Preparation method of high-strength high-modulus polyester fiber and polyester fiber

Abstract

The application relates to the technical field of polyester fibers, and discloses a preparation method of high-strength and high-modulus polyester fibers and the polyester fibers, which comprises the following steps: (1) mixing 4,4'-diphenyldicarboxylic acid, 1,3-propanediol, a catalyst and a thermal stabilizer to perform esterification; (2) after the esterification is completed, first-stage polycondensation reaction is performed, and then second-stage polycondensation reaction is performed, small molecules and water are removed during the reaction, and a polymer is obtained; (3) the polymer is subjected to melt spinning, and then sequentially passes through first-stage side blowing, second-stage side blowing and post-stretching to obtain polyester fibers. The PET melt is prepared through esterification and polycondensation reaction of 4,4'-diphenyldicarboxylic acid monomers and 1,3-propanediol monomers, the relative molecular mass can be increased, the stereoregularity of the macromolecular chain can be increased, and finally, the polyester fibers with high breaking strength, elastic modulus and melting point can be prepared through melt spinning.

Description

Technical Field

[0001] This invention relates to the technical field of polyester fibers, and in particular to a method for preparing high-strength, high-modulus polyester fibers and the polyester fibers themselves. Background Technology

[0002] Currently, the main method for preparing high-strength, high-modulus polyester (PET) fibers is to use terephthalic acid (PTA) and ethylene glycol (EG) as monomers and polymerize them via direct esterification. First, polyester esters (BHET) are generated, then polycondensation is performed under certain conditions to produce polyester chips, which are finally spun using melt spinning. However, the polyester fibers prepared by this traditional method generally have a breaking strength of 4–6 cN / dtex, an elastic modulus of 60–100 cN / dtex, and a melting point of 255–263℃. These characteristics are insufficient to meet the specific mechanical property requirements of industrial applications. Therefore, improving the strength and modulus of polyester fibers to produce high-strength, high-modulus polyester fibers is a worthy research topic.

[0003] The main reason why polyester fibers prepared by traditional methods have insufficient strength and modulus is that the PTA monomer has a low molecular weight and high reactivity. Therefore, the polyester produced after polycondensation has a relatively low molecular weight, which first affects the increase of melt viscosity, leading to easy fiber breakage during spinning. The fibers cannot withstand high stretching ratios, ultimately resulting in poor mechanical properties. Simultaneously, because the PTA monomer contains only one benzene ring structure, the synthesized polyester macromolecule lacks rigidity, thus resulting in a low melting point for the fiber.

[0004] Patent CN114000226A discloses a cationic dyeable flame-retardant high-strength polyester fiber. It first mixes oligomer A, oligomer B, and BHET and performs a polycondensation reaction to obtain a cationic dyeable flame-retardant polyester masterbatch. This masterbatch is then mixed with polyester chips in a certain proportion and melt-spun. The polyester fiber prepared by this method has a maximum breaking strength of only 4.8 cN / dtex, and the preparation process is complex. Patent CN106397749A discloses a method for synthesizing high-strength, high-modulus polyester. It first prepares a composite alcohol solution and a composite accelerator, and then prepares high-strength, high-modulus polyester by controlling different proportions of these components through polycondensation. However, it does not include spinning or research on the fiber's mechanical properties. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention provides a method for preparing high-strength, high-modulus polyester fibers and the polyester fibers themselves. By using 4,4'-biphenyldicarboxylic acid (BBA) monomer instead of the traditional terephthalic acid (PTA) monomer, and 1,3-propanediol (PDO) monomer instead of the traditional ethylene glycol (EG) monomer, PET melt is prepared by sequentially performing esterification and polycondensation reactions with these two monomers. Then, polyester fibers are obtained through melt spinning. This process not only imparts a higher relative molecular mass to the macromolecular chains and increases the rigidity of the molecular chain structure, but also increases the stereoregularity of the macromolecular chains. Ultimately, polyester fibers with high breaking strength, elastic modulus, and melting point are obtained.

