RU2639910C1 - Laboratory line of production and research of carbon fibres - Google Patents

Abstract

FIELD: technological processes.

SUBSTANCE: line includes two interconnected independent units: a thermal chamber for oxidative thermostabilization of polymer fibres up to 300°C, a through furnace for treatment of oxidized polymer fibres from 800 to 3200°C and an aggregate for possible finishing of the carbon fibre produced. The thermal chamber unit contains a thermostatically controlled sealed thermal chamber 1 with a temperature control system configured to control the temperature of the walls and the supply air according to a predetermined program in an automatic mode, a system 4 of fibre feeding, receiving and holding, equipped with a worm gear, a heated air supply system including an air pump 3 and a heater 2, a fibre tension measuring system comprising of a device 6 for fixing the deformation changes in the fibre, a roller 7 and a weight 8 for creating the required load. The through furnace unit of the oxidized polymer fibre heat treatment includes a heat treatment furnace body, divided into a precarbonization furnace 9 and a carbonization furnace 10, hermetically connected to each other, a system for fixing and controlling the temperature in the furnace, a system for removing and neutralizing the thermal destruction gases, a fibre feeding system containing a creel 11 and seven-rolls 13, a system for receiving fibre from the furnace, including the seven-rolls 13 and a receiving-winding device 12, a roll speed control system, a tension force measuring system and an inert gas supply system including a container 15. The apparatus for finishing the produced carbon fibre comprises of an impregnating bath 19, three-rolls 18 and a drying oven 20.

EFFECT: study of the mechanism of thermostabilization, carbonization and graphitization, improvement of fibre characteristics.

5 cl, 6 dwg

Description

The invention relates to equipment for the production of carbon fibers from polyacrylonitrile flagella (PAN fibers), in particular to the production of high-strength and high-modulus carbon fibers used for the production of high-quality composites, as well as the study of PAN fibers and oxidized PAN fibers during the development of oxidative thermal stabilization modes ( oxidation), carbonization in the production of high-strength carbon fibers, and subsequently graphitization in the production of high-modulus carbon fibers.

The present invention relates to laboratory lines for studying the characteristics of PAN fibers, chemical and structural transformations during the pyrolysis of PAN fibers into carbon fibers in the temperature range of 100-3200 ° C, namely, equipment and instruments for research.

A device for producing carbon fibers is known, comprising a sealed chamber, working bodies located therein for transporting the fiber through it, and means for removing heat generated during the oxidation of the fiber, having distinctive features in that the chamber is thermostatically controlled, the working bodies are made in the form of surface drums, and means for heat dissipation are made in the form of ribs, with heat conductivity uneven along the length, installed in different quantities at the ends of the drum. Means for heat removal are made in the form of fixed plates connected by means of heat-conducting elements to the walls of the chamber, or fixed tubes, the ends of which extend outside the chamber, and their cavity is in communication with the atmosphere. The drums are mounted on the axes installed in the cooled bearings [1].

The disadvantage of this device is the increased power consumption and complex design. In addition, with such a device design, it is practically impossible to carry out the necessary deformation of the fiber. One-sided contact heating leads to an undesirable temperature gradient along the thickness of the bundle and the formation of surface defects of the fiber when sliding along the heating surface due to natural shrinkage.

A known chamber for continuous temperature processing of long fibrous material [2], where the heating of the working space is carried out by resistive heating elements, which can be made in the form of heating elements of a direct or U-shape, in the form of electrically conductive nets, in particular from a nichrome or stainless metal mesh with with a wire diameter of 0.1-2 mm and a mesh size of 0.5-2 mm. The supply of a gas medium heated to a temperature of 200-220 ° C, into the working space of the chamber is carried out under a pressure exceeding the pressure in the working channels of the chamber.

The disadvantages include: the unevenness of the temperature field inside the furnace channel in the case of using resistive heating elements, which can be made in the form of direct or U-shaped heating elements, and when using electrically conductive nichrome or stainless metal mesh, the possibility of local overheating on the heating grid surface.

