A method and device for laser pre-oxidation of polyacrylonitrile-based carbon fiber

Abstract

The invention discloses a method and device for laser preoxidation of polyacrylonitrile-based carbon fiber, which adopts infrared laser heating in the waveband of 2μm to 5μm or 9μm to 11μm. The method and device for preoxidation can accurately control the preoxidation heating temperature curve and heating area of ​​polyacrylonitrile fiber bundles, and monitor the degree and state of preoxidation of polyacrylonitrile fiber bundles in real time. The device for laser preoxidation of polyacrylonitrile-based carbon fiber comprises a fiber spreading module (1), a preoxidation device body (2), an air supply module (3), a laser module (4), an exhaust gas recovery module (5), an infrared temperature measurement module (6), an image monitoring module (7), a control module (8) and a host computer (9). The device for laser preoxidation of polyacrylonitrile-based carbon fiber has the advantages of high energy utilization rate, small equipment volume, and accurate control of the heating area and heating temperature curve.

Description

Technical Field

[0001] The invention relates to a method and a device for laser pre-oxidation of polyacrylonitrile-based carbon fiber, belonging to the technical field of polymer materials and laser application. Background Art

[0002] Pre-oxidation is an important step before carbonization in the preparation process of polyacrylonitrile (PAN)-based carbon fibers. In the pre-oxidation furnace at a temperature of 200℃ to 300℃, the polyacrylonitrile fiber tow undergoes chemical reactions such as cyclization, dehydrogenation, and oxygen absorption reaction, which converts the linear molecular chain into a heat-resistant trapezoidal six-membered ring structure. The color of the polyacrylonitrile fiber changes from milky white to yellow, brown, and finally black, so that the PAN-based carbon fiber products are infusible and non-flammable during high-temperature carbonization. At present, the carbon fiber pre-oxidation process mainly achieves high temperature by heating the ambient gas in the pre-oxidation furnace through electric heating tubes, and transfers heat to the PAN-based fibers through the environment. The energy utilization efficiency is low, the equipment is large in size and high in energy consumption, the production efficiency is low, and the power consumption is huge. In addition, since the chemical reaction in the pre-oxidation process is an exothermic process, the temperature controllability is poor, which is easy to cause fire. Summary of the invention

[0003] In view of the series of problems such as low energy utilization efficiency, large equipment size and high energy consumption, low production efficiency, huge power consumption, and poor temperature controllability of traditional polyacrylonitrile carbon fiber pre-oxidation process, the present invention provides a method and device for laser pre-oxidation of polyacrylonitrile-based carbon fiber.

[0004] The technical solution of the present invention is as follows:

[0005] A method for laser pre-oxidation of polyacrylonitrile-based carbon fiber is disclosed. The method comprises the following steps: using a medium- and long-wave infrared band laser spot to uniformly irradiate and heat the upper and lower surfaces of a polyacrylonitrile fiber bundle, and the polyacrylonitrile fiber bundle absorbs the irradiated laser energy and rapidly heats up to a set pre-oxidation temperature; in order to ensure sufficient pre-oxidation time, a plurality of laser spots with uniform intensity distribution are spliced ​​into a long strip-shaped uniform spot along the moving direction of the polyacrylonitrile fiber bundle; the intensity of each laser spot is adjusted to achieve precise control of the irradiation heating temperature curve; the degree and state of pre-oxidation of the polyacrylonitrile fiber bundle are judged by monitoring the color of the polyacrylonitrile fiber bundle; the pre-oxidation temperature curve is obtained by measuring the temperature information at different positions along the direction of the polyacrylonitrile fiber bundle, and the irradiation laser power is controlled according to the comparison result of the measured temperature and the set temperature; at a specific moving speed v of the polyacrylonitrile fiber bundle, the product of the set pre-oxidation time and the moving speed v of the polyacrylonitrile fiber bundle is not greater than the length of the strip-shaped uniform spot, and the width of the strip-shaped uniform spot is not less than the width of the polyacrylonitrile fiber bundle.

[0006] As attached Figure 1As shown, a polyacrylonitrile-based carbon fiber laser pre-oxidation device provided by the present invention comprises a fiber spreading module 1, a pre-oxidation device body 2, an air supply module 3, a laser module 4, an exhaust gas recovery module 5, an infrared temperature measurement module 6, an image monitoring module 7, a control module 8 and a host computer 9; under the control of the control module 8 and the host computer 9, the polyacrylonitrile fiber tow is widened by the fiber spreading module 1 and then enters the pre-oxidation device body 2, and is irradiated and heated by the laser module 4 inside the pre-oxidation device body 2, and the air supply module 3 supplies clean compressed air to the pre-oxidation device body 2 to promote the polyacrylonitrile The acrylonitrile fiber tow undergoes a chemical reaction, the tail gas recovery module 5 recovers the tail gas generated in the pre-oxidation stage and outputs it to an external incinerator for harmless treatment, the infrared temperature measurement module 6 measures the surface temperature of the polyacrylonitrile fiber tow at different pre-oxidation stages and sends the acquired temperature information to the control module 8 and the host computer 9 for processing, the control module 8 controls the output power of the laser module 4 according to the acquired temperature information, the host computer 9 displays the temperature data measured by the infrared temperature measurement module 6, and the image monitoring module 7 monitors the color information of the polyacrylonitrile fiber tow and sends it to the host computer 9 for processing;

