Low-denier high-modulus low-shrinkage polyester industrial yarn as well as manufacturing method and application thereof

Abstract

The invention belongs to the technical field of polyester industrial yarn manufacturing, and particularly relates to a low-denier high-modulus low-shrinkage polyester industrial yarn and a manufacturing method and application thereof. Comprising the following steps: tackifying polyester chips; melting and extruding; stretching and shaping; and coiling to obtain the low-denier high-modulus low-shrinkage polyester industrial yarn. The low-fineness polyester industrial yarn is obtained by adopting a spinneret plate with a special number of holes and a special process, and the performance indexes meet the requirements of the high-modulus low-shrinkage polyester industrial yarn.

Description

Technical Field

[0001] The invention belongs to the technical field of polyester industrial yarn manufacturing, and specifically relates to a low-denier high-modulus low-shrinkage polyester industrial yarn and a manufacturing method and application thereof. Background Art

[0002] The unit of the size of polyester industrial yarn is denier (D). The larger the denier, the thicker the yarn, and the smaller the denier, the thinner the yarn. At present, the conventional high modulus and low shrinkage polyester industrial yarn in the market has a denier range of 800D or more, and there is a lack of development of polyester industrial yarn below 800D. For example, in Chinese patent application 201110178723.7 (production method of high dimensional stability, high modulus and low shrinkage polyester industrial yarn), polyester industrial yarn with a denier of 1100 to 3340 dtex is prepared.

[0003] If polyester industrial yarn below 800D is produced, the difficulty of industrial production will increase significantly; low fineness leads to low strength; insufficient spinnability; and problems of broken yarn and hairy yarn are prone to occur during the production process. Summary of the invention

[0004] In view of the deficiencies in the prior art, the present invention aims to provide a low-denier high-modulus low-shrinkage polyester industrial yarn and a manufacturing method and application thereof.

[0005] In order to solve the above technical problems, the technical solution adopted by the present invention is: a method for manufacturing low-denier high-modulus low-shrinkage polyester industrial yarn, comprising the following steps:

[0006] (1) Polyester chip viscosity enhancement: low viscosity polyester chips are crystallized and then enter the solid phase polymerization reactor for viscosity enhancement; the solid phase polymerization reactor adopts a two-stage reactor, namely the first reactor and the second reactor, and the reaction time is 50-60h; the viscosity of the low viscosity PET chips is 0.655-0.685dl / g, the temperature of the solid phase polymerization reactor is 195-225°C, and the viscosity of the polyester chips after viscosity enhancement is 1.10-1.15;

[0007] (2) melt extrusion: the tackified polyester chips obtained in step (1) are put into a screw extruder for heating and melt extrusion;

[0008] Then the melt reaches the spinning assembly, and the spinneret in the spinning assembly extrude the melt into primary fibers. The spinneret holes of the spinneret have a large aspect ratio, with a length of 1.0-1.2 mm, a diameter of 0.5-0.6 mm, an aspect ratio of more than 2.0, and 120-200 holes. The primary fibers are cooled slowly by 3-6 layers of gradient cooling and then cooled by blowing air.

[0009] (3) Stretching and shaping: the surface of the cooled spun fiber obtained in step (2) is oiled; then the fiber is stretched and shaped by passing through a first hot roller, a second hot roller, a third hot roller, a fourth hot roller, a fifth hot roller, and a sixth hot roller in sequence; the speed of the first hot roller is 2800-3400 m / min, the speed of the second hot roller is 3900-4400 m / min, the speeds of the third, fourth, and fifth hot rollers are the same, 5500-6200 m / min, and the speed of the sixth hot roller is 5500-6000 m / min; the temperature of the first hot roller is 80-100° C., the temperature of the second hot roller is 80-100° C., the temperature of the third, fourth, and fifth hot rollers is 240-260° C., and the temperature of the sixth hot roller is 90-140° C.;

[0010] (4) Winding: The polyester filaments after stretching and shaping in step (3) are wound into a yarn cake at a winding speed of 5500-6000 m / min to obtain low-denier high-modulus low-shrinkage polyester industrial yarn.