[0006] The objective of this invention is achieved through the following technical solution:

[0007] In a first aspect, the present invention provides a method for preparing high-strength, high-modulus polyester fibers, comprising the following steps:

[0008] (1) Mix 4,4'-biphenyldicarboxylic acid, 1,3-propanediol, catalyst and heat stabilizer, and carry out esterification reaction;

[0009] (2) After esterification, the first stage of polycondensation reaction is carried out, followed by the second stage of polycondensation reaction. The reaction removes small molecules and water at the same time to obtain the polymer.

[0010] The reaction equation for the condensation reaction is as follows:

[0011]

[0012] (3) The polymer is melt-spun and then passed through the first stage of side blowing, the second stage of side blowing and post-stretching to obtain polyester fiber.

[0013] This invention uses 4,4'-biphenyl dicarboxylic acid (BBA) monomer instead of the traditional terephthalic acid (PTA) monomer, and 1,3-propanediol (PDO) monomer instead of the traditional ethylene glycol (EG) monomer. PET melt is prepared by sequentially esterifying and polycondensing these two monomers. Compared with existing technologies that use both PTA and EG monomers for esterification and polycondensation to prepare PET melt, the new monomers have larger molecular weights and lower reactivity than PTA and EG, respectively, making it easier to obtain higher molecular weight PET macromolecules. The BBA monomer also has a unique structure with two benzene rings, which increases the proportion of rigid structures in the PET macromolecule during polymerization, thereby helping to increase the melting temperature of PET fibers.

[0014] Furthermore, if only PTA is replaced with BBA monomer while EG monomer remains unchanged, although polycondensation can give PET macromolecules a more rigid structure, the excessive rigidity of the macromolecular chains can lead to insufficient flexibility, which is detrimental to spinning. However, replacing EG monomer with PDO monomer, due to the longer carbon chain linkages in PDO monomer, increases the mobility of macromolecular chain segments and allows for different stereoregularities through internal rotation of carbon-carbon bonds within the molecular chain. Simultaneously, because the biphenyl structure has a greater steric hindrance effect compared to a single benzene ring structure, it is also more conducive to improving the stereoregularity of PET molecular chains, ultimately benefiting the compact aggregation and crystallinity of macromolecules.

[0015] Therefore, this invention introduces BBA and PDO monomers to replace the original two monomers. This not only gives the macromolecular chain a higher relative molecular mass and increases the rigidity of the molecular chain, but also increases the stereoregularity of the macromolecular chain, which is beneficial to preparing polyester fibers with better mechanical properties and thermal stability.

[0016] Preferably, the molar ratio of 4,4'-biphenyldicarboxylic acid and 1,3-propanediol is 1:1.1-1.4.

[0017] Preferably, the amount of catalyst used is 0.04-0.1% of the mass of 4,4'-biphenyldicarboxylic acid; the catalyst is Sb2O3 or GeO2.

[0018] Preferably, the amount of heat stabilizer is 0.02-0.1% of the mass of 4,4'-biphenyl dicarboxylic acid; the heat stabilizer is triphenyl phosphite.

[0019] Preferably, the esterification reaction is carried out at a temperature of 280-310℃, a pressure of 100-120kPa, and a reaction time of 2-4h.

[0020] Preferably, the temperature of the first stage polycondensation reaction is 260-270℃, the pressure is 5-7kPa, and the polycondensation time is 2-3h.

[0021] Preferably, the temperature of the second-stage polycondensation reaction is 270-290℃, the pressure is 50-90Pa, and the polycondensation time is 2-3h.

[0022] Preferably, the polymer has a relative molecular mass of not less than 23,000; more preferably, the polymer has a relative molecular mass of not less than 24,000.

[0023] Preferably, the melt spinning temperature is 265-290℃ and the pressure is 40-60MPa; the melt spinning speed is 2500-2800m / min.

[0024] The present invention employs a high-pressure melt spinning process, including a gradual heating and preheating process during the feeding stage, and a high-pressure compression, degassing, and gradual melting process in the spinning box.

[0025] Preferably, the blowing temperature of the first-stage side-blowing air is 8-15℃, the relative humidity is 70-90%, and the wind speed is 0.2-0.4m / s.

