RU2171867C2 - Method and apparatus for collecting fibers drawn by gas flow from carbonaceous resin - Google Patents

Abstract

FIELD: production of fibers from carbonaceous resin. SUBSTANCE: method involves drawing fibers by means of at least one gas flow, with following additional drawing of fiber by additional gas flow creating stress in fiber, with flow rate of at least one additional gas flow exceeding fiber motion rate; directing fiber and additional gas flow through Venturi pipe and thermosetting fiber under stress. Additional gas flow may be exposed to dissipation by directing it and fiber through diffusion chamber, with following discharging and collecting of fiber. Resin may be heated to melting temperature and supplied into restrictor of fiber forming head. Apparatus has fiber-forming head having at least one restrictor with first carbonaceous resin inlet opening and second opening, from which carbonaceous resin is discharged in the form of fiber, device for exposing fiber discharged from restrictor to at least one fiber drawing gas flow, Venturi pipe arranged at distance of 0.5-254 cm under fiber-forming head and provided with through opening having open ends, and device for supplying second gas flow into first open end of through opening of Venturi pipe. Apparatus may be further equipped with diffusion chamber, which may be arranged under Venturi pipe. Fibers are produced from carbonaceous resins, including solvated mesophase resin. EFFECT: increased efficiency, simplified method and construction and enhanced reliability in operation. 13 cl, 2 dwg

Description

 The present invention provides a method and apparatus for collecting and stacking fibers pulled by a gas stream that are substantially free of kinks and kinks. In addition, the present invention provides a method and apparatus for collecting fibers in a substantially unmixed or two-dimensional configuration.

 Methods and devices for drawing fibers by a gas stream are well known. As you know, the material from which the fibers are obtained is heated to a temperature at which it becomes fluid. This material is then passed, usually under pressure, through a forming head that has one or more capillary holes. At the exit of the capillary from the material, fiber is obtained. The fiber emerging from the capillary is exposed to a drawing means, which is usually a gas. The stretching agent stretches or pulls the fiber, increasing its length and decreasing the diameter.

 Various types of forming heads are used to make fibers pulled by the gas stream. Typically, angle and slotted heads are used for this purpose. Angle and slotted heads differ in the type of direction of the fiber drawing gas to the fiber exiting the head. The present invention in this regard relates to all types of forming heads with fiber drawing by a gas stream.

 In known methods of drawing elongated fibers after elongation fall on the substrate. Depending on the composition of the material of the fibers, the latter are obtained to one degree or another curved or twisted and randomly assembled with each other into one three-dimensional bundle. One of the main reasons this depends on the occurrence of turbulence in the flow of fiber-drawing gas.

 Thus, the present invention provides a method and apparatus for stacking and collecting substantially straight fibers pulled by a gas stream. In addition, the method and apparatus of the present invention provide for relatively two-dimensional collection of fibers with little or no confusion with each other.

 The present invention provides a method and apparatus for stacking and collecting fibers pulled by a gas stream. In accordance with the method of the present invention, the material being pulled into the fiber is heated to a temperature sufficient to make it flowable. After reaching the required temperature, the material under pressure is passed through the forming head with the drawing of fibers by a gas stream. After passing the material under pressure through the capillary hole of the head, fiber is obtained from it. The resulting fibers are drawn by exposing them to a drawing agent. Typically, a gas stream is used as such a means.

 Although the above operations are well known in the art, the present invention nonetheless provides a method and apparatus for eliminating bending, twisting and tangling of fibers pulled by a gas stream. In accordance with the method of the invention, the fibers, after the initial drawing, enter the heat-setting zone and pass through it. To avoid bending and twisting, the fiber in this area should be straight.

 According to the present invention, the relatively rectilinear shape of the fiber during thermosetting is provided by the tension of the fiber, which reduces or completely neutralizes the effect of turbulence. In a preferred embodiment of the invention, the tension of the fiber is created by exposing it to a second gas stream during thermosetting. A second gas stream acts on the fiber either before, after, or during entry of the fiber from the venturi. Since the gas velocity of the second stream exceeds the velocity of the fiber, the fiber due to this remains relatively straight up to its final thermoset. Depending on the location of the second gas stream, the speed and properties of the material from which the fiber is obtained, the second gas stream can, to one degree or another, provide further elongation of the fiber. At this stage of the process, the resulting fiber is essentially completely thermoset and has virtually no bends or twists.