[0011] The reason why the viscosity of polyester chips after thickening is 1.10-1.15 is that too high viscosity of polyester chips reduces spinnability, while too low viscosity of polyester chips after spinning has insufficient mechanical properties. The thickening of polyester chips is carried out under nitrogen protection.

[0012] The spinneret holes are designed with a large aspect ratio, with a length of 1.0-1.2mm, a diameter of 0.5-0.6mm, and an aspect ratio of more than 2.0. The high aspect ratio can reduce the breakage rate and improve the uniformity of the fiber when producing low-denier high-modulus low-shrinkage polyester industrial yarns, and it has a synergistic effect with a longer solid phase polymerization time and multi-stage gradient slow cooling.

[0013] In a preferred embodiment, in step (1), the crystallization temperature is 160-190° C., and a fluidized bed crystallizer is used for crystallization.

[0014] Furthermore, in step (1), the temperature of the first reactor is 205-225°C, and the temperature of the second reactor is 0-5°C lower than that of the first reactor; the reaction time in the first reactor is 30-35h, and the reaction time in the second reactor is 20-25h. The first reactor and the second reactor are independent of each other and are connected by a pipeline, and the polyester chips are transported from the first reactor to the second reactor through the pipeline. The reaction time of the first reactor is longer than that of the second reactor, and the reaction temperature of the second reactor is slightly lower than that of the first reactor, which is convenient for controlling the viscosity. The reaction temperature of the second reactor is appropriately reduced, the molecular chain growth rate and the viscosity increase rate are reduced, and the final viscosity is better controlled. If the total reaction time is short, the viscosity is low and uneven, and the stretching effect is poor at the same stretching ratio, resulting in low strength.

[0015] In a preferred embodiment, in step (2), the temperature of the screw extruder is 285-330°C, and the extrusion pressure is 10-15 MPa; the melt reaches the metering pump through the melt delivery pipe, and the extrusion rate of the melt is controlled by the metering pump, and the extrusion rate of the melt is 200-420 g / min. In the prior art, the extrusion rate of 1000D-3000D wire is 600-1800 g / min, and the melt extrusion rate in the present invention is significantly less.

[0016] Furthermore, in step (2), the heating temperature of the 3-6 layers of gradient slow cooling is 300-350°C and the temperature decreases gradually.

[0017] In step (2), after 3-6 layers of gradient slow cooling (extending the slow cooling time, constructing the slow cooling temperature gradient, increasing the elongation at break of the polyester precursor, and reducing the breakage rate), it passes through an insulation cylinder with a height of 40-60 mm, and then is cooled by an annular blowing air with an annular blowing air temperature of 40-80° C. In the prior art, the slow cooling device has 1-2 layers, and the heating temperature of each layer is the same.

[0018] The starting temperature of the slow cooling device can be higher than the extrusion temperature. This is because the fiber is not in direct contact with the post-heater, but only passes through the middle of the post-heater. The post-heater heats the surrounding air, and the air temperature cannot reach the heating temperature of the post-heater. The temperature of the slow cooling device controls the degree of fiber orientation crystallization. A multi-layer slow cooling device can better control the degree of fiber orientation crystallization.

[0019] In a preferred embodiment, in step (3), the stretching ratio is the speed ratio of the third hot roller to the first hot roller, and the stretching ratio is 1.8-2.0.

[0020] The present invention can adopt a single-position 6-head machine model during stretching and forming, and use 6 pairs of hot rollers to produce low-denier high-modulus low-shrinkage polyester industrial yarns. Compared with the production method using 3-5 pairs of hot rollers, the fixed load elongation and dry heat shrinkage rate can be optimized. The temperature of the sixth pair of hot rollers is relatively low, which is conducive to the cooling of the yarn bundle to achieve balance. If the sixth pair of hot rollers use a higher temperature, there is no gain in the mechanical properties of the polyester industrial yarn, and the higher temperature is likely to cause the high-temperature tripping of the winding machine equipment.

