JPS6144992A - Production of crude raw pitch for carbon fiber - Google Patents

Abstract

PURPOSE:To produce pitch which gives high-quality pitch carbon fiber in high yields, by mixing a heavy soln. layer separated from a mixture of coal tar pitch and a hydrocarbon solvent with a hydrocarbon solvent, and removing the solvents from a light soln. layer separated from the resulting mixture. CONSTITUTION:Coal tar pitch having an initial b.p. of 190-400 deg.C is mixed with a first solvent consisting of an aliph. hydrocarbon and/or an alicyclic hydrocarbon. The resulting first mixture is subjected to a first gravity separation to separate it into a first light soln. layer and a first heavy soln. layer. The resulting first heavy soln. layer is mixed with a second solvent consisting of a mixture of an arom. hydrocarbon and an aliph. hydrocarbon and/or an alicyclic hydrocarbon. The resulting second mixture is subjected to a second gravity separation to separate it into a second light soln. layer and a second heavy soln. layer. The solvents are removed from the second light soln. layer.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for producing pitch as a raw material for carbon fibers, and more specifically, to a method for producing pitch-based raw material pitch for carbon fibers, and more specifically, a method for producing pitch-based pitch-based carbon fibers with high properties in a high yield. The present invention relates to a method for producing raw material pitch for use.

[Conventional technology]

In recent years, carbon fiber has been highly evaluated for its performance as a composite material with plastic or metal, and in particular, various studies have been conducted on pitch-based carbon fiber.

In order to improve the properties of pitch-based carbon fibers, instead of the isotropic pitch that was conventionally used as a spinning raw material, raw material pitch is heated to develop anisotropy and form molecular species that are easily oriented. That is, menphasic pitch is used, and this is accomplished mainly by adjusting the properties of the spinning pitch.

However, ordinary pitches contain a component useful for forming menphase produced by heat treatment, that is, β
- Since the content of the resin component is low and it has a wide molecular weight distribution from low molecules to rope molecules, when producing spinning pitch using these raw material pitches, there are few parts involved in the formation of the menphase. In addition, the generation of mesophase in the low molecular region and the polymer region differs depending on the heat treatment, making it difficult to age a uniform mesophase.

Therefore, as a method to overcome these drawbacks, method C is proposed in which coal tar or hacoal tar soft pitch is treated with an aromatic solvent or a mixed solvent of an aromatic solvent and an aliphatic solvent.
% Kaishoj (4-/40da No. 7 Publication, JP Kaisho!rg-IJ
[Problems to be Solved by the Invention] However, in any of these methods, it is difficult to efficiently obtain components useful for forming carbon fibers and to create a uniform structure. It was still not enough to generate a phase.

[Means to solve problems]

Therefore, the present inventors have been busy with these solvent treatment methods, and as a result of further studies, we have used coal tar pitch having an initial boiling point in a specific range, obtained by removing light boiling components from coal tar, and using a specific type of coal tar pitch. We discovered that using a two-stage extraction method using a combination of solvents, the components useful for forming carbon fibers were concentrated, improving the yield of carbon fibers, and narrowing the molecular weight distribution and improving spinnability. Based on this, the present invention was completed.

That is, one object of the present invention is to provide a method for producing pitch-based raw material pitch for carbon fibers that can yield pitch-based carbon fibers with high properties;
Coal tar pitch having an initial boiling point of ~qoo°C is mixed with a first solvent consisting of an aliphatic hydrocarbon bulk substance υ and/l- or an alicyclic hydrocarbon substance, and the obtained primary mixture is A first light liquid layer and a first heavy liquid layer are separated by stratification, and then the obtained first heavy liquid layer is separated from aromatic hydrocarbon substances, aliphatic hydrocarbon bulk substances and/or alicyclic carbonization. A second solvent consisting of a mixture of hydrogen substances is mixed with -L, the resulting second
This is achieved by performing a second stratification separation of the mixture into a second light liquid layer and a second heavy liquid layer, and removing the solvent from the obtained first light liquid layer.

