A method for producing coal-based pitch-based melt-blown carbon fiber

Abstract

The present invention discloses a method for producing coal-based pitch-based meltblown carbon fibers, belonging to the field of novel carbon material preparation. Specifically, coal-based spinning pitch is used as raw material, heated by a screw extruder, and then passed through a spinneret under gravity and slight positive pressure to obtain meltblown carbon fiber precursor. The carbon fibers are then oxidized and carbonized to produce the coal-based pitch-based meltblown carbon fibers. This method offers a simple production process and low cost, and the resulting meltblown carbon fibers possess stable and excellent physical, chemical, and mechanical properties.

Description

Technical Field

[0001] The present invention relates to the technical field of novel carbon material preparation, and more particularly to a method for producing coal-based pitch-based melt-blown carbon fibers. Background Art

[0002] Currently, domestic research and development of asphalt-based general-grade carbon fibers include the Anshan Institute of Thermal Energy, the Shanxi Coal Chemistry Research Institute of the Chinese Academy of Sciences, and the Petrochemical Research Institute. However, the only company currently engaged in mass production is Anshan Senoda, which imported a 200-ton annual production line from Ashland Petroleum Company in the early 1990s. The Shanxi Coal Chemistry Research Institute of the Chinese Academy of Sciences was the first in China to conduct research on asphalt-based general-grade carbon fibers, and its production has passed both small-scale and pilot-scale tests. The Petrochemical Research Institute has also made significant progress in research on asphalt-based general-grade carbon fibers. Its production technology has been evaluated, meeting all expected performance indicators, and an annual production capacity of 1-5 tons of asphalt-based general-grade carbon fibers has been approved. While domestic production of asphalt-based general-grade carbon fibers has been successfully developed, it should be noted that all domestic manufacturers are currently in the pilot-scale scale-up phase, far from reaching industrial scale. Consequently, production volumes are far from meeting domestic demand.

[0003] Although my country's asphalt-based general-grade carbon fiber has undergone a period of development, there is still a significant gap in technological level compared to foreign countries. This has led to problems such as high impurity content in the precursor, unstable carbon fiber production, and single carbon fiber specifications. Currently, the production cost of domestic asphalt-based general-grade carbon fiber is high and expensive, and has not yet achieved economic scale. The present invention provides a production method for melt-blown carbon fiber, which will break the foreign blockade of similar products in my country, provide a certain raw material guarantee for the production of asphalt-based carbon fiber composite materials in my country, and greatly promote the development of national defense and civilian fields.

[0004] Therefore, providing a stable, simple, low-cost production method for carbon fibers with excellent performance is an urgent problem to be solved by those skilled in the art. Summary of the Invention

[0005] In view of this, the present invention provides a method for producing coal-based asphalt-based melt-blown carbon fibers. The coal-based spinning asphalt is passed through the spinneret of the mosaic hole-in-hole structure defined in the present invention, and then subjected to oxidation and carbonization treatment under a certain gradient temperature rise to obtain coal-based asphalt-based melt-blown carbon fibers with excellent mechanical and physical and chemical properties. The production method of melt-blown carbon fibers defined in the present invention has stable overall operation, which can last up to half a month; low cost, suitable for large-scale production; and the spinneret can be replaced at room temperature. It overcomes the problems of high temperature (>200°C) when replacing traditional spinnerets, high labor intensity, and low output in the existing technology.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] A method for producing coal-based pitch-based melt-blown carbon fibers, comprising the following steps:

[0008] (1) Coal-based spinning pitch is heated by a screw machine and then pumped into a spinning device through a metering pump. Hot air is used as the medium to obtain melt-blown carbon fiber precursor under the action of gravity and slight positive pressure;

[0009] (2) The melt-blown carbon fiber precursor is conveyed into an oxidation furnace via a belt and oxidized under the action of hot air to obtain oxidized fibers;

[0010] (3) The oxidized fiber is fed into a carbonization furnace and carbonized under the protection of an inert gas to obtain coal-based pitch-based melt-blown carbon fiber.