[0021] Another object of the present invention is to provide low-denier high-modulus low-shrinkage polyester industrial yarn produced by the aforementioned manufacturing method.

[0022] In a preferred embodiment, the low-denier high-modulus low-shrinkage polyester industrial yarn has a fineness of 400D-600D.

[0023] The low-denier high-modulus low-shrinkage polyester industrial yarn has a strength of ≥7.2 cN / dtex and a dimensional stability of ≤7.9%.

[0024] The last object of the present invention is to disclose the use of the aforementioned low-denier high-modulus low-shrinkage polyester industrial yarn in the preparation of cords. The use of low-denier high-modulus low-shrinkage polyester industrial yarn to prepare cords can reduce the weight of corresponding products containing cords (such as tires, conveyor belts, transmission belts, etc.).

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] By using a special number of holes spinneret and a special process, low-denier polyester industrial yarn is obtained, and the performance indicators meet the requirements of high-modulus and low-shrinkage polyester industrial yarn.

[0027] The requirements for the uniformity of slice viscosity of low-denier high-modulus low-shrinkage polyester industrial yarn are higher than those of high-denier high-modulus low-shrinkage polyester industrial yarn. In the solid phase polymerization viscosity enhancement, the present invention adopts a secondary reactor. The use of the secondary reactor can prolong the reaction time to improve the uniformity of slice viscosity. When the low-denier polyester industrial yarn is subsequently formed, it is not easy to have fuzz or breakage, and the stability of mechanical properties can be maintained, and the yield of the viscosity-enhanced polyester slice is significantly improved. If the reaction time is extended only in the primary reactor, the polyester slice will advance slowly, by-products cannot be removed in time, the production efficiency is low, the slice quality is reduced, and agglomeration occurs.

[0028] Compared with high-strength low-shrinkage polyester industrial yarn with high denier, low-denier high-modulus low-shrinkage polyester industrial yarn with low denier is more likely to break and become fuzzy during air-cooling, and has a lower elongation at break. In the present invention, the spun fiber is subjected to 3-6 layers of gradient slow cooling, and the gradient slow cooling device is composed of 3-6 layers of post-heaters, which are arranged in sequence from top to bottom, and each layer of post-heaters is 30-50mm high, and the temperature is 300-350℃ and gradually decreases, which can effectively improve the elongation at break of the polyester raw yarn and reduce the breakage rate.

[0029] Compared with high-denier high-strength low-shrinkage polyester industrial yarns, low-denier high-modulus low-shrinkage polyester industrial yarns have higher requirements for stretching and forming during air-cooling. The present invention adopts six pairs of hot rollers, and adopts a higher stretching ratio (the reason why a higher stretching ratio can be adopted is that a secondary reactor is adopted and the reaction time is extended during solid-phase polymerization and the primary fiber is subjected to 3-6 levels of gradient slow cooling) in the preparation process of low-denier (i.e. low-denier) high-strength low-shrinkage polyester industrial yarns through a higher hot roller speed and a suitable temperature, so as to improve the mechanical properties of low-denier (i.e. low-denier) high-strength low-shrinkage polyester industrial yarns.

[0030] During solid-phase polymerization, the reaction time is prolonged and a polymerization temperature gradient is constructed, and then combined with 3-6 layers of gradient slow cooling, the elongation at break of the final fiber filaments is further improved, while the breakage and hairy fiber rates are significantly reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1It is a structural diagram of a first reactor and a second reactor for solid phase polymerization reaction;

[0032] Figure 2 A diagram of a device for making the melt become primary fibers after passing through a spinneret;

[0033] In the figure: 1 first reactor; 2 second reactor; 3 feed rotary valve; 4 feed fan; 5 metering pump; 6 spinning assembly; 7 spinneret; 8 first layer post heater; 9 second layer post heater; 10 third layer post heater; 11 insulation cylinder; 12 annular air cooling device; 13 melt direction; 14 nascent fiber. DETAILED DESCRIPTION

[0034] The technical solution of the present invention is further described in detail below in conjunction with specific embodiments and drawings. It should be understood that the following embodiments are only used to explain the present invention and are not used to limit the present invention.