[0026] The temperature of the first-stage side-blowing device is relatively low because the macromolecular chains of the filaments extruded from the spinneret are subjected to the shear force of the spinneret and the large temperature difference (the temperature difference between the spinning solution in the spinneret and the temperature of the first-stage side-blowing) which rapidly reduces the thermal motion of the macromolecular chains and causes the fibers to solidify quickly, thus maintaining the straightened state of the macromolecules.

[0027] Preferably, the blowing temperature of the second-stage side-blowing air is 50-70℃, the relative humidity is 50-60%, and the wind speed is 0.3-0.6m / s.

[0028] The second-stage side-blowing device operates at a higher temperature because the macromolecular chains of the fiber relax due to the temperature effect after entering the high-temperature region. At this time, under a certain multiple of winding tension, the macromolecules can maintain a straight chain structure, which ultimately helps to increase the stretch ratio. The crystallinity and orientation of the fiber will also increase accordingly, thereby improving the breaking strength, elastic modulus and melting point.

[0029] Preferably, the stretching ratio of the post-stretch is not less than 4.0.

[0030] Secondly, the present invention also provides a high-strength, high-modulus polyester fiber prepared by the above-described preparation method.

[0031] Compared with the prior art, the present invention has the following beneficial effects:

[0032] (1) This invention introduces 4,4'-biphenyl dicarboxylic acid (BBA) monomer and 1,3-propanediol (PDO) monomer to replace the original two monomers. This not only gives the macromolecular chain a higher molecular weight and increases the rigidity of the molecular chain, but also increases the stereoregularity of the macromolecular chain, which is beneficial to the preparation of polyester fibers with better mechanical properties and thermal stability.

[0033] (2) The existing synthesis process mainly involves first using a multi-stage esterification method to generate polyester ester (BHET), and then performing a multi-step polycondensation reaction under certain conditions to generate PET chips. This method has the disadvantages of long polymerization process, low efficiency and high energy consumption. However, the present invention uses a direct esterification method and carries out polycondensation reaction in the same reactor, which can significantly shorten the reaction process and save energy consumption.

[0034] (3) The preparation process of the present invention is simple and generates no waste. Detailed Implementation

[0035] The technical solution of the present invention will be illustrated below with specific embodiments, but the scope of protection of the present invention is not limited thereto.

[0036] The preparation of high-strength, high-modulus polyester fibers in this invention includes the following steps:

[0037] (1) First, the air in the polymerization reactor is replaced with nitrogen. Then, 4,4'-biphenyl dicarboxylic acid (BBA), 1,3-propanediol (PDO), catalyst and heat stabilizer are thoroughly mixed and stirred evenly before being added to the reactor. The molar ratio of 4,4'-biphenyl dicarboxylic acid to 1,3-propanediol is 1:1.1-1.4. The amount of catalyst is 0.04-0.1% of the mass of 4,4'-biphenyl dicarboxylic acid, and the amount of heat stabilizer is 0.02-0.1% of the mass of 4,4'-biphenyl dicarboxylic acid. The esterification reaction is carried out at a temperature of 280-310℃, a pressure of 100-120kPa, and a reaction time of 2-4h to prepare BHET.

[0038] (2) After esterification, the temperature inside the reactor is adjusted to 260-270℃, the pressure to 5-7kPa, and the polycondensation time to 2-3h to carry out the first stage of polycondensation reaction; the temperature inside the reactor is adjusted again to 270-290℃, the pressure to 50-90Pa, and the polycondensation time to 2-3h to carry out the second stage of polycondensation reaction. During the polycondensation reaction, pure circulating N2 is used to carry out the generated PDO and water out of the system, and the PDO and water in the circulating nitrogen are removed by an adsorption tower equipped with artificial molecular sieves. After polycondensation, a polymer with a higher molecular weight is obtained, and then PET chips are prepared.

[0039] (3) After drying the PET chips, melt spinning is carried out. The filaments are compressed, vented and melted in the spinning box under high pressure. The high pressure of the high-pressure spinning is 40-60 MPa, the spinning temperature is 265-290℃ and the spinning speed is 2500-2800 m / min. The filaments obtained by spinning are passed through two-stage side blowing devices. The distance between the first-stage side blowing device and the spinneret is 10-20 cm, the blowing temperature is 8-15℃, the relative humidity is 70-90% and the wind speed is 0.2-0.4 m / s. The blowing temperature in the second-stage side blowing device is 50-70℃, the relative humidity is 50-60% and the wind speed is 0.3-0.6 m / s. Then, the fibers are stretched to obtain polyester fibers.

