JPS6030368B2 - Manufacturing method of phenolic resin carbon fiber - Google Patents

Description

[Detailed description of the invention] The present invention relates to a method for producing phenolic resin carbon fiber.

Specifically, the present invention relates to a method for easily producing high-strength carbon fibers by firing and carbonizing phenolic resin fibers. Phenol resin fibers have the excellent feature of having a low shrinkage rate when fired and carbonized.

That is, unless fibers made of acrylonitrile, vinyl chloride, vinyl alcohol, etc. are fired while being stretched, they will lack tensile strength and will have difficulty maintaining their fiber shape, resulting in lumpy carbides with low strength. On the other hand, phenolic resin fibers do not have this problem at all, so
There is an advantage that no stretching device is required and the equipment is extremely simple. Conventionally, acrylonitrile, vinyl chloride,
It is known that when producing carbon fiber using thermoplastic resin fibers such as vinyl alcohol as a raw material, after performing infusibility treatment by air oxidation, ozone oxidation, etc. at low temperatures, the temperature is raised in an inert atmosphere and carbonized. However, when thermosetting resin fibers such as phenolic resin fibers are fired and carbonized, it was thought that it was unnecessary to react with oxygen because the fibers do not melt.

Reacting with oxygen will only promote the frack-breaking reaction (a reaction in which carbon is dissipated in the form of carbon dioxide gas or carbon monoxide, slowing down the rate of carbonization), so it should not be used exclusively. It has been considered desirable to carry out pyrocarbonization in an inert atmosphere. (Refer to British Patent No. 1258277) However, when we examine in detail the method of carbonizing phenolic resin fibers in an inert atmosphere, we find that, for example, when phenolic resin fiber cloth is layered thickly and fired, the lower layer It was found that the carbon fibers became extremely porous, the strength deteriorated to a considerable extent, and the carbonization yield was poor. As a result of extensive research to eliminate the above-mentioned defects, the present inventors discovered that while actively supplying a specific amount of oxygen in a relatively low temperature range when carbonizing phenolic fibers, discovered that a homogeneous and strong carbonized product could be obtained at a high yield by replacing oxygen with an inert gas, and completed the present invention.

That is, the gist of the present invention is to provide a method for producing phenolic resin carbon fibers by firing and carbonizing phenolic resin fibers, in which the phenolic resin fibers are fired at a low temperature of 100 qo to 200 qo, and the phenolic resin fibers are fired at a temperature of 10 ta or more per lk9 of the phenolic resin fibers. The method comprises heat treating the yield fibers in the presence of oxygen, followed by firing and carbonizing the fibers at a temperature of at least about 50,000 in an inert gas atmosphere.

The present invention will be explained in detail below.

The phenolic resin fiber used in the method of the present invention is produced by fiberizing a nopolac resin produced by condensing phenol with aldehyde under acidic conditions or a resol resin condensed under alkaline conditions, and then Manufactured by curing.

Novolak resins are generally prepared by reacting phenol in excess of aldehyde, which is permanently meltable and soluble.

As the aldehyde, formaldehyde is usually used, but acetaldehyde, butyraldehyde, chloral, acrolein, furfural, etc. can also be used.

Phenol itself is the most commonly used phenol in fer/fer resins. Other phenols that have been used include monohydric phenols such as cresols and xylenols. Acidic catalysts that can be used during the condensation process include hydrochloric acid, sulfuric acid, formic acid, acetic acid, hakamic acid, tartaric acid and aromatic sulfonic acids. Generally, the condensation process is carried out in a reaction vessel under reflux conditions for an extended period of time. The novolak resin of the present invention has a number average molecular weight of 500 to 20.
00 is preferred.

Novolak resin must be dried before it can be drawn into fibers.

