Device and method for improving monofilament consistency of polyacrylonitrile precursor

Abstract

The invention provides a device and a method for improving the monofilament consistency of polyacrylonitrile protofilaments, and particularly relates to a device and a method for heating air by using waste heat of recycled hot water, reducing the heating temperature gradient of protofilament walking, and reducing the problems of poor monofilament consistency of the protofilaments and the like caused by overlarge heating difference of tows. The invention discloses a device for reducing roller sticking of polyacrylonitrile precursor oil. The device comprises a drying densification unit and a hot air circulation injection device, wherein the drying and compacting unit comprises a pneumatic valve, a pressure gauge, a pressure sensor, a temperature sensor and a drying and compacting roller; the hot air circulation jetting device comprises a fan, a plate heat exchanger, a sight glass and a hot air distribution box. The method solves the problem of poor monofilament consistency of the protofilament caused by overlarge heating difference of the tows in the prior art, is low in operation cost and low in energy consumption, and can be well applied to preparation of polyacrylonitrile protofilament fibers.

Description

Technical Field

[0001] The invention relates to a device and a method for improving the consistency of polyacrylonitrile precursor monofilaments, and belongs to the field of high-performance carbon fiber precursor production. Background Art

[0002] Polyacrylonitrile-based carbon fiber has the advantages of high strength, high elastic modulus, and strong heat resistance. It is widely used in cutting-edge fields such as wind power generation, high-pressure vessels, aerospace, and national defense and military. At present, the intra-batch and inter-batch dispersion coefficients of the tensile strength of Japan's Toray T800S carbon fiber are 0.74% and 1.21% respectively, while the domestic T800-grade carbon fiber currently has large performance dispersion and insufficient stability. The intra-batch and inter-batch dispersion coefficients of the tensile strength of carbon fiber products of the same level are much higher than those of Toray products of the same level, resulting in unstable performance of composite materials and low application efficiency conversion rate. The carbon fiber production process is complex and diverse, the preparation technology is difficult, and the control precision requirements are high. Any deviation from the control parameters of the production process will cause discrete fluctuations in the performance of carbon fiber products.

[0003] The drying and densification process is a process of heat treating the water-containing swollen filaments (swollen state, porous state) under certain tension and temperature conditions. Drying and densification can close the pores, make the network structure of the original fibers dense, and eliminate the structural unevenness caused by the mutual diffusion of solvents and precipitants during the solidification process, as well as the numerous holes and crack structures of varying sizes caused by this. The perfect drying and densification process is an important method to reduce the discreteness of polyacrylonitrile precursors to improve the performance stability of carbon fibers. The drying and densification temperature is usually between 150 and 190°C, and the temperature of the washed and oiled tow is usually around 30°C. Therefore, the tow will be subjected to a large temperature difference in a short period of time from oiling to drying. When the yarn bundle contains too much oil and is subjected to a large temperature difference in a short period of time, the oil is likely to aggregate and adhere to the surface of the drying roller, affecting the production continuity and performance stability of the precursor yarn, resulting in the degradation of the consistency of the precursor yarn. Therefore, it is necessary to improve the thermal uniformity of the polyacrylonitrile precursor during the wire feeding process, reduce the thermal temperature gradient of the precursor yarn before drying and densification, and reduce the discreteness of the carbon fiber precursor.

[0004] CN 105525373 A discloses a method for eliminating oil sticking to rollers. By adding a dryer between an oiling machine and a drying and densification device, the raw silk fibers are pretreated, thereby effectively solving the problem of oil sticking to the drying roller. However, this method does not completely solve the problem of uneven heating of the raw silk in the process from oiling to drying and densification, and the invention adds a dryer, which increases energy loss and production costs. Summary of the invention

[0005] The technical problem to be solved by the present invention is to provide a device and method for improving the consistency of polyacrylonitrile precursor filaments, using the waste heat of the recovered hot water to heat the air, reducing the temperature gradient of the precursor wire, and reducing the problems such as poor consistency of the precursor filaments caused by excessive differences in the heating of the filament bundles. The method has the advantages of low production cost and low energy consumption.

[0006] A device for improving the consistency of polyacrylonitrile precursor monofilaments of the present invention comprises:

[0007] Drying and densification unit and hot air circulation injection device;

[0008] Among them, the drying and densification unit includes

[0009] Dry densification chassis and;

[0010] Disposing a plurality of drying and densifying rollers in a drying and densifying cabinet;

[0011] A temperature sensor is provided on the drying and densifying roller;

[0012] The external steam channel of the drying and densification cabinet is connected to the drying and densification roller, and the steam channel is respectively connected with a pneumatic valve, a pressure gauge, and a pressure sensor;

[0013] The hot air circulation injection device comprises a hot air distribution box; the hot air distribution box is arranged at the bottom of the drying and densification cabinet;

[0014] The hot air distribution box is connected to the plate heat exchanger through a circulation pipeline, the plate heat exchanger is connected to the fan, and a sight glass is arranged on the circulation pipeline.