 The second gas stream may be a stream of gas, liquid, or even steam. In addition, the second gas stream may be not one but several separate gas streams. In the future, however, speaking of the composition and number of streams that create the tension of the fiber, we mean a second gas stream or a second gas stream.

 In the invention, by the heat-curing zone is meant the area where the heat-curing of the fiber takes place. The thermosetting zone is located on a site that is directly adjacent to the exit of the capillary and moves away at a certain distance from it. The actual length of the curing zone depends on the fiber drawing mode, the temperature of the second gas stream, and the nature of the feed. The curing zone may be within the venturi; however, it is usually not outside of it.

 After exiting the venturi, the fibers enter the diffusion chamber or section. In the diffusion chamber, the flow of the gas drawing fiber is dissipated. Due to this, in accordance with the present invention, the entanglement of the fibers is reduced when they are collected on a substrate located under the diffusion chamber and intended for laying the fibers.

 The present invention also provides a device for manufacturing relatively straight fibers pulled by a gas stream. This device also provides the collection of fibers with virtually no confusion with each other. The device has a venturi, diffusion chamber or section and a substrate for laying or collecting fibers.

 As you know, the forming head with the extraction of fibers by a gas stream has at least one fiber forming capillary hole. Typically, the number of capillaries in a head is limited only by economic considerations. In addition, the forming head with fiber exhaust gas flow has a device for directing the gas flow to the fibers leaving the capillaries.

 According to the present invention, a venturi is located under the forming head. This tube has a through hole in which the fiber emerging from the capillary enters. The venturi may have a device for creating a fiber-drawing second gas stream. Alternatively, an external device can be used to create a second gas stream, which directs the second gas stream along the fibers in the venturi. A second gas stream holds the thermoset fiber in a relatively straight state. In addition, the second gas stream further draws the fiber. The source of the second gas stream may be a blower, a vacuum pump, or other gas stream generating device.

 A diffusion chamber or zone is located under and / or adjacent to the venturi. The diffusion chamber provides gas flow dissipation without entangling the fibers. In the presence of a diffusion chamber, fibers without entanglement fall and collect on the substrate. The fibers obtained and collected by such a device are relatively straight and not mixed. The diffusion chamber or section can be performed as part of a venturi or as a separate device located next to the venturi.

 Proposed in the present invention, the device can also be equipped with an exhaust duct. The exhaust duct is located next to the diffusion chamber and is provided with a substrate. The form of the substrate can be different, including in the form of a conveyor belt for the continuous process of fiber production. Preferably, the substrate is porous with the possibility of gas passing through it while the fibers are on it.

 The device of the present invention can also provide for the presence of a vacuum pump connected to the exhaust duct. The vacuum created in the exhaust duct by means of a vacuum pump facilitates the collection of fibers in a two-dimensional format. In one embodiment of the invention, the vacuum pump provides for pumping through the venturi such an amount of air or gas that is sufficient to maintain a rectilinear configuration of the fibers. And finally, by connecting the vacuum pump to the forming head, you can use the pressure it creates to form all or part of the first gas stream used in the fiber drawing process.

 In FIG. 1 shows a side section of a device according to the invention, including a forming head, a venturi, a diffusion chamber, an exhaust duct and a fiber-laying substrate.

 In FIG. 2 shows a side section of a preferred embodiment of a venturi and diffusion chamber.

 The drawings show a device 10 according to the present invention for drawing and collecting relatively straight fibers into a relatively non-mixed two-dimensional format. The device 10 consists of a head 20 for forming fibers pulled by a gas stream, a venturi 40, a diffusion chamber 60, and a substrate 65 for laying the fibers. Proposed in the present invention, the device may have an exhaust chamber 80 and a device for creating a flow of moving gas (not shown). As such a device, you can use a vacuum pump, blower or other device designed for this purpose.

 As is known, in order to draw the fibers, the material from which they are obtained must be heated to a temperature sufficient for it to pass through the capillary hole. A device for heating the material pulled into the fiber can be positioned either outside the forming head or inside it. Since methods and devices for drawing a gas stream are well known, they are not described in detail. Such methods and devices are described in detail in US patent 3755527; 4,526,733; 4818463 and in the article "Superfine Thermoplastic Fibers", Van A. Wente, Industrial Engineering Chemistry, T. 48, p. 1342 (1956), which are incorporated herein by reference.