[0011] The coal-based asphalt-based melt-blown carbon fiber prepared by the present invention has good thermal insulation, oxidation resistance, corrosion resistance, high temperature resistance and other properties, and the melt-blown carbon fiber has good linear density, uniform quality, and stable and uniform raw yarn diameter.

[0012] Preferably, the spinning device comprises a first layer and a second layer from top to bottom;

[0013] The first layer comprises a spinning cavity, a detachable spinning plate is provided at the bottom of the spinning cavity, and a spinning needle is provided on the spinning plate;

[0014] The second layer comprises a hot air plate, wherein the hot air plate is provided with hot air needle holes which are nested with the spinnerets, so that the hot air needle holes and the spinneret needle holes form a hole-in-hole structure;

[0015] Wherein, the hot air needle hole is outside the spinneret needle hole;

[0016] The spinneret and the hot air plate are independent of each other.

[0017] The beneficial effects achieved by the above further preferred embodiment are as follows: the heated coal-based spinning pitch is pumped into the first-layer spinneret cavity of the spinneret, while hot air is simultaneously introduced from the periphery of the spinneret cavity into the hot air pinholes on the second-layer hot air plate to heat the spinneret. Then, under the action of gravity and slight positive pressure, the heated spinning pitch enters the feed port of the spinneret on the spinneret and passes through the discharge port to obtain melt-blown carbon fiber precursor. The spinneret holes and hot air pinholes are constructed as a mosaic hole-in-hole structure, and the hot air plate and spinneret operate independently.

[0018] That is, this spinneret structure has the following advantages:

[0019] 1. Stable airflow, stable feed, and overall stable operation;

[0020] 2. The spinned fiber has good linear density, uniform quality, and stable and uniform raw yarn diameter;

[0021] 3. Low cost, good economy, suitable for large-scale production;

[0022] 4. When replacing the spinneret, it can be done at room temperature and pressure, saving time and effort; avoiding the shortcomings of traditional spinneret replacement, which requires high temperature and high pressure, high labor intensity, and poor working environment.

[0023] Preferably, the spinneret hole is funnel-shaped.

[0024] Preferably, the diameter of the spinneret outlet is 0.2 to 0.6 mm.

[0025] The beneficial effect achieved by the above further preferred solution is that the raw yarns ejected within the spinneret aperture range defined by the present invention have a thin diameter, a long raw yarn, and are overall soft.

[0026] Preferably, the spinnerets are arranged in two equal rows on the spinneret, with a total of 204 to 206 spinnerets.

[0027] Preferably, the spinneret is 1 m long and 0.2 m wide.

[0028] Preferably, the softening point of the coal-based spinning pitch in step (1) is 278-282°C.

[0029] Preferably, the heating temperature of the screw machine in step (1) is gradually increased from 200° C. to 360-400° C. within 2 hours.

[0030] The above preferred embodiment achieves the following beneficial effects: A gradual temperature increase within the screw extruder's defined temperature range provides a relatively gentle temperature increase, resulting in a temperature profile that completely melts the raw spinning pitch without causing coking. If the temperature is too low, the pitch will not fully melt, resulting in grainy yarns; if the temperature is too high, the pitch will coke near the screw wall, gradually clogging the screw extruder.

[0031] Preferably, the twin screws in the screw machine have a diameter of 65 mm.

[0032] Preferably, the hot air temperature in step (1) is 370-420°C.

[0033] Preferably, after the hot air enters the hot air plate, the temperature of the hot air plate is controlled at 360-370°C.

[0034] The beneficial effects achieved by the above further preferred solution are: if the temperature of the hot air plate is too high, the spinning pitch in the spinneret will be coked and blocked; if the temperature is too low, the spinning pitch in the spinneret will have poor fluidity, the diameter of the ejected raw yarn will be thick, and it will be easy to break.