The present invention will be described in detail below.The present invention is obtained by removing light boiling components from the uninvented starting material, coal tar, by ordinary pressure distillation or vacuum distillation. Those with a boiling point of /90 to 00°C, preferably aoo to 3zOc, more preferably aa
O ~ Rich (7C coal tar pitch.

Specifically, there are various pitches commonly referred to as road tar, tar pitch, soft pitch, hard pitch, etc.

The initial boiling point is adjusted by the boiling point of the light ladder component to be removed.In other words, by setting the distillation temperature at the top of the distillation column within the above temperature range, the initial boiling point of coal tar pitch obtained from the bottom of the column can be adjusted. is determined. Especially, the distillation temperature range is determined by 2-
When selecting from the range of 〇-Code OC, the concentration ratio of components useful for forming carbon fibers is improved.

In other words, the fraction up to 360C in the pitch of the extraction raw material obtained as the bottom fraction varies by adjusting the tower top temperature, but if the amount of this fraction is small, the solubility of pitch in the solvent will decrease. In stratified separation of a mixture of pitch and solvent, the proportion of useful components concentrated in the lower layer decreases,
During single-stage extraction, the concentration of useful components is reduced.

On the other hand, if the amount increases, the effective components will be carried away to the upper layer due to increased compatibility with the solvent and low-boiling substances, and the concentration ratio to the lower layer will decrease, which is preferable because the concentration of useful components that can be brought in during the first stage extraction will be small. As the first solvent used in the present invention, an aliphatic hydrocarbon substance or an alicyclic hydrocarbon substance having a boiling point or a distillation temperature of 65-co90C1, preferably tro-co50C is used. .

If a heavy hydrocarbon oil of 2"10C or more is used, it is not advantageous because the heat load becomes large in the operation for removing the solvent after the extraction process.These aliphatic hydrocarbon substances include hexane, Examples include paraffins of 06 to Cl1l such as heptane, octane, decane, and pentadecane, naphtha, and kerosene.Also, examples of alicyclic hydrocarbon substances include cyclohexane, methylcyclohexane, ethylcyclohexane, cycloheptane, methylcycloheptane, and ethyl cyclohexane. Examples include alicyclic hydrocarbons of 06 to CIG, such as cycloheptane, cyclooctane, and decalin, or alicyclic hydrocarbons having an alkyl group, but naphtha or kerosene is preferably used from the viewpoint of economy and operability. It is preferable to select these solvents whose dry point is several degrees Celsius or more lower than the initial distillation temperature of the coal tar pitch used as the extraction raw material.Especially when recycling the recovered solvent, this selection method is recommended. becomes important.

If the recovered solvent contains a low boiling point substance, the recovered solvent may be further purified by distillation and recycled.

The above-mentioned solvents can be used in combination of one or more kinds. If the amount of the first solvent used is too small, it will be difficult to perform stratified separation in the next step, and if it is used in too large a amount, it will take time to recover the first solvent from the stratified separation liquid, making it uneconomical. Usually, t''-t o parts by weight, preferably 2 to 1 part by weight, per 1 part by weight of coal tar pitch used as a starting material.
6 parts by weight are used.◎' The coal tar pitch and the solvent are mixed using a stirring tank, an axial flow mixer, a two-river nozzle, an ejector, a static mixer, etc. at room temperature to 200°C, preferably tθO/IOc. carried out at a temperature of The mixing time varies depending on the type of mixer, and in the case of a stirring tank, several minutes or more is required, but in the case of other mixers, a few seconds to about one minute is sufficient. The obtained primary mixture is heated at a temperature at which the light liquid layer stratified and separated from the mixture can be separated while maintaining its liquid state, for example, room temperature to
The first stratified separation is carried out into a first light liquid layer and a first heavy liquid layer by holding the mixture at 200°C, preferably /DO~7gDCK0.2~2 hours under normal pressure or increased pressure.・Standing and separating the above mixture using a heating jacket)
- The obtained first heavy liquid layer is then mixed with a first solvent, which has a boiling point or a distillation temperature of 95% by volume. But 65~+000. Preferably, the aliphatic hydrocarbon material and/or the alicyclic hydrocarbon material is go-2!6C and the boiling point or distillation temperature of 95 cm volume is 100 to 4 Io.
o C, preferably from 210 to 300 C - using a mixture with aromatic hydrocarbon substances - these aliphatic and/or cycloaliphatic hydrocarbon substances, such as those mentioned above as the first solvent. Something similar to can be used.