[0007] The fiber spreading module 1 is preferably an ultrasonic fiber spreading mechanism or a mechanical fiber spreading mechanism, which uniformly spreads the polyacrylonitrile fiber bundle to a set width under the control of the control module 8;

[0008] The pre-oxidation device body 2 is a supporting mechanism and a shielding shell of the polyacrylonitrile-based carbon fiber laser pre-oxidation device. The left and right ends of the shielding shell are respectively provided with a wire feeding port and a wire outlet. The widened polyacrylonitrile fiber bundle enters from the wire feeding port and is transmitted from the wire outlet. The upper and lower sides of the shielding shell both contain rectangular strip optical window glass for transmitting the laser beam output by the laser module 4, so that the laser beam can irradiate the upper and lower surfaces of the polyacrylonitrile fiber bundle.

[0009] The air supply module 3 is composed of an air compression pump, a multi-stage filter, a cold drying module and an air storage tank, which generates clean compressed air for replenishing compressed air into the shell of the pre-oxidation device body 2;

[0010] The laser module 4 is formed by arraying and splicing a plurality of medium- and long-wave infrared laser systems. The light spot after seamless splicing is a square or rectangular light band with uniform intensity distribution. The light band is irradiated on the upper and lower surfaces of the polyacrylonitrile fiber bundle through the optical windows on the upper and lower sides of the shielding shell, and outputs the corresponding laser power according to the control signal of the control module 8; the infrared laser system is composed of an infrared laser and a beam shaping device, preferably an infrared laser with a wavelength in the 2μm to 5μm band or the 9μm to 11μm band;

[0011] The exhaust gas recovery module 5 is composed of a motor with an impeller and a PVC pipe. The motor drives the impeller to rotate at high speed to suck the exhaust gas from the pre-oxidation device body 2 and output it to an external incinerator for harmless treatment.

[0012] The infrared temperature measurement module 6 is composed of a plurality of infrared temperature measurement sensors, which are evenly distributed along the direction of the polyacrylonitrile fiber tow and fixed on the upper surface of the shielding shell in the pre-oxidation device body 2, and are used to measure the surface temperature of the polyacrylonitrile fiber tow at different positions, and send the acquired temperature information to the control module 8 for processing. The host computer 9 displays the temperature measured by each infrared temperature sensor, so that the operator can obtain the heating temperature curve of the polyacrylonitrile fiber tow in the pre-oxidation stage.

[0013] The image monitoring module 7 is composed of a visible light camera and an imaging optical system, and is fixed to the upper side of the pre-oxidation device body 2 by screws, and is used to monitor the color information of different positions of the polyacrylonitrile fiber tow and send it to the host computer 9 for processing, so that the operator can observe the degree and state of pre-oxidation of the polyacrylonitrile fiber tow;

[0014] The control module 8 is a PLC control system, which is used to control the operation of the fiber spreading module 1, the air supply module 3 and the tail gas recovery module 5, collect the temperature information of the infrared temperature measurement module 6, and control the laser power output by the laser module 4 according to the temperature information;

[0015] The host computer 9 is a computer, which is used to process and display information from the infrared temperature measurement module 6, the image monitoring module 7 and the control module 8, and send a control signal to the control module 8.

[0016] Beneficial effects: The present invention provides a method and device for laser pre-oxidation of polyacrylonitrile-based carbon fiber, which adopts infrared laser heating in the 2μm-5μm band or the 9μm-11μm band, overcoming the problem of selective absorption of laser wavelength by polyacrylonitrile fiber. The pre-oxidation device can accurately control the pre-oxidation heating temperature curve and heating area of ​​the polyacrylonitrile fiber bundle, and monitor the degree and state of pre-oxidation of the polyacrylonitrile fiber bundle in real time. It has the advantages of high energy utilization rate, small equipment size, and precise control of the heating area and heating temperature curve, which is beneficial to improving the quality, production efficiency and production capacity of the pre-oxidation of polyacrylonitrile fiber, and reducing energy consumption and manufacturing costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is a schematic diagram of a polyacrylonitrile-based carbon fiber laser pre-oxidation device.

