Preparation method of super-strong high-heat-resistance polyamide 66 industrial yarn

Abstract

The invention discloses a preparation method of super-strong high-heat-resistance polyamide 66 industrial yarn. The preparation method comprises the following steps: manufacturing high-viscosity polyamide 66 slices; the preparation method comprises the following steps: slicing high-viscosity polyamide 66, adding a heat-resistant agent, feeding into a screw extruder together, and heating and melting to obtain a polyamide 66 melt; a polyamide 66 melt is metered by a metering pump and then evenly distributed into a spinning assembly through an equal-length pipe, the polyamide 66 melt is filtered by a filtering device and sprayed out from a spinneret plate at the bottom of the spinning assembly at high pressure, melt trickles sprayed out from the spinneret plate enter a spinning channel to be cooled and formed, and a side blowing device is arranged in the spinning channel. A cooling plate is arranged above one side of the lateral blowing device; oiling the cooled and formed nascent fiber through an oiling roller; and stretching and shaping the oiled tows by using five pairs of hot rollers, and finally winding. The breaking strength of the prepared polyamide 66 industrial yarn is improved, the heat resistance is remarkably improved, and the requirements of aircraft tires, characteristic tires and other high-load scenes are met.

Description

Technical Field

[0001] The present invention relates to the technical field of polyamide materials, and in particular to a method for preparing super-strong and high-heat-resistant polyamide 66 industrial yarn. Background Art

[0002] Polyamide 66 industrial yarn, with its excellent properties such as high strength, high wear resistance, and fatigue resistance, continues to play a key role in the reinforcement of rubber products such as tire cord, conveyor belts, and hoses. With the development of the automotive and transportation industries, the demand for high-performance tires continues to increase, providing a stable market for polyamide 66 industrial yarn.

[0003] The batch polycondensation process for polyamide 66 industrial yarn is a key method for domestic production. Under current production technology, polyamide 66 chips are melted, compressed, homogenized, and metered before being extruded at a constant pressure through a screw die. The resulting stream of melt is then distributed through pipes into various spinning boxes. After passing through a metering pump and spinning assembly, it is ejected. After cooling and shaping, the melt stream passes through a tunnel and enters a drafting machine. After oiling, it is stretched and shaped by four pairs of heated rollers before being wound on a winder. The resulting conventional polyamide 66 industrial yarn for domestic industrial use has a breaking strength of 9.5g / D and a heat resistance of 90%-92%. Due to its specialized application scenarios, the market has placed higher performance demands on polyamide 66 industrial yarn. Conventional polyamide 66 industrial yarn produced by existing processes has low breaking strength and heat resistance, making it unable to meet the high load, high internal pressure, and strong impact of landing required for applications such as aircraft tires and specialty tires, thus limiting its application. Summary of the Invention

[0004] In order to solve the problems of low breaking strength and heat resistance of polyamide 66 industrial yarn produced by existing processes, the present invention proposes a method for preparing ultra-strong and high-heat-resistant polyamide 66 industrial yarn. The polyamide 66 industrial yarn produced by this method has improved breaking strength and significantly improved heat resistance, meeting the requirements of high-load scenarios such as aviation tires and special tires.

[0005] In order to achieve the above object, the technical solution of the present invention is: A method for preparing super-strong and high-heat-resistant polyamide 66 industrial yarn comprises the following steps: Step S1, manufacturing high-viscosity polyamide 66 chips: using conventional viscosity polyamide 66 chips, and performing step-by-step solid phase polycondensation to obtain high-viscosity polyamide 66 chips; Step S2, melt extrusion: taking the high-viscosity polyamide 66 slices obtained in step S1, adding a heat-resistant agent, feeding the slices together into a screw extruder, and heating and melting the slices to obtain a polyamide 66 melt; Step S3, metered spinning: The polyamide 66 melt is metered by a metering pump and evenly distributed into the spinning assembly through equal-length tubes. The polyamide 66 melt in the spinning assembly is filtered by a filtering device and ejected from the spinneret at the bottom of the spinning assembly under high pressure. The melt stream ejected from the spinneret enters the spinning channel for cooling and forming. A side blowing device is provided in the spinning channel, and a cooling plate is provided on the upper side of one side of the side blowing device. Step S4, oiling the tow: the spun fibers formed by cooling in step S3 are oiled by an oiling roller; Step S5, stretching and shaping: using five pairs of hot rollers to stretch and shape the filaments after oiling in step S3; wherein the stretching ratio between the second pair of hot rollers and the first pair of hot rollers is 3.0-3.8, the speed ratio between the third pair of hot rollers and the second pair of hot rollers is 1.0, and the stretching ratio between the fourth pair of hot rollers and the third pair of hot rollers is 1.8-2.3; Step S6, winding: the yarn bundle after being stretched and shaped in step S5 is transported to a winding machine, and is wound to obtain polyamide 66 industrial yarn.