[0035] The structure diagram of the first reactor and the second reactor used for solid phase polymerization is as follows Figure 1 As shown, it is composed of a first reactor 1, a second reactor 2, a feed rotary valve 3, and a feed fan 4. The polyester chips after solid phase polymerization in the first reactor leave the first reactor through the feed rotary valve, and the feed fan pushes the polyester chips in the pipeline into the second reactor. The first reactor, the second reactor, the feed rotary valve, and the feed fan are all connected by pipelines.

[0036] According to the melt direction 13, the melt passes through the spinneret to become the primary fiber 14. Figure 2 As shown, it is composed of a metering pump 5, a spinning assembly 6 (the spinneret 7 is located at the end of the spinning assembly), a first-layer post-heater 8, a second-layer post-heater 9, a third-layer post-heater 10, an insulating cylinder 11, and an annular air cooling device 12. If the number of layers of post-heaters is 6, the fourth-layer post-heater, the fifth-layer post-heater, and the sixth-layer post-heater are arranged in sequence between the third-layer post-heater and the insulating cylinder; if the number of layers of post-heaters is 4 or 5, the same applies.

[0037] Example 1

[0038] A method for producing a low-denier high-modulus low-shrinkage polyester industrial yarn with a fineness of 400D is as follows:

[0039] (1) Thickening of polyester chips: Polyester (PET) chips with a viscosity of 0.675 dl / g are crystallized to remove moisture from the chips, so that the surface layer of the polyester chips is crystallized at a crystallization temperature of 170°C; then the chips are put into a solid phase polymerization reactor for thickening. The temperature of the first reactor is 210°C, the reaction time is 35 hours, the temperature of the second reactor is 206°C, the reaction time is 25 hours, and the total reaction time is 60 hours. After thickening, high-viscosity polyester chips with a viscosity of 1.126 dl / g are obtained.

[0040] (2) Melt extrusion of thickened polyester chips: The high-viscosity polyester chips obtained in step (1) are transported to the spinning silo using nitrogen, and then enter the screw extruder for heating and melting. The temperature of the screw extruder is 295°C and the extrusion pressure is 10MPa. The melt reaches the metering pump through the melt delivery pipe, and the metering pump discharges 220g / min. Finally, the melt reaches the spinning assembly, and the spinneret in the spinning assembly extrude the melt into nascent fibers. The number of spinneret holes is 150, and the spinneret is a disc-type structure with a diameter of 190mm. Six layers of post-heaters are arranged below the spinning assembly, each layer of post-heaters is 50mm high, the temperature of the first layer of post-heaters is 330°C, the temperature of the second layer of post-heaters is 325°C, the temperature of the third layer of post-heaters is 320°C, the temperature of the fourth layer of post-heaters is 315°C, the temperature of the fifth layer of post-heaters is 310°C, and the temperature of the sixth layer of post-heaters is 305°C. An insulation cylinder is arranged below the gradient slow cooling device, and the insulation cylinder height is 60mm. A ring-blowing cooling device is provided below the heat-insulating cylinder, and the ring-blowing temperature is 60° C. The spinneret hole has a length of 1.2 mm and a diameter of 0.5 mm.