 A venturi 40 is located below the forming head 20. Typically, the venturi 40 is about fourteen inches or less in length. Depending on the feedstock from which the fiber is made, the venturi 40 and the forming head 20 can be made either in the form of a single unit, or in the form of two separate devices connected to each other. However, it is preferable, however, to leave some free space between the head 20 and the venturi 40 formed by the opening 27. The length of the opening 27 depends on factors such as determining the heat-curing properties of the elongated fiber and the degree of cooling by the second gas stream. Typically, the opening 27 has a length of approximately 0.25 to 100 inches. In the case, for example, when the fibers are pulled from the solvated mesophase resin, the length of the hole is approximately two to four inches. However, for other types of raw materials, the length of the hole may even exceed 100 inches. The preparation of solvated mesophase resin is described in US Pat. No. 5,259,947 and in US patent application 08/135204, filed October 12, 1993, entitled "Improved Method for the Preparation of Solvated Mesophase Resin", which are incorporated herein by reference.

 For carbon fiber drawn from a solvated mesophase resin, the area between the forming head and the venturi is usually a heat-curing zone of the fiber. However, for some fibers, their curing can also occur inside the venturi. As noted above, the thermoset zone is the area where the fiber becomes thermoset.

 The venturi 40 has a channel 42 extending along its entire length. Channel 42 has a first open end 41 and a second open end 43. Channel 42 is located under the capillary 22 and extruded fibers enter it. The venturi 40 may have two or more nozzles 44 and 45, through which a gas stream is directed to the passing fibers passing through the channel 42. Nozzles 44 and 45 can be made either protruding into the channel 42, or flush with its walls. Nozzles 44 and 45 communicate with a manifold 46 located inside the venturi 40. Compressed gas is supplied to the manifold 46 through channel 47 from an external source (not shown).

 In a preferred embodiment, and in particular when the fibers are drawn from the solvated mesophase resin, the device 10 is located inside a sealed chamber (not shown) with a neutral atmosphere. When pulling the fibers from the solvated mesophase resin, it is advisable to fill the sealed chamber with an inert gas, for example, nitrogen. In addition, in a preferred embodiment, it is advisable to supply compressed gaseous nitrogen to the venturi 40 through its open end 41. The gas, together with the extruded fiber, enters the tube and forms a second gas stream that physically stabilizes the fibers until they are completely thermoset. In this case, the second gas stream passing along with the fiber through the venturi 40 pulls the fiber and reduces or neutralizes the effect of turbulence on the fiber, which to one degree or another is the cause of kinks and twists in the fiber. Furthermore, in this preferred embodiment, as shown in FIG. 2, there is no need to place nozzles 44 and 45, manifold 46 and channel 47 inside the venturi.

 A diffusion chamber or section 60 adjacent to it is located under the venturi 40. In the diffusion chamber 60, into which thermally cured fiber enters from channel 42, gas flow is dissipated. As shown in the drawing, the diffusion chamber 60 has an inner channel 62, the cross-sectional area of which gradually increases from the first open end 63 adjacent to the channel 42 to the second open end 64. Such a gradual increase in the cross-sectional area of the channel around the fiber passing through the diffusion chamber 60 provides dissipation of the velocity and kinetic energy of the gas stream. Such a gradual dissipation of the energy of the second gas stream minimizes and virtually eliminates the occurrence of turbulence around the fiber.

 Obviously, the same effect can be achieved by other constructive solutions, in particular, by making a diffusion chamber with a constant cross section and gradually communicating with the atmosphere as it extends. Examples of such chambers are mesh or perforated chambers. In addition, the present invention provides a venturi and a diffusion chamber as one common unit. In addition, in some cases it may be necessary to heat the walls of the diffusion chamber 60 in order to avoid condensation of the monomer and / or solvent used to draw fibers or solvate them.

 A substrate 65 is located under the diffusion chamber 60. The substrate 65 is preferably configured so that a gas stream can freely pass through it. The substrate can be made in the form of a grid, plate or tape. The most appropriate is the implementation of the substrate 65 in the form of a conveyor belt, which, moving the fibers from the device 10, allows for a continuous process for the production of fibers. The device 10 can be made with an exhaust channel 80. If there is an exhaust channel 80, the substrate 65 is placed inside or, as shown in the drawing, passes through the channel 80. The exhaust channel 80 has an opening 83 that spans the end 64 of the diffusion chamber 60. Under the end 64 is located the substrate 65. The hole 83 allows the fibers to pass through the diffusion chamber 60 and enter the substrate 65. The exhaust duct 80 also has an opening 86 through which the gases are vented to the atmosphere. These gases can again come to the gas source, in which their pressure rises again, after which the compressed gas is supplied either to the forming head 20 or to the venturi 40. In the case when the substrate 65 is made in the form of a conveyor belt, the exhaust channel 80 is supplied seals 82 made in the form of rolling elements or other appropriate devices that allow the conveyor belt to pass through it along with the fibers collected on it when drawing through this gas channel, while the gas flow is not disturbed on channel 80.

