JPS63120113A - Pitch carbon fiber - Google Patents

Abstract

PURPOSE:To obtain a pitch type carbon yarn having excellent processing properties and economic efficiency, having low strength and modulus of elasticity, extremely raising strength and modulus of elasticity by heat-treatment under a relaxed condition, by spinning a high-softening pitch to give yarn, making the yarn infusible and carbonizing. CONSTITUTION:A high-softening pitch (readily graphitizable pitch) is subjected to melt spinning to give yarn, which, for example, is made infusible in an oxidizing atmosphere at 200-400 deg.C and carbonized in an inert gas atmosphere at 400-1,800 deg.C in such a way that the aimed yarn has 15-250kgf/mm<2> strength, 0.3-8.0% elongation and 400-4,000kgf/mm<2> modulus of elasticity and shows 1.1 times as much as the modulus of elasticity by heat-treatment under a relaxed condition. The yarn is woven, carbonized and further graphitized to give yarn having high strength and high modulus of elasticity.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Industrial Application Field The present invention relates to carbon fibers having high performance obtained from pitch. For more details, crystallization and orientation of carbon molecules Ki
The present invention relates to carbon m-fibers that have an imperfect weave and have the ability to grow crystals and oriented structures by heat treatment in a relaxed state, thereby significantly improving strength and elastic modulus.

Among the carbon fibers obtained from pitch, the present invention is easy to process with a low degree of carbonization, and is less expensive than carbon fibers with a high degree of carbonization, so even if processing loss occurs, the proportion of product cost will be reduced. Has a small advantage.

Carbon m of the present invention! i is more durable against bending with a small radius of curvature than those with a high degree of carbonization, and the stress of the bent part is relaxed by the subsequent carbonization process, improving the wear resistance, bending resistance, and It has excellent scratch resistance.

(b) Conventional technology A method of obtaining carbon fibers by oxidizing the surface of fibers obtained by melt-spinning pitch with a high softening point to make them infusible, and then carbonizing them in an inert atmosphere is disclosed in Japanese Patent Publication No. 15728/1983. has been disclosed. This method is certainly an excellent method for producing pitch-based carbon III, but according to the disclosed method, it is necessary to maintain tension during carbonization in order to obtain fibers with a high modulus of elasticity. Since the infusible pitch m fibers are extremely brittle, it is difficult to hold them in a tensioned layer, and it is considered virtually impossible to obtain high modulus fibers by this method.

In order to solve this problem, a method using optical anisotropic pitch has been proposed, as disclosed in Japanese Patent Publication No. 49-8634, Japanese Patent Application Laid-Open No. 49-19127, etc.

Optically anisotropic pitch is an easily carbonizable and graphitizable material, and exhibits excellent properties as a raw material for high-strength, high-modulus carbon fibers, especially since it does not need to be placed under tension during carbonization.
This method is considered to be advantageous in terms of both cost and quality.

Although carbon fibers made from optically anisotropic pitch can easily be made to have high strength and high modulus of elasticity, they have the problem of being easily damaged, such as being broken during processing. These problems exist to a greater or lesser extent with fibers such as glass m fibers and PA fibers.
N-based carbon carbon fiber provides lubricity and cohesiveness,
Applying sizing agent. In the case of carbon fibers made from optically anisotropic pitch, they tend to be easily graphitized and tend to repel sizing agents, and because they cannot be applied uniformly, there are problems in that they lack lubricity and cohesiveness.

In order to solve this problem, Japanese Patent Application Laid-Open No. 60-21911 proposes infusibility 1! Discloses a method of mild charcoal treatment at 400 to 650°C. Although this method is somewhat effective in keeping the elastic modulus of carbon fibers low and making them less susceptible to damage, the carbonization is too mild.

It has the problem of insufficient shape and dimensional stability.

(c) Problems to be Solved by the Invention The present invention addresses the brittleness, lack of lubricity, and cohesiveness of carbon fibers manufactured from optically anisotropic pitch or pitch with a high softening point that has carbonization characteristics similar to the optically anisotropic pitch. The aim is to solve the shortage of

The present invention is a carbon fiber made by relaxing pitch fiber carbonization conditions, which has low strength and elastic modulus, and has good processability. Carbonization of pitch fibers is generally carried out by heat treatment in an inert atmosphere, and is usually carried out at a temperature of 2,000°C or higher until high strength is achieved, and if a high modulus of elasticity is required, the temperature is increased to 2,000°C. Carbon fibers with such high strength and high modulus of elasticity do not have good workability, although they are heat treated at temperatures above
It has been found that carbonization at a lower temperature is preferable.