[0035] Preferably, the diameter of the meltblown carbon fiber precursor in step (1) is 13 to 15 μm.

[0036] Preferably, the ash content of the meltblown carbon fiber precursor in step (1) is less than 0.03%.

[0037] The beneficial effect achieved by the above further preferred scheme is that the ash content of the melt-blown carbon fiber precursor produced in step (1) of the present invention is one order of magnitude lower than that of the general precursor in the prior art (ash content > 0.1%), so the carbon fiber produced using this precursor has better performance and wider application.

[0038] Preferably, the hot air temperature in step (2) is 160-340°C.

[0039] Preferably, the oxidation temperature in step (2) is gradually increased from 160-180° C. to 340° C. within 4-6 hours.

[0040] The beneficial effects achieved by the above further preferred scheme are: if the oxidation temperature is too high and the heating rate is too fast, the fiber will not be oxidized evenly, resulting in the surface oxidation being completed but the inner core not being completed, which is the so-called sandwich structure; similarly, if the oxidation temperature is low and the heating rate is too slow, it will also cause insufficient energy and the fiber cannot be completely oxidized.

[0041] Preferably, the carbonization in step (3) is carried out by heating the temperature from 350° C. to 1100° C. within 2 hours.

[0042] The beneficial effects achieved by the above further preferred solution are: if the heating rate is too fast, the lightweight components will volatilize too quickly, and the carbon fiber will feel burnt and brittle; similarly, if the heating rate is too slow, the energy consumption will be too high and the economic benefits will be poor.

[0043] Preferably, the inert protective gas in step (3) is nitrogen with a purity of ≥99.99%.

[0044] To achieve the above objectives, the present invention also provides a coal-based pitch-based melt-blown carbon fiber produced by the above production method.

[0045] Preferably, the coal-based pitch-based melt-blown carbon fiber has a diameter of 13 to 15.5 μm and a carbon content of >95%.

[0046] It can be seen from the above technical solution that, compared with the prior art, the present invention discloses a method for producing coal-based pitch-based melt-blown carbon fibers, which has the following beneficial effects:

[0047] 1. The inlaid hole-in-hole spinneret structure defined in the present invention has the function of stabilizing the airflow, so that the entire production process can run stably; the melt-blown carbon fiber produced has good linear density, uniform quality, and stable and uniform raw yarn diameter; the spinneret can be replaced at room temperature.

[0048] 2. The meltblown carbon fibers produced by this invention exhibit low thermal conductivity and excellent thermal insulation properties; excellent oxidation and corrosion resistance; high-temperature resistance up to 2400°C; low thermal expansion coefficient; high carbon residue (greater than 95%); and an ash content below 200 ppm. Overall, this product is easier to graphitize and offers a high cost-effectiveness.

[0049] 3. The meltblown carbon fibers produced by this invention can be applied in a variety of fields, such as photovoltaic thermal insulation, carbon-carbon composites, building reinforcements, and friction braking, offering advantages unmatched by other carbon fibers. Furthermore, this invention provides a certain raw material guarantee for the production of pitch-based carbon fiber composites in my country, significantly promoting the development of national defense and civilian applications.

[0050] 4. The production method disclosed in the present invention is simple, easy to implement, low-cost, and suitable for large-scale production. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are merely embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying any creative work.

[0052] Figure 1 The accompanying drawing is a top view of the spinneret of the present invention.

[0053] Figure 2 The attached picture is Figure 1 Schematic diagram of the mesopore-in-hole structure.