[0015] Furthermore, 5 to 7 drying and densification units can be provided, and each drying and densification unit has 3 to 5 rollers.

[0016] Furthermore, openings are reserved on both sides of the drying and densification cabinet for fibers to enter and exit the drying and densification cabinet.

[0017] Furthermore, the air is pressurized by the fan and transported to the plate heat exchanger. The air is heated and pressure-controlled by the heat exchanger and enters the hot air distribution box, and then enters the drying and densification box from the hot air distribution box.

[0018] Furthermore, the hot air distribution box is provided with a gas distribution device to evenly distribute the hot air.

[0019] A method for improving the consistency of polyacrylonitrile precursor monofilaments comprises the following steps:

[0020] (1) The fiber passes through the oiling machine and is squeezed by the squeezing roller after the oiling tank to squeeze out the excess oil in the raw fiber bundle;

[0021] (2) The fibers squeezed by rollers enter the drying box and are preheated by hot air;

[0022] (3) The preheated raw silk fibers enter the drying and densification unit for drying;

[0023] (4) The fan air volume is 9000~15000m 3 / h, the hot air temperature heated by the plate heat exchanger is 80~90℃;

[0024] (5) Drying residence time is 40 to 57 seconds; the drying and densification roller pressure is 0.45 to 1.1 MPa; the drying and densification roller temperature range is 120 to 180°C;

[0025] (6) Steam drawing: The dried fiber bundles are steam drawn to obtain polyacrylonitrile raw yarns. The surface of the fiber bundles is observed for oil retention, color uniformity, and single yarn strength and CV are tested.

[0026] Furthermore, the temperature gradient between the hot rollers is 2-5°C.

[0027] Furthermore, the fan speed ratio is 30 to 80, and the rotation speed is 960 to 2900 r / min.

[0028] Compared with the prior art, the present invention has significant advantages: (1) the method of the present invention can effectively reduce problems such as poor consistency of raw silk and single silk caused by excessive differences in heating of the silk bundles; (2) the method has the advantages of low production cost and low energy consumption. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 The invention discloses a device for improving the consistency of polyacrylonitrile precursor single yarn.

[0030] 1. Pneumatic valve; 2. Pressure gauge; 3. Pressure sensor; 4. Temperature sensor; 5. Hot air distribution box; 6. Sight glass; 7. Plate heat exchanger; 8. Fan. DETAILED DESCRIPTION

[0031] The present invention is further described below in conjunction with embodiments, but the scope of protection claimed by the present invention is not limited to the scope described in the embodiments.

[0032] The present invention is a consistency treatment method carried out on a device for improving the consistency of polyacrylonitrile precursor single yarn, and the device comprises:

[0033] Drying and densification unit and hot air circulation injection device;

[0034] Among them, the drying and densification unit includes

[0035] Dry densification chassis and;

[0036] Disposing a plurality of drying and densifying rollers in a drying and densifying cabinet;

[0037] A temperature sensor 4 is provided on the drying and densifying roller;

[0038] The external steam channel of the drying and densification cabinet is connected to the drying and densification roller, and the steam channel is respectively connected with a pneumatic valve 1, a pressure gauge 2, and a pressure sensor 3;

[0039] The hot air circulation injection device comprises a hot air distribution box 5; the hot air distribution box 5 is arranged at the bottom of the drying and densification cabinet;

[0040] The hot air distribution box 5 is connected to the plate heat exchanger 7 through a circulation pipeline, the plate heat exchanger 7 is connected to the fan 8, and a sight glass 6 is arranged on the circulation pipeline.

[0041] The drying and densification units can be provided with 5 to 7 groups, and each drying and densification unit has 3 to 5 rollers.

[0042] Openings are reserved on both sides of the drying and densification cabinet for fibers to enter and exit the drying and densification cabinet.

[0043] The air is pressurized by the fan 8 and transported to the plate heat exchanger 7. The air is heated and pressure-controlled by the plate heat exchanger 7 and enters the hot air distribution box 5, and then enters the drying and densification box from the hot air distribution box 5.

[0044] The hot air distribution box 5 is provided with a gas distribution device to evenly distribute the hot air.