[0040] In a specific embodiment of the present invention, the catalyst is Sb2O3 or GeO2.

[0041] In a specific embodiment of the present invention, the heat stabilizer is triphenyl phosphite.

[0042] In a specific embodiment of the present invention, the main component of the adsorbent in the adsorption tower containing artificial molecular sieves is a silicate hydroxide containing sodium aluminate.

[0043] In a specific embodiment of the present invention, the temperature for drying PET slices is 100-150°C and the drying time is 3-8 hours.

[0044] Example 1

[0045] (1) First, replace the air in the polymerization reactor with N2, then add BBA and PDO monomers (molar ratio of 1:1.2), Sb2O3 catalyst (0.04% of BBA mass) and triphenyl phosphite (0.02% of BBA mass) to the reactor after thorough mixing. The temperature in the reactor is controlled at 295℃ and the reaction is carried out at a pressure of 110kPa for 3.5h.

[0046] (2) After esterification, the temperature inside the reactor was adjusted to 260℃ and the pressure inside the reactor to 6 kPa for the first stage of polycondensation reaction, which lasted for 2.0 h. The temperature inside the reactor was then adjusted again to 275℃ and the pressure inside the reactor to 50 Pa for the second stage of polycondensation reaction, which lasted for 2.5 h. During the reaction, pure circulating nitrogen was used to remove the generated PDO and water from the system, and the PDO and water in the circulating nitrogen were removed by an adsorption tower containing sodium aluminate silicate hydroxide. Finally, a PET polymer with a relative molecular mass of 25650 was obtained, which was then used to prepare PET chips.

[0047] Example 2

[0048] (1) First, replace the air in the polymerization reactor with N2, then add BBA and PDO monomers (molar ratio of 1:1.1), Sb2O3 catalyst (0.06% of BBA mass) and triphenyl phosphite (0.05% of BBA mass) to the reactor after thorough mixing. The temperature in the reactor is controlled at 310℃ and the reaction is carried out at a pressure of 110kPa for 3.5h.

[0049] (2) After esterification, the temperature inside the reactor was adjusted to 270℃ and the pressure inside the reactor to 6 kPa for the first stage of polycondensation reaction, which lasted for 2.0 h. The temperature inside the reactor was then adjusted again to 290℃ and the pressure inside the reactor to 50 Pa for the second stage of polycondensation reaction, which lasted for 2.5 h. During the reaction, pure circulating nitrogen was used to remove the generated PDO and water from the system, and the PDO and water in the circulating nitrogen were removed by an adsorption tower containing sodium aluminate silicate hydroxide. Finally, a PET polymer with a relative molecular mass of 23240 was obtained, which was then used to prepare PET chips.

[0050] Example 3

[0051] (1) First, replace the air in the polymerization reactor with N2, then add BBA and PDO monomers (molar ratio of 1:1.4), Sb2O3 catalyst (0.1% of BBA mass) and triphenyl phosphite (0.06% of BBA mass) to the reactor after thorough mixing. The temperature in the reactor is controlled at 290℃ and the reaction is carried out at a pressure of 110kPa for 3.5h.

[0052] (2) After esterification, the temperature inside the reactor was adjusted to 265℃ and the pressure inside the reactor to 6 kPa for the first stage of polycondensation reaction, which lasted for 2.0 h. The temperature inside the reactor was then adjusted again to 285℃ and the pressure inside the reactor to 50 Pa for the second stage of polycondensation reaction, which lasted for 2.5 h. During the reaction, pure circulating nitrogen was used to remove the generated PDO and water from the system, and the PDO and water in the circulating nitrogen were removed by an adsorption tower containing sodium aluminate silicate hydroxide. Finally, a PET polymer with a relative molecular mass of 24073 was obtained, which was then used to prepare PET chips.