[0006] Furthermore, the specific process of the step-by-step solid-phase polycondensation thickening in step S1 is as follows: conventional viscosity polyamide 66 slices are taken and loaded into a first solid-phase polycondensation reactor, and 140-150°C nitrogen is used to flow from bottom to top in the first solid-phase polycondensation reactor for the first stage of thickening. The polyamide 66 slices after the first stage of thickening are loaded into a second solid-phase polycondensation reactor again, and 150-160°C nitrogen is used to flow from bottom to top in the second solid-phase polycondensation reactor for the second stage of thickening to obtain the high-viscosity polyamide 66 slices, and the high-viscosity polyamide 66 slices have a relative viscosity greater than 90 measured in a 90% concentration formic acid solution.

[0007] Furthermore, the heat-resistant agent in step S2 is a heat-resistant masterbatch of cuprous iodide and is added through a vector metering device, and the amount of the heat-resistant agent added is 150-300 ppm.

[0008] Furthermore, the filtering device in step S3 includes several groups of foldable filter mesh assemblies spaced apart from each other, the edges of the foldable filter mesh assemblies are wrapped with aluminum edging, and an aluminum block is arranged between the aluminum edgings of two adjacent groups of foldable filter mesh assemblies; the foldable filter mesh assembly is wavy, including a metal mesh 1, a metal fiber sintered felt 1, a metal mesh 2 and a support mesh arranged in sequence from top to bottom.

[0009] Furthermore, in step S3, the cooling plate gradually widens from top to bottom, and a plurality of hexagonal through holes are distributed on the cooling plate, and the through holes are arranged in a honeycomb shape.

[0010] Through the above technical solution, the beneficial effects of the present invention are: The present invention improves the relative viscosity of formic acid of polyamide 66 chips by step-by-step solid-phase viscosity enhancement, and adds a heat-resistant agent through a weight loss metering device to improve the heat resistance of polyamide 66 industrial yarn; a filtering device is used to replace the original metal sand and flat filter screen in the spinning assembly, and each group of folded filter screen components in the filtering device includes three layers of filter screens, namely metal mesh one, metal fiber sintered felt one and metal mesh two, so that the pore channels of polyamide 66 melt passing through the spinning assembly are increased, which is equivalent to increasing the pressure of the melt passing through the spinning assembly. The increase in the pressure of the spinning assembly means that impurities in the melt are easier to filter out, so that broken ends and hairy fibers are less likely to occur during the spinning process, and the use of a wavy filter screen increases the filtration area compared to the flat type, further improving the filtration effect; a cooling plate is arranged on the upper part of one side of the side blowing device, and the cooling plate has through holes arranged in a honeycomb shape. The hot air blown out by the side blowing device passes through the through holes arranged in a honeycomb shape to form parallel Laminar flow, the wind direction is kept parallel to the air flow, avoiding local uneven cooling caused by turbulence, making the temperature field on the fiber surface uniform, thereby achieving the effect of enhanced cooling of the upper part of the nascent fiber, inhibiting the crystallization of the nascent fiber joints, and facilitating the stretching of the subsequent process; by adding a pair of auxiliary heating rollers on the basis of the original four pairs of hot rollers, the stretching ratio is gradually increased, specifically: the first stretching is carried out between the first pair of hot rollers and the second pair of hot rollers; auxiliary heating is carried out on the third pair of hot rollers to give the polyamide macromolecular chain enough heat to move, which is conducive to the second higher multiple stretching; the second stretching is carried out between the third pair of hot rollers and the fourth pair of hot rollers, and heat setting is carried out between the fourth pair of hot rollers and the fifth pair of hot rollers, thereby achieving the purpose of improving the breaking strength of the polyamide 66 industrial yarn; in summary, the breaking strength of the polyamide 66 industrial yarn prepared by the present invention is improved, and the heat resistance is significantly improved, which meets the requirements of high-load scenarios such as aviation tires and special tires. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 It is a structural schematic diagram of the supporting device of the present invention; Figure 2 This is a schematic diagram of the installation position of the internal filtering device of the spinning assembly in the present invention; Figure 3 is a schematic diagram of a foldable filter assembly in the present invention; Figure 4 For the present invention Figure 3 A magnified schematic diagram of point A in the middle; Figure 5 Schematic diagram of the position of the cooling plate between the side-blowing device and the as-spun fiber in the present invention; Figure 6 Schematic diagram of the structure of the cooling plate in the present invention.

