JPH04194029A - Production of lignin-based carbon fiber - Google Patents

Abstract

PURPOSE:To obtain the subject fiber excellent in mechanical characteristics by adding phenol to lignin, heating the resultant mixture, providing phenolated lignin, adding a specific pitch thereto, heating the mixture in a nonoxidizing atmosphere, melt spinning the prepared heavy lignin, infusibilizing and burning the formed fiber. CONSTITUTION:Phenol is added to lignin and the resultant mixture is heated to provide phenolated lignin. Pitch having 70-105 deg.C softening point in an amount of preferably 0.1-1.0 pt.wt. based on 1 pt.wt. aforementioned phenolated lignin is then added thereto and the prepared mixture is heated at 240-280 deg.C in a nonoxidizing atmosphere to afford heavy lignin, which is subsequently melt spun into fiber. The formed fiber is infusibilized and burned according to a conventional method to provide the objective fiber.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application in M Industry] The present invention relates to a method for easily obtaining lignin-based carbon fibers with excellent mechanical properties at a high yield.

[Prior Art] Lignin accounts for about 1/3 of the wood components, and more than 50% of lignin is carbon, so attempts have been made to effectively utilize it by converting it into carbon fibers and phenolic resins. In particular, for carbon fibers with high added value, a method (dry method) has been proposed in which yarns are drawn from a spinning solution prepared by dissolving lignin and polyvinyl alcohol in an aqueous solution of caustic soda (dry method), but this method has not been industrialized.

In recent years, the effective use of wood components has been reconsidered, and efforts are being made to produce carbon fibers using lignin obtained by steaming, crushing, or cooking wood with alcohol, acetic acid, etc. as a raw material. This new lignin-based carbon fiber is modified by hydrogenolyzing or phenolizing lignin to give it thermal fluidity, then heated in a non-oxidizing atmosphere to give it viscosity, and then melt-spun. It is obtained by a method of further infusibility and sintering.

[Problems to be Solved by the Invention] This method of using heavy lignin yields carbon fibers with almost the same strength and yield as pitch-based carbon fibers, but sufficient spinnability is required during spinning. There are problems in that it is extremely difficult to adjust the spinning solution for holding, and spinning conditions must be strictly controlled for long-term continuous spinning. It is also desired to further increase strength and yield.

[Means for Solving the Problems] The present inventors have obtained the knowledge that a heavy lignin with excellent spinnability can be obtained by adding pitch to phenolated lignin and subjecting it to a heating reaction, and as a result of extensive research. This heavy lignin is easy to prepare as a spinning solution and can be continuously spun with high yield, making it a lignin-based carbon with outstanding strength and yield! l
It was discovered that the result was a delicate navy blue color, and the present invention was completed.

That is, in the present invention, phenol is added to lignin. iJ! Wait for the phenolized lignin, then,
Medium pitch with a softening point of 70 to 105° C. is added to the phenolized lignin, heated in a non-oxidizing atmosphere to obtain a heavy lignin, and then the heavy lignin is mu-spun.
The present invention provides a method for producing rigenine-based carbon fiber, which is characterized by making it infusible and firing it by a conventional method. To briefly explain in detail, the lignin used in the present invention is obtained by steaming and IIA crushing wood, or by cooking it with alcohol, acetic acid, etc., and the lignin Ifij18B is chopped into phenol 0.1~
It is preferable to add 1.0 part by weight and react at 180 to 200° C. for 5 to 10 hours under air pressure to phenolize.

At this time, as a catalyst, sulfuric acid was added to lignin at 0, O1 to
If the diameter is increased by about 0,03ffi m%, the reaction will proceed more effectively, but if it is in excess, oxidation will occur rapidly, leading to deterioration of the lignin, which is disadvantageous.

The reacted lignin is subjected to distillation under reduced pressure to remove unrepulsed components, and is then made heavier.

When increasing the weight, a medium pitch with a softening point of 7G-105°C is added, but if the softening point is outside the artiams, it may not lead to improvement in stringiness.

This is not preferable because it may impair infusibility.

To increase the weight, the medium pitch is 0.1-1% per 1 part by weight of phenolated lignin. The reaction is carried out by adding 151 parts of O and heating at 240 to 260° C. under a non-oxidizing atmosphere, preferably under vacuum.

If the amount of medium pitch added exceeds the upper limit of the above range, the spinnability will be improved, but the wA navy blue will melt in the undefeatable process after spinning and will not be able to maintain its shape. This is not preferable because the improvement in stringability is slight, and if the heating conditions for weighting are outside the above range, the reforming reaction will not proceed or will be excessive, which is disadvantageous.