[0053] Example 4

[0054] (1) First, replace the air in the polymerization reactor with N2, then add BBA and PDO monomers (molar ratio of 1:1.3), Sb2O3 catalyst (0.08% of BBA mass) and triphenyl phosphite (0.08% of BBA mass) to the reactor after thorough mixing. The temperature in the reactor is controlled at 285℃ and the reaction is carried out at a pressure of 110kPa for 3.5h.

[0055] (2) After esterification, the temperature inside the reactor was adjusted to 260℃ and the pressure inside the reactor to 6 kPa for the first stage of polycondensation reaction, which lasted for 2.0 h. The temperature inside the reactor was then adjusted again to 270℃ and the pressure inside the reactor to 50 Pa for the second stage of polycondensation reaction, which lasted for 2.5 h. During the reaction, pure circulating nitrogen was used to remove the generated PDO and water from the system, and the PDO and water in the circulating nitrogen were removed by an adsorption tower containing sodium aluminate silicate hydroxide. Finally, a PET polymer with a relative molecular mass of 28762 was obtained, which was then used to prepare PET chips.

[0056] Example 5

[0057] (1) The PET slices obtained in Example 1 were transferred to a vacuum drum dryer for drying at a temperature of 120°C for 5 hours.

[0058] (2) The dried PET chips are added to the spinning barrel. The temperature in the preheating zone of the feeding stage is gradually increased from 50°C to 265°C. Then, in the spinning box at 290°C, the chips are compressed under high pressure in the compression section, vented, and gradually melted and extruded as filaments. The spinneret has an orifice diameter of 0.20 mm, a pressure of 45 MPa, and a spinning speed of 2500 m / min.

[0059] (3) The fibers extruded from the spinneret are cooled in a two-stage side-blowing device at different temperatures. The first-stage side-blowing device is 10 cm away from the spinneret, with a blowing temperature of 10℃, a relative humidity of 80%, and a wind speed of 0.3 m / s. The second-stage side-blowing device has a blowing temperature of 60℃, a relative humidity of 60%, and a wind speed of 0.4 m / s. The final fiber stretch ratio reaches 4.3 times, and a high-strength, high-modulus polyester fiber is finally prepared with a breaking strength of 8.6 cN / dtex, an elastic modulus of 112 cN / dtex, and a melting point of 266℃.

[0060] Example 6

[0061] (1) The PET slices obtained in Example 2 were transferred to a vacuum drum dryer for drying at a temperature of 120°C for 5 hours.

[0062] (2) The dried PET chips are added to the spinning barrel. The temperature in the preheating zone of the feeding stage is gradually increased from 50°C to 265°C. Then, in the spinning box at 290°C, the chips are compressed under high pressure in the compression section, vented, and gradually melted and extruded as filaments. The spinneret has an orifice diameter of 0.20 mm, a pressure of 45 MPa, and a spinning speed of 2500 m / min.

[0063] (3) The fibers extruded from the spinneret are cooled in a two-stage side-blowing device at different temperatures. The first-stage side-blowing device is 10 cm away from the spinneret, with a blowing temperature of 10℃, a relative humidity of 80%, and a wind speed of 0.3 m / s. The second-stage side-blowing device has a blowing temperature of 60℃, a relative humidity of 60%, and a wind speed of 0.4 m / s. The final fiber stretch ratio reaches 4.1 times, and a high-strength, high-modulus polyester fiber is finally prepared with a breaking strength of 7.4 cN / dtex, an elastic modulus of 97 cN / dtex, and a melting point of 264℃.

[0064] Example 7

[0065] (1) The PET slices obtained in Example 3 were transferred to a vacuum drum dryer for drying at a temperature of 120°C for 5 hours.

[0066] (2) The dried PET chips are added to the spinning barrel. The temperature in the preheating zone of the feeding stage is gradually increased from 50°C to 265°C. Then, in the spinning box at 290°C, the chips are compressed under high pressure in the compression section, vented, and gradually melted and extruded as filaments. The spinneret has an orifice diameter of 0.20 mm, a pressure of 45 MPa, and a spinning speed of 2500 m / min.