[0018] In the figure: 1-filament spreading module, 2-pre-oxidation device body, 3-air supply module, 4-laser module, 5-exhaust gas recovery module, 6-infrared temperature measurement module, 7-image monitoring module, 8-control module, 9-host computer. DETAILED DESCRIPTION

[0019] Example 1 A method and device for laser pre-oxidation of polyacrylonitrile-based carbon fiber.

[0020] The technical solution of the present invention is as follows:

[0021] A method for laser pre-oxidation of polyacrylonitrile-based carbon fiber is disclosed. The method comprises the following steps: using a medium- and long-wave infrared band laser spot to uniformly irradiate and heat the upper and lower surfaces of a polyacrylonitrile fiber bundle, and the polyacrylonitrile fiber bundle absorbs the irradiated laser energy and rapidly heats up to a set pre-oxidation temperature; in order to ensure sufficient pre-oxidation time, a plurality of laser spots with uniform intensity distribution are spliced ​​into a long strip-shaped uniform spot along the moving direction of the polyacrylonitrile fiber bundle; the intensity of each laser spot is adjusted to achieve precise control of the irradiation heating temperature curve; the degree and state of pre-oxidation of the polyacrylonitrile fiber bundle are judged by monitoring the color of the polyacrylonitrile fiber bundle; the pre-oxidation temperature curve is obtained by measuring the temperature information at different positions along the direction of the polyacrylonitrile fiber bundle, and the irradiation laser power is controlled according to the comparison result of the measured temperature and the set temperature; at a specific moving speed v of the polyacrylonitrile fiber bundle, the product of the set pre-oxidation time and the moving speed v of the polyacrylonitrile fiber bundle is not greater than the length of the strip-shaped uniform spot, and the width of the strip-shaped uniform spot is not less than the width of the polyacrylonitrile fiber bundle.

[0022] As attached Figure 1 As shown, a polyacrylonitrile-based carbon fiber laser pre-oxidation device provided by the present invention comprises a fiber spreading module 1, a pre-oxidation device body 2, an air supply module 3, a laser module 4, an exhaust gas recovery module 5, an infrared temperature measurement module 6, an image monitoring module 7, a control module 8 and a host computer 9; under the control of the control module 8 and the host computer 9, the polyacrylonitrile fiber tow is widened by the fiber spreading module 1 and then enters the pre-oxidation device body 2, and is irradiated and heated by the laser module 4 inside the pre-oxidation device body 2, and the air supply module 3 supplies clean compressed air to the pre-oxidation device body 2 to promote the polyacrylonitrile The acrylonitrile fiber tow undergoes a chemical reaction, the tail gas recovery module 5 recovers the tail gas generated in the pre-oxidation stage and outputs it to an external incinerator for harmless treatment, the infrared temperature measurement module 6 measures the surface temperature of the polyacrylonitrile fiber tow at different pre-oxidation stages and sends the acquired temperature information to the control module 8 and the host computer 9 for processing, the control module 8 controls the output power of the laser module 4 according to the acquired temperature information, the host computer 9 displays the temperature data measured by the infrared temperature measurement module 6, and the image monitoring module 7 monitors the color information of the polyacrylonitrile fiber tow and sends it to the host computer 9 for processing;

[0023] The fiber spreading module 1 is an ultrasonic fiber spreading mechanism or a mechanical fiber spreading mechanism, which uniformly spreads the polyacrylonitrile fiber bundle to a set width under the control of the control module 8;

[0024] The pre-oxidation device body 2 is a supporting mechanism and a shielding shell of the polyacrylonitrile-based carbon fiber laser pre-oxidation device. The left and right ends of the shielding shell are respectively provided with a wire feeding port and a wire outlet. The widened polyacrylonitrile fiber bundle enters from the wire feeding port and is transmitted from the wire outlet. The upper and lower sides of the shielding shell both contain rectangular strip optical window glass for transmitting the laser beam output by the laser module 4, so that the laser beam can irradiate the upper and lower surfaces of the polyacrylonitrile fiber bundle.

[0025] The air supply module 3 is composed of an air compression pump, a multi-stage filter, a cold drying module and an air storage tank, which generates clean compressed air for replenishing compressed air into the shell of the pre-oxidation device body 2;

[0026] The laser module 4 is formed by arraying and splicing a plurality of medium- and long-wave infrared laser systems. The light spot after seamless splicing is a square or rectangular light band with uniform intensity distribution. The light band is irradiated on the upper and lower surfaces of the polyacrylonitrile fiber bundle through the optical windows on the upper and lower sides of the shielding shell, and outputs the corresponding laser power according to the control signal of the control module 8; the infrared laser system is composed of an infrared laser and a beam shaping device, and the wavelength output by the infrared laser is in the 2μm to 5μm band or the 9μm to 11μm band;

[0027] The exhaust gas recovery module 5 is composed of a motor with an impeller and a PVC pipe. The motor drives the impeller to rotate at high speed to suck the exhaust gas from the pre-oxidation device body 2 and output it to an external incinerator for harmless treatment.