[0041] (3) Stretching and shaping: The spun fibers obtained in step (2) pass through the spinning tunnel to the oiling device, which applies oil to the surface of the spun fibers. The oiling agent model is Takemoto F-7823, and the oiling amount is 0.4% (referring to the mass ratio of the oiling amount to the spun fibers). After the fibers are oiled, they pass through the first hot roller, the second hot roller, the third hot roller, the fourth hot roller, the fifth hot roller, and the sixth hot roller. The speed of the first hot roller is 2900m / min, the speed of the second hot roller is 4040m / min, the speed of the third, fourth, and fifth hot rollers is 5773m / min, and the speed of the sixth hot roller is 5600m / min. The temperature of the first hot roller is 85°C, the temperature of the second hot roller is 90°C, the temperature of the third, fourth, and fifth hot rollers is 250°C, and the temperature of the sixth hot roller is 110°C. The stretching ratio is 1.8.

[0042] (4) Finally, the yarn is wound into a yarn cake by a winding machine at a winding speed of 5600 m / min. Finally, a low-denier high-modulus low-shrinkage polyester industrial yarn with a fineness of 400D and a number of holes of 150f is obtained.

[0043] Example 2

[0044] A method for manufacturing a low-denier, high-modulus, low-shrinkage polyester industrial yarn with a fineness of 500D is as follows:

[0045] (1) Thickening of polyester chips: Polyester chips with a viscosity of 0.681 dl / g are crystallized to remove moisture from the chips, so that the surface of the polyester chips is crystallized at a crystallization temperature of 180°C; then the chips are put into a solid phase polymerization reactor for thickening. The temperature of the first reactor is 215°C, the reaction time is 33 hours, the temperature of the second reactor is 212°C, the reaction time is 22 hours, and the total reaction time is 55 hours. After thickening, high-viscosity polyester chips with a viscosity of 1.135 dl / g are obtained.

[0046] (2) Melt extrusion of the thickened polyester chips: The high-viscosity polyester chips obtained in step (1) are transported to the spinning silo using nitrogen, and then enter the screw extruder for heating and melting. The temperature of the screw extruder is 300°C and the extrusion pressure is 13MPa. The melt reaches the metering pump through the melt delivery pipe, and the metering pump extrusion volume is 330g / min. Finally, the melt reaches the spinning assembly, and the spinneret in the assembly extrude the melt into nascent fibers. The spinneret specification is 180f, and the spinneret is a disc-type structure with a diameter of 190mm. Four layers of post-heaters are arranged below the spinning assembly, each layer of post-heaters is 40mm high, the temperature of the first layer of post-heaters is 330°C, the temperature of the second layer of post-heaters is 325°C, the temperature of the third layer of post-heaters is 320°C, and the temperature of the fourth layer of post-heaters is 315°C. An insulation cylinder is arranged below the gradient slow cooling device, and the insulation cylinder height is 50mm. A ring-blowing cooling device is arranged below the insulation cylinder, and the ring-blowing temperature is 70°C. The spinneret hole has a length of 1.1 mm and a diameter of 0.5 mm.

[0047] (3) Stretching and shaping: The spun fibers obtained in step (2) pass through the spinning tunnel to the oiling device, which applies oil to the surface of the spun fibers. The oiling agent model is Takemoto F-7823, and the oiling amount is 0.5%. After oiling, the fibers pass through the first hot roller, the second hot roller, the third hot roller, the fourth hot roller, the fifth hot roller, and the sixth hot roller. The speed of the first hot roller is 3320 m / min, the speed of the second hot roller is 4260 m / min, the speed of the third, fourth, and fifth hot rollers is 6082 m / min, and the sixth hot roller is 5900 m / min. The temperature of the first hot roller is 80°C, the temperature of the second hot roller is 85°C, the temperature of the third, fourth, and fifth hot rollers is 254°C, and the temperature of the sixth hot roller is 120°C. The stretching ratio is 1.9.

[0048] (4) Finally, the yarn is wound into a yarn cake by a winding machine at a winding speed of 5900 m / min. Finally, a low-denier high-modulus low-shrinkage polyester industrial yarn with a fineness of 500D and a number of holes of 180f is obtained.