[0012] The reference numerals in the accompanying drawings are: 1. Screw extruder; 2. Spinning assembly; 3. Side blowing device; 4. Cooling plate; 5. Spun fiber; 6. Oiling roller; 7. First pair of hot rollers; 8. Second pair of hot rollers; 9. Third pair of hot rollers; 10. Fourth pair of hot rollers; 11. Fifth pair of hot rollers; 12. Winder; 13. First solid-phase polycondensation reactor; 14. Second solid-phase polycondensation reactor; 15. Aluminum edging; 16. Aluminum block; 17. Metal mesh 1; 18. Metal fiber sintered felt 1; 19. Metal mesh 2; 20. Support mesh; 21. Through hole. DETAILED DESCRIPTION

[0013] The present invention will be further described below with reference to the accompanying drawings and specific embodiments: Example 1 like Figures 1-6 As shown, Example 1 provides a method for preparing super-strong and high-heat-resistant polyamide 66 industrial yarn, comprising the following steps: Step S1, manufacturing high-viscosity polyamide 66 chips: using conventional viscosity polyamide 66 chips, and performing step-by-step solid phase polycondensation to increase viscosity to obtain high-viscosity polyamide 66 chips.

[0014] Step S2, melt extrusion: taking the high-viscosity polyamide 66 slices obtained in step S1, adding a heat-resistant agent, and feeding them together into the screw extruder 1, and heating and melting them to obtain a polyamide 66 melt.

[0015] Step S3, metered spinning: The polyamide 66 melt is metered by a metering pump and evenly distributed into the spinning assembly 2 by an equal-length tube. The polyamide 66 melt in the spinning assembly 2 is filtered by a filtering device and ejected from the spinneret at the bottom of the spinning assembly 2 under high pressure. The melt stream ejected from the spinneret enters the spinning channel for cooling and forming. A side blowing device 3 is provided in the spinning channel, and a cooling plate 4 is provided on the upper part of one side of the side blowing device 3.

[0016] Step S4, oiling the tow: the spun fibers 5 formed by cooling in step S3 are oiled by an oiling roller 6.

[0017] Step S5, stretching and shaping: Use five pairs of hot rollers to stretch and shape the filaments after oiling in step S3; wherein, the stretching ratio between the second pair of hot rollers 8 and the first pair of hot rollers 7 is 3.1, the speed ratio between the third pair of hot rollers 9 and the second pair of hot rollers 8 is 1.0, the stretching ratio between the fourth pair of hot rollers 10 and the third pair of hot rollers 9 is 1.8, and the heating temperature of the third pair of hot rollers 9 and the heating temperature of the fourth pair of hot rollers 10 are 220°C.

[0018] By setting up five pairs of hot rollers, the first stretching is carried out between the first pair of hot rollers 7 and the second pair of hot rollers 8, and the first stretching ratio is 3.1; an auxiliary heating is carried out at the third pair of hot rollers 9 to give the polyamide macromolecular chains sufficient heat to move, which is conducive to the second higher-multiple stretching; the second stretching is carried out between the third pair of hot rollers 9 and the fourth pair of hot rollers 10, and the second stretching ratio is 1.8; and a heat setting is carried out between the fourth pair of hot rollers 10 and the fifth pair of hot rollers 11.

[0019] Step S6, winding: the yarn bundle after being stretched and shaped in step S5 is transported to the winding machine 12, and is wound to obtain polyamide 66 industrial yarn.

[0020] Specifically, the specific process of the step-by-step solid-phase polycondensation thickening in step S1 is as follows: conventional viscosity polyamide 66 slices are taken and loaded into the first solid-phase polycondensation reactor 13, and 140-150°C nitrogen is used to flow from bottom to top in the first solid-phase polycondensation reactor 13 in a reverse direction to perform the first stage of thickening. The polyamide 66 slices after the first stage of thickening are loaded into the second solid-phase polycondensation reactor 14 again, and 150-160°C nitrogen is used to flow from bottom to top in the second stage of thickening in the second solid-phase polycondensation reactor 14 to obtain the high-viscosity polyamide 66 slices. The high-viscosity polyamide 66 slices have a relative viscosity of 95 measured in a 90% concentration formic acid solution.

[0021] In Example 1, the heat-resistant agent in step S2 is cuprous iodide heat-resistant masterbatch and is added through a vector metering device. The amount of heat-resistant agent added is 220 ppm.