[0028] The infrared temperature measurement module 6 is composed of a plurality of infrared temperature measurement sensors, which are evenly distributed along the direction of the polyacrylonitrile fiber tow and fixed on the upper surface of the shielding shell in the pre-oxidation device body 2, and are used to measure the surface temperature of the polyacrylonitrile fiber tow at different positions, and send the acquired temperature information to the control module 8 for processing. The host computer 9 displays the temperature measured by each infrared temperature sensor, so that the operator can obtain the heating temperature curve of the polyacrylonitrile fiber tow in the pre-oxidation stage.

[0029] The image monitoring module 7 is composed of a visible light camera and an imaging optical system, and is fixed to the upper side of the pre-oxidation device body 2 by screws, and is used to monitor the color information of different positions of the polyacrylonitrile fiber tow and send it to the host computer 9 for processing, so that the operator can observe the degree and state of pre-oxidation of the polyacrylonitrile fiber tow;

[0030] The control module 8 is a PLC control system, which is used to control the operation of the fiber spreading module 1, the air supply module 3 and the tail gas recovery module 5, collect the temperature information of the infrared temperature measurement module 6, and control the laser power output by the laser module 4 according to the temperature information;

[0031] The host computer 9 is a computer, which is used to process and display information from the infrared temperature measurement module 6, the image monitoring module 7 and the control module 8, and send a control signal to the control module 8.

[0032] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for laser pre-oxidation of polyacrylonitrile-based carbon fiber, characterized in that The method is to use a medium- and long-wave infrared band laser spot to uniformly irradiate and heat the upper and lower surfaces of a polyacrylonitrile fiber bundle, and the polyacrylonitrile fiber bundle absorbs the irradiated laser energy and quickly heats up to a set pre-oxidation temperature; to ensure sufficient pre-oxidation time, multiple laser spots with uniform intensity distribution are spliced ​​into a long strip-shaped uniform spot along the movement direction of the polyacrylonitrile fiber bundle; the intensity of each laser spot is adjusted to achieve precise control of the irradiation heating temperature curve; the degree and state of pre-oxidation of the polyacrylonitrile fiber bundle are judged by monitoring the color of the polyacrylonitrile fiber bundle; the pre-oxidation temperature curve is obtained by measuring the temperature information at different positions along the direction of the polyacrylonitrile fiber bundle, and the irradiation laser power is controlled according to the comparison result of the measured temperature and the set temperature; under a specific movement speed v of the polyacrylonitrile fiber bundle, the product of the set pre-oxidation time and the movement speed v of the polyacrylonitrile fiber bundle is not greater than the length of the strip-shaped uniform spot, and the width of the strip-shaped uniform spot is not less than the width of the polyacrylonitrile fiber bundle; The device used in the polyacrylonitrile-based carbon fiber laser pre-oxidation method comprises a fiber spreading module (1), a pre-oxidation device body (2), an air supply module (3), a laser module (4), an exhaust gas recovery module (5), an infrared temperature measurement module (6), an image monitoring module (7), a control module (8) and a host computer (9); The wire spreading module (1) is an ultrasonic wire spreading mechanism or a mechanical wire spreading mechanism; The pre-oxidation device body (2) is a supporting mechanism and a shielding shell of the device used in the polyacrylonitrile-based carbon fiber laser pre-oxidation method, and the left and right ends of the shielding shell are respectively provided with a wire feeding port and a wire outlet, and the upper and lower sides of the shielding shell both contain rectangular strip-shaped optical window glass; The air supply module (3) is composed of an air compression pump, a multi-stage filter, a cold drying module and an air storage tank; The laser module (4) is formed by arraying and splicing a plurality of medium- and long-wave infrared laser systems. The light spot after seamless splicing is a square or rectangular light band with uniform intensity distribution. The light band is irradiated onto the upper and lower surfaces of the polyacrylonitrile fiber bundle through the optical windows on the upper and lower sides of the shielding shell. The infrared laser system is composed of an infrared laser and a beam shaping device, and is an infrared laser with a wavelength in the 2μm to 5μm band or the 9μm to 11μm band. The exhaust gas recovery module (5) is composed of a motor with an impeller and a PVC pipe; The infrared temperature measurement module (6) is composed of a plurality of infrared temperature measurement sensors, which are evenly distributed along the direction of the polyacrylonitrile fiber bundle and fixed on the upper surface of the shielding shell of the pre-oxidation device body (2); The image monitoring module (7) is composed of a visible light camera and an imaging optical system, and is fixed to the upper side of the pre-oxidation device body (2) by screws; The control module (8) is a PLC control system; The host computer (9) is a computer.

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