(d) Means for solving the problems In the present invention, pitch with a high softening point is melt-spun, and the elongation at 6° is 0.3 to 8.0%, and the modulus of elasticity is K→H to 40. OO
This pitch-based carbon fiber is characterized in that it has the ability to increase to kgf/l'' or more by heat treatment in a relaxed state.

The pitch-based carbon fiber of the present invention is preferably prepared by melt-spinning pitch with a high softening point, and then carrying out the infusibility treatment and carbonization treatment by placing the spun P-7C fiber on a conveying belt.
The pitch fibers are continuously introduced into an oxidizing atmosphere at 00 to 400°C to make them infusible.

Transfer to processing.

In the present invention, the high softening point pitch is an easily graphitized pitch such as an optically anisotropic pitch. Easily graphitizable pitch produces needle coke by carbonization, and pitch 1
When a-male is carbonized, carbon fibers with a high elastic modulus are produced even when carbonized without tension. In addition to optically anisotropic pitch, graphitizable pitch also includes dormant that exhibits graphitizability similar to optically anisotropic pitch.
Contains mesophase pitch and pre-mesophase carbonaceous materials.

j- Charcoal T of the present invention: the fiber has a strength of n to 250 kgf/va
m', elongation is 0.3~8.0%, elastic modulus is ←÷H~4
0,000kgf/mm: TE 150kgf/am" or more, the elastic modulus has the ability to increase to 40.OOQkgf/m+++ or more. If the strength is less than this range, the t!! fiber will be easily damaged during processing, which is not preferable. If the 0 strength is greater than this range, the wear resistance of the part of the product where il!&i forms a loop will decrease, which is not desirable.
m+a'. If the elongation is smaller than this range, the fibers will be easily damaged during processing, which is undesirable. If the elongation is larger than this range, the shape and dimensional stability of the product will deteriorate, which is not preferable. The elongation is preferably 0. 6～
It is 5.0%. An increase in strength and an increase in elastic modulus due to heat treatment in flaccid deafness is a phenomenon that is normally observed in easily graphitized pitch, but if the increase in strength is smaller than this range, the fatigue resistance and oxidation resistance of the product will be poor. So I don't like it.

If the increase in strength is smaller than this range, there is little tendency for the sizing agent to be repelled by heat treatment, and there is little need to use the method of the present invention.

The strength increase rate by heat treatment is preferably 1.2 to 20 times, and the strength after increase is preferably 200 to 450 kgr.
/+++++", which is less than this range, is undesirable because fatigue resistance and oxidation resistance are poor, and dimensional changes during processing are large. The rate of increase in elastic modulus due to heat treatment is preferably 1.2 to 1.2. 25 times, and the elastic modulus after rising is preferably 40,000 to 100,000 kgf/m
It is s'.

Carbon of the invention! ! 1M1 preferably has a specific gravity of 1.35
~1.95, electrical specific resistance is 5X10-'~5Ω・ell
, the product of graphite crystals contained J'AH Le (002) is 8
~45 people, the interplanar spacing d0゜2 of the graphite crystal is 3.45~3.
68 people, the stacking thickness Lc (002) of the graphite crystal after heat treatment to achieve high strength and high elastic modulus is 36 Å or more, the increase in the layer thickness Le (002) is 5 Å or more, and the interplanar spacing d of the graphite crystal
0° is 3.55 Å or less. Most preferably, the specific gravity is 1.40 to 1.65 and the electrical resistivity is 1 x 10-2 to 5 x.
IQ-1Ω・cll, f! The product M thickness Lc (002) of the graphite crystal after high strength and high elasticity modulus treatment is 70
~240 people, the interplanar spacing d0° of the ring 8Ω crystal is 3°36~
3.44 people.

In the present invention, preferably, after melt-spinning pitch with a high softening point, the obtained pitch ia! Place I on the transport bell 1-20
The pitch fibers are continuously introduced into an oxidizing atmosphere at 0 to 400°C to infusible, and then placed on a conveying belt in an inert gas atmosphere at 400 to 1800°C to evaluate the strength of the pitch fibers. 16゛～250kgf/++a12、After performing carbonization treatment until the elongation becomes 0.3～8.0%,
Move on to the next stage of processing. The oil agent and sizing agent are applied after spinning and, if necessary, after infusibility. The presence of these agents has the effect of improving the ease of winding the fibers or during various processing, even if they are absent after carbonization. The reason for this is not clear, but since the take-up performance differs depending on the type of carbonization equipment, it is highly likely that the cause is whether the fiber arrangement form given before carbonization is maintained during the carbonization process. .