A known method of producing carbon fiber from a polyacrylonitrile precursor, having several successive stages [3]. The first stage: oxidative thermal stabilization. The stage consists in low-temperature processing up to 300 ° C, in air, in a continuous furnace. Second stage: carbonation. The stage consists in high-temperature processing in the temperature range 800-1600 ° C of the oxidized precursor in an inert medium. Third stage: graphitization. The stage consists in high-temperature processing from 2400 ° C, in an inert environment, in the case of using a continuous furnace, with high force on the thread. Fourth stage: sizing. The stage is final and consists in applying a protective coating to the surface of the carbon fiber, after stages 2 or 3, to maintain the integrity, presentation and convenience of further processing, depending on the need.

The disadvantages are the high complexity of the manufacture of pigtail nodes, the inability to reproduce the graphitization mode, with this method of tying. The use of finished high-strength carbon fibers. A known carbonization furnace for producing carbon fiber materials [4], comprising a housing, a muffle, a heat exchanger, heating elements, pipelines for cold and hot inert gas and pyrolysis products, a device for refueling bundles of processed material and gas closures, characterized in that the furnace body is formed coaxially arranged set of unified cylindrical modules with muffles, connected by means of movable joints, at the ends of which are made overlapped by gas valves slots for entry and exit of the bundles of the processed material, the device for refueling the bundles is made in the form of endless strings stretched on the guide rollers, the upper branch of which is located in the housing, the lower branch is underneath. Each muffle is equipped with a graphite insert installed with a gap with graphite locking rings forming a cavity connected by pipelines of hot inert gas and gaseous pyrolysis products, while the insert is made with through pair openings, the axes of each pair of which are arranged to intersect in the middle of a horizontal plane passing through slots for entry and exit of harnesses. It contains a heat exchanger connected to the pipeline for the removal of gaseous products of pyrolysis.

The disadvantages are the design complexity, high energy costs for this type of work associated with a long heating time of the furnace, low achievable carbonization temperatures.

The closest technical solution (prototype) is an automated system for researching chemical fibers [5], including a heat chamber, a system for measuring the tension of a thread, a temperature control system in a heat chamber, a system for collecting, processing and presenting information, and a feed system for a heat chamber is introduced into it, a system receiving a thread from a heat chamber, for example, rollers with an electric drive, a system for controlling the angle of the rollers of the system for supplying the thread to the heat chamber, a system for controlling the speed of the system rollers the filing of the thread into the heat chamber, the control system of the angle of rotation of the rollers of the system for receiving the thread from the heat chamber, the speed control system of the rollers of the system for receiving the filament from the heat chamber, the system for controlling the tension of the thread, the program control system, and the temperature control system in the heat chamber, the angle of the roll position of the system the heat chamber, the speed of the rollers of the system for supplying the thread to the heat chamber, the angle of rotation of the rollers of the system for receiving the thread from the heat chamber, the speed of the rollers of the system for receiving the thread from the heat chamber, m yarn tension is obtained from the task program control system implementing the automated execution of programs investigating the characteristics of chemical fibers.

An automated chemical fiber research system is intended only for oxidative thermal stabilization of polymer chemical fibers. In addition, the disadvantages are the very complex design and hardware design of the automated system. Research requires a long continuous thread, there is no removal and neutralization of polymer thermal degradation gases, and there is no system for heating and air supply to the heat chamber.

An object of the invention is to intensify the process of oxidation, carbonization and graphitization, a more detailed study of the mechanism of oxidative thermal stabilization, carbonization and graphitization in all temperature conditions, more suitable for laboratory studies to reduce energy and material costs, increase the uniformity of the characteristics of the resulting fiber, as close as possible to industrial processes.

The invention allows to obtain directly carbon fiber samples, and to study, evaluate the structural characteristics of polymers, obtained semi-finished products and the final product, as well as directly control the parameters of the processes [6-10].