 The device 10 may be provided with a system that allows gas to pass through it (not shown). This system must have a reduced pressure port and an overpressure port. Typically, a vacuum pump or blower is used to create a gas stream, the reduced pressure side of which through the exhaust port 86 communicates with the exhaust channel 80. In this design, the vacuum pump, among other things, allows gas to pass through the fibers collected on the substrate 65. The passage of gas through the fibers facilitates the collection of fibers in a two-dimensional format. The overpressure hole can be connected to a source of gas supplied to the molding head, by recirculating the gas used in the fiber drawing process.

 Below, with reference to the accompanying drawings, a method for laying and assembling on a substrate relatively straight untangled fibers pulled by a gas stream according to the present invention is described. According to the present invention, it is in particular provided for the manufacture of carbon fibers from solvated resin, including solvated mesophase resin. Further in the description, the issue of collecting fibers drawn from solvated mesophase resin is discussed in detail, however, it will be obvious to any person skilled in the art that the present invention may find application in other fields related to fiber drawing by gas flow.

 The process of the present invention begins by heating the material extruded into the fibers, in particular the solvated mesophase resin, to a temperature sufficient to allow it to pass through the capillaries in the forming head for drawing the fiber by a gas stream. Methods of heating and passing the material pulled into the fiber through the capillary are well known in the art and are not described in detail in this case. In addition, it is well known that at the outlet of the head capillary, the fiber drawn by the gas stream is exposed to the gas stream. In a conventional slit head, gas is directed to the fiber from at least two channels. In annular heads, gas passes through one channel, which is located around the capillary. In either case, the gas stream draws the fiber exiting the capillary. After stretching, the fiber becomes thinner and longer.

 When a gas stream extends fibers from a carbon resin, hitherto known methods generally produce curved and twisted carbon fibers. The reason for such kinks and twists of the fibers is the turbulence created by the flow of gas acting on the fiber. Since the formation of kinks and twists occurred before and during the thermosetting of the fiber, the finished fibers also turned out to be curved and twisted. Such fibers are very difficult to collect and usually a low-density three-dimensional mass consisting of entangled fibers is formed from them.

 Proposed in the present invention, the method allows for the collection of relatively straight fibers in a virtually untangled two-dimensional format. In accordance with this method, the fibers drawn out by the gas stream coming out of the molding head pass through the heat-curing zone, as described above, and enter the venturi. The movement of fibers inside the venturi takes place under the action of a second gas stream. Since the speed of the second gas stream exceeds the speed of movement of the fibers, the process of thermosetting takes place in fibers in which tension is created due to this difference in speeds. In other words, the second gas stream keeps the thermoset fibers in a relatively straightforward state.

 With a specific composition of the fibers, the thermosetting process usually takes place before they enter the venturi. However, regardless of the zone in which the curing of the fibers occurs, they, due to the tension created by the second gas stream, remain relatively straight and do not have kinks or twists. This is due to the fact that in the process of thermosetting under the action of the second gas stream, the fibers are in a tense state. In a preferred embodiment, the gas does not change the chemical composition of the fibers, however, a certain amount of solvent is removed from the fibers by the gas flow. Thus, the fibers are completely thermoset and remain straight while not having noticeable kinks and twists.

 Alternatively, as indicated above, a second fiber-acting gas stream can be created inside the venturi. The action of the second gas stream is similar to that described above and consists in creating tension in the fibers and holding them in a relatively straight position until complete thermosetting. In addition, with a certain composition of the material being pulled into the fibers, a second gas stream can provide further elongation or stretching of the fiber in the venturi.

 In order to reduce the cost of the resulting fiber, it is necessary in the process of its manufacture to exclude the possibility of entanglement of the fiber during its accumulation on the substrate. To reduce or preferably completely eliminate the entanglement of the thermoset fiber in accordance with the present invention, the fiber is passed through a diffusion chamber or section. As noted above, the kinetic energy of the second gas stream dissipates in the diffusion chamber. As a result of this, the fibers fall onto the substrate non-mixed and are collected on it in a relatively flat two-dimensional format. Preferably, the substrate is porous so that the gas can pass through the fibers collected on it.