Comparisons were made between those processed by winding Pitch 2a il around a heat-resistant bobbin during carbonization, those processed in a can, and those processed by being placed on a belt. These showed similar values in strength, elongation, and elastic modulus, but the winding! 1. When processed by placing it on a belt during processing such as mW, the convergence was excellent.

The method of placing the pitch fibers after spinning on the conveying belt is such that the formed fiber layer is formed by the fibers placed later slipping into the already formed fiber layer.
Any type of belt may be used as long as it does not cause a reversal of the order of tff.The conveyor belt should be porous so that the fibers placed on the conveyor belt do not move due to vibrations or air currents. It is preferable to press the 4J1 fibers onto the belt by suction from the belt.If the fibers are fed into the conveying belt from a direction close to perpendicular to the belt surface, they will be sucked into the holes of the belt or into the already formed A1 fiber layer. Since it may pierce, move the running m fiber in a circular motion, 8
It is preferable to make the angle between the belt surface and the direction in which the fibers are fed smaller by swinging them in various patterns such as a cross-shaped motion. This may cause the order of fibers to be reversed or cause defects in processing after carbonization. In order to avoid this, it is preferable to attach a large amount of volatile liquid such as water or a highly viscous liquid together with the oil and sizing agent.

The UA fibers placed on the conveyor belt are heated to 200 to 400° C. in an oxidizing atmosphere to make them infusible. Rather than keeping the heating temperature constant, it is preferable to keep the temperature low at the inlet, around 200°C, and gradually increase the temperature to a high temperature around 400°C at the exit.If the inlet temperature is too high, the pitch will reach the melting point. The fibers are fused together. Since the oxidation rate is high near the entrance, the resulting heat generation may cause the pitch to fuse. If necessary, lower the oxidizing gas concentration near the inlet.

The infusibility time varies depending on the thickness of the fiber.

Pitch fibers that have undergone infusibility are extremely fragile and cannot be subjected to any treatment that applies force to the fibers; they are simply placed on a conveyor belt and sent to a carbonization device. During this time, it is possible to apply an oil agent or a sizing agent in the form of a mist.

Carbonization is carried out in an inert atmosphere at a temperature of 400 to 1800°C until the pitch strength is H to 250 kgr/+m and the elongation is 0.3 to 8.0%. It is preferable to start by replacing the oxidizing atmosphere with an inert gas at a temperature of around 400°C.If the replacement with an inert gas is insufficient, there may be problems such as thinning of the toshio or insufficient increase in strength. The treatment time varies depending on the thickness of the fibers, but it is preferable to replace the process with an inert gas atmosphere of 10 to 100 ml at the initial stage, and to maintain the temperature at a constant temperature for several seconds to several hundred seconds at the final stage.

The obtained m-fiber can be subsequently wound onto a bobbin or the like and subjected to the next stage of processing. Furthermore, carbonization can be further progressed to produce carbon fibers with high strength and high modulus of elasticity. Furthermore, it can be processed at a higher temperature to produce graphite fibers.

The subsequent carbonization can be carried out while applying tension to the fibers, thereby increasing the strength and elastic modulus.

When the obtained fibers are wound onto a bobbin or the like on a conveyor belt or sent to the next stage of high temperature treatment, it is necessary to pull them with a roller or the like. At this time, it is preferable to reverse the fiber layer on the LFI transport belt, then pull it out and apply tension to correct the shape into a straight line.In order to reverse the fiber layer on the transport belt, various methods can be used. One possible method is to bring a second belt into contact with the delamination layer, sandwich the fiber layer between both belts, turn it upside down, then place the fiber layer on the second belt, and then Most preferred is the method of drawing out the obtained fibers.

When tension is applied to the obtained fibers, it is difficult to equalize the tension using a normal tension application device, since the elastic modulus of carbon fiber is much larger than that of other fibers. It is preferable to provide resistance through the viscosity of the fluid, and it is particularly preferable to provide resistance by passing a liquid containing an oil or sizing agent. It is preferable to remove this liquid by running it across the width of the tube or pipe.

The fiber thus obtained was highly carbonized.
Unlike ii, it has a small elastic modulus, is easily wetted by liquids such as oil and sizing agents, and has poor convergence, making it excellent for processes that involve bending with a small radius of curvature, such as weaving and knitting. have sex. Also, since it costs less than carbonized 11 fibers, it is very advantageous for products that require a lot of processing loss. In addition, since strain relaxation occurs during processing, the abrasion resistance of parts bent with a small radius of curvature and η
(Fatigue resistance has deteriorated. Also, it is difficult to fuzz due to wear,
It also has excellent bending resistance and scratch resistance.