This goal is achieved by the fact that in the proposed solution, the laboratory line for research and production of carbon fibers includes two interconnected independent units: a heat chamber for oxidative thermal stabilization of polymer fibers up to 300 ° C, a continuous furnace for heat treatment of oxidized polymer fibers from 800 to 3200 ° C and a unit for possible dressing the resulting carbon fiber. A heat chamber assembly for oxidative thermal stabilization of a polymer fiber, comprising a thermostatic heat chamber with a temperature control system, a fiber supply, reception and retention system, a heated air supply system, characterized in that the heat chamber is sealed with the ability to control the temperature of the walls and the air entering it according to a predetermined program in automatic mode, while the unit contains a fiber tension measurement system, and the fiber supply, reception and retention system is equipped with yachnoy transmission. In this case, the heat chamber body has an additional shell for pumping the coolant. A heating element in the form of a spiral is located outside the housing. An assembly of a heat-treated oxidized polymer fiber heat treatment furnace, comprising a heat treatment furnace body, a furnace fixation and temperature control system, a thermal destruction gas removal and neutralization system, a fiber feed system and a fiber receiving system from the furnace, including electric driven rollers, characterized in that the heat treatment furnace divided into a pre-carbonization furnace and a primary heating furnace, hermetically connected to each other, with the removal of volatile components of thermal destruction, while the unit contains a system his speed control rollers, force measurement system and the fiber tension system Inerney feed gas into the furnace.

In FIG. 1 shows a diagram of a laboratory line for the study and production of carbon fibers (line and aggregates in statics).

The laboratory line for research and production of carbon fibers consists of a heat chamber unit for thermal stabilization of polymer fiber, a unit of a continuous heat treatment furnace, and a unit for possible sizing of carbon fibers (Fig. 1). A diagram of a heat chamber assembly for thermal stabilization of a polymer fiber is shown in FIG. 2.

The heat chamber unit for thermal stabilization of the polymer fiber is heated, for example, with a nichrome spiral body 1, body 1 of the heat chamber can have an additional casing for pumping liquid coolant (not shown in the diagram), it has a heat protection layer on the outside, it is blown through with air heated in air heater 2, which is pumped into it by air by the pump 3. The temperature in the heat chamber and air heater is fixed by thermocouples and controlled by a regulator, for example, “Thermodat 19-E3”, using a power installation, the diagrams listed below no items and equipment specified. On the air injection side, the heat chamber body is closed, but has an opening for the transport fiber filament and an opening for injecting hot air. On the other side of the heat chamber, a removable diffuser is installed, not shown on the diagram. Gases of thermal destruction are captured by the ventilation hood 5, which communicates with the filter-neutralizer, not shown in the diagram. The length of the sample is measured between nodes, before and after oxidation. The sample is supplied and held by the device 4 to the heat chamber 1, deformation changes in time are recorded on the device 6. The transport fiber thread is passed through the roller 7, the load 8 is attached to it, to create the required load. After the completion of the oxidation process, it is possible to withdraw the test sample from the heat chamber to study the structure and properties of the obtained product.

The assembly diagram of a continuous heat treatment furnace for threads from 800 to 3200 ° C is shown in FIG. 3.

The assembly of a continuous furnace for heat treatment of threads consists of: a pre-carbonization furnace 9; carbonization (graphitization) furnaces 10; creel for feeding bundles 11, creel has several removable devices that have brake clutches (not shown in the diagram); receiving-winding device 12; giving and receiving Semivalians 13; converter 14; inert gas tanks 15; air capacity 16; gas shutter 17. The assembly of a continuous furnace for heat treatment of filaments from 800 to 3200 ° C further comprises a system for fixing and controlling the temperature in the furnace, a system for supplying inert gas to the furnace, and a system for removing and neutralizing thermal destruction gases, a fiber supply system, and a fiber receiving system from the furnace, including electric driven rollers. This unit of a continuous fiber heat treatment furnace has several distinctive parameters, the precarbonization furnace is hermetically connected to the main heating furnace filled with one inert gas, such as nitrogen, argon, with the removal of volatile components of thermal decomposition from the precarbonization furnace, in order to maintain the purity of the gas medium in the main heating furnace, except of this, it contains a roller speed control system and a system for measuring the tension force of the fiber.