[0067] (3) The fibers extruded from the spinneret are cooled in a two-stage side-blowing device at different temperatures. The first-stage side-blowing device is 10 cm away from the spinneret, with a blowing temperature of 10℃, a relative humidity of 80%, and a wind speed of 0.3 m / s. The second-stage side-blowing device has a blowing temperature of 60℃, a relative humidity of 60%, and a wind speed of 0.4 m / s. The final fiber stretch ratio reaches 4.2 times, and a high-strength, high-modulus polyester fiber is finally prepared with a breaking strength of 7.9 cN / dtex, an elastic modulus of 106 cN / dtex, and a melting point of 265℃.

[0068] Example 8

[0069] (1) The PET slices obtained in Example 4 were transferred to a vacuum drum dryer for drying at a temperature of 120°C for 5 hours.

[0070] (2) The dried PET chips are added to the spinning barrel. The temperature in the preheating zone of the feeding stage is gradually increased from 50°C to 265°C. Then, in the spinning box at 290°C, the chips are compressed under high pressure in the compression section, vented, and gradually melted and extruded as filaments. The spinneret has an orifice diameter of 0.20 mm, a pressure of 45 MPa, and a spinning speed of 2500 m / min.

[0071] (3) The fibers extruded from the spinneret are cooled in a two-stage side-blowing device at different temperatures. The first-stage side-blowing device is 10 cm away from the spinneret, with a blowing temperature of 10℃, a relative humidity of 80%, and a wind speed of 0.3 m / s. The second-stage side-blowing device has a blowing temperature of 60℃, a relative humidity of 60%, and a wind speed of 0.4 m / s. The final fiber stretch ratio reaches 4.6 times, and a high-strength, high-modulus polyester fiber is finally prepared with a breaking strength of 9.2 cN / dtex, an elastic modulus of 129 cN / dtex, and a melting point of 270℃.

[0072] Comparative Example 1 (The difference from Example 1 is that only PTA is replaced with BBA monomer, while EG monomer remains unchanged)

[0073] (1) First, replace the air in the polymerization reactor with N2, then add PTA and PDO monomers (molar ratio of 1:1.2), Sb2O3 catalyst (0.04% of PTA mass) and triphenyl phosphite (0.02% of PTA mass) to the reactor after thorough mixing. The temperature in the reactor is controlled at 295℃ and the reaction is carried out at a pressure of 110kPa for 3.5h.

[0074] (2) After esterification, the temperature inside the reactor was adjusted to 260℃ and the pressure inside the reactor to 6 kPa for the first stage of polycondensation reaction, which lasted for 2.0 h. The temperature inside the reactor was then adjusted again to 275℃ and the pressure inside the reactor to 50 Pa for the second stage of polycondensation reaction, which lasted for 2.5 h. During the reaction, pure circulating nitrogen was used to remove the generated PDO and water from the system, and the PDO and water in the circulating nitrogen were removed by an adsorption tower containing sodium aluminate silicate hydroxide. Finally, a PET polymer with a relative molecular mass of 21370 was obtained, which was then used to prepare PET chips.

[0075] Comparative Example 2 (The difference from Example 5 is that PET slices prepared in Comparative Example 1 were used instead)

[0076] (1) The PET slices prepared in Comparative Example 1 were transferred to a vacuum drum dryer for drying. The drying temperature was 120°C and the drying time was 5 hours.

[0077] (2) The dried PET chips are added to the spinning barrel. The temperature in the preheating zone of the feeding stage is gradually increased from 50°C to 265°C. Then, in the spinning box at 290°C, the chips are compressed under high pressure in the compression section, vented, and gradually melted and extruded as filaments. The spinneret has an orifice diameter of 0.20 mm, a pressure of 45 MPa, and a spinning speed of 2500 m / min.

[0078] (3) The fibers extruded from the spinneret are cooled in a two-stage side-blowing device at different temperatures. The first-stage side-blowing device is 10 cm away from the spinneret, with a blowing temperature of 10℃, a relative humidity of 80%, and a wind speed of 0.3 m / s. The second-stage side-blowing device has a blowing temperature of 60℃, a relative humidity of 60%, and a wind speed of 0.4 m / s. The final fiber stretch ratio reaches 3.9 times, and a high-strength, high-modulus polyester fiber is finally prepared with a breaking strength of 5.6 cN / dtex, an elastic modulus of 92 cN / dtex, and a melting point of 261℃.

