CN109402794B - Apparatus and heat treatment method for weakening skin-core structure in carbon fiber - Google Patents
Apparatus and heat treatment method for weakening skin-core structure in carbon fiber Download PDFInfo
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- D—TEXTILES; PAPER
- D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
- D01F—CHEMICAL FEATURES IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS; APPARATUS SPECIALLY ADAPTED FOR THE MANUFACTURE OF CARBON FILAMENTS
- D01F9/00—Artificial filaments or the like of other substances; Manufacture thereof; Apparatus specially adapted for the manufacture of carbon filaments
- D01F9/08—Artificial filaments or the like of other substances; Manufacture thereof; Apparatus specially adapted for the manufacture of carbon filaments of inorganic material
- D01F9/12—Carbon filaments; Apparatus specially adapted for the manufacture thereof
- D01F9/14—Carbon filaments; Apparatus specially adapted for the manufacture thereof by decomposition of organic filaments
- D01F9/32—Apparatus therefor
- D01F9/328—Apparatus therefor for manufacturing filaments from polyaddition, polycondensation, or polymerisation products
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- D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
- D01F—CHEMICAL FEATURES IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS; APPARATUS SPECIALLY ADAPTED FOR THE MANUFACTURE OF CARBON FILAMENTS
- D01F9/00—Artificial filaments or the like of other substances; Manufacture thereof; Apparatus specially adapted for the manufacture of carbon filaments
- D01F9/08—Artificial filaments or the like of other substances; Manufacture thereof; Apparatus specially adapted for the manufacture of carbon filaments of inorganic material
- D01F9/12—Carbon filaments; Apparatus specially adapted for the manufacture thereof
- D01F9/14—Carbon filaments; Apparatus specially adapted for the manufacture thereof by decomposition of organic filaments
- D01F9/20—Carbon filaments; Apparatus specially adapted for the manufacture thereof by decomposition of organic filaments from polyaddition, polycondensation or polymerisation products
- D01F9/21—Carbon filaments; Apparatus specially adapted for the manufacture thereof by decomposition of organic filaments from polyaddition, polycondensation or polymerisation products from macromolecular compounds obtained by reactions only involving carbon-to-carbon unsaturated bonds
- D01F9/22—Carbon filaments; Apparatus specially adapted for the manufacture thereof by decomposition of organic filaments from polyaddition, polycondensation or polymerisation products from macromolecular compounds obtained by reactions only involving carbon-to-carbon unsaturated bonds from polyacrylonitriles
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Abstract
The invention relates to equipment and a heat treatment technology for weakening a skin-core structure in carbon fiber, mainly solving the problems of serious skin-core structure, poor compactness and large linear density discrete coefficient of pre-oxidized fiber in the existing carbon fiber preparation process, by adopting the equipment for weakening the skin-core structure in the carbon fiber, the equipment comprises at least four oxidation furnaces, namely a first oxidation furnace (1), a second oxidation furnace (2), a third oxidation furnace (3) and a fourth oxidation furnace (4), wherein, the oxidation furnaces all use an electric heating type tubular drying furnace, the inside of the oxidation furnace is a stainless steel hearth, a nickel-chromium alloy wire is wound on the hearth, the winding density of a heating wire (9) on each oxidation furnace hearth (8) is increasingly larger along the wire moving direction, the technical scheme that the temperature difference from the inlet to the outlet of each oxidation furnace can be 10-50 ℃ is realized, the problems are well solved, and the method can be used in the industrial production of carbon fibers.
Description
Technical Field
The invention relates to equipment and a heat treatment method for weakening a skin-core structure in carbon fiber.