[0049] Example 3

[0050] A method for manufacturing a low-denier, high-modulus, low-shrinkage polyester industrial yarn with a fineness of 600D is as follows:

[0051] (1) Thickening of polyester chips: Polyester chips with a viscosity of 0.663 dl / g are crystallized to remove moisture from the chips, so that the surface layer of the polyester chips is crystallized at a crystallization temperature of 185°C. The chips are then put into a solid phase polymerization reactor for thickening. The temperature of the first reactor is 220°C, the reaction time is 30 hours, the temperature of the second reactor is 218°C, the reaction time is 20 hours, and the total reaction time is 50 hours. After thickening, high-viscosity polyester chips with a viscosity of 1.146 dl / g are obtained.

[0052] (2) Melt extrusion of the thickened polyester chips: The high-viscosity polyester chips obtained in step (1) are transported to the spinning silo using nitrogen, and then enter the screw extruder for heating and melting. The temperature of the screw extruder is 310°C and the extrusion pressure is 14MPa. The melt reaches the metering pump through the melt delivery pipe, and the extrusion amount of the metering pump is 390g / min. Finally, the melt reaches the spinning assembly, and the spinneret in the assembly extrude the melt into nascent fibers. The number of spinneret holes is 200, and the spinneret is a disc-type structure with a diameter of 190mm. Three layers of post-heaters are arranged below the spinning assembly, each layer of post-heaters is 40mm high, the temperature of the first layer of post-heaters is 330°C, the temperature of the second layer of post-heaters is 320°C, and the temperature of the third layer of post-heaters is 310°C. An insulation cylinder is arranged below the gradient slow cooling device, and the insulation cylinder is 30mm high. A ring-blowing cooling device is arranged below the insulation cylinder, and the ring-blowing temperature is 65°C. The length of the spinneret hole is 1.2mm and the diameter is 0.5mm.

[0053] (3) Stretching and shaping: The spun fibers obtained in step (2) pass through the spinning tunnel to the oiling device, which applies oil to the surface of the spun fibers. The oiling agent model is Takemoto F-7823, and the oiling amount is 0.45%. After oiling, the fibers pass through the first hot roller, the second hot roller, the third hot roller, the fourth hot roller, the fifth hot roller, and the sixth hot roller. The speed of the first hot roller is 3060 m / min, the speed of the second hot roller is 4100 m / min, the speed of the third, fourth, and fifth hot rollers is 5880 m / min, and the speed of the sixth hot roller is 5700 m / min. The temperature of the first hot roller is 95°C, the temperature of the second hot roller is 95°C, the temperature of the third, fourth, and fifth hot rollers is 258°C, and the temperature of the sixth hot roller is 125°C. The stretching ratio is 2.0.

[0054] (4) Finally, the yarn is wound into a yarn cake by a winding machine at a winding speed of 5700 m / min. Finally, a low-denier high-modulus low-shrinkage polyester industrial yarn with a fineness of 600D and a number of holes of 200f is obtained.

[0055] Table 1 shows the physical properties of the polyester industrial yarn products obtained in Example 1, Example 2, and Example 3 (test standard: GB_T 16604-2017 polyester industrial filament).

[0056]

[0057] Comparative Example 1

[0058] The solid phase polymerization reactor is only one stage and the reaction time is 40 hours. The reactor temperature is 210° C., and the rest is the same as in Example 1.

[0059] Comparative Example 2

[0060] Two layers of afterheaters are used for slow cooling, each layer of afterheaters is 50 mm high, the temperature of the first layer of afterheaters is 330° C., and the temperature of the second layer of afterheaters is 325° C. The rest is the same as in Example 1.