The molarized lignin obtained in this way is heated to a temperature of 200 to 280°C.
Heat it to make a spinning solution with a viscosity of 40 to 80 degrees! 1lf
lj and subjected to spinning. The spinning conditions include discharging nitrogen gas from a nozzle under pressure, stretching and solidifying in air. At this time, the nozzle hole diameter is 0.3 to 1・O■φ・The discharge pressure is 0.
05-1. 0 kg/cm2 and a drawing ratio (nozzle hole diameter l fiber diameter) lθ to 50 are preferable, and conditions other than the above range are disadvantageous because stable discharge and take-up cannot be achieved. The resulting spun fibers are then rendered infusible and fired by conventional methods to obtain carbon fibers. The following conditions for infusibility and firing are sufficient.

Infusibility conditions: in air, 240-250℃, 15℃/I
+? .

■Waiting time: 0 to 60 minutes Firing conditions: Nitrogen or argon gas, 800 to 300
0℃, 200℃/llr.

Holding time: 30-60 minutes The lignin-based carbon fiber thus obtained has a tensile strength of 50-80 kg/ms+2 and a tensile modulus of 3-5 tons.
/m*2 and elongation of 1.1-1.5%, which is almost the same as commercially available pitch-based carbon IIA fibers, and yield (calcined product weight/raw material lignin weight jl) of 45-60%, which is higher than conventional The yield is increased by about 20 to 50% compared to the yield obtained by the hydrogenation method.

[Example] Example 1 To 1 part by weight of lignin obtained by steaming and blasting birch wood, 1.0 part by weight of phenol and 0.02 part by weight of concentrated sulfuric acid were added and reacted at 180°C for 6 hours. phenolized,
This was then distilled under reduced pressure of 5'T o r r to remove unreacted components to obtain phenolated lignin. Softening point: 105°C for 1 part of this phenolized gunnin
Add 0.1 part by weight of medium pitch, and add 0.1 part by weight of medium pitch. The mixture was reacted at 240° C. for 20 minutes under ITorr vacuum to produce heavy lignin. The softening point of this heavy lignin 9 is 181
It was ℃. This heavy lignin was heated and melted at 230° C. to obtain a spinning solution, which was spun at a discharge pressure of 0.1 kg/cw+2 from a nozzle having 8 holes with a hole diameter of 0.5IIIφ. The stretching ratio at this time was 25. Regarding the spinning conditions, there was no yarn breakage even during continuous spinning for 10 minutes. The fibers spun at 100° C. were made infusible at 240° C. in the air, and there was no fusion between the infusible fibers.

Furthermore, this infusible dark blue was fired to 800° C. in a nitrogen atmosphere to obtain lignin-based carbon fibers.

Table 1 shows the properties and yield of the obtained lignin-based carbon fiber.

Examples 2-3, Comparative Examples 1-2 The same phenolated gunnin used in Example 1
Pitches having the softening points shown in Table 1 were added to each part in v1 ratio shown in Table 11, and the mixture was reacted for 30 minutes at the temperature shown in Table 1 under a vacuum of 0.1 Torr to make it heavy. The softening point of the obtained heavy lignin is shown in Table 1. The spinning solution was obtained by heating and melting at a temperature of 50° C. above the softening point of this heavy lignin, and using the nozzle of Example 1, Example 0 Spinning was carried out under the same conditions as 1. Table 1 shows the situation during continuous spinning for 10 minutes.

The spun fibers were then infusible and fired under the same conditions as in Example 1 to obtain lignin-based charcoal purple wA fibers. The infusibility status, properties and yield of the obtained carbon fibers are shown in Table 1.
The fibers of Comparative Example 1 were fused during infusibility, making it difficult to proceed with subsequent steps.

Comparative Example 3゜The same phenolated lignin used in Example 1 was
．． Lignin-based carbon fibers were obtained in the same manner as in Example 1, except that the polymerized lignin was heat-treated at 260° C. for 20 minutes under the vacuum of ITorr, and this was melted at 235° C. to obtain a spinning solution.

Table 1 shows the spinning conditions, infusibility conditions, properties of the obtained carbon fibers, and yield.

[Effects] As is clear from the Examples and Comparative Examples, the present invention adds a specific pitch to lignin to make it heavier, so there is no problem during spinning or infusibility, and it has excellent mechanical properties. This is an industrially extremely useful method that can obtain lignin-based carbon fibers at a higher yield than conventional methods.

Claims (2)

[Claims] (1) Phenol is added to lignin and heated to obtain phenolized lignin, then medium pitch with a softening point of 70 to 105°C is added to the phenolated lignin and heated in a non-oxidizing atmosphere to make it heavy. A method for producing lignin-based carbon fibers, which comprises obtaining lignin, melt-spinning the heavy lignin, and then making it infusible and firing it by a conventional method. (2) Add 0.1 to 1.0 parts by weight of medium pitch to 1 part by weight of phenolated lignin and
The method for producing lignin-based carbon fibers according to claim 1, characterized in that the heavy lignin is obtained by heating at 0 to 280°C.