Technical Field
The carbon fiber is a fibrous polymer having a carbon content of 90% or more, which is obtained by converting an organic fiber through a solid-phase reaction. The fiber has a series of excellent performances of high specific strength, high specific modulus, high temperature resistance, chemical corrosion resistance, fatigue resistance, thermal shock resistance, radiation resistance, small specific gravity and the like, and belongs to typical high-performance fibers. The commercial production of high-strength carbon fibers has been realized abroad, but China is still in the stages of development and trial production, and developed countries such as the United states and the Japanese adopt technical blockade to the China, so that the development of related fields of national defense in China is severely restricted. Therefore, the research work of the high-strength carbon fiber is increasingly emphasized.
The preparation process of the carbon fiber comprises polymerization, spinning, pre-oxidation and carbonization, wherein the pre-oxidation process is a key step in the preparation process of the carbon fiber, and the quality of the pre-oxidized fiber directly determines the mechanical property of the final carbon fiber. Oxygen diffuses from the surface to the inside of the fiber in the pre-oxidation process, and a compact trapezoidal structure thin layer is formed on the surface layer of the fiber along with the progress of the pre-oxidation reaction to block the inward diffusion of the oxygen, so that a core layer with an angle of cyclization and crosslinking is formed at the core part of the fiber, namely a skin-core structure. The sheath-core structure is one of the main causes of the decrease in mechanical properties such as strength of the carbon fiber. Therefore, in recent years, scientists have intensively studied how to eliminate the sheath-core structure from the polymerization spinning and pre-oxidation stages to obtain homogeneous pre-oxidized filaments with uniform inner and outer structures. The preparation of the homogeneous pre-oxidized fiber is one of the main technical approaches for improving the performance of the carbon fiber at present, four or six pre-oxidizing furnaces are generally adopted by domestic scientific research institutions and production enterprises, and the chemical structures of the sheath part and the core part of the pre-oxidized fiber have certain difference due to the temperature gradient between the pre-oxidizing furnaces. The skin-core structure is further inherited and developed in the carbonization process, and develops into a structural defect, so that the structure and the performance of the final carbon fiber are influenced.
A preparation method of polyacrylonitrile-based carbon fiber precursor without skin-core structure (patent number CN201110008396.0) published by Wan actinium et al introduces a preparation method of polyacrylonitrile-based carbon fiber precursor without skin-core structure in the technical field of carbon fiber precursor, water or alcohol compounds are uniformly mixed with organic solvent, polyacrylonitrile resin is added, and polyacrylonitrile spinning solution is obtained by filtering after heating swelling and dissolving treatment; and curing the polyacrylonitrile spinning solution, spraying and extruding to obtain primary protofilaments, and sequentially carrying out water washing stretching, secondary hot water stretching, drying densification and saturated steam stretching on the primary protofilaments to obtain the polyacrylonitrile-based carbon fiber protofilaments. The method can be used for large-scale production on the existing industrial spinning equipment, and preparing the high-quality polyacrylonitrile-based carbon fiber precursor without a skin-core structure, few defects, small titer and high strength, and can effectively reduce the production cost; in the influencing factors and prevention and control measures of the skin-core structure of the polyacrylonitrile pre-oxidized fiber (volume 6 (41) in 2010, p1019-1022) published by Meijie et al, pre-oxidation treatment is carried out on 3 polyacrylonitrile protofilaments with different titer and cross section shapes under two modes of constant temperature and gradient temperature rise, and the skin-core structure and the diffusion of oxygen elements of the pre-oxidized fiber are researched by adopting the technologies of a scanning electron microscope, an optical microscope, element analysis and the like; the cross section shape of the protofilament does not influence the diffusion of oxygen, and under the same heating condition, the thickness of the cortex of the kidney-shaped section pre-oxidized protofilament is the same as that of the circular section; the smaller the fineness of the protofilament is, the easier the homogeneous pre-oxidized filament can be obtained, and the fine denier of the protofilament and the proper gradient heating pre-oxidation process are important guarantees for obtaining high-quality pre-oxidized filament.
