CN110106585A

CN110106585A - A kind of polyacrylonitrile-based carbon fibre and preparation method thereof

Info

Publication number: CN110106585A
Application number: CN201910420905.7A
Authority: CN
Inventors: 吕春祥; 王飞; 孙同庆; 尹大宇; 李永红
Original assignee: Shanxi Institute of Coal Chemistry of CAS
Current assignee: Shanxi Gangke Carbon Materials Co Ltd
Priority date: 2019-05-20
Filing date: 2019-05-20
Publication date: 2019-08-09
Anticipated expiration: 2039-05-20
Also published as: CN110106585B

Abstract

The present invention relates to a kind of polyacrylonitrile-based carbon fibres and preparation method thereof.The technical solution mainly used are as follows: the preparation method of polyacrylonitrile-based carbon fibre includes the following steps: low-temperature carbonization step, is 1.34~1.37g/cm to density³Pre-oxidized fibers body carry out low-temperature carbonization processing, obtain low-temperature carbonization corpus fibrosum；Wherein, in low-temperature carbonization step, according to the density of pre-oxidized fibers body, the tension of pre-oxidized fibers body is controlled as A, and 0 < A≤5000CN；High temperature cabonization step carries out high temperature cabonization to low-temperature carbonization corpus fibrosum, obtains high temperature cabonization corpus fibrosum；Post-processing, post-processes high temperature cabonization corpus fibrosum, obtains polyacrylonitrile-based carbon fibre.Present invention is mainly used on the basis of guaranteeing intensity, the modulus of polyacrylonitrile-based carbon fibre, the volume density of polyacrylonitrile-based carbon fibre is further increased.

Description

A kind of polyacrylonitrile-based carbon fibre and preparation method thereof

Technical field

The present invention relates to a kind of Carbon Fiber Technology fields, more particularly to a kind of polyacrylonitrile-based carbon fibre and its preparation side Method.

Background technique

Since the fifties in last century, carbon fiber have passed through the continuous research and development of scientific research personnel, substantially have at present Viscose rayon, pitch fibers, three kinds of polyacrylonitrile fibre.Due to the light weight of polyacrylonitrile-based carbon fibre, intensity height, modulus Height, and having a series of excellent properties, the overwhelming majority such as conductive, thermally conductive, corrosion-resistant and thermal expansion coefficient is small is with carbon fiber The form of reinforced resin based composites uses, and has been widely used for multiple necks such as aerospace, Leisure Sports, civil construction Domain.

In the prior art, the preparation method of polyacrylonitrile-based carbon fibre is by polyacrylonitrile fibre (that is, precursor) in air Carry out pre-oxidation stabilization processes for 200-300 DEG C in atmosphere, then in an inert atmosphere 300-1000 DEG C of progress low-temperature carbonization, 1000-1500 DEG C of progress high temperature cabonization, can be obtained common carbon fibers.

But aerospace user needs the polyacrylonitrile-based carbon fibre of high density to meet the purposes of special dimension, Such as, the fields such as winding, laying, structural member are required to the polyacrylonitrile-based carbon fibre of some high densities, because of equality strength, mould The compressive strength of carbon fibre composite can be improved in the volume density that carbon fiber is improved under the indexs such as amount, improves carbon fiber composite The tensile pressure ratio of material.Therefore, under conditions of ensuring intensity, modulus, the volume density for improving polyacrylonitrile-based carbon fibre becomes poly- third One problem of alkene itrile group carbon fiber research and development.

Summary of the invention

In view of this, the present invention provides a kind of polyacrylonitrile-based carbon fibre and preparation method thereof, main purpose is to guarantee On the basis of the intensity and modulus of polyacrylonitrile-based carbon fibre, the volume density of polyacrylonitrile-based carbon fibre is improved.

In order to achieve the above objectives, present invention generally provides following technical solutions:

On the one hand, the embodiment of the present invention provides a kind of preparation method of polyacrylonitrile-based carbon fibre comprising following step It is rapid:

Low-temperature carbonization step: being 1.34~1.37g/cm to density³Pre-oxidized fibers body carry out low-temperature carbonization processing, obtain To low-temperature carbonization corpus fibrosum；Wherein, in the low-temperature carbonization step, according to the density of the pre-oxidized fibers body, institute is controlled The tension of pre-oxidized fibers body is stated as A, and 0 < A≤5000CN；

High temperature cabonization step: high temperature cabonization is carried out to the low-temperature carbonization corpus fibrosum, obtains polyacrylonitrile-based carbon fibre.

The object of the invention to solve the technical problems also can be used following technical measures and further realize.

Preferably, in the low-temperature carbonization step, wherein the tension value A of the pre-oxidized fibers body and the pre- oxygen The density for changing corpus fibrosum is substantially in inverse relation.Preferably, if the density of the pre-oxidized fibers body is 1.34~1.355g/ cm³, then it is 2500-5000CN to the tension that the pre-oxidized fibers body applies；If the density of the pre-oxidized fibers body is 1.355~1.37g/cm³, then it is 100-2500CN to the tension that the pre-oxidized fibers body applies.

Preferably, in the low-temperature carbonization step:

If the density of the pre-oxidized fibers body is 1.34~1.345g/cm³, then the pre-oxidized fibers body is applied Tension is 4200~5000CN；

If the density of the pre-oxidized fibers body is 1.345~1.35g/cm³, then the pre-oxidized fibers body is applied Tension is 3500~4200CN；

If the density of the pre-oxidized fibers body is 1.35~1.355g/cm³, then the pre-oxidized fibers body is applied Tension is 2750~3500CN；

If the density of the pre-oxidized fibers body is 1.355~1.36g/cm³, then the pre-oxidized fibers body is applied Tension is 2000~2750CN；

If the density of the pre-oxidized fibers body is 1.36~1.365g/cm³, then the pre-oxidized fibers body is applied Tension is 1300~2000CN；

If the density of the pre-oxidized fibers body is 1.365~1.37g/cm³, then the pre-oxidized fibers body is applied Tension is 600~1300CN.

Preferably, in the low-temperature carbonization step: the pre-oxidized fibers body being made successively to pass through multiple low-temperature carbonization temperature Area carries out low-temperature carbonization processing；Wherein, the latter low-temperature carbonization warm area is higher than the temperature of previous low-temperature carbonization warm area；

Preferably, the temperature of the low-temperature carbonization processing is 300~900 DEG C；

Preferably, in the low-temperature carbonization step, the residence time of fiber is 1~4min；

Preferably, the number of the low-temperature carbonization warm area is 5~7.

Preferably, the number of the low-temperature carbonization warm area is 6, specifically: 300~400 DEG C of the first low-temperature carbonization temperature It is area, 400~500 DEG C of the second low-temperature carbonization warm area, 500~600 DEG C of third low-temperature carbonization warm areas, the 4th of 600~700 DEG C the low Temperature carbonization warm area, 700~800 DEG C of the 5th low-temperature carbonization warm area and 800~900 DEG C of the 6th low-temperature carbonization warm area.

Preferably, in the high temperature cabonization step: low-temperature carbonization corpus fibrosum being made successively to pass through multiple high temperature cabonization warm areas Carry out high temperature cabonization processing；Wherein,

The latter high temperature cabonization warm area is higher than the temperature of previous high temperature cabonization warm area；And in the high temperature cabonization step In, the residence time of fiber is greater than 40 seconds；

Preferably, in the high temperature cabonization step, the residence time of fiber is 0.5~2min；

Preferably, the temperature of the high temperature cabonization processing is 1000~1500 DEG C.