 Alternatively, the method of the invention provides for the use of an exhaust duct in communication with a vacuum pump or blower. In accordance with this embodiment, the fibers passing through the diffusion chamber are collected on a porous substrate located inside the exhaust duct. In a preferred embodiment, the substrate is in the form of a conveyor belt that moves the fibers from the exhaust channel through a seal made in the form of a rolling element or a casing under vacuum.

 The vacuum pump is usually connected to the exhaust duct so that a vacuum can be created inside the exhaust duct. In this case, the vacuum pump pumps additional gas through the fibers collected on the substrate. Thus, the vacuum pump facilitates the collection of fibers on the substrate in a two-dimensional format.

 In addition, the vacuum pump together with the venturi prevents the formation of turbulence around the fiber and eliminates the need to create a second gas stream inside the venturi. In this embodiment of the invention, the vacuum pump pumps a sufficient amount of gas or air through an opening located between the forming head and the venturi, preventing the formation of turbulence around the fiber flowing around the second gas stream, which is created in this case by means of reduced rather than increased pressure. A second gas stream flows inside the venturi along the fiber and holds it in a straightforward state until complete cure. Finally, the use of a vacuum pump allows gas recirculation to anywhere in the system.

 Based on the above description and in the practical implementation of the present invention, for a person skilled in the art, other variants of the proposed device and method are obvious. It should be borne in mind that in the description were considered only examples of the possible implementation of the invention, the main idea and essence of which are set forth in the claims.

Claims (13)

 1. A method of producing relatively direct fibers drawn by a gas stream, comprising drawing fibers from a carbon resin gas stream using at least one gas stream to draw fibers; the subsequent stretching of the fiber by exposing it to at least one additional gas stream creating tension in the fiber, wherein the speed of at least one additional gas stream exceeds the fiber speed, followed by passing the fiber and additional gas stream through the venturi; and thermosetting under tension fiber.  2. The method according to claim 1, further comprising dissipating at least one additional gas stream by passing it and the fiber through a diffusion chamber; fiber withdrawal from the diffusion chamber and fiber collection.  3. The method according to claim 1, in which the fiber is drawn from the solvated mesophase resin.  4. A method of producing relatively direct fibers drawn by a gas stream, comprising heating a carbon resin to a temperature sufficient to make the resin flow, subsequent fiber formation by feeding this resin into the forming fiber by pulling the head and passing it through the capillary existing in the head, stretching the fiber emerging from the capillary by exposing it to at least one stream of pulling gas, characterized in that the subsequent stretching of the fiber by at least one additional gas stream creating tension in the fiber, and the speed of at least one additional gas stream exceeds the speed of the fiber, followed by passing the fiber and additional gas stream through the venturi and thermosetting the fiber in a relatively straight state .  5. The method according to claim 4, further comprising dissipating at least one additional gas stream by passing it and the fiber through a diffusion chamber; fiber withdrawal from the diffusion chamber and fiber collection.  6. The method according to claim 4, in which the fiber emerging from the capillary passes a certain distance before exposure to at least one additional gas stream begins.  7. Device for drawing fibers by a gas stream from a carbon resin, comprising a forming head for drawing fibers by a gas stream, having at least one capillary with a first hole through which a carbon resin enters the capillary, and a second hole from which this resin is in the form of fiber leaves the capillary, and a device for influencing the fiber leaving the capillary with at least one stream of drawing gas; a venturi located under the head forming the fiber by drawing in a gas stream, the distance between the venturi and the forming head being about 0.25-100 inches and this venturi has a through channel, this channel having first and second open ends, the first the open end is positioned so that it enters the fiber emerging from the forming head; also a device for supplying a second gas stream to the first open end of the through channel of the venturi.  8. The device according to claim 7, further comprising a diffusion chamber located under the venturi; moreover, this diffusion chamber has a first open end located below the second open end of the through channel of the venturi, and a second open end through which the fiber exits the diffusion chamber.  9. The device according to claim 8, in which the inner diameter of the diffusion chamber gradually increases from the minimum diameter at the first open end to the maximum diameter at the second open end.  10. The device of claim 8, which further has a substrate located under the second open end of the diffusion chamber.  11. The device of claim 8 which is located inside the sealed chamber.  12. The device according to claim 11, in which there is a neutral atmosphere inside the sealed chamber.  13. The device according to claim 8, in which the venturi and diffusion chamber are made in the form of a single unit.

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