Although some researchers have made some studies on the formation mechanism of the skin-core structure, no apparatus and specific methods for weakening the skin-core structure have been proposed. From the perspective of equipment and process, the invention provides equipment and a heat treatment method for effectively weakening a carbon fiber skin-core structure.
Disclosure of Invention
The invention aims to solve the technical problems of serious skin-core structure, poor compactness and large linear density dispersion coefficient in the pre-oxidation process of the existing carbon fiber, and provides equipment for weakening the skin-core structure in the carbon fiber. The equipment is used in the preparation process of the polyacrylonitrile-based carbon fiber, and has the advantages of weakening the skin-core structure of the pre-oxidized fiber and reducing the linear density discrete coefficient of the pre-oxidized fiber.
The invention aims to solve the technical problems that the skin-core structure is serious, the compactness is poor and the linear density dispersion coefficient is large in the pre-oxidation process of the existing carbon fiber, and provides a heat treatment method for weakening the skin-core structure in the carbon fiber by adopting equipment for weakening the skin-core structure in the carbon fiber, which is used for preparing the polyacrylonitrile-based carbon fiber and has the advantages of weakening the skin-core structure of the pre-oxidized fiber and reducing the linear density dispersion coefficient of the pre-oxidized fiber.
In order to solve one of the technical problems, the technical scheme adopted by the invention is as follows: the utility model provides a weaken equipment of carbon fiber well skin core structure, includes at least oxidation furnace 1, No. two oxidation furnaces 2, No. three oxidation furnaces 3, No. 4 four oxidation furnaces of oxidation furnace, wherein, oxidation furnace all use electrical heating formula tubular drying furnace, inside is furnace, twines the heater strip on the furnace, heater strip 9 winding density on every oxidation furnace 8 is different, along walking the silk direction, winding density is bigger and bigger for the temperature difference of 10 ~ 50 ℃ can be realized to the temperature of export to every oxidation furnace import.
In the above technical scheme, the heating wire is preferably a nichrome wire, and the hearth is preferably a stainless steel hearth.
In the above solution, the apparatus preferably further comprises a driving station 7 for performing the necessary drafting of the fibers; the inside of the oxidation furnace is preferably provided with a blowing device along the wire moving direction; the equipment preferably comprises six oxidation furnaces, wherein the air blowing device in each oxidation furnace blows air horizontally along the wire moving direction; as shown in fig. 1, the blowing device of the oxidation furnace 1 is preferably blowing air from right to left along the wire running direction, the blowing device of the oxidation furnace 2 is preferably blowing air from left to right along the wire running direction, the blowing device of the oxidation furnace 3 is preferably blowing air from right to left along the wire running direction, the blowing device of the oxidation furnace 4 is preferably blowing air from right to left along the wire running direction, the blowing device of the oxidation furnace 5 is preferably blowing air from left to right along the wire running direction, and the blowing device of the oxidation furnace 6 is preferably blowing air from left to right along the wire running direction; the blowing air in the oxidation furnace is preferably air subjected to preheating treatment.
In the above technical scheme, the temperature of the oxidation furnace is preferably equal to the inlet temperature of the next oxidation furnace and the outlet temperature of the previous oxidation furnace, so that the skin-core structure can be better reduced.
In the technical scheme, the equipment can also comprise a filament releasing machine, a low-temperature carbonization furnace, a high-temperature carbonization furnace, a surface treatment and sizing drying device and a filament collecting machine.