[0061] Comparative Example 3

[0062] The stretching is performed through the first hot roller, the second hot roller, the third hot roller, the fourth hot roller, and the fifth hot roller. The speed of the first hot roller is 2900 m / min, the speed of the second hot roller is 4040 m / min, the speed of the third and fourth hot rollers is 5773 m / min, and the fifth hot roller is 5600 m / min. The temperature of the first hot roller is 85°C, the temperature of the second hot roller is 90°C, the temperature of the third and fourth hot rollers is 250°C, and the temperature of the fifth hot roller is 110°C. The rest is the same as in Example 1.

[0063] Comparative Example 4

[0064] Two layers of post-heaters were used for slow cooling, each layer of post-heaters was 50 mm high, the temperature of the first layer of post-heaters was 330° C., and the temperature of the second layer of post-heaters was 325° C. The solid phase polymerization reactor was only one stage, the reaction time was 40 h, and the reactor temperature was 210° C. The rest was the same as in Example 1.

[0065] Comparative Example 5

[0066] The spinneret hole has a length of 1.0 mm and a diameter of 0.6 mm, and the rest is the same as in Example 1.

[0067] Comparative Example 6

[0068] The length of the spinneret hole is 1.0 mm and the diameter is 0.6 mm; the solid phase polymerization reactor is only one stage and the reaction time is 40 h, and the reactor temperature is 210°C; two layers of afterheaters are used for slow cooling, each layer of afterheaters is 50 mm high, the temperature of the first layer of afterheaters is 330°C, and the temperature of the second layer of afterheaters is 325°C, and the rest is the same as Example 1.

[0069] Table 2 shows the physical properties of the polyester industrial yarn products obtained in Examples 1-6.

[0070]

[0071] As shown in Table 2, the number of hot rollers mainly affects the dry heat shrinkage and dimensional stability of the fiber. The polymerization viscosity enhancement and slow cooling conditions have a significant effect on the fiber's breaking strength and dimensional stability. The aspect ratio of the spinneret has a certain effect on the fiber's breaking strength.

[0072] Table 3 shows the indicators of hairiness and number of breaks of Examples 1-3 and Comparative Examples 1-6.

[0073] Implementation Cases Number of hair strands on the end of a single silk cake Number of ends broken per spinning position per day Example 1 8 5 Example 2 11 8 Example 3 9 7 Comparative Example 1 17 11 Comparative Example 2 14 10 Comparative Example 3 9 5 Comparative Example 4 28 19 Comparative Example 5 10 9 Comparative Example 6 32 25

[0074] As shown in Table 3, the number of hot rollers has little effect on the number of filaments at the end of a single fiber cake and the number of fiber breakages per day at a single spinning position. However, the polymerization viscosity enhancement and slow cooling conditions, which work together, have a significant effect on the number of filaments at the end of a single fiber cake and the number of fiber breakages per day at a single spinning position. The aspect ratio of the spinneret has a significant effect on the number of filaments at the end of a single fiber cake and the number of fiber breakages per day at a single spinning position.

[0075] It should be understood that the above embodiments do not limit the present invention in any form, and any technical solutions obtained by equivalent replacement or equivalent transformation shall fall within the protection scope of the present invention.