In addition, examples of aromatic hydrocarbon substances include naphthalene, methylnaphthalene, 1. Hydrocarbon substances with carbon nest rings or carbon polycycles such as anthracene, medium oil obtained by distillation of coal tar, heavy oil, anthracene oil, etc. are used, but if the boiling point of the aromatic solvent is too high, the yield will decrease. I don't like it.

The proportion of the aromatic hydrocarbon substance in the second solvent is selected such that the proportion of the aromatic hydrocarbon substance in the total solvent after mixing with the first heavy liquid layer of the solvent 1 is 30 to 60 volumes. Usually, 0.2 to 1.1 parts by weight are mixed per 1 part by weight of aliphatic hydrocarbon material and/or alicyclic hydrocarbon material. That is, the proportion of aromatic hydrocarbon substances in the second solvent is 30 to 60.
If the mixing ratio of aromatic hydrocarbons is too large, the quinoline solution will neutralize the pitch for hydrogenation, which will increase the filtration process, and if it is too small, the active ingredient goulase will be mixed. , and it is necessary to select an appropriate ratio.

Next, even if the amount of J/C second solvent used is too small, as with the above aromatic component mixing ratio, if it is too small, the removal rate of the quinoline solution will be low, and if too large a quantity is used, the effective ingredient β-resin will be reduced. At the same time, recovering the solvent from the stratified separated liquid takes time and is not economical, so usually the first heavy liquid layer 1 is
Weight part ratio: 0.3 to 1. ! Parts by weight, preferably 0.
j~1.0 part by weight is used and needs to be selected appropriately.

The first heavy liquid layer and the second solvent are mixed and allowed to stand at a temperature of -00
~, yso℃, preferably goo θ ~ 330C, and the standing time is 30 minutes or less, but the process is carried out under the same conditions as in the case of mixing coal tar pitch and the first #l agent described above. If the standing time is too long, the .beta.-resin will settle, which is undesirable.After that, a second stratified separation is performed into an a-th light liquid layer and a second heavy liquid layer.

The obtained second light liquid layer is subjected to distillation under normal pressure or reduced pressure to remove the solvent fraction using an evaporator or a distillation column. The distilled solvent fraction is recycled and used as a solvent as it is or after being purified. The desired product obtained as a bottom fraction or bottom fraction in this distillation varies depending on the quality of the coal tar used as a starting material, but usually the number average molecular weight obtained from a calibration curve of polystyrene and toluene using GPC is bso~tro, toluene insoluble content 20~koj wt
%, quinoline solubility O~1vtlJ, β-resin 2θ
It is a blackish-brown pitch-like material with a weight of 100% by weight, and has physical properties preferable as a raw material pitch for carbon fibers.

The obtained crude raw material pitch is subjected to meso conversion treatment according to a conventional method 2! ! After carrying out this process, it is used as pitch for spinning.The small first light liquid layer obtained by the first stratification separation can be used as raw material oil for carbon black by appropriately treating it. Carbon oil and naphthalene oil obtained by distillation of the distillate and/or coal tar used to obtain coal tar pitch having an initial boiling point of 000°C are thermal cracking or catalytic cracking of petroleum distillation residue or naphtha. It can also be used as a kernel that is mixed with carbon black raw material oil obtained by pyrolysis. It was also obtained by secondary stratified separation. The second heavy liquid layer can be used as fuel or the like, or the solvent fraction can be removed by distillation under normal or reduced pressure or steam distillation using an evaporator or distillation column and an extruder such as an Extri-User. Then, it is cut in a cooling layer with pressure steam and used as fuel, pitch coke, raw material for various return materials, etc. The recovered bath agent fraction is recycled and used as a solvent.Furthermore, the first heavy liquid layer, which is extracted with the first solvent, is distilled using an evaporator or distillation column under normal pressure or reduced pressure to remove the solvent. After distilling off the fraction, it may be mixed with the first solvent. The distilled off solvent fraction is recycled and used as a solvent.