In order to solve the second technical problem, the invention adopts the technical scheme that: a heat treatment method for weakening a skin-core structure in a carbon fiber adopts any one of the technical schemes for solving the technical problems, and sequentially comprises the following steps: uncoiling the protofilament from a filament unreeling machine, then carrying out six oxidation furnaces, low-temperature carbonization furnaces, high-temperature carbonization furnaces, surface treatment and sizing drying, and finally coiling to obtain carbon fiber; the method is characterized in that the temperature of the first pre-oxidation furnace 1 is between 160 ℃ and 210 ℃, and the temperature is continuously changed from the inlet temperature to the outlet temperature; the temperature of the second pre-oxidation furnace 2 is between 185 ℃ and 235 ℃, and the temperature is continuously changed from the inlet temperature to the outlet temperature; the temperature of the third pre-oxidation furnace 3 is between 200 ℃ and 245 ℃, and the temperature is continuously changed from the inlet temperature to the outlet temperature; the temperature of the fourth pre-oxidation furnace 4 is between 215 ℃ and 260 ℃, and is continuously changed from the inlet temperature to the outlet temperature; the temperature of the fifth pre-oxidation furnace 5 is between 230 ℃ and 265 ℃, and the temperature is continuously changed from the inlet temperature to the outlet temperature; the temperature of the sixth pre-oxidation furnace 6 is between 240 ℃ and 270 ℃, and is continuously changed from the inlet temperature to the outlet temperature; meanwhile, the inlet temperature of the same oxidation furnace is lower than the outlet temperature.
In the above technical solution, the temperature of the oxidation furnace is preferably that the inlet temperature of the next oxidation furnace is equal to the outlet temperature of the previous oxidation furnace; the first oxidation furnace and the second oxidation furnace are preferably low-temperature regions, the third oxidation furnace and the fourth oxidation furnace are preferably medium-temperature regions, and the fifth oxidation furnace and the sixth oxidation furnace are preferably high-temperature regions; preferably applying a positive draft in the low temperature zone, preferably applying a zero draft in the medium temperature zone, preferably applying a negative draft in the high temperature zone; the drafting rate of the low-temperature zone is 1-8%, the drafting rate of the medium-temperature zone is 0%, and the drafting rate of the high-temperature zone is-2 to-5%; the fiber after the heat treatment of the oxidation furnace is preferably carbonized at a low temperature of 300-800 ℃ in the inert atmosphere in the low-temperature carbonization furnace, and then carbonized at a high temperature of 900-1400 ℃ in the inert atmosphere in the high-temperature carbonization furnace.
The device used in the method is a continuous pre-oxidation furnace-low temperature carbonization furnace-high temperature carbonization furnace, wherein the continuous pre-oxidation furnace adopts six-section temperature rise, wherein the temperature of the first pre-oxidation furnace is between 180-plus-temperature 195 ℃, the temperature of the second pre-oxidation furnace is between 195-plus-temperature 210 ℃, the temperature of the third pre-oxidation furnace is between 210-plus-temperature 235 ℃, the temperature of the fourth pre-oxidation furnace is between 235-plus-temperature 245 ℃, the temperature of the fifth pre-oxidation furnace is between 245-plus-temperature 255 ℃, and the temperature of the sixth pre-oxidation furnace is between 255-plus-temperature 265 ℃.
In the preparation process of the polyacrylonitrile-based carbon fiber, the polymerization spinning and carbonization processes are not changed, the continuous heating mode is adopted by the oxidation furnace, the temperature in the pre-oxidation furnace is continuously increased and distributed along the fiber direction by changing the winding density of the nickel-chromium alloy resistance wire on the surface of the hearth of the pre-oxidation furnace, the power of each heating point and the gas flow, the temperature gradient in the whole pre-oxidation process is reduced to the minimum, the skin-core structure of the pre-oxidation fiber can be weakened only by changing the temperature and the gas flow direction and the flow in the pre-oxidation process under the condition of not changing the polymerization spinning and carbonization processes, and a foundation is laid for preparing the high-performance carbon fiber.
The prepared pre-oxidized fiber is subjected to skin-core structure test, and the test method is as follows: observing and measuring the skin-core structure of the fiber by adopting an epoxy resin embedding slicing method and enlarging the fiber by 1000 times under an optical microscope, measuring the outer diameter and the core diameter of the cross section of 50 monofilaments of each sample, and taking the average value of the outer diameter and the core diameter.