[0079] Comparative Example 3 (The difference from Example 5 is that the spinning pressure is too low)

[0080] (1) The PET slices prepared in Comparative Example 1 were transferred to a vacuum drum dryer for drying. The drying temperature was 120°C and the drying time was 5 hours.

[0081] (2) The dried PET chips are added to the spinning barrel. The temperature in the preheating zone of the feeding stage is gradually increased from 50°C to 265°C. Then, in the spinning box at 290°C, the chips are compressed under high pressure in the compression section, vented, and gradually melted and filamented. The spinneret has an orifice diameter of 0.20 mm, a pressure of 35 MPa, and a spinning speed of 2500 m / min.

[0082] (3) The fibers extruded from the spinneret are cooled in a two-stage side-blowing device at different temperatures. The first-stage side-blowing device is 10 cm away from the spinneret, with a blowing temperature of 10℃, a relative humidity of 80%, and a wind speed of 0.3 m / s. The second-stage side-blowing device has a blowing temperature of 60℃, a relative humidity of 60%, and a wind speed of 0.4 m / s. The final fiber stretch ratio reaches 4.1 times, and a high-strength, high-modulus polyester fiber is finally prepared with a breaking strength of 6.8 cN / dtex, an elastic modulus of 97 cN / dtex, and a melting point of 263℃.

[0083] Comparative Example 4 (the difference from Example 5 is that only the first stage of side blowing is performed)

[0084] (1) The PET slices obtained in Example 1 were transferred to a vacuum drum dryer for drying at a temperature of 120°C for 5 hours.

[0085] (2) The dried PET chips are added to the spinning barrel. The temperature in the preheating zone of the feeding stage is gradually increased from 50°C to 265°C. Then, in the spinning box at 290°C, the chips are compressed under high pressure in the compression section, vented, and gradually melted and extruded as filaments. The spinneret has an orifice diameter of 0.20 mm, a pressure of 45 MPa, and a spinning speed of 2500 m / min.

[0086] (3) The fibers extruded from the spinneret enter a single-stage side-blowing device for cooling. The distance between the side-blowing device and the spinneret is 10 cm, the blowing temperature is 10℃, the relative humidity is 80%, and the wind speed is 0.3 m / s. The final fiber stretch ratio reaches 4.2 times, and a high-strength, high-modulus polyester fiber is finally prepared with a breaking strength of 8.3 cN / dtex, an elastic modulus of 105 cN / dtex, and a melting point of 264℃.

[0087] Table 1. Relative molecular masses of the PET polymers obtained in Examples 1-4 and Comparative Example 1

[0088] Example 1 Example 2 Example 3 Example 4 Comparative Example 1 relative molecular mass 25650 23240 24073 28762 21370

[0089] Table 2 shows the mechanical properties and melting points of the PET fibers obtained in Examples 5-8 and Comparative Examples 2-4.

[0090]

[0091]

[0092] As shown in Table 1, in Comparative Example 1, only PTA was replaced with BBA monomer while EG monomer remained unchanged. The relative molecular mass of the polymer prepared using BBA and EG monomers was significantly lower than that in Example 1. Furthermore, the high rigidity of the macromolecular chain and insufficient flexibility made it unfavorable for spinning. In Comparative Example 2, PET chips from Comparative Example 1 were used for spinning, resulting in poor spinning performance. The tensile strength, elastic modulus, and melting point of the PET fibers prepared were all reduced.

[0093] As shown in Table 2, compared with the traditional method of preparing PET melt using PTA and EG monomers through esterification and polycondensation, the PET melt prepared using BBA and PDO monomers has a higher relative molecular weight. This is because the new monomers have a larger molecular weight and lower reactivity than PTA and EG, respectively, making it easier to obtain higher molecular weight PET macromolecules. When spinning PET melt prepared using BBA and PDO monomers, it is easier to obtain high-strength, high-modulus, and high-melting-point polyester fibers. This is mainly because the high molecular weight PET melt has higher viscosity, allowing the fibers to withstand higher tensile strengths. Furthermore, the PET macromolecules prepared by this method have a higher proportion of rigid structures, which is beneficial for the crystallization of macromolecules within the fiber, resulting in higher heat resistance.