The resin is then heated until it melts and is forced to flow out of the orifice. The melt emerging from the orifice is attenuated into fibers as a result of being drawn off, for example by the rotation of a spool that takes up the fibers. When the fibers are exposed to the atmosphere and cool, they solidify and can then be wound onto a spool. After forming into fibers, it is preferable to cure the fibers by heating in an atmosphere containing both formaldehyde and acid. The atmosphere can be a gas, but is preferably a liquid, such as a solution of acid and formaldehyde. In either gas or liquid atmospheres, the curing rate increases rapidly with increasing temperature. However, it is usually desirable to perform the curing process while gradually increasing the temperature. The curing time must be long enough to render the uncured fibers non-fusible. After curing, it may be possible to supplement the curing by further treatment with an amount of formaldehyde or a formaldehyde product in an alkaline solution. During curing/Polac linear polymers cross-polymerize with each other, thereby becoming immovable and non-melting. On the other hand, resol resins are generally produced by reacting phenol with excess aldehyde under alkaline conditions, and are made into fibers in substantially the same manner as novolac resins. However, unlike the case of novolak resin, after fiberization, it is cured simply by heating. Although the present invention is effective for all types of phenolic resin fibers, it is particularly suitable for novolac resin fibers.

If necessary, polyamide, polyvinyl chloride, polyvinyl alcohol, etc. may be mixed with the novolak resin. Therefore, the feature of the present invention is that the cured film/
When firing and carbonizing the resin fibers, a specific amount of oxygen is actively supplied and heated in a low temperature firing zone from 100° C. to 200 qo.

At temperatures above 200°C, oxygen must be replaced by inert gas.

After replacing with inert gas, the carbonization is completed by heating to at least about 50 CO, preferably 800 to 1100 CO. The heating rate is selected from the range of 0.5 to 500°C/hour, preferably 10 to 200°C/hour. Oxygen to be added is a cumulative amount of 10 to 200 degrees Celsius after the start of temperature rise, and at least 10 days per lk9 of F/F resin fibers.
Preferably it is 50 ta or more. There is no particular limit to the upper limit of the amount of oxygen added as long as oxygen is not present in the firing zone of 20 pi or more.

This is because in the low-temperature firing zone of 100 to 200°C, oxygen mainly acts on the dehydrogenation reaction of phenolic resin fibers and hardly participates in the decarburization and firing reactions, so even if excess oxygen is present, carbonization does not occur. This is because the reaction is effectively promoted. On the other hand, the oxygen-based dehydrogenation reaction for phenolic resin fibers does not substantially occur at temperatures below 10°C, so if the predetermined amount of oxygen is present in the firing range from room temperature to 200qo, 100~200q
The result is the same as when the same amount of oxygen is present in the low temperature firing belt of o. However, if oxygen remains in the firing zone above 200℃, it will promote the combustion reaction, which is inconvenient, so the oxygen supply amount is controlled so that the oxygen is completely consumed in the zone up to 200℃. It is preferable to do so.

According to the findings of the present inventors, if the amount of oxygen supplied is kept below 200°C per lk9 of phenolic resin fiber,
Almost the entire amount is consumed in the band up to. The amount of oxygen consumed may vary depending on the firing temperature, firing time, type of fiber, method of binding, etc., so phenolic resin fibers
It is particularly preferred to supply 50 to 150 hours of oxygen per 9 hours. If oxygen remains in the firing zone of 20,000°C or more, the carbonization atmosphere must be replaced with an inert gas when the temperature is raised to 200°C.

Next, a case where firing is performed while moving the fiber material will be explained using the drawings. FIG. 1 is a conceptual diagram showing the method of the present invention. In FIG. 1, 1 is a firing furnace, 2 is a raw material, 3 is a product, A is a low temperature firing zone, B is a firing carbonization zone, and C is a cooling zone.

Raw material 2 (phenolic resin fiber cloth) is used for low-temperature firing obijo A.
Supplies more than 10 ta of oxygen per lk9, maximum 20,000
Heat until.

An inert gas is supplied to the sintered carbonization zone B as needed.
The phenolic resin fiber cloth is heated to a temperature of 0 to 1,100 °C to complete firing carbonization, and then cooled in cooling zone C. Specifically, the case where the method of the present invention is used using a tunnel furnace will be explained with reference to FIGS. 2 and 3.