[0045] The following provides a specific embodiment based on the above device to illustrate the working

[0046] Example 1

[0047] (1) Copolymerization: A mixed solution consisting of 90wt.% acrylonitrile, 6wt.% itaconic acid and 4wt.% methyl methacrylate in dimethyl sulfoxide is subjected to free radical solution polymerization to obtain a polyacrylonitrile polymer with a solid content of 20.1%. (2) De-aeration and degassing: The polymer is first de-aerated at a pressure of -76KPa in a de-aeration kettle, and then de-aerated at 3μm in a primary filtration process, and then de-aerated at a pressure of -97KPa in a degassing kettle, and then sent to a 1μm secondary filtration process. (3) Coagulation bath: The refined spinning solution is pressurized and transported to the spinning unit, and the spinning solution temperature is maintained at 45°C. The spinning solution passes through an air layer and then goes to a coagulation bath for coagulation and molding. The air layer is 2mm, the coagulation bath concentration is 45wt%, and the coagulation bath temperature is 5°C. At the same time, a drafting multiple of 1.1 is applied to obtain primary fibers.

[0048] (4) Washing and stretching: The spun fiber is passed through multiple stages of desalted water at 33-36°C to remove the solvent, and then washed in hot water at 60-80°C while being stretched at 1.3 times.

[0049] (5) Oiling and drying densification: The fibers after hot water drawing are passed through a 1.1% silicone oil bath for drying and densification. The hot air circulation injection device has a fan speed ratio of 61, a rotation speed of 1500 r / min, and an air volume of 9000 m 3 / h, the hot air temperature is 90℃; there are 7 drying and densification units, each drying and densification unit has 5 rollers, the drying and densification roller pressure is 0.30MPa, the drying roller temperature gradient is 2℃, the temperature range is 135-150℃, and the drying residence time is 57s.

[0050] (6) Steam drawing: The dried fiber bundles were steam drawn at a saturated steam pressure of 0.45 MPa and a steam drawing multiple of 3.5 to obtain polyacrylonitrile raw yarn, and the single yarn strength and CV were tested.

[0051] (7) The fiber is evenly oiled, the fiber surface is bright, the color is uniform without color spots, and the fiber has no lint; the single fiber strength is 10.3 cN / dtex, and the CV value is 4.8%.

[0052] Example 2

[0053] (1) Copolymerization: A mixed solution consisting of 90wt.% acrylonitrile, 6wt.% itaconic acid and 4wt.% methyl methacrylate in dimethyl sulfoxide is subjected to free radical solution polymerization to obtain a polyacrylonitrile polymer with a solid content of 20.1%. (2) De-aeration and degassing: The polymer is first de-aerated at a pressure of -76KPa in a de-aeration kettle, and then de-aerated at 3μm in a primary filtration process, and then de-aerated at a pressure of -97KPa in a degassing kettle, and then sent to a 1μm secondary filtration process. (3) Coagulation bath: The refined spinning solution is pressurized and transported to the spinning unit, and the spinning solution temperature is maintained at 45°C. The spinning solution passes through an air layer and then goes to a coagulation bath for coagulation and molding. The air layer is 2mm, the coagulation bath concentration is 45wt%, and the coagulation bath temperature is 5°C. At the same time, a drafting multiple of 1.1 is applied to obtain primary fibers.

[0054] (4) Washing and stretching: The spun fiber is passed through multiple stages of desalted water at 33-36°C to remove the solvent, and then washed in hot water at 60-80°C while being stretched at 1.3 times.

[0055] (5) Oiling and drying densification: The fibers after hot water drawing are passed through a 1.1% silicone oil bath for drying and densification. The hot air circulation injection device has a fan speed ratio of 61, a rotation speed of 2000 r / min, and an air volume of 12000 m 3 / h, the hot air temperature is 90℃; there are 7 drying and densification units, each drying and densification unit has 5 rollers, the drying and densification roller pressure is 0.45MPa, the drying roller temperature gradient is 2℃, the temperature range is 125-140℃, and the drying residence time is 57s.

[0056] (6) Steam drawing: The dried fiber bundles were steam drawn at a saturated steam pressure of 0.45 MPa and a steam drawing multiple of 3.5 to obtain polyacrylonitrile raw yarn, and the single yarn strength and CV were tested.

[0057] (7) The fiber is evenly oiled, the fiber surface is bright, the color is uniform without color spots, and the fiber has no lint; the single fiber strength is 10.6 cN / dtex, and the CV value is 5.1%.