Preferably, in the high temperature cabonization step, the tension for controlling the low-temperature carbonization corpus fibrosum is B, wherein 0 < B ≤8000CN。

Preferably, the number of the high temperature cabonization warm area is 3~6；Preferably,

Preferably, the number of the high temperature cabonization warm area is 3 or 4；Wherein,

When the high temperature cabonization warm area be 3 when, specifically: the first high temperature cabonization warm area, the second high temperature cabonization warm area and Third high temperature carbonization warm area；Wherein, the temperature of the first high temperature cabonization warm area be 1000~1300 DEG C, preferably 1100~ 1300℃；The temperature of the second high temperature cabonization warm area is 1150~1400 DEG C, preferably 1200~1400 DEG C；The third is high The temperature of temperature carbonization warm area is 1300~1500 DEG C；

When the high temperature cabonization warm area is 4, specifically: 900~1000 DEG C of the first high temperature cabonization warm area, 1000~ 1100 DEG C of second high temperature cabonization warm area, 1100~1300 DEG C of third high temperature carbonization warm areas and 1300~1500 DEG C of the 4th high temperature cabonization Warm area.

Preferably, before the low-temperature carbonization step, further includes:

Pre-oxidation step: so that polyacrylonitrile fibre is carried out pre-oxidation in pre-oxidation device, obtain pre-oxidized fibers Body；Wherein, the initial temperature of the pre-oxidation is 200~300 DEG C, end temperature is 250~280 DEG C, heating gradient 8 ~20 DEG C；

Preferably, in the pre-oxidation step, the total time of pre-oxidation is 30~70min；

Preferably, in the pre-oxidation step, the tension of the polyacrylonitrile fibre is controlled as C, and 0 < C≤ 5000CN；

Preferably, in the pre-oxidation step, the speed of service of the polyacrylonitrile fibre is 240~400m/h.

Preferably, when the pre-oxidized fibers volume density is 1.360~1.370g/cm³When, obtained polyacrylonitrile-radical The tensile strength of carbon fiber is 3.5~4.5GPa, stretch modulus is 230~250GPa, volume density 1.760-1.800g/cm³；

When the pre-oxidized fibers volume density is 1.345~1.355g/cm³When, obtained polyacrylonitrile-based carbon fibre Tensile strength be 4.9~5.2GPa, stretch modulus is 230~250GPa, volume density 1.780-1.810g/cm³；

When the pre-oxidized fibers volume density is 1.355~1.360g/cm³When, obtained polyacrylonitrile-based carbon fibre Tensile strength be 4.3~4.9GPa, stretch modulus is 230~250GPa, volume density 1.770-1.790g/cm³；

When the pre-oxidized fibers volume density is 1.340~1.345g/cm³When, obtained polyacrylonitrile-based carbon fibre Tensile strength be 3.0~3.5GPa, stretch modulus is 230~250GPa, volume density 1.790-1.810g/cm³。

On the other hand, the embodiment of the present invention provides a kind of polyacrylonitrile-based carbon fibre, wherein the polyacrylonitrile-based carbon Fiber is prepared by the preparation method of polyacrylonitrile-based carbon fibre described in any of the above embodiments；Preferably, the polyacrylonitrile The density of base carbon fibre is 1.760~1.810g/cm³；Preferably, the section of the polyacrylonitrile-based carbon fibre is substantially round Shape；Preferably, the diameter of the polyacrylonitrile-based carbon fibre is 4~8 μm.

Compared with prior art, polyacrylonitrile-based carbon fibre of the invention and preparation method thereof at least has following beneficial to effect Fruit:

1. the preparation method of polyacrylonitrile-based carbon fibre of the invention first exists the density domination of pre-oxidized fibers body 1.34~1.37g/cm³Between, the tensile strength for the polyacrylonitrile-based carbon fibre that the later period prepares is ensured that in this way, is stretched Modulus；Further, it after the density of pre-oxidized fibers body determines, is determined according to specific pre-oxidation density to pre-oxidized fibers The suitable tension that body applies, then can be improved the degree of orientation of fiber, and suitably increase the degree of orientation of fiber, will increase polypropylene The volume density of itrile group carbon fiber.Further, the present invention makes the tension applied to pre-oxidized fibers body and pre-oxidized fibers body Density phase coordinated, which is adjusted, (closes the density of the tension value A and pre-oxidized fibers body that apply to pre-oxidized fibers body in inverse ratio System), preferably to improve the volume density of polyacrylonitrile-based carbon fibre while carbon fiber being avoided to generate lousiness.

2. the preparation method of polyacrylonitrile-based carbon fibre of the invention is in high temperature cabonization step, by adjusting high-carbon warm area Distribution, with suitably increase fiber effective stay time (here, effective stay time refer to it is incremented by successively in warm area temperature When, residence time of the fiber in high temperature cabonization step), it is further able to improve volume density (the warm area increasing of polyacrylonitrile-based carbon fibre It will increase the volume density and modulus of fiber after long).

3. high density carbon fiber prepared by the preparation method using polyacrylonitrile-based carbon fibre of the invention is conducive to mention The compressive strength of high carbon fibre composite improves the tensile pressure ratio of carbon fibre composite.The present invention does not need to carry out equipment Transformation and upgrade, it is only necessary to can realize the preparation of high density carbon fiber by the optimum organization to process conditions, meet special The needs of different user.In addition, preoxidation process of the present invention, low-temperature carbonization process, high temperature cabonization process are unlike traditional patent control Drawing-off processed but control tow tension, control precision it is higher, the equipment for being adapted to different length, effectively avoid fiber lousiness and Industrialization quality stability is realized in the generation of fracture of wire.

The above description is only an overview of the technical scheme of the present invention, in order to better understand the technical means of the present invention, And can be implemented in accordance with the contents of the specification, the following is a detailed description of the preferred embodiments of the present invention and the accompanying drawings.

Detailed description of the invention

Figure 1A, Figure 1B, Fig. 1 C, Fig. 1 D are the scanning electron microscope of polyacrylonitrile-based carbon fibre prepared by the embodiment of the present invention 1 Figure；

Fig. 2A, Fig. 2 B, Fig. 2 C, Fig. 2 D are the scanning electron microscope of polyacrylonitrile-based carbon fibre prepared by the embodiment of the present invention 5 Figure；

Fig. 3 A, Fig. 3 B, Fig. 3 C, Fig. 3 D are the scanning electron microscope (SEM) photographs of pan based fibers prepared by the embodiment of the present invention 6.

Specific embodiment

It is of the invention to reach the technical means and efficacy that predetermined goal of the invention is taken further to illustrate, below in conjunction with Specific embodiment, structure, feature and its effect applied according to the present invention is described in detail such as in attached drawing and preferred embodiment Afterwards.In the following description, what different " embodiment " or " embodiment " referred to is not necessarily the same embodiment.In addition, one or more Special characteristic, structure or feature in a embodiment can be combined by any suitable form.

The technical issues of embodiment of the present invention provides a kind of preparation method of polyacrylonitrile-based carbon fibre, solves and invention Conceive as follows: the pressure of carbon fibre composite can be improved in the volume density that carbon fiber is improved under the indexs such as equality strength, modulus Contracting intensity improves the tensile pressure ratio of carbon fibre composite, and therefore, present invention is primarily intended to guarantee polyacrylonitrile-based carbon fibre Intensity, on the basis of modulus, improve the volume density of polyacrylonitrile-based carbon fibre.

Specific scheme is as follows:

A kind of preparation method of polyacrylonitrile-based carbon fibre, includes the following steps:

High temperature cabonization step: high temperature cabonization is carried out to the low-temperature carbonization corpus fibrosum, obtains high temperature cabonization corpus fibrosum；

Post-processing: the high temperature cabonization corpus fibrosum is post-processed, polyacrylonitrile-based carbon fibre is obtained.