Claims

1. A method for producing low-denier high-modulus low-shrinkage polyester industrial yarn, characterized in that: The following steps are involved: (1) Polyester chip viscosity enhancement: low viscosity polyester chips are crystallized and then enter the solid phase polymerization reactor for viscosity enhancement; the solid phase polymerization reactor adopts a two-stage reactor, namely the first reactor and the second reactor, and the reaction time is 50-60h; the viscosity of low viscosity PET chips is 0.655-0.685dl / g, the temperature of the solid phase polymerization reactor is 195-225℃, and the viscosity of the polyester chips after viscosity enhancement is 1.10-1.15; (2) Melt extrusion: the tackified polyester chips obtained in step (1) are heated and melt extruded in a screw extruder; the melt then reaches a spinning assembly, and a spinneret in the spinning assembly extrudes the melt into nascent fibers, the spinneret holes of the spinneret having a large aspect ratio, the spinneret holes having a length of 1.0-1.2 mm, a diameter of 0.5-0.6 mm, an aspect ratio of more than 2.0, and a hole number of 120-200 holes; the nascent fibers are subjected to 3-6 layers of gradient slow cooling, and then cooled by annular blowing; (3) Stretching and shaping: The surface of the cooled spun fiber obtained in step (2) is oiled; then the fiber is stretched and shaped by passing through a first hot roller, a second hot roller, a third hot roller, a fourth hot roller, a fifth hot roller, and a sixth hot roller in sequence; the speed of the first hot roller is 2800-3400 m / min, the speed of the second hot roller is 3900-4400 m / min, the speeds of the third, fourth, and fifth hot rollers are the same, 5500-6200 m / min, and the speed of the sixth hot roller is 5500-6000 m / min; the temperature of the first hot roller is 80-100°C, the temperature of the second hot roller is 80-100°C, the temperature of the third, fourth, and fifth hot rollers is 240-260°C, and the temperature of the sixth hot roller is 90-140°C; (5) Winding: The polyester filaments stretched and shaped in step (3) are wound into yarn cakes at a winding speed of 5500-6000 m / min to obtain low-denier high-modulus low-shrinkage polyester industrial yarns.

2. The method for producing a low-denier high-modulus low-shrinkage polyester industrial yarn according to claim 1, characterized in that: In step (1), the crystallization temperature is 160-190°C.

3. The method for producing a low-denier high-modulus low-shrinkage polyester industrial yarn according to claim 1, characterized in that: In step (1), the temperature of the first reactor is 215-225°C, and the temperature of the second reactor is 0-5°C lower than that of the first reactor; the reaction time in the first reactor is 30-35h, and the reaction time in the second reactor is 20-25h.

4. The method for producing a low-denier high-modulus low-shrinkage polyester industrial yarn according to claim 1, characterized in that: In step (2), the temperature of the screw extruder is 285-330° C., and the extrusion pressure is 10-15 MPa; the melt reaches the metering pump through the melt delivery pipe, and the metering pump controls the extrusion rate of the melt, and the extrusion rate of the melt is 200-420 g / min.

5. The method for producing a low-denier high-modulus low-shrinkage polyester industrial yarn according to claim 1, characterized in that: In step (2), the heating temperature of the 3-6 layers of gradient slow cooling is 300-350°C and the temperature gradually decreases; the gradient slow cooling device is composed of 3-6 layers of post-heaters, and the 3-6 layers of post-heaters are arranged in sequence from top to bottom, and the height of each layer of post-heaters is 30-50 mm.

6. The method for producing a low-denier high-modulus low-shrinkage polyester industrial yarn according to claim 1, characterized in that: In step (2), after 3-6 layers of gradient slow cooling, it passes through an insulation cylinder with a height of 40-60 mm, and then is cooled by ring blowing, with the temperature of the ring blowing being 40-80°C.

7. The method for producing a low-denier high-modulus low-shrinkage polyester industrial yarn according to claim 1, characterized in that: In step (3), the stretching ratio is the speed ratio of the third hot roller to the first hot roller, and the stretching ratio is 1.8-2.

0.

8. Low-denier high-modulus low-shrinkage polyester industrial yarn obtained by the manufacturing method according to any one of claims 1 to 7.

9. The low-denier high-modulus low-shrinkage polyester industrial yarn according to claim 8, characterized in that: The low-denier high-modulus low-shrinkage polyester industrial yarn has a fineness of 400D-600D.

10. The low-denier high-modulus low-shrinkage polyester industrial yarn according to claim 8, characterized in that: The low-denier high-modulus low-shrinkage polyester industrial yarn has a strength of ≥7.2 cN / dtex and a dimensional stability of ≤7.9%.

11. Use of the low-denier high-modulus low-shrinkage polyester industrial yarn according to claim 8 in the preparation of cord.

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