slices are added to the screw extruder to obtain the nascent filament, wherein the extruder temperature is 250℃ and the extrusion die temperature is 250℃; the nascent filament is cooled in a cold water bath, stretched by a stretching roller, and heat-set in an oven and a setting roller, and then wound to obtain TPEE monofilament, wherein the cold water bath temperature is 18℃, the stretching ratio is 3.0 times, the oven temperature is 100℃, and the heat-setting roller temperature is 160℃.

[0060] Comparative Example 2 (1) Add 3 kg of terephthalic acid (PTA), 4.5 kg of 1,4-butanediol (BDO) and 1.45 g of tetrabutyl titanate to the reactor and carry out the esterification reaction at a temperature of 210-230℃ and an absolute pressure of 60-100 kPa. (2) After the water output from the esterification reaction reaches 95% of the theoretical value, 1 kg of polytetrahydrofuran with a number average molecular weight of 1000 (in polytetrahydrofuran, the percentage content of the component with a molecular weight Mn < 500 is less than 3 wt%, the percentage content of the component with a number average molecular weight Mn > 8000 is less than 2 wt%, the cyclic ether content is less than 0.2 wt%, and the percentage content of the component with a number average molecular weight 800 ≤ Mn ≤ 2500 is greater than 35 wt%) and 0.32 g of lanthanum acetylacetonate are added. The pre-condensation reaction is carried out for 60 min at a temperature of 230℃ and an absolute pressure of 0-4 kPa. Then, the final condensation reaction is carried out at a temperature of 235℃ and a vacuum < 100 Pa. After the stirring current reaches the rated value, the material is discharged to obtain TPEE elastomer. (3) The TPEE elastomer slices are added to the screw extruder to obtain the nascent filament, wherein the extruder temperature is 250℃ and the extrusion die temperature is 250℃; the nascent filament is cooled in a cold water bath, stretched by a stretching roller, and heat-set in an oven and a setting roller, and then wound to obtain TPEE monofilament, wherein the cold water bath temperature is 18℃, the stretching ratio is 4.0 times, the oven temperature is 100℃, and the heat-setting roller temperature is 160℃.

[0061] Comparative Example 3 (1) Add 3 kg of terephthalic acid (PTA), 4.5 kg of 1,4-butanediol (BDO) and 1.45 g of antimony acetate to the reaction vessel and carry out the esterification reaction at a temperature of 210-230℃ and an absolute pressure of 60-100 kPa. (2) After the water output from the esterification reaction reaches 95% of the theoretical value, 1 kg of polytetrahydrofuran with a number average molecular weight of 1000 (in polytetrahydrofuran, the percentage content of the component with a molecular weight Mn < 500 is less than 3 wt%, the percentage content of the component with a number average molecular weight Mn > 8000 is less than 2 wt%, the cyclic ether content is less than 0.2 wt%, and the percentage content of the component with a number average molecular weight 800 ≤ Mn ≤ 1500 is greater than 35 wt%) and 0.32 g of hafnium acetylacetone are added. The pre-condensation reaction is carried out for 60 min at a temperature of 230℃ and an absolute pressure of 0-4 kPa. Then, the final condensation reaction is carried out at a temperature of 235℃ and a vacuum < 100 Pa. After the stirring current reaches the rated value, the material is discharged to obtain TPEE elastomer. (3) The TPEE elastomer slices are added to the screw extruder to obtain the nascent filament, wherein the extruder temperature is 250℃ and the extrusion die temperature is 250℃; the nascent filament is cooled in a cold water bath, stretched by a stretching roller, and heat-set in an oven and a setting roller, and then wound to obtain TPEE monofilament, wherein the cold water bath temperature is 18℃, the stretching ratio is 3.0 times, the oven temperature is 100℃, and the heat-setting roller temperature is 160℃.

[0062] Comparative Example 4 (1) Add 3 kg of terephthalic acid (PTA), 4.5 kg of 1,4-butanediol (BDO) and 1.63 g of tetrabutyl titanate to the reactor and carry out the esterification reaction at a temperature of 210-230℃ and an absolute pressure of 60-100 kPa. (2) After the water output from the esterification reaction reaches 95% of the theoretical value, 1 kg of polytetrahydrofuran with a number average molecular weight of 1000 (in polytetrahydrofuran, the percentage content of the component with a molecular weight Mn < 500 is less than 3 wt%, the percentage content of the component with a number average molecular weight Mn > 8000 is less than 2 wt%, the cyclic ether content is less than 0.2 wt%, and the percentage content of the component with a number average molecular weight 800 ≤ Mn ≤ 1500 is greater than 35 wt%) and 0.24 g of hafnium acetylacetone are added, and the pre-condensation reaction is carried out for 60 min at a temperature of 230℃ and an absolute pressure of 0-4 kPa; then the final condensation reaction is carried out at a temperature of 235℃ and a vacuum < 100 Pa. After the stirring current reaches the rated value, the material is discharged to obtain TPEE elastomer. (3) The TPEE elastomer slices are added to the screw extruder to obtain the nascent filament, wherein the extruder temperature is 240℃ and the extrusion die temperature is 250℃; the nascent filament is cooled in a cold water bath, stretched by a stretching roller, and heat-set in an oven and a setting roller, and then wound to obtain TPEE monofilament, wherein the cold water bath temperature is 18℃, the stretching ratio is 4.0 times, the oven temperature is 100℃, and the heat-setting roller temperature is 160℃.

[0063] Test Example 1 The titanium content, hafnium content, cyclic oligomer content, molecular weight distribution index Mw / Mn, ester unit content of the structure shown in formula (I), and melt index of the TPEE elastomers prepared in Examples 1-8 and Comparative Examples 1-4 were tested. The results are shown in Table 1.