The load on the heat-treatable oxidized PAN fiber can be controlled not only by the difference in the speeds of the feeding and receiving mechanisms, but also by controlling the deformation of the fiber in the zones of preliminary and main heating by temperature changes in these zones. It is known that the deformation of oxidized fiber obtained as a result of its heat treatment depends on the temperature level, heating rate, and exposure time [6]. In this unit, the change in deformation in the zones of the main and preheating in the fiber section between the receiving and feeding devices is summed up, thereby determining the change in the load on the fiber depending on the heating conditions in these zones. In FIG. 6 shows the change in the load on the oxidized fiber depending on the heating conditions in the preliminary and main heating zones. At temperatures up to 1550 ° C, the total deformation shrinks with increasing temperature, which leads to an increase in load, however, at temperatures above 1600 ° C, the nature of the deformations changes due to an increase in temperature and heating rate, as a result, the total shrinkage decreases. which leads to a decrease in the load on the fiber at the same speed of the feed and receiving rollers. With increasing temperature of the preheating zone, the total load decreases, and its maximum shifts toward lower temperatures.

A diagram of an aggregate for possible sizing of carbon fibers is shown in FIG. 4. The production of high-strength or high-modulus carbon fiber may additionally include applying a sizing agent with the installation of an additional heating zone - for drying the fiber with a sizing agent. The installation includes the steps of: an additional option - refueling the processed flagellum through three rollers 18; impregnation bath 19; passing through the drying oven 20; and further to the receiving-winding device 12.

The laboratory line of research and production of carbon fibers works as follows (the line in dynamics in work).

In examples of direct (specific) application, PAN-based polymer fibers, thermostabilized PAN-fibers and PAN-based carbon fibers of a limited length, from 0.5 to 500 meters were used

For broaching, the test sample (s) is tied according to the method (3). A carbon fiber, for example, T-700 or others, is used as a transport elastic fiber. A test sample of a polymer fiber based on PAN from 0.5 to 2.0 meters in length is tied to an elastic transport fiber that is wound on a feed-extracting device 4. On the other hand, a similar elastic transport fiber passed through the roller 7, on which the load 8 is attached to create the required load, and an extension measurement sensor 6 are tied in the same way.

The sample is located outside the heat chamber unit for thermal stabilization. The housing 1 of the heat chamber is heated by a spiral heater, for example, a nichrome one located outside the housing, or it is heated with a liquid coolant, at the same time it is blown with air heated in the heater 2 according to the established research program (enters the operating mode), the temperature of the heat chamber and air is recorded by thermocouples (not shown in the diagram) . When stabilizing the specific temperature established in the study, the sample is introduced by device 4 into the heat chamber at a speed of at least 500 m / h, stopped and maintained. In the system for feeding, receiving and holding fiber in a heat chamber, the drive feeding, receiving and holding fiber is carried out by means of a worm gear, which makes it possible to hold the fiber when rotation is stopped. Further, thermal stabilization is carried out according to the established research program, possibly as a change in temperature over time, and repeated introduction and retention of the sample in a heat chamber at different temperatures. The load is regulated by changing the load 8, the extension is fixed by the device 6. Gases of thermal destruction are captured and neutralized in the device 5.