Skin to core ratio (FS%) measurement formula:
by adopting the technical scheme of the invention, the oxidation furnace adopts a continuous heating mode, the temperature in the pre-oxidation furnace is continuously increased and distributed along the fiber direction by changing the winding density of the nickel-chromium alloy resistance wire on the surface of the hearth of the pre-oxidation furnace, the power of each heating point and the air flow, the skin-core ratio of the prepared carbon fiber is more than 90 percent, and better technical effect is achieved.
The invention is further illustrated by the following examples:
drawings
FIG. 1 is a pre-oxidation process for weakening a skin-core structure in carbon fibers, carbon fiber precursors are pretreated and then enter an oxidation furnace No. 1, an oxidation furnace No. 2, an oxidation furnace No. 3, an oxidation furnace No. 4, an oxidation furnace No. 5 and an oxidation furnace No. 6 in sequence, the blowing mode in each oxidation furnace is horizontal blowing, and the wind direction is the same as the filament moving direction.
FIG. 2 is a view showing the construction of the apparatus of the pre-oxidation furnace.
Fig. 3 is a schematic diagram of the sheath-core structure of the carbon fiber mentioned in the sheath-core ratio test method.
In fig. 1, 1 is an oxidation oven No. 1, 2 is an oxidation oven No. 2, 3 is an oxidation oven No. 3, 4 is an oxidation oven No. 4, 5 is an oxidation oven No. 5, 6 is an oxidation oven No. 6, and 7 is a draft roller.
In fig. 2, 8 is a hearth of the oxidation furnace, and 9 is a nichrome wire wound on the surface of a furnace tube of the oxidation furnace.
In fig. 3, Rs is the fiber section radius and Rc is the fiber core radius.
The present invention will be further illustrated by the following examples, but is not limited to these examples.
Detailed Description
[ example 1 ]
The polyacrylonitrile protofilament is pre-oxidized in a six-section pre-oxidation furnace, and the heat treatment process is shown in figure 1. The temperature in each pre-oxidation furnace is gradually increased along the fiber advancing direction by adjusting the power of each heating point in each pre-oxidation furnace, the horizontal blowing mode is adopted in each oxidation furnace, and the wind direction is consistent with the filament moving direction. Wherein the temperature of the No. 1 pre-oxidation furnace is gradually increased between 175 ℃ and 190 ℃; the temperature of the No. 2 pre-oxygen furnace is gradually increased between 190-210 ℃, the temperature of the No. 3 pre-oxygen furnace is gradually increased between 210-225 ℃, the temperature of the No. 4 pre-oxygen furnace is gradually increased between 225-240 ℃, the temperature of the No. 5 pre-oxygen furnace is gradually increased between 240-255 ℃, and the temperature of the No. 6 pre-oxygen furnace is gradually increased between 255-270 ℃. The prepared pre-oxidized fiber was subjected to skin-core structure test, and the test results are shown in table 1.
[ example 2 ]
The polyacrylonitrile protofilament is pre-oxidized in a six-section pre-oxidation furnace, and the heat treatment process is shown in figure 1. The temperature in each pre-oxidation furnace is gradually increased along the fiber advancing direction by adjusting the power of each heating point in each pre-oxidation furnace, the horizontal blowing mode is adopted in each oxidation furnace, and the wind direction is consistent with the filament moving direction. Wherein the temperature of the No. 1 pre-oxidation furnace is gradually increased between 175 ℃ and 195 ℃; the temperature of the No. 2 pre-oxygen furnace is gradually increased between 195-215 ℃, the temperature of the No. 3 pre-oxygen furnace is gradually increased between 215-230 ℃, the temperature of the No. 4 pre-oxygen furnace is gradually increased between 230-245 ℃, the temperature of the No. 5 pre-oxygen furnace is gradually increased between 245-260 ℃, and the temperature of the No. 6 pre-oxygen furnace is gradually increased between 260-270 ℃. The prepared pre-oxidized fiber was subjected to skin-core structure test, and the test results are shown in table 1.