[0094] Furthermore, because the PET melt prepared using BBA and PDO monomers in this invention has a higher relative molecular weight and viscosity, pressure is required during melt spinning. Controlling the pressure and temperature within a suitable range during spinning is crucial for better subsequent spinning results. In Comparative Example 3, the pressure setting during pressurized melt spinning was too low, resulting in lower breaking strength and elastic modulus of the obtained PET fibers compared to Example 5. Moreover, after obtaining the fibers through pressurized melt spinning, a two-stage side-blowing device is needed for cooling. This device is more suitable for the internal structure of the PET polymer in this invention. Entering regions with different temperature gradients, the macromolecular chains relax due to the temperature effect, not only maintaining the extended chain structure of the macromolecules, which is beneficial for stretching at higher post-stretch ratios, but also increasing the crystallinity and orientation of the fibers, thus improving the mechanical properties of the PET fibers and enhancing the breaking strength, elastic modulus, and melting point of the final PET fibers. Therefore, Comparative Example 4, which only uses a first-stage side-blowing device, resulted in lower breaking strength, elastic modulus, and melting point of the PET fibers compared to Example 5.

[0095] The above are merely preferred embodiments of the present invention and do not limit the patent scope of the present invention. Any equivalent structural or procedural transformations made using the present invention specification, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A process for the production of high-strength high-modulus polyester fiber, characterized by, The method comprises the following steps: (1) mixing 4,4'-diphenyl dicarboxylic acid, 1,3-propanediol, a catalyst and a thermal stabilizer to perform esterification; (2) after the esterification is completed, performing first-stage polycondensation and second-stage polycondensation in the same reactor to remove small molecules and water, and obtaining a polymer; (3) performing melt spinning on the polymer, wherein the temperature of melt spinning is 265-290 ℃, and the pressure is 40-60 MPa; then sequentially performing first-stage side blowing, second-stage side blowing and post-drawing, wherein the blowing temperature of the first-stage side blowing is 8-15 ℃, and the blowing temperature of the second-stage side blowing is 50-70 ℃, and obtaining a polyester fiber.

2. The method of producing high-strength high-modulus polyester fiber according to claim 1, characterized by, The molar ratio of the 4,4'-diphenyl dicarboxylic acid to the 1,3-propanediol is 1:1.1-1.

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3. The method of producing high-strength high-modulus polyester fiber according to claim 1, characterized by, The amount of the catalyst is 0.04-0.1% of the mass of the 4,4'-diphenyl dicarboxylic acid; and the amount of the thermal stabilizer is 0.02-0.1% of the mass of the 4,4'-diphenyl dicarboxylic acid.

4. The process for producing high-strength and high-modulus polyester fiber according to any one of claims 1 to 3, characterized in that, The temperature of the esterification is 280-310 ℃, the pressure is 100-120 kPa, and the reaction time is 2-4 h.

5. The method of producing high-strength high-modulus polyester fiber according to claim 1, characterized by, The temperature of the first-stage polycondensation is 260-270 ℃, the pressure is 5-7 kPa, and the polycondensation time is 2-3 h.

6. The process for producing high-strength and high-modulus polyester fiber according to claim 1 or 5, characterized by, The temperature of the second-stage polycondensation is 270-290 ℃, the pressure is 50-90 Pa, and the polycondensation time is 2-3 h.

7. The method of producing high-strength high-modulus polyester fiber according to claim 1, characterized by, The spinning speed of the melt spinning is 2500-2800 m / min.

8. The method of producing high-strength high-modulus polyester fiber according to claim 1, characterized by, The relative humidity of the first-stage side blowing is 70-90%, and the wind speed is 0.2-0.4 m / s.

9. The process for producing high-strength and high-modulus polyester fiber according to claim 1 or 7 or 8, characterized by, The relative humidity of the second-stage side blowing is 50-60%, and the wind speed is 0.3-0.6 m / s.

10. A high-strength and high-modulus polyester fiber prepared by the method according to any one of claims 1-9.

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