[0022] Please refer again Figure 2 、 Figure 3 and Figure 4 The filtering device in step S3 includes several groups of foldable filter screen assemblies spaced apart from each other, the edges of the foldable filter screen assemblies are wrapped with aluminum edging 15, and an aluminum block 16 is arranged between the aluminum edging 15 of two adjacent groups of foldable filter screen assemblies; the foldable filter screen assembly is wavy and includes a metal mesh 17, a metal fiber sintered felt 18, a metal mesh 2 19 and a support mesh 20 arranged in sequence from top to bottom.

[0023] The applicant wishes to clarify that the function of the spinning assembly is to finely filter, thoroughly mix, and evenly distribute the melt, and then eject it through the spinneret under a certain pressure to produce a fine stream of melt. Currently, in the production of polyamide 66 industrial yarn, the spinning assembly 2 uses metal sand and a flat filter screen. Metal sands of different specifications are coarsely mixed in the sand cup. This can easily cause fine metal sand to be ejected along with the melt under high-pressure spinning conditions. Furthermore, the metal sand mesh size is relatively low, resulting in a small filtration area and poor filtration effect, making it ineffective in removing impurities from the polyamide 66 melt.

[0024] The present invention adopts a filtering device to replace the original metal sand and flat filter screen in the spinning assembly 2. Each group of folded filter screen components in the filtering device includes three layers of filter screens, namely metal screen 17, metal fiber sintered felt 18 and metal screen 2 19, so that the pore channels of the polyamide 66 melt passing through the spinning assembly 2 are increased, which is equivalent to increasing the pressure of the melt passing through the spinning assembly 2. The increase in the pressure of the spinning assembly 2 means that impurities in the melt are easier to filter out, so that broken ends and hairs are less likely to occur during the spinning process. In addition, the use of a wavy filter screen increases the filtration area from 0.03-0.06m2 compared to the flat type. 2 Increased to 0.08-0.1m 2 , further improving the filtering effect; wherein, the existence of the support net 20 improves the strength of the foldable filter net assembly.

[0025] Please refer again Figure 5 and Figure 6 In step S3, the cooling plate 4 gradually widens from top to bottom, and a plurality of hexagonal through holes 21 are distributed on the cooling plate 4, and the through holes 21 are arranged in a honeycomb shape.

[0026] In order to achieve high-magnification stretching in the later stage, the orientation degree of the spun fibers 5 is required to be as high as possible and the crystallinity is as low as possible. In the actual production process, strengthening the cooling process of the upper section of the spun fibers 5 can achieve the effect of inhibiting crystallization. To this end, a cooling plate 4 is provided on the upper part of one side of the side-blowing device. The cooling plate 4 has through holes 21 arranged in a honeycomb shape. The hot air blown out by the side-blowing device 3 forms a parallel laminar flow after passing through the through holes 21 arranged in a honeycomb shape. The wind direction is kept parallel to the air outlet to avoid uneven local cooling caused by turbulence, so that the temperature field on the fiber surface is uniform, thereby achieving the effect of strengthening the cooling of the upper part of the spun fibers 5 and inhibiting the crystallization of the spun fibers 5, thereby obtaining spun fibers 5 with good tensile properties, which is beneficial to the stretching in the subsequent process.

[0027] Example 2 It is basically the same as Example 1, except that: In the second embodiment, the stretching ratio between the fourth pair of hot rollers 10 and the third pair of hot rollers 9 is 1.9, and the heating temperature of the third pair of hot rollers 9 and the heating temperature of the fourth pair of hot rollers 10 are 235°C.

[0028] Comparative Example In the comparative example, conventional viscosity polyamide 66 chips were used, having a relative viscosity of 75 measured in a 90% concentration formic acid solution, and no heat-resistant agent was added using a vector addition device before entering the screw extruder.

[0029] In the comparative example, four pairs of hot rollers are used for stretching and shaping. The first stretching is carried out between the first pair of hot rollers and the second pair of hot rollers, and the first stretching ratio is 3.1; the second stretching is carried out between the second pair of hot rollers and the third pair of hot rollers, and the second stretching ratio is 1.7; the temperature of the second pair of hot rollers is 220°C, and the temperature of the third pair of hot rollers is 215°C; and heat shaping is carried out between the third pair of hot rollers and the fourth pair of hot rollers.

[0030] Table 1 is a table showing the properties of polyamide 66 industrial yarns of Example 1, Example 2 and Comparative Example project Comparative Example Example 1 Example 2 Viscosity 75 95 95 Effective amount of heat-resistant agent (ppm) 0 220 220 Temperature of the second pair of hot rollers (°C) 200 / / Temperature of the third pair of hot rollers (°C) 215 220 235 Temperature of the fourth pair of hot rollers (°C) / 220 235 First stretch ratio 3.1 3.1 3.1 Second stretch ratio 1.7 1.8 1.9 Linear density (dtex) 1400 1401 1400 Breaking strength (g / D) 9.6 10.6 11.0 Heat resistance (%) 92 96 97 The data in the above table show that the breaking strength of the polyamide 66 industrial yarn prepared by the present invention is improved, and the heat resistance is significantly improved, meeting the requirements of high-load scenarios such as aviation tires and special tires.