[ example 3 ]
The polyacrylonitrile protofilament is pre-oxidized in a six-section pre-oxidation furnace, and the heat treatment process is shown in figure 1. The temperature in each pre-oxidation furnace is gradually increased along the fiber advancing direction by adjusting the power of each heating point in each pre-oxidation furnace, the horizontal blowing mode is adopted in each oxidation furnace, and the wind direction is consistent with the filament moving direction. Wherein the temperature of the No. 1 pre-oxidation furnace is gradually increased between 175 ℃ and 185 ℃; the temperature of the No. 2 pre-oxidation furnace is gradually increased between 185-plus-205 ℃, the temperature of the No. 3 pre-oxidation furnace is gradually increased between 205-plus-220 ℃, the temperature of the No. 4 pre-oxidation furnace is gradually increased between 220-plus-235 ℃, the temperature of the No. 5 pre-oxidation furnace is gradually increased between 235-plus-250 ℃, and the temperature of the No. 6 pre-oxidation furnace is gradually increased between 250-plus-265 ℃. The prepared pre-oxidized fiber was subjected to skin-core structure test, and the test results are shown in table 1.
[ example 4 ]
The polyacrylonitrile protofilament is pre-oxidized in a six-section pre-oxidation furnace, and the heat treatment process is shown in figure 1. The temperature in each pre-oxidation furnace is gradually increased along the fiber advancing direction by adjusting the power of each heating point in each pre-oxidation furnace, and meanwhile, the blowing mode in each oxidation furnace adopts vertical blowing, and the blowing direction is vertical to the filament moving direction. Wherein the temperature of the No. 1 pre-oxidation furnace is gradually increased between 175 ℃ and 190 ℃; the temperature of the No. 2 pre-oxygen furnace is gradually increased between 190-210 ℃, the temperature of the No. 3 pre-oxygen furnace is gradually increased between 210-225 ℃, the temperature of the No. 4 pre-oxygen furnace is gradually increased between 225-240 ℃, the temperature of the No. 5 pre-oxygen furnace is gradually increased between 240-255 ℃, and the temperature of the No. 6 pre-oxygen furnace is gradually increased between 255-270 ℃. The prepared pre-oxidized fiber was subjected to skin-core structure test, and the test results are shown in table 1.
[ example 5 ]
The polyacrylonitrile protofilament is pre-oxidized in a six-section pre-oxidation furnace, and the heat treatment process is shown in figure 1. The temperature in each pre-oxidation furnace is gradually increased along the fiber advancing direction by adjusting the power of each heating point in each pre-oxidation furnace, and meanwhile, the blowing mode in each oxidation furnace adopts horizontal blowing, and the wind direction is consistent with the filament moving direction. Wherein the temperature of the No. 1 pre-oxidation furnace is gradually increased between 175 ℃ and 195 ℃; the temperature of the No. 2 pre-oxygen furnace is gradually increased between 190-215 ℃, the temperature of the No. 3 pre-oxygen furnace is gradually increased between 210-230 ℃, the temperature of the No. 4 pre-oxygen furnace is gradually increased between 225-245 ℃, the temperature of the No. 5 pre-oxygen furnace is gradually increased between 240-260 ℃, and the temperature of the No. 6 pre-oxygen furnace is gradually increased between 255-270 ℃. The prepared pre-oxidized fiber was subjected to skin-core structure test, and the test results are shown in table 1.