[0054] Among them, in the figure: 1-spinneret, 2-hole-in-hole structure, 3-air inlet, 4-feed port, 5-discharge port, 6-spinneret needle. DETAILED DESCRIPTION

[0055] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0056] A method for producing coal-based pitch-based melt-blown carbon fibers, comprising the following steps:

[0057] Step (1): Add spinning pitch with a softening point of 278-282°C into a twin-screw extruder, heat it from 200°C to 360-400°C, and heat the hot air to 370-420°C. Pump it into the spinning device through a metering pump, and obtain melt-blown carbon fiber precursor under the action of gravity and slight positive pressure;

[0058] Step (2): The melt-blown carbon fiber precursor obtained in step (1) is conveyed to an oxidation furnace by a belt, and the hot air temperature is 160-340° C., and gradually heated from 160-180° C. to 340° C. within 4-6 hours to obtain oxidized fiber.

[0059] Step (3): The oxidized fiber belt obtained in step (2) is transported to a carbonization furnace, and the temperature is raised from 350° C. to 1100° C. within 2 hours to finally obtain melt-blown carbon fiber.

[0060] The produced coal-based asphalt-based melt-blown carbon fibers have a diameter of 13 to 15.5 μm and a carbon content of more than 95%.

[0061] The spinning device used in step (1) comprises a first layer and a second layer from top to bottom;

[0062] The first layer includes a spinning cavity, a detachable spinning plate 1 is provided at the bottom of the spinning cavity, and a spinning needle 6 is provided on the spinning plate 1;

[0063] The second layer includes a hot air plate, which is provided with hot air needle holes that are nested with the spinnerets. The hot air needle holes are outside the spinneret holes, thereby forming a mosaic hole-in-hole structure 2; and the spinneret 1 and the hot air plate are independent of each other.

[0064] In step (1), under the action of a distributor plate, the heated spinning pitch enters the spinneret on the spinneret 1 through the feed port 4, and then melt-blown carbon fiber precursor is obtained through the discharge port 5. At the same time, hot air enters the hot air plate through the air inlet 3. The hot air is at 370-420°C, and the temperature of the hot air plate is controlled to be 360-370°C. The spinneret is 1m long and 0.2m wide; the spinneret hole is funnel-shaped, and its discharge port aperture is 0.2-0.6mm.

[0065] The heating temperature in step (1) is divided into 14 zones, and the specific temperature parameters of each zone are shown in Table 1.

[0066] Table 1

[0067] 1 2 3 4 5 6 7 200 200 200 260 260 260 300 8 9 10 11 12 13 14 300 320 335 350 355(360 / 365) 360(370 / 380) 370(380 / 390)

[0068] The carbonization temperature rise in step (3) is divided into 24 zones, and the specific temperature parameters of each zone are shown in Table 2.

[0069] Table 2

[0070] 1 2 3 4 5 6 7 8 300 350 375 400 420 440 460 480 9 10 11 12 13 14 15 16 500 520 540 580 600 650 700 750 17 18 19 20 21 22 23 24 800 850 900 950 1000 1100 950 800

[0071] The spinning pitch mentioned in the following examples is a product produced and sold by our company (Jining Carbon Group Co., Ltd.), and its indicators are: softening point: 280±2°C; toluene insoluble matter: 58±2wt%; quinoline insoluble matter: 20±2wt%; volatile matter: 33.5±1wt%; ash content <0.025%.

[0072] Example 1

[0073] Step (1): Add spinning pitch with a softening point of 280°C into a twin-screw extruder and heat it from 200°C to 385°C. The hot air is at 380°C. The pitch is pumped into the spinneret cavity via a metering pump and enters the spinneret under the action of a distributor plate. The spinneret needle hole has a diameter of 0.6 mm. The hot air enters the hot air plate, and the hot air plate temperature is controlled at 365°C to obtain a raw yarn with a yarn diameter of 15 μm.

[0074] Step (2): The raw silk obtained in step (1) is conveyed to an oxidation furnace by a belt, and gradually heated from 180° C. to 340° C. using hot air heating for 5 hours to obtain oxidized fiber.

[0075] Step (3): The oxidized fiber belt obtained in step (2) is transported to a carbonization furnace with a temperature curve of 350° C. to 1100° C. Under this temperature curve, the carbonization time is 150 minutes.