Here, in the above-mentioned preparation method of the embodiment of the present invention, first by the density domination of pre-oxidized fibers body 1.34 ~1.37g/cm³Between, tensile strength, the stretching die of the polyacrylonitrile-based carbon fibre that the later period prepares are ensured that in this way Amount.Further, it after the density of pre-oxidized fibers body determines, is determined according to specific pre-oxidized fibers volume density to pre-oxidation The suitable tension that corpus fibrosum applies, then can be improved the degree of orientation of fiber, and suitably increase the degree of orientation of fiber, will increase poly- Volume density and modulus, the intensity of acrylonitrile base carbon fiber.

Further, in order to preferably improving the volume density of polyacrylonitrile-based carbon fibre while reducing, avoid carbon fiber Lousiness is generated, the present invention further adjusts the tension of pre-oxidized fibers body and the density coordinated of pre-oxidized fibers body, tool Body coordinated adjusting method is as follows: the tension value A of pre-oxidized fibers body and the density of pre-oxidized fibers body are in inverse relation.Tool Body, if the density of pre-oxidized fibers body is 1.34~1.355g/cm³, then it is 2500 to the tension that pre-oxidized fibers body applies ~5000CN；If the density of pre-oxidized fibers body is 1.355~1.37g/cm³, then it is to the tension of pre-oxidized fibers body application 100-2500CN.Further, if the density of the pre-oxidized fibers body is 1.34~1.345g/cm³, then to the pre-oxidation The tension that corpus fibrosum applies is 4200~5000CN；If the density of the pre-oxidized fibers body is 1.345~1.35g/cm³, then It is 3500~4200CN to the tension that the pre-oxidized fibers body applies；If the density of the pre-oxidized fibers body be 1.35~ 1.355g/cm³, then it is 2750~3500CN to the tension that the pre-oxidized fibers body applies；If the pre-oxidized fibers body Density is 1.355~1.36g/cm³, then it is 2000~2750CN to the tension that the pre-oxidized fibers body applies；If described pre- The density of oxidized fibre body is 1.36~1.365g/cm³, then to the pre-oxidized fibers body apply tension be 1300~ 2000CN；If the density of the pre-oxidized fibers body is 1.365~1.37g/cm³, then the pre-oxidized fibers body is applied Tension is 600~1300CN.

Preferably, in the low-temperature carbonization step: pre-oxidized fibers enter the cryogenic carbon under high pure nitrogen ambiance Change furnace, points of 5~7 warm areas carry out low-temperature carbonizations, and 300~900 DEG C of temperature, Oxygen in Nitrogen content is lower than 2ppm, the residence time 1~ 4min, each warm area residence time is the same (warm area length is the same), and fibre bundle tension force is in 0-5000CN.Preferably, Select 6 warm areas: 1 300~400 DEG C of warm area, 2 400~500 DEG C of warm areas, 3 500~600 DEG C of warm areas, 4 600~700 DEG C of warm areas, 5 700~800 DEG C of warm area, 6 800~900 DEG C of warm areas.

Preferably, point 3~6 warm areas carry out high temperature cabonization reaction, using high pure nitrogen as protective gas, Oxygen in Nitrogen Content is lower than 2ppm, and carburizing temperature is 1000~1500 DEG C, 0.5~2min of residence time, and each warm area residence time is the same (warm area length is the same), fibre bundle tension force is in 0-8000CN.Preferably, three warm areas: 1 warm area of high-carbon temperature are selected 1100~1300 DEG C, 2 1200~1400 DEG C of warm areas, 3 1300~1500 DEG C of warm areas.

Here, the present invention is by the way that in high temperature cabonization step, by adjusting the distribution of high-carbon warm area, appropriate increase fiber has The residence time is imitated (here, effective stay time refers to that fiber is in high temperature cabonization step when warm area temperature is incremented by successively Residence time), can also be improved the volume density of polyacrylonitrile-based carbon fibre, warm area will increase after increasing fiber volume density and Modulus.

Preferably, before the low-temperature carbonization step further include: pre-oxidation step, polyacrylonitrile carbon fiber precursor are (right In the requirement of polyacrylonitrile-based precursor, can be used as long as being able to satisfy and preparing the pre-oxidized fibers body of required density) 200~ Under 230 DEG C of initial temperature, with 10~20 DEG C of heating gradient, the total time for controlling pre-oxidation is 30~70min, is warming up to knot 250~280 DEG C of Shu Wendu, point 3~5 warm areas carry out pre-oxidation, and the tow speed of service is 240~400m/h, fiber filament In 0~5000CN, obtained pre-oxidized fibers volume density is controlled in 1.34~1.37g/cm beam tension force³。

Preferably, the step of post-processing include: the high temperature cabonization corpus fibrosum is successively surface-treated, water It washes, starching, drying, winding, obtains polyacrylonitrile-based carbon fibre.

It is further described below below by specific embodiment:

Following embodiment is to be 1.185-1.195g/cm to density³, pan based fibers that diameter is 10-12 μm it is (former Silk) it is pre-oxidized, for low-temperature carbonization, high temperature cabonization, polyacrylonitrile-based carbon can be improved to illustrate the present invention program The volume density of fiber.Certainly, the present invention is not limited to above-mentioned precursor, other kinds of precursor is also suitable, as long as precursor is in pre- oxygen The density of the pre-oxidized fibers body obtained after change is 1.34~1.37g/cm³?.

Embodiment 1

Pre-oxidation step: make to density 1.190g/cm³, diameter be that 12 μm of pan based fibers are pre-oxidized Reaction, obtains pre-oxidized fibers body；Wherein, pre-oxidation heating initial temperature is 220 DEG C, end temperature is 260 DEG C, heating 10 DEG C of gradient；The speed of service 360m/h of polyacrylonitrile fibre tow；The pre-oxidation residence time is 54min；In pre-oxidation In, it is 1000CN to the tension that tow applies, pre-oxidized fibers volume density obtained is 1.37g/cm³,

Low-temperature carbonization step: low-temperature carbonization processing is carried out to pre-oxidized fibers body, obtains low-temperature carbonization corpus fibrosum；Specifically Ground, the low-temperature carbonization warm area for making pre-oxidized fibers body successively pass through 300 DEG C, 400 DEG C of low-temperature carbonization warm area, 500 DEG C of low temperature Be carbonized warm area, 600 DEG C of low-temperature carbonization warm area, 700 DEG C of low-temperature carbonization warm area, and 900 DEG C of low-temperature carbonization warm area carries out low temperature Carbonization treatment.Wherein, in low-temperature carbonization step, the residence time of fiber is 2min, to the tension of pre-oxidized fibers body application For 600CN；In low-temperature carbonization device, it is passed through nitrogen, and Oxygen in Nitrogen content is lower than 2ppm.

High temperature cabonization step: high temperature cabonization processing is carried out to low-temperature carbonization corpus fibrosum, obtains high temperature cabonization corpus fibrosum.Specifically Ground, the high temperature cabonization warm area for making low-temperature carbonization corpus fibrosum successively pass through 1000 DEG C, 1200 DEG C of high temperature cabonization warm area, 1300 DEG C High temperature cabonization warm area carries out high temperature cabonization processing.Wherein, in high temperature cabonization step, the residence time of fiber is 1min, to low The tension that warm carbon fibre body applies is 1200CN；In high temperature cabonization device, it is passed through nitrogen, and Oxygen in Nitrogen content is lower than 2ppm。

Post-processing: high temperature cabonization corpus fibrosum is successively surface-treated, is washed, starching, drying, winding, is obtained Polyacrylonitrile-based carbon fibre finished product.