[0031] The embodiments described above are only preferred embodiments of the present invention and do not limit the scope of implementation of the present invention. Therefore, any equivalent changes or modifications made according to the structure, characteristics and principles described in the patent scope of the present invention should be included in the scope of the patent application of the present invention.

Claims

1. A method for preparing super-strong and high-heat-resistant polyamide 66 industrial yarn, characterized in that: The following steps are involved: Step S1, manufacturing high-viscosity polyamide 66 chips: using conventional viscosity polyamide 66 chips, and performing step-by-step solid phase polycondensation to obtain high-viscosity polyamide 66 chips; Step S2, melt extrusion: taking the high-viscosity polyamide 66 slices obtained in step S1, adding a heat-resistant agent, and feeding the slices into a screw extruder (1), and heating and melting the slices to obtain a polyamide 66 melt; Step S3, metered spinning: the polyamide 66 melt is metered by a metering pump and evenly distributed into the spinning assembly (2) through an equal-length tube. The polyamide 66 melt in the spinning assembly (2) is filtered by a filtering device and ejected from a spinneret at the bottom of the spinning assembly (2) at high pressure. The melt stream ejected from the spinneret enters the spinning channel for cooling and forming. A side blowing device (3) is provided in the spinning channel, and a cooling plate (4) is provided on the upper part of one side of the side blowing device (3). Step S4, oiling the tow: the spun fibers (5) obtained in step S3 after cooling and forming are oiled by an oiling roller (6); Step S5, stretching and shaping: using five pairs of hot rollers to stretch and shape the filaments after oiling in step S3; wherein the stretching ratio between the second pair of hot rollers (8) and the first pair of hot rollers (7) is 3.0-3.8, the speed ratio between the third pair of hot rollers (9) and the second pair of hot rollers (8) is 1.0, and the stretching ratio between the fourth pair of hot rollers (10) and the third pair of hot rollers (9) is 1.8-2.3; Step S6, winding: the yarn bundle after being stretched and shaped in step S5 is transported to a winding machine (12), and is wound to obtain polyamide 66 industrial yarn.

2. The method for preparing super-strong and high-heat-resistant polyamide 66 industrial yarn according to claim 1, characterized in that: The specific process of the step-by-step solid phase polycondensation thickening in step S1 is as follows: conventional viscosity polyamide 66 slices are taken and loaded into a first solid phase polycondensation reactor (13), 140-150°C nitrogen is used to flow from bottom to top in the first solid phase polycondensation reactor (13) in a reverse direction to perform first stage thickening, the polyamide 66 slices after the first stage thickening are loaded into a second solid phase polycondensation reactor (14) again, 150-160°C nitrogen is used to flow from bottom to top in the second solid phase polycondensation reactor (14) in a reverse direction to perform second stage thickening, and the high viscosity polyamide 66 slices are obtained, and the high viscosity polyamide 66 slices have a relative viscosity greater than 90 measured in a 90% concentration formic acid solution.

3. The method for preparing super-strong and high-heat-resistant polyamide 66 industrial yarn according to claim 1, characterized in that: The heat-resistant agent in step S2 is a heat-resistant masterbatch of cuprous iodide and is added through a vector metering device. The amount of heat-resistant agent added is 150-300 ppm.

4. The method for preparing super-strong and high-heat-resistant polyamide 66 industrial yarn according to claim 1, characterized in that: The filtering device in step S3 includes a plurality of groups of foldable filter screen assemblies spaced apart from each other, wherein the edges of the foldable filter screen assemblies are wrapped with aluminum edging (15), and an aluminum block (16) is provided between the aluminum edging (15) of two adjacent groups of foldable filter screen assemblies; the foldable filter screen assembly is wavy and includes a metal mesh 1 (17), a metal fiber sintered felt 1 (18), a metal mesh 2 (19), and a support mesh (20) arranged in sequence from top to bottom.

5. The method for preparing super-strong and high-heat-resistant polyamide 66 industrial yarn according to claim 1, characterized in that: In step S3, the cooling plate (4) gradually widens from top to bottom, and a plurality of hexagonal through holes (21) are distributed on the cooling plate (4), and the through holes (21) are arranged in a honeycomb shape.

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