〔effect〕

As described in detail above, in the present invention, t
The bottom fraction from which the light boiling point fraction below qoz has been removed is extracted in stages using a specific solvent, and the solvent is distilled off from the stratified light liquid layer. As such, ingredients (β-resin) useful for metsuphase generation are
It is extremely useful as a method for producing raw material pitch for carbon fibers because it can be contained at a high concentration of 0- or more and a narrow pitch in the molecular weight can be obtained.

In addition, the raw material pitch obtained in the present invention can be subjected to a conventional method to easily obtain spinning pitch with good spinnability. After this, pm' may be performed.The spinning pitch obtained in this way is melt-spun according to a conventional method, and subjected to infusibility treatment, carbonization treatment, and graphitization treatment if necessary. Pitch-based carbon fibers with higher properties can be obtained by doing more.

〔Example〕

Next, the present invention will be explained in more detail with reference to examples, but the present invention is not limited to the following examples unless it exceeds the gist thereof.

Example 1 Coal tar pitch obtained by distillation of coal tar (initial boiling point 30°C, fraction up to J40C 3°t, 9% by weight, toluene insoluble content 7.3% by weight, quinoline soluble content) Overlapping part, β-resin!, ?wt%) cooo weight part, initial boiling point/'II℃, ? ,! Mix 340 parts by weight of light kerosene (I solvent) with t% distillation point/9D°C at 740°C for 10 minutes,
It was left at the same temperature for 10 minutes. Next, 100x parts of the lower layer subjected to the second stratification separation and an initial boiling point of ieo°C, ? ,t9G
1 of light kerosene and naphthalene oil with a distillation point of 1toc:
90 parts by weight of a mixture (second solvent) with a weight ratio of 1.15 and stirred at 3 ooc for tslJ, then heated at the same temperature Vc.
15 of the stratified upper layer after the apparatus was left standing for o, g hours.
1 part by weight was collected, and the solvent was removed from the collected material by vacuum distillation to obtain 40 parts by weight of pitch.The physical properties of the obtained pitch were measured and the results are shown in Table 1.

Example Coat tar pitch obtained by distillation of cocoa tar (initial boiling point AOC up to 1340°C: 5 wt.
200 parts by weight of the resin (5.3% by weight) and qoo parts by weight of the same first solvent used in Example 1 were mixed at @t4Ioc for -O minutes, and left to stand at the same temperature for 20 minutes. Next, 100 parts by weight of the lower layer separated into the first order layer and the same second solvent as in Example 1 were added. Mix everything with the OM place and heat at 300°C.
The mixture was stirred for 3 minutes and then allowed to stand at the same temperature for 0 and 5 hours. 1 part by weight of the upper layer subjected to the second stratified separation was collected, and the solvent was removed from the collected product by distillation under reduced pressure to obtain a box quantity. Measure the physical properties of the obtained pitch and use the results as the first
Shown in the table Comparative Example 1 Heavy liquid layer separated into the first several layers at iyo°C in Example 1
o parts by weight The solvent was removed by total vacuum distillation to obtain 5 parts by weight. The obtained pitch physical properties are shown in Table 1.

Reference Example 1 41.3 parts by weight of the pitch obtained in Example 1 and 100 parts by weight of 29f in tetrahydro were mixed in a closed container with stirring.
The temperature was raised to 0°C and maintained at the same temperature for 1 minute. Next, the contents were filtered, and light boiling components were removed by vacuum distillation.

The obtained hydrogenated pitch bO overlapping part t was heated at qso° C. for 40 minutes while stirring and introducing nitrogen gas to obtain menphasic pitch having an anisotropy of factor 95.