Polyacrylonitrile-based carbon fibre is tested, the density of the obtained polyacrylonitrile-based carbon fibre of embodiment 1 is 1.800g/cm³(density gradient method test), intensity 4.0GPa, extensometer modulus are 235GPa.

The D from Figure 1A to Fig. 1 is it can be seen that polyacrylonitrile-based carbon fibre prepared by embodiment 1 has circle or approximate circle Section, diameter is at 7 μm or so.

Comparative example 1

Pre-oxidation step: make density 1.190g/cm³, that diameter is that 12 μm of pan based fibers pre-oxidize is anti- It answers, obtains pre-oxidized fibers body；Wherein, pre-oxidation heating initial temperature is 220 DEG C, end temperature is 260 DEG C, heating ladder 10 DEG C of degree；The speed of service 360m/h of polyacrylonitrile fibre tow；The pre-oxidation residence time is 54min；In pre-oxidation, It is 1000CN to the tension that tow applies, pre-oxidized fibers volume density obtained is 1.370g/cm³,

High temperature cabonization step: high temperature cabonization processing is carried out to low-temperature carbonization corpus fibrosum, obtains high temperature cabonization corpus fibrosum.Specifically Ground, the high temperature cabonization warm area for making low-temperature carbonization corpus fibrosum successively pass through 1100 DEG C, 1380 DEG C of high temperature cabonization warm area carry out high temperature Carbonization treatment.Wherein, in high temperature cabonization step, the residence time of fiber is 0.67min, applies to low-temperature carbonization corpus fibrosum Tension is 1200CN；In high temperature cabonization device, it is passed through nitrogen, and Oxygen in Nitrogen content is lower than 2ppm.

Polyacrylonitrile-based carbon fibre is tested, the density of the obtained polyacrylonitrile-based carbon fibre of comparative example 1 is 1.770g/cm³(density gradient method test), intensity 4.0GPa, extensometer modulus are 235GPa.

By comparing embodiment 1 and comparative example 1, in high temperature cabonization step, the present invention is by adjusting high temperature cabonization temperature And warm area distribution, realize the proper extension of fiber retention time, and then improve the volume density of polyacrylonitrile-based carbon fibre.

Embodiment 2

Pre-oxidation step: make to density 1.185g/cm³, diameter be that 11 μm of pan based fibers are pre-oxidized Reaction, obtains pre-oxidized fibers body；Wherein, pre-oxidation heating initial temperature is 220 DEG C, end temperature is 254 DEG C, heating 12 DEG C of gradient；The speed of service 360m/h of polyacrylonitrile fibre tow；The pre-oxidation residence time is 54min；In pre-oxidation In, it is 1000CN to the tension that tow applies, pre-oxidized fibers volume density obtained is 1.364g/cm³。

Low-temperature carbonization step: low-temperature carbonization processing is carried out to pre-oxidized fibers body, obtains low-temperature carbonization corpus fibrosum；Specifically Ground, the low-temperature carbonization warm area for making pre-oxidized fibers body successively pass through 300 DEG C, 400 DEG C of low-temperature carbonization warm area, 500 DEG C of low temperature Be carbonized warm area, 600 DEG C of low-temperature carbonization warm area, and 700 DEG C of low-temperature carbonization warm area, 800 DEG C of low-temperature carbonization warm area carry out low temperature Carbonization treatment.Wherein, in low-temperature carbonization step, the residence time of fiber is 2min, to the tension of pre-oxidized fibers body application For 1300CN；In low-temperature carbonization device, it is passed through nitrogen, and Oxygen in Nitrogen content is lower than 2ppm.

High temperature cabonization step: high temperature cabonization processing is carried out to low-temperature carbonization corpus fibrosum, obtains high temperature cabonization corpus fibrosum.Specifically Ground, the high temperature cabonization warm area for making low-temperature carbonization corpus fibrosum successively pass through 1000 DEG C, 1150 DEG C of high temperature cabonization warm area, 1300 DEG C High temperature cabonization warm area carries out high temperature cabonization processing.Wherein, in high temperature cabonization step, the residence time of fiber is 1min, to low The tension that warm carbon fibre body applies is 1200CN；In high temperature cabonization device, it is passed through nitrogen, and Oxygen in Nitrogen content is lower than 2ppm。

Polyacrylonitrile-based carbon fibre is tested, the density of the obtained polyacrylonitrile-based carbon fibre of embodiment 2 is 1.790g/cm³(density gradient method test), intensity 4.0GPa, extensometer modulus are 235GPa.

Embodiment 3

Pre-oxidation step: make to density 1.185g/cm³, diameter be that 11 μm of pan based fibers are pre-oxidized Reaction, obtains pre-oxidized fibers body；Wherein, pre-oxidation heating initial temperature is 220 DEG C, end temperature is 250 DEG C, heating 10 DEG C of gradient；The speed of service 360m/h of polyacrylonitrile fibre tow；The pre-oxidation residence time is 54min；In pre-oxidation In, it is 1000CN to the tension that tow applies, pre-oxidized fibers volume density obtained is 1.362g/cm³。

Low-temperature carbonization step: low-temperature carbonization processing is carried out to pre-oxidized fibers body, obtains low-temperature carbonization corpus fibrosum；Specifically Ground, the low-temperature carbonization warm area for making pre-oxidized fibers body successively pass through 300 DEG C, 400 DEG C of low-temperature carbonization warm area, 500 DEG C of low temperature Be carbonized warm area, 600 DEG C of low-temperature carbonization warm area, and 700 DEG C of low-temperature carbonization warm area, 800 DEG C of low-temperature carbonization warm area carry out low temperature Carbonization treatment.Wherein, in low-temperature carbonization step, the residence time of fiber is 2min, to the tension of pre-oxidized fibers body application For 1400CN；In low-temperature carbonization device, it is passed through nitrogen, and Oxygen in Nitrogen content is lower than 2ppm.

Polyacrylonitrile-based carbon fibre is tested, the density of the obtained polyacrylonitrile-based carbon fibre of embodiment 3 is 1.795g/cm³(density gradient method test), intensity 4.0GPa, extensometer modulus are 235GPa.

Embodiment 4

Pre-oxidation step: make to density 1.185g/cm³, diameter be that 10 μm of pan based fibers are pre-oxidized Reaction, obtains pre-oxidized fibers body；Wherein, pre-oxidation heating initial temperature is 230 DEG C, end temperature is 248 DEG C；Poly- third The speed of service 360m/h of alkene nitrile fibre bundle；The pre-oxidation residence time is 54min；In pre-oxidation, tow is applied Tension be 1000CN, pre-oxidized fibers volume density obtained be 1.360g/cm³。

Low-temperature carbonization step: low-temperature carbonization processing is carried out to pre-oxidized fibers body, obtains low-temperature carbonization corpus fibrosum；Specifically Ground, the low-temperature carbonization warm area for making pre-oxidized fibers body successively pass through 300 DEG C, 400 DEG C of low-temperature carbonization warm area, 500 DEG C of low temperature Be carbonized warm area, 600 DEG C of low-temperature carbonization warm area, and 700 DEG C of low-temperature carbonization warm area, 800 DEG C of low-temperature carbonization warm area carry out low temperature Carbonization treatment.Wherein, in low-temperature carbonization step, the residence time of fiber is 2min, to the tension of pre-oxidized fibers body application For 1600CN；In low-temperature carbonization device, it is passed through nitrogen, and Oxygen in Nitrogen content is lower than 2ppm.