In Figures 2 and 3, 4 is a phenolic resin fiber cloth, 5 is an oxygen supply port, 6 and 8 are inert gas supply ports, 7 is a waste gas discharge port, 9 is a partition plate, and 10 is a subheater. , 1 1 is a heater for firing carbonization, 12 is a lo-fu, 13
is the water level for sealing, D is the oxygen supply zone (low temperature firing zone),
E is an inert gas supply zone (calcination carbonization zone).

In FIG. 2, the phenolic resin fiber cloth 4 is heated in the presence of oxygen in the oxygen supply zone D to 200 q0 from the subheater 10', and then heated from 200 qo to 500 q0 in the inert gas supply zone E. ~110pi0
It is heated to competitive carbonization.

The waste gas is discharged from the waste gas outlet 7. From the oxygen supply port 5, 10 times more oxygen per phenolic resin fiber cloth 1 is supplied. When firing is carried out in a closed container, the amount of oxygen sealed in the container is adjusted to 10 to 200 days, preferably 50 to 150 days, per phenolic resin fiber IX9, and then Once the temperature starts to rise, the oxygen is completely consumed in the low temperature firing range up to 200°C, so in this case too, abnormal oxidation will not occur in the range of 20°C or higher. In this way, in the low-temperature firing zone of up to 20 mm, decarburization reaction does not occur even if heated while supplying oxygen; instead, dehydrogenation reaction occurs preferentially, so the firing The carbonization yield can be increased during the process.

Furthermore, although the reason is not clear, it must be noted that by firing under the above-mentioned specific conditions while adding oxygen, a homogeneous and strong carbonized product can be obtained without deterioration of strength. In particular, it has been found that the present invention is extremely effective in firing and carbonizing thickly stacked phenolic resin fibers, yarns, cloth, nonwoven fabrics, mats, and the like. Next, the present invention will be specifically explained using Examples and Comparative Examples, but the present invention is not limited to the following Examples unless it exceeds the gist thereof.

Example 1 and Comparative Examples 1 to 4 Two denier novolak resin fibers were produced from novolac having a number average molecular weight of about 800 and a melting point of about 110 qo and cured in a mixed solution of hydrochloric acid and formaldehyde.

A novolac resin fiber cloth with a basis weight of 320 mm/m was produced from the cured fibers. Next, the fiber cloth was heated in a tunnel furnace as shown in FIG. 2 by supplying a predetermined amount of oxygen to a predetermined firing zone. A small amount of nitrogen gas was supplied to heat the temperature range other than the oxygen supply temperature range. Heating was continued to 800°C to complete firing.

The stiffness and strength of the obtained carbon fiber cloth were measured and the results are shown in Table 1. Table 1 Example 2 and Comparative Examples 5 and 6 Using 2 denier novolac resin fibers produced in the same manner as in Example 1, a novolac resin fiber cloth with a basis weight of 250 yen/pillow was produced.

Next, a predetermined amount of the fiber cloth was placed in a stainless steel kiln having a volume of 100 and sealed. The total amount of oxygen present in a closed kiln without fiber cloth being charged is 28.
It was the 5th evening. After preparation, it was heated to 800°C and fired.
The heating rate is 50 qo/hour. The carbonization rate and strength of the obtained carbon fiber cloth were measured and the results are shown in Table 2.
Table 2

[Brief explanation of the drawing]

FIG. 1 is a conceptual diagram showing the method of the present invention, FIG. 2 is a side sectional view of a tunnel furnace, and FIG. 3 is a vertical sectional view of the tunnel furnace. Ude' Picture Spear 2 Picture Next Picture J

Claims (1)

[Claims] 1. A method for producing phenolic resin-based carbon fibers by firing and carbonizing phenolic resin-based fibers from 100°C to 2
1 kg of phenolic resin fiber is placed in the low temperature firing zone of 00°C.
A method for producing phenolic resin-based carbon fibers, which comprises heat-treating the fibers in the presence of 10 g or more of oxygen per fiber, and then firing and carbonizing the fibers at at least about 500° C. in an inert gas atmosphere. 2. Claim 1, characterized in that 50 to 150 g of oxygen is present per 1 kg of phenolic resin fiber.
The method described in section.