Preferably, after such post-processing, the present example 1 thermal catalytic cracking (FCC) residual oil is heated to an initial layer of 404°C and a final distillate of 560°C.
(While feeding methane gas into the dissolved substance at normal pressure [1),
The mixture was heat-treated at 320° C. for 2 hours, and further heated at 320° C. for 18 hours to grow mesophase, which was separated by sedimentation based on the difference in specific gravity. This pitch contains 96% optically anisotropic components, 47% quinoline soluble content, 82% toluene insoluble content,
It contained.

This pitch is spun from a spinning hole with an expanded part at the exit,
11270m coated with oil emulsion using conventional method
It was picked up in 1 minute and was allowed to boil while being rocked so as to draw a spiral trajectory on the conveyor m-belt.

Subsequently, in a furnace with an inlet temperature of 200°C and an outlet temperature of 400°C, oxidation treatment was performed with air at a heating rate of 20°C/min to make it infusible. After applying an oil agent in the form of an aerosol to the fibers coming out of the furnace, the fibers were sent to a carbonization furnace. The temperature at the inlet of the furnace is 450℃, 6
5℃/min until it reaches 00℃, 2℃ until it reaches 800℃
While heating at 0°C for 7 minutes, U
I went to la. After that, the temperature was increased to 95°C at a heating rate of 100°C/min.
After raising the temperature to 0°C and processing at 950°C for 45 seconds,
Take out from the furnace, transfer belt and second peru tΩ・C
I was hesitant.

When this fiber was treated in argon at 2800°C for 2 minutes, it had a strength of 288 kgf/am', an elongation of 0.4%, an elastic modulus of 78, an OOO kgr/am' strength, and an elasticity of QX w! It became a maintenance.

The weavability of the fibers was investigated before and after heat treatment in argon. In the case of plain weave, the difference between the two was not significant, but with double weave, the fibers before heat treatment were easy to weave, and with multiaxial weave and three-dimensional weave, it was difficult to weave the fibers after heat treatment.

The performance of plain weave fibers before and after heat treatment in argon was investigated. The fiber fabrics before heat treatment were heat treated in argon and compared. There was almost no difference in strength, elongation, and elastic modulus between the two, but the heat treated fiber fabrics were slightly bulkier and tended to fuzz easily when worn. Yes, bending resistance,
The scratch resistance was slightly inferior, and the abrasion resistance of the ears was inferior to Daifuku.

Comparative Example 1 The spun pitch m fiber of Example 1 was wound around an alumina porcelain bobbin, and subjected to infusibility and carbonization treatment under substantially the same temperature raising conditions as in Example 1.

The strength, elongation, elastic modulus, and crystalline state of the obtained fibers were not significantly different from those in Example 1, but the weavability was significantly inferior, and the multiaxial m
Weaving objects and three-dimensional fabrics was difficult.

Comparative Example 2 The spun pitch fibers of Example 1 were placed in a can made of a heat-resistant alloy, and subjected to infusibility and carbonization treatment under substantially the same heating conditions as in Example-1. The strength, elongation, elastic modulus, and crystalline state of the obtained m-fibers were not significantly different from those in Example 1, but it was difficult to take them out of the can, making it difficult to evaluate the fiber-making properties.

Example 2 Using the same pitch as in Example 1, the fibers were spun with the same preface (no change in content) in the spinning specification and were infusible treated while stacked on a conveyor belt. After carbonization treatment with varying salinity, processability was evaluated by winding and weaving in the same manner.

# the result! It is shown in Table 1.

Table #41 Weaving performance example 3 of carbonized fibers after carbonization The fibers of Example 1 were further carbonized at 1700°C under tension giving 1.5% elongation. went. The obtained fiber has a strength of 279 kgr/as' and an elastic modulus of 62.
, OOO kgf/as'' in a relaxed state, it had much higher strength and higher elastic modulus.

(;l:) Effects of the Invention The pitch-based carbon fiber of the present invention has a higher degree of carbonization, is easier to process, and is lower in cost.
I compared to those with a high degree of carbonization.

It is strong against bending with a small radius of curvature, and the stress of the bent portion is relaxed by the subsequent carbonization treatment, and the bent portion has excellent wear resistance, bending resistance, and scratch resistance.

that's all

Claims (1)

[Claims] It is a carbon fiber obtained by melt-spinning pitch with a high softening point, followed by infusibility treatment and carbonization treatment, and the carbon fiber has a strength of 15 to 250 kgf/mm^2 and an elongation of 0.3 to 0.3.
8.0%, elastic modulus 400-40,000kgf/mm
^2, and the pitch-based carbon fiber has the ability to increase both strength and elastic modulus by 1.1 times or more than before heat treatment by heat treatment in a relaxed state.