Polyacrylonitrile-based carbon fibre is tested, the density of the obtained polyacrylonitrile-based carbon fibre of embodiment 4 is 1.800g/cm³(density gradient method test), intensity 4.0GPa, extensometer modulus are 235GPa.

Comparative example 2

Pre-oxidation step: make to density 1.185g/cm³, diameter be that 10 μm of pan based fibers are pre-oxidized Reaction, obtains pre-oxidized fibers body；Wherein, pre-oxidation heating initial temperature is 220 DEG C, end temperature is 260 DEG C；Poly- third The speed of service 360m/h of alkene nitrile fibre bundle；The pre-oxidation residence time is 54min；In pre-oxidation, tow is applied Tension be 1000CN, pre-oxidized fibers volume density obtained be 1.367g/cm³。

Low-temperature carbonization step: low-temperature carbonization processing is carried out to pre-oxidized fibers body, obtains low-temperature carbonization corpus fibrosum；Specifically Ground, the low-temperature carbonization warm area for making pre-oxidized fibers body successively pass through 300 DEG C, 400 DEG C of low-temperature carbonization warm area, 500 DEG C of low temperature Be carbonized warm area, 600 DEG C of low-temperature carbonization warm area, and 700 DEG C of low-temperature carbonization warm area, 800 DEG C of low-temperature carbonization warm area carry out low temperature Carbonization treatment.Wherein, in low-temperature carbonization step, the residence time of fiber is 2min, to the tension of pre-oxidized fibers body application For 400CN；In low-temperature carbonization device, it is passed through nitrogen, and Oxygen in Nitrogen content is lower than 2ppm.

Polyacrylonitrile-based carbon fibre is tested, the density of the obtained polyacrylonitrile-based carbon fibre of comparative example 2 is 1.780g/cm³(density gradient method test), intensity 4.0GPa, extensometer modulus are 235GPa.

In conjunction with the embodiments 2, embodiment 3, embodiment 4 and comparative example 2 as can be seen that by make low-temperature carbonization react tension with Pre-oxidized fibers volume density matches, and can effectively adjust fiber orientation degree, improves carbon fibrous body density.

Embodiment 5

Pre-oxidation step: being 1.190g/cm to density³, that diameter is that 12 μm of pan based fibers pre-oxidize is anti- It answers, obtains pre-oxidized fibers body；Wherein, pre-oxidation heating initial temperature is 220 DEG C, end temperature is 250 DEG C, heating ladder Degree is 8 DEG C；The speed of service 360m/h of polyacrylonitrile fibre tow；The pre-oxidation residence time is 50min；In pre-oxidation In, it is 2000CN to the tension that tow applies, pre-oxidized fibers volume density obtained is 1.345g/cm³,

Low-temperature carbonization step: low-temperature carbonization processing is carried out to pre-oxidized fibers body, obtains low-temperature carbonization corpus fibrosum；Specifically Ground, the low-temperature carbonization warm area for making pre-oxidized fibers body successively pass through 400 DEG C, 450 DEG C of low-temperature carbonization warm area, 520 DEG C of low temperature Be carbonized warm area, 600 DEG C of low-temperature carbonization warm area, 750 DEG C of low-temperature carbonization warm area, and 780 DEG C of low-temperature carbonization warm area carries out low temperature Carbonization treatment.Wherein, in low-temperature carbonization step, the residence time of fiber is 2.4min, opens to pre-oxidized fibers body application Power is 4200CN；In low-temperature carbonization device, it is passed through nitrogen, and Oxygen in Nitrogen content is lower than 2ppm.

High temperature cabonization step: high temperature cabonization processing is carried out to low-temperature carbonization corpus fibrosum, obtains high temperature cabonization corpus fibrosum.Specifically Ground, the high temperature cabonization warm area for making low-temperature carbonization corpus fibrosum successively pass through 900 DEG C, 1100 DEG C of high temperature cabonization warm area, 1300 DEG C High temperature cabonization warm area and 1400 DEG C of high temperature cabonization warm area carry out high temperature cabonization processing.Wherein, in high temperature cabonization step, fiber Residence time be 1.4min, to low-temperature carbonization corpus fibrosum apply tension be 1600CN；In high temperature cabonization device, it is passed through nitrogen Gas, and Oxygen in Nitrogen content is lower than 2ppm.

Polyacrylonitrile-based carbon fibre is tested, the density of the obtained polyacrylonitrile-based carbon fibre of embodiment 5 is 1.810g/cm³(density gradient method test), intensity 5.02GPa, extensometer modulus are 238GPa.

The D from Fig. 2A to Fig. 2 is it can be seen that polyacrylonitrile-based carbon fibre prepared by embodiment 5 has circle or approximate circle Section, diameter is at 7 μm or so.

Comparative example 3

High temperature cabonization step: high temperature cabonization processing is carried out to low-temperature carbonization corpus fibrosum, obtains high temperature cabonization corpus fibrosum.Specifically Ground, the high temperature cabonization warm area for making low-temperature carbonization corpus fibrosum successively pass through 900 DEG C, 1100 DEG C of high temperature cabonization warm area and 1400 DEG C High temperature cabonization warm area carry out high temperature cabonization processing.Wherein, in high temperature cabonization step, residence time of fiber be 1.05min, It is 1600CN to the tension that low-temperature carbonization corpus fibrosum applies；In high temperature cabonization device, it is passed through nitrogen, and Oxygen in Nitrogen content is low In 2ppm.

Polyacrylonitrile-based carbon fibre is tested, the density of the obtained polyacrylonitrile-based carbon fibre of comparative example 3 is 1.770g/cm³(density gradient method test), intensity 5.02GPa, extensometer modulus are 238GPa.

By comparing embodiment 5 and comparative example 3, in high temperature cabonization step, the present invention is by adjusting high temperature cabonization temperature And warm area distribution, realize the proper extension of fiber retention time, and then improve the volume density of polyacrylonitrile-based carbon fibre.

Embodiment 6

Pre-oxidation step: being 1.185g/cm to density³, that diameter is that 10 μm of pan based fibers pre-oxidize is anti- It answers, obtains pre-oxidized fibers body；Wherein, pre-oxidation heating initial temperature is 220 DEG C, end temperature is 250 DEG C, heating ladder Degree is 8 DEG C；The speed of service 240m/h of polyacrylonitrile fibre tow；The pre-oxidation residence time is 50min；In pre-oxidation In, it is 2000CN to the tension that tow applies, pre-oxidized fibers volume density obtained is 1.350g/cm³,

Low-temperature carbonization step: low-temperature carbonization processing is carried out to pre-oxidized fibers body, obtains low-temperature carbonization corpus fibrosum；Specifically Ground, the low-temperature carbonization warm area for making pre-oxidized fibers body successively pass through 400 DEG C, 450 DEG C of low-temperature carbonization warm area, 520 DEG C of low temperature Be carbonized warm area, 600 DEG C of low-temperature carbonization warm area, 750 DEG C of low-temperature carbonization warm area, and 780 DEG C of low-temperature carbonization warm area carries out low temperature Carbonization treatment.Wherein, in low-temperature carbonization step, the residence time of fiber is 2.4min, opens to pre-oxidized fibers body application Power is 3500CN；In low-temperature carbonization device, it is passed through nitrogen, and Oxygen in Nitrogen content is lower than 2ppm.