The oxidized PAN fibers are heat-treated on the aggregate of a continuous heat treatment furnace for fiber from 800 to 3200 ° C in an inert medium, for example argon, nitrogen. The initial oxidized fiber is transported through a heating element having a high-temperature heating zone. The heat treatment furnace is divided into a pre-carbonization furnace and a main heating furnace, hermetically connected to each other, with the removal of volatile components of thermal decomposition from the pre-carbonization furnace, to maintain the purity of the gas medium in the main heating furnace. The maximum temperature in the pre-carbonization furnace is 800 ° C, and in the main heating furnace 3200 ° C. The type of heating element installed in the continuous furnace of the fiber heat treatment unit makes it possible to maintain a temperature from 2800 ° C to 3200 ° C for a long time. Transportation is carried out by passing the fiber through the feeding and receiving mechanisms 13 (using mechanisms such as the Semivlets 13 with or without electric actuators using the brake clutch on the feeding creel and in the receiving-winding device) with different speeds of the feeding and receiving mechanisms. The transportation of the initial fiber is carried out with the application of a load on it due to the difference in the speeds of the feeding and receiving mechanisms in the load range F = 0.1-0.3 g / tex at carbonization temperatures [11, 12]. Under graphitization conditions, the load on the processed carbon fiber is maintained within the range of F = 0.1–4.0 g / tex [13, 14].

It is possible to use one transport fiber filament, but then the requirements for the physicomechanical properties of the transport fiber filament are quite large. The fiber thread should have a high load factor in the loop. When using one transport fiber filament, the probability of its destruction when tying a filament with samples of the studied fibers to it or slipping a knot along the transport filament of a fiber when passing a knot through the hot zone of the furnace increases. Therefore, a method is also proposed using two transport filaments of low-quality carbon fiber (for example, UKN-5000 or T-300), which allows, in case of destruction of the oxidized PAN fiber strands in the carbonization furnace, not to stop the carbonization process, but to tie up the remaining studied strands fiber. If necessary, it is possible to twist the filament of an oxidized PAN fiber sample through two transporting filaments and heat treatment, then the properties of the obtained carbon fiber will not be maximum, and shrinkage will not be controlled.

In all cases, we use creel cord 11 for fiber supply, carbonization kilns 9-10, conveying conveyers 13 installed before and after the carbonization kiln, take-up device 12. The creel has several removable devices that have brake clutches (not shown on the diagram) . Fiber transport threads are installed on two seats of creel, fiber threads with samples on the third seat. A system for transporting fiber filaments is launched and a unit of a continuous heat treatment furnace is launched. When the unit furnaces enter the carbonization operating mode, a carbon fiber fiber is fastened to the transporting fiber filaments, with samples intertwined with this fiber filament through the transporting fiber filaments, as in the patent (3), followed by fixing by two nodes of FIG. 5. To successfully pass the bundle assembly through the installation, to eliminate the slippage effect, the load on the tied fiber thread should be reduced to a minimum. When the bundle assembly leaves the carbonization furnace, it should be strengthened with fiber transporting threads, for example, paper tape, and the required load should be set. If necessary, the transporting filaments can be cut and removed.

Obtaining a high-strength or high-modulus carbon fiber may additionally include applying a sizing with the installation of an additional heating zone - for drying the fiber with a sizing.

The invention allows: to obtain direct and indirect estimates of the parameters of the structure of polymers at all stages of oxidation and to directly control the structural characteristics of polymers; to carry out oxidative thermal stabilization on samples of PAN fibers of limited length (up to 2000 mm), with full simulation of the oxidative thermal stabilization mode of an industrial multi-pass furnace.

The pre-measured length of the oxidized PAN fibers and the subsequent measurement of the length of the obtained carbon fibers make it possible to control the change in the linear dimensions of the samples of oxidized PAN fibers during carbonization and to carry out their further comparison.

Carrying out the process of carbonization of samples of oxidized PAN fibers, upon receipt of carbon fiber, using transporting fiber fibers makes it possible to fully investigate both the initial parameters of oxidized PAN fibers and the final product, carbon fiber.

Information sources

1. RF patent No. 2089680, publ. 09/10/1997. "A method of producing carbon fiber and a device for its implementation", D01F 9/22.

2. RF patent No. 2423561, publ. 07/10/2011. “Chamber for continuous heat treatment of long fibrous material”, D01F 9/22.

3. RF patent No. 2534794, publ. 09/27/2014. "A method for bonding a fibrous PAN material during the steps of producing carbon fiber from it," D01F 9/22.