[ COMPARATIVE EXAMPLE 1 ]
The polyacrylonitrile protofilament is pre-oxidized in a six-section pre-oxidation furnace, and the heat treatment process is shown in figure 1. The temperature in each pre-oxidizing furnace is uniform by adjusting the power of each heating point in each pre-oxidizing furnace, the temperature uniformity in each oxidizing furnace along the fiber running direction reaches +/-1.5 ℃, meanwhile, the horizontal air blowing mode is adopted in each oxidizing furnace, and the air direction is consistent with the fiber running direction. Wherein the temperature of the No. 1 pre-oxidation furnace is 180 ℃; the temperature of the No. 2 pre-oxidation furnace is 210 ℃, the temperature of the No. 3 pre-oxidation furnace is 225 ℃, the temperature of the No. 4 pre-oxidation furnace is 240 ℃, the temperature of the No. 5 pre-oxidation furnace is 255 ℃, and the temperature of the No. 6 pre-oxidation furnace is 265 ℃. The prepared pre-oxidized fiber was subjected to skin-core structure test, and the test results are shown in table 1.
[ COMPARATIVE EXAMPLE 2 ]
The polyacrylonitrile protofilament is pre-oxidized in a six-section pre-oxidation furnace, and the heat treatment process is shown in figure 1. The temperature in each pre-oxidizing furnace is uniform by adjusting the power of each heating point in each pre-oxidizing furnace, the temperature uniformity in each oxidizing furnace along the fiber running direction reaches +/-1.5 ℃, and meanwhile, the air blowing mode in each oxidizing furnace adopts vertical air blowing, and the air blowing direction is vertical to the fiber running direction. Wherein the temperature of the No. 1 pre-oxidation furnace is 180 ℃; the temperature of the No. 2 pre-oxidation furnace is 210 ℃, the temperature of the No. 3 pre-oxidation furnace is 225 ℃, the temperature of the No. 4 pre-oxidation furnace is 240 ℃, the temperature of the No. 5 pre-oxidation furnace is 255 ℃, and the temperature of the No. 6 pre-oxidation furnace is 265 ℃. The prepared pre-oxidized fiber was subjected to skin-core structure test, and the test results are shown in table 1.
Obviously, the device and the method can achieve the aim of reducing the skin-core structure in the carbon fiber, have greater technical advantages and can be used in the industrial production of the carbon fiber.
TABLE 1
| Sample numbering | Skin to core ratio (%) |
| Example 1 | 96.2 |
| Example 2 | 94.7 |
| Example 3 | 93.6 |
| Example 4 | 85.6 |
| Example 5 | 86.2 |
| Comparative example 1 | 81.6 |
| Comparative example 2 | 84.2 |
Claims (9)
1. The equipment for weakening the skin-core structure in the carbon fiber comprises at least four oxidation furnaces, namely a first oxidation furnace (1), a second oxidation furnace (2), a third oxidation furnace (3) and a fourth oxidation furnace (4), wherein the oxidation furnaces are all electric heating type tubular drying furnaces, the interior of each oxidation furnace is a hearth, heating wires are wound on the hearths, the winding density of the heating wires (9) on each oxidation furnace hearth (8) is gradually increased along the wire running direction, and the inlet temperature of the same oxidation furnace is lower than the outlet temperature; and the temperature difference between the inlet and the outlet of each oxidation furnace can be 10-50 ℃; and the oxidation furnace is internally provided with a blowing device along the wire moving direction, wherein the blowing device in each oxidation furnace horizontally blows along the wire moving direction.
2. The apparatus for weakening a sheath-core structure in a carbon fiber according to claim 1, wherein said heating wire is a nichrome wire and said furnace is a stainless steel furnace.
3. The apparatus for attenuating a skin-core structure in carbon fiber according to claim 1, characterized in that the apparatus comprises six oxidation ovens.
4. The apparatus for weakening a sheath core structure in carbon fiber according to claim 1 or 3, wherein the air blowing in said oxidation furnace is air after a preheating treatment.