High temperature cabonization step: high temperature cabonization processing is carried out to low-temperature carbonization corpus fibrosum, obtains high temperature cabonization corpus fibrosum.Specifically Ground, the high temperature cabonization warm area for making low-temperature carbonization corpus fibrosum successively pass through 1200 DEG C, 1350 DEG C of high temperature cabonization warm area, 1500 DEG C High temperature cabonization warm area carries out high temperature cabonization processing.Wherein, in high temperature cabonization step, residence time of fiber is 1.05min, right The tension that low-temperature carbonization corpus fibrosum applies is 4000CN；In high temperature cabonization device, it is passed through nitrogen, and Oxygen in Nitrogen content is lower than 2ppm。

Polyacrylonitrile-based carbon fibre is tested, the density of the obtained polyacrylonitrile-based carbon fibre of embodiment 6 is 1.809g/cm³(density gradient method test), intensity 5.07GPa, extensometer modulus are 295GPa.

From Fig. 3 A to Fig. 3 D it can be seen that polyacrylonitrile-based carbon fibre prepared by embodiment 6 has circle or approximate circle Section, diameter is at 5 μm or so.

Comparative example 4

High temperature cabonization step: high temperature cabonization processing is carried out to low-temperature carbonization corpus fibrosum, obtains high temperature cabonization corpus fibrosum.Specifically Ground, the high temperature cabonization warm area for making low-temperature carbonization corpus fibrosum successively pass through 1200 DEG C, 1500 DEG C of high temperature cabonization warm area carry out high temperature Carbonization treatment.Wherein, in high temperature cabonization step, the residence time of fiber is 1.07min, applies to low-temperature carbonization corpus fibrosum Tension is 4000CN；In high temperature cabonization device, it is passed through nitrogen, and Oxygen in Nitrogen content is lower than 2ppm.

Polyacrylonitrile-based carbon fibre is tested, the density of the obtained polyacrylonitrile-based carbon fibre of embodiment 6 is 1.770g/cm³(density gradient method test), intensity 5.66GPa, extensometer modulus are 235GPa.

By comparing embodiment 6 and comparative example 4, in high temperature cabonization step, the present invention is by adjusting high temperature cabonization temperature And warm area distribution, realize the proper extension of fiber retention time, and then improve the volume density of polyacrylonitrile-based carbon fibre.

Embodiment 7

Pre-oxidation step: being 1.195g/cm to density³, diameter is 11 μm pre-oxidizes pan based fibers Reaction, obtains pre-oxidized fibers body；Wherein, pre-oxidation heating initial temperature is 220 DEG C, end temperature is 254 DEG C, heating 12 DEG C of gradient；The speed of service 360m/h of polyacrylonitrile fibre tow；The pre-oxidation residence time is 54min；In pre-oxidation In, it is 1000CN to the tension that tow applies, pre-oxidized fibers volume density obtained is 1.354g/cm³。

Low-temperature carbonization step: low-temperature carbonization processing is carried out to pre-oxidized fibers body, obtains low-temperature carbonization corpus fibrosum；Specifically Ground, the low-temperature carbonization warm area for making pre-oxidized fibers body successively pass through 300 DEG C, 400 DEG C of low-temperature carbonization warm area, 500 DEG C of low temperature Be carbonized warm area, 600 DEG C of low-temperature carbonization warm area, and 700 DEG C of low-temperature carbonization warm area, 800 DEG C of low-temperature carbonization warm area carry out low temperature Carbonization treatment.Wherein, in low-temperature carbonization step, the residence time of fiber is 2min, to the tension of pre-oxidized fibers body application For 3000CN；In low-temperature carbonization device, it is passed through nitrogen, and Oxygen in Nitrogen content is lower than 2ppm.

High temperature cabonization step: high temperature cabonization processing is carried out to low-temperature carbonization corpus fibrosum, obtains high temperature cabonization corpus fibrosum.Specifically Ground, the high temperature cabonization warm area for making low-temperature carbonization corpus fibrosum successively pass through 1100 DEG C, 1300 DEG C of high temperature cabonization warm area, 1400 DEG C High temperature cabonization warm area carries out high temperature cabonization processing.Wherein, in high temperature cabonization step, the residence time of fiber is 1min, to low The tension that warm carbon fibre body applies is 1200CN；In high temperature cabonization device, it is passed through nitrogen, and Oxygen in Nitrogen content is lower than 2ppm。

Polyacrylonitrile-based carbon fibre is tested, the density of the obtained polyacrylonitrile-based carbon fibre of embodiment 7 is 1.790g/cm³(density gradient method test), intensity 5.05GPa, extensometer modulus are 235GPa.

Embodiment 8

Pre-oxidation step: being 1.195g/cm to density³, that diameter is that 11 μm of pan based fibers pre-oxidize is anti- It answers, obtains pre-oxidized fibers body；Wherein, pre-oxidation heating initial temperature is 220 DEG C, end temperature is 250 DEG C, heating ladder 10 DEG C of degree；The speed of service 360m/h of polyacrylonitrile fibre tow；The pre-oxidation residence time is 54min；In pre-oxidation, It is 1000CN to the tension that tow applies, pre-oxidized fibers volume density obtained is 1.352g/cm³。

Low-temperature carbonization step: low-temperature carbonization processing is carried out to pre-oxidized fibers body, obtains low-temperature carbonization corpus fibrosum；Specifically Ground, the low-temperature carbonization warm area for making pre-oxidized fibers body successively pass through 300 DEG C, 400 DEG C of low-temperature carbonization warm area, 500 DEG C of low temperature Be carbonized warm area, 600 DEG C of low-temperature carbonization warm area, and 700 DEG C of low-temperature carbonization warm area, 800 DEG C of low-temperature carbonization warm area carry out low temperature Carbonization treatment.Wherein, in low-temperature carbonization step, the residence time of fiber is 2min, to the tension of pre-oxidized fibers body application For 3300CN；In low-temperature carbonization device, it is passed through nitrogen, and Oxygen in Nitrogen content is lower than 2ppm.

Polyacrylonitrile-based carbon fibre is tested, the density of the obtained polyacrylonitrile-based carbon fibre of embodiment 8 is 1.800g/cm³(density gradient method test), intensity 5.02GPa, extensometer modulus are 235GPa.

Embodiment 9

Pre-oxidation step: being 1.195g/cm to density³, that diameter is that 11 μm of pan based fibers pre-oxidize is anti- It answers, obtains pre-oxidized fibers body；Wherein, pre-oxidation heating initial temperature is 230 DEG C, end temperature is 248 DEG C；Polypropylene The speed of service 360m/h of nitrile fibre bundle；The pre-oxidation residence time is 54min；In pre-oxidation, tow is applied Tension is 1000CN, and pre-oxidized fibers volume density obtained is 1.350g/cm³。

Low-temperature carbonization step: low-temperature carbonization processing is carried out to pre-oxidized fibers body, obtains low-temperature carbonization corpus fibrosum；Specifically Ground, the low-temperature carbonization warm area for making pre-oxidized fibers body successively pass through 300 DEG C, 400 DEG C of low-temperature carbonization warm area, 500 DEG C of low temperature Be carbonized warm area, 600 DEG C of low-temperature carbonization warm area, and 700 DEG C of low-temperature carbonization warm area, 800 DEG C of low-temperature carbonization warm area carry out low temperature Carbonization treatment.Wherein, in low-temperature carbonization step, the residence time of fiber is 2min, to the tension of pre-oxidized fibers body application For 3500CN；In low-temperature carbonization device, it is passed through nitrogen, and Oxygen in Nitrogen content is lower than 2ppm.

Polyacrylonitrile-based carbon fibre is tested, the density of the obtained polyacrylonitrile-based carbon fibre of embodiment 9 is 1.810g/cm³(density gradient method test), intensity 5.06GPa, extensometer modulus are 235GPa.