[0076] Example 2

[0077] Step (1): Add spinning pitch with a softening point of 278°C into a twin-screw extruder and heat it from 200°C to 365°C. The hot air is at 380°C. The pitch is pumped into the spinneret cavity via a metering pump and enters the spinneret under the action of a distributor plate. The spinneret needle hole has a diameter of 0.4 mm. The hot air enters the hot air plate, and the hot air plate temperature is controlled at 360°C to obtain a raw yarn with a yarn diameter of 14 μm.

[0078] Step (2): The raw silk obtained in step (1) is conveyed to an oxidation furnace by a belt, and gradually heated from 170° C. to 340° C. using hot air heating for 4.5 hours to obtain oxidized fiber.

[0079] Step (3): The oxidized fiber belt obtained in step (2) is transported to a carbonization furnace with a temperature curve of 350° C. to 1100° C. Under this temperature curve, the carbonization time is 130 minutes.

[0080] Example 3

[0081] Step (1): Add spinning pitch with a softening point of 279°C into a twin-screw extruder and heat it from 200°C to 375°C. The hot air is at 380°C. The pitch is pumped into the spinneret cavity via a metering pump and enters the spinneret under the action of a distributor plate. The spinneret needle hole has a diameter of 0.5 mm. The hot air enters the hot air plate, and the hot air plate temperature is controlled at 365°C to obtain a raw yarn with a yarn diameter of 14 μm.

[0082] Step (2): The raw silk obtained in step (1) is conveyed to an oxidation furnace by a belt, and gradually heated from 160° C. to 340° C. using hot air heating for 5 hours to obtain oxidized fiber.

[0083] Step (3): The oxidized fiber belt obtained in step (2) is transported to a carbonization furnace with a temperature curve of 350° C. to 1100° C. Under this temperature curve, the carbonization time is 140 minutes.

[0084] Example 4

[0085] Step (1): Add spinning pitch with a softening point of 278°C to the twin-screw extruder and heat it from 200°C to 370°C. The hot air is at 380°C. The pitch is pumped into the spinneret cavity via a metering pump and enters the spinneret under the action of a distributor plate. The spinneret needle hole has a diameter of 0.3mm. The hot air enters the hot air plate, and the hot air plate temperature is controlled at 367°C to obtain a raw yarn with a yarn diameter of 13.5μm.

[0086] Step (2): The raw silk obtained in step (1) is conveyed to an oxidation furnace by a belt, and gradually heated from 160° C. to 340° C. using hot air heating for 4 hours to obtain oxidized fiber.

[0087] Step (3): transporting the oxidized fiber belt obtained in step (2) to a carbonization furnace with a temperature curve of 350°C to 1100°C, a heating rate of 0.5°C / min, and a carbonization time of 135 min.

[0088] Example 5

[0089] Step (1): Add spinning pitch with a softening point of 278°C into a twin-screw extruder and heat it from 200°C to 368°C. The hot air is at 380°C. The pitch is pumped into the spinneret cavity via a metering pump and enters the spinneret under the action of a distributor plate. The spinneret needle hole has a diameter of 0.25 mm. The hot air enters the hot air plate, and the hot air plate temperature is controlled at 365°C to obtain a raw yarn with a yarn diameter of 13 μm.

[0090] Step (2): The raw silk obtained in step (1) is conveyed to an oxidation furnace by a belt, and gradually heated from 170° C. to 340° C. using hot air heating for 4 hours to obtain oxidized fiber.

[0091] Step (3): transporting the oxidized fiber belt obtained in step (2) to a carbonization furnace with a temperature curve of 350°C to 1100°C, a heating rate of 0.4°C / min, and a carbonization time of 130 min.

[0092] Example 6

[0093] Step (1): Add spinning pitch with a softening point of 278°C into a twin-screw extruder and heat it from 200°C to 369°C. The hot air is at 380°C. The pitch is pumped into the spinneret cavity via a metering pump and enters the spinneret under the action of a distributor plate. The spinneret needle hole has a diameter of 0.20 mm. The hot air enters the hot air plate, and the hot air plate temperature is controlled at 360°C to obtain a raw yarn with a yarn diameter of 13 μm.