5. A method of heat treatment for weakening a sheath-core structure in a carbon fiber, using the apparatus of claim 3, sequentially through the steps of: uncoiling the protofilament from a filament unreeling machine, then carrying out six oxidation furnaces, low-temperature carbonization furnaces, high-temperature carbonization furnaces, surface treatment and sizing drying, and finally coiling to obtain carbon fiber; the method is characterized in that the temperature of the first oxidation furnace (1) is between 160 ℃ and 210 ℃, and the temperature is continuously changed from the inlet temperature to the outlet temperature; the temperature of the second oxidation furnace (2) is between 185 ℃ and 235 ℃, and the temperature is continuously changed from the inlet temperature to the outlet temperature; the temperature of the third oxidation furnace (3) is between 200 ℃ and 245 ℃, and the temperature is continuously changed from the inlet temperature to the outlet temperature; the temperature of the oxidation furnace IV (4) is between 215 ℃ and 260 ℃ and is continuously changed from the inlet temperature to the outlet temperature; the temperature of the oxidation furnace V (5) is between 230 ℃ and 265 ℃, and the temperature is continuously changed from the inlet temperature to the outlet temperature; the temperature of the No. six oxidation furnace (6) is between 240 ℃ and 270 ℃, and the temperature is continuously changed from the inlet temperature to the outlet temperature; meanwhile, the inlet temperature of the same oxidation furnace is lower than the outlet temperature.
6. The method for thermally treating a core-sheath structure in attenuated carbon fiber according to claim 5, wherein the temperature of the oxidation furnace is such that the inlet temperature of the subsequent oxidation furnace is equal to the outlet temperature of the previous oxidation furnace.
7. The method according to claim 5, wherein the first and second oxidation furnaces are low-temperature zones, the third and fourth oxidation furnaces are medium-temperature zones, the fifth and sixth oxidation furnaces are high-temperature zones, positive draft is applied to the low-temperature zone, zero draft is applied to the medium-temperature zone, and negative draft is applied to the high-temperature zone.
8. The method for heat-treating a core-sheath structure in a weakened carbon fiber according to claim 7, wherein the draft ratio in the low-temperature zone is 1 to 8%, the draft ratio in the medium-temperature zone is 0%, and the draft ratio in the high-temperature zone is-2 to-5%.
9. The method for heat treatment of the core-sheath structure in the weakened carbon fiber as recited in claim 5, wherein the fiber after heat treatment in the oxidation furnace is carbonized at a low temperature of 300-800 ℃ in the inert atmosphere in the low-temperature carbonization furnace, and then carbonized at a high temperature of 900-1400 ℃ in the inert atmosphere in the high-temperature carbonization furnace.
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| CN102704043A (en) * | 2012-06-20 | 2012-10-03 | 北京化工大学 | Preparation method of polyacrylonitrile pre-oxidation fiber and carbon fiber |
| CN103352269A (en) * | 2013-06-19 | 2013-10-16 | 合肥日新高温技术有限公司 | Pre-oxidation furnace with air uniformizing structure |
| CN105568432A (en) * | 2014-10-14 | 2016-05-11 | 中国石油化工股份有限公司 | Device and method for producing low-dispersion coefficient carbon fibers |
| CN106480553A (en) * | 2016-10-31 | 2017-03-08 | 哈尔滨天顺化工科技开发有限公司 | A kind of pre-oxidation device for carbon fiber production |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102704043A (en) * | 2012-06-20 | 2012-10-03 | 北京化工大学 | Preparation method of polyacrylonitrile pre-oxidation fiber and carbon fiber |
| CN103352269A (en) * | 2013-06-19 | 2013-10-16 | 合肥日新高温技术有限公司 | Pre-oxidation furnace with air uniformizing structure |
| CN105568432A (en) * | 2014-10-14 | 2016-05-11 | 中国石油化工股份有限公司 | Device and method for producing low-dispersion coefficient carbon fibers |
| CN106480553A (en) * | 2016-10-31 | 2017-03-08 | 哈尔滨天顺化工科技开发有限公司 | A kind of pre-oxidation device for carbon fiber production |
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