Comparative example 5

Pre-oxidation step: being 1.195g/cm to density³, that diameter is that 11 μm of pan based fibers pre-oxidize is anti- It answers, obtains pre-oxidized fibers body；Wherein, pre-oxidation heating initial temperature is 220 DEG C, end temperature is 254 DEG C, heating ladder 12 DEG C of degree；The speed of service 360m/h of polyacrylonitrile fibre tow；The pre-oxidation residence time is 54min；In pre-oxidation, It is 1000CN to the tension that tow applies, pre-oxidized fibers volume density obtained is 1.354g/cm³。

Low-temperature carbonization step: low-temperature carbonization processing is carried out to pre-oxidized fibers body, obtains low-temperature carbonization corpus fibrosum；Specifically Ground, the low-temperature carbonization warm area for making pre-oxidized fibers body successively pass through 300 DEG C, 400 DEG C of low-temperature carbonization warm area, 500 DEG C of low temperature Be carbonized warm area, 600 DEG C of low-temperature carbonization warm area, and 700 DEG C of low-temperature carbonization warm area, 800 DEG C of low-temperature carbonization warm area carry out low temperature Carbonization treatment.Wherein, in low-temperature carbonization step, the residence time of fiber is 2min, to the tension of pre-oxidized fibers body application For 600CN；In low-temperature carbonization device, it is passed through nitrogen, and Oxygen in Nitrogen content is lower than 2ppm.

Polyacrylonitrile-based carbon fibre is tested, the density of the obtained polyacrylonitrile-based carbon fibre of comparative example 5 is 1.780g/cm³(density gradient method test), intensity 5.0GPa, extensometer modulus are 235GPa.

In conjunction with the embodiments 7, embodiment 8, embodiment 9 and comparative example 5 as can be seen that by make low-temperature carbonization react tension with Pre-oxidized fibers volume density matches, and can effectively adjust fiber orientation degree, improve the volume density of carbon fiber.

Embodiment 10

Pre-oxidation step: make to density 1.185g/cm³, diameter be that 10 μm of pan based fibers are pre-oxidized Reaction, obtains pre-oxidized fibers body；Wherein, pre-oxidation heating initial temperature is 220 DEG C, end temperature is 260 DEG C, heating 10 DEG C of gradient；The speed of service 360m/h of polyacrylonitrile fibre tow；The pre-oxidation residence time is 54min；In pre-oxidation In, it is 1000CN to the tension that tow applies, pre-oxidized fibers volume density obtained is 1.356g/cm³,

Low-temperature carbonization step: low-temperature carbonization processing is carried out to pre-oxidized fibers body, obtains low-temperature carbonization corpus fibrosum；Specifically Ground, the low-temperature carbonization warm area for making pre-oxidized fibers body successively pass through 300 DEG C, 400 DEG C of low-temperature carbonization warm area, 500 DEG C of low temperature Be carbonized warm area, 600 DEG C of low-temperature carbonization warm area, 700 DEG C of low-temperature carbonization warm area, and 900 DEG C of low-temperature carbonization warm area carries out low temperature Carbonization treatment.Wherein, in low-temperature carbonization step, the residence time of fiber is 2min, to the tension of pre-oxidized fibers body application For 2500CN；In low-temperature carbonization device, it is passed through nitrogen, and Oxygen in Nitrogen content is lower than 2ppm.

Polyacrylonitrile-based carbon fibre is tested, the density of the obtained polyacrylonitrile-based carbon fibre of embodiment 10 is 1.785g/cm³(density gradient method test), intensity 4.7GPa, extensometer modulus are 235GPa.

Comparative example 6

Low-temperature carbonization step: low-temperature carbonization processing is carried out to pre-oxidized fibers body, obtains low-temperature carbonization corpus fibrosum；Specifically Ground, the low-temperature carbonization warm area for making pre-oxidized fibers body successively pass through 300 DEG C, 400 DEG C of low-temperature carbonization warm area, 500 DEG C of low temperature Be carbonized warm area, 600 DEG C of low-temperature carbonization warm area, 700 DEG C of low-temperature carbonization warm area, and 900 DEG C of low-temperature carbonization warm area carries out low temperature Carbonization treatment.Wherein, in low-temperature carbonization step, the residence time of fiber is 2min, to the tension of pre-oxidized fibers body application For 1000CN；In low-temperature carbonization device, it is passed through nitrogen, and Oxygen in Nitrogen content is lower than 2ppm.

Polyacrylonitrile-based carbon fibre is tested, the density of the obtained polyacrylonitrile-based carbon fibre of comparative example 6 is 1.770g/cm³(density gradient method test), intensity 4.3GPa, extensometer modulus are 235GPa.

In conjunction with the embodiments 10 and comparative example 6 as can be seen that by make low-temperature carbonization react tension and pre-oxidized fibers body it is close Degree matches, and can effectively adjust fiber orientation degree, improve the volume density of polyacrylonitrile-based carbon fibre.

Embodiment 11

Pre-oxidation step: being 1.186g/cm to density³, that diameter is that 12 μm of pan based fibers pre-oxidize is anti- It answers, obtains pre-oxidized fibers body；Wherein, pre-oxidation heating initial temperature is 220 DEG C, end temperature is 250 DEG C, heating ladder Degree is 8 DEG C；The speed of service 240m/h of polyacrylonitrile fibre tow；The pre-oxidation residence time is 50min；In pre-oxidation In, it is 2000CN to the tension that tow applies, pre-oxidized fibers volume density obtained is 1.344g/cm³,

Low-temperature carbonization step: low-temperature carbonization processing is carried out to pre-oxidized fibers body, obtains low-temperature carbonization corpus fibrosum；Specifically Ground, the low-temperature carbonization warm area for making pre-oxidized fibers body successively pass through 400 DEG C, 450 DEG C of low-temperature carbonization warm area, 520 DEG C of low temperature Be carbonized warm area, 600 DEG C of low-temperature carbonization warm area, 750 DEG C of low-temperature carbonization warm area, and 780 DEG C of low-temperature carbonization warm area carries out low temperature Carbonization treatment.Wherein, in low-temperature carbonization step, the residence time of fiber is 2.4min, opens to pre-oxidized fibers body application Power is 4500CN；In low-temperature carbonization device, it is passed through nitrogen, and Oxygen in Nitrogen content is lower than 2ppm.

Polyacrylonitrile-based carbon fibre is tested, the density of the obtained polyacrylonitrile-based carbon fibre of embodiment 11 is 1.803g/cm³(density gradient method test), intensity 3.5GPa, extensometer modulus are 235GPa.

Comparative example 7

High temperature cabonization step: high temperature cabonization processing is carried out to low-temperature carbonization corpus fibrosum, obtains high temperature cabonization corpus fibrosum.Specifically Ground, the high temperature cabonization warm area for making low-temperature carbonization corpus fibrosum successively pass through 1300 DEG C, 1450 DEG C of high temperature cabonization warm area carry out high temperature Carbonization treatment.Wherein, in high temperature cabonization step, the residence time of fiber is 35s, to the tension of low-temperature carbonization corpus fibrosum application For 4000CN；In high temperature cabonization device, it is passed through nitrogen, and Oxygen in Nitrogen content is lower than 2ppm.

Polyacrylonitrile-based carbon fibre is tested, the density of the obtained polyacrylonitrile-based carbon fibre of comparative example 7 is 1.790g/cm³(density gradient method test), intensity 3.4GPa, extensometer modulus are 235GPa.