This menphase pitch? , temperature z3'io℃・Spinning nozzle inner diameter f: J, j 11111, spinning speed 3 u D O
When spun under condition -F for 7 minutes, a fiber t having a yarn diameter of 1λμ could be stably obtained for a long time (1 hour or more).Furthermore, this pitch fiber was infusible at f3/117°C. After treatment/Carbonization at 200C? From Do K, 9.
Carbon fibers having a thread diameter of 7μ were obtained.

The tensile strength and tensile modulus of this carbon fiber were measured and found that the core was 0kf/2 and the core was soo k11/Il.
It was "l".

Reference Example λ P1 obtained in Example 1. The meso 7Aze pitch was subjected to KM processing in the same manner as in Reference Example 1 to obtain a meso 7Aze pitch having an anisotropy of 95% @ When this meso 7Aze pitch was spun under the same conditions as Reference Example 1, it had a yarn diameter of /Jμ. Although the fibers could be stably obtained for a long time (over 1 hour), the carbon fibers obtained by treating the pitch fibers in the same manner as in Reference Example 1 had a tensile strength of 0 to #/all'' and a tensile strength of Elastic modulus here b0
It was 0 kt/2 parrots.

Reference Example 3 The pitch obtained in Comparative Example 1 was treated in the same manner as Reference Example/l. , a mesophase pitch having an anisotropy of t% was obtained. When this mesophase pitch was spun under the same conditions as in Reference Example 1, a fiber Vi having a yarn diameter of Jμ could be obtained stably for more than 1 hour. However, Example 1. - Compared to the pitch, the yarn properties are slightly lower, and the tensile strength is 150k.
p/ym", tensile modulus tttoo kg/wa"tetb) f, knee.

Table 1

Claims (10)

[Claims] (1) Coal tar pitch having an initial boiling point of 190 to 400°C and a first solvent consisting of an aliphatic hydrocarbon substance and/or an alicyclic hydrocarbon substance are mixed, and the obtained first mixture is First stratified separation into a first light liquid layer and a first heavy liquid layer, and then the obtained first heavy liquid layer and aromatic hydrocarbon substances, aliphatic hydrocarbon substances and/or alicyclic and a second solvent consisting of a mixture of hydrocarbon substances, and the obtained second mixture is subjected to second stratification separation into a second light liquid layer and a second heavy liquid layer, and the obtained second A method for producing raw material pitch for carbon fibers, characterized in that the solvent is removed from the second light liquid layer. (2) The boiling point of the first solvent or the distillation temperature of 95% by volume is 65
Claim 1 characterized in that the temperature is ~290°C
A method for producing raw material pitch for carbon fibers as described in . (3) The boiling point of the second solvent or the distillation temperature of 95% by volume is 65
Claim 1 characterized in that the temperature is ~400°C
A method for producing raw material pitch for carbon fibers as described in . (4) The aromatic hydrocarbon substance contained in the second solvent is 30%
60% by weight of the raw material pitch for carbon fibers according to claim 1. (5) The method for producing coarse raw material pitch for carbon fibers according to claim 1, wherein the amount of the first solvent used is 1 to 10 parts by weight per 1 part by weight of coal tar pitch. (6) The carbon fiber according to claim 1, wherein the amount of the second solvent used is 0.3 to 1.5 parts by weight per 1 part by weight of the first heavy liquid layer. Production method of crude raw material pitch. (7) The method for producing coarse raw material pitch for carbon fibers according to claim 1, wherein the first stratification separation is carried out at a temperature of room temperature to 200°C. (8) The method for producing coarse raw material pitch for carbon fibers according to claim 1, wherein the secondary stratification separation is carried out at a temperature of 200 to 350°C. (9) Transfer the first heavy liquid layer that does not substantially contain the first solvent to the second heavy liquid layer.
2. A method for producing pitch as a raw material for carbon fibers according to claim 1, which comprises mixing the pitch with a solvent. (10) The method for producing crude pitch for carbon fibers according to claim 1, wherein the first bath agent is naphtha or kerosene.