[0064] Table 1

[0065] As can be seen from the results in Table 1, compared with Comparative Examples 1-4, the copolyesters prepared by the method provided by the present invention in Examples 1-8 can effectively reduce the content of cyclic oligomers in the copolyester, and the molecular weight distribution of the copolyester is more concentrated and the crystallinity is higher.

[0066] Test Example 2 The coefficient of dynamic friction, tensile strength and elongation at break of the TPEE monofilaments prepared in Examples 1-8 and Comparative Examples 1-4 were tested, and the results are shown in Table 2.

[0067] Table 2

[0068] As can be seen from the results in Table 2, compared with Comparative Examples 1-4, the polyester fibers obtained by using the copolyester provided by the present invention in Examples 1-8 do not exhibit oligomer precipitation during the production process, resulting in stable production. The polyester fibers have high mechanical properties and uniform dyeing, and have significant market prospects.

[0069] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A copolyester, characterized in that, The copolyester contains ester units as shown in formula (I), and the weight ratio of titanium to hafnium in the copolyester is 1.5-2.5:1; Equation (I); wherein R1is selected from at least one of C6-C10 arylene, C7-C10 alkarylene and C7-C10 aralkylene, R I and R II each independently is selected from hydrogen or C1-C4 alkyl, m is an integer from 2 to 4, and n is an integer from 5 to 40.

2. The copolyester according to claim 1, characterized in that, R1is C6-C10 arylene, R I and R II each independently is hydrogen or methyl, n is an integer from 10 to 25; Preferably, the total content of titanium and hafnium in the copolyester is 40-100 ppm; Preferably, the content of the ester unit represented by formula (I) in the copolyester is 20-30 wt%.

3. The copolyester according to claim 1 or 2, characterized in that, The copolyester contains less than 0.5 wt% cyclic oligomers. Preferably, the molecular weight distribution index (Mw / Mn) of the copolyester is less than 1.

95.

4. A method for preparing a copolyester, characterized in that, Includes the following steps: (1) Under esterification reaction conditions, a diol monomer, a diacid monomer having the structure shown in formula (II) and a titanium catalyst are mixed to carry out the first stage reaction to obtain a prepolymer; (2) Under polycondensation reaction conditions, the prepolymer and the modified monomer having the structure shown in formula (III) are subjected to a second-stage reaction; A hafnium-based catalyst is added to the first stage reaction and / or the second stage reaction; Formula (II); Formula (III); wherein R1is selected from at least one of C6-C10 arylene, C7-C10 alkylaryl, and C7-C10 aralkyl, R I and R II each independently selected from hydrogen or C1-C4 alkyl, m is an integer from 2 to 4, and n is an integer from 5 to 40.

5. The preparation method according to claim 4, characterized in that, The titanium-based catalyst is selected from at least one of tetrabutyl titanate, titanium glycolate and isopropyl titanate, preferably tetrabutyl titanate; Preferably, the hafnium-based catalyst is selected from at least one of hafnium acetylacetonate, hafnium oxide, and hafnium trifluoromethanesulfonate, and more preferably hafnium acetylacetonate; Preferably, the weight ratio of the titanium-based catalyst to the hafnium-based catalyst is 3.5-5.5:

1.

6. The preparation method according to claim 4, characterized in that, R1is C6-C10 arylene, R I and R II each independently hydrogen or methyl; Preferably, the number-average molecular weight of the modified monomer is 1000-2000; Preferably, in the modified monomer, the content of the component with a number average molecular weight less than 500 is less than 3 wt%, the content of the component with a number average molecular weight greater than 8000 is less than 2 wt%, the content of the component with a number average molecular weight greater than or equal to 800 and less than or equal to 2500 is greater than 35 wt%, and the content of cyclic ether is less than 0.2 wt%. Preferably, the diol monomer is a diol having the structure shown in formula (IV); Formula (IV); Wherein, R2 is a C2-C10 alkylene group, and more preferably a C2-C4 alkylene group.

7. The preparation method according to any one of claims 4 to 6, characterized in that, The molar ratio of the diol monomer to the diacid monomer is 2.5-3:1; compared to 1000g of the diol monomer, the weight of the modified monomer is 200-250g, and the weight of the titanium catalyst is 0.2-0.6g. Preferably, in step (1), the conditions for the esterification reaction include at least: a temperature of 210-230°C and an absolute pressure of 60-100 kPa; Preferably, in step (2), the second stage reaction includes: performing a prepolymerization reaction on the prepolymer and the modified monomer to obtain a prepolymerization product, and performing a final polymerization reaction on the prepolymerization product; Preferably, the conditions for the pre-condensation reaction include at least: a temperature of 230-245℃, an absolute pressure of 0-4kPa, and a time of 45-60min; the conditions for the final condensation reaction include at least: a temperature of 235-255℃ and an absolute pressure of 0-100Pa.

8. The use of the copolyester according to any one of claims 1 to 3 and / or the copolyester obtained by the preparation method according to any one of claims 4 to 7 in the preparation of polyester fibers.

9. A polyester fiber, characterized in that, The copolyester is prepared by using the copolyester described in any one of claims 1 to 3 and / or the copolyester obtained by the preparation method described in any one of claims 4 to 7.

10. The polyester fiber according to claim 9, characterized in that, The tensile strength of the polyester fiber is higher than 39 MPa, and the elongation at break is higher than 550%. Preferably, the coefficient of kinetic friction of the polyester fiber is not higher than 0.2.

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