By comparing embodiment 11 and comparative example 7, in high temperature cabonization step, the present invention is by adjusting high temperature cabonization temperature And warm area distribution, realize the proper extension of fiber retention time, and then improve the volume density of polyacrylonitrile-based carbon fibre.

The above described is only a preferred embodiment of the present invention, be not intended to limit the present invention in any form, according to According to technical spirit any simple modification, equivalent change and modification to the above embodiments of the invention, this hair is still fallen within In the range of bright technical solution.

Claims

1. a kind of preparation method of polyacrylonitrile-based carbon fibre, which is characterized in that it includes the following steps:

Low-temperature carbonization step: being 1.34~1.37g/cm to density³Pre-oxidized fibers body carry out low-temperature carbonization processing, obtain low Warm carbon fibre body；Wherein, it in the low-temperature carbonization step, according to the density of the pre-oxidized fibers body, controls described pre- The tension of oxidized fibre body is A, and 0 < A≤5000CN；

2. the preparation method of polyacrylonitrile-based carbon fibre according to claim 1, which is characterized in that in the low-temperature carbonization In step, wherein the density of the tension value A of the pre-oxidized fibers body and the pre-oxidized fibers body is in inverse relation；

Preferably, if the density of the pre-oxidized fibers body is 1.34~1.355g/cm³, then the pre-oxidized fibers body is applied Tension be 2500~5000CN；

If the density of the pre-oxidized fibers body is 1.355~1.37g/cm³, then to the tension of pre-oxidized fibers body application For 100~2500CN.

3. the preparation method of polyacrylonitrile-based carbon fibre according to claim 2, which is characterized in that in the low-temperature carbonization In step:

If the density of the pre-oxidized fibers body is 1.34~1.345g/cm³, then to the tension of pre-oxidized fibers body application For 4200~5000CN；

If the density of the pre-oxidized fibers body is 1.345~1.35g/cm³, then to the tension of pre-oxidized fibers body application For 3500~4200CN；

If the density of the pre-oxidized fibers body is 1.35~1.355g/cm³, then to the tension of pre-oxidized fibers body application For 2750~3500CN；

If the density of the pre-oxidized fibers body is 1.355~1.36g/cm³, then to the tension of pre-oxidized fibers body application For 2000~2750CN；

If the density of the pre-oxidized fibers body is 1.36~1.365g/cm³, then to the tension of pre-oxidized fibers body application For 1300~2000CN；

If the density of the pre-oxidized fibers body is 1.365~1.37g/cm³, then to the tension of pre-oxidized fibers body application For 600~1300CN.

4. the preparation method of polyacrylonitrile carbon fiber according to claim 1-3, which is characterized in that described low In warm carburising step: the pre-oxidized fibers body being made successively to carry out low-temperature carbonization processing by multiple low-temperature carbonization warm areas；Wherein, The latter low-temperature carbonization warm area is higher than the temperature of previous low-temperature carbonization warm area；

Preferably, in the low-temperature carbonization step, the residence time of fiber is 1-4min；

Preferably, the number of the low-temperature carbonization warm area is 5~7；

Preferably, the number of the low-temperature carbonization warm area is 6, specifically: 300~400 DEG C of the first low-temperature carbonization warm area, 400~500 DEG C of the second low-temperature carbonization warm area, 500~600 DEG C of third low-temperature carbonization warm areas, 600~700 DEG C of the 4th low temperature Be carbonized warm area, 700~800 DEG C of the 5th low-temperature carbonization warm area and 800~900 DEG C of the 6th low-temperature carbonization warm area.

5. the preparation method of polyacrylonitrile-based carbon fibre according to claim 1-4, which is characterized in that described In high temperature cabonization step: low-temperature carbonization corpus fibrosum being made successively to carry out high temperature cabonization processing by multiple high temperature cabonization warm areas；Wherein,

The latter high temperature cabonization warm area is higher than the temperature of previous high temperature cabonization warm area；It is fine and in the high temperature cabonization step The residence time of dimension is greater than 40 seconds；

Preferably, the temperature of the high temperature cabonization processing is 1000~1500 DEG C；

Preferably, in the high temperature cabonization step, the tension for controlling the low-temperature carbonization corpus fibrosum is B, wherein 0 < B≤ 8000CN。

6. the preparation method of polyacrylonitrile-based carbon fibre according to claim 5, which is characterized in that the high temperature cabonization temperature The number in area is 3~6；

When the high temperature cabonization warm area is 3, specifically: the first high temperature cabonization warm area, the second high temperature cabonization warm area and third High temperature cabonization warm area；Wherein, the temperature of the first high temperature cabonization warm area be 1000~1300 DEG C, preferably 1100~1300 ℃；The temperature of the second high temperature cabonization warm area is 1150~1400 DEG C, preferably 1200~1400 DEG C；The third high temperature carbon The temperature for changing warm area is 1300~1500 DEG C；

When the high temperature cabonization warm area is 4, specifically: 900~1000 DEG C of the first high temperature cabonization warm area, 1000~1100 DEG C the second high temperature cabonization warm area, 1100~1300 DEG C of third high temperatures carbonization warm areas and 1300~1500 DEG C of the 4th high temperature cabonization temperature Area.

7. the preparation method of polyacrylonitrile-based carbon fibre described in -6 according to claim 1, which is characterized in that in the cryogenic carbon Before change step, further includes:

Pre-oxidation step: so that polyacrylonitrile fibre is carried out pre-oxidation in pre-oxidation device, obtain pre-oxidized fibers body；Its In, the initial temperature of the pre-oxidation is 200~300 DEG C, end temperature is 250~280 DEG C, heating gradient is 8~20 ℃；

Preferably, in the pre-oxidation step, the tension of the polyacrylonitrile fibre is controlled as C, and 0 < C≤5000CN；

8. polyacrylonitrile-based carbon fibre according to claim 1-7, which is characterized in that the step of the post-processing Include: the high temperature cabonization corpus fibrosum is successively surface-treated, is washed, starching, drying, winding, obtain polyacrylonitrile-radical Carbon fiber.

9. the preparation method of polyacrylonitrile-based carbon fibre according to claim 1-8, which is characterized in that when described Pre-oxidized fibers volume density is 1.360~1.370g/cm³When: the tensile strength of obtained polyacrylonitrile-based carbon fibre is 3.5 ~4.5GPa, stretch modulus be 230~250GPa, volume density 1.760-1.800g/cm³；

When the pre-oxidized fibers volume density is 1.345~1.355g/cm³When, the stretching of obtained polyacrylonitrile-based carbon fibre Intensity is 4.9~5.2GPa, stretch modulus is 230~250GPa, volume density 1.780-1.810g/cm³；

When the pre-oxidized fibers volume density is 1.355~1.360g/cm³When, the stretching of obtained polyacrylonitrile-based carbon fibre Intensity is 4.3~4.9GPa, stretch modulus is 230~250GPa, volume density 1.770-1.790g/cm³；

When the pre-oxidized fibers volume density is 1.340~1.345g/cm³When, the stretching of obtained polyacrylonitrile-based carbon fibre Intensity is 3.0~3.5GPa, stretch modulus is 230~250GPa, volume density 1.790-1.810g/cm³。

10. a kind of polyacrylonitrile-based carbon fibre, which is characterized in that the polyacrylonitrile-based carbon fibre is any by claim 1-9 The preparation method of polyacrylonitrile-based carbon fibre described in is prepared；

Preferably, the density of the polyacrylonitrile-based carbon fibre is 1.760~1.810g/cm³；

Preferably, the section of the polyacrylonitrile-based carbon fibre is generally circular；

Preferably, the diameter of the polyacrylonitrile-based carbon fibre is 4~8 μm.