[0094] Step (2): The raw silk obtained in step (1) is conveyed to an oxidation furnace by a belt, and gradually heated from 165° C. to 340° C. using hot air heating for 4 hours to obtain oxidized fiber.

[0095] Step (3): transporting the oxidized fiber belt obtained in step (2) to a carbonization furnace with a temperature curve of 350°C to 1100°C, a heating rate of 0.35°C / min, and a carbonization time of 125min.

[0096] Effect test

[0097] The coal-based pitch-based melt-blown carbon fibers obtained in Examples 1 to 6 above were tested for tensile strength, tensile modulus, and ash content. The test results are shown in Table 2:

[0098] Table 2 Performance indexes of coal-based asphalt-based melt-blown carbon fibers

[0099]

[0100] The coal tar-based general-grade melt-blown carbon fiber finally prepared by the production method defined in the present invention has excellent technical indicators: the melt-blown carbon fiber diameter is 13 to 15.5 μm, the carbon content is greater than 95%, the tensile strength is greater than 650 MPa, the Young's modulus is greater than 35 GPa, and the ash content is less than 200 ppm.

[0101] In addition, the 1 cm thick felt made of the melt-blown carbon fiber produced by the present invention has a thermal conductivity of 0.2398 W / (mk) at 1500°C, which makes it have good thermal insulation performance; and when the melt-blown carbon fiber of the present invention is used to make the insulation felt, the service life is 3-4 months longer than that of the PAN grade, and it has good anti-oxidation and corrosion resistance; it is resistant to high temperatures, up to 2400°C, and has a low thermal expansion coefficient; the residual carbon value is high, greater than 95%.

[0102] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. Reference can be made to the common and similar parts between the various embodiments. For the devices disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the description is relatively simple, and the relevant parts can be referred to the method description.

[0103] The above description of the disclosed embodiments is intended to enable one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be readily apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention is not limited to the embodiments shown herein but is intended to conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for producing coal-based pitch-based melt-blown carbon fiber, characterized in that: The following steps are involved: (1) heating the coal-based spinning pitch and conveying it to a spinning device, using hot air as a medium to obtain melt-blown carbon fiber precursor under the action of gravity and slight positive pressure; (2) oxidizing the meltblown carbon fiber precursor under the action of hot air to obtain oxidized fibers; (3) carbonizing the oxidized fiber under the protection of an inert gas to obtain a coal-based pitch-based melt-blown carbon fiber; The spinning device in step (1) comprises a first layer and a second layer from top to bottom; The first layer comprises a spinning cavity, a detachable spinning plate is provided at the bottom of the spinning cavity, and a spinning needle is provided on the spinning plate; The second layer comprises a hot air plate, wherein the hot air plate is provided with hot air needle holes which are nested with the spinnerets; Wherein, the hot air needle hole is outside the spinneret needle hole; the spinneret plate and the hot air plate are independent of each other; The diameter of the spinneret outlet is 0.2 to 0.6 mm; The softening point of the coal-based spinning pitch in step (1) is 278-282° C.; the heating in step (1) is gradually heated from 200° C. to 360-400° C. within 2 hours; the temperature of the hot air in step (1) is 370-420° C.; The oxidation in step (2) is carried out by gradually increasing the temperature from 160 to 180° C. to 340° C. within 4 to 6 hours; The carbonization in step (3) is carried out by heating the temperature from 350°C to 1100°C within 2 hours.

2. Coal-based pitch-based melt-blown carbon fiber produced according to the production method of claim 1.

3. The coal-based pitch-based melt-blown carbon fiber according to claim 2, characterized in that: The coal-based asphalt-based melt-blown carbon fiber has a diameter of 13 to 15.5 μm and a carbon content greater than 95%.

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