4. RF patent No. 2046846, publ. 10/27/1995. “Carbonization Furnace for Carbon Fiber Materials,” D01F 9/22.

5. RF patent No. 2375294, publ. 12/10/2009. Automated Chemical Fiber Research System, D01F 9/22.

6. Konkin A.A. Carbon and other heat-resistant fibrous materials. M., Chemistry, 1974, 374 p.

7. Carbon fibers and carbon composites: Per. from English / Ed. E. Fittser. - M .: Mir, 1988 .-- 336 p., Ill.

8. The structure, properties and technological production of carbon fibers: Sat. scientific Art. / Aut. - comp. S.A. Podkopaev. Chelyabinsk. Chelyab. state Univ., 2006, 217 p.

9. Phase transformations, a change in the fine structure of the polyacrylonitrile thread in the process of thermal stabilization. Ed. Podkopaeva S.A., Bulletin of the Chelyabinsk State University, 2009 No. 8 (146). Physics, vol. 4, p. 48-53.

10. Morgan P. "Carbon Fibers and their Composites" // Taylor & Francis Group, LLC, 2005.

11. The influence of processing temperature in the range from 900 to 3200 ° C on the strength and modulus of elasticity of carbon fibers based on polyacrylonitrile [Text] / DB Verbets, L.M. Buchnev, Z.V. Eismont, V.M. Samoilov, D.V.Sergeev // News of higher educational institutions: "Chemistry and chemical technology." - 2014. - T. 57. - Issue. 5. - S. 43-48.

12. Verbets, D. B. Changes in the physicomechanical characteristics of hydrocarbons during carbonization of oxidized PAN fibers at different rates. [Text] / Verbets DB, Buchnev LM, Smyslov. A.I., Samoilov V.M., Eismont Z.V., Sergeev D.V. // 10th Int. conf. "Carbon: fundamental problems of science, materials science, technology." // 10th Int. conf. "Carbon: fundamental problems of science, materials science, technology." 2016 year

14. Verbets, D. B. Changes in physicomechanical characteristics of hydrocarbons at a temperature of 3000 ° C from the processing speed. [Text] / Verbets DB, Buchnev LM, Smyslov. A.I., Samoilov V.M., Eismont Z.V., Sergeev D.V. // 10th Int. conf. "Carbon: fundamental problems of science, materials science, technology." 2016 year

Claims (5)

1. The laboratory line for research and production of carbon fibers includes two interconnected independent units: a heat chamber for oxidative thermal stabilization of polymer fibers up to 300 ° C, a continuous furnace for heat treatment of oxidized polymer fibers from 800 to 3200 ° C; and an aggregate for possible sizing of the obtained carbon fiber. 2. A heat chamber assembly for oxidative thermal stabilization of a polymer fiber, comprising a thermostatically controlled heat chamber with a temperature control system, a fiber supply, reception and retention system, a heated air supply system, characterized in that the heat chamber is sealed with the ability to control the temperature of the walls and the air entering it according to a predetermined the program in automatic mode, while the unit contains a fiber tension measurement system, and the fiber supply, reception and retention system is equipped with girth gear. 3. The heat chamber assembly for oxidative thermal stabilization of the polymer fiber according to claim 2, characterized in that the heat chamber body has an additional shell for pumping the coolant. 4. The heat chamber assembly for oxidative thermal stabilization of a polymer fiber according to claim 2, characterized in that a heating element in the form of a spiral is located outside the housing. 5. The assembly of a continuous furnace for heat treatment of oxidized polymer fiber, comprising a body of a heat treatment furnace, a system for fixing and controlling the temperature in the furnace, a system for removing and neutralizing thermal degradation gases, a fiber supply system and a fiber receiving system from the furnace, including electric driven rollers, characterized in that the heat treatment furnace is divided into a pre-carbonization furnace and a main heating furnace, hermetically connected to each other, with the removal of volatile components of thermal destruction, while the unit contains a roller speed control system, a fiber tension force measuring system, and an inert gas supply system to the furnace.

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