[0058] Example 3

[0059] (1) Copolymerization: A mixed solution consisting of 90wt.% acrylonitrile, 6wt.% itaconic acid and 4wt.% methyl methacrylate in dimethyl sulfoxide is subjected to free radical solution polymerization to obtain a polyacrylonitrile polymer with a solid content of 20.1%. (2) De-aeration and degassing: The polymer is first de-aerated at a pressure of -76KPa in a de-aeration kettle, and then de-aerated at 3μm in a primary filtration process, and then de-aerated at a pressure of -97KPa in a degassing kettle, and then sent to a 1μm secondary filtration process. (3) Coagulation bath: The refined spinning solution is pressurized and transported to the spinning unit, and the spinning solution temperature is maintained at 45°C. The spinning solution passes through an air layer and then goes to a coagulation bath for coagulation and molding. The air layer is 2mm, the coagulation bath concentration is 45wt%, and the coagulation bath temperature is 5°C. At the same time, a drafting multiple of 1.1 is applied to obtain primary fibers.

[0060] (4) Washing and stretching: The spun fiber is passed through multiple stages of desalted water at 33-36°C to remove the solvent, and then washed in hot water at 60-80°C while being stretched at 1.3 times.

[0061] (5) Oiling and drying densification: The fibers after hot water drawing are passed through a 1.1% silicone oil bath for drying and densification. The hot air circulation injection device has a fan speed ratio of 61, a rotation speed of 2500 r / min, and an air volume of 14000 m 3 / h, the hot air temperature is 90℃; there are 7 drying and densification units, each drying and densification unit has 5 rollers, the drying and densification roller pressure is 0.45MPa, the drying roller temperature gradient is 2℃, the temperature range is 125-140℃, and the drying residence time is 57s.

[0062] (6) Steam drawing: The dried fiber bundles were steam drawn at a saturated steam pressure of 0.45 MPa and a steam drawing multiple of 3.5 to obtain polyacrylonitrile raw yarn, and the single yarn strength and CV were tested.

[0063] (7) The fiber is evenly oiled, the fiber surface is bright, the color is uniform without color spots, and the fiber has no lint; the single fiber strength is 10.2 cN / dtex, and the CV value is 4.9%.

[0064] Comparative Example 1

[0065] (1) Copolymerization: A mixed solution consisting of 90wt.% acrylonitrile, 6wt.% itaconic acid and 4wt.% methyl methacrylate in dimethyl sulfoxide is subjected to free radical solution polymerization to obtain a polyacrylonitrile polymer with a solid content of 20.1%. (2) De-aeration and degassing: The polymer is first de-aerated at a pressure of -76KPa in a de-aeration kettle, and then de-aerated at 3μm in a primary filtration process, and then de-aerated at a pressure of -97KPa in a degassing kettle, and then sent to a 1μm secondary filtration process. (3) Coagulation bath: The refined spinning solution is pressurized and transported to the spinning unit, and the spinning solution temperature is maintained at 45°C. The spinning solution passes through an air layer and then goes to a coagulation bath for coagulation and molding. The air layer is 2mm, the coagulation bath concentration is 45wt%, and the coagulation bath temperature is 5°C. At the same time, a drafting multiple of 1.1 is applied to obtain primary fibers.

[0066] (4) Washing and stretching: The spun fiber is passed through multiple stages of desalted water at 33-36°C to remove the solvent, and then washed in hot water at 60-80°C while being stretched at 1.3 times.

[0067] (5) Oiling and drying densification: The fibers after hot water drawing are passed through a 1.1% silicone oil bath for drying densification. There are 7 drying densification units, each with 5 rollers. The drying densification roller pressure is 0.30 MPa, the drying roller temperature gradient is 2°C, the temperature range is 135-150°C, and the drying residence time is 57s.

[0068] (6) Steam drawing: The dried fiber bundles were steam drawn at a saturated steam pressure of 0.45 MPa and a steam drawing multiple of 3.5 to obtain polyacrylonitrile raw yarn, and the single yarn strength and CV were tested.

[0069] (7) The fiber is evenly oiled, the fiber surface is bright, the color is uniform without color spots, and the fiber has no lint; the single fiber strength is 9.1 cN / dtex, and the CV value is 9.6%.

[0070] Comparative Example 2

[0071] (1) Copolymerization: A mixed solution consisting of 90wt.% acrylonitrile, 6wt.% itaconic acid and 4wt.% methyl methacrylate in dimethyl sulfoxide is subjected to free radical solution polymerization to obtain a polyacrylonitrile polymer with a solid content of 20.1%. (2) De-aeration and degassing: The polymer is first de-aerated at a pressure of -76KPa in a de-aeration kettle, and then de-aerated at 3μm in a primary filtration process, and then de-aerated at a pressure of -97KPa in a degassing kettle, and then sent to a 1μm secondary filtration process. (3) Coagulation bath: The refined spinning solution is pressurized and transported to the spinning unit, and the spinning solution temperature is maintained at 45°C. The spinning solution passes through an air layer and then goes to a coagulation bath for coagulation and molding. The air layer is 2mm, the coagulation bath concentration is 45wt%, and the coagulation bath temperature is 5°C. At the same time, a drafting multiple of 1.1 is applied to obtain primary fibers.

[0072] (4) Washing and stretching: The spun fiber is passed through multiple stages of desalted water at 33-36°C to remove the solvent, and then washed in hot water at 60-80°C while being stretched at 1.3 times.

[0073] (5) Oiling and drying densification: The fibers after hot water drawing are passed through a 1.1% silicone oil bath for drying and densification. The hot air circulation injection device has a fan speed ratio of 61, a speed of 3000 r / min, and an air volume of 15000 m 3 / h, hot air temperature is 90℃; there are 7 drying and densification units, each with 5 rollers, the drying and densification roller pressure is 0.30MPa, the drying roller temperature gradient is 2℃, the temperature range is 135-150℃, and the drying residence time is 57s. The drying silk vibrates violently due to excessive ventilation and cannot pass the steam drawing device.

Claims

1. A device for improving the consistency of polyacrylonitrile precursor monofilaments, characterized in that: The device includes: Drying and densification unit and hot air circulation injection device; Among them, the drying and densification unit includes Dry densification chassis and; Disposing a plurality of drying and densifying rollers in a drying and densifying cabinet; A temperature sensor (4) is provided on the drying and densifying roller; The external steam channel of the drying and densification cabinet is connected to the drying and densification roller, and the steam channel is respectively connected to a pneumatic valve (1), a pressure gauge (2), and a pressure sensor (3); The hot air circulation injection device comprises a hot air distribution box (5); the hot air distribution box (5) is arranged at the bottom of the drying and densification cabinet; The hot air distribution box (5) is connected to the plate heat exchanger (7) through a circulation pipeline, the plate heat exchanger (7) is connected to the fan (8), and a sight glass (6) is arranged on the circulation pipeline.

2. The device for improving the consistency of polyacrylonitrile precursor yarn according to claim 1, characterized in that: The drying and densification units can be provided with 5 to 7 groups, and each drying and densification unit has 3 to 5 rollers.

3. The device for improving the consistency of polyacrylonitrile precursor yarn according to claim 1, characterized in that: Openings are reserved on both sides of the drying and densification cabinet for fibers to enter and exit the drying and densification cabinet.

4. The device for improving the consistency of polyacrylonitrile precursor yarn according to claim 1, characterized in that: The fan (8) pressurizes the air and delivers it to the plate heat exchanger (7). The air is heated and pressure-controlled by the plate heat exchanger (7) and then enters the hot air distribution box (5). From the hot air distribution box (5), the air enters the drying and densification cabinet.

5. The device for improving the consistency of polyacrylonitrile precursor yarn according to claim 4, characterized in that: The hot air distribution box (5) is provided with a gas distribution device to evenly distribute the hot air.

6. A method for improving the consistency of polyacrylonitrile precursor yarn based on the device of claims 1 to 5, characterized in that: The following steps are involved: (1) The fiber passes through the oiling machine and is squeezed by the squeezing roller after the oiling tank to squeeze out the excess oil in the raw fiber bundle; (2) The fibers squeezed by rollers enter the drying box and are preheated by hot air; (3) The preheated raw silk fibers enter the drying and densification unit for drying; (4) Fan (8) air volume is 9000~15000m 3 / h, the temperature of the hot air heated by the plate heat exchanger (7) is 80-90°C; (5) Drying residence time is 40 to 57 seconds; the drying and densification roller pressure is 0.45 to 1.1 MPa; the drying and densification roller temperature range is 120 to 180°C; (6) Steam drawing: The dried fiber bundles are steam drawn to obtain polyacrylonitrile raw yarns. The surface of the fiber bundles is observed for oil retention, color uniformity, and single yarn strength and CV are tested.

7. The method according to claim 6, characterized in that The temperature gradient between the hot rollers is 2 to 5°C.

8. The method according to claim 6, characterized in that The specific speed of the fan (8) is 30 to 80, and the rotation speed is 960 to 2900 r / min.

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